linux-kernel - Re: [PATCH v2 08/10] mm: rmap: make try_to

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Date:   Thu, 10 Jun 2021 07:57:25 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Hugh Dickins <hughd@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Minchan Kim <minchan@...nel.org>, Jue Wang <juew@...gle.com>,
        Peter Xu <peterx@...hat.com>, Jan Kara <jack@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 08/10] mm: rmap: make try_to_unmap() void function

On Tue, Jun 08, 2021 at 09:25:22PM -0700, Hugh Dickins wrote:
> From: Yang Shi <shy828301@...il.com>
> 
> Currently try_to_unmap() return bool value by checking page_mapcount(),
> however this may return false positive since page_mapcount() doesn't
> check all subpages of compound page.  The total_mapcount() could be used
> instead, but its cost is higher since it traverses all subpages.
> 
> Actually the most callers of try_to_unmap() don't care about the
> return value at all.  So just need check if page is still mapped by
> page_mapped() when necessary.  And page_mapped() does bail out early
> when it finds mapped subpage.
> 
> Suggested-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Yang Shi <shy828301@...il.com>
> Acked-by: Minchan Kim <minchan@...nel.org>
> Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Looks good to me, thank you.

Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>