linux-kernel - Re: [PATCH] add procfs tunable to enable immediate panic when there are busy inodes after umount

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Message-Id: <20070530074745.15b8355b.jlayton@redhat.com>
Date:	Wed, 30 May 2007 07:47:45 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	David Chinner <dgc@....com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] add procfs tunable to enable immediate panic when there
 are busy inodes after umount

On Wed, 30 May 2007 10:28:57 +1000
David Chinner <dgc@....com> wrote:

> On Tue, May 29, 2007 at 11:40:42AM -0400, Jeff Layton wrote:
> > After spending quite a bit of time tracking down a "VFS: busy inodes
> > after unmount" problem, it occurs to me that it would be nice to be
> > able to force a panic when that occurs. While an oops message alone is
> > not generally helpful for tracking down this sort of problem,
> > collecting and analyzing a coredump when this occurs can be.
> 
> Agreed - we've found that we've had roughly 50% success in finding
> the cause of these problems from crash dumps triggered immediately
> like this vs ~0% from a crash that occurred some time later.
> 
> Given that this problem will always result in a crash of the kernel
> at some random time in the future, why don't we just make this error
> an unconditional panic on get the crash over and done with?
> 

Perhaps that's the best course of action. Then again, there can be a
long time between the problem and crash (weeks even). For someone who
can't collect a coredump, it might be preferable to not immediately
crash the box and allow them to try to reboot it at a convenient time.
That was my reasoning for adding the procfs tunable.

Either way, if the machine doesn't crash immediately, I'd like to see a
different error message here. The current one is confusing to users.
They see it and figure "my box didn't crash in 5 mins, so everything
must be OK!"

-- 
Jeff Layton <jlayton@...hat.com>
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