block: add a blk_mq_init_queue_data helper

This allows a driver to pass a queuedata member before ->init_hctx is
called.  null_blk currently open codes this logic, but I'd rather have
it in the core to ease future maintainance.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -2724,13 +2724,15 @@ void blk_mq_release(struct request_queue *q)
 	blk_mq_sysfs_deinit(q);
 }
 
-struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
+struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
+		void *queuedata)
 {
 	struct request_queue *uninit_q, *q;
 
 	uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
 	if (!uninit_q)
 		return ERR_PTR(-ENOMEM);
+	uninit_q->queuedata = queuedata;
 
 	/*
 	 * Initialize the queue without an elevator. device_add_disk() will do
@@ -2742,6 +2744,12 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 
 	return q;
 }
+EXPORT_SYMBOL_GPL(blk_mq_init_queue_data);
+
+struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
+{
+	return blk_mq_init_queue_data(set, NULL);
+}
 EXPORT_SYMBOL(blk_mq_init_queue);
 
 /*

include/linux/blk-mq.h

@@ -412,6 +412,8 @@ enum {
 		<< BLK_MQ_F_ALLOC_POLICY_START_BIT)
 
 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);