Re: Qgroups are not applied when snapshotting a subvol?

[Andrei Borzenkov <arvidjaar@gmail.com>]

27.03.2017 03:39, Qu Wenruo пишет:
> 
> 
> At 03/26/2017 06:03 AM, Moritz Sichert wrote:
>> Hi,
>>
>> I tried to configure qgroups on a btrfs filesystem but was really
>> surprised that when you snapshot a subvolume, the snapshot will not be
>> assigned to the qgroup the subvolume was in.
>>
>> As an example consider the small terminal session in the attachment: I
>> create a subvol A, assign it to qgroup 1/1 and set a limit of 5M on
>> that qgroup. Then I write a file into A and eventually get "disk quota
>> exceeded". Then I create a snapshot of A and call it B. B will not be
>> assigned to 1/1 and writing a file into B confirms that no limits at
>> all are imposed for B.
>>
>> I feel like I must be missing something here. Considering that
>> creating a snapshot does not require root privileges this would mean
>> that any user can just circumvent any quota and therefore make them
>> useless.
>>
>> Is there a way to enforce quotas even when a user creates snapshots?
>>
> 
> Yes, there is always method to attach the subvolume/snapshot to
> specified higher level qgroup.
> 
> Just use "btrfs subvolume snapshot -i 1/1".
> 

This requires cooperation from whoever creates subvolume, while the
question was - is it possible to enforce it, without need for explicit
option/action when snapshot is created.

To reiterate - if user omits "-i 1/1" (s)he "escapes" from quota
enforcement.