tipc: use rcu dereference functions properly

For these places are protected by rcu_read_lock, we change from
rcu_dereference_rtnl to rcu_dereference, as there is no need to
check if rtnl lock is held.

For these places are protected by rtnl_lock, we change from
rcu_dereference_rtnl to rtnl_dereference/rcu_dereference_protected,
as no extra memory barriers are needed under rtnl_lock() which also
protects tn->bearer_list[] and dev->tipc_ptr/b->media_ptr updating.

rcu_dereference_rtnl will be only used in the places where it could
be under rcu_read_lock or rtnl_lock.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/bearer.c

@@ -62,7 +62,7 @@ static struct tipc_bearer *bearer_get(struct net *net, int bearer_id)
 {
 	struct tipc_net *tn = tipc_net(net);
 
-	return rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
+	return rcu_dereference(tn->bearer_list[bearer_id]);
 }
 
 static void bearer_disable(struct net *net, struct tipc_bearer *b);
@@ -210,7 +210,7 @@ void tipc_bearer_add_dest(struct net *net, u32 bearer_id, u32 dest)
 	struct tipc_bearer *b;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
+	b = rcu_dereference(tn->bearer_list[bearer_id]);
 	if (b)
 		tipc_disc_add_dest(b->disc);
 	rcu_read_unlock();
@@ -222,7 +222,7 @@ void tipc_bearer_remove_dest(struct net *net, u32 bearer_id, u32 dest)
 	struct tipc_bearer *b;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
+	b = rcu_dereference(tn->bearer_list[bearer_id]);
 	if (b)
 		tipc_disc_remove_dest(b->disc);
 	rcu_read_unlock();
@@ -444,7 +444,7 @@ int tipc_l2_send_msg(struct net *net, struct sk_buff *skb,
 	struct net_device *dev;
 	int delta;
 
-	dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
+	dev = (struct net_device *)rcu_dereference(b->media_ptr);
 	if (!dev)
 		return 0;
 
@@ -481,7 +481,7 @@ int tipc_bearer_mtu(struct net *net, u32 bearer_id)
 	struct tipc_bearer *b;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tipc_net(net)->bearer_list[bearer_id]);
+	b = rcu_dereference(tipc_net(net)->bearer_list[bearer_id]);
 	if (b)
 		mtu = b->mtu;
 	rcu_read_unlock();
@@ -574,8 +574,8 @@ static int tipc_l2_rcv_msg(struct sk_buff *skb, struct net_device *dev,
 	struct tipc_bearer *b;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(dev->tipc_ptr) ?:
-		rcu_dereference_rtnl(orig_dev->tipc_ptr);
+	b = rcu_dereference(dev->tipc_ptr) ?:
+		rcu_dereference(orig_dev->tipc_ptr);
 	if (likely(b && test_bit(0, &b->up) &&
 		   (skb->pkt_type <= PACKET_MULTICAST))) {
 		skb_mark_not_on_list(skb);

net/tipc/udp_media.c

@@ -231,7 +231,7 @@ static int tipc_udp_send_msg(struct net *net, struct sk_buff *skb,
 	}
 
 	skb_set_inner_protocol(skb, htons(ETH_P_TIPC));
-	ub = rcu_dereference_rtnl(b->media_ptr);
+	ub = rcu_dereference(b->media_ptr);
 	if (!ub) {
 		err = -ENODEV;
 		goto out;
@@ -490,7 +490,7 @@ int tipc_udp_nl_dump_remoteip(struct sk_buff *skb, struct netlink_callback *cb)
 		}
 	}
 
-	ub = rcu_dereference_rtnl(b->media_ptr);
+	ub = rtnl_dereference(b->media_ptr);
 	if (!ub) {
 		rtnl_unlock();
 		return -EINVAL;
@@ -532,7 +532,7 @@ int tipc_udp_nl_add_bearer_data(struct tipc_nl_msg *msg, struct tipc_bearer *b)
 	struct udp_bearer *ub;
 	struct nlattr *nest;
 
-	ub = rcu_dereference_rtnl(b->media_ptr);
+	ub = rtnl_dereference(b->media_ptr);
 	if (!ub)
 		return -ENODEV;
 
@@ -806,7 +806,7 @@ static void tipc_udp_disable(struct tipc_bearer *b)
 {
 	struct udp_bearer *ub;
 
-	ub = rcu_dereference_rtnl(b->media_ptr);
+	ub = rtnl_dereference(b->media_ptr);
 	if (!ub) {
 		pr_err("UDP bearer instance not found\n");
 		return;