Hugepages: Use page_to_nid rather than traversing zone pointers

I found two location in hugetlb.c where we chase pointer instead of
using page_to_nid(). Page_to_nid is more effective and can get the node
directly from page flags.

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

Index: linux-2.6.18-rc5-mm1/mm/hugetlb.c
===================================================================
--- linux-2.6.18-rc5-mm1.orig/mm/hugetlb.c	2006-09-03 20:42:28.000000000 -0700
+++ linux-2.6.18-rc5-mm1/mm/hugetlb.c	2006-09-03 20:48:39.000000000 -0700
@@ -177,7 +177,7 @@
 {
 	int i;
 	nr_huge_pages--;
-	nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
+	nr_huge_pages_node[page_to_nid(page)]--;
 	for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
 		page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
 				1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
@@ -191,7 +191,8 @@
 #ifdef CONFIG_HIGHMEM
 static void try_to_free_low(unsigned long count)
 {
-	int i, nid;
+	int i;
+
 	for (i = 0; i < MAX_NUMNODES; ++i) {
 		struct page *page, *next;
 		list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
@@ -199,9 +200,8 @@
 				continue;
 			list_del(&page->lru);
 			update_and_free_page(page);
-			nid = page_zone(page)->zone_pgdat->node_id;
 			free_huge_pages--;
-			free_huge_pages_node[nid]--;
+			free_huge_pages_node[page_to_nid(page)]--;
 			if (count >= nr_huge_pages)
 				return;
 		}