Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756202AbYGLDFM (ORCPT ); Fri, 11 Jul 2008 23:05:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752572AbYGLDE7 (ORCPT ); Fri, 11 Jul 2008 23:04:59 -0400 Received: from netrider.rowland.org ([192.131.102.5]:1904 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752363AbYGLDE7 (ORCPT ); Fri, 11 Jul 2008 23:04:59 -0400 Date: Fri, 11 Jul 2008 23:04:57 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: "Eric W. Biederman" cc: "Rafael J. Wysocki" , , Kexec Mailing List , , Pavel Machek , Andrew Morton , , Vivek Goyal Subject: Re: [linux-pm] [PATCH -mm 1/2] kexec jump -v12: kexec jump In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1286 Lines: 32 On Fri, 11 Jul 2008, Eric W. Biederman wrote: > I just realized with a little care the block layer does have support for this, > or something very close. > > You setup a software raid mirror with one disk device. The physical > device can come in and out while the filesystems depend on the real device. Do you mean "the filesystems depend on the logical RAID device"? What's to prevent userspace from accessing the physical device directly? What this amounts to, in the end, is having a way to distinguish the set of I/O requests coming from the hibernation code (reading or writing the memory image) from the set of all other I/O requests. The driver or the block layer has to be set up to allow the first set through while blocking the second set. (And don't forget about the complications caused by error-recovery I/O during the hibernation activity!) Forcing the second set of requests to filter through an extra software layer is a clumsy way of accomplishing this. There ought to be a better approach. Alan Stern -- 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/