From 14af4a5e9b26ad251f81c174e8a43f3e179434a5 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Thu, 5 May 2016 16:22:15 -0700 Subject: [PATCH] mm, cma: prevent nr_isolated_* counters from going negative /proc/sys/vm/stat_refresh warns nr_isolated_anon and nr_isolated_file go increasingly negative under compaction: which would add delay when should be none, or no delay when should delay. The bug in compaction was due to a recent mmotm patch, but much older instance of the bug was also noticed in isolate_migratepages_range() which is used for CMA and gigantic hugepage allocations. The bug is caused by putback_movable_pages() in an error path decrementing the isolated counters without them being previously incremented by acct_isolated(). Fix isolate_migratepages_range() by removing the error-path putback, thus reaching acct_isolated() with migratepages still isolated, and leaving putback to caller like most other places do. Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from isolate_migratepages_range()") [vbabka@suse.cz: expanded the changelog] Signed-off-by: Hugh Dickins Signed-off-by: Vlastimil Babka Acked-by: Joonsoo Kim Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index ccf97b02b85f..4a0d4b8ccde8 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -852,16 +852,8 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, ISOLATE_UNEVICTABLE); - /* - * In case of fatal failure, release everything that might - * have been isolated in the previous iteration, and signal - * the failure back to caller. - */ - if (!pfn) { - putback_movable_pages(&cc->migratepages); - cc->nr_migratepages = 0; + if (!pfn) break; - } if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) break; -- 2.20.1