[PATCH] mm: add populated_zone() helper

There are numerous places we check whether a zone is populated or not.

Provide a helper function to check for populated zones and convert all
checks for zone->present_pages.

Signed-off-by: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mmzone.h

@@ -388,6 +388,11 @@ static inline struct zone *next_zone(struct zone *zone)
 #define for_each_zone(zone) \
 	for (zone = pgdat_list->node_zones; zone; zone = next_zone(zone))
 
+static inline int populated_zone(struct zone *zone)
+{
+	return (!!zone->present_pages);
+}
+
 static inline int is_highmem_idx(int idx)
 {
 	return (idx == ZONE_HIGHMEM);

mm/page_alloc.c

@@ -1358,7 +1358,7 @@ void show_free_areas(void)
 		show_node(zone);
 		printk("%s per-cpu:", zone->name);
 
-		if (!zone->present_pages) {
+		if (!populated_zone(zone)) {
 			printk(" empty\n");
 			continue;
 		} else
@@ -1435,7 +1435,7 @@ void show_free_areas(void)
 
 		show_node(zone);
 		printk("%s: ", zone->name);
-		if (!zone->present_pages) {
+		if (!populated_zone(zone)) {
 			printk("empty\n");
 			continue;
 		}
@@ -2134,7 +2134,7 @@ static int frag_show(struct seq_file *m, void *arg)
 	int order;
 
 	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
-		if (!zone->present_pages)
+		if (!populated_zone(zone))
 			continue;
 
 		spin_lock_irqsave(&zone->lock, flags);
@@ -2167,7 +2167,7 @@ static int zoneinfo_show(struct seq_file *m, void *arg)
 	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; zone++) {
 		int i;
 
-		if (!zone->present_pages)
+		if (!populated_zone(zone))
 			continue;
 
 		spin_lock_irqsave(&zone->lock, flags);

mm/vmscan.c

@@ -897,7 +897,7 @@ shrink_caches(struct zone **zones, struct scan_control *sc)
 	for (i = 0; zones[i] != NULL; i++) {
 		struct zone *zone = zones[i];
 
-		if (zone->present_pages == 0)
+		if (!populated_zone(zone))
 			continue;
 
 		if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
@@ -1069,7 +1069,7 @@ static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
 			for (i = pgdat->nr_zones - 1; i >= 0; i--) {
 				struct zone *zone = pgdat->node_zones + i;
 
-				if (zone->present_pages == 0)
+				if (!populated_zone(zone))
 					continue;
 
 				if (zone->all_unreclaimable &&
@@ -1106,7 +1106,7 @@ static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
 			struct zone *zone = pgdat->node_zones + i;
 			int nr_slab;
 
-			if (zone->present_pages == 0)
+			if (!populated_zone(zone))
 				continue;
 
 			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
@@ -1258,7 +1258,7 @@ void wakeup_kswapd(struct zone *zone, int order)
 {
 	pg_data_t *pgdat;
 
-	if (zone->present_pages == 0)
+	if (!populated_zone(zone))
 		return;
 
 	pgdat = zone->zone_pgdat;