From: Douglas Gilbert <dgilbert@interlog.com>
Date: Thu, 12 Jul 2018 13:35:42 -0400
Subject: [PATCH] scsi: scsi_debug: skip long delays when ndelay small
Git-commit: 75aa3209c945fc711163ff1ecbc031bd13962a9d
Patch-mainline: v4.19-rc1
References: bsc#1118139

A test program's runtime became impractically long since any non zero
ndelay (e.g. 1 nanosec) caused Start Stop Unit to delay over 8 magnitudes
greater than other commands. This patch skips long delays (on Start Stop
Unit and Synchronize Cache) if ndelay is less than or equal to 10
microsecs.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/scsi_debug.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 24d7496cd9e2..4dda192b8fba 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5790,11 +5790,13 @@ static int scsi_debug_queuecommand(struct Scsi_Host *shost,
 fini:
 	if (F_DELAY_OVERR & flags)
 		return schedule_resp(scp, devip, errsts, pfp, 0, 0);
-	else if ((sdebug_jdelay || sdebug_ndelay) && (flags & F_LONG_DELAY)) {
+	else if ((flags & F_LONG_DELAY) && (sdebug_jdelay > 0 ||
+					    sdebug_ndelay > 10000)) {
 		/*
-		 * If any delay is active, for F_SSU_DELAY want at least 1
-		 * second and if sdebug_jdelay>0 want a long delay of that
-		 * many seconds; for F_SYNC_DELAY want 1/20 of that.
+		 * Skip long delays if ndelay <= 10 microseconds. Otherwise
+		 * for Start Stop Unit (SSU) want at least 1 second delay and
+		 * if sdebug_jdelay>1 want a long delay of that many seconds.
+		 * For Synchronize Cache want 1/20 of SSU's delay.
 		 */
 		int jdelay = (sdebug_jdelay < 2) ? 1 : sdebug_jdelay;
 		int denom = (flags & F_SYNC_DELAY) ? 20 : 1;
-- 
2.16.4