[S390] tape: cleanup reference counting

Rename tape_get_device to tape_find_device and tape_get_device_reference
to tape_get_device. The old names didn't make too much sense.

Follow the get_device()/put_device() semantic and convert tape_put_device
to a void function.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/tape.h

@@ -292,9 +292,9 @@ extern int tape_generic_pm_suspend(struct ccw_device *);
 extern int tape_generic_probe(struct ccw_device *);
 extern void tape_generic_remove(struct ccw_device *);
 
-extern struct tape_device *tape_get_device(int devindex);
-extern struct tape_device *tape_get_device_reference(struct tape_device *);
-extern struct tape_device *tape_put_device(struct tape_device *);
+extern struct tape_device *tape_find_device(int devindex);
+extern struct tape_device *tape_get_device(struct tape_device *);
+extern void tape_put_device(struct tape_device *);
 
 /* Externals from tape_char.c */
 extern int tapechar_init(void);

drivers/s390/char/tape_34xx.c

@@ -113,16 +113,16 @@ tape_34xx_work_handler(struct work_struct *work)
 {
 	struct tape_34xx_work *p =
 		container_of(work, struct tape_34xx_work, work);
+	struct tape_device *device = p->device;
 
 	switch(p->op) {
 		case TO_MSEN:
-			tape_34xx_medium_sense(p->device);
+			tape_34xx_medium_sense(device);
 			break;
 		default:
 			DBF_EVENT(3, "T34XX: internal error: unknown work\n");
 	}
-
-	p->device = tape_put_device(p->device);
+	tape_put_device(device);
 	kfree(p);
 }
 
@@ -136,7 +136,7 @@ tape_34xx_schedule_work(struct tape_device *device, enum tape_op op)
 
 	INIT_WORK(&p->work, tape_34xx_work_handler);
 
-	p->device = tape_get_device_reference(device);
+	p->device = tape_get_device(device);
 	p->op     = op;
 
 	schedule_work(&p->work);

drivers/s390/char/tape_3590.c

@@ -608,7 +608,7 @@ tape_3590_schedule_work(struct tape_device *device, enum tape_op op)
 
 	INIT_WORK(&p->work, tape_3590_work_handler);
 
-	p->device = tape_get_device_reference(device);
+	p->device = tape_get_device(device);
 	p->op = op;
 
 	schedule_work(&p->work);

drivers/s390/char/tape_block.c

@@ -239,7 +239,7 @@ tapeblock_setup_device(struct tape_device * device)
 	disk->major = tapeblock_major;
 	disk->first_minor = device->first_minor;
 	disk->fops = &tapeblock_fops;
-	disk->private_data = tape_get_device_reference(device);
+	disk->private_data = tape_get_device(device);
 	disk->queue = blkdat->request_queue;
 	set_capacity(disk, 0);
 	sprintf(disk->disk_name, "btibm%d",
@@ -247,11 +247,11 @@ tapeblock_setup_device(struct tape_device * device)
 
 	blkdat->disk = disk;
 	blkdat->medium_changed = 1;
-	blkdat->request_queue->queuedata = tape_get_device_reference(device);
+	blkdat->request_queue->queuedata = tape_get_device(device);
 
 	add_disk(disk);
 
-	tape_get_device_reference(device);
+	tape_get_device(device);
 	INIT_WORK(&blkdat->requeue_task, tapeblock_requeue);
 
 	return 0;
@@ -274,13 +274,14 @@ tapeblock_cleanup_device(struct tape_device *device)
 	}
 
 	del_gendisk(device->blk_data.disk);
-	device->blk_data.disk->private_data =
-		tape_put_device(device->blk_data.disk->private_data);
+	device->blk_data.disk->private_data = NULL;
+	tape_put_device(device);
 	put_disk(device->blk_data.disk);
 
 	device->blk_data.disk = NULL;
 cleanup_queue:
-	device->blk_data.request_queue->queuedata = tape_put_device(device);
+	device->blk_data.request_queue->queuedata = NULL;
+	tape_put_device(device);
 
 	blk_cleanup_queue(device->blk_data.request_queue);
 	device->blk_data.request_queue = NULL;
@@ -363,7 +364,7 @@ tapeblock_open(struct block_device *bdev, fmode_t mode)
 	struct tape_device *	device;
 	int			rc;
 
