nbd: remove nbd_del_disk

Fold nbd_del_disk and remove the pointless NULL check on ->disk given
that it is always set for a successfully allocated nbd_device structure.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-4-hch@lst.deReviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/nbd.c

@@ -235,17 +235,6 @@ static const struct device_attribute backend_attr = {
 	.show = backend_show,
 };
 
-static void nbd_del_disk(struct nbd_device *nbd)
-{
-	struct gendisk *disk = nbd->disk;
-
-	if (disk) {
-		del_gendisk(disk);
-		blk_cleanup_disk(disk);
-		blk_mq_free_tag_set(&nbd->tag_set);
-	}
-}
-
 /*
  * Place this in the last just before the nbd is freed to
  * make sure that the disk and the related kobject are also
@@ -261,7 +250,11 @@ static void nbd_notify_destroy_completion(struct nbd_device *nbd)
 
 static void nbd_dev_remove(struct nbd_device *nbd)
 {
-	nbd_del_disk(nbd);
+	struct gendisk *disk = nbd->disk;
+
+	del_gendisk(disk);
+	blk_cleanup_disk(disk);
+	blk_mq_free_tag_set(&nbd->tag_set);
 
 	/*
 	 * Remove from idr after del_gendisk() completes, so if the same ID is