Btrfs: simplify iteration codes

[mirror_ubuntu-artful-kernel.git] / fs / btrfs / transaction.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/fs.h>
#include <linux/sched.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "locking.h"
#include "ref-cache.h"
#include "tree-log.h"

#define BTRFS_ROOT_TRANS_TAG 0

static noinline void put_transaction(struct btrfs_transaction *transaction)
{
        WARN_ON(transaction->use_count == 0);
        transaction->use_count--;
        if (transaction->use_count == 0) {
                list_del_init(&transaction->list);
                memset(transaction, 0, sizeof(*transaction));
                kmem_cache_free(btrfs_transaction_cachep, transaction);
        }
}

/*
 * either allocate a new transaction or hop into the existing one
 */
static noinline int join_transaction(struct btrfs_root *root)
{
        struct btrfs_transaction *cur_trans;
        cur_trans = root->fs_info->running_transaction;
        if (!cur_trans) {
                cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
                                             GFP_NOFS);
                BUG_ON(!cur_trans);
                root->fs_info->generation++;
                root->fs_info->last_alloc = 0;
                root->fs_info->last_data_alloc = 0;
                cur_trans->num_writers = 1;
                cur_trans->num_joined = 0;
                cur_trans->transid = root->fs_info->generation;
                init_waitqueue_head(&cur_trans->writer_wait);
                init_waitqueue_head(&cur_trans->commit_wait);
                cur_trans->in_commit = 0;
                cur_trans->blocked = 0;
                cur_trans->use_count = 1;
                cur_trans->commit_done = 0;
                cur_trans->start_time = get_seconds();
                INIT_LIST_HEAD(&cur_trans->pending_snapshots);
                list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
                extent_io_tree_init(&cur_trans->dirty_pages,
                                     root->fs_info->btree_inode->i_mapping,
                                     GFP_NOFS);
                spin_lock(&root->fs_info->new_trans_lock);
                root->fs_info->running_transaction = cur_trans;
                spin_unlock(&root->fs_info->new_trans_lock);
        } else {
                cur_trans->num_writers++;
                cur_trans->num_joined++;
        }

        return 0;
}

/*
 * this does all the record keeping required to make sure that a reference
 * counted root is properly recorded in a given transaction.  This is required
 * to make sure the old root from before we joined the transaction is deleted
 * when the transaction commits
 */
noinline int btrfs_record_root_in_trans(struct btrfs_root *root)
{
        struct btrfs_dirty_root *dirty;
        u64 running_trans_id = root->fs_info->running_transaction->transid;
        if (root->ref_cows && root->last_trans < running_trans_id) {
                WARN_ON(root == root->fs_info->extent_root);
                if (root->root_item.refs != 0) {
                        radix_tree_tag_set(&root->fs_info->fs_roots_radix,
                                   (unsigned long)root->root_key.objectid,
                                   BTRFS_ROOT_TRANS_TAG);

                        dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
                        BUG_ON(!dirty);
                        dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
                        BUG_ON(!dirty->root);
                        dirty->latest_root = root;
                        INIT_LIST_HEAD(&dirty->list);

                        root->commit_root = btrfs_root_node(root);

                        memcpy(dirty->root, root, sizeof(*root));
                        spin_lock_init(&dirty->root->node_lock);
                        spin_lock_init(&dirty->root->list_lock);
                        mutex_init(&dirty->root->objectid_mutex);
                        mutex_init(&dirty->root->log_mutex);
                        INIT_LIST_HEAD(&dirty->root->dead_list);
                        dirty->root->node = root->commit_root;
                        dirty->root->commit_root = NULL;

                        spin_lock(&root->list_lock);
                        list_add(&dirty->root->dead_list, &root->dead_list);
                        spin_unlock(&root->list_lock);

                        root->dirty_root = dirty;
                } else {
                        WARN_ON(1);
                }
                root->last_trans = running_trans_id;
        }
        return 0;
}

