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: Salam Noureddine <noureddine@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 64c6bed..98a30a5 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -413,7 +413,10 @@
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 @@
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) {