Supporting Removable Media
File systems and removable-media device drivers share the responsibility for ensuring that the correct media is mounted when a file is opened on a removable-media device and that the correct media remains mounted during operations that access the media. Any intermediate driver layered between a file system and a removable-media device driver also shares this responsibility.
Drivers that work with removable-media devices therefore should be capable of doing one or more of the following:
Responding to check-verify requests from the file system
Notifying the file system of possible media changes