ipv6: drop some rcu_read_lock in mcast

Similarly the code is already protected by rtnl lock.
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/mcast.c

@@ -162,7 +162,6 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	mc_lst->addr = *addr;
 
 	rtnl_lock();
-	rcu_read_lock();
 	if (ifindex == 0) {
 		struct rt6_info *rt;
 		rt = rt6_lookup(net, addr, NULL, 0, 0);
@@ -171,10 +170,9 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 			ip6_rt_put(rt);
 		}
 	} else
-		dev = dev_get_by_index_rcu(net, ifindex);
+		dev = __dev_get_by_index(net, ifindex);
 
 	if (dev == NULL) {
-		rcu_read_unlock();
 		rtnl_unlock();
 		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
 		return -ENODEV;
@@ -192,7 +190,6 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	err = ipv6_dev_mc_inc(dev, addr);
 
 	if (err) {
-		rcu_read_unlock();
 		rtnl_unlock();
 		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
 		return err;
@@ -201,7 +198,6 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	mc_lst->next = np->ipv6_mc_list;
 	rcu_assign_pointer(np->ipv6_mc_list, mc_lst);
 
-	rcu_read_unlock();
 	rtnl_unlock();
 
 	return 0;
@@ -230,8 +226,7 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 
 			*lnk = mc_lst->next;
 
-			rcu_read_lock();
-			dev = dev_get_by_index_rcu(net, mc_lst->ifindex);
+			dev = __dev_get_by_index(net, mc_lst->ifindex);
 			if (dev != NULL) {
 				struct inet6_dev *idev = __in6_dev_get(dev);
 
@@ -240,7 +235,6 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 					__ipv6_dev_mc_dec(idev, &mc_lst->addr);
 			} else
 				(void) ip6_mc_leave_src(sk, mc_lst, NULL);
-			rcu_read_unlock();
 			rtnl_unlock();
 
 			atomic_sub(sizeof(*mc_lst), &sk->sk_omem_alloc);
@@ -299,8 +293,7 @@ void ipv6_sock_mc_close(struct sock *sk)
 
 		np->ipv6_mc_list = mc_lst->next;
 
-		rcu_read_lock();
-		dev = dev_get_by_index_rcu(net, mc_lst->ifindex);
+		dev = __dev_get_by_index(net, mc_lst->ifindex);
 		if (dev) {
 			struct inet6_dev *idev = __in6_dev_get(dev);
 
@@ -309,7 +302,6 @@ void ipv6_sock_mc_close(struct sock *sk)
 				__ipv6_dev_mc_dec(idev, &mc_lst->addr);
 		} else
 			(void) ip6_mc_leave_src(sk, mc_lst, NULL);
-		rcu_read_unlock();
 
 		atomic_sub(sizeof(*mc_lst), &sk->sk_omem_alloc);
 		kfree_rcu(mc_lst, rcu);
@@ -934,7 +926,7 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)
 	struct inet6_dev *idev;
 	int err;
 
-	rcu_read_lock();
+	ASSERT_RTNL();
 
 	idev = __in6_dev_get(dev);
 	if (!idev)
@@ -942,7 +934,6 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)
 	else
 		err = __ipv6_dev_mc_dec(idev, addr);
 
-	rcu_read_unlock();
 	return err;
 }