From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com ([209.85.213.176]:35769 "EHLO mail-ig0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754718AbbLPMNI (ORCPT ); Wed, 16 Dec 2015 07:13:08 -0500 Received: by mail-ig0-f176.google.com with SMTP id to4so61414493igc.0 for ; Wed, 16 Dec 2015 04:13:07 -0800 (PST) Subject: Re: [PATCH v3] btrfs: Introduce new mount option to disable tree log replay To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org References: <1449714846-18174-1-git-send-email-quwenruo@cn.fujitsu.com> <20151214173200.GO4227@twin.jikos.cz> <5670C017.5010104@cn.fujitsu.com> From: "Austin S. Hemmelgarn" Message-ID: <56715518.8080808@gmail.com> Date: Wed, 16 Dec 2015 07:12:08 -0500 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2015-12-16 06:10, Duncan wrote: > Qu Wenruo posted on Wed, 16 Dec 2015 09:36:23 +0800 as excerpted: > >> David Sterba wrote on 2015/12/14 18:32 +0100: >>> On Thu, Dec 10, 2015 at 10:34:06AM +0800, Qu Wenruo wrote: >>>> Introduce a new mount option "nologreplay" to co-operate with "ro" >>>> mount option to get real readonly mount, like "norecovery" in ext* and >>>> xfs. >>>> >>>> Since the new parse_options() need to check new flags at remount time, >>>> so add a new parameter for parse_options(). >>>> >>>> Signed-off-by: Qu Wenruo >>>> Reviewed-by: Chandan Rajendra >>>> Tested-by: Austin S. Hemmelgarn >>> >>> I've read the discussions around the change and from the user's POV I'd >>> suggest to add another mount option that would be just an alias for any >>> mount options that would implement the 'hard-ro' semantics. >>> >>> Say it's called 'nowr'. Now it would imply 'nologreplay', but may cover >>> more options in the future. >>> >>> mount -o ro,nowr /dev/sdx /mnt >>> >>> would work when switching kernels. >>> >>> >> That would be nice. >> >> I'd like to forward the idea/discussion to filesystem ml, not only btrfs >> maillist. >> >> Such behavior should better be coordinated between all(at least xfs and >> ext4 and btrfs) filesystems. >> >> One sad example is, we can't use 'norecovery' mount option to disable >> log replay in btrfs, as there is 'recovery' mount option already. >> >> So I hope we can have a unified mount option between mainline >> filesystems. > > FWIW, I was just reading the mount manpage in connection with a reply for > a different thread, and noticed... > > mount (8) (from util-linux 2.27.1) says noload and norecovery are the > same option, for ext3/4 at least. It refers to the xfs (5) manpage, from > xfsprogs, for xfs mount options, and that's not installed here, so I > can't confirm noload for it, but it's there for ext3/4. Unless it's undocumented, XFS doesn't have it (as much as I hate XFS, I have to have xfsprogs installed so that I can do recovery for the few systems at work that actually use it if the need arises). > > And noload doesn't have the namespace collision problem norecovery does > on btrfs, so I'd strongly suggest using it, at least as an alias for > whatever other btrfs-specific name we might choose. I kind of agree with Christoph here. I don't think that noload should be the what we actually use, although I do think having it as an alias for whatever name we end up using would be a good thing.