RE: [PATCH v3] scsi_debug: add new defer_type for mq_poll

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

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> Kashyap,
> There is another issue here, namely iodepth > host_max_queue (64 > 32) and
> in my setup that is not handled well. So there is a problem with
> scsi_debug
> *** or the mid-level in handling this case.
>
> If you have modified the sd driver to call blk_poll() then perhaps you
> could try
> the above test again with a reduced iodepth.

Doug -

I debug the issue and found the fix. We need to remove below code to handle
this new defer type for mq poll.
Earlier I did not used " REQ_HIPRI" to handle mq poll, but now you are
managing it through REQ_HIPRI check, it is safe and required to have below
patch.


diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index b9ec3a47fbf1..c50de49a2c2f 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5437,13 +5437,6 @@ static int schedule_resp(struct scsi_cmnd *cmnd,
struct sdebug_dev_info *devip,
        sd_dp = sqcp->sd_dp;
        spin_unlock_irqrestore(&sqp->qc_lock, iflags);

-       /* Do not complete IO from default completion path.
-        * Let it to be on queue.
-        * Completion should happen from mq_poll interface.
-        */
-       if ((sqp - sdebug_q_arr) >= (submit_queues - poll_queues))
-               return 0;
-
        if (!sd_dp) {
                sd_dp = kzalloc(sizeof(*sd_dp), GFP_ATOMIC);
                if (!sd_dp) {


On top of your v3 patch + above fix, I am able to run IO and there are no
issues.  There is no issue with higher QD as well, so we are good to go.

Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>

So how shall we progress now ? Shall I ask Martin to pick all the patches
from " [PATCH v3 0/4] io_uring iopoll in scsi layer" since this patch has
dependency on my series.

Kashyap

>
> Doug Gilbert
>
> *** the scsi_debug should either yield a TASK SET FULL status or return
>      SCSI_MLQUEUE_HOST_BUSY from queuecommand() when it has run out of
>      slots.
>
> > [seqprecon]
> > filename=/dev/sdd
> > [seqprecon]
> > filename=/dev/sde
> > [seqprecon]
> > filename=/dev/sdf
> >
> >
> > I will ask Martin to pick all the patches from "[v3,1/4] add io_uring
> > with IOPOLL support in the scsi layer" except scsi_debug. We can work
> > on scsi_debug and send standalone patch.
> >
> > Kashyap

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