Prepare to fix possible deadlock to create blk-mq debugfs entries while
queue is still freezed.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/blk-mq-debugfs.c | 23 +++++++++++++++--------
 block/blk-mq-debugfs.h |  5 +++++
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 66864ed0b77f..1de9bab7ba80 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -633,6 +633,20 @@ static void debugfs_create_files(struct request_queue *q, struct dentry *parent,
 				    (void *)attr, data, &blk_mq_debugfs_fops);
 }
 
+void blk_mq_debugfs_register_rq_qos(struct request_queue *q)
+{
+	lockdep_assert_held(&q->debugfs_mutex);
+
+	if (q->rq_qos) {
+		struct rq_qos *rqos = q->rq_qos;
+
+		while (rqos) {
+			blk_mq_debugfs_register_rqos(rqos);
+			rqos = rqos->next;
+		}
+	}
+}
+
 void blk_mq_debugfs_register(struct request_queue *q)
 {
 	struct blk_mq_hw_ctx *hctx;
@@ -645,14 +659,7 @@ void blk_mq_debugfs_register(struct request_queue *q)
 			blk_mq_debugfs_register_hctx(q, hctx);
 	}
 
-	if (q->rq_qos) {
-		struct rq_qos *rqos = q->rq_qos;
-
-		while (rqos) {
-			blk_mq_debugfs_register_rqos(rqos);
-			rqos = rqos->next;
-		}
-	}
+	blk_mq_debugfs_register_rq_qos(q);
 }
 
 static void blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx,
diff --git a/block/blk-mq-debugfs.h b/block/blk-mq-debugfs.h
index c80e453e3014..9f76603792fe 100644
--- a/block/blk-mq-debugfs.h
+++ b/block/blk-mq-debugfs.h
@@ -34,6 +34,7 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
 void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx);
 
 void blk_mq_debugfs_register_rqos(struct rq_qos *rqos);
+void blk_mq_debugfs_register_rq_qos(struct request_queue *q);
 void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos);
 #else
 static inline void blk_mq_debugfs_register(struct request_queue *q)
@@ -78,6 +79,10 @@ static inline void blk_mq_debugfs_register_rqos(struct rq_qos *rqos)
 {
 }
 
+static inline void blk_mq_debugfs_register_rq_qos(struct request_queue *q)
+{
+}
+
 static inline void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos)
 {
 }
-- 
2.39.2