[BUG fix] vmscan: Clear PageActive before synchronous shrink_page_list

[Minchan Kim]

Normally, shrink_page_list doesn't reclaim working set page(ie, PG_referenced).
So it should return active lru list
For it, shrink_page_list does SetPageActive for them.
Sometime, we can ignore that and try to reclaim them when we reclaim high-order pages
through consecutive second call of synchronous shrink_page_list.
At that time, the pages which have PG_active could be caught by VM_BUG_ON(PageActive(page))
in shrink_page_list.

This patch clears PG_active before entering synchronous shrink_page_list.

Reported-by: Andrew Lutomirski <luto@xxxxxxx>
Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
---
 mm/vmscan.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8bfd450..a5c01e9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1430,7 +1430,10 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 
 	/* Check if we should syncronously wait for writeback */
 	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
+		unsigned long nr_active;
 		set_reclaim_mode(priority, sc, true);
+		nr_active = clear_active_flags(&page_list, NULL);
+		count_vm_events(PGDEACTIVATE, nr_active);
 		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
 	}
 
-- 
1.7.1

-- 
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/