[S390] cio: Use path verification for last path gone after vary off.

If the last path to a device is gone after a chpid has been varied
off, putting it on the slow queue doesn't prevent a device driver
from still attempting to use it (it may stay on the slow queue for a
long time). Instead, trigger a verify event which will prevent I/O
attempts from the device driver immediately.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/chsc.c

@@ -744,20 +744,22 @@ __s390_subchannel_vary_chpid(struct subchannel *sch, __u8 chpid, int on)
 				device_trigger_reprobe(sch);
 			else if (sch->driver && sch->driver->verify)
 				sch->driver->verify(&sch->dev);
-		} else {
+			break;
+		}
 		sch->opm &= ~(0x80 >> chp);
 		sch->lpm &= ~(0x80 >> chp);
 		if (check_for_io_on_path(sch, chp))
 			/* Path verification is done after killing. */
 			device_kill_io(sch);
 		else if (!sch->lpm) {
+			if (device_trigger_verify(sch) != 0) {
 				if (css_enqueue_subchannel_slow(sch->schid)) {
 					css_clear_subchannel_slow_list();
 					need_rescan = 1;
 				}
+			}
 		} else if (sch->driver && sch->driver->verify)
 			sch->driver->verify(&sch->dev);
-		}
 		break;
 	}
 	spin_unlock_irqrestore(&sch->lock, flags);

drivers/s390/cio/css.h

@@ -171,6 +171,7 @@ void device_trigger_reprobe(struct subchannel *);
 /* Helper functions for vary on/off. */
 int device_is_online(struct subchannel *);
 void device_kill_io(struct subchannel *);
+int device_trigger_verify(struct subchannel *sch);
 
 /* Machine check helper function. */
 void device_kill_pending_timer(struct subchannel *);

drivers/s390/cio/device_fsm.c

@@ -59,6 +59,17 @@ device_set_disconnected(struct subchannel *sch)
 	cdev->private->state = DEV_STATE_DISCONNECTED;
 }
 
+int device_trigger_verify(struct subchannel *sch)
+{
+	struct ccw_device *cdev;
+
+	cdev = sch->dev.driver_data;
+	if (!cdev || !cdev->online)
+		return -EINVAL;
+	dev_fsm_event(cdev, DEV_EVENT_VERIFY);
+	return 0;
+}
+
 /*
  * Timeout function. It just triggers a DEV_EVENT_TIMEOUT.
  */