INT 2F U - DOS 3+ internal - FLUSH AND FREE DISK BUFFER
AX = 1209h
DS:DI -> disk buffer
Return: disk buffer marked unused, contents written to disk if buffer dirty
Note:   can be called only from within DOS
SeeAlso: AX=1215h

See also: 2F120E

2F1209 - DOS 3+ internal - FLUSH AND FREE DISK BUFFER