[PATCH] define for_each_online_pgdat

This patch defines for_each_online_pgdat() as a replacement of
for_each_pgdat()

Now, online nodes are managed by node_online_map.  But for_each_pgdat()
uses pgdat_link to iterate over all nodes(pgdat).  This means management
structure for online pgdat is duplicated.

I think using node_online_map for for_each_pgdat() is simple and sane
rather ather than pgdat_link.  New macro is named as
for_each_online_pgdat().  Following patch will fix callers of
for_each_pgdat().

The bootmem allocater uses for_each_pgdat() before pgdat initialization.  I
don't think it's sane.  Following patch will fix it.
Signed-off-by: Yasunori Goto     <y-goto@jp.fujitsu.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mmzone.h

@@ -13,6 +13,7 @@
 #include <linux/numa.h>
 #include <linux/init.h>
 #include <linux/seqlock.h>
+#include <linux/nodemask.h>
 #include <asm/atomic.h>
 
 /* Free memory management - zoned buddy allocator.  */
@@ -349,57 +350,6 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
  */
 #define zone_idx(zone)		((zone) - (zone)->zone_pgdat->node_zones)
 
-/**
- * for_each_pgdat - helper macro to iterate over all nodes
- * @pgdat - pointer to a pg_data_t variable
- *
- * Meant to help with common loops of the form
- * pgdat = pgdat_list;
- * while(pgdat) {
- * 	...
- * 	pgdat = pgdat->pgdat_next;
- * }
- */
-#define for_each_pgdat(pgdat) \
-	for (pgdat = pgdat_list; pgdat; pgdat = pgdat->pgdat_next)
-
-/*
- * next_zone - helper magic for for_each_zone()
- * Thanks to William Lee Irwin III for this piece of ingenuity.
- */
-static inline struct zone *next_zone(struct zone *zone)
-{
-	pg_data_t *pgdat = zone->zone_pgdat;
-
-	if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
-		zone++;
-	else if (pgdat->pgdat_next) {
-		pgdat = pgdat->pgdat_next;
-		zone = pgdat->node_zones;
-	} else
-		zone = NULL;
-
-	return zone;
-}
-
-/**
- * for_each_zone - helper macro to iterate over all memory zones
- * @zone - pointer to struct zone variable
- *
- * The user only needs to declare the zone variable, for_each_zone
- * fills it in. This basically means for_each_zone() is an
- * easier to read version of this piece of code:
- *
- * for (pgdat = pgdat_list; pgdat; pgdat = pgdat->node_next)
- * 	for (i = 0; i < MAX_NR_ZONES; ++i) {
- * 		struct zone * z = pgdat->node_zones + i;
- * 		...
- * 	}
- * }
- */
-#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);
@@ -471,6 +421,62 @@ extern struct pglist_data contig_page_data;
 
 #endif /* !CONFIG_NEED_MULTIPLE_NODES */
 
+static inline struct pglist_data *first_online_pgdat(void)
+{
+	return NODE_DATA(first_online_node);
+}
+
+static inline struct pglist_data *next_online_pgdat(struct pglist_data *pgdat)
+{
+	int nid = next_online_node(pgdat->node_id);
+
+	if (nid == MAX_NUMNODES)
+		return NULL;
+	return NODE_DATA(nid);
+}
+
+
+/**
+ * for_each_pgdat - helper macro to iterate over all nodes
+ * @pgdat - pointer to a pg_data_t variable
+ */
+#define for_each_online_pgdat(pgdat)			\
+	for (pgdat = first_online_pgdat();		\
+	     pgdat;					\
+	     pgdat = next_online_pgdat(pgdat))
+
+/*
+ * next_zone - helper magic for for_each_zone()
+ * Thanks to William Lee Irwin III for this piece of ingenuity.
+ */
+static inline struct zone *next_zone(struct zone *zone)
+{
+	pg_data_t *pgdat = zone->zone_pgdat;
+
+	if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
+		zone++;
+	else {
+		pgdat = next_online_pgdat(pgdat);
+		if (pgdat)
+			zone = pgdat->node_zones;
+		else
+			zone = NULL;
+	}
+	return zone;
+}
+
+/**
+ * for_each_zone - helper macro to iterate over all memory zones
+ * @zone - pointer to struct zone variable
+ *
+ * The user only needs to declare the zone variable, for_each_zone
+ * fills it in.
+ */
+#define for_each_zone(zone)			        \
+	for (zone = (first_online_pgdat())->node_zones; \
+	     zone;					\
+	     zone = next_zone(zone))
+
 #ifdef CONFIG_SPARSEMEM
 #include <asm/sparsemem.h>
 #endif

include/linux/nodemask.h

@@ -350,11 +350,15 @@ extern nodemask_t node_possible_map;
 #define num_possible_nodes()	nodes_weight(node_possible_map)
 #define node_online(node)	node_isset((node), node_online_map)
 #define node_possible(node)	node_isset((node), node_possible_map)
+#define first_online_node	first_node(node_online_map)
+#define next_online_node(nid)	next_node((nid), node_online_map)
 #else
 #define num_online_nodes()	1
 #define num_possible_nodes()	1
 #define node_online(node)	((node) == 0)
 #define node_possible(node)	((node) == 0)
+#define first_online_node	0
+#define next_online_node(nid)	(MAX_NUMNODES)
 #endif
 
 #define any_online_node(mask)			\