[PATCH 2/3] alua: retry alua rtpg extended header for illegal request response

[Rob Evers <revers@redhat.com>]

From: Rob Evers <revers@redhat.com>

Some storage arrays are known to return 'illegal request'
when an rtpg extended header request is made.  T10 says the
array should ignore the bit, and return the non-extended
rtpg as the array doesn't support the request.  Working
around this by retrying the rtpg request without the extended
header bit set when the extended rtpg request results in
illegal request.

Signed-off-by: Rob Evers <revers@redhat.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c |   25 ++++++++++++++++++++++---
 1 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 6a7efd3..ca414ae 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -173,7 +173,8 @@ done:
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
  */
-static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
+static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h,
+			    bool rtpg_ext_hdr_req)
 {
 	struct request *rq;
 	int err = SCSI_DH_RES_TEMP_UNAVAIL;
@@ -184,7 +185,10 @@ 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 | MI_EXT_HDR_PARAM_FMT;
+	if (rtpg_ext_hdr_req)
+		rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
+	else
+		rq->cmd[1] = MI_REPORT_TARGET_PGS;
 	rq->cmd[6] = (h->bufflen >> 24) & 0xff;
 	rq->cmd[7] = (h->bufflen >> 16) & 0xff;
 	rq->cmd[8] = (h->bufflen >>  8) & 0xff;
@@ -517,6 +521,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 	int len, k, off, valid_states = 0;
 	unsigned char *ucp;
 	unsigned err;
+	bool rtpg_ext_hdr_req = 1;
 	unsigned long expiry, interval = 1000;
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;
@@ -527,7 +532,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
 
  retry:
-	err = submit_rtpg(sdev, h);
+	err = submit_rtpg(sdev, h, rtpg_ext_hdr_req);
 
 	if (err == SCSI_DH_IO && h->senselen > 0) {
 		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
@@ -535,6 +540,20 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		if (!err)
 			return SCSI_DH_IO;
 
+		/*
+		 * submit_rtpb() has failed on existing arrays
+		 * when requesting extended header info, and
+		 * the array doesn't support extended headers,
+		 * even though it shouldn't according to T10.
+		 * The retry without the ALUA_RTPG_EXT_HDR_REQ
+		 * handles this.
+		 */
+		if (sense_hdr.sense_key == ILLEGAL_REQUEST &&
+		    sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
+			rtpg_ext_hdr_req = 0;
+			goto retry;
+		}
+
 		err = alua_check_sense(sdev, &sense_hdr);
 		if (err == ADD_TO_MLQUEUE && time_before(jiffies, expiry))
 			goto retry;
-- 
1.7.7.2