RE: [ogfs-dev]RE: [Opendlm-devel] ODLM/OGFS Recovery

Stanley Wang <stanley.wang@xxxxxxxxxxxxxxxxxx> · Tue, 04 May 2004 10:08:06 +0000

On Mon, 2004-05-03 at 16:20, Cahill, Ben M wrote:
>  
> > -----Original Message-----
> > From: opendlm-devel-admin@xxxxxxxxxxxxxxxxxxxxx 
> > [mailto:opendlm-devel-admin@xxxxxxxxxxxxxxxxxxxxx] On Behalf 
> > Of Stanley Wang
> > Sent: Saturday, May 01, 2004 6:34 AM
> > To: OpenDLM-DEV; John T Devine
> > Cc: Zickus II, Don; OpenGFS-DEV
> > Subject: RE: [ogfs-dev]RE: [Opendlm-devel] ODLM/OGFS Recovery
> > 
> > Hi John,
> > 
> > Thanks for your great comments!
> > 
> > On Fri, 2004-04-30 at 15:04, Devine, John T wrote:
> > > Don, locks granted due to the owner of the blocking lock 
> > releasing them
> > > due to node failure MUST be granted with an invalidated 
> > lock value block
> > > if the blocking mode was PW or stronger.   If this is not so, then
> > > unless dead man locks had a mechanism guaranteeing they are 
> > granted 1st
> > > (they don't), any OpenDLM user could wind up with a 
> > consistency problem
> > > as resources could be granted before node failure detected.
> > 
> > It's exactly my concern for OpenGFS.
> > 
> 
> I think this is handled during ODLM's lock recovery process, which
> invalidates LVBs that might have been altered by a dead node.  See
> clmr_clean() and clmr_lkvlb().

Yes, ODLM will invalidate LVBs that might have been altered by a dead
node. But my concern is : 

If there is only one PW or EX lock request in the wait queue of this
resource, we won't get DLM_VALNOTVALID (even the LVB of this resouce is
invalid) when the queued request is granted.

It means that we might miss some locks held by dead node. Please read:
rc_barrier6->wake_all_locks->convert_locks->grant_convert->valueblock

Any comments?

Best Regards,
Stan 

> -- Ben --
> 
> Opinions are mine, not Intel's
> 
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