From ff59909a077b3c51c168cb658601c6b63136a347 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Thu, 12 Feb 2015 15:00:28 -0800 Subject: [PATCH] mm: fix negative nr_isolated counts The vmstat interfaces are good at hiding negative counts (at least when CONFIG_SMP); but if you peer behind the curtain, you find that nr_isolated_anon and nr_isolated_file soon go negative, and grow ever more negative: so they can absorb larger and larger numbers of isolated pages, yet still appear to be zero. I'm happy to avoid a congestion_wait() when too_many_isolated() myself; but I guess it's there for a good reason, in which case we ought to get too_many_isolated() working again. The imbalance comes from isolate_migratepages()'s ISOLATE_ABORT case: putback_movable_pages() decrements the NR_ISOLATED counts, but we forgot to call acct_isolated() to increment them. It is possible that the bug whcih this patch fixes could cause OOM kills when the system still has a lot of reclaimable page cache. Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from isolate_migratepages_range()") Signed-off-by: Hugh Dickins Acked-by: Vlastimil Babka Acked-by: Joonsoo Kim Cc: [3.18+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index 782772df62c8..d50d6de6f1b6 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1103,8 +1103,10 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn, isolate_mode); - if (!low_pfn || cc->contended) + if (!low_pfn || cc->contended) { + acct_isolated(zone, cc); return ISOLATE_ABORT; + } /* * Either we isolated something and proceed with migration. Or -- 2.20.1