linux-kernel - Re: [PATCH 3/3] mm,thp,rmap: clean up the end of __split_huge_pmd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20221121132404.sebpecbc5joto7h7@box.shutemov.name>
Date:   Mon, 21 Nov 2022 16:24:04 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, Peter Xu <peterx@...hat.com>,
        Yang Shi <shy828301@...il.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Mina Almasry <almasrymina@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 3/3] mm,thp,rmap: clean up the end of
 __split_huge_pmd_locked()

On Fri, Nov 18, 2022 at 01:16:20AM -0800, Hugh Dickins wrote:
> It's hard to add a page_add_anon_rmap() into __split_huge_pmd_locked()'s
> HPAGE_PMD_NR set_pte_at() loop, without wincing at the "freeze" case's
> HPAGE_PMD_NR page_remove_rmap() loop below it.
> 
> It's just a mistake to add rmaps in the "freeze" (insert migration entries
> prior to splitting huge page) case: the pmd_migration case already avoids
> doing that, so just follow its lead.  page_add_ref() versus put_page()
> likewise.  But why is one more put_page() needed in the "freeze" case?
> Because it's removing the pmd rmap, already removed when pmd_migration
> (and freeze and pmd_migration are mutually exclusive cases).
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov