Re: [PATCH v2 01/34] mm: Add PAGE_TYPE_OP folio functions

On Thu, May 25, 2023 at 1:20 PM Mike Rapoport <[email protected]> wrote:
>
> On Thu, May 25, 2023 at 10:00:23AM -0700, Vishal Moola wrote:
> > On Thu, May 25, 2023 at 1:56 AM Mike Rapoport <[email protected]> wrote:
> > >
> > > Hi,
> > >
> > > On Mon, May 01, 2023 at 12:27:56PM -0700, Vishal Moola (Oracle) wrote:
> > > > No folio equivalents for page type operations have been defined, so
> > > > define them for later folio conversions.
> > >
> > > Can you please elaborate why would we need folios for page table descriptors?
> >
> > Thanks for the review!
> >
> > These macros are for callers that care about the page type, i.e. Table and
> > Buddy. Aside from accounting for those cases, the page tables don't use folios.
> > These are more for the cleanliness of those callers.
>
> But why using folio APIs for PageType will be cleaner than using page APIs?
> Do you have an example?

Ah, for example in mm/memory-failure.c there are a couple uses of PageTable.
Like the line :
if (folio_test_slab(folio) || PageTable(&folio->page) ||
folio_test_reserved(folio))
where that PageTable(&folio->page) can now be written as folio_test_table(folio)
instead.

Also there are numerous uses of PageBuddy in mm/compaction.c that will
likely need to be converted to folios as well.