]> git.proxmox.com Git - mirror_zfs.git/blobdiff - module/zfs/spa.c
Simplify spa_sync by breaking it up to smaller functions
[mirror_zfs.git] / module / zfs / spa.c
index 1e9e7b0131b935ed2c3cdde7011468ebe15cf691..bbe2f89629a5ab1a905522dbf396e53728f3e8a9 100644 (file)
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
- * Copyright (c) 2015, Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2013, 2014, Nexenta Systems, Inc.  All rights reserved.
+ * Copyright (c) 2018, Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  * Copyright 2013 Saso Kiselkov. All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
  * Copyright 2016 Toomas Soome <tsoome@me.com>
  * Copyright (c) 2016 Actifio, Inc. All rights reserved.
+ * Copyright 2018 Joyent, Inc.
  * Copyright (c) 2017 Datto Inc.
  * Copyright 2017 Joyent, Inc.
+ * Copyright (c) 2017, Intel Corporation.
  */
 
 /*
 #include <sys/zil.h>
 #include <sys/ddt.h>
 #include <sys/vdev_impl.h>
+#include <sys/vdev_removal.h>
+#include <sys/vdev_indirect_mapping.h>
+#include <sys/vdev_indirect_births.h>
+#include <sys/vdev_initialize.h>
 #include <sys/vdev_disk.h>
 #include <sys/metaslab.h>
 #include <sys/metaslab_impl.h>
@@ -59,6 +64,7 @@
 #include <sys/uberblock_impl.h>
 #include <sys/txg.h>
 #include <sys/avl.h>
+#include <sys/bpobj.h>
 #include <sys/dmu_traverse.h>
 #include <sys/dmu_objset.h>
 #include <sys/unique.h>
 #ifdef _KERNEL
 #include <sys/fm/protocol.h>
 #include <sys/fm/util.h>
-#include <sys/bootprops.h>
 #include <sys/callb.h>
-#include <sys/cpupart.h>
-#include <sys/pool.h>
-#include <sys/sysdc.h>
 #include <sys/zone.h>
 #endif /* _KERNEL */
 
@@ -96,7 +98,7 @@
  * The interval, in seconds, at which failed configuration cache file writes
  * should be retried.
  */
-static int zfs_ccw_retry_interval = 300;
+int zfs_ccw_retry_interval = 300;
 
 typedef enum zti_modes {
        ZTI_MODE_FIXED,                 /* value is # of threads (min 1) */
@@ -150,30 +152,84 @@ const zio_taskq_info_t zio_taskqs[ZIO_TYPES][ZIO_TASKQ_TYPES] = {
        { ZTI_ONE,      ZTI_NULL,       ZTI_ONE,        ZTI_NULL }, /* IOCTL */
 };
 
-static sysevent_t *spa_event_create(spa_t *spa, vdev_t *vd, nvlist_t *hist_nvl,
-    const char *name);
-static void spa_event_post(sysevent_t *ev);
 static void spa_sync_version(void *arg, dmu_tx_t *tx);
 static void spa_sync_props(void *arg, dmu_tx_t *tx);
 static boolean_t spa_has_active_shared_spare(spa_t *spa);
-static inline int spa_load_impl(spa_t *spa, uint64_t, nvlist_t *config,
-    spa_load_state_t state, spa_import_type_t type, boolean_t mosconfig,
-    char **ereport);
+static int spa_load_impl(spa_t *spa, spa_import_type_t type, char **ereport);
 static void spa_vdev_resilver_done(spa_t *spa);
 
 uint_t         zio_taskq_batch_pct = 75;       /* 1 thread per cpu in pset */
-id_t           zio_taskq_psrset_bind = PS_NONE;
 boolean_t      zio_taskq_sysdc = B_TRUE;       /* use SDC scheduling class */
 uint_t         zio_taskq_basedc = 80;          /* base duty cycle */
 
 boolean_t      spa_create_process = B_TRUE;    /* no process ==> no sysdc */
 
+/*
+ * Report any spa_load_verify errors found, but do not fail spa_load.
+ * This is used by zdb to analyze non-idle pools.
+ */
+boolean_t      spa_load_verify_dryrun = B_FALSE;
+
 /*
  * This (illegal) pool name is used when temporarily importing a spa_t in order
  * to get the vdev stats associated with the imported devices.
  */
 #define        TRYIMPORT_NAME  "$import"
 
+/*
+ * For debugging purposes: print out vdev tree during pool import.
+ */
+int            spa_load_print_vdev_tree = B_FALSE;
+
+/*
+ * A non-zero value for zfs_max_missing_tvds means that we allow importing
+ * pools with missing top-level vdevs. This is strictly intended for advanced
+ * pool recovery cases since missing data is almost inevitable. Pools with
+ * missing devices can only be imported read-only for safety reasons, and their
+ * fail-mode will be automatically set to "continue".
+ *
+ * With 1 missing vdev we should be able to import the pool and mount all
+ * datasets. User data that was not modified after the missing device has been
+ * added should be recoverable. This means that snapshots created prior to the
+ * addition of that device should be completely intact.
+ *
+ * With 2 missing vdevs, some datasets may fail to mount since there are
+ * dataset statistics that are stored as regular metadata. Some data might be
+ * recoverable if those vdevs were added recently.
+ *
+ * With 3 or more missing vdevs, the pool is severely damaged and MOS entries
+ * may be missing entirely. Chances of data recovery are very low. Note that
+ * there are also risks of performing an inadvertent rewind as we might be
+ * missing all the vdevs with the latest uberblocks.
+ */
+unsigned long  zfs_max_missing_tvds = 0;
+
+/*
+ * The parameters below are similar to zfs_max_missing_tvds but are only
+ * intended for a preliminary open of the pool with an untrusted config which
+ * might be incomplete or out-dated.
+ *
+ * We are more tolerant for pools opened from a cachefile since we could have
+ * an out-dated cachefile where a device removal was not registered.
+ * We could have set the limit arbitrarily high but in the case where devices
+ * are really missing we would want to return the proper error codes; we chose
+ * SPA_DVAS_PER_BP - 1 so that some copies of the MOS would still be available
+ * and we get a chance to retrieve the trusted config.
+ */
+uint64_t       zfs_max_missing_tvds_cachefile = SPA_DVAS_PER_BP - 1;
+
+/*
+ * In the case where config was assembled by scanning device paths (/dev/dsks
+ * by default) we are less tolerant since all the existing devices should have
+ * been detected and we want spa_load to return the right error codes.
+ */
+uint64_t       zfs_max_missing_tvds_scan = 0;
+
+/*
+ * Debugging aid that pauses spa_sync() towards the end.
+ */
+boolean_t      zfs_pause_spa_sync = B_FALSE;
+
 /*
  * ==========================================================================
  * SPA properties routines
@@ -218,13 +274,21 @@ spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
        ASSERT(MUTEX_HELD(&spa->spa_props_lock));
 
        if (rvd != NULL) {
-               alloc = metaslab_class_get_alloc(spa_normal_class(spa));
-               size = metaslab_class_get_space(spa_normal_class(spa));
+               alloc = metaslab_class_get_alloc(mc);
+               alloc += metaslab_class_get_alloc(spa_special_class(spa));
+               alloc += metaslab_class_get_alloc(spa_dedup_class(spa));
+
+               size = metaslab_class_get_space(mc);
+               size += metaslab_class_get_space(spa_special_class(spa));
+               size += metaslab_class_get_space(spa_dedup_class(spa));
+
                spa_prop_add_list(*nvp, ZPOOL_PROP_NAME, spa_name(spa), 0, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_SIZE, NULL, size, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_ALLOCATED, NULL, alloc, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_FREE, NULL,
                    size - alloc, src);
+               spa_prop_add_list(*nvp, ZPOOL_PROP_CHECKPOINT, NULL,
+                   spa->spa_checkpoint_info.sci_dspace, src);
 
                spa_prop_add_list(*nvp, ZPOOL_PROP_FRAGMENTATION, NULL,
                    metaslab_class_fragmentation(mc), src);
@@ -250,6 +314,8 @@ spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
                        spa_prop_add_list(*nvp, ZPOOL_PROP_VERSION, NULL,
                            version, ZPROP_SRC_LOCAL);
                }
+               spa_prop_add_list(*nvp, ZPOOL_PROP_LOAD_GUID,
+                   NULL, spa_load_guid(spa), src);
        }
 
        if (pool != NULL) {
@@ -369,8 +435,9 @@ spa_prop_get(spa_t *spa, nvlist_t **nvp)
 
                                dp = spa_get_dsl(spa);
                                dsl_pool_config_enter(dp, FTAG);
-                               if ((err = dsl_dataset_hold_obj(dp,
-                                   za.za_first_integer, FTAG, &ds))) {
+                               err = dsl_dataset_hold_obj(dp,
+                                   za.za_first_integer, FTAG, &ds);
+                               if (err != 0) {
                                        dsl_pool_config_exit(dp, FTAG);
                                        break;
                                }
@@ -536,7 +603,7 @@ spa_prop_validate(spa_t *spa, nvlist_t *props)
                                }
 
                                error = dmu_objset_hold(strval, FTAG, &os);
-                               if (error)
+                               if (error != 0)
                                        break;
 
                                /*
@@ -762,6 +829,12 @@ spa_change_guid_check(void *arg, dmu_tx_t *tx)
        vdev_t *rvd = spa->spa_root_vdev;
        uint64_t vdev_state;
 
+       if (spa_feature_is_active(spa, SPA_FEATURE_POOL_CHECKPOINT)) {
+               int error = (spa_has_checkpoint(spa)) ?
+                   ZFS_ERR_CHECKPOINT_EXISTS : ZFS_ERR_DISCARDING_CHECKPOINT;
+               return (SET_ERROR(error));
+       }
+
        spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
        vdev_state = rvd->vdev_state;
        spa_config_exit(spa, SCL_STATE, FTAG);
@@ -817,7 +890,7 @@ spa_change_guid(spa_t *spa)
            spa_change_guid_sync, &guid, 5, ZFS_SPACE_CHECK_RESERVED);
 
        if (error == 0) {
-               spa_config_sync(spa, B_FALSE, B_TRUE);
+               spa_write_cachefile(spa, B_FALSE, B_TRUE);
                spa_event_notify(spa, NULL, NULL, ESC_ZFS_POOL_REGUID);
        }
 
@@ -874,7 +947,6 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
        uint_t value = ztip->zti_value;
        uint_t count = ztip->zti_count;
        spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
-       char name[32];
        uint_t flags = 0;
        boolean_t batch = B_FALSE;
 
@@ -911,14 +983,10 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
 
        for (uint_t i = 0; i < count; i++) {
                taskq_t *tq;
+               char name[32];
 
-               if (count > 1) {
-                       (void) snprintf(name, sizeof (name), "%s_%s_%u",
-                           zio_type_name[t], zio_taskq_types[q], i);
-               } else {
-                       (void) snprintf(name, sizeof (name), "%s_%s",
-                           zio_type_name[t], zio_taskq_types[q]);
-               }
+               (void) snprintf(name, sizeof (name), "%s_%s",
+                   zio_type_name[t], zio_taskq_types[q]);
 
                if (zio_taskq_sysdc && spa->spa_proc != &p0) {
                        if (batch)
@@ -1034,6 +1102,7 @@ spa_create_zio_taskqs(spa_t *spa)
 static void
 spa_thread(void *arg)
 {
+       psetid_t zio_taskq_psrset_bind = PS_NONE;
        callb_cpr_t cprinfo;
 
        spa_t *spa = arg;
@@ -1113,6 +1182,8 @@ spa_activate(spa_t *spa, int mode)
 
        spa->spa_normal_class = metaslab_class_create(spa, zfs_metaslab_ops);
        spa->spa_log_class = metaslab_class_create(spa, zfs_metaslab_ops);
+       spa->spa_special_class = metaslab_class_create(spa, zfs_metaslab_ops);
+       spa->spa_dedup_class = metaslab_class_create(spa, zfs_metaslab_ops);
 
        /* Try to create a covering process */
        mutex_enter(&spa->spa_proc_lock);
@@ -1149,6 +1220,11 @@ spa_activate(spa_t *spa, int mode)
                spa_create_zio_taskqs(spa);
        }
 
+       for (size_t i = 0; i < TXG_SIZE; i++) {
+               spa->spa_txg_zio[i] = zio_root(spa, NULL, NULL,
+                   ZIO_FLAG_CANFAIL);
+       }
+
        list_create(&spa->spa_config_dirty_list, sizeof (vdev_t),
            offsetof(vdev_t, vdev_config_dirty_node));
        list_create(&spa->spa_evicting_os_list, sizeof (objset_t),
@@ -1186,6 +1262,14 @@ spa_activate(spa_t *spa, int mode)
        spa->spa_zvol_taskq = taskq_create("z_zvol", 1, defclsyspri,
            1, INT_MAX, 0);
 
+       /*
+        * Taskq dedicated to prefetcher threads: this is used to prevent the
+        * pool traverse code from monopolizing the global (and limited)
+        * system_taskq by inappropriately scheduling long running tasks on it.
+        */
+       spa->spa_prefetch_taskq = taskq_create("z_prefetch", boot_ncpus,
+           defclsyspri, 1, INT_MAX, TASKQ_DYNAMIC);
+
        /*
         * The taskq to upgrade datasets in this pool. Currently used by
         * feature SPA_FEATURE_USEROBJ_ACCOUNTING/SPA_FEATURE_PROJECT_QUOTA.
@@ -1213,6 +1297,11 @@ spa_deactivate(spa_t *spa)
                spa->spa_zvol_taskq = NULL;
        }
 
