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[140.211.169.12]) by mx.google.com with ESMTPS id e129si33018609pgc.333.2019.01.28.13.10.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 13:10:58 -0800 (PST) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id E77252863; Mon, 28 Jan 2019 21:10:57 +0000 (UTC) Date: Mon, 28 Jan 2019 13:10:56 -0800 From: Andrew Morton To: Jason Gunthorpe Cc: Davidlohr Bueso , dledford@redhat.com, jack@suse.de, ira.weiny@intel.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Davidlohr Bueso , Christoph Lameter , Jan Kara , Daniel Jordan Subject: Re: [PATCH 1/6] mm: make mm->pinned_vm an atomic64 counter Message-Id: <20190128131056.101a126f222929318bb2ea83@linux-foundation.org> In-Reply-To: <20190123183353.GA15768@ziepe.ca> References: <20190121174220.10583-1-dave@stgolabs.net> <20190121174220.10583-2-dave@stgolabs.net> <20190123183353.GA15768@ziepe.ca> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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, 23 Jan 2019 11:33:53 -0700 Jason Gunthorpe wrote: > On Mon, Jan 21, 2019 at 09:42:15AM -0800, Davidlohr Bueso wrote: > > Taking a sleeping lock to _only_ increment a variable is quite the > > overkill, and pretty much all users do this. Furthermore, some drivers > > (ie: infiniband and scif) that need pinned semantics can go to quite > > some trouble to actually delay via workqueue (un)accounting for pinned > > pages when not possible to acquire it. > > > > By making the counter atomic we no longer need to hold the mmap_sem > > and can simply some code around it for pinned_vm users. The counter > > is 64-bit such that we need not worry about overflows such as rdma > > user input controlled from userspace. > > I see a number of MM people Reviewed-by this so are we good to take > this in the RDMA tree now? Please do.