[PATCH] NUMA: Add zone_to_nid function

There are many places where we need to determine the node of a zone.
Currently we use a difficult to read sequence of pointer dereferencing.
Put that into an inline function and use throughout VM.  Maybe we can find
a way to optimize the lookup in the future.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cf913bd..51070b6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1217,7 +1217,7 @@
 #ifdef CONFIG_NUMA
 static void show_node(struct zone *zone)
 {
-	printk("Node %d ", zone->zone_pgdat->node_id);
+	printk("Node %ld ", zone_to_nid(zone));
 }
 #else
 #define show_node(zone)	do { } while (0)