xfs: fix brainos in the refcount scrubber's rmap fragment processor

[ Upstream commit 54e9b09e153842ab5adb8a460b891e11b39e9c3d ]

Fix some serious WTF in the reference count scrubber's rmap fragment
processing.  The code comment says that this loop is supposed to move
all fragment records starting at or before bno onto the worklist, but
there's no obvious reason why nr (the number of items added) should
increment starting from 1, and breaking the loop when we've added the
target number seems dubious since we could have more rmap fragments that
should have been added to the worklist.

This seems to manifest in xfs/411 when adding one to the refcount field.

Fixes: dbde19da9637 ("xfs: cross-reference the rmapbt data with the refcountbt")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/xfs/scrub/refcount.c b/fs/xfs/scrub/refcount.c
index e8c82b026083e5b8e49c4d76c16be36c454cf62f..76e4f16a9fab239d4202724674458be2358c3125 100644 (file)
--- a/fs/xfs/scrub/refcount.c
+++ b/fs/xfs/scrub/refcount.c
@@ -180,7 +180,6 @@ xchk_refcountbt_process_rmap_fragments(
         */
        INIT_LIST_HEAD(&worklist);
        rbno = NULLAGBLOCK;
-       nr = 1;
 
        /* Make sure the fragments actually /are/ in agbno order. */
        bno = 0;
@@ -194,15 +193,14 @@ xchk_refcountbt_process_rmap_fragments(
         * Find all the rmaps that start at or before the refc extent,
         * and put them on the worklist.
         */
+       nr = 0;
        list_for_each_entry_safe(frag, n, &refchk->fragments, list) {
-               if (frag->rm.rm_startblock > refchk->bno)
-                       goto done;
+               if (frag->rm.rm_startblock > refchk->bno || nr > target_nr)
+                       break;
                bno = frag->rm.rm_startblock + frag->rm.rm_blockcount;
                if (bno < rbno)
                        rbno = bno;
                list_move_tail(&frag->list, &worklist);
-               if (nr == target_nr)
-                       break;
                nr++;
        }