IN  PIRP Irp

Routine Description:

    This is the driver entry to all of the Fsd dispatch points.

    Conceptually the Io routine will call this routine on all requests
    to the file system.  We case on the type of request and invoke the
    correct handler for this type of request.  There is an exception filter
    to catch any exceptions in the CDFS code as well as the CDFS process
    exception routine.

    This routine allocates and initializes the IrpContext for this request as
    well as updating the top-level thread context as necessary.  We may loop
    in this routine if we need to retry the request for any reason.  The
    status code STATUS_CANT_WAIT is used to indicate this.  Suppose the disk
    in the drive has changed.  An Fsd request will proceed normally until it
    recognizes this condition.  STATUS_VERIFY_REQUIRED is raised at that point
    and the exception code will handle the verify and either return
    STATUS_CANT_WAIT or STATUS_PENDING depending on whether the request was


    VolumeDeviceObject - Supplies the volume device object for this request

    Irp - Supplies the Irp being processed

Return Value:

    NTSTATUS - The FSD status for the IRP