netdev - Re: nfs NULL-dereferencing in net-next

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Date:   Wed, 26 Oct 2016 14:17:14 -0400
From:   Anna Schumaker <Anna.Schumaker@...app.com>
To:     Jakub Kicinski <kubakici@...pl>
CC:     Yotam Gigi <yotamg@...lanox.com>, Andy Adamson <andros@...app.com>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Trond Myklebust <Trond.Myklebust@...app.com>,
        Yotam Gigi <yotam.gi@...il.com>, mlxsw <mlxsw@...lanox.com>
Subject: Re: nfs NULL-dereferencing in net-next

On 10/26/2016 02:08 PM, Jakub Kicinski wrote:
> On Wed, 26 Oct 2016 16:15:24 +0000, Yotam Gigi wrote:
>>> -----Original Message-----
>>> From: Anna Schumaker [mailto:Anna.Schumaker@...app.com]
>>> Sent: Wednesday, October 26, 2016 5:40 PM
>>> To: Yotam Gigi <yotamg@...lanox.com>; Jakub Kicinski <kubakici@...pl>; Andy
>>> Adamson <andros@...app.com>; Anna Schumaker
>>> <Anna.Schumaker@...app.com>; linux-nfs@...r.kernel.org
>>> Cc: netdev@...r.kernel.org; Trond Myklebust <Trond.Myklebust@...app.com>;
>>> Yotam Gigi <yotam.gi@...il.com>; mlxsw <mlxsw@...lanox.com>
>>> Subject: Re: nfs NULL-dereferencing in net-next
>>>
>>> On 10/25/2016 01:19 PM, Yotam Gigi wrote:  
>>>>  
>>>>> -----Original Message-----
>>>>> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org]  
>>> On  
>>>>> Behalf Of Jakub Kicinski
>>>>> Sent: Monday, October 17, 2016 10:20 PM
>>>>> To: Andy Adamson <andros@...app.com>; Anna Schumaker
>>>>> <Anna.Schumaker@...app.com>; linux-nfs@...r.kernel.org
>>>>> Cc: netdev@...r.kernel.org; Trond Myklebust  
>>> <Trond.Myklebust@...app.com>  
>>>>> Subject: nfs NULL-dereferencing in net-next
>>>>>
>>>>> Hi!
>>>>>
>>>>> I'm hitting this reliably on net-next, HEAD at 3f3177bb680f
>>>>> ("fsl/fman: fix error return code in mac_probe()").  
>>>>
>>>>
>>>> I see the same thing. It happens constantly on some of my machines, making  
>>> them  
>>>> completely unusable.
>>>>
>>>> I bisected it and got to the commit:
>>>>
>>>> commit 04ea1b3e6d8ed4978bb608c1748530af3de8c274
>>>> Author: Andy Adamson <andros@...app.com>
>>>> Date:   Fri Sep 9 09:22:27 2016 -0400
>>>>
>>>>     NFS add xprt switch addrs test to match client
>>>>
>>>>     Signed-off-by: Andy Adamson <andros@...app.com>
>>>>     Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>  
>>>
>>> Thanks for reporting on this everyone!  Does this patch help?  
>>
>> Actually, I still see the same bug with the same trace.

Well, it was worth a shot.  I'll keep poking at it.

> 
> I rebuild the latest net-next and I'm not seeing the trace any more...
> I'm only seeing this (with or without your patch):
> 
> [   23.465877] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0
> [   23.473784] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0
> [   23.588890] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0
> [   23.596746] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0
> [   23.781574] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0
> [   23.789599] NFS: set_pnfs_layoutdriver: cl_exchange_flags 0x0

Interesting, I get that too when I try to use NFS v4.1.  It's weird that the crash would stop happening like that, so maybe something is racy in this area.

Thanks for testing, Yotam and Jakub!
Anna

> 
> HTH
>