More page_state function optimisation from Marcelo.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -858,7 +858,7 @@ int __set_page_dirty_buffers(struct page
 		write_lock_irq(&mapping->tree_lock);
 		if (page->mapping) {	/* Race with truncate? */
 			if (mapping_cap_account_dirty(mapping))
-				inc_page_state(nr_dirty);
+				__inc_page_state(nr_dirty);
 			radix_tree_tag_set(&mapping->page_tree,
 						page_index(page),
 						PAGECACHE_TAG_DIRTY);
Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h
+++ linux-2.6/include/linux/page-flags.h
@@ -91,10 +91,12 @@
  * commented here.
  */
 struct page_state {
-	unsigned long nr_dirty;		/* Dirty writeable pages */
+	unsigned long nr_dirty;		/* Dirty writeable pages.
+					 * only modified from process context */
 	unsigned long nr_writeback;	/* Pages under writeback */
 	unsigned long nr_unstable;	/* NFS unstable pages */
-	unsigned long nr_page_table_pages;/* Pages used for pagetables */
+	unsigned long nr_page_table_pages;/* Pages used for pagetables.
+					 * only modified from process context */
 	unsigned long nr_mapped;	/* mapped into pagetables.
 					 * only modified from process context */
 	unsigned long nr_slab;		/* In slab */
@@ -118,8 +120,10 @@ struct page_state {
 	unsigned long pgactivate;	/* pages moved inactive->active */
 	unsigned long pgdeactivate;	/* pages moved active->inactive */
 
-	unsigned long pgfault;		/* faults (major+minor) */
-	unsigned long pgmajfault;	/* faults (major only) */
+	unsigned long pgfault;		/* faults (major+minor)
+					 * only modified from process context */
+	unsigned long pgmajfault;	/* faults (major only)
+					 * only modified from process context */
 
 	unsigned long pgrefill_high;	/* inspected in refill_inactive_zone */
 	unsigned long pgrefill_normal;
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c
+++ linux-2.6/mm/memory.c
@@ -312,7 +312,7 @@ int __pte_alloc(struct mm_struct *mm, pm
 		pte_free(new);
 	} else {
 		mm->nr_ptes++;
-		inc_page_state(nr_page_table_pages);
+		__inc_page_state(nr_page_table_pages);
 		pmd_populate(mm, pmd, new);
 	}
 	spin_unlock(&mm->page_table_lock);
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -633,7 +633,7 @@ int __set_page_dirty_nobuffers(struct pa
 			if (mapping2) { /* Race with truncate? */
 				BUG_ON(mapping2 != mapping);
 				if (mapping_cap_account_dirty(mapping))
-					inc_page_state(nr_dirty);
+					__inc_page_state(nr_dirty);
 				radix_tree_tag_set(&mapping->page_tree,
 					page_index(page), PAGECACHE_TAG_DIRTY);
 			}
@@ -717,9 +717,9 @@ int test_clear_page_dirty(struct page *p
 			radix_tree_tag_clear(&mapping->page_tree,
 						page_index(page),
 						PAGECACHE_TAG_DIRTY);
-			write_unlock_irqrestore(&mapping->tree_lock, flags);
 			if (mapping_cap_account_dirty(mapping))
-				dec_page_state(nr_dirty);
+				__dec_page_state(nr_dirty);
+			write_unlock_irqrestore(&mapping->tree_lock, flags);
 			return 1;
 		}
 		write_unlock_irqrestore(&mapping->tree_lock, flags);
Index: linux-2.6/mm/swap.c
===================================================================
--- linux-2.6.orig/mm/swap.c
+++ linux-2.6/mm/swap.c
@@ -88,7 +88,7 @@ int rotate_reclaimable_page(struct page 
 	if (PageLRU(page) && !PageActive(page)) {
 		list_del(&page->lru);
 		list_add_tail(&page->lru, &zone->inactive_list);
-		inc_page_state(pgrotated);
+		__inc_page_state(pgrotated);
 	}
 	if (!test_clear_page_writeback(page))
 		BUG();
@@ -108,7 +108,7 @@ void fastcall activate_page(struct page 
 		del_page_from_inactive_list(zone, page);
 		SetPageActive(page);
 		add_page_to_active_list(zone, page);
-		inc_page_state(pgactivate);
+		__inc_page_state(pgactivate);
 	}
 	spin_unlock_irq(&zone->lru_lock);
 }