From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757993AbXJOHfL (ORCPT ); Mon, 15 Oct 2007 03:35:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753370AbXJOHe6 (ORCPT ); Mon, 15 Oct 2007 03:34:58 -0400 Received: from moutng.kundenserver.de ([212.227.126.179]:63241 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753298AbXJOHe5 (ORCPT ); Mon, 15 Oct 2007 03:34:57 -0400 From: Arnd Bergmann To: Linus Torvalds , dm-devel@redhat.com, linux-kernel@vger.kernel.org, Milan Broz , Guido Guenther , Kevin Corry , stable@kernel.org Subject: Re: [2.6.24 PATCH 02/25] dm io:ctl use constant struct size Date: Mon, 15 Oct 2007 09:34:09 +0200 User-Agent: KMail/1.9.6 (enterprise 0.20070907.709405) References: <20071012170509.GM24157@agk.fab.redhat.com> <200710130016.29937.arnd@arndb.de> <20071015012621.GD10006@agk.fab.redhat.com> In-Reply-To: <20071015012621.GD10006@agk.fab.redhat.com> X-Face: >j"dOR3XO=^3iw?0`(E1wZ/&le9!.ok[JrI=S~VlsF~}"P\+jx.GT@=?utf-8?q?=0A=09-oaEG?=,9Ba>v;3>:kcw#yO5?B:l{(Ln.2)=?utf-8?q?=27=7Dfw07+4-=26=5E=7CScOpE=3F=5D=5EXdv=5B/zWkA7=60=25M!DxZ=0A=09?= =?utf-8?q?8MJ=2EU5?="hi+2yT(k`PF~Zt;tfT,i,JXf=x@eLP{7B:"GyA\=UnN) =?utf-8?q?=26=26qdaA=3A=7D-Y*=7D=3A3YvzV9=0A=09=7E=273a=7E7I=7CWQ=5D?=<50*%U-6Ewmxfzdn/CK_E/ouMU(r?FAQG/ev^JyuX.%(By`" =?utf-8?q?L=5F=0A=09H=3Dbj?=)"y7*XOqz|SS"mrZ$`Q_syCd MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200710150934.09842.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX1+BsTMZViqlbdo0aOt0xOIWQEX23g/ysWqG0sZ 2PVWQpSferO3ew3r0GuMS/5iIxqGoI3Gfz+s5DrnWan3O4psUZ 8Hkrs+YUQeuOe1adxMdGw== Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 15 October 2007, Alasdair G Kergon wrote: > The underlying ABI is not changing, I hope - the trailing padding in the > struct should not affect the processing of the data by dm, and I see no > reason to continue maintaining the fiction that the 32-bit and 64-bit > ioctls are in some way incompatible with each other when they aren't > AFAIK. It's a corner case of some sort, as DM uses ioctl numbers differently from most subsystems by splitting to code from the size argument during processing. Your change is certainly not an _incompatible_ change to the ABI, but 32 bit binaries compiled against the new headers will use different ioctl numbers from those built against older headers. This may break other code that expects a specific number, even if your handler does not care. The old compat code handles both variants (no variable size arguments), but /usr/bin/strace may have encoded only one set of numbers AFAICT. > And yes, a follow-up patch can clean up our use of the compatibility > mechanism, going a little bit further than the patch you attached, I > hope. Ok, sounds good. I don't think it's the kind of patch that should go into stable backports though. Arnd <><