linux-kernel - Re: [PATCH v2 3/8] mm/hugetlb: Add page_mask for hugetlb_follow_page

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Message-ID: <d1f6c2c5-07d0-d430-49b3-68e9f5978534@redhat.com>
Date:   Tue, 20 Jun 2023 17:23:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        John Hubbard <jhubbard@...dia.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        James Houghton <jthoughton@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Hugh Dickins <hughd@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2 3/8] mm/hugetlb: Add page_mask for
 hugetlb_follow_page_mask()

On 20.06.23 01:10, Peter Xu wrote:
> follow_page() doesn't need it, but we'll start to need it when unifying gup
> for hugetlb.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>   include/linux/hugetlb.h | 8 +++++---
>   mm/gup.c                | 3 ++-
>   mm/hugetlb.c            | 5 ++++-
>   3 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index beb7c63d2871..2e2d89e79d6c 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -131,7 +131,8 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
>   int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *,
>   			    struct vm_area_struct *, struct vm_area_struct *);
>   struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
> -				unsigned long address, unsigned int flags);
> +				      unsigned long address, unsigned int flags,
> +				      unsigned int *page_mask);
>   long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
>   			 struct page **, unsigned long *, unsigned long *,
>   			 long, unsigned int, int *);
> @@ -297,8 +298,9 @@ static inline void adjust_range_if_pmd_sharing_possible(
>   {
>   }
>   
> -static inline struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
> -				unsigned long address, unsigned int flags)
> +static inline struct page *hugetlb_follow_page_mask(
> +    struct vm_area_struct *vma, unsigned long address, unsigned int flags,
> +    unsigned int *page_mask)
>   {
>   	BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/
>   }
> diff --git a/mm/gup.c b/mm/gup.c
> index abcd841d94b7..9fc9271cba8d 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -780,7 +780,8 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
>   	 * Ordinary GUP uses follow_hugetlb_page for hugetlb processing.
>   	 */
>   	if (is_vm_hugetlb_page(vma))
> -		return hugetlb_follow_page_mask(vma, address, flags);
> +		return hugetlb_follow_page_mask(vma, address, flags,
> +						&ctx->page_mask);
>   
>   	pgd = pgd_offset(mm, address);
>   
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 9a6918c4250a..fbf6a09c0ec4 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6454,7 +6454,8 @@ static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma,
>   }
>   
>   struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
> -				unsigned long address, unsigned int flags)
> +				      unsigned long address, unsigned int flags,
> +				      unsigned int *page_mask)
>   {
>   	struct hstate *h = hstate_vma(vma);
>   	struct mm_struct *mm = vma->vm_mm;
> @@ -6499,6 +6500,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>   			page = NULL;
>   			goto out;
>   		}
> +
> +		*page_mask = ~huge_page_mask(h) >> PAGE_SHIFT;

As discussed, can be simplified. But can be done on top (or not at all, 
but it is confusing code).

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb