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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id t197sm1407918qke.2.2019.06.06.12.46.52 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 06 Jun 2019 12:46:52 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hYyLc-0007zs-5h; Thu, 06 Jun 2019 16:46:52 -0300 Date: Thu, 6 Jun 2019 16:46:52 -0300 From: Jason Gunthorpe To: Ira Weiny Cc: John Hubbard , Dan Williams , Jan Kara , Theodore Ts'o , Jeff Layton , Dave Chinner , Matthew Wilcox , linux-xfs@vger.kernel.org, Andrew Morton , =?utf-8?B?SsOpcsO0bWU=?= Glisse , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal Message-ID: <20190606194652.GI17373@ziepe.ca> References: <20190606014544.8339-1-ira.weiny@intel.com> <20190606171158.GB11374@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190606171158.GB11374@iweiny-DESK2.sc.intel.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 Thu, Jun 06, 2019 at 10:11:58AM -0700, Ira Weiny wrote: > 2) This is a bit more subtle and something I almost delayed sending these out > for. Currently the implementation of a lease break actually removes the > lease from the file. I did not want this to happen and I was thinking of > delaying this patch set to implement something which keeps the lease around > but I figured I should get something out for comments. Jan has proposed > something along these lines and I agree with him so I'm going to ask you to > read my response to him about the details. > > > Anyway so the key here is that currently an app needs the SIGIO to retake > the lease if they want to map the file again or in parts based on usage. > For example, they may only want to map some of the file for when they are > using it and then map another part later. Without the SIGIO they would lose > their lease or would have to just take the lease for each GUP pin (which > adds overhead). Like I said I did not like this but I left it to get > something which works out. So to be clear.. Even though the lease is broken the GUP remains, the pages remain pined, and truncate/etc continues to fail? I like Jan's take on this actually.. see other email. Jason