ip6_vti: use exit_batch_rtnl() method

exit_batch_rtnl() is called while RTNL is held,
and devices to be unregistered can be queued in the dev_kill_list.

This saves one rtnl_lock()/rtnl_unlock() pair
and one unregister_netdevice_many() call.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://lore.kernel.org/r/20240206144313.2050392-13-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/ip6_vti.c

@@ -1174,24 +1174,22 @@ static int __net_init vti6_init_net(struct net *net)
 	return err;
 }
 
-static void __net_exit vti6_exit_batch_net(struct list_head *net_list)
+static void __net_exit vti6_exit_batch_rtnl(struct list_head *net_list,
+					    struct list_head *dev_to_kill)
 {
 	struct vti6_net *ip6n;
 	struct net *net;
-	LIST_HEAD(list);
 
-	rtnl_lock();
+	ASSERT_RTNL();
 	list_for_each_entry(net, net_list, exit_list) {
 		ip6n = net_generic(net, vti6_net_id);
-		vti6_destroy_tunnels(ip6n, &list);
+		vti6_destroy_tunnels(ip6n, dev_to_kill);
 	}
-	unregister_netdevice_many(&list);
-	rtnl_unlock();
 }
 
 static struct pernet_operations vti6_net_ops = {
 	.init = vti6_init_net,
-	.exit_batch = vti6_exit_batch_net,
+	.exit_batch_rtnl = vti6_exit_batch_rtnl,
 	.id   = &vti6_net_id,
 	.size = sizeof(struct vti6_net),
 };