dm: fix congested_fn for request-based device

We neither assign congested_fn for requested-based blk-mq device nor
implement it correctly. So fix both.

Also, remove incorrect comment from dm_init_normal_md_queue and rename
it to dm_init_congested_fn.

Fixes: 4aa9c692 ("bdi: separate out congested state into a separate struct")
Cc: stable@vger.kernel.org
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -1788,7 +1788,8 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
 			 * With request-based DM we only need to check the
 			 * top-level queue for congestion.
 			 */
-			r = md->queue->backing_dev_info->wb.state & bdi_bits;
+			struct backing_dev_info *bdi = md->queue->backing_dev_info;
+			r = bdi->wb.congested->state & bdi_bits;
 		} else {
 			map = dm_get_live_table_fast(md);
 			if (map)
@@ -1854,15 +1855,6 @@ static const struct dax_operations dm_dax_ops;
 
 static void dm_wq_work(struct work_struct *work);
 
-static void dm_init_normal_md_queue(struct mapped_device *md)
-{
-	/*
-	 * Initialize aspects of queue that aren't relevant for blk-mq
-	 */
-	md->queue->backing_dev_info->congested_data = md;
-	md->queue->backing_dev_info->congested_fn = dm_any_congested;
-}
-
 static void cleanup_mapped_device(struct mapped_device *md)
 {
 	if (md->wq)
@@ -2249,6 +2241,12 @@ struct queue_limits *dm_get_queue_limits(struct mapped_device *md)
 }
 EXPORT_SYMBOL_GPL(dm_get_queue_limits);
 
+static void dm_init_congested_fn(struct mapped_device *md)
+{
+	md->queue->backing_dev_info->congested_data = md;
+	md->queue->backing_dev_info->congested_fn = dm_any_congested;
+}
+
 /*
  * Setup the DM device's queue based on md's type
  */
@@ -2265,11 +2263,12 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
 			DMERR("Cannot initialize queue for request-based dm-mq mapped device");
 			return r;
 		}
+		dm_init_congested_fn(md);
 		break;
 	case DM_TYPE_BIO_BASED:
 	case DM_TYPE_DAX_BIO_BASED:
 	case DM_TYPE_NVME_BIO_BASED:
-		dm_init_normal_md_queue(md);
+		dm_init_congested_fn(md);
 		break;
 	case DM_TYPE_NONE:
 		WARN_ON_ONCE(true);