scsi: scsi_debug: Add two new parameters to scsi_debug driver

This patch adds two new parameters to the scsi_debug driver.

During various fault injection scenarios it would be useful to be able
to pick a specific starting sector and number of follow on sectors where
a MEDIUM ERROR for reads would be returned against a scsi-debug device.

Right now this only works against sector 0x1234 and OPT_MEDIUM_ERR_NUM
follow on sectors.  However during testing of md-raid and other
scenarios I wanted more flexibility.

The idea is add 2 new parameters:

    medium_error_start
    medium_error_count

If medium_error_start is set then we don't use the default of
OPT_MEDIUM_ERR_ADDR, but use that set value.

If medium_error_count is set we use that value otherwise default to
OPT_MEDIUM_ERR_NUM.
Signed-off-by: Laurence Oberman <loberman@redhat.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_debug.c

@@ -616,6 +616,8 @@ static unsigned int sdebug_guard = DEF_GUARD;
 static int sdebug_lowest_aligned = DEF_LOWEST_ALIGNED;
 static int sdebug_max_luns = DEF_MAX_LUNS;
 static int sdebug_max_queue = SDEBUG_CANQUEUE;	/* per submit queue */
+static unsigned int sdebug_medium_error_start = OPT_MEDIUM_ERR_ADDR;
+static int sdebug_medium_error_count = OPT_MEDIUM_ERR_NUM;
 static atomic_t retired_max_queue;	/* if > 0 then was prior max_queue */
 static int sdebug_ndelay = DEF_NDELAY;	/* if > 0 then unit is nanoseconds */
 static int sdebug_no_lun_0 = DEF_NO_LUN_0;
@@ -2711,8 +2713,8 @@ static int resp_read_dt0(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 	}
 
 	if (unlikely((SDEBUG_OPT_MEDIUM_ERR & sdebug_opts) &&
-		     (lba <= (OPT_MEDIUM_ERR_ADDR + OPT_MEDIUM_ERR_NUM - 1)) &&
-		     ((lba + num) > OPT_MEDIUM_ERR_ADDR))) {
+		     (lba <= (sdebug_medium_error_start + sdebug_medium_error_count - 1)) &&
+		     ((lba + num) > sdebug_medium_error_start))) {
 		/* claim unrecoverable read error */
 		mk_sense_buffer(scp, MEDIUM_ERROR, UNRECOVERED_READ_ERR, 0);
 		/* set info field and valid bit for fixed descriptor */
@@ -4432,6 +4434,8 @@ module_param_named(lbprz, sdebug_lbprz, int, S_IRUGO);
 module_param_named(lowest_aligned, sdebug_lowest_aligned, int, S_IRUGO);
 module_param_named(max_luns, sdebug_max_luns, int, S_IRUGO | S_IWUSR);
 module_param_named(max_queue, sdebug_max_queue, int, S_IRUGO | S_IWUSR);
+module_param_named(medium_error_start, sdebug_medium_error_start, int, S_IRUGO | S_IWUSR);
+module_param_named(medium_error_count, sdebug_medium_error_count, int, S_IRUGO | S_IWUSR);
 module_param_named(ndelay, sdebug_ndelay, int, S_IRUGO | S_IWUSR);
 module_param_named(no_lun_0, sdebug_no_lun_0, int, S_IRUGO | S_IWUSR);
 module_param_named(no_uld, sdebug_no_uld, int, S_IRUGO);
@@ -4489,6 +4493,8 @@ MODULE_PARM_DESC(lbprz,
 MODULE_PARM_DESC(lowest_aligned, "lowest aligned lba (def=0)");
 MODULE_PARM_DESC(max_luns, "number of LUNs per target to simulate(def=1)");
 MODULE_PARM_DESC(max_queue, "max number of queued commands (1 to max(def))");
+MODULE_PARM_DESC(medium_error_start, "starting sector number to return MEDIUM error");
+MODULE_PARM_DESC(medium_error_count, "count of sectors to return follow on MEDIUM error");
 MODULE_PARM_DESC(ndelay, "response delay in nanoseconds (def=0 -> ignore)");
 MODULE_PARM_DESC(no_lun_0, "no LU number 0 (def=0 -> have lun 0)");
 MODULE_PARM_DESC(no_uld, "stop ULD (e.g. sd driver) attaching (def=0))");