When multipathd restores a previously failed path, it currently doesn't know the persistent reservation state of the path, and must assume that it needs to be registered. This is often unnecessary work. Worse, it is possible, although very unlikely, that a multipath device could get into a state where it couldn't determine it a preempt occurred at the same time as the automatic path registration. In this case a multipath device could get a path automatically re-registered after being preempted. To avoid this, multipathd needs to track the persistent reservation status of its paths, so that it can avoid getting into this state, as well as avoid doing unnecessary work when a path is restored.