6. [3] when a user program makes a system call to read or write a disk file, it provides indication of which file it wants, a pointer to the data buffer, and the count. control is then transferred to the os, which calls the appropriate driver. suppose that the driver starts the disk and then terminates until an interrupt occurs. in the case of reading from the disk, obviously the caller will have to be blocked (because there is no data for it). what about the case of writing to the disk? need the caller be blocking awaiting completion of the disk transfer?