Re: [LSF/MM/BPF BoF] BoF for Zoned Storage

Johannes Thumshirn
2022-03-07T16:23:53Z

On 07/03/2022 16:44, Luis Chamberlain wrote:
> On Mon, Mar 07, 2022 at 08:56:30AM +0900, Damien Le Moal wrote:
>> btrfs maps zones to block groups and the sectors between zone capacity
>> and zone size are marked as unusable. The report above is not showing
>> that. The coding is correct though. The block allocation will not be
>> attempted beyond zone capacity.
>
> That does not explain or justify why zone size was used instead of zone
> capacity. Using the zones size gives an incorrect inflated sense of actual
> capacity, and users / userspace applications can easily missuse that.
>
> Should other filesystems follow this logic as well? If so why?
>

The justification is, when btrfs zoned support was implemented there was no
zone capacity. This started with zns and thus btrfs' knowledge of
zone_capacity came with it's zns support. So instead of playing the blame
game for whatever reason I don't want to know, you could have reported the
bug or fixed it yourself.

It's not that Naohiro, Damien or I aren't following bug reports of zoned btrfs
on the mailing lists.

Byte,
Johannes