Btrfs: Remove extent back refs in batches, and avoid duplicate searches

[mirror_ubuntu-artful-kernel.git] / fs / btrfs / extent-tree.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/crc32c.h>
#include <linux/pagemap.h>
#include "hash.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
#include "transaction.h"

#define BLOCK_GROUP_DATA EXTENT_WRITEBACK
#define BLOCK_GROUP_METADATA EXTENT_UPTODATE
#define BLOCK_GROUP_DIRTY EXTENT_DIRTY

static int finish_current_insert(struct btrfs_trans_handle *trans, struct
                                 btrfs_root *extent_root);
static int del_pending_extents(struct btrfs_trans_handle *trans, struct
                               btrfs_root *extent_root);
static int find_previous_extent(struct btrfs_root *root,
                                struct btrfs_path *path)
{
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
        int ret;

        while(1) {
                if (path->slots[0] == 0) {
                        ret = btrfs_prev_leaf(root, path);
                        if (ret != 0)
                                return ret;
                } else {
                        path->slots[0]--;
                }
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.type == BTRFS_EXTENT_ITEM_KEY)
                        return 0;
        }
        return 1;
}

static int cache_block_group(struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group)
{
        struct btrfs_path *path;
        int ret;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct extent_io_tree *free_space_cache;
        int slot;
        u64 last = 0;
        u64 hole_size;
        u64 first_free;
        int found = 0;

        if (!block_group)
                return 0;

        root = root->fs_info->extent_root;
        free_space_cache = &root->fs_info->free_space_cache;

        if (block_group->cached)
                return 0;

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

        path->reada = 2;
        first_free = block_group->key.objectid;
        key.objectid = block_group->key.objectid;
        key.offset = 0;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                return ret;
        ret = find_previous_extent(root, path);
        if (ret < 0)
                return ret;
        if (ret == 0) {
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                if (key.objectid + key.offset > first_free)
                        first_free = key.objectid + key.offset;
        }
        while(1) {
                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;
                        if (ret == 0) {
                                continue;
                        } else {
                                break;
                        }
                }
                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (key.objectid < block_group->key.objectid) {
                        goto next;
                }
                if (key.objectid >= block_group->key.objectid +
                    block_group->key.offset) {
                        break;
                }

                if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
                        if (!found) {
                                last = first_free;
                                found = 1;
                        }
                        if (key.objectid > last) {
                                hole_size = key.objectid - last;
                                set_extent_dirty(free_space_cache, last,
                                                 last + hole_size - 1,
                                                 GFP_NOFS);
                        }
                        last = key.objectid + key.offset;
                }
next:
                path->slots[0]++;
        }

        if (!found)
                last = first_free;
        if (block_group->key.objectid +
            block_group->key.offset > last) {
                hole_size = block_group->key.objectid +
                        block_group->key.offset - last;
                set_extent_dirty(free_space_cache, last,
                                 last + hole_size - 1, GFP_NOFS);
        }
        block_group->cached = 1;
err:
        btrfs_free_path(path);
        return 0;
}

struct btrfs_block_group_cache *btrfs_lookup_block_group(struct
                                                         btrfs_fs_info *info,
                                                         u64 bytenr)
{
        struct extent_io_tree *block_group_cache;
        struct btrfs_block_group_cache *block_group = NULL;
        u64 ptr;
        u64 start;
        u64 end;
        int ret;

        block_group_cache = &info->block_group_cache;
        ret = find_first_extent_bit(block_group_cache,
                                    bytenr, &start, &end,
                                    BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA);
        if (ret) {
                return NULL;
        }
        ret = get_state_private(block_group_cache, start, &ptr);
        if (ret)
                return NULL;

        block_group = (struct btrfs_block_group_cache *)(unsigned long)ptr;
        if (block_group->key.objectid <= bytenr && bytenr <
            block_group->key.objectid + block_group->key.offset)
                return block_group;
        return NULL;
}
static u64 noinline find_search_start(struct btrfs_root *root,
                              struct btrfs_block_group_cache **cache_ret,
                              u64 search_start, int num, int data)
{
        int ret;
        struct btrfs_block_group_cache *cache = *cache_ret;
        struct extent_io_tree *free_space_cache;
        struct extent_state *state;
        u64 last;
        u64 start = 0;
        u64 cache_miss = 0;
        u64 total_fs_bytes;
        int wrapped = 0;

        if (!cache) {
                goto out;
        }
        total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
        free_space_cache = &root->fs_info->free_space_cache;

again:
        ret = cache_block_group(root, cache);
        if (ret)
                goto out;

        last = max(search_start, cache->key.objectid);

        spin_lock_irq(&free_space_cache->lock);
        state = find_first_extent_bit_state(free_space_cache, last, EXTENT_DIRTY);
        while(1) {
                if (!state) {
                        if (!cache_miss)
                                cache_miss = last;
                        spin_unlock_irq(&free_space_cache->lock);
                        goto new_group;
                }

                start = max(last, state->start);
                last = state->end + 1;
                if (last - start < num) {
                        if (last == cache->key.objectid + cache->key.offset)
                                cache_miss = start;
                        do {
                                state = extent_state_next(state);
                        } while(state && !(state->state & EXTENT_DIRTY));
                        continue;
                }
                spin_unlock_irq(&free_space_cache->lock);
                if (data != BTRFS_BLOCK_GROUP_MIXED &&
                    start + num > cache->key.objectid + cache->key.offset)
                        goto new_group;
                if (start + num  > total_fs_bytes)
                        goto new_group;
                return start;
        }
out:
        cache = btrfs_lookup_block_group(root->fs_info, search_start);
        if (!cache) {
                printk("Unable to find block group for %Lu\n",
                       search_start);
                WARN_ON(1);
                return search_start;
        }
        return search_start;

new_group:
        last = cache->key.objectid + cache->key.offset;
wrapped:
        cache = btrfs_lookup_block_group(root->fs_info, last);
        if (!cache || cache->key.objectid >= total_fs_bytes) {
no_cache:
                if (!wrapped) {
                        wrapped = 1;
                        last = search_start;
                        data = BTRFS_BLOCK_GROUP_MIXED;
                        goto wrapped;
                }
                goto out;
        }
        if (cache_miss && !cache->cached) {
                cache_block_group(root, cache);
                last = cache_miss;
                cache = btrfs_lookup_block_group(root->fs_info, last);
        }
        cache = btrfs_find_block_group(root, cache, last, data, 0);
        if (!cache)
                goto no_cache;
        *cache_ret = cache;
        cache_miss = 0;
        goto again;
}

static u64 div_factor(u64 num, int factor)
{
        if (factor == 10)
                return num;
        num *= factor;
        do_div(num, 10);
        return num;
}

struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
                                                 struct btrfs_block_group_cache
                                                 *hint, u64 search_start,
                                                 int data, int owner)
{
        struct btrfs_block_group_cache *cache;
        struct extent_io_tree *block_group_cache;
        struct btrfs_block_group_cache *found_group = NULL;
        struct btrfs_fs_info *info = root->fs_info;
        u64 used;
        u64 last = 0;
        u64 hint_last;
        u64 start;
        u64 end;
        u64 free_check;
        u64 ptr;
        u64 total_fs_bytes;
        int bit;
        int ret;
        int full_search = 0;
        int factor = 8;
        int data_swap = 0;

        block_group_cache = &info->block_group_cache;
        total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);

        if (!owner)
                factor = 8;

        if (data == BTRFS_BLOCK_GROUP_MIXED) {
                bit = BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA;
                factor = 10;
        } else if (data)
                bit = BLOCK_GROUP_DATA;
        else
                bit = BLOCK_GROUP_METADATA;

        if (search_start && search_start < total_fs_bytes) {
                struct btrfs_block_group_cache *shint;
                shint = btrfs_lookup_block_group(info, search_start);
                if (shint && (shint->data == data ||
                              shint->data == BTRFS_BLOCK_GROUP_MIXED)) {
                        used = btrfs_block_group_used(&shint->item);
                        if (used + shint->pinned <
                            div_factor(shint->key.offset, factor)) {
                                return shint;
                        }
                }
        }
        if (hint && hint->key.objectid < total_fs_bytes &&
            (hint->data == data || hint->data == BTRFS_BLOCK_GROUP_MIXED)) {
                used = btrfs_block_group_used(&hint->item);
                if (used + hint->pinned <
                    div_factor(hint->key.offset, factor)) {
                        return hint;
                }
                last = hint->key.objectid + hint->key.offset;
                hint_last = last;
        } else {
                if (hint)
                        hint_last = max(hint->key.objectid, search_start);
                else
                        hint_last = search_start;

                if (hint_last >= total_fs_bytes)
                        hint_last = search_start;
                last = hint_last;
        }
again:
        while(1) {
                ret = find_first_extent_bit(block_group_cache, last,
                                            &start, &end, bit);
                if (ret)
                        break;

                ret = get_state_private(block_group_cache, start, &ptr);
                if (ret)
                        break;

                cache = (struct btrfs_block_group_cache *)(unsigned long)ptr;
                last = cache->key.objectid + cache->key.offset;
                used = btrfs_block_group_used(&cache->item);

                if (cache->key.objectid > total_fs_bytes)
                        break;

                if (full_search)
                        free_check = cache->key.offset;
                else
                        free_check = div_factor(cache->key.offset, factor);
                if (used + cache->pinned < free_check) {
                        found_group = cache;
                        goto found;
                }
                cond_resched();
        }
        if (!full_search) {
                last = search_start;
                full_search = 1;
                goto again;
        }
        if (!data_swap) {
                data_swap = 1;
                bit = BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA;
                last = search_start;
                goto again;
        }
found:
        return found_group;
}

static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
                           u64 owner, u64 owner_offset)
{
        u32 high_crc = ~(u32)0;
        u32 low_crc = ~(u32)0;
        __le64 lenum;

