1.  IRP Cancellation vs IRP Ownership vs IoCompleteRequest

    I need to recall/investigate and document the gory details
    surrounding IRP cancellation.

    Paul had an interesting idea: If we avoid touching the IRP after
    setting the cancel routine, can we get avoid holding a lock?

2.  PendingReturned vs IoMarkIrpPending vs STATUS_PENDING

    I need to recall/investigate and document the gory details
    surrounding the annoying Irp->PendingReturned flag, the
    IoMarkIrpPending( Irp ) routine, and the act of returning
    STATUS_PENDING from within an IRP handler.