diff --git a/tests/runfiles/common.run b/tests/runfiles/common.run
index 005c539fc89d..2b4497133d1c 100644
--- a/tests/runfiles/common.run
+++ b/tests/runfiles/common.run
@@ -606,6 +606,10 @@ pre =
 post =
 tags = ['functional', 'deadman']
 
+[tests/functional/direct_mmap]
+tests = ['dio_mmap']
+tags = ['functional', 'direct_mmap']
+
 [tests/functional/delegate]
 tests = ['zfs_allow_001_pos', 'zfs_allow_002_pos', 'zfs_allow_003_pos',
     'zfs_allow_004_pos', 'zfs_allow_005_pos', 'zfs_allow_006_pos',
diff --git a/tests/zfs-tests/tests/Makefile.am b/tests/zfs-tests/tests/Makefile.am
index bbe94f9177ae..b0fee2708b77 100644
--- a/tests/zfs-tests/tests/Makefile.am
+++ b/tests/zfs-tests/tests/Makefile.am
@@ -259,6 +259,8 @@ nobase_dist_datadir_zfs_tests_tests_DATA += \
 	functional/delegate/delegate_common.kshlib \
 	functional/devices/devices.cfg \
 	functional/devices/devices_common.kshlib \
+	functional/direct_mmap/dio.cfg \
+	functional/direct_mmap/dio.kshlib \
 	functional/events/events.cfg \
 	functional/events/events_common.kshlib \
 	functional/fault/fault.cfg \
@@ -1359,6 +1361,9 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/devices/devices_002_neg.ksh \
 	functional/devices/devices_003_pos.ksh \
 	functional/devices/setup.ksh \
+	functional/direct_mmap/cleanup.ksh \
+	functional/direct_mmap/dio_mmap.ksh \
+	functional/direct_mmap/setup.ksh \
 	functional/dos_attributes/cleanup.ksh \
 	functional/dos_attributes/read_dos_attrs_001.ksh \
 	functional/dos_attributes/setup.ksh \
diff --git a/tests/zfs-tests/tests/functional/direct_mmap/cleanup.ksh b/tests/zfs-tests/tests/functional/direct_mmap/cleanup.ksh
new file mode 100755
index 000000000000..382e9b1734b0
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/direct_mmap/cleanup.ksh
@@ -0,0 +1,31 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or https://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2021 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+verify_runnable "global"
+
+default_cleanup
diff --git a/tests/zfs-tests/tests/functional/direct_mmap/dio.cfg b/tests/zfs-tests/tests/functional/direct_mmap/dio.cfg
new file mode 100644
index 000000000000..6472610d7b41
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/direct_mmap/dio.cfg
@@ -0,0 +1,26 @@
+#
+# CDDL HEADER START
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2018 by Lawrence Livermore National Security, LLC.
+#
+
+DIO_VDEV1=$TEST_BASE_DIR/file1
+DIO_VDEV2=$TEST_BASE_DIR/file2
+DIO_VDEV3=$TEST_BASE_DIR/file3
+DIO_VDEVS="$DIO_VDEV1 $DIO_VDEV2 $DIO_VDEV3"
+
+DIO_FILESIZE=4M
+DIO_BS=128K
diff --git a/tests/zfs-tests/tests/functional/direct_mmap/dio.kshlib b/tests/zfs-tests/tests/functional/direct_mmap/dio.kshlib
new file mode 100644
index 000000000000..caf4b782f660
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/direct_mmap/dio.kshlib
@@ -0,0 +1,302 @@
+#
+# CDDL HEADER START
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2021 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/direct_mmap/dio.cfg
+
+function dio_cleanup
+{
+	if poolexists $TESTPOOL1; then
+		destroy_pool $TESTPOOL1
+	fi
+
+	rm -f $DIO_VDEVS
+}
+
+#
+# Generate an IO workload using fio and then verify the resulting data.
+#
+function dio_and_verify # mode file-size block-size directory ioengine extra-args
+{
+	typeset mode=$1
+	typeset size=$2
+	typeset bs=$3
+	typeset mntpnt=$4
+	typeset ioengine=$5
+	typeset extra_args=$6
+
+	# Invoke an fio workload via direct IO and verify with direct IO.