+       if (spa->spa_prefetch_taskq) {
+               taskq_destroy(spa->spa_prefetch_taskq);
+               spa->spa_prefetch_taskq = NULL;
+       }
+
        if (spa->spa_upgrade_taskq) {
                taskq_destroy(spa->spa_upgrade_taskq);
                spa->spa_upgrade_taskq = NULL;
@@ -1232,12 +1321,24 @@ spa_deactivate(spa_t *spa)
                }
        }
 
+       for (size_t i = 0; i < TXG_SIZE; i++) {
+               ASSERT3P(spa->spa_txg_zio[i], !=, NULL);
+               VERIFY0(zio_wait(spa->spa_txg_zio[i]));
+               spa->spa_txg_zio[i] = NULL;
+       }
+
        metaslab_class_destroy(spa->spa_normal_class);
        spa->spa_normal_class = NULL;
 
        metaslab_class_destroy(spa->spa_log_class);
        spa->spa_log_class = NULL;
 
+       metaslab_class_destroy(spa->spa_special_class);
+       spa->spa_special_class = NULL;
+
+       metaslab_class_destroy(spa->spa_dedup_class);
+       spa->spa_dedup_class = NULL;
+
        /*
         * If this was part of an import or the open otherwise failed, we may
         * still have errors left in the queues.  Empty them just in case.
@@ -1333,11 +1434,18 @@ spa_unload(spa_t *spa)
 
        ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
+       spa_load_note(spa, "UNLOADING");
+
        /*
         * Stop async tasks.
         */
        spa_async_suspend(spa);
 
+       if (spa->spa_root_vdev) {
+               vdev_initialize_stop_all(spa->spa_root_vdev,
+                   VDEV_INITIALIZE_ACTIVE);
+       }
+
        /*
         * Stop syncing.
         */
@@ -1353,10 +1461,10 @@ spa_unload(spa_t *spa)
         * calling taskq_wait(mg_taskq).
         */
        if (spa->spa_root_vdev != NULL) {
-               spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+               spa_config_enter(spa, SCL_ALL, spa, RW_WRITER);
                for (int c = 0; c < spa->spa_root_vdev->vdev_children; c++)
                        vdev_metaslab_fini(spa->spa_root_vdev->vdev_child[c]);
-               spa_config_exit(spa, SCL_ALL, FTAG);
+               spa_config_exit(spa, SCL_ALL, spa);
        }
 
        if (spa->spa_mmp.mmp_thread)
@@ -1372,9 +1480,26 @@ spa_unload(spa_t *spa)
                spa->spa_async_zio_root = NULL;
        }
 
+       if (spa->spa_vdev_removal != NULL) {
+               spa_vdev_removal_destroy(spa->spa_vdev_removal);
+               spa->spa_vdev_removal = NULL;
+       }
+
+       if (spa->spa_condense_zthr != NULL) {
+               zthr_destroy(spa->spa_condense_zthr);
+               spa->spa_condense_zthr = NULL;
+       }
+
+       if (spa->spa_checkpoint_discard_zthr != NULL) {
+               zthr_destroy(spa->spa_checkpoint_discard_zthr);
+               spa->spa_checkpoint_discard_zthr = NULL;
+       }
+
+       spa_condense_fini(spa);
+
        bpobj_close(&spa->spa_deferred_bpobj);
 
-       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+       spa_config_enter(spa, SCL_ALL, spa, RW_WRITER);
 
        /*
         * Close all vdevs.
@@ -1429,12 +1554,14 @@ spa_unload(spa_t *spa)
 
        spa->spa_async_suspended = 0;
 
+       spa->spa_indirect_vdevs_loaded = B_FALSE;
+
        if (spa->spa_comment != NULL) {
                spa_strfree(spa->spa_comment);
                spa->spa_comment = NULL;
        }
 
-       spa_config_exit(spa, SCL_ALL, FTAG);
+       spa_config_exit(spa, SCL_ALL, spa);
 }
 
 /*
@@ -1443,7 +1570,7 @@ spa_unload(spa_t *spa)
  * 'spa_spares.sav_config'.  We parse this into vdevs, try to open them, and
  * then re-generate a more complete list including status information.
  */
-static void
+void
 spa_load_spares(spa_t *spa)
 {
        nvlist_t **spares;
@@ -1451,6 +1578,18 @@ spa_load_spares(spa_t *spa)
        int i;
        vdev_t *vd, *tvd;
 
+#ifndef _KERNEL
+       /*
+        * zdb opens both the current state of the pool and the
+        * checkpointed state (if present), with a different spa_t.
+        *
+        * As spare vdevs are shared among open pools, we skip loading
+        * them when we load the checkpointed state of the pool.
+        */
+       if (!spa_writeable(spa))
+               return;
+#endif
+
        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
        /*
@@ -1560,7 +1699,7 @@ spa_load_spares(spa_t *spa)
  * Devices which are already active have their details maintained, and are
  * not re-opened.
  */
-static void
+void
 spa_load_l2cache(spa_t *spa)
 {
        nvlist_t **l2cache = NULL;
@@ -1570,6 +1709,19 @@ spa_load_l2cache(spa_t *spa)
        vdev_t *vd, **oldvdevs, **newvdevs;
        spa_aux_vdev_t *sav = &spa->spa_l2cache;
 
+#ifndef _KERNEL
+       /*
+        * zdb opens both the current state of the pool and the
+        * checkpointed state (if present), with a different spa_t.
+        *
+        * As L2 caches are part of the ARC which is shared among open
+        * pools, we skip loading them when we load the checkpointed
+        * state of the pool.
+        */
+       if (!spa_writeable(spa))
+               return;
+#endif
+
        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
        oldvdevs = sav->sav_vdevs;
@@ -1710,6 +1862,27 @@ load_nvlist(spa_t *spa, uint64_t obj, nvlist_t **value)
        return (error);
 }
 
+/*
+ * Concrete top-level vdevs that are not missing and are not logs. At every
+ * spa_sync we write new uberblocks to at least SPA_SYNC_MIN_VDEVS core tvds.
+ */
+static uint64_t
+spa_healthy_core_tvds(spa_t *spa)
+{
+       vdev_t *rvd = spa->spa_root_vdev;
+       uint64_t tvds = 0;
+
+       for (uint64_t i = 0; i < rvd->vdev_children; i++) {
+               vdev_t *vd = rvd->vdev_child[i];
+               if (vd->vdev_islog)
+                       continue;
+               if (vdev_is_concrete(vd) && !vdev_is_dead(vd))
+                       tvds++;
+       }
+
+       return (tvds);
+}
+
 /*
  * Checks to see if the given vdev could not be opened, in which case we post a
  * sysevent to notify the autoreplace code that the device has been removed.
@@ -1717,48 +1890,24 @@ load_nvlist(spa_t *spa, uint64_t obj, nvlist_t **value)
 static void
 spa_check_removed(vdev_t *vd)
 {
-       for (int c = 0; c < vd->vdev_children; c++)
+       for (uint64_t c = 0; c < vd->vdev_children; c++)
                spa_check_removed(vd->vdev_child[c]);
 
        if (vd->vdev_ops->vdev_op_leaf && vdev_is_dead(vd) &&
-           !vd->vdev_ishole) {
+           vdev_is_concrete(vd)) {
                zfs_post_autoreplace(vd->vdev_spa, vd);
                spa_event_notify(vd->vdev_spa, vd, NULL, ESC_ZFS_VDEV_CHECK);
        }
 }
 
-static void
-spa_config_valid_zaps(vdev_t *vd, vdev_t *mvd)
-{
-       ASSERT3U(vd->vdev_children, ==, mvd->vdev_children);
-
-       vd->vdev_top_zap = mvd->vdev_top_zap;
-       vd->vdev_leaf_zap = mvd->vdev_leaf_zap;
-
-       for (uint64_t i = 0; i < vd->vdev_children; i++) {
-               spa_config_valid_zaps(vd->vdev_child[i], mvd->vdev_child[i]);
-       }
-}
-
-/*
- * Validate the current config against the MOS config
- */
-static boolean_t
-spa_config_valid(spa_t *spa, nvlist_t *config)
+static int
+spa_check_for_missing_logs(spa_t *spa)
 {
-       vdev_t *mrvd, *rvd = spa->spa_root_vdev;
-       nvlist_t *nv;
-
-       VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nv) == 0);
-
-       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-       VERIFY(spa_config_parse(spa, &mrvd, nv, NULL, 0, VDEV_ALLOC_LOAD) == 0);
-
-       ASSERT3U(rvd->vdev_children, ==, mrvd->vdev_children);
+       vdev_t *rvd = spa->spa_root_vdev;
 
        /*
         * If we're doing a normal import, then build up any additional
-        * diagnostic information about missing devices in this config.
+        * diagnostic information about missing log devices.
         * We'll pass this up to the user for further processing.
         */
        if (!(spa->spa_import_flags & ZFS_IMPORT_MISSING_LOG)) {
@@ -1769,106 +1918,54 @@ spa_config_valid(spa_t *spa, nvlist_t *config)
                    KM_SLEEP);
                VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0);
 
-               for (int c = 0; c < rvd->vdev_children; c++) {
+               for (uint64_t c = 0; c < rvd->vdev_children; c++) {
                        vdev_t *tvd = rvd->vdev_child[c];
-                       vdev_t *mtvd  = mrvd->vdev_child[c];
 
-                       if (tvd->vdev_ops == &vdev_missing_ops &&
-                           mtvd->vdev_ops != &vdev_missing_ops &&
-                           mtvd->vdev_islog)
-                               child[idx++] = vdev_config_generate(spa, mtvd,
-                                   B_FALSE, 0);
+                       /*
+                        * We consider a device as missing only if it failed
+                        * to open (i.e. offline or faulted is not considered
+                        * as missing).
+                        */
+                       if (tvd->vdev_islog &&
+                           tvd->vdev_state == VDEV_STATE_CANT_OPEN) {
+                               child[idx++] = vdev_config_generate(spa, tvd,
+                                   B_FALSE, VDEV_CONFIG_MISSING);
+                       }
                }
 
-               if (idx) {
-                       VERIFY(nvlist_add_nvlist_array(nv,
-                           ZPOOL_CONFIG_CHILDREN, child, idx) == 0);
-                       VERIFY(nvlist_add_nvlist(spa->spa_load_info,
-                           ZPOOL_CONFIG_MISSING_DEVICES, nv) == 0);
+               if (idx > 0) {
+                       fnvlist_add_nvlist_array(nv,
+                           ZPOOL_CONFIG_CHILDREN, child, idx);
+                       fnvlist_add_nvlist(spa->spa_load_info,
+                           ZPOOL_CONFIG_MISSING_DEVICES, nv);
 
-                       for (int i = 0; i < idx; i++)
+                       for (uint64_t i = 0; i < idx; i++)
                                nvlist_free(child[i]);
                }
                nvlist_free(nv);
                kmem_free(child, rvd->vdev_children * sizeof (char **));
-       }
-
-       /*
-        * Compare the root vdev tree with the information we have
-        * from the MOS config (mrvd). Check each top-level vdev
-        * with the corresponding MOS config top-level (mtvd).
-        */
-       for (int c = 0; c < rvd->vdev_children; c++) {
-               vdev_t *tvd = rvd->vdev_child[c];
-               vdev_t *mtvd  = mrvd->vdev_child[c];
-
-               /*
-                * Resolve any "missing" vdevs in the current configuration.
-                * If we find that the MOS config has more accurate information
-                * about the top-level vdev then use that vdev instead.
-                */
-               if (tvd->vdev_ops == &vdev_missing_ops &&
-                   mtvd->vdev_ops != &vdev_missing_ops) {
 
-                       if (!(spa->spa_import_flags & ZFS_IMPORT_MISSING_LOG))
-                               continue;
+               if (idx > 0) {
+                       spa_load_failed(spa, "some log devices are missing");
+                       vdev_dbgmsg_print_tree(rvd, 2);
+                       return (SET_ERROR(ENXIO));
+               }
+       } else {
+               for (uint64_t c = 0; c < rvd->vdev_children; c++) {
+                       vdev_t *tvd = rvd->vdev_child[c];
 
-                       /*
-                        * Device specific actions.
-                        */
-                       if (mtvd->vdev_islog) {
+                       if (tvd->vdev_islog &&
+                           tvd->vdev_state == VDEV_STATE_CANT_OPEN) {
                                spa_set_log_state(spa, SPA_LOG_CLEAR);
-                       } else {
-                               /*
-                                * XXX - once we have 'readonly' pool
-                                * support we should be able to handle
-                                * missing data devices by transitioning
-                                * the pool to readonly.
-                                */
-                               continue;
-                       }
-
-                       /*
-                        * Swap the missing vdev with the data we were
-                        * able to obtain from the MOS config.
-                        */
-                       vdev_remove_child(rvd, tvd);
-                       vdev_remove_child(mrvd, mtvd);
-
-                       vdev_add_child(rvd, mtvd);
-                       vdev_add_child(mrvd, tvd);
-
-                       spa_config_exit(spa, SCL_ALL, FTAG);
-                       vdev_load(mtvd);
-                       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-
-                       vdev_reopen(rvd);
-               } else {
-                       if (mtvd->vdev_islog) {
-                               /*
-                                * Load the slog device's state from the MOS
-                                * config since it's possible that the label
-                                * does not contain the most up-to-date
-                                * information.
-                                */
-                               vdev_load_log_state(tvd, mtvd);
-                               vdev_reopen(tvd);
+                               spa_load_note(spa, "some log devices are "
+                                   "missing, ZIL is dropped.");
+                               vdev_dbgmsg_print_tree(rvd, 2);
+                               break;
                        }
-
-                       /*
-                        * Per-vdev ZAP info is stored exclusively in the MOS.
-                        */
-                       spa_config_valid_zaps(tvd, mtvd);
                }
        }
 
