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Subject[PATCH 04/11] mm: vmscan: Do not OOM if aborting reclaim to start compaction
Date
When direct reclaim is entered is is possible that reclaim will be
aborted so that compaction can be attempted to satisfy a high-order
allocation. If this decision is made before any pages are reclaimed,
it is possible for 0 to be returned to the page allocator potentially
triggering an OOM. This has not been observed but it is a possibility
so this patch addresses it.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/vmscan.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3421746..5f4c789 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2222,6 +2222,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
struct zoneref *z;
struct zone *zone;
unsigned long writeback_threshold;
+ bool should_abort_reclaim;

get_mems_allowed();
delayacct_freepages_start();
@@ -2233,7 +2234,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
sc->nr_scanned = 0;
if (!priority)
disable_swap_token(sc->mem_cgroup);
- if (shrink_zones(priority, zonelist, sc))
+ should_abort_reclaim = shrink_zones(priority, zonelist, sc);
+ if (should_abort_reclaim)
break;

/*
@@ -2301,6 +2303,10 @@ out:
if (oom_killer_disabled)
return 0;

+ /* Aborting reclaim to try compaction? don't OOM, then */
+ if (should_abort_reclaim)
+ return 1;
+
/* top priority shrink_zones still had more to do? don't OOM, then */
if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
return 1;
--
1.7.3.4


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