From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id B074E8E0001 for ; Wed, 12 Sep 2018 08:21:34 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id z30-v6so795215edd.19 for ; Wed, 12 Sep 2018 05:21:34 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w7-v6si518025edd.362.2018.09.12.05.21.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 12 Sep 2018 05:21:33 -0700 (PDT) Date: Wed, 12 Sep 2018 14:21:32 +0200 From: Michal Hocko Subject: Re: [PATCH] memory_hotplug: fix the panic when memory end is not on the section boundary Message-ID: <20180912122132.GF10951@dhcp22.suse.cz> References: <20180910123527.71209-1-zaslonko@linux.ibm.com> <20180910131754.GG10951@dhcp22.suse.cz> <04b427ad-df4e-67bd-2942-2a7a2cccf1aa@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04b427ad-df4e-67bd-2942-2a7a2cccf1aa@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Zaslonko Mikhail Cc: Mikhail Zaslonko , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pavel.Tatashin@microsoft.com, osalvador@suse.de, gerald.schaefer@de.ibm.com On Tue 11-09-18 16:06:23, Zaslonko Mikhail wrote: [...] > > Well, I am afraid this is not the proper solution. We are relying on the > > full pageblock worth of initialized struct pages at many other place. We > > used to do that in the past because we have initialized the full > > section but this has been changed recently. Pavel, do you have any ideas > > how to deal with this partial mem sections now? > > I think this is not related to the recent changes of memory initialization. > If > you mean deferred init case, the problem exists even without > CONFIG_DEFERRED_STRUCT_PAGE_INIT kernel option. This is more about struct page initialization (which doesn't clear whole) memmap area and as such it stays unitialized. So you are right this is a much older issue we just happened to not notice without explicit memmap poisoning. -- Michal Hocko SUSE Labs