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| author | Johannes Weiner <hannes@cmpxchg.org> | 2011-01-20 14:44:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-01-20 17:02:05 -0800 |
| commit | 82478fb7bca28e3ca2f3c55c14e690f749dd4dbb (patch) | |
| tree | 71023f480667dc3bfd255673437c76db77a05aa0 | |
| parent | 3305de51bf612603c9a4e4dc98ceb839ef933749 (diff) | |
| download | linux-82478fb7bca28e3ca2f3c55c14e690f749dd4dbb.tar.gz linux-82478fb7bca28e3ca2f3c55c14e690f749dd4dbb.tar.bz2 linux-82478fb7bca28e3ca2f3c55c14e690f749dd4dbb.zip | |
mm: compaction: prevent division-by-zero during user-requested compaction
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@linux-foundation.org: add comment, per Mel]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/compaction.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 6d592a021072..8be430b812de 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -406,6 +406,10 @@ static int compact_finished(struct zone *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 zone *zone, int order) 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 * |