xfs: reduce stack usage of _reflink_clear_inode_flag

The loop in _reflink_clear_inode_flag isn't necessary since we
jump out if any part of any extent is shared.  Remove the loop
and we no longer need two maps, so we can save some stack use.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 9c58b4a..c4e35dc 100644 (file)
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1507,7 +1507,7 @@ xfs_reflink_clear_inode_flag(
        xfs_extlen_t            aglen;
        xfs_agblock_t           rbno;
        xfs_extlen_t            rlen;
-       struct xfs_bmbt_irec    map[2];
+       struct xfs_bmbt_irec    map;
        int                     nmaps;
        int                     error = 0;
 
@@ -1521,37 +1521,29 @@ xfs_reflink_clear_inode_flag(
                 * Look for extents in the file.  Skip holes, delalloc, or
                 * unwritten extents; they can't be reflinked.
                 */
-               error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
+               error = xfs_bmapi_read(ip, fbno, end - fbno, &map, &nmaps, 0);
                if (error)
                        return error;
                if (nmaps == 0)
                        break;
-               if (map[0].br_startblock == HOLESTARTBLOCK ||
-                   map[0].br_startblock == DELAYSTARTBLOCK ||
-                   ISUNWRITTEN(&map[0]))
+               if (map.br_startblock == HOLESTARTBLOCK ||
+                   map.br_startblock == DELAYSTARTBLOCK ||
+                   ISUNWRITTEN(&map))
                        goto next;
 
-               map[1] = map[0];
-               while (map[1].br_blockcount) {
-                       agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
-                       agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
-                       aglen = map[1].br_blockcount;
-
-                       error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
-                                       &rbno, &rlen, false);
-                       if (error)
-                               return error;
-                       /* Is there still a shared block here? */
-                       if (rbno != NULLAGBLOCK)
-                               return 0;
-
-                       map[1].br_blockcount -= aglen;
-                       map[1].br_startoff += aglen;
-                       map[1].br_startblock += aglen;
-               }
+               agno = XFS_FSB_TO_AGNO(mp, map.br_startblock);
+               agbno = XFS_FSB_TO_AGBNO(mp, map.br_startblock);
+               aglen = map.br_blockcount;
 
+               error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
+                               &rbno, &rlen, false);
+               if (error)
+                       return error;
+               /* Is there still a shared block here? */
+               if (rbno != NULLAGBLOCK)
+                       return 0;
 next:
-               fbno = map[0].br_startoff + map[0].br_blockcount;
+               fbno = map.br_startoff + map.br_blockcount;
        }
 
        /*