[PATCH v2 3/4] scsi: st: Modify st.c to use the new scsi_error counters

[Kai Mäkisara <Kai.Makisara@xxxxxxxxxxx>]

Compare the stored values of por_ctr and new_media_ctr against
the values in the device struct. In case of mismatch, the
Unit Attention corresponding to the counter has happened.
This is a safeguard against another ULD catching the
Unit Attention sense data.

Remove use of the was_reset flag in struct scsi_device.

Signed-off-by: Kai Mäkisara <Kai.Makisara@xxxxxxxxxxx>
---
 drivers/scsi/st.c | 28 +++++++++++++++++++++++++---
 drivers/scsi/st.h |  4 ++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index a0667a0ae4c9..ad86dfbc8919 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -163,9 +163,11 @@ static const char *st_formats[] = {
 
 static int debugging = DEBUG;
 
+/* Setting these non-zero may risk recognizing resets */
 #define MAX_RETRIES 0
 #define MAX_WRITE_RETRIES 0
 #define MAX_READY_RETRIES 0
+
 #define NO_TAPE  NOT_READY
 
 #define ST_TIMEOUT (900 * HZ)
@@ -357,10 +359,18 @@ static int st_chk_result(struct scsi_tape *STp, struct st_request * SRpnt)
 {
 	int result = SRpnt->result;
 	u8 scode;
+	unsigned int ctr;
 	DEB(const char *stp;)
 	char *name = STp->name;
 	struct st_cmdstatus *cmdstatp;
 
+	ctr = scsi_get_ua_por_ctr(STp->device);
+	if (ctr != STp->por_ctr) {
+		STp->por_ctr = ctr;
+		STp->pos_unknown = 1; /* ASC => power on / reset */
+		st_printk(KERN_WARNING, STp, "Power on/reset recognized.");
+	}
+
 	if (!result)
 		return 0;
 
@@ -413,10 +423,11 @@ static int st_chk_result(struct scsi_tape *STp, struct st_request * SRpnt)
 	if (cmdstatp->have_sense &&
 	    cmdstatp->sense_hdr.asc == 0 && cmdstatp->sense_hdr.ascq == 0x17)
 		STp->cleaning_req = 1; /* ASC and ASCQ => cleaning requested */
-	if (cmdstatp->have_sense && scode == UNIT_ATTENTION && cmdstatp->sense_hdr.asc == 0x29)
+	if (cmdstatp->have_sense && scode == UNIT_ATTENTION &&
+		cmdstatp->sense_hdr.asc == 0x29 && !STp->pos_unknown) {
 		STp->pos_unknown = 1; /* ASC => power on / reset */
-
-	STp->pos_unknown |= STp->device->was_reset;
+		st_printk(KERN_WARNING, STp, "Power on/reset recognized.");
+	}
 
 	if (cmdstatp->have_sense &&
 	    scode == RECOVERED_ERROR
@@ -968,6 +979,7 @@ static int test_ready(struct scsi_tape *STp, int do_wait)
 {
 	int attentions, waits, max_wait, scode;
 	int retval = CHKRES_READY, new_session = 0;
+	unsigned int ctr;
 	unsigned char cmd[MAX_COMMAND_SIZE];
 	struct st_request *SRpnt = NULL;
 	struct st_cmdstatus *cmdstatp = &STp->buffer->cmdstat;
@@ -1024,6 +1036,13 @@ static int test_ready(struct scsi_tape *STp, int do_wait)
 			}
 		}
 
+		ctr = scsi_get_ua_new_media_ctr(STp->device);
+		if (ctr != STp->new_media_ctr) {
+			STp->new_media_ctr = ctr;
+			new_session = 1;
+			DEBC_printk(STp, "New tape session.");
+		}
+
 		retval = (STp->buffer)->syscall_result;
 		if (!retval)
 			retval = new_session ? CHKRES_NEW_SESSION : CHKRES_READY;
@@ -4394,6 +4413,9 @@ static int st_probe(struct device *dev)
 		goto out_idr_remove;
 	}
 
+	tpnt->new_media_ctr = scsi_get_ua_new_media_ctr(SDp);
+	tpnt->por_ctr = scsi_get_ua_por_ctr(SDp);
+
 	dev_set_drvdata(dev, tpnt);
 
 
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index 2105c6a5b458..47b0e31b7828 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -178,6 +178,10 @@ struct scsi_tape {
 	int recover_count;     /* From tape opening */
 	int recover_reg;       /* From last status call */
 
+	/* The saved values of midlevel counters */
+	unsigned int new_media_ctr;
+	unsigned int por_ctr;
+
 #if DEBUG
 	unsigned char write_pending;
 	int nbr_finished;
-- 
2.43.0