z2ram: add error handling support for add_disk()

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling. Only the disk is cleaned up inside
z2ram_register_disk() as the caller deals with the rest.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20211103230437.1639990-8-mcgrof@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/z2ram.c

@@ -318,6 +318,7 @@ static const struct blk_mq_ops z2_mq_ops = {
 static int z2ram_register_disk(int minor)
 {
 	struct gendisk *disk;
+	int err;
 
 	disk = blk_mq_alloc_disk(&tag_set, NULL);
 	if (IS_ERR(disk))
@@ -333,8 +334,10 @@ static int z2ram_register_disk(int minor)
 		sprintf(disk->disk_name, "z2ram");
 
 	z2ram_gendisk[minor] = disk;
-	add_disk(disk);
-	return 0;
+	err = add_disk(disk);
+	if (err)
+		blk_cleanup_disk(disk);
+	return err;
 }
 
 static int __init z2_init(void)