linux-kernel - Re: [mm-unstable PATCH v4 3/9] mm/hugetlb: make pud_huge() and follow_huge

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Date:   Wed, 6 Jul 2022 15:21:12 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [mm-unstable PATCH v4 3/9] mm/hugetlb: make pud_huge() and
 follow_huge_pud() aware of non-present pud entry

On 07/04/22 10:33, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> follow_pud_mask() does not support non-present pud entry now.  As long as
> I tested on x86_64 server, follow_pud_mask() still simply returns
> no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe
> user-visible effect should happen.  But generally we should call
> follow_huge_pud() for non-present pud entry for 1GB hugetlb page.
> 
> Update pud_huge() and follow_huge_pud() to handle non-present pud entries.
> The changes are similar to previous works for pud entries commit e66f17ff7177
> ("mm/hugetlb: take page table lock in follow_huge_pmd()") and commit
> cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present hugepage").
> 
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> ---
> v2 -> v3:
> - fixed typos in subject and description,
> - added comment on pud_huge(),
> - added comment about fallback for hwpoisoned entry,
> - updated initial check about FOLL_{PIN,GET} flags.
> ---
>  arch/x86/mm/hugetlbpage.c |  8 +++++++-
>  mm/hugetlb.c              | 32 ++++++++++++++++++++++++++++++--
>  2 files changed, 37 insertions(+), 3 deletions(-)

Thanks!

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz