btrfs: remove item_size member of struct btrfs_clone_extent_info

[mirror_ubuntu-hirsute-kernel.git] / fs / btrfs / inode.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <crypto/hash.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/writeback.h>
#include <linux/compat.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/falloc.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/btrfs.h>
#include <linux/blkdev.h>
#include <linux/posix_acl_xattr.h>
#include <linux/uio.h>
#include <linux/magic.h>
#include <linux/iversion.h>
#include <linux/swap.h>
#include <linux/migrate.h>
#include <linux/sched/mm.h>
#include <linux/iomap.h>
#include <asm/unaligned.h>
#include "misc.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "print-tree.h"
#include "ordered-data.h"
#include "xattr.h"
#include "tree-log.h"
#include "volumes.h"
#include "compression.h"
#include "locking.h"
#include "free-space-cache.h"
#include "inode-map.h"
#include "props.h"
#include "qgroup.h"
#include "delalloc-space.h"
#include "block-group.h"
#include "space-info.h"

struct btrfs_iget_args {
        u64 ino;
        struct btrfs_root *root;
};

struct btrfs_dio_data {
        u64 reserve;
        loff_t length;
        ssize_t submitted;
        struct extent_changeset *data_reserved;
        bool sync;
};

static const struct inode_operations btrfs_dir_inode_operations;
static const struct inode_operations btrfs_symlink_inode_operations;
static const struct inode_operations btrfs_special_inode_operations;
static const struct inode_operations btrfs_file_inode_operations;
static const struct address_space_operations btrfs_aops;
static const struct file_operations btrfs_dir_file_operations;
static const struct extent_io_ops btrfs_extent_io_ops;

static struct kmem_cache *btrfs_inode_cachep;
struct kmem_cache *btrfs_trans_handle_cachep;
struct kmem_cache *btrfs_path_cachep;
struct kmem_cache *btrfs_free_space_cachep;
struct kmem_cache *btrfs_free_space_bitmap_cachep;

static int btrfs_setsize(struct inode *inode, struct iattr *attr);
static int btrfs_truncate(struct inode *inode, bool skip_writeback);
static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent);
static noinline int cow_file_range(struct btrfs_inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written, int unlock);
static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start,
                                       u64 len, u64 orig_start, u64 block_start,
                                       u64 block_len, u64 orig_block_len,
                                       u64 ram_bytes, int compress_type,
                                       int type);

static void __endio_write_update_ordered(struct btrfs_inode *inode,
                                         const u64 offset, const u64 bytes,
                                         const bool uptodate);

/*
 * Cleanup all submitted ordered extents in specified range to handle errors
 * from the btrfs_run_delalloc_range() callback.
 *
 * NOTE: caller must ensure that when an error happens, it can not call
 * extent_clear_unlock_delalloc() to clear both the bits EXTENT_DO_ACCOUNTING
 * and EXTENT_DELALLOC simultaneously, because that causes the reserved metadata
 * to be released, which we want to happen only when finishing the ordered
 * extent (btrfs_finish_ordered_io()).
 */
static inline void btrfs_cleanup_ordered_extents(struct btrfs_inode *inode,
                                                 struct page *locked_page,
                                                 u64 offset, u64 bytes)
{
        unsigned long index = offset >> PAGE_SHIFT;
        unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
        u64 page_start = page_offset(locked_page);
        u64 page_end = page_start + PAGE_SIZE - 1;

        struct page *page;

        while (index <= end_index) {
                page = find_get_page(inode->vfs_inode.i_mapping, index);
                index++;
                if (!page)
                        continue;
                ClearPagePrivate2(page);
                put_page(page);
        }

        /*
         * In case this page belongs to the delalloc range being instantiated
         * then skip it, since the first page of a range is going to be
         * properly cleaned up by the caller of run_delalloc_range
         */
        if (page_start >= offset && page_end <= (offset + bytes - 1)) {
                offset += PAGE_SIZE;
                bytes -= PAGE_SIZE;
        }

        return __endio_write_update_ordered(inode, offset, bytes, false);
}

static int btrfs_dirty_inode(struct inode *inode);

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
void btrfs_test_inode_set_ops(struct inode *inode)
{
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
}
#endif

static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
                                     struct inode *inode,  struct inode *dir,
                                     const struct qstr *qstr)
{
        int err;

        err = btrfs_init_acl(trans, inode, dir);
        if (!err)
                err = btrfs_xattr_security_init(trans, inode, dir, qstr);
        return err;
}

/*
 * this does all the hard work for inserting an inline extent into
 * the btree.  The caller should have done a btrfs_drop_extents so that
 * no overlapping inline items exist in the btree
 */
static int insert_inline_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_path *path, int extent_inserted,
                                struct btrfs_root *root, struct inode *inode,
                                u64 start, size_t size, size_t compressed_size,
                                int compress_type,
                                struct page **compressed_pages)
{
        struct extent_buffer *leaf;
        struct page *page = NULL;
        char *kaddr;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        int ret;
        size_t cur_size = size;
        unsigned long offset;

        ASSERT((compressed_size > 0 && compressed_pages) ||
               (compressed_size == 0 && !compressed_pages));

        if (compressed_size && compressed_pages)
                cur_size = compressed_size;

        inode_add_bytes(inode, size);

        if (!extent_inserted) {
                struct btrfs_key key;
                size_t datasize;

                key.objectid = btrfs_ino(BTRFS_I(inode));
                key.offset = start;
                key.type = BTRFS_EXTENT_DATA_KEY;

                datasize = btrfs_file_extent_calc_inline_size(cur_size);
                path->leave_spinning = 1;
                ret = btrfs_insert_empty_item(trans, root, path, &key,
                                              datasize);
                if (ret)
                        goto fail;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei, BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, size);
        ptr = btrfs_file_extent_inline_start(ei);

        if (compress_type != BTRFS_COMPRESS_NONE) {
                struct page *cpage;
                int i = 0;
                while (compressed_size > 0) {
                        cpage = compressed_pages[i];
                        cur_size = min_t(unsigned long, compressed_size,
                                       PAGE_SIZE);

                        kaddr = kmap_atomic(cpage);
                        write_extent_buffer(leaf, kaddr, ptr, cur_size);
                        kunmap_atomic(kaddr);

                        i++;
                        ptr += cur_size;
                        compressed_size -= cur_size;
                }
                btrfs_set_file_extent_compression(leaf, ei,
                                                  compress_type);
        } else {
                page = find_get_page(inode->i_mapping,
                                     start >> PAGE_SHIFT);
                btrfs_set_file_extent_compression(leaf, ei, 0);
                kaddr = kmap_atomic(page);
                offset = offset_in_page(start);
                write_extent_buffer(leaf, kaddr + offset, ptr, size);
                kunmap_atomic(kaddr);
                put_page(page);
        }
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(path);

        /*
         * We align size to sectorsize for inline extents just for simplicity
         * sake.
         */
        size = ALIGN(size, root->fs_info->sectorsize);
        ret = btrfs_inode_set_file_extent_range(BTRFS_I(inode), start, size);
        if (ret)
                goto fail;

        /*
         * we're an inline extent, so nobody can
         * extend the file past i_size without locking
         * a page we already have locked.
         *
         * We must do any isize and inode updates
         * before we unlock the pages.  Otherwise we
         * could end up racing with unlink.
         */
        BTRFS_I(inode)->disk_i_size = inode->i_size;
        ret = btrfs_update_inode(trans, root, inode);

fail:
        return ret;
}


/*
 * conditionally insert an inline extent into the file.  This
 * does the checks required to make sure the data is small enough
 * to fit as an inline extent.
 */
static noinline int cow_file_range_inline(struct btrfs_inode *inode, u64 start,
                                          u64 end, size_t compressed_size,
                                          int compress_type,
                                          struct page **compressed_pages)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_trans_handle *trans;
        u64 isize = i_size_read(&inode->vfs_inode);
        u64 actual_end = min(end + 1, isize);
        u64 inline_len = actual_end - start;
        u64 aligned_end = ALIGN(end, fs_info->sectorsize);
        u64 data_len = inline_len;
        int ret;
        struct btrfs_path *path;
        int extent_inserted = 0;
        u32 extent_item_size;

        if (compressed_size)
                data_len = compressed_size;

        if (start > 0 ||
            actual_end > fs_info->sectorsize ||
            data_len > BTRFS_MAX_INLINE_DATA_SIZE(fs_info) ||
            (!compressed_size &&
            (actual_end & (fs_info->sectorsize - 1)) == 0) ||
            end + 1 < isize ||
            data_len > fs_info->max_inline) {
                return 1;
        }

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                btrfs_free_path(path);
                return PTR_ERR(trans);
        }
        trans->block_rsv = &inode->block_rsv;

        if (compressed_size && compressed_pages)
                extent_item_size = btrfs_file_extent_calc_inline_size(
                   compressed_size);
        else
                extent_item_size = btrfs_file_extent_calc_inline_size(
                    inline_len);

        ret = __btrfs_drop_extents(trans, root, inode, path, start, aligned_end,
                                   NULL, 1, 1, extent_item_size,
                                   &extent_inserted);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        }

        if (isize > actual_end)
                inline_len = min_t(u64, isize, actual_end);
        ret = insert_inline_extent(trans, path, extent_inserted,
                                   root, &inode->vfs_inode, start,
                                   inline_len, compressed_size,
                                   compress_type, compressed_pages);
        if (ret && ret != -ENOSPC) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        } else if (ret == -ENOSPC) {
                ret = 1;
                goto out;
        }

        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &inode->runtime_flags);
        btrfs_drop_extent_cache(inode, start, aligned_end - 1, 0);
out:
        /*
         * Don't forget to free the reserved space, as for inlined extent
         * it won't count as data extent, free them directly here.
         * And at reserve time, it's always aligned to page size, so
         * just free one page here.
         */
        btrfs_qgroup_free_data(inode, NULL, 0, PAGE_SIZE);
        btrfs_free_path(path);
        btrfs_end_transaction(trans);
        return ret;
}

struct async_extent {
        u64 start;
        u64 ram_size;
        u64 compressed_size;
        struct page **pages;
        unsigned long nr_pages;
        int compress_type;
        struct list_head list;
};

struct async_chunk {
        struct inode *inode;
        struct page *locked_page;
        u64 start;
        u64 end;
        unsigned int write_flags;
        struct list_head extents;
        struct cgroup_subsys_state *blkcg_css;
        struct btrfs_work work;
        atomic_t *pending;
};

struct async_cow {
        /* Number of chunks in flight; must be first in the structure */
        atomic_t num_chunks;
        struct async_chunk chunks[];
};

static noinline int add_async_extent(struct async_chunk *cow,
                                     u64 start, u64 ram_size,
                                     u64 compressed_size,
                                     struct page **pages,
                                     unsigned long nr_pages,
                                     int compress_type)
{
        struct async_extent *async_extent;

        async_extent = kmalloc(sizeof(*async_extent), GFP_NOFS);
        BUG_ON(!async_extent); /* -ENOMEM */
        async_extent->start = start;
        async_extent->ram_size = ram_size;
        async_extent->compressed_size = compressed_size;
        async_extent->pages = pages;
        async_extent->nr_pages = nr_pages;
        async_extent->compress_type = compress_type;
        list_add_tail(&async_extent->list, &cow->extents);
        return 0;
}

/*
 * Check if the inode has flags compatible with compression
 */
static inline bool inode_can_compress(struct btrfs_inode *inode)
{
        if (inode->flags & BTRFS_INODE_NODATACOW ||
            inode->flags & BTRFS_INODE_NODATASUM)
                return false;
        return true;
}

/*
 * Check if the inode needs to be submitted to compression, based on mount
 * options, defragmentation, properties or heuristics.
 */
static inline int inode_need_compress(struct btrfs_inode *inode, u64 start,
                                      u64 end)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;

        if (!inode_can_compress(inode)) {
                WARN(IS_ENABLED(CONFIG_BTRFS_DEBUG),
                        KERN_ERR "BTRFS: unexpected compression for ino %llu\n",
                        btrfs_ino(inode));
                return 0;
        }
        /* force compress */
        if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
                return 1;
        /* defrag ioctl */
        if (inode->defrag_compress)
                return 1;
        /* bad compression ratios */
        if (inode->flags & BTRFS_INODE_NOCOMPRESS)
                return 0;
        if (btrfs_test_opt(fs_info, COMPRESS) ||
            inode->flags & BTRFS_INODE_COMPRESS ||
            inode->prop_compress)
                return btrfs_compress_heuristic(&inode->vfs_inode, start, end);
        return 0;
}

static inline void inode_should_defrag(struct btrfs_inode *inode,
                u64 start, u64 end, u64 num_bytes, u64 small_write)
{
        /* If this is a small write inside eof, kick off a defrag */
        if (num_bytes < small_write &&
            (start > 0 || end + 1 < inode->disk_i_size))
                btrfs_add_inode_defrag(NULL, inode);
}

/*
 * we create compressed extents in two phases.  The first
 * phase compresses a range of pages that have already been
 * locked (both pages and state bits are locked).
 *
 * This is done inside an ordered work queue, and the compression
 * is spread across many cpus.  The actual IO submission is step
 * two, and the ordered work queue takes care of making sure that
 * happens in the same order things were put onto the queue by
 * writepages and friends.
 *
 * If this code finds it can't get good compression, it puts an
 * entry onto the work queue to write the uncompressed bytes.  This
 * makes sure that both compressed inodes and uncompressed inodes
 * are written in the same order that the flusher thread sent them
 * down.
 */
static noinline int compress_file_range(struct async_chunk *async_chunk)
{
        struct inode *inode = async_chunk->inode;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        u64 blocksize = fs_info->sectorsize;
        u64 start = async_chunk->start;
        u64 end = async_chunk->end;
        u64 actual_end;
        u64 i_size;
        int ret = 0;
        struct page **pages = NULL;
        unsigned long nr_pages;
        unsigned long total_compressed = 0;
        unsigned long total_in = 0;
        int i;
        int will_compress;
        int compress_type = fs_info->compress_type;
        int compressed_extents = 0;
        int redirty = 0;

        inode_should_defrag(BTRFS_I(inode), start, end, end - start + 1,
                        SZ_16K);

        /*
         * We need to save i_size before now because it could change in between
         * us evaluating the size and assigning it.  This is because we lock and
         * unlock the page in truncate and fallocate, and then modify the i_size
         * later on.
         *
         * The barriers are to emulate READ_ONCE, remove that once i_size_read
         * does that for us.
         */
        barrier();
        i_size = i_size_read(inode);
        barrier();
        actual_end = min_t(u64, i_size, end + 1);
again:
        will_compress = 0;
        nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
        BUILD_BUG_ON((BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0);
        nr_pages = min_t(unsigned long, nr_pages,
                        BTRFS_MAX_COMPRESSED / PAGE_SIZE);

        /*
         * we don't want to send crud past the end of i_size through
         * compression, that's just a waste of CPU time.  So, if the
         * end of the file is before the start of our current
         * requested range of bytes, we bail out to the uncompressed
         * cleanup code that can deal with all of this.
         *
         * It isn't really the fastest way to fix things, but this is a
         * very uncommon corner.
         */
        if (actual_end <= start)
                goto cleanup_and_bail_uncompressed;

        total_compressed = actual_end - start;

        /*
         * skip compression for a small file range(<=blocksize) that
         * isn't an inline extent, since it doesn't save disk space at all.
         */
        if (total_compressed <= blocksize &&
           (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
                goto cleanup_and_bail_uncompressed;

        total_compressed = min_t(unsigned long, total_compressed,
                        BTRFS_MAX_UNCOMPRESSED);
        total_in = 0;
        ret = 0;

        /*
         * we do compression for mount -o compress and when the
         * inode has not been flagged as nocompress.  This flag can
         * change at any time if we discover bad compression ratios.
         */
        if (inode_need_compress(BTRFS_I(inode), start, end)) {
                WARN_ON(pages);
                pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
                if (!pages) {
                        /* just bail out to the uncompressed code */
                        nr_pages = 0;
                        goto cont;
                }

                if (BTRFS_I(inode)->defrag_compress)
                        compress_type = BTRFS_I(inode)->defrag_compress;
                else if (BTRFS_I(inode)->prop_compress)
                        compress_type = BTRFS_I(inode)->prop_compress;

                /*
                 * we need to call clear_page_dirty_for_io on each
                 * page in the range.  Otherwise applications with the file
                 * mmap'd can wander in and change the page contents while
                 * we are compressing them.
                 *
                 * If the compression fails for any reason, we set the pages
                 * dirty again later on.
                 *
                 * Note that the remaining part is redirtied, the start pointer
                 * has moved, the end is the original one.
                 */
                if (!redirty) {
                        extent_range_clear_dirty_for_io(inode, start, end);
                        redirty = 1;
                }

                /* Compression level is applied here and only here */
                ret = btrfs_compress_pages(
                        compress_type | (fs_info->compress_level << 4),
                                           inode->i_mapping, start,
                                           pages,
                                           &nr_pages,
                                           &total_in,
                                           &total_compressed);

                if (!ret) {
                        unsigned long offset = offset_in_page(total_compressed);
                        struct page *page = pages[nr_pages - 1];
                        char *kaddr;

                        /* zero the tail end of the last page, we might be
                         * sending it down to disk
                         */
                        if (offset) {
                                kaddr = kmap_atomic(page);
                                memset(kaddr + offset, 0,
                                       PAGE_SIZE - offset);
                                kunmap_atomic(kaddr);
                        }
                        will_compress = 1;
                }
        }
cont:
        if (start == 0) {
                /* lets try to make an inline extent */
                if (ret || total_in < actual_end) {
                        /* we didn't compress the entire range, try
                         * to make an uncompressed inline extent.
                         */
                        ret = cow_file_range_inline(BTRFS_I(inode), start, end,
                                                    0, BTRFS_COMPRESS_NONE,
                                                    NULL);
                } else {
                        /* try making a compressed inline extent */
                        ret = cow_file_range_inline(BTRFS_I(inode), start, end,
                                                    total_compressed,
                                                    compress_type, pages);
                }
                if (ret <= 0) {
                        unsigned long clear_flags = EXTENT_DELALLOC |
                                EXTENT_DELALLOC_NEW | EXTENT_DEFRAG |
                                EXTENT_DO_ACCOUNTING;
                        unsigned long page_error_op;

                        page_error_op = ret < 0 ? PAGE_SET_ERROR : 0;

                        /*
                         * inline extent creation worked or returned error,
                         * we don't need to create any more async work items.
                         * Unlock and free up our temp pages.
                         *
                         * We use DO_ACCOUNTING here because we need the
                         * delalloc_release_metadata to be done _after_ we drop
                         * our outstanding extent for clearing delalloc for this
                         * range.
                         */
                        extent_clear_unlock_delalloc(BTRFS_I(inode), start, end,
                                                     NULL,
                                                     clear_flags,
                                                     PAGE_UNLOCK |
                                                     PAGE_CLEAR_DIRTY |
                                                     PAGE_SET_WRITEBACK |
                                                     page_error_op |
                                                     PAGE_END_WRITEBACK);

                        /*
                         * Ensure we only free the compressed pages if we have
                         * them allocated, as we can still reach here with
                         * inode_need_compress() == false.
                         */
                        if (pages) {
                                for (i = 0; i < nr_pages; i++) {
                                        WARN_ON(pages[i]->mapping);
                                        put_page(pages[i]);
                                }
                                kfree(pages);
                        }
                        return 0;
                }
        }

        if (will_compress) {
                /*
                 * we aren't doing an inline extent round the compressed size
                 * up to a block size boundary so the allocator does sane
                 * things
                 */
                total_compressed = ALIGN(total_compressed, blocksize);

                /*
                 * one last check to make sure the compression is really a
                 * win, compare the page count read with the blocks on disk,
                 * compression must free at least one sector size
                 */
                total_in = ALIGN(total_in, PAGE_SIZE);
                if (total_compressed + blocksize <= total_in) {
                        compressed_extents++;

                        /*
                         * The async work queues will take care of doing actual
                         * allocation on disk for these compressed pages, and
                         * will submit them to the elevator.
                         */
                        add_async_extent(async_chunk, start, total_in,
                                        total_compressed, pages, nr_pages,
                                        compress_type);

                        if (start + total_in < end) {
                                start += total_in;
                                pages = NULL;
                                cond_resched();
                                goto again;
                        }
                        return compressed_extents;
                }
        }
        if (pages) {
                /*
                 * the compression code ran but failed to make things smaller,
                 * free any pages it allocated and our page pointer array
                 */
                for (i = 0; i < nr_pages; i++) {
                        WARN_ON(pages[i]->mapping);
                        put_page(pages[i]);
                }
                kfree(pages);
                pages = NULL;
                total_compressed = 0;
                nr_pages = 0;

                /* flag the file so we don't compress in the future */
                if (!btrfs_test_opt(fs_info, FORCE_COMPRESS) &&
                    !(BTRFS_I(inode)->prop_compress)) {
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
                }
        }
cleanup_and_bail_uncompressed:
        /*
         * No compression, but we still need to write the pages in the file
         * we've been given so far.  redirty the locked page if it corresponds
         * to our extent and set things up for the async work queue to run
         * cow_file_range to do the normal delalloc dance.
         */
        if (async_chunk->locked_page &&
            (page_offset(async_chunk->locked_page) >= start &&
             page_offset(async_chunk->locked_page)) <= end) {
                __set_page_dirty_nobuffers(async_chunk->locked_page);
                /* unlocked later on in the async handlers */
        }

        if (redirty)
                extent_range_redirty_for_io(inode, start, end);
        add_async_extent(async_chunk, start, end - start + 1, 0, NULL, 0,
                         BTRFS_COMPRESS_NONE);
        compressed_extents++;

        return compressed_extents;
}

static void free_async_extent_pages(struct async_extent *async_extent)
{
        int i;

        if (!async_extent->pages)
                return;

        for (i = 0; i < async_extent->nr_pages; i++) {
                WARN_ON(async_extent->pages[i]->mapping);
                put_page(async_extent->pages[i]);
        }
        kfree(async_extent->pages);
        async_extent->nr_pages = 0;
        async_extent->pages = NULL;
}

/*
 * phase two of compressed writeback.  This is the ordered portion
 * of the code, which only gets called in the order the work was
 * queued.  We walk all the async extents created by compress_file_range
 * and send them down to the disk.
 */
static noinline void submit_compressed_extents(struct async_chunk *async_chunk)
{
        struct btrfs_inode *inode = BTRFS_I(async_chunk->inode);
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct async_extent *async_extent;
        u64 alloc_hint = 0;
        struct btrfs_key ins;
        struct extent_map *em;
        struct btrfs_root *root = inode->root;
        struct extent_io_tree *io_tree = &inode->io_tree;
        int ret = 0;

again:
        while (!list_empty(&async_chunk->extents)) {
                async_extent = list_entry(async_chunk->extents.next,
                                          struct async_extent, list);
                list_del(&async_extent->list);

retry:
                lock_extent(io_tree, async_extent->start,
                            async_extent->start + async_extent->ram_size - 1);
                /* did the compression code fall back to uncompressed IO? */
                if (!async_extent->pages) {
                        int page_started = 0;
                        unsigned long nr_written = 0;

                        /* allocate blocks */
                        ret = cow_file_range(inode, async_chunk->locked_page,
                                             async_extent->start,
                                             async_extent->start +
                                             async_extent->ram_size - 1,
                                             &page_started, &nr_written, 0);

                        /* JDM XXX */

                        /*
                         * if page_started, cow_file_range inserted an
                         * inline extent and took care of all the unlocking
                         * and IO for us.  Otherwise, we need to submit
                         * all those pages down to the drive.
                         */
                        if (!page_started && !ret)
                                extent_write_locked_range(&inode->vfs_inode,
                                                  async_extent->start,
                                                  async_extent->start +
                                                  async_extent->ram_size - 1,
                                                  WB_SYNC_ALL);
                        else if (ret && async_chunk->locked_page)
                                unlock_page(async_chunk->locked_page);
                        kfree(async_extent);
                        cond_resched();
                        continue;
                }

                ret = btrfs_reserve_extent(root, async_extent->ram_size,
                                           async_extent->compressed_size,
                                           async_extent->compressed_size,
                                           0, alloc_hint, &ins, 1, 1);
                if (ret) {
                        free_async_extent_pages(async_extent);

                        if (ret == -ENOSPC) {
                                unlock_extent(io_tree, async_extent->start,
                                              async_extent->start +
                                              async_extent->ram_size - 1);

                                /*
                                 * we need to redirty the pages if we decide to
                                 * fallback to uncompressed IO, otherwise we
                                 * will not submit these pages down to lower
                                 * layers.
                                 */
                                extent_range_redirty_for_io(&inode->vfs_inode,
                                                async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1);

                                goto retry;
                        }
                        goto out_free;
                }
                /*
                 * here we're doing allocation and writeback of the
                 * compressed pages
                 */
                em = create_io_em(inode, async_extent->start,
                                  async_extent->ram_size, /* len */
                                  async_extent->start, /* orig_start */
                                  ins.objectid, /* block_start */
                                  ins.offset, /* block_len */
                                  ins.offset, /* orig_block_len */
                                  async_extent->ram_size, /* ram_bytes */
                                  async_extent->compress_type,
                                  BTRFS_ORDERED_COMPRESSED);
                if (IS_ERR(em))
                        /* ret value is not necessary due to void function */
                        goto out_free_reserve;
                free_extent_map(em);

                ret = btrfs_add_ordered_extent_compress(inode,
                                                async_extent->start,
                                                ins.objectid,
                                                async_extent->ram_size,
                                                ins.offset,
                                                BTRFS_ORDERED_COMPRESSED,
                                                async_extent->compress_type);
                if (ret) {
                        btrfs_drop_extent_cache(inode, async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1, 0);
                        goto out_free_reserve;
                }
                btrfs_dec_block_group_reservations(fs_info, ins.objectid);

                /*
                 * clear dirty, set writeback and unlock the pages.
                 */
                extent_clear_unlock_delalloc(inode, async_extent->start,
                                async_extent->start +
                                async_extent->ram_size - 1,
                                NULL, EXTENT_LOCKED | EXTENT_DELALLOC,
                                PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                                PAGE_SET_WRITEBACK);
                if (btrfs_submit_compressed_write(inode, async_extent->start,
                                    async_extent->ram_size,
                                    ins.objectid,
                                    ins.offset, async_extent->pages,
                                    async_extent->nr_pages,
                                    async_chunk->write_flags,
                                    async_chunk->blkcg_css)) {
                        struct page *p = async_extent->pages[0];
                        const u64 start = async_extent->start;
                        const u64 end = start + async_extent->ram_size - 1;

                        p->mapping = inode->vfs_inode.i_mapping;
                        btrfs_writepage_endio_finish_ordered(p, start, end, 0);

                        p->mapping = NULL;
                        extent_clear_unlock_delalloc(inode, start, end, NULL, 0,
                                                     PAGE_END_WRITEBACK |
                                                     PAGE_SET_ERROR);
                        free_async_extent_pages(async_extent);
                }
                alloc_hint = ins.objectid + ins.offset;
                kfree(async_extent);
                cond_resched();
        }
        return;
out_free_reserve:
        btrfs_dec_block_group_reservations(fs_info, ins.objectid);
        btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1);
out_free:
        extent_clear_unlock_delalloc(inode, async_extent->start,
                                     async_extent->start +
                                     async_extent->ram_size - 1,
                                     NULL, EXTENT_LOCKED | EXTENT_DELALLOC |
                                     EXTENT_DELALLOC_NEW |
                                     EXTENT_DEFRAG | EXTENT_DO_ACCOUNTING,
                                     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                                     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK |
                                     PAGE_SET_ERROR);
        free_async_extent_pages(async_extent);
        kfree(async_extent);
        goto again;
}

static u64 get_extent_allocation_hint(struct btrfs_inode *inode, u64 start,
                                      u64 num_bytes)
{
        struct extent_map_tree *em_tree = &inode->extent_tree;
        struct extent_map *em;
        u64 alloc_hint = 0;

        read_lock(&em_tree->lock);
        em = search_extent_mapping(em_tree, start, num_bytes);
        if (em) {
                /*
                 * if block start isn't an actual block number then find the
                 * first block in this inode and use that as a hint.  If that
                 * block is also bogus then just don't worry about it.
                 */
                if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
                        free_extent_map(em);
                        em = search_extent_mapping(em_tree, 0, 0);
                        if (em && em->block_start < EXTENT_MAP_LAST_BYTE)
                                alloc_hint = em->block_start;
                        if (em)
                                free_extent_map(em);
                } else {
                        alloc_hint = em->block_start;
                        free_extent_map(em);
                }
        }
        read_unlock(&em_tree->lock);

        return alloc_hint;
}

/*
 * when extent_io.c finds a delayed allocation range in the file,
 * the call backs end up in this code.  The basic idea is to
 * allocate extents on disk for the range, and create ordered data structs
 * in ram to track those extents.
 *
 * locked_page is the page that writepage had locked already.  We use
 * it to make sure we don't do extra locks or unlocks.
 *
 * *page_started is set to one if we unlock locked_page and do everything
 * required to start IO on it.  It may be clean and already done with
 * IO when we return.
 */
static noinline int cow_file_range(struct btrfs_inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written, int unlock)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        u64 alloc_hint = 0;
        u64 num_bytes;
        unsigned long ram_size;
        u64 cur_alloc_size = 0;
        u64 min_alloc_size;
        u64 blocksize = fs_info->sectorsize;
        struct btrfs_key ins;
        struct extent_map *em;
        unsigned clear_bits;
        unsigned long page_ops;
        bool extent_reserved = false;
        int ret = 0;

        if (btrfs_is_free_space_inode(inode)) {
                WARN_ON_ONCE(1);
                ret = -EINVAL;
                goto out_unlock;
        }

        num_bytes = ALIGN(end - start + 1, blocksize);
        num_bytes = max(blocksize,  num_bytes);
        ASSERT(num_bytes <= btrfs_super_total_bytes(fs_info->super_copy));

        inode_should_defrag(inode, start, end, num_bytes, SZ_64K);

        if (start == 0) {
                /* lets try to make an inline extent */
                ret = cow_file_range_inline(inode, start, end, 0,
                                            BTRFS_COMPRESS_NONE, NULL);
                if (ret == 0) {
                        /*
                         * We use DO_ACCOUNTING here because we need the
                         * delalloc_release_metadata to be run _after_ we drop
                         * our outstanding extent for clearing delalloc for this
                         * range.
                         */
                        extent_clear_unlock_delalloc(inode, start, end, NULL,
                                     EXTENT_LOCKED | EXTENT_DELALLOC |
                                     EXTENT_DELALLOC_NEW | EXTENT_DEFRAG |
                                     EXTENT_DO_ACCOUNTING, PAGE_UNLOCK |
                                     PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
                                     PAGE_END_WRITEBACK);
                        *nr_written = *nr_written +
                             (end - start + PAGE_SIZE) / PAGE_SIZE;
                        *page_started = 1;
                        goto out;
                } else if (ret < 0) {
                        goto out_unlock;
                }
        }

        alloc_hint = get_extent_allocation_hint(inode, start, num_bytes);
        btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);

        /*
         * Relocation relies on the relocated extents to have exactly the same
         * size as the original extents. Normally writeback for relocation data
         * extents follows a NOCOW path because relocation preallocates the
         * extents. However, due to an operation such as scrub turning a block
         * group to RO mode, it may fallback to COW mode, so we must make sure
         * an extent allocated during COW has exactly the requested size and can
         * not be split into smaller extents, otherwise relocation breaks and
         * fails during the stage where it updates the bytenr of file extent
         * items.
         */
        if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                min_alloc_size = num_bytes;
        else
                min_alloc_size = fs_info->sectorsize;

        while (num_bytes > 0) {
                cur_alloc_size = num_bytes;
                ret = btrfs_reserve_extent(root, cur_alloc_size, cur_alloc_size,
                                           min_alloc_size, 0, alloc_hint,
                                           &ins, 1, 1);
                if (ret < 0)
                        goto out_unlock;
                cur_alloc_size = ins.offset;
                extent_reserved = true;

                ram_size = ins.offset;
                em = create_io_em(inode, start, ins.offset, /* len */
                                  start, /* orig_start */
                                  ins.objectid, /* block_start */
                                  ins.offset, /* block_len */
                                  ins.offset, /* orig_block_len */
                                  ram_size, /* ram_bytes */
                                  BTRFS_COMPRESS_NONE, /* compress_type */
                                  BTRFS_ORDERED_REGULAR /* type */);
                if (IS_ERR(em)) {
                        ret = PTR_ERR(em);
                        goto out_reserve;
                }
                free_extent_map(em);

                ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
                                               ram_size, cur_alloc_size, 0);
                if (ret)
                        goto out_drop_extent_cache;

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
                        ret = btrfs_reloc_clone_csums(inode, start,
                                                      cur_alloc_size);
                        /*
                         * Only drop cache here, and process as normal.
                         *
                         * We must not allow extent_clear_unlock_delalloc()
                         * at out_unlock label to free meta of this ordered
                         * extent, as its meta should be freed by
                         * btrfs_finish_ordered_io().
                         *
                         * So we must continue until @start is increased to
                         * skip current ordered extent.
                         */
                        if (ret)
                                btrfs_drop_extent_cache(inode, start,
                                                start + ram_size - 1, 0);
                }

                btrfs_dec_block_group_reservations(fs_info, ins.objectid);

                /* we're not doing compressed IO, don't unlock the first
                 * page (which the caller expects to stay locked), don't
                 * clear any dirty bits and don't set any writeback bits
                 *
                 * Do set the Private2 bit so we know this page was properly
                 * setup for writepage
                 */
                page_ops = unlock ? PAGE_UNLOCK : 0;
                page_ops |= PAGE_SET_PRIVATE2;

                extent_clear_unlock_delalloc(inode, start, start + ram_size - 1,
                                             locked_page,
                                             EXTENT_LOCKED | EXTENT_DELALLOC,
                                             page_ops);
                if (num_bytes < cur_alloc_size)
                        num_bytes = 0;
                else
                        num_bytes -= cur_alloc_size;
                alloc_hint = ins.objectid + ins.offset;
                start += cur_alloc_size;
                extent_reserved = false;

                /*
                 * btrfs_reloc_clone_csums() error, since start is increased
                 * extent_clear_unlock_delalloc() at out_unlock label won't
                 * free metadata of current ordered extent, we're OK to exit.
                 */
                if (ret)
                        goto out_unlock;
        }
out:
        return ret;

out_drop_extent_cache:
        btrfs_drop_extent_cache(inode, start, start + ram_size - 1, 0);
out_reserve:
        btrfs_dec_block_group_reservations(fs_info, ins.objectid);
        btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1);
out_unlock:
        clear_bits = EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DELALLOC_NEW |
                EXTENT_DEFRAG | EXTENT_CLEAR_META_RESV;
        page_ops = PAGE_UNLOCK | PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
                PAGE_END_WRITEBACK;
        /*
         * If we reserved an extent for our delalloc range (or a subrange) and
         * failed to create the respective ordered extent, then it means that
         * when we reserved the extent we decremented the extent's size from
         * the data space_info's bytes_may_use counter and incremented the
         * space_info's bytes_reserved counter by the same amount. We must make
         * sure extent_clear_unlock_delalloc() does not try to decrement again
         * the data space_info's bytes_may_use counter, therefore we do not pass
         * it the flag EXTENT_CLEAR_DATA_RESV.
         */
        if (extent_reserved) {
                extent_clear_unlock_delalloc(inode, start,
                                             start + cur_alloc_size - 1,
                                             locked_page,
                                             clear_bits,
                                             page_ops);
                start += cur_alloc_size;
                if (start >= end)
                        goto out;
        }
        extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                     clear_bits | EXTENT_CLEAR_DATA_RESV,
                                     page_ops);
        goto out;
}

/*
 * work queue call back to started compression on a file and pages
 */
static noinline void async_cow_start(struct btrfs_work *work)
{
        struct async_chunk *async_chunk;
        int compressed_extents;

        async_chunk = container_of(work, struct async_chunk, work);

        compressed_extents = compress_file_range(async_chunk);
        if (compressed_extents == 0) {
                btrfs_add_delayed_iput(async_chunk->inode);
                async_chunk->inode = NULL;
        }
}

/*
 * work queue call back to submit previously compressed pages
 */
static noinline void async_cow_submit(struct btrfs_work *work)
{
        struct async_chunk *async_chunk = container_of(work, struct async_chunk,
                                                     work);
        struct btrfs_fs_info *fs_info = btrfs_work_owner(work);
        unsigned long nr_pages;

        nr_pages = (async_chunk->end - async_chunk->start + PAGE_SIZE) >>
                PAGE_SHIFT;

        /* atomic_sub_return implies a barrier */
        if (atomic_sub_return(nr_pages, &fs_info->async_delalloc_pages) <
            5 * SZ_1M)
                cond_wake_up_nomb(&fs_info->async_submit_wait);

