[OpenAFS] OpenAFS+Samba file locking issues

[Jeffrey Altman]

This is a cryptographically signed message in MIME format.

--------------ms040300070207080509000409
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

Eric Chris Garrison wrote:
> So, I think it's some kind of file locking issue, possibly due to
> disconnecting and reconnecting to another server due to round-robin, but
> I'm not sure that's the actual case, it's just a theory at this point. The
> users have claimed to map to a specific machine and then get the error
> anyway, but I haven't been able to reproduce that so far.
> 
> We get a lot of errors in the logs that say, "kernel: afs: byte-range
> lock/unlock ignored; make sure no one else is running this program."
> That's probably from openafs-client since it's kernel-level where smbd
> isn't.  Not sure if that's related. The intermittent nature of the problem
> makes it especially frustrating.  Samba logs don't even indicate a problem
> at the time of the error message, so I guess it's all on the client's side.

Eric:

Using a cluster of Samba servers as a front-end to AFS is not going to
be safe in my opinion.  Samba has to claim to support mandatory locking
semantics which AFS does not support.  Even if Samba server A issues a
lock that was granted from the AFS file server, there is nothing to
prevent Samba server B to perform a store operation against that locked
file.  The various Samba servers cannot perform distributed file locking.

The OpenAFS Windows client goes to great lengths to implement file
locking in a safe manner.  It isn't easy to get correct and I'm not sure
if the Samba file locking code is AFS aware enough to take the necessary
steps.

The "xxx is read only" error is a bit weird though.  I would expect a
sharing violation error not a "is read only" error.  On IRC yesterday
someone was asking about a volume that temporarily appeared to be read
only.  A restart of the cache manager caused the problem to go away so
perhaps the issue that you are seeing is related.

If you can identify a user at the time the problem occurs it would be
useful to obtain a tcp dump of the smb traffic to the samba server as
well as the afs traffic to the afs file server.  At least then you would
know what was actually being requested and what is failing.

Jeffrey Altman


--------------ms040300070207080509000409
Content-Type: application/x-pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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--------------ms040300070207080509000409--