linux-kernel - Re: [PATCH v3 3/5] mm/khugepaged: Convert is_refcount

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Date:   Tue, 24 Oct 2023 10:39:10 -0700
From:   Yang Shi <shy828301@...il.com>
To:     "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org
Subject: Re: [PATCH v3 3/5] mm/khugepaged: Convert is_refcount_suitable() to
 use folios

On Fri, Oct 20, 2023 at 11:34 AM Vishal Moola (Oracle)
<vishal.moola@...il.com> wrote:
>
> Both callers of is_refcount_suitable() have been converted to use
> folios, so convert it to take in a folio. Both callers only operate on
> head pages of folios so mapcount/refcount conversions here are trivial.
>
> Removes 3 calls to compound head, and removes 315 bytes of kernel text.
>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>

Reviewed-by: Yang Shi <shy828301@...il.com>

> ---
>  mm/khugepaged.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 6c4b5af43371..9efd8ff68f06 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -524,15 +524,15 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
>         }
>  }
>
> -static bool is_refcount_suitable(struct page *page)
> +static bool is_refcount_suitable(struct folio *folio)
>  {
>         int expected_refcount;
>
> -       expected_refcount = total_mapcount(page);
> -       if (PageSwapCache(page))
> -               expected_refcount += compound_nr(page);
> +       expected_refcount = folio_mapcount(folio);
> +       if (folio_test_swapcache(folio))
> +               expected_refcount += folio_nr_pages(folio);
>
> -       return page_count(page) == expected_refcount;
> +       return folio_ref_count(folio) == expected_refcount;
>  }
>
>  static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> @@ -625,7 +625,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                  * but not from this process. The other process cannot write to
>                  * the page, only trigger CoW.
>                  */
> -               if (!is_refcount_suitable(&folio->page)) {
> +               if (!is_refcount_suitable(folio)) {
>                         folio_unlock(folio);
>                         result = SCAN_PAGE_COUNT;
>                         goto out;
> @@ -1371,7 +1371,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
>                  * has excessive GUP pins (i.e. 512).  Anyway the same check
>                  * will be done again later the risk seems low.
>                  */
> -               if (!is_refcount_suitable(&folio->page)) {
> +               if (!is_refcount_suitable(folio)) {
>                         result = SCAN_PAGE_COUNT;
>                         goto out_unmap;
>                 }
> --
> 2.40.1
>
>