zpool: Dryrun fails to list some devices

`zpool create -n` fails to list cache and spare vdevs.
`zpool add -n` fails to list spare devices.
`zpool split -n` fails to list `special` and `dedup` labels.
`zpool add -n` and `zpool split -n` shouldn't list hole devices.

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Attila Fülöp <[email protected]>
Closes #11122
Closes #11167 

10 files changed, 593 insertions, 14 deletions

diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index 1e16c89ad..c84f30ccb 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -669,9 +669,16 @@ print_vdev_tree(zpool_handle_t *zhp, const char *name, nvlist_t *nv, int indent,
 	}
 
 	for (c = 0; c < children; c++) {
-		uint64_t is_log = B_FALSE;
+		uint64_t is_log = B_FALSE, is_hole = B_FALSE;
 		char *class = "";
 
+		(void) nvlist_lookup_uint64(child[c], ZPOOL_CONFIG_IS_HOLE,
+		    &is_hole);
+
+		if (is_hole == B_TRUE) {
+			continue;
+		}
+
 		(void) nvlist_lookup_uint64(child[c], ZPOOL_CONFIG_IS_LOG,
 		    &is_log);
 		if (is_log)
@@ -692,6 +699,54 @@ print_vdev_tree(zpool_handle_t *zhp, const char *name, nvlist_t *nv, int indent,
 	}
 }
 
+/*
+ * Print the list of l2cache devices for dry runs.
+ */
+static void
+print_cache_list(nvlist_t *nv, int indent)
+{
+	nvlist_t **child;
+	uint_t c, children;
+
+	if (nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_L2CACHE,
+	    &child, &children) == 0 && children > 0) {
+		(void) printf("\t%*s%s\n", indent, "", "cache");
+	} else {
+		return;
+	}
+	for (c = 0; c < children; c++) {
+		char *vname;
+
+		vname = zpool_vdev_name(g_zfs, NULL, child[c], 0);
+		(void) printf("\t%*s%s\n", indent + 2, "", vname);
+		free(vname);
+	}
+}
+
+/*
+ * Print the list of spares for dry runs.
+ */
+static void
+print_spare_list(nvlist_t *nv, int indent)
+{
+	nvlist_t **child;
+	uint_t c, children;
+
+	if (nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_SPARES,
+	    &child, &children) == 0 && children > 0) {
+		(void) printf("\t%*s%s\n", indent, "", "spares");
+	} else {
+		return;
+	}
+	for (c = 0; c < children; c++) {
+		char *vname;
+
+		vname = zpool_vdev_name(g_zfs, NULL, child[c], 0);
+		(void) printf("\t%*s%s\n", indent + 2, "", vname);
+		free(vname);
+	}
+}
+
 static boolean_t
 prop_list_contains_feature(nvlist_t *proplist)
 {
@@ -921,16 +976,16 @@ zpool_do_add(int argc, char **argv)
 
 	if (dryrun) {
 		nvlist_t *poolnvroot;
-		nvlist_t **l2child;
-		uint_t l2children, c;
+		nvlist_t **l2child, **sparechild;
+		uint_t l2children, sparechildren, c;
 		char *vname;
-		boolean_t hadcache = B_FALSE;
+		boolean_t hadcache = B_FALSE, hadspare = B_FALSE;
 
 		verify(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
 		    &poolnvroot) == 0);
 
 		(void) printf(gettext("would update '%s' to the following "
-		    "configuration:\n"), zpool_get_name(zhp));
+		    "configuration:\n\n"), zpool_get_name(zhp));
 