        /*
         * ->inode could be NULL if async_chunk_start has failed to compress,
         * in which case we don't have anything to submit, yet we need to
         * always adjust ->async_delalloc_pages as its paired with the init
         * happening in cow_file_range_async
         */
        if (async_chunk->inode)
                submit_compressed_extents(async_chunk);
}

static noinline void async_cow_free(struct btrfs_work *work)
{
        struct async_chunk *async_chunk;

        async_chunk = container_of(work, struct async_chunk, work);
        if (async_chunk->inode)
                btrfs_add_delayed_iput(async_chunk->inode);
        if (async_chunk->blkcg_css)
                css_put(async_chunk->blkcg_css);
        /*
         * Since the pointer to 'pending' is at the beginning of the array of
         * async_chunk's, freeing it ensures the whole array has been freed.
         */
        if (atomic_dec_and_test(async_chunk->pending))
                kvfree(async_chunk->pending);
}

static int cow_file_range_async(struct btrfs_inode *inode,
                                struct writeback_control *wbc,
                                struct page *locked_page,
                                u64 start, u64 end, int *page_started,
                                unsigned long *nr_written)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct cgroup_subsys_state *blkcg_css = wbc_blkcg_css(wbc);
        struct async_cow *ctx;
        struct async_chunk *async_chunk;
        unsigned long nr_pages;
        u64 cur_end;
        u64 num_chunks = DIV_ROUND_UP(end - start, SZ_512K);
        int i;
        bool should_compress;
        unsigned nofs_flag;
        const unsigned int write_flags = wbc_to_write_flags(wbc);

        unlock_extent(&inode->io_tree, start, end);

        if (inode->flags & BTRFS_INODE_NOCOMPRESS &&
            !btrfs_test_opt(fs_info, FORCE_COMPRESS)) {
                num_chunks = 1;
                should_compress = false;
        } else {
                should_compress = true;
        }

        nofs_flag = memalloc_nofs_save();
        ctx = kvmalloc(struct_size(ctx, chunks, num_chunks), GFP_KERNEL);
        memalloc_nofs_restore(nofs_flag);

        if (!ctx) {
                unsigned clear_bits = EXTENT_LOCKED | EXTENT_DELALLOC |
                        EXTENT_DELALLOC_NEW | EXTENT_DEFRAG |
                        EXTENT_DO_ACCOUNTING;
                unsigned long page_ops = PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                        PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK |
                        PAGE_SET_ERROR;

                extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                             clear_bits, page_ops);
                return -ENOMEM;
        }

        async_chunk = ctx->chunks;
        atomic_set(&ctx->num_chunks, num_chunks);

        for (i = 0; i < num_chunks; i++) {
                if (should_compress)
                        cur_end = min(end, start + SZ_512K - 1);
                else
                        cur_end = end;

                /*
                 * igrab is called higher up in the call chain, take only the
                 * lightweight reference for the callback lifetime
                 */
                ihold(&inode->vfs_inode);
                async_chunk[i].pending = &ctx->num_chunks;
                async_chunk[i].inode = &inode->vfs_inode;
                async_chunk[i].start = start;
                async_chunk[i].end = cur_end;
                async_chunk[i].write_flags = write_flags;
                INIT_LIST_HEAD(&async_chunk[i].extents);

                /*
                 * The locked_page comes all the way from writepage and its
                 * the original page we were actually given.  As we spread
                 * this large delalloc region across multiple async_chunk
                 * structs, only the first struct needs a pointer to locked_page
                 *
                 * This way we don't need racey decisions about who is supposed
                 * to unlock it.
                 */
                if (locked_page) {
                        /*
                         * Depending on the compressibility, the pages might or
                         * might not go through async.  We want all of them to
                         * be accounted against wbc once.  Let's do it here
                         * before the paths diverge.  wbc accounting is used
                         * only for foreign writeback detection and doesn't
                         * need full accuracy.  Just account the whole thing
                         * against the first page.
                         */
                        wbc_account_cgroup_owner(wbc, locked_page,
                                                 cur_end - start);
                        async_chunk[i].locked_page = locked_page;
                        locked_page = NULL;
                } else {
                        async_chunk[i].locked_page = NULL;
                }

                if (blkcg_css != blkcg_root_css) {
                        css_get(blkcg_css);
                        async_chunk[i].blkcg_css = blkcg_css;
                } else {
                        async_chunk[i].blkcg_css = NULL;
                }

                btrfs_init_work(&async_chunk[i].work, async_cow_start,
                                async_cow_submit, async_cow_free);

                nr_pages = DIV_ROUND_UP(cur_end - start, PAGE_SIZE);
                atomic_add(nr_pages, &fs_info->async_delalloc_pages);

                btrfs_queue_work(fs_info->delalloc_workers, &async_chunk[i].work);

                *nr_written += nr_pages;
                start = cur_end + 1;
        }
        *page_started = 1;
        return 0;
}

static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
                                        u64 bytenr, u64 num_bytes)
{
        int ret;
        struct btrfs_ordered_sum *sums;
        LIST_HEAD(list);

        ret = btrfs_lookup_csums_range(fs_info->csum_root, bytenr,
                                       bytenr + num_bytes - 1, &list, 0);
        if (ret == 0 && list_empty(&list))
                return 0;

        while (!list_empty(&list)) {
                sums = list_entry(list.next, struct btrfs_ordered_sum, list);
                list_del(&sums->list);
                kfree(sums);
        }
        if (ret < 0)
                return ret;
        return 1;
}

static int fallback_to_cow(struct btrfs_inode *inode, struct page *locked_page,
                           const u64 start, const u64 end,
                           int *page_started, unsigned long *nr_written)
{
        const bool is_space_ino = btrfs_is_free_space_inode(inode);
        const bool is_reloc_ino = (inode->root->root_key.objectid ==
                                   BTRFS_DATA_RELOC_TREE_OBJECTID);
        const u64 range_bytes = end + 1 - start;
        struct extent_io_tree *io_tree = &inode->io_tree;
        u64 range_start = start;
        u64 count;

        /*
         * If EXTENT_NORESERVE is set it means that when the buffered write was
         * made we had not enough available data space and therefore we did not
         * reserve data space for it, since we though we could do NOCOW for the
         * respective file range (either there is prealloc extent or the inode
         * has the NOCOW bit set).
         *
         * However when we need to fallback to COW mode (because for example the
         * block group for the corresponding extent was turned to RO mode by a
         * scrub or relocation) we need to do the following:
         *
         * 1) We increment the bytes_may_use counter of the data space info.
         *    If COW succeeds, it allocates a new data extent and after doing
         *    that it decrements the space info's bytes_may_use counter and
         *    increments its bytes_reserved counter by the same amount (we do
         *    this at btrfs_add_reserved_bytes()). So we need to increment the
         *    bytes_may_use counter to compensate (when space is reserved at
         *    buffered write time, the bytes_may_use counter is incremented);
         *
         * 2) We clear the EXTENT_NORESERVE bit from the range. We do this so
         *    that if the COW path fails for any reason, it decrements (through
         *    extent_clear_unlock_delalloc()) the bytes_may_use counter of the
         *    data space info, which we incremented in the step above.
         *
         * If we need to fallback to cow and the inode corresponds to a free
         * space cache inode or an inode of the data relocation tree, we must
         * also increment bytes_may_use of the data space_info for the same
         * reason. Space caches and relocated data extents always get a prealloc
         * extent for them, however scrub or balance may have set the block
         * group that contains that extent to RO mode and therefore force COW
         * when starting writeback.
         */
        count = count_range_bits(io_tree, &range_start, end, range_bytes,
                                 EXTENT_NORESERVE, 0);
        if (count > 0 || is_space_ino || is_reloc_ino) {
                u64 bytes = count;
                struct btrfs_fs_info *fs_info = inode->root->fs_info;
                struct btrfs_space_info *sinfo = fs_info->data_sinfo;

                if (is_space_ino || is_reloc_ino)
                        bytes = range_bytes;

                spin_lock(&sinfo->lock);
                btrfs_space_info_update_bytes_may_use(fs_info, sinfo, bytes);
                spin_unlock(&sinfo->lock);

                if (count > 0)
                        clear_extent_bit(io_tree, start, end, EXTENT_NORESERVE,
                                         0, 0, NULL);
        }

        return cow_file_range(inode, locked_page, start, end, page_started,
                              nr_written, 1);
}

/*
 * when nowcow writeback call back.  This checks for snapshots or COW copies
 * of the extents that exist in the file, and COWs the file as required.
 *
 * If no cow copies or snapshots exist, we write directly to the existing
 * blocks on disk
 */
static noinline int run_delalloc_nocow(struct btrfs_inode *inode,
                                       struct page *locked_page,
                                       const u64 start, const u64 end,
                                       int *page_started, int force,
                                       unsigned long *nr_written)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_root *root = inode->root;
        struct btrfs_path *path;
        u64 cow_start = (u64)-1;
        u64 cur_offset = start;
        int ret;
        bool check_prev = true;
        const bool freespace_inode = btrfs_is_free_space_inode(inode);
        u64 ino = btrfs_ino(inode);
        bool nocow = false;
        u64 disk_bytenr = 0;

        path = btrfs_alloc_path();
        if (!path) {
                extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                             EXTENT_LOCKED | EXTENT_DELALLOC |
                                             EXTENT_DO_ACCOUNTING |
                                             EXTENT_DEFRAG, PAGE_UNLOCK |
                                             PAGE_CLEAR_DIRTY |
                                             PAGE_SET_WRITEBACK |
                                             PAGE_END_WRITEBACK);
                return -ENOMEM;
        }

        while (1) {
                struct btrfs_key found_key;
                struct btrfs_file_extent_item *fi;
                struct extent_buffer *leaf;
                u64 extent_end;
                u64 extent_offset;
                u64 num_bytes = 0;
                u64 disk_num_bytes;
                u64 ram_bytes;
                int extent_type;

                nocow = false;

                ret = btrfs_lookup_file_extent(NULL, root, path, ino,
                                               cur_offset, 0);
                if (ret < 0)
                        goto error;

                /*
                 * If there is no extent for our range when doing the initial
                 * search, then go back to the previous slot as it will be the
                 * one containing the search offset
                 */
                if (ret > 0 && path->slots[0] > 0 && check_prev) {
                        leaf = path->nodes[0];
                        btrfs_item_key_to_cpu(leaf, &found_key,
                                              path->slots[0] - 1);
                        if (found_key.objectid == ino &&
                            found_key.type == BTRFS_EXTENT_DATA_KEY)
                                path->slots[0]--;
                }
                check_prev = false;
next_slot:
                /* Go to next leaf if we have exhausted the current one */
                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0) {
                                if (cow_start != (u64)-1)
                                        cur_offset = cow_start;
                                goto error;
                        }
                        if (ret > 0)
                                break;
                        leaf = path->nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                /* Didn't find anything for our INO */
                if (found_key.objectid > ino)
                        break;
                /*
                 * Keep searching until we find an EXTENT_ITEM or there are no
                 * more extents for this inode
                 */
                if (WARN_ON_ONCE(found_key.objectid < ino) ||
                    found_key.type < BTRFS_EXTENT_DATA_KEY) {
                        path->slots[0]++;
                        goto next_slot;
                }

                /* Found key is not EXTENT_DATA_KEY or starts after req range */
                if (found_key.type > BTRFS_EXTENT_DATA_KEY ||
                    found_key.offset > end)
                        break;

                /*
                 * If the found extent starts after requested offset, then
                 * adjust extent_end to be right before this extent begins
                 */
                if (found_key.offset > cur_offset) {
                        extent_end = found_key.offset;
                        extent_type = 0;
                        goto out_check;
                }

                /*
                 * Found extent which begins before our range and potentially
                 * intersect it
                 */
                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_type = btrfs_file_extent_type(leaf, fi);

                ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
                if (extent_type == BTRFS_FILE_EXTENT_REG ||
                    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                        extent_offset = btrfs_file_extent_offset(leaf, fi);
                        extent_end = found_key.offset +
                                btrfs_file_extent_num_bytes(leaf, fi);
                        disk_num_bytes =
                                btrfs_file_extent_disk_num_bytes(leaf, fi);
                        /*
                         * If the extent we got ends before our current offset,
                         * skip to the next extent.
                         */
                        if (extent_end <= cur_offset) {
                                path->slots[0]++;
                                goto next_slot;
                        }
                        /* Skip holes */
                        if (disk_bytenr == 0)
                                goto out_check;
                        /* Skip compressed/encrypted/encoded extents */
                        if (btrfs_file_extent_compression(leaf, fi) ||
                            btrfs_file_extent_encryption(leaf, fi) ||
                            btrfs_file_extent_other_encoding(leaf, fi))
                                goto out_check;
                        /*
                         * If extent is created before the last volume's snapshot
                         * this implies the extent is shared, hence we can't do
                         * nocow. This is the same check as in
                         * btrfs_cross_ref_exist but without calling
                         * btrfs_search_slot.
                         */
                        if (!freespace_inode &&
                            btrfs_file_extent_generation(leaf, fi) <=
                            btrfs_root_last_snapshot(&root->root_item))
                                goto out_check;
                        if (extent_type == BTRFS_FILE_EXTENT_REG && !force)
                                goto out_check;
                        /* If extent is RO, we must COW it */
                        if (btrfs_extent_readonly(fs_info, disk_bytenr))
                                goto out_check;
                        ret = btrfs_cross_ref_exist(root, ino,
                                                    found_key.offset -
                                                    extent_offset, disk_bytenr, false);
                        if (ret) {
                                /*
                                 * ret could be -EIO if the above fails to read
                                 * metadata.
                                 */
                                if (ret < 0) {
                                        if (cow_start != (u64)-1)
                                                cur_offset = cow_start;
                                        goto error;
                                }

                                WARN_ON_ONCE(freespace_inode);
                                goto out_check;
                        }
                        disk_bytenr += extent_offset;
                        disk_bytenr += cur_offset - found_key.offset;
                        num_bytes = min(end + 1, extent_end) - cur_offset;
                        /*
                         * If there are pending snapshots for this root, we
                         * fall into common COW way
                         */
                        if (!freespace_inode && atomic_read(&root->snapshot_force_cow))
                                goto out_check;
                        /*
                         * force cow if csum exists in the range.
                         * this ensure that csum for a given extent are
                         * either valid or do not exist.
                         */
                        ret = csum_exist_in_range(fs_info, disk_bytenr,
                                                  num_bytes);
                        if (ret) {
                                /*
                                 * ret could be -EIO if the above fails to read
                                 * metadata.
                                 */
                                if (ret < 0) {
                                        if (cow_start != (u64)-1)
                                                cur_offset = cow_start;
                                        goto error;
                                }
                                WARN_ON_ONCE(freespace_inode);
                                goto out_check;
                        }
                        if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr))
                                goto out_check;
                        nocow = true;
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        extent_end = found_key.offset + ram_bytes;
                        extent_end = ALIGN(extent_end, fs_info->sectorsize);
                        /* Skip extents outside of our requested range */
                        if (extent_end <= start) {
                                path->slots[0]++;
                                goto next_slot;
                        }
                } else {
                        /* If this triggers then we have a memory corruption */
                        BUG();
                }
out_check:
                /*
                 * If nocow is false then record the beginning of the range
                 * that needs to be COWed
                 */
                if (!nocow) {
                        if (cow_start == (u64)-1)
                                cow_start = cur_offset;
                        cur_offset = extent_end;
                        if (cur_offset > end)
                                break;
                        path->slots[0]++;
                        goto next_slot;
                }

                btrfs_release_path(path);

                /*
                 * COW range from cow_start to found_key.offset - 1. As the key
                 * will contain the beginning of the first extent that can be
                 * NOCOW, following one which needs to be COW'ed
                 */
                if (cow_start != (u64)-1) {
                        ret = fallback_to_cow(inode, locked_page,
                                              cow_start, found_key.offset - 1,
                                              page_started, nr_written);
                        if (ret)
                                goto error;
                        cow_start = (u64)-1;
                }

                if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        u64 orig_start = found_key.offset - extent_offset;
                        struct extent_map *em;

                        em = create_io_em(inode, cur_offset, num_bytes,
                                          orig_start,
                                          disk_bytenr, /* block_start */
                                          num_bytes, /* block_len */
                                          disk_num_bytes, /* orig_block_len */
                                          ram_bytes, BTRFS_COMPRESS_NONE,
                                          BTRFS_ORDERED_PREALLOC);
                        if (IS_ERR(em)) {
                                ret = PTR_ERR(em);
                                goto error;
                        }
                        free_extent_map(em);
                        ret = btrfs_add_ordered_extent(inode, cur_offset,
                                                       disk_bytenr, num_bytes,
                                                       num_bytes,
                                                       BTRFS_ORDERED_PREALLOC);
                        if (ret) {
                                btrfs_drop_extent_cache(inode, cur_offset,
                                                        cur_offset + num_bytes - 1,
                                                        0);
                                goto error;
                        }
                } else {
                        ret = btrfs_add_ordered_extent(inode, cur_offset,
                                                       disk_bytenr, num_bytes,
                                                       num_bytes,
                                                       BTRFS_ORDERED_NOCOW);
                        if (ret)
                                goto error;
                }

                if (nocow)
                        btrfs_dec_nocow_writers(fs_info, disk_bytenr);
                nocow = false;

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID)
                        /*
                         * Error handled later, as we must prevent
                         * extent_clear_unlock_delalloc() in error handler
                         * from freeing metadata of created ordered extent.
                         */
                        ret = btrfs_reloc_clone_csums(inode, cur_offset,
                                                      num_bytes);

                extent_clear_unlock_delalloc(inode, cur_offset,
                                             cur_offset + num_bytes - 1,
                                             locked_page, EXTENT_LOCKED |
                                             EXTENT_DELALLOC |
                                             EXTENT_CLEAR_DATA_RESV,
                                             PAGE_UNLOCK | PAGE_SET_PRIVATE2);

                cur_offset = extent_end;

                /*
                 * btrfs_reloc_clone_csums() error, now we're OK to call error
                 * handler, as metadata for created ordered extent will only
                 * be freed by btrfs_finish_ordered_io().
                 */
                if (ret)
                        goto error;
                if (cur_offset > end)
                        break;
        }
        btrfs_release_path(path);

        if (cur_offset <= end && cow_start == (u64)-1)
                cow_start = cur_offset;

        if (cow_start != (u64)-1) {
                cur_offset = end;
                ret = fallback_to_cow(inode, locked_page, cow_start, end,
                                      page_started, nr_written);
                if (ret)
                        goto error;
        }

error:
        if (nocow)
                btrfs_dec_nocow_writers(fs_info, disk_bytenr);

        if (ret && cur_offset < end)
                extent_clear_unlock_delalloc(inode, cur_offset, end,
                                             locked_page, EXTENT_LOCKED |
                                             EXTENT_DELALLOC | EXTENT_DEFRAG |
                                             EXTENT_DO_ACCOUNTING, PAGE_UNLOCK |
                                             PAGE_CLEAR_DIRTY |
                                             PAGE_SET_WRITEBACK |
                                             PAGE_END_WRITEBACK);
        btrfs_free_path(path);
        return ret;
}

static inline int need_force_cow(struct btrfs_inode *inode, u64 start, u64 end)
{

        if (!(inode->flags & BTRFS_INODE_NODATACOW) &&
            !(inode->flags & BTRFS_INODE_PREALLOC))
                return 0;

        /*
         * @defrag_bytes is a hint value, no spinlock held here,
         * if is not zero, it means the file is defragging.
         * Force cow if given extent needs to be defragged.
         */
        if (inode->defrag_bytes &&
            test_range_bit(&inode->io_tree, start, end, EXTENT_DEFRAG, 0, NULL))
                return 1;

        return 0;
}

/*
 * Function to process delayed allocation (create CoW) for ranges which are
 * being touched for the first time.
 */
int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page,
                u64 start, u64 end, int *page_started, unsigned long *nr_written,
                struct writeback_control *wbc)
{
        int ret;
        int force_cow = need_force_cow(inode, start, end);

        if (inode->flags & BTRFS_INODE_NODATACOW && !force_cow) {
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 1, nr_written);
        } else if (inode->flags & BTRFS_INODE_PREALLOC && !force_cow) {
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 0, nr_written);
        } else if (!inode_can_compress(inode) ||
                   !inode_need_compress(inode, start, end)) {
                ret = cow_file_range(inode, locked_page, start, end,
                                     page_started, nr_written, 1);
        } else {
                set_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, &inode->runtime_flags);
                ret = cow_file_range_async(inode, wbc, locked_page, start, end,
                                           page_started, nr_written);
        }
        if (ret)
                btrfs_cleanup_ordered_extents(inode, locked_page, start,
                                              end - start + 1);
        return ret;
}

void btrfs_split_delalloc_extent(struct inode *inode,
                                 struct extent_state *orig, u64 split)
{
        u64 size;

        /* not delalloc, ignore it */
        if (!(orig->state & EXTENT_DELALLOC))
                return;

        size = orig->end - orig->start + 1;
        if (size > BTRFS_MAX_EXTENT_SIZE) {
                u32 num_extents;
                u64 new_size;

                /*
                 * See the explanation in btrfs_merge_delalloc_extent, the same
                 * applies here, just in reverse.
                 */
                new_size = orig->end - split + 1;
                num_extents = count_max_extents(new_size);
                new_size = split - orig->start;
                num_extents += count_max_extents(new_size);
                if (count_max_extents(size) >= num_extents)
                        return;
        }

        spin_lock(&BTRFS_I(inode)->lock);
        btrfs_mod_outstanding_extents(BTRFS_I(inode), 1);
        spin_unlock(&BTRFS_I(inode)->lock);
}

/*
 * Handle merged delayed allocation extents so we can keep track of new extents
 * that are just merged onto old extents, such as when we are doing sequential
 * writes, so we can properly account for the metadata space we'll need.
 */
void btrfs_merge_delalloc_extent(struct inode *inode, struct extent_state *new,
                                 struct extent_state *other)
{
        u64 new_size, old_size;
        u32 num_extents;

        /* not delalloc, ignore it */
        if (!(other->state & EXTENT_DELALLOC))
                return;

        if (new->start > other->start)
                new_size = new->end - other->start + 1;
        else
                new_size = other->end - new->start + 1;

        /* we're not bigger than the max, unreserve the space and go */
        if (new_size <= BTRFS_MAX_EXTENT_SIZE) {
                spin_lock(&BTRFS_I(inode)->lock);
                btrfs_mod_outstanding_extents(BTRFS_I(inode), -1);
                spin_unlock(&BTRFS_I(inode)->lock);
                return;
        }

        /*
         * We have to add up either side to figure out how many extents were
         * accounted for before we merged into one big extent.  If the number of
         * extents we accounted for is <= the amount we need for the new range
         * then we can return, otherwise drop.  Think of it like this
         *
         * [ 4k][MAX_SIZE]
         *
         * So we've grown the extent by a MAX_SIZE extent, this would mean we
         * need 2 outstanding extents, on one side we have 1 and the other side
         * we have 1 so they are == and we can return.  But in this case
         *
         * [MAX_SIZE+4k][MAX_SIZE+4k]
         *
         * Each range on their own accounts for 2 extents, but merged together
         * they are only 3 extents worth of accounting, so we need to drop in
         * this case.
         */
        old_size = other->end - other->start + 1;
        num_extents = count_max_extents(old_size);
        old_size = new->end - new->start + 1;
        num_extents += count_max_extents(old_size);
        if (count_max_extents(new_size) >= num_extents)
                return;

        spin_lock(&BTRFS_I(inode)->lock);
        btrfs_mod_outstanding_extents(BTRFS_I(inode), -1);
        spin_unlock(&BTRFS_I(inode)->lock);
}

static void btrfs_add_delalloc_inodes(struct btrfs_root *root,
                                      struct inode *inode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

        spin_lock(&root->delalloc_lock);
        if (list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
                list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
                              &root->delalloc_inodes);
                set_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                        &BTRFS_I(inode)->runtime_flags);
                root->nr_delalloc_inodes++;
                if (root->nr_delalloc_inodes == 1) {
                        spin_lock(&fs_info->delalloc_root_lock);
                        BUG_ON(!list_empty(&root->delalloc_root));
                        list_add_tail(&root->delalloc_root,
                                      &fs_info->delalloc_roots);
                        spin_unlock(&fs_info->delalloc_root_lock);
                }
        }
        spin_unlock(&root->delalloc_lock);
}


void __btrfs_del_delalloc_inode(struct btrfs_root *root,
                                struct btrfs_inode *inode)
{
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (!list_empty(&inode->delalloc_inodes)) {
                list_del_init(&inode->delalloc_inodes);
                clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                          &inode->runtime_flags);
                root->nr_delalloc_inodes--;
                if (!root->nr_delalloc_inodes) {
                        ASSERT(list_empty(&root->delalloc_inodes));
                        spin_lock(&fs_info->delalloc_root_lock);
                        BUG_ON(list_empty(&root->delalloc_root));
                        list_del_init(&root->delalloc_root);
                        spin_unlock(&fs_info->delalloc_root_lock);
                }
        }
}

static void btrfs_del_delalloc_inode(struct btrfs_root *root,
                                     struct btrfs_inode *inode)
{
        spin_lock(&root->delalloc_lock);
        __btrfs_del_delalloc_inode(root, inode);
        spin_unlock(&root->delalloc_lock);
}

/*
 * Properly track delayed allocation bytes in the inode and to maintain the
 * list of inodes that have pending delalloc work to be done.
 */
void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
                               unsigned *bits)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

        if ((*bits & EXTENT_DEFRAG) && !(*bits & EXTENT_DELALLOC))
                WARN_ON(1);
        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                u64 len = state->end + 1 - state->start;
                u32 num_extents = count_max_extents(len);
                bool do_list = !btrfs_is_free_space_inode(BTRFS_I(inode));

                spin_lock(&BTRFS_I(inode)->lock);
                btrfs_mod_outstanding_extents(BTRFS_I(inode), num_extents);
                spin_unlock(&BTRFS_I(inode)->lock);

                /* For sanity tests */
                if (btrfs_is_testing(fs_info))
                        return;

                percpu_counter_add_batch(&fs_info->delalloc_bytes, len,
                                         fs_info->delalloc_batch);
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->delalloc_bytes += len;
                if (*bits & EXTENT_DEFRAG)
                        BTRFS_I(inode)->defrag_bytes += len;
                if (do_list && !test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                                         &BTRFS_I(inode)->runtime_flags))
                        btrfs_add_delalloc_inodes(root, inode);
                spin_unlock(&BTRFS_I(inode)->lock);
        }

        if (!(state->state & EXTENT_DELALLOC_NEW) &&
            (*bits & EXTENT_DELALLOC_NEW)) {
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->new_delalloc_bytes += state->end + 1 -
                        state->start;
                spin_unlock(&BTRFS_I(inode)->lock);
        }
}

/*
 * Once a range is no longer delalloc this function ensures that proper
 * accounting happens.
 */
void btrfs_clear_delalloc_extent(struct inode *vfs_inode,
                                 struct extent_state *state, unsigned *bits)
{
        struct btrfs_inode *inode = BTRFS_I(vfs_inode);
        struct btrfs_fs_info *fs_info = btrfs_sb(vfs_inode->i_sb);
        u64 len = state->end + 1 - state->start;
        u32 num_extents = count_max_extents(len);

        if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) {
                spin_lock(&inode->lock);
                inode->defrag_bytes -= len;
                spin_unlock(&inode->lock);
        }

        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if ((state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = inode->root;
                bool do_list = !btrfs_is_free_space_inode(inode);

                spin_lock(&inode->lock);
                btrfs_mod_outstanding_extents(inode, -num_extents);
                spin_unlock(&inode->lock);

                /*
                 * We don't reserve metadata space for space cache inodes so we
                 * don't need to call delalloc_release_metadata if there is an
                 * error.
                 */
                if (*bits & EXTENT_CLEAR_META_RESV &&
                    root != fs_info->tree_root)
                        btrfs_delalloc_release_metadata(inode, len, false);

                /* For sanity tests. */
                if (btrfs_is_testing(fs_info))
                        return;

                if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID &&
                    do_list && !(state->state & EXTENT_NORESERVE) &&
                    (*bits & EXTENT_CLEAR_DATA_RESV))
                        btrfs_free_reserved_data_space_noquota(fs_info, len);

                percpu_counter_add_batch(&fs_info->delalloc_bytes, -len,
                                         fs_info->delalloc_batch);
                spin_lock(&inode->lock);
                inode->delalloc_bytes -= len;
                if (do_list && inode->delalloc_bytes == 0 &&
                    test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                                        &inode->runtime_flags))
                        btrfs_del_delalloc_inode(root, inode);
                spin_unlock(&inode->lock);
        }

        if ((state->state & EXTENT_DELALLOC_NEW) &&
            (*bits & EXTENT_DELALLOC_NEW)) {
                spin_lock(&inode->lock);
                ASSERT(inode->new_delalloc_bytes >= len);
                inode->new_delalloc_bytes -= len;
                spin_unlock(&inode->lock);
        }
}

/*
 * btrfs_bio_fits_in_stripe - Checks whether the size of the given bio will fit
 * in a chunk's stripe. This function ensures that bios do not span a
 * stripe/chunk
 *
 * @page - The page we are about to add to the bio
 * @size - size we want to add to the bio
 * @bio - bio we want to ensure is smaller than a stripe
 * @bio_flags - flags of the bio
 *
 * return 1 if page cannot be added to the bio
 * return 0 if page can be added to the bio
 * return error otherwise
 */
int btrfs_bio_fits_in_stripe(struct page *page, size_t size, struct bio *bio,
                             unsigned long bio_flags)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        u64 logical = (u64)bio->bi_iter.bi_sector << 9;
        u64 length = 0;
        u64 map_length;
        int ret;
        struct btrfs_io_geometry geom;

        if (bio_flags & EXTENT_BIO_COMPRESSED)
                return 0;

        length = bio->bi_iter.bi_size;
        map_length = length;
        ret = btrfs_get_io_geometry(fs_info, btrfs_op(bio), logical, map_length,
                                    &geom);
        if (ret < 0)
                return ret;

        if (geom.len < length + size)
                return 1;
        return 0;
}

/*
 * in order to insert checksums into the metadata in large chunks,
 * we wait until bio submission time.   All the pages in the bio are
 * checksummed and sums are attached onto the ordered extent record.
 *
 * At IO completion time the cums attached on the ordered extent record
 * are inserted into the btree
 */
static blk_status_t btrfs_submit_bio_start(void *private_data, struct bio *bio,
                                    u64 bio_offset)
{
        struct inode *inode = private_data;

        return btrfs_csum_one_bio(BTRFS_I(inode), bio, 0, 0);
}

/*
 * extent_io.c submission hook. This does the right thing for csum calculation
 * on write, or reading the csums from the tree before a read.
 *
 * Rules about async/sync submit,
 * a) read:                             sync submit
 *
 * b) write without checksum:           sync submit
 *
 * c) write with checksum:
 *    c-1) if bio is issued by fsync:   sync submit
 *         (sync_writers != 0)
 *
 *    c-2) if root is reloc root:       sync submit
 *         (only in case of buffered IO)
 *
 *    c-3) otherwise:                   async submit
 */
static blk_status_t btrfs_submit_bio_hook(struct inode *inode, struct bio *bio,
                                          int mirror_num,
                                          unsigned long bio_flags)

{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        enum btrfs_wq_endio_type metadata = BTRFS_WQ_ENDIO_DATA;
        blk_status_t ret = 0;
        int skip_sum;
        int async = !atomic_read(&BTRFS_I(inode)->sync_writers);

        skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        if (btrfs_is_free_space_inode(BTRFS_I(inode)))
                metadata = BTRFS_WQ_ENDIO_FREE_SPACE;

        if (bio_op(bio) != REQ_OP_WRITE) {
                ret = btrfs_bio_wq_end_io(fs_info, bio, metadata);
                if (ret)
                        goto out;

                if (bio_flags & EXTENT_BIO_COMPRESSED) {
                        ret = btrfs_submit_compressed_read(inode, bio,
                                                           mirror_num,
                                                           bio_flags);
                        goto out;
                } else if (!skip_sum) {
                        ret = btrfs_lookup_bio_sums(inode, bio, (u64)-1, NULL);
                        if (ret)
                                goto out;
                }
                goto mapit;
        } else if (async && !skip_sum) {
                /* csum items have already been cloned */
                if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                        goto mapit;
                /* we're doing a write, do the async checksumming */
                ret = btrfs_wq_submit_bio(fs_info, bio, mirror_num, bio_flags,
                                          0, inode, btrfs_submit_bio_start);
                goto out;
        } else if (!skip_sum) {
                ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, 0, 0);
                if (ret)
                        goto out;
        }

mapit:
        ret = btrfs_map_bio(fs_info, bio, mirror_num);

out:
        if (ret) {
                bio->bi_status = ret;
                bio_endio(bio);
        }
        return ret;
}

/*
 * given a list of ordered sums record them in the inode.  This happens
 * at IO completion time based on sums calculated at bio submission time.
 */
static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
                             struct inode *inode, struct list_head *list)
{
        struct btrfs_ordered_sum *sum;
        int ret;

        list_for_each_entry(sum, list, list) {
                trans->adding_csums = true;
                ret = btrfs_csum_file_blocks(trans,
                       BTRFS_I(inode)->root->fs_info->csum_root, sum);
                trans->adding_csums = false;
                if (ret)
                        return ret;
        }
        return 0;
}

int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
                              unsigned int extra_bits,
                              struct extent_state **cached_state)
{
        WARN_ON(PAGE_ALIGNED(end));
        return set_extent_delalloc(&inode->io_tree, start, end, extra_bits,
                                   cached_state);
}

/* see btrfs_writepage_start_hook for details on why this is required */
struct btrfs_writepage_fixup {
        struct page *page;
        struct inode *inode;
        struct btrfs_work work;
};

static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
{
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        struct extent_changeset *data_reserved = NULL;
        struct page *page;
        struct btrfs_inode *inode;
        u64 page_start;
        u64 page_end;
        int ret = 0;
        bool free_delalloc_space = true;

        fixup = container_of(work, struct btrfs_writepage_fixup, work);
        page = fixup->page;
        inode = BTRFS_I(fixup->inode);
        page_start = page_offset(page);
        page_end = page_offset(page) + PAGE_SIZE - 1;

        /*
         * This is similar to page_mkwrite, we need to reserve the space before
         * we take the page lock.
         */
        ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
                                           PAGE_SIZE);
again:
        lock_page(page);

        /*
         * Before we queued this fixup, we took a reference on the page.
         * page->mapping may go NULL, but it shouldn't be moved to a different
         * address space.
         */
        if (!page->mapping || !PageDirty(page) || !PageChecked(page)) {
                /*
                 * Unfortunately this is a little tricky, either
                 *
                 * 1) We got here and our page had already been dealt with and
                 *    we reserved our space, thus ret == 0, so we need to just
                 *    drop our space reservation and bail.  This can happen the
                 *    first time we come into the fixup worker, or could happen
                 *    while waiting for the ordered extent.
                 * 2) Our page was already dealt with, but we happened to get an
                 *    ENOSPC above from the btrfs_delalloc_reserve_space.  In
                 *    this case we obviously don't have anything to release, but
                 *    because the page was already dealt with we don't want to
                 *    mark the page with an error, so make sure we're resetting
                 *    ret to 0.  This is why we have this check _before_ the ret
                 *    check, because we do not want to have a surprise ENOSPC
                 *    when the page was already properly dealt with.
                 */
                if (!ret) {
                        btrfs_delalloc_release_extents(inode, PAGE_SIZE);
                        btrfs_delalloc_release_space(inode, data_reserved,
                                                     page_start, PAGE_SIZE,
                                                     true);
                }
                ret = 0;
                goto out_page;
        }

        /*
         * We can't mess with the page state unless it is locked, so now that
         * it is locked bail if we failed to make our space reservation.
         */
        if (ret)
                goto out_page;

        lock_extent_bits(&inode->io_tree, page_start, page_end, &cached_state);

        /* already ordered? We're done */
        if (PagePrivate2(page))
                goto out_reserved;

        ordered = btrfs_lookup_ordered_range(inode, page_start, PAGE_SIZE);
        if (ordered) {
                unlock_extent_cached(&inode->io_tree, page_start, page_end,
                                     &cached_state);
                unlock_page(page);
                btrfs_start_ordered_extent(&inode->vfs_inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
                                        &cached_state);
        if (ret)
                goto out_reserved;

        /*
         * Everything went as planned, we're now the owner of a dirty page with
         * delayed allocation bits set and space reserved for our COW
         * destination.
         *
         * The page was dirty when we started, nothing should have cleaned it.
         */
        BUG_ON(!PageDirty(page));
        free_delalloc_space = false;
out_reserved:
        btrfs_delalloc_release_extents(inode, PAGE_SIZE);
        if (free_delalloc_space)
                btrfs_delalloc_release_space(inode, data_reserved, page_start,
                                             PAGE_SIZE, true);
        unlock_extent_cached(&inode->io_tree, page_start, page_end,
                             &cached_state);
out_page:
        if (ret) {
                /*
                 * We hit ENOSPC or other errors.  Update the mapping and page
                 * to reflect the errors and clean the page.
                 */
                mapping_set_error(page->mapping, ret);
                end_extent_writepage(page, ret, page_start, page_end);
                clear_page_dirty_for_io(page);
                SetPageError(page);
        }
        ClearPageChecked(page);
        unlock_page(page);
        put_page(page);
        kfree(fixup);
        extent_changeset_free(data_reserved);
        /*
         * As a precaution, do a delayed iput in case it would be the last iput
         * that could need flushing space. Recursing back to fixup worker would
         * deadlock.
         */
        btrfs_add_delayed_iput(&inode->vfs_inode);
}

/*
 * There are a few paths in the higher layers of the kernel that directly
 * set the page dirty bit without asking the filesystem if it is a
 * good idea.  This causes problems because we want to make sure COW
 * properly happens and the data=ordered rules are followed.
 *
 * In our case any range that doesn't have the ORDERED bit set
 * hasn't been properly setup for IO.  We kick off an async process
 * to fix it up.  The async helper will wait for ordered extents, set
 * the delalloc bit and make it safe to write the page.
 */
int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_writepage_fixup *fixup;

        /* this page is properly in the ordered list */
        if (TestClearPagePrivate2(page))
                return 0;

