There are 2 exclusion paths in the Capacity filter of Cinder scheduler that don't log anything, which makes it hard to determine the cause of some exclusions. Logging should be added to these paths.
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-2018:1611