diff --git a/drivers/s390/char/vmur.c b/drivers/s390/char/vmur.c
index 2d96c95..d70a6e6 100644
--- a/drivers/s390/char/vmur.c
+++ b/drivers/s390/char/vmur.c
@@ -69,8 +69,26 @@
 	.set_offline	= ur_set_offline,
 };
 
+static DEFINE_MUTEX(vmur_mutex);
+
 /*
  * Allocation, freeing, getting and putting of urdev structures
+ *
+ * Each ur device (urd) contains a reference to its corresponding ccw device
+ * (cdev) using the urd->cdev pointer. Each ccw device has a reference to the
+ * ur device using the cdev->dev.driver_data pointer.
+ *
+ * urd references:
+ * - ur_probe gets a urd reference, ur_remove drops the reference
+ *   (cdev->dev.driver_data)
+ * - ur_open gets a urd reference, ur_relase drops the reference
+ *   (urf->urd)
+ *
+ * cdev references:
+ * - urdev_alloc get a cdev reference (urd->cdev)
+ * - urdev_free drops the cdev reference (urd->cdev)
+ *
+ * Setting and clearing of cdev->dev.driver_data is protected by the ccwdev lock
  */
 static struct urdev *urdev_alloc(struct ccw_device *cdev)
 {
@@ -79,42 +97,61 @@
 	urd = kzalloc(sizeof(struct urdev), GFP_KERNEL);
 	if (!urd)
 		return NULL;
-	urd->cdev = cdev;
 	urd->reclen = cdev->id.driver_info;
 	ccw_device_get_id(cdev, &urd->dev_id);
 	mutex_init(&urd->io_mutex);
 	mutex_init(&urd->open_mutex);
+	atomic_set(&urd->ref_count,  1);
+	urd->cdev = cdev;
+	get_device(&cdev->dev);
 	return urd;
 }
 
 static void urdev_free(struct urdev *urd)
 {
+	TRACE("urdev_free: %p\n", urd);
+	if (urd->cdev)
+		put_device(&urd->cdev->dev);
 	kfree(urd);
 }
 
-/*
- * This is how the character device driver gets a reference to a
- * ur device. When this call returns successfully, a reference has
- * been taken (by get_device) on the underlying kobject. The recipient
- * of this urdev pointer must eventually drop it with urdev_put(urd)
- * which does the corresponding put_device().
- */
+static void urdev_get(struct urdev *urd)
+{
+	atomic_inc(&urd->ref_count);
+}
+
+static struct urdev *urdev_get_from_cdev(struct ccw_device *cdev)
+{
+	struct urdev *urd;
+	unsigned long flags;
+
+	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+	urd = cdev->dev.driver_data;
+	if (urd)
+		urdev_get(urd);
+	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+	return urd;
+}
+
 static struct urdev *urdev_get_from_devno(u16 devno)
 {
 	char bus_id[16];
 	struct ccw_device *cdev;
+	struct urdev *urd;
 
 	sprintf(bus_id, "0.0.%04x", devno);
 	cdev = get_ccwdev_by_busid(&ur_driver, bus_id);
 	if (!cdev)
 		return NULL;
-
-	return cdev->dev.driver_data;
+	urd = urdev_get_from_cdev(cdev);
+	put_device(&cdev->dev);
+	return urd;
 }
 
 static void urdev_put(struct urdev *urd)
 {
-	put_device(&urd->cdev->dev);
+	if (atomic_dec_and_test(&urd->ref_count))
+		urdev_free(urd);
 }
 
 /*
@@ -246,6 +283,7 @@
 		return;
 	}
 	urd = cdev->dev.driver_data;
+	BUG_ON(!urd);
 	/* On special conditions irb is an error pointer */
 	if (IS_ERR(irb))
 		urd->io_request_rc = PTR_ERR(irb);
@@ -263,9 +301,15 @@
 static ssize_t ur_attr_reclen_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
-	struct urdev *urd = dev->driver_data;
+	struct urdev *urd;
+	int rc;
 
