[S390] dasd: fix refcounting.

The function dasd_device_from_cdev returns a reference to the dasd
device and increases the refcount by one. If an exception occurs,
the refcount was not decreased in all cases
e.g. in dasd_discipline_show.
Prevent the offline processing from hang by correcting two functions
to decrease the refcount even if an error occured.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index 4cac5b5..d49766f 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -874,12 +874,19 @@
 	ssize_t len;
 
 	device = dasd_device_from_cdev(to_ccwdev(dev));
-	if (!IS_ERR(device) && device->discipline) {
+	if (IS_ERR(device))
+		goto out;
+	else if (!device->discipline) {
+		dasd_put_device(device);
+		goto out;
+	} else {
 		len = snprintf(buf, PAGE_SIZE, "%s\n",
 			       device->discipline->name);
 		dasd_put_device(device);
-	} else
-		len = snprintf(buf, PAGE_SIZE, "none\n");
+		return len;
+	}
+out:
+	len = snprintf(buf, PAGE_SIZE, "none\n");
 	return len;
 }