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Fri, 17 Apr 2020 07:26:21 -0700 (PDT) Received: from localhost ([43.224.245.179]) by smtp.gmail.com with ESMTPSA id j23sm1414657pjz.13.2020.04.17.07.26.20 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Fri, 17 Apr 2020 07:26:20 -0700 (PDT) Date: Fri, 17 Apr 2020 22:26:18 +0800 From: chenqiwu To: Michal Hocko Cc: akpm@linux-foundation.org, linux-mm@kvack.org, chenqiwu Subject: Re: [PATCH] mm/memory: add refcount for special mapping page in copy_one_pte() Message-ID: <20200417142618.GA31882@cqw-OptiPlex-7050> References: <1587119514-29679-1-git-send-email-qiwuchen55@gmail.com> <20200417114312.GM26707@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417114312.GM26707@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) 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 Fri, Apr 17, 2020 at 01:43:12PM +0200, Michal Hocko wrote: > On Fri 17-04-20 18:31:54, qiwuchen55@gmail.com wrote: > > From: chenqiwu > > > > If we get a special mapping page like device mapping page or zero page > > when copy_one_pte, it's necessary add the page refcount count. > > From the changelog it is not clear what is the actual problem and how > the patch address it. Please be more verbose. > I don't find any actual problem, but I think there should be addressed to update the page refcount for special mappings include devmap and zero page instead of doing nothing else, since we copy the pte from one task to the other.