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

Luis Chamberlain
2022-03-07T16:36:40Z

On Mon, Mar 07, 2022 at 04:23:46PM +0000, Johannes Thumshirn wrote:
> 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.

I didn't realize it would be acknowledged as a bug, now that it is I'll
just go send a fix, thanks!

Luis