From: Ric Wheeler Subject: Re: [PATCH v2] ext4: Deprecate data=journal mount option Date: Fri, 12 Aug 2011 09:25:24 +0100 Message-ID: <4E44E374.7080103@redhat.com> References: <1309260363-19012-1-git-send-email-lczerner@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Andreas Dilger , linux-ext4 List , "Theodore Ts'o" , Jan Kara , Eric Sandeen To: Lukas Czerner Return-path: Received: from mx1.redhat.com ([209.132.183.28]:14863 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750992Ab1HLIZi (ORCPT ); Fri, 12 Aug 2011 04:25:38 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On 08/12/2011 09:16 AM, Lukas Czerner wrote: > On Thu, 11 Aug 2011, Andreas Dilger wrote: > >> On 2011-08-11, at 9:01 AM, Lukas Czerner wrote: >>> On Tue, 28 Jun 2011, Lukas Czerner wrote: >>>> Data journalling mode (data=journal) is known to be neglected by >>>> developers and only minority of people is actually using it. This >>>> mode is also less tested than the other two modes by the developers. >>>> >>>> This creates a dangerous combination, because the option which seems >>>> *safer* is actually less safe the others. So this commit adds a warning >>>> message in case that data=journal mode is used, so the user is informed >>>> that the mode might be removed in the future. >>> Any comments on this ? Is that feasible to remove is someday ? >> I'm less in favour of removing data=journal. Jan made some fixes to >> data=journal mode in the last few weeks, which means that people are >> still using this. > I think that Jan was actually the one who was in favour of this change > IIRC. But you're right that there are still some (very little possibly?) > users of this. But this change does not remove it, but just let the > users know that it might be removed someday, hence discouraging them from > using it. > > Also we were discussing that several times, so I think that letting > users know that we are considering it is a good thing. > > Thanks! > -Lukas I think that this will be very useful to have - users should definitely chime in when they see this warning if they are using data journal mode. The only work load that I know that benefits from a performance point of view is one which involves an fsync() heavy, small file creation workload. Any workload with larger files tends to lose roughly 50% of the write bandwidth under streaming writes since we end up writing everything twice. Regards, Ric > >>>> Signed-off-by: Lukas Czerner >>>> --- >>>> fs/ext4/super.c | 5 +++++ >>>> 1 files changed, 5 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >>>> index 9ea71aa..9d189cf 100644 >>>> --- a/fs/ext4/super.c >>>> +++ b/fs/ext4/super.c >>>> @@ -1631,6 +1631,11 @@ static int parse_options(char *options, struct super_block *sb, >>>> sbi->s_min_batch_time = option; >>>> break; >>>> case Opt_data_journal: >>>> + ext4_msg(sb, KERN_WARNING, >>>> + "Using data=journal may be removed in the " >>>> + "future. Please, contact " >>>> + "linux-ext4@vger.kernel.org if you are " >>>> + "using this feature."); >>>> data_opt = EXT4_MOUNT_JOURNAL_DATA; >>>> goto datacheck; >>>> case Opt_data_ordered: >>>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> Cheers, Andreas >> >> >> >> >> >>