The patch titled
mm: compaction: fix special case -1 order checks
has been added to the -mm tree. Its filename is
mm-compaction-fix-special-case-1-order-checks.patch
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------------------------------------------------------
Subject: mm: compaction: fix special case -1 order checks
From: Michal Hocko <mhocko@xxxxxxx>
56de7263 ("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 by 82478fb7 (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@xxxxxxxxx> - caught compaction_suitable]
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hioryu@xxxxxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
diff -puN mm/compaction.c~mm-compaction-fix-special-case-1-order-checks mm/compaction.c
--- a/mm/compaction.c~mm-compaction-fix-special-case-1-order-checks
+++ a/mm/compaction.c
@@ -420,13 +420,6 @@ static int compact_finished(struct zone
if (cc->free_pfn <= cc->migrate_pfn)
return COMPACT_COMPLETE;
- /* Compaction run is not finished if the watermark is not met */
- watermark = low_wmark_pages(zone);
- watermark += (1 << cc->order);
-
- 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
@@ -434,6 +427,13 @@ static int compact_finished(struct zone
if (cc->order == -1)
return COMPACT_CONTINUE;
+ /* Compaction run is not finished if the watermark is not met */
+ watermark = low_wmark_pages(zone);
+ watermark += (1 << cc->order);
+
+ if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
+ return COMPACT_CONTINUE;
+
/* Direct compactor: Is a suitable page free? */
for (order = cc->order; order < MAX_ORDER; order++) {
/* Job done if page is free of the right migratetype */
@@ -461,6 +461,13 @@ unsigned long compaction_suitable(struct
unsigned long watermark;
/*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+ if (order == -1)
+ return COMPACT_CONTINUE;
+
+ /*
* Watermarks for order-0 must be met for compaction. Note the 2UL.
* This is because during migration, copies of pages need to be
* allocated and for a short time, the footprint is higher
@@ -470,13 +477,6 @@ 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 mhocko@xxxxxxx are
fs-execc-use-build_bug_on-for-vm_stack_flags-vm_stack_incomplete_setup.patch
mm-compaction-fix-special-case-1-order-checks.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-fix-2.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily-fix.patch
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