Comment 4 for bug 1310186

It's difficult to see how to fix this. External devices are scanned because people quite often use USB sticks or external drives with their music collections.

I'm not sure whether it is even possible for mediascanner to find out that some other arbitrary process has asked for a filesystem to be unmounted. If so, the daemon could back off. If not, I don't know what else it could/should do.

For what it's worth, placing a file called .nomedia into a directory prevents scanning of that directory (and all its subdirectories).