s390/cio: dont unregister subchannel from child-drivers

The devices owned by the parent-driver (css) was getting unregistered
from the io-subchannel driver is clearly a layering violation.
Remove the subchannel unregistration from the child-drivers.

This also means, if the device connected to the subchannel is not
operational, or not accessible, the subchannel will not be unregistered.
Instead the CIO layer will allow valid subchannels without any operational
devices in sysfs. And the userspace tooling might need to be modified to
optimally handle this new situation.

Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/cio/blacklist.c

@@ -262,7 +262,10 @@ static int blacklist_parse_proc_parameters(char *buf)
 
 	if (strcmp("free", parm) == 0) {
 		rc = blacklist_parse_parameters(buf, free, 0);
-		css_schedule_eval_all_unreg(0);
+		/* There could be subchannels without proper devices connected.
+		 * evaluate all the entries
+		 */
+		css_schedule_eval_all();
 	} else if (strcmp("add", parm) == 0)
 		rc = blacklist_parse_parameters(buf, add, 0);
 	else if (strcmp("purge", parm) == 0)

drivers/s390/cio/device.c

@@ -867,19 +867,6 @@ static void io_subchannel_register(struct ccw_device *cdev)
 		wake_up(&ccw_device_init_wq);
 }
 
-static void ccw_device_call_sch_unregister(struct ccw_device *cdev)
-{
-	struct subchannel *sch;
-
-	/* Get subchannel reference for local processing. */
-	if (!get_device(cdev->dev.parent))
-		return;
-	sch = to_subchannel(cdev->dev.parent);
-	css_sch_device_unregister(sch);
-	/* Release subchannel reference for local processing. */
-	put_device(&sch->dev);
-}
-
 /*
  * subchannel recognition done. Called from the state machine.
  */
@@ -1860,10 +1847,10 @@ static void ccw_device_todo(struct work_struct *work)
 			css_schedule_eval(sch->schid);
 		fallthrough;
 	case CDEV_TODO_UNREG:
-		if (sch_is_pseudo_sch(sch))
-			ccw_device_unregister(cdev);
-		else
-			ccw_device_call_sch_unregister(cdev);
+		spin_lock_irq(sch->lock);
+		sch_set_cdev(sch, NULL);
+		spin_unlock_irq(sch->lock);
+		ccw_device_unregister(cdev);
 		break;
 	default:
 		break;