scsi: device handlers must have attach and detach methods

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Hannes Reinecke <hare@suse.de>

drivers/scsi/device_handler/scsi_dh.c

@@ -108,7 +108,6 @@ static int scsi_dh_handler_attach(struct scsi_device *sdev,
 		return 0;
 	}
 
-	if (scsi_dh->attach) {
 	if (!try_module_get(scsi_dh->module))
 		return -EINVAL;
 
@@ -120,7 +119,6 @@ static int scsi_dh_handler_attach(struct scsi_device *sdev,
 
 	kref_init(&sdev->scsi_dh_data->kref);
 	sdev->scsi_dh_data->sdev = sdev;
-	}
 	return err;
 }
 
@@ -154,7 +152,7 @@ static void scsi_dh_handler_detach(struct scsi_device *sdev,
 	if (!scsi_dh)
 		scsi_dh = sdev->scsi_dh_data->scsi_dh;
 
-	if (scsi_dh && scsi_dh->detach)
+	if (scsi_dh)
 		kref_put(&sdev->scsi_dh_data->kref, __detach_handler);
 }
 
@@ -343,6 +341,9 @@ int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
 	if (get_device_handler(scsi_dh->name))
 		return -EBUSY;
 
+	if (!scsi_dh->attach || !scsi_dh->detach)
+		return -EINVAL;
+
 	spin_lock(&list_lock);
 	list_add(&scsi_dh->list, &scsi_dh_list);
 	spin_unlock(&list_lock);