 		/* print original main pool and new tree */
 		print_vdev_tree(zhp, poolname, poolnvroot, 0, "",
@@ -991,6 +1046,29 @@ zpool_do_add(int argc, char **argv)
 				free(vname);
 			}
 		}
+		/* And finaly the spares */
+		if (nvlist_lookup_nvlist_array(poolnvroot, ZPOOL_CONFIG_SPARES,
+		    &sparechild, &sparechildren) == 0 && sparechildren > 0) {
+			hadspare = B_TRUE;
+			(void) printf(gettext("\tspares\n"));
+			for (c = 0; c < sparechildren; c++) {
+				vname = zpool_vdev_name(g_zfs, NULL,
+				    sparechild[c], name_flags);
+				(void) printf("\t  %s\n", vname);
+				free(vname);
+			}
+		}
+		if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
+		    &sparechild, &sparechildren) == 0 && sparechildren > 0) {
+			if (!hadspare)
+				(void) printf(gettext("\tspares\n"));
+			for (c = 0; c < sparechildren; c++) {
+				vname = zpool_vdev_name(g_zfs, NULL,
+				    sparechild[c], name_flags);
+				(void) printf("\t  %s\n", vname);
+				free(vname);
+			}
+		}
 
 		ret = 0;
 	} else {
@@ -1548,6 +1626,8 @@ zpool_do_create(int argc, char **argv)
 		    VDEV_ALLOC_BIAS_SPECIAL, 0);
 		print_vdev_tree(NULL, "logs", nvroot, 0,
 		    VDEV_ALLOC_BIAS_LOG, 0);
+		print_cache_list(nvroot, 0);
+		print_spare_list(nvroot, 0);
 
 		ret = 0;
 	} else {
@@ -6515,6 +6595,10 @@ zpool_do_split(int argc, char **argv)
 			    "following layout:\n\n"), newpool);
 			print_vdev_tree(NULL, newpool, config, 0, "",
 			    flags.name_flags);
+			print_vdev_tree(NULL, "dedup", config, 0,
+			    VDEV_ALLOC_BIAS_DEDUP, 0);
+			print_vdev_tree(NULL, "special", config, 0,
+			    VDEV_ALLOC_BIAS_SPECIAL, 0);
 		}
 	}
 
diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index c1dc0d75b..c661ab313 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -3431,7 +3431,7 @@ zpool_vdev_split(zpool_handle_t *zhp, char *newname, nvlist_t **newroot,
     nvlist_t *props, splitflags_t flags)
 {
 	zfs_cmd_t zc = {"\0"};
-	char msg[1024];
+	char msg[1024], *bias;
 	nvlist_t *tree, *config, **child, **newchild, *newconfig = NULL;
 	nvlist_t **varray = NULL, *zc_props = NULL;
 	uint_t c, children, newchildren, lastlog = 0, vcount, found = 0;
@@ -3489,6 +3489,7 @@ zpool_vdev_split(zpool_handle_t *zhp, char *newname, nvlist_t **newroot,
 
 	for (c = 0; c < children; c++) {
 		uint64_t is_log = B_FALSE, is_hole = B_FALSE;
+		boolean_t is_special = B_FALSE, is_dedup = B_FALSE;
 		char *type;
 		nvlist_t **mchild, *vdev;
 		uint_t mchildren;
@@ -3535,6 +3536,13 @@ zpool_vdev_split(zpool_handle_t *zhp, char *newname, nvlist_t **newroot,
 			goto out;
 		}
 
+		if (nvlist_lookup_string(child[c],
+		    ZPOOL_CONFIG_ALLOCATION_BIAS, &bias) == 0) {
+			if (strcmp(bias, VDEV_ALLOC_BIAS_SPECIAL) == 0)
+				is_special = B_TRUE;
+			else if (strcmp(bias, VDEV_ALLOC_BIAS_DEDUP) == 0)
+				is_dedup = B_TRUE;
+		}
 		verify(nvlist_lookup_nvlist_array(child[c],
 		    ZPOOL_CONFIG_CHILDREN, &mchild, &mchildren) == 0);
 
@@ -3552,6 +3560,20 @@ zpool_vdev_split(zpool_handle_t *zhp, char *newname, nvlist_t **newroot,
 
 		if (nvlist_dup(vdev, &varray[vcount++], 0) != 0)
 			goto out;
+
+		if (flags.dryrun != 0) {
+			if (is_dedup == B_TRUE) {
+				if (nvlist_add_string(varray[vcount - 1],
+				    ZPOOL_CONFIG_ALLOCATION_BIAS,
+				    VDEV_ALLOC_BIAS_DEDUP) != 0)
+					goto out;
+			} else if (is_special == B_TRUE) {
+				if (nvlist_add_string(varray[vcount - 1],
+				    ZPOOL_CONFIG_ALLOCATION_BIAS,
+				    VDEV_ALLOC_BIAS_SPECIAL) != 0)
+					goto out;
+			}
+		}
 	}
 
