RE: [PATCH v1 3/3] scsi_debug: iouring iopoll support

[Kashyap Desai <kashyap.desai@broadcom.com>]

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>
> On 2020-10-15 9:37 a.m., Kashyap Desai wrote:
> > Add support of iouring iopoll interface in scsi_debug.
> > This feature requires shared hosttag support in kernel and driver.
>
> I am continuing to test this patch. There is one fix shown inline below
> plus a
> question near the end.

Hi Doug,  I have created add-on patch which includes all your comment. I am
also able to see the issue you reported and below patch fix it.
I will hold V2 revision of the series and I will wait for your Review-by and
Tested-by Tag.

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 4d9cc6af588c..fb328253086d 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5675,6 +5675,7 @@ MODULE_PARM_DESC(opt_xferlen_exp, "optimal transfer
length granularity exponent
 MODULE_PARM_DESC(opts, "1->noise, 2->medium_err, 4->timeout,
8->recovered_err... (def=0)");
 MODULE_PARM_DESC(per_host_store, "If set, next positive add_host will get
new store (def=0)");
 MODULE_PARM_DESC(physblk_exp, "physical block exponent (def=0)");
+MODULE_PARM_DESC(poll_queues, "support for iouring iopoll queues (1 to
max(submit_queues - 1)");
 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)");
@@ -5683,7 +5684,6 @@ MODULE_PARM_DESC(sector_size, "logical block size in
bytes (def=512)");
 MODULE_PARM_DESC(statistics, "collect statistics on commands, queues
(def=0)");
 MODULE_PARM_DESC(strict, "stricter checks: reserved field in cdb (def=0)");
 MODULE_PARM_DESC(submit_queues, "support for block multi-queue (def=1)");
-MODULE_PARM_DESC(poll_queues, "support for iouring iopoll queues");
 MODULE_PARM_DESC(tur_ms_to_ready, "TEST UNIT READY millisecs before initial
good status (def=0)");
 MODULE_PARM_DESC(unmap_alignment, "lowest aligned thin provisioning lba
(def=0)");
 MODULE_PARM_DESC(unmap_granularity, "thin provisioning granularity in
blocks (def=1)");
@@ -7199,7 +7199,7 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost,
unsigned int queue_num)
        do {
                spin_lock_irqsave(&sqp->qc_lock, iflags);
                qc_idx = find_first_bit(sqp->in_use_bm, sdebug_max_queue);
-               if (unlikely((qc_idx < 0) || (qc_idx >= SDEBUG_CANQUEUE)))
+               if (unlikely((qc_idx < 0) || (qc_idx >= sdebug_max_queue)))
                        goto out;

                sqcp = &sqp->qc_arr[qc_idx];
@@ -7477,10 +7477,17 @@ static int sdebug_driver_probe(struct device *dev)
                hpnt->host_tagset = 1;

        /* poll queues are possible for nr_hw_queues > 1 */
-       if (hpnt->nr_hw_queues == 1)
+       if (hpnt->nr_hw_queues == 1 || (poll_queues < 1)) {
+               pr_warn("%s: trim poll_queues to 0. poll_q/nr_hw = (%d/%d)
\n",
+                        my_name, poll_queues, hpnt->nr_hw_queues);
                poll_queues = 0;
+       }

-       /* poll queues  */
+       /*
+        * Poll queues don't need interrupts, but we need at least one I/O
queue
+        * left over for non-polled I/O.
+        * If condition not met, trim poll_queues to 1 (just for
simplicity).
+        */
        if (poll_queues >= submit_queues) {
                pr_warn("%s: trim poll_queues to 1\n", my_name);
                poll_queues = 1;


> > +	do {
> > +		spin_lock_irqsave(&sqp->qc_lock, iflags);
> > +		qc_idx = find_first_bit(sqp->in_use_bm, sdebug_max_queue);
> > +		if (unlikely((qc_idx < 0) || (qc_idx >= SDEBUG_CANQUEUE)))
>
> The above line IMO needs to be:
> 		if (unlikely((qc_idx < 0) || (qc_idx >= sdebug_max_queue)))
>
> If not, when sdebug_max_queue < SDEBUG_CANQUEUE and there is no
> request waiting then "scp is NULL, ..." is reported suggesting there is an
> error.

BTW -  Is below piece of code at sdebug_q_cmd_complete() requires similar
change ?
Use sdebug_max_queue instead of SDEBUG_CANQUEUE
        if (unlikely((qc_idx < 0) || (qc_idx >= SDEBUG_CANQUEUE))) {
                pr_err("wild qc_idx=%d\n", qc_idx);
                return;
        }

Kashyap

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