+	log_must fio --directory=$mntpnt --name=direct-$mode \
+	    --rw=$mode --size=$size --bs=$bs --direct=1 --numjobs=1 \
+	    --verify=sha1 --ioengine=$ioengine --fallocate=none \
+	    --group_reporting --minimal --do_verify=1 $extra_args
+
+	# Now just read back the file without direct IO into the ARC as an additional
+	# verfication step.
+	log_must fio --directory=$mntpnt --name=direct-$mode \
+	    --rw=read --size=$size --bs=$bs --direct=0 --numjobs=1 \
+		--ioengine=$ioengine --group_reporting --minimal
+
+	log_must rm -f "$mntpnt/direct-*"
+}
+
+#
+# Get zpool status -d checksum verify failures
+#
+function get_zpool_status_chksum_verify_failures # pool_name vdev_type
+{
+	typeset pool=$1
+	typeset vdev_type=$2
+
+	if [[ "$vdev_type" == "stripe" ]]; then
+		val=$(zpool status -dp $pool | \
+		    awk '{s+=$6} END {print s}' )
+	elif [[ "$vdev_type" == "mirror" || "$vdev_type" == "raidz" ||
+	    "$vdev_type" == "draid" ]]; then 
+		val=$(zpool status -dp $pool | \
+		    awk -v d="$vdev_type" '$0 ~ d {print $6}' )
+	else
+		log_fail "Unsupported VDEV type in \
+		   get_zpool_status_chksum_verify_failures(): $vdev_type"
+	fi
+	echo "$val"
+}
+
+#
+# Get ZED dio_verify events
+#
+function get_zed_dio_verify_events # pool
+{
+	typeset pool=$1
+
+	val=$(zpool events $pool | grep -c dio_verify)
+
+	echo "$val"
+}
+
+#
+# Checking for checksum verify write failures with:
+# zpool status -d
+# zpool events
+# After getting that counts will clear the out the ZPool errors and events
+#
+function check_dio_write_chksum_verify_failures # pool vdev_type expect_errors
+{
+	typeset pool=$1
+	typeset vdev_type=$2
+	typeset expect_errors=$3
+	typeset note_str="expecting none"
+
+	if [[ $expect_errors -ne 0 ]]; then
+		note_str="expecting some"
+	fi
+
+	log_note "Checking for Direct I/O write checksum verify errors \
+	    $note_str on ZPool: $pool"
+
+	status_failures=$(get_zpool_status_chksum_verify_failures $pool $vdev_type)
+	zed_dio_verify_events=$(get_zed_dio_verify_events $pool)
+
+	if [[ $expect_errors -ne 0 ]]; then
+		if [[ $status_failures -eq 0 ||
+		    $zed_dio_verify_events -eq 0 ]]; then
+			zpool status -dp $pool
+			zpool events $pool
+			log_fail "Checksum verifies in zpool status -d  \
+			    $status_failures. ZED dio_verify events \
+			    $zed_dio_verify_events. Neither should be 0."
+		fi
+	else
+		if [[ $status_failures -ne 0 ||
+		    $zed_dio_verify_events -ne 0 ]]; then
+			zpool status -dp $pool
+			zpool events $pool
+			log_fail "Checksum verifies in zpool status -d  \
+			    $status_failures. ZED dio_verify events \
+			    $zed_dio_verify_events. Both should be zero."
+		fi
+	fi
+
+	log_must zpool clear $pool
+	log_must zpool events -c
+
+}
+
+#
+# Get the value of a counter from
+# Linux: /proc/spl/kstat/zfs/$pool/iostats file.
+# FreeBSD: kstat.zfs.$pool.msic.iostats.$stat
+#
+function get_iostats_stat # pool stat
+{
+	typeset pool=$1
+	typeset stat=$2
+
+	if is_linux; then
+		iostats_file=/proc/spl/kstat/zfs/$pool/iostats
+		val=$(grep -m1 "$stat" $iostats_file | awk '{ print $3 }')
+	else
+		val=$(sysctl -n kstat.zfs.$pool.misc.iostats.$stat)
+	fi
+	if [[ -z "$val" ]]; then
+		log_fail "Unable to read $stat counter"
+	fi
+
+	echo "$val"
+}
+
+#
+# Evict any buffered blocks by overwritting them using an O_DIRECT request.
