netdev - Re: Reproducible data corruption with sendfile+vsftp

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Message-ID:  <pan.2007.12.13.02.19.40.200510@wizards.de>
Date:	Thu, 13 Dec 2007 03:19:43 +0100
From:	"Holger Hoffstaette" <holger@...ards.de>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject:  Re: Reproducible data corruption with sendfile+vsftp - splice regression?

On Thu, 06 Dec 2007 19:44:26 +0100, Francois Romieu wrote:

> Holger Hoffstaette <holger@...ards.de> : [...]
>> Maybe turning off sendfile or NAPI just lead to random success - so far
>> it really looks like tso on the r8169 is the common cause.
> 
> TSO on the r8169 is the magic switch but the regression makes imvho more
> sense from a VM pov:
> 
> - the corrupted file has the same size as the expected file - the
> corrupted file exhibits holes which come as a multiple of 4096 bytes
>   (8*4k, 2 places, there may be more)
> - the r8169 driver does not know what a page is - the 8169 hardware has a
> small 8192 bytes Tx buffer
> 
> It would be nice if someone could do a sendfile + vsftp test with TSO on a
> different hardware. While I could not reproduce the corruption when simply
> downloading a file that I had copied on the server with scp, it triggered
> almost immediately after I copied it locally and tried to download the
> copy.

Here's an update - sorry for the delay but I need that machine for everyday work.

I have now gone back to enable TSO since vsftp with sendfile really seems
to be the only app that causes this. I have simply set it to
use_sendfile=NO and no corruption occurs at all; the machine is stable and
fast.

FWIW the corruption can still be reproduced with 2.6.24-rc5. For kicks I
have also tried -rc5 with SLAB instead of SLUB, but that didn't help
either.

The directory with the tcpdump & test data now also contains a few more
corrupted files; maybe comparing the corruption offsets gives someone a
better idea.

thanks
Holger

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