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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id 6sm1139978pfv.30.2019.02.04.09.51.11 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Feb 2019 09:51:11 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gqiOk-0003oc-Or; Mon, 04 Feb 2019 10:51:10 -0700 Date: Mon, 4 Feb 2019 10:51:10 -0700 From: Jason Gunthorpe To: Christopher Lameter Cc: john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Christoph Hellwig , Dan Williams , Dave Chinner , Dennis Dalessandro , Doug Ledford , Jan Kara , 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 0/6] RFC v2: mm: gup/dma tracking Message-ID: <20190204175110.GA10237@ziepe.ca> References: <20190204052135.25784-1-jhubbard@nvidia.com> <01000168b980e880-a7d8e0db-84fb-4398-8269-149c66b701b4-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01000168b980e880-a7d8e0db-84fb-4398-8269-149c66b701b4-000000@email.amazonses.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 Mon, Feb 04, 2019 at 05:14:19PM +0000, Christopher Lameter wrote: > Frankly I still think this does not solve anything. > > Concurrent write access from two sources to a single page is simply wrong. > You cannot make this right by allowing long term RDMA pins in a filesystem > and thus the filesystem can never update part of its files on disk. Fundamentally this patch series is fixing O_DIRECT to not crash the kernel in extreme cases.. RDMA has the same problem, but it is much easier to hit. I think questions related to RDMA are somewhat separate, and maybe it should be blocked, or not, but either way O_DIRECT has to be fixed. Jason