Index: lib/geom/nop/gnop.8
===================================================================
--- lib/geom/nop/gnop.8
+++ lib/geom/nop/gnop.8
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 17, 2018
+.Dd July 24, 2019
 .Dt GNOP 8
 .Os
 .Sh NAME
@@ -34,22 +34,28 @@
 .Nm
 .Cm create
 .Op Fl v
+.Op Fl d Ar delaymsec
 .Op Fl e Ar error
 .Op Fl o Ar offset
 .Op Fl p Ar stripesize
 .Op Fl P Ar stripeoffset
+.Op Fl q Ar rdelayprob
 .Op Fl r Ar rfailprob
 .Op Fl s Ar size
 .Op Fl S Ar secsize
 .Op Fl w Ar wfailprob
+.Op Fl x Ar wdelayprob
 .Op Fl z Ar physpath
 .Ar dev ...
 .Nm
 .Cm configure
 .Op Fl v
+.Op Fl d Ar delaymsec
 .Op Fl e Ar error
+.Op Fl q Ar rdelayprob
 .Op Fl r Ar rfailprob
 .Op Fl w Ar wfailprob
+.Op Fl x Ar wdelayprob
 .Ar prov ...
 .Nm
 .Cm destroy
@@ -113,26 +119,32 @@
 .Pp
 Additional options:
 .Bl -tag -width ".Fl r Ar rfailprob"
+.It Fl d Ar delaymsec
+Specifies the delay of the requests in millisecond.
 .It Fl e Ar error
 Specifies the error number to return on failure.
 .It Fl f
 Force the removal of the specified provider.
 .It Fl o Ar offset
 Where to begin on the original provider.
-.It Fl p Ar stripesize
-Value of the stripesize property of the transparent provider.
+.it fl p ar stripesize
+value of the stripesize property of the transparent provider.
 .It Fl P Ar stripeoffset
 Value of the stripeoffset property of the transparent provider.
+.It Fl q Ar rdelayprob
+Specifies read delay probability in percent.
 .It Fl r Ar rfailprob
 Specifies read failure probability in percent.
 .It Fl s Ar size
 Size of the transparent provider.
 .It Fl S Ar secsize
 Sector size of the transparent provider.
-.It Fl w Ar wfailprob
+.it fl w ar wfailprob
 Specifies write failure probability in percent.
 .It Fl v
 Be more verbose.
+.It Fl x Ar wdelayprob
+Specifies write delay probability in percent.
 .It Fl z Ar physpath
 Physical path of the transparent provider.
 .El
Index: sys/geom/nop/g_nop.h
===================================================================
--- sys/geom/nop/g_nop.h
+++ sys/geom/nop/g_nop.h
@@ -62,26 +62,38 @@
 	}								\
 } while (0)
 
+struct g_nop_delay {
+	struct callout			dl_cal;
+	struct bio			*dl_bio;
+	TAILQ_ENTRY(g_nop_delay)	dl_next;
+};
+
+TAILQ_HEAD(g_nop_delay_head, g_nop_delay);
+
 struct g_nop_softc {
-	int		sc_error;
-	off_t		sc_offset;
-	off_t		sc_explicitsize;
-	off_t		sc_stripesize;
-	off_t		sc_stripeoffset;
-	u_int		sc_rfailprob;
-	u_int		sc_wfailprob;
-	uintmax_t	sc_reads;
-	uintmax_t	sc_writes;
-	uintmax_t	sc_deletes;
-	uintmax_t	sc_getattrs;
-	uintmax_t	sc_flushes;
-	uintmax_t	sc_cmd0s;
-	uintmax_t	sc_cmd1s;
-	uintmax_t	sc_cmd2s;
-	uintmax_t	sc_readbytes;
-	uintmax_t	sc_wrotebytes;
-	char*		sc_physpath;
-	struct mtx	sc_lock;
+	int	  		sc_error;
+	off_t	  		sc_offset;
+	off_t	  		sc_explicitsize;
+	off_t	  		sc_stripesize;
+	off_t	  		sc_stripeoffset;
+	u_int	  		sc_rfailprob;
+	u_int	  		sc_wfailprob;
+	u_int	  		sc_delaymsec;
+	u_int	  		sc_rdelayprob;
+	u_int	  		sc_wdelayprob;
+	uintmax_t 		sc_reads;
+	uintmax_t 		sc_writes;
+	uintmax_t 		sc_deletes;
+	uintmax_t 		sc_getattrs;
+	uintmax_t 		sc_flushes;
+	uintmax_t 		sc_cmd0s;
+	uintmax_t 		sc_cmd1s;
+	uintmax_t 		sc_cmd2s;
+	uintmax_t 		sc_readbytes;
+	uintmax_t 		sc_wrotebytes;
+	char*	  		sc_physpath;
+	struct mtx		sc_lock;
+	struct g_nop_delay_head	sc_head_delay;
 };
 #endif	/* _KERNEL */
 
Index: sys/geom/nop/g_nop.c
===================================================================
--- sys/geom/nop/g_nop.c
+++ sys/geom/nop/g_nop.c
@@ -142,6 +142,35 @@
 	g_io_deliver(bp, 0);
 }
 