-       vdev_free(mrvd);
-       spa_config_exit(spa, SCL_ALL, FTAG);
-
-       /*
-        * Ensure we were able to validate the config.
-        */
-       return (rvd->vdev_guid_sum == spa->spa_uberblock.ub_guid_sum);
+       return (0);
 }
 
 /*
@@ -1936,11 +2033,11 @@ spa_activate_log(spa_t *spa)
 }
 
 int
-spa_offline_log(spa_t *spa)
+spa_reset_logs(spa_t *spa)
 {
        int error;
 
-       error = dmu_objset_find(spa_name(spa), zil_vdev_offline,
+       error = dmu_objset_find(spa_name(spa), zil_reset,
            NULL, DS_FIND_CHILDREN);
        if (error == 0) {
                /*
@@ -2059,13 +2156,13 @@ spa_load_verify(spa_t *spa)
 {
        zio_t *rio;
        spa_load_error_t sle = { 0 };
-       zpool_rewind_policy_t policy;
+       zpool_load_policy_t policy;
        boolean_t verify_ok = B_FALSE;
        int error = 0;
 
-       zpool_get_rewind_policy(spa->spa_config, &policy);
+       zpool_get_load_policy(spa->spa_config, &policy);
 
-       if (policy.zrp_request & ZPOOL_NEVER_REWIND)
+       if (policy.zlp_rewind & ZPOOL_NEVER_REWIND)
                return (0);
 
        dsl_pool_config_enter(spa->spa_dsl_pool, FTAG);
@@ -2080,6 +2177,13 @@ spa_load_verify(spa_t *spa)
            ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE);
 
        if (spa_load_verify_metadata) {
+               if (spa->spa_extreme_rewind) {
+                       spa_load_note(spa, "performing a complete scan of the "
+                           "pool since extreme rewind is on. This may take "
+                           "a very long time.\n  (spa_load_verify_data=%u, "
+                           "spa_load_verify_metadata=%u)",
+                           spa_load_verify_data, spa_load_verify_metadata);
+               }
                error = traverse_pool(spa, spa->spa_verify_min_txg,
                    TRAVERSE_PRE | TRAVERSE_PREFETCH_METADATA |
                    TRAVERSE_NO_DECRYPT, spa_load_verify_cb, rio);
@@ -2090,8 +2194,15 @@ spa_load_verify(spa_t *spa)
        spa->spa_load_meta_errors = sle.sle_meta_count;
        spa->spa_load_data_errors = sle.sle_data_count;
 
-       if (!error && sle.sle_meta_count <= policy.zrp_maxmeta &&
-           sle.sle_data_count <= policy.zrp_maxdata) {
+       if (sle.sle_meta_count != 0 || sle.sle_data_count != 0) {
+               spa_load_note(spa, "spa_load_verify found %llu metadata errors "
+                   "and %llu data errors", (u_longlong_t)sle.sle_meta_count,
+                   (u_longlong_t)sle.sle_data_count);
+       }
+
+       if (spa_load_verify_dryrun ||
+           (!error && sle.sle_meta_count <= policy.zlp_maxmeta &&
+           sle.sle_data_count <= policy.zlp_maxdata)) {
                int64_t loss = 0;
 
                verify_ok = B_TRUE;
@@ -2109,6 +2220,9 @@ spa_load_verify(spa_t *spa)
                spa->spa_load_max_txg = spa->spa_uberblock.ub_txg;
        }
 
+       if (spa_load_verify_dryrun)
+               return (0);
+
        if (error) {
                if (error != ENXIO && error != EIO)
                        error = SET_ERROR(EIO);
@@ -2132,17 +2246,39 @@ spa_prop_find(spa_t *spa, zpool_prop_t prop, uint64_t *val)
  * Find a value in the pool directory object.
  */
 static int
-spa_dir_prop(spa_t *spa, const char *name, uint64_t *val)
+spa_dir_prop(spa_t *spa, const char *name, uint64_t *val, boolean_t log_enoent)
 {
-       return (zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
-           name, sizeof (uint64_t), 1, val));
+       int error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+           name, sizeof (uint64_t), 1, val);
+
+       if (error != 0 && (error != ENOENT || log_enoent)) {
+               spa_load_failed(spa, "couldn't get '%s' value in MOS directory "
+                   "[error=%d]", name, error);
+       }
+
+       return (error);
 }
 
 static int
 spa_vdev_err(vdev_t *vdev, vdev_aux_t aux, int err)
 {
        vdev_set_state(vdev, B_TRUE, VDEV_STATE_CANT_OPEN, aux);
-       return (err);
+       return (SET_ERROR(err));
+}
+
+static void
+spa_spawn_aux_threads(spa_t *spa)
+{
+       ASSERT(spa_writeable(spa));
+
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+
+       spa_start_indirect_condensing_thread(spa);
+
+       ASSERT3P(spa->spa_checkpoint_discard_zthr, ==, NULL);
+       spa->spa_checkpoint_discard_zthr =
+           zthr_create(spa_checkpoint_discard_thread_check,
+           spa_checkpoint_discard_thread, spa);
 }
 
 /*
@@ -2228,60 +2364,22 @@ spa_try_repair(spa_t *spa, nvlist_t *config)
 }
 
 static int
-spa_load(spa_t *spa, spa_load_state_t state, spa_import_type_t type,
-    boolean_t mosconfig)
+spa_load(spa_t *spa, spa_load_state_t state, spa_import_type_t type)
 {
-       nvlist_t *config = spa->spa_config;
        char *ereport = FM_EREPORT_ZFS_POOL;
-       char *comment;
        int error;
-       uint64_t pool_guid;
-       nvlist_t *nvl;
-
-       if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid))
-               return (SET_ERROR(EINVAL));
-
-       ASSERT(spa->spa_comment == NULL);
-       if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMMENT, &comment) == 0)
-               spa->spa_comment = spa_strdup(comment);
-
-       /*
-        * Versioning wasn't explicitly added to the label until later, so if
-        * it's not present treat it as the initial version.
-        */
-       if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VERSION,
-           &spa->spa_ubsync.ub_version) != 0)
-               spa->spa_ubsync.ub_version = SPA_VERSION_INITIAL;
-
-       (void) nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG,
-           &spa->spa_config_txg);
-
-       if ((state == SPA_LOAD_IMPORT || state == SPA_LOAD_TRYIMPORT) &&
-           spa_guid_exists(pool_guid, 0)) {
-               error = SET_ERROR(EEXIST);
-       } else {
-               spa->spa_config_guid = pool_guid;
-
-               if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_SPLIT,
-                   &nvl) == 0) {
-                       VERIFY(nvlist_dup(nvl, &spa->spa_config_splitting,
-                           KM_SLEEP) == 0);
-               }
 
-               nvlist_free(spa->spa_load_info);
-               spa->spa_load_info = fnvlist_alloc();
+       spa->spa_load_state = state;
 
-               gethrestime(&spa->spa_loaded_ts);
-               error = spa_load_impl(spa, pool_guid, config, state, type,
-                   mosconfig, &ereport);
-       }
+       gethrestime(&spa->spa_loaded_ts);
+       error = spa_load_impl(spa, type, &ereport);
 
        /*
         * Don't count references from objsets that are already closed
         * and are making their way through the eviction process.
         */
        spa_evicting_os_wait(spa);
-       spa->spa_minref = refcount_count(&spa->spa_refcount);
+       spa->spa_minref = zfs_refcount_count(&spa->spa_refcount);
        if (error) {
                if (error != EEXIST) {
                        spa->spa_loaded_ts.tv_sec = 0;
@@ -2449,6 +2547,10 @@ spa_activity_check(spa_t *spa, uberblock_t *ub, nvlist_t *config)
        import_delay = MAX(import_delay, import_intervals *
            MSEC2NSEC(MAX(zfs_multihost_interval, MMP_MIN_INTERVAL)));
 
+       zfs_dbgmsg("import_delay=%llu ub_mmp_delay=%llu import_intervals=%u "
+           "leaves=%u", import_delay, ub->ub_mmp_delay, import_intervals,
+           vdev_count_leaves(spa));
+
        /* Add a small random factor in case of simultaneous imports (0-25%) */
        import_expire = gethrtime() + import_delay +
            (import_delay * spa_get_random(250) / 1000);
@@ -2523,44 +2625,104 @@ out:
        return (error);
 }
 
-/*
- * Load an existing storage pool, using the pool's builtin spa_config as a
- * source of configuration information.
- */
-__attribute__((always_inline))
-static inline int
-spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
-    spa_load_state_t state, spa_import_type_t type, boolean_t mosconfig,
-    char **ereport)
+static int
+spa_verify_host(spa_t *spa, nvlist_t *mos_config)
+{
+       uint64_t hostid;
+       char *hostname;
+       uint64_t myhostid = 0;
+
+       if (!spa_is_root(spa) && nvlist_lookup_uint64(mos_config,
+           ZPOOL_CONFIG_HOSTID, &hostid) == 0) {
+               hostname = fnvlist_lookup_string(mos_config,
+                   ZPOOL_CONFIG_HOSTNAME);
+
+               myhostid = zone_get_hostid(NULL);
+
+               if (hostid != 0 && myhostid != 0 && hostid != myhostid) {
+                       cmn_err(CE_WARN, "pool '%s' could not be "
+                           "loaded as it was last accessed by "
+                           "another system (host: %s hostid: 0x%llx). "
+                           "See: http://illumos.org/msg/ZFS-8000-EY",
+                           spa_name(spa), hostname, (u_longlong_t)hostid);
+                       spa_load_failed(spa, "hostid verification failed: pool "
+                           "last accessed by host: %s (hostid: 0x%llx)",
+                           hostname, (u_longlong_t)hostid);
+                       return (SET_ERROR(EBADF));
+               }
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_parse_config(spa_t *spa, spa_import_type_t type)
 {
        int error = 0;
-       nvlist_t *nvroot = NULL;
-       nvlist_t *label;
-       vdev_t *rvd;
-       uberblock_t *ub = &spa->spa_uberblock;
-       uint64_t children, config_cache_txg = spa->spa_config_txg;
-       int orig_mode = spa->spa_mode;
+       nvlist_t *nvtree, *nvl, *config = spa->spa_config;
        int parse;
-       uint64_t obj;
-       boolean_t missing_feat_write = B_FALSE;
-       boolean_t activity_check = B_FALSE;
+       vdev_t *rvd;
+       uint64_t pool_guid;
+       char *comment;
 
        /*
-        * If this is an untrusted config, access the pool in read-only mode.
-        * This prevents things like resilvering recently removed devices.
+        * Versioning wasn't explicitly added to the label until later, so if
+        * it's not present treat it as the initial version.
         */
-       if (!mosconfig)
-               spa->spa_mode = FREAD;
+       if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VERSION,
+           &spa->spa_ubsync.ub_version) != 0)
+               spa->spa_ubsync.ub_version = SPA_VERSION_INITIAL;
 
-       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid)) {
+               spa_load_failed(spa, "invalid config provided: '%s' missing",
+                   ZPOOL_CONFIG_POOL_GUID);
+               return (SET_ERROR(EINVAL));
+       }
 
-       spa->spa_load_state = state;
+       /*
+        * If we are doing an import, ensure that the pool is not already
+        * imported by checking if its pool guid already exists in the
+        * spa namespace.
+        *
+        * The only case that we allow an already imported pool to be
+        * imported again, is when the pool is checkpointed and we want to
+        * look at its checkpointed state from userland tools like zdb.
+        */
+#ifdef _KERNEL
+       if ((spa->spa_load_state == SPA_LOAD_IMPORT ||
+           spa->spa_load_state == SPA_LOAD_TRYIMPORT) &&
+           spa_guid_exists(pool_guid, 0)) {
+#else
+       if ((spa->spa_load_state == SPA_LOAD_IMPORT ||
+           spa->spa_load_state == SPA_LOAD_TRYIMPORT) &&
+           spa_guid_exists(pool_guid, 0) &&
+           !spa_importing_readonly_checkpoint(spa)) {
+#endif
+               spa_load_failed(spa, "a pool with guid %llu is already open",
+                   (u_longlong_t)pool_guid);
+               return (SET_ERROR(EEXIST));
+       }
 
-       if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nvroot))
-               return (SET_ERROR(EINVAL));
+       spa->spa_config_guid = pool_guid;
 
-       parse = (type == SPA_IMPORT_EXISTING ?
-           VDEV_ALLOC_LOAD : VDEV_ALLOC_SPLIT);
+       nvlist_free(spa->spa_load_info);
+       spa->spa_load_info = fnvlist_alloc();
+
+       ASSERT(spa->spa_comment == NULL);
+       if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMMENT, &comment) == 0)
+               spa->spa_comment = spa_strdup(comment);
+
+       (void) nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG,
+           &spa->spa_config_txg);
+
+       if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_SPLIT, &nvl) == 0)
+               spa->spa_config_splitting = fnvlist_dup(nvl);
+
+       if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nvtree)) {
+               spa_load_failed(spa, "invalid config provided: '%s' missing",
+                   ZPOOL_CONFIG_VDEV_TREE);
+               return (SET_ERROR(EINVAL));
+       }
 
