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Wed, 26 May 2021 15:29:32 -0700 (PDT) Received: from google.com ([2620:15c:211:201:3dcc:6421:abe4:95d0]) by smtp.gmail.com with ESMTPSA id 4sm87124pgn.31.2021.05.26.15.29.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 May 2021 15:29:32 -0700 (PDT) Date: Wed, 26 May 2021 15:29:30 -0700 From: Minchan Kim To: Yang Shi 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 Message-ID: References: <20210526201239.3351-1-shy828301@gmail.com> <20210526201239.3351-2-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210526201239.3351-2-shy828301@gmail.com> Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=r9U6b0w6; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=pass (imf26.hostedemail.com: domain of minchankim@gmail.com designates 209.85.215.180 as permitted sender) smtp.mailfrom=minchankim@gmail.com X-Stat-Signature: ox8oaj36cpqn5w6cowrt1r1edqq1w66p X-Rspamd-Queue-Id: 4ED0C40B8CF4 X-Rspamd-Server: rspam02 X-HE-Tag: 1622068170-414266 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > Acked-by: Hugh Dickins > Signed-off-by: Yang Shi Acked-by: Minchan Kim Thanks for the update, Yang Shi.