linux-kernel - Re: [RFC PATCH 19/26] hugetlb: add HGM support for copy_hugetlb_page

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Message-ID: <Ysy1EySRmjxl2TmQ@monkey>
Date:   Mon, 11 Jul 2022 16:41:07 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     James Houghton <jthoughton@...gle.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Jue Wang <juew@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 19/26] hugetlb: add HGM support for
 copy_hugetlb_page_range

On 06/24/22 17:36, James Houghton wrote:
> This allows fork() to work with high-granularity mappings. The page
> table structure is copied such that partially mapped regions will remain
> partially mapped in the same way for the new process.
> 
> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>  mm/hugetlb.c | 74 +++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 59 insertions(+), 15 deletions(-)

FYI -
With https://lore.kernel.org/linux-mm/20220621235620.291305-5-mike.kravetz@oracle.com/
copy_hugetlb_page_range() should never be called for shared mappings.
Since HGM only works on shared mappings, code in this patch will never
be executed.

I have a TODO to remove shared mapping support from copy_hugetlb_page_range.
-- 
Mike Kravetz