[Users] ploop ext4 reserved_ratio

[Igor Sukhih]

On 7/17/19 12:21 PM, Vasily Averin wrote:
> Dear Jonathan,
> thank you for reporting the problem,
> we did no saw such behaviour before.
>
> In fact ploop grow should call resize2fs and probably it ignores reserved ratio setting.
> You can try to run it under strace and look at details, ploop sources are public available too.
>
> Igor (in cc:) is going to check this behaviour, I hope he will clarify the situation soon.

Unable to reproduce, resize 10G to 1Tb

10G

Block count:              2620928
Reserved block count:     131046


1TB

Block count:              268434944
Reserved block count:     10763323

>
> Thank you,
> 	Vasily Averin
>
> On 7/16/19 8:15 PM, Jonathan Wright wrote:
>> What seems to be happening is if you set a reserved_ratio on an image and grow the image, that ratio is maintained and will stay at that ratio.
>>
>> When shrinking the image however, mke2fs.conf is referenced and that's the ratio that gets used.
>>
>> Is there a reason for this behavior to be inconsistent?  I was incorrect about making new ploop images using mke2fs.conf - it seems they don't - at least not through vzctl create.  It appears to be hard coded at 5%.
>>
>> On 7/16/19 11:55 AM, Jonathan Wright wrote:
>>> ext4's default 5% reserved ratio is set on ploop images.  If you update /etc/mke2fs.conf and adjust this ratio to say 1%, that's used when the ploop image is created.
>>>
>>> This is great.
>>>
>>> When you then resize that image though, the stock 5% is put back in place instead of the 1% that was on the filesystem (or whatever might be set in /etc/mke2fs.conf).
>>>
>>> Is this intentional functionality for some reason, a bug, or something simple no one has tried before?
>>>