FYI, we noticed the below changes on git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master commit 9f53f9fa4ad1d8bddd4d14359cdabc531aedffe8 ("libnvdimm, pmem: add libnvdimm support to the pmem driver") We found the following new message in kernel log. [ 17.884728] user_verbs: couldn't register device number [ 17.884728] user_verbs: couldn't register device number [ 17.886026] ucm: couldn't register device number [ 17.886026] ucm: couldn't register device number Thanks, Ying Huang