block: Use pointer to backing_dev_info from request_queue

We will want to have struct backing_dev_info allocated separately from
struct request_queue. As the first step add pointer to backing_dev_info
to request_queue and convert all users touching it. No functional
changes in this patch.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index aa8c4e5c..d457afa 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -169,7 +169,7 @@ static int multipath_congested(struct mddev *mddev, int bits)
 		if (rdev && !test_bit(Faulty, &rdev->flags)) {
 			struct request_queue *q = bdev_get_queue(rdev->bdev);
 
-			ret |= bdi_congested(&q->backing_dev_info, bits);
+			ret |= bdi_congested(q->backing_dev_info, bits);
 			/* Just like multipath_map, we just check the
 			 * first available device
 			 */