tty: Simplify tty_ldisc_release() interface

Passing the 'other' tty to tty_ldisc_release() only makes sense
for a pty pair; make o_tty function local instead.
Reviewed-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -1892,7 +1892,7 @@ int tty_release(struct inode *inode, struct file *filp)
 	/*
 	 * Ask the line discipline code to release its structures
 	 */
-	tty_ldisc_release(tty, o_tty);
+	tty_ldisc_release(tty);
 
 	/* Wait for pending work before tty destruction commmences */
 	tty_flush_works(tty);

drivers/tty/tty_ldisc.c

@@ -756,18 +756,17 @@ static void tty_ldisc_kill(struct tty_struct *tty)
 
 /**
  *	tty_ldisc_release		-	release line discipline
- *	@tty: tty being shut down
- *	@o_tty: pair tty for pty/tty pairs
- *
- *	Called during the final close of a tty/pty pair in order to shut down
- *	the line discpline layer. On exit the ldisc assigned is N_TTY and the
- *	ldisc has not been opened.
+ *	@tty: tty being shut down (or one end of pty pair)
  *
- *	Holding ldisc_sem write lock serializes tty->ldisc changes.
+ *	Called during the final close of a tty or a pty pair in order to shut
+ *	down the line discpline layer. On exit, each ldisc assigned is N_TTY and
+ *	each ldisc has not been opened.
  */
 
-void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
+void tty_ldisc_release(struct tty_struct *tty)
 {
+	struct tty_struct *o_tty = tty->link;
+
 	/*
 	 * Shutdown this line discipline. As this is the final close,
 	 * it does not race with the set_ldisc code path.

include/linux/tty.h

@@ -557,7 +557,7 @@ extern int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc);
 extern int tty_unregister_ldisc(int disc);
 extern int tty_set_ldisc(struct tty_struct *tty, int ldisc);
 extern int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
-extern void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty);
+extern void tty_ldisc_release(struct tty_struct *tty);
 extern void tty_ldisc_init(struct tty_struct *tty);
 extern void tty_ldisc_deinit(struct tty_struct *tty);
 extern void tty_ldisc_begin(void);