ipv6: drop ipv6_sk_mc_lock in mcast

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

net/ipv6/mcast.c

@@ -73,9 +73,6 @@ static void *__mld2_query_bugs[] __attribute__((__unused__)) = {
 
 static struct in6_addr mld2_all_mcr = MLD2_ALL_MCR_INIT;
 
-/* Big mc list lock for all the sockets */
-static DEFINE_SPINLOCK(ipv6_sk_mc_lock);
-
 static void igmp6_join_group(struct ifmcaddr6 *ma);
 static void igmp6_leave_group(struct ifmcaddr6 *ma);
 static void igmp6_timer_handler(unsigned long data);
@@ -201,10 +198,8 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 		return err;
 	}
 
-	spin_lock(&ipv6_sk_mc_lock);
 	mc_lst->next = np->ipv6_mc_list;
 	rcu_assign_pointer(np->ipv6_mc_list, mc_lst);
-	spin_unlock(&ipv6_sk_mc_lock);
 
 	rcu_read_unlock();
 	rtnl_unlock();
@@ -226,17 +221,14 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 		return -EINVAL;
 
 	rtnl_lock();
-	spin_lock(&ipv6_sk_mc_lock);
 	for (lnk = &np->ipv6_mc_list;
-	     (mc_lst = rcu_dereference_protected(*lnk,
-			lockdep_is_held(&ipv6_sk_mc_lock))) != NULL;
+	     (mc_lst = rtnl_dereference(*lnk)) != NULL;
 	      lnk = &mc_lst->next) {
 		if ((ifindex == 0 || mc_lst->ifindex == ifindex) &&
 		    ipv6_addr_equal(&mc_lst->addr, addr)) {
 			struct net_device *dev;
 
 			*lnk = mc_lst->next;
-			spin_unlock(&ipv6_sk_mc_lock);
 
 			rcu_read_lock();
 			dev = dev_get_by_index_rcu(net, mc_lst->ifindex);
@@ -256,7 +248,6 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 			return 0;
 		}
 	}
-	spin_unlock(&ipv6_sk_mc_lock);
 	rtnl_unlock();
 
 	return -EADDRNOTAVAIL;
@@ -303,13 +294,10 @@ void ipv6_sock_mc_close(struct sock *sk)
 		return;
 
 	rtnl_lock();
-	spin_lock(&ipv6_sk_mc_lock);
-	while ((mc_lst = rcu_dereference_protected(np->ipv6_mc_list,
-				lockdep_is_held(&ipv6_sk_mc_lock))) != NULL) {
+	while ((mc_lst = rtnl_dereference(np->ipv6_mc_list)) != NULL) {
 		struct net_device *dev;
 
 		np->ipv6_mc_list = mc_lst->next;
-		spin_unlock(&ipv6_sk_mc_lock);
 
 		rcu_read_lock();
 		dev = dev_get_by_index_rcu(net, mc_lst->ifindex);
@@ -326,9 +314,7 @@ void ipv6_sock_mc_close(struct sock *sk)
 		atomic_sub(sizeof(*mc_lst), &sk->sk_omem_alloc);
 		kfree_rcu(mc_lst, rcu);
 
-		spin_lock(&ipv6_sk_mc_lock);
 	}
-	spin_unlock(&ipv6_sk_mc_lock);
 	rtnl_unlock();
 }