[Samba] strict locking and kernel oplocks in the smb.conf

Philip Ong phong at nvidia.com
Fri Sep 30 12:48:52 MDT 2011

-----Original Message-----
From: Jeremy Allison [mailto:jra at samba.org] 
Sent: Friday, September 30, 2011 11:31 AM
To: Philip Ong
Cc: 'samba at lists.samba.org'
Subject: Re: [Samba] strict locking and kernel oplocks in the smb.conf

On Fri, Sep 30, 2011 at 11:28:43AM -0700, Philip Ong wrote:
> 1) Does "strict locking = no" negate "kernel oplocks = yes" ?


> 2) What's the difference between the two?

One controls kernel oplocks, the other one controls whether smbd
checks SMB/SMB2/CIFS read/write requests against existing mandatory
[Philip Ong] What are the repercussions of having "strict locking = no" or scenarios where this might be a problem?

> 3) What a good way to test if a file got a lock seen from the linux side and the windows side?

cat /proc/locks

On windows, write a Win32 program.

> 4) If a file has a lock, does that mean you can still open the file in linux or in windows, but can't write to it?

A lock from who ? CIFS/NFS/local process ?[Philip Ong]  A lock from kernel if on NFS.

> Any clarification between the two would be helpful.

Hope this helps.
[Philip Ong] Thanks, yes, it does. I'm having a problem with being able to copy a local Windows file to NFS area shared by samba on WinXP. If I set "strict locking = no", I'm able to copy the file to the NFS area shared via samba. This seems to only happen when upgrading from a kernel.org kernel of and higher. I've tried on Centos 4.5 and 5.6 and all seems to point to either kernel or samba mix (3.5.11 and 3.6). I'd like to know the damage setting "strict locking = no" could possibly cause especially since I'm not sure if I'd want to ignore mandatory locks. Is this going to be a big problem? What are considered mandatory locks?

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