From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: 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@xxxxxxx: expanded the changelog]
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff -puN mm/compaction.c~mm-cma-prevent-nr_isolated_-counters-from-going-negative mm/compaction.c
--- a/mm/compaction.c~mm-cma-prevent-nr_isolated_-counters-from-going-negative
+++ a/mm/compaction.c
@@ -852,16 +852,8 @@ isolate_migratepages_range(struct compac
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;
_
--
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