Index: head/lib/geom/nop/geom_nop.c
===================================================================
--- head/lib/geom/nop/geom_nop.c
+++ head/lib/geom/nop/geom_nop.c
@@ -43,6 +43,7 @@
 struct g_command class_commands[] = {
 	{ "create", G_FLAG_VERBOSE | G_FLAG_LOADKLD, NULL,
 	    {
+		{ 'c', "count_until_fail", "-1", G_TYPE_NUMBER },
 		{ 'd', "delaymsec", "-1", G_TYPE_NUMBER },
 		{ 'e', "error", "-1", G_TYPE_NUMBER },
 		{ 'o', "offset", "0", G_TYPE_NUMBER },
@@ -57,12 +58,14 @@
 		{ 'z', "physpath", G_NOP_PHYSPATH_PASSTHROUGH, G_TYPE_STRING },
 		G_OPT_SENTINEL
 	    },
-	    "[-v] [-d delaymsec] [-e error] [-o offset] [-p stripesize] "
-	    "[-P stripeoffset] [-q rdelayprob] [-r rfailprob] [-s size] "
-	    "[-S secsize] [-w wfailprob] [-x wdelayprob] [-z physpath] dev ..."
+	    "[-v] [-c count_until_fail] [-d delaymsec] [-e error] [-o offset] "
+	    "[-p stripesize] [-P stripeoffset] [-q rdelayprob] [-r rfailprob] "
+	    "[-s size]  [-S secsize] [-w wfailprob] [-x wdelayprob] "
+	    "[-z physpath] dev ..."
 	},
 	{ "configure", G_FLAG_VERBOSE, NULL,
 	    {
+		{ 'c', "count_until_fail", "-1", G_TYPE_NUMBER },
 		{ 'd', "delaymsec", "-1", G_TYPE_NUMBER },
 		{ 'e', "error", "-1", G_TYPE_NUMBER },
 		{ 'q', "rdelayprob", "-1", G_TYPE_NUMBER },
@@ -71,8 +74,9 @@
 		{ 'x', "wdelayprob", "-1", G_TYPE_NUMBER },
 		G_OPT_SENTINEL
 	    },
-	    "[-v] [-d delaymsec] [-e error] [-q rdelayprob] [-r rfailprob] "
-	    "[-w wfailprob] [-x wdelayprob] prov ..."
+	    "[-v] [-c count_until_fail] [-d delaymsec] [-e error] "
+	    "[-q rdelayprob] [-r rfailprob] [-w wfailprob] [-x wdelayprob] "
+	    "prov ..."
 	},
 	{ "destroy", G_FLAG_VERBOSE, NULL,
 	    {
Index: head/lib/geom/nop/gnop.8
===================================================================
--- head/lib/geom/nop/gnop.8
+++ head/lib/geom/nop/gnop.8
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 31, 2019
+.Dd September 13, 2019
 .Dt GNOP 8
 .Os
 .Sh NAME
@@ -34,6 +34,7 @@
 .Nm
 .Cm create
 .Op Fl v
+.Op Fl c Ar count_until_fail
 .Op Fl d Ar delaymsec
 .Op Fl e Ar error
 .Op Fl o Ar offset
@@ -50,6 +51,7 @@
 .Nm
 .Cm configure
 .Op Fl v
+.Op Fl c Ar count_until_fail
 .Op Fl d Ar delaymsec
 .Op Fl e Ar error
 .Op Fl q Ar rdelayprob
@@ -118,7 +120,10 @@
 .El
 .Pp
 Additional options:
-.Bl -tag -width ".Fl r Ar rfailprob"
+.Bl -tag -width "-c count_until_fail"
+.It Fl c Ar count_until_fail
+Specifies the number of I/O requests to allow before setting the read and write
+failure probabilities to 100%.
 .It Fl d Ar delaymsec
 Specifies the delay of the requests in milliseconds.
 Note that requests will be delayed before they are sent to the backing device.
Index: head/sys/geom/nop/g_nop.h
===================================================================
--- head/sys/geom/nop/g_nop.h
+++ head/sys/geom/nop/g_nop.h
@@ -62,6 +62,7 @@
 	u_int			 sc_delaymsec;
 	u_int			 sc_rdelayprob;
 	u_int			 sc_wdelayprob;
+	u_int			 sc_count_until_fail;
 	uintmax_t		 sc_reads;
 	uintmax_t		 sc_writes;
 	uintmax_t		 sc_deletes;
Index: head/sys/geom/nop/g_nop.c
===================================================================
--- head/sys/geom/nop/g_nop.c
+++ head/sys/geom/nop/g_nop.c
@@ -195,6 +195,10 @@
 
