xfs: clean up the error handling in xfs_swap_extents

Make sure we release resources properly if we cannot clean out the COW
extents in preparation for an extent swap.

Fixes: 96987eea ("xfs: cancel COW blocks before swapext")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_bmap_util.c

@@ -1606,7 +1606,7 @@ xfs_swap_extents(
 	if (xfs_inode_has_cow_data(tip)) {
 		error = xfs_reflink_cancel_cow_range(tip, 0, NULLFILEOFF, true);
 		if (error)
-			return error;
+			goto out_unlock;
 	}
 
 	/*