Parallel pool import

This commit allow spa_load() to drop the spa_namespace_lock so
that imports can happen concurrently. Prior to dropping the
spa_namespace_lock, the import logic will set the spa_load_thread
value to track the thread which is doing the import.

Consumers of spa_lookup() retain the same behavior by blocking
when either a thread is holding the spa_namespace_lock or the
spa_load_thread value is set. This will ensure that critical
concurrent operations cannot take place while a pool is being
imported.

The zpool command is also enhanced to provide multi-threaded support
when invoking zpool import -a.

Lastly, zinject provides a mechanism to insert artificial delays
when importing a pool and new zfs tests are added to verify parallel
import functionality.

Contributions-by: Don Brady <don.brady@klarasystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Wilson <gwilson@delphix.com>
Closes #16093

cmd/zinject/zinject.c

@@ -22,7 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2017, Intel Corporation.
- * Copyright (c) 2024, Klara Inc.
+ * Copyright (c) 2023-2024, Klara Inc.
  */
 
 /*
@@ -310,6 +310,11 @@ usage(void)
 	    "\t\tcreate 3 lanes on the device; one lane with a latency\n"
 	    "\t\tof 10 ms and two lanes with a 25 ms latency.\n"
 	    "\n"
+	    "\tzinject -P import|export -s <seconds> pool\n"
+	    "\t\tAdd an artificial delay to a future pool import or export,\n"
+	    "\t\tsuch that the operation takes a minimum of supplied seconds\n"
+	    "\t\tto complete.\n"
+	    "\n"
 	    "\tzinject -I [-s <seconds> | -g <txgs>] pool\n"
 	    "\t\tCause the pool to stop writing blocks yet not\n"
 	    "\t\treport errors for a duration.  Simulates buggy hardware\n"
@@ -392,8 +397,10 @@ print_data_handler(int id, const char *pool, zinject_record_t *record,
 {
 	int *count = data;
 
-	if (record->zi_guid != 0 || record->zi_func[0] != '\0')
+	if (record->zi_guid != 0 || record->zi_func[0] != '\0' ||
+	    record->zi_duration != 0) {
 		return (0);
+	}
 
 	if (*count == 0) {
 		(void) printf("%3s  %-15s  %-6s  %-6s  %-8s  %3s  %-4s  "
@@ -507,6 +514,33 @@ print_panic_handler(int id, const char *pool, zinject_record_t *record,
 	return (0);
 }
 
+static int
+print_pool_delay_handler(int id, const char *pool, zinject_record_t *record,
+    void *data)
+{
+	int *count = data;
+
+	if (record->zi_cmd != ZINJECT_DELAY_IMPORT &&
+	    record->zi_cmd != ZINJECT_DELAY_EXPORT) {
+		return (0);
+	}
+
+	if (*count == 0) {
+		(void) printf("%3s  %-19s  %-11s  %s\n",
+		    "ID", "POOL", "DELAY (sec)", "COMMAND");
+		(void) printf("---  -------------------  -----------"
+		    "  -------\n");
+	}
+
+	*count += 1;
+
+	(void) printf("%3d  %-19s  %-11llu  %s\n",
+	    id, pool, (u_longlong_t)record->zi_duration,
+	    record->zi_cmd == ZINJECT_DELAY_IMPORT ? "import": "export");
+
+	return (0);
+}
+
 /*
  * Print all registered error handlers.  Returns the number of handlers
  * registered.
@@ -537,6 +571,13 @@ print_all_handlers(void)
 		count = 0;
 	}
 
+	(void) iter_handlers(print_pool_delay_handler, &count);
+	if (count > 0) {
+		total += count;
+		(void) printf("\n");
+		count = 0;
+	}
+
 	(void) iter_handlers(print_panic_handler, &count);
 
 	return (count + total);
@@ -609,9 +650,27 @@ register_handler(const char *pool, int flags, zinject_record_t *record,
 	zc.zc_guid = flags;
 
 	if (zfs_ioctl(g_zfs, ZFS_IOC_INJECT_FAULT, &zc) != 0) {
-		(void) fprintf(stderr, "failed to add handler: %s\n",
+		const char *errmsg = strerror(errno);
-		    errno == EDOM ? "block level exceeds max level of object" :
+
-		    strerror(errno));
+		switch (errno) {
+		case EDOM:
+			errmsg = "block level exceeds max level of object";
+			break;
+		case EEXIST:
+			if (record->zi_cmd == ZINJECT_DELAY_IMPORT)
+				errmsg = "pool already imported";
+			if (record->zi_cmd == ZINJECT_DELAY_EXPORT)
+				errmsg = "a handler already exists";
+			break;
+		case ENOENT:
+			/* import delay injector running on older zfs module */
+			if (record->zi_cmd == ZINJECT_DELAY_IMPORT)
+				errmsg = "import delay injector not supported";
+			break;
+		default:
+			break;
+		}
+		(void) fprintf(stderr, "failed to add handler: %s\n", errmsg);
 		return (1);
 	}
 
@@ -636,6 +695,9 @@ register_handler(const char *pool, int flags, zinject_record_t *record,
 		} else if (record->zi_duration < 0) {
 			(void) printf(" txgs: %lld \n",
 			    (u_longlong_t)-record->zi_duration);
+		} else if (record->zi_timer > 0) {
+			(void) printf(" timer: %lld ms\n",
+			    (u_longlong_t)NSEC2MSEC(record->zi_timer));
 		} else {
 			(void) printf("objset: %llu\n",
 			    (u_longlong_t)record->zi_objset);
@@ -834,7 +896,7 @@ main(int argc, char **argv)
 	}
 
 	while ((c = getopt(argc, argv,
-	    ":aA:b:C:d:D:f:Fg:qhIc:t:T:l:mr:s:e:uL:p:")) != -1) {
+	    ":aA:b:C:d:D:f:Fg:qhIc:t:T:l:mr:s:e:uL:p:P:")) != -1) {
 		switch (c) {
 		case 'a':
 			flags |= ZINJECT_FLUSH_ARC;
@@ -952,6 +1014,19 @@ main(int argc, char **argv)
 			    sizeof (record.zi_func));
 			record.zi_cmd = ZINJECT_PANIC;
 			break;
+		case 'P':
+			if (strcasecmp(optarg, "import") == 0) {
+				record.zi_cmd = ZINJECT_DELAY_IMPORT;
+			} else if (strcasecmp(optarg, "export") == 0) {
+				record.zi_cmd = ZINJECT_DELAY_EXPORT;
+			} else {
+				(void) fprintf(stderr, "invalid command '%s': "
+				    "must be 'import' or 'export'\n", optarg);
+				usage();
+				libzfs_fini(g_zfs);
+				return (1);
+			}
+			break;
 		case 'q':
 			quiet = 1;
 			break;
@@ -1033,7 +1108,7 @@ main(int argc, char **argv)
 	argc -= optind;
 	argv += optind;
 