        lenum = cpu_to_le64(root_objectid);
        high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
        lenum = cpu_to_le64(ref_generation);
        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
        if (owner >= BTRFS_FIRST_FREE_OBJECTID) {
                lenum = cpu_to_le64(owner);
                low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
                lenum = cpu_to_le64(owner_offset);
                low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
        }
        return ((u64)high_crc << 32) | (u64)low_crc;
}

static int match_extent_ref(struct extent_buffer *leaf,
                            struct btrfs_extent_ref *disk_ref,
                            struct btrfs_extent_ref *cpu_ref)
{
        int ret;
        int len;

        if (cpu_ref->objectid)
                len = sizeof(*cpu_ref);
        else
                len = 2 * sizeof(u64);
        ret = memcmp_extent_buffer(leaf, cpu_ref, (unsigned long)disk_ref,
                                   len);
        return ret == 0;
}

static int noinline lookup_extent_backref(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct btrfs_path *path, u64 bytenr,
                                          u64 root_objectid,
                                          u64 ref_generation, u64 owner,
                                          u64 owner_offset, int del)
{
        u64 hash;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_extent_ref ref;
        struct extent_buffer *leaf;
        struct btrfs_extent_ref *disk_ref;
        int ret;
        int ret2;

        btrfs_set_stack_ref_root(&ref, root_objectid);
        btrfs_set_stack_ref_generation(&ref, ref_generation);
        btrfs_set_stack_ref_objectid(&ref, owner);
        btrfs_set_stack_ref_offset(&ref, owner_offset);

        hash = hash_extent_ref(root_objectid, ref_generation, owner,
                               owner_offset);
        key.offset = hash;
        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_REF_KEY;

        while (1) {
                ret = btrfs_search_slot(trans, root, &key, path,
                                        del ? -1 : 0, del);
                if (ret < 0)
                        goto out;
                leaf = path->nodes[0];
                if (ret != 0) {
                        u32 nritems = btrfs_header_nritems(leaf);
                        if (path->slots[0] >= nritems) {
                                ret2 = btrfs_next_leaf(root, path);
                                if (ret2)
                                        goto out;
                                leaf = path->nodes[0];
                        }
                        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                        if (found_key.objectid != bytenr ||
                            found_key.type != BTRFS_EXTENT_REF_KEY)
                                goto out;
                        key.offset = found_key.offset;
                        if (del) {
                                btrfs_release_path(root, path);
                                continue;
                        }
                }
                disk_ref = btrfs_item_ptr(path->nodes[0],
                                          path->slots[0],
                                          struct btrfs_extent_ref);
                if (match_extent_ref(path->nodes[0], disk_ref, &ref)) {
                        ret = 0;
                        goto out;
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                key.offset = found_key.offset + 1;
                btrfs_release_path(root, path);
        }
out:
        return ret;
}

/*
 * Back reference rules.  Back refs have three main goals:
 *
 * 1) differentiate between all holders of references to an extent so that
 *    when a reference is dropped we can make sure it was a valid reference
 *    before freeing the extent.
 *
 * 2) Provide enough information to quickly find the holders of an extent
 *    if we notice a given block is corrupted or bad.
 *
 * 3) Make it easy to migrate blocks for FS shrinking or storage pool
 *    maintenance.  This is actually the same as #2, but with a slightly
 *    different use case.
 *
 * File extents can be referenced by:
 *
 * - multiple snapshots, subvolumes, or different generations in one subvol
 * - different files inside a single subvolume (in theory, not implemented yet)
 * - different offsets inside a file (bookend extents in file.c)
 *
 * The extent ref structure has fields for:
 *
 * - Objectid of the subvolume root
 * - Generation number of the tree holding the reference
 * - objectid of the file holding the reference
 * - offset in the file corresponding to the key holding the reference
 *
 * When a file extent is allocated the fields are filled in:
 *     (root_key.objectid, trans->transid, inode objectid, offset in file)
 *
 * When a leaf is cow'd new references are added for every file extent found
 * in the leaf.  It looks the same as the create case, but trans->transid
 * will be different when the block is cow'd.
 *
 *     (root_key.objectid, trans->transid, inode objectid, offset in file)
 *
 * When a file extent is removed either during snapshot deletion or file
 * truncation, the corresponding back reference is found
 * by searching for:
 *
 *     (btrfs_header_owner(leaf), btrfs_header_generation(leaf),
 *      inode objectid, offset in file)
 *
 * Btree extents can be referenced by:
 *
 * - Different subvolumes
 * - Different generations of the same subvolume
 *
 * Storing sufficient information for a full reverse mapping of a btree
 * block would require storing the lowest key of the block in the backref,
 * and it would require updating that lowest key either before write out or
 * every time it changed.  Instead, the objectid of the lowest key is stored
 * along with the level of the tree block.  This provides a hint
 * about where in the btree the block can be found.  Searches through the
 * btree only need to look for a pointer to that block, so they stop one
 * level higher than the level recorded in the backref.
 *
 * Some btrees do not do reference counting on their extents.  These
 * include the extent tree and the tree of tree roots.  Backrefs for these
 * trees always have a generation of zero.
 *
 * When a tree block is created, back references are inserted:
 *
 * (root->root_key.objectid, trans->transid or zero, level, lowest_key_objectid)
 *
 * When a tree block is cow'd in a reference counted root,
 * new back references are added for all the blocks it points to.
 * These are of the form (trans->transid will have increased since creation):
 *
 * (root->root_key.objectid, trans->transid, level, lowest_key_objectid)
 *
 * Because the lowest_key_objectid and the level are just hints
 * they are not used when backrefs are deleted.  When a backref is deleted:
 *
 * if backref was for a tree root:
 *     root_objectid = root->root_key.objectid
 * else
 *     root_objectid = btrfs_header_owner(parent)
 *
 * (root_objectid, btrfs_header_generation(parent) or zero, 0, 0)
 *
 * Back Reference Key hashing:
 *
 * Back references have four fields, each 64 bits long.  Unfortunately,
 * This is hashed into a single 64 bit number and placed into the key offset.
 * The key objectid corresponds to the first byte in the extent, and the
 * key type is set to BTRFS_EXTENT_REF_KEY
 */
int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path, u64 bytenr,
                                 u64 root_objectid, u64 ref_generation,
                                 u64 owner, u64 owner_offset)
{
        u64 hash;
        struct btrfs_key key;
        struct btrfs_extent_ref ref;
        struct btrfs_extent_ref *disk_ref;
        int ret;

        btrfs_set_stack_ref_root(&ref, root_objectid);
        btrfs_set_stack_ref_generation(&ref, ref_generation);
        btrfs_set_stack_ref_objectid(&ref, owner);
        btrfs_set_stack_ref_offset(&ref, owner_offset);

        hash = hash_extent_ref(root_objectid, ref_generation, owner,
                               owner_offset);
        key.offset = hash;
        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_REF_KEY;

        ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(ref));
        while (ret == -EEXIST) {
                disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                          struct btrfs_extent_ref);
                if (match_extent_ref(path->nodes[0], disk_ref, &ref))
                        goto out;
                key.offset++;
                btrfs_release_path(root, path);
                ret = btrfs_insert_empty_item(trans, root, path, &key,
                                              sizeof(ref));
        }
        if (ret)
                goto out;
        disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                  struct btrfs_extent_ref);
        write_extent_buffer(path->nodes[0], &ref, (unsigned long)disk_ref,
                            sizeof(ref));
        btrfs_mark_buffer_dirty(path->nodes[0]);
out:
        btrfs_release_path(root, path);
        return ret;
}

int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                u64 bytenr, u64 num_bytes,
                                u64 root_objectid, u64 ref_generation,
                                u64 owner, u64 owner_offset)
{
        struct btrfs_path *path;
        int ret;
        struct btrfs_key key;
        struct extent_buffer *l;
        struct btrfs_extent_item *item;
        u32 refs;

        WARN_ON(num_bytes < root->sectorsize);
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 0;
        key.objectid = bytenr;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        key.offset = num_bytes;
        ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
                                0, 1);
        if (ret < 0)
                return ret;
        if (ret != 0) {
                BUG();
        }
        BUG_ON(ret != 0);
        l = path->nodes[0];
        item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
        refs = btrfs_extent_refs(l, item);
        btrfs_set_extent_refs(l, item, refs + 1);
        btrfs_mark_buffer_dirty(path->nodes[0]);

        btrfs_release_path(root->fs_info->extent_root, path);

        path->reada = 0;
        ret = btrfs_insert_extent_backref(trans, root->fs_info->extent_root,
                                          path, bytenr, root_objectid,
                                          ref_generation, owner, owner_offset);
        BUG_ON(ret);
        finish_current_insert(trans, root->fs_info->extent_root);
        del_pending_extents(trans, root->fs_info->extent_root);

        btrfs_free_path(path);
        return 0;
}

int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root)
{
        finish_current_insert(trans, root->fs_info->extent_root);
        del_pending_extents(trans, root->fs_info->extent_root);
        return 0;
}

static int lookup_extent_ref(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root, u64 bytenr,
                             u64 num_bytes, u32 *refs)
{
        struct btrfs_path *path;
        int ret;
        struct btrfs_key key;
        struct extent_buffer *l;
        struct btrfs_extent_item *item;

        WARN_ON(num_bytes < root->sectorsize);
        path = btrfs_alloc_path();
        path->reada = 0;
        key.objectid = bytenr;
        key.offset = num_bytes;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(trans, root->fs_info->extent_root, &key, path,
                                0, 0);
        if (ret < 0)
                goto out;
        if (ret != 0) {
                btrfs_print_leaf(root, path->nodes[0]);
                printk("failed to find block number %Lu\n", bytenr);
                BUG();
        }
        l = path->nodes[0];
        item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
        *refs = btrfs_extent_refs(l, item);
out:
        btrfs_free_path(path);
        return 0;
}

u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
                                  struct btrfs_path *count_path,
                                  u64 first_extent)
{
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_path *path;
        u64 bytenr;
        u64 found_objectid;
        u64 root_objectid = root->root_key.objectid;
        u32 total_count = 0;
        u32 cur_count;
        u32 nritems;
        int ret;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *l;
        struct btrfs_extent_item *item;
        struct btrfs_extent_ref *ref_item;
        int level = -1;

        path = btrfs_alloc_path();
again:
        if (level == -1)
                bytenr = first_extent;
        else
                bytenr = count_path->nodes[level]->start;

        cur_count = 0;
        key.objectid = bytenr;
        key.offset = 0;