        /*
         * PageChecked is set below when we create a fixup worker for this page,
         * don't try to create another one if we're already PageChecked()
         *
         * The extent_io writepage code will redirty the page if we send back
         * EAGAIN.
         */
        if (PageChecked(page))
                return -EAGAIN;

        fixup = kzalloc(sizeof(*fixup), GFP_NOFS);
        if (!fixup)
                return -EAGAIN;

        /*
         * We are already holding a reference to this inode from
         * write_cache_pages.  We need to hold it because the space reservation
         * takes place outside of the page lock, and we can't trust
         * page->mapping outside of the page lock.
         */
        ihold(inode);
        SetPageChecked(page);
        get_page(page);
        btrfs_init_work(&fixup->work, btrfs_writepage_fixup_worker, NULL, NULL);
        fixup->page = page;
        fixup->inode = inode;
        btrfs_queue_work(fs_info->fixup_workers, &fixup->work);

        return -EAGAIN;
}

static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
                                       struct btrfs_inode *inode, u64 file_pos,
                                       struct btrfs_file_extent_item *stack_fi,
                                       u64 qgroup_reserved)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key ins;
        u64 disk_num_bytes = btrfs_stack_file_extent_disk_num_bytes(stack_fi);
        u64 disk_bytenr = btrfs_stack_file_extent_disk_bytenr(stack_fi);
        u64 num_bytes = btrfs_stack_file_extent_num_bytes(stack_fi);
        u64 ram_bytes = btrfs_stack_file_extent_ram_bytes(stack_fi);
        int extent_inserted = 0;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /*
         * we may be replacing one extent in the tree with another.
         * The new extent is pinned in the extent map, and we don't want
         * to drop it from the cache until it is completely in the btree.
         *
         * So, tell btrfs_drop_extents to leave this extent in the cache.
         * the caller is expected to unpin it and allow it to be merged
         * with the others.
         */
        ret = __btrfs_drop_extents(trans, root, inode, path, file_pos,
                                   file_pos + num_bytes, NULL, 0,
                                   1, sizeof(*stack_fi), &extent_inserted);
        if (ret)
                goto out;

        if (!extent_inserted) {
                ins.objectid = btrfs_ino(inode);
                ins.offset = file_pos;
                ins.type = BTRFS_EXTENT_DATA_KEY;

                path->leave_spinning = 1;
                ret = btrfs_insert_empty_item(trans, root, path, &ins,
                                              sizeof(*stack_fi));
                if (ret)
                        goto out;
        }
        leaf = path->nodes[0];
        btrfs_set_stack_file_extent_generation(stack_fi, trans->transid);
        write_extent_buffer(leaf, stack_fi,
                        btrfs_item_ptr_offset(leaf, path->slots[0]),
                        sizeof(struct btrfs_file_extent_item));

        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(path);

        inode_add_bytes(&inode->vfs_inode, num_bytes);

        ins.objectid = disk_bytenr;
        ins.offset = disk_num_bytes;
        ins.type = BTRFS_EXTENT_ITEM_KEY;

        ret = btrfs_inode_set_file_extent_range(inode, file_pos, ram_bytes);
        if (ret)
                goto out;

        ret = btrfs_alloc_reserved_file_extent(trans, root, btrfs_ino(inode),
                                               file_pos, qgroup_reserved, &ins);
out:
        btrfs_free_path(path);

        return ret;
}

static void btrfs_release_delalloc_bytes(struct btrfs_fs_info *fs_info,
                                         u64 start, u64 len)
{
        struct btrfs_block_group *cache;

        cache = btrfs_lookup_block_group(fs_info, start);
        ASSERT(cache);

        spin_lock(&cache->lock);
        cache->delalloc_bytes -= len;
        spin_unlock(&cache->lock);

        btrfs_put_block_group(cache);
}

static int insert_ordered_extent_file_extent(struct btrfs_trans_handle *trans,
                                             struct inode *inode,
                                             struct btrfs_ordered_extent *oe)
{
        struct btrfs_file_extent_item stack_fi;
        u64 logical_len;

        memset(&stack_fi, 0, sizeof(stack_fi));
        btrfs_set_stack_file_extent_type(&stack_fi, BTRFS_FILE_EXTENT_REG);
        btrfs_set_stack_file_extent_disk_bytenr(&stack_fi, oe->disk_bytenr);
        btrfs_set_stack_file_extent_disk_num_bytes(&stack_fi,
                                                   oe->disk_num_bytes);
        if (test_bit(BTRFS_ORDERED_TRUNCATED, &oe->flags))
                logical_len = oe->truncated_len;
        else
                logical_len = oe->num_bytes;
        btrfs_set_stack_file_extent_num_bytes(&stack_fi, logical_len);
        btrfs_set_stack_file_extent_ram_bytes(&stack_fi, logical_len);
        btrfs_set_stack_file_extent_compression(&stack_fi, oe->compress_type);
        /* Encryption and other encoding is reserved and all 0 */

        return insert_reserved_file_extent(trans, BTRFS_I(inode), oe->file_offset,
                                           &stack_fi, oe->qgroup_rsv);
}

/*
 * As ordered data IO finishes, this gets called so we can finish
 * an ordered extent if the range of bytes in the file it covers are
 * fully written.
 */
static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
{
        struct inode *inode = ordered_extent->inode;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans = NULL;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_state *cached_state = NULL;
        u64 start, end;
        int compress_type = 0;
        int ret = 0;
        u64 logical_len = ordered_extent->num_bytes;
        bool freespace_inode;
        bool truncated = false;
        bool range_locked = false;
        bool clear_new_delalloc_bytes = false;
        bool clear_reserved_extent = true;
        unsigned int clear_bits;

        start = ordered_extent->file_offset;
        end = start + ordered_extent->num_bytes - 1;

        if (!test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
            !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags) &&
            !test_bit(BTRFS_ORDERED_DIRECT, &ordered_extent->flags))
                clear_new_delalloc_bytes = true;

        freespace_inode = btrfs_is_free_space_inode(BTRFS_I(inode));

        if (test_bit(BTRFS_ORDERED_IOERR, &ordered_extent->flags)) {
                ret = -EIO;
                goto out;
        }

        btrfs_free_io_failure_record(BTRFS_I(inode), start, end);

        if (test_bit(BTRFS_ORDERED_TRUNCATED, &ordered_extent->flags)) {
                truncated = true;
                logical_len = ordered_extent->truncated_len;
                /* Truncated the entire extent, don't bother adding */
                if (!logical_len)
                        goto out;
        }

        if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags)) {
                BUG_ON(!list_empty(&ordered_extent->list)); /* Logic error */

                btrfs_inode_safe_disk_i_size_write(inode, 0);
                if (freespace_inode)
                        trans = btrfs_join_transaction_spacecache(root);
                else
                        trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        trans = NULL;
                        goto out;
                }
                trans->block_rsv = &BTRFS_I(inode)->block_rsv;
                ret = btrfs_update_inode_fallback(trans, root, inode);
                if (ret) /* -ENOMEM or corruption */
                        btrfs_abort_transaction(trans, ret);
                goto out;
        }

        range_locked = true;
        lock_extent_bits(io_tree, start, end, &cached_state);

        if (freespace_inode)
                trans = btrfs_join_transaction_spacecache(root);
        else
                trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                trans = NULL;
                goto out;
        }

        trans->block_rsv = &BTRFS_I(inode)->block_rsv;

        if (test_bit(BTRFS_ORDERED_COMPRESSED, &ordered_extent->flags))
                compress_type = ordered_extent->compress_type;
        if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
                BUG_ON(compress_type);
                ret = btrfs_mark_extent_written(trans, BTRFS_I(inode),
                                                ordered_extent->file_offset,
                                                ordered_extent->file_offset +
                                                logical_len);
        } else {
                BUG_ON(root == fs_info->tree_root);
                ret = insert_ordered_extent_file_extent(trans, inode,
                                                        ordered_extent);
                if (!ret) {
                        clear_reserved_extent = false;
                        btrfs_release_delalloc_bytes(fs_info,
                                                ordered_extent->disk_bytenr,
                                                ordered_extent->disk_num_bytes);
                }
        }
        unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
                           ordered_extent->file_offset,
                           ordered_extent->num_bytes, trans->transid);
        if (ret < 0) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        }

        ret = add_pending_csums(trans, inode, &ordered_extent->list);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        }

        btrfs_inode_safe_disk_i_size_write(inode, 0);
        ret = btrfs_update_inode_fallback(trans, root, inode);
        if (ret) { /* -ENOMEM or corruption */
                btrfs_abort_transaction(trans, ret);
                goto out;
        }
        ret = 0;
out:
        clear_bits = EXTENT_DEFRAG;
        if (range_locked)
                clear_bits |= EXTENT_LOCKED;
        if (clear_new_delalloc_bytes)
                clear_bits |= EXTENT_DELALLOC_NEW;
        clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, clear_bits,
                         (clear_bits & EXTENT_LOCKED) ? 1 : 0, 0,
                         &cached_state);

        if (trans)
                btrfs_end_transaction(trans);

        if (ret || truncated) {
                u64 unwritten_start = start;

                if (truncated)
                        unwritten_start += logical_len;
                clear_extent_uptodate(io_tree, unwritten_start, end, NULL);

                /* Drop the cache for the part of the extent we didn't write. */
                btrfs_drop_extent_cache(BTRFS_I(inode), unwritten_start, end, 0);

                /*
                 * If the ordered extent had an IOERR or something else went
                 * wrong we need to return the space for this ordered extent
                 * back to the allocator.  We only free the extent in the
                 * truncated case if we didn't write out the extent at all.
                 *
                 * If we made it past insert_reserved_file_extent before we
                 * errored out then we don't need to do this as the accounting
                 * has already been done.
                 */
                if ((ret || !logical_len) &&
                    clear_reserved_extent &&
                    !test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
                    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
                        /*
                         * Discard the range before returning it back to the
                         * free space pool
                         */
                        if (ret && btrfs_test_opt(fs_info, DISCARD_SYNC))
                                btrfs_discard_extent(fs_info,
                                                ordered_extent->disk_bytenr,
                                                ordered_extent->disk_num_bytes,
                                                NULL);
                        btrfs_free_reserved_extent(fs_info,
                                        ordered_extent->disk_bytenr,
                                        ordered_extent->disk_num_bytes, 1);
                }
        }

        /*
         * This needs to be done to make sure anybody waiting knows we are done
         * updating everything for this ordered extent.
         */
        btrfs_remove_ordered_extent(inode, ordered_extent);

        /* once for us */
        btrfs_put_ordered_extent(ordered_extent);
        /* once for the tree */
        btrfs_put_ordered_extent(ordered_extent);

        return ret;
}

static void finish_ordered_fn(struct btrfs_work *work)
{
        struct btrfs_ordered_extent *ordered_extent;
        ordered_extent = container_of(work, struct btrfs_ordered_extent, work);
        btrfs_finish_ordered_io(ordered_extent);
}

void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
                                          u64 end, int uptodate)
{
        struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_ordered_extent *ordered_extent = NULL;
        struct btrfs_workqueue *wq;

        trace_btrfs_writepage_end_io_hook(page, start, end, uptodate);

        ClearPagePrivate2(page);
        if (!btrfs_dec_test_ordered_pending(inode, &ordered_extent, start,
                                            end - start + 1, uptodate))
                return;

        if (btrfs_is_free_space_inode(inode))
                wq = fs_info->endio_freespace_worker;
        else
                wq = fs_info->endio_write_workers;

        btrfs_init_work(&ordered_extent->work, finish_ordered_fn, NULL, NULL);
        btrfs_queue_work(wq, &ordered_extent->work);
}

static int check_data_csum(struct inode *inode, struct btrfs_io_bio *io_bio,
                           int icsum, struct page *page, int pgoff, u64 start,
                           size_t len)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
        char *kaddr;
        u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
        u8 *csum_expected;
        u8 csum[BTRFS_CSUM_SIZE];

        csum_expected = ((u8 *)io_bio->csum) + icsum * csum_size;

        kaddr = kmap_atomic(page);
        shash->tfm = fs_info->csum_shash;

        crypto_shash_digest(shash, kaddr + pgoff, len, csum);

        if (memcmp(csum, csum_expected, csum_size))
                goto zeroit;

        kunmap_atomic(kaddr);
        return 0;
zeroit:
        btrfs_print_data_csum_error(BTRFS_I(inode), start, csum, csum_expected,
                                    io_bio->mirror_num);
        if (io_bio->device)
                btrfs_dev_stat_inc_and_print(io_bio->device,
                                             BTRFS_DEV_STAT_CORRUPTION_ERRS);
        memset(kaddr + pgoff, 1, len);
        flush_dcache_page(page);
        kunmap_atomic(kaddr);
        return -EIO;
}

/*
 * when reads are done, we need to check csums to verify the data is correct
 * if there's a match, we allow the bio to finish.  If not, the code in
 * extent_io.c will try to find good copies for us.
 */
static int btrfs_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
                                      u64 phy_offset, struct page *page,
                                      u64 start, u64 end, int mirror)
{
        size_t offset = start - page_offset(page);
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (PageChecked(page)) {
                ClearPageChecked(page);
                return 0;
        }

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
                return 0;

        if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID &&
            test_range_bit(io_tree, start, end, EXTENT_NODATASUM, 1, NULL)) {
                clear_extent_bits(io_tree, start, end, EXTENT_NODATASUM);
                return 0;
        }

        phy_offset >>= inode->i_sb->s_blocksize_bits;
        return check_data_csum(inode, io_bio, phy_offset, page, offset, start,
                               (size_t)(end - start + 1));
}

/*
 * btrfs_add_delayed_iput - perform a delayed iput on @inode
 *
 * @inode: The inode we want to perform iput on
 *
 * This function uses the generic vfs_inode::i_count to track whether we should
 * just decrement it (in case it's > 1) or if this is the last iput then link
 * the inode to the delayed iput machinery. Delayed iputs are processed at
 * transaction commit time/superblock commit/cleaner kthread.
 */
void btrfs_add_delayed_iput(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_inode *binode = BTRFS_I(inode);

        if (atomic_add_unless(&inode->i_count, -1, 1))
                return;

        atomic_inc(&fs_info->nr_delayed_iputs);
        spin_lock(&fs_info->delayed_iput_lock);
        ASSERT(list_empty(&binode->delayed_iput));
        list_add_tail(&binode->delayed_iput, &fs_info->delayed_iputs);
        spin_unlock(&fs_info->delayed_iput_lock);
        if (!test_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags))
                wake_up_process(fs_info->cleaner_kthread);
}

static void run_delayed_iput_locked(struct btrfs_fs_info *fs_info,
                                    struct btrfs_inode *inode)
{
        list_del_init(&inode->delayed_iput);
        spin_unlock(&fs_info->delayed_iput_lock);
        iput(&inode->vfs_inode);
        if (atomic_dec_and_test(&fs_info->nr_delayed_iputs))
                wake_up(&fs_info->delayed_iputs_wait);
        spin_lock(&fs_info->delayed_iput_lock);
}

static void btrfs_run_delayed_iput(struct btrfs_fs_info *fs_info,
                                   struct btrfs_inode *inode)
{
        if (!list_empty(&inode->delayed_iput)) {
                spin_lock(&fs_info->delayed_iput_lock);
                if (!list_empty(&inode->delayed_iput))
                        run_delayed_iput_locked(fs_info, inode);
                spin_unlock(&fs_info->delayed_iput_lock);
        }
}

void btrfs_run_delayed_iputs(struct btrfs_fs_info *fs_info)
{

        spin_lock(&fs_info->delayed_iput_lock);
        while (!list_empty(&fs_info->delayed_iputs)) {
                struct btrfs_inode *inode;

                inode = list_first_entry(&fs_info->delayed_iputs,
                                struct btrfs_inode, delayed_iput);
                run_delayed_iput_locked(fs_info, inode);
        }
        spin_unlock(&fs_info->delayed_iput_lock);
}

/**
 * btrfs_wait_on_delayed_iputs - wait on the delayed iputs to be done running
 * @fs_info - the fs_info for this fs
 * @return - EINTR if we were killed, 0 if nothing's pending
 *
 * This will wait on any delayed iputs that are currently running with KILLABLE
 * set.  Once they are all done running we will return, unless we are killed in
 * which case we return EINTR. This helps in user operations like fallocate etc
 * that might get blocked on the iputs.
 */
int btrfs_wait_on_delayed_iputs(struct btrfs_fs_info *fs_info)
{
        int ret = wait_event_killable(fs_info->delayed_iputs_wait,
                        atomic_read(&fs_info->nr_delayed_iputs) == 0);
        if (ret)
                return -EINTR;
        return 0;
}

/*
 * This creates an orphan entry for the given inode in case something goes wrong
 * in the middle of an unlink.
 */
int btrfs_orphan_add(struct btrfs_trans_handle *trans,
                     struct btrfs_inode *inode)
{
        int ret;

        ret = btrfs_insert_orphan_item(trans, inode->root, btrfs_ino(inode));
        if (ret && ret != -EEXIST) {
                btrfs_abort_transaction(trans, ret);
                return ret;
        }

        return 0;
}

/*
 * We have done the delete so we can go ahead and remove the orphan item for
 * this particular inode.
 */
static int btrfs_orphan_del(struct btrfs_trans_handle *trans,
                            struct btrfs_inode *inode)
{
        return btrfs_del_orphan_item(trans, inode->root, btrfs_ino(inode));
}

/*
 * this cleans up any orphans that may be left on the list from the last use
 * of this root.
 */
int btrfs_orphan_cleanup(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key key, found_key;
        struct btrfs_trans_handle *trans;
        struct inode *inode;
        u64 last_objectid = 0;
        int ret = 0, nr_unlink = 0;

        if (cmpxchg(&root->orphan_cleanup_state, 0, ORPHAN_CLEANUP_STARTED))
                return 0;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto out;
        }
        path->reada = READA_BACK;

        key.objectid = BTRFS_ORPHAN_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = (u64)-1;

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;

                /*
                 * if ret == 0 means we found what we were searching for, which
                 * is weird, but possible, so only screw with path if we didn't
                 * find the key and see if we have stuff that matches
                 */
                if (ret > 0) {
                        ret = 0;
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }

                /* pull out the item */
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                /* make sure the item matches what we want */
                if (found_key.objectid != BTRFS_ORPHAN_OBJECTID)
                        break;
                if (found_key.type != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                /* release the path since we're done with it */
                btrfs_release_path(path);

                /*
                 * this is where we are basically btrfs_lookup, without the
                 * crossing root thing.  we store the inode number in the
                 * offset of the orphan item.
                 */

                if (found_key.offset == last_objectid) {
                        btrfs_err(fs_info,
                                  "Error removing orphan entry, stopping orphan cleanup");
                        ret = -EINVAL;
                        goto out;
                }

                last_objectid = found_key.offset;

                found_key.objectid = found_key.offset;
                found_key.type = BTRFS_INODE_ITEM_KEY;
                found_key.offset = 0;
                inode = btrfs_iget(fs_info->sb, last_objectid, root);
                ret = PTR_ERR_OR_ZERO(inode);
                if (ret && ret != -ENOENT)
                        goto out;

                if (ret == -ENOENT && root == fs_info->tree_root) {
                        struct btrfs_root *dead_root;
                        int is_dead_root = 0;

                        /*
                         * this is an orphan in the tree root. Currently these
                         * could come from 2 sources:
                         *  a) a snapshot deletion in progress
                         *  b) a free space cache inode
                         * We need to distinguish those two, as the snapshot
                         * orphan must not get deleted.
                         * find_dead_roots already ran before us, so if this
                         * is a snapshot deletion, we should find the root
                         * in the fs_roots radix tree.
                         */

                        spin_lock(&fs_info->fs_roots_radix_lock);
                        dead_root = radix_tree_lookup(&fs_info->fs_roots_radix,
                                                         (unsigned long)found_key.objectid);
                        if (dead_root && btrfs_root_refs(&dead_root->root_item) == 0)
                                is_dead_root = 1;
                        spin_unlock(&fs_info->fs_roots_radix_lock);

                        if (is_dead_root) {
                                /* prevent this orphan from being found again */
                                key.offset = found_key.objectid - 1;
                                continue;
                        }

                }

                /*
                 * If we have an inode with links, there are a couple of
                 * possibilities. Old kernels (before v3.12) used to create an
                 * orphan item for truncate indicating that there were possibly
                 * extent items past i_size that needed to be deleted. In v3.12,
                 * truncate was changed to update i_size in sync with the extent
                 * items, but the (useless) orphan item was still created. Since
                 * v4.18, we don't create the orphan item for truncate at all.
                 *
                 * So, this item could mean that we need to do a truncate, but
                 * only if this filesystem was last used on a pre-v3.12 kernel
                 * and was not cleanly unmounted. The odds of that are quite
                 * slim, and it's a pain to do the truncate now, so just delete
                 * the orphan item.
                 *
                 * It's also possible that this orphan item was supposed to be
                 * deleted but wasn't. The inode number may have been reused,
                 * but either way, we can delete the orphan item.
                 */
                if (ret == -ENOENT || inode->i_nlink) {
                        if (!ret)
                                iput(inode);
                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                goto out;
                        }
                        btrfs_debug(fs_info, "auto deleting %Lu",
                                    found_key.objectid);
                        ret = btrfs_del_orphan_item(trans, root,
                                                    found_key.objectid);
                        btrfs_end_transaction(trans);
                        if (ret)
                                goto out;
                        continue;
                }

                nr_unlink++;

                /* this will do delete_inode and everything for us */
                iput(inode);
        }
        /* release the path since we're done with it */
        btrfs_release_path(path);

        root->orphan_cleanup_state = ORPHAN_CLEANUP_DONE;

        if (test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state)) {
                trans = btrfs_join_transaction(root);
                if (!IS_ERR(trans))
                        btrfs_end_transaction(trans);
        }

        if (nr_unlink)
                btrfs_debug(fs_info, "unlinked %d orphans", nr_unlink);

out:
        if (ret)
                btrfs_err(fs_info, "could not do orphan cleanup %d", ret);
        btrfs_free_path(path);
        return ret;
}

/*
 * very simple check to peek ahead in the leaf looking for xattrs.  If we
 * don't find any xattrs, we know there can't be any acls.
 *
 * slot is the slot the inode is in, objectid is the objectid of the inode
 */
static noinline int acls_after_inode_item(struct extent_buffer *leaf,
                                          int slot, u64 objectid,
                                          int *first_xattr_slot)
{
        u32 nritems = btrfs_header_nritems(leaf);
        struct btrfs_key found_key;
        static u64 xattr_access = 0;
        static u64 xattr_default = 0;
        int scanned = 0;

        if (!xattr_access) {
                xattr_access = btrfs_name_hash(XATTR_NAME_POSIX_ACL_ACCESS,
                                        strlen(XATTR_NAME_POSIX_ACL_ACCESS));
                xattr_default = btrfs_name_hash(XATTR_NAME_POSIX_ACL_DEFAULT,
                                        strlen(XATTR_NAME_POSIX_ACL_DEFAULT));
        }

        slot++;
        *first_xattr_slot = -1;
        while (slot < nritems) {
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                /* we found a different objectid, there must not be acls */
                if (found_key.objectid != objectid)
                        return 0;

                /* we found an xattr, assume we've got an acl */
                if (found_key.type == BTRFS_XATTR_ITEM_KEY) {
                        if (*first_xattr_slot == -1)
                                *first_xattr_slot = slot;
                        if (found_key.offset == xattr_access ||
                            found_key.offset == xattr_default)
                                return 1;
                }

                /*
                 * we found a key greater than an xattr key, there can't
                 * be any acls later on
                 */
                if (found_key.type > BTRFS_XATTR_ITEM_KEY)
                        return 0;

                slot++;
                scanned++;

                /*
                 * it goes inode, inode backrefs, xattrs, extents,
                 * so if there are a ton of hard links to an inode there can
                 * be a lot of backrefs.  Don't waste time searching too hard,
                 * this is just an optimization
                 */
                if (scanned >= 8)
                        break;
        }
        /* we hit the end of the leaf before we found an xattr or
         * something larger than an xattr.  We have to assume the inode
         * has acls
         */
        if (*first_xattr_slot == -1)
                *first_xattr_slot = slot;
        return 1;
}

/*
 * read an inode from the btree into the in-memory inode
 */
static int btrfs_read_locked_inode(struct inode *inode,
                                   struct btrfs_path *in_path)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_path *path = in_path;
        struct extent_buffer *leaf;
        struct btrfs_inode_item *inode_item;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key location;
        unsigned long ptr;
        int maybe_acls;
        u32 rdev;
        int ret;
        bool filled = false;
        int first_xattr_slot;

        ret = btrfs_fill_inode(inode, &rdev);
        if (!ret)
                filled = true;

        if (!path) {
                path = btrfs_alloc_path();
                if (!path)
                        return -ENOMEM;
        }

        memcpy(&location, &BTRFS_I(inode)->location, sizeof(location));

        ret = btrfs_lookup_inode(NULL, root, path, &location, 0);
        if (ret) {
                if (path != in_path)
                        btrfs_free_path(path);
                return ret;
        }

        leaf = path->nodes[0];

        if (filled)
                goto cache_index;

        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);
        inode->i_mode = btrfs_inode_mode(leaf, inode_item);
        set_nlink(inode, btrfs_inode_nlink(leaf, inode_item));
        i_uid_write(inode, btrfs_inode_uid(leaf, inode_item));
        i_gid_write(inode, btrfs_inode_gid(leaf, inode_item));
        btrfs_i_size_write(BTRFS_I(inode), btrfs_inode_size(leaf, inode_item));
        btrfs_inode_set_file_extent_range(BTRFS_I(inode), 0,
                        round_up(i_size_read(inode), fs_info->sectorsize));

        inode->i_atime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->atime);
        inode->i_atime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->atime);

        inode->i_mtime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->mtime);
        inode->i_mtime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->mtime);

        inode->i_ctime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->ctime);
        inode->i_ctime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->ctime);

        BTRFS_I(inode)->i_otime.tv_sec =
                btrfs_timespec_sec(leaf, &inode_item->otime);
        BTRFS_I(inode)->i_otime.tv_nsec =
                btrfs_timespec_nsec(leaf, &inode_item->otime);

        inode_set_bytes(inode, btrfs_inode_nbytes(leaf, inode_item));
        BTRFS_I(inode)->generation = btrfs_inode_generation(leaf, inode_item);
        BTRFS_I(inode)->last_trans = btrfs_inode_transid(leaf, inode_item);

        inode_set_iversion_queried(inode,
                                   btrfs_inode_sequence(leaf, inode_item));
        inode->i_generation = BTRFS_I(inode)->generation;
        inode->i_rdev = 0;
        rdev = btrfs_inode_rdev(leaf, inode_item);

        BTRFS_I(inode)->index_cnt = (u64)-1;
        BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);

cache_index:
        /*
         * If we were modified in the current generation and evicted from memory
         * and then re-read we need to do a full sync since we don't have any
         * idea about which extents were modified before we were evicted from
         * cache.
         *
         * This is required for both inode re-read from disk and delayed inode
         * in delayed_nodes_tree.
         */
        if (BTRFS_I(inode)->last_trans == fs_info->generation)
                set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                        &BTRFS_I(inode)->runtime_flags);

        /*
         * We don't persist the id of the transaction where an unlink operation
         * against the inode was last made. So here we assume the inode might
         * have been evicted, and therefore the exact value of last_unlink_trans
         * lost, and set it to last_trans to avoid metadata inconsistencies
         * between the inode and its parent if the inode is fsync'ed and the log
         * replayed. For example, in the scenario:
         *
         * touch mydir/foo
         * ln mydir/foo mydir/bar
         * sync
         * unlink mydir/bar
         * echo 2 > /proc/sys/vm/drop_caches   # evicts inode
         * xfs_io -c fsync mydir/foo
         * <power failure>
         * mount fs, triggers fsync log replay
         *
         * We must make sure that when we fsync our inode foo we also log its
         * parent inode, otherwise after log replay the parent still has the
         * dentry with the "bar" name but our inode foo has a link count of 1
         * and doesn't have an inode ref with the name "bar" anymore.
         *
         * Setting last_unlink_trans to last_trans is a pessimistic approach,
         * but it guarantees correctness at the expense of occasional full
         * transaction commits on fsync if our inode is a directory, or if our
         * inode is not a directory, logging its parent unnecessarily.
         */
        BTRFS_I(inode)->last_unlink_trans = BTRFS_I(inode)->last_trans;

        /*
         * Same logic as for last_unlink_trans. We don't persist the generation
         * of the last transaction where this inode was used for a reflink
         * operation, so after eviction and reloading the inode we must be
         * pessimistic and assume the last transaction that modified the inode.
         */
        BTRFS_I(inode)->last_reflink_trans = BTRFS_I(inode)->last_trans;

        path->slots[0]++;
        if (inode->i_nlink != 1 ||
            path->slots[0] >= btrfs_header_nritems(leaf))
                goto cache_acl;

        btrfs_item_key_to_cpu(leaf, &location, path->slots[0]);
        if (location.objectid != btrfs_ino(BTRFS_I(inode)))
                goto cache_acl;

        ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
        if (location.type == BTRFS_INODE_REF_KEY) {
                struct btrfs_inode_ref *ref;

                ref = (struct btrfs_inode_ref *)ptr;
                BTRFS_I(inode)->dir_index = btrfs_inode_ref_index(leaf, ref);
        } else if (location.type == BTRFS_INODE_EXTREF_KEY) {
                struct btrfs_inode_extref *extref;

                extref = (struct btrfs_inode_extref *)ptr;
                BTRFS_I(inode)->dir_index = btrfs_inode_extref_index(leaf,
                                                                     extref);
        }
cache_acl:
        /*
         * try to precache a NULL acl entry for files that don't have
         * any xattrs or acls
         */
        maybe_acls = acls_after_inode_item(leaf, path->slots[0],
                        btrfs_ino(BTRFS_I(inode)), &first_xattr_slot);
        if (first_xattr_slot != -1) {
                path->slots[0] = first_xattr_slot;
                ret = btrfs_load_inode_props(inode, path);
                if (ret)
                        btrfs_err(fs_info,
                                  "error loading props for ino %llu (root %llu): %d",
                                  btrfs_ino(BTRFS_I(inode)),
                                  root->root_key.objectid, ret);
        }
        if (path != in_path)
                btrfs_free_path(path);

        if (!maybe_acls)
                cache_no_acl(inode);

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_mapping->a_ops = &btrfs_aops;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                break;
        case S_IFDIR:
                inode->i_fop = &btrfs_dir_file_operations;
                inode->i_op = &btrfs_dir_inode_operations;
                break;
        case S_IFLNK:
                inode->i_op = &btrfs_symlink_inode_operations;
                inode_nohighmem(inode);
                inode->i_mapping->a_ops = &btrfs_aops;
                break;
        default:
                inode->i_op = &btrfs_special_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                break;
        }

        btrfs_sync_inode_flags_to_i_flags(inode);
        return 0;
}

/*
 * given a leaf and an inode, copy the inode fields into the leaf
 */
static void fill_inode_item(struct btrfs_trans_handle *trans,
                            struct extent_buffer *leaf,
                            struct btrfs_inode_item *item,
                            struct inode *inode)
{
        struct btrfs_map_token token;

        btrfs_init_map_token(&token, leaf);

        btrfs_set_token_inode_uid(&token, item, i_uid_read(inode));
        btrfs_set_token_inode_gid(&token, item, i_gid_read(inode));
        btrfs_set_token_inode_size(&token, item, BTRFS_I(inode)->disk_i_size);
        btrfs_set_token_inode_mode(&token, item, inode->i_mode);
        btrfs_set_token_inode_nlink(&token, item, inode->i_nlink);

        btrfs_set_token_timespec_sec(&token, &item->atime,
                                     inode->i_atime.tv_sec);
        btrfs_set_token_timespec_nsec(&token, &item->atime,
                                      inode->i_atime.tv_nsec);

        btrfs_set_token_timespec_sec(&token, &item->mtime,
                                     inode->i_mtime.tv_sec);
        btrfs_set_token_timespec_nsec(&token, &item->mtime,
                                      inode->i_mtime.tv_nsec);

        btrfs_set_token_timespec_sec(&token, &item->ctime,
                                     inode->i_ctime.tv_sec);
        btrfs_set_token_timespec_nsec(&token, &item->ctime,
                                      inode->i_ctime.tv_nsec);

        btrfs_set_token_timespec_sec(&token, &item->otime,
                                     BTRFS_I(inode)->i_otime.tv_sec);
        btrfs_set_token_timespec_nsec(&token, &item->otime,
                                      BTRFS_I(inode)->i_otime.tv_nsec);

        btrfs_set_token_inode_nbytes(&token, item, inode_get_bytes(inode));
        btrfs_set_token_inode_generation(&token, item,
                                         BTRFS_I(inode)->generation);
        btrfs_set_token_inode_sequence(&token, item, inode_peek_iversion(inode));
        btrfs_set_token_inode_transid(&token, item, trans->transid);
        btrfs_set_token_inode_rdev(&token, item, inode->i_rdev);
        btrfs_set_token_inode_flags(&token, item, BTRFS_I(inode)->flags);
        btrfs_set_token_inode_block_group(&token, item, 0);
}

/*
 * copy everything in the in-memory inode into the btree.
 */
static noinline int btrfs_update_inode_item(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode)
{
        struct btrfs_inode_item *inode_item;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->leave_spinning = 1;
        ret = btrfs_lookup_inode(trans, root, path, &BTRFS_I(inode)->location,
                                 1);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto failed;
        }

        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);

        fill_inode_item(trans, leaf, inode_item, inode);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_set_inode_last_trans(trans, BTRFS_I(inode));
        ret = 0;
failed:
        btrfs_free_path(path);
        return ret;
}

/*
 * copy everything in the in-memory inode into the btree.
 */
noinline int btrfs_update_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        int ret;

        /*
         * If the inode is a free space inode, we can deadlock during commit
         * if we put it into the delayed code.
         *
         * The data relocation inode should also be directly updated
         * without delay
         */
        if (!btrfs_is_free_space_inode(BTRFS_I(inode))
            && root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
            && !test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags)) {
                btrfs_update_root_times(trans, root);

                ret = btrfs_delayed_update_inode(trans, root, inode);
                if (!ret)
                        btrfs_set_inode_last_trans(trans, BTRFS_I(inode));
                return ret;
        }

        return btrfs_update_inode_item(trans, root, inode);
}

noinline int btrfs_update_inode_fallback(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root,
                                         struct inode *inode)
{
        int ret;

        ret = btrfs_update_inode(trans, root, inode);
        if (ret == -ENOSPC)
                return btrfs_update_inode_item(trans, root, inode);
        return ret;
}

/*
 * unlink helper that gets used here in inode.c and in the tree logging
 * recovery code.  It remove a link in a directory with a given name, and
 * also drops the back refs in the inode to the directory
 */
static int __btrfs_unlink_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_inode *dir,
                                struct btrfs_inode *inode,
                                const char *name, int name_len)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_path *path;
        int ret = 0;
        struct btrfs_dir_item *di;
        u64 index;
        u64 ino = btrfs_ino(inode);
        u64 dir_ino = btrfs_ino(dir);

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto out;
        }

        path->leave_spinning = 1;
        di = btrfs_lookup_dir_item(trans, root, path, dir_ino,
                                    name, name_len, -1);
        if (IS_ERR_OR_NULL(di)) {
                ret = di ? PTR_ERR(di) : -ENOENT;
                goto err;
        }
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret)
                goto err;
        btrfs_release_path(path);

        /*
         * If we don't have dir index, we have to get it by looking up
         * the inode ref, since we get the inode ref, remove it directly,
         * it is unnecessary to do delayed deletion.
         *
         * But if we have dir index, needn't search inode ref to get it.
         * Since the inode ref is close to the inode item, it is better
         * that we delay to delete it, and just do this deletion when
         * we update the inode item.
         */
        if (inode->dir_index) {
                ret = btrfs_delayed_delete_inode_ref(inode);
                if (!ret) {
                        index = inode->dir_index;
                        goto skip_backref;
                }
        }

        ret = btrfs_del_inode_ref(trans, root, name, name_len, ino,
                                  dir_ino, &index);
        if (ret) {
                btrfs_info(fs_info,
                        "failed to delete reference to %.*s, inode %llu parent %llu",
                        name_len, name, ino, dir_ino);
                btrfs_abort_transaction(trans, ret);
                goto err;
        }
skip_backref:
        ret = btrfs_delete_delayed_dir_index(trans, dir, index);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto err;
        }

        ret = btrfs_del_inode_ref_in_log(trans, root, name, name_len, inode,
                        dir_ino);
        if (ret != 0 && ret != -ENOENT) {
                btrfs_abort_transaction(trans, ret);
                goto err;
        }

        ret = btrfs_del_dir_entries_in_log(trans, root, name, name_len, dir,
                        index);
        if (ret == -ENOENT)
                ret = 0;
        else if (ret)
                btrfs_abort_transaction(trans, ret);

