vxlan: speedup vxlan tunnels dismantle

Since we now hold RTNL lock in vxlan_exit_net, it's better to batch them
to speedup vxlan tunnels dismantle.
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -3692,18 +3692,16 @@ static __net_init int vxlan_init_net(struct net *net)
 	return 0;
 }
 
-static void __net_exit vxlan_exit_net(struct net *net)
+static void vxlan_destroy_tunnels(struct net *net, struct list_head *head)
 {
 	struct vxlan_net *vn = net_generic(net, vxlan_net_id);
 	struct vxlan_dev *vxlan, *next;
 	struct net_device *dev, *aux;
 	unsigned int h;
-	LIST_HEAD(list);
 
-	rtnl_lock();
 	for_each_netdev_safe(net, dev, aux)
 		if (dev->rtnl_link_ops == &vxlan_link_ops)
-			unregister_netdevice_queue(dev, &list);
+			unregister_netdevice_queue(dev, head);
 
 	list_for_each_entry_safe(vxlan, next, &vn->vxlan_list, next) {
 		/* If vxlan->dev is in the same netns, it has already been added
@@ -3711,20 +3709,30 @@ static void __net_exit vxlan_exit_net(struct net *net)
 		 */
 		if (!net_eq(dev_net(vxlan->dev), net)) {
 			gro_cells_destroy(&vxlan->gro_cells);
-			unregister_netdevice_queue(vxlan->dev, &list);
+			unregister_netdevice_queue(vxlan->dev, head);
 		}
 	}
 
-	unregister_netdevice_many(&list);
-	rtnl_unlock();
-
 	for (h = 0; h < PORT_HASH_SIZE; ++h)
 		WARN_ON_ONCE(!hlist_empty(&vn->sock_list[h]));
 }
 
+static void __net_exit vxlan_exit_batch_net(struct list_head *net_list)
+{
+	struct net *net;
+	LIST_HEAD(list);
+
+	rtnl_lock();
+	list_for_each_entry(net, net_list, exit_list)
+		vxlan_destroy_tunnels(net, &list);
+
+	unregister_netdevice_many(&list);
+	rtnl_unlock();
+}
+
 static struct pernet_operations vxlan_net_ops = {
 	.init = vxlan_init_net,
-	.exit = vxlan_exit_net,
+	.exit_batch = vxlan_exit_batch_net,
 	.id   = &vxlan_net_id,
 	.size = sizeof(struct vxlan_net),
 };