linux-kernel - Re: [2.6.39] CIFS write failures where 2.6.38 works

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Date:	Thu, 23 Jun 2011 13:25:36 +0200
From:	Helge Hafting <helge.hafting@...t.no>
To:	Jeff Layton <jlayton@...hat.com>
CC:	Suresh Jayaraman <sjayaraman@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-cifs <linux-cifs@...r.kernel.org>
Subject: Re: [2.6.39] CIFS write failures where 2.6.38 works

On 22. juni 2011 22:36, Jeff Layton wrote:
> On Thu, 9 Jun 2011 18:28:45 -0400
> Jeff Layton<jlayton@...hat.com>  wrote:
>
>> On Fri, 03 Jun 2011 17:11:05 +0200
>> Helge Hafting<helge.hafting@...t.no>  wrote:
>>
>>> On 03. juni 2011 12:15, Suresh Jayaraman wrote:
>>>> [Cc linux-cifs@...r.kernel.org]
>>>>
>>>> On 06/01/2011 03:41 PM, Helge Hafting wrote:
>>>>> At work I use cifs for accessing a windows server. This has worked fine
>>>>> for a long time, up to and including Debian's 2.6.38-2.
>>>>>
>>>>> I just installed Debians's 2.6.39-1, and had to give up on it.
>>>>> Mounting CIFS works, and I can see the files. But if I
>>>>> try to make a new file (with cp), I get a long delay.
>>>>
>>>> What is the security mechanism you are using? If you seeing the problem
>>>> with ntlm, could you try using ntlmv2 and see whether the problem is
>>>> reproducible?
>>>
>>> In the beginning, I did not specify the mechanism. So, whatever the
>>> default is.
>>>
>>> The fstab entry was like this:
>>> \\servername\resource /mountpoint cifs
>>> domain=MYDOMAIN,credentials=/etc/fstabcred,rw,noauto,iocharset=utf8,uid=username,gid=group,sockopt=TCP_NODELAY,users,file_mode=0640,dir_mode=0750,relatime
>>> 0 0
>>>
>>> I looked at cifs options, and tried to add "sign" and "sec=ntlmv2i". It
>>> made no difference. Still failure with 2.6.39, and mounting with these
>>> new options works fine with 2.6.38
>>>
>>
>> I think we need to understand what's happening on the wire. Are you
>> still able to reproduce this? If so, can you turn up debug logging and
>> reproduce this?. Instructions for how to do that are here:
>>
>>      http://wiki.samba.org/index.php/LinuxCIFS_troubleshooting#Enabling_Debugging
>>
>> Also, it looks like someone opened a bug at kernel.org too:
>>
>>      https://bugzilla.kernel.org/show_bug.cgi?id=36952
>>
>> ...so if you can attach the resulting log there, that would be great.
>>
>
> I think that this is probably due to the change that added the
> page_mkwrite function to cifs.ko. Prior to that, cifs did single-page
> writes on signed connections. Now we do multi-page writes and windows
> servers apparently reject large write calls on signed connections.
>
> One way to test this theory would be to set the wsize to something
> smaller when you mount. For instance:
>
>      wsize=16384
>
> ...assuming that doesn't go over the server's MaxBufferSize, then that
> should act as a workaround. Can you try that and let me know if it
> helps?


Yes, that seemed to fix it. I added wsize=16384 and mounted using 
debians 2.6.39-1-amd64 kernel.

I tried a recursive copy of 26MB from one directory tree to another on 
that mount. It completed in 24s with no error messages. 1MB/s is not 
much, but there may be 40 other users.

The server runs windows 2008r2, 64-bit.

Helge Hafting
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