Many SCSI HBAs support a hostwide tagset, whereby each command submitted
to the HW from all submission queues must have a unique tag identifier.
Normally this unique tag will be in the range [0, max queue), where "max
queue" is the depth of each of the submission queues.
Add support for this hostwide tag feature, via module parameter
"host_max_queue". A non-zero value means that the feature is enabled. In
this case, the submission queues are not exposed to upper layer, i.e. from
blk-mq prespective, the device has a single hw queue. There are 2 reasons
for this:
a. it is assumed that the host can support nr_hw_queues * can_queue
commands, but this is not true for hostwide tags
b. for nr_hw_queues != 0, the request tag is not unique over all HW queues,
and some HBA drivers want to use this tag for the hostwide tag
However, like many SCSI HBA drivers today - megaraid sas being an example -
the full set of HW submission queues are still used in the LLDD driver. So
instead of using a complicated "reply_map" to create a per-CPU submission
queue mapping like megaraid sas (as it depends on a PCI device + MSIs) -
use a simple algorithm:
hwq = cpu % queue count
If the host max queue param is set non-zero, then the max queue depth is
fixed at this value also.
If and when hostwide shared tags are supported in blk-mq/scsi mid-layer,
then the policy to set nr_hw_queues = 0 for hostwide tags can be revised.
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
---
drivers/scsi/scsi_debug.c | 80 +++++++++++++++++++++++++++++++++------
1 file changed, 68 insertions(+), 12 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 68534a23866e..2246d721ec88 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -344,6 +344,7 @@ struct sdebug_defer {
struct execute_work ew;
int sqa_idx; /* index of sdebug_queue array */
int qc_idx; /* index of sdebug_queued_cmd array within sqa_idx */
+ int hc_idx; /* hostwide tag index */
int issuing_cpu;
bool init_hrt;
bool init_wq;
@@ -759,6 +760,7 @@ static int sdebug_dsense = DEF_D_SENSE;
static int sdebug_every_nth = DEF_EVERY_NTH;
static int sdebug_fake_rw = DEF_FAKE_RW;
static unsigned int sdebug_guard = DEF_GUARD;
+static int sdebug_host_max_queue; /* per host */
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 */
@@ -4707,15 +4709,28 @@ static int resp_rwp_zone(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
static struct sdebug_queue *get_queue(struct scsi_cmnd *cmnd)
{
- u32 tag = blk_mq_unique_tag(cmnd->request);
- u16 hwq = blk_mq_unique_tag_to_hwq(tag);
+ u16 hwq;
- pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
- if (WARN_ON_ONCE(hwq >= submit_queues))
- hwq = 0;
+ if (sdebug_host_max_queue) {
+ /* Provide a simple method to choose the hwq */
+ hwq = smp_processor_id() % submit_queues;
+ } else {
+ u32 tag = blk_mq_unique_tag(cmnd->request);
+
+ hwq = blk_mq_unique_tag_to_hwq(tag);
+
+ pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
+ if (WARN_ON_ONCE(hwq >= submit_queues))
+ hwq = 0;
+ }
return sdebug_q_arr + hwq;
}
+static u32 get_tag(struct scsi_cmnd *cmnd)
+{
+ return blk_mq_unique_tag(cmnd->request);
+}
+
/* Queued (deferred) command completions converge here. */
static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
{
@@ -4747,8 +4762,8 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
scp = sqcp->a_cmnd;
if (unlikely(scp == NULL)) {
spin_unlock_irqrestore(&sqp->qc_lock, iflags);
- pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d\n",
- sd_dp->sqa_idx, qc_idx);
+ pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d, hc_idx=%d\n",
+ sd_dp->sqa_idx, qc_idx, sd_dp->hc_idx);
return;
}
devip = (struct sdebug_dev_info *)scp->device->hostdata;
@@ -5451,6 +5466,10 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
new_sd_dp = false;
}
+ /* Set the hostwide tag */
+ if (sdebug_host_max_queue)
+ sd_dp->hc_idx = get_tag(cmnd);
+
if (ndelay > 0 && ndelay < INCLUSIVE_TIMING_MAX_NS)
ns_from_boot = ktime_get_boottime_ns();
