[SRU X] [PATCH 5/5] tty: Simplify tty->count math in tty_reopen()

[Guilherme G. Piccoli]

From: Dmitry Safonov <dima at arista.com>

BugLink: https://bugs.launchpad.net/bugs/1791758

As notted by Jiri, tty_ldisc_reinit() shouldn't rely on tty counter.
Simplify math by increasing the counter after reinit success.

Cc: Jiri Slaby <jslaby at suse.com>
Link: lkml.kernel.org/r/<20180829022353.23568-2-dima at arista.com>
Suggested-by: Jiri Slaby <jslaby at suse.com>
Reviewed-by: Jiri Slaby <jslaby at suse.cz>
Tested-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Dmitry Safonov <dima at arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry-picked from cf62a1a13749db0d32b5cdd800ea91a4087319de upstream)
Signed-off-by: Guilherme G. Piccoli <gpiccoli at canonical.com>
---
 drivers/tty/tty_io.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 3784f55f3dc9..a7511d5fad9e 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1490,16 +1490,13 @@ static int tty_reopen(struct tty_struct *tty)
 	if (retval)
 		return retval;
 
-	tty->count++;
-	if (tty->ldisc)
-		goto out_unlock;
-
-	retval = tty_ldisc_reinit(tty, tty->termios.c_line);
-	if (retval)
-		tty->count--;
-
-out_unlock:
+	if (!tty->ldisc)
+		retval = tty_ldisc_reinit(tty, tty->termios.c_line);
 	tty_ldisc_unlock(tty);
+
+	if (retval == 0)
+		tty->count++;
+
 	return retval;
 }
 
-- 
2.19.2