scsi_dh: add 'rescan' callback

If a device needs to be rescanned the device_handler might need
to be rechecked, too.
So add a 'rescan' callback to the device handler and call it
upon scsi_rescan_device(). The rescan callback will be invoked
from the Unit Attention handling of ASC/ASCQ 3F 03
(INQUIRY DATA HAS CHANGED).

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/device_handler/scsi_dh_alua.c

@@ -1026,6 +1026,13 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 
 }
 
+static void alua_rescan(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+
+	alua_initialize(sdev, h);
+}
+
 /*
  * alua_bus_attach - Attach device handler
  * @sdev: device to be attached to
@@ -1086,6 +1093,7 @@ static struct scsi_device_handler alua_dh = {
 	.prep_fn = alua_prep_fn,
 	.check_sense = alua_check_sense,
 	.activate = alua_activate,
+	.rescan = alua_rescan,
 	.set_params = alua_set_params,
 };