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[198.145.29.99]) by mx.google.com with ESMTPS id cp14si1906890plb.183.2019.05.14.14.25.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 May 2019 14:25:28 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=in6s4kav; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5477C20850; Tue, 14 May 2019 21:25:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557869128; bh=UZ4GiHlaes+DK9pTRaINLCCHnDA+gTfRjxFFWYfxM7A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=in6s4kavbJOqz1htYNcOrmRgNhqbR7debNloGeI2j6UOlezuFCKfAmXN7F5c9pKYh uskx6J3YJLPlJeih8oVt5Lw4Q3e7lrzehsr6+Wwm0nz95Kyyi6g1d5+nS7LASkZZ7Q xvOsJhAsaMVwkubJO9XAemKPjMf8QHfxQN/hX+ws= Date: Tue, 14 May 2019 14:25:27 -0700 From: Andrew Morton To: Yu Zhao Cc: Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: don't expose page to fast gup before it's ready Message-Id: <20190514142527.356cb071155cd1077536f3da@linux-foundation.org> In-Reply-To: <20180109101050.GA83229@google.com> References: <20180108225632.16332-1-yuzhao@google.com> <20180109084622.GF1732@dhcp22.suse.cz> <20180109101050.GA83229@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Tue, 9 Jan 2018 02:10:50 -0800 Yu Zhao wrote: > > Also what prevents reordering here? There do not seem to be any barriers > > to prevent __SetPageSwapBacked leak after set_pte_at with your patch. > > I assumed mem_cgroup_commit_charge() acted as full barrier. Since you > explicitly asked the question, I realized my assumption doesn't hold > when memcg is disabled. So we do need something to prevent reordering > in my patch. And it brings up the question whether we want to add more > barrier to other places that call page_add_new_anon_rmap() and > set_pte_at(). Is a new version of this patch planned?