-	if (record.zi_duration != 0)
+	if (record.zi_duration != 0 && record.zi_cmd == 0)
 		record.zi_cmd = ZINJECT_IGNORED_WRITES;
 
 	if (cancel != NULL) {
@@ -1179,8 +1254,8 @@ main(int argc, char **argv)
 		if (raw != NULL || range != NULL || type != TYPE_INVAL ||
 		    level != 0 || device != NULL || record.zi_freq > 0 ||
 		    dvas != 0) {
-			(void) fprintf(stderr, "panic (-p) incompatible with "
+			(void) fprintf(stderr, "%s incompatible with other "
-			    "other options\n");
+			    "options\n", "import|export delay (-P)");
 			usage();
 			libzfs_fini(g_zfs);
 			return (2);
@@ -1198,6 +1273,28 @@ main(int argc, char **argv)
 		if (argv[1] != NULL)
 			record.zi_type = atoi(argv[1]);
 		dataset[0] = '\0';
+	} else if (record.zi_cmd == ZINJECT_DELAY_IMPORT ||
+	    record.zi_cmd == ZINJECT_DELAY_EXPORT) {
+		if (raw != NULL || range != NULL || type != TYPE_INVAL ||
+		    level != 0 || device != NULL || record.zi_freq > 0 ||
+		    dvas != 0) {
+			(void) fprintf(stderr, "%s incompatible with other "
+			    "options\n", "import|export delay (-P)");
+			usage();
+			libzfs_fini(g_zfs);
+			return (2);
+		}
+
+		if (argc != 1 || record.zi_duration <= 0) {
+			(void) fprintf(stderr, "import|export delay (-P) "
+			    "injection requires a duration (-s) and a single "
+			    "pool name\n");
+			usage();
+			libzfs_fini(g_zfs);
+			return (2);
+		}
+
+		(void) strlcpy(pool, argv[0], sizeof (pool));
 	} else if (record.zi_cmd == ZINJECT_IGNORED_WRITES) {
 		if (raw != NULL || range != NULL || type != TYPE_INVAL ||
 		    level != 0 || record.zi_freq > 0 || dvas != 0) {

cmd/zpool/zpool_main.c

@@ -50,6 +50,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <thread_pool.h>
 #include <time.h>
 #include <unistd.h>
 #include <pwd.h>
@@ -3455,15 +3456,40 @@ do_import(nvlist_t *config, const char *newname, const char *mntopts,
 	return (ret);
 }
 
+typedef struct import_parameters {
+	nvlist_t *ip_config;
+	const char *ip_mntopts;
+	nvlist_t *ip_props;
+	int ip_flags;
+	int *ip_err;
+} import_parameters_t;
+
+static void
+do_import_task(void *arg)
+{
+	import_parameters_t *ip = arg;
+	*ip->ip_err |= do_import(ip->ip_config, NULL, ip->ip_mntopts,
+	    ip->ip_props, ip->ip_flags);
+	free(ip);
+}
+
+
 static int
 import_pools(nvlist_t *pools, nvlist_t *props, char *mntopts, int flags,
-    char *orig_name, char *new_name,
+    char *orig_name, char *new_name, importargs_t *import)
-    boolean_t do_destroyed, boolean_t pool_specified, boolean_t do_all,
-    importargs_t *import)
 {
 	nvlist_t *config = NULL;
 	nvlist_t *found_config = NULL;
 	uint64_t pool_state;
+	boolean_t pool_specified = (import->poolname != NULL ||
+	    import->guid != 0);
+
+
+	tpool_t *tp = NULL;
+	if (import->do_all) {
+		tp = tpool_create(1, 5 * sysconf(_SC_NPROCESSORS_ONLN),
+		    0, NULL);
+	}
 
 	/*
 	 * At this point we have a list of import candidate configs. Even if
@@ -3480,9 +3506,11 @@ import_pools(nvlist_t *pools, nvlist_t *props, char *mntopts, int flags,
 
 		verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_STATE,
 		    &pool_state) == 0);
-		if (!do_destroyed && pool_state == POOL_STATE_DESTROYED)
+		if (!import->do_destroyed &&
+		    pool_state == POOL_STATE_DESTROYED)
 			continue;
-		if (do_destroyed && pool_state != POOL_STATE_DESTROYED)
+		if (import->do_destroyed &&
+		    pool_state != POOL_STATE_DESTROYED)
 			continue;
 
 		verify(nvlist_add_nvlist(config, ZPOOL_LOAD_POLICY,
@@ -3491,12 +3519,21 @@ import_pools(nvlist_t *pools, nvlist_t *props, char *mntopts, int flags,
 		if (!pool_specified) {
 			if (first)
 				first = B_FALSE;
-			else if (!do_all)
+			else if (!import->do_all)
 				(void) fputc('\n', stdout);
 
-			if (do_all) {
+			if (import->do_all) {
-				err |= do_import(config, NULL, mntopts,
+				import_parameters_t *ip = safe_malloc(
-				    props, flags);
+				    sizeof (import_parameters_t));
+
+				ip->ip_config = config;
+				ip->ip_mntopts = mntopts;
+				ip->ip_props = props;
+				ip->ip_flags = flags;
+				ip->ip_err = &err;
+
+				(void) tpool_dispatch(tp, do_import_task,
+				    (void *)ip);
 			} else {
 				/*
 				 * If we're importing from cachefile, then
@@ -3544,6 +3581,10 @@ import_pools(nvlist_t *pools, nvlist_t *props, char *mntopts, int flags,
 				found_config = config;
 		}
 	}
+	if (import->do_all) {
+		tpool_wait(tp);
+		tpool_destroy(tp);
+	}
 