/* wait for commit against the current transaction to become unblocked
 * when this is done, it is safe to start a new transaction, but the current
 * transaction might not be fully on disk.
 */
static void wait_current_trans(struct btrfs_root *root)
{
        struct btrfs_transaction *cur_trans;

        cur_trans = root->fs_info->running_transaction;
        if (cur_trans && cur_trans->blocked) {
                DEFINE_WAIT(wait);
                cur_trans->use_count++;
                while (1) {
                        prepare_to_wait(&root->fs_info->transaction_wait, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (cur_trans->blocked) {
                                mutex_unlock(&root->fs_info->trans_mutex);
                                schedule();
                                mutex_lock(&root->fs_info->trans_mutex);
                                finish_wait(&root->fs_info->transaction_wait,
                                            &wait);
                        } else {
                                finish_wait(&root->fs_info->transaction_wait,
                                            &wait);
                                break;
                        }
                }
                put_transaction(cur_trans);
        }
}

static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
                                             int num_blocks, int wait)
{
        struct btrfs_trans_handle *h =
                kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
        int ret;

        mutex_lock(&root->fs_info->trans_mutex);
        if (!root->fs_info->log_root_recovering &&
            ((wait == 1 && !root->fs_info->open_ioctl_trans) || wait == 2))
                wait_current_trans(root);
        ret = join_transaction(root);
        BUG_ON(ret);

        btrfs_record_root_in_trans(root);
        h->transid = root->fs_info->running_transaction->transid;
        h->transaction = root->fs_info->running_transaction;
        h->blocks_reserved = num_blocks;
        h->blocks_used = 0;
        h->block_group = 0;
        h->alloc_exclude_nr = 0;
        h->alloc_exclude_start = 0;
        root->fs_info->running_transaction->use_count++;
        mutex_unlock(&root->fs_info->trans_mutex);
        return h;
}

struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
                                                   int num_blocks)
{
        return start_transaction(root, num_blocks, 1);
}
struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
                                                   int num_blocks)
{
        return start_transaction(root, num_blocks, 0);
}

struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
                                                         int num_blocks)
{
        return start_transaction(r, num_blocks, 2);
}

/* wait for a transaction commit to be fully complete */
static noinline int wait_for_commit(struct btrfs_root *root,
                                    struct btrfs_transaction *commit)
{
        DEFINE_WAIT(wait);
        mutex_lock(&root->fs_info->trans_mutex);
        while (!commit->commit_done) {
                prepare_to_wait(&commit->commit_wait, &wait,
                                TASK_UNINTERRUPTIBLE);
                if (commit->commit_done)
                        break;
                mutex_unlock(&root->fs_info->trans_mutex);
                schedule();
                mutex_lock(&root->fs_info->trans_mutex);
        }
        mutex_unlock(&root->fs_info->trans_mutex);
        finish_wait(&commit->commit_wait, &wait);
        return 0;
}

/*
 * rate limit against the drop_snapshot code.  This helps to slow down new
 * operations if the drop_snapshot code isn't able to keep up.
 */
static void throttle_on_drops(struct btrfs_root *root)
{
        struct btrfs_fs_info *info = root->fs_info;
        int harder_count = 0;

harder:
        if (atomic_read(&info->throttles)) {
                DEFINE_WAIT(wait);
                int thr;
                thr = atomic_read(&info->throttle_gen);

                do {
                        prepare_to_wait(&info->transaction_throttle,
                                        &wait, TASK_UNINTERRUPTIBLE);
                        if (!atomic_read(&info->throttles)) {
                                finish_wait(&info->transaction_throttle, &wait);
                                break;
                        }
                        schedule();
                        finish_wait(&info->transaction_throttle, &wait);
                } while (thr == atomic_read(&info->throttle_gen));
                harder_count++;

                if (root->fs_info->total_ref_cache_size > 1 * 1024 * 1024 &&
                    harder_count < 2)
                        goto harder;

                if (root->fs_info->total_ref_cache_size > 5 * 1024 * 1024 &&
                    harder_count < 10)
                        goto harder;

                if (root->fs_info->total_ref_cache_size > 10 * 1024 * 1024 &&
                    harder_count < 20)
                        goto harder;
        }
}

