bcache: 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.

This driver doesn't do any unwinding with blk_cleanup_disk()
even on errors after add_disk() and so we follow that
tradition.
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20211015233028.2167651-5-mcgrof@kernel.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/super.c

@@ -1080,7 +1080,9 @@ int bch_cached_dev_run(struct cached_dev *dc)
 		closure_sync(&cl);
 	}
 
-	add_disk(d->disk);
+	ret = add_disk(d->disk);
+	if (ret)
+		goto out;
 	bd_link_disk_holder(dc->bdev, dc->disk.disk);
 	/*
 	 * won't show up in the uevent file, use udevadm monitor -e instead
@@ -1526,10 +1528,11 @@ static void flash_dev_flush(struct closure *cl)
 
 static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
 {
+	int err = -ENOMEM;
 	struct bcache_device *d = kzalloc(sizeof(struct bcache_device),
 					  GFP_KERNEL);
 	if (!d)
-		return -ENOMEM;
+		goto err_ret;
 
 	closure_init(&d->cl, NULL);
 	set_closure_fn(&d->cl, flash_dev_flush, system_wq);
@@ -1543,9 +1546,12 @@ static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
 	bcache_device_attach(d, c, u - c->uuids);
 	bch_sectors_dirty_init(d);
 	bch_flash_dev_request_init(d);
-	add_disk(d->disk);
+	err = add_disk(d->disk);
+	if (err)
+		goto err;
 
-	if (kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache"))
+	err = kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache");
+	if (err)
 		goto err;
 
 	bcache_device_link(d, c, "volume");
@@ -1559,7 +1565,8 @@ static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
 	return 0;
 err:
 	kobject_put(&d->kobj);
-	return -ENOMEM;
+err_ret:
+	return err;
 }
 
 static int flash_devs_run(struct cache_set *c)