blk-mq: improve the blk_mq_init_allocated_queue interface

Don't return the passed in request_queue but a normal error code, and
drop the elevator_init argument in favor of just calling elevator_init_mq
directly from dm-rq.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -3115,21 +3115,18 @@ void blk_mq_release(struct request_queue *q)
 struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
 		void *queuedata)
 {
-	struct request_queue *uninit_q, *q;
+	struct request_queue *q;
+	int ret;
 
-	uninit_q = blk_alloc_queue(set->numa_node);
-	if (!uninit_q)
+	q = blk_alloc_queue(set->numa_node);
+	if (!q)
 		return ERR_PTR(-ENOMEM);
-	uninit_q->queuedata = queuedata;
-
-	/*
-	 * Initialize the queue without an elevator. device_add_disk() will do
-	 * the initialization.
-	 */
-	q = blk_mq_init_allocated_queue(set, uninit_q, false);
-	if (IS_ERR(q))
-		blk_cleanup_queue(uninit_q);
-
+	q->queuedata = queuedata;
+	ret = blk_mq_init_allocated_queue(set, q);
+	if (ret) {
+		blk_cleanup_queue(q);
+		return ERR_PTR(ret);
+	}
 	return q;
 }
 EXPORT_SYMBOL_GPL(blk_mq_init_queue_data);
@@ -3273,9 +3270,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 	mutex_unlock(&q->sysfs_lock);
 }
 
-struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
-						  struct request_queue *q,
-						  bool elevator_init)
+int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
+		struct request_queue *q)
 {
 	/* mark the queue as mq asap */
 	q->mq_ops = set->ops;
@@ -3325,11 +3321,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
 	blk_mq_add_queue_tag_set(set, q);
 	blk_mq_map_swqueue(q);
-
-	if (elevator_init)
-		elevator_init_mq(q);
-
-	return q;
+	return 0;
 
 err_hctxs:
 	kfree(q->queue_hw_ctx);
@@ -3340,7 +3332,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	q->poll_cb = NULL;
 err_exit:
 	q->mq_ops = NULL;
-	return ERR_PTR(-ENOMEM);
+	return -ENOMEM;
 }
 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
 

block/blk.h

@@ -192,7 +192,6 @@ void blk_account_io_done(struct request *req, u64 now);
 
 void blk_insert_flush(struct request *rq);
 
-void elevator_init_mq(struct request_queue *q);
 int elevator_switch_mq(struct request_queue *q,
 			      struct elevator_type *new_e);
 void __elevator_exit(struct request_queue *, struct elevator_queue *);

block/elevator.c

@@ -693,7 +693,7 @@ void elevator_init_mq(struct request_queue *q)
 		elevator_put(e);
 	}
 }
-
+EXPORT_SYMBOL_GPL(elevator_init_mq); /* only for dm-rq */
 
 /*
  * switch to new_e io scheduler. be careful not to introduce deadlocks -

drivers/md/dm-rq.c

@@ -530,7 +530,6 @@ static const struct blk_mq_ops dm_mq_ops = {
 
 int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
 {
-	struct request_queue *q;
 	struct dm_target *immutable_tgt;
 	int err;
 
@@ -557,12 +556,10 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
 	if (err)
 		goto out_kfree_tag_set;
 
-	q = blk_mq_init_allocated_queue(md->tag_set, md->queue, true);
-	if (IS_ERR(q)) {
-		err = PTR_ERR(q);
+	err = blk_mq_init_allocated_queue(md->tag_set, md->queue);
+	if (err)
 		goto out_tag_set;
-	}
-
+	elevator_init_mq(md->queue);
 	return 0;
 
 out_tag_set:

include/linux/blk-mq.h

@@ -429,9 +429,8 @@ enum {
 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
 struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
 		void *queuedata);
-struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
-						  struct request_queue *q,
-						  bool elevator_init);
+int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
+		struct request_queue *q);
 struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
 						const struct blk_mq_ops *ops,
 						unsigned int queue_depth,

include/linux/elevator.h

@@ -120,6 +120,7 @@ extern void elv_merged_request(struct request_queue *, struct request *,
 extern bool elv_attempt_insert_merge(struct request_queue *, struct request *);
 extern struct request *elv_former_request(struct request_queue *, struct request *);
 extern struct request *elv_latter_request(struct request_queue *, struct request *);
+void elevator_init_mq(struct request_queue *q);
 
 /*
  * io scheduler registration