blk-mq: provide helper for setting up an SQ queue and tag set

This pattern is repeated throughout all the blk-mq conversions.
Provide a basic helper to get it done.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -2507,6 +2507,39 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 }
 EXPORT_SYMBOL(blk_mq_init_queue);
 
+/*
+ * Helper for setting up a queue with mq ops, given queue depth, and
+ * the passed in mq ops flags.
+ */
+struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
+					   const struct blk_mq_ops *ops,
+					   unsigned int queue_depth,
+					   unsigned int set_flags)
+{
+	struct request_queue *q;
+	int ret;
+
+	memset(set, 0, sizeof(*set));
+	set->ops = ops;
+	set->nr_hw_queues = 1;
+	set->queue_depth = queue_depth;
+	set->numa_node = NUMA_NO_NODE;
+	set->flags = set_flags;
+
+	ret = blk_mq_alloc_tag_set(set);
+	if (ret)
+		return ERR_PTR(ret);
+
+	q = blk_mq_init_queue(set);
+	if (IS_ERR(q)) {
+		blk_mq_free_tag_set(set);
+		return q;
+	}
+
+	return q;
+}
+EXPORT_SYMBOL(blk_mq_init_sq_queue);
+
 static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
 {
 	int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);

include/linux/blk-mq.h

@@ -203,6 +203,10 @@ enum {
 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
 struct request_queue *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,
+						unsigned int set_flags);
 int blk_mq_register_dev(struct device *, struct request_queue *);
 void blk_mq_unregister_dev(struct device *, struct request_queue *);