zfs initialize performance enhancements

PROBLEM
========

When invoking "zpool initialize" on a pool the command will
create a thread to initialize each disk. Unfortunately, it does
this serially across many transaction groups which can result
in commands taking a long time to return to the user and may
appear hung. The same thing is true when trying to suspend/cancel
the operation.

SOLUTION
=========

This change refactors the way we invoke the initialize interface
to ensure we can start or stop the intialization in just a few
transaction groups.

When stopping or cancelling a vdev initialization perform it
in two phases.  First signal each vdev initialization thread
that it should exit, then after all threads have been signaled
wait for them to exit.

On a pool with 40 leaf vdevs this reduces the vdev initialize
stop/cancel time from ~10 minutes to under a second.  The reason
for this is spa_vdev_initialize() no longer needs to wait on
multiple full TXGs per leaf vdev being stopped.

This commit additionally adds some missing checks for the passed
"initialize_vdevs" input nvlist.  The contents of the user provided
input "initialize_vdevs" nvlist must be validated to ensure all
values are uint64s.  This is done in zfs_ioc_pool_initialize() in
order to keep all of these checks in a single location.

Updated the innvl and outnvl comments to match the formatting used
for all other new sytle ioctls.

Reviewed by: Matt Ahrens <[email protected]>
Reviewed-by: loli10K <[email protected]>
Reviewed-by: Tim Chase <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: George Wilson <[email protected]>
Closes #8230

10 files changed, 175 insertions, 79 deletions

diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 385984f84..e98fe8cd3 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -6404,7 +6404,14 @@ ztest_initialize(ztest_ds_t *zd, uint64_t id)
 	spa_config_exit(spa, SCL_VDEV, FTAG);
 
 	uint64_t cmd = ztest_random(POOL_INITIALIZE_FUNCS);
-	error = spa_vdev_initialize(spa, guid, cmd);
+
+	nvlist_t *vdev_guids = fnvlist_alloc();
+	nvlist_t *vdev_errlist = fnvlist_alloc();
+	fnvlist_add_uint64(vdev_guids, path, guid);
+	error = spa_vdev_initialize(spa, vdev_guids, cmd, vdev_errlist);
+	fnvlist_free(vdev_guids);
+	fnvlist_free(vdev_errlist);
+
 	switch (cmd) {
 	case POOL_INITIALIZE_CANCEL:
 		if (ztest_opts.zo_verbose >= 4) {
diff --git a/include/sys/spa.h b/include/sys/spa.h
index 4a66260ef..febf0e8f2 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -788,7 +788,8 @@ extern int spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid,
     int replace_done);
 extern int spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare);
 extern boolean_t spa_vdev_remove_active(spa_t *spa);
-extern int spa_vdev_initialize(spa_t *spa, uint64_t guid, uint64_t cmd_type);
+extern int spa_vdev_initialize(spa_t *spa, nvlist_t *nv, uint64_t cmd_type,
+    nvlist_t *vdev_errlist);
 extern int spa_vdev_setpath(spa_t *spa, uint64_t guid, const char *newpath);
 extern int spa_vdev_setfru(spa_t *spa, uint64_t guid, const char *newfru);
 extern int spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h
index ae21e037e..5fe05c54b 100644
--- a/include/sys/vdev_impl.h
+++ b/include/sys/vdev_impl.h
@@ -263,6 +263,7 @@ struct vdev {
 
 	boolean_t	vdev_initialize_exit_wanted;
 	vdev_initializing_state_t	vdev_initialize_state;
+	list_node_t	vdev_initialize_node;
 	kthread_t	*vdev_initialize_thread;
 	/* Protects vdev_initialize_thread and vdev_initialize_state. */
 	kmutex_t	vdev_initialize_lock;
diff --git a/include/sys/vdev_initialize.h b/include/sys/vdev_initialize.h
index db4b0572c..319fb9bc0 100644
--- a/include/sys/vdev_initialize.h
+++ b/include/sys/vdev_initialize.h
@@ -26,15 +26,18 @@
 #ifndef _SYS_VDEV_INITIALIZE_H
 #define	_SYS_VDEV_INITIALIZE_H
 
