scsi: scsi_debug: Fix check for sdev queue full

There is a report that the blktests scsi/004 test for "TASK SET FULL" (TSF)
now fails.

The condition upon we should issue this TSF is when the sdev queue is
full. The check for a full queue has an off-by-1 error. Previously we would
increment the number of requests in the queue after testing if the queue
would be full, i.e. test if one less than full. Since we now use
scsi_device_busy() to count the number of requests in the queue, this would
already account for the current request, so fix the test for queue full
accordingly.

Fixes: 151f0ec ("scsi: scsi_debug: Drop sdebug_dev_info.num_in_q")
Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/oe-lkp/202303201334.18b30edc-oliver.sang@intel.com
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230327074310.1862889-2-john.g.garry@oracle.com
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: johnpgarry

drivers/scsi/scsi_debug.c

@@ -5580,7 +5580,7 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
 		int num_in_q = scsi_device_busy(sdp);
 		int qdepth = cmnd->device->queue_depth;
 
-		if ((num_in_q == (qdepth - 1)) &&
+		if ((num_in_q == qdepth) &&
 		    (atomic_inc_return(&sdebug_a_tsf) >=
 		     abs(sdebug_every_nth))) {
 			atomic_set(&sdebug_a_tsf, 0);