From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932265AbdKCJAJ (ORCPT ); Fri, 3 Nov 2017 05:00:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:55119 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755752AbdKCJAC (ORCPT ); Fri, 3 Nov 2017 05:00:02 -0400 Date: Fri, 3 Nov 2017 09:59:58 +0100 From: Michal Hocko To: Pavel Tatashin Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, akpm@linux-foundation.org, mgorman@techsingularity.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 1/1] mm: buddy page accessed before initialized Message-ID: <20171103085958.pewhlyvkr5oa2fgf@dhcp22.suse.cz> References: <20171031155002.21691-1-pasha.tatashin@oracle.com> <20171031155002.21691-2-pasha.tatashin@oracle.com> <20171102133235.2vfmmut6w4of2y3j@dhcp22.suse.cz> <20171102135423.voxnzk2qkvfgu5l3@dhcp22.suse.cz> <94ab73c0-cd18-f58f-eebe-d585fde319e4@oracle.com> <20171102140830.z5uqmrurb6ohfvlj@dhcp22.suse.cz> <813ed7e3-9347-a1f2-1629-464d920f877d@oracle.com> <20171102142742.gpkif3hgnd62nyol@dhcp22.suse.cz> <8b3bb799-818b-b6b6-7c6b-9eee709decb7@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8b3bb799-818b-b6b6-7c6b-9eee709decb7@oracle.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 02-11-17 12:10:39, Pavel Tatashin wrote: > > > > > > Yes, but as I said, unfortunately memset(1) with CONFIG_VM_DEBUG does not > > > catch this case. So, when CONFIG_VM_DEBUG is enabled kexec reboots without > > > issues. > > > > Can we make the init pattern to catch this? > > Unfortunately, that is not easy: memset() gives us only one byte to play > with, and if we use something else that will make CONFIG_VM_DEBUG > unacceptably slow. Why cannot we do something similar to the optimized struct page initialization and write 8B at the time and fill up the size unaligned chunk in 1B? -- Michal Hocko SUSE Labs