[PATCH] s390: dasd reference counting

When using the dasd diag discipline, the base discipline module (eckd or fba)
can be unloaded, even though the dasd driver requires both discipline modules
(base and diag) to work correctly.

Implement reference counting for both base and diag discipline modules in
order to fix this.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/s390/block/dasd.c

@@ -156,7 +156,12 @@ dasd_state_known_to_new(struct dasd_device * device)
 	/* disable extended error reporting for this device */
 	dasd_disable_eer(device);
 	/* Forget the discipline information. */
+	if (device->discipline)
+		module_put(device->discipline->owner);
 	device->discipline = NULL;
+	if (device->base_discipline)
+		module_put(device->base_discipline->owner);
+	device->base_discipline = NULL;
 	device->state = DASD_STATE_NEW;
 
 	dasd_free_queue(device);
@@ -1880,9 +1885,10 @@ dasd_generic_remove (struct ccw_device *cdev)
  */
 int
 dasd_generic_set_online (struct ccw_device *cdev,
-			 struct dasd_discipline *discipline)
+			 struct dasd_discipline *base_discipline)
 
 {
+	struct dasd_discipline *discipline;
 	struct dasd_device *device;
 	int rc;
 
@@ -1890,6 +1896,7 @@ dasd_generic_set_online (struct ccw_device *cdev,
 	if (IS_ERR(device))
 		return PTR_ERR(device);
 
+	discipline = base_discipline;
 	if (device->features & DASD_FEATURE_USEDIAG) {
 	  	if (!dasd_diag_discipline_pointer) {
 		        printk (KERN_WARNING
@@ -1901,6 +1908,16 @@ dasd_generic_set_online (struct ccw_device *cdev,
 		}
 		discipline = dasd_diag_discipline_pointer;
 	}
+	if (!try_module_get(base_discipline->owner)) {
+		dasd_delete_device(device);
+		return -EINVAL;
+	}
+	if (!try_module_get(discipline->owner)) {
+		module_put(base_discipline->owner);
+		dasd_delete_device(device);
+		return -EINVAL;
+	}
+	device->base_discipline = base_discipline;
 	device->discipline = discipline;
 
 	rc = discipline->check_device(device);
@@ -1909,6 +1926,8 @@ dasd_generic_set_online (struct ccw_device *cdev,
 			"dasd_generic couldn't online device %s "
 			"with discipline %s rc=%i\n",
 			cdev->dev.bus_id, discipline->name, rc);
+		module_put(discipline->owner);
+		module_put(base_discipline->owner);
 		dasd_delete_device(device);
 		return rc;
 	}

drivers/s390/block/dasd_int.h

@@ -321,6 +321,7 @@ struct dasd_device {
 
 	/* Device discipline stuff. */
 	struct dasd_discipline *discipline;
+	struct dasd_discipline *base_discipline;
 	char *private;
 
 	/* Device state and target state. */