dm-delay: remove timer_lock

Instead of manually checking the timer details in queue_timeout(), call
timer_reduce() to start the timer or reduce the expiration time. This
avoids needing a lock.

Signed-off-by: Benjamin Marzinski <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-delay.c

···
 
 struct delay_c {
 	struct timer_list delay_timer;
-	struct mutex timer_lock;
 	struct mutex process_bios_lock; /* hold while removing bios to be processed from list */
 	spinlock_t delayed_bios_lock; /* hold on all accesses to delayed_bios list */
 	struct workqueue_struct *kdelayd_wq;
···
 
 static void queue_timeout(struct delay_c *dc, unsigned long expires)
 {
-	mutex_lock(&dc->timer_lock);
-
-	if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
-		mod_timer(&dc->delay_timer, expires);
-
-	mutex_unlock(&dc->timer_lock);
+	timer_reduce(&dc->delay_timer, expires);
 }
 
 static inline bool delay_is_fast(struct delay_c *dc)
···
 		kthread_stop(dc->worker);
 
 	mutex_destroy(&dc->process_bios_lock);
-	mutex_destroy(&dc->timer_lock);
 
 	kfree(dc);
 }
···
 
 	ti->private = dc;
 	INIT_LIST_HEAD(&dc->delayed_bios);
-	mutex_init(&dc->timer_lock);
 	mutex_init(&dc->process_bios_lock);
 	spin_lock_init(&dc->delayed_bios_lock);
 	dc->may_delay = true;