[PATCH] Use NODES_SHIFT to calculate ZONE_SHIFT

From: jbarnes@sgi.com (Jesse Barnes)

Now that we have a proper NODES_SHIFT value, we need to use it to define
ZONE_SHIFT otherwise we'll spill over 8 bits if we have more than 85 nodes.

include/linux/mm.h

@@ -322,8 +322,10 @@ static inline void put_page(struct page *page)
 /*
  * The zone field is never updated after free_area_init_core()
  * sets it, so none of the operations on it need to be atomic.
+ * We'll have up to log2(MAX_NUMNODES * MAX_NR_ZONES) zones
+ * total, so we use NODES_SHIFT here to get enough bits.
  */
-#define ZONE_SHIFT (BITS_PER_LONG - 8)
+#define ZONE_SHIFT (BITS_PER_LONG - NODES_SHIFT - MAX_NR_ZONES_SHIFT)
 
 struct zone;
 extern struct zone *zone_table[];

include/linux/mmzone.h

@@ -159,7 +159,10 @@ struct zone {
 #define ZONE_DMA		0
 #define ZONE_NORMAL		1
 #define ZONE_HIGHMEM		2
-#define MAX_NR_ZONES		3
+
+#define MAX_NR_ZONES		3	/* Sync this with MAX_NR_ZONES_SHIFT */
+#define MAX_NR_ZONES_SHIFT	2	/* ceil(log2(MAX_NR_ZONES)) */
+
 #define GFP_ZONEMASK	0x03
 
 /*