Date: Mon, 12 Dec 2016 16:28:37 +0100
From: Olaf Hering <olaf@aepfle.de>
To: "Theodore Ts'o" <tytso@mit.edu>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: 4.8.12, crash in ext4, __d_lookup_rcu
Message-ID: <20161212152837.GA3034@aepfle.de>
References: <20161212085754.GA22535@aepfle.de>
 <20161212090045.GA24313@aepfle.de>
 <20161212150359.ylhq7ocs7idqxjwv@thunk.org>
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On Mon, Dec 12, Theodore Ts'o wrote:

> What was going on at the time of the crash, and can you reproduce this?

Its the 'rm -rf $dir/$oldbackup.N' at the end of each rsnapshot run.
I will try to reproduce it, see if it happens again during the hourly
rsnapshot runs. So far I have not seen it with 4.8.x, cant remember if
it already happend with earlier kernels.

> There was a huge number of messages about ISO 9660 and accesses beyond
> the end of the loop device, and I wonder if any of this might have
> been connected to the crash.

This was an ISO image with download in progress. Since the download was
slow I mounted what was already available, which was enough to make the
installer happy. But a few files are located at the end of the image,
and the loopN block device does not autogrow as more data became
available. The ISOs are on another drive than the backup disk. Not sure
if such an incomplete iso9660 filesystem can confuse the vfs layer?

Olaf

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