KREF: shrink the size of struct kref down to just a single atomic_t

This was based on a patch from Kiran, but tweaked further by me.
Signed-off-by: Ravikiran Thirumalai <kiran@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

include/linux/kref.h

@@ -18,15 +18,12 @@
 #include <linux/types.h>
 #include <asm/atomic.h>
 
-
 struct kref {
 	atomic_t refcount;
-	void (*release)(struct kref *kref);
 };
 
-void kref_init(struct kref *kref, void (*release)(struct kref *));
+void kref_init(struct kref *kref);
 struct kref *kref_get(struct kref *kref);
-void kref_put(struct kref *kref);
-
+void kref_put(struct kref *kref, void (*release) (struct kref *kref));
 
 #endif /* _KREF_H_ */

lib/kref.c

@@ -11,23 +11,16 @@
  *
  */
 
-/* #define DEBUG */
-
 #include <linux/kref.h>
 #include <linux/module.h>
 
 /**
  * kref_init - initialize object.
  * @kref: object in question.
- * @release: pointer to a function that will clean up the object
- *	     when the last reference to the object is released.
- *	     This pointer is required.
  */
-void kref_init(struct kref *kref, void (*release)(struct kref *kref))
+void kref_init(struct kref *kref)
 {
-	WARN_ON(release == NULL);
 	atomic_set(&kref->refcount,1);
-	kref->release = release;
 }
 
 /**
@@ -44,15 +37,20 @@ struct kref *kref_get(struct kref *kref)
 /**
  * kref_put - decrement refcount for object.
  * @kref: object.
+ * @release: pointer to the function that will clean up the object when the
+ *	     last reference to the object is released.
+ *	     This pointer is required, and it is not acceptable to pass kfree
+ *	     in as this function.
  *
- * Decrement the refcount, and if 0, call kref->release().
+ * Decrement the refcount, and if 0, call release().
  */
-void kref_put(struct kref *kref)
+void kref_put(struct kref *kref, void (*release) (struct kref *kref))
 {
-	if (atomic_dec_and_test(&kref->refcount)) {
-		pr_debug("kref cleaning up\n");
-		kref->release(kref);
-	}
+	WARN_ON(release == NULL);
+	WARN_ON(release == (void (*)(struct kref *))kfree);
+
+	if (atomic_dec_and_test(&kref->refcount))
+		release(kref);
 }
 
 EXPORT_SYMBOL(kref_init);