 	/* did we find every disk the user specified? */
diff --git a/tests/runfiles/common.run b/tests/runfiles/common.run
index d6077e292..d8345f62b 100644
--- a/tests/runfiles/common.run
+++ b/tests/runfiles/common.run
@@ -318,7 +318,7 @@ tags = ['functional', 'cli_root', 'zpool']
 tests = ['zpool_add_001_pos', 'zpool_add_002_pos', 'zpool_add_003_pos',
     'zpool_add_004_pos', 'zpool_add_006_pos', 'zpool_add_007_neg',
     'zpool_add_008_neg', 'zpool_add_009_neg', 'zpool_add_010_pos',
-    'add-o_ashift', 'add_prop_ashift']
+    'add-o_ashift', 'add_prop_ashift', 'zpool_add_dryrun_output']
 tags = ['functional', 'cli_root', 'zpool_add']
 
 [tests/functional/cli_root/zpool_attach]
@@ -345,7 +345,7 @@ tests = ['zpool_create_001_pos', 'zpool_create_002_pos',
     'zpool_create_features_001_pos', 'zpool_create_features_002_pos',
     'zpool_create_features_003_pos', 'zpool_create_features_004_neg',
     'zpool_create_features_005_pos',
-    'create-o_ashift', 'zpool_create_tempname']
+    'create-o_ashift', 'zpool_create_tempname', 'zpool_create_dryrun_output']
 tags = ['functional', 'cli_root', 'zpool_create']
 
 [tests/functional/cli_root/zpool_destroy]
@@ -462,7 +462,8 @@ tags = ['functional', 'cli_root', 'zpool_set']
 [tests/functional/cli_root/zpool_split]
 tests = ['zpool_split_cliargs', 'zpool_split_devices',
     'zpool_split_encryption', 'zpool_split_props', 'zpool_split_vdevs',
-    'zpool_split_resilver', 'zpool_split_indirect']
+    'zpool_split_resilver', 'zpool_split_indirect',
+    'zpool_split_dryrun_output']
 tags = ['functional', 'cli_root', 'zpool_split']
 
 [tests/functional/cli_root/zpool_status]
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_add/Makefile.am b/tests/zfs-tests/tests/functional/cli_root/zpool_add/Makefile.am
index a7f62b6f9..8d54d13f7 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_add/Makefile.am
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_add/Makefile.am
@@ -14,7 +14,8 @@ dist_pkgdata_SCRIPTS = \
 	zpool_add_010_pos.ksh \
 	add-o_ashift.ksh \
 	add_prop_ashift.ksh \
-	add_nested_replacing_spare.ksh
+	add_nested_replacing_spare.ksh \
+	zpool_add_dryrun_output.ksh
 
 dist_pkgdata_DATA = \
 	zpool_add.cfg \
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_003_pos.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_003_pos.ksh
index f27004130..a6b03ff32 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_003_pos.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_003_pos.ksh
@@ -61,7 +61,7 @@ log_onexit cleanup
 typeset TMPFILE_PREFIX="$TEST_BASE_DIR/zpool_add_003"
 typeset STR_DRYRUN="would update '$TESTPOOL' to the following configuration:"
 typeset VDEV_PREFIX="$TEST_BASE_DIR/filedev"
-typeset -a VDEV_TYPES=("" "dedup" "special" "log" "cache")
+typeset -a VDEV_TYPES=("" "dedup" "special" "log" "cache" "spare")
 
 vdevs=""
 config=""
@@ -91,7 +91,7 @@ log_must zpool add -f $TESTPOOL $config
 zpool status $TESTPOOL | awk 'NR == 1, /NAME/ { next } /^$/ {exit}
 	{print $1}' > "$TMPFILE_PREFIX-vdevtree"
 cat "$TMPFILE_PREFIX-dryrun" | awk 'NR == 1, /would/ {next}
-	{print $1}' > "$TMPFILE_PREFIX-vdevtree-n"
+	/^$/ {next} {print $1}' > "$TMPFILE_PREFIX-vdevtree-n"
 log_must eval "diff $TMPFILE_PREFIX-vdevtree-n $TMPFILE_PREFIX-vdevtree"
 
