Bug#615998: linux-image-2.6.32-5-xen-amd64: Repeatable "kernel BUG at fs/jbd2/commit.c:534" from Postfix on ext4
- To: Ted Ts'o <email@example.com>
- Cc: Lukas Czerner <firstname.lastname@example.org>, Jan Kara <email@example.com>, "Moffett, Kyle D" <Kyle.D.Moffett@boeing.com>, Sean Ryle <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, Sachin Sant <email@example.com>, "Aneesh Kumar K.V" <firstname.lastname@example.org>
- Subject: Bug#615998: linux-image-2.6.32-5-xen-amd64: Repeatable "kernel BUG at fs/jbd2/commit.c:534" from Postfix on ext4
- From: Jan Kara <email@example.com>
- Date: Mon, 27 Jun 2011 22:27:51 +0200
- Message-id: <[🔎] 20110627202751.GJ5597@quack.suse.cz>
- Reply-to: Jan Kara <firstname.lastname@example.org>, email@example.com
- In-reply-to: <[🔎] 20110627160140.GC2729@thunk.org>
- References: <[🔎] AF621113-8320-4973-A88A-1FC048EA4293@boeing.com> <[🔎] BANLkTi=5BLA07tvbv3PFcZ0cc8FmBtg+UA@mail.gmail.com> <[🔎] 404FD5CC-8F27-4336-B7D4-10675C53A588@boeing.com> <[🔎] 20110624134659.GB26380@quack.suse.cz> <[🔎] 2F80BF45-28FA-46D3-9A28-CA9416DC5813@boeing.com> <[🔎] 20110624200231.GA32176@quack.suse.cz> <[🔎] alpine.LFD.firstname.lastname@example.org> <[🔎] 20110627140251.GI5597@quack.suse.cz> <[🔎] alpine.LFD.email@example.com> <[🔎] 20110627160140.GC2729@thunk.org>
On Mon 27-06-11 12:01:40, Ted Tso wrote:
> On Mon, Jun 27, 2011 at 05:30:11PM +0200, Lukas Czerner wrote:
> > > I've found some. So although data=journal users are minority, there are
> > > some. That being said I agree with you we should do something about it
> > > - either state that we want to fully support data=journal - and then we
> > > should really do better with testing it or deprecate it and remove it
> > > (which would save us some complications in the code).
> > >
> > > I would be slightly in favor of removing it (code simplicity, less options
> > > to configure for admin, less options to test for us, some users I've come
> > > across actually were not quite sure why they are using it - they just
> > > thought it looks safer).
> Hmm... FYI, I hope to be able to bring on line automated testing for
> ext4 later this summer (there's a testing person at Google is has
> signed up to work on setting this up as his 20% project). The test
> matrix that I have him included data=journal, so we will be getting
> better testing in the near future.
> At least historically, data=journalling was the *simpler* case, and
> was the first thing supported by ext4. (data=ordered required revoke
> handling which didn't land for six months or so). So I'm not really
> that convinced that removing really buys us that much code
It does buy us some reduction in number of variants (e.g. write_begin,
write_end, writepage), we also wouldn't have to care about journalled data
during invalidatepage() or releasepage() calls.
> That being siad, it is true that data=journalled isn't necessarily
> faster. For heavy disk-bound workloads, it can be slower. So I can
> imagine adding some documentation that warns people not to use
> data=journal unless they really know what they are doing, but at least
> personally, I'm a bit reluctant to dispense with a bug report like
> this by saying, "oh, that feature should be deprecated".
No, I didn't want to dispense the bug report - we should definitely fix
the bug. I just remarked that data=journal is currently not well tested and
thus using it in production has its problems.
Jan Kara <firstname.lastname@example.org>
SUSE Labs, CR