svn commit: r344569 - in head/cddl/contrib/opensolaris: cmd/zfs lib/libzfs/common

[John Baldwin]

On 2/26/19 8:59 AM, Rodney W. Grimes wrote:
>> On Tue, Feb 26, 2019 at 10:14 AM Cy Schubert <Cy.Schubert at cschubert.com>
>> wrote:
>>
>>> On February 26, 2019 7:48:27 AM PST, Cy Schubert <
>>> Cy.Schubert at cschubert.com> wrote:
>>>> On February 26, 2019 12:18:35 AM PST, Baptiste Daroussin
>>>> <bapt at FreeBSD.org> wrote:
>>>
>>
>> [trimming the unneeded pile of commit body]
>>
>>
>>>> This broke my systems, many filesystems fail to mount causing nullfs
>>>> late mounts to fail. No details now until tonight.
>>>>
>>>> Suggest we back this out until it is properly tested.
>>>
>>> Nested zfs filesystems seem not to be handled properly or possibly not
>>> supported any more. This explains my mail gateway also not mounting all
>>> filesystems in /home. It was odd that dovecot stopped working.
>>>
>>> The symptom of the problem is zfs mount -a no longer mounts all
>>> filesystems. Zfs mount fails saying the filesystem is already mounted. The
>>> workaround is to zfs umount each affected zfs dataset by hand and zfs mount
>>> it by hand.
>>>
>>> Generally this has screwed up sites that have hundreds (in my case 122)
>>> zfs datasets. The work around might be to script testing each mount,
>>> unmounting and remounting if necessary.
>>>
>>> I'm being sarcastic about creating an rc script to clean this up. This
>>> needs to be backed out and tested properly before being committed.
>>>
>>>
>> I don't know what you mean by "nested zfs filesystems" -- do you mean a
>> zpool within a zvol?
>> That has been unsupported for a long time, IIRC.  And
> That had better not be unsupported, that is the prefered technology
> for all of the virtualization stuff, bhyve, virtualbox, qemu, etc.

I think Ben is referring to using the nested zpool on the host itself rather
than in the guest.  We do actually let you do such crazy things I think (I
use UFS in my VMs usually and fsck on the host against /dev/zvol/bhyve/<foo>p2
can be faster than fsck in the booted guest), but normally the host just hosts
the zvol and the guest manages filesystems in the volume.  Mounting the
nested zpool on the host is probably best characterized as running with
scissors.

-- 
John Baldwin