From 99c4a26a159b28fa46a3e746a9b41b297e73d261 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@davemloft.net>
Date: Wed, 18 Mar 2015 22:52:33 -0400
Subject: 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>
---
net/core/dev.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
(limited to 'net/core/dev.c')
diff --git a/net/core/dev.c b/net/core/dev.c
index a1f24151db5b..5d43e010ef87 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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. */
--
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