[PATCH 02/30] blk-mq: improve the blk_mq_init_allocated_queue interface

[Christoph Hellwig]

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 at lst.de>
---
 block/blk-mq.c           | 36 ++++++++++++++----------------------
 block/blk.h              |  1 -
 block/elevator.c         |  2 +-
 drivers/md/dm-rq.c       |  9 +++------
 include/linux/blk-mq.h   |  5 ++---
 include/linux/elevator.h |  1 +
 6 files changed, 21 insertions(+), 33 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index eaacfa963a73..6112741e1ff9 100644
--- a/block/blk-mq.c
+++ b/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);
 
diff --git a/block/blk.h b/block/blk.h
index 3440142f029b..d3fa47af3607 100644
--- a/block/blk.h
+++ b/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 *);
diff --git a/block/elevator.c b/block/elevator.c
index 440699c28119..06e203426410 100644
--- a/block/elevator.c
+++ b/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 -
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 9c3bc3711b33..0dbd48cbdff9 100644
--- a/drivers/md/dm-rq.c
+++ b/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:
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index bb950fc669ef..73750b2838d2 100644
--- a/include/linux/blk-mq.h
+++ b/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,
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index dcb2f9022c1d..783ecb3cb77a 100644
--- a/include/linux/elevator.h
+++ b/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
-- 
2.30.2