linux-kernel - Re: [PATCH v3 09/16] mm/rmap: use page_move_anon_rmap() when reusing a mapped PageAnon() page exclusively

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Message-ID: <a1ef20a1-6eda-2350-e5dc-bb32dcff8a1d@redhat.com>
Date:   Tue, 12 Apr 2022 11:28:13 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>, Michal Hocko <mhocko@...nel.org>,
        Nadav Amit <namit@...are.com>, Rik van Riel <riel@...riel.com>,
        Roman Gushchin <guro@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Donald Dutile <ddutile@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
        Liang Zhang <zhangliang5@...wei.com>,
        Pedro Gomes <pedrodemargomes@...il.com>,
        Oded Gabbay <oded.gabbay@...il.com>, linux-mm@...ck.org
Subject: Re: [PATCH v3 09/16] mm/rmap: use page_move_anon_rmap() when reusing
 a mapped PageAnon() page exclusively

On 12.04.22 11:26, Vlastimil Babka wrote:
> On 3/29/22 18:04, David Hildenbrand wrote:
>> We want to mark anonymous pages exclusive, and when using
>> page_move_anon_rmap() we know that we are the exclusive user, as
>> properly documented. This is a preparation for marking anonymous pages
>> exclusive in page_move_anon_rmap().
>>
>> In both instances, we're holding page lock and are sure that we're the
>> exclusive owner (page_count() == 1). hugetlb already properly uses
>> page_move_anon_rmap() in the write fault handler.
> 
> Yeah, note that do_wp_page() used to call page_move_anon_rmap() always since
> the latter was introduced, until commit 09854ba94c6a ("mm: do_wp_page()
> simplification"). Probably not intended.

Yeah, it was buried underneath all that reuse_swap_page() complexity.


-- 
Thanks,

David / dhildenb