Merge patch series "scsi: st: scsi_error: More reset patches"

Kai Mäkisara <Kai.Makisara@kolumbus.fi> says:

The first patch re-applies after device reset some settings changed
by the user (partition, density, block size).

The second and third patch address the case where more than one ULD
access the same device. The Unit Attention (UA) sense data is sent only
to one ULD and the others miss it. The st driver needs to find out
if device reset or media change has happened.

The second patch adds counters for New Media and Power On/Reset (POR)
Unit Attentions to the scsi_device struct. The third one changes st
so that these are used: if the value in the scsi_device struct does
not match the one stored locally, the corresponding UA has happened.
Use of the was_reset flag has been removed.

The fourth patch adds a file to sysfs to tell the user if reads/writes
to a tape are blocked following a device reset.

Link: https://lore.kernel.org/r/20250120194925.44432-1-Kai.Makisara@kolumbus.fi
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

5 files changed, 97 insertions, 8 deletions

diff --git a/Documentation/scsi/st.rst b/Documentation/scsi/st.rst
index d3b28c28d74c..b4a092faa9c8 100644
--- a/Documentation/scsi/st.rst
+++ b/Documentation/scsi/st.rst
@@ -157,6 +157,11 @@ enabled driver and mode options. The value in the file is a bit mask where the
 bit definitions are the same as those used with MTSETDRVBUFFER in setting the
 options.
 
+Each directory contains the entry 'position_lost_in_reset'. If this value is
+one, reading and writing to the device is blocked after device reset. Most
+devices rewind the tape after reset and the writes/read don't access the
+tape position the user expects.
+
 A link named 'tape' is made from the SCSI device directory to the class
 directory corresponding to the mode 0 auto-rewind device (e.g., st0).
 
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 815e7d63f3e2..ec60e8a96b11 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -547,6 +547,18 @@ enum scsi_disposition scsi_check_sense(struct scsi_cmnd *scmd)
 
 	scsi_report_sense(sdev, &sshdr);
 
+	if (sshdr.sense_key == UNIT_ATTENTION) {
+		/*
+		 * Increment the counters for Power on/Reset or New Media so
+		 * that all ULDs interested in these can see that those have
+		 * happened, even if someone else gets the sense data.
+		 */
+		if (sshdr.asc == 0x28)
+			scmd->device->ua_new_media_ctr++;
+		else if (sshdr.asc == 0x29)
+			scmd->device->ua_por_ctr++;
+	}
+
 	if (scsi_sense_is_deferred(&sshdr))
 		return NEEDS_RETRY;
 
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index ebbd50ec0cda..85867120c8a9 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
@@ -952,7 +963,6 @@ static void reset_state(struct scsi_tape *STp)
 		STp->partition = find_partition(STp);
 		if (STp->partition < 0)
 			STp->partition = 0;
-		STp->new_partition = STp->partition;
 	}
 }
 
@@ -969,6 +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;
@@ -1025,6 +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;
@@ -2930,14 +2948,17 @@ static int st_int_ioctl(struct scsi_tape *STp, unsigned int cmd_in, unsigned lon
 		if (cmd_in == MTSETDENSITY) {
 			(STp->buffer)->b_data[4] = arg;
 			STp->density_changed = 1;	/* At least we tried ;-) */
+			STp->changed_density = arg;
 		} else if (cmd_in == SET_DENS_AND_BLK)
 			(STp->buffer)->b_data[4] = arg >> 24;
 		else
 			(STp->buffer)->b_data[4] = STp->density;
 		if (cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK) {
 			ltmp = arg & MT_ST_BLKSIZE_MASK;
-			if (cmd_in == MTSETBLK)
+			if (cmd_in == MTSETBLK) {
 				STp->blksize_changed = 1; /* At least we tried ;-) */
+				STp->changed_blksize = arg;
+			}
 		} else
 			ltmp = STp->block_size;
 		(STp->buffer)->b_data[9] = (ltmp >> 16);
@@ -3636,9 +3657,23 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
 				retval = (-EIO);
 				goto out;
 			}
-			reset_state(STp);
-			/* remove this when the midlevel properly clears was_reset */
-			STp->device->was_reset = 0;
+			reset_state(STp); /* Clears pos_unknown */
+
+			/* Fix the device settings after reset, ignore errors */
+			if (mtc.mt_op == MTREW || mtc.mt_op == MTSEEK ||
+				mtc.mt_op == MTEOM) {
+				if (STp->can_partitions) {
+					/* STp->new_partition contains the
+					 *  latest partition set
+					 */
+					STp->partition = 0;
+					switch_partition(STp);
+				}
+				if (STp->density_changed)
+					st_int_ioctl(STp, MTSETDENSITY, STp->changed_density);
+				if (STp->blksize_changed)
+					st_int_ioctl(STp, MTSETBLK, STp->changed_blksize);
+			}
 		}
 
