From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: Can nfs lock can be upgraded ?
Date: Mon, 24 Apr 2006 08:34:57 -0400
Message-ID: <1145882097.10974.19.camel@lade.trondhjem.org>
References: <4445EA51020000840002C088@lucius.provo.novell.com>
	 <444CB9A8020000840000B796@lucius.provo.novell.com>
	 <444CB945.C935.0084.0@novell.com>
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Cc: nfs@lists.sourceforge.net
To: Madhan P <PMadhan@novell.com>
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On Mon, 2006-04-24 at 00:12 -0600, Madhan P wrote:
> Hi All,
> 
> Have a query, over which a definitive statement in standard material
> seems to be hard to trace.  Hope people on the list can throw some light
> on this.  Have a situation where, (this is all with nfs version 3)
> 
> - client asks for non-exclusive lock of a certain file handle.  range
> is the entire file.
> - server grants the lock.
> - client asks for an exclusive lock of the same file, entire file. 
> uses a different cookie than the first lock request.
> - server denies the lock, as a exclusive lock cannot be granted on a
> file that is already non-exclusively locked.  (The only multiple locks
> that can exists must all be non-exclusive).
> - client asks to unlock the file.
> - server grants the unlock.
> - client starts the same process over.
> 
> The clients versions, that reported this behaviour include,
> - Linux diablo 2.6.13-15.8-default
> - SunOS csns28 5.9 Generic_112233-12 sun4u sparc
> 
> This seems to be fine and working as expected.  But, in a situation
> where, server has granted a non-exclusive lock to the client, and if
> that is the only client holding a non-exclusive lock - Is/Can the server
> be expected to allow the upgrade of non-exclusive lock to an exclusive
> lock without going thro' a release of the non-exclusive lock ?

Yes. Provided that nobody else holds a conflicting lock, the server
should allow you to upgrade or downgrade a byte range lock.

The cookie entry in the lock request shouldn't matter, but if the svid
or 'oh' field are different, then the server will treat it as being a
conflicting request.

Cheers,
  Trond


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