        /*
         * If we have a pending delayed iput we could end up with the final iput
         * being run in btrfs-cleaner context.  If we have enough of these built
         * up we can end up burning a lot of time in btrfs-cleaner without any
         * way to throttle the unlinks.  Since we're currently holding a ref on
         * the inode we can run the delayed iput here without any issues as the
         * final iput won't be done until after we drop the ref we're currently
         * holding.
         */
        btrfs_run_delayed_iput(fs_info, inode);
err:
        btrfs_free_path(path);
        if (ret)
                goto out;

        btrfs_i_size_write(dir, dir->vfs_inode.i_size - name_len * 2);
        inode_inc_iversion(&inode->vfs_inode);
        inode_inc_iversion(&dir->vfs_inode);
        inode->vfs_inode.i_ctime = dir->vfs_inode.i_mtime =
                dir->vfs_inode.i_ctime = current_time(&inode->vfs_inode);
        ret = btrfs_update_inode(trans, root, &dir->vfs_inode);
out:
        return ret;
}

int btrfs_unlink_inode(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct btrfs_inode *dir, struct btrfs_inode *inode,
                       const char *name, int name_len)
{
        int ret;
        ret = __btrfs_unlink_inode(trans, root, dir, inode, name, name_len);
        if (!ret) {
                drop_nlink(&inode->vfs_inode);
                ret = btrfs_update_inode(trans, root, &inode->vfs_inode);
        }
        return ret;
}

/*
 * helper to start transaction for unlink and rmdir.
 *
 * unlink and rmdir are special in btrfs, they do not always free space, so
 * if we cannot make our reservations the normal way try and see if there is
 * plenty of slack room in the global reserve to migrate, otherwise we cannot
 * allow the unlink to occur.
 */
static struct btrfs_trans_handle *__unlink_start_trans(struct inode *dir)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;

        /*
         * 1 for the possible orphan item
         * 1 for the dir item
         * 1 for the dir index
         * 1 for the inode ref
         * 1 for the inode
         */
        return btrfs_start_transaction_fallback_global_rsv(root, 5);
}

static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        struct inode *inode = d_inode(dentry);
        int ret;

        trans = __unlink_start_trans(dir);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_record_unlink_dir(trans, BTRFS_I(dir), BTRFS_I(d_inode(dentry)),
                        0);

        ret = btrfs_unlink_inode(trans, root, BTRFS_I(dir),
                        BTRFS_I(d_inode(dentry)), dentry->d_name.name,
                        dentry->d_name.len);
        if (ret)
                goto out;

        if (inode->i_nlink == 0) {
                ret = btrfs_orphan_add(trans, BTRFS_I(inode));
                if (ret)
                        goto out;
        }

out:
        btrfs_end_transaction(trans);
        btrfs_btree_balance_dirty(root->fs_info);
        return ret;
}

static int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
                               struct inode *dir, struct dentry *dentry)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_inode *inode = BTRFS_I(d_inode(dentry));
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        const char *name = dentry->d_name.name;
        int name_len = dentry->d_name.len;
        u64 index;
        int ret;
        u64 objectid;
        u64 dir_ino = btrfs_ino(BTRFS_I(dir));

        if (btrfs_ino(inode) == BTRFS_FIRST_FREE_OBJECTID) {
                objectid = inode->root->root_key.objectid;
        } else if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
                objectid = inode->location.objectid;
        } else {
                WARN_ON(1);
                return -EINVAL;
        }

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        di = btrfs_lookup_dir_item(trans, root, path, dir_ino,
                                   name, name_len, -1);
        if (IS_ERR_OR_NULL(di)) {
                ret = di ? PTR_ERR(di) : -ENOENT;
                goto out;
        }

        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        WARN_ON(key.type != BTRFS_ROOT_ITEM_KEY || key.objectid != objectid);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        }
        btrfs_release_path(path);

        /*
         * This is a placeholder inode for a subvolume we didn't have a
         * reference to at the time of the snapshot creation.  In the meantime
         * we could have renamed the real subvol link into our snapshot, so
         * depending on btrfs_del_root_ref to return -ENOENT here is incorret.
         * Instead simply lookup the dir_index_item for this entry so we can
         * remove it.  Otherwise we know we have a ref to the root and we can
         * call btrfs_del_root_ref, and it _shouldn't_ fail.
         */
        if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
                di = btrfs_search_dir_index_item(root, path, dir_ino,
                                                 name, name_len);
                if (IS_ERR_OR_NULL(di)) {
                        if (!di)
                                ret = -ENOENT;
                        else
                                ret = PTR_ERR(di);
                        btrfs_abort_transaction(trans, ret);
                        goto out;
                }

                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                index = key.offset;
                btrfs_release_path(path);
        } else {
                ret = btrfs_del_root_ref(trans, objectid,
                                         root->root_key.objectid, dir_ino,
                                         &index, name, name_len);
                if (ret) {
                        btrfs_abort_transaction(trans, ret);
                        goto out;
                }
        }

        ret = btrfs_delete_delayed_dir_index(trans, BTRFS_I(dir), index);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out;
        }

        btrfs_i_size_write(BTRFS_I(dir), dir->i_size - name_len * 2);
        inode_inc_iversion(dir);
        dir->i_mtime = dir->i_ctime = current_time(dir);
        ret = btrfs_update_inode_fallback(trans, root, dir);
        if (ret)
                btrfs_abort_transaction(trans, ret);
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * Helper to check if the subvolume references other subvolumes or if it's
 * default.
 */
static noinline int may_destroy_subvol(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_path *path;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 dir_id;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /* Make sure this root isn't set as the default subvol */
        dir_id = btrfs_super_root_dir(fs_info->super_copy);
        di = btrfs_lookup_dir_item(NULL, fs_info->tree_root, path,
                                   dir_id, "default", 7, 0);
        if (di && !IS_ERR(di)) {
                btrfs_dir_item_key_to_cpu(path->nodes[0], di, &key);
                if (key.objectid == root->root_key.objectid) {
                        ret = -EPERM;
                        btrfs_err(fs_info,
                                  "deleting default subvolume %llu is not allowed",
                                  key.objectid);
                        goto out;
                }
                btrfs_release_path(path);
        }

        key.objectid = root->root_key.objectid;
        key.type = BTRFS_ROOT_REF_KEY;
        key.offset = (u64)-1;

        ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        BUG_ON(ret == 0);

        ret = 0;
        if (path->slots[0] > 0) {
                path->slots[0]--;
                btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
                if (key.objectid == root->root_key.objectid &&
                    key.type == BTRFS_ROOT_REF_KEY)
                        ret = -ENOTEMPTY;
        }
out:
        btrfs_free_path(path);
        return ret;
}

/* Delete all dentries for inodes belonging to the root */
static void btrfs_prune_dentries(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct rb_node *node;
        struct rb_node *prev;
        struct btrfs_inode *entry;
        struct inode *inode;
        u64 objectid = 0;

        if (!test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
                WARN_ON(btrfs_root_refs(&root->root_item) != 0);

        spin_lock(&root->inode_lock);
again:
        node = root->inode_tree.rb_node;
        prev = NULL;
        while (node) {
                prev = node;
                entry = rb_entry(node, struct btrfs_inode, rb_node);

                if (objectid < btrfs_ino(entry))
                        node = node->rb_left;
                else if (objectid > btrfs_ino(entry))
                        node = node->rb_right;
                else
                        break;
        }
        if (!node) {
                while (prev) {
                        entry = rb_entry(prev, struct btrfs_inode, rb_node);
                        if (objectid <= btrfs_ino(entry)) {
                                node = prev;
                                break;
                        }
                        prev = rb_next(prev);
                }
        }
        while (node) {
                entry = rb_entry(node, struct btrfs_inode, rb_node);
                objectid = btrfs_ino(entry) + 1;
                inode = igrab(&entry->vfs_inode);
                if (inode) {
                        spin_unlock(&root->inode_lock);
                        if (atomic_read(&inode->i_count) > 1)
                                d_prune_aliases(inode);
                        /*
                         * btrfs_drop_inode will have it removed from the inode
                         * cache when its usage count hits zero.
                         */
                        iput(inode);
                        cond_resched();
                        spin_lock(&root->inode_lock);
                        goto again;
                }

                if (cond_resched_lock(&root->inode_lock))
                        goto again;

                node = rb_next(node);
        }
        spin_unlock(&root->inode_lock);
}

int btrfs_delete_subvolume(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dentry->d_sb);
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = d_inode(dentry);
        struct btrfs_root *dest = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct btrfs_block_rsv block_rsv;
        u64 root_flags;
        int ret;
        int err;

        /*
         * Don't allow to delete a subvolume with send in progress. This is
         * inside the inode lock so the error handling that has to drop the bit
         * again is not run concurrently.
         */
        spin_lock(&dest->root_item_lock);
        if (dest->send_in_progress) {
                spin_unlock(&dest->root_item_lock);
                btrfs_warn(fs_info,
                           "attempt to delete subvolume %llu during send",
                           dest->root_key.objectid);
                return -EPERM;
        }
        root_flags = btrfs_root_flags(&dest->root_item);
        btrfs_set_root_flags(&dest->root_item,
                             root_flags | BTRFS_ROOT_SUBVOL_DEAD);
        spin_unlock(&dest->root_item_lock);

        down_write(&fs_info->subvol_sem);

        err = may_destroy_subvol(dest);
        if (err)
                goto out_up_write;

        btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
        /*
         * One for dir inode,
         * two for dir entries,
         * two for root ref/backref.
         */
        err = btrfs_subvolume_reserve_metadata(root, &block_rsv, 5, true);
        if (err)
                goto out_up_write;

        trans = btrfs_start_transaction(root, 0);
        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                goto out_release;
        }
        trans->block_rsv = &block_rsv;
        trans->bytes_reserved = block_rsv.size;

        btrfs_record_snapshot_destroy(trans, BTRFS_I(dir));

        ret = btrfs_unlink_subvol(trans, dir, dentry);
        if (ret) {
                err = ret;
                btrfs_abort_transaction(trans, ret);
                goto out_end_trans;
        }

        btrfs_record_root_in_trans(trans, dest);

        memset(&dest->root_item.drop_progress, 0,
                sizeof(dest->root_item.drop_progress));
        dest->root_item.drop_level = 0;
        btrfs_set_root_refs(&dest->root_item, 0);

        if (!test_and_set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &dest->state)) {
                ret = btrfs_insert_orphan_item(trans,
                                        fs_info->tree_root,
                                        dest->root_key.objectid);
                if (ret) {
                        btrfs_abort_transaction(trans, ret);
                        err = ret;
                        goto out_end_trans;
                }
        }

        ret = btrfs_uuid_tree_remove(trans, dest->root_item.uuid,
                                  BTRFS_UUID_KEY_SUBVOL,
                                  dest->root_key.objectid);
        if (ret && ret != -ENOENT) {
                btrfs_abort_transaction(trans, ret);
                err = ret;
                goto out_end_trans;
        }
        if (!btrfs_is_empty_uuid(dest->root_item.received_uuid)) {
                ret = btrfs_uuid_tree_remove(trans,
                                          dest->root_item.received_uuid,
                                          BTRFS_UUID_KEY_RECEIVED_SUBVOL,
                                          dest->root_key.objectid);
                if (ret && ret != -ENOENT) {
                        btrfs_abort_transaction(trans, ret);
                        err = ret;
                        goto out_end_trans;
                }
        }

        free_anon_bdev(dest->anon_dev);
        dest->anon_dev = 0;
out_end_trans:
        trans->block_rsv = NULL;
        trans->bytes_reserved = 0;
        ret = btrfs_end_transaction(trans);
        if (ret && !err)
                err = ret;
        inode->i_flags |= S_DEAD;
out_release:
        btrfs_subvolume_release_metadata(root, &block_rsv);
out_up_write:
        up_write(&fs_info->subvol_sem);
        if (err) {
                spin_lock(&dest->root_item_lock);
                root_flags = btrfs_root_flags(&dest->root_item);
                btrfs_set_root_flags(&dest->root_item,
                                root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
                spin_unlock(&dest->root_item_lock);
        } else {
                d_invalidate(dentry);
                btrfs_prune_dentries(dest);
                ASSERT(dest->send_in_progress == 0);

                /* the last ref */
                if (dest->ino_cache_inode) {
                        iput(dest->ino_cache_inode);
                        dest->ino_cache_inode = NULL;
                }
        }

        return err;
}

static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        int err = 0;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        u64 last_unlink_trans;

        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                return -ENOTEMPTY;
        if (btrfs_ino(BTRFS_I(inode)) == BTRFS_FIRST_FREE_OBJECTID)
                return btrfs_delete_subvolume(dir, dentry);

        trans = __unlink_start_trans(dir);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        if (unlikely(btrfs_ino(BTRFS_I(inode)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                err = btrfs_unlink_subvol(trans, dir, dentry);
                goto out;
        }

        err = btrfs_orphan_add(trans, BTRFS_I(inode));
        if (err)
                goto out;

        last_unlink_trans = BTRFS_I(inode)->last_unlink_trans;

        /* now the directory is empty */
        err = btrfs_unlink_inode(trans, root, BTRFS_I(dir),
                        BTRFS_I(d_inode(dentry)), dentry->d_name.name,
                        dentry->d_name.len);
        if (!err) {
                btrfs_i_size_write(BTRFS_I(inode), 0);
                /*
                 * Propagate the last_unlink_trans value of the deleted dir to
                 * its parent directory. This is to prevent an unrecoverable
                 * log tree in the case we do something like this:
                 * 1) create dir foo
                 * 2) create snapshot under dir foo
                 * 3) delete the snapshot
                 * 4) rmdir foo
                 * 5) mkdir foo
                 * 6) fsync foo or some file inside foo
                 */
                if (last_unlink_trans >= trans->transid)
                        BTRFS_I(dir)->last_unlink_trans = last_unlink_trans;
        }
out:
        btrfs_end_transaction(trans);
        btrfs_btree_balance_dirty(root->fs_info);

        return err;
}

/*
 * Return this if we need to call truncate_block for the last bit of the
 * truncate.
 */
#define NEED_TRUNCATE_BLOCK 1

/*
 * this can truncate away extent items, csum items and directory items.
 * It starts at a high offset and removes keys until it can't find
 * any higher than new_size
 *
 * csum items that cross the new i_size are truncated to the new size
 * as well.
 *
 * min_type is the minimum key type to truncate down to.  If set to 0, this
 * will kill all the items on this inode, including the INODE_ITEM_KEY.
 */
int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct inode *inode,
                               u64 new_size, u32 min_type)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u64 extent_start = 0;
        u64 extent_num_bytes = 0;
        u64 extent_offset = 0;
        u64 item_end = 0;
        u64 last_size = new_size;
        u32 found_type = (u8)-1;
        int found_extent;
        int del_item;
        int pending_del_nr = 0;
        int pending_del_slot = 0;
        int extent_type = -1;
        int ret;
        u64 ino = btrfs_ino(BTRFS_I(inode));
        u64 bytes_deleted = 0;
        bool be_nice = false;
        bool should_throttle = false;
        const u64 lock_start = ALIGN_DOWN(new_size, fs_info->sectorsize);
        struct extent_state *cached_state = NULL;

        BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);

        /*
         * For non-free space inodes and non-shareable roots, we want to back
         * off from time to time.  This means all inodes in subvolume roots,
         * reloc roots, and data reloc roots.
         */
        if (!btrfs_is_free_space_inode(BTRFS_I(inode)) &&
            test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
                be_nice = true;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        path->reada = READA_BACK;

        if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
                lock_extent_bits(&BTRFS_I(inode)->io_tree, lock_start, (u64)-1,
                                 &cached_state);

                /*
                 * We want to drop from the next block forward in case this
                 * new size is not block aligned since we will be keeping the
                 * last block of the extent just the way it is.
                 */
                btrfs_drop_extent_cache(BTRFS_I(inode), ALIGN(new_size,
                                        fs_info->sectorsize),
                                        (u64)-1, 0);
        }

        /*
         * This function is also used to drop the items in the log tree before
         * we relog the inode, so if root != BTRFS_I(inode)->root, it means
         * it is used to drop the logged items. So we shouldn't kill the delayed
         * items.
         */
        if (min_type == 0 && root == BTRFS_I(inode)->root)
                btrfs_kill_delayed_inode_items(BTRFS_I(inode));

        key.objectid = ino;
        key.offset = (u64)-1;
        key.type = (u8)-1;

search_again:
        /*
         * with a 16K leaf size and 128MB extents, you can actually queue
         * up a huge file in a single leaf.  Most of the time that
         * bytes_deleted is > 0, it will be huge by the time we get here
         */
        if (be_nice && bytes_deleted > SZ_32M &&
            btrfs_should_end_transaction(trans)) {
                ret = -EAGAIN;
                goto out;
        }

        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0)
                goto out;

        if (ret > 0) {
                ret = 0;
                /* there are no items in the tree for us to truncate, we're
                 * done
                 */
                if (path->slots[0] == 0)
                        goto out;
                path->slots[0]--;
        }

        while (1) {
                u64 clear_start = 0, clear_len = 0;

                fi = NULL;
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                found_type = found_key.type;

                if (found_key.objectid != ino)
                        break;

                if (found_type < min_type)
                        break;

                item_end = found_key.offset;
                if (found_type == BTRFS_EXTENT_DATA_KEY) {
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        extent_type = btrfs_file_extent_type(leaf, fi);
                        if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                                item_end +=
                                    btrfs_file_extent_num_bytes(leaf, fi);

                                trace_btrfs_truncate_show_fi_regular(
                                        BTRFS_I(inode), leaf, fi,
                                        found_key.offset);
                        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                                item_end += btrfs_file_extent_ram_bytes(leaf,
                                                                        fi);

                                trace_btrfs_truncate_show_fi_inline(
                                        BTRFS_I(inode), leaf, fi, path->slots[0],
                                        found_key.offset);
                        }
                        item_end--;
                }
                if (found_type > min_type) {
                        del_item = 1;
                } else {
                        if (item_end < new_size)
                                break;
                        if (found_key.offset >= new_size)
                                del_item = 1;
                        else
                                del_item = 0;
                }
                found_extent = 0;
                /* FIXME, shrink the extent if the ref count is only 1 */
                if (found_type != BTRFS_EXTENT_DATA_KEY)
                        goto delete;

                if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                        u64 num_dec;

                        clear_start = found_key.offset;
                        extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
                        if (!del_item) {
                                u64 orig_num_bytes =
                                        btrfs_file_extent_num_bytes(leaf, fi);
                                extent_num_bytes = ALIGN(new_size -
                                                found_key.offset,
                                                fs_info->sectorsize);
                                clear_start = ALIGN(new_size, fs_info->sectorsize);
                                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                         extent_num_bytes);
                                num_dec = (orig_num_bytes -
                                           extent_num_bytes);
                                if (test_bit(BTRFS_ROOT_SHAREABLE,
                                             &root->state) &&
                                    extent_start != 0)
                                        inode_sub_bytes(inode, num_dec);
                                btrfs_mark_buffer_dirty(leaf);
                        } else {
                                extent_num_bytes =
                                        btrfs_file_extent_disk_num_bytes(leaf,
                                                                         fi);
                                extent_offset = found_key.offset -
                                        btrfs_file_extent_offset(leaf, fi);

                                /* FIXME blocksize != 4096 */
                                num_dec = btrfs_file_extent_num_bytes(leaf, fi);
                                if (extent_start != 0) {
                                        found_extent = 1;
                                        if (test_bit(BTRFS_ROOT_SHAREABLE,
                                                     &root->state))
                                                inode_sub_bytes(inode, num_dec);
                                }
                        }
                        clear_len = num_dec;
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        /*
                         * we can't truncate inline items that have had
                         * special encodings
                         */
                        if (!del_item &&
                            btrfs_file_extent_encryption(leaf, fi) == 0 &&
                            btrfs_file_extent_other_encoding(leaf, fi) == 0 &&
                            btrfs_file_extent_compression(leaf, fi) == 0) {
                                u32 size = (u32)(new_size - found_key.offset);

                                btrfs_set_file_extent_ram_bytes(leaf, fi, size);
                                size = btrfs_file_extent_calc_inline_size(size);
                                btrfs_truncate_item(path, size, 1);
                        } else if (!del_item) {
                                /*
                                 * We have to bail so the last_size is set to
                                 * just before this extent.
                                 */
                                ret = NEED_TRUNCATE_BLOCK;
                                break;
                        } else {
                                /*
                                 * Inline extents are special, we just treat
                                 * them as a full sector worth in the file
                                 * extent tree just for simplicity sake.
                                 */
                                clear_len = fs_info->sectorsize;
                        }

                        if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
                                inode_sub_bytes(inode, item_end + 1 - new_size);
                }
delete:
                /*
                 * We use btrfs_truncate_inode_items() to clean up log trees for
                 * multiple fsyncs, and in this case we don't want to clear the
                 * file extent range because it's just the log.
                 */
                if (root == BTRFS_I(inode)->root) {
                        ret = btrfs_inode_clear_file_extent_range(BTRFS_I(inode),
                                                  clear_start, clear_len);
                        if (ret) {
                                btrfs_abort_transaction(trans, ret);
                                break;
                        }
                }

                if (del_item)
                        last_size = found_key.offset;
                else
                        last_size = new_size;
                if (del_item) {
                        if (!pending_del_nr) {
                                /* no pending yet, add ourselves */
                                pending_del_slot = path->slots[0];
                                pending_del_nr = 1;
                        } else if (pending_del_nr &&
                                   path->slots[0] + 1 == pending_del_slot) {
                                /* hop on the pending chunk */
                                pending_del_nr++;
                                pending_del_slot = path->slots[0];
                        } else {
                                BUG();
                        }
                } else {
                        break;
                }
                should_throttle = false;

                if (found_extent &&
                    root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
                        struct btrfs_ref ref = { 0 };

                        bytes_deleted += extent_num_bytes;

                        btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF,
                                        extent_start, extent_num_bytes, 0);
                        ref.real_root = root->root_key.objectid;
                        btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
                                        ino, extent_offset);
                        ret = btrfs_free_extent(trans, &ref);
                        if (ret) {
                                btrfs_abort_transaction(trans, ret);
                                break;
                        }
                        if (be_nice) {
                                if (btrfs_should_throttle_delayed_refs(trans))
                                        should_throttle = true;
                        }
                }

                if (found_type == BTRFS_INODE_ITEM_KEY)
                        break;

                if (path->slots[0] == 0 ||
                    path->slots[0] != pending_del_slot ||
                    should_throttle) {
                        if (pending_del_nr) {
                                ret = btrfs_del_items(trans, root, path,
                                                pending_del_slot,
                                                pending_del_nr);
                                if (ret) {
                                        btrfs_abort_transaction(trans, ret);
                                        break;
                                }
                                pending_del_nr = 0;
                        }
                        btrfs_release_path(path);

                        /*
                         * We can generate a lot of delayed refs, so we need to
                         * throttle every once and a while and make sure we're
                         * adding enough space to keep up with the work we are
                         * generating.  Since we hold a transaction here we
                         * can't flush, and we don't want to FLUSH_LIMIT because
                         * we could have generated too many delayed refs to
                         * actually allocate, so just bail if we're short and
                         * let the normal reservation dance happen higher up.
                         */
                        if (should_throttle) {
                                ret = btrfs_delayed_refs_rsv_refill(fs_info,
                                                        BTRFS_RESERVE_NO_FLUSH);
                                if (ret) {
                                        ret = -EAGAIN;
                                        break;
                                }
                        }
                        goto search_again;
                } else {
                        path->slots[0]--;
                }
        }
out:
        if (ret >= 0 && pending_del_nr) {
                int err;

                err = btrfs_del_items(trans, root, path, pending_del_slot,
                                      pending_del_nr);
                if (err) {
                        btrfs_abort_transaction(trans, err);
                        ret = err;
                }
        }
        if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
                ASSERT(last_size >= new_size);
                if (!ret && last_size > new_size)
                        last_size = new_size;
                btrfs_inode_safe_disk_i_size_write(inode, last_size);
                unlock_extent_cached(&BTRFS_I(inode)->io_tree, lock_start,
                                     (u64)-1, &cached_state);
        }

        btrfs_free_path(path);
        return ret;
}

/*
 * btrfs_truncate_block - read, zero a chunk and write a block
 * @inode - inode that we're zeroing
 * @from - the offset to start zeroing
 * @len - the length to zero, 0 to zero the entire range respective to the
 *      offset
 * @front - zero up to the offset instead of from the offset on
 *
 * This will find the block for the "from" offset and cow the block and zero the
 * part we want to zero.  This is used with truncate and hole punching.
 */
int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
                        int front)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct address_space *mapping = inode->i_mapping;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        struct extent_changeset *data_reserved = NULL;
        char *kaddr;
        bool only_release_metadata = false;
        u32 blocksize = fs_info->sectorsize;
        pgoff_t index = from >> PAGE_SHIFT;
        unsigned offset = from & (blocksize - 1);
        struct page *page;
        gfp_t mask = btrfs_alloc_write_mask(mapping);
        size_t write_bytes = blocksize;
        int ret = 0;
        u64 block_start;
        u64 block_end;

        if (IS_ALIGNED(offset, blocksize) &&
            (!len || IS_ALIGNED(len, blocksize)))
                goto out;

        block_start = round_down(from, blocksize);
        block_end = block_start + blocksize - 1;

        ret = btrfs_check_data_free_space(BTRFS_I(inode), &data_reserved,
                                          block_start, blocksize);
        if (ret < 0) {
                if (btrfs_check_nocow_lock(BTRFS_I(inode), block_start,
                                           &write_bytes) > 0) {
                        /* For nocow case, no need to reserve data space */
                        only_release_metadata = true;
                } else {
                        goto out;
                }
        }
        ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), blocksize);
        if (ret < 0) {
                if (!only_release_metadata)
                        btrfs_free_reserved_data_space(BTRFS_I(inode),
                                        data_reserved, block_start, blocksize);
                goto out;
        }
again:
        page = find_or_create_page(mapping, index, mask);
        if (!page) {
                btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved,
                                             block_start, blocksize, true);
                btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize);
                ret = -ENOMEM;
                goto out;
        }

        if (!PageUptodate(page)) {
                ret = btrfs_readpage(NULL, page);
                lock_page(page);
                if (page->mapping != mapping) {
                        unlock_page(page);
                        put_page(page);
                        goto again;
                }
                if (!PageUptodate(page)) {
                        ret = -EIO;
                        goto out_unlock;
                }
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, block_start, block_end, &cached_state);
        set_page_extent_mapped(page);

        ordered = btrfs_lookup_ordered_extent(BTRFS_I(inode), block_start);
        if (ordered) {
                unlock_extent_cached(io_tree, block_start, block_end,
                                     &cached_state);
                unlock_page(page);
                put_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        clear_extent_bit(&BTRFS_I(inode)->io_tree, block_start, block_end,
                         EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
                         0, 0, &cached_state);

        ret = btrfs_set_extent_delalloc(BTRFS_I(inode), block_start, block_end, 0,
                                        &cached_state);
        if (ret) {
                unlock_extent_cached(io_tree, block_start, block_end,
                                     &cached_state);
                goto out_unlock;
        }

        if (offset != blocksize) {
                if (!len)
                        len = blocksize - offset;
                kaddr = kmap(page);
                if (front)
                        memset(kaddr + (block_start - page_offset(page)),
                                0, offset);
                else
                        memset(kaddr + (block_start - page_offset(page)) +  offset,
                                0, len);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        unlock_extent_cached(io_tree, block_start, block_end, &cached_state);

        if (only_release_metadata)
                set_extent_bit(&BTRFS_I(inode)->io_tree, block_start,
                                block_end, EXTENT_NORESERVE, NULL, NULL,
                                GFP_NOFS);

out_unlock:
        if (ret) {
                if (only_release_metadata)
                        btrfs_delalloc_release_metadata(BTRFS_I(inode),
                                        blocksize, true);
                else
                        btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved,
                                        block_start, blocksize, true);
        }
        btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize);
        unlock_page(page);
        put_page(page);
out:
        if (only_release_metadata)
                btrfs_check_nocow_unlock(BTRFS_I(inode));
        extent_changeset_free(data_reserved);
        return ret;
}

static int maybe_insert_hole(struct btrfs_root *root, struct inode *inode,
                             u64 offset, u64 len)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_trans_handle *trans;
        int ret;

        /*
         * Still need to make sure the inode looks like it's been updated so
         * that any holes get logged if we fsync.
         */
        if (btrfs_fs_incompat(fs_info, NO_HOLES)) {
                BTRFS_I(inode)->last_trans = fs_info->generation;
                BTRFS_I(inode)->last_sub_trans = root->log_transid;
                BTRFS_I(inode)->last_log_commit = root->last_log_commit;
                return 0;
        }

        /*
         * 1 - for the one we're dropping
         * 1 - for the one we're adding
         * 1 - for updating the inode.
         */
        trans = btrfs_start_transaction(root, 3);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_drop_extents(trans, root, inode, offset, offset + len, 1);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                btrfs_end_transaction(trans);
                return ret;
        }

        ret = btrfs_insert_file_extent(trans, root, btrfs_ino(BTRFS_I(inode)),
                        offset, 0, 0, len, 0, len, 0, 0, 0);
        if (ret)
                btrfs_abort_transaction(trans, ret);
        else
                btrfs_update_inode(trans, root, inode);
        btrfs_end_transaction(trans);
        return ret;
}

/*
 * This function puts in dummy file extents for the area we're creating a hole
 * for.  So if we are truncating this file to a larger size we need to insert
 * these file extents so that btrfs_get_extent will return a EXTENT_MAP_HOLE for
 * the range between oldsize and size
 */
int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map *em = NULL;
        struct extent_state *cached_state = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        u64 hole_start = ALIGN(oldsize, fs_info->sectorsize);
        u64 block_end = ALIGN(size, fs_info->sectorsize);
        u64 last_byte;
        u64 cur_offset;
        u64 hole_size;
        int err = 0;

        /*
         * If our size started in the middle of a block we need to zero out the
         * rest of the block before we expand the i_size, otherwise we could
         * expose stale data.
         */
        err = btrfs_truncate_block(inode, oldsize, 0, 0);
        if (err)
                return err;

        if (size <= hole_start)
                return 0;

        btrfs_lock_and_flush_ordered_range(BTRFS_I(inode), hole_start,
                                           block_end - 1, &cached_state);
        cur_offset = hole_start;
        while (1) {
                em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, cur_offset,
                                      block_end - cur_offset);
                if (IS_ERR(em)) {
                        err = PTR_ERR(em);
                        em = NULL;
                        break;
                }
                last_byte = min(extent_map_end(em), block_end);
                last_byte = ALIGN(last_byte, fs_info->sectorsize);
                hole_size = last_byte - cur_offset;

                if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
                        struct extent_map *hole_em;

                        err = maybe_insert_hole(root, inode, cur_offset,
                                                hole_size);
                        if (err)
                                break;

                        err = btrfs_inode_set_file_extent_range(BTRFS_I(inode),
                                                        cur_offset, hole_size);
                        if (err)
                                break;

                        btrfs_drop_extent_cache(BTRFS_I(inode), cur_offset,
                                                cur_offset + hole_size - 1, 0);
                        hole_em = alloc_extent_map();
                        if (!hole_em) {
                                set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                                        &BTRFS_I(inode)->runtime_flags);
                                goto next;
                        }
                        hole_em->start = cur_offset;
                        hole_em->len = hole_size;
                        hole_em->orig_start = cur_offset;

                        hole_em->block_start = EXTENT_MAP_HOLE;
                        hole_em->block_len = 0;
                        hole_em->orig_block_len = 0;
                        hole_em->ram_bytes = hole_size;
                        hole_em->compress_type = BTRFS_COMPRESS_NONE;
                        hole_em->generation = fs_info->generation;

                        while (1) {
                                write_lock(&em_tree->lock);
                                err = add_extent_mapping(em_tree, hole_em, 1);
                                write_unlock(&em_tree->lock);
                                if (err != -EEXIST)
                                        break;
                                btrfs_drop_extent_cache(BTRFS_I(inode),
                                                        cur_offset,
                                                        cur_offset +
                                                        hole_size - 1, 0);
                        }
                        free_extent_map(hole_em);
                } else {
                        err = btrfs_inode_set_file_extent_range(BTRFS_I(inode),
                                                        cur_offset, hole_size);
                        if (err)
                                break;
                }
next:
                free_extent_map(em);
                em = NULL;
                cur_offset = last_byte;
                if (cur_offset >= block_end)
                        break;
        }
        free_extent_map(em);
        unlock_extent_cached(io_tree, hole_start, block_end - 1, &cached_state);
        return err;
}

static int btrfs_setsize(struct inode *inode, struct iattr *attr)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        loff_t oldsize = i_size_read(inode);
        loff_t newsize = attr->ia_size;
        int mask = attr->ia_valid;
        int ret;

        /*
         * The regular truncate() case without ATTR_CTIME and ATTR_MTIME is a
         * special case where we need to update the times despite not having
         * these flags set.  For all other operations the VFS set these flags
         * explicitly if it wants a timestamp update.
         */
        if (newsize != oldsize) {
                inode_inc_iversion(inode);
                if (!(mask & (ATTR_CTIME | ATTR_MTIME)))
                        inode->i_ctime = inode->i_mtime =
                                current_time(inode);
        }

        if (newsize > oldsize) {
                /*
                 * Don't do an expanding truncate while snapshotting is ongoing.
                 * This is to ensure the snapshot captures a fully consistent
                 * state of this file - if the snapshot captures this expanding
                 * truncation, it must capture all writes that happened before
                 * this truncation.
                 */
                btrfs_drew_write_lock(&root->snapshot_lock);
                ret = btrfs_cont_expand(inode, oldsize, newsize);
                if (ret) {
                        btrfs_drew_write_unlock(&root->snapshot_lock);
                        return ret;
                }

                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans)) {
                        btrfs_drew_write_unlock(&root->snapshot_lock);
                        return PTR_ERR(trans);
                }

                i_size_write(inode, newsize);
                btrfs_inode_safe_disk_i_size_write(inode, 0);
                pagecache_isize_extended(inode, oldsize, newsize);
                ret = btrfs_update_inode(trans, root, inode);
                btrfs_drew_write_unlock(&root->snapshot_lock);
                btrfs_end_transaction(trans);
        } else {

                /*
                 * We're truncating a file that used to have good data down to
                 * zero. Make sure it gets into the ordered flush list so that
                 * any new writes get down to disk quickly.
                 */
                if (newsize == 0)
                        set_bit(BTRFS_INODE_ORDERED_DATA_CLOSE,
                                &BTRFS_I(inode)->runtime_flags);

                truncate_setsize(inode, newsize);

                /* Disable nonlocked read DIO to avoid the endless truncate */
                btrfs_inode_block_unlocked_dio(BTRFS_I(inode));
                inode_dio_wait(inode);
                btrfs_inode_resume_unlocked_dio(BTRFS_I(inode));

                ret = btrfs_truncate(inode, newsize == oldsize);
                if (ret && inode->i_nlink) {
                        int err;

                        /*
                         * Truncate failed, so fix up the in-memory size. We
                         * adjusted disk_i_size down as we removed extents, so
                         * wait for disk_i_size to be stable and then update the
                         * in-memory size to match.
                         */
                        err = btrfs_wait_ordered_range(inode, 0, (u64)-1);
                        if (err)
                                return err;
                        i_size_write(inode, BTRFS_I(inode)->disk_i_size);
                }
        }

        return ret;
}

static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int err;

        if (btrfs_root_readonly(root))
                return -EROFS;

        err = setattr_prepare(dentry, attr);
        if (err)
                return err;

        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
                err = btrfs_setsize(inode, attr);
                if (err)
                        return err;
        }

        if (attr->ia_valid) {
                setattr_copy(inode, attr);
                inode_inc_iversion(inode);
                err = btrfs_dirty_inode(inode);

                if (!err && attr->ia_valid & ATTR_MODE)
                        err = posix_acl_chmod(inode, inode->i_mode);
        }

        return err;
}

/*
 * While truncating the inode pages during eviction, we get the VFS calling
 * btrfs_invalidatepage() against each page of the inode. This is slow because
 * the calls to btrfs_invalidatepage() result in a huge amount of calls to
 * lock_extent_bits() and clear_extent_bit(), which keep merging and splitting
 * extent_state structures over and over, wasting lots of time.
 *
 * Therefore if the inode is being evicted, let btrfs_invalidatepage() skip all
 * those expensive operations on a per page basis and do only the ordered io
 * finishing, while we release here the extent_map and extent_state structures,
 * without the excessive merging and splitting.
 */
static void evict_inode_truncate_pages(struct inode *inode)
{
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map_tree *map_tree = &BTRFS_I(inode)->extent_tree;
        struct rb_node *node;

        ASSERT(inode->i_state & I_FREEING);
        truncate_inode_pages_final(&inode->i_data);

        write_lock(&map_tree->lock);
        while (!RB_EMPTY_ROOT(&map_tree->map.rb_root)) {
                struct extent_map *em;

                node = rb_first_cached(&map_tree->map);
                em = rb_entry(node, struct extent_map, rb_node);
                clear_bit(EXTENT_FLAG_PINNED, &em->flags);
                clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
                remove_extent_mapping(map_tree, em);
                free_extent_map(em);
                if (need_resched()) {
                        write_unlock(&map_tree->lock);
                        cond_resched();
                        write_lock(&map_tree->lock);
                }
        }
        write_unlock(&map_tree->lock);

        /*
         * Keep looping until we have no more ranges in the io tree.
         * We can have ongoing bios started by readahead that have
         * their endio callback (extent_io.c:end_bio_extent_readpage)
         * still in progress (unlocked the pages in the bio but did not yet
         * unlocked the ranges in the io tree). Therefore this means some
         * ranges can still be locked and eviction started because before
         * submitting those bios, which are executed by a separate task (work
         * queue kthread), inode references (inode->i_count) were not taken
         * (which would be dropped in the end io callback of each bio).
         * Therefore here we effectively end up waiting for those bios and
         * anyone else holding locked ranges without having bumped the inode's
         * reference count - if we don't do it, when they access the inode's
         * io_tree to unlock a range it may be too late, leading to an
         * use-after-free issue.
         */
        spin_lock(&io_tree->lock);
        while (!RB_EMPTY_ROOT(&io_tree->state)) {
                struct extent_state *state;
                struct extent_state *cached_state = NULL;
                u64 start;
                u64 end;
                unsigned state_flags;

                node = rb_first(&io_tree->state);
                state = rb_entry(node, struct extent_state, rb_node);
                start = state->start;
                end = state->end;
                state_flags = state->state;
                spin_unlock(&io_tree->lock);

                lock_extent_bits(io_tree, start, end, &cached_state);

