Stub out kmem cache defrag API

At some point we are going to need to implement the kmem cache
move callbacks to allow for kmem cache defragmentation.  This
commit simply lays a small part of the API ground work, it does
not actually implement any of this feature.  This is safe for
now because the move callbacks are just an optimization.  Even
if they are registered we don't ever really have to call them.

include/sys/kmem.h

@@ -296,6 +296,15 @@ enum {
 	KMC_BIT_DESTROY		= 17,	/* Destroy in progress */
 };
 
+/* kmem move callback return values */
+typedef enum kmem_cbrc {
+	KMEM_CBRC_YES		= 0,	/* Object moved */
+	KMEM_CBRC_NO		= 1,	/* Object not moved */
+	KMEM_CBRC_LATER		= 2,	/* Object not moved, try again later */
+	KMEM_CBRC_DONT_NEED	= 3,	/* Neither object is needed */
+	KMEM_CBRC_DONT_KNOW	= 4,	/* Object unknown */
+} kmem_cbrc_t;
+
 #define KMC_NOTOUCH		(1 << KMC_BIT_NOTOUCH)
 #define KMC_NODEBUG		(1 << KMC_BIT_NODEBUG)
 #define KMC_NOMAGAZINE		(1 << KMC_BIT_NOMAGAZINE)
@@ -324,6 +333,9 @@ extern struct rw_semaphore spl_kmem_cache_sem;
 #define SPL_KMEM_CACHE_OBJ_PER_SLAB_MIN	8	/* Minimum objects per slab */
 #define SPL_KMEM_CACHE_ALIGN		8	/* Default object alignment */
 
+#define POINTER_IS_VALID(p)		0	/* Unimplemented */
+#define POINTER_INVALIDATE(pp)			/* Unimplemented */
+
 typedef int (*spl_kmem_ctor_t)(void *, void *, int);
 typedef void (*spl_kmem_dtor_t)(void *, void *);
 typedef void (*spl_kmem_reclaim_t)(void *);
@@ -393,11 +405,11 @@ typedef struct spl_kmem_cache {
 } spl_kmem_cache_t;
 #define kmem_cache_t		spl_kmem_cache_t
 
-extern spl_kmem_cache_t *
-spl_kmem_cache_create(char *name, size_t size, size_t align,
-        spl_kmem_ctor_t ctor, spl_kmem_dtor_t dtor, spl_kmem_reclaim_t reclaim,
-        void *priv, void *vmp, int flags);
-
+extern spl_kmem_cache_t *spl_kmem_cache_create(char *name, size_t size,
+	size_t align, spl_kmem_ctor_t ctor, spl_kmem_dtor_t dtor,
+	spl_kmem_reclaim_t reclaim, void *priv, void *vmp, int flags);
+extern void spl_kmem_cache_set_move(kmem_cache_t *,
+	kmem_cbrc_t (*)(void *, void *, size_t, void *));
 extern void spl_kmem_cache_destroy(spl_kmem_cache_t *skc);
 extern void *spl_kmem_cache_alloc(spl_kmem_cache_t *skc, int flags);
 extern void spl_kmem_cache_free(spl_kmem_cache_t *skc, void *obj);
@@ -410,6 +422,7 @@ void spl_kmem_fini(void);
 
 #define kmem_cache_create(name,size,align,ctor,dtor,rclm,priv,vmp,flags) \
         spl_kmem_cache_create(name,size,align,ctor,dtor,rclm,priv,vmp,flags)
+#define kmem_cache_set_move(skc, move)	spl_kmem_cache_set_move(skc, move)
 #define kmem_cache_destroy(skc)		spl_kmem_cache_destroy(skc)
 #define kmem_cache_alloc(skc, flags)	spl_kmem_cache_alloc(skc, flags)
 #define kmem_cache_free(skc, obj)	spl_kmem_cache_free(skc, obj)

module/spl/spl-kmem.c

@@ -1434,6 +1434,18 @@ spl_kmem_cache_create(char *name, size_t size, size_t align,
 }
 EXPORT_SYMBOL(spl_kmem_cache_create);
 
+/*
+ * Register a move callback to for cache defragmentation.
+ * XXX: Unimplemented but harmless to stub out for now.
+ */
+void
+spl_kmem_cache_set_move(kmem_cache_t *skc,
+    kmem_cbrc_t (move)(void *, void *, size_t, void *))
+{
+        ASSERT(move != NULL);
+}
+EXPORT_SYMBOL(spl_kmem_cache_set_move);
+
 /*
  * Destroy a cache and all objects assoicated with the cache.
  */