[lxc-users] Using shiftfs with NFS mounted filesystem

[Michael Eager]

On 7/21/20 5:20 PM, Serge E. Hallyn wrote:
> 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?

No, I didn't try that.  I only used the option with LXD.