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

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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: Salam Noureddine <noureddine@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2015-03-18 22:52:33 -04:00
parent 738e6d30d3
commit 99c4a26a15
3 changed files with 21 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/netdevice.h
View file

@ -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);

18
net/8021q/vlan.c
View file

@ -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);
netif_stacked_transfer_operstate(dev, vlandev);
list_add(&vlandev->close_list, &close_list);
}
break;
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) {

10
net/core/dev.c
View file

@ -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);
list_del_init(&dev->close_list);
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. */