Re: Non-existent qgroup in parent-child relation prevents makes qgroup commands fail

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2019/8/3 下午2:49, Andrei Borzenkov wrote:
> 03.08.2019 9:17, Qu Wenruo пишет:
>>
>>
>> On 2019/8/3 下午1:31, Andrei Borzenkov wrote:
>>> 03.08.2019 2:09, Qu Wenruo пишет:
>>>>
>>>>
>>>> On 2019/8/3 上午2:08, Andrei Borzenkov wrote:
>>>>> bor@tw:~> sudo btrfs qgroup show .
>>>>> ERROR: cannot find the qgroup 0/789
>>>>> bor@tw:~>
>>>>>
>>>>> Fine. This openSUSE with snapper which creates and automatically
>>>>> destroys snapshots and apparently either kernel or snapper now also
>>>>> remove corresponding qgroup. I played with snapshots and created several
>>>>> top level qgroups that included snapshot qgroups existing at this time.
>>>>> Now these snapshots are gone, their qgroups are gone ...
>>>>
>>>> Kernel version please.
>>>>
>>>> IIRC latest upstream kernel doesn't remove the level 0 qgroup.
>>>
>>> Yes?
>>>
>>>> It may be the userspace doing it improperly.
>>>>
>>>
>>> Not sure what "improperly" means here. snapper removes qgroup after
>>> deleting snapshot. What is "improper" here?
>>
>> Doing without using the qgroup ioctl, but some extra flag in snapshot
>> creation/deletion, which can also add relation at subv/snapshot creation
>> time.
>>
> 
> As far as I can tell, this is exactly what snapper does:
> 
>             if (qgroup != no_qgroup)
>             {
>                 size_t size = sizeof(btrfs_qgroup_inherit) +
> sizeof(((btrfs_qgroup_inherit*) 0)->qgroups[0]);
>                 vector<char> buffer(size, 0);
>                 struct btrfs_qgroup_inherit* inherit =
> (btrfs_qgroup_inherit*) &buffer[0];
> 
>                 inherit->num_qgroups = 1;
>                 inherit->num_ref_copies = 0;
>                 inherit->num_excl_copies = 0;
>                 inherit->qgroups[0] = qgroup;
> 
>                 args_v2.flags |= BTRFS_SUBVOL_QGROUP_INHERIT;
>                 args_v2.size = size;
>                 args_v2.qgroup_inherit = inherit;
>             }
> 
> Do you say it should not be doing it?
> 

For creation, that's OK, as long as it's not using the deprecated copy
version..

Thanks,
Qu


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