-	device = tape_get_device_reference(disk->private_data);
+	device = tape_get_device(disk->private_data);
 
 	if (device->required_tapemarks) {
 		DBF_EVENT(2, "TBLOCK: missing tapemarks\n");

drivers/s390/char/tape_char.c

@@ -286,9 +286,9 @@ tapechar_open (struct inode *inode, struct file *filp)
 
 	lock_kernel();
 	minor = iminor(filp->f_path.dentry->d_inode);
-	device = tape_get_device(minor / TAPE_MINORS_PER_DEV);
+	device = tape_find_device(minor / TAPE_MINORS_PER_DEV);
 	if (IS_ERR(device)) {
-		DBF_EVENT(3, "TCHAR:open: tape_get_device() failed\n");
+		DBF_EVENT(3, "TCHAR:open: tape_find_device() failed\n");
 		rc = PTR_ERR(device);
 		goto out;
 	}
@@ -340,7 +340,8 @@ tapechar_release(struct inode *inode, struct file *filp)
 		device->char_data.idal_buf = NULL;
 	}
 	tape_release(device);
-	filp->private_data = tape_put_device(device);
+	filp->private_data = NULL;
+	tape_put_device(device);
 
 	return 0;
 }

drivers/s390/char/tape_core.c

@@ -511,11 +511,12 @@ tape_alloc_device(void)
  * increment the reference count.
  */
 struct tape_device *
-tape_get_device_reference(struct tape_device *device)
+tape_get_device(struct tape_device *device)
 {
-	DBF_EVENT(4, "tape_get_device_reference(%p) = %i\n", device,
-		atomic_inc_return(&device->ref_count));
+	int count;
 
+	count = atomic_inc_return(&device->ref_count);
+	DBF_EVENT(4, "tape_get_device(%p) = %i\n", device, count);
 	return device;
 }
 
@@ -525,32 +526,25 @@ tape_get_device_reference(struct tape_device *device)
  * The function returns a NULL pointer to be used by the caller
  * for clearing reference pointers.
  */
-struct tape_device *
+void
 tape_put_device(struct tape_device *device)
 {
-	int remain;
+	int count;
 
-	remain = atomic_dec_return(&device->ref_count);
-	if (remain > 0) {
-		DBF_EVENT(4, "tape_put_device(%p) -> %i\n", device, remain);
-	} else {
-		if (remain < 0) {
-			DBF_EVENT(4, "put device without reference\n");
-		} else {
-			DBF_EVENT(4, "tape_free_device(%p)\n", device);
-			kfree(device->modeset_byte);
-			kfree(device);
-		}
+	count = atomic_dec_return(&device->ref_count);
+	DBF_EVENT(4, "tape_put_device(%p) -> %i\n", device, count);
+	BUG_ON(count < 0);
+	if (count == 0) {
+		kfree(device->modeset_byte);
+		kfree(device);
 	}
-
-	return NULL;			
 }
 
 /*
  * Find tape device by a device index.
  */
 struct tape_device *
-tape_get_device(int devindex)
+tape_find_device(int devindex)
 {
 	struct tape_device *device, *tmp;
 
@@ -558,7 +552,7 @@ tape_get_device(int devindex)
 	read_lock(&tape_device_lock);
 	list_for_each_entry(tmp, &tape_device_list, node) {
 		if (tmp->first_minor / TAPE_MINORS_PER_DEV == devindex) {
-			device = tape_get_device_reference(tmp);
+			device = tape_get_device(tmp);
 			break;
 		}
 	}
@@ -607,7 +601,8 @@ __tape_discard_requests(struct tape_device *device)
 		list_del(&request->list);
 
