Better interop for NFS/SMB file share mode/reservation

[J. Bruce Fields]

On Tue, Mar 05, 2019 at 04:47:48PM -0500, J. Bruce Fields wrote:
> On Thu, Feb 14, 2019 at 04:06:52PM -0500, J. Bruce Fields wrote:
> > After this:
> > 
> > 	https://marc.info/?l=linux-nfs&m=154966239918297&w=2
> > 
> > delegations would no longer conflict with opens from the same tgid.  So
> > if your threads all run in the same process and you're willing to manage
> > conflicts among your own clients, that should still allow you to do
> > multiple opens of the same file without giving up your lease/delegation.
> > 
> > I'd be curious to know whether that works with Samba's design.
> 
> Any idea whether that would work?
> 
> (Easy?  Impossible?  Possible, but realistically the changes required to
> Samba would be painful enough that it'd be unlikely to get done?)

Volker reminds me off-list that he'd like to see Ganesha and Samba work
out an API in userspace first before commiting to a user<->kernel API.

Jeff, wasn't there some work (on Ceph maybe?) on a userspace delegation
API?  Is that close to what's needed?

In any case, my immediate goal is just to get knfsd fixed, which doesn't
really commit us to anything--knfsd only needs kernel internal
interfaces.  But it'd be nice to have at least some idea if we're on the
right track, to save having to redo that work later.

--b.