vmscan: avoid setting zone congested if no page dirty

nr_dirty and nr_congested are increased only when the page is dirty.  So
if all pages are clean, both them will be zero.  In this case, we should
not mark the zone congested.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b8a6fdc2131258db15321021375117cae27cec0d..d31d7ce52c0ea2dbbf85b26019c9fdd70fab624a 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -913,7 +913,7 @@ keep_lumpy:
         * back off and wait for congestion to clear because further reclaim
         * will encounter the same problem
         */
-       if (nr_dirty == nr_congested)
+       if (nr_dirty == nr_congested && nr_dirty != 0)
                zone_set_flag(zone, ZONE_CONGESTED);
 
        free_page_list(&free_pages);