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

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Date:	Tue, 6 Jan 2009 19:37:05 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	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 Tue, Jan 06 2009, Evgeniy Polyakov wrote:
> Hi Willy.
> 
> Unfortunately I can not work on this problem right now, but will do if
> things are not resolved after Jan 11 (long vacations will be finished in
> Russia and I will return to my test machines :) But right now I have
> one quesstion: I read several times your mail but still can not figure
> out if receiving or sending side is broken?
> 
> I.e. can you splice from socket into the file, check the file, and then
> splice to the another socket and check received data to find out which
> side is broken? Or did I just missed that in the problem description?
> 
> Thanks a lot for the test application, it will greatly help to resolve
> this issue.

I'll give this a spin tomorrow as well. A hunch tells me that this is
likely a page reuse issue, that splice is getting the reference to the
buffer dropped before the data has really been transmitted. IOW, the
page is likely fine reaching the ->sendpage() bit, but will be reused
before the data has actually been transmitted. So once you get that far,
other random data from that page is going out.

Just a guess, I'll try and reproduce this tomorrow!

-- 
Jens Axboe

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