linux-ext4 - Re: xfstests generic/130 hang with non-4k block size ext4 on 4.7-rc1 kernel

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Message-ID: <20160601165800.GI10350@eguan.usersys.redhat.com>
Date:	Thu, 2 Jun 2016 00:58:00 +0800
From:	Eryu Guan <guaneryu@...il.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Eryu Guan <eguan@...hat.com>, linux-ext4@...r.kernel.org,
	Jan Kara <jack@...e.cz>
Subject: Re: xfstests generic/130 hang with non-4k block size ext4 on 4.7-rc1
 kernel

On Wed, Jun 01, 2016 at 02:38:22PM +0800, Eryu Guan wrote:
> On Tue, May 31, 2016 at 11:40:17AM -0400, Theodore Ts'o wrote:
> > On Tue, May 31, 2016 at 10:09:22PM +0800, Eryu Guan wrote:
> > > 
> > > I noticed that generic/130 hangs starting from 4.7-rc1 kernel, on non-4k
> > > block size ext4 (x86_64 host). And I bisected to commit 06bd3c36a733
> > > ("ext4: fix data exposure after a crash").
> > > 
> > > It's the sub-test "Small Vector Sync" in generic/130 hangs the kernel,
> > > and I can reproduce it on different hosts, both bare metal and kvm
> > > guest.
> > 
> > Hmm, it's not reproducing for me, either using your simplified repro
> > or generic/130.  Is there something specific with your kernel config,
> > which is needed for the reproduction, perhaps?
> 
> That's weird, it's easily reproduced for me on different hosts/guests.
> The kernel config I'm using is based on the config from RHEL7.2 kernel,
> leaving all new config options to their default choices. i.e
> 
> cp /boot/<config-rhel7.2> ./.config && yes "" | make oldconfig && make
> 
> I attached my kernel config file.
> 
> And my test vm has 8G memory & 4 vcpus, with RHEL7.2 installed running
> upstream kernel, host is RHEL6.7. xfsprogs version 3.2.2 (shipped with
> RHEL7.2) and version 4.5.0 (compiled from upstream) made no difference.
> 
> I think I can try configs from other venders such as SuSE, Ubuntu. If
> you can share your config file I'll test it as well.

I've tried kernel config from Ubuntu 16.04, and I can reproduce the hang
as well. If I add "-o data=journal" or "-o data=writeback" mount option,
I don't see the hang. So seems it only happens in data=ordered mode,
which matches the code change in commit 06bd3c36a733, I think.

I had some troubles booting the kernel compiled with your config file,
I'll dig into it more tomorrow.

Thanks,
Eryu
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