page allocator ZONE_HIGHMEM fixups

1. We do not need to do an #ifdef in si_meminfo since both counters
   in use are zero if !CONFIG_HIGHMEM.

2. Add #ifdef in si_meminfo_node instead to avoid referencing zone
   information for ZONE_HIGHMEM if we do not have HIGHMEM
   (may not be there after the following patches).

3. Replace the use of ZONE_HIGHMEM with MAX_NR_ZONES in build_zonelists_node

4. build_zonelists_node: Remove BUG_ON for ZONE_HIGHMEM. Zone will
   be optional soon and thus BUG_ON cannot be triggered anymore.

5. init_free_area_core: Replace a use of ZONE_HIGHMEM with NR_MAX_ZONES.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.17-mm6/mm/page_alloc.c
===================================================================
--- linux-2.6.17-mm6.orig/mm/page_alloc.c	2006-07-05 20:49:58.340089640 -0700
+++ linux-2.6.17-mm6/mm/page_alloc.c	2006-07-07 15:07:41.676482357 -0700
@@ -1289,13 +1289,8 @@ void si_meminfo(struct sysinfo *val)
 	val->sharedram = 0;
 	val->freeram = nr_free_pages();
 	val->bufferram = nr_blockdev_pages();
-#ifdef CONFIG_HIGHMEM
 	val->totalhigh = totalhigh_pages;
 	val->freehigh = nr_free_highpages();
-#else
-	val->totalhigh = 0;
-	val->freehigh = 0;
-#endif
 	val->mem_unit = PAGE_SIZE;
 }
 
@@ -1308,8 +1303,13 @@ void si_meminfo_node(struct sysinfo *val
 
 	val->totalram = pgdat->node_present_pages;
 	val->freeram = nr_free_pages_pgdat(pgdat);
+#ifdef CONFIG_HIGHMEM
 	val->totalhigh = pgdat->node_zones[ZONE_HIGHMEM].present_pages;
 	val->freehigh = pgdat->node_zones[ZONE_HIGHMEM].free_pages;
+#else
+	val->totalhigh = 0;
+	val->freehigh = 0;
+#endif
 	val->mem_unit = PAGE_SIZE;
 }
 #endif
@@ -1442,14 +1442,11 @@ static int __meminit build_zonelists_nod
 {
 	struct zone *zone;
 
-	BUG_ON(zone_type > ZONE_HIGHMEM);
+	BUG_ON(zone_type >= MAX_NR_ZONES);
 
 	do {
 		zone = pgdat->node_zones + zone_type;
 		if (populated_zone(zone)) {
-#ifndef CONFIG_HIGHMEM
-			BUG_ON(zone_type > ZONE_NORMAL);
-#endif
 			zonelist->zones[nr_zones++] = zone;
 			check_highest_zone(zone_type);
 		}
@@ -2080,7 +2077,7 @@ static void __meminit free_area_init_cor
 		if (zholes_size)
 			realsize -= zholes_size[j];
 
-		if (j < ZONE_HIGHMEM)
+		if (!is_highmem_idx(j))
 			nr_kernel_pages += realsize;
 		nr_all_pages += realsize;