                /*
                 * If still has DELALLOC flag, the extent didn't reach disk,
                 * and its reserved space won't be freed by delayed_ref.
                 * So we need to free its reserved space here.
                 * (Refer to comment in btrfs_invalidatepage, case 2)
                 *
                 * Note, end is the bytenr of last byte, so we need + 1 here.
                 */
                if (state_flags & EXTENT_DELALLOC)
                        btrfs_qgroup_free_data(BTRFS_I(inode), NULL, start,
                                               end - start + 1);

                clear_extent_bit(io_tree, start, end,
                                 EXTENT_LOCKED | EXTENT_DELALLOC |
                                 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 1, 1,
                                 &cached_state);

                cond_resched();
                spin_lock(&io_tree->lock);
        }
        spin_unlock(&io_tree->lock);
}

static struct btrfs_trans_handle *evict_refill_and_join(struct btrfs_root *root,
                                                        struct btrfs_block_rsv *rsv)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
        struct btrfs_trans_handle *trans;
        u64 delayed_refs_extra = btrfs_calc_insert_metadata_size(fs_info, 1);
        int ret;

        /*
         * Eviction should be taking place at some place safe because of our
         * delayed iputs.  However the normal flushing code will run delayed
         * iputs, so we cannot use FLUSH_ALL otherwise we'll deadlock.
         *
         * We reserve the delayed_refs_extra here again because we can't use
         * btrfs_start_transaction(root, 0) for the same deadlocky reason as
         * above.  We reserve our extra bit here because we generate a ton of
         * delayed refs activity by truncating.
         *
         * If we cannot make our reservation we'll attempt to steal from the
         * global reserve, because we really want to be able to free up space.
         */
        ret = btrfs_block_rsv_refill(root, rsv, rsv->size + delayed_refs_extra,
                                     BTRFS_RESERVE_FLUSH_EVICT);
        if (ret) {
                /*
                 * Try to steal from the global reserve if there is space for
                 * it.
                 */
                if (btrfs_check_space_for_delayed_refs(fs_info) ||
                    btrfs_block_rsv_migrate(global_rsv, rsv, rsv->size, 0)) {
                        btrfs_warn(fs_info,
                                   "could not allocate space for delete; will truncate on mount");
                        return ERR_PTR(-ENOSPC);
                }
                delayed_refs_extra = 0;
        }

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans))
                return trans;

        if (delayed_refs_extra) {
                trans->block_rsv = &fs_info->trans_block_rsv;
                trans->bytes_reserved = delayed_refs_extra;
                btrfs_block_rsv_migrate(rsv, trans->block_rsv,
                                        delayed_refs_extra, 1);
        }
        return trans;
}

void btrfs_evict_inode(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *rsv;
        int ret;

        trace_btrfs_inode_evict(inode);

        if (!root) {
                clear_inode(inode);
                return;
        }

        evict_inode_truncate_pages(inode);

        if (inode->i_nlink &&
            ((btrfs_root_refs(&root->root_item) != 0 &&
              root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID) ||
             btrfs_is_free_space_inode(BTRFS_I(inode))))
                goto no_delete;

        if (is_bad_inode(inode))
                goto no_delete;

        btrfs_free_io_failure_record(BTRFS_I(inode), 0, (u64)-1);

        if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
                goto no_delete;

        if (inode->i_nlink > 0) {
                BUG_ON(btrfs_root_refs(&root->root_item) != 0 &&
                       root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID);
                goto no_delete;
        }

        ret = btrfs_commit_inode_delayed_inode(BTRFS_I(inode));
        if (ret)
                goto no_delete;

        rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);
        if (!rsv)
                goto no_delete;
        rsv->size = btrfs_calc_metadata_size(fs_info, 1);
        rsv->failfast = 1;

        btrfs_i_size_write(BTRFS_I(inode), 0);

        while (1) {
                trans = evict_refill_and_join(root, rsv);
                if (IS_ERR(trans))
                        goto free_rsv;

                trans->block_rsv = rsv;

                ret = btrfs_truncate_inode_items(trans, root, inode, 0, 0);
                trans->block_rsv = &fs_info->trans_block_rsv;
                btrfs_end_transaction(trans);
                btrfs_btree_balance_dirty(fs_info);
                if (ret && ret != -ENOSPC && ret != -EAGAIN)
                        goto free_rsv;
                else if (!ret)
                        break;
        }

        /*
         * Errors here aren't a big deal, it just means we leave orphan items in
         * the tree. They will be cleaned up on the next mount. If the inode
         * number gets reused, cleanup deletes the orphan item without doing
         * anything, and unlink reuses the existing orphan item.
         *
         * If it turns out that we are dropping too many of these, we might want
         * to add a mechanism for retrying these after a commit.
         */
        trans = evict_refill_and_join(root, rsv);
        if (!IS_ERR(trans)) {
                trans->block_rsv = rsv;
                btrfs_orphan_del(trans, BTRFS_I(inode));
                trans->block_rsv = &fs_info->trans_block_rsv;
                btrfs_end_transaction(trans);
        }

        if (!(root == fs_info->tree_root ||
              root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID))
                btrfs_return_ino(root, btrfs_ino(BTRFS_I(inode)));

free_rsv:
        btrfs_free_block_rsv(fs_info, rsv);
no_delete:
        /*
         * If we didn't successfully delete, the orphan item will still be in
         * the tree and we'll retry on the next mount. Again, we might also want
         * to retry these periodically in the future.
         */
        btrfs_remove_delayed_node(BTRFS_I(inode));
        clear_inode(inode);
}

/*
 * Return the key found in the dir entry in the location pointer, fill @type
 * with BTRFS_FT_*, and return 0.
 *
 * If no dir entries were found, returns -ENOENT.
 * If found a corrupted location in dir entry, returns -EUCLEAN.
 */
static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry,
                               struct btrfs_key *location, u8 *type)
{
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int ret = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        di = btrfs_lookup_dir_item(NULL, root, path, btrfs_ino(BTRFS_I(dir)),
                        name, namelen, 0);
        if (IS_ERR_OR_NULL(di)) {
                ret = di ? PTR_ERR(di) : -ENOENT;
                goto out;
        }

        btrfs_dir_item_key_to_cpu(path->nodes[0], di, location);
        if (location->type != BTRFS_INODE_ITEM_KEY &&
            location->type != BTRFS_ROOT_ITEM_KEY) {
                ret = -EUCLEAN;
                btrfs_warn(root->fs_info,
"%s gets something invalid in DIR_ITEM (name %s, directory ino %llu, location(%llu %u %llu))",
                           __func__, name, btrfs_ino(BTRFS_I(dir)),
                           location->objectid, location->type, location->offset);
        }
        if (!ret)
                *type = btrfs_dir_type(path->nodes[0], di);
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * when we hit a tree root in a directory, the btrfs part of the inode
 * needs to be changed to reflect the root directory of the tree root.  This
 * is kind of like crossing a mount point.
 */
static int fixup_tree_root_location(struct btrfs_fs_info *fs_info,
                                    struct inode *dir,
                                    struct dentry *dentry,
                                    struct btrfs_key *location,
                                    struct btrfs_root **sub_root)
{
        struct btrfs_path *path;
        struct btrfs_root *new_root;
        struct btrfs_root_ref *ref;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        int ret;
        int err = 0;

        path = btrfs_alloc_path();
        if (!path) {
                err = -ENOMEM;
                goto out;
        }

        err = -ENOENT;
        key.objectid = BTRFS_I(dir)->root->root_key.objectid;
        key.type = BTRFS_ROOT_REF_KEY;
        key.offset = location->objectid;

        ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
        if (ret) {
                if (ret < 0)
                        err = ret;
                goto out;
        }

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
        if (btrfs_root_ref_dirid(leaf, ref) != btrfs_ino(BTRFS_I(dir)) ||
            btrfs_root_ref_name_len(leaf, ref) != dentry->d_name.len)
                goto out;

        ret = memcmp_extent_buffer(leaf, dentry->d_name.name,
                                   (unsigned long)(ref + 1),
                                   dentry->d_name.len);
        if (ret)
                goto out;

        btrfs_release_path(path);

        new_root = btrfs_get_fs_root(fs_info, location->objectid, true);
        if (IS_ERR(new_root)) {
                err = PTR_ERR(new_root);
                goto out;
        }

        *sub_root = new_root;
        location->objectid = btrfs_root_dirid(&new_root->root_item);
        location->type = BTRFS_INODE_ITEM_KEY;
        location->offset = 0;
        err = 0;
out:
        btrfs_free_path(path);
        return err;
}

static void inode_tree_add(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_inode *entry;
        struct rb_node **p;
        struct rb_node *parent;
        struct rb_node *new = &BTRFS_I(inode)->rb_node;
        u64 ino = btrfs_ino(BTRFS_I(inode));

        if (inode_unhashed(inode))
                return;
        parent = NULL;
        spin_lock(&root->inode_lock);
        p = &root->inode_tree.rb_node;
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct btrfs_inode, rb_node);

                if (ino < btrfs_ino(entry))
                        p = &parent->rb_left;
                else if (ino > btrfs_ino(entry))
                        p = &parent->rb_right;
                else {
                        WARN_ON(!(entry->vfs_inode.i_state &
                                  (I_WILL_FREE | I_FREEING)));
                        rb_replace_node(parent, new, &root->inode_tree);
                        RB_CLEAR_NODE(parent);
                        spin_unlock(&root->inode_lock);
                        return;
                }
        }
        rb_link_node(new, parent, p);
        rb_insert_color(new, &root->inode_tree);
        spin_unlock(&root->inode_lock);
}

static void inode_tree_del(struct btrfs_inode *inode)
{
        struct btrfs_root *root = inode->root;
        int empty = 0;

        spin_lock(&root->inode_lock);
        if (!RB_EMPTY_NODE(&inode->rb_node)) {
                rb_erase(&inode->rb_node, &root->inode_tree);
                RB_CLEAR_NODE(&inode->rb_node);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
        }
        spin_unlock(&root->inode_lock);

        if (empty && btrfs_root_refs(&root->root_item) == 0) {
                spin_lock(&root->inode_lock);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
                spin_unlock(&root->inode_lock);
                if (empty)
                        btrfs_add_dead_root(root);
        }
}


static int btrfs_init_locked_inode(struct inode *inode, void *p)
{
        struct btrfs_iget_args *args = p;

        inode->i_ino = args->ino;
        BTRFS_I(inode)->location.objectid = args->ino;
        BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
        BTRFS_I(inode)->location.offset = 0;
        BTRFS_I(inode)->root = btrfs_grab_root(args->root);
        BUG_ON(args->root && !BTRFS_I(inode)->root);
        return 0;
}

static int btrfs_find_actor(struct inode *inode, void *opaque)
{
        struct btrfs_iget_args *args = opaque;

        return args->ino == BTRFS_I(inode)->location.objectid &&
                args->root == BTRFS_I(inode)->root;
}

static struct inode *btrfs_iget_locked(struct super_block *s, u64 ino,
                                       struct btrfs_root *root)
{
        struct inode *inode;
        struct btrfs_iget_args args;
        unsigned long hashval = btrfs_inode_hash(ino, root);

        args.ino = ino;
        args.root = root;

        inode = iget5_locked(s, hashval, btrfs_find_actor,
                             btrfs_init_locked_inode,
                             (void *)&args);
        return inode;
}

/*
 * Get an inode object given its inode number and corresponding root.
 * Path can be preallocated to prevent recursing back to iget through
 * allocator. NULL is also valid but may require an additional allocation
 * later.
 */
struct inode *btrfs_iget_path(struct super_block *s, u64 ino,
                              struct btrfs_root *root, struct btrfs_path *path)
{
        struct inode *inode;

        inode = btrfs_iget_locked(s, ino, root);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        if (inode->i_state & I_NEW) {
                int ret;

                ret = btrfs_read_locked_inode(inode, path);
                if (!ret) {
                        inode_tree_add(inode);
                        unlock_new_inode(inode);
                } else {
                        iget_failed(inode);
                        /*
                         * ret > 0 can come from btrfs_search_slot called by
                         * btrfs_read_locked_inode, this means the inode item
                         * was not found.
                         */
                        if (ret > 0)
                                ret = -ENOENT;
                        inode = ERR_PTR(ret);
                }
        }

        return inode;
}

struct inode *btrfs_iget(struct super_block *s, u64 ino, struct btrfs_root *root)
{
        return btrfs_iget_path(s, ino, root, NULL);
}

static struct inode *new_simple_dir(struct super_block *s,
                                    struct btrfs_key *key,
                                    struct btrfs_root *root)
{
        struct inode *inode = new_inode(s);

        if (!inode)
                return ERR_PTR(-ENOMEM);

        BTRFS_I(inode)->root = btrfs_grab_root(root);
        memcpy(&BTRFS_I(inode)->location, key, sizeof(*key));
        set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);

        inode->i_ino = BTRFS_EMPTY_SUBVOL_DIR_OBJECTID;
        /*
         * We only need lookup, the rest is read-only and there's no inode
         * associated with the dentry
         */
        inode->i_op = &simple_dir_inode_operations;
        inode->i_opflags &= ~IOP_XATTR;
        inode->i_fop = &simple_dir_operations;
        inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO;
        inode->i_mtime = current_time(inode);
        inode->i_atime = inode->i_mtime;
        inode->i_ctime = inode->i_mtime;
        BTRFS_I(inode)->i_otime = inode->i_mtime;

        return inode;
}

static inline u8 btrfs_inode_type(struct inode *inode)
{
        /*
         * Compile-time asserts that generic FT_* types still match
         * BTRFS_FT_* types
         */
        BUILD_BUG_ON(BTRFS_FT_UNKNOWN != FT_UNKNOWN);
        BUILD_BUG_ON(BTRFS_FT_REG_FILE != FT_REG_FILE);
        BUILD_BUG_ON(BTRFS_FT_DIR != FT_DIR);
        BUILD_BUG_ON(BTRFS_FT_CHRDEV != FT_CHRDEV);
        BUILD_BUG_ON(BTRFS_FT_BLKDEV != FT_BLKDEV);
        BUILD_BUG_ON(BTRFS_FT_FIFO != FT_FIFO);
        BUILD_BUG_ON(BTRFS_FT_SOCK != FT_SOCK);
        BUILD_BUG_ON(BTRFS_FT_SYMLINK != FT_SYMLINK);

        return fs_umode_to_ftype(inode->i_mode);
}

struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct inode *inode;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_root *sub_root = root;
        struct btrfs_key location;
        u8 di_type = 0;
        int ret = 0;

        if (dentry->d_name.len > BTRFS_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        ret = btrfs_inode_by_name(dir, dentry, &location, &di_type);
        if (ret < 0)
                return ERR_PTR(ret);

        if (location.type == BTRFS_INODE_ITEM_KEY) {
                inode = btrfs_iget(dir->i_sb, location.objectid, root);
                if (IS_ERR(inode))
                        return inode;

                /* Do extra check against inode mode with di_type */
                if (btrfs_inode_type(inode) != di_type) {
                        btrfs_crit(fs_info,
"inode mode mismatch with dir: inode mode=0%o btrfs type=%u dir type=%u",
                                  inode->i_mode, btrfs_inode_type(inode),
                                  di_type);
                        iput(inode);
                        return ERR_PTR(-EUCLEAN);
                }
                return inode;
        }

        ret = fixup_tree_root_location(fs_info, dir, dentry,
                                       &location, &sub_root);
        if (ret < 0) {
                if (ret != -ENOENT)
                        inode = ERR_PTR(ret);
                else
                        inode = new_simple_dir(dir->i_sb, &location, sub_root);
        } else {
                inode = btrfs_iget(dir->i_sb, location.objectid, sub_root);
        }
        if (root != sub_root)
                btrfs_put_root(sub_root);

        if (!IS_ERR(inode) && root != sub_root) {
                down_read(&fs_info->cleanup_work_sem);
                if (!sb_rdonly(inode->i_sb))
                        ret = btrfs_orphan_cleanup(sub_root);
                up_read(&fs_info->cleanup_work_sem);
                if (ret) {
                        iput(inode);
                        inode = ERR_PTR(ret);
                }
        }

        return inode;
}

static int btrfs_dentry_delete(const struct dentry *dentry)
{
        struct btrfs_root *root;
        struct inode *inode = d_inode(dentry);

        if (!inode && !IS_ROOT(dentry))
                inode = d_inode(dentry->d_parent);

        if (inode) {
                root = BTRFS_I(inode)->root;
                if (btrfs_root_refs(&root->root_item) == 0)
                        return 1;

                if (btrfs_ino(BTRFS_I(inode)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                        return 1;
        }
        return 0;
}

static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
                                   unsigned int flags)
{
        struct inode *inode = btrfs_lookup_dentry(dir, dentry);

        if (inode == ERR_PTR(-ENOENT))
                inode = NULL;
        return d_splice_alias(inode, dentry);
}

/*
 * All this infrastructure exists because dir_emit can fault, and we are holding
 * the tree lock when doing readdir.  For now just allocate a buffer and copy
 * our information into that, and then dir_emit from the buffer.  This is
 * similar to what NFS does, only we don't keep the buffer around in pagecache
 * because I'm afraid I'll mess that up.  Long term we need to make filldir do
 * copy_to_user_inatomic so we don't have to worry about page faulting under the
 * tree lock.
 */
static int btrfs_opendir(struct inode *inode, struct file *file)
{
        struct btrfs_file_private *private;

        private = kzalloc(sizeof(struct btrfs_file_private), GFP_KERNEL);
        if (!private)
                return -ENOMEM;
        private->filldir_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!private->filldir_buf) {
                kfree(private);
                return -ENOMEM;
        }
        file->private_data = private;
        return 0;
}

struct dir_entry {
        u64 ino;
        u64 offset;
        unsigned type;
        int name_len;
};

static int btrfs_filldir(void *addr, int entries, struct dir_context *ctx)
{
        while (entries--) {
                struct dir_entry *entry = addr;
                char *name = (char *)(entry + 1);

                ctx->pos = get_unaligned(&entry->offset);
                if (!dir_emit(ctx, name, get_unaligned(&entry->name_len),
                                         get_unaligned(&entry->ino),
                                         get_unaligned(&entry->type)))
                        return 1;
                addr += sizeof(struct dir_entry) +
                        get_unaligned(&entry->name_len);
                ctx->pos++;
        }
        return 0;
}

static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
{
        struct inode *inode = file_inode(file);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_private *private = file->private_data;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_path *path;
        void *addr;
        struct list_head ins_list;
        struct list_head del_list;
        int ret;
        struct extent_buffer *leaf;
        int slot;
        char *name_ptr;
        int name_len;
        int entries = 0;
        int total_len = 0;
        bool put = false;
        struct btrfs_key location;

        if (!dir_emit_dots(file, ctx))
                return 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        addr = private->filldir_buf;
        path->reada = READA_FORWARD;

        INIT_LIST_HEAD(&ins_list);
        INIT_LIST_HEAD(&del_list);
        put = btrfs_readdir_get_delayed_items(inode, &ins_list, &del_list);

again:
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = ctx->pos;
        key.objectid = btrfs_ino(BTRFS_I(inode));

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        while (1) {
                struct dir_entry *entry;

                leaf = path->nodes[0];
                slot = path->slots[0];
                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
                        else if (ret > 0)
                                break;
                        continue;
                }

                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.objectid != key.objectid)
                        break;
                if (found_key.type != BTRFS_DIR_INDEX_KEY)
                        break;
                if (found_key.offset < ctx->pos)
                        goto next;
                if (btrfs_should_delete_dir_index(&del_list, found_key.offset))
                        goto next;
                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                name_len = btrfs_dir_name_len(leaf, di);
                if ((total_len + sizeof(struct dir_entry) + name_len) >=
                    PAGE_SIZE) {
                        btrfs_release_path(path);
                        ret = btrfs_filldir(private->filldir_buf, entries, ctx);
                        if (ret)
                                goto nopos;
                        addr = private->filldir_buf;
                        entries = 0;
                        total_len = 0;
                        goto again;
                }

                entry = addr;
                put_unaligned(name_len, &entry->name_len);
                name_ptr = (char *)(entry + 1);
                read_extent_buffer(leaf, name_ptr, (unsigned long)(di + 1),
                                   name_len);
                put_unaligned(fs_ftype_to_dtype(btrfs_dir_type(leaf, di)),
                                &entry->type);
                btrfs_dir_item_key_to_cpu(leaf, di, &location);
                put_unaligned(location.objectid, &entry->ino);
                put_unaligned(found_key.offset, &entry->offset);
                entries++;
                addr += sizeof(struct dir_entry) + name_len;
                total_len += sizeof(struct dir_entry) + name_len;
next:
                path->slots[0]++;
        }
        btrfs_release_path(path);

        ret = btrfs_filldir(private->filldir_buf, entries, ctx);
        if (ret)
                goto nopos;

        ret = btrfs_readdir_delayed_dir_index(ctx, &ins_list);
        if (ret)
                goto nopos;

        /*
         * Stop new entries from being returned after we return the last
         * entry.
         *
         * New directory entries are assigned a strictly increasing
         * offset.  This means that new entries created during readdir
         * are *guaranteed* to be seen in the future by that readdir.
         * This has broken buggy programs which operate on names as
         * they're returned by readdir.  Until we re-use freed offsets
         * we have this hack to stop new entries from being returned
         * under the assumption that they'll never reach this huge
         * offset.
         *
         * This is being careful not to overflow 32bit loff_t unless the
         * last entry requires it because doing so has broken 32bit apps
         * in the past.
         */
        if (ctx->pos >= INT_MAX)
                ctx->pos = LLONG_MAX;
        else
                ctx->pos = INT_MAX;
nopos:
        ret = 0;
err:
        if (put)
                btrfs_readdir_put_delayed_items(inode, &ins_list, &del_list);
        btrfs_free_path(path);
        return ret;
}

/*
 * This is somewhat expensive, updating the tree every time the
 * inode changes.  But, it is most likely to find the inode in cache.
 * FIXME, needs more benchmarking...there are no reasons other than performance
 * to keep or drop this code.
 */
static int btrfs_dirty_inode(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret;

        if (test_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags))
                return 0;

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_update_inode(trans, root, inode);
        if (ret && ret == -ENOSPC) {
                /* whoops, lets try again with the full transaction */
                btrfs_end_transaction(trans);
                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans))
                        return PTR_ERR(trans);

                ret = btrfs_update_inode(trans, root, inode);
        }
        btrfs_end_transaction(trans);
        if (BTRFS_I(inode)->delayed_node)
                btrfs_balance_delayed_items(fs_info);

        return ret;
}

/*
 * This is a copy of file_update_time.  We need this so we can return error on
 * ENOSPC for updating the inode in the case of file write and mmap writes.
 */
static int btrfs_update_time(struct inode *inode, struct timespec64 *now,
                             int flags)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        bool dirty = flags & ~S_VERSION;

        if (btrfs_root_readonly(root))
                return -EROFS;

        if (flags & S_VERSION)
                dirty |= inode_maybe_inc_iversion(inode, dirty);
        if (flags & S_CTIME)
                inode->i_ctime = *now;
        if (flags & S_MTIME)
                inode->i_mtime = *now;
        if (flags & S_ATIME)
                inode->i_atime = *now;
        return dirty ? btrfs_dirty_inode(inode) : 0;
}

/*
 * find the highest existing sequence number in a directory
 * and then set the in-memory index_cnt variable to reflect
 * free sequence numbers
 */
static int btrfs_set_inode_index_count(struct btrfs_inode *inode)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_key key, found_key;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        key.objectid = btrfs_ino(inode);
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = (u64)-1;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        /* FIXME: we should be able to handle this */
        if (ret == 0)
                goto out;
        ret = 0;

        /*
         * MAGIC NUMBER EXPLANATION:
         * since we search a directory based on f_pos we have to start at 2
         * since '.' and '..' have f_pos of 0 and 1 respectively, so everybody
         * else has to start at 2
         */
        if (path->slots[0] == 0) {
                inode->index_cnt = 2;
                goto out;
        }

        path->slots[0]--;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

        if (found_key.objectid != btrfs_ino(inode) ||
            found_key.type != BTRFS_DIR_INDEX_KEY) {
                inode->index_cnt = 2;
                goto out;
        }

        inode->index_cnt = found_key.offset + 1;
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * helper to find a free sequence number in a given directory.  This current
 * code is very simple, later versions will do smarter things in the btree
 */
int btrfs_set_inode_index(struct btrfs_inode *dir, u64 *index)
{
        int ret = 0;

        if (dir->index_cnt == (u64)-1) {
                ret = btrfs_inode_delayed_dir_index_count(dir);
                if (ret) {
                        ret = btrfs_set_inode_index_count(dir);
                        if (ret)
                                return ret;
                }
        }

        *index = dir->index_cnt;
        dir->index_cnt++;

        return ret;
}

static int btrfs_insert_inode_locked(struct inode *inode)
{
        struct btrfs_iget_args args;

        args.ino = BTRFS_I(inode)->location.objectid;
        args.root = BTRFS_I(inode)->root;

        return insert_inode_locked4(inode,
                   btrfs_inode_hash(inode->i_ino, BTRFS_I(inode)->root),
                   btrfs_find_actor, &args);
}

/*
 * Inherit flags from the parent inode.
 *
 * Currently only the compression flags and the cow flags are inherited.
 */
static void btrfs_inherit_iflags(struct inode *inode, struct inode *dir)
{
        unsigned int flags;

        if (!dir)
                return;

        flags = BTRFS_I(dir)->flags;

        if (flags & BTRFS_INODE_NOCOMPRESS) {
                BTRFS_I(inode)->flags &= ~BTRFS_INODE_COMPRESS;
                BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
        } else if (flags & BTRFS_INODE_COMPRESS) {
                BTRFS_I(inode)->flags &= ~BTRFS_INODE_NOCOMPRESS;
                BTRFS_I(inode)->flags |= BTRFS_INODE_COMPRESS;
        }

        if (flags & BTRFS_INODE_NODATACOW) {
                BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW;
                if (S_ISREG(inode->i_mode))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
        }

        btrfs_sync_inode_flags_to_i_flags(inode);
}

static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct inode *dir,
                                     const char *name, int name_len,
                                     u64 ref_objectid, u64 objectid,
                                     umode_t mode, u64 *index)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct inode *inode;
        struct btrfs_inode_item *inode_item;
        struct btrfs_key *location;
        struct btrfs_path *path;
        struct btrfs_inode_ref *ref;
        struct btrfs_key key[2];
        u32 sizes[2];
        int nitems = name ? 2 : 1;
        unsigned long ptr;
        unsigned int nofs_flag;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return ERR_PTR(-ENOMEM);

        nofs_flag = memalloc_nofs_save();
        inode = new_inode(fs_info->sb);
        memalloc_nofs_restore(nofs_flag);
        if (!inode) {
                btrfs_free_path(path);
                return ERR_PTR(-ENOMEM);
        }

        /*
         * O_TMPFILE, set link count to 0, so that after this point,
         * we fill in an inode item with the correct link count.
         */
        if (!name)
                set_nlink(inode, 0);

        /*
         * we have to initialize this early, so we can reclaim the inode
         * number if we fail afterwards in this function.
         */
        inode->i_ino = objectid;

        if (dir && name) {
                trace_btrfs_inode_request(dir);

                ret = btrfs_set_inode_index(BTRFS_I(dir), index);
                if (ret) {
                        btrfs_free_path(path);
                        iput(inode);
                        return ERR_PTR(ret);
                }
        } else if (dir) {
                *index = 0;
        }
        /*
         * index_cnt is ignored for everything but a dir,
         * btrfs_set_inode_index_count has an explanation for the magic
         * number
         */
        BTRFS_I(inode)->index_cnt = 2;
        BTRFS_I(inode)->dir_index = *index;
        BTRFS_I(inode)->root = btrfs_grab_root(root);
        BTRFS_I(inode)->generation = trans->transid;
        inode->i_generation = BTRFS_I(inode)->generation;

        /*
         * We could have gotten an inode number from somebody who was fsynced
         * and then removed in this same transaction, so let's just set full
         * sync since it will be a full sync anyway and this will blow away the
         * old info in the log.
         */
        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags);

        key[0].objectid = objectid;
        key[0].type = BTRFS_INODE_ITEM_KEY;
        key[0].offset = 0;

        sizes[0] = sizeof(struct btrfs_inode_item);

        if (name) {
                /*
                 * Start new inodes with an inode_ref. This is slightly more
                 * efficient for small numbers of hard links since they will
                 * be packed into one item. Extended refs will kick in if we
                 * add more hard links than can fit in the ref item.
                 */
                key[1].objectid = objectid;
                key[1].type = BTRFS_INODE_REF_KEY;
                key[1].offset = ref_objectid;

                sizes[1] = name_len + sizeof(*ref);
        }

        location = &BTRFS_I(inode)->location;
        location->objectid = objectid;
        location->offset = 0;
        location->type = BTRFS_INODE_ITEM_KEY;

        ret = btrfs_insert_inode_locked(inode);
        if (ret < 0) {
                iput(inode);
                goto fail;
        }

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, nitems);
        if (ret != 0)
                goto fail_unlock;

        inode_init_owner(inode, dir, mode);
        inode_set_bytes(inode, 0);

        inode->i_mtime = current_time(inode);
        inode->i_atime = inode->i_mtime;
        inode->i_ctime = inode->i_mtime;
        BTRFS_I(inode)->i_otime = inode->i_mtime;

        inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                  struct btrfs_inode_item);
        memzero_extent_buffer(path->nodes[0], (unsigned long)inode_item,
                             sizeof(*inode_item));
        fill_inode_item(trans, path->nodes[0], inode_item, inode);

        if (name) {
                ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                                     struct btrfs_inode_ref);
                btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
                btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
                ptr = (unsigned long)(ref + 1);
                write_extent_buffer(path->nodes[0], name, ptr, name_len);
        }

        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_free_path(path);

        btrfs_inherit_iflags(inode, dir);

        if (S_ISREG(mode)) {
                if (btrfs_test_opt(fs_info, NODATASUM))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
                if (btrfs_test_opt(fs_info, NODATACOW))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW |
                                BTRFS_INODE_NODATASUM;
        }

        inode_tree_add(inode);

        trace_btrfs_inode_new(inode);
        btrfs_set_inode_last_trans(trans, BTRFS_I(inode));

        btrfs_update_root_times(trans, root);

        ret = btrfs_inode_inherit_props(trans, inode, dir);
        if (ret)
                btrfs_err(fs_info,
                          "error inheriting props for ino %llu (root %llu): %d",
                        btrfs_ino(BTRFS_I(inode)), root->root_key.objectid, ret);

        return inode;

fail_unlock:
        discard_new_inode(inode);
fail:
        if (dir && name)
                BTRFS_I(dir)->index_cnt--;
        btrfs_free_path(path);
        return ERR_PTR(ret);
}

/*
 * utility function to add 'inode' into 'parent_inode' with
 * a give name and a given sequence number.
 * if 'add_backref' is true, also insert a backref from the
 * inode to the parent directory.
 */
int btrfs_add_link(struct btrfs_trans_handle *trans,
                   struct btrfs_inode *parent_inode, struct btrfs_inode *inode,
                   const char *name, int name_len, int add_backref, u64 index)
{
        int ret = 0;
        struct btrfs_key key;
        struct btrfs_root *root = parent_inode->root;
        u64 ino = btrfs_ino(inode);
        u64 parent_ino = btrfs_ino(parent_inode);

        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                memcpy(&key, &inode->root->root_key, sizeof(key));
        } else {
                key.objectid = ino;
                key.type = BTRFS_INODE_ITEM_KEY;
                key.offset = 0;
        }

        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                ret = btrfs_add_root_ref(trans, key.objectid,
                                         root->root_key.objectid, parent_ino,
                                         index, name, name_len);
        } else if (add_backref) {
                ret = btrfs_insert_inode_ref(trans, root, name, name_len, ino,
                                             parent_ino, index);
        }

        /* Nothing to clean up yet */
        if (ret)
                return ret;

        ret = btrfs_insert_dir_item(trans, name, name_len, parent_inode, &key,
                                    btrfs_inode_type(&inode->vfs_inode), index);
        if (ret == -EEXIST || ret == -EOVERFLOW)
                goto fail_dir_item;
        else if (ret) {
                btrfs_abort_transaction(trans, ret);
                return ret;
        }

        btrfs_i_size_write(parent_inode, parent_inode->vfs_inode.i_size +
                           name_len * 2);
        inode_inc_iversion(&parent_inode->vfs_inode);
        /*
         * If we are replaying a log tree, we do not want to update the mtime
         * and ctime of the parent directory with the current time, since the
         * log replay procedure is responsible for setting them to their correct
         * values (the ones it had when the fsync was done).
         */
        if (!test_bit(BTRFS_FS_LOG_RECOVERING, &root->fs_info->flags)) {
                struct timespec64 now = current_time(&parent_inode->vfs_inode);

                parent_inode->vfs_inode.i_mtime = now;
                parent_inode->vfs_inode.i_ctime = now;
        }
        ret = btrfs_update_inode(trans, root, &parent_inode->vfs_inode);
        if (ret)
                btrfs_abort_transaction(trans, ret);
        return ret;

fail_dir_item:
        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                u64 local_index;
                int err;
                err = btrfs_del_root_ref(trans, key.objectid,
                                         root->root_key.objectid, parent_ino,
                                         &local_index, name, name_len);
                if (err)
                        btrfs_abort_transaction(trans, err);
        } else if (add_backref) {
                u64 local_index;
                int err;

                err = btrfs_del_inode_ref(trans, root, name, name_len,
                                          ino, parent_ino, &local_index);
                if (err)
                        btrfs_abort_transaction(trans, err);
        }

        /* Return the original error code */
        return ret;
}

static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
                            struct btrfs_inode *dir, struct dentry *dentry,
                            struct btrfs_inode *inode, int backref, u64 index)
{
        int err = btrfs_add_link(trans, dir, inode,
                                 dentry->d_name.name, dentry->d_name.len,
                                 backref, index);
        if (err > 0)
                err = -EEXIST;
        return err;
}

static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
                        umode_t mode, dev_t rdev)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        u64 objectid;
        u64 index = 0;

        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                        dentry->d_name.len, btrfs_ino(BTRFS_I(dir)), objectid,
                        mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                inode = NULL;
                goto out_unlock;
        }

        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_op = &btrfs_special_inode_operations;
        init_special_inode(inode, inode->i_mode, rdev);

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock;

        err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry, BTRFS_I(inode),
                        0, index);
        if (err)
                goto out_unlock;

        btrfs_update_inode(trans, root, inode);
        d_instantiate_new(dentry, inode);

out_unlock:
        btrfs_end_transaction(trans);
        btrfs_btree_balance_dirty(fs_info);
        if (err && inode) {
                inode_dec_link_count(inode);
                discard_new_inode(inode);
        }
        return err;
}

static int btrfs_create(struct inode *dir, struct dentry *dentry,
                        umode_t mode, bool excl)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        u64 objectid;
        u64 index = 0;

        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                        dentry->d_name.len, btrfs_ino(BTRFS_I(dir)), objectid,
                        mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                inode = NULL;
                goto out_unlock;
        }
        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;
        inode->i_mapping->a_ops = &btrfs_aops;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock;

        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_unlock;

        err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry, BTRFS_I(inode),
                        0, index);
        if (err)
                goto out_unlock;

        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
        d_instantiate_new(dentry, inode);

out_unlock:
        btrfs_end_transaction(trans);
        if (err && inode) {
                inode_dec_link_count(inode);
                discard_new_inode(inode);
        }
        btrfs_btree_balance_dirty(fs_info);
        return err;
}

static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
                      struct dentry *dentry)
{
        struct btrfs_trans_handle *trans = NULL;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = d_inode(old_dentry);
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        u64 index;
        int err;
        int drop_inode = 0;

        /* do not allow sys_link's with other subvols of the same device */
        if (root->root_key.objectid != BTRFS_I(inode)->root->root_key.objectid)
                return -EXDEV;

        if (inode->i_nlink >= BTRFS_LINK_MAX)
                return -EMLINK;

        err = btrfs_set_inode_index(BTRFS_I(dir), &index);
        if (err)
                goto fail;

        /*
         * 2 items for inode and inode ref
         * 2 items for dir items
         * 1 item for parent inode
         * 1 item for orphan item deletion if O_TMPFILE
         */
        trans = btrfs_start_transaction(root, inode->i_nlink ? 5 : 6);
        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                trans = NULL;
                goto fail;
        }

        /* There are several dir indexes for this inode, clear the cache. */
        BTRFS_I(inode)->dir_index = 0ULL;
        inc_nlink(inode);
        inode_inc_iversion(inode);
        inode->i_ctime = current_time(inode);
        ihold(inode);
        set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);

        err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry, BTRFS_I(inode),
                        1, index);

        if (err) {
                drop_inode = 1;
        } else {
                struct dentry *parent = dentry->d_parent;

                err = btrfs_update_inode(trans, root, inode);
                if (err)
                        goto fail;
                if (inode->i_nlink == 1) {
                        /*
                         * If new hard link count is 1, it's a file created
                         * with open(2) O_TMPFILE flag.
                         */
                        err = btrfs_orphan_del(trans, BTRFS_I(inode));
                        if (err)
                                goto fail;
                }
                d_instantiate(dentry, inode);
                btrfs_log_new_name(trans, BTRFS_I(inode), NULL, parent);
        }

fail:
        if (trans)
                btrfs_end_transaction(trans);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(fs_info);
        return err;
}

static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct inode *inode = NULL;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int err = 0;
        u64 objectid = 0;
        u64 index = 0;

