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[54.240.9.36]) by mx.google.com with ESMTPS id y14si2681615qvc.45.2019.03.13.12.21.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 13 Mar 2019 12:21:38 -0700 (PDT) Received-SPF: pass (google.com: domain of 010001697880bfdc-4503d0dd-03cd-4c91-84a0-c18af1eab145-000000@amazonses.com designates 54.240.9.36 as permitted sender) client-ip=54.240.9.36; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw header.b=aVKPXXb2; spf=pass (google.com: domain of 010001697880bfdc-4503d0dd-03cd-4c91-84a0-c18af1eab145-000000@amazonses.com designates 54.240.9.36 as permitted sender) smtp.mailfrom=010001697880bfdc-4503d0dd-03cd-4c91-84a0-c18af1eab145-000000@amazonses.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw; d=amazonses.com; t=1552504897; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=SfWdjvUkwZe+2Dd4vugu5sfhOkXcR0c1mSWLWevFMhQ=; b=aVKPXXb2dmDsuNCuoE242Hhb6DL9Dz/3VVvfCRCmcoewVXQ6E4W2y6kaNFzmhegf 51+NZvO/T47ln0z/M/zfOaOCUdoOyyj+3J/3laE7SgaayKBr3K6nkMnGUYrJyPUO6C/ SnwSnQZll03tXHxBP9oj1tuhomYOFHWeP3Zt4SD8= Date: Wed, 13 Mar 2019 19:21:37 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Christoph Hellwig cc: Dave Chinner , Ira Weiny , john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Dan Williams , Dennis Dalessandro , Doug Ledford , Jan Kara , Jason Gunthorpe , Jerome Glisse , Matthew Wilcox , Michal Hocko , Mike Rapoport , Mike Marciniszyn , Ralph Campbell , Tom Talpey , LKML , linux-fsdevel@vger.kernel.org, John Hubbard Subject: Re: [PATCH v3 0/1] mm: introduce put_user_page*(), placeholder versions In-Reply-To: <20190313160319.GA15134@infradead.org> Message-ID: <010001697880bfdc-4503d0dd-03cd-4c91-84a0-c18af1eab145-000000@email.amazonses.com> References: <20190306235455.26348-1-jhubbard@nvidia.com> <010001695b4631cd-f4b8fcbf-a760-4267-afce-fb7969e3ff87-000000@email.amazonses.com> <20190310224742.GK26298@dastard> <01000169705aecf0-76f2b83d-ac18-4872-9421-b4b6efe19fc7-000000@email.amazonses.com> <20190312103932.GD1119@iweiny-DESK2.sc.intel.com> <20190312221113.GF23020@dastard> <20190313160319.GA15134@infradead.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.03.13-54.240.9.36 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 Wed, 13 Mar 2019, Christoph Hellwig wrote: > On Wed, Mar 13, 2019 at 09:11:13AM +1100, Dave Chinner wrote: > > On Tue, Mar 12, 2019 at 03:39:33AM -0700, Ira Weiny wrote: > > > IMHO I don't think that the copy_file_range() is going to carry us through the > > > next wave of user performance requirements. RDMA, while the first, is not the > > > only technology which is looking to have direct access to files. XDP is > > > another.[1] > > > > Sure, all I doing here was demonstrating that people have been > > trying to get local direct access to file mappings to DMA directly > > into them for a long time. Direct Io games like these are now > > largely unnecessary because we now have much better APIs to do > > zero-copy data transfer between files (which can do hardware offload > > if it is available!). > > And that is just the file to file case. There are tons of other > users of get_user_pages, including various drivers that do large > amounts of I/O like video capture. For them it makes tons of sense > to transfer directly to/from a mmap()ed file. That is very similar to the RDMA case and DAX etc. We need to have a way to tell a filesystem that this is going to happen and that things need to be setup for this to work properly. But if that has not been done then I think its proper to fail a long term pin operation on page cache pages. Meaning the regular filesystems maintain control of whats happening with their pages.