Re: Adding a non-empty subvol to a qgroup

[Arne Jansen <sensille@gmx.net>]

On 22.03.2013 13:03, Wang Shilong wrote:
> Hello Arne,
> 
> Since "quota rescan" has not been implemented yet,
> 
> overflow can happen, so until now, we can have a check when
> doing accounting in the kernel, if the referenced/exclusive is not
> enough to delete, we just make it to be 0 and give a warning.
> 
> Otherwise, user may get a strange integer(because of type u64).
> How do you think ? or we just wait for the implement of rescan.

I think we already print it negatively. Please just leave it as
it is.

Thanks,
Arne

> 
> Thanks,
> Wang
> 
>> All,
>>
>> When adding a subvolume to a qgroup, pre-existing files in that subvolume are not counted in the referenced/exclusive space of the qgroup. Is this intended behavior ?
>>
>> I create a subvol with one file:
>>
>>  # mkfs.btrfs /dev/sdg
>>  # mount /dev/sdg /mnt/fulldisk
>>  # cd /mnt/fulldisk
>>  # btrfs quota enable ./
>>  # btrfs sub create sub1
>>  # dd if=/dev/zero of=sub1/file1 bs=100000 count=1
>>  # sync
>>  # btrfs qgroup show ./
>>  0/257 106496 106496
>>
>> Now I create a new qgroup on level 1 and add the qgroup of sub1 to it :
>>
>>  # btrfs qgroup create 1/0 ./
>>  # btrfs qgroup assign 0/257 1/0 ./
>>  # sync
>>  # btrfs fi sync ./
>>  # btrfs quota rescan ./
>>  # btrfs quota rescan ./sub1
>>  # btrfs qgroup show ./
>>  0/257 106496 106496
>>  1/0 0 0
>>
>> The pre-existing file does not contribute to the space numbers.
>>
>> Let's create a new file:
>>
>>  # dd if=/dev/zero of=sub1/file2 bs=50000 count=1
>>  # sync
>>  # btrfs qgroup show ./
>>  0/257 159744 159744
>>  1/0 53248 53248
>>
>> We see that only the new file is included in the space numbers.
>>
>> Now I remove the first file:
>>
>>  # rm -f sub1/file1
>>  # sync
>>  # btrfs qgroup show ./
>>  0/257 57344 57344
>>  1/0 -49152 -49152
>>
>> The space numbers go below zero. Even if the behavior above is intended, the removal of the pre-existing file should not result in negative space numbers.
>>
>> Koen.
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>