        /*
         * 2 items for inode and ref
         * 2 items for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_fail;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                        dentry->d_name.len, btrfs_ino(BTRFS_I(dir)), objectid,
                        S_IFDIR | mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                inode = NULL;
                goto out_fail;
        }

        /* these must be set before we unlock the inode */
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_fail;

        btrfs_i_size_write(BTRFS_I(inode), 0);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_fail;

        err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
                        dentry->d_name.name,
                        dentry->d_name.len, 0, index);
        if (err)
                goto out_fail;

        d_instantiate_new(dentry, inode);

out_fail:
        btrfs_end_transaction(trans);
        if (err && inode) {
                inode_dec_link_count(inode);
                discard_new_inode(inode);
        }
        btrfs_btree_balance_dirty(fs_info);
        return err;
}

static noinline int uncompress_inline(struct btrfs_path *path,
                                      struct page *page,
                                      size_t pg_offset, u64 extent_offset,
                                      struct btrfs_file_extent_item *item)
{
        int ret;
        struct extent_buffer *leaf = path->nodes[0];
        char *tmp;
        size_t max_size;
        unsigned long inline_size;
        unsigned long ptr;
        int compress_type;

        WARN_ON(pg_offset != 0);
        compress_type = btrfs_file_extent_compression(leaf, item);
        max_size = btrfs_file_extent_ram_bytes(leaf, item);
        inline_size = btrfs_file_extent_inline_item_len(leaf,
                                        btrfs_item_nr(path->slots[0]));
        tmp = kmalloc(inline_size, GFP_NOFS);
        if (!tmp)
                return -ENOMEM;
        ptr = btrfs_file_extent_inline_start(item);

        read_extent_buffer(leaf, tmp, ptr, inline_size);

        max_size = min_t(unsigned long, PAGE_SIZE, max_size);
        ret = btrfs_decompress(compress_type, tmp, page,
                               extent_offset, inline_size, max_size);

        /*
         * decompression code contains a memset to fill in any space between the end
         * of the uncompressed data and the end of max_size in case the decompressed
         * data ends up shorter than ram_bytes.  That doesn't cover the hole between
         * the end of an inline extent and the beginning of the next block, so we
         * cover that region here.
         */

        if (max_size + pg_offset < PAGE_SIZE) {
                char *map = kmap(page);
                memset(map + pg_offset + max_size, 0, PAGE_SIZE - max_size - pg_offset);
                kunmap(page);
        }
        kfree(tmp);
        return ret;
}

/**
 * btrfs_get_extent - Lookup the first extent overlapping a range in a file.
 * @inode:      file to search in
 * @page:       page to read extent data into if the extent is inline
 * @pg_offset:  offset into @page to copy to
 * @start:      file offset
 * @len:        length of range starting at @start
 *
 * This returns the first &struct extent_map which overlaps with the given
 * range, reading it from the B-tree and caching it if necessary. Note that
 * there may be more extents which overlap the given range after the returned
 * extent_map.
 *
 * If @page is not NULL and the extent is inline, this also reads the extent
 * data directly into the page and marks the extent up to date in the io_tree.
 *
 * Return: ERR_PTR on error, non-NULL extent_map on success.
 */
struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
                                    struct page *page, size_t pg_offset,
                                    u64 start, u64 len)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        int ret = 0;
        u64 extent_start = 0;
        u64 extent_end = 0;
        u64 objectid = btrfs_ino(inode);
        int extent_type = -1;
        struct btrfs_path *path = NULL;
        struct btrfs_root *root = inode->root;
        struct btrfs_file_extent_item *item;
        struct extent_buffer *leaf;
        struct btrfs_key found_key;
        struct extent_map *em = NULL;
        struct extent_map_tree *em_tree = &inode->extent_tree;
        struct extent_io_tree *io_tree = &inode->io_tree;

        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        read_unlock(&em_tree->lock);

        if (em) {
                if (em->start > start || em->start + em->len <= start)
                        free_extent_map(em);
                else if (em->block_start == EXTENT_MAP_INLINE && page)
                        free_extent_map(em);
                else
                        goto out;
        }
        em = alloc_extent_map();
        if (!em) {
                ret = -ENOMEM;
                goto out;
        }
        em->start = EXTENT_MAP_HOLE;
        em->orig_start = EXTENT_MAP_HOLE;
        em->len = (u64)-1;
        em->block_len = (u64)-1;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto out;
        }

        /* Chances are we'll be called again, so go ahead and do readahead */
        path->reada = READA_FORWARD;

        /*
         * Unless we're going to uncompress the inline extent, no sleep would
         * happen.
         */
        path->leave_spinning = 1;

        path->recurse = btrfs_is_free_space_inode(inode);

        ret = btrfs_lookup_file_extent(NULL, root, path, objectid, start, 0);
        if (ret < 0) {
                goto out;
        } else if (ret > 0) {
                if (path->slots[0] == 0)
                        goto not_found;
                path->slots[0]--;
                ret = 0;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_file_extent_item);
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
        if (found_key.objectid != objectid ||
            found_key.type != BTRFS_EXTENT_DATA_KEY) {
                /*
                 * If we backup past the first extent we want to move forward
                 * and see if there is an extent in front of us, otherwise we'll
                 * say there is a hole for our whole search range which can
                 * cause problems.
                 */
                extent_end = start;
                goto next;
        }

        extent_type = btrfs_file_extent_type(leaf, item);
        extent_start = found_key.offset;
        extent_end = btrfs_file_extent_end(path);
        if (extent_type == BTRFS_FILE_EXTENT_REG ||
            extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                /* Only regular file could have regular/prealloc extent */
                if (!S_ISREG(inode->vfs_inode.i_mode)) {
                        ret = -EUCLEAN;
                        btrfs_crit(fs_info,
                "regular/prealloc extent found for non-regular inode %llu",
                                   btrfs_ino(inode));
                        goto out;
                }
                trace_btrfs_get_extent_show_fi_regular(inode, leaf, item,
                                                       extent_start);
        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                trace_btrfs_get_extent_show_fi_inline(inode, leaf, item,
                                                      path->slots[0],
                                                      extent_start);
        }
next:
        if (start >= extent_end) {
                path->slots[0]++;
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out;
                        else if (ret > 0)
                                goto not_found;

                        leaf = path->nodes[0];
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != objectid ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY)
                        goto not_found;
                if (start + len <= found_key.offset)
                        goto not_found;
                if (start > found_key.offset)
                        goto next;

                /* New extent overlaps with existing one */
                em->start = start;
                em->orig_start = start;
                em->len = found_key.offset - start;
                em->block_start = EXTENT_MAP_HOLE;
                goto insert;
        }

        btrfs_extent_item_to_extent_map(inode, path, item, !page, em);

        if (extent_type == BTRFS_FILE_EXTENT_REG ||
            extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                goto insert;
        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                unsigned long ptr;
                char *map;
                size_t size;
                size_t extent_offset;
                size_t copy_size;

                if (!page)
                        goto out;

                size = btrfs_file_extent_ram_bytes(leaf, item);
                extent_offset = page_offset(page) + pg_offset - extent_start;
                copy_size = min_t(u64, PAGE_SIZE - pg_offset,
                                  size - extent_offset);
                em->start = extent_start + extent_offset;
                em->len = ALIGN(copy_size, fs_info->sectorsize);
                em->orig_block_len = em->len;
                em->orig_start = em->start;
                ptr = btrfs_file_extent_inline_start(item) + extent_offset;

                btrfs_set_path_blocking(path);
                if (!PageUptodate(page)) {
                        if (btrfs_file_extent_compression(leaf, item) !=
                            BTRFS_COMPRESS_NONE) {
                                ret = uncompress_inline(path, page, pg_offset,
                                                        extent_offset, item);
                                if (ret)
                                        goto out;
                        } else {
                                map = kmap(page);
                                read_extent_buffer(leaf, map + pg_offset, ptr,
                                                   copy_size);
                                if (pg_offset + copy_size < PAGE_SIZE) {
                                        memset(map + pg_offset + copy_size, 0,
                                               PAGE_SIZE - pg_offset -
                                               copy_size);
                                }
                                kunmap(page);
                        }
                        flush_dcache_page(page);
                }
                set_extent_uptodate(io_tree, em->start,
                                    extent_map_end(em) - 1, NULL, GFP_NOFS);
                goto insert;
        }
not_found:
        em->start = start;
        em->orig_start = start;
        em->len = len;
        em->block_start = EXTENT_MAP_HOLE;
insert:
        ret = 0;
        btrfs_release_path(path);
        if (em->start > start || extent_map_end(em) <= start) {
                btrfs_err(fs_info,
                          "bad extent! em: [%llu %llu] passed [%llu %llu]",
                          em->start, em->len, start, len);
                ret = -EIO;
                goto out;
        }

        write_lock(&em_tree->lock);
        ret = btrfs_add_extent_mapping(fs_info, em_tree, &em, start, len);
        write_unlock(&em_tree->lock);
out:
        btrfs_free_path(path);

        trace_btrfs_get_extent(root, inode, em);

        if (ret) {
                free_extent_map(em);
                return ERR_PTR(ret);
        }
        return em;
}

struct extent_map *btrfs_get_extent_fiemap(struct btrfs_inode *inode,
                                           u64 start, u64 len)
{
        struct extent_map *em;
        struct extent_map *hole_em = NULL;
        u64 delalloc_start = start;
        u64 end;
        u64 delalloc_len;
        u64 delalloc_end;
        int err = 0;

        em = btrfs_get_extent(inode, NULL, 0, start, len);
        if (IS_ERR(em))
                return em;
        /*
         * If our em maps to:
         * - a hole or
         * - a pre-alloc extent,
         * there might actually be delalloc bytes behind it.
         */
        if (em->block_start != EXTENT_MAP_HOLE &&
            !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                return em;
        else
                hole_em = em;

        /* check to see if we've wrapped (len == -1 or similar) */
        end = start + len;
        if (end < start)
                end = (u64)-1;
        else
                end -= 1;

        em = NULL;

        /* ok, we didn't find anything, lets look for delalloc */
        delalloc_len = count_range_bits(&inode->io_tree, &delalloc_start,
                                 end, len, EXTENT_DELALLOC, 1);
        delalloc_end = delalloc_start + delalloc_len;
        if (delalloc_end < delalloc_start)
                delalloc_end = (u64)-1;

        /*
         * We didn't find anything useful, return the original results from
         * get_extent()
         */
        if (delalloc_start > end || delalloc_end <= start) {
                em = hole_em;
                hole_em = NULL;
                goto out;
        }

        /*
         * Adjust the delalloc_start to make sure it doesn't go backwards from
         * the start they passed in
         */
        delalloc_start = max(start, delalloc_start);
        delalloc_len = delalloc_end - delalloc_start;

        if (delalloc_len > 0) {
                u64 hole_start;
                u64 hole_len;
                const u64 hole_end = extent_map_end(hole_em);

                em = alloc_extent_map();
                if (!em) {
                        err = -ENOMEM;
                        goto out;
                }

                ASSERT(hole_em);
                /*
                 * When btrfs_get_extent can't find anything it returns one
                 * huge hole
                 *
                 * Make sure what it found really fits our range, and adjust to
                 * make sure it is based on the start from the caller
                 */
                if (hole_end <= start || hole_em->start > end) {
                       free_extent_map(hole_em);
                       hole_em = NULL;
                } else {
                       hole_start = max(hole_em->start, start);
                       hole_len = hole_end - hole_start;
                }

                if (hole_em && delalloc_start > hole_start) {
                        /*
                         * Our hole starts before our delalloc, so we have to
                         * return just the parts of the hole that go until the
                         * delalloc starts
                         */
                        em->len = min(hole_len, delalloc_start - hole_start);
                        em->start = hole_start;
                        em->orig_start = hole_start;
                        /*
                         * Don't adjust block start at all, it is fixed at
                         * EXTENT_MAP_HOLE
                         */
                        em->block_start = hole_em->block_start;
                        em->block_len = hole_len;
                        if (test_bit(EXTENT_FLAG_PREALLOC, &hole_em->flags))
                                set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                } else {
                        /*
                         * Hole is out of passed range or it starts after
                         * delalloc range
                         */
                        em->start = delalloc_start;
                        em->len = delalloc_len;
                        em->orig_start = delalloc_start;
                        em->block_start = EXTENT_MAP_DELALLOC;
                        em->block_len = delalloc_len;
                }
        } else {
                return hole_em;
        }
out:

        free_extent_map(hole_em);
        if (err) {
                free_extent_map(em);
                return ERR_PTR(err);
        }
        return em;
}

static struct extent_map *btrfs_create_dio_extent(struct btrfs_inode *inode,
                                                  const u64 start,
                                                  const u64 len,
                                                  const u64 orig_start,
                                                  const u64 block_start,
                                                  const u64 block_len,
                                                  const u64 orig_block_len,
                                                  const u64 ram_bytes,
                                                  const int type)
{
        struct extent_map *em = NULL;
        int ret;

        if (type != BTRFS_ORDERED_NOCOW) {
                em = create_io_em(inode, start, len, orig_start, block_start,
                                  block_len, orig_block_len, ram_bytes,
                                  BTRFS_COMPRESS_NONE, /* compress_type */
                                  type);
                if (IS_ERR(em))
                        goto out;
        }
        ret = btrfs_add_ordered_extent_dio(inode, start, block_start, len,
                                           block_len, type);
        if (ret) {
                if (em) {
                        free_extent_map(em);
                        btrfs_drop_extent_cache(inode, start, start + len - 1, 0);
                }
                em = ERR_PTR(ret);
        }
 out:

        return em;
}

static struct extent_map *btrfs_new_extent_direct(struct btrfs_inode *inode,
                                                  u64 start, u64 len)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_map *em;
        struct btrfs_key ins;
        u64 alloc_hint;
        int ret;

        alloc_hint = get_extent_allocation_hint(inode, start, len);
        ret = btrfs_reserve_extent(root, len, len, fs_info->sectorsize,
                                   0, alloc_hint, &ins, 1, 1);
        if (ret)
                return ERR_PTR(ret);

        em = btrfs_create_dio_extent(inode, start, ins.offset, start,
                                     ins.objectid, ins.offset, ins.offset,
                                     ins.offset, BTRFS_ORDERED_REGULAR);
        btrfs_dec_block_group_reservations(fs_info, ins.objectid);
        if (IS_ERR(em))
                btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset,
                                           1);

        return em;
}

/*
 * Check if we can do nocow write into the range [@offset, @offset + @len)
 *
 * @offset:     File offset
 * @len:        The length to write, will be updated to the nocow writeable
 *              range
 * @orig_start: (optional) Return the original file offset of the file extent
 * @orig_len:   (optional) Return the original on-disk length of the file extent
 * @ram_bytes:  (optional) Return the ram_bytes of the file extent
 * @strict:     if true, omit optimizations that might force us into unnecessary
 *              cow. e.g., don't trust generation number.
 *
 * This function will flush ordered extents in the range to ensure proper
 * nocow checks for (nowait == false) case.
 *
 * Return:
 * >0   and update @len if we can do nocow write
 *  0   if we can't do nocow write
 * <0   if error happened
 *
 * NOTE: This only checks the file extents, caller is responsible to wait for
 *       any ordered extents.
 */
noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
                              u64 *orig_start, u64 *orig_block_len,
                              u64 *ram_bytes, bool strict)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_path *path;
        int ret;
        struct extent_buffer *leaf;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 disk_bytenr;
        u64 backref_offset;
        u64 extent_end;
        u64 num_bytes;
        int slot;
        int found_type;
        bool nocow = (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_lookup_file_extent(NULL, root, path,
                        btrfs_ino(BTRFS_I(inode)), offset, 0);
        if (ret < 0)
                goto out;

        slot = path->slots[0];
        if (ret == 1) {
                if (slot == 0) {
                        /* can't find the item, must cow */
                        ret = 0;
                        goto out;
                }
                slot--;
        }
        ret = 0;
        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, slot);
        if (key.objectid != btrfs_ino(BTRFS_I(inode)) ||
            key.type != BTRFS_EXTENT_DATA_KEY) {
                /* not our file or wrong item type, must cow */
                goto out;
        }

        if (key.offset > offset) {
                /* Wrong offset, must cow */
                goto out;
        }

        fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
        found_type = btrfs_file_extent_type(leaf, fi);
        if (found_type != BTRFS_FILE_EXTENT_REG &&
            found_type != BTRFS_FILE_EXTENT_PREALLOC) {
                /* not a regular extent, must cow */
                goto out;
        }

        if (!nocow && found_type == BTRFS_FILE_EXTENT_REG)
                goto out;

        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
        if (extent_end <= offset)
                goto out;

        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
        if (disk_bytenr == 0)
                goto out;

        if (btrfs_file_extent_compression(leaf, fi) ||
            btrfs_file_extent_encryption(leaf, fi) ||
            btrfs_file_extent_other_encoding(leaf, fi))
                goto out;

        /*
         * Do the same check as in btrfs_cross_ref_exist but without the
         * unnecessary search.
         */
        if (!strict &&
            (btrfs_file_extent_generation(leaf, fi) <=
             btrfs_root_last_snapshot(&root->root_item)))
                goto out;

        backref_offset = btrfs_file_extent_offset(leaf, fi);

        if (orig_start) {
                *orig_start = key.offset - backref_offset;
                *orig_block_len = btrfs_file_extent_disk_num_bytes(leaf, fi);
                *ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
        }

        if (btrfs_extent_readonly(fs_info, disk_bytenr))
                goto out;

        num_bytes = min(offset + *len, extent_end) - offset;
        if (!nocow && found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                u64 range_end;

                range_end = round_up(offset + num_bytes,
                                     root->fs_info->sectorsize) - 1;
                ret = test_range_bit(io_tree, offset, range_end,
                                     EXTENT_DELALLOC, 0, NULL);
                if (ret) {
                        ret = -EAGAIN;
                        goto out;
                }
        }

        btrfs_release_path(path);

        /*
         * look for other files referencing this extent, if we
         * find any we must cow
         */

        ret = btrfs_cross_ref_exist(root, btrfs_ino(BTRFS_I(inode)),
                                    key.offset - backref_offset, disk_bytenr,
                                    strict);
        if (ret) {
                ret = 0;
                goto out;
        }

        /*
         * adjust disk_bytenr and num_bytes to cover just the bytes
         * in this extent we are about to write.  If there
         * are any csums in that range we have to cow in order
         * to keep the csums correct
         */
        disk_bytenr += backref_offset;
        disk_bytenr += offset - key.offset;
        if (csum_exist_in_range(fs_info, disk_bytenr, num_bytes))
                goto out;
        /*
         * all of the above have passed, it is safe to overwrite this extent
         * without cow
         */
        *len = num_bytes;
        ret = 1;
out:
        btrfs_free_path(path);
        return ret;
}

static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
                              struct extent_state **cached_state, bool writing)
{
        struct btrfs_ordered_extent *ordered;
        int ret = 0;

        while (1) {
                lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                 cached_state);
                /*
                 * We're concerned with the entire range that we're going to be
                 * doing DIO to, so we need to make sure there's no ordered
                 * extents in this range.
                 */
                ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), lockstart,
                                                     lockend - lockstart + 1);

                /*
                 * We need to make sure there are no buffered pages in this
                 * range either, we could have raced between the invalidate in
                 * generic_file_direct_write and locking the extent.  The
                 * invalidate needs to happen so that reads after a write do not
                 * get stale data.
                 */
                if (!ordered &&
                    (!writing || !filemap_range_has_page(inode->i_mapping,
                                                         lockstart, lockend)))
                        break;

                unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                     cached_state);

                if (ordered) {
                        /*
                         * If we are doing a DIO read and the ordered extent we
                         * found is for a buffered write, we can not wait for it
                         * to complete and retry, because if we do so we can
                         * deadlock with concurrent buffered writes on page
                         * locks. This happens only if our DIO read covers more
                         * than one extent map, if at this point has already
                         * created an ordered extent for a previous extent map
                         * and locked its range in the inode's io tree, and a
                         * concurrent write against that previous extent map's
                         * range and this range started (we unlock the ranges
                         * in the io tree only when the bios complete and
                         * buffered writes always lock pages before attempting
                         * to lock range in the io tree).
                         */
                        if (writing ||
                            test_bit(BTRFS_ORDERED_DIRECT, &ordered->flags))
                                btrfs_start_ordered_extent(inode, ordered, 1);
                        else
                                ret = -ENOTBLK;
                        btrfs_put_ordered_extent(ordered);
                } else {
                        /*
                         * We could trigger writeback for this range (and wait
                         * for it to complete) and then invalidate the pages for
                         * this range (through invalidate_inode_pages2_range()),
                         * but that can lead us to a deadlock with a concurrent
                         * call to readahead (a buffered read or a defrag call
                         * triggered a readahead) on a page lock due to an
                         * ordered dio extent we created before but did not have
                         * yet a corresponding bio submitted (whence it can not
                         * complete), which makes readahead wait for that
                         * ordered extent to complete while holding a lock on
                         * that page.
                         */
                        ret = -ENOTBLK;
                }

                if (ret)
                        break;

                cond_resched();
        }

        return ret;
}

/* The callers of this must take lock_extent() */
static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start,
                                       u64 len, u64 orig_start, u64 block_start,
                                       u64 block_len, u64 orig_block_len,
                                       u64 ram_bytes, int compress_type,
                                       int type)
{
        struct extent_map_tree *em_tree;
        struct extent_map *em;
        int ret;

        ASSERT(type == BTRFS_ORDERED_PREALLOC ||
               type == BTRFS_ORDERED_COMPRESSED ||
               type == BTRFS_ORDERED_NOCOW ||
               type == BTRFS_ORDERED_REGULAR);

        em_tree = &inode->extent_tree;
        em = alloc_extent_map();
        if (!em)
                return ERR_PTR(-ENOMEM);

        em->start = start;
        em->orig_start = orig_start;
        em->len = len;
        em->block_len = block_len;
        em->block_start = block_start;
        em->orig_block_len = orig_block_len;
        em->ram_bytes = ram_bytes;
        em->generation = -1;
        set_bit(EXTENT_FLAG_PINNED, &em->flags);
        if (type == BTRFS_ORDERED_PREALLOC) {
                set_bit(EXTENT_FLAG_FILLING, &em->flags);
        } else if (type == BTRFS_ORDERED_COMPRESSED) {
                set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
                em->compress_type = compress_type;
        }

        do {
                btrfs_drop_extent_cache(inode, em->start,
                                        em->start + em->len - 1, 0);
                write_lock(&em_tree->lock);
                ret = add_extent_mapping(em_tree, em, 1);
                write_unlock(&em_tree->lock);
                /*
                 * The caller has taken lock_extent(), who could race with us
                 * to add em?
                 */
        } while (ret == -EEXIST);

        if (ret) {
                free_extent_map(em);
                return ERR_PTR(ret);
        }

        /* em got 2 refs now, callers needs to do free_extent_map once. */
        return em;
}


static int btrfs_get_blocks_direct_write(struct extent_map **map,
                                         struct inode *inode,
                                         struct btrfs_dio_data *dio_data,
                                         u64 start, u64 len)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct extent_map *em = *map;
        int ret = 0;

        /*
         * We don't allocate a new extent in the following cases
         *
         * 1) The inode is marked as NODATACOW. In this case we'll just use the
         * existing extent.
         * 2) The extent is marked as PREALLOC. We're good to go here and can
         * just use the extent.
         *
         */
        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
            ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
             em->block_start != EXTENT_MAP_HOLE)) {
                int type;
                u64 block_start, orig_start, orig_block_len, ram_bytes;

                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                        type = BTRFS_ORDERED_PREALLOC;
                else
                        type = BTRFS_ORDERED_NOCOW;
                len = min(len, em->len - (start - em->start));
                block_start = em->block_start + (start - em->start);

                if (can_nocow_extent(inode, start, &len, &orig_start,
                                     &orig_block_len, &ram_bytes, false) == 1 &&
                    btrfs_inc_nocow_writers(fs_info, block_start)) {
                        struct extent_map *em2;

                        em2 = btrfs_create_dio_extent(BTRFS_I(inode), start, len,
                                                      orig_start, block_start,
                                                      len, orig_block_len,
                                                      ram_bytes, type);
                        btrfs_dec_nocow_writers(fs_info, block_start);
                        if (type == BTRFS_ORDERED_PREALLOC) {
                                free_extent_map(em);
                                *map = em = em2;
                        }

                        if (em2 && IS_ERR(em2)) {
                                ret = PTR_ERR(em2);
                                goto out;
                        }
                        /*
                         * For inode marked NODATACOW or extent marked PREALLOC,
                         * use the existing or preallocated extent, so does not
                         * need to adjust btrfs_space_info's bytes_may_use.
                         */
                        btrfs_free_reserved_data_space_noquota(fs_info, len);
                        goto skip_cow;
                }
        }

        /* this will cow the extent */
        free_extent_map(em);
        *map = em = btrfs_new_extent_direct(BTRFS_I(inode), start, len);
        if (IS_ERR(em)) {
                ret = PTR_ERR(em);
                goto out;
        }

        len = min(len, em->len - (start - em->start));

skip_cow:
        /*
         * Need to update the i_size under the extent lock so buffered
         * readers will get the updated i_size when we unlock.
         */
        if (start + len > i_size_read(inode))
                i_size_write(inode, start + len);

        dio_data->reserve -= len;
out:
        return ret;
}

static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
                loff_t length, unsigned int flags, struct iomap *iomap,
                struct iomap *srcmap)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct extent_map *em;
        struct extent_state *cached_state = NULL;
        struct btrfs_dio_data *dio_data = NULL;
        u64 lockstart, lockend;
        const bool write = !!(flags & IOMAP_WRITE);
        int ret = 0;
        u64 len = length;
        bool unlock_extents = false;
        bool sync = (current->journal_info == BTRFS_DIO_SYNC_STUB);

        /*
         * We used current->journal_info here to see if we were sync, but
         * there's a lot of tests in the enospc machinery to not do flushing if
         * we have a journal_info set, so we need to clear this out and re-set
         * it in iomap_end.
         */
        ASSERT(current->journal_info == NULL ||
               current->journal_info == BTRFS_DIO_SYNC_STUB);
        current->journal_info = NULL;

        if (!write)
                len = min_t(u64, len, fs_info->sectorsize);

        lockstart = start;
        lockend = start + len - 1;

        /*
         * The generic stuff only does filemap_write_and_wait_range, which
         * isn't enough if we've written compressed pages to this area, so we
         * need to flush the dirty pages again to make absolutely sure that any
         * outstanding dirty pages are on disk.
         */
        if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                     &BTRFS_I(inode)->runtime_flags)) {
                ret = filemap_fdatawrite_range(inode->i_mapping, start,
                                               start + length - 1);
                if (ret)
                        return ret;
        }

        dio_data = kzalloc(sizeof(*dio_data), GFP_NOFS);
        if (!dio_data)
                return -ENOMEM;

        dio_data->sync = sync;
        dio_data->length = length;
        if (write) {
                dio_data->reserve = round_up(length, fs_info->sectorsize);
                ret = btrfs_delalloc_reserve_space(BTRFS_I(inode),
                                &dio_data->data_reserved,
                                start, dio_data->reserve);
                if (ret) {
                        extent_changeset_free(dio_data->data_reserved);
                        kfree(dio_data);
                        return ret;
                }
        }
        iomap->private = dio_data;


        /*
         * If this errors out it's because we couldn't invalidate pagecache for
         * this range and we need to fallback to buffered.
         */
        if (lock_extent_direct(inode, lockstart, lockend, &cached_state, write)) {
                ret = -ENOTBLK;
                goto err;
        }

        em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
        if (IS_ERR(em)) {
                ret = PTR_ERR(em);
                goto unlock_err;
        }

        /*
         * Ok for INLINE and COMPRESSED extents we need to fallback on buffered
         * io.  INLINE is special, and we could probably kludge it in here, but
         * it's still buffered so for safety lets just fall back to the generic
         * buffered path.
         *
         * For COMPRESSED we _have_ to read the entire extent in so we can
         * decompress it, so there will be buffering required no matter what we
         * do, so go ahead and fallback to buffered.
         *
         * We return -ENOTBLK because that's what makes DIO go ahead and go back
         * to buffered IO.  Don't blame me, this is the price we pay for using
         * the generic code.
         */
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) ||
            em->block_start == EXTENT_MAP_INLINE) {
                free_extent_map(em);
                ret = -ENOTBLK;
                goto unlock_err;
        }

        len = min(len, em->len - (start - em->start));
        if (write) {
                ret = btrfs_get_blocks_direct_write(&em, inode, dio_data,
                                                    start, len);
                if (ret < 0)
                        goto unlock_err;
                unlock_extents = true;
                /* Recalc len in case the new em is smaller than requested */
                len = min(len, em->len - (start - em->start));
        } else {
                /*
                 * We need to unlock only the end area that we aren't using.
                 * The rest is going to be unlocked by the endio routine.
                 */
                lockstart = start + len;
                if (lockstart < lockend)
                        unlock_extents = true;
        }

        if (unlock_extents)
                unlock_extent_cached(&BTRFS_I(inode)->io_tree,
                                     lockstart, lockend, &cached_state);
        else
                free_extent_state(cached_state);

        /*
         * Translate extent map information to iomap.
         * We trim the extents (and move the addr) even though iomap code does
         * that, since we have locked only the parts we are performing I/O in.
         */
        if ((em->block_start == EXTENT_MAP_HOLE) ||
            (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) && !write)) {
                iomap->addr = IOMAP_NULL_ADDR;
                iomap->type = IOMAP_HOLE;
        } else {
                iomap->addr = em->block_start + (start - em->start);
                iomap->type = IOMAP_MAPPED;
        }
        iomap->offset = start;
        iomap->bdev = fs_info->fs_devices->latest_bdev;
        iomap->length = len;

        free_extent_map(em);

        return 0;

unlock_err:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                             &cached_state);
err:
        if (dio_data) {
                btrfs_delalloc_release_space(BTRFS_I(inode),
                                dio_data->data_reserved, start,
                                dio_data->reserve, true);
                btrfs_delalloc_release_extents(BTRFS_I(inode), dio_data->reserve);
                extent_changeset_free(dio_data->data_reserved);
                kfree(dio_data);
        }
        return ret;
}

static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos, loff_t length,
                ssize_t written, unsigned int flags, struct iomap *iomap)
{
        int ret = 0;
        struct btrfs_dio_data *dio_data = iomap->private;
        size_t submitted = dio_data->submitted;
        const bool write = !!(flags & IOMAP_WRITE);

        if (!write && (iomap->type == IOMAP_HOLE)) {
                /* If reading from a hole, unlock and return */
                unlock_extent(&BTRFS_I(inode)->io_tree, pos, pos + length - 1);
                goto out;
        }

        if (submitted < length) {
                pos += submitted;
                length -= submitted;
                if (write)
                        __endio_write_update_ordered(BTRFS_I(inode), pos,
                                        length, false);
                else
                        unlock_extent(&BTRFS_I(inode)->io_tree, pos,
                                      pos + length - 1);
                ret = -ENOTBLK;
        }

        if (write) {
                if (dio_data->reserve)
                        btrfs_delalloc_release_space(BTRFS_I(inode),
                                        dio_data->data_reserved, pos,
                                        dio_data->reserve, true);
                btrfs_delalloc_release_extents(BTRFS_I(inode), dio_data->length);
                extent_changeset_free(dio_data->data_reserved);
        }
out:
        /*
         * We're all done, we can re-set the current->journal_info now safely
         * for our endio.
         */
        if (dio_data->sync) {
                ASSERT(current->journal_info == NULL);
                current->journal_info = BTRFS_DIO_SYNC_STUB;
        }
        kfree(dio_data);
        iomap->private = NULL;

        return ret;
}

static void btrfs_dio_private_put(struct btrfs_dio_private *dip)
{
        /*
         * This implies a barrier so that stores to dio_bio->bi_status before
         * this and loads of dio_bio->bi_status after this are fully ordered.
         */
        if (!refcount_dec_and_test(&dip->refs))
                return;

        if (bio_op(dip->dio_bio) == REQ_OP_WRITE) {
                __endio_write_update_ordered(BTRFS_I(dip->inode),
                                             dip->logical_offset,
                                             dip->bytes,
                                             !dip->dio_bio->bi_status);
        } else {
                unlock_extent(&BTRFS_I(dip->inode)->io_tree,
                              dip->logical_offset,
                              dip->logical_offset + dip->bytes - 1);
        }

        bio_endio(dip->dio_bio);
        kfree(dip);
}

static blk_status_t submit_dio_repair_bio(struct inode *inode, struct bio *bio,
                                          int mirror_num,
                                          unsigned long bio_flags)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        blk_status_t ret;

        BUG_ON(bio_op(bio) == REQ_OP_WRITE);

        ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
        if (ret)
                return ret;

        refcount_inc(&dip->refs);
        ret = btrfs_map_bio(fs_info, bio, mirror_num);
        if (ret)
                refcount_dec(&dip->refs);
        return ret;
}

static blk_status_t btrfs_check_read_dio_bio(struct inode *inode,
                                             struct btrfs_io_bio *io_bio,
                                             const bool uptodate)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        const u32 sectorsize = fs_info->sectorsize;
        struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
        struct bio_vec bvec;
        struct bvec_iter iter;
        u64 start = io_bio->logical;
        int icsum = 0;
        blk_status_t err = BLK_STS_OK;

        __bio_for_each_segment(bvec, &io_bio->bio, iter, io_bio->iter) {
                unsigned int i, nr_sectors, pgoff;

                nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);
                pgoff = bvec.bv_offset;
                for (i = 0; i < nr_sectors; i++) {
                        ASSERT(pgoff < PAGE_SIZE);
                        if (uptodate &&
                            (!csum || !check_data_csum(inode, io_bio, icsum,
                                                       bvec.bv_page, pgoff,
                                                       start, sectorsize))) {
                                clean_io_failure(fs_info, failure_tree, io_tree,
                                                 start, bvec.bv_page,
                                                 btrfs_ino(BTRFS_I(inode)),
                                                 pgoff);
                        } else {
                                blk_status_t status;

                                status = btrfs_submit_read_repair(inode,
                                                        &io_bio->bio,
                                                        start - io_bio->logical,
                                                        bvec.bv_page, pgoff,
                                                        start,
                                                        start + sectorsize - 1,
                                                        io_bio->mirror_num,
                                                        submit_dio_repair_bio);
                                if (status)
                                        err = status;
                        }
                        start += sectorsize;
                        icsum++;
                        pgoff += sectorsize;
                }
        }
        return err;
}

static void __endio_write_update_ordered(struct btrfs_inode *inode,
                                         const u64 offset, const u64 bytes,
                                         const bool uptodate)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_ordered_extent *ordered = NULL;
        struct btrfs_workqueue *wq;
        u64 ordered_offset = offset;
        u64 ordered_bytes = bytes;
        u64 last_offset;

        if (btrfs_is_free_space_inode(inode))
                wq = fs_info->endio_freespace_worker;
        else
                wq = fs_info->endio_write_workers;

        while (ordered_offset < offset + bytes) {
                last_offset = ordered_offset;
                if (btrfs_dec_test_first_ordered_pending(inode, &ordered,
                                                         &ordered_offset,
                                                         ordered_bytes,
                                                         uptodate)) {
                        btrfs_init_work(&ordered->work, finish_ordered_fn, NULL,
                                        NULL);
                        btrfs_queue_work(wq, &ordered->work);
                }
                /*
                 * If btrfs_dec_test_ordered_pending does not find any ordered
                 * extent in the range, we can exit.
                 */
                if (ordered_offset == last_offset)
                        return;
                /*
                 * Our bio might span multiple ordered extents. In this case
                 * we keep going until we have accounted the whole dio.
                 */
                if (ordered_offset < offset + bytes) {
                        ordered_bytes = offset + bytes - ordered_offset;
                        ordered = NULL;
                }
        }
}

static blk_status_t btrfs_submit_bio_start_direct_io(void *private_data,
                                    struct bio *bio, u64 offset)
{
        struct inode *inode = private_data;

        return btrfs_csum_one_bio(BTRFS_I(inode), bio, offset, 1);
}

static void btrfs_end_dio_bio(struct bio *bio)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        blk_status_t err = bio->bi_status;

        if (err)
                btrfs_warn(BTRFS_I(dip->inode)->root->fs_info,
                           "direct IO failed ino %llu rw %d,%u sector %#Lx len %u err no %d",
                           btrfs_ino(BTRFS_I(dip->inode)), bio_op(bio),
                           bio->bi_opf,
                           (unsigned long long)bio->bi_iter.bi_sector,
                           bio->bi_iter.bi_size, err);

        if (bio_op(bio) == REQ_OP_READ) {
                err = btrfs_check_read_dio_bio(dip->inode, btrfs_io_bio(bio),
                                               !err);
        }

        if (err)
                dip->dio_bio->bi_status = err;

        bio_put(bio);
        btrfs_dio_private_put(dip);
}

static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
                struct inode *inode, u64 file_offset, int async_submit)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_dio_private *dip = bio->bi_private;
        bool write = bio_op(bio) == REQ_OP_WRITE;
        blk_status_t ret;

