mm, vmscan: remove duplicate logic clearing node congestion and dirty state

Reclaim may stall if there is too much dirty or congested data on a
node.  This was previously based on zone flags and the logic for
clearing the flags is in two places.  As congestion/dirty tracking is
now tracked on a per-node basis, we can remove some duplicate logic.

Link: http://lkml.kernel.org/r/1467970510-21195-12-git-send-email-mgorman@techsingularity.netSigned-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -3008,7 +3008,17 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx)
 {
 	unsigned long mark = high_wmark_pages(zone);
 
-	return zone_watermark_ok_safe(zone, order, mark, classzone_idx);
+	if (!zone_watermark_ok_safe(zone, order, mark, classzone_idx))
+		return false;
+
+	/*
+	 * If any eligible zone is balanced then the node is not considered
+	 * to be congested or dirty
+	 */
+	clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags);
+	clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags);
+
+	return true;
 }
 
 /*
@@ -3154,13 +3164,6 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 			if (!zone_balanced(zone, order, 0)) {
 				classzone_idx = i;
 				break;
-			} else {
-				/*
-				 * If any eligible zone is balanced then the
-				 * node is not considered congested or dirty.
-				 */
-				clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags);
-				clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags);
 			}
 		}
 
@@ -3219,12 +3222,9 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 			if (!populated_zone(zone))
 				continue;
 
-			if (zone_balanced(zone, sc.order, classzone_idx)) {
-				clear_bit(PGDAT_CONGESTED, &pgdat->flags);
-				clear_bit(PGDAT_DIRTY, &pgdat->flags);
+			if (zone_balanced(zone, sc.order, classzone_idx))
 				goto out;
 		}
-		}
 
 		/*
 		 * Raise priority if scanning rate is too low or there was no