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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id 64sm9553472pff.101.2019.02.06.10.52.34 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 06 Feb 2019 10:52:34 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1grSJF-0004c2-Pk; Wed, 06 Feb 2019 11:52:33 -0700 Date: Wed, 6 Feb 2019 11:52:33 -0700 From: Jason Gunthorpe To: Matthew Wilcox Cc: Doug Ledford , Jan Kara , Ira Weiny , lsf-pc@lists.linux-foundation.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard , Jerome Glisse , Dan Williams , Dave Chinner , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190206185233.GE12227@ziepe.ca> References: <20190205175059.GB21617@iweiny-DESK2.sc.intel.com> <20190206095000.GA12006@quack2.suse.cz> <20190206173114.GB12227@ziepe.ca> <20190206175233.GN21860@bombadil.infradead.org> <47820c4d696aee41225854071ec73373a273fd4a.camel@redhat.com> <20190206183503.GO21860@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190206183503.GO21860@bombadil.infradead.org> 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 Wed, Feb 06, 2019 at 10:35:04AM -0800, Matthew Wilcox wrote: > > Admittedly, I'm coming in late to this conversation, but did I miss the > > portion where that alternative was ruled out? > > That's my preferred option too, but the preponderance of opinion leans > towards "We can't give people a way to make files un-truncatable". I haven't heard an explanation why blocking ftruncate is worse than giving people a way to break RDMA using process by calling ftruncate?? Isn't it exactly the same argument the other way? Jason