Btrfs: fix unclosed transaction handler when the async transaction commitment fails

If the async transaction commitment failed, we need close the
current transaction handler, or the current transaction will be
blocked to commit because of this orphan handler.

We fix the problem by doing sync transaction commitment, that is
to invoke btrfs_commit_transaction().
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/ioctl.c

@@ -527,6 +527,8 @@ static noinline int create_subvol(struct inode *dir,
 	if (async_transid) {
 		*async_transid = trans->transid;
 		err = btrfs_commit_transaction_async(trans, root, 1);
+		if (err)
+			err = btrfs_commit_transaction(trans, root);
 	} else {
 		err = btrfs_commit_transaction(trans, root);
 	}
@@ -592,6 +594,8 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 		*async_transid = trans->transid;
 		ret = btrfs_commit_transaction_async(trans,
 				     root->fs_info->extent_root, 1);
+		if (ret)
+			ret = btrfs_commit_transaction(trans, root);
 	} else {
 		ret = btrfs_commit_transaction(trans,
 					       root->fs_info->extent_root);