[PATCH 13/13] scsi_debug: Maintain write statistics per group number

[Bart Van Assche <bvanassche@acm.org>]

Track per GROUP NUMBER how many write commands have been processed. Make
this information available in sysfs. Reset these statistics if any data
is written into the sysfs attribute.

Note: SCSI devices should only interpret the information in the GROUP
NUMBER field as a stream identifier if the ST_ENBLE bit has been set to
one. This patch follows a simpler approach: count the number of writes
per GROUP NUMBER whether or not the group number represents a stream
identifier.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_debug.c | 51 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index ae46bcf8374b..728d9a1831e2 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -841,6 +841,8 @@ static int sdeb_zbc_nr_conv = DEF_ZBC_NR_CONV_ZONES;
 static int submit_queues = DEF_SUBMIT_QUEUES;  /* > 1 for multi-queue (mq) */
 static int poll_queues; /* iouring iopoll interface.*/
 
+static atomic_long_t writes_by_group_number[64];
+
 static char sdebug_proc_name[] = MY_NAME;
 static const char *my_name = MY_NAME;
 
@@ -3032,7 +3034,8 @@ static inline struct sdeb_store_info *devip2sip(struct sdebug_dev_info *devip,
 
 /* Returns number of bytes copied or -1 if error. */
 static int do_device_access(struct sdeb_store_info *sip, struct scsi_cmnd *scp,
-			    u32 sg_skip, u64 lba, u32 num, bool do_write)
+			    u32 sg_skip, u64 lba, u32 num, bool do_write,
+			    u8 group_number)
 {
 	int ret;
 	u64 block, rest = 0;
@@ -3051,6 +3054,10 @@ static int do_device_access(struct sdeb_store_info *sip, struct scsi_cmnd *scp,
 		return 0;
 	if (scp->sc_data_direction != dir)
 		return -1;
+
+	if (do_write && group_number < ARRAY_SIZE(writes_by_group_number))
+		atomic_long_inc(&writes_by_group_number[group_number]);
+
 	fsp = sip->storep;
 
 	block = do_div(lba, sdebug_store_sectors);
@@ -3424,7 +3431,7 @@ static int resp_read_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 		}
 	}
 
-	ret = do_device_access(sip, scp, 0, lba, num, false);
+	ret = do_device_access(sip, scp, 0, lba, num, false, 0);
 	sdeb_read_unlock(sip);
 	if (unlikely(ret == -1))
 		return DID_ERROR << 16;
@@ -3609,6 +3616,7 @@ static int resp_write_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 {
 	bool check_prot;
 	u32 num;
+	u8 group = 0;
 	u32 ei_lba;
 	int ret;
 	u64 lba;
@@ -3620,11 +3628,13 @@ static int resp_write_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 		ei_lba = 0;
 		lba = get_unaligned_be64(cmd + 2);
 		num = get_unaligned_be32(cmd + 10);
+		group = cmd[14] & 0x3f;
 		check_prot = true;
 		break;
 	case WRITE_10:
 		ei_lba = 0;
 		lba = get_unaligned_be32(cmd + 2);
+		group = cmd[6] & 0x3f;
 		num = get_unaligned_be16(cmd + 7);
 		check_prot = true;
 		break;
@@ -3639,15 +3649,18 @@ static int resp_write_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 		ei_lba = 0;
 		lba = get_unaligned_be32(cmd + 2);
 		num = get_unaligned_be32(cmd + 6);
+		group = cmd[6] & 0x3f;
 		check_prot = true;
 		break;
 	case 0x53:	/* XDWRITEREAD(10) */
 		ei_lba = 0;
 		lba = get_unaligned_be32(cmd + 2);
+		group = cmd[6] & 0x1f;
 		num = get_unaligned_be16(cmd + 7);
 		check_prot = false;
 		break;
 	default:	/* assume WRITE(32) */
+		group = cmd[6] & 0x3f;
 		lba = get_unaligned_be64(cmd + 12);
 		ei_lba = get_unaligned_be32(cmd + 20);
 		num = get_unaligned_be32(cmd + 28);
@@ -3702,7 +3715,7 @@ static int resp_write_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 		}
 	}
 
-	ret = do_device_access(sip, scp, 0, lba, num, true);
+	ret = do_device_access(sip, scp, 0, lba, num, true, group);
 	if (unlikely(scsi_debug_lbp()))
 		map_region(sip, lba, num);
 	/* If ZBC zone then bump its write pointer */
@@ -3754,12 +3767,14 @@ static int resp_write_scat(struct scsi_cmnd *scp,
 	u32 lb_size = sdebug_sector_size;
 	u32 ei_lba;
 	u64 lba;
+	u8 group;
 	int ret, res;
 	bool is_16;
 	static const u32 lrd_size = 32; /* + parameter list header size */
 
 	if (cmd[0] == VARIABLE_LENGTH_CMD) {
 		is_16 = false;
+		group = cmd[6] & 0x3f;
 		wrprotect = (cmd[10] >> 5) & 0x7;
 		lbdof = get_unaligned_be16(cmd + 12);
 		num_lrd = get_unaligned_be16(cmd + 16);
@@ -3770,6 +3785,7 @@ static int resp_write_scat(struct scsi_cmnd *scp,
 		lbdof = get_unaligned_be16(cmd + 4);
 		num_lrd = get_unaligned_be16(cmd + 8);
 		bt_len = get_unaligned_be32(cmd + 10);
+		group = cmd[14] & 0x3f;
 		if (unlikely(have_dif_prot)) {
 			if (sdebug_dif == T10_PI_TYPE2_PROTECTION &&
 			    wrprotect) {
@@ -3858,7 +3874,8 @@ static int resp_write_scat(struct scsi_cmnd *scp,
 			}
 		}
 
-		ret = do_device_access(sip, scp, sg_off, lba, num, true);
+		ret = do_device_access(sip, scp, sg_off, lba, num, true,
+				       group);
 		/* If ZBC zone then bump its write pointer */
 		if (sdebug_dev_is_zoned(devip))
 			zbc_inc_wp(devip, lba, num);
@@ -6783,6 +6800,31 @@ static ssize_t tur_ms_to_ready_show(struct device_driver *ddp, char *buf)
 }
 static DRIVER_ATTR_RO(tur_ms_to_ready);
 
+static ssize_t group_number_stats_show(struct device_driver *ddp, char *buf)
+{
+	char *p = buf, *end = buf + PAGE_SIZE;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(writes_by_group_number); i++)
+		p += scnprintf(p, end - p, "%d %ld\n", i,
+			       atomic_long_read(&writes_by_group_number[i]));
+
+	return p - buf;
+}
+
+static ssize_t group_number_stats_store(struct device_driver *ddp,
+					const char *buf,
+				  size_t count)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(writes_by_group_number); i++)
+		atomic_long_set(&writes_by_group_number[i], 0);
+
+	return 0;
+}
+static DRIVER_ATTR_RW(group_number_stats);
+
 /* Note: The following array creates attribute files in the
    /sys/bus/pseudo/drivers/scsi_debug directory. The advantage of these
    files (over those found in the /sys/module/scsi_debug/parameters
@@ -6829,6 +6871,7 @@ static struct attribute *sdebug_drv_attrs[] = {
 	&driver_attr_cdb_len.attr,
 	&driver_attr_tur_ms_to_ready.attr,
 	&driver_attr_zbc.attr,
+	&driver_attr_group_number_stats.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(sdebug_drv);