memcg: fix zone congestion

ZONE_CONGESTED should be a state of global memory reclaim.  If not, a busy
memcg sets this and give unnecessary throttoling in wait_iff_congested()
against memory recalim in other contexts.  This makes system performance
bad.

I'll think about "memcg is congested!" flag is required or not, later.
But this fix is required first.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Ying Han <yinghan@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f6b435c80079..8bfd45050a61 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -937,7 +937,7 @@ keep_lumpy:
          * back off and wait for congestion to clear because further reclaim
          * will encounter the same problem
          */
-        if (nr_dirty == nr_congested && nr_dirty != 0)
+        if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
                 zone_set_flag(zone, ZONE_CONGESTED);
 
         free_page_list(&free_pages);