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>

6 files changed, 27 insertions, 48 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 1aca6cebbb78..26ef24076b76 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -806,6 +806,14 @@ extern struct zone *next_zone(struct zone *zone);
              zone;                                      \
              zone = next_zone(zone))
 
+#define for_each_populated_zone(zone)                   \
+        for (zone = (first_online_pgdat())->node_zones; \
+             zone;                                      \
+             zone = next_zone(zone))                    \
+                if (!populated_zone(zone))              \
+                        ; /* do nothing */              \
+                else
+
 static inline struct zone *zonelist_zone(struct zoneref *zoneref)
 {
         return zoneref->zone;
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index f5fc2d7680f2..33e2e4a819f9 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -321,13 +321,10 @@ static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
 
         INIT_LIST_HEAD(list);
 
-        for_each_zone(zone) {
+        for_each_populated_zone(zone) {
                 unsigned long zone_start, zone_end;
                 struct mem_extent *ext, *cur, *aux;
 
-                if (!populated_zone(zone))
-                        continue;
-
                 zone_start = zone->zone_start_pfn;
                 zone_end = zone->zone_start_pfn + zone->spanned_pages;
 
@@ -804,8 +801,8 @@ static unsigned int count_free_highmem_pages(void)
         struct zone *zone;
         unsigned int cnt = 0;
 
-        for_each_zone(zone)
-                if (populated_zone(zone) && is_highmem(zone))
+        for_each_populated_zone(zone)
+                if (is_highmem(zone))
                         cnt += zone_page_state(zone, NR_FREE_PAGES);
 
         return cnt;
diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
index a92c91451559..1ee6636414b2 100644
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -229,17 +229,16 @@ int swsusp_shrink_memory(void)
                 size = count_data_pages() + PAGES_FOR_IO + SPARE_PAGES;
                 tmp = size;
                 size += highmem_size;
-                for_each_zone (zone)
-                        if (populated_zone(zone)) {
-                                tmp += snapshot_additional_pages(zone);
-                                if (is_highmem(zone)) {
-                                        highmem_size -=
+                for_each_populated_zone(zone) {
+                        tmp += snapshot_additional_pages(zone);
+                        if (is_highmem(zone)) {
+                                highmem_size -=
                                         zone_page_state(zone, NR_FREE_PAGES);
-                                } else {
-                                        tmp -= zone_page_state(zone, NR_FREE_PAGES);
-                                        tmp += zone->lowmem_reserve[ZONE_NORMAL];
-                                }
+                        } else {
+                                tmp -= zone_page_state(zone, NR_FREE_PAGES);
+                                tmp += zone->lowmem_reserve[ZONE_NORMAL];
                         }
+                }
 
                 if (highmem_size < 0)
                         highmem_size = 0;
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++)