Re: GPF on access to presumably corrupted file

[Josef Bacik <jbacik@fb.com>]

On 01/31/2014 02:24 AM, Russell Coker wrote:
> The attached dmesg log shows the results of trying to cat a file on a BTRFS
> filesystem when running the latest Debian/Unstable kernel (upstream 3.12.8
> with some Debian patches that probably aren't relevant to BTRFS).
>
> I've rebooted the Thinkpad in question and repeated the problem after a
> reboot.  So I am fairly sure that the problem isn't directly caused by memory
> corruption.  I presume that it's corruption on disk causing this repeatable
> problem and such corruption could be caused by a memory error (which is
> something I've had happen before on a different system).  But I don't think
> that such corruption should cause a GPF.
>
> So while I think we should consider the possibility that the filesystem was
> corrupted due to a hardware fault (of which there are several possibilities
> when dealing with a laptop) the inability to recover seems like a bug in
> BTRFS.
>
> When this happens every process that tries to access the file in question is
> reported as being stuck in D state.  Sometimes such processes respond to kill
> -9 (I thought that was impossible) and sometimes they remain until reboot.
>
This may be a bug we just fixed in the recent git pull, are you running 
with compression?  If you are try the recent for-linus branch from Chris 
and see if you still have the problem.  Thanks,

Josef