 	/*
 	 * If we were searching for a specific pool, verify that we found a
@@ -3773,7 +3814,6 @@ zpool_do_import(int argc, char **argv)
 	boolean_t xtreme_rewind = B_FALSE;
 	boolean_t do_scan = B_FALSE;
 	boolean_t pool_exists = B_FALSE;
-	boolean_t pool_specified = B_FALSE;
 	uint64_t txg = -1ULL;
 	char *cachefile = NULL;
 	importargs_t idata = { 0 };
@@ -3972,7 +4012,6 @@ zpool_do_import(int argc, char **argv)
 			searchname = argv[0];
 			searchguid = 0;
 		}
-		pool_specified = B_TRUE;
 
 		/*
 		 * User specified a name or guid.  Ensure it's unique.
@@ -4005,6 +4044,8 @@ zpool_do_import(int argc, char **argv)
 	idata.cachefile = cachefile;
 	idata.scan = do_scan;
 	idata.policy = policy;
+	idata.do_destroyed = do_destroyed;
+	idata.do_all = do_all;
 
 	libpc_handle_t lpch = {
 		.lpc_lib_handle = g_zfs,
@@ -4047,9 +4088,7 @@ zpool_do_import(int argc, char **argv)
 	}
 
 	err = import_pools(pools, props, mntopts, flags,
-	    argc >= 1 ? argv[0] : NULL,
+	    argc >= 1 ? argv[0] : NULL, argc >= 2 ? argv[1] : NULL, &idata);
-	    argc >= 2 ? argv[1] : NULL,
-	    do_destroyed, pool_specified, do_all, &idata);
 
 	/*
 	 * If we're using the cachefile and we failed to import, then
@@ -4070,9 +4109,8 @@ zpool_do_import(int argc, char **argv)
 		pools = zpool_search_import(&lpch, &idata);
 
 		err = import_pools(pools, props, mntopts, flags,
-		    argc >= 1 ? argv[0] : NULL,
+		    argc >= 1 ? argv[0] : NULL, argc >= 2 ? argv[1] : NULL,
-		    argc >= 2 ? argv[1] : NULL,
+		    &idata);
-		    do_destroyed, pool_specified, do_all, &idata);
 	}
 
 error:

include/libzutil.h

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2018 by Delphix. All rights reserved.
+ * Copyright (c) 2018, 2024 by Delphix. All rights reserved.
  */
 
 #ifndef	_LIBZUTIL_H
@@ -79,6 +79,8 @@ typedef struct importargs {
 	boolean_t can_be_active; /* can the pool be active?		*/
 	boolean_t scan;		/* prefer scanning to libblkid cache    */
 	nvlist_t *policy;	/* load policy (max txg, rewind, etc.)	*/
+	boolean_t do_destroyed;
+	boolean_t do_all;
 } importargs_t;
 
 typedef struct libpc_handle {

include/sys/spa.h

@@ -833,6 +833,8 @@ void spa_select_allocator(zio_t *zio);
 
 /* spa namespace global mutex */
 extern kmutex_t spa_namespace_lock;
+extern avl_tree_t spa_namespace_avl;
+extern kcondvar_t spa_namespace_cv;
 
 /*
  * SPA configuration functions in spa_config.c

include/sys/spa_impl.h

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2024 by Delphix. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  * Copyright 2013 Saso Kiselkov. All rights reserved.
@@ -237,6 +237,7 @@ struct spa {
 	dsl_pool_t	*spa_dsl_pool;
 	boolean_t	spa_is_initializing;	/* true while opening pool */
 	boolean_t	spa_is_exporting;	/* true while exporting pool */
+	kthread_t	*spa_load_thread;	/* loading, no namespace lock */
 	metaslab_class_t *spa_normal_class;	/* normal data class */
 	metaslab_class_t *spa_log_class;	/* intent log data class */
 	metaslab_class_t *spa_embedded_log_class; /* log on normal vdevs */

include/sys/zfs_ioctl.h

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2020 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2024 by Delphix. All rights reserved.
  * Copyright 2016 RackTop Systems.
  * Copyright (c) 2017, Intel Corporation.
  */
@@ -454,6 +454,8 @@ typedef enum zinject_type {
 	ZINJECT_PANIC,
 	ZINJECT_DELAY_IO,
 	ZINJECT_DECRYPT_FAULT,
+	ZINJECT_DELAY_IMPORT,
+	ZINJECT_DELAY_EXPORT,
 } zinject_type_t;
 
 typedef struct zfs_share {

include/sys/zio.h

@@ -22,7 +22,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
- * Copyright (c) 2012, 2020 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2024 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright 2016 Toomas Soome <tsoome@me.com>
@@ -686,6 +686,8 @@ extern int zio_handle_device_injections(vdev_t *vd, zio_t *zio, int err1,
 extern int zio_handle_label_injection(zio_t *zio, int error);
 extern void zio_handle_ignored_writes(zio_t *zio);
 extern hrtime_t zio_handle_io_delay(zio_t *zio);
+extern void zio_handle_import_delay(spa_t *spa, hrtime_t elapsed);
+extern void zio_handle_export_delay(spa_t *spa, hrtime_t elapsed);
 
 /*
  * Checksum ereport functions

man/man8/zinject.8

@@ -129,6 +129,14 @@ Force a vdev error.
 .
 .It Xo
 .Nm zinject
+.Fl i Ar seconds
+.Ar pool
+.Xc
+Add an artificial delay during the future import of a pool.
+This injector is automatically cleared after the import is finished.
+.
+.It Xo
+.Nm zinject
 .Fl I
 .Op Fl s Ar seconds Ns | Ns Fl g Ar txgs
 .Ar pool

module/zfs/spa.c

@@ -3273,8 +3273,6 @@ spa_spawn_aux_threads(spa_t *spa)
 {
 	ASSERT(spa_writeable(spa));
 
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
-
 	spa_start_raidz_expansion_thread(spa);
 	spa_start_indirect_condensing_thread(spa);
 	spa_start_livelist_destroy_thread(spa);
@@ -4981,7 +4979,8 @@ spa_ld_read_checkpoint_txg(spa_t *spa)
 	int error = 0;
 
