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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed, 26 May 2021 15:29:30 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Yang Shi <shy828301@gmail.com>
Cc:     hughd@google.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com,
        naoya.horiguchi@nec.com, wangyugui@e16-tech.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [v4 PATCH 2/2] mm: rmap: make try_to_unmap() void function
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References: <20210526201239.3351-1-shy828301@gmail.com>
 <20210526201239.3351-2-shy828301@gmail.com>
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On Wed, May 26, 2021 at 01:12:39PM -0700, Yang Shi wrote:
> 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@google.com>
> Acked-by: Hugh Dickins <hughd@google.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>

Thanks for the update, Yang Shi.