bsg: update check for rq based driver for blk-mq

bsg currently checks ->request_fn to check whether a queue can
handle struct request. But with blk-mq, we don't have a request_fn
yet are request based. Add a queue_is_rq_based() helper and use
that in bsg, I'm guessing this is not the last place we need to
update for this. Besides, it better explains what is being
checked.

Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 20b26d4e53a..74ee55fefcf 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -612,6 +612,15 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
 
 #define rq_data_dir(rq)		(((rq)->cmd_flags & 1) != 0)
 
+/*
+ * Driver can handle struct request, if it either has an old style
+ * request_fn defined, or is blk-mq based.
+ */
+static inline bool queue_is_rq_based(struct request_queue *q)
+{
+	return q->request_fn || q->mq_ops;
+}
+
 static inline unsigned int blk_queue_cluster(struct request_queue *q)
 {
 	return q->limits.cluster;