Re: unlock during lockd recovery

[Olaf Kirch <okir@suse.de>]

On Tue, Nov 23, 2004 at 09:44:10AM -0800, Marc Eshel wrote:
> If the client application unlocks the lock before it was reclaimed than it
> should not be reclaimed.

The problem is that your lockd server would make assumptions about the
client's implementation; in particular, this would mandate that the client
prevents any regular NLM activity while it's in the middle of a reclaim.

However, the X/Open spec for NLM says about NLM_LOCK: "During the grace
period, the server will only accept locks with reclaim set to true."
So the client is free to assume that it's okay to keep on retransmitting
LOCK/UNLOCK request all along, without having to care about reclaim or not,
because the spec says the server will ignore them anyway.

Consider this scenario:

 -	Server tells client to start reclaim
 -	Client sends reclaim request for lock X
 -	RPC packet gets lost
 -	Application requests to unlock X
 -	Client calls server, server finds there's nothing to
 	unlock, ACKs the RPC call
 -	Client retransmits reclaim packet, server re-installs
 	the lock
 -	you have a stale lock

Olaf
-- 
Olaf Kirch     | Things that make Monday morning interesting, #2:
okir@suse.de   |        "We have 8,000 NFS mount points, why do we keep
---------------+ 	 running out of privileged ports?"


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