 		if (mtc.mt_op != MTNOP && mtc.mt_op != MTSETBLK &&
@@ -4384,6 +4419,9 @@ 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);
 
 
@@ -4665,6 +4703,24 @@ options_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(options);
 
+/**
+ * position_lost_in_reset_show - Value 1 indicates that reads, writes, etc.
+ * are blocked because a device reset has occurred and no operation positioning
+ * the tape has been issued.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t position_lost_in_reset_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct st_modedef *STm = dev_get_drvdata(dev);
+	struct scsi_tape *STp = STm->tape;
+
+	return sprintf(buf, "%d", STp->pos_unknown);
+}
+static DEVICE_ATTR_RO(position_lost_in_reset);
+
 /* Support for tape stats */
 
 /**
@@ -4849,6 +4905,7 @@ static struct attribute *st_dev_attrs[] = {
 	&dev_attr_default_density.attr,
 	&dev_attr_default_compression.attr,
 	&dev_attr_options.attr,
+	&dev_attr_position_lost_in_reset.attr,
 	NULL,
 };
 
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index 1aaaf5369a40..0d7c4b8c2c8a 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -165,6 +165,7 @@ struct scsi_tape {
 	unsigned char compression_changed;
 	unsigned char drv_buffer;
 	unsigned char density;
+	unsigned char changed_density;
 	unsigned char door_locked;
 	unsigned char autorew_dev;   /* auto-rewind device */
 	unsigned char rew_at_close;  /* rewind necessary at close */
@@ -172,11 +173,16 @@ struct scsi_tape {
 	unsigned char cleaning_req;  /* cleaning requested? */
 	unsigned char first_tur;     /* first TEST UNIT READY */
 	int block_size;
+	int changed_blksize;
 	int min_block;
 	int max_block;
 	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;
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 7acd0ec82bb0..68dd49947d04 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -247,6 +247,9 @@ struct scsi_device {
 	unsigned int queue_stopped;	/* request queue is quiesced */
 	bool offline_already;		/* Device offline message logged */
 
+	unsigned int ua_new_media_ctr;	/* Counter for New Media UNIT ATTENTIONs */
+	unsigned int ua_por_ctr;	/* Counter for Power On / Reset UAs */
+
 	atomic_t disk_events_disable_depth; /* disable depth for disk events */
 
 	DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
@@ -684,6 +687,12 @@ static inline int scsi_device_busy(struct scsi_device *sdev)
 	return sbitmap_weight(&sdev->budget_map);
 }
 
+/* Macros to access the UNIT ATTENTION counters */
+#define scsi_get_ua_new_media_ctr(sdev) \
+	((const unsigned int)(sdev->ua_new_media_ctr))
+#define scsi_get_ua_por_ctr(sdev) \
+	((const unsigned int)(sdev->ua_por_ctr))
+
 #define MODULE_ALIAS_SCSI_DEVICE(type) \
 	MODULE_ALIAS("scsi:t-" __stringify(type) "*")
 #define SCSI_DEVICE_MODALIAS_FMT "scsi:t-0x%02x"