From: Hugh Dickins <hu...@google.com>
/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.
[vba...@suse.cz: expanded the changelog]
Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from
isolate_migratepages_range()")
Cc: sta...@vger.kernel.org
Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
Signed-off-by: Hugh Dickins <hu...@google.com>
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
mm/compaction.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 2427fe547a20..759c3ac73ced 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -924,16 +924,8 @@ 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;
--
2.8.1
