From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162817AbdD0Qdr (ORCPT ); Thu, 27 Apr 2017 12:33:47 -0400 Received: from ale.deltatee.com ([207.54.116.67]:57168 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S938536AbdD0Qdj (ORCPT ); Thu, 27 Apr 2017 12:33:39 -0400 To: Dan Williams References: <20170423233125.nehmgtzldgi25niy@node.shutemov.name> <149325431313.40660.7404075559824162131.stgit@dwillia2-desk3.amr.corp.intel.com> <3e595ba6-2ea1-e25d-e254-6c7edcf23f88@deltatee.com> Cc: Andrew Morton , Linux MM , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , "linux-kernel@vger.kernel.org" , Kirill Shutemov From: Logan Gunthorpe Message-ID: Date: Thu, 27 Apr 2017 10:33:37 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.111 X-SA-Exim-Rcpt-To: kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, jglisse@redhat.com, linux-mm@kvack.org, akpm@linux-foundation.org, dan.j.williams@intel.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH] mm, zone_device: replace {get, put}_zone_device_page() with a single reference X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/04/17 10:14 AM, Dan Williams wrote: > You're overlooking that the page reference count 1 after > arch_add_memory(). So at the end of time we're just dropping the > arch_add_memory() reference to release the page and related > dev_pagemap. Thanks, that does actually make a lot more sense to me now. However, there still appears to be an asymmetry in that the pgmap->ref is incremented once and decremented once per page... Logan