From: "Darrick J. Wong" <darrick.wong@oracle.com>
Subject: Re: Difference in jbd2 behavior between CentOS and Ubuntu while
 unmounting
Date: Tue, 17 May 2016 23:18:34 -0700
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 <782fe069-c14f-4bae-609e-bbad554cb657@redhat.com>
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Cc: Kamran Khan <krkhan@inspirated.com>, linux-ext4@vger.kernel.org
To: Eric Sandeen <sandeen@redhat.com>
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On Tue, May 17, 2016 at 09:41:07PM -0500, Eric Sandeen wrote:
> On 5/17/16 9:35 PM, Kamran Khan wrote:
> > Yup, the kernel versions are drastically different. It's 3.10 vs 4.2.
> > 
> > The problem on 3.10 though is, while jbd2 holds on to the unmounted
> > device I cannot even rmmod jbd2 or ext4 *even if no other ext
> > filesystems are mounted*. That lock makes it all but impossible to do
> > anything with the block device.
> 
> You may as well try Centos7.2, at least, there are 50+ updates to
> jbd2 & ext4 since 7.1.  If it still persists we can dig further.

Just to throw some gasoline on this fire, I hit the same set of symptoms
a couple of weeks ago while trying to umount /home on 4.5.0 + Ubuntu 16.04.
Ted mused that it could be some process running in a funny mount namespace.
Or systemd dragons.  Or something.

<shrug> I rebooted and haven't seen it since, tho...

--D

> 
> -Eric
> 
> > On Tue, May 17, 2016 at 7:17 PM, Eric Sandeen <sandeen@redhat.com> wrote:
> >> On 5/17/16 7:46 PM, Kamran Khan wrote:
> >>> I'm trying to understand the difference in jbd2 behavior across Ubuntu
> >>> 14.04 and Centos 7.1. Will appreciate any help.
> >>
> >> For starters, what kernel versions are those?  (I know what centos
> >> is, "3.10.0" with updates, which I can check out, but I have no idea
> >> what might be in the Ubuntu distro)
> >>
> >> -Eric
> > 
> > 
> > 
> 
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