[SCSI] scsi_dh: fix reference counting in scsi_dh_activate error path

Commit db422318cbca55168cf965f655471dbf8be82433 ([SCSI] scsi_dh:
propagate SCSI device deletion) introduced a regression where the device
reference is not dropped prior to scsi_dh_activate's early return from
the error path.

Signed-off-by: Mike Snitzer <[e-mail]>
Cc: [e-mail] # 2.6.38
Reviewed-by: Mike Christie <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/device_handler/scsi_dh.c

···
 	unsigned long flags;
 	struct scsi_device *sdev;
 	struct scsi_device_handler *scsi_dh = NULL;
+	struct device *dev = NULL;
 
 	spin_lock_irqsave(q->queue_lock, flags);
 	sdev = q->queuedata;
 	if (sdev && sdev->scsi_dh_data)
 		scsi_dh = sdev->scsi_dh_data->scsi_dh;
-	if (!scsi_dh || !get_device(&sdev->sdev_gendev) ||
+	dev = get_device(&sdev->sdev_gendev);
+	if (!scsi_dh || !dev ||
 	    sdev->sdev_state == SDEV_CANCEL ||
 	    sdev->sdev_state == SDEV_DEL)
 		err = SCSI_DH_NOSYS;
···
 	if (err) {
 		if (fn)
 			fn(data, err);
-		return err;
+		goto out;
 	}
 
 	if (scsi_dh->activate)
 		err = scsi_dh->activate(sdev, fn, data);
-	put_device(&sdev->sdev_gendev);
+out:
+	put_device(dev);
 	return err;
 }
 EXPORT_SYMBOL_GPL(scsi_dh_activate);