diff --git a/tools/test/stress2/misc/fsync3.sh b/tools/test/stress2/misc/fsync3.sh
new file mode 100755
index 000000000000..f220d19b8c24
--- /dev/null
+++ b/tools/test/stress2/misc/fsync3.sh
@@ -0,0 +1,156 @@
+#!/bin/sh
+
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2023 Peter Holm <pho@FreeBSD.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+
+# Regression test for D37997: ffs_syncvnode(): avoid a LoR for SU
+# https://people.freebsd.org/~pho/stress/log/log0402.txt
+# Fixed by 6e1eabadcb1d - main - ffs_syncvnode(): avoid a LoR for SU
+
+# Test scenario based on report by jkim
+
+. ../default.cfg
+[ `id -u` -ne 0 ] && echo "Must be root!" && exit 1
+
+dir=/tmp
+odir=`pwd`
+prog=$(basename "$0" .sh)
+cd $dir
+sed '1,/^EOF/d' < $odir/$0 > $dir/$prog.c
+mycc -o $prog -Wall -Wextra -O0 -g $prog.c -lpthread || exit 1
+rm -f $prog.c
+cd $odir
+
+set -eu
+mount | grep "on $mntpoint " | grep -q /dev/md && umount -f $mntpoint
+[ -c /dev/md$mdstart ] &&  mdconfig -d -u $mdstart
+mdconfig -a -t swap -s 1g -u $mdstart
+newfs -U md$mdstart > /dev/null
+mount /dev/md$mdstart $mntpoint
+set +e
+
+cd $odir
+../testcases/swap/swap -t 1m -i 20 -l 100 > /dev/null &
+sleep .5
+cd $mntpoint
+mkdir -p d1/d2/d3/d4/d5
+for i in `jot 8`; do
+	$dir/$prog $i &
+done
+cd $odir
+wait
+
+for i in `jot 6`; do
+	mount | grep -q "on $mntpoint " || break
+	umount $mntpoint && break || sleep 10
+	[ $i -eq 6 ] &&
+	    { echo FATAL; fstat -mf $mntpoint; exit 1; }
+done
+mdconfig -d -u $mdstart
+rm -rf $dir/$prog
+exit 0
+EOF
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <pthread_np.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define RUNTIME 60
+
+static time_t start;
+static volatile int fd, n;
+static char buf[4096];
+
+static void *
+t1(void *data __unused)
+{
+	char *path = "d1/d2/d3/d4/d5";
+	char d1[1024], d2[1024], file[1024];
+
+	pthread_set_name_np(pthread_self(), __func__);
+	snprintf(d1, sizeof(d1), "%s/dir.%d", path, getpid());
+	snprintf(d2, sizeof(d2), "%s/new.%d", path, getpid());
+	snprintf(file, sizeof(file), "%s/../file.%d", path, getpid());
+	while (time(NULL) - start < RUNTIME) {
+		if (mkdir(d1, 0740) == -1)
+			err(1, "mkdir(%s)", d1);
+		if (rename(d1, d2) == -1)
+			err(1, "rename(%s, %s)", d1, d2);
+		if ((fd = open(file, O_RDWR | O_CREAT | O_TRUNC, 0600)) == -1)
+			err(1, "open%s()", file);
+		if (write(fd, buf, sizeof(buf)) != sizeof(buf))
+			err(1, "write()");
+		close(fd);
+		if (rename(d2, d1) == -1)
+			err(1, "rename(%s, %s)", d2, d1);
+		if (rmdir(d1) == -1)
+			err(1, "rmdir(%s)", d1);
+	}
+
+	return (NULL);
+}
+
+static void *
+t2(void *data __unused)
+{
+	pthread_set_name_np(pthread_self(), __func__);
+	while (time(NULL) - start < RUNTIME) {
+		fsync(fd);
+		usleep(arc4random() % 500);
+	}
+
+	return (NULL);
+}
+
+int
+main(int argc __unused, char *argv[])
+{
+	pthread_t tid[2];
+	int r;
+
+	n = atoi(argv[1]);
+	start = time(NULL);
+	if ((r = pthread_create(&tid[0], NULL, t1, NULL)) != 0)
+		errc(1, r, "pthread_create");
+	if ((r = pthread_create(&tid[1], NULL, t2, NULL)) != 0)
+		errc(1, r, "pthread_create");
+
+	if ((r = pthread_join(tid[0], NULL)) != 0)
+		errc(1, r, "pthread_join");
+	if ((r = pthread_join(tid[1], NULL)) != 0)
+		errc(1, r, "pthread_join");
+
+	return (0);
+}