netdev - Re: [PATCH] bonding: reset queue mapping prior to transmission to physical device

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Message-ID: <4DE7F0F1.3010800@gmail.com>
Date:	Thu, 02 Jun 2011 22:22:09 +0200
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	David Miller <davem@...emloft.net>
CC:	nhorman@...driver.com, netdev@...r.kernel.org, fubar@...ibm.com,
	andy@...yhouse.net
Subject: Re: [PATCH] bonding: reset queue mapping prior to transmission to
 physical device

Le 02/06/2011 22:07, David Miller a écrit :
> From: Neil Horman<nhorman@...driver.com>
> Date: Thu,  2 Jun 2011 14:03:19 -0400
>
>> The bonding driver is multiqueue enabled, in which each queue represents a slave
>> to enable optional steering of output frames to given slaves against the default
>> output policy.  However, it needs to reset the skb->queue_mapping prior to
>> queuing to the physical device or the physical slave (if it is multiqueue) could
>> wind up transmitting on an unintended tx queue (one that was reserved for
>> specific traffic classes for instance)
>>
>> Signed-off-by: Neil Horman<nhorman@...driver.com>
>
> Since, as I mentioned, the idea when we are forwarding and bridging is that
> we use the input receive classification to influence the spread on transmit,
> I think things like this bonding case should remember the rxhash setting
> before they override it and then restore that value right before invoking
> dev_queue_xmit().

Ok, now I understand. Maybe, using queue mapping for special slave selection wasn't such a good idea 
at the very beginning, because it pollutes the RX mapping that is expected to be propagated up to 
TX. Restoring the original value before invoking dev_queue_xmit() would fix this, but I'm not sure 
it is the cleanest way to do it.

	Nicolas.
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