        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        BUG_ON(ret == 0);

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

        if (found_key.objectid != bytenr ||
            found_key.type != BTRFS_EXTENT_ITEM_KEY) {
                goto out;
        }

        item = btrfs_item_ptr(l, path->slots[0], struct btrfs_extent_item);
        while (1) {
                l = path->nodes[0];
                nritems = btrfs_header_nritems(l);
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(extent_root, path);
                        if (ret == 0)
                                continue;
                        break;
                }
                btrfs_item_key_to_cpu(l, &found_key, path->slots[0]);
                if (found_key.objectid != bytenr)
                        break;

                if (found_key.type != BTRFS_EXTENT_REF_KEY) {
                        path->slots[0]++;
                        continue;
                }

                cur_count++;
                ref_item = btrfs_item_ptr(l, path->slots[0],
                                          struct btrfs_extent_ref);
                found_objectid = btrfs_ref_root(l, ref_item);

                if (found_objectid != root_objectid) {
                        total_count = 2;
                        goto out;
                }
                total_count = 1;
                path->slots[0]++;
        }
        if (cur_count == 0) {
                total_count = 0;
                goto out;
        }
        if (level >= 0 && root->node == count_path->nodes[level])
                goto out;
        level++;
        btrfs_release_path(root, path);
        goto again;

out:
        btrfs_free_path(path);
        return total_count;
}
int btrfs_inc_root_ref(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root, u64 owner_objectid)
{
        u64 generation;
        u64 key_objectid;
        u64 level;
        u32 nritems;
        struct btrfs_disk_key disk_key;

        level = btrfs_header_level(root->node);
        generation = trans->transid;
        nritems = btrfs_header_nritems(root->node);
        if (nritems > 0) {
                if (level == 0)
                        btrfs_item_key(root->node, &disk_key, 0);
                else
                        btrfs_node_key(root->node, &disk_key, 0);
                key_objectid = btrfs_disk_key_objectid(&disk_key);
        } else {
                key_objectid = 0;
        }
        return btrfs_inc_extent_ref(trans, root, root->node->start,
                                    root->node->len, owner_objectid,
                                    generation, level, key_objectid);
}

int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                  struct extent_buffer *buf)
{
        u64 bytenr;
        u32 nritems;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int level;
        int ret;
        int faili;

        if (!root->ref_cows)
                return 0;

        level = btrfs_header_level(buf);
        nritems = btrfs_header_nritems(buf);
        for (i = 0; i < nritems; i++) {
                if (level == 0) {
                        u64 disk_bytenr;
                        btrfs_item_key_to_cpu(buf, &key, i);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, i,
                                            struct btrfs_file_extent_item);
                        if (btrfs_file_extent_type(buf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE)
                                continue;
                        disk_bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                        if (disk_bytenr == 0)
                                continue;
                        ret = btrfs_inc_extent_ref(trans, root, disk_bytenr,
                                    btrfs_file_extent_disk_num_bytes(buf, fi),
                                    root->root_key.objectid, trans->transid,
                                    key.objectid, key.offset);
                        if (ret) {
                                faili = i;
                                goto fail;
                        }
                } else {
                        bytenr = btrfs_node_blockptr(buf, i);
                        btrfs_node_key_to_cpu(buf, &key, i);
                        ret = btrfs_inc_extent_ref(trans, root, bytenr,
                                           btrfs_level_size(root, level - 1),
                                           root->root_key.objectid,
                                           trans->transid,
                                           level - 1, key.objectid);
                        if (ret) {
                                faili = i;
                                goto fail;
                        }
                }
        }
        return 0;
fail:
        WARN_ON(1);
#if 0
        for (i =0; i < faili; i++) {
                if (level == 0) {
                        u64 disk_bytenr;
                        btrfs_item_key_to_cpu(buf, &key, i);
                        if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, i,
                                            struct btrfs_file_extent_item);
                        if (btrfs_file_extent_type(buf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE)
                                continue;
                        disk_bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                        if (disk_bytenr == 0)
                                continue;
                        err = btrfs_free_extent(trans, root, disk_bytenr,
                                    btrfs_file_extent_disk_num_bytes(buf,
                                                                      fi), 0);
                        BUG_ON(err);
                } else {
                        bytenr = btrfs_node_blockptr(buf, i);
                        err = btrfs_free_extent(trans, root, bytenr,
                                        btrfs_level_size(root, level - 1), 0);
                        BUG_ON(err);
                }
        }
#endif
        return ret;
}

static int write_one_cache_group(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 struct btrfs_block_group_cache *cache)
{
        int ret;
        int pending_ret;
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        unsigned long bi;
        struct extent_buffer *leaf;

        ret = btrfs_search_slot(trans, extent_root, &cache->key, path, 0, 1);
        if (ret < 0)
                goto fail;
        BUG_ON(ret);

        leaf = path->nodes[0];
        bi = btrfs_item_ptr_offset(leaf, path->slots[0]);
        write_extent_buffer(leaf, &cache->item, bi, sizeof(cache->item));
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(extent_root, path);
fail:
        finish_current_insert(trans, extent_root);
        pending_ret = del_pending_extents(trans, extent_root);
        if (ret)
                return ret;
        if (pending_ret)
                return pending_ret;
        return 0;

}

int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root)
{
        struct extent_io_tree *block_group_cache;
        struct btrfs_block_group_cache *cache;
        int ret;
        int err = 0;
        int werr = 0;
        struct btrfs_path *path;
        u64 last = 0;
        u64 start;
        u64 end;
        u64 ptr;

        block_group_cache = &root->fs_info->block_group_cache;
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        while(1) {
                ret = find_first_extent_bit(block_group_cache, last,
                                            &start, &end, BLOCK_GROUP_DIRTY);
                if (ret)
                        break;

                last = end + 1;
                ret = get_state_private(block_group_cache, start, &ptr);
                if (ret)
                        break;

                cache = (struct btrfs_block_group_cache *)(unsigned long)ptr;
                err = write_one_cache_group(trans, root,
                                            path, cache);
                /*
                 * if we fail to write the cache group, we want
                 * to keep it marked dirty in hopes that a later
                 * write will work
                 */
                if (err) {
                        werr = err;
                        continue;
                }
                clear_extent_bits(block_group_cache, start, end,
                                  BLOCK_GROUP_DIRTY, GFP_NOFS);
        }
        btrfs_free_path(path);
        return werr;
}

static int update_block_group(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              u64 bytenr, u64 num_bytes, int alloc,
                              int mark_free, int data)
{
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *info = root->fs_info;
        u64 total = num_bytes;
        u64 old_val;
        u64 byte_in_group;
        u64 start;
        u64 end;

        while(total) {
                cache = btrfs_lookup_block_group(info, bytenr);
                if (!cache) {
                        return -1;
                }
                byte_in_group = bytenr - cache->key.objectid;
                WARN_ON(byte_in_group > cache->key.offset);
                start = cache->key.objectid;
                end = start + cache->key.offset - 1;
                set_extent_bits(&info->block_group_cache, start, end,
                                BLOCK_GROUP_DIRTY, GFP_NOFS);

                old_val = btrfs_block_group_used(&cache->item);
                num_bytes = min(total, cache->key.offset - byte_in_group);
                if (alloc) {
                        if (cache->data != data &&
                            old_val < (cache->key.offset >> 1)) {
                                int bit_to_clear;
                                int bit_to_set;
                                cache->data = data;
                                if (data) {
                                        bit_to_clear = BLOCK_GROUP_METADATA;
                                        bit_to_set = BLOCK_GROUP_DATA;
                                        cache->item.flags &=
                                                ~BTRFS_BLOCK_GROUP_MIXED;
                                        cache->item.flags |=
                                                BTRFS_BLOCK_GROUP_DATA;
                                } else {
                                        bit_to_clear = BLOCK_GROUP_DATA;
                                        bit_to_set = BLOCK_GROUP_METADATA;
                                        cache->item.flags &=
                                                ~BTRFS_BLOCK_GROUP_MIXED;
                                        cache->item.flags &=
                                                ~BTRFS_BLOCK_GROUP_DATA;
                                }
                                clear_extent_bits(&info->block_group_cache,
                                                  start, end, bit_to_clear,
                                                  GFP_NOFS);
                                set_extent_bits(&info->block_group_cache,
                                                start, end, bit_to_set,
                                                GFP_NOFS);
                        } else if (cache->data != data &&
                                   cache->data != BTRFS_BLOCK_GROUP_MIXED) {
                                cache->data = BTRFS_BLOCK_GROUP_MIXED;
                                set_extent_bits(&info->block_group_cache,
                                                start, end,
                                                BLOCK_GROUP_DATA |
                                                BLOCK_GROUP_METADATA,
                                                GFP_NOFS);
                        }
                        old_val += num_bytes;
                } else {
                        old_val -= num_bytes;
                        if (mark_free) {
                                set_extent_dirty(&info->free_space_cache,
                                                 bytenr, bytenr + num_bytes - 1,
                                                 GFP_NOFS);
                        }
                }
                btrfs_set_block_group_used(&cache->item, old_val);
                total -= num_bytes;
                bytenr += num_bytes;
        }
        return 0;
}
static int update_pinned_extents(struct btrfs_root *root,
                                u64 bytenr, u64 num, int pin)
{
        u64 len;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (pin) {
                set_extent_dirty(&fs_info->pinned_extents,
                                bytenr, bytenr + num - 1, GFP_NOFS);
        } else {
                clear_extent_dirty(&fs_info->pinned_extents,
                                bytenr, bytenr + num - 1, GFP_NOFS);
        }
        while (num > 0) {
                cache = btrfs_lookup_block_group(fs_info, bytenr);
                WARN_ON(!cache);
                len = min(num, cache->key.offset -
                          (bytenr - cache->key.objectid));
                if (pin) {
                        cache->pinned += len;
                        fs_info->total_pinned += len;
                } else {
                        cache->pinned -= len;
                        fs_info->total_pinned -= len;
                }
                bytenr += len;
                num -= len;
        }
        return 0;
}

