From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id DBA836B0003 for ; Wed, 10 Oct 2018 14:52:46 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id e7-v6so3641899edb.23 for ; Wed, 10 Oct 2018 11:52:46 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id z2-v6si1783703ejg.230.2018.10.10.11.52.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Oct 2018 11:52:45 -0700 (PDT) Date: Wed, 10 Oct 2018 20:52:42 +0200 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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