 	ASSERT0(spa->spa_checkpoint_txg);
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+	ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
+	    spa->spa_load_thread == curthread);
 
 	error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 	    DMU_POOL_ZPOOL_CHECKPOINT, sizeof (uint64_t),
@@ -5228,6 +5227,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	boolean_t checkpoint_rewind =
 	    (spa->spa_import_flags & ZFS_IMPORT_CHECKPOINT);
 	boolean_t update_config_cache = B_FALSE;
+	hrtime_t load_start = gethrtime();
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 	ASSERT(spa->spa_config_source != SPA_CONFIG_SRC_NONE);
@@ -5272,13 +5272,19 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 			return (error);
 	}
 
+	/*
+	 * Drop the namespace lock for the rest of the function.
+	 */
+	spa->spa_load_thread = curthread;
+	mutex_exit(&spa_namespace_lock);
+
 	/*
 	 * Retrieve the checkpoint txg if the pool has a checkpoint.
 	 */
 	spa_import_progress_set_notes(spa, "Loading checkpoint txg");
 	error = spa_ld_read_checkpoint_txg(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Retrieve the mapping of indirect vdevs. Those vdevs were removed
@@ -5291,7 +5297,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Loading indirect vdev metadata");
 	error = spa_ld_open_indirect_vdev_metadata(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Retrieve the full list of active features from the MOS and check if
@@ -5300,7 +5306,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Checking feature flags");
 	error = spa_ld_check_features(spa, &missing_feat_write);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Load several special directories from the MOS needed by the dsl_pool
@@ -5309,7 +5315,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Loading special MOS directories");
 	error = spa_ld_load_special_directories(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Retrieve pool properties from the MOS.
@@ -5317,7 +5323,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Loading properties");
 	error = spa_ld_get_props(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Retrieve the list of auxiliary devices - cache devices and spares -
@@ -5326,7 +5332,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Loading AUX vdevs");
 	error = spa_ld_open_aux_vdevs(spa, type);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Load the metadata for all vdevs. Also check if unopenable devices
@@ -5335,17 +5341,17 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Loading vdev metadata");
 	error = spa_ld_load_vdev_metadata(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	spa_import_progress_set_notes(spa, "Loading dedup tables");
 	error = spa_ld_load_dedup_tables(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	spa_import_progress_set_notes(spa, "Loading BRT");
 	error = spa_ld_load_brt(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Verify the logs now to make sure we don't have any unexpected errors
@@ -5354,7 +5360,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Verifying Log Devices");
 	error = spa_ld_verify_logs(spa, type, ereport);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	if (missing_feat_write) {
 		ASSERT(spa->spa_load_state == SPA_LOAD_TRYIMPORT);
@@ -5364,8 +5370,9 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 		 * read-only mode but not read-write mode. We now have enough
 		 * information and can return to userland.
 		 */
-		return (spa_vdev_err(spa->spa_root_vdev, VDEV_AUX_UNSUP_FEAT,
+		error = spa_vdev_err(spa->spa_root_vdev, VDEV_AUX_UNSUP_FEAT,
-		    ENOTSUP));
+		    ENOTSUP);
+		goto fail;
 	}
 
 	/*
@@ -5376,7 +5383,7 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 	spa_import_progress_set_notes(spa, "Verifying pool data");
 	error = spa_ld_verify_pool_data(spa);
 	if (error != 0)
-		return (error);
+		goto fail;
 
 	/*
 	 * Calculate the deflated space for the pool. This must be done before
@@ -5501,13 +5508,19 @@ spa_load_impl(spa_t *spa, spa_import_type_t type, const char **ereport)
 		spa_config_exit(spa, SCL_CONFIG, FTAG);
 		spa_import_progress_set_notes(spa, "Finished importing");
 	}
+	zio_handle_import_delay(spa, gethrtime() - load_start);
 
 	spa_import_progress_remove(spa_guid(spa));
 	spa_async_request(spa, SPA_ASYNC_L2CACHE_REBUILD);
 
 	spa_load_note(spa, "LOADED");
+fail:
+	mutex_enter(&spa_namespace_lock);
+	spa->spa_load_thread = NULL;
+	cv_broadcast(&spa_namespace_cv);
+
+	return (error);
 
-	return (0);
 }
 
 static int
@@ -6757,9 +6770,14 @@ spa_tryimport(nvlist_t *tryconfig)
 	/*
 	 * Create and initialize the spa structure.
 	 */
+	char *name = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+	(void) snprintf(name, MAXPATHLEN, "%s-%llx-%s",
+	    TRYIMPORT_NAME, (u_longlong_t)curthread, poolname);
+
 	mutex_enter(&spa_namespace_lock);
-	spa = spa_add(TRYIMPORT_NAME, tryconfig, NULL);
+	spa = spa_add(name, tryconfig, NULL);
 	spa_activate(spa, SPA_MODE_READ);
+	kmem_free(name, MAXPATHLEN);
 
 	/*
 	 * Rewind pool if a max txg was provided.
@@ -6874,6 +6892,7 @@ spa_export_common(const char *pool, int new_state, nvlist_t **oldconfig,
 {
 	int error;
 	spa_t *spa;
+	hrtime_t export_start = gethrtime();
 
 	if (oldconfig)
 		*oldconfig = NULL;
@@ -7018,6 +7037,9 @@ export_spa:
 		spa->spa_is_exporting = B_FALSE;
 	}
 
+	if (new_state == POOL_STATE_EXPORTED)
+		zio_handle_export_delay(spa, gethrtime() - export_start);
+
 	mutex_exit(&spa_namespace_lock);
 	return (0);
 

module/zfs/spa_misc.c

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2024 by Delphix. All rights reserved.
  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  * Copyright 2013 Saso Kiselkov. All rights reserved.
@@ -82,7 +82,8 @@
  *		- Check if spa_refcount is zero
  *		- Rename a spa_t
  *		- add/remove/attach/detach devices
- *		- Held for the duration of create/destroy/import/export
+ *		- Held for the duration of create/destroy/export
+ *		- Held at the start and end of import
  *
  *	It does not need to handle recursion.  A create or destroy may
  *	reference objects (files or zvols) in other pools, but by
@@ -235,9 +236,9 @@
  * locking is, always, based on spa_namespace_lock and spa_config_lock[].
  */
 
