The patch titled
mm: compaction: prevent division-by-zero during user-requested compaction
has been removed from the -mm tree. Its filename was
mm-compaction-prevent-division-by-zero-during-user-requested-compaction.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
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.
[akpm@xxxxxxxxxxxxxxxxxxxx: add comment, per Mel]
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Mel Gorman <mel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 11 +++++++++++
1 file changed, 11 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
@@ -406,6 +406,10 @@ static int compact_finished(struct zone
if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
return COMPACT_CONTINUE;
+ /*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
if (cc->order == -1)
return COMPACT_CONTINUE;
@@ -454,6 +458,13 @@ unsigned long compaction_suitable(struct
return COMPACT_SKIPPED;
/*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+ 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
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