linux-kernel - Re: SMP read() stopping at memory page boundaries

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Message-Id: <1182361700.3768.107.camel@hurina>
Date:	Wed, 20 Jun 2007 20:48:20 +0300
From:	Timo Sirainen <tss@....fi>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Ray Lee <ray-lk@...rabbit.org>, linux-kernel@...r.kernel.org
Subject: Re: SMP read() stopping at memory page boundaries

On Wed, 2007-06-20 at 18:05 +0100, Alan Cox wrote:
> > I thought this wouldn't happen when reading from local filesystems.
> > Anyway, my real program was doing that, and it was still seeing partial
> > data. But looks like I can't reproduce it in my test program with two
> > pread()s, so I'll have to do some more debugging.

Found the problem in my code. A buggy program, buggy test program and a
buggy brain while debugging doesn't seem to give the best results. :)

> It will occur if you are reading as someone else changes the file size.
> Use file locking, it exists for a reason ;)

Annoying extra overhead. Especially with NFS, when nowadays you can't
even use flock() to create local locks..


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