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[209.85.220.65]) by mx.google.com with SMTPS id w26sor10913718qth.47.2019.03.12.08.53.09 for (Google Transport Security); Tue, 12 Mar 2019 08:53:09 -0700 (PDT) Received-SPF: pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@ziepe.ca header.s=google header.b=dbPP9lBM; spf=pass (google.com: domain of jgg@ziepe.ca designates 209.85.220.65 as permitted sender) smtp.mailfrom=jgg@ziepe.ca DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=QcPGxotBvu4iLj90nikA7ZEmDk5xqgqrWN30Zzt/GHo=; b=dbPP9lBM9Vpwl8UqgK2FiG73wqfxxhFr5e/jw73ZhZcIhH6CkbAN6oCvQDucYiWs5I JDALIPaDkwHb9EbDQOT2uIcCJchKq5aPZRNB+scgKHVFC8HZwrEMpA+W4lU0Fb1Vx7qV aq/C8eg1BT488SLziv9InsoOWyVPjr0B+KEaidQrgJH3iJpsAYV7a/nHR4BVRH6NXQoK ZqK6wD7Ox7rAvobJjG2GPPrEUhdKDozEkuDMO1KsUBEfGcWVTg8yl1yk6lpURTBJiYp8 TFAty+mWGYB7KnRqfP3UkkDJdWQjjlSll/wWP6+tv3C+L2De8lgUqO+G7NZV7xowViW0 cOpw== X-Google-Smtp-Source: APXvYqx+bB0cu7zBn/5pp5qfiV/PWk0wKQn1c5Yq7D+NffNMoWoccLsBRobU7B2oICXVHxWT2ZqYPA== X-Received: by 2002:ac8:5297:: with SMTP id s23mr29738624qtn.371.1552405989409; Tue, 12 Mar 2019 08:53:09 -0700 (PDT) Received: from ziepe.ca ([24.137.65.181]) by smtp.gmail.com with ESMTPSA id h18sm4893517qkj.50.2019.03.12.08.53.08 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 12 Mar 2019 08:53:08 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1h3jiF-0002rT-AW; Tue, 12 Mar 2019 12:53:07 -0300 Date: Tue, 12 Mar 2019 12:53:07 -0300 From: Jason Gunthorpe To: Jerome Glisse Cc: Christopher Lameter , john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Christoph Hellwig , Dan Williams , Dave Chinner , Dennis Dalessandro , Doug Ledford , Ira Weiny , Jan Kara , 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 Message-ID: <20190312155307.GD20037@ziepe.ca> References: <20190306235455.26348-1-jhubbard@nvidia.com> <010001695b4631cd-f4b8fcbf-a760-4267-afce-fb7969e3ff87-000000@email.amazonses.com> <20190308190704.GC5618@redhat.com> <01000169703e5495-2815ba73-34e8-45d5-b970-45784f653a34-000000@email.amazonses.com> <20190312153528.GB3233@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190312153528.GB3233@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) 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, Mar 12, 2019 at 11:35:29AM -0400, Jerome Glisse wrote: > > > > Yes you now have the filesystem as well as the GUP pinner claiming > > > > authority over the contents of a single memory segment. Maybe better not > > > > allow that? > > > > > > This goes back to regressing existing driver with existing users. > > > > There is no regression if that behavior never really worked. > > Well RDMA driver maintainer seems to report that this has been a valid > and working workload for their users. I think it is more O_DIRECT that is the history here.. In RDMA land long term GUPs of file backed pages tend to crash the kernel (what John is trying to fix here) so I'm not sure there are actual real & tested users, only people that wish they could do this.. Jason