netdev - Re: [net-next,1/3] bonding: fix vlan 0 addition and removal

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Message-ID: <20130806085111.GL22756@redhat.com>
Date:	Tue, 6 Aug 2013 10:51:11 +0200
From:	Veaceslav Falico <vfalico@...hat.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	netdev@...r.kernel.org, fubar@...ibm.com, andy@...yhouse.net,
	davem@...emloft.net, kaber@...sh.net
Subject: Re: [net-next,1/3] bonding: fix vlan 0 addition and removal

On Tue, Aug 06, 2013 at 10:16:04AM +0200, Nikolay Aleksandrov wrote:
>On 08/05/2013 11:51 PM, Veaceslav Falico wrote:
>> On Mon, Aug 05, 2013 at 03:28:22PM +0200, nikolay@...hat.com wrote:
>> ...snip...
>>> This is fixed by forbidding the addition/removal of vlan 0 through the
>>> bond's ndo_vlan_rx_add/kill_vid functions, and adding/removing it only when
>>> vlan 0 is in fact being created (or destroyed) on top of a bond interface
>>> in the bond's netdev handling function.
>>
>> Isn't that a bit too intrusive/hacky? I don't think we should treat vlan id
>> 0 somehow differently in terms of adding/removing, though I might be
>> wrong...
>>
>I didn't want to touch the vlan code, so I solved the problem entirely in
>the bonding, mind you there's still a bug when loading the 8021q module
>we'll bump up every slave's vlan 0 refcnt without adding the vlan, and it
>won't get bumped down.
>In my patch that problem still persists but only when an actual vlan 0 is
>being created.

I'll look into that, though maybe we'll require another patch to fix it.

>
>> Maybe we should just fix the bond_vlan_used() function? Something like
>> this (I've done only basic testing, can do more thorough if needed), though
>> it's also not a really clean fix:
>>
>Yes, that would be optimal and I agree.
>
>> From 1c89abefebe90568ed52d2df59fcfdd650bc4696 Mon Sep 17 00:00:00 2001
>> From: Veaceslav Falico <vfalico@...hat.com>
>> Date: Mon, 5 Aug 2013 23:29:12 +0200
>> Subject: [PATCH] bonding: add vlan_uses_dev_rcu() and make bond_vlan_used()
>> use it
>>
>> Currently, bond_vlan_used() looks for any vlan, including the pseudo-vlan
>> id 0, and always returns true if 8021q is loaded. This creates several bad
>> situations - some warnings in __bond_release_one() because it thinks that
>> we still have vlans while removing, sending LB packets with vlan id 0 and,
>> possibly, other caused by vlan id 0.
>>
>> Fix it by adding a new call, vlan_uses_dev_rcu(), which is the same as
>> vlan_uses_dev(), but uses rcu_dereference() instead of rtnl, and thus we
>> can use it in bond_vlan_used() wrapped in rcu_read_lock().
>>
>> Also, use the pure vlan_uses_dev() in __bond_release_one() cause the rtnl
>> lock is held there.
>>
>> CC: Jay Vosburgh <fubar@...ibm.com>
>> CC: Andy Gospodarek <andy@...yhouse.net>
>> CC: Patrick McHardy <kaber@...sh.net>
>> CC: "David S. Miller" <davem@...emloft.net>
>> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
>> ---
>I'm okay with this fix, if Dave is also okay with this version then you can
>submit it as a patch, I'll re-base my third one later and resubmit.

Ok, great, then I'll get some testing with this patch and submit it.
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