void btrfs_throttle(struct btrfs_root *root)
{
        mutex_lock(&root->fs_info->trans_mutex);
        if (!root->fs_info->open_ioctl_trans)
                wait_current_trans(root);
        mutex_unlock(&root->fs_info->trans_mutex);

        throttle_on_drops(root);
}

static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, int throttle)
{
        struct btrfs_transaction *cur_trans;
        struct btrfs_fs_info *info = root->fs_info;

        mutex_lock(&info->trans_mutex);
        cur_trans = info->running_transaction;
        WARN_ON(cur_trans != trans->transaction);
        WARN_ON(cur_trans->num_writers < 1);
        cur_trans->num_writers--;

        if (waitqueue_active(&cur_trans->writer_wait))
                wake_up(&cur_trans->writer_wait);
        put_transaction(cur_trans);
        mutex_unlock(&info->trans_mutex);
        memset(trans, 0, sizeof(*trans));
        kmem_cache_free(btrfs_trans_handle_cachep, trans);

        if (throttle)
                throttle_on_drops(root);

        return 0;
}

int btrfs_end_transaction(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root)
{
        return __btrfs_end_transaction(trans, root, 0);
}

int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root)
{
        return __btrfs_end_transaction(trans, root, 1);
}

/*
 * when btree blocks are allocated, they have some corresponding bits set for
 * them in one of two extent_io trees.  This is used to make sure all of
 * those extents are on disk for transaction or log commit
 */
int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
                                        struct extent_io_tree *dirty_pages)
{
        int ret;
        int err = 0;
        int werr = 0;
        struct page *page;
        struct inode *btree_inode = root->fs_info->btree_inode;
        u64 start = 0;
        u64 end;
        unsigned long index;

        while (1) {
                ret = find_first_extent_bit(dirty_pages, start, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;
                while (start <= end) {
                        cond_resched();

                        index = start >> PAGE_CACHE_SHIFT;
                        start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
                        page = find_get_page(btree_inode->i_mapping, index);
                        if (!page)
                                continue;

                        btree_lock_page_hook(page);
                        if (!page->mapping) {
                                unlock_page(page);
                                page_cache_release(page);
                                continue;
                        }

                        if (PageWriteback(page)) {
                                if (PageDirty(page))
                                        wait_on_page_writeback(page);
                                else {
                                        unlock_page(page);
                                        page_cache_release(page);
                                        continue;
                                }
                        }
                        err = write_one_page(page, 0);
                        if (err)
                                werr = err;
                        page_cache_release(page);
                }
        }
        while (1) {
                ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
                                            EXTENT_DIRTY);
                if (ret)
                        break;

                clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
                while (start <= end) {
                        index = start >> PAGE_CACHE_SHIFT;
                        start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
                        page = find_get_page(btree_inode->i_mapping, index);
                        if (!page)
                                continue;
                        if (PageDirty(page)) {
                                btree_lock_page_hook(page);
                                wait_on_page_writeback(page);
                                err = write_one_page(page, 0);
                                if (err)
                                        werr = err;
                        }
                        wait_on_page_writeback(page);
                        page_cache_release(page);
                        cond_resched();
                }
        }
        if (err)
                werr = err;
        return werr;
}

int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root)
{
        if (!trans || !trans->transaction) {
                struct inode *btree_inode;
                btree_inode = root->fs_info->btree_inode;
                return filemap_write_and_wait(btree_inode->i_mapping);
        }
        return btrfs_write_and_wait_marked_extents(root,
                                           &trans->transaction->dirty_pages);
}

/*
 * this is used to update the root pointer in the tree of tree roots.
 *
 * But, in the case of the extent allocation tree, updating the root
 * pointer may allocate blocks which may change the root of the extent
 * allocation tree.
 *
 * So, this loops and repeats and makes sure the cowonly root didn't
 * change while the root pointer was being updated in the metadata.
 */
static int update_cowonly_root(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root)
{
        int ret;
        u64 old_root_bytenr;
        struct btrfs_root *tree_root = root->fs_info->tree_root;

        btrfs_extent_post_op(trans, root);
        btrfs_write_dirty_block_groups(trans, root);
        btrfs_extent_post_op(trans, root);

