linux-kernel - Re: csum errors

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Message-ID: <20100715193551.GM8623@think>
Date:	Thu, 15 Jul 2010 15:35:51 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Johannes Hirte <johannes.hirte@....tu-ilmenau.de>
Cc:	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: csum errors

On Thu, Jul 15, 2010 at 09:32:12PM +0200, Johannes Hirte wrote:
> Am Donnerstag 15 Juli 2010, 21:03:09 schrieb Chris Mason:
> > On Thu, Jul 15, 2010 at 08:30:17PM +0200, Johannes Hirte wrote:
> > > Am Dienstag 13 Juli 2010, 14:23:58 schrieb Johannes Hirte:
> > > > ino 1959333 off 898342912 csum 4271223884 private 4271223883
> > > 
> > > I think, this is a different error. I've only seen them on filesystems
> > > from my Opteron system. It seems that the recorded csums are wrong and
> > > it looks to me like rounding errors. The data itself should be correct,
> > > as I've tested one affected file via md5sum against the original on
> > > another filesystem. Any ideas what is going wrong here?
> > 
> > Are you doing data mirroring?
> 
> No, I don't.
> 
> > We can map that block and do a raw read off the device to see what the
> > data blocks actually contain.
> 
> I've modified the btrfs-source a little to get the data. In inode.c I've 
> changed the code to:

Great.   The bad csums are all just one bit off, that can't be an
accident.  When were they written (which kernel?).  Did you boot a 32
bit kernel on there at any time?

-chris
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