1 files changed, 47 insertions, 3 deletions

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 8e025834f2fb..0a37d97bda75 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -93,6 +93,8 @@ struct rq_wb {
 	struct rq_depth rq_depth;
 };
 
+static int wbt_init(struct gendisk *disk);
+
 static inline struct rq_wb *RQWB(struct rq_qos *rqos)
 {
 	return container_of(rqos, struct rq_wb, rqos);
@@ -506,7 +508,7 @@ u64 wbt_get_min_lat(struct request_queue *q)
 	return RQWB(rqos)->min_lat_nsec;
 }
 
-void wbt_set_min_lat(struct request_queue *q, u64 val)
+static void wbt_set_min_lat(struct request_queue *q, u64 val)
 {
 	struct rq_qos *rqos = wbt_rq_qos(q);
 	if (!rqos)
@@ -741,7 +743,7 @@ void wbt_init_enable_default(struct gendisk *disk)
 		WARN_ON_ONCE(wbt_init(disk));
 }
 
-u64 wbt_default_latency_nsec(struct request_queue *q)
+static u64 wbt_default_latency_nsec(struct request_queue *q)
 {
 	/*
 	 * We default to 2msec for non-rotational storage, and 75msec
@@ -901,7 +903,7 @@ static const struct rq_qos_ops wbt_rqos_ops = {
 #endif
 };
 
-int wbt_init(struct gendisk *disk)
+static int wbt_init(struct gendisk *disk)
 {
 	struct request_queue *q = disk->queue;
 	struct rq_wb *rwb;
@@ -948,3 +950,45 @@ err_free:
 	return ret;
 
 }
+
+int wbt_set_lat(struct gendisk *disk, s64 val)
+{
+	struct request_queue *q = disk->queue;
+	unsigned int memflags;
+	struct rq_qos *rqos;
+	int ret = 0;
+
+	/*
+	 * Ensure that the queue is idled, in case the latency update
+	 * ends up either enabling or disabling wbt completely. We can't
+	 * have IO inflight if that happens.
+	 */
+	memflags = blk_mq_freeze_queue(q);
+
+	rqos = wbt_rq_qos(q);
+	if (!rqos) {
+		ret = wbt_init(disk);
+		if (ret)
+			goto out;
+	}
+
+	if (val == -1)
+		val = wbt_default_latency_nsec(q);
+	else if (val >= 0)
+		val *= 1000ULL;
+
+	if (wbt_get_min_lat(q) == val)
+		goto out;
+
+	blk_mq_quiesce_queue(q);
+
+	mutex_lock(&disk->rqos_state_mutex);
+	wbt_set_min_lat(q, val);
+	mutex_unlock(&disk->rqos_state_mutex);
+
+	blk_mq_unquiesce_queue(q);
+out:
+	blk_mq_unfreeze_queue(q, memflags);
+
+	return ret;
+}