linux-kernel - Re: NFS oops in 2.6.26rc4

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Message-Id: <CEA741EF-8E34-40FD-82A8-747AE1B6E78F@oracle.com>
Date:	Fri, 30 May 2008 15:37:01 -0400
From:	Chuck Lever <chuck.lever@...cle.com>
To:	Dave Jones <davej@...hat.com>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>, chucklever@...il.com,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: NFS oops in 2.6.26rc4

On May 30, 2008, at 3:03 PM, Dave Jones wrote:
> On Fri, May 30, 2008 at 11:31:48AM -0700, Trond Myklebust wrote:
>> On Fri, 2008-05-30 at 14:21 -0400, Dave Jones wrote:
>>
>>> mount point in the fstab is ..
>>>
>>> gelk:/mnt/data      /mnt/nfs/gelk       nfs      
>>> nfsvers=3,tcp        0 0
>>>
>>>> What "brand" of server were you trying to mount?
>>>
>>> It's just another linux box. A no-name core2 duo, running 2.6.25.
>>>
>>>> How often can you reproduce this?
>>>
>>> Seems to do it every time I ask it to.
>>
>> Could you provide us with a binary tcpdump in that case? I'd love to
>> have a look at the actual filehandle the server is producing.
>
> This is from the client side: http://www.codemonkey.org.uk/junk/ 
> tcp.out
> Wireshark picks up some of those packets as being 'malformed', which
> could be a clue ?

Wireshark is overly cautious, and sometimes throws spurious warnings.

> Something else of note which I hadn't seen before, usually things lock
> up just after that first oops. For some reason, today it survived
> a little longer, but things really went downhill fast.
> It survived a 'dmesg ; scp dmesg davej@...k', and then wedged solid.
> So as well as the oops, it seems we're corrupting memory too.
> For reference, this kernel has both SLUB_DEBUG and PAGEALLOC_DEBUG  
> enabled.

I haven't seen this kind of problem here with .26, but yes, it does  
look like something is clobbering memory during an NFS mount.

I introduced some NFS mount parsing changes in this commit range:

   2d767432..82d101d5

A quick bisect should show which, if any of these, is the guilty  
party.  If any of these are the problem, I suspect it's 3f8400d1.

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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