afs: Use kfree_rcu() instead of casting kfree() to rcu_callback_t

afs_put_addrlist() casts kfree() to rcu_callback_t. Apart from being wrong
in theory, this might also blow up when people start enforcing function
types via compiler instrumentation, and it means the rcu_head has to be
first in struct afs_addr_list.

Use kfree_rcu() instead, it's simpler and more correct.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/addr_list.c

@@ -19,7 +19,7 @@
 void afs_put_addrlist(struct afs_addr_list *alist)
 {
 	if (alist && refcount_dec_and_test(&alist->usage))
-		call_rcu(&alist->rcu, (rcu_callback_t)kfree);
+		kfree_rcu(alist, rcu);
 }
 
 /*

fs/afs/internal.h

@@ -81,7 +81,7 @@ enum afs_call_state {
  * List of server addresses.
  */
 struct afs_addr_list {
-	struct rcu_head		rcu;		/* Must be first */
+	struct rcu_head		rcu;
 	refcount_t		usage;
 	u32			version;	/* Version */
 	unsigned char		max_addrs;