From 3063d29f2a4d4a4e9fa1ec77c124514f287c6da7 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Tue, 8 Jan 2008 15:46:30 -0500 Subject: Btrfs: Move snapshot creation to commit time It is very difficult to create a consistent snapshot of the btree when other writers may update the btree before the commit is done. This changes the snapshot creation to happen during the commit, while no other updates are possible. Signed-off-by: Chris Mason --- fs/btrfs/inode.c | 79 +++++++++++--------------------------------------------- 1 file changed, 15 insertions(+), 64 deletions(-) (limited to 'fs/btrfs/inode.c') diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 6d6e1ac0a9a0..10cece11dbd8 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -2250,13 +2250,10 @@ fail_commit: static int create_snapshot(struct btrfs_root *root, char *name, int namelen) { + struct btrfs_pending_snapshot *pending_snapshot; struct btrfs_trans_handle *trans; - struct btrfs_key key; - struct btrfs_root_item new_root_item; - struct extent_buffer *tmp; int ret; int err; - u64 objectid; unsigned long nr = 0; if (!root->ref_cows) @@ -2267,72 +2264,26 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen) if (ret) goto fail_unlock; + pending_snapshot = kmalloc(sizeof(*pending_snapshot), GFP_NOFS); + if (!pending_snapshot) { + ret = -ENOMEM; + goto fail_unlock; + } + pending_snapshot->name = kstrndup(name, namelen, GFP_NOFS); + if (!pending_snapshot->name) { + ret = -ENOMEM; + kfree(pending_snapshot); + goto fail_unlock; + } trans = btrfs_start_transaction(root, 1); BUG_ON(!trans); - err = btrfs_commit_transaction(trans, root); - - trans = btrfs_start_transaction(root, 1); + pending_snapshot->root = root; + list_add(&pending_snapshot->list, + &trans->transaction->pending_snapshots); ret = btrfs_update_inode(trans, root, root->inode); - if (ret) - goto fail; - - ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root, - 0, &objectid); - if (ret) - goto fail; memcpy(&new_root_item, &root->root_item, - sizeof(new_root_item)); - - key.objectid = objectid; - key.offset = 1; - btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY); - - extent_buffer_get(root->node); - btrfs_cow_block(trans, root, root->node, NULL, 0, &tmp); - free_extent_buffer(tmp); - - /* write the ordered inodes to force all delayed allocations to - * be filled. Once this is done, we can copy the root - */ - mutex_lock(&root->fs_info->trans_mutex); - btrfs_write_ordered_inodes(trans, root); - mutex_unlock(&root->fs_info->trans_mutex); - - btrfs_copy_root(trans, root, root->node, &tmp, objectid); - - btrfs_set_root_bytenr(&new_root_item, tmp->start); - btrfs_set_root_level(&new_root_item, btrfs_header_level(tmp)); - ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key, - &new_root_item); -printk("new root %Lu node %Lu\n", objectid, tmp->start); - free_extent_buffer(tmp); - if (ret) - goto fail; - - /* - * insert the directory item - */ - key.offset = (u64)-1; - ret = btrfs_insert_dir_item(trans, root->fs_info->tree_root, - name, namelen, - root->fs_info->sb->s_root->d_inode->i_ino, - &key, BTRFS_FT_DIR); - - if (ret) - goto fail; - - ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root, - name, namelen, objectid, - root->fs_info->sb->s_root->d_inode->i_ino); - - if (ret) - goto fail; -fail: - nr = trans->blocks_used; err = btrfs_commit_transaction(trans, root); - if (err && !ret) - ret = err; fail_unlock: mutex_unlock(&root->fs_info->fs_mutex); btrfs_btree_balance_dirty(root, nr); -- cgit v1.2.3