Commit 54e9b09e authored Nov 08, 2020 by Darrick J. Wong

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

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: dbde19da ("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>

parent 6ff646b2

fs/xfs/scrub/refcount.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -170,7 +170,6 @@ xchk_refcountbt_process_rmap_fragments(
		*/
		INIT_LIST_HEAD(&worklist);
		rbno = NULLAGBLOCK;
		nr = 1;

		/* Make sure the fragments actually /are/ in agbno order. */
		bno = 0;
		@@ -184,15 +183,14 @@ 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++;
		}

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