Index: linux-2.6.21-rc6/include/linux/slab.h
===================================================================
--- linux-2.6.21-rc6.orig/include/linux/slab.h	2007-04-20 22:20:15.000000000 -0700
+++ linux-2.6.21-rc6/include/linux/slab.h	2007-04-20 22:28:27.000000000 -0700
@@ -32,9 +32,21 @@ typedef struct kmem_cache kmem_cache_t _
 #define SLAB_MEM_SPREAD		0x00100000UL	/* Spread some memory over cpuset */
 #define SLAB_TRACE		0x00200000UL	/* Trace allocations and frees */
 
-/* Flags passed to a constructor functions */
-#define SLAB_CTOR_CONSTRUCTOR	0x001UL		/* If not set, then deconstructor */
-#define SLAB_CTOR_ATOMIC	0x002UL		/* Tell constructor it can't sleep */
+#define SLAB_HAVE_CTOR		0x00000001UL	/* Cache has constructor */
+#define SLAB_HAVE_DTOR		0x00000002UL	/* Cache has destructor */
+#define SLAB_CAN_FREE		0x00000004UL	/* Cache can free objects */
+
+/* Flags passed through the callback function */
+#define SLAB_CALLBACK_CTOR	0x00000001UL	/* Constructor callback */
+#define SLAB_CALLBACK_DTOR	0x00000002UL	/* Destructor callback */
+#define SLAB_CALLBACK_GETREF	0x00000004UL	/* Get a reference */
+#define SLAB_CALLBACK_FREE	0x00000008UL	/* Free/Move object */
+
+#define SLAB_CALLBACK_ATOMIC	0x00010000UL	/* The callback is atomic */
+
+/* Compatibility definitions */
+#define SLAB_CTOR_CONSTRUCTOR	SLAB_CALLBACK_CTOR
+#define SLAB_CTOR_ATOMIC	SLAB_CALLBACK_ATOMIC
 
 /*
  * struct kmem_cache related prototypes
@@ -44,8 +56,7 @@ int slab_is_available(void);
 
 struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
 			unsigned long,
-			void (*)(void *, struct kmem_cache *, unsigned long),
-			void (*)(void *, struct kmem_cache *, unsigned long));
+			int (*)(void *, struct kmem_cache *, unsigned long));
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);
 void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
@@ -65,7 +76,7 @@ int kmem_ptr_validate(struct kmem_cache 
  */
 #define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\
 		sizeof(struct __struct), __alignof__(struct __struct),\
-		(__flags), NULL, NULL)
+		(__flags), NULL)
 
 #ifdef CONFIG_NUMA
 extern void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
Index: linux-2.6.21-rc6/include/linux/slub_def.h
===================================================================
--- linux-2.6.21-rc6.orig/include/linux/slub_def.h	2007-04-20 22:25:54.000000000 -0700
+++ linux-2.6.21-rc6/include/linux/slub_def.h	2007-04-20 22:26:10.000000000 -0700
@@ -41,8 +41,7 @@ struct kmem_cache {
 	/* Allocation and freeing of slabs */
 	int objects;		/* Number of objects in slab */
 	int refcount;		/* Refcount for slab cache destroy */
-	void (*ctor)(void *, struct kmem_cache *, unsigned long);
-	void (*dtor)(void *, struct kmem_cache *, unsigned long);
+	int (*callback)(void *, struct kmem_cache *, unsigned long);
 	int inuse;		/* Offset to metadata */
 	int align;		/* Alignment */
 	const char *name;	/* Name (only for display!) */
Index: linux-2.6.21-rc6/mm/slub.c
===================================================================
--- linux-2.6.21-rc6.orig/mm/slub.c	2007-04-20 22:28:32.000000000 -0700
+++ linux-2.6.21-rc6/mm/slub.c	2007-04-20 22:30:17.000000000 -0700
@@ -784,13 +784,14 @@ static void setup_object(struct kmem_cac
 		init_tracking(s, object);
 	}
 
-	if (unlikely(s->ctor)) {
-		int mode = SLAB_CTOR_CONSTRUCTOR;
+	if (s->flags & SLAB_HAVE_CTOR)
+		callback(object, s, SLAB_CALLBACK_CTOR{
+		int mode = SLAB_CALLBACK_CTOR;
 
 		if (!(s->flags & __GFP_WAIT))
-			mode |= SLAB_CTOR_ATOMIC;
+			mode |= SLAB_CALLBACK_ATOMIC;
 
-		s->ctor(object, s, mode);
+		s->callback(object, s, mode);
 	}
 }