From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751893AbdF3Pma (ORCPT ); Fri, 30 Jun 2017 11:42:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:50231 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751322AbdF3Pm3 (ORCPT ); Fri, 30 Jun 2017 11:42:29 -0400 Date: Fri, 30 Jun 2017 17:42:24 +0200 From: Michal Hocko To: Yang Shi Cc: Joonsoo Kim , Mel Gorman , Andrew Morton , Vlastimil Babka , linux-mm@kvack.org, LKML Subject: Re: "mm: use early_pfn_to_nid in page_ext_init" broken on some configurations? Message-ID: <20170630154224.GA9714@dhcp22.suse.cz> References: <20170630141847.GN22917@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170630141847.GN22917@dhcp22.suse.cz> 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 On Fri 30-06-17 16:18:47, Michal Hocko wrote: > fe53ca54270a ("mm: use early_pfn_to_nid in page_ext_init") seem > to silently depend on CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID resp. > CONFIG_HAVE_MEMBLOCK_NODE_MAP. early_pfn_to_nid is returning zero with > !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) > I am not sure how widely is this used but such a code is tricky. I see > how catching early allocations during defered initialization might be > useful but a subtly broken code sounds like a problem to me. So is > fe53ca54270a worth this or we should revert it? I've dug little bit further. It seems that only s390 and ia64 select HAVE_ARCH_EARLY_PFN_TO_NID. Much more architectures enabled HAVE_MEMBLOCK_NODE_MAP though but still alpha, arc, arm, avr32, blackfin, c6x, cris, frv, h8300, hexagon, Kconfig, m32r, m68k, mn10300, nios2, openrisc, parisc, tile, um, unicore32, xtensa do not. I can only see alpha having NUMA and even that is marked BROKEN. So it seems that this is not a real problem after all. Still subtle, so I guess we want to have the following. What do you think? diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 16532fa0bb64..894697c1e6f5 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1055,6 +1055,7 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist, !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) static inline unsigned long early_pfn_to_nid(unsigned long pfn) { + BUILD_BUG_ON(!IS_ENABLED(CONFIG_NUMA)); return 0; } #endif -- Michal Hocko SUSE Labs