 log_pass "'zpool add -n <pool> <vdev> ...' executes successfully."
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_dryrun_output.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_dryrun_output.ksh
new file mode 100755
index 000000000..5e16cddab
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_add/zpool_add_dryrun_output.ksh
@@ -0,0 +1,177 @@
+#!/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 http://www.opensolaris.org/os/licensing.
+# 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 2020 Attila Fülöp <[email protected]>
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zpool_add/zpool_add.kshlib
+
+typeset TMPFILE_PREFIX="$TEST_BASE_DIR/zpool_add_dryrun_output"
+typeset STR_DRYRUN="would update '$TESTPOOL' to the following configuration:"
+typeset VDEV_PREFIX="$TEST_BASE_DIR/filedev"
+
+#
+# DESCRIPTION:
+# 'zpool add -n <pool> <vdev> ...' can display the correct configuration
+#
+# STRATEGY:
+# 1. Create different storage pools, use -n to add devices to the pool and
+#    verify the output is as expected.
+# 2. Create a pool whith a hole vdev and verify it's not listed with add -n.
+#
+
+typeset -a dev=(
+	"${VDEV_PREFIX}00" "${VDEV_PREFIX}01" "${VDEV_PREFIX}02"
+	"${VDEV_PREFIX}03" "${VDEV_PREFIX}04" "${VDEV_PREFIX}05"
+	"${VDEV_PREFIX}06" "${VDEV_PREFIX}07" "${VDEV_PREFIX}08"
+	"${VDEV_PREFIX}09" "${VDEV_PREFIX}10" "${VDEV_PREFIX}11"
+)
+
+typeset -a tests=(
+    (
+	tree="'${dev[0]}' log '${dev[1]}' special '${dev[2]}' dedup '${dev[3]}'"
+	add="spare '${dev[4]}' cache '${dev[5]}'"
+	want="$STR_DRYRUN
+
+	$TESTPOOL
+	  ${dev[0]}
+	dedup
+	  ${dev[3]}
+	special
+	  ${dev[2]}
+	logs
+	  ${dev[1]}
+	cache
+	  ${dev[5]}
+	spares
+	  ${dev[4]}"
+    )
+    (
+	tree="'${dev[0]}' log '${dev[1]}' special '${dev[2]}' dedup '${dev[3]}' \
+	    spare '${dev[4]}' cache '${dev[5]}'"
+
+	add="'${dev[6]}' log '${dev[7]}' special '${dev[8]}' dedup '${dev[9]}' \
+	    spare '${dev[10]}' cache '${dev[11]}'"
+
+	want="$STR_DRYRUN
+
+	$TESTPOOL
+	  ${dev[0]}
+	  ${dev[6]}
+	dedup
+	  ${dev[3]}
+	  ${dev[9]}
+	special
+	  ${dev[2]}
+	  ${dev[8]}
+	logs
+	  ${dev[1]}
+	  ${dev[7]}
+	cache
+	  ${dev[5]}
+	  ${dev[11]}
+	spares
+	  ${dev[4]}
+	  ${dev[10]}"
+    )
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}' \
+	    log mirror '${dev[2]}' '${dev[3]}' \