int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy)
{
        u64 last = 0;
        u64 start;
        u64 end;
        struct extent_io_tree *pinned_extents = &root->fs_info->pinned_extents;
        int ret;

        while(1) {
                ret = find_first_extent_bit(pinned_extents, last,
                                            &start, &end, EXTENT_DIRTY);
                if (ret)
                        break;
                set_extent_dirty(copy, start, end, GFP_NOFS);
                last = end + 1;
        }
        return 0;
}

int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct extent_io_tree *unpin)
{
        u64 start;
        u64 end;
        int ret;
        struct extent_io_tree *free_space_cache;
        free_space_cache = &root->fs_info->free_space_cache;

        while(1) {
                ret = find_first_extent_bit(unpin, 0, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;
                update_pinned_extents(root, start, end + 1 - start, 0);
                clear_extent_dirty(unpin, start, end, GFP_NOFS);
                set_extent_dirty(free_space_cache, start, end, GFP_NOFS);
        }
        return 0;
}

static int finish_current_insert(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *extent_root)
{
        u64 start;
        u64 end;
        struct btrfs_fs_info *info = extent_root->fs_info;
        struct extent_buffer *eb;
        struct btrfs_path *path;
        struct btrfs_key ins;
        struct btrfs_disk_key first;
        struct btrfs_extent_item extent_item;
        int ret;
        int level;
        int err = 0;

        btrfs_set_stack_extent_refs(&extent_item, 1);
        btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
        path = btrfs_alloc_path();

        while(1) {
                ret = find_first_extent_bit(&info->extent_ins, 0, &start,
                                            &end, EXTENT_LOCKED);
                if (ret)
                        break;

                ins.objectid = start;
                ins.offset = end + 1 - start;
                err = btrfs_insert_item(trans, extent_root, &ins,
                                        &extent_item, sizeof(extent_item));
                clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
                                  GFP_NOFS);
                eb = read_tree_block(extent_root, ins.objectid, ins.offset);
                level = btrfs_header_level(eb);
                if (level == 0) {
                        btrfs_item_key(eb, &first, 0);
                } else {
                        btrfs_node_key(eb, &first, 0);
                }
                err = btrfs_insert_extent_backref(trans, extent_root, path,
                                          start, extent_root->root_key.objectid,
                                          0, level,
                                          btrfs_disk_key_objectid(&first));
                BUG_ON(err);
                free_extent_buffer(eb);
        }
        btrfs_free_path(path);
        return 0;
}

static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
                          int pending)
{
        int err = 0;
        struct extent_buffer *buf;

        if (!pending) {
                buf = btrfs_find_tree_block(root, bytenr, num_bytes);
                if (buf) {
                        if (btrfs_buffer_uptodate(buf)) {
                                u64 transid =
                                    root->fs_info->running_transaction->transid;
                                u64 header_transid =
                                        btrfs_header_generation(buf);
                                if (header_transid == transid) {
                                        clean_tree_block(NULL, root, buf);
                                        free_extent_buffer(buf);
                                        return 1;
                                }
                        }
                        free_extent_buffer(buf);
                }
                update_pinned_extents(root, bytenr, num_bytes, 1);
        } else {
                set_extent_bits(&root->fs_info->pending_del,
                                bytenr, bytenr + num_bytes - 1,
                                EXTENT_LOCKED, GFP_NOFS);
        }
        BUG_ON(err < 0);
        return 0;
}

/*
 * remove an extent from the root, returns 0 on success
 */
static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                         *root, u64 bytenr, u64 num_bytes,
                         u64 root_objectid, u64 ref_generation,
                         u64 owner_objectid, u64 owner_offset, int pin,
                         int mark_free)
{
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_root *extent_root = info->extent_root;
        struct extent_buffer *leaf;
        int ret;
        int extent_slot = 0;
        int found_extent = 0;
        int num_to_del = 1;
        struct btrfs_extent_item *ei;
        u32 refs;

        key.objectid = bytenr;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        key.offset = num_bytes;
        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 0;
        ret = lookup_extent_backref(trans, extent_root, path,
                                    bytenr, root_objectid,
                                    ref_generation,
                                    owner_objectid, owner_offset, 1);
        if (ret == 0) {
                struct btrfs_key found_key;
                extent_slot = path->slots[0];
                while(extent_slot > 0) {
                        extent_slot--;
                        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                                              extent_slot);
                        if (found_key.objectid != bytenr)
                                break;
                        if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
                            found_key.offset == num_bytes) {
                                found_extent = 1;
                                break;
                        }
                        if (path->slots[0] - extent_slot > 5)
                                break;
                }
                if (!found_extent)
                        ret = btrfs_del_item(trans, extent_root, path);
        } else {
                btrfs_print_leaf(extent_root, path->nodes[0]);
                WARN_ON(1);
                printk("Unable to find ref byte nr %Lu root %Lu "
                       " gen %Lu owner %Lu offset %Lu\n", bytenr,
                       root_objectid, ref_generation, owner_objectid,
                       owner_offset);
        }
        if (!found_extent) {
                btrfs_release_path(extent_root, path);
                ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
                if (ret < 0)
                        return ret;
                BUG_ON(ret);
                extent_slot = path->slots[0];
        }

        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, extent_slot,
                            struct btrfs_extent_item);
        refs = btrfs_extent_refs(leaf, ei);
        BUG_ON(refs == 0);
        refs -= 1;
        btrfs_set_extent_refs(leaf, ei, refs);

        btrfs_mark_buffer_dirty(leaf);

        if (refs == 0 && found_extent && path->slots[0] == extent_slot + 1) {
                /* if the back ref and the extent are next to each other
                 * they get deleted below in one shot
                 */
                path->slots[0] = extent_slot;
                num_to_del = 2;
        } else if (found_extent) {
                /* otherwise delete the extent back ref */
                ret = btrfs_del_item(trans, extent_root, path);
                BUG_ON(ret);
                /* if refs are 0, we need to setup the path for deletion */
                if (refs == 0) {
                        btrfs_release_path(extent_root, path);
                        ret = btrfs_search_slot(trans, extent_root, &key, path,
                                                -1, 1);
                        if (ret < 0)
                                return ret;
                        BUG_ON(ret);
                }
        }

        if (refs == 0) {
                u64 super_used;
                u64 root_used;

                if (pin) {
                        ret = pin_down_bytes(root, bytenr, num_bytes, 0);
                        if (ret > 0)
                                mark_free = 1;
                        BUG_ON(ret < 0);
                }

                /* block accounting for super block */
                super_used = btrfs_super_bytes_used(&info->super_copy);
                btrfs_set_super_bytes_used(&info->super_copy,
                                           super_used - num_bytes);

                /* block accounting for root item */
                root_used = btrfs_root_used(&root->root_item);
                btrfs_set_root_used(&root->root_item,
                                           root_used - num_bytes);
                ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
                                      num_to_del);
                if (ret) {
                        return ret;
                }
                ret = update_block_group(trans, root, bytenr, num_bytes, 0,
                                         mark_free, 0);
                BUG_ON(ret);
        }
        btrfs_free_path(path);
        finish_current_insert(trans, extent_root);
        return ret;
}

/*
 * find all the blocks marked as pending in the radix tree and remove
 * them from the extent map
 */
static int del_pending_extents(struct btrfs_trans_handle *trans, struct
                               btrfs_root *extent_root)
{
        int ret;
        int err = 0;
        u64 start;
        u64 end;
        struct extent_io_tree *pending_del;
        struct extent_io_tree *pinned_extents;

        pending_del = &extent_root->fs_info->pending_del;
        pinned_extents = &extent_root->fs_info->pinned_extents;

        while(1) {
                ret = find_first_extent_bit(pending_del, 0, &start, &end,
                                            EXTENT_LOCKED);
                if (ret)
                        break;
                update_pinned_extents(extent_root, start, end + 1 - start, 1);
                clear_extent_bits(pending_del, start, end, EXTENT_LOCKED,
                                  GFP_NOFS);
                ret = __free_extent(trans, extent_root,
                                     start, end + 1 - start,
                                     extent_root->root_key.objectid,
                                     0, 0, 0, 0, 0);
                if (ret)
                        err = ret;
        }
        return err;
}

/*
 * remove an extent from the root, returns 0 on success
 */
int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, u64 bytenr, u64 num_bytes,
                      u64 root_objectid, u64 ref_generation,
                      u64 owner_objectid, u64 owner_offset, int pin)
{
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        int pending_ret;
        int ret;

        WARN_ON(num_bytes < root->sectorsize);
        if (!root->ref_cows)
                ref_generation = 0;

        if (root == extent_root) {
                pin_down_bytes(root, bytenr, num_bytes, 1);
                return 0;
        }
        ret = __free_extent(trans, root, bytenr, num_bytes, root_objectid,
                            ref_generation, owner_objectid, owner_offset,
                            pin, pin == 0);
        pending_ret = del_pending_extents(trans, root->fs_info->extent_root);
        return ret ? ret : pending_ret;
}

static u64 stripe_align(struct btrfs_root *root, u64 val)
{
        u64 mask = ((u64)root->stripesize - 1);
        u64 ret = (val + mask) & ~mask;
        return ret;
}

