[PATCH v2 3/4] scsi: scsi_dh_alua: Start a port group in the scanned access state

[Brian Bunker <brian@purestorage.com>]

A new port group starts out active/optimized until the first RTPG of
the handler completes, so alua_prep_fn() lets I/O through to a path
that is actually unavailable. For a device whose driver is bound
straight away, the first I/O, typically the partition table read, then
reaches the target and fails with LOGICAL UNIT NOT ACCESSIBLE, TARGET
PORT IN UNAVAILABLE STATE, logging an I/O error.

The SCSI core now reads sdev->access_state when the device is scanned,
before the handler attaches. Start a new port group in that state. If
the core did not read one, sdev->access_state is zero, which is
active/optimized, so nothing changes for those devices.

Co-developed-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Brian Bunker <brian@purestorage.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 06eb35cc9d7c..15471e7bf19a 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -208,7 +208,14 @@ static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 	}
 	pg->group_id = group_id;
 	pg->tpgs = tpgs;
-	pg->state = SCSI_ACCESS_STATE_OPTIMAL;
+	/*
+	 * Start in the access state the SCSI core read when the device was
+	 * scanned. That is active/optimized if it did not read one, as it
+	 * was before. alua_prep_fn() then already fails I/O to a path that
+	 * is unavailable before the first RTPG of the handler completes.
+	 */
+	pg->state = FIELD_GET(SCSI_ACCESS_STATE_MASK, sdev->access_state);
+	pg->pref = FIELD_GET(SCSI_ACCESS_STATE_PREFERRED, sdev->access_state);
 	pg->valid_states = TPGS_SUPPORT_ALL;
 	if (optimize_stpg)
 		pg->flags |= ALUA_OPTIMIZE_STPG;
-- 
2.56.0