        while (1) {
                old_root_bytenr = btrfs_root_bytenr(&root->root_item);
                if (old_root_bytenr == root->node->start)
                        break;
                btrfs_set_root_bytenr(&root->root_item,
                                       root->node->start);
                btrfs_set_root_level(&root->root_item,
                                     btrfs_header_level(root->node));
                btrfs_set_root_generation(&root->root_item, trans->transid);

                btrfs_extent_post_op(trans, root);

                ret = btrfs_update_root(trans, tree_root,
                                        &root->root_key,
                                        &root->root_item);
                BUG_ON(ret);
                btrfs_write_dirty_block_groups(trans, root);
                btrfs_extent_post_op(trans, root);
        }
        return 0;
}

/*
 * update all the cowonly tree roots on disk
 */
int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct list_head *next;
        struct extent_buffer *eb;

        btrfs_extent_post_op(trans, fs_info->tree_root);

        eb = btrfs_lock_root_node(fs_info->tree_root);
        btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb, 0);
        btrfs_tree_unlock(eb);
        free_extent_buffer(eb);

        btrfs_extent_post_op(trans, fs_info->tree_root);

        while (!list_empty(&fs_info->dirty_cowonly_roots)) {
                next = fs_info->dirty_cowonly_roots.next;
                list_del_init(next);
                root = list_entry(next, struct btrfs_root, dirty_list);

                update_cowonly_root(trans, root);
        }
        return 0;
}

/*
 * dead roots are old snapshots that need to be deleted.  This allocates
 * a dirty root struct and adds it into the list of dead roots that need to
 * be deleted
 */
int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest)
{
        struct btrfs_dirty_root *dirty;

        dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
        if (!dirty)
                return -ENOMEM;
        dirty->root = root;
        dirty->latest_root = latest;

        mutex_lock(&root->fs_info->trans_mutex);
        list_add(&dirty->list, &latest->fs_info->dead_roots);
        mutex_unlock(&root->fs_info->trans_mutex);
        return 0;
}

/*
 * at transaction commit time we need to schedule the old roots for
 * deletion via btrfs_drop_snapshot.  This runs through all the
 * reference counted roots that were modified in the current
 * transaction and puts them into the drop list
 */
static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
                                    struct radix_tree_root *radix,
                                    struct list_head *list)
{
        struct btrfs_dirty_root *dirty;
        struct btrfs_root *gang[8];
        struct btrfs_root *root;
        int i;
        int ret;
        int err = 0;
        u32 refs;

        while (1) {
                ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
                                                 ARRAY_SIZE(gang),
                                                 BTRFS_ROOT_TRANS_TAG);
                if (ret == 0)
                        break;
                for (i = 0; i < ret; i++) {
                        root = gang[i];
                        radix_tree_tag_clear(radix,
                                     (unsigned long)root->root_key.objectid,
                                     BTRFS_ROOT_TRANS_TAG);

                        BUG_ON(!root->ref_tree);
                        dirty = root->dirty_root;

                        btrfs_free_log(trans, root);
                        btrfs_free_reloc_root(trans, root);

                        if (root->commit_root == root->node) {
                                WARN_ON(root->node->start !=
                                        btrfs_root_bytenr(&root->root_item));

                                free_extent_buffer(root->commit_root);
                                root->commit_root = NULL;
                                root->dirty_root = NULL;

                                spin_lock(&root->list_lock);
                                list_del_init(&dirty->root->dead_list);
                                spin_unlock(&root->list_lock);

                                kfree(dirty->root);
                                kfree(dirty);

                                /* make sure to update the root on disk
                                 * so we get any updates to the block used
                                 * counts
                                 */
                                err = btrfs_update_root(trans,
                                                root->fs_info->tree_root,
                                                &root->root_key,
                                                &root->root_item);
                                continue;
                        }

                        memset(&root->root_item.drop_progress, 0,
                               sizeof(struct btrfs_disk_key));
                        root->root_item.drop_level = 0;
                        root->commit_root = NULL;
                        root->dirty_root = NULL;
                        root->root_key.offset = root->fs_info->generation;
                        btrfs_set_root_bytenr(&root->root_item,
                                              root->node->start);
                        btrfs_set_root_level(&root->root_item,
                                             btrfs_header_level(root->node));
                        btrfs_set_root_generation(&root->root_item,
                                                  root->root_key.offset);