/*
 * walks the btree of allocated extents and find a hole of a given size.
 * The key ins is changed to record the hole:
 * ins->objectid == block start
 * ins->flags = BTRFS_EXTENT_ITEM_KEY
 * ins->offset == number of blocks
 * Any available blocks before search_start are skipped.
 */
static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *orig_root,
                                     u64 num_bytes, u64 empty_size,
                                     u64 search_start, u64 search_end,
                                     u64 hint_byte, struct btrfs_key *ins,
                                     u64 exclude_start, u64 exclude_nr,
                                     int data)
{
        struct btrfs_path *path;
        struct btrfs_key key;
        u64 hole_size = 0;
        u64 aligned;
        int ret;
        int slot = 0;
        u64 last_byte = 0;
        u64 *last_ptr = NULL;
        u64 orig_search_start = search_start;
        int start_found;
        struct extent_buffer *l;
        struct btrfs_root * root = orig_root->fs_info->extent_root;
        struct btrfs_fs_info *info = root->fs_info;
        u64 total_needed = num_bytes;
        int level;
        struct btrfs_block_group_cache *block_group;
        int full_scan = 0;
        int wrapped = 0;
        int empty_cluster;
        u64 cached_start;

        WARN_ON(num_bytes < root->sectorsize);
        btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);

        level = btrfs_header_level(root->node);

        if (num_bytes >= 32 * 1024 * 1024 && hint_byte) {
                data = BTRFS_BLOCK_GROUP_MIXED;
        }

        if (!data) {
                last_ptr = &root->fs_info->last_alloc;
                empty_cluster = 128 * 1024;
        }

        if (data && btrfs_test_opt(root, SSD)) {
                last_ptr = &root->fs_info->last_data_alloc;
                empty_cluster = 2 * 1024 * 1024;
        }

        if (last_ptr) {
                if (*last_ptr)
                        hint_byte = *last_ptr;
                else {
                        hint_byte = hint_byte &
                                ~((u64)BTRFS_BLOCK_GROUP_SIZE - 1);
                        empty_size += empty_cluster;
                }
                search_start = max(search_start, hint_byte);
        }

        search_end = min(search_end,
                         btrfs_super_total_bytes(&info->super_copy));
        if (hint_byte) {
                block_group = btrfs_lookup_block_group(info, hint_byte);
                if (!block_group)
                        hint_byte = search_start;
                block_group = btrfs_find_block_group(root, block_group,
                                                     hint_byte, data, 1);
        } else {
                block_group = btrfs_find_block_group(root,
                                                     trans->block_group,
                                                     search_start, data, 1);
        }

        total_needed += empty_size;
        path = btrfs_alloc_path();
check_failed:
        if (!block_group) {
                block_group = btrfs_lookup_block_group(info, search_start);
                if (!block_group)
                        block_group = btrfs_lookup_block_group(info,
                                                       orig_search_start);
        }
        search_start = find_search_start(root, &block_group, search_start,
                                         total_needed, data);

        if (last_ptr && *last_ptr && search_start != *last_ptr) {
                *last_ptr = 0;
                if (!empty_size) {
                        empty_size += empty_cluster;
                        total_needed += empty_size;
                }
                search_start = find_search_start(root, &block_group,
                                                 search_start, total_needed,
                                                 data);
        }

        search_start = stripe_align(root, search_start);
        cached_start = search_start;
        btrfs_init_path(path);
        ins->objectid = search_start;
        ins->offset = 0;
        start_found = 0;
        path->reada = 2;

        ret = btrfs_search_slot(trans, root, ins, path, 0, 0);
        if (ret < 0)
                goto error;
        ret = find_previous_extent(root, path);
        if (ret < 0)
                goto error;
        l = path->nodes[0];
        btrfs_item_key_to_cpu(l, &key, path->slots[0]);
        while (1) {
                l = path->nodes[0];
                slot = path->slots[0];
                if (slot >= btrfs_header_nritems(l)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret == 0)
                                continue;
                        if (ret < 0)
                                goto error;

                        search_start = max(search_start,
                                           block_group->key.objectid);
                        if (!start_found) {
                                aligned = stripe_align(root, search_start);
                                ins->objectid = aligned;
                                if (aligned >= search_end) {
                                        ret = -ENOSPC;
                                        goto error;
                                }
                                ins->offset = search_end - aligned;
                                start_found = 1;
                                goto check_pending;
                        }
                        ins->objectid = stripe_align(root,
                                                     last_byte > search_start ?
                                                     last_byte : search_start);
                        if (search_end <= ins->objectid) {
                                ret = -ENOSPC;
                                goto error;
                        }
                        ins->offset = search_end - ins->objectid;
                        BUG_ON(ins->objectid >= search_end);
                        goto check_pending;
                }
                btrfs_item_key_to_cpu(l, &key, slot);

                if (key.objectid >= search_start && key.objectid > last_byte &&
                    start_found) {
                        if (last_byte < search_start)
                                last_byte = search_start;
                        aligned = stripe_align(root, last_byte);
                        hole_size = key.objectid - aligned;
                        if (key.objectid > aligned && hole_size >= num_bytes) {
                                ins->objectid = aligned;
                                ins->offset = hole_size;
                                goto check_pending;
                        }
                }
                if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY) {
                        if (!start_found && btrfs_key_type(&key) ==
                            BTRFS_BLOCK_GROUP_ITEM_KEY) {
                                last_byte = key.objectid;
                                start_found = 1;
                        }
                        goto next;
                }


                start_found = 1;
                last_byte = key.objectid + key.offset;

                if (!full_scan && data != BTRFS_BLOCK_GROUP_MIXED &&
                    last_byte >= block_group->key.objectid +
                    block_group->key.offset) {
                        btrfs_release_path(root, path);
                        search_start = block_group->key.objectid +
                                block_group->key.offset;
                        goto new_group;
                }
next:
                path->slots[0]++;
                cond_resched();
        }
check_pending:
        /* we have to make sure we didn't find an extent that has already
         * been allocated by the map tree or the original allocation
         */
        btrfs_release_path(root, path);
        BUG_ON(ins->objectid < search_start);

        if (ins->objectid + num_bytes >= search_end)
                goto enospc;
        if (!full_scan && data != BTRFS_BLOCK_GROUP_MIXED &&
            ins->objectid + num_bytes > block_group->
            key.objectid + block_group->key.offset) {
                search_start = block_group->key.objectid +
                        block_group->key.offset;
                goto new_group;
        }
        if (test_range_bit(&info->extent_ins, ins->objectid,
                           ins->objectid + num_bytes -1, EXTENT_LOCKED, 0)) {
                search_start = ins->objectid + num_bytes;
                goto new_group;
        }
        if (test_range_bit(&info->pinned_extents, ins->objectid,
                           ins->objectid + num_bytes -1, EXTENT_DIRTY, 0)) {
                search_start = ins->objectid + num_bytes;
                goto new_group;
        }
        if (exclude_nr > 0 && (ins->objectid + num_bytes > exclude_start &&
            ins->objectid < exclude_start + exclude_nr)) {
                search_start = exclude_start + exclude_nr;
                goto new_group;
        }
        if (!data) {
                block_group = btrfs_lookup_block_group(info, ins->objectid);
                if (block_group)
                        trans->block_group = block_group;
        }
        ins->offset = num_bytes;
        btrfs_free_path(path);
        if (last_ptr) {
                *last_ptr = ins->objectid + ins->offset;
                if (*last_ptr ==
                    btrfs_super_total_bytes(&root->fs_info->super_copy)) {
                        *last_ptr = 0;
                }
        }
        return 0;

new_group:
        if (search_start + num_bytes >= search_end) {
enospc:
                search_start = orig_search_start;
                if (full_scan) {
                        ret = -ENOSPC;
                        goto error;
                }
                if (wrapped) {
                        if (!full_scan)
                                total_needed -= empty_size;
                        full_scan = 1;
                        data = BTRFS_BLOCK_GROUP_MIXED;
                } else
                        wrapped = 1;
        }
        block_group = btrfs_lookup_block_group(info, search_start);
        cond_resched();
        block_group = btrfs_find_block_group(root, block_group,
                                             search_start, data, 0);
        goto check_failed;

error:
        btrfs_release_path(root, path);
        btrfs_free_path(path);
        return ret;
}
/*
 * finds a free extent and does all the dirty work required for allocation
 * returns the key for the extent through ins, and a tree buffer for
 * the first block of the extent through buf.
 *
 * returns 0 if everything worked, non-zero otherwise.
 */
int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       u64 num_bytes, u64 root_objectid, u64 ref_generation,
                       u64 owner, u64 owner_offset,
                       u64 empty_size, u64 hint_byte,
                       u64 search_end, struct btrfs_key *ins, int data)
{
        int ret;
        int pending_ret;
        u64 super_used;
        u64 root_used;
        u64 search_start = 0;
        u64 new_hint;
        u32 sizes[2];
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_root *extent_root = info->extent_root;
        struct btrfs_extent_item *extent_item;
        struct btrfs_extent_ref *ref;
        struct btrfs_path *path;
        struct btrfs_key keys[2];

        new_hint = max(hint_byte, root->fs_info->alloc_start);
        if (new_hint < btrfs_super_total_bytes(&info->super_copy))
                hint_byte = new_hint;

        WARN_ON(num_bytes < root->sectorsize);
        ret = find_free_extent(trans, root, num_bytes, empty_size,
                               search_start, search_end, hint_byte, ins,
                               trans->alloc_exclude_start,
                               trans->alloc_exclude_nr, data);
        BUG_ON(ret);
        if (ret)
                return ret;

        /* block accounting for super block */
        super_used = btrfs_super_bytes_used(&info->super_copy);
        btrfs_set_super_bytes_used(&info->super_copy, super_used + num_bytes);

        /* block accounting for root item */
        root_used = btrfs_root_used(&root->root_item);
        btrfs_set_root_used(&root->root_item, root_used + num_bytes);

        clear_extent_dirty(&root->fs_info->free_space_cache,
                           ins->objectid, ins->objectid + ins->offset - 1,
                           GFP_NOFS);

        if (root == extent_root) {
                set_extent_bits(&root->fs_info->extent_ins, ins->objectid,
                                ins->objectid + ins->offset - 1,
                                EXTENT_LOCKED, GFP_NOFS);
                WARN_ON(data == 1);
                goto update_block;
        }

