Message-ID: <1ade4724a4e505baf7b7c23a76e44d58b931da1f.camel@kernel.org>
Subject: Re: Better interop for NFS/SMB file share mode/reservation
From:   Jeff Layton <jlayton@kernel.org>
To:     "J. Bruce Fields" <bfields@fieldses.org>,
        Amir Goldstein <amir73il@gmail.com>
Cc:     Jeremy Allison <jra@samba.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Volker.Lendecke@sernet.de, samba-technical@lists.samba.org,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        devel@lists.nfs-ganesha.org
Date:   Wed, 06 Mar 2019 15:31:08 -0500
In-Reply-To: <20190306151150.GC2426@fieldses.org>
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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>