        /* Check btrfs_submit_bio_hook() for rules about async submit. */
        if (async_submit)
                async_submit = !atomic_read(&BTRFS_I(inode)->sync_writers);

        if (!write) {
                ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
                if (ret)
                        goto err;
        }

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
                goto map;

        if (write && async_submit) {
                ret = btrfs_wq_submit_bio(fs_info, bio, 0, 0,
                                          file_offset, inode,
                                          btrfs_submit_bio_start_direct_io);
                goto err;
        } else if (write) {
                /*
                 * If we aren't doing async submit, calculate the csum of the
                 * bio now.
                 */
                ret = btrfs_csum_one_bio(BTRFS_I(inode), bio, file_offset, 1);
                if (ret)
                        goto err;
        } else {
                u64 csum_offset;

                csum_offset = file_offset - dip->logical_offset;
                csum_offset >>= inode->i_sb->s_blocksize_bits;
                csum_offset *= btrfs_super_csum_size(fs_info->super_copy);
                btrfs_io_bio(bio)->csum = dip->csums + csum_offset;
        }
map:
        ret = btrfs_map_bio(fs_info, bio, 0);
err:
        return ret;
}

/*
 * If this succeeds, the btrfs_dio_private is responsible for cleaning up locked
 * or ordered extents whether or not we submit any bios.
 */
static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio,
                                                          struct inode *inode,
                                                          loff_t file_offset)
{
        const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
        const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
        size_t dip_size;
        struct btrfs_dio_private *dip;

        dip_size = sizeof(*dip);
        if (!write && csum) {
                struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
                const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
                size_t nblocks;

                nblocks = dio_bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
                dip_size += csum_size * nblocks;
        }

        dip = kzalloc(dip_size, GFP_NOFS);
        if (!dip)
                return NULL;

        dip->inode = inode;
        dip->logical_offset = file_offset;
        dip->bytes = dio_bio->bi_iter.bi_size;
        dip->disk_bytenr = (u64)dio_bio->bi_iter.bi_sector << 9;
        dip->dio_bio = dio_bio;
        refcount_set(&dip->refs, 1);
        return dip;
}

static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
                struct bio *dio_bio, loff_t file_offset)
{
        const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
        const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        const bool raid56 = (btrfs_data_alloc_profile(fs_info) &
                             BTRFS_BLOCK_GROUP_RAID56_MASK);
        struct btrfs_dio_private *dip;
        struct bio *bio;
        u64 start_sector;
        int async_submit = 0;
        u64 submit_len;
        int clone_offset = 0;
        int clone_len;
        int ret;
        blk_status_t status;
        struct btrfs_io_geometry geom;
        struct btrfs_dio_data *dio_data = iomap->private;

        dip = btrfs_create_dio_private(dio_bio, inode, file_offset);
        if (!dip) {
                if (!write) {
                        unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,
                                file_offset + dio_bio->bi_iter.bi_size - 1);
                }
                dio_bio->bi_status = BLK_STS_RESOURCE;
                bio_endio(dio_bio);
                return BLK_QC_T_NONE;
        }

        if (!write && csum) {
                /*
                 * Load the csums up front to reduce csum tree searches and
                 * contention when submitting bios.
                 */
                status = btrfs_lookup_bio_sums(inode, dio_bio, file_offset,
                                               dip->csums);
                if (status != BLK_STS_OK)
                        goto out_err;
        }

        start_sector = dio_bio->bi_iter.bi_sector;
        submit_len = dio_bio->bi_iter.bi_size;

        do {
                ret = btrfs_get_io_geometry(fs_info, btrfs_op(dio_bio),
                                            start_sector << 9, submit_len,
                                            &geom);
                if (ret) {
                        status = errno_to_blk_status(ret);
                        goto out_err;
                }
                ASSERT(geom.len <= INT_MAX);

                clone_len = min_t(int, submit_len, geom.len);

                /*
                 * This will never fail as it's passing GPF_NOFS and
                 * the allocation is backed by btrfs_bioset.
                 */
                bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len);
                bio->bi_private = dip;
                bio->bi_end_io = btrfs_end_dio_bio;
                btrfs_io_bio(bio)->logical = file_offset;

                ASSERT(submit_len >= clone_len);
                submit_len -= clone_len;

                /*
                 * Increase the count before we submit the bio so we know
                 * the end IO handler won't happen before we increase the
                 * count. Otherwise, the dip might get freed before we're
                 * done setting it up.
                 *
                 * We transfer the initial reference to the last bio, so we
                 * don't need to increment the reference count for the last one.
                 */
                if (submit_len > 0) {
                        refcount_inc(&dip->refs);
                        /*
                         * If we are submitting more than one bio, submit them
                         * all asynchronously. The exception is RAID 5 or 6, as
                         * asynchronous checksums make it difficult to collect
                         * full stripe writes.
                         */
                        if (!raid56)
                                async_submit = 1;
                }

                status = btrfs_submit_dio_bio(bio, inode, file_offset,
                                                async_submit);
                if (status) {
                        bio_put(bio);
                        if (submit_len > 0)
                                refcount_dec(&dip->refs);
                        goto out_err;
                }

                dio_data->submitted += clone_len;
                clone_offset += clone_len;
                start_sector += clone_len >> 9;
                file_offset += clone_len;
        } while (submit_len > 0);
        return BLK_QC_T_NONE;

out_err:
        dip->dio_bio->bi_status = status;
        btrfs_dio_private_put(dip);
        return BLK_QC_T_NONE;
}

static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
                               const struct iov_iter *iter, loff_t offset)
{
        int seg;
        int i;
        unsigned int blocksize_mask = fs_info->sectorsize - 1;
        ssize_t retval = -EINVAL;

        if (offset & blocksize_mask)
                goto out;

        if (iov_iter_alignment(iter) & blocksize_mask)
                goto out;

        /* If this is a write we don't need to check anymore */
        if (iov_iter_rw(iter) != READ || !iter_is_iovec(iter))
                return 0;
        /*
         * Check to make sure we don't have duplicate iov_base's in this
         * iovec, if so return EINVAL, otherwise we'll get csum errors
         * when reading back.
         */
        for (seg = 0; seg < iter->nr_segs; seg++) {
                for (i = seg + 1; i < iter->nr_segs; i++) {
                        if (iter->iov[seg].iov_base == iter->iov[i].iov_base)
                                goto out;
                }
        }
        retval = 0;
out:
        return retval;
}

static inline int btrfs_maybe_fsync_end_io(struct kiocb *iocb, ssize_t size,
                                           int error, unsigned flags)
{
        /*
         * Now if we're still in the context of our submitter we know we can't
         * safely run generic_write_sync(), so clear our flag here so that the
         * caller knows to follow up with a sync.
         */
        if (current->journal_info == BTRFS_DIO_SYNC_STUB) {
                current->journal_info = NULL;
                return error;
        }

        if (error)
                return error;

        if (size) {
                iocb->ki_flags |= IOCB_DSYNC;
                return generic_write_sync(iocb, size);
        }

        return 0;
}

static const struct iomap_ops btrfs_dio_iomap_ops = {
        .iomap_begin            = btrfs_dio_iomap_begin,
        .iomap_end              = btrfs_dio_iomap_end,
};

static const struct iomap_dio_ops btrfs_dio_ops = {
        .submit_io              = btrfs_submit_direct,
};

static const struct iomap_dio_ops btrfs_sync_dops = {
        .submit_io              = btrfs_submit_direct,
        .end_io                 = btrfs_maybe_fsync_end_io,
};

ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct extent_changeset *data_reserved = NULL;
        loff_t offset = iocb->ki_pos;
        size_t count = 0;
        bool relock = false;
        ssize_t ret;

        if (check_direct_IO(fs_info, iter, offset))
                return 0;

        count = iov_iter_count(iter);
        if (iov_iter_rw(iter) == WRITE) {
                /*
                 * If the write DIO is beyond the EOF, we need update
                 * the isize, but it is protected by i_mutex. So we can
                 * not unlock the i_mutex at this case.
                 */
                if (offset + count <= inode->i_size) {
                        inode_unlock(inode);
                        relock = true;
                }
                down_read(&BTRFS_I(inode)->dio_sem);
        }

        /*
         * We have are actually a sync iocb, so we need our fancy endio to know
         * if we need to sync.
         */
        if (current->journal_info)
                ret = iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops,
                                   &btrfs_sync_dops, is_sync_kiocb(iocb));
        else
                ret = iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops,
                                   &btrfs_dio_ops, is_sync_kiocb(iocb));

        if (ret == -ENOTBLK)
                ret = 0;

        if (iov_iter_rw(iter) == WRITE)
                up_read(&BTRFS_I(inode)->dio_sem);

        if (relock)
                inode_lock(inode);

        extent_changeset_free(data_reserved);
        return ret;
}

static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                        u64 start, u64 len)
{
        int     ret;

        ret = fiemap_prep(inode, fieinfo, start, &len, 0);
        if (ret)
                return ret;

        return extent_fiemap(BTRFS_I(inode), fieinfo, start, len);
}

int btrfs_readpage(struct file *file, struct page *page)
{
        return extent_read_full_page(page, btrfs_get_extent, 0);
}

static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        int ret;

        if (current->flags & PF_MEMALLOC) {
                redirty_page_for_writepage(wbc, page);
                unlock_page(page);
                return 0;
        }

        /*
         * If we are under memory pressure we will call this directly from the
         * VM, we need to make sure we have the inode referenced for the ordered
         * extent.  If not just return like we didn't do anything.
         */
        if (!igrab(inode)) {
                redirty_page_for_writepage(wbc, page);
                return AOP_WRITEPAGE_ACTIVATE;
        }
        ret = extent_write_full_page(page, wbc);
        btrfs_add_delayed_iput(inode);
        return ret;
}

static int btrfs_writepages(struct address_space *mapping,
                            struct writeback_control *wbc)
{
        return extent_writepages(mapping, wbc);
}

static void btrfs_readahead(struct readahead_control *rac)
{
        extent_readahead(rac);
}

static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        int ret = try_release_extent_mapping(page, gfp_flags);
        if (ret == 1)
                detach_page_private(page);
        return ret;
}

static int btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        if (PageWriteback(page) || PageDirty(page))
                return 0;
        return __btrfs_releasepage(page, gfp_flags);
}

#ifdef CONFIG_MIGRATION
static int btrfs_migratepage(struct address_space *mapping,
                             struct page *newpage, struct page *page,
                             enum migrate_mode mode)
{
        int ret;

        ret = migrate_page_move_mapping(mapping, newpage, page, 0);
        if (ret != MIGRATEPAGE_SUCCESS)
                return ret;

        if (page_has_private(page))
                attach_page_private(newpage, detach_page_private(page));

        if (PagePrivate2(page)) {
                ClearPagePrivate2(page);
                SetPagePrivate2(newpage);
        }

        if (mode != MIGRATE_SYNC_NO_COPY)
                migrate_page_copy(newpage, page);
        else
                migrate_page_states(newpage, page);
        return MIGRATEPAGE_SUCCESS;
}
#endif

static void btrfs_invalidatepage(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
        struct extent_io_tree *tree = &inode->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        u64 page_start = page_offset(page);
        u64 page_end = page_start + PAGE_SIZE - 1;
        u64 start;
        u64 end;
        int inode_evicting = inode->vfs_inode.i_state & I_FREEING;

        /*
         * we have the page locked, so new writeback can't start,
         * and the dirty bit won't be cleared while we are here.
         *
         * Wait for IO on this page so that we can safely clear
         * the PagePrivate2 bit and do ordered accounting
         */
        wait_on_page_writeback(page);

        if (offset) {
                btrfs_releasepage(page, GFP_NOFS);
                return;
        }

        if (!inode_evicting)
                lock_extent_bits(tree, page_start, page_end, &cached_state);
again:
        start = page_start;
        ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1);
        if (ordered) {
                end = min(page_end,
                          ordered->file_offset + ordered->num_bytes - 1);
                /*
                 * IO on this page will never be started, so we need
                 * to account for any ordered extents now
                 */
                if (!inode_evicting)
                        clear_extent_bit(tree, start, end,
                                         EXTENT_DELALLOC | EXTENT_DELALLOC_NEW |
                                         EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
                                         EXTENT_DEFRAG, 1, 0, &cached_state);
                /*
                 * whoever cleared the private bit is responsible
                 * for the finish_ordered_io
                 */
                if (TestClearPagePrivate2(page)) {
                        struct btrfs_ordered_inode_tree *tree;
                        u64 new_len;

                        tree = &inode->ordered_tree;

                        spin_lock_irq(&tree->lock);
                        set_bit(BTRFS_ORDERED_TRUNCATED, &ordered->flags);
                        new_len = start - ordered->file_offset;
                        if (new_len < ordered->truncated_len)
                                ordered->truncated_len = new_len;
                        spin_unlock_irq(&tree->lock);

                        if (btrfs_dec_test_ordered_pending(inode, &ordered,
                                                           start,
                                                           end - start + 1, 1))
                                btrfs_finish_ordered_io(ordered);
                }
                btrfs_put_ordered_extent(ordered);
                if (!inode_evicting) {
                        cached_state = NULL;
                        lock_extent_bits(tree, start, end,
                                         &cached_state);
                }

                start = end + 1;
                if (start < page_end)
                        goto again;
        }

        /*
         * Qgroup reserved space handler
         * Page here will be either
         * 1) Already written to disk or ordered extent already submitted
         *    Then its QGROUP_RESERVED bit in io_tree is already cleaned.
         *    Qgroup will be handled by its qgroup_record then.
         *    btrfs_qgroup_free_data() call will do nothing here.
         *
         * 2) Not written to disk yet
         *    Then btrfs_qgroup_free_data() call will clear the QGROUP_RESERVED
         *    bit of its io_tree, and free the qgroup reserved data space.
         *    Since the IO will never happen for this page.
         */
        btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE);
        if (!inode_evicting) {
                clear_extent_bit(tree, page_start, page_end, EXTENT_LOCKED |
                                 EXTENT_DELALLOC | EXTENT_DELALLOC_NEW |
                                 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 1, 1,
                                 &cached_state);

                __btrfs_releasepage(page, GFP_NOFS);
        }

        ClearPageChecked(page);
        detach_page_private(page);
}

/*
 * btrfs_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
 * truncate_setsize() writes the inode size before removing pages, once we have
 * the page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
 */
vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct inode *inode = file_inode(vmf->vma->vm_file);
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        struct extent_changeset *data_reserved = NULL;
        char *kaddr;
        unsigned long zero_start;
        loff_t size;
        vm_fault_t ret;
        int ret2;
        int reserved = 0;
        u64 reserved_space;
        u64 page_start;
        u64 page_end;
        u64 end;

        reserved_space = PAGE_SIZE;

        sb_start_pagefault(inode->i_sb);
        page_start = page_offset(page);
        page_end = page_start + PAGE_SIZE - 1;
        end = page_end;

        /*
         * Reserving delalloc space after obtaining the page lock can lead to
         * deadlock. For example, if a dirty page is locked by this function
         * and the call to btrfs_delalloc_reserve_space() ends up triggering
         * dirty page write out, then the btrfs_writepage() function could
         * end up waiting indefinitely to get a lock on the page currently
         * being processed by btrfs_page_mkwrite() function.
         */
        ret2 = btrfs_delalloc_reserve_space(BTRFS_I(inode), &data_reserved,
                                            page_start, reserved_space);
        if (!ret2) {
                ret2 = file_update_time(vmf->vma->vm_file);
                reserved = 1;
        }
        if (ret2) {
                ret = vmf_error(ret2);
                if (reserved)
                        goto out;
                goto out_noreserve;
        }

        ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
again:
        lock_page(page);
        size = i_size_read(inode);

        if ((page->mapping != inode->i_mapping) ||
            (page_start >= size)) {
                /* page got truncated out from underneath us */
                goto out_unlock;
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, page_start, page_end, &cached_state);
        set_page_extent_mapped(page);

        /*
         * we can't set the delalloc bits if there are pending ordered
         * extents.  Drop our locks and wait for them to finish
         */
        ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), page_start,
                        PAGE_SIZE);
        if (ordered) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        if (page->index == ((size - 1) >> PAGE_SHIFT)) {
                reserved_space = round_up(size - page_start,
                                          fs_info->sectorsize);
                if (reserved_space < PAGE_SIZE) {
                        end = page_start + reserved_space - 1;
                        btrfs_delalloc_release_space(BTRFS_I(inode),
                                        data_reserved, page_start,
                                        PAGE_SIZE - reserved_space, true);
                }
        }

        /*
         * page_mkwrite gets called when the page is firstly dirtied after it's
         * faulted in, but write(2) could also dirty a page and set delalloc
         * bits, thus in this case for space account reason, we still need to
         * clear any delalloc bits within this page range since we have to
         * reserve data&meta space before lock_page() (see above comments).
         */
        clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, end,
                          EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
                          EXTENT_DEFRAG, 0, 0, &cached_state);

        ret2 = btrfs_set_extent_delalloc(BTRFS_I(inode), page_start, end, 0,
                                        &cached_state);
        if (ret2) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state);
                ret = VM_FAULT_SIGBUS;
                goto out_unlock;
        }

        /* page is wholly or partially inside EOF */
        if (page_start + PAGE_SIZE > size)
                zero_start = offset_in_page(size);
        else
                zero_start = PAGE_SIZE;

        if (zero_start != PAGE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + zero_start, 0, PAGE_SIZE - zero_start);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        SetPageUptodate(page);

        BTRFS_I(inode)->last_trans = fs_info->generation;
        BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;
        BTRFS_I(inode)->last_log_commit = BTRFS_I(inode)->root->last_log_commit;

        unlock_extent_cached(io_tree, page_start, page_end, &cached_state);

        btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
        sb_end_pagefault(inode->i_sb);
        extent_changeset_free(data_reserved);
        return VM_FAULT_LOCKED;

out_unlock:
        unlock_page(page);
out:
        btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
        btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved, page_start,
                                     reserved_space, (ret != 0));
out_noreserve:
        sb_end_pagefault(inode->i_sb);
        extent_changeset_free(data_reserved);
        return ret;
}

static int btrfs_truncate(struct inode *inode, bool skip_writeback)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *rsv;
        int ret;
        struct btrfs_trans_handle *trans;
        u64 mask = fs_info->sectorsize - 1;
        u64 min_size = btrfs_calc_metadata_size(fs_info, 1);

        if (!skip_writeback) {
                ret = btrfs_wait_ordered_range(inode, inode->i_size & (~mask),
                                               (u64)-1);
                if (ret)
                        return ret;
        }

        /*
         * Yes ladies and gentlemen, this is indeed ugly.  We have a couple of
         * things going on here:
         *
         * 1) We need to reserve space to update our inode.
         *
         * 2) We need to have something to cache all the space that is going to
         * be free'd up by the truncate operation, but also have some slack
         * space reserved in case it uses space during the truncate (thank you
         * very much snapshotting).
         *
         * And we need these to be separate.  The fact is we can use a lot of
         * space doing the truncate, and we have no earthly idea how much space
         * we will use, so we need the truncate reservation to be separate so it
         * doesn't end up using space reserved for updating the inode.  We also
         * need to be able to stop the transaction and start a new one, which
         * means we need to be able to update the inode several times, and we
         * have no idea of knowing how many times that will be, so we can't just
         * reserve 1 item for the entirety of the operation, so that has to be
         * done separately as well.
         *
         * So that leaves us with
         *
         * 1) rsv - for the truncate reservation, which we will steal from the
         * transaction reservation.
         * 2) fs_info->trans_block_rsv - this will have 1 items worth left for
         * updating the inode.
         */
        rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);
        if (!rsv)
                return -ENOMEM;
        rsv->size = min_size;
        rsv->failfast = 1;

        /*
         * 1 for the truncate slack space
         * 1 for updating the inode.
         */
        trans = btrfs_start_transaction(root, 2);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out;
        }

        /* Migrate the slack space for the truncate to our reserve */
        ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,
                                      min_size, false);
        BUG_ON(ret);

        /*
         * So if we truncate and then write and fsync we normally would just
         * write the extents that changed, which is a problem if we need to
         * first truncate that entire inode.  So set this flag so we write out
         * all of the extents in the inode to the sync log so we're completely
         * safe.
         */
        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags);
        trans->block_rsv = rsv;

        while (1) {
                ret = btrfs_truncate_inode_items(trans, root, inode,
                                                 inode->i_size,
                                                 BTRFS_EXTENT_DATA_KEY);
                trans->block_rsv = &fs_info->trans_block_rsv;
                if (ret != -ENOSPC && ret != -EAGAIN)
                        break;

                ret = btrfs_update_inode(trans, root, inode);
                if (ret)
                        break;

                btrfs_end_transaction(trans);
                btrfs_btree_balance_dirty(fs_info);

                trans = btrfs_start_transaction(root, 2);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        trans = NULL;
                        break;
                }

                btrfs_block_rsv_release(fs_info, rsv, -1, NULL);
                ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,
                                              rsv, min_size, false);
                BUG_ON(ret);    /* shouldn't happen */
                trans->block_rsv = rsv;
        }

        /*
         * We can't call btrfs_truncate_block inside a trans handle as we could
         * deadlock with freeze, if we got NEED_TRUNCATE_BLOCK then we know
         * we've truncated everything except the last little bit, and can do
         * btrfs_truncate_block and then update the disk_i_size.
         */
        if (ret == NEED_TRUNCATE_BLOCK) {
                btrfs_end_transaction(trans);
                btrfs_btree_balance_dirty(fs_info);

                ret = btrfs_truncate_block(inode, inode->i_size, 0, 0);
                if (ret)
                        goto out;
                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        goto out;
                }
                btrfs_inode_safe_disk_i_size_write(inode, 0);
        }

        if (trans) {
                int ret2;

                trans->block_rsv = &fs_info->trans_block_rsv;
                ret2 = btrfs_update_inode(trans, root, inode);
                if (ret2 && !ret)
                        ret = ret2;

                ret2 = btrfs_end_transaction(trans);
                if (ret2 && !ret)
                        ret = ret2;
                btrfs_btree_balance_dirty(fs_info);
        }
out:
        btrfs_free_block_rsv(fs_info, rsv);

        return ret;
}

/*
 * create a new subvolume directory/inode (helper for the ioctl).
 */
int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
                             struct btrfs_root *new_root,
                             struct btrfs_root *parent_root,
                             u64 new_dirid)
{
        struct inode *inode;
        int err;
        u64 index = 0;

        inode = btrfs_new_inode(trans, new_root, NULL, "..", 2,
                                new_dirid, new_dirid,
                                S_IFDIR | (~current_umask() & S_IRWXUGO),
                                &index);
        if (IS_ERR(inode))
                return PTR_ERR(inode);
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;

        set_nlink(inode, 1);
        btrfs_i_size_write(BTRFS_I(inode), 0);
        unlock_new_inode(inode);

        err = btrfs_subvol_inherit_props(trans, new_root, parent_root);
        if (err)
                btrfs_err(new_root->fs_info,
                          "error inheriting subvolume %llu properties: %d",
                          new_root->root_key.objectid, err);

        err = btrfs_update_inode(trans, new_root, inode);

        iput(inode);
        return err;
}

struct inode *btrfs_alloc_inode(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_inode *ei;
        struct inode *inode;

        ei = kmem_cache_alloc(btrfs_inode_cachep, GFP_KERNEL);
        if (!ei)
                return NULL;

        ei->root = NULL;
        ei->generation = 0;
        ei->last_trans = 0;
        ei->last_sub_trans = 0;
        ei->logged_trans = 0;
        ei->delalloc_bytes = 0;
        ei->new_delalloc_bytes = 0;
        ei->defrag_bytes = 0;
        ei->disk_i_size = 0;
        ei->flags = 0;
        ei->csum_bytes = 0;
        ei->index_cnt = (u64)-1;
        ei->dir_index = 0;
        ei->last_unlink_trans = 0;
        ei->last_reflink_trans = 0;
        ei->last_log_commit = 0;

        spin_lock_init(&ei->lock);
        ei->outstanding_extents = 0;
        if (sb->s_magic != BTRFS_TEST_MAGIC)
                btrfs_init_metadata_block_rsv(fs_info, &ei->block_rsv,
                                              BTRFS_BLOCK_RSV_DELALLOC);
        ei->runtime_flags = 0;
        ei->prop_compress = BTRFS_COMPRESS_NONE;
        ei->defrag_compress = BTRFS_COMPRESS_NONE;

        ei->delayed_node = NULL;

        ei->i_otime.tv_sec = 0;
        ei->i_otime.tv_nsec = 0;

        inode = &ei->vfs_inode;
        extent_map_tree_init(&ei->extent_tree);
        extent_io_tree_init(fs_info, &ei->io_tree, IO_TREE_INODE_IO, inode);
        extent_io_tree_init(fs_info, &ei->io_failure_tree,
                            IO_TREE_INODE_IO_FAILURE, inode);
        extent_io_tree_init(fs_info, &ei->file_extent_tree,
                            IO_TREE_INODE_FILE_EXTENT, inode);
        ei->io_tree.track_uptodate = true;
        ei->io_failure_tree.track_uptodate = true;
        atomic_set(&ei->sync_writers, 0);
        mutex_init(&ei->log_mutex);
        btrfs_ordered_inode_tree_init(&ei->ordered_tree);
        INIT_LIST_HEAD(&ei->delalloc_inodes);
        INIT_LIST_HEAD(&ei->delayed_iput);
        RB_CLEAR_NODE(&ei->rb_node);
        init_rwsem(&ei->dio_sem);

        return inode;
}

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
void btrfs_test_destroy_inode(struct inode *inode)
{
        btrfs_drop_extent_cache(BTRFS_I(inode), 0, (u64)-1, 0);
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}
#endif

void btrfs_free_inode(struct inode *inode)
{
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}

void btrfs_destroy_inode(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_ordered_extent *ordered;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        WARN_ON(!hlist_empty(&inode->i_dentry));
        WARN_ON(inode->i_data.nrpages);
        WARN_ON(BTRFS_I(inode)->block_rsv.reserved);
        WARN_ON(BTRFS_I(inode)->block_rsv.size);
        WARN_ON(BTRFS_I(inode)->outstanding_extents);
        WARN_ON(BTRFS_I(inode)->delalloc_bytes);
        WARN_ON(BTRFS_I(inode)->new_delalloc_bytes);
        WARN_ON(BTRFS_I(inode)->csum_bytes);
        WARN_ON(BTRFS_I(inode)->defrag_bytes);

        /*
         * This can happen where we create an inode, but somebody else also
         * created the same inode and we need to destroy the one we already
         * created.
         */
        if (!root)
                return;

        while (1) {
                ordered = btrfs_lookup_first_ordered_extent(BTRFS_I(inode),
                                                            (u64)-1);
                if (!ordered)
                        break;
                else {
                        btrfs_err(fs_info,
                                  "found ordered extent %llu %llu on inode cleanup",
                                  ordered->file_offset, ordered->num_bytes);
                        btrfs_remove_ordered_extent(inode, ordered);
                        btrfs_put_ordered_extent(ordered);
                        btrfs_put_ordered_extent(ordered);
                }
        }
        btrfs_qgroup_check_reserved_leak(BTRFS_I(inode));
        inode_tree_del(BTRFS_I(inode));
        btrfs_drop_extent_cache(BTRFS_I(inode), 0, (u64)-1, 0);
        btrfs_inode_clear_file_extent_range(BTRFS_I(inode), 0, (u64)-1);
        btrfs_put_root(BTRFS_I(inode)->root);
}

int btrfs_drop_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (root == NULL)
                return 1;

        /* the snap/subvol tree is on deleting */
        if (btrfs_root_refs(&root->root_item) == 0)
                return 1;
        else
                return generic_drop_inode(inode);
}

static void init_once(void *foo)
{
        struct btrfs_inode *ei = (struct btrfs_inode *) foo;

        inode_init_once(&ei->vfs_inode);
}

void __cold btrfs_destroy_cachep(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        kmem_cache_destroy(btrfs_inode_cachep);
        kmem_cache_destroy(btrfs_trans_handle_cachep);
        kmem_cache_destroy(btrfs_path_cachep);
        kmem_cache_destroy(btrfs_free_space_cachep);
        kmem_cache_destroy(btrfs_free_space_bitmap_cachep);
}

int __init btrfs_init_cachep(void)
{
        btrfs_inode_cachep = kmem_cache_create("btrfs_inode",
                        sizeof(struct btrfs_inode), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | SLAB_ACCOUNT,
                        init_once);
        if (!btrfs_inode_cachep)
                goto fail;

        btrfs_trans_handle_cachep = kmem_cache_create("btrfs_trans_handle",
                        sizeof(struct btrfs_trans_handle), 0,
                        SLAB_TEMPORARY | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_trans_handle_cachep)
                goto fail;

        btrfs_path_cachep = kmem_cache_create("btrfs_path",
                        sizeof(struct btrfs_path), 0,
                        SLAB_MEM_SPREAD, NULL);
        if (!btrfs_path_cachep)
                goto fail;

        btrfs_free_space_cachep = kmem_cache_create("btrfs_free_space",
                        sizeof(struct btrfs_free_space), 0,
                        SLAB_MEM_SPREAD, NULL);
        if (!btrfs_free_space_cachep)
                goto fail;

        btrfs_free_space_bitmap_cachep = kmem_cache_create("btrfs_free_space_bitmap",
                                                        PAGE_SIZE, PAGE_SIZE,
                                                        SLAB_RED_ZONE, NULL);
        if (!btrfs_free_space_bitmap_cachep)
                goto fail;

        return 0;
fail:
        btrfs_destroy_cachep();
        return -ENOMEM;
}

static int btrfs_getattr(const struct path *path, struct kstat *stat,
                         u32 request_mask, unsigned int flags)
{
        u64 delalloc_bytes;
        struct inode *inode = d_inode(path->dentry);
        u32 blocksize = inode->i_sb->s_blocksize;
        u32 bi_flags = BTRFS_I(inode)->flags;

        stat->result_mask |= STATX_BTIME;
        stat->btime.tv_sec = BTRFS_I(inode)->i_otime.tv_sec;
        stat->btime.tv_nsec = BTRFS_I(inode)->i_otime.tv_nsec;
        if (bi_flags & BTRFS_INODE_APPEND)
                stat->attributes |= STATX_ATTR_APPEND;
        if (bi_flags & BTRFS_INODE_COMPRESS)
                stat->attributes |= STATX_ATTR_COMPRESSED;
        if (bi_flags & BTRFS_INODE_IMMUTABLE)
                stat->attributes |= STATX_ATTR_IMMUTABLE;
        if (bi_flags & BTRFS_INODE_NODUMP)
                stat->attributes |= STATX_ATTR_NODUMP;

        stat->attributes_mask |= (STATX_ATTR_APPEND |
                                  STATX_ATTR_COMPRESSED |
                                  STATX_ATTR_IMMUTABLE |
                                  STATX_ATTR_NODUMP);

        generic_fillattr(inode, stat);
        stat->dev = BTRFS_I(inode)->root->anon_dev;

        spin_lock(&BTRFS_I(inode)->lock);
        delalloc_bytes = BTRFS_I(inode)->new_delalloc_bytes;
        spin_unlock(&BTRFS_I(inode)->lock);
        stat->blocks = (ALIGN(inode_get_bytes(inode), blocksize) +
                        ALIGN(delalloc_bytes, blocksize)) >> 9;
        return 0;
}

static int btrfs_rename_exchange(struct inode *old_dir,
                              struct dentry *old_dentry,
                              struct inode *new_dir,
                              struct dentry *new_dentry)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(old_dir->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(old_dir)->root;
        struct btrfs_root *dest = BTRFS_I(new_dir)->root;
        struct inode *new_inode = new_dentry->d_inode;
        struct inode *old_inode = old_dentry->d_inode;
        struct timespec64 ctime = current_time(old_inode);
        u64 old_ino = btrfs_ino(BTRFS_I(old_inode));
        u64 new_ino = btrfs_ino(BTRFS_I(new_inode));
        u64 old_idx = 0;
        u64 new_idx = 0;
        int ret;
        int ret2;
        bool root_log_pinned = false;
        bool dest_log_pinned = false;

        /* we only allow rename subvolume link between subvolumes */
        if (old_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest)
                return -EXDEV;

        /* close the race window with snapshot create/destroy ioctl */
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID ||
            new_ino == BTRFS_FIRST_FREE_OBJECTID)
                down_read(&fs_info->subvol_sem);

        /*
         * We want to reserve the absolute worst case amount of items.  So if
         * both inodes are subvols and we need to unlink them then that would
         * require 4 item modifications, but if they are both normal inodes it
         * would require 5 item modifications, so we'll assume their normal
         * inodes.  So 5 * 2 is 10, plus 2 for the new links, so 12 total items
         * should cover the worst case number of items we'll modify.
         */
        trans = btrfs_start_transaction(root, 12);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out_notrans;
        }

        if (dest != root)
                btrfs_record_root_in_trans(trans, dest);

        /*
         * We need to find a free sequence number both in the source and
         * in the destination directory for the exchange.
         */
        ret = btrfs_set_inode_index(BTRFS_I(new_dir), &old_idx);
        if (ret)
                goto out_fail;
        ret = btrfs_set_inode_index(BTRFS_I(old_dir), &new_idx);
        if (ret)
                goto out_fail;

        BTRFS_I(old_inode)->dir_index = 0ULL;
        BTRFS_I(new_inode)->dir_index = 0ULL;

        /* Reference for the source. */
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
                /* force full log commit if subvolume involved. */
                btrfs_set_log_full_commit(trans);
        } else {
                btrfs_pin_log_trans(root);
                root_log_pinned = true;
                ret = btrfs_insert_inode_ref(trans, dest,
                                             new_dentry->d_name.name,
                                             new_dentry->d_name.len,
                                             old_ino,
                                             btrfs_ino(BTRFS_I(new_dir)),
                                             old_idx);
                if (ret)
                        goto out_fail;
        }

        /* And now for the dest. */
        if (new_ino == BTRFS_FIRST_FREE_OBJECTID) {
                /* force full log commit if subvolume involved. */
                btrfs_set_log_full_commit(trans);
        } else {
                btrfs_pin_log_trans(dest);
                dest_log_pinned = true;
                ret = btrfs_insert_inode_ref(trans, root,
                                             old_dentry->d_name.name,
                                             old_dentry->d_name.len,
                                             new_ino,
                                             btrfs_ino(BTRFS_I(old_dir)),
                                             new_idx);
                if (ret)
                        goto out_fail;
        }

        /* Update inode version and ctime/mtime. */
        inode_inc_iversion(old_dir);
        inode_inc_iversion(new_dir);
        inode_inc_iversion(old_inode);
        inode_inc_iversion(new_inode);
        old_dir->i_ctime = old_dir->i_mtime = ctime;
        new_dir->i_ctime = new_dir->i_mtime = ctime;
        old_inode->i_ctime = ctime;
        new_inode->i_ctime = ctime;

        if (old_dentry->d_parent != new_dentry->d_parent) {
                btrfs_record_unlink_dir(trans, BTRFS_I(old_dir),
                                BTRFS_I(old_inode), 1);
                btrfs_record_unlink_dir(trans, BTRFS_I(new_dir),
                                BTRFS_I(new_inode), 1);
        }

        /* src is a subvolume */
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
                ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
        } else { /* src is an inode */
                ret = __btrfs_unlink_inode(trans, root, BTRFS_I(old_dir),
                                           BTRFS_I(old_dentry->d_inode),
                                           old_dentry->d_name.name,
                                           old_dentry->d_name.len);
                if (!ret)
                        ret = btrfs_update_inode(trans, root, old_inode);
        }
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        /* dest is a subvolume */
        if (new_ino == BTRFS_FIRST_FREE_OBJECTID) {
                ret = btrfs_unlink_subvol(trans, new_dir, new_dentry);
        } else { /* dest is an inode */
                ret = __btrfs_unlink_inode(trans, dest, BTRFS_I(new_dir),
                                           BTRFS_I(new_dentry->d_inode),
                                           new_dentry->d_name.name,
                                           new_dentry->d_name.len);
                if (!ret)
                        ret = btrfs_update_inode(trans, dest, new_inode);
        }
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        ret = btrfs_add_link(trans, BTRFS_I(new_dir), BTRFS_I(old_inode),
                             new_dentry->d_name.name,
                             new_dentry->d_name.len, 0, old_idx);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        ret = btrfs_add_link(trans, BTRFS_I(old_dir), BTRFS_I(new_inode),
                             old_dentry->d_name.name,
                             old_dentry->d_name.len, 0, new_idx);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        if (old_inode->i_nlink == 1)
                BTRFS_I(old_inode)->dir_index = old_idx;
        if (new_inode->i_nlink == 1)
                BTRFS_I(new_inode)->dir_index = new_idx;

        if (root_log_pinned) {
                btrfs_log_new_name(trans, BTRFS_I(old_inode), BTRFS_I(old_dir),
                                   new_dentry->d_parent);
                btrfs_end_log_trans(root);
                root_log_pinned = false;
        }
        if (dest_log_pinned) {
                btrfs_log_new_name(trans, BTRFS_I(new_inode), BTRFS_I(new_dir),
                                   old_dentry->d_parent);
                btrfs_end_log_trans(dest);
                dest_log_pinned = false;
        }
out_fail:
        /*
         * If we have pinned a log and an error happened, we unpin tasks
         * trying to sync the log and force them to fallback to a transaction
         * commit if the log currently contains any of the inodes involved in
         * this rename operation (to ensure we do not persist a log with an
         * inconsistent state for any of these inodes or leading to any
         * inconsistencies when replayed). If the transaction was aborted, the
         * abortion reason is propagated to userspace when attempting to commit
         * the transaction. If the log does not contain any of these inodes, we
         * allow the tasks to sync it.
         */
        if (ret && (root_log_pinned || dest_log_pinned)) {
                if (btrfs_inode_in_log(BTRFS_I(old_dir), fs_info->generation) ||
                    btrfs_inode_in_log(BTRFS_I(new_dir), fs_info->generation) ||
                    btrfs_inode_in_log(BTRFS_I(old_inode), fs_info->generation) ||
                    (new_inode &&
                     btrfs_inode_in_log(BTRFS_I(new_inode), fs_info->generation)))
                        btrfs_set_log_full_commit(trans);

                if (root_log_pinned) {
                        btrfs_end_log_trans(root);
                        root_log_pinned = false;
                }
                if (dest_log_pinned) {
                        btrfs_end_log_trans(dest);
                        dest_log_pinned = false;
                }
        }
        ret2 = btrfs_end_transaction(trans);
        ret = ret ? ret : ret2;
out_notrans:
        if (new_ino == BTRFS_FIRST_FREE_OBJECTID ||
            old_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&fs_info->subvol_sem);

        return ret;
}

static int btrfs_whiteout_for_rename(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct inode *dir,
                                     struct dentry *dentry)
{
        int ret;
        struct inode *inode;
        u64 objectid;
        u64 index;

        ret = btrfs_find_free_ino(root, &objectid);
        if (ret)
                return ret;

        inode = btrfs_new_inode(trans, root, dir,
                                dentry->d_name.name,
                                dentry->d_name.len,
                                btrfs_ino(BTRFS_I(dir)),
                                objectid,
                                S_IFCHR | WHITEOUT_MODE,
                                &index);

