x86_64: Use lru instead of page->index and page->private for pgd lists management.

x86_64 currently simulates a list using the index and private fields of the page struct.
Seems that the code was inherited from i386. But x86_64 does not use the slab to
allocate pgds and pmds etc. So the lru field is not used by the slab and therefore
available.

This patch uses standard list operations on page->lru to realize pgd tracking.

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

Index: linux-2.6.21-rc4/arch/x86_64/mm/fault.c
===================================================================
--- linux-2.6.21-rc4.orig/arch/x86_64/mm/fault.c	2007-03-26 11:03:46.000000000 -0700
+++ linux-2.6.21-rc4/arch/x86_64/mm/fault.c	2007-03-26 11:04:43.000000000 -0700
@@ -585,7 +585,7 @@
 }
 
 DEFINE_SPINLOCK(pgd_lock);
-struct page *pgd_list;
+LIST_HEAD(pgd_list);
 
 void vmalloc_sync_all(void)
 {
@@ -605,8 +605,7 @@
 			if (pgd_none(*pgd_ref))
 				continue;
 			spin_lock(&pgd_lock);
-			for (page = pgd_list; page;
-			     page = (struct page *)page->index) {
+			list_for_each_entry(page, &pgd_list, lru) {
 				pgd_t *pgd;
 				pgd = (pgd_t *)page_address(page) + pgd_index(address);
 				if (pgd_none(*pgd))
Index: linux-2.6.21-rc4/include/asm-x86_64/pgtable.h
===================================================================
--- linux-2.6.21-rc4.orig/include/asm-x86_64/pgtable.h	2007-03-26 11:03:46.000000000 -0700
+++ linux-2.6.21-rc4/include/asm-x86_64/pgtable.h	2007-03-26 11:04:43.000000000 -0700
@@ -403,7 +403,7 @@
 #define __swp_entry_to_pte(x)		((pte_t) { (x).val })
 
 extern spinlock_t pgd_lock;
-extern struct page *pgd_list;
+extern struct list_head pgd_list;
 void vmalloc_sync_all(void);
 
 #endif /* !__ASSEMBLY__ */
Index: linux-2.6.21-rc4/include/asm-x86_64/pgalloc.h
===================================================================
--- linux-2.6.21-rc4.orig/include/asm-x86_64/pgalloc.h	2007-03-26 11:04:52.000000000 -0700
+++ linux-2.6.21-rc4/include/asm-x86_64/pgalloc.h	2007-03-26 11:08:11.000000000 -0700
@@ -45,24 +45,16 @@
 	struct page *page = virt_to_page(pgd);
 
 	spin_lock(&pgd_lock);
-	page->index = (pgoff_t)pgd_list;
-	if (pgd_list)
-		pgd_list->private = (unsigned long)&page->index;
-	pgd_list = page;
-	page->private = (unsigned long)&pgd_list;
+	list_add(&page->lru, &pgd_list);
 	spin_unlock(&pgd_lock);
 }
 
 static inline void pgd_list_del(pgd_t *pgd)
 {
-	struct page *next, **pprev, *page = virt_to_page(pgd);
+	struct page *page = virt_to_page(pgd);
 
 	spin_lock(&pgd_lock);
-	next = (struct page *)page->index;
-	pprev = (struct page **)page->private;
-	*pprev = next;
-	if (next)
-		next->private = (unsigned long)pprev;
+	list_del(&page->lru);
 	spin_unlock(&pgd_lock);
 }