Comment 1 for bug 1612854

This is an odd one. I can consistently reproduce it using the Xenial kernel (4.4.0-34.53-generic) but cannot reproduce it using other kernels.

u-d-f works when running under a development kernel build of 4.7. It also works when running under 4.7, 4.6, 4.5, and 4.4 kernels from http://kernel.ubuntu.com/~kernel-ppa/mainline/.