+static void
+g_nop_pass(struct bio *cbp, struct g_geom *gp)
+{
+
+	G_NOP_LOGREQ(cbp, "Sending request.");
+	g_io_request(cbp, LIST_FIRST(&gp->consumer));
+}
+
+static void
+g_nop_pass_timeout(void *data)
+{
+	struct g_nop_softc *sc;
+	struct g_geom *gp;
+	struct g_nop_delay *gndelay;
+
+	gndelay = (struct g_nop_delay *)data;
+
+	gp = gndelay->dl_bio->bio_to->geom;
+	sc = gp->softc;
+
+	mtx_lock(&sc->sc_lock);
+	TAILQ_REMOVE(&sc->sc_head_delay, gndelay, dl_next);
+	mtx_unlock(&sc->sc_lock);
+
+	g_nop_pass(gndelay->dl_bio, gp);
+
+	g_free(data);
+}
+
 static void
 g_nop_start(struct bio *bp)
 {
@@ -149,10 +178,13 @@
 	struct g_geom *gp;
 	struct g_provider *pp;
 	struct bio *cbp;
-	u_int failprob = 0;
+	u_int failprob, delayprob;
+
+	failprob = delayprob = 0;
 
 	gp = bp->bio_to->geom;
 	sc = gp->softc;
+
 	G_NOP_LOGREQ(bp, "Request received.");
 	mtx_lock(&sc->sc_lock);
 	switch (bp->bio_cmd) {
@@ -160,11 +192,13 @@
 		sc->sc_reads++;
 		sc->sc_readbytes += bp->bio_length;
 		failprob = sc->sc_rfailprob;
+		delayprob = sc->sc_rdelayprob;
 		break;
 	case BIO_WRITE:
 		sc->sc_writes++;
 		sc->sc_wrotebytes += bp->bio_length;
 		failprob = sc->sc_wfailprob;
+		delayprob = sc->sc_wdelayprob;
 		break;
 	case BIO_DELETE:
 		sc->sc_deletes++;
@@ -208,6 +242,7 @@
 			return;
 		}
 	}
+
 	cbp = g_clone_bio(bp);
 	if (cbp == NULL) {
 		g_io_deliver(bp, ENOMEM);
@@ -218,8 +253,35 @@
 	pp = LIST_FIRST(&gp->provider);
 	KASSERT(pp != NULL, ("NULL pp"));
 	cbp->bio_to = pp;
-	G_NOP_LOGREQ(cbp, "Sending request.");
-	g_io_request(cbp, LIST_FIRST(&gp->consumer));
+
+	if (delayprob > 0) {
+		struct g_nop_delay *gndelay;
+		u_int rval;
+
+		rval = arc4random() % 100;
+		if (rval < delayprob) {
+			gndelay = g_malloc(sizeof(*gndelay), M_NOWAIT | M_ZERO);
+			if (gndelay == NULL) {
+				g_io_deliver(bp, ENOMEM);
+				g_destroy_bio(cbp);
+				return;
+			}
+			callout_init(&gndelay->dl_cal, 0);
+
+			gndelay->dl_bio = cbp;
+
+			mtx_lock(&sc->sc_lock);
+			TAILQ_INSERT_TAIL(&sc->sc_head_delay, gndelay, dl_next);
+			mtx_unlock(&sc->sc_lock);
+
+			callout_reset(&gndelay->dl_cal,
+			    MSEC_2_TICKS(sc->sc_delaymsec),
+			    g_nop_pass_timeout, gndelay);
+			return;
+		}
+	}
+
+	g_nop_pass(cbp, gp);
 }
 
 static int
@@ -331,9 +393,9 @@
 	sc->sc_cmd2s = 0;
 	sc->sc_readbytes = 0;
 	sc->sc_wrotebytes = 0;
+	TAILQ_INIT(&sc->sc_head_delay);
 	mtx_init(&sc->sc_lock, "gnop lock", NULL, MTX_DEF);
 	gp->softc = sc;
-
 	newpp = g_new_providerf(gp, "%s", gp->name);
 	newpp->flags |= G_PF_DIRECT_SEND | G_PF_DIRECT_RECEIVE;
 	newpp->mediasize = size;
@@ -368,9 +430,20 @@
 static void
 g_nop_providergone(struct g_provider *pp)
 {
+	struct g_nop_delay *dthis;
 	struct g_geom *gp = pp->geom;
 	struct g_nop_softc *sc = gp->softc;
 
+	for (;;) {
+		dthis = TAILQ_FIRST(&sc->sc_head_delay);
+		if (dthis == NULL)
+			break;
+		TAILQ_REMOVE(&sc->sc_head_delay, dthis, dl_next);
+
+		callout_drain(&dthis->dl_cal);
+		g_free(dthis);
+	}
+
 	gp->softc = NULL;
 	free(sc->sc_physpath, M_GEOM);
 	mtx_destroy(&sc->sc_lock);
@@ -400,6 +473,7 @@
 	} else {
 		G_NOP_DEBUG(0, "Device %s removed.", gp->name);
 	}
+
 	g_wither_geom(gp, ENXIO);
 
 	return (0);
@@ -826,7 +900,7 @@
 	    sc->sc_wfailprob);
 	sbuf_printf(sb, "%s<ReadDelayedProb>%u</ReadDelayedProb>\n", indent,
 	    sc->sc_rdelayprob);
-	sbuf_printf(sb, "%s<WriteDelayedProb>%u</WriteDelayedProbe\n", indent,
+	sbuf_printf(sb, "%s<WriteDelayedProb>%u</WriteDelayedProb>\n", indent,
 	    sc->sc_wdelayprob);
 	sbuf_printf(sb, "%s<Delay>%d</Delay>\n", indent, sc->sc_delaymsec);
 	sbuf_printf(sb, "%s<Error>%d</Error>\n", indent, sc->sc_error);