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

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