Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755533Ab1BNOjU (ORCPT ); Mon, 14 Feb 2011 09:39:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:31352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755513Ab1BNOjT (ORCPT ); Mon, 14 Feb 2011 09:39:19 -0500 Date: Mon, 14 Feb 2011 14:39:04 +0000 From: Alasdair G Kergon To: Tejun Heo Cc: Milan Broz , Jens Axboe , Tao Ma , linux-kernel@vger.kernel.org, device-mapper development Subject: Re: [dm-devel] [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings Message-ID: <20110214143904.GB5825@agk-dp.fab.redhat.com> Mail-Followup-To: Tejun Heo , Milan Broz , Jens Axboe , Tao Ma , linux-kernel@vger.kernel.org, device-mapper development References: <4D573BBB.6090200@redhat.com> <1297594735-5593-1-git-send-email-tm@tao.ma> <4D57E67E.1030707@redhat.com> <4D57F357.6060708@tao.ma> <4D580A8B.5050508@redhat.com> <20110214103026.GA18742@htj.dyndns.org> <4D591664.6090203@redhat.com> <4D592AD1.6020500@redhat.com> <20110214140940.GM18742@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110214140940.GM18742@htj.dyndns.org> Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 813 Lines: 21 On Mon, Feb 14, 2011 at 03:09:40PM +0100, Tejun Heo wrote: > But if the underlying device is marked ro, dm shouldn't update it at > all. The device should be opened ro and ro policy should be enforced. Indeed, but dm isn't tracking this today because it didn't need to up-to now. I can think of a few scenarios where dm can have the underlying device open read-write when it only needs read-only. (E.g. we track and cater for read-only->read-write transitions but not the opposite and don't propagate changes through the stack.) We'll do an audit... Alasdair -- 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/