netdev - Re: [PATCH 04/11] bridge: Cache vlan in the cb for faster egress lookup.

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Date:	Tue, 18 Dec 2012 12:50:13 -0500
From:	Vlad Yasevich <vyasevic@...hat.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	netdev@...r.kernel.org, davem@...emloft.net, mst@...hat.com,
	john.r.fastabend@...el.com
Subject: Re: [PATCH 04/11] bridge: Cache vlan in the cb for faster egress
 lookup.

On 12/18/2012 12:04 PM, Stephen Hemminger wrote:
> On Wed, 12 Dec 2012 15:01:10 -0500
> Vlad Yasevich <vyasevic@...hat.com> wrote:
>
>> On input, cache the pointer to the bridge vlan info, so that
>> on egress, we have can simply look at the port bitmap instead
>> of traversing a vlan list.
>>
>> Signed-off-by: Vlad Yasevich <vyasevic@...hat.com>
>
> This isn't going to be safe. Once packet is passed up, the cb[]
> can get overwritten by other things.
>

Right, but only care about it while in bridging code.  We don't look
at it anywhere else...

Or are you saying that cb is not guaranteed to be preserved between 
br_handle_frame_finish and br_forward?

-vlad
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