[dm-devel] [PATCH 3/3] scsi_dh_rdac : decide on whether to send mode select or not based on operating mode

[Moger, Babu]

Based on the operating modes, handler decides whether to send mode select or not. Purpose here is to reduce
io-shipping as much as possible whenever there is an option.

Signed-off-by: Babu Moger <babu.moger at lsi.com>
Reviewed-by: Yanling Qi <yanling.qi at lsi.com> 
Reviewed-by: Sudhir Dachepalli <Sudhir.Dachepalli at lis.com>
Reviewed-by: Somasundaram Krishnasamy <Somasundaram.Krishnasamy at lsi.com>
Reviewed-by: Bob Stankey <Robert.Stankey at lsi.com>
Reviewed-by: Vijay Chauhan <Vijay.Chauhan at lsi.com>

---
--- linux-2.6.38/drivers/scsi/device_handler/scsi_dh_rdac.c.orig	2011-03-17 16:57:51.000000000 -0500
+++ linux-2.6.38/drivers/scsi/device_handler/scsi_dh_rdac.c	2011-03-17 16:59:11.000000000 -0500
@@ -670,12 +670,27 @@ static int rdac_activate(struct scsi_dev
 {
 	struct rdac_dh_data *h = get_rdac_data(sdev);
 	int err = SCSI_DH_OK;
+	int act = 0;
 
 	err = check_ownership(sdev, h);
 	if (err != SCSI_DH_OK)
 		goto done;
 
-	if (h->lun_state == RDAC_LUN_UNOWNED) {
+	switch (h->mode) {
+	case RDAC_MODE:
+		if (h->lun_state == RDAC_LUN_UNOWNED)
+			act = 1;
+		break;
+	case RDAC_MODE_IOSHIP:
+		if ((h->lun_state == RDAC_LUN_UNOWNED) &&
+		    (h->preferred == RDAC_PREFERRED))
+			act = 1;
+		break;
+	default:
+		break;
+	}
+
+	if (act) {
 		err = queue_mode_select(sdev, fn, data);
 		if (err == SCSI_DH_OK)
 			return 0;