        /*
         * Create "The Godfather" zio to hold all async IOs
@@ -2579,11 +2741,16 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         * configuration requires knowing the version number.
         */
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-       error = spa_config_parse(spa, &rvd, nvroot, NULL, 0, parse);
+       parse = (type == SPA_IMPORT_EXISTING ?
+           VDEV_ALLOC_LOAD : VDEV_ALLOC_SPLIT);
+       error = spa_config_parse(spa, &rvd, nvtree, NULL, 0, parse);
        spa_config_exit(spa, SCL_ALL, FTAG);
 
-       if (error != 0)
+       if (error != 0) {
+               spa_load_failed(spa, "unable to parse config [error=%d]",
+                   error);
                return (error);
+       }
 
        ASSERT(spa->spa_root_vdev == rvd);
        ASSERT3U(spa->spa_min_ashift, >=, SPA_MINBLOCKSHIFT);
@@ -2593,38 +2760,144 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                ASSERT(spa_guid(spa) == pool_guid);
        }
 
-       /*
-        * Try to open all vdevs, loading each label in the process.
-        */
-       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-       error = vdev_open(rvd);
-       spa_config_exit(spa, SCL_ALL, FTAG);
-       if (error != 0)
-               return (error);
+       return (0);
+}
+
+/*
+ * Recursively open all vdevs in the vdev tree. This function is called twice:
+ * first with the untrusted config, then with the trusted config.
+ */
+static int
+spa_ld_open_vdevs(spa_t *spa)
+{
+       int error = 0;
 
        /*
-        * We need to validate the vdev labels against the configuration that
-        * we have in hand, which is dependent on the setting of mosconfig. If
-        * mosconfig is true then we're validating the vdev labels based on
-        * that config.  Otherwise, we're validating against the cached config
-        * (zpool.cache) that was read when we loaded the zfs module, and then
-        * later we will recursively call spa_load() and validate against
-        * the vdev config.
-        *
-        * If we're assembling a new pool that's been split off from an
-        * existing pool, the labels haven't yet been updated so we skip
-        * validation for now.
+        * spa_missing_tvds_allowed defines how many top-level vdevs can be
+        * missing/unopenable for the root vdev to be still considered openable.
         */
-       if (type != SPA_IMPORT_ASSEMBLE) {
-               spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-               error = vdev_validate(rvd, mosconfig);
-               spa_config_exit(spa, SCL_ALL, FTAG);
+       if (spa->spa_trust_config) {
+               spa->spa_missing_tvds_allowed = zfs_max_missing_tvds;
+       } else if (spa->spa_config_source == SPA_CONFIG_SRC_CACHEFILE) {
+               spa->spa_missing_tvds_allowed = zfs_max_missing_tvds_cachefile;
+       } else if (spa->spa_config_source == SPA_CONFIG_SRC_SCAN) {
+               spa->spa_missing_tvds_allowed = zfs_max_missing_tvds_scan;
+       } else {
+               spa->spa_missing_tvds_allowed = 0;
+       }
 
-               if (error != 0)
-                       return (error);
+       spa->spa_missing_tvds_allowed =
+           MAX(zfs_max_missing_tvds, spa->spa_missing_tvds_allowed);
 
-               if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN)
-                       return (SET_ERROR(ENXIO));
+       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+       error = vdev_open(spa->spa_root_vdev);
+       spa_config_exit(spa, SCL_ALL, FTAG);
+
+       if (spa->spa_missing_tvds != 0) {
+               spa_load_note(spa, "vdev tree has %lld missing top-level "
+                   "vdevs.", (u_longlong_t)spa->spa_missing_tvds);
+               if (spa->spa_trust_config && (spa->spa_mode & FWRITE)) {
+                       /*
+                        * Although theoretically we could allow users to open
+                        * incomplete pools in RW mode, we'd need to add a lot
+                        * of extra logic (e.g. adjust pool space to account
+                        * for missing vdevs).
+                        * This limitation also prevents users from accidentally
+                        * opening the pool in RW mode during data recovery and
+                        * damaging it further.
+                        */
+                       spa_load_note(spa, "pools with missing top-level "
+                           "vdevs can only be opened in read-only mode.");
+                       error = SET_ERROR(ENXIO);
+               } else {
+                       spa_load_note(spa, "current settings allow for maximum "
+                           "%lld missing top-level vdevs at this stage.",
+                           (u_longlong_t)spa->spa_missing_tvds_allowed);
+               }
+       }
+       if (error != 0) {
+               spa_load_failed(spa, "unable to open vdev tree [error=%d]",
+                   error);
+       }
+       if (spa->spa_missing_tvds != 0 || error != 0)
+               vdev_dbgmsg_print_tree(spa->spa_root_vdev, 2);
+
+       return (error);
+}
+
+/*
+ * We need to validate the vdev labels against the configuration that
+ * we have in hand. This function is called twice: first with an untrusted
+ * config, then with a trusted config. The validation is more strict when the
+ * config is trusted.
+ */
+static int
+spa_ld_validate_vdevs(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
+       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+       error = vdev_validate(rvd);
+       spa_config_exit(spa, SCL_ALL, FTAG);
+
+       if (error != 0) {
+               spa_load_failed(spa, "vdev_validate failed [error=%d]", error);
+               return (error);
+       }
+
+       if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN) {
+               spa_load_failed(spa, "cannot open vdev tree after invalidating "
+                   "some vdevs");
+               vdev_dbgmsg_print_tree(rvd, 2);
+               return (SET_ERROR(ENXIO));
+       }
+
+       return (0);
+}
+
+static void
+spa_ld_select_uberblock_done(spa_t *spa, uberblock_t *ub)
+{
+       spa->spa_state = POOL_STATE_ACTIVE;
+       spa->spa_ubsync = spa->spa_uberblock;
+       spa->spa_verify_min_txg = spa->spa_extreme_rewind ?
+           TXG_INITIAL - 1 : spa_last_synced_txg(spa) - TXG_DEFER_SIZE - 1;
+       spa->spa_first_txg = spa->spa_last_ubsync_txg ?
+           spa->spa_last_ubsync_txg : spa_last_synced_txg(spa) + 1;
+       spa->spa_claim_max_txg = spa->spa_first_txg;
+       spa->spa_prev_software_version = ub->ub_software_version;
+}
+
+static int
+spa_ld_select_uberblock(spa_t *spa, spa_import_type_t type)
+{
+       vdev_t *rvd = spa->spa_root_vdev;
+       nvlist_t *label;
+       uberblock_t *ub = &spa->spa_uberblock;
+       boolean_t activity_check = B_FALSE;
+
+       /*
+        * If we are opening the checkpointed state of the pool by
+        * rewinding to it, at this point we will have written the
+        * checkpointed uberblock to the vdev labels, so searching
+        * the labels will find the right uberblock.  However, if
+        * we are opening the checkpointed state read-only, we have
+        * not modified the labels. Therefore, we must ignore the
+        * labels and continue using the spa_uberblock that was set
+        * by spa_ld_checkpoint_rewind.
+        *
+        * Note that it would be fine to ignore the labels when
+        * rewinding (opening writeable) as well. However, if we
+        * crash just after writing the labels, we will end up
+        * searching the labels. Doing so in the common case means
+        * that this code path gets exercised normally, rather than
+        * just in the edge case.
+        */
+       if (ub->ub_checkpoint_txg != 0 &&
+           spa_importing_readonly_checkpoint(spa)) {
+               spa_ld_select_uberblock_done(spa, ub);
+               return (0);
        }
 
        /*
@@ -2637,15 +2910,21 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         */
        if (ub->ub_txg == 0) {
                nvlist_free(label);
+               spa_load_failed(spa, "no valid uberblock found");
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, ENXIO));
        }
 
+       spa_load_note(spa, "using uberblock with txg=%llu",
+           (u_longlong_t)ub->ub_txg);
+
+
        /*
         * For pools which have the multihost property on determine if the
         * pool is truly inactive and can be safely imported.  Prevent
         * hosts which don't have a hostid set from importing the pool.
         */
-       activity_check = spa_activity_check_required(spa, ub, label, config);
+       activity_check = spa_activity_check_required(spa, ub, label,
+           spa->spa_config);
        if (activity_check) {
                if (ub->ub_mmp_magic == MMP_MAGIC && ub->ub_mmp_delay &&
                    spa_get_hostid() == 0) {
@@ -2655,7 +2934,7 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                        return (spa_vdev_err(rvd, VDEV_AUX_ACTIVE, EREMOTEIO));
                }
 
-               error = spa_activity_check(spa, ub, config);
+               int error = spa_activity_check(spa, ub, spa->spa_config);
                if (error) {
                        nvlist_free(label);
                        return (error);
@@ -2672,6 +2951,8 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         */
        if (!SPA_VERSION_IS_SUPPORTED(ub->ub_version)) {
                nvlist_free(label);
+               spa_load_failed(spa, "version %llu is not supported",
+                   (u_longlong_t)ub->ub_version);
                return (spa_vdev_err(rvd, VDEV_AUX_VERSION_NEWER, ENOTSUP));
        }
 
@@ -2682,9 +2963,17 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                 * If we weren't able to find what's necessary for reading the
                 * MOS in the label, return failure.
                 */
-               if (label == NULL || nvlist_lookup_nvlist(label,
-                   ZPOOL_CONFIG_FEATURES_FOR_READ, &features) != 0) {
+               if (label == NULL) {
+                       spa_load_failed(spa, "label config unavailable");
+                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
+                           ENXIO));
+               }
+
+               if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_FEATURES_FOR_READ,
+                   &features) != 0) {
                        nvlist_free(label);
+                       spa_load_failed(spa, "invalid label: '%s' missing",
+                           ZPOOL_CONFIG_FEATURES_FOR_READ);
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
                            ENXIO));
                }
@@ -2723,6 +3012,7 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                        VERIFY(nvlist_add_nvlist(spa->spa_load_info,
                            ZPOOL_CONFIG_UNSUP_FEAT, unsup_feat) == 0);
                        nvlist_free(unsup_feat);
+                       spa_load_failed(spa, "some features are unsupported");
                        return (spa_vdev_err(rvd, VDEV_AUX_UNSUP_FEAT,
                            ENOTSUP));
                }
@@ -2730,21 +3020,9 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                nvlist_free(unsup_feat);
        }
 
-       /*
-        * If the vdev guid sum doesn't match the uberblock, we have an
-        * incomplete configuration.  We first check to see if the pool
-        * is aware of the complete config (i.e ZPOOL_CONFIG_VDEV_CHILDREN).
-        * If it is, defer the vdev_guid_sum check till later so we
-        * can handle missing vdevs.
-        */
-       if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VDEV_CHILDREN,
-           &children) != 0 && mosconfig && type != SPA_IMPORT_ASSEMBLE &&
-           rvd->vdev_guid_sum != ub->ub_guid_sum)
-               return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM, ENXIO));
-
        if (type != SPA_IMPORT_ASSEMBLE && spa->spa_config_splitting) {
                spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-               spa_try_repair(spa, config);
+               spa_try_repair(spa, spa->spa_config);
                spa_config_exit(spa, SCL_ALL, FTAG);
                nvlist_free(spa->spa_config_splitting);
                spa->spa_config_splitting = NULL;
@@ -2753,39 +3031,245 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
        /*
         * Initialize internal SPA structures.
         */
-       spa->spa_state = POOL_STATE_ACTIVE;
-       spa->spa_ubsync = spa->spa_uberblock;
-       spa->spa_verify_min_txg = spa->spa_extreme_rewind ?
-           TXG_INITIAL - 1 : spa_last_synced_txg(spa) - TXG_DEFER_SIZE - 1;
-       spa->spa_first_txg = spa->spa_last_ubsync_txg ?
-           spa->spa_last_ubsync_txg : spa_last_synced_txg(spa) + 1;
-       spa->spa_claim_max_txg = spa->spa_first_txg;
-       spa->spa_prev_software_version = ub->ub_software_version;
+       spa_ld_select_uberblock_done(spa, ub);
+
+       return (0);
+}
+
+static int
+spa_ld_open_rootbp(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
 
        error = dsl_pool_init(spa, spa->spa_first_txg, &spa->spa_dsl_pool);
-       if (error)
+       if (error != 0) {
+               spa_load_failed(spa, "unable to open rootbp in dsl_pool_init "
+                   "[error=%d]", error);
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
        spa->spa_meta_objset = spa->spa_dsl_pool->dp_meta_objset;
 
