From 1dce071e18b7264457d17c0dec4c7e430bfaee7d Mon Sep 17 00:00:00 2001
From: Shaohua Li <shaohua.li@intel.com>
Date: Thu, 11 Nov 2010 14:05:17 -0800
Subject: [PATCH] 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>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b8a6fdc2131..d31d7ce52c0 100644
--- 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);
-- 
2.39.3