linux-kernel - Re: [External] [PATCH v3 4/5] hugetlb: convert PageHugeTemporary() to HPageTemporary flag

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Date:   Sat, 23 Jan 2021 11:15:46 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Michal Hocko <mhocko@...nel.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [External] [PATCH v3 4/5] hugetlb: convert PageHugeTemporary() to
 HPageTemporary flag

On Sat, Jan 23, 2021 at 3:55 AM Mike Kravetz <mike.kravetz@...cle.com> wrote:
>
> X-Gm-Spam: 0
> X-Gm-Phishy: 0
>
> Use new hugetlb specific HPageTemporary flag to replace the
> PageHugeTemporary() interfaces.  PageHugeTemporary does contain
> a PageHuge() check.  However, this interface is only used within
> hugetlb code where we know we are dealing with a hugetlb page.
> Therefore, the check can be eliminated.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>

Reviewed-by: Muchun Song <songmuchun@...edance.com>

> ---
>  include/linux/hugetlb.h |  6 ++++++
>  mm/hugetlb.c            | 36 +++++++-----------------------------
>  2 files changed, 13 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index cd1960541f2a..3c86c3a0e144 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -483,10 +483,15 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
>   * HPG_migratable  - Set after a newly allocated page is added to the page
>   *     cache and/or page tables.  Indicates the page is a candidate for
>   *     migration.
> + * HPG_temporary - - Set on a page that is temporarily allocated from the buddy
> + *     allocator.  Typically used for migration target pages when no pages
> + *     are available in the pool.  The hugetlb free page path will
> + *     immediately free pages with this flag set to the buddy allocator.
>   */
>  enum hugetlb_page_flags {
>         HPG_restore_reserve = 0,
>         HPG_migratable,
> +       HPG_temporary,
>         __NR_HPAGEFLAGS,
>  };
>
> @@ -530,6 +535,7 @@ static inline void ClearHPage##uname(struct page *page)             \
>   */
>  HPAGEFLAG(RestoreReserve, restore_reserve)
>  HPAGEFLAG(Migratable, migratable)
> +HPAGEFLAG(Temporary, temporary)
>
>  #ifdef CONFIG_HUGETLB_PAGE
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4da1a29ac5e2..70ffa1027988 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1353,28 +1353,6 @@ struct hstate *size_to_hstate(unsigned long size)
>         return NULL;
>  }
>
> -/*
> - * Internal hugetlb specific page flag. Do not use outside of the hugetlb
> - * code
> - */
> -static inline bool PageHugeTemporary(struct page *page)
> -{
> -       if (!PageHuge(page))
> -               return false;
> -
> -       return (unsigned long)page[2].mapping == -1U;
> -}
> -
> -static inline void SetPageHugeTemporary(struct page *page)
> -{
> -       page[2].mapping = (void *)-1U;
> -}
> -
> -static inline void ClearPageHugeTemporary(struct page *page)
> -{
> -       page[2].mapping = NULL;
> -}
> -
>  static void __free_huge_page(struct page *page)
>  {
>         /*
> @@ -1422,9 +1400,9 @@ static void __free_huge_page(struct page *page)
>         if (restore_reserve)
>                 h->resv_huge_pages++;
>
> -       if (PageHugeTemporary(page)) {
> +       if (HPageTemporary(page)) {
>                 list_del(&page->lru);
> -               ClearPageHugeTemporary(page);
> +               ClearHPageTemporary(page);
>                 update_and_free_page(h, page);
>         } else if (h->surplus_huge_pages_node[nid]) {
>                 /* remove the page from active list */
> @@ -1860,7 +1838,7 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
>          * codeflow
>          */
>         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
> -               SetPageHugeTemporary(page);
> +               SetHPageTemporary(page);
>                 spin_unlock(&hugetlb_lock);
>                 put_page(page);
>                 return NULL;
> @@ -1891,7 +1869,7 @@ static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
>          * We do not account these pages as surplus because they are only
>          * temporary and will be released properly on the last reference
>          */
> -       SetPageHugeTemporary(page);
> +       SetHPageTemporary(page);
>
>         return page;
>  }
> @@ -5612,12 +5590,12 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason)
>          * here as well otherwise the global surplus count will not match
>          * the per-node's.
>          */
> -       if (PageHugeTemporary(newpage)) {
> +       if (HPageTemporary(newpage)) {
>                 int old_nid = page_to_nid(oldpage);
>                 int new_nid = page_to_nid(newpage);
>
> -               SetPageHugeTemporary(oldpage);
> -               ClearPageHugeTemporary(newpage);
> +               SetHPageTemporary(oldpage);
> +               ClearHPageTemporary(newpage);
>
>                 spin_lock(&hugetlb_lock);
>                 if (h->surplus_huge_pages_node[old_nid]) {
> --
> 2.29.2
>