Add vdev property to disable vdev scheduler

Added vdev property to disable the vdev scheduler.
The intention behind this property is to improve IOPS
performance when using o_direct.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: MigeljanImeri <ImeriMigel@gmail.com>
Closes #17358

tests/runfiles/common.run

@@ -564,7 +564,7 @@ tags = ['functional', 'cli_root', 'zpool_scrub']
 tests = ['zpool_set_001_pos', 'zpool_set_002_neg', 'zpool_set_003_neg',
     'zpool_set_ashift', 'zpool_set_features', 'vdev_set_001_pos',
     'user_property_001_pos', 'user_property_002_neg',
-    'zpool_set_clear_userprop']
+    'zpool_set_clear_userprop','vdev_set_scheduler']
 tags = ['functional', 'cli_root', 'zpool_set']
 
 [tests/functional/cli_root/zpool_split]

tests/zfs-tests/tests/Makefile.am

@@ -1274,6 +1274,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/cli_root/zpool_set/setup.ksh \
 	functional/cli_root/zpool/setup.ksh \
 	functional/cli_root/zpool_set/vdev_set_001_pos.ksh \
+	functional/cli_root/zpool_set/vdev_set_scheduler.ksh \
 	functional/cli_root/zpool_set/zpool_set_common.kshlib \
 	functional/cli_root/zpool_set/zpool_set_001_pos.ksh \
 	functional/cli_root/zpool_set/zpool_set_002_neg.ksh \

tests/zfs-tests/tests/functional/cli_root/zpool_get/vdev_get.cfg

@@ -77,4 +77,5 @@ typeset -a properties=(
     trim_support
     trim_errors
     slow_ios
+    scheduler
 )

tests/zfs-tests/tests/functional/cli_root/zpool_set/vdev_set_scheduler.ksh

@@ -0,0 +1,93 @@
+#!/bin/ksh -p
+# SPDX-License-Identifier: CDDL-1.0
+#
+# 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) 2025 by Triad National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# Setting vdev scheduler property while reading from vdev should not cause panic.
+#
+# STRATEGY:
+# 1. Create a zpool
+# 2. Write a file to the pool.
+# 3. Start reading from file, while also setting the scheduler property.
+#
+
+verify_runnable "global"
+
+command -v fio > /dev/null || log_unsupported "fio missing"
+
+function set_scheduler
+{
+	for i in auto on off ; do
+		sleep 0.1
+		zpool set scheduler=$i $TESTPOOL1 $FILEDEV
+	done
+}
+
+function cleanup
+{
+	destroy_pool $TESTPOOL1
+	log_must rm -f $FILEDEV
+}
+
+log_assert "Toggling vdev scheduler property while reading from vdev should not cause panic"
+log_onexit cleanup
+
+# 1. Create a pool
+
+FILEDEV="$TEST_BASE_DIR/filedev.$$"
+log_must truncate -s $(($MINVDEVSIZE * 2)) $FILEDEV
+create_pool $TESTPOOL1 $FILEDEV
+
+mntpnt=$(get_prop mountpoint $TESTPOOL1)
+
+# 2. Write a file to the pool, while also setting the scheduler property.
+
+log_must eval "fio --filename=$mntpnt/foobar --name=write-file \
+		--rw=write --size=$MINVDEVSIZE --bs=128k --numjobs=1 --direct=1 \
+		--ioengine=sync --time_based --runtime=2 &"
+
+ITERATIONS=4
+
+for i in $(seq $ITERATIONS); do
+	log_must set_scheduler
+done;
+wait
+
+# 3. Starting reading from file, while also setting the scheduler property.
+
+log_must eval "fio --filename=$mntpnt/foobar --name=read-file \
+		--rw=read --size=$MINVDEVSIZE --bs=128k --numjobs=1 --direct=1 \
+		--ioengine=sync --time_based --runtime=2 &"
+
+for i in $(seq $ITERATIONS); do
+	log_must set_scheduler
+done;
+wait
+
+log_pass "Setting vdev scheduler property while reading from vdev does not cause panic"