+#include <sys/spa.h>
+
 #ifdef	__cplusplus
 extern "C" {
 #endif
 
 extern void vdev_initialize(vdev_t *vd);
 extern void vdev_initialize_stop(vdev_t *vd,
-    vdev_initializing_state_t tgt_state);
+    vdev_initializing_state_t tgt_state, list_t *vd_list);
 extern void vdev_initialize_stop_all(vdev_t *vd,
     vdev_initializing_state_t tgt_state);
+extern void vdev_initialize_stop_wait(spa_t *spa, list_t *vd_list);
 extern void vdev_initialize_restart(vdev_t *vd);
 extern void vdev_xlate(vdev_t *vd, const range_seg_t *logical_rs,
     range_seg_t *physical_rs);
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 622be75f9..c4ff5002b 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -6381,32 +6381,24 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid, int replace_done)
 	return (error);
 }
 
-int
-spa_vdev_initialize(spa_t *spa, uint64_t guid, uint64_t cmd_type)
+static int
+spa_vdev_initialize_impl(spa_t *spa, uint64_t guid, uint64_t cmd_type,
+    list_t *vd_list)
 {
-	/*
-	 * We hold the namespace lock through the whole function
-	 * to prevent any changes to the pool while we're starting or
-	 * stopping initialization. The config and state locks are held so that
-	 * we can properly assess the vdev state before we commit to
-	 * the initializing operation.
-	 */
-	mutex_enter(&spa_namespace_lock);
+	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+
 	spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
 
 	/* Look up vdev and ensure it's a leaf. */
 	vdev_t *vd = spa_lookup_by_guid(spa, guid, B_FALSE);
 	if (vd == NULL || vd->vdev_detached) {
 		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(ENODEV));
 	} else if (!vd->vdev_ops->vdev_op_leaf || !vdev_is_concrete(vd)) {
 		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(EINVAL));
 	} else if (!vdev_writeable(vd)) {
 		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(EROFS));
 	}
 	mutex_enter(&vd->vdev_initialize_lock);
@@ -6423,18 +6415,15 @@ spa_vdev_initialize(spa_t *spa, uint64_t guid, uint64_t cmd_type)
 	    (vd->vdev_initialize_thread != NULL ||
 	    vd->vdev_top->vdev_removing)) {
 		mutex_exit(&vd->vdev_initialize_lock);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(EBUSY));
 	} else if (cmd_type == POOL_INITIALIZE_CANCEL &&
 	    (vd->vdev_initialize_state != VDEV_INITIALIZE_ACTIVE &&
 	    vd->vdev_initialize_state != VDEV_INITIALIZE_SUSPENDED)) {
 		mutex_exit(&vd->vdev_initialize_lock);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(ESRCH));
 	} else if (cmd_type == POOL_INITIALIZE_SUSPEND &&
 	    vd->vdev_initialize_state != VDEV_INITIALIZE_ACTIVE) {
 		mutex_exit(&vd->vdev_initialize_lock);
-		mutex_exit(&spa_namespace_lock);
 		return (SET_ERROR(ESRCH));
 	}
 
@@ -6443,23 +6432,65 @@ spa_vdev_initialize(spa_t *spa, uint64_t guid, uint64_t cmd_type)
 		vdev_initialize(vd);
 		break;
 	case POOL_INITIALIZE_CANCEL:
-		vdev_initialize_stop(vd, VDEV_INITIALIZE_CANCELED);
+		vdev_initialize_stop(vd, VDEV_INITIALIZE_CANCELED, vd_list);
 		break;
 	case POOL_INITIALIZE_SUSPEND:
-		vdev_initialize_stop(vd, VDEV_INITIALIZE_SUSPENDED);
+		vdev_initialize_stop(vd, VDEV_INITIALIZE_SUSPENDED, vd_list);
 		break;
 	default:
 		panic("invalid cmd_type %llu", (unsigned long long)cmd_type);
 	}
 	mutex_exit(&vd->vdev_initialize_lock);
 
