Re: [RFC PATCH v3 1/8] mm/gup: break out gup_fill_pages() helper

[Suren Baghdasaryan]

On Mon, Aug 10, 2026 at 7:53 PM Rik van Riel <riel@xxxxxxxxxxx> wrote:
>
> __get_user_pages() fills pages[] and flushes each page's caches in an
> open-coded loop.
>
> Move it into a gup_fill_pages() helper, which the follow_page_mask()
> call chain can then use to fill its own pages[] slots.
>
> No functional changes intended.
>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>

Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>


> ---
>  mm/gup.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 0692119b7904..7bb40be89529 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -633,6 +633,23 @@ static struct page *no_page_table(struct vm_area_struct *vma,
>         return NULL;
>  }
>
> +static void gup_fill_pages(struct vm_area_struct *vma, unsigned long address,
> +               struct page *page, unsigned long nr, struct page **pages)
> +{
> +       unsigned long i;
> +
> +       if (!pages)
> +               return;
> +
> +       for (i = 0; i < nr; i++) {
> +               struct page *subpage = page + i;
> +
> +               pages[i] = subpage;
> +               flush_anon_page(vma, subpage, address + i * PAGE_SIZE);
> +               flush_dcache_page(subpage);
> +       }
> +}
> +
>  #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
>  /* FOLL_FORCE can write to even unwritable PUDs in COW mappings. */
>  static inline bool can_follow_write_pud(pud_t pud, struct page *page,
> @@ -1461,9 +1478,6 @@ static long __get_user_pages(struct mm_struct *mm,
>                         page_increm = nr_pages;
>
>                 if (pages) {
> -                       struct page *subpage;
> -                       unsigned int j;
> -
>                         /*
>                          * This must be a large folio (and doesn't need to
>                          * be the whole folio; it can be part of it), do
> @@ -1493,12 +1507,7 @@ static long __get_user_pages(struct mm_struct *mm,
>                                 }
>                         }
>
> -                       for (j = 0; j < page_increm; j++) {
> -                               subpage = page + j;
> -                               pages[i + j] = subpage;
> -                               flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
> -                               flush_dcache_page(subpage);
> -                       }
> +                       gup_fill_pages(vma, start, page, page_increm, pages + i);
>                 }
>
>                 i += page_increm;
> --
> 2.55.0
>
>