[NFS] [Cluster-devel] [PATCH 0/4 Revised] NLM - lock failover
Neil Brown
neilb at suse.de
Fri Apr 27 22:22:55 UTC 2007
On Friday April 27, bfields at fieldses.org wrote:
> On Fri, Apr 27, 2007 at 11:36:16AM -0400, Wendy Cheng wrote:
> > J. Bruce Fields wrote:
> > >On Fri, Apr 27, 2007 at 03:17:10PM +0100, Christoph Hellwig wrote:
> > >
> > >>In fact couldn't this be treated as a reexport with a NFSEXP_ flag
> > >>meaning drop all locks to avoid creating new interfaces?
> > >>
> > >
> > >Off hand, I can't see any reason why that wouldn't work. The code to
> > >handle it would probably go in fs/nfsd/export.c:svc_export_parse().
> > >
> > >
> > Sign :( ... folks, we go back to the loop again. That *was* my first
> > proposal ...
Yes, I grinned when I saw it too.
Your first proposal was actually a flag to "unexport", where as
Christoph seems to be a flag to "export". So there is at least a
subtle difference.
A flag to unexport cannot work because we don't call unexport - we
just flush a kernel cache.
A flag to export is just .... weird. All the other export flags are
state flags. This would be an action flag. They are quite different
things. Setting a state flag again is a no-op. Setting an action
flag again has a very real effect.
Also, each filesystem is potentially exported multiple times for
different sets of clients. If such a flag (whether on 'export' or
'unexport') just said "remove locks from this set of clients" it
wouldn't meet the needs, and if it said "remove all locks" it would be
a very irregular interface.
>
> So you're talking about this and followups?:
>
> http://marc.info/?l=linux-nfs&m=115009204513790&w=2
>
> I just took a look and couldn't find any complaints about that
> approach. Were they elsewhere?
https://www.redhat.com/archives/linux-cluster/2006-June/msg00101.html
Is where I said that I don't like the unexport flag.
NeilBrown
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