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[54.240.9.31]) by mx.google.com with ESMTPS id v9si3517926qtf.314.2019.02.12.08.39.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 12 Feb 2019 08:39:43 -0800 (PST) Received-SPF: pass (google.com: domain of 01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@amazonses.com designates 54.240.9.31 as permitted sender) client-ip=54.240.9.31; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug header.b=L9qVsApf; spf=pass (google.com: domain of 01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@amazonses.com designates 54.240.9.31 as permitted sender) smtp.mailfrom=01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@amazonses.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ug7nbtf4gccmlpwj322ax3p6ow6yfsug; d=amazonses.com; t=1549989583; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=QONQxq6NqJ1WQyN3EWBcAnyyjiKu2fZbxNpfP8BUfQw=; b=L9qVsApfysCu2oX2ycOKEAIsoSsfsL401tm3A5JhTNcfPRycrN/SU3q03Yg8CacL iUWr90rd4XwT+bw/1d13ahfJRucia0Sc1lYrTbPfbF243/9D/sIIqLWAb7mYBFB4+aK Iz4Mws7VxD3GCLqKnJO1/FdcgEhND4r84guKpcFE= Date: Tue, 12 Feb 2019 16:39:43 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: John Hubbard cc: Jason Gunthorpe , Ira Weiny , Dan Williams , Jan Kara , Dave Chinner , Doug Ledford , Matthew Wilcox , lsf-pc@lists.linux-foundation.org, linux-rdma , Linux MM , Linux Kernel Mailing List , Jerome Glisse , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA In-Reply-To: <018c1a05-5fd8-886a-573b-42649949bba8@nvidia.com> Message-ID: <01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@email.amazonses.com> 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> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.02.12-54.240.9.31 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES 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 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. > > ie indicate to the FS that is should not attempt to remap physical > > memory addresses backing this VMA. If the FS can't do that it must > > fail. > > > > Yes. Duration is probably less important than the fact that the page > is specially treated. Yup.