Re: [PATCH] btrfs: Allow non-privileged user to delete empty subvolume by default

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2018-03-21 03:46, Nikolay Borisov wrote:
> 
> 
> On 20.03.2018 22:06, Goffredo Baroncelli wrote:
>> On 03/20/2018 07:45 AM, Misono, Tomohiro wrote:
>>> Deletion of subvolume by non-privileged user is completely restricted
>>> by default because we can delete a subvolume even if it is not empty
>>> and may cause data loss. In other words, when user_subvol_rm_allowed
>>> mount option is used, a user can delete a subvolume containing the
>>> directory which cannot be deleted directly by the user.
>>>
>>> However, there should be no harm to allow users to delete empty subvolumes
>>> when rmdir(2) would have been allowed if they were normal directories.
>>> This patch allows deletion of empty subvolume by default.
>>
>> Instead of modifying the ioctl, what about allowing rmdir(2) to work for an _empty_ subvolume (and all the permission check are satisfied) ?
> 
> I'm inclined to agree with Goffredo. user_subvol_rm_allowed flag really
> looks like a hack ontop of the ioctl. I'd rather we modify the generic
> behavior.
I agree as well, with the addendum that I'd love to see a new ioctl that 
does proper permissions checks.  While letting rmdir(2) work for an 
empty subvolume with the appropriate permissions would be great (it will 
let rm -r work correctly), it doesn't address the usefulness of being 
able to just `btrfs subvolume delete` and not have to wait for the 
command to finish before you can reuse the name.