Re: [PATCH v5] btrfs: qgroup: Remove qgroup items along with subvolume deletion

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

[-- Attachment #1.1: Type: text/plain, Size: 1758 bytes --]



On 2018/8/15 下午9:06, David Sterba wrote:
> On Thu, Aug 09, 2018 at 04:05:36PM +0900, Misono Tomohiro wrote:
>> When qgroup is on, subvolume deletion does not remove qgroup items
>> of the subvolume (qgroup info, limit, relation) from quota tree and
>> they need to get removed manually by "btrfs qgroup destroy".
>>
>> Since level 0 qgroup cannot be used/inherited by any other subvolume,
>> let's remove them automatically when subvolume is deleted
>> (to be precise, when the subvolume root is dropped).
> 
> Please note that dropping the 0-level qgroup has user-visible impact
> that needs to be evaluated.

I wonder if this is the case.

Normal btrfs subvolume creation using the highest objectid available in
root tree, thus later subvolume won't take the id of the to-be-deleted
subvolume.

Further more, this auto-removal only happens when the to-be-deleted
subvolume get completely removed, thus there should be no way to access
the subvolume already before we hit the branch in this patch.

So yes, the level 0 qgroup auto-removal is bringing a user visible
change, but user can't do anything anyway, and the result should just
save some "btrfs qgroup destroy/remove" calls.

Or did I miss something?

Thanks,
Qu


> I don't see anything like that in the
> changelog.
> If there's a potential or actual breakage after this patch,
> it needs to be addressed in some way.
> 
> This is not the first time somebody proposes to do the auto deletion.
> While I'm not against it, it still has to be done the right way.
> Anything that touches user interfaces must get extra care, and review
> bandwidth for that is unfortunatelly extra low. I can't give you an ETA
> or merge target for this patch.
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]