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.

Change-Id: Ib99961747ed2d58cc2f9c0581c66c55a49aaee4b
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Git-commit: dc3b17cc8bf21307c7e076e7c778d5db756f7871
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
[riteshh@codeaurora.org: Resolved minor merge conflicts]
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index c817627..bed056c 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2290,7 +2290,7 @@
 static int is_congested(struct dm_dev *dev, int bdi_bits)
 {
 	struct request_queue *q = bdev_get_queue(dev->bdev);
-	return bdi_congested(&q->backing_dev_info, bdi_bits);
+	return bdi_congested(q->backing_dev_info, bdi_bits);
 }
 
 static int cache_is_congested(struct dm_target_callbacks *cb, int bdi_bits)