-static avl_tree_t spa_namespace_avl;
+avl_tree_t spa_namespace_avl;
 kmutex_t spa_namespace_lock;
-static kcondvar_t spa_namespace_cv;
+kcondvar_t spa_namespace_cv;
 static const int spa_max_replication_override = SPA_DVAS_PER_BP;
 
 static kmutex_t spa_spare_lock;
@@ -619,6 +620,7 @@ spa_lookup(const char *name)
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
+retry:
 	(void) strlcpy(search.spa_name, name, sizeof (search.spa_name));
 
 	/*
@@ -630,6 +632,14 @@ spa_lookup(const char *name)
 		*cp = '\0';
 
 	spa = avl_find(&spa_namespace_avl, &search, &where);
+	if (spa == NULL)
+		return (NULL);
+
+	if (spa->spa_load_thread != NULL &&
+	    spa->spa_load_thread != curthread) {
+		cv_wait(&spa_namespace_cv, &spa_namespace_lock);
+		goto retry;
+	}
 
 	return (spa);
 }
@@ -728,6 +738,7 @@ spa_add(const char *name, nvlist_t *config, const char *altroot)
 	spa_config_lock_init(spa);
 	spa_stats_init(spa);
 
+	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 	avl_add(&spa_namespace_avl, spa);
 
 	/*
@@ -826,7 +837,6 @@ spa_remove(spa_t *spa)
 	nvlist_free(spa->spa_config_splitting);
 
 	avl_remove(&spa_namespace_avl, spa);
-	cv_broadcast(&spa_namespace_cv);
 
 	if (spa->spa_root)
 		spa_strfree(spa->spa_root);
@@ -920,7 +930,8 @@ void
 spa_open_ref(spa_t *spa, const void *tag)
 {
 	ASSERT(zfs_refcount_count(&spa->spa_refcount) >= spa->spa_minref ||
-	    MUTEX_HELD(&spa_namespace_lock));
+	    MUTEX_HELD(&spa_namespace_lock) ||
+	    spa->spa_load_thread == curthread);
 	(void) zfs_refcount_add(&spa->spa_refcount, tag);
 }
 
@@ -932,7 +943,8 @@ void
 spa_close(spa_t *spa, const void *tag)
 {
 	ASSERT(zfs_refcount_count(&spa->spa_refcount) > spa->spa_minref ||
-	    MUTEX_HELD(&spa_namespace_lock));
+	    MUTEX_HELD(&spa_namespace_lock) ||
+	    spa->spa_load_thread == curthread);
 	(void) zfs_refcount_remove(&spa->spa_refcount, tag);
 }
 

module/zfs/vdev_initialize.c

@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2016, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2016, 2024 by Delphix. All rights reserved.
  */
 
 #include <sys/spa.h>
@@ -775,7 +775,8 @@ vdev_initialize_stop_all(vdev_t *vd, vdev_initializing_state_t tgt_state)
 void
 vdev_initialize_restart(vdev_t *vd)
 {
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+	ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
+	    vd->vdev_spa->spa_load_thread == curthread);
 	ASSERT(!spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
 
 	if (vd->vdev_leaf_zap != 0) {

module/zfs/vdev_rebuild.c

@@ -23,6 +23,7 @@
  * Copyright (c) 2018, Intel Corporation.
  * Copyright (c) 2020 by Lawrence Livermore National Security, LLC.
  * Copyright (c) 2022 Hewlett Packard Enterprise Development LP.
+ * Copyright (c) 2024 by Delphix. All rights reserved.
  */
 
 #include <sys/vdev_impl.h>
@@ -1071,7 +1072,8 @@ vdev_rebuild_restart_impl(vdev_t *vd)
 void
 vdev_rebuild_restart(spa_t *spa)
 {
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+	ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
+	    spa->spa_load_thread == curthread);
 
 	vdev_rebuild_restart_impl(spa->spa_root_vdev);
 }

module/zfs/vdev_trim.c

@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2016, 2024 by Delphix. All rights reserved.
  * Copyright (c) 2019 by Lawrence Livermore National Security, LLC.
  * Copyright (c) 2021 Hewlett Packard Enterprise Development LP
  * Copyright 2023 RackTop Systems, Inc.
@@ -1148,7 +1148,8 @@ vdev_trim_stop_all(vdev_t *vd, vdev_trim_state_t tgt_state)
 void
 vdev_trim_restart(vdev_t *vd)
 {
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+	ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
+	    vd->vdev_spa->spa_load_thread == curthread);
 	ASSERT(!spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
 
 	if (vd->vdev_leaf_zap != 0) {
@@ -1568,8 +1569,8 @@ vdev_autotrim_stop_all(spa_t *spa)
 void
 vdev_autotrim_restart(spa_t *spa)
 {
-	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+	ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
-
+	    spa->spa_load_thread == curthread);
 	if (spa->spa_autotrim)
 		vdev_autotrim(spa);
 }

module/zfs/zio_inject.c

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2017, Intel Corporation.
+ * Copyright (c) 2024, Klara Inc.
  */
 
 /*
@@ -59,6 +60,7 @@ uint32_t zio_injection_enabled = 0;
 typedef struct inject_handler {
 	int			zi_id;
 	spa_t			*zi_spa;
+	char			*zi_spa_name; /* ZINJECT_DELAY_IMPORT only */
 	zinject_record_t	zi_record;
 	uint64_t		*zi_lanes;
 	int			zi_next_lane;
@@ -703,6 +705,63 @@ zio_handle_io_delay(zio_t *zio)
 	return (min_target);
 }
 
