mm: compaction: fix special case -1 order checks
Commit56de7263fc
("mm: compaction: direct compact when a high-order allocation fails") introduced a check for cc->order == -1 in compact_finished. We should continue compacting in that case because the request came from userspace and there is no particular order to compact for. Similar check has been added by82478fb7
(mm: compaction: prevent division-by-zero during user-requested compaction) for compaction_suitable. The check is, however, done after zone_watermark_ok which uses order as a right hand argument for shifts. Not only watermark check is pointless if we can break out without it but it also uses 1 << -1 which is not well defined (at least from C standard). Let's move the -1 check above zone_watermark_ok. [minchan.kim@gmail.com> - caught compaction_suitable] Signed-off-by: Michal Hocko <mhocko@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hioryu@jp.fujitsu.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -420,13 +420,6 @@ static int compact_finished(struct zone *zone,
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if (cc->free_pfn <= cc->migrate_pfn)
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return COMPACT_COMPLETE;
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/* Compaction run is not finished if the watermark is not met */
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watermark = low_wmark_pages(zone);
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watermark += (1 << cc->order);
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if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
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return COMPACT_CONTINUE;
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/*
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* order == -1 is expected when compacting via
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* /proc/sys/vm/compact_memory
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@ -434,6 +427,13 @@ static int compact_finished(struct zone *zone,
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if (cc->order == -1)
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return COMPACT_CONTINUE;
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/* Compaction run is not finished if the watermark is not met */
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watermark = low_wmark_pages(zone);
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watermark += (1 << cc->order);
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if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
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return COMPACT_CONTINUE;
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/* Direct compactor: Is a suitable page free? */
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for (order = cc->order; order < MAX_ORDER; order++) {
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/* Job done if page is free of the right migratetype */
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@ -460,6 +460,13 @@ unsigned long compaction_suitable(struct zone *zone, int order)
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int fragindex;
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unsigned long watermark;
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/*
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* order == -1 is expected when compacting via
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* /proc/sys/vm/compact_memory
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*/
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if (order == -1)
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return COMPACT_CONTINUE;
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/*
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* Watermarks for order-0 must be met for compaction. Note the 2UL.
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* This is because during migration, copies of pages need to be
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@ -469,13 +476,6 @@ unsigned long compaction_suitable(struct zone *zone, int order)
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if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
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return COMPACT_SKIPPED;
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/*
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* order == -1 is expected when compacting via
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* /proc/sys/vm/compact_memory
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*/
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if (order == -1)
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return COMPACT_CONTINUE;
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/*
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* fragmentation index determines if allocation failures are due to
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* low memory or external fragmentation
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