From: Mike Snitzer <snitzer@redhat.com>
Date: Thu, 23 Sep 2010 21:40:36 -0400
Subject: [scsi] scsi_dh_alua: handle transitioning state correctly
Message-id: <20100923214035.GA13376@redhat.com>
Patchwork-id: 28360
O-Subject: [RHEL5.6 PATCH v3] scsi_dh_alua: Handle transitioning state correctly
Bugzilla: 619361
RH-Acked-by: Mike Christie <mchristi@redhat.com>

BZ 619361
Brew build: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=2778175

For ALUA we should be handling all states, independent of whether
is explicit or implicit. For 'Transitioning' we should be retry
for a certain amount of time; after that we're setting the port
to 'Standby' and return SCSI_DH_RETRY to signal upper layers
a retry is in order here.

Signed-off-by: Hannes Reinecke <hare@suse.de>

NOTE:
This patch is the result of upstream review on linux-scsi.  I did not
backport handling of the TPGS_STATE_LBA_DEPENDENT because it would
require further changes which are outside scope of this BZ -- so
backporting that isn't worth the risk.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a78aaa6..05a012e 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -20,6 +20,7 @@
  *
  */
 #include <linux/list.h>
+#include <linux/delay.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_cmnd.h>
@@ -536,7 +537,9 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 	int len, k, off, valid_states = 0;
 	char *ucp;
 	unsigned err;
+	unsigned long expiry, interval = 10;
 
+	expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT);
  retry:
 	err = submit_rtpg(sdev, h);
 
@@ -547,7 +550,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 			return SCSI_DH_IO;
 
 		err = alua_check_sense(sdev, &sense_hdr);
-		if (err == SCSI_MLQUEUE_IMM_RETRY)
+		if (err == SCSI_MLQUEUE_IMM_RETRY && time_before(jiffies, expiry))
 			goto retry;
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: rtpg sense code %02x/%02x/%02x\n",
@@ -590,29 +593,27 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		    valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 		    valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 
-	if (h->tpgs & TPGS_MODE_EXPLICIT) {
-		switch (h->state) {
-		case TPGS_STATE_TRANSITIONING:
+	switch (h->state) {
+	case TPGS_STATE_TRANSITIONING:
+		if (time_before(jiffies, expiry)) {
 			/* State transition, retry */
+			interval *= 10;
+			msleep(interval);
 			goto retry;
-			break;
-		case TPGS_STATE_OFFLINE:
-			/* Path is offline, fail */
-			err = SCSI_DH_DEV_OFFLINED;
-			break;
-		default:
-			break;
 		}
-	} else {
-		/* Only Implicit ALUA support */
-		if (h->state == TPGS_STATE_OPTIMIZED ||
-		    h->state == TPGS_STATE_NONOPTIMIZED ||
-		    h->state == TPGS_STATE_STANDBY)
-			/* Useable path if active */
-			err = SCSI_DH_OK;
-		else
-			/* Path unuseable for unavailable/offline */
-			err = SCSI_DH_DEV_OFFLINED;
+		/* Transitioning time exceeded, set port to standby */
+		err = SCSI_DH_RETRY;
+		h->state = TPGS_STATE_STANDBY;
+		break;
+	case TPGS_STATE_OFFLINE:
+	case TPGS_STATE_UNAVAILABLE:
+		/* Path unuseable for unavailable/offline */
+		err = SCSI_DH_DEV_OFFLINED;
+		break;
+	default:
+		/* Useable path if active */
+		err = SCSI_DH_OK;
+		break;
 	}
 	return err;
 }
@@ -686,8 +687,10 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 	struct alua_dh_data *h = get_alua_data(sdev);
 	int ret = BLKPREP_OK;
 
-	if (h->state != TPGS_STATE_OPTIMIZED &&
-	    h->state != TPGS_STATE_NONOPTIMIZED) {
+	if (h->state == TPGS_STATE_TRANSITIONING)
+		ret = BLKPREP_DEFER;
+	else if (h->state != TPGS_STATE_OPTIMIZED &&
+		 h->state != TPGS_STATE_NONOPTIMIZED) {
 		ret = BLKPREP_KILL;
 		req->flags |= REQ_QUIET;
 	}