Re: [PATCH 6/8] mm/pdx: Standardize region validation wrt pdx compression

[Julien Grall <julien@xxxxxxx>]

Hi Alejandro,

On 24/07/2023 13:18, Alejandro Vallejo wrote:
> On Fri, Jul 21, 2023 at 06:05:51PM +0100, Julien Grall wrote:
> > Hi Alejandro,
> >
> > On 17/07/2023 17:03, Alejandro Vallejo wrote:
> > > +bool pdx_is_region_compressible(unsigned long smfn, unsigned long emfn)
> > For newer interface, I would rather prefer if we use start + size. It is
> > easier to reason (you don't have to wonder whether 'emfn' is inclusive or
> > not) and avoid issue in the case you are trying to handle a region right at
> > the end of the address space as emfn would be 0 in the non-inclusive case
> > (not much a concern for MFNs as the last one should be invalid, but it makes
> > harder to reason).
> I could agree on this, but every single caller is based on (smfn, emfn),
> so it needlessly forces every caller to perform conversions where the
> callee can do it just once.
That's indeed one way to see it. The problem is that...

> That said, I think your point makes sense and
> it ought to be done. Probably as as part of a bigger refactor where
> (smfn, emfn)-based functions are turned into (base, len) variants.
... clean-up tends to be put in the back-burner and we just continue to 
add new use. This makes the task to remove every use a lot more 
difficult. So there is a point when one has to say no more.
Therefore, I would strongly prefer if each callers are doing the 
computation. The rest can be removed leisurely.
Let see what the opinion of the other maintainers.

Cheers,

--
Julien Grall