netdev - Re: [RFC Patch 2/3] bridge: make bridge support netpoll

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Message-ID: <4BA84B0B.3090908@redhat.com>
Date:	Tue, 23 Mar 2010 13:00:59 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Matt Mackall <mpm@...enic.com>
CC:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	bridge@...ts.linux-foundation.org,
	Andy Gospodarek <gospo@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	bonding-devel@...ts.sourceforge.net,
	Jay Vosburgh <fubar@...ibm.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [RFC Patch 2/3] bridge: make bridge support netpoll

Matt Mackall wrote:
> On Tue, 2010-03-23 at 12:39 +0800, Cong Wang wrote:
>> Matt Mackall wrote:
>>> On Tue, 2010-03-23 at 10:03 +0800, Cong Wang wrote:
>>>> Matt Mackall wrote:
>>>>> On Mon, 2010-03-22 at 04:17 -0400, Amerigo Wang wrote:
>>>>>> Based on the previous patch, make bridge support netpoll by:
>>>>>>
>>>>>> 1) implement the 4 methods to support netpoll for bridge;
>>>>>>
>>>>>> 2) modify netpoll during forwarding packets in bridge;
>>>>>>
>>>>>> 3) disable netpoll support of bridge when a netpoll-unabled device
>>>>>>    is added to bridge;
>>>>> Not sure if this is the right thing to do. Shouldn't we simply enable
>>>>> polling on all devices that support it and warn about the others (aka
>>>>> best effort)?
>>>>>
>>>> I don't think it's a good idea, because we check if a device
>>>> supports netpoll by checking if it has ndo_poll_controller method.
>>> Uh, what? If we have 5 devices on a bridge and 4 support netpoll, then
>>> shouldn't we just send netconsole messages to those 4 devices? Isn't
>>> this much better than simply refusing to work?
>>>
>> How could you let the bridge know netpoll is not sent to
>> the one that doesn't support netpoll during setup? This will
>> be complex, I am afraid.
> 
> I thought I saw a simple loop over bridge devices at poll time in your
> patch. So it should be a simple matter of skipping unsupported devices
> in that loop.

Nope, we need to check if the target address is owned by
a device that doesn't support netpoll or not, simple skipping
will not work.


> 
> But Dave thinks there a bigger problems here, so I recommend first
> figuring out the architecture issues, then we can get back to the policy
> issues.
> 

Ok. Thanks!
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