Re: [PATCH 6/6] nfs: disable leases over NFS

[Christoph Hellwig <hch@infradead.org>]

On Fri, Jun 29, 2007 at 03:21:30PM -0400, J. Bruce Fields wrote:
> From: J. Bruce Fields <bfields@citi.umich.edu>
> 
> As Peter Staubach says elsewhere
> (http://marc.info/?l=linux-kernel&m=118113649526444&w=2):
> 
> > The problem is that some file system such as NFSv2 and NFSv3 do
> > not have sufficient support to be able to support leases correctly.
> > In particular for these two file systems, there is no over the wire
> > protocol support.
> >
> > Currently, these two file systems fail the fcntl(F_SETLEASE) call
> > accidentally, due to a reference counting difference.  These file
> > systems should fail more consciously, with a proper error to
> > indicate that the call is invalid for them.
> 
> Define an nfs setlease method that just returns -EOPNOTSUPP.
> 
> If someone can demonstrate a real need, perhaps we could reenable
> them in the presence of the "nolock" mount option.

I'm not a big fan of default methods that do the wrong thing instead
of just missing functionality.  Would you mind just returning
-EOPNOTSUPP if ->setlease is not implemented and add it to all
the local filesystems while all the network/distributed filesystems
should not have it, not just nfs.