                        err = btrfs_insert_root(trans, root->fs_info->tree_root,
                                                &root->root_key,
                                                &root->root_item);
                        if (err)
                                break;

                        refs = btrfs_root_refs(&dirty->root->root_item);
                        btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
                        err = btrfs_update_root(trans, root->fs_info->tree_root,
                                                &dirty->root->root_key,
                                                &dirty->root->root_item);

                        BUG_ON(err);
                        if (refs == 1) {
                                list_add(&dirty->list, list);
                        } else {
                                WARN_ON(1);
                                free_extent_buffer(dirty->root->node);
                                kfree(dirty->root);
                                kfree(dirty);
                        }
                }
        }
        return err;
}

/*
 * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
 * otherwise every leaf in the btree is read and defragged.
 */
int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
{
        struct btrfs_fs_info *info = root->fs_info;
        int ret;
        struct btrfs_trans_handle *trans;
        unsigned long nr;

        smp_mb();
        if (root->defrag_running)
                return 0;
        trans = btrfs_start_transaction(root, 1);
        while (1) {
                root->defrag_running = 1;
                ret = btrfs_defrag_leaves(trans, root, cacheonly);
                nr = trans->blocks_used;
                btrfs_end_transaction(trans, root);
                btrfs_btree_balance_dirty(info->tree_root, nr);
                cond_resched();

                trans = btrfs_start_transaction(root, 1);
                if (root->fs_info->closing || ret != -EAGAIN)
                        break;
        }
        root->defrag_running = 0;
        smp_mb();
        btrfs_end_transaction(trans, root);
        return 0;
}

/*
 * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on
 * all of them
 */
static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
                                     struct list_head *list)
{
        struct btrfs_dirty_root *dirty;
        struct btrfs_trans_handle *trans;
        unsigned long nr;
        u64 num_bytes;
        u64 bytes_used;
        u64 max_useless;
        int ret = 0;
        int err;

        while (!list_empty(list)) {
                struct btrfs_root *root;

                dirty = list_entry(list->prev, struct btrfs_dirty_root, list);
                list_del_init(&dirty->list);

                num_bytes = btrfs_root_used(&dirty->root->root_item);
                root = dirty->latest_root;
                atomic_inc(&root->fs_info->throttles);

                while (1) {
                        trans = btrfs_start_transaction(tree_root, 1);
                        mutex_lock(&root->fs_info->drop_mutex);
                        ret = btrfs_drop_snapshot(trans, dirty->root);
                        if (ret != -EAGAIN)
                                break;
                        mutex_unlock(&root->fs_info->drop_mutex);

                        err = btrfs_update_root(trans,
                                        tree_root,
                                        &dirty->root->root_key,
                                        &dirty->root->root_item);
                        if (err)
                                ret = err;
                        nr = trans->blocks_used;
                        ret = btrfs_end_transaction(trans, tree_root);
                        BUG_ON(ret);

                        btrfs_btree_balance_dirty(tree_root, nr);
                        cond_resched();
                }
                BUG_ON(ret);
                atomic_dec(&root->fs_info->throttles);
                wake_up(&root->fs_info->transaction_throttle);

                num_bytes -= btrfs_root_used(&dirty->root->root_item);
                bytes_used = btrfs_root_used(&root->root_item);
                if (num_bytes) {
                        btrfs_record_root_in_trans(root);
                        btrfs_set_root_used(&root->root_item,
                                            bytes_used - num_bytes);
                }

                ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
                if (ret) {
                        BUG();
                        break;
                }
                mutex_unlock(&root->fs_info->drop_mutex);

                spin_lock(&root->list_lock);
                list_del_init(&dirty->root->dead_list);
                if (!list_empty(&root->dead_list)) {
                        struct btrfs_root *oldest;
                        oldest = list_entry(root->dead_list.prev,
                                            struct btrfs_root, dead_list);
                        max_useless = oldest->root_key.offset - 1;
                } else {
                        max_useless = root->root_key.offset - 1;
                }
                spin_unlock(&root->list_lock);

                nr = trans->blocks_used;
                ret = btrfs_end_transaction(trans, tree_root);
                BUG_ON(ret);

                ret = btrfs_remove_leaf_refs(root, max_useless, 0);
                BUG_ON(ret);

                free_extent_buffer(dirty->root->node);
                kfree(dirty->root);
                kfree(dirty);

                btrfs_btree_balance_dirty(tree_root, nr);
                cond_resched();
        }
        return ret;
}