        WARN_ON(trans->alloc_exclude_nr);
        trans->alloc_exclude_start = ins->objectid;
        trans->alloc_exclude_nr = ins->offset;

        memcpy(&keys[0], ins, sizeof(*ins));
        keys[1].offset = hash_extent_ref(root_objectid, ref_generation,
                                         owner, owner_offset);
        keys[1].objectid = ins->objectid;
        keys[1].type = BTRFS_EXTENT_REF_KEY;
        sizes[0] = sizeof(*extent_item);
        sizes[1] = sizeof(*ref);

        path = btrfs_alloc_path();
        BUG_ON(!path);

        ret = btrfs_insert_empty_items(trans, extent_root, path, keys,
                                       sizes, 2);

        BUG_ON(ret);
        extent_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                     struct btrfs_extent_item);
        btrfs_set_extent_refs(path->nodes[0], extent_item, 1);
        ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                             struct btrfs_extent_ref);

        btrfs_set_ref_root(path->nodes[0], ref, root_objectid);
        btrfs_set_ref_generation(path->nodes[0], ref, ref_generation);
        btrfs_set_ref_objectid(path->nodes[0], ref, owner);
        btrfs_set_ref_offset(path->nodes[0], ref, owner_offset);

        btrfs_mark_buffer_dirty(path->nodes[0]);

        trans->alloc_exclude_start = 0;
        trans->alloc_exclude_nr = 0;
        btrfs_free_path(path);
        finish_current_insert(trans, extent_root);
        pending_ret = del_pending_extents(trans, extent_root);

        if (ret) {
                return ret;
        }
        if (pending_ret) {
                return pending_ret;
        }

update_block:
        ret = update_block_group(trans, root, ins->objectid, ins->offset, 1, 0,
                                 data);
        if (ret) {
                printk("update block group failed for %Lu %Lu\n",
                       ins->objectid, ins->offset);
                BUG();
        }
        return 0;
}

/*
 * helper function to allocate a block for a given tree
 * returns the tree buffer or NULL.
 */
struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                             struct btrfs_root *root,
                                             u32 blocksize,
                                             u64 root_objectid, u64 hint,
                                             u64 empty_size)
{
        u64 ref_generation;

        if (root->ref_cows)
                ref_generation = trans->transid;
        else
                ref_generation = 0;


        return __btrfs_alloc_free_block(trans, root, blocksize, root_objectid,
                                        ref_generation, 0, 0, hint, empty_size);
}

/*
 * helper function to allocate a block for a given tree
 * returns the tree buffer or NULL.
 */
struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                             struct btrfs_root *root,
                                             u32 blocksize,
                                             u64 root_objectid,
                                             u64 ref_generation,
                                             u64 first_objectid,
                                             int level,
                                             u64 hint,
                                             u64 empty_size)
{
        struct btrfs_key ins;
        int ret;
        struct extent_buffer *buf;

        ret = btrfs_alloc_extent(trans, root, blocksize,
                                 root_objectid, ref_generation,
                                 level, first_objectid, empty_size, hint,
                                 (u64)-1, &ins, 0);
        if (ret) {
                BUG_ON(ret > 0);
                return ERR_PTR(ret);
        }
        buf = btrfs_find_create_tree_block(root, ins.objectid, blocksize);
        if (!buf) {
                btrfs_free_extent(trans, root, ins.objectid, blocksize,
                                  root->root_key.objectid, ref_generation,
                                  0, 0, 0);
                return ERR_PTR(-ENOMEM);
        }
        btrfs_set_header_generation(buf, trans->transid);
        clean_tree_block(trans, root, buf);
        wait_on_tree_block_writeback(root, buf);
        btrfs_set_buffer_uptodate(buf);

        if (PageDirty(buf->first_page)) {
                printk("page %lu dirty\n", buf->first_page->index);
                WARN_ON(1);
        }

        set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
                         buf->start + buf->len - 1, GFP_NOFS);
        set_extent_bits(&BTRFS_I(root->fs_info->btree_inode)->io_tree,
                        buf->start, buf->start + buf->len - 1,
                        EXTENT_CSUM, GFP_NOFS);
        buf->flags |= EXTENT_CSUM;
        if (!btrfs_test_opt(root, SSD))
                btrfs_set_buffer_defrag(buf);
        trans->blocks_used++;
        return buf;
}

static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
                                  struct extent_buffer *leaf)
{
        u64 leaf_owner;
        u64 leaf_generation;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        int i;
        int nritems;
        int ret;

        BUG_ON(!btrfs_is_leaf(leaf));
        nritems = btrfs_header_nritems(leaf);
        leaf_owner = btrfs_header_owner(leaf);
        leaf_generation = btrfs_header_generation(leaf);

        for (i = 0; i < nritems; i++) {
                u64 disk_bytenr;

                btrfs_item_key_to_cpu(leaf, &key, i);
                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                        continue;
                fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(leaf, fi) ==
                    BTRFS_FILE_EXTENT_INLINE)
                        continue;
                /*
                 * FIXME make sure to insert a trans record that
                 * repeats the snapshot del on crash
                 */
                disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                if (disk_bytenr == 0)
                        continue;
                ret = btrfs_free_extent(trans, root, disk_bytenr,
                                btrfs_file_extent_disk_num_bytes(leaf, fi),
                                leaf_owner, leaf_generation,
                                key.objectid, key.offset, 0);
                BUG_ON(ret);
        }
        return 0;
}

static void noinline reada_walk_down(struct btrfs_root *root,
                                     struct extent_buffer *node,
                                     int slot)
{
        u64 bytenr;
        u64 last = 0;
        u32 nritems;
        u32 refs;
        u32 blocksize;
        int ret;
        int i;
        int level;
        int skipped = 0;

        nritems = btrfs_header_nritems(node);
        level = btrfs_header_level(node);
        if (level)
                return;

        for (i = slot; i < nritems && skipped < 32; i++) {
                bytenr = btrfs_node_blockptr(node, i);
                if (last && ((bytenr > last && bytenr - last > 32 * 1024) ||
                             (last > bytenr && last - bytenr > 32 * 1024))) {
                        skipped++;
                        continue;
                }
                blocksize = btrfs_level_size(root, level - 1);
                if (i != slot) {
                        ret = lookup_extent_ref(NULL, root, bytenr,
                                                blocksize, &refs);
                        BUG_ON(ret);
                        if (refs != 1) {
                                skipped++;
                                continue;
                        }
                }
                mutex_unlock(&root->fs_info->fs_mutex);
                ret = readahead_tree_block(root, bytenr, blocksize);
                last = bytenr + blocksize;
                cond_resched();
                mutex_lock(&root->fs_info->fs_mutex);
                if (ret)
                        break;
        }
}

/*
 * helper function for drop_snapshot, this walks down the tree dropping ref
 * counts as it goes.
 */
static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct btrfs_path *path, int *level)
{
        u64 root_owner;
        u64 root_gen;
        u64 bytenr;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        struct extent_buffer *parent;
        u32 blocksize;
        int ret;
        u32 refs;

        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);
        ret = lookup_extent_ref(trans, root,
                                path->nodes[*level]->start,
                                path->nodes[*level]->len, &refs);
        BUG_ON(ret);
        if (refs > 1)
                goto out;

        /*
         * walk down to the last node level and free all the leaves
         */
        while(*level >= 0) {
                WARN_ON(*level < 0);
                WARN_ON(*level >= BTRFS_MAX_LEVEL);
                cur = path->nodes[*level];

                if (btrfs_header_level(cur) != *level)
                        WARN_ON(1);

                if (path->slots[*level] >=
                    btrfs_header_nritems(cur))
                        break;
                if (*level == 0) {
                        ret = drop_leaf_ref(trans, root, cur);
                        BUG_ON(ret);
                        break;
                }
                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                blocksize = btrfs_level_size(root, *level - 1);
                ret = lookup_extent_ref(trans, root, bytenr, blocksize, &refs);
                BUG_ON(ret);
                if (refs != 1) {
                        parent = path->nodes[*level];
                        root_owner = btrfs_header_owner(parent);
                        root_gen = btrfs_header_generation(parent);
                        path->slots[*level]++;
                        ret = btrfs_free_extent(trans, root, bytenr,
                                                blocksize, root_owner,
                                                root_gen, 0, 0, 1);
                        BUG_ON(ret);
                        continue;
                }
                next = btrfs_find_tree_block(root, bytenr, blocksize);
                if (!next || !btrfs_buffer_uptodate(next)) {
                        free_extent_buffer(next);
                        reada_walk_down(root, cur, path->slots[*level]);
                        mutex_unlock(&root->fs_info->fs_mutex);
                        next = read_tree_block(root, bytenr, blocksize);
                        mutex_lock(&root->fs_info->fs_mutex);

                        /* we dropped the lock, check one more time */
                        ret = lookup_extent_ref(trans, root, bytenr,
                                                blocksize, &refs);
                        BUG_ON(ret);
                        if (refs != 1) {
                                parent = path->nodes[*level];
                                root_owner = btrfs_header_owner(parent);
                                root_gen = btrfs_header_generation(parent);

                                path->slots[*level]++;
                                free_extent_buffer(next);
                                ret = btrfs_free_extent(trans, root, bytenr,
                                                        blocksize,
                                                        root_owner,
                                                        root_gen, 0, 0, 1);
                                BUG_ON(ret);
                                continue;
                        }
                }
                WARN_ON(*level <= 0);
                if (path->nodes[*level-1])
                        free_extent_buffer(path->nodes[*level-1]);
                path->nodes[*level-1] = next;
                *level = btrfs_header_level(next);
                path->slots[*level] = 0;
        }
out:
        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);

        if (path->nodes[*level] == root->node) {
                root_owner = root->root_key.objectid;
                parent = path->nodes[*level];
        } else {
                parent = path->nodes[*level + 1];
                root_owner = btrfs_header_owner(parent);
        }

        root_gen = btrfs_header_generation(parent);
        ret = btrfs_free_extent(trans, root, path->nodes[*level]->start,
                                path->nodes[*level]->len,
                                root_owner, root_gen, 0, 0, 1);
        free_extent_buffer(path->nodes[*level]);
        path->nodes[*level] = NULL;
        *level += 1;
        BUG_ON(ret);
        return 0;
}

