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Date:   Wed, 6 Jul 2022 15:21:12 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Liu Shixin <liushixin2@huawei.com>,
        Yang Shi <shy828301@gmail.com>,
        Oscar Salvador <osalvador@suse.de>,
        Muchun Song <songmuchun@bytedance.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        linux-kernel@vger.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
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References: <20220704013312.2415700-1-naoya.horiguchi@linux.dev>
 <20220704013312.2415700-4-naoya.horiguchi@linux.dev>
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On 07/04/22 10:33, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@nec.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@nec.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@oracle.com>
-- 
Mike Kravetz