/*
 * new snapshots need to be created at a very specific time in the
 * transaction commit.  This does the actual creation
 */
static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                                   struct btrfs_fs_info *fs_info,
                                   struct btrfs_pending_snapshot *pending)
{
        struct btrfs_key key;
        struct btrfs_root_item *new_root_item;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *root = pending->root;
        struct extent_buffer *tmp;
        struct extent_buffer *old;
        int ret;
        u64 objectid;

        new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
        if (!new_root_item) {
                ret = -ENOMEM;
                goto fail;
        }
        ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
        if (ret)
                goto fail;

        btrfs_record_root_in_trans(root);
        btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
        memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));

        key.objectid = objectid;
        key.offset = trans->transid;
        btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);

        old = btrfs_lock_root_node(root);
        btrfs_cow_block(trans, root, old, NULL, 0, &old, 0);

        btrfs_copy_root(trans, root, old, &tmp, objectid);
        btrfs_tree_unlock(old);
        free_extent_buffer(old);

        btrfs_set_root_bytenr(new_root_item, tmp->start);
        btrfs_set_root_level(new_root_item, btrfs_header_level(tmp));
        btrfs_set_root_generation(new_root_item, trans->transid);
        ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
                                new_root_item);
        btrfs_tree_unlock(tmp);
        free_extent_buffer(tmp);
        if (ret)
                goto fail;

        key.offset = (u64)-1;
        memcpy(&pending->root_key, &key, sizeof(key));
fail:
        kfree(new_root_item);
        return ret;
}

static noinline int finish_pending_snapshot(struct btrfs_fs_info *fs_info,
                                   struct btrfs_pending_snapshot *pending)
{
        int ret;
        int namelen;
        u64 index = 0;
        struct btrfs_trans_handle *trans;
        struct inode *parent_inode;
        struct inode *inode;
        struct btrfs_root *parent_root;

        parent_inode = pending->dentry->d_parent->d_inode;
        parent_root = BTRFS_I(parent_inode)->root;
        trans = btrfs_join_transaction(parent_root, 1);

        /*
         * insert the directory item
         */
        namelen = strlen(pending->name);
        ret = btrfs_set_inode_index(parent_inode, &index);
        ret = btrfs_insert_dir_item(trans, parent_root,
                            pending->name, namelen,
                            parent_inode->i_ino,
                            &pending->root_key, BTRFS_FT_DIR, index);

        if (ret)
                goto fail;

        btrfs_i_size_write(parent_inode, parent_inode->i_size + namelen * 2);
        ret = btrfs_update_inode(trans, parent_root, parent_inode);
        BUG_ON(ret);

        /* add the backref first */
        ret = btrfs_add_root_ref(trans, parent_root->fs_info->tree_root,
                                 pending->root_key.objectid,
                                 BTRFS_ROOT_BACKREF_KEY,
                                 parent_root->root_key.objectid,
                                 parent_inode->i_ino, index, pending->name,
                                 namelen);

        BUG_ON(ret);

        /* now add the forward ref */
        ret = btrfs_add_root_ref(trans, parent_root->fs_info->tree_root,
                                 parent_root->root_key.objectid,
                                 BTRFS_ROOT_REF_KEY,
                                 pending->root_key.objectid,
                                 parent_inode->i_ino, index, pending->name,
                                 namelen);

        inode = btrfs_lookup_dentry(parent_inode, pending->dentry);
        d_instantiate(pending->dentry, inode);
fail:
        btrfs_end_transaction(trans, fs_info->fs_root);
        return ret;
}