/*
 * helper for dropping snapshots.  This walks back up the tree in the path
 * to find the first node higher up where we haven't yet gone through
 * all the slots
 */
static int noinline walk_up_tree(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path, int *level)
{
        u64 root_owner;
        u64 root_gen;
        struct btrfs_root_item *root_item = &root->root_item;
        int i;
        int slot;
        int ret;

        for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                slot = path->slots[i];
                if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
                        struct extent_buffer *node;
                        struct btrfs_disk_key disk_key;
                        node = path->nodes[i];
                        path->slots[i]++;
                        *level = i;
                        WARN_ON(*level == 0);
                        btrfs_node_key(node, &disk_key, path->slots[i]);
                        memcpy(&root_item->drop_progress,
                               &disk_key, sizeof(disk_key));
                        root_item->drop_level = i;
                        return 0;
                } else {
                        if (path->nodes[*level] == root->node) {
                                root_owner = root->root_key.objectid;
                                root_gen =
                                   btrfs_header_generation(path->nodes[*level]);
                        } else {
                                struct extent_buffer *node;
                                node = path->nodes[*level + 1];
                                root_owner = btrfs_header_owner(node);
                                root_gen = btrfs_header_generation(node);
                        }
                        ret = btrfs_free_extent(trans, root,
                                                path->nodes[*level]->start,
                                                path->nodes[*level]->len,
                                                root_owner, root_gen, 0, 0, 1);
                        BUG_ON(ret);
                        free_extent_buffer(path->nodes[*level]);
                        path->nodes[*level] = NULL;
                        *level = i + 1;
                }
        }
        return 1;
}

/*
 * drop the reference count on the tree rooted at 'snap'.  This traverses
 * the tree freeing any blocks that have a ref count of zero after being
 * decremented.
 */
int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                        *root)
{
        int ret = 0;
        int wret;
        int level;
        struct btrfs_path *path;
        int i;
        int orig_level;
        struct btrfs_root_item *root_item = &root->root_item;

        path = btrfs_alloc_path();
        BUG_ON(!path);

        level = btrfs_header_level(root->node);
        orig_level = level;
        if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                path->nodes[level] = root->node;
                extent_buffer_get(root->node);
                path->slots[level] = 0;
        } else {
                struct btrfs_key key;
                struct btrfs_disk_key found_key;
                struct extent_buffer *node;

                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                level = root_item->drop_level;
                path->lowest_level = level;
                wret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (wret < 0) {
                        ret = wret;
                        goto out;
                }
                node = path->nodes[level];
                btrfs_node_key(node, &found_key, path->slots[level]);
                WARN_ON(memcmp(&found_key, &root_item->drop_progress,
                               sizeof(found_key)));
        }
        while(1) {
                wret = walk_down_tree(trans, root, path, &level);
                if (wret > 0)
                        break;
                if (wret < 0)
                        ret = wret;

                wret = walk_up_tree(trans, root, path, &level);
                if (wret > 0)
                        break;
                if (wret < 0)
                        ret = wret;
                ret = -EAGAIN;
                break;
        }
        for (i = 0; i <= orig_level; i++) {
                if (path->nodes[i]) {
                        free_extent_buffer(path->nodes[i]);
                        path->nodes[i] = NULL;
                }
        }
out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_free_block_groups(struct btrfs_fs_info *info)
{
        u64 start;
        u64 end;
        u64 ptr;
        int ret;
        while(1) {
                ret = find_first_extent_bit(&info->block_group_cache, 0,
                                            &start, &end, (unsigned int)-1);
                if (ret)
                        break;
                ret = get_state_private(&info->block_group_cache, start, &ptr);
                if (!ret)
                        kfree((void *)(unsigned long)ptr);
                clear_extent_bits(&info->block_group_cache, start,
                                  end, (unsigned int)-1, GFP_NOFS);
        }
        while(1) {
                ret = find_first_extent_bit(&info->free_space_cache, 0,
                                            &start, &end, EXTENT_DIRTY);
                if (ret)
                        break;
                clear_extent_dirty(&info->free_space_cache, start,
                                   end, GFP_NOFS);
        }
        return 0;
}

static int noinline relocate_inode_pages(struct inode *inode, u64 start,
                                         u64 len)
{
        u64 page_start;
        u64 page_end;
        u64 delalloc_start;
        u64 existing_delalloc;
        unsigned long last_index;
        unsigned long i;
        struct page *page;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct file_ra_state *ra;

        ra = kzalloc(sizeof(*ra), GFP_NOFS);

        mutex_lock(&inode->i_mutex);
        i = start >> PAGE_CACHE_SHIFT;
        last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;

        file_ra_state_init(ra, inode->i_mapping);
        btrfs_force_ra(inode->i_mapping, ra, NULL, i, last_index);
        kfree(ra);

        for (; i <= last_index; i++) {
                page = grab_cache_page(inode->i_mapping, i);
                if (!page)
                        goto out_unlock;
                if (!PageUptodate(page)) {
                        btrfs_readpage(NULL, page);
                        lock_page(page);
                        if (!PageUptodate(page)) {
                                unlock_page(page);
                                page_cache_release(page);
                                goto out_unlock;
                        }
                }
                page_start = (u64)page->index << PAGE_CACHE_SHIFT;
                page_end = page_start + PAGE_CACHE_SIZE - 1;

                lock_extent(io_tree, page_start, page_end, GFP_NOFS);

                delalloc_start = page_start;
                existing_delalloc = count_range_bits(io_tree,
                                             &delalloc_start, page_end,
                                             PAGE_CACHE_SIZE, EXTENT_DELALLOC);

                set_extent_delalloc(io_tree, page_start,
                                    page_end, GFP_NOFS);

                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
                set_page_dirty(page);
                unlock_page(page);
                page_cache_release(page);
        }

out_unlock:
        mutex_unlock(&inode->i_mutex);
        return 0;
}

/*
 * note, this releases the path
 */
static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                                  struct btrfs_path *path,
                                  struct btrfs_key *extent_key)
{
        struct inode *inode;
        struct btrfs_root *found_root;
        struct btrfs_key *root_location;
        struct btrfs_extent_ref *ref;
        u64 ref_root;
        u64 ref_gen;
        u64 ref_objectid;
        u64 ref_offset;
        int ret;

        ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                             struct btrfs_extent_ref);
        ref_root = btrfs_ref_root(path->nodes[0], ref);
        ref_gen = btrfs_ref_generation(path->nodes[0], ref);
        ref_objectid = btrfs_ref_objectid(path->nodes[0], ref);
        ref_offset = btrfs_ref_offset(path->nodes[0], ref);
        btrfs_release_path(extent_root, path);

        root_location = kmalloc(sizeof(*root_location), GFP_NOFS);
        root_location->objectid = ref_root;
        if (ref_gen == 0)
                root_location->offset = 0;
        else
                root_location->offset = (u64)-1;
        root_location->type = BTRFS_ROOT_ITEM_KEY;

        found_root = btrfs_read_fs_root_no_name(extent_root->fs_info,
                                                root_location);
        BUG_ON(!found_root);
        kfree(root_location);

        if (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                mutex_unlock(&extent_root->fs_info->fs_mutex);
                inode = btrfs_iget_locked(extent_root->fs_info->sb,
                                          ref_objectid, found_root);
                if (inode->i_state & I_NEW) {
                        /* the inode and parent dir are two different roots */
                        BTRFS_I(inode)->root = found_root;
                        BTRFS_I(inode)->location.objectid = ref_objectid;
                        BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
                        BTRFS_I(inode)->location.offset = 0;
                        btrfs_read_locked_inode(inode);
                        unlock_new_inode(inode);

                }
                /* this can happen if the reference is not against
                 * the latest version of the tree root
                 */
                if (is_bad_inode(inode)) {
                        mutex_lock(&extent_root->fs_info->fs_mutex);
                        goto out;
                }
                relocate_inode_pages(inode, ref_offset, extent_key->offset);
                /* FIXME, data=ordered will help get rid of this */
                filemap_fdatawrite(inode->i_mapping);
                iput(inode);
                mutex_lock(&extent_root->fs_info->fs_mutex);
        } else {
                struct btrfs_trans_handle *trans;
                struct btrfs_key found_key;
                struct extent_buffer *eb;
                int level;
                int i;

                trans = btrfs_start_transaction(found_root, 1);
                eb = read_tree_block(found_root, extent_key->objectid,
                                     extent_key->offset);
                level = btrfs_header_level(eb);

                if (level == 0)
                        btrfs_item_key_to_cpu(eb, &found_key, 0);
                else
                        btrfs_node_key_to_cpu(eb, &found_key, 0);

                free_extent_buffer(eb);

                path->lowest_level = level;
                path->reada = 2;
                ret = btrfs_search_slot(trans, found_root, &found_key, path,
                                        0, 1);
                path->lowest_level = 0;
                for (i = level; i < BTRFS_MAX_LEVEL; i++) {
                        if (!path->nodes[i])
                                break;
                        free_extent_buffer(path->nodes[i]);
                        path->nodes[i] = NULL;
                }
                btrfs_release_path(found_root, path);
                btrfs_end_transaction(trans, found_root);
        }

out:
        return 0;
}

static int noinline relocate_one_extent(struct btrfs_root *extent_root,
                                        struct btrfs_path *path,
                                        struct btrfs_key *extent_key)
{
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
        u32 nritems;
        u32 item_size;
        int ret = 0;

        key.objectid = extent_key->objectid;
        key.type = BTRFS_EXTENT_REF_KEY;
        key.offset = 0;

        while(1) {
                ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);

                if (ret < 0)
                        goto out;

                ret = 0;
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                if (path->slots[0] == nritems)
                        goto out;

