mm/kfence: Convert kfence_guarded_alloc() to struct slab

The function sets some fields that are being moved from struct page to
struct slab so it needs to be converted.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <kasan-dev@googlegroups.com>

mm/kfence/core.c

@@ -360,7 +360,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
 {
 	struct kfence_metadata *meta = NULL;
 	unsigned long flags;
-	struct page *page;
+	struct slab *slab;
 	void *addr;
 
 	/* Try to obtain a free object. */
@@ -424,13 +424,13 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
 
 	alloc_covered_add(alloc_stack_hash, 1);
 
-	/* Set required struct page fields. */
-	page = virt_to_page(meta->addr);
-	page->slab_cache = cache;
+	/* Set required slab fields. */
+	slab = virt_to_slab((void *)meta->addr);
+	slab->slab_cache = cache;
 	if (IS_ENABLED(CONFIG_SLUB))
-		page->objects = 1;
+		slab->objects = 1;
 	if (IS_ENABLED(CONFIG_SLAB))
-		page->s_mem = addr;
+		slab->s_mem = addr;
 
 	/* Memory initialization. */
 	for_each_canary(meta, set_canary_byte);

mm/kfence/kfence_test.c

@@ -282,7 +282,7 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
 			alloc = kmalloc(size, gfp);
 
 		if (is_kfence_address(alloc)) {
-			struct page *page = virt_to_head_page(alloc);
+			struct slab *slab = virt_to_slab(alloc);
 			struct kmem_cache *s = test_cache ?:
 					kmalloc_caches[kmalloc_type(GFP_KERNEL)][__kmalloc_index(size, false)];
 
@@ -291,8 +291,8 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
 			 * even for KFENCE objects; these are required so that
 			 * memcg accounting works correctly.
 			 */
-			KUNIT_EXPECT_EQ(test, obj_to_index(s, page_slab(page), alloc), 0U);
-			KUNIT_EXPECT_EQ(test, objs_per_slab(s, page_slab(page)), 1);
+			KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);
+			KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);
 
 			if (policy == ALLOCATE_ANY)
 				return alloc;