Patches 1-4 are almost the same as they are when previously posted
here:
https://www.redhat.com/archives/libguestfs/2017-September/msg00039.html
Patch 5 actually uses the mandatory locking test to turn off locking
in the narrow case where a drive is opened readonly, and then only for
the drive being inspected.
Passes ordinary tests (‘check-direct’ and ‘check-valgrind-direct’).
Rich.