Re: ext4 unknown problem

[Theodore Ts'o <tytso@mit.edu>]

On Tue, Jul 31, 2012 at 08:18:42AM +0100, luvar@plaintext.sk wrote:
> usb 2-4.4: USB disconnect, device number 10

So what's this?  Is this at all related to how you've created your
RAID device?  You haven't told us what your RAID device on dm-3 is
composed of (i.e., what are the underlying devices).

And there were no OOPS or BUG or WARN messages in your dmesg?

> PS: Writing to disk from jbd2/dm-3-8 still active (iotop shows it still on top of I/O activity).

I'm not sure if your kernel has trace debugging enabled, or if you
have debugfs mounted, but try this:

echo 1 > /sys/kernel/debug/tracing/events/jbd2/jbd2_run_stats/enable
cat /sys/kernel/debug/tracing/trace_pipe

If these commands don't work try running this command and see if it
works then:

mount -t debugfs debugfs /sys/kernel/debug

Let us know if you see jbd2 activity.  It's possible that sync isn't
returning because some process is still writing to the file system,
and if I recall correctly, Linux 3.2 didn't have some of the sync
livelock fixes that could cause sync to not return until the file
system had actually quieted down completely.

Regards,

					- Ted