I'm slapping this part of the IRC conversation into email so we don't lose it:
Step #1: Replace all calls to dev_dstrategy() with calls to io_schedule() ins tead. And write an io_schedule() function which then (for now) just calls dev_dstrategy(). Step #2: Implement the process-based policy structure and system calls. Step #3: Associate policy information with each BIO Step #4: Build the dynamic instancing for the (policies x cdev_t) matrix. Step #5: Start implementing the actual I/O scheduler algorithm -Matt