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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
Date: Wed, 26 May 2021 15:29:30 -0700	[thread overview]
Message-ID: <YK7LykQE0LzysBYU@google.com> (raw)
In-Reply-To: <20210526201239.3351-2-shy828301@gmail.com>

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.


  reply	other threads:[~2021-05-26 22:29 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-26 20:12 [v4 PATCH 1/2] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Yang Shi
2021-05-26 20:12 ` [v4 PATCH 2/2] mm: rmap: make try_to_unmap() void function Yang Shi
2021-05-26 22:29   ` Minchan Kim [this message]
2021-05-26 23:03   ` Shakeel Butt
2021-05-26 22:02 ` [v4 PATCH 1/2] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Hugh Dickins
2021-05-27 10:52 ` Kirill A. Shutemov

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