+#
+function evict_blocks
+{
+	typeset pool=$1
+	typeset file=$2
+	typeset size=$3
+
+	log_must stride_dd -i /dev/urandom -o $file -b $size -c 1 -D
+}
+
+#
+# Perform FIO direct IO writes to a file with the given arguments.
+# Then verify thae minimum expected number of blocks were written as
+# direct IO.
+#
+function verify_dio_write_count #pool bs size mnpnt
+{
+	typeset pool=$1
+	typeset bs=$2
+	typeset size=$3
+	typeset mntpnt=$4
+	typeset dio_wr_expected=$(((size / bs) -1))
+
+	log_note "Checking for $dio_wr_expected Direct IO writes"
+
+	prev_dio_wr=$(get_iostats_stat $pool direct_write_count)
+	dio_and_verify write $size $bs $mntpnt "sync"
+	curr_dio_wr=$(get_iostats_stat $pool direct_write_count)
+	dio_wr_actual=$((curr_dio_wr - prev_dio_wr))
+
+	if [[ $dio_wr_actual -lt $dio_wr_expected ]]; then
+		if is_linux; then
+			cat /proc/spl/kstat/zfs/$pool/iostats
+		else
+			sysctl kstat.zfs.$pool.misc.iostats
+		fi
+		log_fail "Direct writes $dio_wr_actual of $dio_wr_expected"
+	fi
+}
+
+#
+# Perform a stride_dd write command to the file with the given arguments.
+# Then verify the minimum expected number of blocks were written as either
+# buffered IO (by the ARC), or direct IO to the application (dd).
+#
+function check_write # pool file bs count seek flags buf_wr dio_wr
+{
+	typeset pool=$1
+	typeset file=$2
+	typeset bs=$3
+	typeset count=$4
+	typeset seek=$5
+	typeset flags=$6
+	typeset buf_wr_expect=$7
+	typeset dio_wr_expect=$8
+
+	log_note "Checking $count * $bs write(s) at offset $seek, $flags"
+
+	prev_buf_wr=$(get_iostats_stat $pool arc_write_count)
+	prev_dio_wr=$(get_iostats_stat $pool direct_write_count)
+
+	log_must stride_dd -i /dev/urandom -o $file -b $bs -c $count \
+	    -k $seek $flags
+
+	curr_buf_wr=$(get_iostats_stat $pool arc_write_count)
+	buf_wr_actual=$((curr_buf_wr - prev_buf_wr))
+
+	curr_dio_wr=$(get_iostats_stat $pool direct_write_count)
+	dio_wr_actual=$((curr_dio_wr - prev_dio_wr))
+
+	if [[ $buf_wr_actual -lt $buf_wr_expect ]]; then
+		if is_linux; then
+			cat /proc/spl/kstat/zfs/$pool/iostats
+		else
+			sysctl kstat.zfs.$pool.misc.iostats
+		fi
+		log_fail "Buffered writes $buf_wr_actual of $buf_wr_expect"
+	fi
+
+	if [[ $dio_wr_actual -lt $dio_wr_expect ]]; then
+		if is_linux; then
+			cat /proc/spl/kstat/zfs/$pool/iostats
+		else
+			sysctl kstat.zfs.$pool.misc.iostats
+		fi
+		log_fail "Direct writes $dio_wr_actual of $dio_wr_expect"
+	fi
+}
+
+#
+# Perform a stride_dd read command to the file with the given arguments.
+# Then verify the minimum expected number of blocks were read as either
+# buffered IO (by the ARC), or direct IO to the application (dd).
