From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753088Ab3KOO0v (ORCPT ); Fri, 15 Nov 2013 09:26:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37980 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751512Ab3KOO0n (ORCPT ); Fri, 15 Nov 2013 09:26:43 -0500 Date: Fri, 15 Nov 2013 09:26:17 -0500 From: Vivek Goyal To: HATAYAMA Daisuke Cc: Baoquan He , Kexec Mailing List , linux kernel mailing list , Atsushi Kumagai , "Eric W. Biederman" , Dave Young , WANG Chao Subject: Re: /proc/vmcore mmap() failure issue Message-ID: <20131115142617.GC6637@redhat.com> References: <20131113204130.GD7613@redhat.com> <5284A689.70903@jp.fujitsu.com> <20131114151359.GA3913@redhat.com> <5285EC60.1060906@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5285EC60.1060906@jp.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 15, 2013 at 06:41:52PM +0900, HATAYAMA Daisuke wrote: [..] > >Given the fact that hpa does not like fixing it in kernel. We are left > >with option of fixing it in following places. > > > >- Drop partial pages in kexec-tools > >- Drop partial pages in makeudmpfile. > >- Read partial pages using read() interface in makedumpfile > >- Modify /proc/vmcore to copy partial pages in second kernel's memory. > > > >It is not clear to me that partial pages are really useful. So I want > >to avoid modifying /proc/vmcore to deal with partial pages and increase > >complexity. > > > >So fixing makedumpfile (either option2 or option 3) seems least risky > >to me. In fact I would say let us keep it simple and truncate partial > >pages in makedumpfile to keep it simple. And look at option 3 once we > >have a strong use case for partial pages. > > > >What do you think? > > > > As you say, it's not clear that partial pages are really useful, but on > the other hand, it seems to me not clear that they are really useless. > I think we should get them as long as we have access to them. > > It seems best to me the option 3). Switching between read and mmap would > be not so complex and also it's by far flexible in makedumpfile than in > kernel. Ok, I am fine with option 3. It is more complicated option but safe option. Is there any chance that you could look into fixing this. I have no experience writing code for makedumpfile. Thanks Vivek