Revert "s390: use device_remove_file_self() instead of device_schedule_callback()"

This reverts commit bdbb0a1376.

Tejun writes:
        I'm sorry but can you please revert the whole series?
        get_active() waiting while a node is deactivated has potential
        to lead to deadlock and that deactivate/reactivate interface is
        something fundamentally flawed and that cgroup will have to work
        with the remove_self() like everybody else.  IOW, I think the
        first posting was correct.

Cc: Tejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/s390/include/asm/ccwgroup.h

@@ -23,7 +23,6 @@ struct ccwgroup_device {
 	unsigned int count;
 	struct device	dev;
 	struct ccw_device *cdev[0];
-	struct work_struct ungroup_work;
 };
 
 /**

arch/s390/pci/pci_sysfs.c

@@ -48,27 +48,29 @@ static ssize_t show_pfgid(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR(pfgid, S_IRUGO, show_pfgid, NULL);
 
-static ssize_t store_recover(struct device *dev, struct device_attribute *attr,
+static void recover_callback(struct device *dev)
-			     const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct zpci_dev *zdev = get_zdev(pdev);
 	int ret;
 
-	if (!device_remove_file_self(dev, attr))
-		return count;
-
 	pci_stop_and_remove_bus_device(pdev);
 	ret = zpci_disable_device(zdev);
 	if (ret)
-		return ret;
+		return;
 
 	ret = zpci_enable_device(zdev);
 	if (ret)
-		return ret;
+		return;
 
 	pci_rescan_bus(zdev->bus);
-	return count;
+}
+
+static ssize_t store_recover(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	int rc = device_schedule_callback(dev, recover_callback);
+	return rc ? rc : count;
 }
 static DEVICE_ATTR(recover, S_IWUSR, NULL, store_recover);
 

drivers/s390/block/dcssblk.c

@@ -304,6 +304,12 @@ dcssblk_load_segment(char *name, struct segment_info **seg_info)
 	return rc;
 }
 
+static void dcssblk_unregister_callback(struct device *dev)
+{
+	device_unregister(dev);
+	put_device(dev);
+}
+
 /*
  * device attribute for switching shared/nonshared (exclusive)
  * operation (show + store)
@@ -391,13 +397,7 @@ dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const ch
 	blk_cleanup_queue(dev_info->dcssblk_queue);
 	dev_info->gd->queue = NULL;
 	put_disk(dev_info->gd);
-	up_write(&dcssblk_devices_sem);
+	rc = device_schedule_callback(dev, dcssblk_unregister_callback);
-
-	if (device_remove_file_self(dev, attr)) {
-		device_unregister(dev);
-		put_device(dev);
-	}
-	return rc;
 out:
 	up_write(&dcssblk_devices_sem);
 	return rc;

drivers/s390/cio/ccwgroup.c

@@ -168,12 +168,14 @@ static ssize_t ccwgroup_online_show(struct device *dev,
  * Provide an 'ungroup' attribute so the user can remove group devices no
  * longer needed or accidentially created. Saves memory :)
  */
-static void ccwgroup_ungroup(struct ccwgroup_device *gdev)
+static void ccwgroup_ungroup_callback(struct device *dev)
 {
+	struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
+
 	mutex_lock(&gdev->reg_mutex);
 	if (device_is_registered(&gdev->dev)) {
 		__ccwgroup_remove_symlinks(gdev);
-		device_unregister(&gdev->dev);
+		device_unregister(dev);
 		__ccwgroup_remove_cdev_refs(gdev);
 	}
 	mutex_unlock(&gdev->reg_mutex);
@@ -193,9 +195,10 @@ static ssize_t ccwgroup_ungroup_store(struct device *dev,
 		rc = -EINVAL;
 		goto out;
 	}
-
+	/* Note that we cannot unregister the device from one of its
-	if (device_remove_file_self(dev, attr))
+	 * attribute methods, so we have to use this roundabout approach.
-		ccwgroup_ungroup(gdev);
+	 */
+	rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
 out:
 	if (rc) {
 		if (rc != -EAGAIN)
@@ -221,14 +224,6 @@ static const struct attribute_group *ccwgroup_attr_groups[] = {
 	NULL,
 };
 
-static void ccwgroup_ungroup_workfn(struct work_struct *work)
-{
-	struct ccwgroup_device *gdev =
-		container_of(work, struct ccwgroup_device, ungroup_work);
-
-	ccwgroup_ungroup(gdev);
-}
-
 static void ccwgroup_release(struct device *dev)
 {
 	kfree(to_ccwgroupdev(dev));
@@ -328,7 +323,6 @@ int ccwgroup_create_dev(struct device *parent, struct ccwgroup_driver *gdrv,
 	atomic_set(&gdev->onoff, 0);
 	mutex_init(&gdev->reg_mutex);
 	mutex_lock(&gdev->reg_mutex);
-	INIT_WORK(&gdev->ungroup_work, ccwgroup_ungroup_workfn);
 	gdev->count = num_devices;
 	gdev->dev.bus = &ccwgroup_bus_type;
 	gdev->dev.parent = parent;
@@ -410,10 +404,10 @@ EXPORT_SYMBOL(ccwgroup_create_dev);
 static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
 			     void *data)
 {
-	struct ccwgroup_device *gdev = to_ccwgroupdev(data);
+	struct device *dev = data;
 
 	if (action == BUS_NOTIFY_UNBIND_DRIVER)
-		schedule_work(&gdev->ungroup_work);
+		device_schedule_callback(dev, ccwgroup_ungroup_callback);
 
 	return NOTIFY_OK;
 }