/*
 * create all the snapshots we've scheduled for creation
 */
static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
                                             struct btrfs_fs_info *fs_info)
{
        struct btrfs_pending_snapshot *pending;
        struct list_head *head = &trans->transaction->pending_snapshots;
        int ret;

        list_for_each_entry(pending, head, list) {
                ret = create_pending_snapshot(trans, fs_info, pending);
                BUG_ON(ret);
        }
        return 0;
}

static noinline int finish_pending_snapshots(struct btrfs_trans_handle *trans,
                                             struct btrfs_fs_info *fs_info)
{
        struct btrfs_pending_snapshot *pending;
        struct list_head *head = &trans->transaction->pending_snapshots;
        int ret;

        while (!list_empty(head)) {
                pending = list_entry(head->next,
                                     struct btrfs_pending_snapshot, list);
                ret = finish_pending_snapshot(fs_info, pending);
                BUG_ON(ret);
                list_del(&pending->list);
                kfree(pending->name);
                kfree(pending);
        }
        return 0;
}

int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root)
{
        unsigned long joined = 0;
        unsigned long timeout = 1;
        struct btrfs_transaction *cur_trans;
        struct btrfs_transaction *prev_trans = NULL;
        struct btrfs_root *chunk_root = root->fs_info->chunk_root;
        struct list_head dirty_fs_roots;
        struct extent_io_tree *pinned_copy;
        DEFINE_WAIT(wait);
        int ret;

        INIT_LIST_HEAD(&dirty_fs_roots);
        mutex_lock(&root->fs_info->trans_mutex);
        if (trans->transaction->in_commit) {
                cur_trans = trans->transaction;
                trans->transaction->use_count++;
                mutex_unlock(&root->fs_info->trans_mutex);
                btrfs_end_transaction(trans, root);

                ret = wait_for_commit(root, cur_trans);
                BUG_ON(ret);

                mutex_lock(&root->fs_info->trans_mutex);
                put_transaction(cur_trans);
                mutex_unlock(&root->fs_info->trans_mutex);

                return 0;
        }

        pinned_copy = kmalloc(sizeof(*pinned_copy), GFP_NOFS);
        if (!pinned_copy)
                return -ENOMEM;

        extent_io_tree_init(pinned_copy,
                             root->fs_info->btree_inode->i_mapping, GFP_NOFS);

        trans->transaction->in_commit = 1;
        trans->transaction->blocked = 1;
        cur_trans = trans->transaction;
        if (cur_trans->list.prev != &root->fs_info->trans_list) {
                prev_trans = list_entry(cur_trans->list.prev,
                                        struct btrfs_transaction, list);
                if (!prev_trans->commit_done) {
                        prev_trans->use_count++;
                        mutex_unlock(&root->fs_info->trans_mutex);

                        wait_for_commit(root, prev_trans);

                        mutex_lock(&root->fs_info->trans_mutex);
                        put_transaction(prev_trans);
                }
        }

        do {
                int snap_pending = 0;
                joined = cur_trans->num_joined;
                if (!list_empty(&trans->transaction->pending_snapshots))
                        snap_pending = 1;

                WARN_ON(cur_trans != trans->transaction);
                prepare_to_wait(&cur_trans->writer_wait, &wait,
                                TASK_UNINTERRUPTIBLE);

                if (cur_trans->num_writers > 1)
                        timeout = MAX_SCHEDULE_TIMEOUT;
                else
                        timeout = 1;

                mutex_unlock(&root->fs_info->trans_mutex);

                if (snap_pending) {
                        ret = btrfs_wait_ordered_extents(root, 1);
                        BUG_ON(ret);
                }

                schedule_timeout(timeout);

                mutex_lock(&root->fs_info->trans_mutex);
                finish_wait(&cur_trans->writer_wait, &wait);
        } while (cur_trans->num_writers > 1 ||
                 (cur_trans->num_joined != joined));

        ret = create_pending_snapshots(trans, root->fs_info);
        BUG_ON(ret);

        WARN_ON(cur_trans != trans->transaction);

