Looking like a very rare trigger case (from Ted Tso Google +)<br><br><b>Update</b>: �It now looks like the reproduction involved something 
very esoteric indeed, involving using umount -l and shutdowns while the 
file system was still being unmounted --- and the user had nobarrier 
specified in the mount options as well. �See:<br><br><a href="http://thread.gmane.org/gmane.linux.kernel/1379725/focus=34994" class="ot-anchor">http://thread.gmane.org/gmane.linux.kernel/1379725/focus=34994</a><br>and<br>
<a href="http://thread.gmane.org/gmane.linux.kernel/1379725/focus=35003" class="ot-anchor">http://thread.gmane.org/gmane.linux.kernel/1379725/focus=35003</a><br>and my reply here<br><a href="http://thread.gmane.org/gmane.linux.kernel/1379725/focus=35006" class="ot-anchor">http://thread.gmane.org/gmane.linux.kernel/1379725/focus=35006</a><br>