From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:42018 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751414AbcISULZ (ORCPT ); Mon, 19 Sep 2016 16:11:25 -0400 Subject: Re: stability matrix To: Christoph Anton Mitterer , "Austin S. Hemmelgarn" , , References: <57D51BF9.2010907@online.no> <20160912142714.GE16983@twin.jikos.cz> <52304724-5bca-a1e6-527f-040085c7ab19@gmail.com> <20160912165107.GG16983@twin.jikos.cz> <58a954fc-bbd5-3fb5-9f23-008ed7f7121d@gmail.com> <20160915010759.GD32452@DigitalMercury.dynalias.net> <5dec6544a78a0301a8e0cd9086179f99@crc.id.au> <1473905644.8603.44.camel@scientia.net> <20160919152753.GG933@twin.jikos.cz> <1474314776.10189.24.camel@scientia.net> From: Chris Mason Message-ID: <7d60b7ae-7a5f-a386-9472-9237cacfb046@fb.com> Date: Mon, 19 Sep 2016 16:07:18 -0400 MIME-Version: 1.0 In-Reply-To: <1474314776.10189.24.camel@scientia.net> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/19/2016 03:52 PM, Christoph Anton Mitterer wrote: > On Mon, 2016-09-19 at 13:18 -0400, Austin S. Hemmelgarn wrote: >>>> - even mounting a fs ro, may cause it to be changed >>> >>> This would go to the UseCases >> My same argument about the UUID issues applies here, just without >> the >> security aspect. > > I personally could agree to have that "just" in the usecases. > > That a fs my be changed even though it's mounted ro is not unique to > btrfs.... and the need for not having that happen goes probably rather > into data-forensics and rescue use cases. > > IMO there's rather a general problem, namely that the different > filesystems don't provide a mount option that implies every other mount > options currently needed to get an actual "hard ro", i.e. one where the > device is never written to. > > Qu was about to add such option when nologreplay was added, but IIRC he > got some resistance by linux-fs, who probably didn't care enough > whether the end-user can easily do such "hard ro" mount ;) > > That's in the blockdev command (blockdev --setro /dev/xxx). We actually try to maintain the established norms where it doesn't conflict with the btrfs use cases. This is one of them ;) -chris