+	return (0);
+}
+
+int
+spa_vdev_initialize(spa_t *spa, nvlist_t *nv, uint64_t cmd_type,
+    nvlist_t *vdev_errlist)
+{
+	int total_errors = 0;
+	list_t vd_list;
+
+	list_create(&vd_list, sizeof (vdev_t),
+	    offsetof(vdev_t, vdev_initialize_node));
+
+	/*
+	 * We hold the namespace lock through the whole function
+	 * to prevent any changes to the pool while we're starting or
+	 * stopping initialization. The config and state locks are held so that
+	 * we can properly assess the vdev state before we commit to
+	 * the initializing operation.
+	 */
+	mutex_enter(&spa_namespace_lock);
+
+	for (nvpair_t *pair = nvlist_next_nvpair(nv, NULL);
+	    pair != NULL; pair = nvlist_next_nvpair(nv, pair)) {
+		uint64_t vdev_guid = fnvpair_value_uint64(pair);
+
+		int error = spa_vdev_initialize_impl(spa, vdev_guid, cmd_type,
+		    &vd_list);
+		if (error != 0) {
+			char guid_as_str[MAXNAMELEN];
+
+			(void) snprintf(guid_as_str, sizeof (guid_as_str),
+			    "%llu", (unsigned long long)vdev_guid);
+			fnvlist_add_int64(vdev_errlist, guid_as_str, error);
+			total_errors++;
+		}
+	}
+
+	/* Wait for all initialize threads to stop. */
+	vdev_initialize_stop_wait(spa, &vd_list);
+
 	/* Sync out the initializing state */
 	txg_wait_synced(spa->spa_dsl_pool, 0);
 	mutex_exit(&spa_namespace_lock);
 
-	return (0);
-}
+	list_destroy(&vd_list);
 
+	return (total_errors);
+}
 
 /*
  * Split a set of devices from their mirrors, and create a new pool from them.
@@ -6669,18 +6700,25 @@ spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
 	spa_activate(newspa, spa_mode_global);
 	spa_async_suspend(newspa);
 
+	/*
+	 * Temporarily stop the initializing activity. We set the state to
+	 * ACTIVE so that we know to resume the initializing once the split
+	 * has completed.
+	 */
+	list_t vd_list;
+	list_create(&vd_list, sizeof (vdev_t),
+	    offsetof(vdev_t, vdev_initialize_node));
+
 	for (c = 0; c < children; c++) {
 		if (vml[c] != NULL) {
-			/*
-			 * Temporarily stop the initializing activity. We set
-			 * the state to ACTIVE so that we know to resume
-			 * the initializing once the split has completed.
-			 */
 			mutex_enter(&vml[c]->vdev_initialize_lock);
-			vdev_initialize_stop(vml[c], VDEV_INITIALIZE_ACTIVE);
+			vdev_initialize_stop(vml[c], VDEV_INITIALIZE_ACTIVE,
+			    &vd_list);
 			mutex_exit(&vml[c]->vdev_initialize_lock);
 		}
 	}
+	vdev_initialize_stop_wait(spa, &vd_list);
+	list_destroy(&vd_list);
 
 	newspa->spa_config_source = SPA_CONFIG_SRC_SPLIT;
 
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index dfac92d45..877f312b1 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -1197,7 +1197,8 @@ spa_vdev_config_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error, char *tag)
 		ASSERT(!vd->vdev_detached || vd->vdev_dtl_sm == NULL);
 		if (vd->vdev_ops->vdev_op_leaf) {
 			mutex_enter(&vd->vdev_initialize_lock);
-			vdev_initialize_stop(vd, VDEV_INITIALIZE_CANCELED);
+			vdev_initialize_stop(vd, VDEV_INITIALIZE_CANCELED,
+			    NULL);
 			mutex_exit(&vd->vdev_initialize_lock);
 		}
 
diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index f808f8ee7..26ef5b4c5 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -530,6 +530,7 @@ vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
 
