linux-kernel - Re: [PATCH v1 01/16] mm: hugetlb: Add huge page size param to huge_ptep_get_and

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Message-ID: <d8ef8240-e202-464c-ad16-1a34953cc872@arm.com>
Date: Thu, 6 Feb 2025 10:33:34 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ryan Roberts <ryan.roberts@....com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Muchun Song <muchun.song@...ux.dev>,
 Pasha Tatashin <pasha.tatashin@...een.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>,
 Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ardb@...nel.org>,
 Dev Jain <dev.jain@....com>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Steve Capper <steve.capper@...aro.org>, Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Huacai Chen <chenhuacai@...nel.org>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
 Helge Deller <deller@....de>, Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
 "David S. Miller" <davem@...emloft.net>,
 Andreas Larsson <andreas@...sler.com>, stable@...r.kernel.org
Subject: Re: [PATCH v1 01/16] mm: hugetlb: Add huge page size param to
 huge_ptep_get_and_clear()

On 2/5/25 20:39, Ryan Roberts wrote:
> In order to fix a bug, arm64 needs to be told the size of the huge page
> for which the huge_pte is being set in huge_ptep_get_and_clear().
> Provide for this by adding an `unsigned long sz` parameter to the
> function. This follows the same pattern as huge_pte_clear() and
> set_huge_pte_at().
> 
> This commit makes the required interface modifications to the core mm as
> well as all arches that implement this function (arm64, loongarch, mips,
> parisc, powerpc, riscv, s390, sparc). The actual arm64 bug will be fixed
> in a separate commit.
> 
> Cc: <stable@...r.kernel.org>
> Fixes: 66b3923a1a0f ("arm64: hugetlb: add support for PTE contiguous bit")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  arch/arm64/include/asm/hugetlb.h     |  4 ++--
>  arch/arm64/mm/hugetlbpage.c          |  8 +++++---
>  arch/loongarch/include/asm/hugetlb.h |  6 ++++--
>  arch/mips/include/asm/hugetlb.h      |  6 ++++--
>  arch/parisc/include/asm/hugetlb.h    |  2 +-
>  arch/parisc/mm/hugetlbpage.c         |  2 +-
>  arch/powerpc/include/asm/hugetlb.h   |  6 ++++--
>  arch/riscv/include/asm/hugetlb.h     |  3 ++-
>  arch/riscv/mm/hugetlbpage.c          |  2 +-
>  arch/s390/include/asm/hugetlb.h      | 12 ++++++++----
>  arch/s390/mm/hugetlbpage.c           | 10 ++++++++--
>  arch/sparc/include/asm/hugetlb.h     |  2 +-
>  arch/sparc/mm/hugetlbpage.c          |  2 +-
>  include/asm-generic/hugetlb.h        |  2 +-
>  include/linux/hugetlb.h              |  4 +++-
>  mm/hugetlb.c                         |  4 ++--
>  16 files changed, 48 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
> index c6dff3e69539..03db9cb21ace 100644
> --- a/arch/arm64/include/asm/hugetlb.h
> +++ b/arch/arm64/include/asm/hugetlb.h
> @@ -42,8 +42,8 @@ extern int huge_ptep_set_access_flags(struct vm_area_struct *vma,
>  				      unsigned long addr, pte_t *ptep,
>  				      pte_t pte, int dirty);
>  #define __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
> -extern pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> -				     unsigned long addr, pte_t *ptep);
> +extern pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
> +				     pte_t *ptep, unsigned long sz);

If VMA could be passed instead of MM, the size of the huge page can
be derived via huge_page_size(hstate_vma(vma)) and another argument
here need not be added. Also MM can be derived from VMA if required.