| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.19 041/177] mm: fix negative nr_isolated counts | Date | Mon, 16 Mar 2015 15:07:28 +0100 |
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3.19-stable review patch. If anyone has any objections, please let me know.
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From: Hugh Dickins <hughd@google.com>
commit ff59909a077b3c51c168cb658601c6b63136a347 upstream.
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@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/compaction.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/mm/compaction.c +++ b/mm/compaction.c @@ -1015,8 +1015,10 @@ 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
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