block: better split mq vs non-mq code in add_disk_fwnode

Add a big conditional for blk-mq vs not mq at the beginning of
add_disk_fwnode so that elevator_init_mq is only called for blk-mq disks,
and add checks that the right methods or set or not set based on the
queue type.

Signed-off-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

block/genhd.c

@@ -400,21 +400,23 @@ int __must_check add_disk_fwnode(struct device *parent, struct gendisk *disk,
 	struct device *ddev = disk_to_dev(disk);
 	int ret;
 
-	/* Only makes sense for bio-based to set ->poll_bio */
-	if (queue_is_mq(disk->queue) && disk->fops->poll_bio)
-		return -EINVAL;
-
-	/*
-	 * The disk queue should now be all set with enough information about
-	 * the device for the elevator code to pick an adequate default
-	 * elevator if one is needed, that is, for devices requesting queue
-	 * registration.
-	 */
-	elevator_init_mq(disk->queue);
+	if (queue_is_mq(disk->queue)) {
+		/*
+		 * ->submit_bio and ->poll_bio are bypassed for blk-mq drivers.
+		 */
+		if (disk->fops->submit_bio || disk->fops->poll_bio)
+			return -EINVAL;
 
-	/* Mark bdev as having a submit_bio, if needed */
-	if (disk->fops->submit_bio)
+		/*
+		 * Initialize the I/O scheduler code and pick a default one if
+		 * needed.
+		 */
+		elevator_init_mq(disk->queue);
+	} else {
+		if (!disk->fops->submit_bio)
+			return -EINVAL;
 		bdev_set_flag(disk->part0, BD_HAS_SUBMIT_BIO);
+	}
 
 	/*
 	 * If the driver provides an explicit major number it also must provide