security,rcu: convert call_rcu(user_update_rcu_disposal) to kfree_rcu()

The rcu callback user_update_rcu_disposal() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(user_update_rcu_disposal).

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

security/keys/user_defined.c

@@ -68,18 +68,6 @@ int user_instantiate(struct key *key, const void *data, size_t datalen)
 
 EXPORT_SYMBOL_GPL(user_instantiate);
 
-/*
- * dispose of the old data from an updated user defined key
- */
-static void user_update_rcu_disposal(struct rcu_head *rcu)
-{
-	struct user_key_payload *upayload;
-
-	upayload = container_of(rcu, struct user_key_payload, rcu);
-
-	kfree(upayload);
-}
-
 /*
  * update a user defined key
  * - the key's semaphore is write-locked
@@ -114,7 +102,7 @@ int user_update(struct key *key, const void *data, size_t datalen)
 		key->expiry = 0;
 	}
 
-	call_rcu(&zap->rcu, user_update_rcu_disposal);
+	kfree_rcu(zap, rcu);
 
 error:
 	return ret;
@@ -145,7 +133,7 @@ void user_revoke(struct key *key)
 
 	if (upayload) {
 		rcu_assign_pointer(key->payload.data, NULL);
-		call_rcu(&upayload->rcu, user_update_rcu_disposal);
+		kfree_rcu(upayload, rcu);
 	}
 }