Re: Better interop for NFS/SMB file share mode/reservation

Jeff Layton
2019-03-06T20:31:12Z

On Wed, 2019-03-06 at 10:11 -0500, J. Bruce Fields wrote:
> 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?
>

Here's the C headers for that stuff:

https://github.com/ceph/ceph/blob/7ba6bece4187eda5d05a9b84211fe6ba8dd287bd/src/include/cephfs/libcephfs.h#L1734

It's simple enough and works for us in ganesha, and I think we can
probably adapt it to samba without too much difficulty. The callback
doesn't seem like it'll do for a kernel API though -- you'd almost
certainly need to do something different there (signals? inotify?).

> 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.
>

--
Jeff Layton <jlayton@kernel.org>