AUFS hang on umount of loop device cleanup script

cleanup.sh

#!/bin/bash

set -x -e

ps aux | grep namespaced | grep -v grep | awk '{print $2}' | xargs -n1 kill -9 || true

umount /root/workspace/4.4-loop-umount-hang-test/mnt/container-2 || true
umount /root/workspace/4.4-loop-umount-hang-test/diff/container-2 || true

umount /root/workspace/4.4-loop-umount-hang-test/mnt/container-1 || true
umount /root/workspace/4.4-loop-umount-hang-test/diff/container-1 || true

rm -rf /root/workspace/4.4-loop-umount-hang-test || true
rm -rf /tmp/pivot-*

echo "Mounts:"
cat /proc/self/mounts | grep aufs || true

echo "Loopback devices:"
losetup -a