+#
+function check_read # pool file bs count skip flags buf_rd dio_rd
+{
+	typeset pool=$1
+	typeset file=$2
+	typeset bs=$3
+	typeset count=$4
+	typeset skip=$5
+	typeset flags=$6
+	typeset buf_rd_expect=$7
+	typeset dio_rd_expect=$8
+
+	log_note "Checking $count * $bs read(s) at offset $skip, $flags"
+
+	prev_buf_rd=$(get_iostats_stat $pool arc_read_count)
+	prev_dio_rd=$(get_iostats_stat $pool direct_read_count)
+
+	log_must stride_dd -i $file -o /dev/null -b $bs -c $count \
+	    -p $skip $flags
+
+	curr_buf_rd=$(get_iostats_stat $pool arc_read_count)
+	buf_rd_actual=$((curr_buf_rd - prev_buf_rd))
+
+	curr_dio_rd=$(get_iostats_stat $pool direct_read_count)
+	dio_rd_actual=$((curr_dio_rd - prev_dio_rd))
+
+	if [[ $buf_rd_actual -lt $buf_rd_expect ]]; then
+		if is_linux; then
+			cat /proc/spl/kstat/zfs/$pool/iostats
+		else
+			sysctl kstat.zfs.$pool.misc.iostats
+		fi
+		log_fail "Buffered reads $buf_rd_actual of $buf_rd_expect"
+	fi
+
+	if [[ $dio_rd_actual -lt $dio_rd_expect ]]; then
+		if is_linux; then
+			cat /proc/spl/kstat/zfs/$pool/iostats
+		else
+			sysctl kstat.zfs.$pool.misc.iostats
+		fi
+		log_fail "Direct reads $dio_rd_actual of $dio_rd_expect"
+	fi
+}
diff --git a/tests/zfs-tests/tests/functional/direct_mmap/dio_mmap.ksh b/tests/zfs-tests/tests/functional/direct_mmap/dio_mmap.ksh
new file mode 100755
index 000000000000..139d0ae16b14
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/direct_mmap/dio_mmap.ksh
@@ -0,0 +1,88 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or https://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2021 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/direct_mmap/dio.cfg
+. $STF_SUITE/tests/functional/direct_mmap/dio.kshlib
+
+#
+# DESCRIPTION:
+# 	Verify mixed direct IO and mmap IO.
+#
+# STRATEGY:
+#	1. Create an empty file.
+#	2. Start a background fio randomly direct writing to the file.
+#	3. Start a background fio randomly mmap writing to the file.
+#
+
+verify_runnable "global"
+
+function cleanup
+{
+	log_must rm -f "$tmp_file"
+	check_dio_write_chksum_verify_failures $TESTPOOL "raidz" 0
+}
+
+log_assert "Verify mixed direct IO and mmap IO"
+
+log_onexit cleanup
+
+mntpnt=$(get_prop mountpoint $TESTPOOL/$TESTFS)
+tmp_file=$mntpnt/file
+bs=$((1024 * 1024))
+blocks=32
+size=$((bs * blocks))
+runtime=10
+
+log_must dd if=/dev/zero of=$tmp_file bs=$bs count=$blocks
+
+# Direct IO writes
+log_must eval "fio --filename=$tmp_file --name=direct-write \
+	--rw=write --size=$size --bs=$bs --direct=0 --numjobs=1 \
+	--ioengine=sync --fallocate=none --verify=sha1 \
+	--group_reporting --minimal --runtime=$runtime --time_based &"
+
+# Direct IO reads
+log_must eval "fio --filename=$tmp_file --name=direct-read \
+	--rw=read --size=$size --bs=$bs --direct=0 --numjobs=1 \
+	--ioengine=sync --fallocate=none --verify=sha1 \
+	--group_reporting --minimal --runtime=$runtime --time_based &"
+
+# mmap IO writes
+log_must eval "fio --filename=$tmp_file --name=mmap-write \
+	--rw=write --size=$size --bs=$bs --numjobs=1 \
+	--ioengine=mmap --fallocate=none --verify=sha1 \
+	--group_reporting --minimal --runtime=$runtime --time_based &"
+
+# mmap IO reads
+log_must eval "fio --filename=$tmp_file --name=mmap-read \
+	--rw=read --size=$size --bs=$bs --numjobs=1 \
+	--ioengine=mmap --fallocate=none --verify=sha1 \
+	--group_reporting --minimal --runtime=$runtime --time_based &"
+
+wait
+
+log_pass "Verfied mixed direct IO and mmap IO"
diff --git a/tests/zfs-tests/tests/functional/direct_mmap/setup.ksh b/tests/zfs-tests/tests/functional/direct_mmap/setup.ksh
new file mode 100755
index 000000000000..5ce95dddf401
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/direct_mmap/setup.ksh
@@ -0,0 +1,32 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or https://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2021 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+verify_runnable "global"
+
+default_raidz_setup_noexit "$DISKS"
+log_must zfs set compression=off $TESTPOOL/$TESTFS
+log_pass