-	return sprintf(buf, "%zu\n", urd->reclen);
+	urd = urdev_get_from_cdev(to_ccwdev(dev));
+	if (!urd)
+		return -ENODEV;
+	rc = sprintf(buf, "%zu\n", urd->reclen);
+	urdev_put(urd);
+	return rc;
 }
 
 static DEVICE_ATTR(reclen, 0444, ur_attr_reclen_show, NULL);
@@ -726,64 +770,63 @@
 
 /*
  * ccw_device infrastructure:
- *     ur_probe gets its own ref to the device (i.e. get_device),
- *     creates the struct urdev, the device attributes, sets up
- *     the interrupt handler and validates the virtual unit record device.
- *     ur_remove removes the device attributes, frees the struct urdev
- *     and drops (put_device) the ref to the device we got in ur_probe.
+ *     ur_probe creates the struct urdev (with refcount = 1), the device
+ *     attributes, sets up the interrupt handler and validates the virtual
+ *     unit record device.
+ *     ur_remove removes the device attributes and drops the reference to
+ *     struct urdev.
+ *
+ *     ur_probe, ur_remove, ur_set_online and ur_set_offline are serialized
+ *     by the vmur_mutex lock.
+ *
+ *     urd->char_device is used as indication that the online function has
+ *     been completed successfully.
  */
 static int ur_probe(struct ccw_device *cdev)
 {
 	struct urdev *urd;
 	int rc;
 
-	TRACE("ur_probe: cdev=%p state=%d\n", cdev, *(int *) cdev->private);
+	TRACE("ur_probe: cdev=%p\n", cdev);
 
-	if (!get_device(&cdev->dev))
-		return -ENODEV;
-
+	mutex_lock(&vmur_mutex);
 	urd = urdev_alloc(cdev);
 	if (!urd) {
 		rc = -ENOMEM;
-		goto fail;
+		goto fail_unlock;
 	}
+
 	rc = ur_create_attributes(&cdev->dev);
 	if (rc) {
 		rc = -ENOMEM;
-		goto fail;
+		goto fail_urdev_put;
 	}
-	cdev->dev.driver_data = urd;
 	cdev->handler = ur_int_handler;
 
 	/* validate virtual unit record device */
 	urd->class = get_urd_class(urd);
 	if (urd->class < 0) {
 		rc = urd->class;
-		goto fail;
+		goto fail_remove_attr;
 	}
 	if ((urd->class != DEV_CLASS_UR_I) && (urd->class != DEV_CLASS_UR_O)) {
 		rc = -ENOTSUPP;
-		goto fail;
+		goto fail_remove_attr;
 	}
+	spin_lock_irq(get_ccwdev_lock(cdev));
+	cdev->dev.driver_data = urd;
+	spin_unlock_irq(get_ccwdev_lock(cdev));
 
+	mutex_unlock(&vmur_mutex);
 	return 0;
 
-fail:
-	urdev_free(urd);
-	put_device(&cdev->dev);
-	return rc;
-}
-
-static void ur_remove(struct ccw_device *cdev)
-{
-	struct urdev *urd = cdev->dev.driver_data;
-
-	TRACE("ur_remove\n");
-	if (cdev->online)
-		ur_set_offline(cdev);
+fail_remove_attr:
 	ur_remove_attributes(&cdev->dev);
-	urdev_free(urd);
-	put_device(&cdev->dev);
+fail_urdev_put:
+	urdev_put(urd);
+fail_unlock:
+	mutex_unlock(&vmur_mutex);
+	return rc;
 }
 
 static int ur_set_online(struct ccw_device *cdev)
@@ -792,20 +835,29 @@
 	int minor, major, rc;
 	char node_id[16];
 
