Re: [PATCH v3 4/6] mm: Introduce a pageflag for partially mapped folios

Andrew Morton
2024-08-15T23:30:15Z

On Thu, 15 Aug 2024 16:25:09 +0100 Usama Arif <usamaarif642@gmail.com> wrote:

>
>
> commit c627655548fa09b59849e942da4decc84fa0b0f2
> Author: Usama Arif <usamaarif642@gmail.com>
> Date: Thu Aug 15 16:07:20 2024 +0100
>
> mm: Introduce a pageflag for partially mapped folios fix
>
> Fixes the original commit by not clearing partially mapped bit
> in hugeTLB folios and fixing deferred split THP stats.
>
> ...
>

Life is getting complicated.

> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1758,7 +1758,6 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
> free_gigantic_folio(folio, huge_page_order(h));
> } else {
> INIT_LIST_HEAD(&folio->_deferred_list);
> - folio_clear_partially_mapped(folio);
> folio_put(folio);
> }
> }

Yu Zhao's "mm/hugetlb: use __GFP_COMP for gigantic folios" was
expecting that folio_clear_partially_mapped() to be there.

I resolved this within
mm-hugetlb-use-__gfp_comp-for-gigantic-folios.patch thusly:

@@ -1748,18 +1704,8 @@ static void __update_and_free_hugetlb_fo

folio_ref_unfreeze(folio, 1);

- /*
- * Non-gigantic pages demoted from CMA allocated gigantic pages
- * need to be given back to CMA in free_gigantic_folio.
- */
- if (hstate_is_gigantic(h) ||
- hugetlb_cma_folio(folio, huge_page_order(h))) {
- destroy_compound_gigantic_folio(folio, huge_page_order(h));
- free_gigantic_folio(folio, huge_page_order(h));
- } else {
- INIT_LIST_HEAD(&folio->_deferred_list);
- folio_put(folio);
- }
+ INIT_LIST_HEAD(&folio->_deferred_list);
+ hugetlb_free_folio(folio);
}

/*

Please check.