From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vishal Moola <vishal.moola@gmail.com>
Subject: Re: [PATCH v2 05/34] mm: add utility functions for ptdesc
Date: Thu, 25 May 2023 13:53:24 -0700
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To: Mike Rapoport <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Matthew Wilcox <willy@infradead.org>, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org

On Thu, May 25, 2023 at 1:26=E2=80=AFPM Mike Rapoport <rppt@kernel.org> wro=
te:
>
> On Thu, May 25, 2023 at 11:04:28AM -0700, Vishal Moola wrote:
> > On Thu, May 25, 2023 at 2:10=E2=80=AFAM Mike Rapoport <rppt@kernel.org>=
 wrote:
> > > > +
> > > > +static inline struct ptdesc *ptdesc_alloc(gfp_t gfp, unsigned int =
order)
> > > > +{
> > > > +     struct page *page =3D alloc_pages(gfp | __GFP_COMP, order);
> > > > +
> > > > +     return page_ptdesc(page);
> > > > +}
> > > > +
> > > > +static inline void ptdesc_free(struct ptdesc *pt)
> > > > +{
> > > > +     struct page *page =3D ptdesc_page(pt);
> > > > +
> > > > +     __free_pages(page, compound_order(page));
> > > > +}
> > >
> > > The ptdesc_{alloc,free} API does not sound right to me. The name
> > > ptdesc_alloc() implies the allocation of the ptdesc itself, rather th=
an
> > > allocation of page table page. The same goes for free.
> >
> > I'm not sure I see the difference. Could you elaborate?
>
> I read ptdesc_alloc() as "allocate a ptdesc" rather than as "allocate a
> page for page table and return ptdesc pointing to that page". Seems very
> confusing to me already and it will be even more confusion when we'll sta=
rt
> allocating actual ptdescs.

Hmm, I see what you're saying. I'm envisioning this function evolving into
one that allocates a ptdesc later. I don't see why we would need to have bo=
th a
page table page AND ptdesc at any point, but that may be a lack of knowledg=
e
from my part.

I was thinking later, if necessary, we could make another function
(only to be used internally) to allocate page table pages.