From: Hugh Dickins <hughd@xxxxxxxxxx> Subject: 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 <hughd@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [3.18+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff -puN mm/compaction.c~mm-fix-negative-nr_isolated-counts mm/compaction.c --- a/mm/compaction.c~mm-fix-negative-nr_isolated-counts +++ a/mm/compaction.c @@ -1103,8 +1103,10 @@ static isolate_migrate_t isolate_migrate 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 _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html