[S390] ccwgroup device unregister.

Work around the problem that a device cannot be unregistered from
driver_for_each_device() because of klist node refcounting: Get device
after device owned by the driver to be unregistered with driver_find_device()
and then unregister it. This works because driver_get_device() gets us out of
the region of the elevated klist node refcount. driver_find_device() will
always get the next device in the list after the found one has been
unregistered.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/ccwgroup.c

@@ -404,21 +404,24 @@ ccwgroup_driver_register (struct ccwgroup_driver *cdriver)
 }
 
 static int
-__ccwgroup_driver_unregister_device(struct device *dev, void *data)
+__ccwgroup_match_all(struct device *dev, void *data)
 {
-	__ccwgroup_remove_symlinks(to_ccwgroupdev(dev));
-	device_unregister(dev);
-	put_device(dev);
-	return 0;
+	return 1;
 }
 
 void
 ccwgroup_driver_unregister (struct ccwgroup_driver *cdriver)
 {
+	struct device *dev;
+
 	/* We don't want ccwgroup devices to live longer than their driver. */
 	get_driver(&cdriver->driver);
-	driver_for_each_device(&cdriver->driver, NULL, NULL,
-			       __ccwgroup_driver_unregister_device);
+	while ((dev = driver_find_device(&cdriver->driver, NULL, NULL,
+					 __ccwgroup_match_all))) {
+		__ccwgroup_remove_symlinks(to_ccwgroupdev(dev));
+		device_unregister(dev);
+		put_device(dev);
+	}
 	put_driver(&cdriver->driver);
 	driver_unregister(&cdriver->driver);
 }