[S390] cio: Fix reference counting for online/offline.

The current code attempts to get an extra reference count
for online devices by doing a get_device() in ccw_device_online()
and a put_device() in ccw_device_done(). However, this
- incorrectly obtains an extra reference for disconnected
  devices becoming available again (since they are already
  online)
- needs special checks for css_init_done in order to handle
  the console device
- is not obvious and
- may incorretly drop a reference count in ccw_device_done() if
  that function is called after path verification for a device
  that just became not operational.

So let's just get the reference in ccw_device_set_online() and
drop it in ccw_device_set_offline(). (Unfortunately, we still
need the special case in io_subchannel_probe().)

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 22 insertions, 7 deletions

diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 647cbaca298..039ef03cf21 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -376,19 +376,23 @@ int ccw_device_set_offline(struct ccw_device *cdev)
 			dev_fsm_event(cdev, DEV_EVENT_NOTOPER);
 		}
 		spin_unlock_irq(cdev->ccwlock);
+		/* Give up reference from ccw_device_set_online(). */
+		put_device(&cdev->dev);
 		return ret;
 	}
 	spin_unlock_irq(cdev->ccwlock);
-	if (ret == 0)
+	if (ret == 0) {
 		wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
-	else {
+		/* Give up reference from ccw_device_set_online(). */
+		put_device(&cdev->dev);
+	} else {
 		CIO_MSG_EVENT(0, "ccw_device_offline returned %d, "
 			      "device 0.%x.%04x\n",
 			      ret, cdev->private->dev_id.ssid,
 			      cdev->private->dev_id.devno);
 		cdev->online = 1;
 	}
- 	return ret;
+	return ret;
 }
 
 /**
@@ -411,6 +415,9 @@ int ccw_device_set_online(struct ccw_device *cdev)
 		return -ENODEV;
 	if (cdev->online || !cdev->drv)
 		return -EINVAL;
+	/* Hold on to an extra reference while device is online. */
+	if (!get_device(&cdev->dev))
+		return -ENODEV;
 
 	spin_lock_irq(cdev->ccwlock);
 	ret = ccw_device_online(cdev);
@@ -422,10 +429,15 @@ int ccw_device_set_online(struct ccw_device *cdev)
 			      "device 0.%x.%04x\n",
 			      ret, cdev->private->dev_id.ssid,
 			      cdev->private->dev_id.devno);
+		/* Give up online reference since onlining failed. */
+		put_device(&cdev->dev);
 		return ret;
 	}
-	if (cdev->private->state != DEV_STATE_ONLINE)
+	if (cdev->private->state != DEV_STATE_ONLINE) {
+		/* Give up online reference since onlining failed. */
+		put_device(&cdev->dev);
 		return -ENODEV;
+	}
 	if (!cdev->drv->set_online || cdev->drv->set_online(cdev) == 0) {
 		cdev->online = 1;
 		return 0;
@@ -440,6 +452,8 @@ int ccw_device_set_online(struct ccw_device *cdev)
 			      "device 0.%x.%04x\n",
 			      ret, cdev->private->dev_id.ssid,
 			      cdev->private->dev_id.devno);
+	/* Give up online reference since onlining failed. */
+	put_device(&cdev->dev);
 	return (ret == 0) ? -ENODEV : ret;
 }
 
@@ -1168,9 +1182,8 @@ static int io_subchannel_probe(struct subchannel *sch)
 		ccw_device_register(cdev);
 		/*
 		 * Check if the device is already online. If it is
-		 * the reference count needs to be corrected
-		 * (see ccw_device_online and css_init_done for the
-		 * ugly details).
+		 * the reference count needs to be corrected since we
+		 * didn't obtain a reference in ccw_device_set_online.
 		 */
 		if (cdev->private->state != DEV_STATE_NOT_OPER &&
 		    cdev->private->state != DEV_STATE_OFFLINE &&
@@ -1806,6 +1819,8 @@ ccw_device_remove (struct device *dev)
 				      "device 0.%x.%04x\n",
 				      ret, cdev->private->dev_id.ssid,
 				      cdev->private->dev_id.devno);
+		/* Give up reference obtained in ccw_device_set_online(). */
+		put_device(&cdev->dev);
 	}
 	ccw_device_set_timeout(cdev, 0);
 	cdev->drv = NULL;