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Btrfs: Move snapshot creation to commit time

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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 <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2008-01-08 15:46:30 -05:00
parent dc17ff8f11
commit 3063d29f2a
3 changed files with 100 additions and 67 deletions
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79
fs/btrfs/inode.c
View File

@@ -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);