Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752133AbdDDHXf (ORCPT ); Tue, 4 Apr 2017 03:23:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:44501 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877AbdDDHXd (ORCPT ); Tue, 4 Apr 2017 03:23:33 -0400 Date: Tue, 4 Apr 2017 09:23:29 +0200 From: Michal Hocko To: Reza Arbab , Gary Hade Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Yasuaki Ishimatsu , Tang Chen , qiuxishi@huawei.com, Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Andi Kleen , Zhang Zhen , David Rientjes , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , LKML , Chris Metcalf , Dan Williams , Heiko Carstens , Lai Jiangshan , Martin Schwidefsky Subject: Re: [PATCH 0/6] mm: make movable onlining suck less Message-ID: <20170404072329.GA15132@dhcp22.suse.cz> References: <20170330115454.32154-1-mhocko@kernel.org> <20170403115545.GK24661@dhcp22.suse.cz> <20170403195830.64libncet5l6vuvb@arbab-laptop> <20170403202337.GA12482@dhcp22.suse.cz> <20170403204213.rs7k2cvsnconel2z@arbab-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170403204213.rs7k2cvsnconel2z@arbab-laptop> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2599 Lines: 66 [Let's add Gary who as introduced this code c04fc586c1a48] On Mon 03-04-17 15:42:13, Reza Arbab wrote: > On Mon, Apr 03, 2017 at 10:23:38PM +0200, Michal Hocko wrote: > >On Mon 03-04-17 14:58:30, Reza Arbab wrote: > >>However, I am seeing a regression. When adding memory to a memoryless > >>node, it shows up in node 0 instead. I'm digging to see if I can help > >>narrow down where things go wrong. > > > >OK, I guess I know what is going on here. online_pages relies on > >pfn_to_nid(pfn) to return a proper node. But we are doing > >page_to_nid(pfn_to_page(__pfn_to_nid_pfn)) so we rely on the page being > >properly initialized. Damn, I should have noticed that. There are two > >ways around that. Either the __add_section stores the nid into the > >struct page and make page_to_nid reliable or store it somewhere else > >(ideally into the memblock). The first is easier (let's do it for now) > >but longterm we do not want to rely on the struct page at all I believe. > > > >Does the following help? > >--- > >diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > >index b9dc1c4e26c3..0e21b9f67c9d 100644 > >--- a/mm/memory_hotplug.c > >+++ b/mm/memory_hotplug.c > >@@ -309,14 +309,19 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn) > > > > /* > > * Make all the pages reserved so that nobody will stumble over half > >- * initialized state. > >+ * initialized state. > >+ * FIXME: We also have to associate it with a node because pfn_to_node > >+ * relies on having page with the proper node. > > */ > > for (i = 0; i < PAGES_PER_SECTION; i++) { > > unsigned long pfn = phys_start_pfn + i; > >+ struct page *page; > > if (!pfn_valid(pfn)) > > continue; > > > >- SetPageReserved(pfn_to_page(phys_start_pfn + i)); > >+ page = pfn_to_page(pfn); > >+ set_page_node(page, nid); > >+ SetPageReserved(page); > > } > > > > return register_new_memory(nid, __pfn_to_section(phys_start_pfn)); > > Almost there. I'm seeing the memory in the correct node now, but the > /sys/devices/system/node/nodeX/memoryY links are not being created. > > I think it's tripping up here, in register_mem_sect_under_node(): > > page_nid = get_nid_for_pfn(pfn); > if (page_nid < 0) > continue; Huh, this code is confusing. How can we have a memblock spanning more nodes? If not then the loop over all sections in the memblock seem pointless as well. Also why do we require page_initialized() in get_nid_for_pfn? The changelog doesn't explain that and there are no comments that would help either. Gary, could you clarify this please? -- Michal Hocko SUSE Labs