Re: [PATCH v1 08/36] mm/hugetlb: check for unreasonable folio sizes when registering hstate

On Fri, Aug 29, 2025 at 12:07:44PM +0200, David Hildenbrand wrote:
> On 28.08.25 16:45, Lorenzo Stoakes wrote:
> > On Thu, Aug 28, 2025 at 12:01:12AM +0200, David Hildenbrand wrote:
> > > Let's check that no hstate that corresponds to an unreasonable folio size
> > > is registered by an architecture. If we were to succeed registering, we
> > > could later try allocating an unsupported gigantic folio size.
> > >
> > > Further, let's add a BUILD_BUG_ON() for checking that HUGETLB_PAGE_ORDER
> > > is sane at build time. As HUGETLB_PAGE_ORDER is dynamic on powerpc, we have
> > > to use a BUILD_BUG_ON_INVALID() to make it compile.
> > >
> > > No existing kernel configuration should be able to trigger this check:
> > > either SPARSEMEM without SPARSEMEM_VMEMMAP cannot be configured or
> > > gigantic folios will not exceed a memory section (the case on sparse).
> >
> > I am guessing it's implicit that MAX_FOLIO_ORDER <= section size?
>
> Yes, we have a build-time bug that somewhere.

OK cool thanks!

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo