[PATCH v2] staging: greybus: uart: convert idr to xarray

[Aviv Levinson <levinson.aviv@gmail.com>]

The legacy IDR API is deprecated in favor of the modern XArray API.
Convert the tty_minors IDR to an XArray.

To prevent locking the entire gb_tty object while loading the minor,
switch IDR to XArray and use the internal XArray's spinlock (xa_lock).
To respect TTY encapsulation, use tty_port_get()
instead of direct kref_get_unless_zero().

Signed-off-by: Aviv Levinson <levinson.aviv@gmail.com>
---
 drivers/staging/greybus/uart.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index 2b1a5d4671dd..054bdc232942 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -339,24 +339,21 @@ static struct gb_tty *get_gb_by_minor(unsigned int minor)
 {
 	struct gb_tty *gb_tty;
 
-	rcu_read_lock();
+	xa_lock(&tty_minors);
 	gb_tty = xa_load(&tty_minors, minor);
-	if (gb_tty) {
-		if (!kref_get_unless_zero(&gb_tty->port.kref))
-			gb_tty = NULL;
-	}
-	rcu_read_unlock();
+	if (gb_tty)
+		tty_port_get(&gb_tty->port);
+	xa_unlock(&tty_minors);
 
-	if (gb_tty) {
-		mutex_lock(&gb_tty->mutex);
-		if (gb_tty->disconnected) {
-			mutex_unlock(&gb_tty->mutex);
-			tty_port_put(&gb_tty->port);
-			gb_tty = NULL;
-		} else {
-			mutex_unlock(&gb_tty->mutex);
-		}
+	if (!gb_tty)
+		return NULL;
+	mutex_lock(&gb_tty->mutex);
+	if (gb_tty->disconnected) {
+		mutex_unlock(&gb_tty->mutex);
+		tty_port_put(&gb_tty->port);
+		return NULL;
 	}
+	mutex_unlock(&gb_tty->mutex);
 
 	return gb_tty;
 }
-- 
2.53.0