btrfs: abort transaction on failure to update root in the received subvol ioctl

If we failed to update the root we don't abort the transaction, which is
wrong since we already used the transaction to remove an item from the
uuid tree.

Fixes: dd5f961 ("Btrfs: maintain subvolume items in the UUID tree")
CC: stable@vger.kernel.org # 3.12+
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/ioctl.c

@@ -3984,7 +3984,8 @@ static long _btrfs_ioctl_set_received_subvol(struct file *file,
 
 	ret = btrfs_update_root(trans, fs_info->tree_root,
 				&root->root_key, &root->root_item);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
+		btrfs_abort_transaction(trans, ret);
 		btrfs_end_transaction(trans);
 		goto out;
 	}