[PATCH 1/3 V2] alua: implement 'implied transition timeout'

[Rob Evers <revers@redhat.com>]

During alua transitions, an array can return transitioning
status in response to rtpg requests.  These requests get
retried for a maximum of 60 seconds by default before timing
out.  Sometimes this timeout isn't sufficient to allow the
array to complete the transition.  T10-spc4 addresses this
under 'Report Target Port Groups' command.

This update retrieves the timeout value from the storage
array if available and retries the transitioning rtpgs
for up to the 'implied transitioning timeout' value

Signed-off-by: Rob Evers <revers@redhat.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c |   41 ++++++++++++++++++++++++---
 include/scsi/scsi.h                        |    2 +
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 04c5cea..6a7efd3 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -46,13 +46,16 @@
 #define TPGS_SUPPORT_OFFLINE		0x40
 #define TPGS_SUPPORT_TRANSITION		0x80
 
+#define RTPG_FMT_MASK			0x70
+#define RTPG_FMT_EXT_HDR		0x10
+
 #define TPGS_MODE_UNINITIALIZED		 -1
 #define TPGS_MODE_NONE			0x0
 #define TPGS_MODE_IMPLICIT		0x1
 #define TPGS_MODE_EXPLICIT		0x2
 
 #define ALUA_INQUIRY_SIZE		36
-#define ALUA_FAILOVER_TIMEOUT		(60 * HZ)
+#define ALUA_FAILOVER_TIMEOUT		60
 #define ALUA_FAILOVER_RETRIES		5
 
 struct alua_dh_data {
@@ -63,6 +66,7 @@ struct alua_dh_data {
 	unsigned char		inq[ALUA_INQUIRY_SIZE];
 	unsigned char		*buff;
 	int			bufflen;
+	unsigned char		transition_tmo;
 	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
 	int			senselen;
 	struct scsi_device	*sdev;
@@ -123,7 +127,7 @@ static struct request *get_alua_req(struct scsi_device *sdev,
 	rq->cmd_flags |= REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 			 REQ_FAILFAST_DRIVER;
 	rq->retries = ALUA_FAILOVER_RETRIES;
-	rq->timeout = ALUA_FAILOVER_TIMEOUT;
+	rq->timeout = ALUA_FAILOVER_TIMEOUT * HZ;
 
 	return rq;
 }
@@ -180,7 +184,7 @@ static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 
 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_IN;
-	rq->cmd[1] = MI_REPORT_TARGET_PGS;
+	rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 	rq->cmd[6] = (h->bufflen >> 24) & 0xff;
 	rq->cmd[7] = (h->bufflen >> 16) & 0xff;
 	rq->cmd[8] = (h->bufflen >>  8) & 0xff;
@@ -514,8 +518,14 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 	unsigned char *ucp;
 	unsigned err;
 	unsigned long expiry, interval = 1000;
+	unsigned int tpg_desc_tbl_off;
+	unsigned char orig_transition_tmo;
+
+	if (!h->transition_tmo)
+		expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
+	else
+		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
 
-	expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT);
  retry:
 	err = submit_rtpg(sdev, h);
 
@@ -551,7 +561,28 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		goto retry;
 	}
 
-	for (k = 4, ucp = h->buff + 4; k < len; k += off, ucp += off) {
+	orig_transition_tmo = h->transition_tmo;
+	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && h->buff[5] != 0)
+		h->transition_tmo = h->buff[5];
+	else
+		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;
+
+	if (orig_transition_tmo != h->transition_tmo) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: transition timeout set to %d seconds\n",
+			    ALUA_DH_NAME, h->transition_tmo);
+		expiry = jiffies + h->transition_tmo * HZ;
+	}
+
+	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
+		tpg_desc_tbl_off = 8;
+	else
+		tpg_desc_tbl_off = 4;
+
+	for (k = tpg_desc_tbl_off, ucp = h->buff + tpg_desc_tbl_off;
+	     k < len;
+	     k += off, ucp += off) {
+
 		if (h->group_id == (ucp[2] << 8) + ucp[3]) {
 			h->state = ucp[0] & 0x0f;
 			valid_states = ucp[1];
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index f34a5a8..c6f0974 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -161,6 +161,8 @@ struct scsi_cmnd;
 #define MI_REPORT_PRIORITY   0x0e
 #define MI_REPORT_TIMESTAMP  0x0f
 #define MI_MANAGEMENT_PROTOCOL_IN 0x10
+/* value for MI_REPORT_TARGET_PGS ext header */
+#define MI_EXT_HDR_PARAM_FMT  0x20
 /* values for maintenance out */
 #define MO_SET_IDENTIFYING_INFORMATION 0x06
 #define MO_SET_TARGET_PGS     0x0a
-- 
1.7.7.2