[Samba] CIFS hang

Shirish Pargaonkar shirishpargaonkar at gmail.com
Tue Apr 14 17:55:59 GMT 2009

On Tue, Apr 14, 2009 at 12:41 PM, Dorrian, William M
<William.M.Dorrian at usace.army.mil> wrote:
> Hi Darrel.
> The first thing I would suggest is to do a "modinfo cifs" and see which
> version you're using. (It should be on the second row). I had a similar
> problem a few months ago-I have a script which mounts a CIFS share every few
> minutes, then does an rsync to a distant end Linux server.
> I was using version 1.50RH, if I'm not mistaken. I actually had to reboot my
> Linux server every time I had the problem.
> I solved it (with the help of Steve French) by upgrading my kernel. A newer
> CIFS module might solve your issue; Steve told me that 1.56 is more robust.
> I'm not sure about 1.54 and 1.55, but they may be better also.
> -----Original Message-----
> From: samba-bounces+william.m.dorrian=usace.army.mil at lists.samba.org
> [mailto:samba-bounces+william.m.dorrian=usace.army.mil at lists.samba.org] On
> Behalf Of Darrel Barton
> Sent: Tuesday, April 14, 2009 1:45 PM
> To: samba at lists.samba.org
> Subject: [Samba] CIFS hang
> I have a Proliant running Red Hat with the 2.6.9-5.ELsmp kernel.
> We have a Windows 2000 Server who's secondary disc drive is mounted on the
> Linux box via CIFS using the following command:
> /sbin/mount.cifs //w2000/docs /var/www/documents -o
> dir_mode=0777,file_mode=0444,gid=100,uid=501,username=winuser,password=winpas
> s
>  From time to time, for whatever reason, the Windows 2000 Server requires
> rebooting and if they reboot it without first allowing us to umount the
> cifs, all requests to the cfis directory will hang.   Requests, cd
> commands, df commands ... all hang ... for as long as three HOURS and they
> cannot be killed (kill -1, -15, -9) and the smb cannot be
> restarted.  Presumably this is all a result of the calls being hung within
> the kernel.
> It has been suggested that we upgrade the kernel to 2.6.9-78.0.13.
> I'm not generally opposed to upgrades, but I'm hesitant to "upgrade to the
> latest version" as a substitute for understanding the root of any problem
> and engineering a proper fix.  Maybe it's the years of Microsoft software,
> but I believe that upgrading to the latest version has become tech support
> slang for "we have NO IDEA what your problem is, so maybe the latest
> version will fix it by accident -- but for very sure you'll be so deep in
> the woods with NEW problems that you'll likely forget about this one
> entirely."
> Would anyone have any first hand knowledge of this problem and experience
> that a later kernel is a solution?
> Regards
> Darrel
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I think 1.56 is more robust because the sockets within cifs are now blocking
instead of non-blockig which solved lot of data integrity issues due to lost
responses etc..

But as soon as you notice hang, you can start a tcpdump on the
cifs client box and issue a command like ls or cd (which hangs) and stop
tcpdump after a while (2/3 minutes) and post tcpdump output file to look at.

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