-       if (spa_dir_prop(spa, DMU_POOL_CONFIG, &spa->spa_config_object) != 0)
+       return (0);
+}
+
+static int
+spa_ld_trusted_config(spa_t *spa, spa_import_type_t type,
+    boolean_t reloading)
+{
+       vdev_t *mrvd, *rvd = spa->spa_root_vdev;
+       nvlist_t *nv, *mos_config, *policy;
+       int error = 0, copy_error;
+       uint64_t healthy_tvds, healthy_tvds_mos;
+       uint64_t mos_config_txg;
+
+       if (spa_dir_prop(spa, DMU_POOL_CONFIG, &spa->spa_config_object, B_TRUE)
+           != 0)
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+
+       /*
+        * If we're assembling a pool from a split, the config provided is
+        * already trusted so there is nothing to do.
+        */
+       if (type == SPA_IMPORT_ASSEMBLE)
+               return (0);
+
+       healthy_tvds = spa_healthy_core_tvds(spa);
+
+       if (load_nvlist(spa, spa->spa_config_object, &mos_config)
+           != 0) {
+               spa_load_failed(spa, "unable to retrieve MOS config");
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
+
+       /*
+        * If we are doing an open, pool owner wasn't verified yet, thus do
+        * the verification here.
+        */
+       if (spa->spa_load_state == SPA_LOAD_OPEN) {
+               error = spa_verify_host(spa, mos_config);
+               if (error != 0) {
+                       nvlist_free(mos_config);
+                       return (error);
+               }
+       }
+
+       nv = fnvlist_lookup_nvlist(mos_config, ZPOOL_CONFIG_VDEV_TREE);
+
+       spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+
+       /*
+        * Build a new vdev tree from the trusted config
+        */
+       VERIFY(spa_config_parse(spa, &mrvd, nv, NULL, 0, VDEV_ALLOC_LOAD) == 0);
+
+       /*
+        * Vdev paths in the MOS may be obsolete. If the untrusted config was
+        * obtained by scanning /dev/dsk, then it will have the right vdev
+        * paths. We update the trusted MOS config with this information.
+        * We first try to copy the paths with vdev_copy_path_strict, which
+        * succeeds only when both configs have exactly the same vdev tree.
+        * If that fails, we fall back to a more flexible method that has a
+        * best effort policy.
+        */
+       copy_error = vdev_copy_path_strict(rvd, mrvd);
+       if (copy_error != 0 || spa_load_print_vdev_tree) {
+               spa_load_note(spa, "provided vdev tree:");
+               vdev_dbgmsg_print_tree(rvd, 2);
+               spa_load_note(spa, "MOS vdev tree:");
+               vdev_dbgmsg_print_tree(mrvd, 2);
+       }
+       if (copy_error != 0) {
+               spa_load_note(spa, "vdev_copy_path_strict failed, falling "
+                   "back to vdev_copy_path_relaxed");
+               vdev_copy_path_relaxed(rvd, mrvd);
+       }
+
+       vdev_close(rvd);
+       vdev_free(rvd);
+       spa->spa_root_vdev = mrvd;
+       rvd = mrvd;
+       spa_config_exit(spa, SCL_ALL, FTAG);
+
+       /*
+        * We will use spa_config if we decide to reload the spa or if spa_load
+        * fails and we rewind. We must thus regenerate the config using the
+        * MOS information with the updated paths. ZPOOL_LOAD_POLICY is used to
+        * pass settings on how to load the pool and is not stored in the MOS.
+        * We copy it over to our new, trusted config.
+        */
+       mos_config_txg = fnvlist_lookup_uint64(mos_config,
+           ZPOOL_CONFIG_POOL_TXG);
+       nvlist_free(mos_config);
+       mos_config = spa_config_generate(spa, NULL, mos_config_txg, B_FALSE);
+       if (nvlist_lookup_nvlist(spa->spa_config, ZPOOL_LOAD_POLICY,
+           &policy) == 0)
+               fnvlist_add_nvlist(mos_config, ZPOOL_LOAD_POLICY, policy);
+       spa_config_set(spa, mos_config);
+       spa->spa_config_source = SPA_CONFIG_SRC_MOS;
+
+       /*
+        * Now that we got the config from the MOS, we should be more strict
+        * in checking blkptrs and can make assumptions about the consistency
+        * of the vdev tree. spa_trust_config must be set to true before opening
+        * vdevs in order for them to be writeable.
+        */
+       spa->spa_trust_config = B_TRUE;
+
+       /*
+        * Open and validate the new vdev tree
+        */
+       error = spa_ld_open_vdevs(spa);
+       if (error != 0)
+               return (error);
+
+       error = spa_ld_validate_vdevs(spa);
+       if (error != 0)
+               return (error);
+
+       if (copy_error != 0 || spa_load_print_vdev_tree) {
+               spa_load_note(spa, "final vdev tree:");
+               vdev_dbgmsg_print_tree(rvd, 2);
+       }
+
+       if (spa->spa_load_state != SPA_LOAD_TRYIMPORT &&
+           !spa->spa_extreme_rewind && zfs_max_missing_tvds == 0) {
+               /*
+                * Sanity check to make sure that we are indeed loading the
+                * latest uberblock. If we missed SPA_SYNC_MIN_VDEVS tvds
+                * in the config provided and they happened to be the only ones
+                * to have the latest uberblock, we could involuntarily perform
+                * an extreme rewind.
+                */
+               healthy_tvds_mos = spa_healthy_core_tvds(spa);
+               if (healthy_tvds_mos - healthy_tvds >=
+                   SPA_SYNC_MIN_VDEVS) {
+                       spa_load_note(spa, "config provided misses too many "
+                           "top-level vdevs compared to MOS (%lld vs %lld). ",
+                           (u_longlong_t)healthy_tvds,
+                           (u_longlong_t)healthy_tvds_mos);
+                       spa_load_note(spa, "vdev tree:");
+                       vdev_dbgmsg_print_tree(rvd, 2);
+                       if (reloading) {
+                               spa_load_failed(spa, "config was already "
+                                   "provided from MOS. Aborting.");
+                               return (spa_vdev_err(rvd,
+                                   VDEV_AUX_CORRUPT_DATA, EIO));
+                       }
+                       spa_load_note(spa, "spa must be reloaded using MOS "
+                           "config");
+                       return (SET_ERROR(EAGAIN));
+               }
+       }
+
+       error = spa_check_for_missing_logs(spa);
+       if (error != 0)
+               return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM, ENXIO));
+
+       if (rvd->vdev_guid_sum != spa->spa_uberblock.ub_guid_sum) {
+               spa_load_failed(spa, "uberblock guid sum doesn't match MOS "
+                   "guid sum (%llu != %llu)",
+                   (u_longlong_t)spa->spa_uberblock.ub_guid_sum,
+                   (u_longlong_t)rvd->vdev_guid_sum);
+               return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM,
+                   ENXIO));
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_open_indirect_vdev_metadata(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
+       /*
+        * Everything that we read before spa_remove_init() must be stored
+        * on concreted vdevs.  Therefore we do this as early as possible.
+        */
+       error = spa_remove_init(spa);
+       if (error != 0) {
+               spa_load_failed(spa, "spa_remove_init failed [error=%d]",
+                   error);
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
+
+       /*
+        * Retrieve information needed to condense indirect vdev mappings.
+        */
+       error = spa_condense_init(spa);
+       if (error != 0) {
+               spa_load_failed(spa, "spa_condense_init failed [error=%d]",
+                   error);
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, error));
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_check_features(spa_t *spa, boolean_t *missing_feat_writep)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
 
        if (spa_version(spa) >= SPA_VERSION_FEATURES) {
                boolean_t missing_feat_read = B_FALSE;
                nvlist_t *unsup_feat, *enabled_feat;
 
                if (spa_dir_prop(spa, DMU_POOL_FEATURES_FOR_READ,
-                   &spa->spa_feat_for_read_obj) != 0) {
+                   &spa->spa_feat_for_read_obj, B_TRUE) != 0) {
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
                }
 
                if (spa_dir_prop(spa, DMU_POOL_FEATURES_FOR_WRITE,
-                   &spa->spa_feat_for_write_obj) != 0) {
+                   &spa->spa_feat_for_write_obj, B_TRUE) != 0) {
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
                }
 
                if (spa_dir_prop(spa, DMU_POOL_FEATURE_DESCRIPTIONS,
-                   &spa->spa_feat_desc_obj) != 0) {
+                   &spa->spa_feat_desc_obj, B_TRUE) != 0) {
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
                }
 
@@ -2796,10 +3280,11 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                    unsup_feat, enabled_feat))
                        missing_feat_read = B_TRUE;
 
-               if (spa_writeable(spa) || state == SPA_LOAD_TRYIMPORT) {
+               if (spa_writeable(spa) ||
+                   spa->spa_load_state == SPA_LOAD_TRYIMPORT) {
                        if (!spa_features_check(spa, B_TRUE,
                            unsup_feat, enabled_feat)) {
-                               missing_feat_write = B_TRUE;
+                               *missing_feat_writep = B_TRUE;
                        }
                }
 
@@ -2838,8 +3323,9 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                 * userland in order to know whether to display the
                 * abovementioned note.
                 */
-               if (missing_feat_read || (missing_feat_write &&
+               if (missing_feat_read || (*missing_feat_writep &&
                    spa_writeable(spa))) {
+                       spa_load_failed(spa, "pool uses unsupported features");
                        return (spa_vdev_err(rvd, VDEV_AUX_UNSUP_FEAT,
                            ENOTSUP));
                }
@@ -2859,6 +3345,9 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                                spa->spa_feat_refcount_cache[i] =
                                    SPA_FEATURE_DISABLED;
                        } else {
+                               spa_load_failed(spa, "error getting refcount "
+                                   "for feature %s [error=%d]",
+                                   spa_feature_table[i].fi_guid, error);
                                return (spa_vdev_err(rvd,
                                    VDEV_AUX_CORRUPT_DATA, EIO));
                        }
@@ -2867,49 +3356,36 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
 
        if (spa_feature_is_active(spa, SPA_FEATURE_ENABLED_TXG)) {
                if (spa_dir_prop(spa, DMU_POOL_FEATURE_ENABLED_TXG,
-                   &spa->spa_feat_enabled_txg_obj) != 0)
+                   &spa->spa_feat_enabled_txg_obj, B_TRUE) != 0)
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
        }
 
+       return (0);
+}
+
+static int
+spa_ld_load_special_directories(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
        spa->spa_is_initializing = B_TRUE;
        error = dsl_pool_open(spa->spa_dsl_pool);
        spa->spa_is_initializing = B_FALSE;
-       if (error != 0)
+       if (error != 0) {
+               spa_load_failed(spa, "dsl_pool_open failed [error=%d]", error);
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
 
-       if (!mosconfig) {
-               uint64_t hostid;
-               nvlist_t *policy = NULL, *nvconfig;
-
-               if (load_nvlist(spa, spa->spa_config_object, &nvconfig) != 0)
-                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
-
-               if (!spa_is_root(spa) && nvlist_lookup_uint64(nvconfig,
-                   ZPOOL_CONFIG_HOSTID, &hostid) == 0) {
-                       char *hostname;
-                       unsigned long myhostid = 0;
-
-                       VERIFY(nvlist_lookup_string(nvconfig,
-                           ZPOOL_CONFIG_HOSTNAME, &hostname) == 0);
-
-                       myhostid = spa_get_hostid();
-                       if (hostid && myhostid && hostid != myhostid) {
-                               nvlist_free(nvconfig);
-                               return (SET_ERROR(EBADF));
-                       }
-               }
-               if (nvlist_lookup_nvlist(spa->spa_config,
-                   ZPOOL_REWIND_POLICY, &policy) == 0)
-                       VERIFY(nvlist_add_nvlist(nvconfig,
-                           ZPOOL_REWIND_POLICY, policy) == 0);
-
-               spa_config_set(spa, nvconfig);
-               spa_unload(spa);
-               spa_deactivate(spa);
-               spa_activate(spa, orig_mode);
+       return (0);
+}
 
-               return (spa_load(spa, state, SPA_IMPORT_EXISTING, B_TRUE));
-       }
+static int
+spa_ld_get_props(spa_t *spa)
+{
+       int error = 0;
+       uint64_t obj;
+       vdev_t *rvd = spa->spa_root_vdev;
 
        /* Grab the checksum salt from the MOS. */
        error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
@@ -2921,26 +3397,31 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                (void) random_get_pseudo_bytes(spa->spa_cksum_salt.zcs_bytes,
                    sizeof (spa->spa_cksum_salt.zcs_bytes));
        } else if (error != 0) {
+               spa_load_failed(spa, "unable to retrieve checksum salt from "
+                   "MOS [error=%d]", error);
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
        }
 
-       if (spa_dir_prop(spa, DMU_POOL_SYNC_BPOBJ, &obj) != 0)
+       if (spa_dir_prop(spa, DMU_POOL_SYNC_BPOBJ, &obj, B_TRUE) != 0)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
        error = bpobj_open(&spa->spa_deferred_bpobj, spa->spa_meta_objset, obj);
-       if (error != 0)
+       if (error != 0) {
+               spa_load_failed(spa, "error opening deferred-frees bpobj "
+                   "[error=%d]", error);
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
 
        /*
         * Load the bit that tells us to use the new accounting function
         * (raid-z deflation).  If we have an older pool, this will not
         * be present.
         */
-       error = spa_dir_prop(spa, DMU_POOL_DEFLATE, &spa->spa_deflate);
+       error = spa_dir_prop(spa, DMU_POOL_DEFLATE, &spa->spa_deflate, B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
        error = spa_dir_prop(spa, DMU_POOL_CREATION_VERSION,
-           &spa->spa_creation_version);
+           &spa->spa_creation_version, B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
@@ -2948,12 +3429,13 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         * Load the persistent error log.  If we have an older pool, this will
         * not be present.
         */
-       error = spa_dir_prop(spa, DMU_POOL_ERRLOG_LAST, &spa->spa_errlog_last);
+       error = spa_dir_prop(spa, DMU_POOL_ERRLOG_LAST, &spa->spa_errlog_last,
+           B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
        error = spa_dir_prop(spa, DMU_POOL_ERRLOG_SCRUB,
-           &spa->spa_errlog_scrub);
+           &spa->spa_errlog_scrub, B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
@@ -2961,7 +3443,7 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         * Load the history object.  If we have an older pool, this
         * will not be present.
         */
-       error = spa_dir_prop(spa, DMU_POOL_HISTORY, &spa->spa_history);
+       error = spa_dir_prop(spa, DMU_POOL_HISTORY, &spa->spa_history, B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
@@ -2974,11 +3456,13 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
 
