linux-kernel - Re: [PATCH 03/13] mm: Provide generic pmd_thp_or

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Message-ID: <135b3189-f459-4b57-9861-bb8acb999d91@linux.dev>
Date: Mon, 25 Dec 2023 14:29:53 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: peterx@...hat.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: Matthew Wilcox <willy@...radead.org>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 Lorenzo Stoakes <lstoakes@...il.com>, David Hildenbrand <david@...hat.com>,
 Vlastimil Babka <vbabka@...e.cz>, Mike Kravetz <mike.kravetz@...cle.com>,
 Mike Rapoport <rppt@...nel.org>, Christoph Hellwig <hch@...radead.org>,
 John Hubbard <jhubbard@...dia.com>, Andrew Jones <andrew.jones@...ux.dev>,
 linux-arm-kernel@...ts.infradead.org, Michael Ellerman <mpe@...erman.id.au>,
 "Kirill A . Shutemov" <kirill@...temov.name>, linuxppc-dev@...ts.ozlabs.org,
 Rik van Riel <riel@...riel.com>, linux-riscv@...ts.infradead.org,
 Yang Shi <shy828301@...il.com>, James Houghton <jthoughton@...gle.com>,
 "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Jason Gunthorpe <jgg@...dia.com>,
 Andrea Arcangeli <aarcange@...hat.com>,
 Axel Rasmussen <axelrasmussen@...gle.com>
Subject: Re: [PATCH 03/13] mm: Provide generic pmd_thp_or_huge()

On 2023/12/19 15:55, peterx@...hat.com wrote:
> From: Peter Xu <peterx@...hat.com>
>
> ARM defines pmd_thp_or_huge(), detecting either a THP or a huge PMD.  It
> can be a helpful helper if we want to merge more THP and hugetlb code
> paths.  Make it a generic default implementation, only exist when
> CONFIG_MMU.  Arch can overwrite it by defining its own version.
>
> For example, ARM's pgtable-2level.h defines it to always return false.
>
> Keep the macro declared with all config, it should be optimized to a false
> anyway if !THP && !HUGETLB.
>
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>   include/linux/pgtable.h | 4 ++++
>   mm/gup.c                | 3 +--
>   2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index af7639c3b0a3..6f2fa1977b8a 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1355,6 +1355,10 @@ static inline int pmd_write(pmd_t pmd)
>   #endif /* pmd_write */
>   #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>   
> +#ifndef pmd_thp_or_huge

I think it may be the time to rename to pmd_thp_or_hugetlb,
the "huge" is really confusing. thp is not huge? Actually,
it is huge. It is better to make it more specific from now on, like
"hugetlb".

BTW, please cc me via the new email (muchun.song@...ux.dev) next edition.

Thanks.

> +#define pmd_thp_or_huge(pmd)	(pmd_huge(pmd) || pmd_trans_huge(pmd))
> +#endif
> +
>   #ifndef pud_write
>   static inline int pud_write(pud_t pud)
>   {
> diff --git a/mm/gup.c b/mm/gup.c
> index 0a5f0e91bfec..efc9847e58fb 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -3004,8 +3004,7 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo
>   		if (!pmd_present(pmd))
>   			return 0;
>   
> -		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
> -			     pmd_devmap(pmd))) {
> +		if (unlikely(pmd_thp_or_huge(pmd) || pmd_devmap(pmd))) {
>   			/* See gup_pte_range() */
>   			if (pmd_protnone(pmd))
>   				return 0;