xfs: handle "raw" delayed extents xfs_reflink_trim_around_shared

Delalloc extents in the extent list contain the number of reserved
indirect blocks in their startblock value and don't use the magic
DELAYSTARTBLOCK constant.  Ensure that xfs_reflink_trim_around_shared
handles them properly by checking for isnullstartblock().
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_reflink.c

@@ -182,7 +182,8 @@ xfs_reflink_trim_around_shared(
 	if (!xfs_is_reflink_inode(ip) ||
 	    ISUNWRITTEN(irec) ||
 	    irec->br_startblock == HOLESTARTBLOCK ||
-	    irec->br_startblock == DELAYSTARTBLOCK) {
+	    irec->br_startblock == DELAYSTARTBLOCK ||
+	    isnullstartblock(irec->br_startblock)) {
 		*shared = false;
 		return 0;
 	}