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/raid10.c b/drivers/md/raid10.c
index 1920756..6bc5c2a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -860,7 +860,7 @@ static int raid10_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);
 		}
 	}
 	rcu_read_unlock();
@@ -3841,8 +3841,8 @@ static int raid10_run(struct mddev *mddev)
 		 * maybe...
 		 */
 		stripe /= conf->geo.near_copies;
-		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
-			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
+		if (mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
+			mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
 	}
 
 	if (md_integrity_register(mddev))
@@ -4643,8 +4643,8 @@ static void end_reshape(struct r10conf *conf)
 		int stripe = conf->geo.raid_disks *
 			((conf->mddev->chunk_sectors << 9) / PAGE_SIZE);
 		stripe /= conf->geo.near_copies;
-		if (conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
-			conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
+		if (conf->mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
+			conf->mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
 	}
 	conf->fullsync = 0;
 }