um/drivers/ubd_kern: 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.

ubd_disk_register() never returned an error, so just fix
that now and let the caller handle the error condition.

Reviewed-by: Gabriel Krisman Bertazi <[e-mail]>
Signed-off-by: Luis Chamberlain <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

arch/um/drivers/ubd_kern.c

···
 	NULL,
 };
 
-static void ubd_disk_register(int major, u64 size, int unit,
-			      struct gendisk *disk)
+static int ubd_disk_register(int major, u64 size, int unit,
+			     struct gendisk *disk)
 {
 	disk->major = major;
 	disk->first_minor = unit << UBD_SHIFT;
···
 
 	disk->private_data = &ubd_devs[unit];
 	disk->queue = ubd_devs[unit].queue;
-	device_add_disk(&ubd_devs[unit].pdev.dev, disk, ubd_attr_groups);
+	return device_add_disk(&ubd_devs[unit].pdev.dev, disk, ubd_attr_groups);
 }
 
 #define ROUND_BLOCK(n) ((n + (SECTOR_SIZE - 1)) & (-SECTOR_SIZE))
···
 	blk_queue_write_cache(ubd_dev->queue, true, false);
 	blk_queue_max_segments(ubd_dev->queue, MAX_SG);
 	blk_queue_segment_boundary(ubd_dev->queue, PAGE_SIZE - 1);
-	ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, disk);
+	err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, disk);
+	if (err)
+		goto out_cleanup_disk;
+
 	ubd_gendisk[n] = disk;
 	return 0;
 
+out_cleanup_disk:
+	blk_cleanup_disk(disk);
 out_cleanup_tags:
 	blk_mq_free_tag_set(&ubd_dev->tag_set);
 out: