From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90E17C43441 for ; Wed, 10 Oct 2018 18:52:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55C522085B for ; Wed, 10 Oct 2018 18:52:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55C522085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727267AbeJKCQN (ORCPT ); Wed, 10 Oct 2018 22:16:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:54468 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726911AbeJKCQM (ORCPT ); Wed, 10 Oct 2018 22:16:12 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 90104ADBD; Wed, 10 Oct 2018 18:52:44 +0000 (UTC) Date: Wed, 10 Oct 2018 20:52:42 +0200 From: Michal Hocko To: Alexander Duyck Cc: Dan Williams , Linux MM , Andrew Morton , Linux Kernel Mailing List , linux-nvdimm , Pasha Tatashin , Dave Hansen , =?iso-8859-1?B?Suly9G1l?= Glisse , rppt@linux.vnet.ibm.com, Ingo Molnar , "Kirill A. Shutemov" , yi.z.zhang@linux.intel.com Subject: Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Message-ID: <20181010185242.GP5873@dhcp22.suse.cz> References: <20180925200551.3576.18755.stgit@localhost.localdomain> <20180925202053.3576.66039.stgit@localhost.localdomain> <20181009170051.GA40606@tiger-server> <25092df0-b7b4-d456-8409-9c004cb6e422@linux.intel.com> <20181010095838.GG5873@dhcp22.suse.cz> <20181010172451.GK5873@dhcp22.suse.cz> <98c35e19-13b9-0913-87d9-b3f1ab738b61@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <98c35e19-13b9-0913-87d9-b3f1ab738b61@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 10-10-18 10:39:01, Alexander Duyck wrote: > On 10/10/2018 10:24 AM, Michal Hocko wrote: [...] > > I thought I have already made it clear that these zone device hacks are > > not acceptable to the generic hotplug code. If the current reserve bit > > handling is not correct then give us a specific reason for that and we > > can start thinking about the proper fix. > > I might have misunderstood your earlier comment then. I thought you were > saying that we shouldn't bother with setting the reserved bit. Now it sounds > like you were thinking more along the lines of what I was here in my comment > where I thought the bit should be cleared later in some code specifically > related to DAX when it is exposing it for use to userspace or KVM. It seems I managed to confuse myself completely. Sorry, it's been a long day and I am sick so the brain doesn't work all that well. I will get back to this tomorrow or on Friday with a fresh brain. My recollection was that we do clear the reserved bit in move_pfn_range_to_zone and we indeed do in __init_single_page. But then we set the bit back right afterwards. This seems to be the case since d0dc12e86b319 which reorganized the code. I have to study this some more obviously. -- Michal Hocko SUSE Labs