        /* btrfs_commit_tree_roots is responsible for getting the
         * various roots consistent with each other.  Every pointer
         * in the tree of tree roots has to point to the most up to date
         * root for every subvolume and other tree.  So, we have to keep
         * the tree logging code from jumping in and changing any
         * of the trees.
         *
         * At this point in the commit, there can't be any tree-log
         * writers, but a little lower down we drop the trans mutex
         * and let new people in.  By holding the tree_log_mutex
         * from now until after the super is written, we avoid races
         * with the tree-log code.
         */
        mutex_lock(&root->fs_info->tree_log_mutex);
        /*
         * keep tree reloc code from adding new reloc trees
         */
        mutex_lock(&root->fs_info->tree_reloc_mutex);


        ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
                              &dirty_fs_roots);
        BUG_ON(ret);

        /* add_dirty_roots gets rid of all the tree log roots, it is now
         * safe to free the root of tree log roots
         */
        btrfs_free_log_root_tree(trans, root->fs_info);

        ret = btrfs_commit_tree_roots(trans, root);
        BUG_ON(ret);

        cur_trans = root->fs_info->running_transaction;
        spin_lock(&root->fs_info->new_trans_lock);
        root->fs_info->running_transaction = NULL;
        spin_unlock(&root->fs_info->new_trans_lock);
        btrfs_set_super_generation(&root->fs_info->super_copy,
                                   cur_trans->transid);
        btrfs_set_super_root(&root->fs_info->super_copy,
                             root->fs_info->tree_root->node->start);
        btrfs_set_super_root_level(&root->fs_info->super_copy,
                           btrfs_header_level(root->fs_info->tree_root->node));

        btrfs_set_super_chunk_root(&root->fs_info->super_copy,
                                   chunk_root->node->start);
        btrfs_set_super_chunk_root_level(&root->fs_info->super_copy,
                                         btrfs_header_level(chunk_root->node));
        btrfs_set_super_chunk_root_generation(&root->fs_info->super_copy,
                                btrfs_header_generation(chunk_root->node));

        if (!root->fs_info->log_root_recovering) {
                btrfs_set_super_log_root(&root->fs_info->super_copy, 0);
                btrfs_set_super_log_root_level(&root->fs_info->super_copy, 0);
        }

        memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
               sizeof(root->fs_info->super_copy));

        btrfs_copy_pinned(root, pinned_copy);

        trans->transaction->blocked = 0;
        wake_up(&root->fs_info->transaction_throttle);
        wake_up(&root->fs_info->transaction_wait);

        mutex_unlock(&root->fs_info->trans_mutex);
        ret = btrfs_write_and_wait_transaction(trans, root);
        BUG_ON(ret);
        write_ctree_super(trans, root, 0);

        /*
         * the super is written, we can safely allow the tree-loggers
         * to go about their business
         */
        mutex_unlock(&root->fs_info->tree_log_mutex);

        btrfs_finish_extent_commit(trans, root, pinned_copy);
        kfree(pinned_copy);

        btrfs_drop_dead_reloc_roots(root);
        mutex_unlock(&root->fs_info->tree_reloc_mutex);

        /* do the directory inserts of any pending snapshot creations */
        finish_pending_snapshots(trans, root->fs_info);

        mutex_lock(&root->fs_info->trans_mutex);

        cur_trans->commit_done = 1;
        root->fs_info->last_trans_committed = cur_trans->transid;
        wake_up(&cur_trans->commit_wait);

        put_transaction(cur_trans);
        put_transaction(cur_trans);

        list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
        if (root->fs_info->closing)
                list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);

        mutex_unlock(&root->fs_info->trans_mutex);

        kmem_cache_free(btrfs_trans_handle_cachep, trans);

        if (root->fs_info->closing)
                drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
        return ret;
}

/*
 * interface function to delete all the snapshots we have scheduled for deletion
 */
int btrfs_clean_old_snapshots(struct btrfs_root *root)
{
        struct list_head dirty_roots;
        INIT_LIST_HEAD(&dirty_roots);
again:
        mutex_lock(&root->fs_info->trans_mutex);
        list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
        mutex_unlock(&root->fs_info->trans_mutex);

        if (!list_empty(&dirty_roots)) {
                drop_dirty_roots(root, &dirty_roots);
                goto again;
        }
        return 0;
}