+static void
+zio_handle_pool_delay(spa_t *spa, hrtime_t elapsed, zinject_type_t command)
+{
+	inject_handler_t *handler;
+	hrtime_t delay = 0;
+	int id = 0;
+
+	rw_enter(&inject_lock, RW_READER);
+
+	for (handler = list_head(&inject_handlers);
+	    handler != NULL && handler->zi_record.zi_cmd == command;
+	    handler = list_next(&inject_handlers, handler)) {
+		ASSERT3P(handler->zi_spa_name, !=, NULL);
+		if (strcmp(spa_name(spa), handler->zi_spa_name) == 0) {
+			uint64_t pause =
+			    SEC2NSEC(handler->zi_record.zi_duration);
+			if (pause > elapsed) {
+				delay = pause - elapsed;
+			}
+			id = handler->zi_id;
+			break;
+		}
+	}
+
+	rw_exit(&inject_lock);
+
+	if (delay) {
+		if (command == ZINJECT_DELAY_IMPORT) {
+			spa_import_progress_set_notes(spa, "injecting %llu "
+			    "sec delay", (u_longlong_t)NSEC2SEC(delay));
+		}
+		zfs_sleep_until(gethrtime() + delay);
+	}
+	if (id) {
+		/* all done with this one-shot handler */
+		zio_clear_fault(id);
+	}
+}
+
+/*
+ * For testing, inject a delay during an import
+ */
+void
+zio_handle_import_delay(spa_t *spa, hrtime_t elapsed)
+{
+	zio_handle_pool_delay(spa, elapsed, ZINJECT_DELAY_IMPORT);
+}
+
+/*
+ * For testing, inject a delay during an export
+ */
+void
+zio_handle_export_delay(spa_t *spa, hrtime_t elapsed)
+{
+	zio_handle_pool_delay(spa, elapsed, ZINJECT_DELAY_EXPORT);
+}
+
 static int
 zio_calculate_range(const char *pool, zinject_record_t *record)
 {
@@ -760,6 +819,28 @@ zio_calculate_range(const char *pool, zinject_record_t *record)
 	return (0);
 }
 
+static boolean_t
+zio_pool_handler_exists(const char *name, zinject_type_t command)
+{
+	boolean_t exists = B_FALSE;
+
+	rw_enter(&inject_lock, RW_READER);
+	for (inject_handler_t *handler = list_head(&inject_handlers);
+	    handler != NULL; handler = list_next(&inject_handlers, handler)) {
+		if (command != handler->zi_record.zi_cmd)
+			continue;
+
+		const char *pool = (handler->zi_spa_name != NULL) ?
+		    handler->zi_spa_name : spa_name(handler->zi_spa);
+		if (strcmp(name, pool) == 0) {
+			exists = B_TRUE;
+			break;
+		}
+	}
+	rw_exit(&inject_lock);
+
+	return (exists);
+}
 /*
  * Create a new handler for the given record.  We add it to the list, adding
  * a reference to the spa_t in the process.  We increment zio_injection_enabled,
@@ -810,16 +891,42 @@ zio_inject_fault(char *name, int flags, int *id, zinject_record_t *record)
 
 	if (!(flags & ZINJECT_NULL)) {
 		/*
-		 * spa_inject_ref() will add an injection reference, which will
+		 * Pool delays for import or export don't take an
-		 * prevent the pool from being removed from the namespace while
+		 * injection reference on the spa. Instead they
-		 * still allowing it to be unloaded.
+		 * rely on matching by name.
+		 */
+		if (record->zi_cmd == ZINJECT_DELAY_IMPORT ||
+		    record->zi_cmd == ZINJECT_DELAY_EXPORT) {
+			if (record->zi_duration <= 0)
+				return (SET_ERROR(EINVAL));
+			/*
+			 * Only one import | export delay handler per pool.
+			 */
+			if (zio_pool_handler_exists(name, record->zi_cmd))
+				return (SET_ERROR(EEXIST));
+
+			mutex_enter(&spa_namespace_lock);
+			boolean_t has_spa = spa_lookup(name) != NULL;
+			mutex_exit(&spa_namespace_lock);
+
+			if (record->zi_cmd == ZINJECT_DELAY_IMPORT && has_spa)
+				return (SET_ERROR(EEXIST));
+			if (record->zi_cmd == ZINJECT_DELAY_EXPORT && !has_spa)
+				return (SET_ERROR(ENOENT));
+			spa = NULL;
+		} else {
+			/*
+			 * spa_inject_ref() will add an injection reference,
+			 * which will prevent the pool from being removed
+			 * from the namespace while still allowing it to be
+			 * unloaded.
 			 */
 			if ((spa = spa_inject_addref(name)) == NULL)
 				return (SET_ERROR(ENOENT));
+		}
 
 		handler = kmem_alloc(sizeof (inject_handler_t), KM_SLEEP);
-
+		handler->zi_spa = spa;	/* note: can be NULL */
-		handler->zi_spa = spa;
 		handler->zi_record = *record;
 
 		if (handler->zi_record.zi_cmd == ZINJECT_DELAY_IO) {
@@ -832,6 +939,11 @@ zio_inject_fault(char *name, int flags, int *id, zinject_record_t *record)
 			handler->zi_next_lane = 0;
 		}
 
+		if (handler->zi_spa == NULL)
+			handler->zi_spa_name = spa_strdup(name);
+		else
+			handler->zi_spa_name = NULL;
+
 		rw_enter(&inject_lock, RW_WRITER);
 
 		/*
@@ -891,7 +1003,11 @@ zio_inject_list_next(int *id, char *name, size_t buflen,
 	if (handler) {
 		*record = handler->zi_record;
 		*id = handler->zi_id;
+		ASSERT(handler->zi_spa || handler->zi_spa_name);
+		if (handler->zi_spa != NULL)
 			(void) strlcpy(name, spa_name(handler->zi_spa), buflen);
+		else
+			(void) strlcpy(name, handler->zi_spa_name, buflen);
 		ret = 0;
 	} else {
 		ret = SET_ERROR(ENOENT);
@@ -941,6 +1057,10 @@ zio_clear_fault(int id)
 		ASSERT3P(handler->zi_lanes, ==, NULL);
 	}
 
