Add an option to use the given command delay (in nanoseconds)
as the upper limit for command durations. A pseudo random
number generator chooses each duration uniformly from the range:
[0..delay_in_ns)
If it chooses 0 the scsi_debug driver will return to the
SCSI midlevel within the command submission call.
Main benefit: allows testing with out-of-order responses. Helped
the author track down a seldom encountered state transition
problem in another driver.
ChangeLog since version 2:
- drop %p cleanup
- use kstrtoint instead of sscanf
- change scaling if long delay exceeds around 4.2 seconds
to 4 microsecond precision with a 4.6 hour maximum,
beyond that don't randomize
- expand MODULE_PARM_DESC() message as suggested
- use jiffies_to_nsecs() macro instead of open code
This patch is against Martin Petersen's 5.5/scsi-queue branch.
It will also apply against lk 5.4 and 5.3, maybe earlier as well.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/scsi_debug.c | 42 ++++++++++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index d323523f5f9d..7804c165408f 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -38,6 +38,7 @@
#include <linux/hrtimer.h>
#include <linux/uuid.h>
#include <linux/t10-pi.h>
+#include <linux/random.h>
#include <net/checksum.h>
@@ -125,6 +126,7 @@ static const char *sdebug_version_date = "20190125";
#define DEF_PHYSBLK_EXP 0
#define DEF_OPT_XFERLEN_EXP 0
#define DEF_PTYPE TYPE_DISK
+#define DEF_RANDOM false
#define DEF_REMOVABLE false
#define DEF_SCSI_LEVEL 7 /* INQUIRY, byte2 [6->SPC-4; 7->SPC-5] */
#define DEF_SECTOR_SIZE 512
@@ -655,6 +657,7 @@ static unsigned int sdebug_unmap_max_blocks = DEF_UNMAP_MAX_BLOCKS;
static unsigned int sdebug_unmap_max_desc = DEF_UNMAP_MAX_DESC;
static unsigned int sdebug_write_same_length = DEF_WRITESAME_LENGTH;
static int sdebug_uuid_ctl = DEF_UUID_CTL;
+static bool sdebug_random = DEF_RANDOM;
static bool sdebug_removable = DEF_REMOVABLE;
static bool sdebug_clustering;
static bool sdebug_host_lock = DEF_HOST_LOCK;
@@ -4354,9 +4357,21 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
ktime_t kt;
if (delta_jiff > 0) {
- kt = ns_to_ktime((u64)delta_jiff * (NSEC_PER_SEC / HZ));
- } else
- kt = ndelay;
+ u64 ns = jiffies_to_nsecs(delta_jiff);
+
+ if (sdebug_random && ns < U32_MAX) {
+ ns = prandom_u32_max((u32)ns);
+ } else if (sdebug_random) {
+ ns >>= 12; /* scale to 4 usec precision */
+ if (ns < U32_MAX) /* over 4 hours max */
+ ns = prandom_u32_max((u32)ns);
+ ns <<= 12;
+ }
+ kt = ns_to_ktime(ns);
+ } else { /* ndelay has a 4.2 second max */
+ kt = sdebug_random ? prandom_u32_max((u32)ndelay) :
+ (u32)ndelay;
+ }
if (!sd_dp->init_hrt) {
sd_dp->init_hrt = true;
sqcp->sd_dp = sd_dp;
@@ -4451,6 +4466,7 @@ module_param_named(opts, sdebug_opts, int, S_IRUGO | S_IWUSR);
module_param_named(physblk_exp, sdebug_physblk_exp, int, S_IRUGO);
module_param_named(opt_xferlen_exp, sdebug_opt_xferlen_exp, int, S_IRUGO);
module_param_named(ptype, sdebug_ptype, int, S_IRUGO | S_IWUSR);
+module_param_named(random, sdebug_random, bool, S_IRUGO | S_IWUSR);
module_param_named(removable, sdebug_removable, bool, S_IRUGO | S_IWUSR);
module_param_named(scsi_level, sdebug_scsi_level, int, S_IRUGO);
module_param_named(sector_size, sdebug_sector_size, int, S_IRUGO);
@@ -4511,6 +4527,7 @@ MODULE_PARM_DESC(opts, "1->noise, 2->medium_err, 4->timeout, 8->recovered_err...
MODULE_PARM_DESC(physblk_exp, "physical block exponent (def=0)");
MODULE_PARM_DESC(opt_xferlen_exp, "optimal transfer length granularity exponent (def=physblk_exp)");
MODULE_PARM_DESC(ptype, "SCSI peripheral type(def=0[disk])");
+MODULE_PARM_DESC(random, "If set, uniformly randomize command duration between 0 and delay_in_ns");
MODULE_PARM_DESC(removable, "claim to have removable media (def=0)");
MODULE_PARM_DESC(scsi_level, "SCSI level to simulate(def=7[SPC-5])");
MODULE_PARM_DESC(sector_size, "logical block size in bytes (def=512)");
@@ -5101,6 +5118,24 @@ static ssize_t map_show(struct device_driver *ddp, char *buf)
}
static DRIVER_ATTR_RO(map);
+static ssize_t random_show(struct device_driver *ddp, char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "%d\n", (int)sdebug_random);
+}
+
+static ssize_t random_store(struct device_driver *ddp, const char *buf,
+ size_t count)
+{
+ int n;
+
+ if (count > 0 && kstrtoint(buf, 10, &n) == 0 && n >= 0) {
+ sdebug_random = (n > 0);
+ return count;
+ }
+ return -EINVAL;
+}
+static DRIVER_ATTR_RW(random);
+
static ssize_t removable_show(struct device_driver *ddp, char *buf)
{
return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_removable ? 1 : 0);
@@ -5211,6 +5246,7 @@ static struct attribute *sdebug_drv_attrs[] = {
&driver_attr_guard.attr,
&driver_attr_ato.attr,
&driver_attr_map.attr,
+ &driver_attr_random.attr,
&driver_attr_removable.attr,
&driver_attr_host_lock.attr,
&driver_attr_ndelay.attr,
--
2.23.0
