net: rtnl: use rcu_replace_pointer_rtnl in rtnl_unregister_*

With the introduction of the rcu_replace_pointer_rtnl helper,
cleanup the rtnl_unregister_* functions to use the helper instead
of open coding it.
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -342,8 +342,7 @@ int rtnl_unregister(int protocol, int msgtype)
 		return -ENOENT;
 	}
 
-	link = rtnl_dereference(tab[msgindex]);
-	RCU_INIT_POINTER(tab[msgindex], NULL);
+	link = rcu_replace_pointer_rtnl(tab[msgindex], NULL);
 	rtnl_unlock();
 
 	kfree_rcu(link, rcu);
@@ -368,18 +367,13 @@ void rtnl_unregister_all(int protocol)
 	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
 
 	rtnl_lock();
-	tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
+	tab = rcu_replace_pointer_rtnl(rtnl_msg_handlers[protocol], NULL);
 	if (!tab) {
 		rtnl_unlock();
 		return;
 	}
-	RCU_INIT_POINTER(rtnl_msg_handlers[protocol], NULL);
 	for (msgindex = 0; msgindex < RTM_NR_MSGTYPES; msgindex++) {
-		link = rtnl_dereference(tab[msgindex]);
-		if (!link)
-			continue;
-
-		RCU_INIT_POINTER(tab[msgindex], NULL);
+		link = rcu_replace_pointer_rtnl(tab[msgindex], NULL);
 		kfree_rcu(link, rcu);
 	}
 	rtnl_unlock();