[OpenAFS] Re: safe+portable way to determine if byte-range-locking is dangerous?

[Jeffrey Altman]

This is a cryptographically signed message in MIME format.

--------------ms000506010202070502020806
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Adam Megacz wrote:
> Russ Allbery <rra@stanford.edu> writes:
>> I thought, on Linux at least, that some combination of the cache manager
>> and the generic file system layer caused byte-range locking to work on the
>> local host even though other hosts wouldn't see the lock.
> 
> Crud, you're right.  Argh.  I wrote+tested the sqlite patch on MacOSX
> (and it worked properly there, too).
> 
> Any suggestions?  Is Linux the only client platform that engages in
> this degree of superfakery?

The OpenAFS for Windows 1.5.x client enforces byte range locking and
mandatory locks locally but can't do so for remote users.
Previously, all lock requests were granted even though no locks were
obtained.

> I'm really convinced at this point that the byte-range-lock-faking
> (which I assume was introduced by Transarc) was/is an incredibly bad
> idea and a dangerous thing.  I mean really... unix/posix apps don't
> ask for byte range locks unless they have a good reason for doing so.

There is nothing wrong with a client grabbing a full file lock on behalf
of an application when the application requests a lock on a subset of
the range provided that the client is capable of managing all of the
byte range allocations locally.   A remote client in that case would in
turn see that the file is locked (even if the locks are advisory.)

What is dangerous is when a request for a byte-range lock succeeds
when no lock on the file is actually obtained from the file server.
Matt Benjamin had been working on patches for the UNIX AFS client that
would provide equivalent functionality to that which is now found in
the Windows client.

Jeffrey Altman

--------------ms000506010202070502020806
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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--------------ms000506010202070502020806--