linux-kernel - Re: [PATCH v3 5/5] hugetlb: Do early cow when page pinned on src mm

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Date:   Mon, 8 Feb 2021 16:09:26 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Gal Pressman <galpress@...zon.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Kirill Shutemov <kirill@...temov.name>,
        Jann Horn <jannh@...gle.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        David Gibson <david@...son.dropbear.id.au>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Wei Zhang <wzam@...zon.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 5/5] hugetlb: Do early cow when page pinned on src mm

On 2/5/21 8:54 AM, Peter Xu wrote:
> This is the last missing piece of the COW-during-fork effort when there're
> pinned pages found.  One can reference 70e806e4e645 ("mm: Do early cow for
> pinned pages during fork() for ptes", 2020-09-27) for more information, since
> we do similar things here rather than pte this time, but just for hugetlb.

Thanks for all the changes, the patch looks much better.

I did not look at 70e806e4e645 in detail until now.  That commit had the
'write protect trick' which was removed in subsequent commits.  It took me
a bit of git history tracking to figure out the state of that code today and
the reasons for the subsequent changes.  I guess that was a good way to
educate me. :) 

> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  mm/hugetlb.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 62 insertions(+), 4 deletions(-)

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