+	if (handler->zi_spa_name != NULL)
+		spa_strfree(handler->zi_spa_name);
+
+	if (handler->zi_spa != NULL)
 		spa_inject_delref(handler->zi_spa);
 	kmem_free(handler, sizeof (inject_handler_t));
 	atomic_dec_32(&zio_injection_enabled);

tests/runfiles/common.run

@@ -466,7 +466,8 @@ tests = ['zpool_import_001_pos', 'zpool_import_002_pos',
     'import_paths_changed',
     'import_rewind_config_changed',
     'import_rewind_device_replaced',
-    'zpool_import_status']
+    'zpool_import_status', 'zpool_import_parallel_pos',
+    'zpool_import_parallel_neg', 'zpool_import_parallel_admin']
 tags = ['functional', 'cli_root', 'zpool_import']
 timeout = 1200
 

tests/zfs-tests/tests/Makefile.am

@@ -1144,6 +1144,9 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/cli_root/zpool_import/zpool_import_missing_003_pos.ksh \
 	functional/cli_root/zpool_import/zpool_import_rename_001_pos.ksh \
 	functional/cli_root/zpool_import/zpool_import_status.ksh \
+	functional/cli_root/zpool_import/zpool_import_parallel_admin.ksh \
+	functional/cli_root/zpool_import/zpool_import_parallel_neg.ksh \
+	functional/cli_root/zpool_import/zpool_import_parallel_pos.ksh \
 	functional/cli_root/zpool_initialize/cleanup.ksh \
 	functional/cli_root/zpool_initialize/zpool_initialize_attach_detach_add_remove.ksh \
 	functional/cli_root/zpool_initialize/zpool_initialize_fault_export_import_online.ksh \

tests/zfs-tests/tests/functional/cli_root/zpool_import/zpool_import_parallel_admin.ksh

@@ -0,0 +1,165 @@
+#!/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) 2023 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
+
+#
+# DESCRIPTION:
+# 	Verify that admin commands to different pool are not blocked by import
+#
+# STRATEGY:
+#	1. Create 2 pools
+#	2. Export one of the pools
+#	4. Import the pool with an injected delay
+#	5. Execute some admin commands against both pools
+#	6. Verify that the admin commands to the non-imported pool don't stall
+#
+
+verify_runnable "global"
+
+function cleanup
+{
+	zinject -c all
+	destroy_pool $TESTPOOL1
+	destroy_pool $TESTPOOL2
+}
+
+function pool_import
+{
+	typeset dir=$1
+	typeset pool=$2
+
+	SECONDS=0
+	errmsg=$(zpool import -d $dir -f $pool 2>&1 > /dev/null)
+	if [[ $? -eq 0 ]]; then
+		echo ${pool}: imported in $SECONDS secs
+		echo $SECONDS > ${DEVICE_DIR}/${pool}-import
+	else
+		echo ${pool}: import failed $errmsg in $SECONDS secs
+	fi
+}
+
+function pool_add_device
+{
+	typeset pool=$1
+	typeset device=$2
+	typeset devtype=$3
+
+	SECONDS=0
+	errmsg=$(zpool add $pool $devtype $device 2>&1 > /dev/null)
+	if [[ $? -eq 0 ]]; then
+		echo ${pool}: added $devtype vdev in $SECONDS secs
+		echo $SECONDS > ${DEVICE_DIR}/${pool}-add
+	else
+		echo ${pool}: add $devtype vdev failed ${errmsg}, in $SECONDS secs
+	fi
+}
+
+function pool_stats
+{
+	typeset stats=$1
+	typeset pool=$2
+
+	SECONDS=0
+	errmsg=$(zpool $stats $pool 2>&1 > /dev/null)
+	if [[ $? -eq 0 ]]; then
+		echo ${pool}: $stats in $SECONDS secs
+		echo $SECONDS > ${DEVICE_DIR}/${pool}-${stats}
+	else
+		echo ${pool}: $stats failed ${errmsg}, in $SECONDS secs
+	fi
+}
+
+function pool_create
+{
+	typeset pool=$1
+	typeset device=$2
+
+	SECONDS=0
+	errmsg=$(zpool create $pool $device 2>&1 > /dev/null)
+	if [[ $? -eq 0 ]]; then
+		echo ${pool}: created in $SECONDS secs
+		echo $SECONDS > ${DEVICE_DIR}/${pool}-create
+	else
+		echo ${pool}: create failed ${errmsg}, in $SECONDS secs
+	fi
+}
+
+log_assert "Simple admin commands to different pool not blocked by import"
+
+log_onexit cleanup
+
+#
+# create two pools and export one
+#
+log_must zpool create $TESTPOOL1 $VDEV0
+log_must zpool export $TESTPOOL1
+log_must zpool create $TESTPOOL2 $VDEV1
+
+#
+# import pool asyncronously with an injected 10 second delay
+#
+log_must zinject -P import -s 10 $TESTPOOL1
+pool_import $DEVICE_DIR $TESTPOOL1 &
+
+sleep 2
+
+#
+# run some admin commands on the pools while the import is in progress
+#
+
+pool_add_device $TESTPOOL1 $VDEV2 "log" &
+pool_add_device $TESTPOOL2 $VDEV3 "cache" &
+pool_stats "status" $TESTPOOL1 &
+pool_stats "status" $TESTPOOL2 &
+pool_stats "list" $TESTPOOL1 &
+pool_stats "list" $TESTPOOL2 &
+pool_create $TESTPOOL1 $VDEV4 &
+wait
+
+log_must zpool sync $TESTPOOL1 $TESTPOOL2
+
+zpool history $TESTPOOL1
+zpool history $TESTPOOL2
+
+log_must test "5" -lt $(<${DEVICE_DIR}/${TESTPOOL1}-import)
+
+#
+# verify that commands to second pool did not wait for import to finish
+#
+log_must test "2" -gt $(<${DEVICE_DIR}/${TESTPOOL2}-status)
+log_must test "2" -gt $(<${DEVICE_DIR}/${TESTPOOL2}-list)
+log_must test "2" -gt $(<${DEVICE_DIR}/${TESTPOOL2}-add)
+[[ -e ${DEVICE_DIR}/${TESTPOOL1}-create ]] && log_fail "unexpected pool create"
+
+log_pass "Simple admin commands to different pool not blocked by import"

tests/zfs-tests/tests/functional/cli_root/zpool_import/zpool_import_parallel_neg.ksh