+	    dedup mirror '${dev[6]}' '${dev[7]}' \
+	    spare '${dev[8]}'"
+
+	add="special mirror '${dev[4]}' '${dev[5]}' \
+	    spare '${dev[9]}' cache '${dev[10]}' '${dev[11]}'"
+
+	want="$STR_DRYRUN
+
+	$TESTPOOL
+	  mirror-0
+	    ${dev[0]}
+	    ${dev[1]}
+	dedup
+	  mirror
+	    ${dev[6]}
+	    ${dev[7]}
+	special
+	  mirror
+	    ${dev[4]}
+	    ${dev[5]}
+	logs
+	  mirror
+	    ${dev[2]}
+	    ${dev[3]}
+	cache
+	  ${dev[10]}
+	  ${dev[11]}
+	spares
+	  ${dev[8]}
+	  ${dev[9]}"
+    )
+)
+
+verify_runnable "global"
+
+function cleanup
+{
+	destroy_pool "$TESTPOOL"
+	rm -f "$TMPFILE_PREFIX"* "$VDEV_PREFIX"*
+}
+
+log_assert "'zpool add -n <pool> <vdev> ...' can display the configuration"
+
+log_onexit cleanup
+
+# Create needed file vdevs.
+for (( i=0; i < ${#dev[@]}; i+=1 )); do
+	log_must truncate -s $SPA_MINDEVSIZE "${dev[$i]}"
+done
+
+# Foreach test create pool, add -n devices and check output.
+for (( i=0; i < ${#tests[@]}; i+=1 )); do
+	typeset tree="${tests[$i].tree}"
+	typeset add="${tests[$i].add}"
+	typeset want="${tests[$i].want}"
+
+	log_must eval zpool create "$TESTPOOL" $tree
+	log_must poolexists "$TESTPOOL"
+	typeset out="$(log_must eval "zpool add -n '$TESTPOOL' $add" | \
+	    sed /^SUCCESS/d)"
+
+	if [[ "$out" != "$want" ]]; then
+		log_fail "Got:\n" "$out" "\nbut expected:\n" "$want"
+	fi
+	log_must destroy_pool "$TESTPOOL"
+done
+
+# Make sure hole vdevs are skiped in output.
+log_must eval "zpool create '$TESTPOOL' '${dev[0]}' log '${dev[1]}' \
+    cache '${dev[2]}'"
+
+# Create a hole vdev.
+log_must eval "zpool remove '$TESTPOOL' '${dev[1]}'"
+log_mustnot eval "zpool add -n '$TESTPOOL' '${dev[1]}' | \
+    grep -qE '[[:space:]]+hole'"
+
+log_pass "'zpool add -n <pool> <vdev> ...' displays config correctly."
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_create/Makefile.am b/tests/zfs-tests/tests/functional/cli_root/zpool_create/Makefile.am
index 4d75851bd..ea0cc49b0 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_create/Makefile.am
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_create/Makefile.am
@@ -37,7 +37,8 @@ dist_pkgdata_SCRIPTS = \
 	zpool_create_features_004_neg.ksh \
 	zpool_create_features_005_pos.ksh \
 	create-o_ashift.ksh \
-	zpool_create_tempname.ksh
+	zpool_create_tempname.ksh \
+	zpool_create_dryrun_output.ksh
 
