Re: [PATCH v3 1/5] mm/khugepaged: Convert __collapse_huge_page_isolate() to use folios

[Yang Shi]

On Fri, Oct 20, 2023 at 11:33 AM Vishal Moola (Oracle)
<vishal.moola@xxxxxxxxx> wrote:
>
> Replaces 11 calls to compound_head() with 1, and removes 1348 bytes of
> kernel text.
>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>

Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>

> ---
>  mm/khugepaged.c | 45 +++++++++++++++++++++++----------------------
>  1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 88433cc25d8a..500756604488 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -542,6 +542,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                                         struct list_head *compound_pagelist)
>  {
>         struct page *page = NULL;
> +       struct folio *folio = NULL;
>         pte_t *_pte;
>         int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
>         bool writable = false;
> @@ -576,7 +577,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                         goto out;
>                 }
>
> -               VM_BUG_ON_PAGE(!PageAnon(page), page);
> +               folio = page_folio(page);
> +               VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio);
>
>                 if (page_mapcount(page) > 1) {
>                         ++shared;
> @@ -588,16 +590,15 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                         }
>                 }
>
> -               if (PageCompound(page)) {
> -                       struct page *p;
> -                       page = compound_head(page);
> +               if (folio_test_large(folio)) {
> +                       struct folio *f;
>
>                         /*
>                          * Check if we have dealt with the compound page
>                          * already
>                          */
> -                       list_for_each_entry(p, compound_pagelist, lru) {
> -                               if (page == p)
> +                       list_for_each_entry(f, compound_pagelist, lru) {
> +                               if (folio == f)
>                                         goto next;
>                         }
>                 }
> @@ -608,7 +609,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                  * is needed to serialize against split_huge_page
>                  * when invoked from the VM.
>                  */
> -               if (!trylock_page(page)) {
> +               if (!folio_trylock(folio)) {
>                         result = SCAN_PAGE_LOCK;
>                         goto out;
>                 }
> @@ -624,8 +625,8 @@ 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(page)) {
> -                       unlock_page(page);
> +               if (!is_refcount_suitable(&folio->page)) {
> +                       folio_unlock(folio);
>                         result = SCAN_PAGE_COUNT;
>                         goto out;
>                 }
> @@ -634,27 +635,27 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                  * Isolate the page to avoid collapsing an hugepage
>                  * currently in use by the VM.
>                  */
> -               if (!isolate_lru_page(page)) {
> -                       unlock_page(page);
> +               if (!folio_isolate_lru(folio)) {
> +                       folio_unlock(folio);
>                         result = SCAN_DEL_PAGE_LRU;
>                         goto out;
>                 }
> -               mod_node_page_state(page_pgdat(page),
> -                               NR_ISOLATED_ANON + page_is_file_lru(page),
> -                               compound_nr(page));
> -               VM_BUG_ON_PAGE(!PageLocked(page), page);
> -               VM_BUG_ON_PAGE(PageLRU(page), page);
> +               node_stat_mod_folio(folio,
> +                               NR_ISOLATED_ANON + folio_is_file_lru(folio),
> +                               folio_nr_pages(folio));
> +               VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
> +               VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
>
> -               if (PageCompound(page))
> -                       list_add_tail(&page->lru, compound_pagelist);
> +               if (folio_test_large(folio))
> +                       list_add_tail(&folio->lru, compound_pagelist);
>  next:
>                 /*
>                  * If collapse was initiated by khugepaged, check that there is
>                  * enough young pte to justify collapsing the page
>                  */
>                 if (cc->is_khugepaged &&
> -                   (pte_young(pteval) || page_is_young(page) ||
> -                    PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
> +                   (pte_young(pteval) || folio_test_young(folio) ||
> +                    folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
>                                                                      address)))
>                         referenced++;
>
> @@ -668,13 +669,13 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>                 result = SCAN_LACK_REFERENCED_PAGE;
>         } else {
>                 result = SCAN_SUCCEED;
> -               trace_mm_collapse_huge_page_isolate(page, none_or_zero,
> +               trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero,
>                                                     referenced, writable, result);
>                 return result;
>         }
>  out:
>         release_pte_pages(pte, _pte, compound_pagelist);
> -       trace_mm_collapse_huge_page_isolate(page, none_or_zero,
> +       trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero,
>                                             referenced, writable, result);
>         return result;
>  }
> --
> 2.40.1
>