[PATCH] driver: block: release the lo_work_lock before queue_work

[zhaoyang.huang]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

queue_work could spin on wq->cpu_pwq->pool->lock which could lead to
concurrent loop_process_work failed on lo_work_lock contention and
increase the request latency. Remove this combination by moving the
lock release ahead of queue_work.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
 drivers/block/loop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 8f6761c27c68..33e31cd95953 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -890,8 +890,8 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
 		cmd_list = &lo->rootcg_cmd_list;
 	}
 	list_add_tail(&cmd->list_entry, cmd_list);
-	queue_work(lo->workqueue, work);
 	spin_unlock_irq(&lo->lo_work_lock);
+	queue_work(lo->workqueue, work);
 }
 
 static void loop_set_timer(struct loop_device *lo)
-- 
2.25.1