 	list_link_init(&vd->vdev_config_dirty_node);
 	list_link_init(&vd->vdev_state_dirty_node);
+	list_link_init(&vd->vdev_initialize_node);
 	mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_NOLOCKDEP, NULL);
 	mutex_init(&vd->vdev_stat_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_probe_lock, NULL, MUTEX_DEFAULT, NULL);
diff --git a/module/zfs/vdev_initialize.c b/module/zfs/vdev_initialize.c
index fcd2c76f9..939a5e938 100644
--- a/module/zfs/vdev_initialize.c
+++ b/module/zfs/vdev_initialize.c
@@ -702,18 +702,51 @@ vdev_initialize(vdev_t *vd)
 }
 
 /*
- * Stop initializng a device, with the resultant initialing state being
- * tgt_state. Blocks until the initializing thread has exited.
- * Caller must hold vdev_initialize_lock and must not be writing to the spa
- * config, as the initializing thread may try to enter the config as a reader
- * before exiting.
+ * Wait for the initialize thread to be terminated (cancelled or stopped).
+ */
+static void
+vdev_initialize_stop_wait_impl(vdev_t *vd)
+{
+	ASSERT(MUTEX_HELD(&vd->vdev_initialize_lock));
+
+	while (vd->vdev_initialize_thread != NULL)
+		cv_wait(&vd->vdev_initialize_cv, &vd->vdev_initialize_lock);
+
+	ASSERT3P(vd->vdev_initialize_thread, ==, NULL);
+	vd->vdev_initialize_exit_wanted = B_FALSE;
+}
+
+/*
+ * Wait for vdev initialize threads which were either to cleanly exit.
  */
 void
-vdev_initialize_stop(vdev_t *vd, vdev_initializing_state_t tgt_state)
+vdev_initialize_stop_wait(spa_t *spa, list_t *vd_list)
 {
-	ASSERTV(spa_t *spa = vd->vdev_spa);
-	ASSERT(!spa_config_held(spa, SCL_CONFIG | SCL_STATE, RW_WRITER));
+	vdev_t *vd;
+
+	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+
+	while ((vd = list_remove_head(vd_list)) != NULL) {
+		mutex_enter(&vd->vdev_initialize_lock);
+		vdev_initialize_stop_wait_impl(vd);
+		mutex_exit(&vd->vdev_initialize_lock);
+	}
+}
 
+/*
+ * Stop initializing a device, with the resultant initialing state being
+ * tgt_state.  For blocking behavior pass NULL for vd_list.  Otherwise, when
+ * a list_t is provided the stopping vdev is inserted in to the list.  Callers
+ * are then required to call vdev_initialize_stop_wait() to block for all the
+ * initialization threads to exit.  The caller must hold vdev_initialize_lock
+ * and must not be writing to the spa config, as the initializing thread may
+ * try to enter the config as a reader before exiting.
+ */
+void
+vdev_initialize_stop(vdev_t *vd, vdev_initializing_state_t tgt_state,
+    list_t *vd_list)
+{
+	ASSERT(!spa_config_held(vd->vdev_spa, SCL_CONFIG|SCL_STATE, RW_WRITER));
 	ASSERT(MUTEX_HELD(&vd->vdev_initialize_lock));
 	ASSERT(vd->vdev_ops->vdev_op_leaf);
 	ASSERT(vdev_is_concrete(vd));
@@ -729,25 +762,29 @@ vdev_initialize_stop(vdev_t *vd, vdev_initializing_state_t tgt_state)
 
 	vdev_initialize_change_state(vd, tgt_state);
 	vd->vdev_initialize_exit_wanted = B_TRUE;
-	while (vd->vdev_initialize_thread != NULL)
-		cv_wait(&vd->vdev_initialize_cv, &vd->vdev_initialize_lock);
 
