mkiss: Use refcount_t for refcount

refcount_t is better for reference counters since its
implementation can prevent overflows.
So convert atomic_t ref counters to refcount_t.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hamradio/mkiss.c

@@ -25,6 +25,7 @@
 #include <linux/skbuff.h>
 #include <linux/if_arp.h>
 #include <linux/jiffies.h>
+#include <linux/refcount.h>
 
 #include <net/ax25.h>
 
@@ -70,7 +71,7 @@ struct mkiss {
 #define CRC_MODE_FLEX_TEST	3
 #define CRC_MODE_SMACK_TEST	4
 
-	atomic_t		refcnt;
+	refcount_t		refcnt;
 	struct completion	dead;
 };
 
@@ -668,15 +669,15 @@ static struct mkiss *mkiss_get(struct tty_struct *tty)
 	read_lock(&disc_data_lock);
 	ax = tty->disc_data;
 	if (ax)
-		atomic_inc(&ax->refcnt);
+		refcount_inc(&ax->refcnt);
 	read_unlock(&disc_data_lock);
 
 	return ax;
 }
 
 static void mkiss_put(struct mkiss *ax)
 {
-	if (atomic_dec_and_test(&ax->refcnt))
+	if (refcount_dec_and_test(&ax->refcnt))
 		complete(&ax->dead);
 }
 
@@ -704,7 +705,7 @@ static int mkiss_open(struct tty_struct *tty)
 	ax->dev = dev;
 
 	spin_lock_init(&ax->buflock);
-	atomic_set(&ax->refcnt, 1);
+	refcount_set(&ax->refcnt, 1);
 	init_completion(&ax->dead);
 
 	ax->tty = tty;
@@ -784,7 +785,7 @@ static void mkiss_close(struct tty_struct *tty)
 	 * We have now ensured that nobody can start using ap from now on, but
 	 * we have to wait for all existing users to finish.
 	 */
-	if (!atomic_dec_and_test(&ax->refcnt))
+	if (!refcount_dec_and_test(&ax->refcnt))
 		wait_for_completion(&ax->dead);
 	/*
 	 * Halt the transmit queue so that a new transmit cannot scribble