@@ -5572,6 +5591,7 @@ module_param_named(every_nth, sdebug_every_nth, int, S_IRUGO | S_IWUSR);
module_param_named(fake_rw, sdebug_fake_rw, int, S_IRUGO | S_IWUSR);
module_param_named(guard, sdebug_guard, uint, S_IRUGO);
module_param_named(host_lock, sdebug_host_lock, bool, S_IRUGO | S_IWUSR);
+module_param_named(host_max_queue, sdebug_host_max_queue, int, S_IRUGO);
module_param_string(inq_product, sdebug_inq_product_id,
sizeof(sdebug_inq_product_id), S_IRUGO | S_IWUSR);
module_param_string(inq_rev, sdebug_inq_product_rev,
@@ -5642,6 +5662,8 @@ MODULE_PARM_DESC(every_nth, "timeout every nth command(def=0)");
MODULE_PARM_DESC(fake_rw, "fake reads/writes instead of copying (def=0)");
MODULE_PARM_DESC(guard, "protection checksum: 0=crc, 1=ip (def=0)");
MODULE_PARM_DESC(host_lock, "host_lock is ignored (def=0)");
+MODULE_PARM_DESC(host_max_queue,
+ "host max # of queued cmds (0 to max(def) [max_queue fixed equal for !0])");
MODULE_PARM_DESC(inq_product, "SCSI INQUIRY product string (def=\"scsi_debug\")");
MODULE_PARM_DESC(inq_rev, "SCSI INQUIRY revision string (def=\""
SDEBUG_VERSION "\")");
@@ -6141,7 +6163,8 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
struct sdebug_queue *sqp;
if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n > 0) &&
- (n <= SDEBUG_CANQUEUE)) {
+ (n <= SDEBUG_CANQUEUE) &&
+ (sdebug_host_max_queue == 0)) {
block_unblock_all_queues(true);
k = 0;
for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
@@ -6164,6 +6187,17 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
}
static DRIVER_ATTR_RW(max_queue);
+static ssize_t host_max_queue_show(struct device_driver *ddp, char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_host_max_queue);
+}
+
+/*
+ * Since this is used for .can_queue, and we get the hc_idx tag from the bitmap
+ * in range [0, sdebug_host_max_queue), we can't change it.
+ */
+static DRIVER_ATTR_RO(host_max_queue);
+
static ssize_t no_uld_show(struct device_driver *ddp, char *buf)
{
return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_no_uld);
@@ -6503,6 +6537,7 @@ static struct attribute *sdebug_drv_attrs[] = {
&driver_attr_ptype.attr,
&driver_attr_dsense.attr,
&driver_attr_fake_rw.attr,
+ &driver_attr_host_max_queue.attr,
&driver_attr_no_lun_0.attr,
&driver_attr_num_tgts.attr,
&driver_attr_dev_size_mb.attr,
@@ -6619,6 +6654,20 @@ static int __init scsi_debug_init(void)
return -EINVAL;
}
+ if ((sdebug_host_max_queue > SDEBUG_CANQUEUE) ||
+ (sdebug_host_max_queue < 0)) {
+ pr_err("host_max_queue must be in range [0 %d]\n",
+ SDEBUG_CANQUEUE);
+ return -EINVAL;
+ }
+
+ if (sdebug_host_max_queue &&
+ (sdebug_max_queue != sdebug_host_max_queue)) {
+ sdebug_max_queue = sdebug_host_max_queue;
+ pr_warn("fixing max submit queue depth to host max queue depth, %d\n",
+ sdebug_max_queue);
+ }
+
sdebug_q_arr = kcalloc(submit_queues, sizeof(struct sdebug_queue),
GFP_KERNEL);
if (sdebug_q_arr == NULL)
@@ -7257,7 +7306,10 @@ static int sdebug_driver_probe(struct device *dev)
sdbg_host = to_sdebug_host(dev);
- sdebug_driver_template.can_queue = sdebug_max_queue;
+ if (sdebug_host_max_queue)
+ sdebug_driver_template.can_queue = sdebug_host_max_queue;
+ else
+ sdebug_driver_template.can_queue = sdebug_max_queue;
if (!sdebug_clustering)
sdebug_driver_template.dma_boundary = PAGE_SIZE - 1;
@@ -7272,9 +7324,13 @@ static int sdebug_driver_probe(struct device *dev)
my_name, submit_queues, nr_cpu_ids);
submit_queues = nr_cpu_ids;
}
- /* Decide whether to tell scsi subsystem that we want mq */
- /* Following should give the same answer for each host */
- hpnt->nr_hw_queues = submit_queues;
+ /*
+ * Decide whether to tell scsi subsystem that we want mq. The
+ * following should give the same answer for each host. If the host
+ * has a limit of hostwide max commands, then do not set.
+ */
+ if (!sdebug_host_max_queue)
+ hpnt->nr_hw_queues = submit_queues;
sdbg_host->shost = hpnt;
*((struct sdebug_host_info **)hpnt->hostdata) = sdbg_host;
--
2.26.2
