Btrfs: fix possible memory leak in btrfs_create_tree()

In btrfs_create_tree(), if btrfs_insert_root() fails, we should
free root->commit_root.

Reported-by: Alex Lyakas <alex@zadarastorage.com>
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/disk-io.c

@@ -1366,6 +1366,7 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
 fail:
 	if (leaf) {
 		btrfs_tree_unlock(leaf);
+		free_extent_buffer(root->commit_root);
 		free_extent_buffer(leaf);
 	}
 	kfree(root);