netdev - Re: sendfile() broken with 2.6.26 + Apache 2 ?

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Date:	Sat, 19 Jul 2008 07:31:46 -0500
From:	"J. K. Cliburn" <jcliburn@...il.com>
To:	Ian Jeffray <ian@...fray.co.uk>
CC:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: sendfile() broken with 2.6.26 + Apache 2 ?

Ian Jeffray wrote:
> All,
> 
> I moved from kernel 2.6.25.4 to 2.6.26 yesterday and observed that
> large files sent via Apache2 are partially corrupt.
> 
> This appears to be linked to sendfile() -- disabling the use of
> sendfile in the apache config (EnableSendfile Off) allows it to
> function as normal.
> 
> My system is a simple Core2Duo running Debian lenny/sid; nothing
> special, and I have never observed problems like this before.
> 
> The problem feels certainly related to sendfile() since the data
> reads correctly from disc in other programs, and via CIFS etc.
> 
> The corruption happens part-way in to the file... I've no exact
> figure but it would seem like maybe 32KB -- I'm seeing broken
> PNGs served from Apache, where the top few dozen lines decode
> correctly, and the rest is garbage.
> 
> I've made basically no configuration changes between 2.6.25.4 and
> 2.6.26 and have explicitly tried both enabling and disabling the
> new PAT support to no effect.
> 
> This is completely repeatable and reproducible.
> 
> Is anyone else seeing this broken behaviour?

Can you please enable verbose logging

echo 8 > /proc/sys/kernel/printk
ethtool -s eth0 msglvl 0xffff

and see if the driver issues any error messages as the file is transferred?
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