From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751529Ab0JBVmy (ORCPT ); Sat, 2 Oct 2010 17:42:54 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:38021 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255Ab0JBVmx (ORCPT ); Sat, 2 Oct 2010 17:42:53 -0400 From: "Rafael J. Wysocki" To: Nigel Cunningham Subject: Re: [RFC][PATCH] PM / Hibernate: Modify signature used to mark swap Date: Sat, 2 Oct 2010 23:41:30 +0200 User-Agent: KMail/1.13.5 (Linux/2.6.36-rc6-rjw+; KDE/4.4.4; x86_64; ; ) Cc: "Linux-pm mailing list" , LKML References: <201009292313.23601.rjw@sisk.pl> <201009300002.03412.rjw@sisk.pl> <4CA799C5.3060106@tuxonice.net> In-Reply-To: <4CA799C5.3060106@tuxonice.net> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201010022341.30789.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday, October 02, 2010, Nigel Cunningham wrote: > Hi. > > On 30/09/10 08:02, Rafael J. Wysocki wrote: > > On Wednesday, September 29, 2010, Nigel Cunningham wrote: > >> Hi. > >> > >> On 30/09/10 07:13, Rafael J. Wysocki wrote: > >>> From: Rafael J. Wysocki > >>> Subject: PM / Hibernate: Modify signature used to mark swap > >>> > >>> Since we are adding compression to the kernel's hibernate code, > >>> change signature used by it to mark swap spaces, so that earlier > >>> kernels don't attempt to restore compressed images they cannot > >>> handle. > >>> > >>> Signed-off-by: Rafael J. Wysocki > >>> --- > >>> kernel/power/swap.c | 6 +++--- > >>> 1 file changed, 3 insertions(+), 3 deletions(-) > >>> > >>> Index: linux-2.6/kernel/power/swap.c > >>> =================================================================== > >>> --- linux-2.6.orig/kernel/power/swap.c > >>> +++ linux-2.6/kernel/power/swap.c > >>> @@ -29,7 +29,7 @@ > >>> > >>> #include "power.h" > >>> > >>> -#define SWSUSP_SIG "S1SUSPEND" > >>> +#define HIBERNATE_SIG "LINHIB0001" > >>> > >>> /* > >>> * The swap map is a data structure used for keeping track of each page > >>> @@ -195,7 +195,7 @@ static int mark_swapfiles(struct swap_ma > >>> if (!memcmp("SWAP-SPACE",swsusp_header->sig, 10) || > >>> !memcmp("SWAPSPACE2",swsusp_header->sig, 10)) { > >>> memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10); > >> > >> if no compression > >> > >>> - memcpy(swsusp_header->sig,SWSUSP_SIG, 10); > >> > >> else > >> > >>> + memcpy(swsusp_header->sig, HIBERNATE_SIG, 10); > >> > >> ?? > > > > I thought about that, but we'll need to drop the old signature when the image > > format changes (I think it will after your patch series) anyway. And the > > benefit is not really worth it IMO (it only affects people using the in-kernel > > hibernation on x86-64). > > Okay. I'm just a little weary because if everything I want to get in > gets in, we're going to then be changing this signature multiple times. That most likely is correct. > I want to eventually reach a situation where we have a 'proper' header > section to the image that stores (among other things) whether > compression is enabled and which cryptoapi algorithm is used, allowing a > person to en/disable compression at runtime without recompiling or > rebooting. I suppose if I seek to put that stuff in earlier rather than > later, that will simplify things. I don't have a problem with changing the signature. If the image format changes, it's probably the best we can do. > Oh, while I'm writing to you: let's not worry about getting my patches > in for 2.6.37. I won't be working on them much today, and want to put > the time into making sure they're right before they get merged. As you > said - let's seek to get things right first time. OK Thanks, Rafael