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[216.228.121.143]) by mx.google.com with ESMTPS id n185si9022868ywe.430.2019.02.12.18.58.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Feb 2019 18:58:12 -0800 (PST) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) client-ip=216.228.121.143; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=ZxwYf3wv; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqemgate14.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 12 Feb 2019 18:58:14 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Tue, 12 Feb 2019 18:58:11 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Tue, 12 Feb 2019 18:58:11 -0800 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 13 Feb 2019 02:58:10 +0000 Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA To: Christopher Lameter CC: Jason Gunthorpe , Ira Weiny , Dan Williams , Jan Kara , Dave Chinner , Doug Ledford , Matthew Wilcox , , linux-rdma , Linux MM , Linux Kernel Mailing List , Jerome Glisse , Michal Hocko References: <01000168c8e2de6b-9ab820ed-38ad-469c-b210-60fcff8ea81c-000000@email.amazonses.com> <20190208044302.GA20493@dastard> <20190208111028.GD6353@quack2.suse.cz> <20190211102402.GF19029@quack2.suse.cz> <20190211180654.GB24692@ziepe.ca> <20190211181921.GA5526@iweiny-DESK2.sc.intel.com> <20190211221247.GI24692@ziepe.ca> <018c1a05-5fd8-886a-573b-42649949bba8@nvidia.com> <01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@email.amazonses.com> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Tue, 12 Feb 2019 18:58:10 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@email.amazonses.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL108.nvidia.com (172.18.146.13) To HQMAIL101.nvidia.com (172.20.187.10) Content-Type: text/plain; charset="utf-8" Content-Language: en-US-large Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1550026694; bh=pYuUD8ixt0DUBPAmr4vJCg8DY/4XZggnruE+tkGT2iI=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=ZxwYf3wvJ76h2srywAkRBqh0CcEH377shxMYRyeclrKz53nOM8sGge/1XvuYsP9ar TmhlGr4nkQbxlKf+4H6dRCTef9wcC0cdAvx0n9d4KZZ6x0utDA4UkbGE/+pYafrpvv 7VlWtcpwsZCx/7SNoI5JM5QydMnIWsESr6vNbAQLIrbmrdJhCcsD5Vq+Pi0tnHtoCf C8DwXWTDxFBDspe1bsrv4GSrCIGlrtw70AhRbRUx0jlk1wqIDcwavouzCD+43Ded6A KE35oMbqiXM0mWUKd1ikOhSMlmUS2v6yk7v1Dw2fBg+r1nI6bk33DSg7f9eGF2bRWn bOYN0flqnZMPA== 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 2/12/19 8:39 AM, Christopher Lameter wrote: > On Mon, 11 Feb 2019, John Hubbard wrote: > >> But anyway, Jan's proposal a bit earlier today [1] is finally sinking into >> my head--if we actually go that way, and prevent the caller from setting up >> a problematic gup pin in the first place, then that may make this point sort >> of moot. > > Ok well can be document how we think it would work somewhere? Long term > mapping a page cache page could a problem and we need to explain that > somewhere. > Yes, once the dust settles, I think Documentation/vm/get_user_pages.rst is the right place. I started to create that file, but someone observed that my initial content was entirely backward-looking (described the original problem, instead of describing how the new system would work). So I'll use this opportunity for a do-over. :) thanks, -- John Hubbard NVIDIA