[PATCH v3 5/6] ledtrig-blk: add interface to stop and restart polling disk stats

[Akinobu Mita <akinobu.mita@gmail.com>]

The LED block device activity trigger periodically polls the disk stats
to collect the activity.  However, it is pointless to poll while the
block device is in quiescent state.

This provides an optional interface to stop and restart polling disk stats
for the lower-level block drivers.

Cc: Frank Steiner <fsteiner-mail1@bio.ifi.lmu.de>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Dan Murphy <dmurphy@ti.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Hannes Reinecke <hare@suse.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 drivers/leds/trigger/ledtrig-blk.c | 37 +++++++++++++++++++++++++++++++++++--
 include/linux/leds.h               | 11 +++++++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-blk.c b/drivers/leds/trigger/ledtrig-blk.c
index d5808c9..6b826ed 100644
--- a/drivers/leds/trigger/ledtrig-blk.c
+++ b/drivers/leds/trigger/ledtrig-blk.c
@@ -153,8 +153,9 @@ static void ledtrig_blk_work(struct work_struct *work)
 		trig_data->last_activity = activity;
 	}
 
-	schedule_delayed_work(&trig_data->work,
-			      atomic_read(&trig_data->interval) * 2);
+	if (atomic_read(&disk->led.enable_count))
+		schedule_delayed_work(&trig_data->work,
+				      atomic_read(&trig_data->interval) * 2);
 }
 
 static int ledtrig_blk_activate(struct led_classdev *led_cdev)
@@ -190,6 +191,36 @@ static void ledtrig_blk_deactivate(struct led_classdev *led_cdev)
 	kfree(trig_data);
 }
 
+void ledtrig_blk_disable(struct gendisk *disk)
+{
+	if (disk)
+		atomic_dec(&disk->led.enable_count);
+}
+EXPORT_SYMBOL_GPL(ledtrig_blk_disable);
+
+void ledtrig_blk_enable(struct gendisk *disk)
+{
+	struct led_classdev *led_cdev;
+
+	if (!disk)
+		return;
+
+	atomic_inc(&disk->led.enable_count);
+
+	read_lock(&disk->led.trig.leddev_list_lock);
+
+	list_for_each_entry(led_cdev, &disk->led.trig.led_cdevs, trig_list) {
+		struct ledtrig_blk_data *trig_data =
+			led_get_trigger_data(led_cdev);
+
+		schedule_delayed_work(&trig_data->work,
+				      atomic_read(&trig_data->interval) * 2);
+	}
+
+	read_unlock(&disk->led.trig.leddev_list_lock);
+}
+EXPORT_SYMBOL_GPL(ledtrig_blk_enable);
+
 int ledtrig_blk_register(struct gendisk *disk)
 {
 	int ret;
@@ -203,6 +234,8 @@ int ledtrig_blk_register(struct gendisk *disk)
 	disk->led.trig.deactivate = ledtrig_blk_deactivate;
 	disk->led.trig.groups = ledtrig_blk_groups;
 
+	atomic_set(&disk->led.enable_count, 1);
+
 	ret = led_trigger_register(&disk->led.trig);
 	if (ret) {
 		kfree(disk->led.trig.name);
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 395fa61..fd2eb7c 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -523,8 +523,11 @@ struct gendisk;
 
 struct ledtrig_blk {
 	struct led_trigger trig;
+	atomic_t enable_count;
 };
 
+void ledtrig_blk_enable(struct gendisk *disk);
+void ledtrig_blk_disable(struct gendisk *disk);
 int ledtrig_blk_register(struct gendisk *disk);
 void ledtrig_blk_unregister(struct gendisk *disk);
 
@@ -533,6 +536,14 @@ void ledtrig_blk_unregister(struct gendisk *disk);
 struct ledtrig_blk {
 };
 
+static inline void ledtrig_blk_enable(struct gendisk *disk)
+{
+}
+
+static inline void ledtrig_blk_disable(struct gendisk *disk)
+{
+}
+
 static inline int ledtrig_blk_register(struct gendisk *disk)
 {
 	return 0;
-- 
2.7.4