[RFC PATCH 8/8] block: Blink device LED when request is sent to low-level driver

[Ian Pilcher]

* Don't wait to lock the device's LED trigger mutex; just don't
  blink the LED this time if it can't be locked right away, i.e.
  if mutex_trylock() fails.

Signed-off-by: Ian Pilcher <arequipeno at gmail.com>
---
 block/blk-ledtrig.c | 24 ++++++++++++++++++++++++
 block/blk-ledtrig.h |  9 +++++++++
 block/blk-mq.c      |  2 ++
 3 files changed, 35 insertions(+)

diff --git a/block/blk-ledtrig.c b/block/blk-ledtrig.c
index 2d324df45149..1b475530ce6c 100644
--- a/block/blk-ledtrig.c
+++ b/block/blk-ledtrig.c
@@ -544,3 +544,27 @@ ssize_t blk_ledtrig_devattr_show(struct device *const dev,
 
 	return (ssize_t)(name_len + 1);
 }
+
+
+/*
+ *
+ *	Try to blink an LED
+ *
+ */
+
+void __blk_ledtrig_try_blink(struct gendisk *const gd)
+{
+	if (mutex_trylock(&gd->ledtrig_mutex)) {
+
+		if (gd->ledtrig != NULL) {
+
+			unsigned long delay_on = 75;
+			unsigned long delay_off = 25;
+
+			led_trigger_blink_oneshot(&gd->ledtrig->trigger,
+						  &delay_on, &delay_off, 0);
+		}
+
+		mutex_unlock(&gd->ledtrig_mutex);
+	}
+}
diff --git a/block/blk-ledtrig.h b/block/blk-ledtrig.h
index 5d228905edbf..146deda92a8e 100644
--- a/block/blk-ledtrig.h
+++ b/block/blk-ledtrig.h
@@ -27,10 +27,19 @@ ssize_t blk_ledtrig_devattr_show(struct device *const dev,
 				 struct device_attribute *const attr,
 				 char *const buf);
 
+void __blk_ledtrig_try_blink(struct gendisk *gd);
+
+static inline void blk_ledtrig_try_blink(struct gendisk *const gd)
+{
+	if (gd != NULL)
+		__blk_ledtrig_try_blink(gd);
+}
+
 #else	// CONFIG_BLK_LED_TRIGGERS
 
 static inline void blk_ledtrig_init(void) {}
 static inline void blk_ledtrig_disk_init(const struct gendisk *gd) {}
+static inline void blk_ledtrig_try_blink(const struct gendisk *gd) {}
 
 // Real function (declared in include/linux/blk-ledtrig.h) returns a bool.
 // This is only here for del_gendisk() (in genhd.c), which doesn't check
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2c4ac51e54eb..5593ece7b676 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -40,6 +40,7 @@
 #include "blk-stat.h"
 #include "blk-mq-sched.h"
 #include "blk-rq-qos.h"
+#include "blk-ledtrig.h"
 
 static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);
 
@@ -1381,6 +1382,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 		switch (ret) {
 		case BLK_STS_OK:
 			queued++;
+			blk_ledtrig_try_blink(rq->rq_disk);
 			break;
 		case BLK_STS_RESOURCE:
 		case BLK_STS_DEV_RESOURCE:
-- 
2.31.1