-	ASSERT3P(vd->vdev_initialize_thread, ==, NULL);
-	vd->vdev_initialize_exit_wanted = B_FALSE;
+	if (vd_list == NULL) {
+		vdev_initialize_stop_wait_impl(vd);
+	} else {
+		ASSERT(MUTEX_HELD(&spa_namespace_lock));
+		list_insert_tail(vd_list, vd);
+	}
 }
 
 static void
-vdev_initialize_stop_all_impl(vdev_t *vd, vdev_initializing_state_t tgt_state)
+vdev_initialize_stop_all_impl(vdev_t *vd, vdev_initializing_state_t tgt_state,
+    list_t *vd_list)
 {
 	if (vd->vdev_ops->vdev_op_leaf && vdev_is_concrete(vd)) {
 		mutex_enter(&vd->vdev_initialize_lock);
-		vdev_initialize_stop(vd, tgt_state);
+		vdev_initialize_stop(vd, tgt_state, vd_list);
 		mutex_exit(&vd->vdev_initialize_lock);
 		return;
 	}
 
 	for (uint64_t i = 0; i < vd->vdev_children; i++) {
-		vdev_initialize_stop_all_impl(vd->vdev_child[i], tgt_state);
+		vdev_initialize_stop_all_impl(vd->vdev_child[i], tgt_state,
+		    vd_list);
 	}
 }
 
@@ -758,12 +795,23 @@ vdev_initialize_stop_all_impl(vdev_t *vd, vdev_initializing_state_t tgt_state)
 void
 vdev_initialize_stop_all(vdev_t *vd, vdev_initializing_state_t tgt_state)
 {
-	vdev_initialize_stop_all_impl(vd, tgt_state);
+	spa_t *spa = vd->vdev_spa;
+	list_t vd_list;
+
+	ASSERT(MUTEX_HELD(&spa_namespace_lock));
+
+	list_create(&vd_list, sizeof (vdev_t),
+	    offsetof(vdev_t, vdev_initialize_node));
+
+	vdev_initialize_stop_all_impl(vd, tgt_state, &vd_list);
+	vdev_initialize_stop_wait(spa, &vd_list);
 
 	if (vd->vdev_spa->spa_sync_on) {
 		/* Make sure that our state has been synced to disk */
 		txg_wait_synced(spa_get_dsl(vd->vdev_spa), 0);
 	}
+
+	list_destroy(&vd_list);
 }
 
 void
@@ -808,9 +856,10 @@ vdev_initialize_restart(vdev_t *vd)
 #if defined(_KERNEL)
 EXPORT_SYMBOL(vdev_initialize_restart);
 EXPORT_SYMBOL(vdev_xlate);
-EXPORT_SYMBOL(vdev_initialize_stop_all);
 EXPORT_SYMBOL(vdev_initialize);
 EXPORT_SYMBOL(vdev_initialize_stop);
+EXPORT_SYMBOL(vdev_initialize_stop_all);
+EXPORT_SYMBOL(vdev_initialize_stop_wait);
 
 /* CSTYLED */
 module_param(zfs_initialize_value, ulong, 0644);
diff --git a/module/zfs/vdev_removal.c b/module/zfs/vdev_removal.c
index d0824aa84..1896e824f 100644
--- a/module/zfs/vdev_removal.c
+++ b/module/zfs/vdev_removal.c
@@ -1899,7 +1899,7 @@ spa_vdev_remove_log(vdev_t *vd, uint64_t *txg)
 	spa_vdev_config_exit(spa, NULL, *txg, 0, FTAG);
 
 	/* Stop initializing */
-	(void) vdev_initialize_stop_all(vd, VDEV_INITIALIZE_CANCELED);
+	vdev_initialize_stop_all(vd, VDEV_INITIALIZE_CANCELED);
 
 	*txg = spa_vdev_config_enter(spa);
 
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 3c36502d8..0dfa01684 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -3846,73 +3846,68 @@ zfs_ioc_destroy(zfs_cmd_t *zc)
 
