mm: introduce for_each_populated_zone() macro

Impact: cleanup

In almost cases, for_each_zone() is used with populated_zone().  It's
because almost function doesn't need memoryless node information.
Therefore, for_each_populated_zone() can help to make code simplify.

This patch has no functional change.

[akpm@linux-foundation.org: small cleanup]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 8 insertions, 33 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a3803ea8c27d..cbd532161f68 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -922,13 +922,10 @@ static void drain_pages(unsigned int cpu)
         unsigned long flags;
         struct zone *zone;
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 struct per_cpu_pageset *pset;
                 struct per_cpu_pages *pcp;
 
-                if (!populated_zone(zone))
-                        continue;
-
                 pset = zone_pcp(zone, cpu);
 
                 pcp = &pset->pcp;
@@ -1879,10 +1876,7 @@ void show_free_areas(void)
         int cpu;
         struct zone *zone;
 
-        for_each_zone(zone) {
-                if (!populated_zone(zone))
-                        continue;
-
+        for_each_populated_zone(zone) {
                 show_node(zone);
                 printk("%s per-cpu:\n", zone->name);
 
@@ -1922,12 +1916,9 @@ void show_free_areas(void)
                 global_page_state(NR_PAGETABLE),
                 global_page_state(NR_BOUNCE));
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 int i;
 
-                if (!populated_zone(zone))
-                        continue;
-
                 show_node(zone);
                 printk("%s"
                         " free:%lukB"
@@ -1967,12 +1958,9 @@ void show_free_areas(void)
                 printk("\n");
         }
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 unsigned long nr[MAX_ORDER], flags, order, total = 0;
 
-                if (!populated_zone(zone))
-                        continue;
-
                 show_node(zone);
                 printk("%s: ", zone->name);
 
@@ -2784,11 +2772,7 @@ static int __cpuinit process_zones(int cpu)
 
         node_set_state(node, N_CPU);    /* this node has a cpu */
 
-        for_each_zone(zone) {
-
-                if (!populated_zone(zone))
-                        continue;
-
+        for_each_populated_zone(zone) {
                 zone_pcp(zone, cpu) = kmalloc_node(sizeof(struct per_cpu_pageset),
                                          GFP_KERNEL, node);
                 if (!zone_pcp(zone, cpu))
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1bca60f0c527..301f057fd115 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2061,11 +2061,9 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
         struct zone *zone;
         unsigned long ret = 0;
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 enum lru_list l;
 
-                if (!populated_zone(zone))
-                        continue;
                 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
                         continue;
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8cd81ea1ddc1..9826766f1274 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -135,11 +135,7 @@ static void refresh_zone_stat_thresholds(void)
         int cpu;
         int threshold;
 
-        for_each_zone(zone) {
-
-                if (!zone->present_pages)
-                        continue;
-
+        for_each_populated_zone(zone) {
                 threshold = calculate_threshold(zone);
 
                 for_each_online_cpu(cpu)
@@ -301,12 +297,9 @@ void refresh_cpu_vm_stats(int cpu)
         int i;
         int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 struct per_cpu_pageset *p;
 
-                if (!populated_zone(zone))
-                        continue;
-
                 p = zone_pcp(zone, cpu);
 
                 for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)