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Message-ID: <Z73Szw4rSHSyfpoy@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Tue, 25 Feb 2025 15:25:19 +0100
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
        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>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Naveen N Rao <naveen@...nel.org>,
        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>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Andreas Larsson <andreas@...sler.com>, Arnd Bergmann <arnd@...db.de>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Dev Jain <dev.jain@....com>, Kevin Brodsky <kevin.brodsky@....com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/4] mm: hugetlb: Add huge page size param to
 huge_ptep_get_and_clear()

On Mon, Feb 17, 2025 at 02:04:14PM +0000, Ryan Roberts wrote:

Hi Ryan,

> 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>
> ---
...
> diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
> index 7c52acaf9f82..420c74306779 100644
> --- a/arch/s390/include/asm/hugetlb.h
> +++ b/arch/s390/include/asm/hugetlb.h
> @@ -26,7 +26,11 @@ void __set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
>  pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
>  
>  #define __HAVE_ARCH_HUGE_PTEP_GET_AND_CLEAR
> -pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
> +pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> +			      unsigned long addr, pte_t *ptep,
> +			      unsigned long sz);

Please, format parameters similarily to set_huge_pte_at() few lines above.

> +pte_t __huge_ptep_get_and_clear(struct mm_struct *mm,
> +			      unsigned long addr, pte_t *ptep);

The formatting is broken, but please see below.

>  static inline void arch_clear_hugetlb_flags(struct folio *folio)
>  {
> @@ -48,7 +52,7 @@ static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>  static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
>  					  unsigned long address, pte_t *ptep)
>  {
> -	return huge_ptep_get_and_clear(vma->vm_mm, address, ptep);
> +	return __huge_ptep_get_and_clear(vma->vm_mm, address, ptep);
>  }
>  
>  #define  __HAVE_ARCH_HUGE_PTEP_SET_ACCESS_FLAGS
> @@ -59,7 +63,7 @@ static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
>  	int changed = !pte_same(huge_ptep_get(vma->vm_mm, addr, ptep), pte);
>  
>  	if (changed) {
> -		huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
> +		__huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
>  		__set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
>  	}
>  	return changed;
> @@ -69,7 +73,7 @@ static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
>  static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
>  					   unsigned long addr, pte_t *ptep)
>  {
> -	pte_t pte = huge_ptep_get_and_clear(mm, addr, ptep);
> +	pte_t pte = __huge_ptep_get_and_clear(mm, addr, ptep);
>  
>  	__set_huge_pte_at(mm, addr, ptep, pte_wrprotect(pte));
>  }
> diff --git a/arch/s390/mm/hugetlbpage.c b/arch/s390/mm/hugetlbpage.c
> index d9ce199953de..52ee8e854195 100644
> --- a/arch/s390/mm/hugetlbpage.c
> +++ b/arch/s390/mm/hugetlbpage.c
> @@ -188,8 +188,8 @@ pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
>  	return __rste_to_pte(pte_val(*ptep));
>  }
>  
> -pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> -			      unsigned long addr, pte_t *ptep)
> +pte_t __huge_ptep_get_and_clear(struct mm_struct *mm,
> +				unsigned long addr, pte_t *ptep)
>  {
>  	pte_t pte = huge_ptep_get(mm, addr, ptep);
>  	pmd_t *pmdp = (pmd_t *) ptep;
> @@ -202,6 +202,12 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
>  	return pte;
>  }
>  
> +pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> +			      unsigned long addr, pte_t *ptep, unsigned long sz)
> +{
> +	return __huge_ptep_get_and_clear(mm, addr, ptep);
> +}

Is there a reason why this is not a header inline, as other callers of
__huge_ptep_get_and_clear()?

>  pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
>  			unsigned long addr, unsigned long sz)
>  {
...

Thanks!

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