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>

1 files changed, 8 insertions, 0 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;