        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                return ret;
        }

        inode->i_op = &btrfs_special_inode_operations;
        init_special_inode(inode, inode->i_mode,
                WHITEOUT_DEV);

        ret = btrfs_init_inode_security(trans, inode, dir,
                                &dentry->d_name);
        if (ret)
                goto out;

        ret = btrfs_add_nondir(trans, BTRFS_I(dir), dentry,
                                BTRFS_I(inode), 0, index);
        if (ret)
                goto out;

        ret = btrfs_update_inode(trans, root, inode);
out:
        unlock_new_inode(inode);
        if (ret)
                inode_dec_link_count(inode);
        iput(inode);

        return ret;
}

static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                           struct inode *new_dir, struct dentry *new_dentry,
                           unsigned int flags)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(old_dir->i_sb);
        struct btrfs_trans_handle *trans;
        unsigned int trans_num_items;
        struct btrfs_root *root = BTRFS_I(old_dir)->root;
        struct btrfs_root *dest = BTRFS_I(new_dir)->root;
        struct inode *new_inode = d_inode(new_dentry);
        struct inode *old_inode = d_inode(old_dentry);
        u64 index = 0;
        int ret;
        int ret2;
        u64 old_ino = btrfs_ino(BTRFS_I(old_inode));
        bool log_pinned = false;

        if (btrfs_ino(BTRFS_I(new_dir)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                return -EPERM;

        /* we only allow rename subvolume link between subvolumes */
        if (old_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest)
                return -EXDEV;

        if (old_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID ||
            (new_inode && btrfs_ino(BTRFS_I(new_inode)) == BTRFS_FIRST_FREE_OBJECTID))
                return -ENOTEMPTY;

        if (S_ISDIR(old_inode->i_mode) && new_inode &&
            new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                return -ENOTEMPTY;


        /* check for collisions, even if the  name isn't there */
        ret = btrfs_check_dir_item_collision(dest, new_dir->i_ino,
                             new_dentry->d_name.name,
                             new_dentry->d_name.len);

        if (ret) {
                if (ret == -EEXIST) {
                        /* we shouldn't get
                         * eexist without a new_inode */
                        if (WARN_ON(!new_inode)) {
                                return ret;
                        }
                } else {
                        /* maybe -EOVERFLOW */
                        return ret;
                }
        }
        ret = 0;

        /*
         * we're using rename to replace one file with another.  Start IO on it
         * now so  we don't add too much work to the end of the transaction
         */
        if (new_inode && S_ISREG(old_inode->i_mode) && new_inode->i_size)
                filemap_flush(old_inode->i_mapping);

        /* close the racy window with snapshot create/destroy ioctl */
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
                down_read(&fs_info->subvol_sem);
        /*
         * We want to reserve the absolute worst case amount of items.  So if
         * both inodes are subvols and we need to unlink them then that would
         * require 4 item modifications, but if they are both normal inodes it
         * would require 5 item modifications, so we'll assume they are normal
         * inodes.  So 5 * 2 is 10, plus 1 for the new link, so 11 total items
         * should cover the worst case number of items we'll modify.
         * If our rename has the whiteout flag, we need more 5 units for the
         * new inode (1 inode item, 1 inode ref, 2 dir items and 1 xattr item
         * when selinux is enabled).
         */
        trans_num_items = 11;
        if (flags & RENAME_WHITEOUT)
                trans_num_items += 5;
        trans = btrfs_start_transaction(root, trans_num_items);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out_notrans;
        }

        if (dest != root)
                btrfs_record_root_in_trans(trans, dest);

        ret = btrfs_set_inode_index(BTRFS_I(new_dir), &index);
        if (ret)
                goto out_fail;

        BTRFS_I(old_inode)->dir_index = 0ULL;
        if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                /* force full log commit if subvolume involved. */
                btrfs_set_log_full_commit(trans);
        } else {
                btrfs_pin_log_trans(root);
                log_pinned = true;
                ret = btrfs_insert_inode_ref(trans, dest,
                                             new_dentry->d_name.name,
                                             new_dentry->d_name.len,
                                             old_ino,
                                             btrfs_ino(BTRFS_I(new_dir)), index);
                if (ret)
                        goto out_fail;
        }

        inode_inc_iversion(old_dir);
        inode_inc_iversion(new_dir);
        inode_inc_iversion(old_inode);
        old_dir->i_ctime = old_dir->i_mtime =
        new_dir->i_ctime = new_dir->i_mtime =
        old_inode->i_ctime = current_time(old_dir);

        if (old_dentry->d_parent != new_dentry->d_parent)
                btrfs_record_unlink_dir(trans, BTRFS_I(old_dir),
                                BTRFS_I(old_inode), 1);

        if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
        } else {
                ret = __btrfs_unlink_inode(trans, root, BTRFS_I(old_dir),
                                        BTRFS_I(d_inode(old_dentry)),
                                        old_dentry->d_name.name,
                                        old_dentry->d_name.len);
                if (!ret)
                        ret = btrfs_update_inode(trans, root, old_inode);
        }
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        if (new_inode) {
                inode_inc_iversion(new_inode);
                new_inode->i_ctime = current_time(new_inode);
                if (unlikely(btrfs_ino(BTRFS_I(new_inode)) ==
                             BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                        ret = btrfs_unlink_subvol(trans, new_dir, new_dentry);
                        BUG_ON(new_inode->i_nlink == 0);
                } else {
                        ret = btrfs_unlink_inode(trans, dest, BTRFS_I(new_dir),
                                                 BTRFS_I(d_inode(new_dentry)),
                                                 new_dentry->d_name.name,
                                                 new_dentry->d_name.len);
                }
                if (!ret && new_inode->i_nlink == 0)
                        ret = btrfs_orphan_add(trans,
                                        BTRFS_I(d_inode(new_dentry)));
                if (ret) {
                        btrfs_abort_transaction(trans, ret);
                        goto out_fail;
                }
        }

        ret = btrfs_add_link(trans, BTRFS_I(new_dir), BTRFS_I(old_inode),
                             new_dentry->d_name.name,
                             new_dentry->d_name.len, 0, index);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_fail;
        }

        if (old_inode->i_nlink == 1)
                BTRFS_I(old_inode)->dir_index = index;

        if (log_pinned) {
                btrfs_log_new_name(trans, BTRFS_I(old_inode), BTRFS_I(old_dir),
                                   new_dentry->d_parent);
                btrfs_end_log_trans(root);
                log_pinned = false;
        }

        if (flags & RENAME_WHITEOUT) {
                ret = btrfs_whiteout_for_rename(trans, root, old_dir,
                                                old_dentry);

                if (ret) {
                        btrfs_abort_transaction(trans, ret);
                        goto out_fail;
                }
        }
out_fail:
        /*
         * If we have pinned the log and an error happened, we unpin tasks
         * trying to sync the log and force them to fallback to a transaction
         * commit if the log currently contains any of the inodes involved in
         * this rename operation (to ensure we do not persist a log with an
         * inconsistent state for any of these inodes or leading to any
         * inconsistencies when replayed). If the transaction was aborted, the
         * abortion reason is propagated to userspace when attempting to commit
         * the transaction. If the log does not contain any of these inodes, we
         * allow the tasks to sync it.
         */
        if (ret && log_pinned) {
                if (btrfs_inode_in_log(BTRFS_I(old_dir), fs_info->generation) ||
                    btrfs_inode_in_log(BTRFS_I(new_dir), fs_info->generation) ||
                    btrfs_inode_in_log(BTRFS_I(old_inode), fs_info->generation) ||
                    (new_inode &&
                     btrfs_inode_in_log(BTRFS_I(new_inode), fs_info->generation)))
                        btrfs_set_log_full_commit(trans);

                btrfs_end_log_trans(root);
                log_pinned = false;
        }
        ret2 = btrfs_end_transaction(trans);
        ret = ret ? ret : ret2;
out_notrans:
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&fs_info->subvol_sem);

        return ret;
}

static int btrfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
                         struct inode *new_dir, struct dentry *new_dentry,
                         unsigned int flags)
{
        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
                return -EINVAL;

        if (flags & RENAME_EXCHANGE)
                return btrfs_rename_exchange(old_dir, old_dentry, new_dir,
                                          new_dentry);

        return btrfs_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
}

struct btrfs_delalloc_work {
        struct inode *inode;
        struct completion completion;
        struct list_head list;
        struct btrfs_work work;
};

static void btrfs_run_delalloc_work(struct btrfs_work *work)
{
        struct btrfs_delalloc_work *delalloc_work;
        struct inode *inode;

        delalloc_work = container_of(work, struct btrfs_delalloc_work,
                                     work);
        inode = delalloc_work->inode;
        filemap_flush(inode->i_mapping);
        if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                                &BTRFS_I(inode)->runtime_flags))
                filemap_flush(inode->i_mapping);

        iput(inode);
        complete(&delalloc_work->completion);
}

static struct btrfs_delalloc_work *btrfs_alloc_delalloc_work(struct inode *inode)
{
        struct btrfs_delalloc_work *work;

        work = kmalloc(sizeof(*work), GFP_NOFS);
        if (!work)
                return NULL;

        init_completion(&work->completion);
        INIT_LIST_HEAD(&work->list);
        work->inode = inode;
        btrfs_init_work(&work->work, btrfs_run_delalloc_work, NULL, NULL);

        return work;
}

/*
 * some fairly slow code that needs optimization. This walks the list
 * of all the inodes with pending delalloc and forces them to disk.
 */
static int start_delalloc_inodes(struct btrfs_root *root, u64 *nr, bool snapshot)
{
        struct btrfs_inode *binode;
        struct inode *inode;
        struct btrfs_delalloc_work *work, *next;
        struct list_head works;
        struct list_head splice;
        int ret = 0;

        INIT_LIST_HEAD(&works);
        INIT_LIST_HEAD(&splice);

        mutex_lock(&root->delalloc_mutex);
        spin_lock(&root->delalloc_lock);
        list_splice_init(&root->delalloc_inodes, &splice);
        while (!list_empty(&splice)) {
                binode = list_entry(splice.next, struct btrfs_inode,
                                    delalloc_inodes);

                list_move_tail(&binode->delalloc_inodes,
                               &root->delalloc_inodes);
                inode = igrab(&binode->vfs_inode);
                if (!inode) {
                        cond_resched_lock(&root->delalloc_lock);
                        continue;
                }
                spin_unlock(&root->delalloc_lock);

                if (snapshot)
                        set_bit(BTRFS_INODE_SNAPSHOT_FLUSH,
                                &binode->runtime_flags);
                work = btrfs_alloc_delalloc_work(inode);
                if (!work) {
                        iput(inode);
                        ret = -ENOMEM;
                        goto out;
                }
                list_add_tail(&work->list, &works);
                btrfs_queue_work(root->fs_info->flush_workers,
                                 &work->work);
                if (*nr != U64_MAX) {
                        (*nr)--;
                        if (*nr == 0)
                                goto out;
                }
                cond_resched();
                spin_lock(&root->delalloc_lock);
        }
        spin_unlock(&root->delalloc_lock);

out:
        list_for_each_entry_safe(work, next, &works, list) {
                list_del_init(&work->list);
                wait_for_completion(&work->completion);
                kfree(work);
        }

        if (!list_empty(&splice)) {
                spin_lock(&root->delalloc_lock);
                list_splice_tail(&splice, &root->delalloc_inodes);
                spin_unlock(&root->delalloc_lock);
        }
        mutex_unlock(&root->delalloc_mutex);
        return ret;
}

int btrfs_start_delalloc_snapshot(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        u64 nr = U64_MAX;

        if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
                return -EROFS;

        return start_delalloc_inodes(root, &nr, true);
}

int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr)
{
        struct btrfs_root *root;
        struct list_head splice;
        int ret;

        if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
                return -EROFS;

        INIT_LIST_HEAD(&splice);

        mutex_lock(&fs_info->delalloc_root_mutex);
        spin_lock(&fs_info->delalloc_root_lock);
        list_splice_init(&fs_info->delalloc_roots, &splice);
        while (!list_empty(&splice) && nr) {
                root = list_first_entry(&splice, struct btrfs_root,
                                        delalloc_root);
                root = btrfs_grab_root(root);
                BUG_ON(!root);
                list_move_tail(&root->delalloc_root,
                               &fs_info->delalloc_roots);
                spin_unlock(&fs_info->delalloc_root_lock);

                ret = start_delalloc_inodes(root, &nr, false);
                btrfs_put_root(root);
                if (ret < 0)
                        goto out;
                spin_lock(&fs_info->delalloc_root_lock);
        }
        spin_unlock(&fs_info->delalloc_root_lock);

        ret = 0;
out:
        if (!list_empty(&splice)) {
                spin_lock(&fs_info->delalloc_root_lock);
                list_splice_tail(&splice, &fs_info->delalloc_roots);
                spin_unlock(&fs_info->delalloc_root_lock);
        }
        mutex_unlock(&fs_info->delalloc_root_mutex);
        return ret;
}

static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                         const char *symname)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct inode *inode = NULL;
        int err;
        u64 objectid;
        u64 index = 0;
        int name_len;
        int datasize;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        struct extent_buffer *leaf;

        name_len = strlen(symname);
        if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(fs_info))
                return -ENAMETOOLONG;

        /*
         * 2 items for inode item and ref
         * 2 items for dir items
         * 1 item for updating parent inode item
         * 1 item for the inline extent item
         * 1 item for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 7);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, btrfs_ino(BTRFS_I(dir)),
                                objectid, S_IFLNK|S_IRWXUGO, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                inode = NULL;
                goto out_unlock;
        }

        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;
        inode->i_mapping->a_ops = &btrfs_aops;
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock;

        path = btrfs_alloc_path();
        if (!path) {
                err = -ENOMEM;
                goto out_unlock;
        }
        key.objectid = btrfs_ino(BTRFS_I(inode));
        key.offset = 0;
        key.type = BTRFS_EXTENT_DATA_KEY;
        datasize = btrfs_file_extent_calc_inline_size(name_len);
        err = btrfs_insert_empty_item(trans, root, path, &key,
                                      datasize);
        if (err) {
                btrfs_free_path(path);
                goto out_unlock;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei,
                                   BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_compression(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, name_len);

        ptr = btrfs_file_extent_inline_start(ei);
        write_extent_buffer(leaf, symname, ptr, name_len);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        inode->i_op = &btrfs_symlink_inode_operations;
        inode_nohighmem(inode);
        inode_set_bytes(inode, name_len);
        btrfs_i_size_write(BTRFS_I(inode), name_len);
        err = btrfs_update_inode(trans, root, inode);
        /*
         * Last step, add directory indexes for our symlink inode. This is the
         * last step to avoid extra cleanup of these indexes if an error happens
         * elsewhere above.
         */
        if (!err)
                err = btrfs_add_nondir(trans, BTRFS_I(dir), dentry,
                                BTRFS_I(inode), 0, index);
        if (err)
                goto out_unlock;

        d_instantiate_new(dentry, inode);

out_unlock:
        btrfs_end_transaction(trans);
        if (err && inode) {
                inode_dec_link_count(inode);
                discard_new_inode(inode);
        }
        btrfs_btree_balance_dirty(fs_info);
        return err;
}

static struct btrfs_trans_handle *insert_prealloc_file_extent(
                                       struct btrfs_trans_handle *trans_in,
                                       struct inode *inode, struct btrfs_key *ins,
                                       u64 file_offset)
{
        struct btrfs_file_extent_item stack_fi;
        struct btrfs_clone_extent_info extent_info;
        struct btrfs_trans_handle *trans = trans_in;
        struct btrfs_path *path;
        u64 start = ins->objectid;
        u64 len = ins->offset;
        int ret;

        memset(&stack_fi, 0, sizeof(stack_fi));

        btrfs_set_stack_file_extent_type(&stack_fi, BTRFS_FILE_EXTENT_PREALLOC);
        btrfs_set_stack_file_extent_disk_bytenr(&stack_fi, start);
        btrfs_set_stack_file_extent_disk_num_bytes(&stack_fi, len);
        btrfs_set_stack_file_extent_num_bytes(&stack_fi, len);
        btrfs_set_stack_file_extent_ram_bytes(&stack_fi, len);
        btrfs_set_stack_file_extent_compression(&stack_fi, BTRFS_COMPRESS_NONE);
        /* Encryption and other encoding is reserved and all 0 */

        ret = btrfs_qgroup_release_data(BTRFS_I(inode), file_offset, len);
        if (ret < 0)
                return ERR_PTR(ret);

        if (trans) {
                ret = insert_reserved_file_extent(trans, BTRFS_I(inode),
                                                  file_offset, &stack_fi, ret);
                if (ret)
                        return ERR_PTR(ret);
                return trans;
        }

        extent_info.disk_offset = start;
        extent_info.disk_len = len;
        extent_info.data_offset = 0;
        extent_info.data_len = len;
        extent_info.file_offset = file_offset;
        extent_info.extent_buf = (char *)&stack_fi;
        extent_info.is_new_extent = true;
        extent_info.qgroup_reserved = ret;
        extent_info.insertions = 0;

        path = btrfs_alloc_path();
        if (!path)
                return ERR_PTR(-ENOMEM);

        ret = btrfs_punch_hole_range(inode, path, file_offset,
                                     file_offset + len - 1, &extent_info,
                                     &trans);
        btrfs_free_path(path);
        if (ret)
                return ERR_PTR(ret);

        return trans;
}

static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
                                       u64 start, u64 num_bytes, u64 min_size,
                                       loff_t actual_len, u64 *alloc_hint,
                                       struct btrfs_trans_handle *trans)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key ins;
        u64 cur_offset = start;
        u64 clear_offset = start;
        u64 i_size;
        u64 cur_bytes;
        u64 last_alloc = (u64)-1;
        int ret = 0;
        bool own_trans = true;
        u64 end = start + num_bytes - 1;

        if (trans)
                own_trans = false;
        while (num_bytes > 0) {
                cur_bytes = min_t(u64, num_bytes, SZ_256M);
                cur_bytes = max(cur_bytes, min_size);
                /*
                 * If we are severely fragmented we could end up with really
                 * small allocations, so if the allocator is returning small
                 * chunks lets make its job easier by only searching for those
                 * sized chunks.
                 */
                cur_bytes = min(cur_bytes, last_alloc);
                ret = btrfs_reserve_extent(root, cur_bytes, cur_bytes,
                                min_size, 0, *alloc_hint, &ins, 1, 0);
                if (ret)
                        break;

                /*
                 * We've reserved this space, and thus converted it from
                 * ->bytes_may_use to ->bytes_reserved.  Any error that happens
                 * from here on out we will only need to clear our reservation
                 * for the remaining unreserved area, so advance our
                 * clear_offset by our extent size.
                 */
                clear_offset += ins.offset;
                btrfs_dec_block_group_reservations(fs_info, ins.objectid);

                last_alloc = ins.offset;
                trans = insert_prealloc_file_extent(trans, inode, &ins, cur_offset);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        btrfs_free_reserved_extent(fs_info, ins.objectid,
                                                   ins.offset, 0);
                        break;
                }

                btrfs_drop_extent_cache(BTRFS_I(inode), cur_offset,
                                        cur_offset + ins.offset -1, 0);

                em = alloc_extent_map();
                if (!em) {
                        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                                &BTRFS_I(inode)->runtime_flags);
                        goto next;
                }

                em->start = cur_offset;
                em->orig_start = cur_offset;
                em->len = ins.offset;
                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->orig_block_len = ins.offset;
                em->ram_bytes = ins.offset;
                set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                em->generation = trans->transid;

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em, 1);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST)
                                break;
                        btrfs_drop_extent_cache(BTRFS_I(inode), cur_offset,
                                                cur_offset + ins.offset - 1,
                                                0);
                }
                free_extent_map(em);
next:
                num_bytes -= ins.offset;
                cur_offset += ins.offset;
                *alloc_hint = ins.objectid + ins.offset;

                inode_inc_iversion(inode);
                inode->i_ctime = current_time(inode);
                BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
                if (!(mode & FALLOC_FL_KEEP_SIZE) &&
                    (actual_len > inode->i_size) &&
                    (cur_offset > inode->i_size)) {
                        if (cur_offset > actual_len)
                                i_size = actual_len;
                        else
                                i_size = cur_offset;
                        i_size_write(inode, i_size);
                        btrfs_inode_safe_disk_i_size_write(inode, 0);
                }

                ret = btrfs_update_inode(trans, root, inode);

                if (ret) {
                        btrfs_abort_transaction(trans, ret);
                        if (own_trans)
                                btrfs_end_transaction(trans);
                        break;
                }

                if (own_trans) {
                        btrfs_end_transaction(trans);
                        trans = NULL;
                }
        }
        if (clear_offset < end)
                btrfs_free_reserved_data_space(BTRFS_I(inode), NULL, clear_offset,
                        end - clear_offset + 1);
        return ret;
}

int btrfs_prealloc_file_range(struct inode *inode, int mode,
                              u64 start, u64 num_bytes, u64 min_size,
                              loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint,
                                           NULL);
}

int btrfs_prealloc_file_range_trans(struct inode *inode,
                                    struct btrfs_trans_handle *trans, int mode,
                                    u64 start, u64 num_bytes, u64 min_size,
                                    loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint, trans);
}

static int btrfs_set_page_dirty(struct page *page)
{
        return __set_page_dirty_nobuffers(page);
}

static int btrfs_permission(struct inode *inode, int mask)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        umode_t mode = inode->i_mode;

        if (mask & MAY_WRITE &&
            (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) {
                if (btrfs_root_readonly(root))
                        return -EROFS;
                if (BTRFS_I(inode)->flags & BTRFS_INODE_READONLY)
                        return -EACCES;
        }
        return generic_permission(inode, mask);
}

static int btrfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        u64 objectid;
        u64 index;
        int ret = 0;

        /*
         * 5 units required for adding orphan entry
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_find_free_ino(root, &objectid);
        if (ret)
                goto out;

        inode = btrfs_new_inode(trans, root, dir, NULL, 0,
                        btrfs_ino(BTRFS_I(dir)), objectid, mode, &index);
        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                inode = NULL;
                goto out;
        }

        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;

        inode->i_mapping->a_ops = &btrfs_aops;
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;

        ret = btrfs_init_inode_security(trans, inode, dir, NULL);
        if (ret)
                goto out;

        ret = btrfs_update_inode(trans, root, inode);
        if (ret)
                goto out;
        ret = btrfs_orphan_add(trans, BTRFS_I(inode));
        if (ret)
                goto out;

        /*
         * We set number of links to 0 in btrfs_new_inode(), and here we set
         * it to 1 because d_tmpfile() will issue a warning if the count is 0,
         * through:
         *
         *    d_tmpfile() -> inode_dec_link_count() -> drop_nlink()
         */
        set_nlink(inode, 1);
        d_tmpfile(dentry, inode);
        unlock_new_inode(inode);
        mark_inode_dirty(inode);
out:
        btrfs_end_transaction(trans);
        if (ret && inode)
                discard_new_inode(inode);
        btrfs_btree_balance_dirty(fs_info);
        return ret;
}

void btrfs_set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
{
        struct inode *inode = tree->private_data;
        unsigned long index = start >> PAGE_SHIFT;
        unsigned long end_index = end >> PAGE_SHIFT;
        struct page *page;

        while (index <= end_index) {
                page = find_get_page(inode->i_mapping, index);
                ASSERT(page); /* Pages should be in the extent_io_tree */
                set_page_writeback(page);
                put_page(page);
                index++;
        }
}

#ifdef CONFIG_SWAP
/*
 * Add an entry indicating a block group or device which is pinned by a
 * swapfile. Returns 0 on success, 1 if there is already an entry for it, or a
 * negative errno on failure.
 */
static int btrfs_add_swapfile_pin(struct inode *inode, void *ptr,
                                  bool is_block_group)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct btrfs_swapfile_pin *sp, *entry;
        struct rb_node **p;
        struct rb_node *parent = NULL;

        sp = kmalloc(sizeof(*sp), GFP_NOFS);
        if (!sp)
                return -ENOMEM;
        sp->ptr = ptr;
        sp->inode = inode;
        sp->is_block_group = is_block_group;

        spin_lock(&fs_info->swapfile_pins_lock);
        p = &fs_info->swapfile_pins.rb_node;
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct btrfs_swapfile_pin, node);
                if (sp->ptr < entry->ptr ||
                    (sp->ptr == entry->ptr && sp->inode < entry->inode)) {
                        p = &(*p)->rb_left;
                } else if (sp->ptr > entry->ptr ||
                           (sp->ptr == entry->ptr && sp->inode > entry->inode)) {
                        p = &(*p)->rb_right;
                } else {
                        spin_unlock(&fs_info->swapfile_pins_lock);
                        kfree(sp);
                        return 1;
                }
        }
        rb_link_node(&sp->node, parent, p);
        rb_insert_color(&sp->node, &fs_info->swapfile_pins);
        spin_unlock(&fs_info->swapfile_pins_lock);
        return 0;
}

/* Free all of the entries pinned by this swapfile. */
static void btrfs_free_swapfile_pins(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct btrfs_swapfile_pin *sp;
        struct rb_node *node, *next;

        spin_lock(&fs_info->swapfile_pins_lock);
        node = rb_first(&fs_info->swapfile_pins);
        while (node) {
                next = rb_next(node);
                sp = rb_entry(node, struct btrfs_swapfile_pin, node);
                if (sp->inode == inode) {
                        rb_erase(&sp->node, &fs_info->swapfile_pins);
                        if (sp->is_block_group)
                                btrfs_put_block_group(sp->ptr);
                        kfree(sp);
                }
                node = next;
        }
        spin_unlock(&fs_info->swapfile_pins_lock);
}

struct btrfs_swap_info {
        u64 start;
        u64 block_start;
        u64 block_len;
        u64 lowest_ppage;
        u64 highest_ppage;
        unsigned long nr_pages;
        int nr_extents;
};

static int btrfs_add_swap_extent(struct swap_info_struct *sis,
                                 struct btrfs_swap_info *bsi)
{
        unsigned long nr_pages;
        u64 first_ppage, first_ppage_reported, next_ppage;
        int ret;

        first_ppage = ALIGN(bsi->block_start, PAGE_SIZE) >> PAGE_SHIFT;
        next_ppage = ALIGN_DOWN(bsi->block_start + bsi->block_len,
                                PAGE_SIZE) >> PAGE_SHIFT;

        if (first_ppage >= next_ppage)
                return 0;
        nr_pages = next_ppage - first_ppage;

        first_ppage_reported = first_ppage;
        if (bsi->start == 0)
                first_ppage_reported++;
        if (bsi->lowest_ppage > first_ppage_reported)
                bsi->lowest_ppage = first_ppage_reported;
        if (bsi->highest_ppage < (next_ppage - 1))
                bsi->highest_ppage = next_ppage - 1;

        ret = add_swap_extent(sis, bsi->nr_pages, nr_pages, first_ppage);
        if (ret < 0)
                return ret;
        bsi->nr_extents += ret;
        bsi->nr_pages += nr_pages;
        return 0;
}

static void btrfs_swap_deactivate(struct file *file)
{
        struct inode *inode = file_inode(file);

        btrfs_free_swapfile_pins(inode);
        atomic_dec(&BTRFS_I(inode)->root->nr_swapfiles);
}

static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                               sector_t *span)
{
        struct inode *inode = file_inode(file);
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_state *cached_state = NULL;
        struct extent_map *em = NULL;
        struct btrfs_device *device = NULL;
        struct btrfs_swap_info bsi = {
                .lowest_ppage = (sector_t)-1ULL,
        };
        int ret = 0;
        u64 isize;
        u64 start;

        /*
         * If the swap file was just created, make sure delalloc is done. If the
         * file changes again after this, the user is doing something stupid and
         * we don't really care.
         */
        ret = btrfs_wait_ordered_range(inode, 0, (u64)-1);
        if (ret)
                return ret;

        /*
         * The inode is locked, so these flags won't change after we check them.
         */
        if (BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS) {
                btrfs_warn(fs_info, "swapfile must not be compressed");
                return -EINVAL;
        }
        if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW)) {
                btrfs_warn(fs_info, "swapfile must not be copy-on-write");
                return -EINVAL;
        }
        if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
                btrfs_warn(fs_info, "swapfile must not be checksummed");
                return -EINVAL;
        }

        /*
         * Balance or device remove/replace/resize can move stuff around from
         * under us. The exclop protection makes sure they aren't running/won't
         * run concurrently while we are mapping the swap extents, and
         * fs_info->swapfile_pins prevents them from running while the swap
         * file is active and moving the extents. Note that this also prevents
         * a concurrent device add which isn't actually necessary, but it's not
         * really worth the trouble to allow it.
         */
        if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_SWAP_ACTIVATE)) {
                btrfs_warn(fs_info,
           "cannot activate swapfile while exclusive operation is running");
                return -EBUSY;
        }
        /*
         * Snapshots can create extents which require COW even if NODATACOW is
         * set. We use this counter to prevent snapshots. We must increment it
         * before walking the extents because we don't want a concurrent
         * snapshot to run after we've already checked the extents.
         */
        atomic_inc(&BTRFS_I(inode)->root->nr_swapfiles);

        isize = ALIGN_DOWN(inode->i_size, fs_info->sectorsize);

        lock_extent_bits(io_tree, 0, isize - 1, &cached_state);
        start = 0;
        while (start < isize) {
                u64 logical_block_start, physical_block_start;
                struct btrfs_block_group *bg;
                u64 len = isize - start;

                em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
                if (IS_ERR(em)) {
                        ret = PTR_ERR(em);
                        goto out;
                }

                if (em->block_start == EXTENT_MAP_HOLE) {
                        btrfs_warn(fs_info, "swapfile must not have holes");
                        ret = -EINVAL;
                        goto out;
                }
                if (em->block_start == EXTENT_MAP_INLINE) {
                        /*
                         * It's unlikely we'll ever actually find ourselves
                         * here, as a file small enough to fit inline won't be
                         * big enough to store more than the swap header, but in
                         * case something changes in the future, let's catch it
                         * here rather than later.
                         */
                        btrfs_warn(fs_info, "swapfile must not be inline");
                        ret = -EINVAL;
                        goto out;
                }
                if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
                        btrfs_warn(fs_info, "swapfile must not be compressed");
                        ret = -EINVAL;
                        goto out;
                }

                logical_block_start = em->block_start + (start - em->start);
                len = min(len, em->len - (start - em->start));
                free_extent_map(em);
                em = NULL;

                ret = can_nocow_extent(inode, start, &len, NULL, NULL, NULL, true);
                if (ret < 0) {
                        goto out;
                } else if (ret) {
                        ret = 0;
                } else {
                        btrfs_warn(fs_info,
                                   "swapfile must not be copy-on-write");
                        ret = -EINVAL;
                        goto out;
                }

                em = btrfs_get_chunk_map(fs_info, logical_block_start, len);
                if (IS_ERR(em)) {
                        ret = PTR_ERR(em);
                        goto out;
                }

                if (em->map_lookup->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
                        btrfs_warn(fs_info,
                                   "swapfile must have single data profile");
                        ret = -EINVAL;
                        goto out;
                }

                if (device == NULL) {
                        device = em->map_lookup->stripes[0].dev;
                        ret = btrfs_add_swapfile_pin(inode, device, false);
                        if (ret == 1)
                                ret = 0;
                        else if (ret)
                                goto out;
                } else if (device != em->map_lookup->stripes[0].dev) {
                        btrfs_warn(fs_info, "swapfile must be on one device");
                        ret = -EINVAL;
                        goto out;
                }

                physical_block_start = (em->map_lookup->stripes[0].physical +
                                        (logical_block_start - em->start));
                len = min(len, em->len - (logical_block_start - em->start));
                free_extent_map(em);
                em = NULL;

                bg = btrfs_lookup_block_group(fs_info, logical_block_start);
                if (!bg) {
                        btrfs_warn(fs_info,
                           "could not find block group containing swapfile");
                        ret = -EINVAL;
                        goto out;
                }

                ret = btrfs_add_swapfile_pin(inode, bg, true);
                if (ret) {
                        btrfs_put_block_group(bg);
                        if (ret == 1)
                                ret = 0;
                        else
                                goto out;
                }

                if (bsi.block_len &&
                    bsi.block_start + bsi.block_len == physical_block_start) {
                        bsi.block_len += len;
                } else {
                        if (bsi.block_len) {
                                ret = btrfs_add_swap_extent(sis, &bsi);
                                if (ret)
                                        goto out;
                        }
                        bsi.start = start;
                        bsi.block_start = physical_block_start;
                        bsi.block_len = len;
                }

                start += len;
        }

        if (bsi.block_len)
                ret = btrfs_add_swap_extent(sis, &bsi);

out:
        if (!IS_ERR_OR_NULL(em))
                free_extent_map(em);

        unlock_extent_cached(io_tree, 0, isize - 1, &cached_state);

        if (ret)
                btrfs_swap_deactivate(file);

        btrfs_exclop_finish(fs_info);

        if (ret)
                return ret;

        if (device)
                sis->bdev = device->bdev;
        *span = bsi.highest_ppage - bsi.lowest_ppage + 1;
        sis->max = bsi.nr_pages;
        sis->pages = bsi.nr_pages - 1;
        sis->highest_bit = bsi.nr_pages - 1;
        return bsi.nr_extents;
}
#else
static void btrfs_swap_deactivate(struct file *file)
{
}

static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                               sector_t *span)
{
        return -EOPNOTSUPP;
}
#endif

static const struct inode_operations btrfs_dir_inode_operations = {
        .getattr        = btrfs_getattr,
        .lookup         = btrfs_lookup,
        .create         = btrfs_create,
        .unlink         = btrfs_unlink,
        .link           = btrfs_link,
        .mkdir          = btrfs_mkdir,
        .rmdir          = btrfs_rmdir,
        .rename         = btrfs_rename2,
        .symlink        = btrfs_symlink,
        .setattr        = btrfs_setattr,
        .mknod          = btrfs_mknod,
        .listxattr      = btrfs_listxattr,
        .permission     = btrfs_permission,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
        .tmpfile        = btrfs_tmpfile,
};

static const struct file_operations btrfs_dir_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = btrfs_real_readdir,
        .open           = btrfs_opendir,
        .unlocked_ioctl = btrfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = btrfs_compat_ioctl,
#endif
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
};

static const struct extent_io_ops btrfs_extent_io_ops = {
        /* mandatory callbacks */
        .submit_bio_hook = btrfs_submit_bio_hook,
        .readpage_end_io_hook = btrfs_readpage_end_io_hook,
};

/*
 * btrfs doesn't support the bmap operation because swapfiles
 * use bmap to make a mapping of extents in the file.  They assume
 * these extents won't change over the life of the file and they
 * use the bmap result to do IO directly to the drive.
 *
 * the btrfs bmap call would return logical addresses that aren't
 * suitable for IO and they also will change frequently as COW
 * operations happen.  So, swapfile + btrfs == corruption.
 *
 * For now we're avoiding this by dropping bmap.
 */
static const struct address_space_operations btrfs_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .writepages     = btrfs_writepages,
        .readahead      = btrfs_readahead,
        .direct_IO      = noop_direct_IO,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
#ifdef CONFIG_MIGRATION
        .migratepage    = btrfs_migratepage,
#endif
        .set_page_dirty = btrfs_set_page_dirty,
        .error_remove_page = generic_error_remove_page,
        .swap_activate  = btrfs_swap_activate,
        .swap_deactivate = btrfs_swap_deactivate,
};

static const struct inode_operations btrfs_file_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .listxattr      = btrfs_listxattr,
        .permission     = btrfs_permission,
        .fiemap         = btrfs_fiemap,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
};
static const struct inode_operations btrfs_special_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .listxattr      = btrfs_listxattr,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
};
static const struct inode_operations btrfs_symlink_inode_operations = {
        .get_link       = page_get_link,
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .listxattr      = btrfs_listxattr,
        .update_time    = btrfs_update_time,
};

const struct dentry_operations btrfs_dentry_operations = {
        .d_delete       = btrfs_dentry_delete,
};