        /* The sentinel is only available in the MOS config. */
        nvlist_t *mos_config;
-       if (load_nvlist(spa, spa->spa_config_object, &mos_config) != 0)
+       if (load_nvlist(spa, spa->spa_config_object, &mos_config) != 0) {
+               spa_load_failed(spa, "unable to retrieve MOS config");
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
 
        error = spa_dir_prop(spa, DMU_POOL_VDEV_ZAP_MAP,
-           &spa->spa_all_vdev_zaps);
+           &spa->spa_all_vdev_zaps, B_FALSE);
 
        if (error == ENOENT) {
                VERIFY(!nvlist_exists(mos_config,
@@ -3002,43 +3486,92 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
        }
        nvlist_free(mos_config);
 
-       /*
-        * If we're assembling the pool from the split-off vdevs of
-        * an existing pool, we don't want to attach the spares & cache
-        * devices.
-        */
+       spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);
 
-       /*
-        * Load any hot spares for this pool.
-        */
-       error = spa_dir_prop(spa, DMU_POOL_SPARES, &spa->spa_spares.sav_object);
-       if (error != 0 && error != ENOENT)
+       error = spa_dir_prop(spa, DMU_POOL_PROPS, &spa->spa_pool_props_object,
+           B_FALSE);
+       if (error && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
-       if (error == 0 && type != SPA_IMPORT_ASSEMBLE) {
-               ASSERT(spa_version(spa) >= SPA_VERSION_SPARES);
-               if (load_nvlist(spa, spa->spa_spares.sav_object,
-                   &spa->spa_spares.sav_config) != 0)
-                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
-               spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-               spa_load_spares(spa);
-               spa_config_exit(spa, SCL_ALL, FTAG);
-       } else if (error == 0) {
-               spa->spa_spares.sav_sync = B_TRUE;
-       }
+       if (error == 0) {
+               uint64_t autoreplace;
 
-       /*
+               spa_prop_find(spa, ZPOOL_PROP_BOOTFS, &spa->spa_bootfs);
+               spa_prop_find(spa, ZPOOL_PROP_AUTOREPLACE, &autoreplace);
+               spa_prop_find(spa, ZPOOL_PROP_DELEGATION, &spa->spa_delegation);
+               spa_prop_find(spa, ZPOOL_PROP_FAILUREMODE, &spa->spa_failmode);
+               spa_prop_find(spa, ZPOOL_PROP_AUTOEXPAND, &spa->spa_autoexpand);
+               spa_prop_find(spa, ZPOOL_PROP_MULTIHOST, &spa->spa_multihost);
+               spa_prop_find(spa, ZPOOL_PROP_DEDUPDITTO,
+                   &spa->spa_dedup_ditto);
+
+               spa->spa_autoreplace = (autoreplace != 0);
+       }
+
+       /*
+        * If we are importing a pool with missing top-level vdevs,
+        * we enforce that the pool doesn't panic or get suspended on
+        * error since the likelihood of missing data is extremely high.
+        */
+       if (spa->spa_missing_tvds > 0 &&
+           spa->spa_failmode != ZIO_FAILURE_MODE_CONTINUE &&
+           spa->spa_load_state != SPA_LOAD_TRYIMPORT) {
+               spa_load_note(spa, "forcing failmode to 'continue' "
+                   "as some top level vdevs are missing");
+               spa->spa_failmode = ZIO_FAILURE_MODE_CONTINUE;
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_open_aux_vdevs(spa_t *spa, spa_import_type_t type)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
+       /*
+        * If we're assembling the pool from the split-off vdevs of
+        * an existing pool, we don't want to attach the spares & cache
+        * devices.
+        */
+
+       /*
+        * Load any hot spares for this pool.
+        */
+       error = spa_dir_prop(spa, DMU_POOL_SPARES, &spa->spa_spares.sav_object,
+           B_FALSE);
+       if (error != 0 && error != ENOENT)
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       if (error == 0 && type != SPA_IMPORT_ASSEMBLE) {
+               ASSERT(spa_version(spa) >= SPA_VERSION_SPARES);
+               if (load_nvlist(spa, spa->spa_spares.sav_object,
+                   &spa->spa_spares.sav_config) != 0) {
+                       spa_load_failed(spa, "error loading spares nvlist");
+                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+               }
+
+               spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+               spa_load_spares(spa);
+               spa_config_exit(spa, SCL_ALL, FTAG);
+       } else if (error == 0) {
+               spa->spa_spares.sav_sync = B_TRUE;
+       }
+
+       /*
         * Load any level 2 ARC devices for this pool.
         */
        error = spa_dir_prop(spa, DMU_POOL_L2CACHE,
-           &spa->spa_l2cache.sav_object);
+           &spa->spa_l2cache.sav_object, B_FALSE);
        if (error != 0 && error != ENOENT)
                return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
        if (error == 0 && type != SPA_IMPORT_ASSEMBLE) {
                ASSERT(spa_version(spa) >= SPA_VERSION_L2CACHE);
                if (load_nvlist(spa, spa->spa_l2cache.sav_object,
-                   &spa->spa_l2cache.sav_config) != 0)
+                   &spa->spa_l2cache.sav_config) != 0) {
+                       spa_load_failed(spa, "error loading l2cache nvlist");
                        return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+               }
 
                spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
                spa_load_l2cache(spa);
@@ -3047,26 +3580,14 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                spa->spa_l2cache.sav_sync = B_TRUE;
        }
 
-       spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);
-
-       error = spa_dir_prop(spa, DMU_POOL_PROPS, &spa->spa_pool_props_object);
-       if (error && error != ENOENT)
-               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
-
-       if (error == 0) {
-               uint64_t autoreplace = 0;
-
-               spa_prop_find(spa, ZPOOL_PROP_BOOTFS, &spa->spa_bootfs);
-               spa_prop_find(spa, ZPOOL_PROP_AUTOREPLACE, &autoreplace);
-               spa_prop_find(spa, ZPOOL_PROP_DELEGATION, &spa->spa_delegation);
-               spa_prop_find(spa, ZPOOL_PROP_FAILUREMODE, &spa->spa_failmode);
-               spa_prop_find(spa, ZPOOL_PROP_AUTOEXPAND, &spa->spa_autoexpand);
-               spa_prop_find(spa, ZPOOL_PROP_MULTIHOST, &spa->spa_multihost);
-               spa_prop_find(spa, ZPOOL_PROP_DEDUPDITTO,
-                   &spa->spa_dedup_ditto);
+       return (0);
+}
 
-               spa->spa_autoreplace = (autoreplace != 0);
-       }
+static int
+spa_ld_load_vdev_metadata(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
 
        /*
         * If the 'multihost' property is set, then never allow a pool to
@@ -3087,120 +3608,597 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
         * unopenable vdevs so that the normal autoreplace handler can take
         * over.
         */
-       if (spa->spa_autoreplace && state != SPA_LOAD_TRYIMPORT) {
+       if (spa->spa_autoreplace && spa->spa_load_state != SPA_LOAD_TRYIMPORT) {
                spa_check_removed(spa->spa_root_vdev);
                /*
                 * For the import case, this is done in spa_import(), because
                 * at this point we're using the spare definitions from
                 * the MOS config, not necessarily from the userland config.
                 */
-               if (state != SPA_LOAD_IMPORT) {
+               if (spa->spa_load_state != SPA_LOAD_IMPORT) {
                        spa_aux_check_removed(&spa->spa_spares);
                        spa_aux_check_removed(&spa->spa_l2cache);
                }
        }
 
        /*
-        * Load the vdev state for all toplevel vdevs.
+        * Load the vdev metadata such as metaslabs, DTLs, spacemap object, etc.
         */
-       vdev_load(rvd);
+       error = vdev_load(rvd);
+       if (error != 0) {
+               spa_load_failed(spa, "vdev_load failed [error=%d]", error);
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, error));
+       }
 
        /*
-        * Propagate the leaf DTLs we just loaded all the way up the tree.
+        * Propagate the leaf DTLs we just loaded all the way up the vdev tree.
         */
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        vdev_dtl_reassess(rvd, 0, 0, B_FALSE);
        spa_config_exit(spa, SCL_ALL, FTAG);
 
+       return (0);
+}
+
+static int
+spa_ld_load_dedup_tables(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
+       error = ddt_load(spa);
+       if (error != 0) {
+               spa_load_failed(spa, "ddt_load failed [error=%d]", error);
+               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_verify_logs(spa_t *spa, spa_import_type_t type, char **ereport)
+{
+       vdev_t *rvd = spa->spa_root_vdev;
+
+       if (type != SPA_IMPORT_ASSEMBLE && spa_writeable(spa)) {
+               boolean_t missing = spa_check_logs(spa);
+               if (missing) {
+                       if (spa->spa_missing_tvds != 0) {
+                               spa_load_note(spa, "spa_check_logs failed "
+                                   "so dropping the logs");
+                       } else {
+                               *ereport = FM_EREPORT_ZFS_LOG_REPLAY;
+                               spa_load_failed(spa, "spa_check_logs failed");
+                               return (spa_vdev_err(rvd, VDEV_AUX_BAD_LOG,
+                                   ENXIO));
+                       }
+               }
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_verify_pool_data(spa_t *spa)
+{
+       int error = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+
        /*
-        * Load the DDTs (dedup tables).
+        * We've successfully opened the pool, verify that we're ready
+        * to start pushing transactions.
         */
-       error = ddt_load(spa);
+       if (spa->spa_load_state != SPA_LOAD_TRYIMPORT) {
+               error = spa_load_verify(spa);
+               if (error != 0) {
+                       spa_load_failed(spa, "spa_load_verify failed "
+                           "[error=%d]", error);
+                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
+                           error));
+               }
+       }
+
+       return (0);
+}
+
+static void
+spa_ld_claim_log_blocks(spa_t *spa)
+{
+       dmu_tx_t *tx;
+       dsl_pool_t *dp = spa_get_dsl(spa);
+
+       /*
+        * Claim log blocks that haven't been committed yet.
+        * This must all happen in a single txg.
+        * Note: spa_claim_max_txg is updated by spa_claim_notify(),
+        * invoked from zil_claim_log_block()'s i/o done callback.
+        * Price of rollback is that we abandon the log.
+        */
+       spa->spa_claiming = B_TRUE;
+
+       tx = dmu_tx_create_assigned(dp, spa_first_txg(spa));
+       (void) dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
+           zil_claim, tx, DS_FIND_CHILDREN);
+       dmu_tx_commit(tx);
+
+       spa->spa_claiming = B_FALSE;
+
+       spa_set_log_state(spa, SPA_LOG_GOOD);
+}
+
+static void
+spa_ld_check_for_config_update(spa_t *spa, uint64_t config_cache_txg,
+    boolean_t update_config_cache)
+{
+       vdev_t *rvd = spa->spa_root_vdev;
+       int need_update = B_FALSE;
+
+       /*
+        * If the config cache is stale, or we have uninitialized
+        * metaslabs (see spa_vdev_add()), then update the config.
+        *
+        * If this is a verbatim import, trust the current
+        * in-core spa_config and update the disk labels.
+        */
+       if (update_config_cache || config_cache_txg != spa->spa_config_txg ||
+           spa->spa_load_state == SPA_LOAD_IMPORT ||
+           spa->spa_load_state == SPA_LOAD_RECOVER ||
+           (spa->spa_import_flags & ZFS_IMPORT_VERBATIM))
+               need_update = B_TRUE;
+
+       for (int c = 0; c < rvd->vdev_children; c++)
+               if (rvd->vdev_child[c]->vdev_ms_array == 0)
+                       need_update = B_TRUE;
+
+       /*
+        * Update the config cache asychronously in case we're the
+        * root pool, in which case the config cache isn't writable yet.
+        */
+       if (need_update)
+               spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
+}
+
+static void
+spa_ld_prepare_for_reload(spa_t *spa)
+{
+       int mode = spa->spa_mode;
+       int async_suspended = spa->spa_async_suspended;
+
+       spa_unload(spa);
+       spa_deactivate(spa);
+       spa_activate(spa, mode);
+
+       /*
+        * We save the value of spa_async_suspended as it gets reset to 0 by
+        * spa_unload(). We want to restore it back to the original value before
+        * returning as we might be calling spa_async_resume() later.
+        */
+       spa->spa_async_suspended = async_suspended;
+}
+
+static int
+spa_ld_read_checkpoint_txg(spa_t *spa)
+{
+       uberblock_t checkpoint;
+       int error = 0;
+
+       ASSERT0(spa->spa_checkpoint_txg);
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+
+       error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+           DMU_POOL_ZPOOL_CHECKPOINT, sizeof (uint64_t),
+           sizeof (uberblock_t) / sizeof (uint64_t), &checkpoint);
+
+       if (error == ENOENT)
+               return (0);
+
        if (error != 0)
-               return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+               return (error);
 
