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

[Andrei Borzenkov <arvidjaar@gmail.com>]

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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?


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