@@ -0,0 +1,130 @@
+#!/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) 2023 Klara, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.cfg
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.kshlib
+
+#
+# DESCRIPTION:
+# 	Verify that pool imports by same name only have one winner
+#
+# STRATEGY:
+#	1. Create 4 single disk pools with the same name
+#	2. Generate some ZIL records (for a longer import)
+#	3. Export the pools
+#	4. Import the pools in parallel
+#	5. Repeat with using matching guids
+#
+
+verify_runnable "global"
+
+POOLNAME="import_pool"
+DEV_DIR_PREFIX="$DEVICE_DIR/$POOLNAME"
+VDEVSIZE=$((512 * 1024 * 1024))
+
+log_assert "parallel pool imports by same name only have one winner"
+
+# each pool has its own device directory
+for i in {0..3}; do
+	log_must mkdir -p ${DEV_DIR_PREFIX}$i
+	log_must truncate -s $VDEVSIZE ${DEV_DIR_PREFIX}$i/${DEVICE_FILE}$i
+done
+
+function cleanup
+{
+	zinject -c all
+	log_must set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 0
+	log_must set_tunable64 METASLAB_DEBUG_LOAD 0
+
+	destroy_pool $POOLNAME
+
+	log_must rm -rf $DEV_DIR_PREFIX*
+}
+
+log_onexit cleanup
+
+log_must set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 1
+log_must set_tunable64 METASLAB_DEBUG_LOAD 1
+
+function import_pool
+{
+	typeset dir=$1
+	typeset pool=$2
+	typeset newname=$3
+
+	SECONDS=0
+	errmsg=$(zpool import -N -d $dir -f $pool $newname 2>&1 > /dev/null)
+	if [[ $? -eq 0 ]]; then
+		touch $dir/imported
+		echo "imported $pool in $SECONDS secs"
+	elif [[ $errmsg == *"cannot import"* ]]; then
+		echo "pool import failed: $errmsg, waited $SECONDS secs"
+		touch $dir/failed
+	fi
+}
+
+#
+# create four exported pools with the same name
+#
+for i in {0..3}; do
+	log_must zpool create $POOLNAME ${DEV_DIR_PREFIX}$i/${DEVICE_FILE}$i
+	log_must zpool export $POOLNAME
+done
+log_must zinject -P import -s 10 $POOLNAME
+
+#
+# import the pools in parallel, expecting only one winner
+#
+for i in {0..3}; do
+	import_pool ${DEV_DIR_PREFIX}$i $POOLNAME &
+done
+wait
+
+# check the result of background imports
+typeset num_imports=0
+typeset num_cannot=0
+for i in {0..3}; do
+	if [[ -f ${DEV_DIR_PREFIX}$i/imported ]]; then
+		((num_imports += 1))
+	fi
+	if [[ -f ${DEV_DIR_PREFIX}$i/failed ]]; then
+		((num_cannot += 1))
+		loser=$i
+	fi
+done
+[[ $num_imports -eq "1" ]] || log_fail "expecting an import"
+[[ $num_cannot -eq "3" ]] || \
+    log_fail "expecting 3 pool exists errors, found $num_cannot"
+
+log_note "$num_imports imported and $num_cannot failed (expected)"
+
+log_pass "parallel pool imports by same name only have one winner"

tests/zfs-tests/tests/functional/cli_root/zpool_import/zpool_import_parallel_pos.ksh

@@ -0,0 +1,137 @@
+#!/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) 2023 Klara, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.cfg
+. $STF_SUITE/tests/functional/cli_root/zpool_import/zpool_import.kshlib
+
+# test uses 8 vdevs
+export MAX_NUM=8
+
+#
+# DESCRIPTION:
+# 	Verify that pool imports can occur in parallel
+#
+# STRATEGY:
+#	1. Create 8 pools
+#	2. Generate some ZIL records
+#	3. Export the pools
+#	4. Import half of the pools synchronously to baseline sequential cost
+#	5. Import the other half asynchronously to demonstrate parallel savings
+#	6. Export 4 pools
+#	7. Test zpool import -a
+#
+
+verify_runnable "global"
+
+#
+# override the minimum sized vdevs
+#
+VDEVSIZE=$((512 * 1024 * 1024))
+increase_device_sizes $VDEVSIZE
+
+POOLNAME="import_pool"
+
+function cleanup
+{
+	zinject -c all
+	log_must set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 0
+	log_must set_tunable64 METASLAB_DEBUG_LOAD 0
+
+	for i in {0..$(($MAX_NUM - 1))}; do
+		destroy_pool $POOLNAME-$i
+	done
+	# reset the devices
+	increase_device_sizes 0
+	increase_device_sizes $FILE_SIZE
+}
+
+log_assert "Pool imports can occur in parallel"
+
+log_onexit cleanup
+
+log_must set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 1
+log_must set_tunable64 METASLAB_DEBUG_LOAD 1
+
+
+#
+# create some exported pools with import delay injectors
+#
+for i in {0..$(($MAX_NUM - 1))}; do
+	log_must zpool create $POOLNAME-$i $DEVICE_DIR/${DEVICE_FILE}$i
+	log_must zpool export $POOLNAME-$i
+	log_must zinject -P import -s 12 $POOLNAME-$i
+done
+wait
+
+#
+# import half of the pools synchronously
+#
+SECONDS=0
+for i in {0..3}; do
+	log_must zpool import -d $DEVICE_DIR -f $POOLNAME-$i
+done
+sequential_time=$SECONDS
+log_note "sequentially imported 4 pools in $sequential_time seconds"
+
+#
+# import half of the pools in parallel
+#
+SECONDS=0
+for i in {4..7}; do
+	log_must zpool import -d $DEVICE_DIR -f $POOLNAME-$i &
+done
+wait
+parallel_time=$SECONDS
+log_note "asyncronously imported 4 pools in $parallel_time seconds"
+
+log_must test $parallel_time -lt $(($sequential_time / 3))
+
+#
+# export pools with import delay injectors
+#
+for i in {4..7}; do
+	log_must zpool export $POOLNAME-$i
+	log_must zinject -P import -s 12 $POOLNAME-$i
+done
+wait
+
+#
+# now test zpool import -a
+#
+SECONDS=0
+log_must zpool import -a -d $DEVICE_DIR -f
+parallel_time=$SECONDS
+log_note "asyncronously imported 4 pools in $parallel_time seconds"
+
+log_must test $parallel_time -lt $(($sequential_time / 3))
+
+log_pass "Pool imports occur in parallel"