The patch titled
mm: compaction: prevent division-by-zero during user-requested compaction
has been added to the -mm tree. Its filename is
mm-compaction-prevent-division-by-zero-during-user-requested-compaction.patch
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------------------------------------------------------
Subject: mm: compaction: prevent division-by-zero during user-requested compaction
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Up until 3e7d344 ("mm: vmscan: reclaim order-0 and use compaction instead
of lumpy reclaim"), compaction skipped calculating the fragmentation index
of a zone when compaction was explicitely requested through the procfs
knob.
However, when compaction_suitable was introduced, it did not come with an
extra check for order == -1, set on explicit compaction requests, and
passed this order on to the fragmentation index calculation, where it
overshifts the number of requested pages, leading to a division by zero.
This patch makes sure that order == -1 is recognized as the flag it is
rather than passing it along as valid order parameter.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN mm/compaction.c~mm-compaction-prevent-division-by-zero-during-user-requested-compaction mm/compaction.c
--- a/mm/compaction.c~mm-compaction-prevent-division-by-zero-during-user-requested-compaction
+++ a/mm/compaction.c
@@ -453,6 +453,9 @@ unsigned long compaction_suitable(struct
if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
return COMPACT_SKIPPED;
+ if (order == -1)
+ return COMPACT_CONTINUE;
+
/*
* fragmentation index determines if allocation failures are due to
* low memory or external fragmentation
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
origin.patch
mm-compaction-prevent-division-by-zero-during-user-requested-compaction.patch
mm-compaction-prevent-division-by-zero-during-user-requested-compaction-fix.patch
writeback-check-skipped-pages-on-wb_sync_all.patch
mm-deactivate-invalidated-pages.patch
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