-       spa_update_dspace(spa);
+       ASSERT3U(checkpoint.ub_txg, !=, 0);
+       ASSERT3U(checkpoint.ub_checkpoint_txg, !=, 0);
+       ASSERT3U(checkpoint.ub_timestamp, !=, 0);
+       spa->spa_checkpoint_txg = checkpoint.ub_txg;
+       spa->spa_checkpoint_info.sci_timestamp = checkpoint.ub_timestamp;
+
+       return (0);
+}
+
+static int
+spa_ld_mos_init(spa_t *spa, spa_import_type_t type)
+{
+       int error = 0;
+
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       ASSERT(spa->spa_config_source != SPA_CONFIG_SRC_NONE);
 
        /*
-        * Validate the config, using the MOS config to fill in any
-        * information which might be missing.  If we fail to validate
-        * the config then declare the pool unfit for use. If we're
-        * assembling a pool from a split, the log is not transferred
-        * over.
+        * Never trust the config that is provided unless we are assembling
+        * a pool following a split.
+        * This means don't trust blkptrs and the vdev tree in general. This
+        * also effectively puts the spa in read-only mode since
+        * spa_writeable() checks for spa_trust_config to be true.
+        * We will later load a trusted config from the MOS.
+        */
+       if (type != SPA_IMPORT_ASSEMBLE)
+               spa->spa_trust_config = B_FALSE;
+
+       /*
+        * Parse the config provided to create a vdev tree.
+        */
+       error = spa_ld_parse_config(spa, type);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Now that we have the vdev tree, try to open each vdev. This involves
+        * opening the underlying physical device, retrieving its geometry and
+        * probing the vdev with a dummy I/O. The state of each vdev will be set
+        * based on the success of those operations. After this we'll be ready
+        * to read from the vdevs.
+        */
+       error = spa_ld_open_vdevs(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Read the label of each vdev and make sure that the GUIDs stored
+        * there match the GUIDs in the config provided.
+        * If we're assembling a new pool that's been split off from an
+        * existing pool, the labels haven't yet been updated so we skip
+        * validation for now.
         */
        if (type != SPA_IMPORT_ASSEMBLE) {
-               nvlist_t *nvconfig;
+               error = spa_ld_validate_vdevs(spa);
+               if (error != 0)
+                       return (error);
+       }
 
-               if (load_nvlist(spa, spa->spa_config_object, &nvconfig) != 0)
-                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
+       /*
+        * Read all vdev labels to find the best uberblock (i.e. latest,
+        * unless spa_load_max_txg is set) and store it in spa_uberblock. We
+        * get the list of features required to read blkptrs in the MOS from
+        * the vdev label with the best uberblock and verify that our version
+        * of zfs supports them all.
+        */
+       error = spa_ld_select_uberblock(spa, type);
+       if (error != 0)
+               return (error);
 
-               if (!spa_config_valid(spa, nvconfig)) {
-                       nvlist_free(nvconfig);
-                       return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM,
-                           ENXIO));
+       /*
+        * Pass that uberblock to the dsl_pool layer which will open the root
+        * blkptr. This blkptr points to the latest version of the MOS and will
+        * allow us to read its contents.
+        */
+       error = spa_ld_open_rootbp(spa);
+       if (error != 0)
+               return (error);
+
+       return (0);
+}
+
+static int
+spa_ld_checkpoint_rewind(spa_t *spa)
+{
+       uberblock_t checkpoint;
+       int error = 0;
+
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       ASSERT(spa->spa_import_flags & ZFS_IMPORT_CHECKPOINT);
+
+       error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
+           DMU_POOL_ZPOOL_CHECKPOINT, sizeof (uint64_t),
+           sizeof (uberblock_t) / sizeof (uint64_t), &checkpoint);
+
+       if (error != 0) {
+               spa_load_failed(spa, "unable to retrieve checkpointed "
+                   "uberblock from the MOS config [error=%d]", error);
+
+               if (error == ENOENT)
+                       error = ZFS_ERR_NO_CHECKPOINT;
+
+               return (error);
+       }
+
+       ASSERT3U(checkpoint.ub_txg, <, spa->spa_uberblock.ub_txg);
+       ASSERT3U(checkpoint.ub_txg, ==, checkpoint.ub_checkpoint_txg);
+
+       /*
+        * We need to update the txg and timestamp of the checkpointed
+        * uberblock to be higher than the latest one. This ensures that
+        * the checkpointed uberblock is selected if we were to close and
+        * reopen the pool right after we've written it in the vdev labels.
+        * (also see block comment in vdev_uberblock_compare)
+        */
+       checkpoint.ub_txg = spa->spa_uberblock.ub_txg + 1;
+       checkpoint.ub_timestamp = gethrestime_sec();
+
+       /*
+        * Set current uberblock to be the checkpointed uberblock.
+        */
+       spa->spa_uberblock = checkpoint;
+
+       /*
+        * If we are doing a normal rewind, then the pool is open for
+        * writing and we sync the "updated" checkpointed uberblock to
+        * disk. Once this is done, we've basically rewound the whole
+        * pool and there is no way back.
+        *
+        * There are cases when we don't want to attempt and sync the
+        * checkpointed uberblock to disk because we are opening a
+        * pool as read-only. Specifically, verifying the checkpointed
+        * state with zdb, and importing the checkpointed state to get
+        * a "preview" of its content.
+        */
+       if (spa_writeable(spa)) {
+               vdev_t *rvd = spa->spa_root_vdev;
+
+               spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+               vdev_t *svd[SPA_SYNC_MIN_VDEVS] = { NULL };
+               int svdcount = 0;
+               int children = rvd->vdev_children;
+               int c0 = spa_get_random(children);
+
+               for (int c = 0; c < children; c++) {
+                       vdev_t *vd = rvd->vdev_child[(c0 + c) % children];
+
+                       /* Stop when revisiting the first vdev */
+                       if (c > 0 && svd[0] == vd)
+                               break;
+
+                       if (vd->vdev_ms_array == 0 || vd->vdev_islog ||
+                           !vdev_is_concrete(vd))
+                               continue;
+
+                       svd[svdcount++] = vd;
+                       if (svdcount == SPA_SYNC_MIN_VDEVS)
+                               break;
+               }
+               error = vdev_config_sync(svd, svdcount, spa->spa_first_txg);
+               if (error == 0)
+                       spa->spa_last_synced_guid = rvd->vdev_guid;
+               spa_config_exit(spa, SCL_ALL, FTAG);
+
+               if (error != 0) {
+                       spa_load_failed(spa, "failed to write checkpointed "
+                           "uberblock to the vdev labels [error=%d]", error);
+                       return (error);
                }
-               nvlist_free(nvconfig);
+       }
+
+       return (0);
+}
+
+static int
+spa_ld_mos_with_trusted_config(spa_t *spa, spa_import_type_t type,
+    boolean_t *update_config_cache)
+{
+       int error;
+
+       /*
+        * Parse the config for pool, open and validate vdevs,
+        * select an uberblock, and use that uberblock to open
+        * the MOS.
+        */
+       error = spa_ld_mos_init(spa, type);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Retrieve the trusted config stored in the MOS and use it to create
+        * a new, exact version of the vdev tree, then reopen all vdevs.
+        */
+       error = spa_ld_trusted_config(spa, type, B_FALSE);
+       if (error == EAGAIN) {
+               if (update_config_cache != NULL)
+                       *update_config_cache = B_TRUE;
 
                /*
-                * Now that we've validated the config, check the state of the
-                * root vdev.  If it can't be opened, it indicates one or
-                * more toplevel vdevs are faulted.
+                * Redo the loading process with the trusted config if it is
+                * too different from the untrusted config.
                 */
-               if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN)
-                       return (SET_ERROR(ENXIO));
+               spa_ld_prepare_for_reload(spa);
+               spa_load_note(spa, "RELOADING");
+               error = spa_ld_mos_init(spa, type);
+               if (error != 0)
+                       return (error);
 
-               if (spa_writeable(spa) && spa_check_logs(spa)) {
-                       *ereport = FM_EREPORT_ZFS_LOG_REPLAY;
-                       return (spa_vdev_err(rvd, VDEV_AUX_BAD_LOG, ENXIO));
-               }
+               error = spa_ld_trusted_config(spa, type, B_TRUE);
+               if (error != 0)
+                       return (error);
+
+       } else if (error != 0) {
+               return (error);
+       }
+
+       return (0);
+}
+
+/*
+ * Load an existing storage pool, using the config provided. This config
+ * describes which vdevs are part of the pool and is later validated against
+ * partial configs present in each vdev's label and an entire copy of the
+ * config stored in the MOS.
+ */
+static int
+spa_load_impl(spa_t *spa, spa_import_type_t type, char **ereport)
+{
+       int error = 0;
+       boolean_t missing_feat_write = B_FALSE;
+       boolean_t checkpoint_rewind =
+           (spa->spa_import_flags & ZFS_IMPORT_CHECKPOINT);
+       boolean_t update_config_cache = B_FALSE;
+
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       ASSERT(spa->spa_config_source != SPA_CONFIG_SRC_NONE);
+
+       spa_load_note(spa, "LOADING");
+
+       error = spa_ld_mos_with_trusted_config(spa, type, &update_config_cache);
+       if (error != 0)
+               return (error);
+
+       /*
+        * If we are rewinding to the checkpoint then we need to repeat
+        * everything we've done so far in this function but this time
+        * selecting the checkpointed uberblock and using that to open
+        * the MOS.
+        */
+       if (checkpoint_rewind) {
+               /*
+                * If we are rewinding to the checkpoint update config cache
+                * anyway.
+                */
+               update_config_cache = B_TRUE;
+
+               /*
+                * Extract the checkpointed uberblock from the current MOS
+                * and use this as the pool's uberblock from now on. If the
+                * pool is imported as writeable we also write the checkpoint
+                * uberblock to the labels, making the rewind permanent.
+                */
+               error = spa_ld_checkpoint_rewind(spa);
+               if (error != 0)
+                       return (error);
+
+               /*
+                * Redo the loading process process again with the
+                * checkpointed uberblock.
+                */
+               spa_ld_prepare_for_reload(spa);
+               spa_load_note(spa, "LOADING checkpointed uberblock");
+               error = spa_ld_mos_with_trusted_config(spa, type, NULL);
+               if (error != 0)
+                       return (error);
        }
 
+       /*
+        * Retrieve the checkpoint txg if the pool has a checkpoint.
+        */
+       error = spa_ld_read_checkpoint_txg(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Retrieve the mapping of indirect vdevs. Those vdevs were removed
+        * from the pool and their contents were re-mapped to other vdevs. Note
+        * that everything that we read before this step must have been
+        * rewritten on concrete vdevs after the last device removal was
+        * initiated. Otherwise we could be reading from indirect vdevs before
+        * we have loaded their mappings.
+        */
+       error = spa_ld_open_indirect_vdev_metadata(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Retrieve the full list of active features from the MOS and check if
+        * they are all supported.
+        */
+       error = spa_ld_check_features(spa, &missing_feat_write);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Load several special directories from the MOS needed by the dsl_pool
+        * layer.
+        */
+       error = spa_ld_load_special_directories(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Retrieve pool properties from the MOS.
+        */
+       error = spa_ld_get_props(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Retrieve the list of auxiliary devices - cache devices and spares -
+        * and open them.
+        */
+       error = spa_ld_open_aux_vdevs(spa, type);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Load the metadata for all vdevs. Also check if unopenable devices
+        * should be autoreplaced.
+        */
+       error = spa_ld_load_vdev_metadata(spa);
+       if (error != 0)
+               return (error);
+
+       error = spa_ld_load_dedup_tables(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Verify the logs now to make sure we don't have any unexpected errors
+        * when we claim log blocks later.
+        */
+       error = spa_ld_verify_logs(spa, type, ereport);
+       if (error != 0)
+               return (error);
+
        if (missing_feat_write) {
-               ASSERT(state == SPA_LOAD_TRYIMPORT);
+               ASSERT(spa->spa_load_state == SPA_LOAD_TRYIMPORT);
 
                /*
                 * At this point, we know that we can open the pool in
                 * read-only mode but not read-write mode. We now have enough
                 * information and can return to userland.
                 */
-               return (spa_vdev_err(rvd, VDEV_AUX_UNSUP_FEAT, ENOTSUP));
+               return (spa_vdev_err(spa->spa_root_vdev, VDEV_AUX_UNSUP_FEAT,
+                   ENOTSUP));
        }
 
        /*
-        * We've successfully opened the pool, verify that we're ready
-        * to start pushing transactions.
+        * Traverse the last txgs to make sure the pool was left off in a safe
+        * state. When performing an extreme rewind, we verify the whole pool,
+        * which can take a very long time.
         */
-       if (state != SPA_LOAD_TRYIMPORT) {
-               if ((error = spa_load_verify(spa)))
-                       return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
-                           error));
-       }
+       error = spa_ld_verify_pool_data(spa);
+       if (error != 0)
+               return (error);
+
+       /*
+        * Calculate the deflated space for the pool. This must be done before
+        * we write anything to the pool because we'd need to update the space
+        * accounting using the deflated sizes.
+        */
+       spa_update_dspace(spa);
 
