Int 2F Fn 120F  U - DOS 3+ Internal - Make Buffer Most Recently Used       [D]

   AX = 120Fh
   DS:DI -> disk buffer
   SS = DOS DS (must be using a DOS internal stack)

Return: DS:DI -> next buffer in buffer list
Desc:  move the indicated buffer to the end of the disk buffer chain (least-
     recently used is first); under DOS 3.3, the buffer is then moved to
     the start of the disk buffer chain if it was marked unused

Note:  this function is the same as AX=1207h except that it returns a
     pointer to the buffer following the specified buffer in the buffer
     chain

See Also: AX=1207h