 		/* Decrease ref_count for removed request. */
-		request->device = tape_put_device(device);
+		request->device = NULL;
+		tape_put_device(device);
 		request->rc = -EIO;
 		if (request->callback != NULL)
 			request->callback(request, request->callback_data);
@@ -665,9 +660,11 @@ tape_generic_remove(struct ccw_device *cdev)
 			tape_cleanup_device(device);
 	}
 
-	if (dev_get_drvdata(&cdev->dev)) {
+	device = dev_get_drvdata(&cdev->dev);
+	if (device) {
 		sysfs_remove_group(&cdev->dev.kobj, &tape_attr_group);
-		dev_set_drvdata(&cdev->dev, tape_put_device(dev_get_drvdata(&cdev->dev)));
+		dev_set_drvdata(&cdev->dev, NULL);
+		tape_put_device(device);
 	}
 }
 
@@ -722,9 +719,8 @@ tape_free_request (struct tape_request * request)
 {
 	DBF_LH(6, "Free request %p\n", request);
 
-	if (request->device != NULL) {
-		request->device = tape_put_device(request->device);
-	}
+	if (request->device)
+		tape_put_device(request->device);
 	kfree(request->cpdata);
 	kfree(request->cpaddr);
 	kfree(request);
@@ -839,7 +835,8 @@ static void tape_long_busy_timeout(unsigned long data)
 	BUG_ON(request->status != TAPE_REQUEST_LONG_BUSY);
 	DBF_LH(6, "%08x: Long busy timeout.\n", device->cdev_id);
 	__tape_start_next_request(device);
-	device->lb_timeout.data = (unsigned long) tape_put_device(device);
+	device->lb_timeout.data = 0UL;
+	tape_put_device(device);
 	spin_unlock_irq(get_ccwdev_lock(device->cdev));
 }
 
@@ -919,7 +916,7 @@ __tape_start_request(struct tape_device *device, struct tape_request *request)
 	}
 
 	/* Increase use count of device for the added request. */
-	request->device = tape_get_device_reference(device);
+	request->device = tape_get_device(device);
 
 	if (list_empty(&device->req_queue)) {
 		/* No other requests are on the queue. Start this one. */
@@ -1118,8 +1115,8 @@ __tape_do_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
 		if (req->status == TAPE_REQUEST_LONG_BUSY) {
 			DBF_EVENT(3, "(%08x): del timer\n", device->cdev_id);
 			if (del_timer(&device->lb_timeout)) {
-				device->lb_timeout.data = (unsigned long)
-					tape_put_device(device);
+				device->lb_timeout.data = 0UL;
+				tape_put_device(device);
 				__tape_start_next_request(device);
 			}
 			return;
@@ -1174,7 +1171,7 @@ __tape_do_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
 			break;
 		case TAPE_IO_LONG_BUSY:
 			device->lb_timeout.data =
-				(unsigned long)tape_get_device_reference(device);
+				(unsigned long) tape_get_device(device);
 			device->lb_timeout.expires = jiffies +
 				LONG_BUSY_TIMEOUT * HZ;
 			DBF_EVENT(3, "(%08x): add timer\n", device->cdev_id);
@@ -1327,7 +1324,7 @@ EXPORT_SYMBOL(tape_generic_online);
 EXPORT_SYMBOL(tape_generic_offline);
 EXPORT_SYMBOL(tape_generic_pm_suspend);
 EXPORT_SYMBOL(tape_put_device);
-EXPORT_SYMBOL(tape_get_device_reference);
+EXPORT_SYMBOL(tape_get_device);
 EXPORT_SYMBOL(tape_state_verbose);
 EXPORT_SYMBOL(tape_op_verbose);
 EXPORT_SYMBOL(tape_state_set);

drivers/s390/char/tape_proc.c

@@ -45,7 +45,7 @@ static int tape_proc_show(struct seq_file *m, void *v)
 		seq_printf(m, "TapeNo\tBusID      CuType/Model\t"
 			"DevType/Model\tBlkSize\tState\tOp\tMedState\n");
 	}
-	device = tape_get_device(n);
+	device = tape_find_device(n);
 	if (IS_ERR(device))
 		return 0;
 	spin_lock_irq(get_ccwdev_lock(device->cdev));