linux-kernel - Re: Data corruption issue with splice() on 2.6.27.10

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Message-ID: <20090107122238.GB25673@gondor.apana.org.au>
Date:	Wed, 7 Jan 2009 23:22:38 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	Jens Axboe <jens.axboe@...cle.com>, Willy Tarreau <w@....eu>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: Data corruption issue with splice() on 2.6.27.10

On Wed, Jan 07, 2009 at 03:15:30PM +0300, Evgeniy Polyakov wrote:
> 
> Looks like we are talking about different directions of the dataflow.
> I meant that set of pages submitted into the sending part will be copied
> if sending interface does not support acceleration, and thus it will
> copy part of the page corresponding to the linear part of the skb prior
> the transmission, so even if skb will be freed right after that call
> (prior data transmission by the hardware), it should not affect copied
> data.

You must be looking at a different tcp.c than the one I've got
because mine clearly always uses skb frags in sendpage regardless
of SG support.

Yes we will linearize the packet in dev_queue_xmit but as soon
as the netdev stops the tx queue you'll get corruption.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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