 	G_NOP_LOGREQ(bp, "Request received.");
 	mtx_lock(&sc->sc_lock);
+	if (sc->sc_count_until_fail != 0 && --sc->sc_count_until_fail == 0) {
+		sc->sc_rfailprob = 100;
+		sc->sc_wfailprob = 100;
+	}
 	switch (bp->bio_cmd) {
 	case BIO_READ:
 		sc->sc_reads++;
@@ -308,9 +312,10 @@
 
 static int
 g_nop_create(struct gctl_req *req, struct g_class *mp, struct g_provider *pp,
-    int ioerror, u_int rfailprob, u_int wfailprob, u_int delaymsec, u_int rdelayprob,
-    u_int wdelayprob, off_t offset, off_t size, u_int secsize, off_t stripesize,
-    off_t stripeoffset, const char *physpath)
+    int ioerror, u_int count_until_fail, u_int rfailprob, u_int wfailprob,
+    u_int delaymsec, u_int rdelayprob, u_int wdelayprob, off_t offset,
+    off_t size, u_int secsize, off_t stripesize, off_t stripeoffset,
+    const char *physpath)
 {
 	struct g_nop_softc *sc;
 	struct g_geom *gp;
@@ -386,6 +391,7 @@
 	} else
 		sc->sc_physpath = NULL;
 	sc->sc_error = ioerror;
+	sc->sc_count_until_fail = count_until_fail;
 	sc->sc_rfailprob = rfailprob;
 	sc->sc_wfailprob = wfailprob;
 	sc->sc_delaymsec = delaymsec;
@@ -491,8 +497,9 @@
 g_nop_ctl_create(struct gctl_req *req, struct g_class *mp)
 {
 	struct g_provider *pp;
-	intmax_t *error, *rfailprob, *wfailprob, *offset, *secsize, *size,
-	    *stripesize, *stripeoffset, *delaymsec, *rdelayprob, *wdelayprob;
+	intmax_t *error, *rfailprob, *wfailprob, *count_until_fail, *offset,
+	    *secsize, *size, *stripesize, *stripeoffset, *delaymsec,
+	    *rdelayprob, *wdelayprob;
 	const char *name, *physpath;
 	char param[16];
 	int i, *nargs;
@@ -558,6 +565,16 @@
 		gctl_error(req, "Invalid '%s' argument", "wdelayprob");
 		return;
 	}
+	count_until_fail = gctl_get_paraml(req, "count_until_fail",
+	    sizeof(*count_until_fail));
+	if (count_until_fail == NULL) {
+		gctl_error(req, "No '%s' argument", "count_until_fail");
+		return;
+	}
+	if (*count_until_fail < -1) {
+		gctl_error(req, "Invalid '%s' argument", "count_until_fail");
+		return;
+	}
 	offset = gctl_get_paraml(req, "offset", sizeof(*offset));
 	if (offset == NULL) {
 		gctl_error(req, "No '%s' argument", "offset");
@@ -622,6 +639,7 @@
 		}
 		if (g_nop_create(req, mp, pp,
 		    *error == -1 ? EIO : (int)*error,
+		    *count_until_fail == -1 ? 0 : (u_int)*count_until_fail,
 		    *rfailprob == -1 ? 0 : (u_int)*rfailprob,
 		    *wfailprob == -1 ? 0 : (u_int)*wfailprob,
 		    *delaymsec == -1 ? 1 : (u_int)*delaymsec,
@@ -640,7 +658,8 @@
 {
 	struct g_nop_softc *sc;
 	struct g_provider *pp;
-	intmax_t *delaymsec, *error, *rdelayprob, *rfailprob, *wdelayprob, *wfailprob;
+	intmax_t *delaymsec, *error, *rdelayprob, *rfailprob, *wdelayprob,
+	    *wfailprob, *count_until_fail;
 	const char *name;
 	char param[16];
 	int i, *nargs;
@@ -661,6 +680,12 @@
 		gctl_error(req, "No '%s' argument", "error");
 		return;
 	}
+	count_until_fail = gctl_get_paraml(req, "count_until_fail",
+	    sizeof(*count_until_fail));
+	if (count_until_fail == NULL) {
+		gctl_error(req, "No '%s' argument", "count_until_fail");
+		return;
+	}
 	rfailprob = gctl_get_paraml(req, "rfailprob", sizeof(*rfailprob));
 	if (rfailprob == NULL) {
 		gctl_error(req, "No '%s' argument", "rfailprob");
@@ -736,6 +761,8 @@
 			sc->sc_wdelayprob = (u_int)*wdelayprob;
 		if (*delaymsec != -1)
 			sc->sc_delaymsec = (u_int)*delaymsec;
+		if (*count_until_fail != -1)
+			sc->sc_count_until_fail = (u_int)*count_until_fail;
 	}
 }
 
@@ -904,6 +931,8 @@
 	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<CountUntilFail>%u</CountUntilFail>\n", indent,
+	    sc->sc_count_until_fail);
 	sbuf_printf(sb, "%s<Error>%d</Error>\n", indent, sc->sc_error);
 	sbuf_printf(sb, "%s<Reads>%ju</Reads>\n", indent, sc->sc_reads);
 	sbuf_printf(sb, "%s<Writes>%ju</Writes>\n", indent, sc->sc_writes);