mm/slab: factor out debugging initialization in cache_init_objs()

cache_init_objs() will be changed in following patch and current form
doesn't fit well for that change.  So, before doing it, this patch
separates debugging initialization.  This would cause two loop iteration
when debugging is enabled, but, this overhead seems too light than debug
feature itself so effect may not be visible.  This patch will greatly
simplify changes in cache_init_objs() in following patch.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.c

@@ -2460,14 +2460,14 @@ static inline void set_free_obj(struct page *page,
 	((freelist_idx_t *)(page->freelist))[idx] = val;
 }
 
-static void cache_init_objs(struct kmem_cache *cachep,
-			    struct page *page)
+static void cache_init_objs_debug(struct kmem_cache *cachep, struct page *page)
 {
+#if DEBUG
 	int i;
 
 	for (i = 0; i < cachep->num; i++) {
 		void *objp = index_to_obj(cachep, page, i);
-#if DEBUG
+
 		if (cachep->flags & SLAB_STORE_USER)
 			*dbg_userword(cachep, objp) = NULL;
 
@@ -2496,10 +2496,22 @@ static void cache_init_objs(struct kmem_cache *cachep,
 			poison_obj(cachep, objp, POISON_FREE);
 			slab_kernel_map(cachep, objp, 0, 0);
 		}
-#else
-		if (cachep->ctor)
-			cachep->ctor(objp);
+	}
 #endif
+}
+
+static void cache_init_objs(struct kmem_cache *cachep,
+			    struct page *page)
+{
+	int i;
+
+	cache_init_objs_debug(cachep, page);
+
+	for (i = 0; i < cachep->num; i++) {
+		/* constructor could break poison info */
+		if (DEBUG == 0 && cachep->ctor)
+			cachep->ctor(index_to_obj(cachep, page, i));
+
 		set_free_obj(page, i, i);
 	}
 }