slub: Do not use frozen page flag but a bit in the page counters

Do not use a page flag for the frozen bit. It needs to be part
of the state that is handled with cmpxchg_double(). So use a bit
in the counter struct in the page struct for that purpose.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

include/linux/mm_types.h

@@ -41,8 +41,9 @@ struct page {
 					 * & limit reverse map searches.
 					 */
 		struct {		/* SLUB */
-			u16 inuse;
-			u16 objects;
+			unsigned inuse:16;
+			unsigned objects:15;
+			unsigned frozen:1;
 		};
 	};
 	union {

include/linux/page-flags.h

@@ -124,9 +124,6 @@ enum pageflags {
 
 	/* SLOB */
 	PG_slob_free = PG_private,
-
-	/* SLUB */
-	PG_slub_frozen = PG_active,
 };
 
 #ifndef __GENERATING_BOUNDS_H
@@ -212,8 +209,6 @@ PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 
 __PAGEFLAG(SlobFree, slob_free)
 
-__PAGEFLAG(SlubFrozen, slub_frozen)
-
 /*
  * Private page markings that may be used by the filesystem that owns the page
  * for its own purposes.

mm/slub.c

@@ -166,7 +166,7 @@ static inline int kmem_cache_debug(struct kmem_cache *s)
 
 #define OO_SHIFT	16
 #define OO_MASK		((1 << OO_SHIFT) - 1)
-#define MAX_OBJS_PER_PAGE	65535 /* since page.objects is u16 */
+#define MAX_OBJS_PER_PAGE	32767 /* since page.objects is u15 */
 
 /* Internal SLUB flags */
 #define __OBJECT_POISON		0x80000000UL /* Poison object */
@@ -1025,7 +1025,7 @@ static noinline int free_debug_processing(struct kmem_cache *s,
 	}
 
 	/* Special debug activities for freeing objects */
-	if (!PageSlubFrozen(page) && !page->freelist)
+	if (!page->frozen && !page->freelist)
 		remove_full(s, page);
 	if (s->flags & SLAB_STORE_USER)
 		set_track(s, object, TRACK_FREE, addr);
@@ -1424,7 +1424,7 @@ static inline int lock_and_freeze_slab(struct kmem_cache_node *n,
 {
 	if (slab_trylock(page)) {
 		__remove_partial(n, page);
-		__SetPageSlubFrozen(page);
+		page->frozen = 1;
 		return 1;
 	}
 	return 0;
@@ -1538,7 +1538,7 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
 {
 	struct kmem_cache_node *n = get_node(s, page_to_nid(page));
 
-	__ClearPageSlubFrozen(page);
+	page->frozen = 0;
 	if (page->inuse) {
 
 		if (page->freelist) {
@@ -1868,7 +1868,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 			flush_slab(s, c);
 
 		slab_lock(page);
-		__SetPageSlubFrozen(page);
+		page->frozen = 1;
 		c->node = page_to_nid(page);
 		c->page = page;
 		goto load_freelist;
@@ -2048,7 +2048,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page,
 	page->freelist = object;
 	page->inuse--;
 
-	if (unlikely(PageSlubFrozen(page))) {
+	if (unlikely(page->frozen)) {
 		stat(s, FREE_FROZEN);
 		goto out_unlock;
 	}