blk-wbt: factor out a helper wbt_set_lat()

To move implementation details inside blk-wbt.c, prepare to fix possible
deadlock to call wbt_init() while queue is frozen in the next patch.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 37 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e0a70d26972b..a580688c3ad5 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -636,11 +636,8 @@ out:
 static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
 				  size_t count)
 {
-	struct request_queue *q = disk->queue;
-	struct rq_qos *rqos;
 	ssize_t ret;
 	s64 val;
-	unsigned int memflags;
 
 	ret = queue_var_store64(&val, page);
 	if (ret < 0)
@@ -648,40 +645,8 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
 	if (val < -1)
 		return -EINVAL;
 
-	/*
-	 * 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;
-	}
-
-	ret = count;
-	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;
+	ret = wbt_set_lat(disk, val);
+	return ret ? ret : count;
 }
 
 QUEUE_RW_ENTRY(queue_wb_lat, "wbt_lat_usec");