-	TRACE("ur_set_online: cdev=%p state=%d\n", cdev,
-	      *(int *) cdev->private);
+	TRACE("ur_set_online: cdev=%p\n", cdev);
 
-	if (!try_module_get(ur_driver.owner))
-		return -EINVAL;
+	mutex_lock(&vmur_mutex);
+	urd = urdev_get_from_cdev(cdev);
+	if (!urd) {
+		/* ur_remove already deleted our urd */
+		rc = -ENODEV;
+		goto fail_unlock;
+	}
 
-	urd = (struct urdev *) cdev->dev.driver_data;
+	if (urd->char_device) {
+		/* Another ur_set_online was faster */
+		rc = -EBUSY;
+		goto fail_urdev_put;
+	}
+
 	minor = urd->dev_id.devno;
 	major = MAJOR(ur_first_dev_maj_min);
 
 	urd->char_device = cdev_alloc();
 	if (!urd->char_device) {
 		rc = -ENOMEM;
-		goto fail_module_put;
+		goto fail_urdev_put;
 	}
 
 	cdev_init(urd->char_device, &ur_fops);
@@ -834,29 +886,79 @@
 		TRACE("ur_set_online: device_create rc=%d\n", rc);
 		goto fail_free_cdev;
 	}
-
+	urdev_put(urd);
+	mutex_unlock(&vmur_mutex);
 	return 0;
 
 fail_free_cdev:
 	cdev_del(urd->char_device);
-fail_module_put:
-	module_put(ur_driver.owner);
+	urd->char_device = NULL;
+fail_urdev_put:
+	urdev_put(urd);
+fail_unlock:
+	mutex_unlock(&vmur_mutex);
+	return rc;
+}
 
+static int ur_set_offline_force(struct ccw_device *cdev, int force)
+{
+	struct urdev *urd;
+	int rc;
+
+	TRACE("ur_set_offline: cdev=%p\n", cdev);
+	urd = urdev_get_from_cdev(cdev);
+	if (!urd)
+		/* ur_remove already deleted our urd */
+		return -ENODEV;
+	if (!urd->char_device) {
+		/* Another ur_set_offline was faster */
+		rc = -EBUSY;
+		goto fail_urdev_put;
+	}
+	if (!force && (atomic_read(&urd->ref_count) > 2)) {
+		/* There is still a user of urd (e.g. ur_open) */
+		TRACE("ur_set_offline: BUSY\n");
+		rc = -EBUSY;
+		goto fail_urdev_put;
+	}
+	device_destroy(vmur_class, urd->char_device->dev);
+	cdev_del(urd->char_device);
+	urd->char_device = NULL;
+	rc = 0;
+
+fail_urdev_put:
+	urdev_put(urd);
 	return rc;
 }
 
 static int ur_set_offline(struct ccw_device *cdev)
 {
-	struct urdev *urd;
+	int rc;
 
-	TRACE("ur_set_offline: cdev=%p cdev->private=%p state=%d\n",
-		cdev, cdev->private, *(int *) cdev->private);
-	urd = (struct urdev *) cdev->dev.driver_data;
-	device_destroy(vmur_class, urd->char_device->dev);
-	cdev_del(urd->char_device);
-	module_put(ur_driver.owner);
+	mutex_lock(&vmur_mutex);
+	rc = ur_set_offline_force(cdev, 0);
+	mutex_unlock(&vmur_mutex);
+	return rc;
+}
 
-	return 0;
+static void ur_remove(struct ccw_device *cdev)
+{
+	unsigned long flags;
+
+	TRACE("ur_remove\n");
+
+	mutex_lock(&vmur_mutex);
+
+	if (cdev->online)
+		ur_set_offline_force(cdev, 1);
+	ur_remove_attributes(&cdev->dev);
+
+	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+	urdev_put(cdev->dev.driver_data);
+	cdev->dev.driver_data = NULL;
+	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+
+	mutex_unlock(&vmur_mutex);
 }
 
 /*