From: Lukas Czerner Subject: Re: [PATCH v2] ext4: Deprecate data=journal mount option Date: Fri, 12 Aug 2011 18:08:21 +0200 (CEST) Message-ID: References: <1309260363-19012-1-git-send-email-lczerner@redhat.com>

<4E44E374.7080103@redhat.com> Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323328-1065660080-1313165306=:3088" Cc: Ric Wheeler , Lukas Czerner , Andreas Dilger , linux-ext4 List , "Theodore Ts'o" , Jan Kara , Eric Sandeen To: Curt Wohlgemuth Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36906 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750944Ab1HLQIn (ORCPT ); Fri, 12 Aug 2011 12:08:43 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323328-1065660080-1313165306=:3088 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT On Fri, 12 Aug 2011, Curt Wohlgemuth wrote: > I don't know much about data=journal, but I've been running xfstests > with it, and it's a disaster, given that data=journal doesn't support > O_DIRECT. What kind of testing do people do on data=journal? Short answer is probably none :). Even though that it seems like an radical answer I believe that it is mostly true, because simply said almost no-one care. But I think that Ted mentioned that he actually do some tests with that mode, but I am not sure about that. > > And worse, I consistently crash my machine running xfstests 074 on a > data=journal partition. I just repeated this to make sure, on > 3.1.0-rc1; I've also seen it with 3.0.0. There's a BUG_ON firing in > jbd2_journal_dirty_metadata(): > > [ 2174.697692] ------------[ cut here ]------------ > [ 2174.698627] kernel BUG at fs/jbd2/transaction.c:1112! > [ 2174.698627] invalid opcode: 0000 [#1] SMP > [ 2174.698627] CPU 11 > ... > [ 2174.698627] Call Trace: > [ 2174.698627] [] __ext4_handle_dirty_metadata+0x83/0x120 > [ 2174.698627] [] ? __ext4_journal_get_write_access+0x3e/0x80 > [ 2174.698627] [] __ext4_journalled_writepage+0x338/0x3e0 > [ 2174.698627] [] ext4_writepage+0x234/0x2f0 > [ 2174.698627] [] __writepage+0x17/0x40 > [ 2174.698627] [] write_cache_pages+0x1fe/0x650 > > This is at the J_ASSERT_JH below: > > /* > * Metadata already on the current transaction list doesn't > * need to be filed. Metadata on another transaction's list must > * be committing, and will be refiled once the commit completes: > * leave it alone for now. > */ > if (jh->b_transaction != transaction) { > JBUFFER_TRACE(jh, "already on other transaction"); > J_ASSERT_JH(jh, jh->b_transaction == > journal->j_committing_transaction); <=============== > J_ASSERT_JH(jh, jh->b_next_transaction == transaction); > /* And this case is illegal: we can't reuse another > * transaction's data buffer, ever. */ > goto out_unlock_bh; > } Wow, that backtrace seems like a flash-back to me I believe that I have seen it several times, probably in different modes and probably already fixed. Do no know about this one though. Thanks! -Lukas > > Curt > > On Fri, Aug 12, 2011 at 1:25 AM, Ric Wheeler wrote: > > 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 > >>> > >>> > >>> > >>> > >>> > >>> > > > > -- > > 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 > > > -- --8323328-1065660080-1313165306=:3088--