[lxc-users] Using shiftfs with NFS mounted filesystem

[Serge E. Hallyn]

On Tue, Jul 21, 2020 at 08:42:17AM -0700, Michael Eager wrote:
> On 7/20/20 7:46 PM, Serge E. Hallyn wrote:
> > On Mon, Jul 20, 2020 at 09:21:08AM -0700, Michael Eager wrote:
> > > On 7/19/20 2:04 PM, Serge E. Hallyn wrote:
> > > > On Sun, Jul 19, 2020 at 07:53:08PM +0300, Amir Goldstein wrote:
> > > > > On Sun, Jul 19, 2020 at 5:13 PM Serge E. Hallyn <serge at hallyn.com> wrote:
> > > > > > 
> > > > > > On Sun, Jul 19, 2020 at 06:53:03AM -0700, Michael Eager wrote:
> > > > > > > On 7/18/20 8:37 PM, Serge E. Hallyn wrote:
> > > > > > > > On Sat, Jul 18, 2020 at 11:16:16AM -0700, Michael Eager wrote:
> > > > > > > > > I'm running LXD on a Centos 8 host, kernel-4.18.0.  I built and installed
> > > > > > > > > the shiftfs module.
> > > > > > > > 
> > > > > > > >    From what source?
> > > > > > > 
> > > > > > > https://github.com/toby63/shiftfs-dkms
> > > > > > 
> > > > > > Interesting.  Yeah the shiftfs.c looks identical to what's in
> > > > > > ubuntu's, but when I backported that to 4.14 I had to also take
> > > > > > a bunch of other patches (https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=v4.14.180-shiftfs)
> > > > > > which may or may not be in 4.18.  Still, I don't actually think
> > > > > > that's the problem.  NFS has always been difficult to use
> > > > > > with layered filesystems.
> > > > > > 
> > > > > > Amir, as far as you know, does overlay on top of NFS work
> > > > > > these days?
> > > > > > 
> > > > > 
> > > > > I know people are using it, but only as lower fs, which are files that
> > > > > are not expected to be changed.
> > > > > NFS is not supported as upper fs.
> > > > 
> > > > Thanks Amir.  I over-snipped, but Michael is having problems
> > > > when NFS is the underlay for shiftfs.  If overlay works fine,
> > > > then that's an interesting complication :)
> > > > 
> > > > I'm hoping to have some time to try it out soon.
> > > > 
> > > > thanks,
> > > > -serge
> > > 
> > > If you would like me to submit a bug report, just tell me where.
> > 
> > Since it's shipped with the Ubuntu kernel, you could test it in an
> > Ubuntu VM and then file it at
> > https://bugs.launchpad.net/ubuntu/+source/linux/+filebug  I don't
> > have any better place to suggest tracking it.
> 
> I'm running LXD on CentOS 8, kernel-4.18.0.  I built the shiftfs module from
> https://github.com/toby63/shiftfs-dkms.
> 
> I can submit an issue on GitHub or bugzilla.kernel.org.  Setting up a Ubunut
> VM with LXD seems like a bit of work.

So just to make sure, you've not reproduced this by hand doing a shiftfs
mount on top of NFS?