The cache_load call in mount_action ignores the device name parameter:

As such, each hotplug event (specifically, each /sbin/block hotplug invoked via /etc/hotplug.d/block/10-mount via /sbin/hotplug-call through the machinations of /etc/hotplug.json) probes all the block devices named here:

That's rather a lot, if not all, of the block devices on the system, making the total block hotplug sequence accidentally quadratic.

I hope this is the right place to raise this issue, and I've also documented a bit about how I found this over in this forum thread, but if it belongs somewhere else, please let me know.