Re: [PATCH] xfs: validate that zoned RT devices are zone aligned

[Christoph Hellwig <hch@lst.de>]

On Wed, Dec 10, 2025 at 11:18:25AM -0800, Darrick J. Wong wrote:
> How nasty is it, exactly?  AFAICT,
> 
>  * The zone targetting code (aka the zone we copy into) then has to
>    know to avoid a runt endzone?

Yes.  And I don't really have a good idea how to do that.

>  * Thresholding gets weird because they don't apply right to the runt
>    zone, which means the victim selection is also off.

Yes.

>  * The code that reserves zones for gc or other ENOSPC handling then has
>    to ensure it never picks a runt zone to avoid corner case problems

This is what is needed for 1) above with all the same issues.

> Any other reasons?  Given that zoned is still experimental I think I'm
> ok with adding this restriction, but only after some more thorough
> understanding. :)

Yeah.

> Also does growfs need patching so that it doesn't create a runt zone?

I think we run the buffer verifier there, but a nicer check to abort
early would be helpful.  As would be a test case.