[Devel] [PATCH] mm: Fix mis accounting of isolated pages in memcg_numa_isolate_pages()

[Kirill Tkhai]

When split_huge_page_to_list() fails, and a huge page is going back
to LRU, the number of isolated pages is decreasing. So we must
subtract HPAGE_PMD_NR from NR_ISOLATED_ANON counter, not to add it.

Otherwise, we may bumped into a situation, when number of isolated
pages grows up to number of inactive pages, and direct reclaim hangs in:

  shrink_inactive_list()
     while (too_many_isolated())
        congestion_wait(BLK_RW_ASYNC, HZ/10),

waiting for the counter becomes less. But it has no a chance
to finish, and hangs forever. Fix that.

https://jira.sw.ru/browse/PSBM-76970

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 mm/memcontrol.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a7fa84a9980..a165a221e87 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4963,7 +4963,7 @@ static long memcg_numa_isolate_pages(struct lruvec *lruvec, enum lru_list lru,
 		if (PageTransHuge(page) && split_huge_page_to_list(page, dst)) {
 			list_del(&page->lru);
 			mod_zone_page_state(zone, NR_ISOLATED_ANON,
-					HPAGE_PMD_NR);
+					-HPAGE_PMD_NR);
 			putback_lru_page(page);
 		}
 	}