Re: [PATCH V5 4/5] mm/hugetlb: Add prot_modify_start/commit sequence for hugetlb update

[Michael Ellerman <mpe@ellerman.id.au>]

"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:

> Architectures like ppc64 require to do a conditional tlb flush based on the old
> and new value of pte. Follow the regular pte change protection sequence for
> hugetlb too. This allows the architectures to override the update sequence.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  include/linux/hugetlb.h | 20 ++++++++++++++++++++
>  mm/hugetlb.c            |  8 +++++---
>  2 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 087fd5f48c91..39e78b80375c 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -543,6 +543,26 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
>  	set_huge_pte_at(mm, addr, ptep, pte);
>  }
>  #endif
> +
> +#ifndef huge_ptep_modify_prot_start
> +#define huge_ptep_modify_prot_start huge_ptep_modify_prot_start
> +static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma,
> +						unsigned long addr, pte_t *ptep)
> +{
> +	return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
> +}
> +#endif
> +
> +#ifndef huge_ptep_modify_prot_commit
> +#define huge_ptep_modify_prot_commit huge_ptep_modify_prot_commit
> +static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
> +						unsigned long addr, pte_t *ptep,
> +						pte_t old_pte, pte_t pte)
> +{
> +	set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
> +}
> +#endif
> +
>  #else	/* CONFIG_HUGETLB_PAGE */
>  struct hstate {};
>  #define alloc_huge_page(v, a, r) NULL
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index df2e7dd5ff17..f824d2200ca9 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4387,10 +4387,12 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
>  			continue;
>  		}
>  		if (!huge_pte_none(pte)) {
> -			pte = huge_ptep_get_and_clear(mm, address, ptep);
> -			pte = pte_mkhuge(huge_pte_modify(pte, newprot));
> +			pte_t old_pte;
> +
> +			old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
> +			pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
>  			pte = arch_make_huge_pte(pte, vma, NULL, 0);
> -			set_huge_pte_at(mm, address, ptep, pte);
> +			huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
>  			pages++;
>  		}
>  		spin_unlock(ptl);

Looks like a faithful conversion.

Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>

cheers