 dist_pkgdata_DATA = \
 	draidcfg.gz \
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_create/zpool_create_dryrun_output.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_create/zpool_create_dryrun_output.ksh
new file mode 100755
index 000000000..97c0c207d
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_create/zpool_create_dryrun_output.ksh
@@ -0,0 +1,141 @@
+#!/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 http://www.opensolaris.org/os/licensing.
+# 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 2020 Attila Fülöp <[email protected]>
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zpool_create/zpool_create.shlib
+
+typeset TMPFILE_PREFIX="$TEST_BASE_DIR/zpool_create_dryrun_output"
+typeset STR_DRYRUN="would create '$TESTPOOL' with the following layout:"
+typeset VDEV_PREFIX="$TEST_BASE_DIR/filedev"
+
+#
+# DESCRIPTION:
+# 'zpool create -n <pool> <vdev> ...' can display the correct configuration
+#
+# STRATEGY:
+# 1. Create a storage pool
+#
+
+typeset -a dev=(
+	"${VDEV_PREFIX}00" "${VDEV_PREFIX}01" "${VDEV_PREFIX}02"
+	"${VDEV_PREFIX}03" "${VDEV_PREFIX}04" "${VDEV_PREFIX}05"
+	"${VDEV_PREFIX}06" "${VDEV_PREFIX}07" "${VDEV_PREFIX}08"
+	"${VDEV_PREFIX}09" "${VDEV_PREFIX}10" "${VDEV_PREFIX}11"
+)
+
+typeset -a tests=(
+    (
+	tree="'${dev[0]}' '${dev[1]}' log '${dev[2]}' '${dev[3]}' \
+	    special '${dev[4]}' '${dev[5]}' dedup '${dev[6]}' '${dev[7]}' \
+		spare '${dev[8]}' '${dev[9]}' cache '${dev[10]}' '${dev[11]}'"
+
+	want="$STR_DRYRUN
+
+	$TESTPOOL
+	  ${dev[0]}
+	  ${dev[1]}
+	dedup
+	  ${dev[6]}
+	  ${dev[7]}
+	special
+	  ${dev[4]}
+	  ${dev[5]}
+	logs
+	  ${dev[2]}
+	  ${dev[3]}
+	cache
+	  ${dev[10]}
+	  ${dev[11]}
+	spares
+	  ${dev[8]}
+	  ${dev[9]}"
+    )
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}' \
+	    log mirror '${dev[2]}' '${dev[3]}' \
+	    special mirror '${dev[4]}' '${dev[5]}' \
+	    dedup mirror '${dev[6]}' '${dev[7]}' \
+		spare '${dev[8]}' '${dev[9]}' \
+	    cache '${dev[10]}' '${dev[11]}'"
+
+	want="$STR_DRYRUN
+
+	$TESTPOOL
+	  mirror
+	    ${dev[0]}
+	    ${dev[1]}
+	dedup
+	  mirror
+	    ${dev[6]}
+	    ${dev[7]}
+	special
+	  mirror
+	    ${dev[4]}
+	    ${dev[5]}
+	logs
+	  mirror
+	    ${dev[2]}
+	    ${dev[3]}
+	cache
+	  ${dev[10]}
+	  ${dev[11]}
+	spares
+	  ${dev[8]}
+	  ${dev[9]}"
+    )
+)
+
+verify_runnable "global"
+
+function cleanup
+{
+	rm -f "$TMPFILE_PREFIX"* "$VDEV_PREFIX"*
+}
+
+log_assert "'zpool add -n <pool> <vdev> ...' can display the configuration"
+
+log_onexit cleanup
+typeset disk1=$(create_blockfile $FILESIZE)
+
+# Create needed file vdevs.
+for (( i=0; i < ${#dev[@]}; i+=1 )); do
+	log_must truncate -s $SPA_MINDEVSIZE "${dev[$i]}"
+done
+
+# Foreach test create pool, add -n devices and check output.
+for (( i=0; i < ${#tests[@]}; i+=1 )); do
+	typeset tree="${tests[$i].tree}"
+	typeset want="${tests[$i].want}"
+
+	typeset out="$(log_must eval "zpool create -n '$TESTPOOL' $tree" | \
+	    sed /^SUCCESS/d)"
+
+	if [[ "$out" != "$want" ]]; then
+		log_fail "Got:\n" "$out" "\nbut expected:\n" "$want"
+	fi
+done
+
+log_pass "'zpool add -n <pool> <vdev> ...' displays config correctly."
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_split/Makefile.am b/tests/zfs-tests/tests/functional/cli_root/zpool_split/Makefile.am
index 1ca05a4e8..aac5e0d6e 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zpool_split/Makefile.am
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_split/Makefile.am
@@ -12,7 +12,8 @@ dist_pkgdata_SCRIPTS = \
 	zpool_split_vdevs.ksh \
 	zpool_split_resilver.ksh \
 	zpool_split_wholedisk.ksh \
-	zpool_split_indirect.ksh
+	zpool_split_indirect.ksh \
+	zpool_split_dryrun_output.ksh
 