 /*
  * innvl: {
- *     vdevs: {
- *         guid 1, guid 2, ...
+ *     "initialize_command" -> POOL_INITIALIZE_{CANCEL|DO|SUSPEND} (uint64)
+ *     "initialize_vdevs": { -> guids to initialize (nvlist)
+ *         "vdev_path_1": vdev_guid_1, (uint64),
+ *         "vdev_path_2": vdev_guid_2, (uint64),
+ *         ...
  *     },
- *     func: POOL_INITIALIZE_{CANCEL|DO|SUSPEND}
  * }
  *
  * outnvl: {
- *     [func: EINVAL (if provided command type didn't make sense)],
- *     [vdevs: {
- *         guid1: errno, (see function body for possible errnos)
+ *     "initialize_vdevs": { -> initialization errors (nvlist)
+ *         "vdev_path_1": errno, see function body for possible errnos (uint64)
+ *         "vdev_path_2": errno, ... (uint64)
  *         ...
- *     }]
+ *     }
  * }
  *
+ * EINVAL is returned for an unknown commands or if any of the provided vdev
+ * guids have be specified with a type other than uint64.
  */
 static const zfs_ioc_key_t zfs_keys_pool_initialize[] = {
-	{ZPOOL_INITIALIZE_COMMAND,	DATA_TYPE_UINT64, 	0},
+	{ZPOOL_INITIALIZE_COMMAND,	DATA_TYPE_UINT64,	0},
 	{ZPOOL_INITIALIZE_VDEVS,	DATA_TYPE_NVLIST,	0}
 };
 
 static int
 zfs_ioc_pool_initialize(const char *poolname, nvlist_t *innvl, nvlist_t *outnvl)
 {
-	spa_t *spa;
-	int error;
-
-	error = spa_open(poolname, &spa, FTAG);
-	if (error != 0)
-		return (error);
-
 	uint64_t cmd_type;
 	if (nvlist_lookup_uint64(innvl, ZPOOL_INITIALIZE_COMMAND,
 	    &cmd_type) != 0) {
-		spa_close(spa, FTAG);
 		return (SET_ERROR(EINVAL));
 	}
+
 	if (!(cmd_type == POOL_INITIALIZE_CANCEL ||
 	    cmd_type == POOL_INITIALIZE_DO ||
 	    cmd_type == POOL_INITIALIZE_SUSPEND)) {
-		spa_close(spa, FTAG);
 		return (SET_ERROR(EINVAL));
 	}
 
 	nvlist_t *vdev_guids;
 	if (nvlist_lookup_nvlist(innvl, ZPOOL_INITIALIZE_VDEVS,
 	    &vdev_guids) != 0) {
-		spa_close(spa, FTAG);
 		return (SET_ERROR(EINVAL));
 	}
 
-	nvlist_t *vdev_errlist = fnvlist_alloc();
-	int total_errors = 0;
-
 	for (nvpair_t *pair = nvlist_next_nvpair(vdev_guids, NULL);
 	    pair != NULL; pair = nvlist_next_nvpair(vdev_guids, pair)) {
-		uint64_t vdev_guid = fnvpair_value_uint64(pair);
-
-		error = spa_vdev_initialize(spa, vdev_guid, cmd_type);
-		if (error != 0) {
-			char guid_as_str[MAXNAMELEN];
-
-			(void) snprintf(guid_as_str, sizeof (guid_as_str),
-			    "%llu", (unsigned long long)vdev_guid);
-			fnvlist_add_int64(vdev_errlist, guid_as_str, error);
-			total_errors++;
+		uint64_t vdev_guid;
+		if (nvpair_value_uint64(pair, &vdev_guid) != 0) {
+			return (SET_ERROR(EINVAL));
 		}
 	}
+
+	spa_t *spa;
+	int error = spa_open(poolname, &spa, FTAG);
+	if (error != 0)
+		return (error);
+
+	nvlist_t *vdev_errlist = fnvlist_alloc();
+	int total_errors = spa_vdev_initialize(spa, vdev_guids, cmd_type,
+	    vdev_errlist);
+
 	if (fnvlist_size(vdev_errlist) > 0) {
 		fnvlist_add_nvlist(outnvl, ZPOOL_INITIALIZE_VDEVS,
 		    vdev_errlist);