Add support for parallel pool exports

Changed spa_export_common() such that it no longer holds the
spa_namespace_lock for the entire duration and instead sets
spa_export_thread to indicate an import is in progress on the
spa.  This allows for an export to a diffent pool to proceed
in parallel while an export is still processing potentially
long operations like spa_unload_log_sm_flush_all().

Calls like spa_lookup() and spa_vdev_enter() that rely on
the spa_namespace_lock to serialize them against a concurrent
export, now wait for any in-progress export thread to complete
before proceeding.

The 'zpool import -a' sub-command also provides multi-threaded
support, using a thread pool to submit the exports in parallel.

Sponsored-By: Klara Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Wilson <gwilson@delphix.com>
Signed-off-by: Don Brady <don.brady@klarasystems.com>
Closes #16153

tests/runfiles/common.run

@@ -430,7 +430,8 @@ tags = ['functional', 'cli_root', 'zpool_events']
 
 [tests/functional/cli_root/zpool_export]
 tests = ['zpool_export_001_pos', 'zpool_export_002_pos',
-    'zpool_export_003_neg', 'zpool_export_004_pos']
+    'zpool_export_003_neg', 'zpool_export_004_pos',
+    'zpool_export_parallel_pos', 'zpool_export_parallel_admin']
 tags = ['functional', 'cli_root', 'zpool_export']
 
 [tests/functional/cli_root/zpool_get]

tests/zfs-tests/tests/Makefile.am

@@ -1084,6 +1084,8 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/cli_root/zpool_export/zpool_export_002_pos.ksh \
 	functional/cli_root/zpool_export/zpool_export_003_neg.ksh \
 	functional/cli_root/zpool_export/zpool_export_004_pos.ksh \
+	functional/cli_root/zpool_export/zpool_export_parallel_admin.ksh \
+	functional/cli_root/zpool_export/zpool_export_parallel_pos.ksh \
 	functional/cli_root/zpool_get/cleanup.ksh \
 	functional/cli_root/zpool_get/setup.ksh \
 	functional/cli_root/zpool_get/vdev_get_001_pos.ksh \

tests/zfs-tests/tests/functional/cli_root/zpool_export/zpool_export_parallel_admin.ksh

@@ -0,0 +1,72 @@
+#!/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 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2024 Klara, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# 	Verify that admin commands cannot race a pool export
+#
+# STRATEGY:
+#	1. Create a pool
+#	2. Import the pool with an injected delay in the background
+#	3. Execute some admin commands against the pool
+#
+
+verify_runnable "global"
+
+DEVICE_DIR=$TEST_BASE_DIR/dev_export-test
+
+function cleanup
+{
+	zinject -c all
+	poolexists $TESTPOOL1 && destroy_pool $TESTPOOL1
+	[[ -d $DEVICE_DIR ]] && log_must rm -rf $DEVICE_DIR
+}
+
+log_assert "admin commands cannot race a pool export"
+
+log_onexit cleanup
+
+[[ ! -d $DEVICE_DIR ]] && log_must mkdir -p $DEVICE_DIR
+log_must truncate -s $MINVDEVSIZE ${DEVICE_DIR}/disk0 ${DEVICE_DIR}/disk1
+
+log_must zpool create -f $TESTPOOL1 mirror ${DEVICE_DIR}/disk0 ${DEVICE_DIR}/disk1
+
+log_must zinject -P export -s 10 $TESTPOOL1
+
+log_must zpool export $TESTPOOL1 &
+
+zpool set comment=hello $TESTPOOL1
+zpool reguid $TESTPOOL1 &
+zpool split $TESTPOOL1 &
+
+log_pass "admin commands cannot race a pool export"

tests/zfs-tests/tests/functional/cli_root/zpool_export/zpool_export_parallel_pos.ksh

@@ -0,0 +1,129 @@
+#!/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 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2024 Klara, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.cfg
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.kshlib
+
+# test uses 8 vdevs
+MAX_NUM=8
+DEVICE_DIR=$TEST_BASE_DIR/dev_import-test
+
+
+#
+# DESCRIPTION:
+# 	Verify that pool exports can occur in parallel
+#
+# STRATEGY:
+#	1. Create 8 pools
+#	2. Inject an export delay using zinject
+#	3. Export half of the pools synchronously to baseline sequential cost
+#	4. Export the other half asynchronously to demonstrate parallel savings
+#	6. Import 4 pools
+#	7. Test zpool export -a
+#
+
+verify_runnable "global"
+
+#
+# override the minimum sized vdevs
+#
+
+POOLNAME="test_pool"
+
+function cleanup
+{
+	zinject -c all
+
+	for i in {0..$(($MAX_NUM - 1))}; do
+		poolexists $POOLNAME-$i && destroy_pool $POOLNAME-$i
+	done
+
+	[[ -d $DEVICE_DIR ]] && log_must rm -rf $DEVICE_DIR
+}
+
+log_assert "Pool exports can occur in parallel"
+
+log_onexit cleanup
+
+[[ ! -d $DEVICE_DIR ]] && log_must mkdir -p $DEVICE_DIR
+
+#
+# Create some pools with export delay injectors
+#
+for i in {0..$(($MAX_NUM - 1))}; do
+	log_must truncate -s $MINVDEVSIZE ${DEVICE_DIR}/disk$i
+	log_must zpool create $POOLNAME-$i $DEVICE_DIR/disk$i
+	log_must zinject -P export -s 8 $POOLNAME-$i
+done
+
+#
+# Export half of the pools synchronously
+#
+SECONDS=0
+for i in {0..3}; do
+	log_must zpool export $POOLNAME-$i
+done
+sequential_time=$SECONDS
+log_note "sequentially exported 4 pools in $sequential_time seconds"
+
+#
+# Export half of the pools in parallel
+#
+SECONDS=0
+for i in {4..7}; do
+	log_must zpool export $POOLNAME-$i &
+done
+wait
+parallel_time=$SECONDS
+log_note "asyncronously exported 4 pools in $parallel_time seconds"
+
+log_must test $parallel_time -lt $(($sequential_time / 3))
+
+#
+# import 4 pools with export delay injectors
+#
+for i in {4..7}; do
+	log_must zpool import -d $DEVICE_DIR/disk$i $POOLNAME-$i
+	log_must zinject -P export -s 8 $POOLNAME-$i
+done
+
+#
+# now test zpool export -a
+#
+SECONDS=0
+log_must zpool export -a
+parallel_time=$SECONDS
+log_note "asyncronously exported 4 pools, using '-a', in $parallel_time seconds"
+
+log_must test $parallel_time -lt $(($sequential_time / 3))
+
+log_pass "Pool exports occur in parallel"