linux-kernel - Re: 4.7.0-rc7 ext4 error in dx

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Date:	Sun, 7 Aug 2016 23:28:10 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	"Theodore Ts'o" <tytso@....edu>,
	Johannes Stezenbach <js@...21.net>,
	Török Edwin <edwin@...rok.net>,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: 4.7.0-rc7 ext4 error in dx_probe

On Sun, Aug 07, 2016 at 11:56:34PM -0400, Theodore Ts'o wrote:
> On Fri, Aug 05, 2016 at 12:15:48PM -0700, Darrick J. Wong wrote:
> > > > [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/fs/ext4/inode.c?id=b47820edd1634dc1208f9212b7ecfb4230610a23
> > > 
> > > I added the patch, rebuilt and rebooted.  It will take some time
> > > before I'll report back since the issue is so hard to reproduce.
> > 
> > FWIW I could trigger it reliably by running a bunch of directory traversal
> > programs simultaneously on the same directory.  I have a script that fires
> > up multiple mutts pointing to the Maildirs for the high traffic Linux lists.
> 
> Hmm, I wonder if we should request that this patch be backported to
> -stable.  Darrick, what do you think?

Seems like an excellent idea.

I have one lingering concern -- is it a bug that two processes could be
computing the checksum of a buffer simultaneously?  I would have thought ext4
would serialize that kind of buffer_head access...

--D
> 
> 						- Ted