[PATCH] more slab page checking

Add checks for kfree() of a page which was allocated with __alloc_pages(),
and for free_pages() of a page which was allocated with kmalloc().

include/linux/page-flags.h

@@ -191,6 +191,8 @@ extern void get_full_page_state(struct page_state *ret);
 #define PageSlab(page)		test_bit(PG_slab, &(page)->flags)
 #define SetPageSlab(page)	set_bit(PG_slab, &(page)->flags)
 #define ClearPageSlab(page)	clear_bit(PG_slab, &(page)->flags)
+#define TestClearPageSlab(page)	test_and_clear_bit(PG_slab, &(page)->flags)
+#define TestSetPageSlab(page)	test_and_set_bit(PG_slab, &(page)->flags)
 
 #ifdef CONFIG_HIGHMEM
 #define PageHighMem(page)	test_bit(PG_highmem, &(page)->flags)

mm/page_alloc.c

@@ -220,6 +220,7 @@ static inline void free_pages_check(const char *function, struct page *page)
 			1 << PG_locked	|
 			1 << PG_active	|
 			1 << PG_reclaim	|
+			1 << PG_slab	|
 			1 << PG_writeback )))
 		bad_page(function, page);
 	if (PageDirty(page))

mm/slab.c

@@ -787,7 +787,8 @@ static inline void kmem_freepages (kmem_cache_t *cachep, void *addr)
 	 * vm_scan(). Shouldn't be a worry.
 	 */
 	while (i--) {
-		ClearPageSlab(page);
+		if (!TestClearPageSlab(page))
+			BUG();
 		page++;
 	}
 	sub_page_state(nr_slab, nr_freed);