Fix zone policy determination

The use k in the inner loop means that the highest zone nr is always
used if any zone of a node is populated. Change the loop to decrement
k which also simplifies the BUG_ON.

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

Index: linux-2.6.15-rc5-mm2/mm/page_alloc.c
===================================================================
--- linux-2.6.15-rc5-mm2.orig/mm/page_alloc.c	2005-12-12 09:10:34.000000000 -0800
+++ linux-2.6.15-rc5-mm2/mm/page_alloc.c	2005-12-12 14:56:25.000000000 -0800
@@ -1579,15 +1579,19 @@ static int __init build_zonelists_node(p
 	struct zone *zone;
 
 	BUG_ON(k > ZONE_HIGHMEM);
-	for (zone = pgdat->node_zones + k; zone >= pgdat->node_zones; zone--) {
+
+	do {
+		zone = pgdat->node_zones + k;
 		if (populated_zone(zone)) {
 #ifndef CONFIG_HIGHMEM
-			BUG_ON(zone - pgdat->node_zones > ZONE_NORMAL);
+			BUG_ON(k > ZONE_NORMAL);
 #endif
 			zonelist->zones[j++] = zone;
 			check_highest_zone(k);
 		}
-	}
+		k--;
+
+	} while (k >= 0);
 	return j;
 }