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[192.55.52.151]) by mx.google.com with ESMTPS id i13si8941555pgj.199.2019.02.07.08.54.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 Feb 2019 08:54:26 -0800 (PST) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.151 as permitted sender) client-ip=192.55.52.151; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.151 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Feb 2019 08:54:25 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,344,1544515200"; d="scan'208";a="142417351" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga004.fm.intel.com with ESMTP; 07 Feb 2019 08:54:24 -0800 Date: Thu, 7 Feb 2019 08:54:08 -0800 From: Ira Weiny To: Jason Gunthorpe Cc: Dave Chinner , Doug Ledford , Christopher Lameter , Matthew Wilcox , Jan Kara , 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 , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190207165407.GA29531@iweiny-DESK2.sc.intel.com> References: <20190206095000.GA12006@quack2.suse.cz> <20190206173114.GB12227@ziepe.ca> <20190206175233.GN21860@bombadil.infradead.org> <47820c4d696aee41225854071ec73373a273fd4a.camel@redhat.com> <01000168c43d594c-7979fcf8-b9c1-4bda-b29a-500efe001d66-000000@email.amazonses.com> <20190206210356.GZ6173@dastard> <20190206220828.GJ12227@ziepe.ca> <0c868bc615a60c44d618fb0183fcbe0c418c7c83.camel@redhat.com> <20190207035258.GD6173@dastard> <20190207052310.GA22726@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190207052310.GA22726@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) 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 10:23:10PM -0700, Jason Gunthorpe wrote: > On Thu, Feb 07, 2019 at 02:52:58PM +1100, Dave Chinner wrote: > > > Requiring ODP capable hardware and applications that control RDMA > > access to use file leases and be able to cancel/recall client side > > delegations (like NFS is already able to do!) seems like a pretty > > So, what happens on NFS if the revoke takes too long? This is the fundamental issue with RDMA revoke. With RDMA and some hardware you are going to end up killing processes. If the decision is that only processes on non-ODP hardware get killed and the user basically "should not have done that" then I'm ok with that. However, then we really need to prevented them from registering the memory in the first place. Which means we leave in the "longterm" GUP registration and fail those registrations can't be supported. Ira