[PATCH v4] scsi: scsi_dh_alua: increase default ALUA timeout to maximum spec value

[Brian Bunker <brian@purestorage.com>]

The ALUA handler maps a 0 value (no implicit transition timeout provided
by the target) to the ALUA_FAILOVER_TIMEOUT constant, currently 60
seconds. This means the kernel already does not accept an infinite
transition time.

However, 60 seconds is insufficient for some arrays that may take
longer to complete ALUA transitions. Since the highest value allowed
by the SCSI specification for the implicit transition timeout is a
single byte (255 seconds), change the default to 255. This way,
when a target does not provide an explicit transition timeout, we
default to the maximum value the spec allows rather than an arbitrary
60 second limit.

Signed-off-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Riya Savla <rsavla@purestorage.com>
Signed-off-by: Brian Bunker <brian@purestorage.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index efb08b9b145a1..80ab0ff921d43 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -37,7 +37,7 @@
 #define TPGS_MODE_EXPLICIT		0x2
 
 #define ALUA_RTPG_SIZE			128
-#define ALUA_FAILOVER_TIMEOUT		60
+#define ALUA_FAILOVER_TIMEOUT		255	/* max 255 (8-bit value) */
 #define ALUA_FAILOVER_RETRIES		5
 #define ALUA_RTPG_DELAY_MSECS		5
 #define ALUA_RTPG_RETRY_DELAY		2
-- 
2.50.1 (Apple Git-155)