 dist_pkgdata_DATA = \
 	zpool_split.cfg
diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_split/zpool_split_dryrun_output.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_split/zpool_split_dryrun_output.ksh
new file mode 100755
index 000000000..f06339cea
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cli_root/zpool_split/zpool_split_dryrun_output.ksh
@@ -0,0 +1,151 @@
+#!/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 http://www.opensolaris.org/os/licensing.
+# 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 2020 Attila Fülöp <[email protected]>
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+typeset NEWPOOL="${TESTPOOL}split"
+typeset STR_DRYRUN="would create '$NEWPOOL' with the following layout:"
+typeset VDEV_PREFIX="$TEST_BASE_DIR/filedev"
+
+#
+# DESCRIPTION:
+# 'zpool split -n <pool> <newpool> [<vdev> ...]' can display the correct
+# configuration
+#
+# STRATEGY:
+# 1. Create a mirrored storage pool, split -n and verify the output is as
+#    expected.
+#
+
+typeset -a dev=(
+	"${VDEV_PREFIX}00" "${VDEV_PREFIX}01" "${VDEV_PREFIX}02"
+	"${VDEV_PREFIX}03" "${VDEV_PREFIX}04" "${VDEV_PREFIX}05"
+	"${VDEV_PREFIX}06" "${VDEV_PREFIX}07" "${VDEV_PREFIX}08"
+	"${VDEV_PREFIX}09" "${VDEV_PREFIX}10" "${VDEV_PREFIX}11"
+)
+
+typeset -a tests=(
+    # Test for hole.
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}' log mirror '${dev[2]}' '${dev[3]}' \
+	    special mirror '${dev[4]}' '${dev[5]}'"
+
+	devs=""
+	want="$STR_DRYRUN
+
+	$NEWPOOL
+	  ${dev[1]}
+	special
+	  ${dev[5]}"
+    )
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}' log mirror '${dev[2]}' '${dev[3]}' \
+	    special mirror '${dev[4]}' '${dev[5]}'"
+
+	devs="'${dev[0]}' '${dev[4]}'"
+	want="$STR_DRYRUN
+
+	$NEWPOOL
+	  ${dev[0]}
+	special
+	  ${dev[4]}"
+    )
+
+	# Full set of vdev types.
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}'
+	    dedup mirror '${dev[2]}' '${dev[3]}' \
+	    special mirror '${dev[4]}' '${dev[5]}' \
+	    cache '${dev[6]}' '${dev[7]}' \
+	    spare '${dev[8]}' '${dev[9]}'\
+		log mirror '${dev[10]}' '${dev[11]}'"
+
+	devs=""
+	want="$STR_DRYRUN
+
+	$NEWPOOL
+	  ${dev[1]}
+	dedup
+	  ${dev[3]}
+	special
+	  ${dev[5]}"
+    )
+    (
+	tree="mirror '${dev[0]}' '${dev[1]}'
+	    dedup mirror '${dev[2]}' '${dev[3]}' \
+	    special mirror '${dev[4]}' '${dev[5]}' \
+	    cache '${dev[6]}' '${dev[7]}' \
+	    spare '${dev[8]}' '${dev[9]}'\
+		log mirror '${dev[10]}' '${dev[11]}'"
+
+	devs="'${dev[0]}' '${dev[2]}' '${dev[4]}'"
+	want="$STR_DRYRUN
+
+	$NEWPOOL
+	  ${dev[0]}
+	dedup
+	  ${dev[2]}
+	special
+	  ${dev[4]}"
+    )
+)
+
+verify_runnable "global"
+
+function cleanup
+{
+	destroy_pool "$TESTPOOL"
+}
+
+log_assert \
+"'zpool split -n <pool> <newpool> [<vdev>]...' can display the configuration"
+
+log_onexit cleanup
+
+# Create needed file vdevs.
+for (( i=0; i < ${#dev[@]}; i+=1 )); do
+	log_must truncate -s $SPA_MINDEVSIZE "${dev[$i]}"
+done
+
+# Foreach test create pool, add -n devices and check output.
+for (( i=0; i < ${#tests[@]}; i+=1 )); do
+	typeset tree="${tests[$i].tree}"
+	typeset devs="${tests[$i].devs}"
+	typeset want="${tests[$i].want}"
+
+	log_must eval zpool create "$TESTPOOL" $tree
+	log_must poolexists "$TESTPOOL"
+	typeset out="$(log_must eval "zpool split -n \
+	    '$TESTPOOL' '$NEWPOOL' $devs" | sed /^SUCCESS/d)"
+
+	if [[ "$out" != "$want" ]]; then
+		log_fail "Got:\n" "$out" "\nbut expected:\n" "$want"
+	fi
+	log_must destroy_pool "$TESTPOOL"
+done
+
+log_pass \
+"'zpool split -n <pool> <newpool> [<vdev>]...' displays config correctly."