scsi_dh_alua: Add new blacklist flag 'BLIST_SYNC_ALUA'

Add a new blacklist flag BLIST_SYNC_ALUA to instruct the
alua device handler to use synchronous command submission
for ALUA commands.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a3cb069..fbbe85e 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -366,6 +366,8 @@
 		/* port group has changed. Update to new port group */
 		rcu_assign_pointer(h->pg, pg);
 	}
+	if (sdev->synchronous_alua)
+		pg->flags |= ALUA_SYNC_STPG;
 	alua_rtpg_queue(h->pg, sdev, NULL);
 	spin_unlock(&h->pg_lock);