blk-cgroup: remove blkcg_drain_queue

Since blk_drain_queue had already been removed, so this function
is not needed anymore.
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -1061,26 +1061,6 @@ int blkcg_init_queue(struct request_queue *q)
 	return PTR_ERR(blkg);
 }
 
-/**
- * blkcg_drain_queue - drain blkcg part of request_queue
- * @q: request_queue to drain
- *
- * Called from blk_drain_queue().  Responsible for draining blkcg part.
- */
-void blkcg_drain_queue(struct request_queue *q)
-{
-	lockdep_assert_held(&q->queue_lock);
-
-	/*
-	 * @q could be exiting and already have destroyed all blkgs as
-	 * indicated by NULL root_blkg.  If so, don't confuse policies.
-	 */
-	if (!q->root_blkg)
-		return;
-
-	blk_throtl_drain(q);
-}
-
 /**
  * blkcg_exit_queue - exit and release blkcg part of request_queue
  * @q: request_queue being released

include/linux/blk-cgroup.h

@@ -188,7 +188,6 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 				    struct request_queue *q);
 int blkcg_init_queue(struct request_queue *q);
-void blkcg_drain_queue(struct request_queue *q);
 void blkcg_exit_queue(struct request_queue *q);
 
 /* Blkio controller policy registration */
@@ -720,7 +719,6 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { ret
 static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 { return NULL; }
 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
-static inline void blkcg_drain_queue(struct request_queue *q) { }
 static inline void blkcg_exit_queue(struct request_queue *q) { }
 static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
 static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }