IN  PIRP_CONTEXT IrpContext,
  IN  PVCB Vcb,
  IN  BOOLEAN DismountUnderway

Routine Description:

    This routine is called to purge the volume.  The purpose is to make all the stale file
    objects in the system go away in order to lock the volume.

    The Vcb is already acquired exclusively.  We will lock out all file operations by
    acquiring the global file resource.  Then we will walk through all of the Fcb's and
    perform the purge.


    Vcb - Vcb for the volume to purge.

    DismountUnderway - Indicates that we are trying to delete all of the objects.
        We will purge the Path Table and VolumeDasd and dereference all
        internal streams.

Return Value:

    NTSTATUS - The first failure of the purge operation.