linux-kernel - Re: [PATCH v1 01/10] mm: Expose clear_huge

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Message-ID: <CAOUHufacvArJh7NjL_3LT-e3s1X+bazkvbgvEU+KPKGKEoW+dw@mail.gmail.com>
Date:   Mon, 26 Jun 2023 19:55:42 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Ryan Roberts <ryan.roberts@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yin Fengwei <fengwei.yin@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v1 01/10] mm: Expose clear_huge_page() unconditionally

On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@....com> wrote:
>
> In preparation for extending vma_alloc_zeroed_movable_folio() to
> allocate a arbitrary order folio, expose clear_huge_page()
> unconditionally, so that it can be used to zero the allocated folio in
> the generic implementation of vma_alloc_zeroed_movable_folio().
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  include/linux/mm.h | 3 ++-
>  mm/memory.c        | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7f1741bd870a..7e3bf45e6491 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3684,10 +3684,11 @@ enum mf_action_page_type {
>   */
>  extern const struct attribute_group memory_failure_attr_group;
>
> -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
>  extern void clear_huge_page(struct page *page,
>                             unsigned long addr_hint,
>                             unsigned int pages_per_huge_page);
> +
> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)

We might not want to depend on THP eventually. Right now, we still
have to, unless splitting is optional, which seems to contradict
06/10. (deferred_split_folio()  is a nop without THP.)