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

From: "J. Bruce Fields" <bfields@fieldses.org>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jeremy Allison <jra@samba.org>,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	Volker.Lendecke@sernet.de, Jeff Layton <jlayton@kernel.org>,
	samba-technical@lists.samba.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Ralph Boehme <slow@samba.org>,
	devel@lists.nfs-ganesha.org
Subject: Re: Better interop for NFS/SMB file share mode/reservation
Date: Wed, 6 Mar 2019 10:17:35 -0500	[thread overview]
Message-ID: <20190306151735.GD2426@fieldses.org> (raw)
In-Reply-To: <CAOQ4uxigRpjjni8nvYxCqeyTnr0Zf7Stj9h2+24_S9n4i0euYA@mail.gmail.com>

On Wed, Mar 06, 2019 at 09:09:21AM +0200, Amir Goldstein wrote:
> On Tue, Mar 5, 2019 at 11:48 PM J. Bruce Fields <bfields@fieldses.org> 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?)
> >
> 
> [CC Ralph Boehme]
> 
> I am not a samba team member, but seems to me that your proposal
> fits samba design like a glove. With one smbd process per client connection,
> with your proposal, opens (for read) from same smbd process will not break the
> shared read lease from same client, so oplocks level II could be implemented
> using kernel oplocks (new flavor).

OK.  So I wonder about Ganesha.  I'm not sure, but I *think* it's like
knfsd in that it has a bunch of worker threads that can each take rpc's
from any client.  I don't remember if they're actually threads or
processes.

> IOW, can someone from samba team please elaborate on this quote
> from samba wiki [1]: "Linux kernel oplocks don't provide the needed features.
> (They don't even work correctly for oplocks...) ==> SMB-only feature."
> 
> [1] https://wiki.samba.org/index.php/Samba3/SMB2#new_concepts

Yes, it'd be useful to get those details written down in one place.

> I would like to use this opportunity to ask samba team members to raise
> any (*) other pain points about missing or lacking Linux kernel interfaces.
> I promise to use my time in LSF/MM 2019 to try and promote samba
> needs among Linux filesystem developers.

I feel like this particular problem is about details of
oplock/lease/delegation semantics that will interest a small number of
people, so should mainly be handled as a hallway-track thing.  But,
maybe it's good to bring it up in a session if only to make sure anyone
interested is aware.

> (*) OK, not RichACLs. I know my own limitations.

Hah.

--b.