linux-kernel - Re: [PATCH v2] mm: thp: fix flags for pmd migration when split

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Date:   Tue, 11 Dec 2018 14:07:49 -0500
From:   "Zi Yan" <zi.yan@...rutgers.edu>
To:     "Konstantin Khlebnikov" <khlebnikov@...dex-team.ru>,
        "Peter Xu" <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        "Andrea Arcangeli" <aarcange@...hat.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Matthew Wilcox" <willy@...radead.org>,
        "Michal Hocko" <mhocko@...e.com>,
        "Dave Jiang" <dave.jiang@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        "Souptick Joarder" <jrdr.linux@...il.com>, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: thp: fix flags for pmd migration when split

On 11 Dec 2018, at 3:21, Konstantin Khlebnikov wrote:
>
> Write/read-only is encoded into migration entry.
> I suppose there should be something like this:
>
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2151,16 +2151,21 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>
>                 entry = pmd_to_swp_entry(old_pmd);
>                 page = pfn_to_page(swp_offset(entry));
> +               write = is_write_migration_entry(entry);
> +               young = false;
> +               soft_dirty = pmd_swp_soft_dirty(old_pmd);
>         } else
>  #endif
> +       {
>                 page = pmd_page(old_pmd);
> +               if (pmd_dirty(old_pmd))
> +                       SetPageDirty(page);
> +               write = pmd_write(old_pmd);
> +               young = pmd_young(old_pmd);
> +               soft_dirty = pmd_soft_dirty(old_pmd);
> +       }
>         VM_BUG_ON_PAGE(!page_count(page), page);
>         page_ref_add(page, HPAGE_PMD_NR - 1);
> -       if (pmd_dirty(old_pmd))
> -               SetPageDirty(page);
> -       write = pmd_write(old_pmd);
> -       young = pmd_young(old_pmd);
> -       soft_dirty = pmd_soft_dirty(old_pmd);
>
>         /*
>          * Withdraw the table only after we mark the pmd entry invalid.
>

This one should fix the issue. Thanks.

Reviewed-by: Zi Yan <zi.yan@...rutgers.edu>
Fixes 84c3fc4e9c563 ("mm: thp: check pmd migration entry in common path")

Do we need to cc: stable@...r.kernel.org # 4.14+ ?


--
Best Regards,
Yan Zi

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