linux-ext4 - Re: Regression in next with ext4 oops

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Message-ID: <20161004191633.muirbg7mvb3ylhhl@atomide.com>
Date:   Tue, 4 Oct 2016 12:16:34 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>,
        Eric Biggers <ebiggers@...gle.com>,
        Andreas Dilger <adilger@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        Kalle Valo <kvalo@...eaurora.org>
Subject: Re: Regression in next with ext4 oops

Hi,

* Al Viro <viro@...IV.linux.org.uk> [161004 08:00]:
> On Tue, Oct 04, 2016 at 10:02:31AM -0400, Theodore Ts'o wrote:
> > On Tue, Oct 04, 2016 at 11:00:41AM +0200, Jan Kara wrote:
> > > Never seen this but I suspect it is a fallout from Al's directory locking
> > > changes. In particular ext4_htree_fill_tree() builds rb-tree of found
> > > directory entries in file->private_data (and generally modifies the
> > > structure stored there) but after Al's changes we don't have exclusive
> > > access to struct file if I'm right so if two processes end up calling
> > > getdents() for the same 'struct file' we are doomed.
> > 
> > I haven't seen it either, and I've been doing a lot of testing on the
> > ext4 test branch.  So I'm guessing Tony has the only reliable repro
> > for the problem at the moment.  That being said, it shouldn't be that
> > hard to create a test case for this and add it to xfstests.
> > 
> > I'm pretty sure Jan is right about this, though, but it would be great
> > to a get a quick confirmation from Tony if at all possible.
> 
> Jan is wrong - we do have per-struct-file serialization for getdents()
> et.al.  It might be a race between getdents() on *different* struct
> file for the same directory, but ->private_data is not a problem.

OK found the guilty person after git bisect and that's me.

Git bisect points to commit d776fc86b82f ("wlcore: sdio: Populate config
firmware data"), so adding Kalle to Cc.

Looks like update-initramfs does rmmod of wlcore_sdio and that triggers
some issue with the wlcore driver or with SDIO/MMC. Or maybe it's a memory
corruption issue. I don't know yet exactly what's going on here yet but
I plan to find out after some lunch.

Regards,

Tony
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