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != extent_key->objectid)
                        break;

                if (found_key.type != BTRFS_EXTENT_REF_KEY)
                        break;

                key.offset = found_key.offset + 1;
                item_size = btrfs_item_size_nr(leaf, path->slots[0]);

                ret = relocate_one_reference(extent_root, path, extent_key);
                if (ret)
                        goto out;
        }
        ret = 0;
out:
        btrfs_release_path(extent_root, path);
        return ret;
}

int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *tree_root = root->fs_info->tree_root;
        struct btrfs_path *path;
        u64 cur_byte;
        u64 total_found;
        struct btrfs_fs_info *info = root->fs_info;
        struct extent_io_tree *block_group_cache;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
        u32 nritems;
        int ret;
        int progress = 0;

        btrfs_set_super_total_bytes(&info->super_copy, new_size);
        clear_extent_dirty(&info->free_space_cache, new_size, (u64)-1,
                           GFP_NOFS);
        block_group_cache = &info->block_group_cache;
        path = btrfs_alloc_path();
        root = root->fs_info->extent_root;
        path->reada = 2;

again:
        total_found = 0;
        key.objectid = new_size;
        key.offset = 0;
        key.type = 0;
        cur_byte = key.objectid;

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

        ret = find_previous_extent(root, path);
        if (ret < 0)
                goto out;
        if (ret == 0) {
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid + found_key.offset > new_size) {
                        cur_byte = found_key.objectid;
                        key.objectid = cur_byte;
                }
        }
        btrfs_release_path(root, path);

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

                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
next:
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out;
                        if (ret == 1) {
                                ret = 0;
                                break;
                        }
                        leaf = path->nodes[0];
                        nritems = btrfs_header_nritems(leaf);
                }

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

                if (progress && need_resched()) {
                        memcpy(&key, &found_key, sizeof(key));
                        mutex_unlock(&root->fs_info->fs_mutex);
                        cond_resched();
                        mutex_lock(&root->fs_info->fs_mutex);
                        btrfs_release_path(root, path);
                        btrfs_search_slot(NULL, root, &key, path, 0, 0);
                        progress = 0;
                        goto next;
                }
                progress = 1;

                if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
                    found_key.objectid + found_key.offset <= cur_byte) {
                        path->slots[0]++;
                        goto next;
                }

                total_found++;
                cur_byte = found_key.objectid + found_key.offset;
                key.objectid = cur_byte;
                btrfs_release_path(root, path);
                ret = relocate_one_extent(root, path, &found_key);
        }

        btrfs_release_path(root, path);

        if (total_found > 0) {
                trans = btrfs_start_transaction(tree_root, 1);
                btrfs_commit_transaction(trans, tree_root);

                mutex_unlock(&root->fs_info->fs_mutex);
                btrfs_clean_old_snapshots(tree_root);
                mutex_lock(&root->fs_info->fs_mutex);

                trans = btrfs_start_transaction(tree_root, 1);
                btrfs_commit_transaction(trans, tree_root);
                goto again;
        }

        trans = btrfs_start_transaction(root, 1);
        key.objectid = new_size;
        key.offset = 0;
        key.type = 0;
        while(1) {
                u64 ptr;

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

                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
bg_next:
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                break;
                        if (ret == 1) {
                                ret = 0;
                                break;
                        }
                        leaf = path->nodes[0];
                        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                        /*
                         * btrfs_next_leaf doesn't cow buffers, we have to
                         * do the search again
                         */
                        memcpy(&key, &found_key, sizeof(key));
                        btrfs_release_path(root, path);
                        goto resched_check;
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (btrfs_key_type(&found_key) != BTRFS_BLOCK_GROUP_ITEM_KEY) {
                        printk("shrinker found key %Lu %u %Lu\n",
                                found_key.objectid, found_key.type,
                                found_key.offset);
                        path->slots[0]++;
                        goto bg_next;
                }
                ret = get_state_private(&info->block_group_cache,
                                        found_key.objectid, &ptr);
                if (!ret)
                        kfree((void *)(unsigned long)ptr);

                clear_extent_bits(&info->block_group_cache, found_key.objectid,
                                  found_key.objectid + found_key.offset - 1,
                                  (unsigned int)-1, GFP_NOFS);

                key.objectid = found_key.objectid + 1;
                btrfs_del_item(trans, root, path);
                btrfs_release_path(root, path);
resched_check:
                if (need_resched()) {
                        mutex_unlock(&root->fs_info->fs_mutex);
                        cond_resched();
                        mutex_lock(&root->fs_info->fs_mutex);
                }
        }
        clear_extent_dirty(&info->free_space_cache, new_size, (u64)-1,
                           GFP_NOFS);
        btrfs_commit_transaction(trans, root);
out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_grow_extent_tree(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, u64 new_size)
{
        struct btrfs_path *path;
        u64 nr = 0;
        u64 cur_byte;
        u64 old_size;
        unsigned long rem;
        struct btrfs_block_group_cache *cache;
        struct btrfs_block_group_item *item;
        struct btrfs_fs_info *info = root->fs_info;
        struct extent_io_tree *block_group_cache;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        int ret;
        int bit;

        old_size = btrfs_super_total_bytes(&info->super_copy);
        block_group_cache = &info->block_group_cache;

        root = info->extent_root;

        cache = btrfs_lookup_block_group(root->fs_info, old_size - 1);

        cur_byte = cache->key.objectid + cache->key.offset;
        if (cur_byte >= new_size)
                goto set_size;

        key.offset = BTRFS_BLOCK_GROUP_SIZE;
        btrfs_set_key_type(&key, BTRFS_BLOCK_GROUP_ITEM_KEY);

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

        while(cur_byte < new_size) {
                key.objectid = cur_byte;
                ret = btrfs_insert_empty_item(trans, root, path, &key,
                                        sizeof(struct btrfs_block_group_item));
                BUG_ON(ret);
                leaf = path->nodes[0];
                item = btrfs_item_ptr(leaf, path->slots[0],
                                      struct btrfs_block_group_item);

                btrfs_set_disk_block_group_used(leaf, item, 0);
                div_long_long_rem(nr, 3, &rem);
                if (rem) {
                        btrfs_set_disk_block_group_flags(leaf, item,
                                                 BTRFS_BLOCK_GROUP_DATA);
                } else {
                        btrfs_set_disk_block_group_flags(leaf, item, 0);
                }
                nr++;

                cache = kmalloc(sizeof(*cache), GFP_NOFS);
                BUG_ON(!cache);

                read_extent_buffer(leaf, &cache->item, (unsigned long)item,
                                   sizeof(cache->item));

                memcpy(&cache->key, &key, sizeof(key));
                cache->cached = 0;
                cache->pinned = 0;
                cur_byte = key.objectid + key.offset;
                btrfs_release_path(root, path);

                if (cache->item.flags & BTRFS_BLOCK_GROUP_DATA) {
                        bit = BLOCK_GROUP_DATA;
                        cache->data = BTRFS_BLOCK_GROUP_DATA;
                } else {
                        bit = BLOCK_GROUP_METADATA;
                        cache->data = 0;
                }

                /* use EXTENT_LOCKED to prevent merging */
                set_extent_bits(block_group_cache, key.objectid,
                                key.objectid + key.offset - 1,
                                bit | EXTENT_LOCKED, GFP_NOFS);
                set_state_private(block_group_cache, key.objectid,
                                  (unsigned long)cache);
        }
        btrfs_free_path(path);
set_size:
        btrfs_set_super_total_bytes(&info->super_copy, new_size);
        return 0;
}

int btrfs_read_block_groups(struct btrfs_root *root)
{
        struct btrfs_path *path;
        int ret;
        int err = 0;
        int bit;
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *info = root->fs_info;
        struct extent_io_tree *block_group_cache;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;

        block_group_cache = &info->block_group_cache;

        root = info->extent_root;
        key.objectid = 0;
        key.offset = BTRFS_BLOCK_GROUP_SIZE;
        btrfs_set_key_type(&key, BTRFS_BLOCK_GROUP_ITEM_KEY);

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

        while(1) {
                ret = btrfs_search_slot(NULL, info->extent_root,
                                        &key, path, 0, 0);
                if (ret != 0) {
                        err = ret;
                        break;
                }
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                cache = kmalloc(sizeof(*cache), GFP_NOFS);
                if (!cache) {
                        err = -1;
                        break;
                }

                read_extent_buffer(leaf, &cache->item,
                                   btrfs_item_ptr_offset(leaf, path->slots[0]),
                                   sizeof(cache->item));
                memcpy(&cache->key, &found_key, sizeof(found_key));
                cache->cached = 0;
                cache->pinned = 0;
                key.objectid = found_key.objectid + found_key.offset;
                btrfs_release_path(root, path);

                if (cache->item.flags & BTRFS_BLOCK_GROUP_MIXED) {
                        bit = BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA;
                        cache->data = BTRFS_BLOCK_GROUP_MIXED;
                } else if (cache->item.flags & BTRFS_BLOCK_GROUP_DATA) {
                        bit = BLOCK_GROUP_DATA;
                        cache->data = BTRFS_BLOCK_GROUP_DATA;
                } else {
                        bit = BLOCK_GROUP_METADATA;
                        cache->data = 0;
                }

                /* use EXTENT_LOCKED to prevent merging */
                set_extent_bits(block_group_cache, found_key.objectid,
                                found_key.objectid + found_key.offset - 1,
                                bit | EXTENT_LOCKED, GFP_NOFS);
                set_state_private(block_group_cache, found_key.objectid,
                                  (unsigned long)cache);

                if (key.objectid >=
                    btrfs_super_total_bytes(&info->super_copy))
                        break;
        }

        btrfs_free_path(path);
        return 0;
}