linux-kernel - Re: [PATCH RFC 03/12] mm: Export HPAGE_PXD

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Date:   Thu, 23 Nov 2023 10:27:15 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        John Hubbard <jhubbard@...dia.com>,
        Hugh Dickins <hughd@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        James Houghton <jthoughton@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 03/12] mm: Export HPAGE_PXD_* macros even if !THP

On Thu, Nov 23, 2023 at 11:53:04AM +0200, Mike Rapoport wrote:
> On Wed, Nov 22, 2023 at 11:23:57PM -0800, Christoph Hellwig wrote:
> > No way to export macros :)
> > 
> > I'd say define, but other might have better ideas.
> 
> Make HPAGE_PXD_* macros visible even if !THP

Sounds good, thanks both!

Besides, I do plan to introduce a new macro in the next version to mean
"THP || HUGETLB", so as to put PxD code segments into it and not compile
when unnecessary (!THP && !HUGETLB).

Currently what I had is:

config PGTABLE_HAS_HUGE_LEAVES
	def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE

I didn't use something like CONFIG_HUGE_PAGE because it's too close to
HUGETLB_PAGE, even if generic and short enough.  Please speak if there's
any early comments on that, either the name or the format. For example, I
can also define it in e.g. mm/internal.h, instead of a config entry.

-- 
Peter Xu