s390/dasd: fix double module refcount decrement

BugLink: https://bugs.launchpad.net/bugs/2060097

[ Upstream commit c3116e62ddeff79cae342147753ce596f01fcf06 ]

Once the discipline is associated with the device, deleting the device
takes care of decrementing the module's refcount.  Doing it manually on
this error path causes refcount to artificially decrease on each error
while it should just stay the same.

Fixes: c020d722b1 ("s390/dasd: fix panic during offline processing")
Signed-off-by: Miroslav Franc <mfranc@suse.cz>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20240209124522.3697827-3-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit ebc5a3bd79e54f98c885c26f0862a27a02c487c5)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

drivers/s390/block/dasd.c

@@ -3524,12 +3524,11 @@ int dasd_generic_set_online(struct ccw_device *cdev,
 		dasd_delete_device(device);
 		return -EINVAL;
 	}
+	device->base_discipline = base_discipline;
 	if (!try_module_get(discipline->owner)) {
-		module_put(base_discipline->owner);
 		dasd_delete_device(device);
 		return -EINVAL;
 	}
-	device->base_discipline = base_discipline;
 	device->discipline = discipline;
 
 	/* check_device will allocate block device if necessary */
@@ -3537,8 +3536,6 @@ int dasd_generic_set_online(struct ccw_device *cdev,
 	if (rc) {
 		dev_warn(dev, "Setting the DASD online with discipline %s failed with rc=%i\n",
 			 discipline->name, rc);
-		module_put(discipline->owner);
-		module_put(base_discipline->owner);
 		dasd_delete_device(device);
 		return rc;
 	}