linux-kernel - Re: [PATCH v2 7/8] mm: migrate: remove PageHead() check for HugeTLB in add_page_for

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Message-ID: <B847C18D-984A-4811-A25B-CBEDBC769759@nvidia.com>
Date:   Mon, 28 Aug 2023 10:15:46 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, willy@...radead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        ying.huang@...el.com, david@...hat.com,
        Mike Kravetz <mike.kravetz@...cle.com>, hughd@...gle.com
Subject: Re: [PATCH v2 7/8] mm: migrate: remove PageHead() check for HugeTLB
 in add_page_for_migration()

On 21 Aug 2023, at 7:56, Kefeng Wang wrote:

> There is some different between hugeTLB and THP behave when passed the
> address of a tail page, for THP, it will migrate the entire THP page,
> but for HugeTLB, it will return -EACCES, or -ENOENT before commit
> e66f17ff7177 ("mm/hugetlb: take page table lock in follow_huge_pmd()"),
>
>   -EACCES The page is mapped by multiple processes and can be moved
> 	  only if MPOL_MF_MOVE_ALL is specified.
>   -ENOENT The page is not present.
>
> But when check manual[1], both of the two errnos are not suitable, it
> is better to keep the same behave between hugetlb and THP when passed
> the address of a tail page, so let's just remove the PageHead() check
> for HugeTLB.
>
> [1] https://man7.org/linux/man-pages/man2/move_pages.2.html
>
> Suggested-by: Mike Kravetz <mike.kravetz@...cle.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  mm/migrate.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>

Acked-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi

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