From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 526D36B0279 for ; Tue, 4 Jul 2017 05:28:45 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id z81so45025312wrc.2 for ; Tue, 04 Jul 2017 02:28:45 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o2si12814635wmb.113.2017.07.04.02.28.43 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 04 Jul 2017 02:28:43 -0700 (PDT) Subject: Re: [PATCH] mm: disallow early_pfn_to_nid on configurations which do not implement it References: <20170704075803.15979-1-mhocko@kernel.org> From: Vlastimil Babka Message-ID: <61b4422c-34d7-f46b-2566-779f6a86d917@suse.cz> Date: Tue, 4 Jul 2017 11:28:42 +0200 MIME-Version: 1.0 In-Reply-To: <20170704075803.15979-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Andrew Morton Cc: Joonsoo Kim , Yang Shi , Mel Gorman , linux-mm@kvack.org, LKML , Michal Hocko On 07/04/2017 09:58 AM, Michal Hocko wrote: > From: Michal Hocko > > early_pfn_to_nid will return node 0 if both HAVE_ARCH_EARLY_PFN_TO_NID > and HAVE_MEMBLOCK_NODE_MAP are disabled. It seems we are safe now > because all architectures which support NUMA define one of them (with an > exception of alpha which however has CONFIG_NUMA marked as broken) so > this works as expected. It can get silently and subtly broken too > easily, though. Make sure we fail the compilation if NUMA is enabled and > there is no proper implementation for this function. If that ever > happens we know that either the specific configuration is invalid > and the fix should either disable NUMA or enable one of the above > configs. > > Signed-off-by: Michal Hocko Acked-by: Vlastimil Babka > --- > Hi, > I have brought this up earlier [1] because I thought the deferred > initialization might be broken but then found out that this is not the > case right now. This is an attempt to prevent any subtly broken users in > future. > > [1] http://lkml.kernel.org/r/20170630141847.GN22917@dhcp22.suse.cz > > include/linux/mmzone.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 16532fa0bb64..fc14b8b3f6ce 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 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org