Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932107Ab3GOOWF (ORCPT ); Mon, 15 Jul 2013 10:22:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3078 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756708Ab3GOOWD (ORCPT ); Mon, 15 Jul 2013 10:22:03 -0400 Date: Mon, 15 Jul 2013 10:20:59 -0400 From: Vivek Goyal To: HATAYAMA Daisuke Cc: Michael Holzheu , Martin Schwidefsky , kexec@lists.infradead.org, Heiko Carstens , Jan Willeke , linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range() Message-ID: <20130715142059.GA23772@redhat.com> References: <1372707159-10425-1-git-send-email-holzheu@linux.vnet.ibm.com> <1372707159-10425-4-git-send-email-holzheu@linux.vnet.ibm.com> <51DA4ED9.60903@jp.fujitsu.com> <20130708112839.498ccfc6@holzheu> <20130708142826.GA9094@redhat.com> <51DBA47C.8090708@jp.fujitsu.com> <20130710104252.479a0f92@holzheu> <51DD2E5A.1030200@jp.fujitsu.com> <20130710143309.GD5819@redhat.com> <51DFE2FB.2000804@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51DFE2FB.2000804@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 Content-Length: 1469 Lines: 39 On Fri, Jul 12, 2013 at 08:05:31PM +0900, HATAYAMA Daisuke wrote: [..] > How about > > static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > { > ... > char *buf; > int rc; > > #ifndef CONFIG_S390 > return VM_FAULT_SIGBUS; > #endif > page = find_or_create_page(mapping, index, GFP_KERNEL); > > Considering again, I don't think WARN_ONCE() is good now. The fact that fault occurs on > mmap() region indicates some kind of buggy situation occurs on the process. The process > should be killed as soon as possible. If user still wants to get crash dump, he should > try again in another process. I don't understand that. Process should be killed only if there was no mapping created for the region process is trying to access. If there is a mapping but we are trying to fault in the actual contents, then it is not a problem of process. Process is accessing a region of memory which it is supposed to access. Potential problem here is that remap_pfn_range() did not map everything it was expected to so we have to resort on page fault handler to read that in. So it is more of a kernel issue and not process issue and for that WARN_ONCE() sounds better? Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/