Commit 99c4a26a authored by David S. Miller's avatar David S. Miller
Browse files

net: Fix high overhead of vlan sub-device teardown. 



When a networking device is taken down that has a non-trivial number
of VLAN devices configured under it, we eat a full synchronize_net()
for every such VLAN device.

This is because of the call chain:

	NETDEV_DOWN notifier
	--> vlan_device_event()
		--> dev_change_flags()
		--> __dev_change_flags()
		--> __dev_close()
		--> __dev_close_many()
		--> dev_deactivate_many()
			--> synchronize_net()

This is kind of rediculous because we already have infrastructure for
batching doing operation X to a list of net devices so that we only
incur one sync.

So make use of that by exporting dev_close_many() and adjusting it's
interfaace so that the caller can fully manage the batch list.  Use
this in vlan_device_event() and all the overhead goes away.

Reported-by: default avatarSalam Noureddine <noureddine@arista.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 738e6d30

include/linux/netdevice.h

+1 −0
Original line number Diff line number Diff line
@@ -2156,6 +2156,7 @@ struct net_device *__dev_get_by_name(struct net *net, const char *name); 
int dev_alloc_name(struct net_device *dev, const char *name);

int dev_open(struct net_device *dev);

int dev_close(struct net_device *dev);

int dev_close_many(struct list_head *head, bool unlink);

void dev_disable_lro(struct net_device *dev);

int dev_loopback_xmit(struct sk_buff *newskb);

int dev_queue_xmit(struct sk_buff *skb);

net/8021q/vlan.c

+13 −3
Original line number Diff line number Diff line
@@ -413,7 +413,10 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event, 
			vlan_transfer_features(dev, vlandev);

		break;



	case NETDEV_DOWN:

	case NETDEV_DOWN: {

		struct net_device *tmp;

		LIST_HEAD(close_list);



		if (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER)

			vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
@@ -425,11 +428,18 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event, 


			vlan = vlan_dev_priv(vlandev);

			if (!(vlan->flags & VLAN_FLAG_LOOSE_BINDING))

				dev_change_flags(vlandev, flgs & ~IFF_UP);

				list_add(&vlandev->close_list, &close_list);

		}



		dev_close_many(&close_list, false);



		list_for_each_entry_safe(vlandev, tmp, &close_list, close_list) {

			netif_stacked_transfer_operstate(dev, vlandev);

			list_del_init(&vlandev->close_list);

		}

		list_del(&close_list);

		break;



	}

	case NETDEV_UP:

		/* Put all VLANs for this dev in the up state too.  */

		vlan_group_for_each_dev(grp, i, vlandev) {

net/core/dev.c

+6 −4
Original line number Diff line number Diff line
@@ -1385,7 +1385,7 @@ static int __dev_close(struct net_device *dev) 
	return retval;

}



static int dev_close_many(struct list_head *head)

int dev_close_many(struct list_head *head, bool unlink)

{

	struct net_device *dev, *tmp;
@@ -1399,11 +1399,13 @@ static int dev_close_many(struct list_head *head) 
	list_for_each_entry_safe(dev, tmp, head, close_list) {

		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING, GFP_KERNEL);

		call_netdevice_notifiers(NETDEV_DOWN, dev);

		if (unlink)

			list_del_init(&dev->close_list);

	}



	return 0;

}

EXPORT_SYMBOL(dev_close_many);



/**

 *	dev_close - shutdown an interface.
@@ -1420,7 +1422,7 @@ int dev_close(struct net_device *dev) 
		LIST_HEAD(single);



		list_add(&dev->close_list, &single);

		dev_close_many(&single);

		dev_close_many(&single, true);

		list_del(&single);

	}

	return 0;
@@ -5986,7 +5988,7 @@ static void rollback_registered_many(struct list_head *head) 
	/* If device is running, close it first. */

	list_for_each_entry(dev, head, unreg_list)

		list_add_tail(&dev->close_list, &close_head);

	dev_close_many(&close_head);

	dev_close_many(&close_head, true);



	list_for_each_entry(dev, head, unreg_list) {

		/* And unlink it from device chain. */

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