releases/3.19.2/mm-fix-negative-nr_isolated-counts.patch

   1 From ff59909a077b3c51c168cb658601c6b63136a347 Mon Sep 17 00:00:00 2001
   2 From: Hugh Dickins <hughd@google.com>
   3 Date: Thu, 12 Feb 2015 15:00:28 -0800
   4 Subject: mm: fix negative nr_isolated counts
   5
   6 From: Hugh Dickins <hughd@google.com>
   7
   8 commit ff59909a077b3c51c168cb658601c6b63136a347 upstream.
   9
  10 The vmstat interfaces are good at hiding negative counts (at least when
  11 CONFIG_SMP); but if you peer behind the curtain, you find that
  12 nr_isolated_anon and nr_isolated_file soon go negative, and grow ever
  13 more negative: so they can absorb larger and larger numbers of isolated
  14 pages, yet still appear to be zero.
  15
  16 I'm happy to avoid a congestion_wait() when too_many_isolated() myself;
  17 but I guess it's there for a good reason, in which case we ought to get
  18 too_many_isolated() working again.
  19
  20 The imbalance comes from isolate_migratepages()'s ISOLATE_ABORT case:
  21 putback_movable_pages() decrements the NR_ISOLATED counts, but we forgot
  22 to call acct_isolated() to increment them.
  23
  24 It is possible that the bug whcih this patch fixes could cause OOM kills
  25 when the system still has a lot of reclaimable page cache.
  26
  27 Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from isolate_migratepages_range()")
  28 Signed-off-by: Hugh Dickins <hughd@google.com>
  29 Acked-by: Vlastimil Babka <vbabka@suse.cz>
  30 Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
  31 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  32 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  33 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  34
  35 ---
  36  mm/compaction.c |    4 +++-
  37  1 file changed, 3 insertions(+), 1 deletion(-)
  38
  39 --- a/mm/compaction.c
  40 +++ b/mm/compaction.c
  41 @@ -1015,8 +1015,10 @@ static isolate_migrate_t isolate_migrate
  42                 low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
  43                                                                 isolate_mode);
  44
  45 -               if (!low_pfn || cc->contended)
  46 +               if (!low_pfn || cc->contended) {
  47 +                       acct_isolated(zone, cc);
  48                         return ISOLATE_ABORT;
  49 +               }
  50
  51                 /*
  52                  * Either we isolated something and proceed with migration. Or