Description of problem: The following fix is required in os-brick by bug 1805677 and the associated backports through 16.1, 15 and 13. rbd: Use showmapped to find the root RBD device during disconnect_volume https://review.opendev.org/#/c/720178/
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:3148