ipmr: Optimize multiple unregistration

Speedup module unloading by factorizing synchronize_rcu() calls
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipmr.c

@@ -275,7 +275,8 @@ static struct net_device *ipmr_reg_vif(struct net *net)
  *	@notify: Set to 1, if the caller is a notifier_call
  */
 
-static int vif_delete(struct net *net, int vifi, int notify)
+static int vif_delete(struct net *net, int vifi, int notify,
+		      struct list_head *head)
 {
 	struct vif_device *v;
 	struct net_device *dev;
@@ -319,7 +320,7 @@ static int vif_delete(struct net *net, int vifi, int notify)
 	}
 
 	if (v->flags&(VIFF_TUNNEL|VIFF_REGISTER) && !notify)
-		unregister_netdevice(dev);
+		unregister_netdevice_queue(dev, head);
 
 	dev_put(dev);
 	return 0;
@@ -870,14 +871,16 @@ static int ipmr_mfc_add(struct net *net, struct mfcctl *mfc, int mrtsock)
 static void mroute_clean_tables(struct net *net)
 {
 	int i;
+	LIST_HEAD(list);
 
 	/*
 	 *	Shut down all active vif entries
 	 */
 	for (i = 0; i < net->ipv4.maxvif; i++) {
 		if (!(net->ipv4.vif_table[i].flags&VIFF_STATIC))
-			vif_delete(net, i, 0);
+			vif_delete(net, i, 0, &list);
 	}
+	unregister_netdevice_many(&list);
 
 	/*
 	 *	Wipe the cache
@@ -993,7 +996,7 @@ int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, unsi
 		if (optname == MRT_ADD_VIF) {
 			ret = vif_add(net, &vif, sk == net->ipv4.mroute_sk);
 		} else {
-			ret = vif_delete(net, vif.vifc_vifi, 0);
+			ret = vif_delete(net, vif.vifc_vifi, 0, NULL);
 		}
 		rtnl_unlock();
 		return ret;
@@ -1156,6 +1159,7 @@ static int ipmr_device_event(struct notifier_block *this, unsigned long event, v
 	struct net *net = dev_net(dev);
 	struct vif_device *v;
 	int ct;
+	LIST_HEAD(list);
 
 	if (!net_eq(dev_net(dev), net))
 		return NOTIFY_DONE;
@@ -1165,8 +1169,9 @@ static int ipmr_device_event(struct notifier_block *this, unsigned long event, v
 	v = &net->ipv4.vif_table[0];
 	for (ct = 0; ct < net->ipv4.maxvif; ct++, v++) {
 		if (v->dev == dev)
-			vif_delete(net, ct, 1);
+			vif_delete(net, ct, 1, &list);
 	}
+	unregister_netdevice_many(&list);
 	return NOTIFY_DONE;
 }