-       if (spa_writeable(spa) && (state == SPA_LOAD_RECOVER ||
+       /*
+        * We have now retrieved all the information we needed to open the
+        * pool. If we are importing the pool in read-write mode, a few
+        * additional steps must be performed to finish the import.
+        */
+       if (spa_writeable(spa) && (spa->spa_load_state == SPA_LOAD_RECOVER ||
            spa->spa_load_max_txg == UINT64_MAX)) {
-               dmu_tx_t *tx;
-               int need_update = B_FALSE;
-               dsl_pool_t *dp = spa_get_dsl(spa);
+               uint64_t config_cache_txg = spa->spa_config_txg;
 
-               ASSERT(state != SPA_LOAD_TRYIMPORT);
+               ASSERT(spa->spa_load_state != SPA_LOAD_TRYIMPORT);
 
                /*
-                * Claim log blocks that haven't been committed yet.
-                * This must all happen in a single txg.
-                * Note: spa_claim_max_txg is updated by spa_claim_notify(),
-                * invoked from zil_claim_log_block()'s i/o done callback.
-                * Price of rollback is that we abandon the log.
+                * In case of a checkpoint rewind, log the original txg
+                * of the checkpointed uberblock.
                 */
-               spa->spa_claiming = B_TRUE;
-
-               tx = dmu_tx_create_assigned(dp, spa_first_txg(spa));
-               (void) dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
-                   zil_claim, tx, DS_FIND_CHILDREN);
-               dmu_tx_commit(tx);
+               if (checkpoint_rewind) {
+                       spa_history_log_internal(spa, "checkpoint rewind",
+                           NULL, "rewound state to txg=%llu",
+                           (u_longlong_t)spa->spa_uberblock.ub_checkpoint_txg);
+               }
 
-               spa->spa_claiming = B_FALSE;
+               /*
+                * Traverse the ZIL and claim all blocks.
+                */
+               spa_ld_claim_log_blocks(spa);
 
-               spa_set_log_state(spa, SPA_LOG_GOOD);
+               /*
+                * Kick-off the syncing thread.
+                */
                spa->spa_sync_on = B_TRUE;
                txg_sync_start(spa->spa_dsl_pool);
                mmp_thread_start(spa);
@@ -3209,40 +4207,24 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                 * Wait for all claims to sync.  We sync up to the highest
                 * claimed log block birth time so that claimed log blocks
                 * don't appear to be from the future.  spa_claim_max_txg
-                * will have been set for us by either zil_check_log_chain()
-                * (invoked from spa_check_logs()) or zil_claim() above.
+                * will have been set for us by ZIL traversal operations
+                * performed above.
                 */
                txg_wait_synced(spa->spa_dsl_pool, spa->spa_claim_max_txg);
 
                /*
-                * If the config cache is stale, or we have uninitialized
-                * metaslabs (see spa_vdev_add()), then update the config.
-                *
-                * If this is a verbatim import, trust the current
-                * in-core spa_config and update the disk labels.
-                */
-               if (config_cache_txg != spa->spa_config_txg ||
-                   state == SPA_LOAD_IMPORT ||
-                   state == SPA_LOAD_RECOVER ||
-                   (spa->spa_import_flags & ZFS_IMPORT_VERBATIM))
-                       need_update = B_TRUE;
-
-               for (int c = 0; c < rvd->vdev_children; c++)
-                       if (rvd->vdev_child[c]->vdev_ms_array == 0)
-                               need_update = B_TRUE;
-
-               /*
-                * Update the config cache asychronously in case we're the
-                * root pool, in which case the config cache isn't writable yet.
+                * Check if we need to request an update of the config. On the
+                * next sync, we would update the config stored in vdev labels
+                * and the cachefile (by default /etc/zfs/zpool.cache).
                 */
-               if (need_update)
-                       spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
+               spa_ld_check_for_config_update(spa, config_cache_txg,
+                   update_config_cache);
 
                /*
                 * Check all DTLs to see if anything needs resilvering.
                 */
                if (!dsl_scan_resilvering(spa->spa_dsl_pool) &&
-                   vdev_resilver_needed(rvd, NULL, NULL))
+                   vdev_resilver_needed(spa->spa_root_vdev, NULL, NULL))
                        spa_async_request(spa, SPA_ASYNC_RESILVER);
 
                /*
@@ -3251,8 +4233,17 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                 */
                spa_history_log_version(spa, "open", NULL);
 
+               spa_restart_removal(spa);
+               spa_spawn_aux_threads(spa);
+
                /*
                 * Delete any inconsistent datasets.
+                *
+                * Note:
+                * Since we may be issuing deletes for clones here,
+                * we make sure to do so after we've spawned all the
+                * auxiliary threads above (from which the livelist
+                * deletion zthr is part of).
                 */
                (void) dmu_objset_find(spa_name(spa),
                    dsl_destroy_inconsistent, NULL, DS_FIND_CHILDREN);
@@ -3261,13 +4252,19 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
                 * Clean up any stale temporary dataset userrefs.
                 */
                dsl_pool_clean_tmp_userrefs(spa->spa_dsl_pool);
+
+               spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+               vdev_initialize_restart(spa->spa_root_vdev);
+               spa_config_exit(spa, SCL_CONFIG, FTAG);
        }
 
+       spa_load_note(spa, "LOADED");
+
        return (0);
 }
 
 static int
-spa_load_retry(spa_t *spa, spa_load_state_t state, int mosconfig)
+spa_load_retry(spa_t *spa, spa_load_state_t state)
 {
        int mode = spa->spa_mode;
 
@@ -3279,7 +4276,10 @@ spa_load_retry(spa_t *spa, spa_load_state_t state, int mosconfig)
        spa_activate(spa, mode);
        spa_async_suspend(spa);
 
-       return (spa_load(spa, state, SPA_IMPORT_EXISTING, mosconfig));
+       spa_load_note(spa, "spa_load_retry: rewind, max txg: %llu",
+           (u_longlong_t)spa->spa_load_max_txg);
+
+       return (spa_load(spa, state, SPA_IMPORT_EXISTING));
 }
 
 /*
@@ -3290,8 +4290,8 @@ spa_load_retry(spa_t *spa, spa_load_state_t state, int mosconfig)
  * spa_load().
  */
 static int
-spa_load_best(spa_t *spa, spa_load_state_t state, int mosconfig,
-    uint64_t max_request, int rewind_flags)
+spa_load_best(spa_t *spa, spa_load_state_t state, uint64_t max_request,
+    int rewind_flags)
 {
        nvlist_t *loadinfo = NULL;
        nvlist_t *config = NULL;
@@ -3308,10 +4308,18 @@ spa_load_best(spa_t *spa, spa_load_state_t state, int mosconfig,
                        spa->spa_extreme_rewind = B_TRUE;
        }
 
-       load_error = rewind_error = spa_load(spa, state, SPA_IMPORT_EXISTING,
-           mosconfig);
+       load_error = rewind_error = spa_load(spa, state, SPA_IMPORT_EXISTING);
        if (load_error == 0)
                return (0);
+       if (load_error == ZFS_ERR_NO_CHECKPOINT) {
+               /*
+                * When attempting checkpoint-rewind on a pool with no
+                * checkpoint, we should not attempt to load uberblocks
+                * from previous txgs when spa_load fails.
+                */
+               ASSERT(spa->spa_import_flags & ZFS_IMPORT_CHECKPOINT);
+               return (load_error);
+       }
 
        if (spa->spa_root_vdev != NULL)
                config = spa_config_generate(spa, NULL, -1ULL, B_TRUE);
@@ -3350,7 +4358,7 @@ spa_load_best(spa_t *spa, spa_load_state_t state, int mosconfig,
            spa->spa_uberblock.ub_txg <= spa->spa_load_max_txg) {
                if (spa->spa_load_max_txg < safe_rewind_txg)
                        spa->spa_extreme_rewind = B_TRUE;
-               rewind_error = spa_load_retry(spa, state, mosconfig);
+               rewind_error = spa_load_retry(spa, state);
        }
 
        spa->spa_extreme_rewind = B_FALSE;
@@ -3419,22 +4427,24 @@ spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t *nvpolicy,
        }
 
        if (spa->spa_state == POOL_STATE_UNINITIALIZED) {
-               zpool_rewind_policy_t policy;
+               zpool_load_policy_t policy;
 
                firstopen = B_TRUE;
 
-               zpool_get_rewind_policy(nvpolicy ? nvpolicy : spa->spa_config,
+               zpool_get_load_policy(nvpolicy ? nvpolicy : spa->spa_config,
                    &policy);
-               if (policy.zrp_request & ZPOOL_DO_REWIND)
+               if (policy.zlp_rewind & ZPOOL_DO_REWIND)
                        state = SPA_LOAD_RECOVER;
 
                spa_activate(spa, spa_mode_global);
 
                if (state != SPA_LOAD_RECOVER)
                        spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
+               spa->spa_config_source = SPA_CONFIG_SRC_CACHEFILE;
 
-               error = spa_load_best(spa, state, B_FALSE, policy.zrp_txg,
-                   policy.zrp_request);
+               zfs_dbgmsg("spa_open_common: opening %s", pool);
+               error = spa_load_best(spa, state, policy.zlp_txg,
+                   policy.zlp_rewind);
 
                if (error == EBADF) {
                        /*
@@ -3446,7 +4456,7 @@ spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t *nvpolicy,
                         */
                        spa_unload(spa);
                        spa_deactivate(spa);
-                       spa_config_sync(spa, B_TRUE, B_TRUE);
+                       spa_write_cachefile(spa, B_TRUE, B_TRUE);
                        spa_remove(spa);
                        if (locked)
                                mutex_exit(&spa_namespace_lock);
@@ -3982,7 +4992,7 @@ spa_create_check_encryption_params(dsl_crypto_params_t *dcp,
            !has_encryption)
                return (SET_ERROR(ENOTSUP));
 
-       return (dmu_objset_create_crypt_check(NULL, dcp));
+       return (dmu_objset_create_crypt_check(NULL, dcp, NULL));
 }
 
 /*
@@ -4001,7 +5011,7 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
        uint64_t txg = TXG_INITIAL;
        nvlist_t **spares, **l2cache;
        uint_t nspares, nl2cache;
-       uint64_t version, obj, root_dsobj = 0;
+       uint64_t version, obj;
        boolean_t has_features;
        boolean_t has_encryption;
        spa_feature_t feat;
@@ -4009,7 +5019,8 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
        char *poolname;
        nvlist_t *nvl;
 
-       if (nvlist_lookup_string(props, "tname", &poolname) != 0)
+       if (props == NULL ||
+           nvlist_lookup_string(props, "tname", &poolname) != 0)
                poolname = (char *)pool;
 
        /*
@@ -4081,6 +5092,9 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
        spa->spa_uberblock.ub_version = version;
        spa->spa_ubsync = spa->spa_uberblock;
        spa->spa_load_state = SPA_LOAD_CREATE;
+       spa->spa_removing_phys.sr_state = DSS_NONE;
+       spa->spa_removing_phys.sr_removing_vdev = -1;
+       spa->spa_removing_phys.sr_prev_indirect_vdev = -1;
 
        /*
         * Create "The Godfather" zio to hold all async IOs
@@ -4110,9 +5124,15 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
            (error = vdev_create(rvd, txg, B_FALSE)) == 0 &&
            (error = spa_validate_aux(spa, nvroot, txg,
            VDEV_ALLOC_ADD)) == 0) {
-               for (int c = 0; c < rvd->vdev_children; c++) {
-                       vdev_metaslab_set_size(rvd->vdev_child[c]);
-                       vdev_expand(rvd->vdev_child[c], txg);
+               /*
+                * instantiate the metaslab groups (this will dirty the vdevs)
+                * we can no longer error exit past this point
+                */
+               for (int c = 0; error == 0 && c < rvd->vdev_children; c++) {
+                       vdev_t *vd = rvd->vdev_child[c];
+
+                       vdev_metaslab_set_size(vd);
+                       vdev_expand(vd, txg);
                }
        }
 
@@ -4245,35 +5265,21 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 
        dmu_tx_commit(tx);
 
-       /*
-        * If the root dataset is encrypted we will need to create key mappings
-        * for the zio layer before we start to write any data to disk and hold
-        * them until after the first txg has been synced. Waiting for the first
-        * transaction to complete also ensures that our bean counters are
-        * appropriately updated.
-        */
-       if (dp->dp_root_dir->dd_crypto_obj != 0) {
-               root_dsobj = dsl_dir_phys(dp->dp_root_dir)->dd_head_dataset_obj;
-               VERIFY0(spa_keystore_create_mapping_impl(spa, root_dsobj,
-                   dp->dp_root_dir, FTAG));
-       }
-
        spa->spa_sync_on = B_TRUE;
        txg_sync_start(dp);
        mmp_thread_start(spa);
        txg_wait_synced(dp, txg);
 
-       if (dp->dp_root_dir->dd_crypto_obj != 0)
-               VERIFY0(spa_keystore_remove_mapping(spa, root_dsobj, FTAG));
+       spa_spawn_aux_threads(spa);
 
-       spa_config_sync(spa, B_FALSE, B_TRUE);
+       spa_write_cachefile(spa, B_FALSE, B_TRUE);
 
        /*
         * Don't count references from objsets that are already closed
         * and are making their way through the eviction process.
         */
        spa_evicting_os_wait(spa);
-       spa->spa_minref = refcount_count(&spa->spa_refcount);
+       spa->spa_minref = zfs_refcount_count(&spa->spa_refcount);
        spa->spa_load_state = SPA_LOAD_NONE;
 
        mutex_exit(&spa_namespace_lock);
@@ -4290,7 +5296,7 @@ spa_import(char *pool, nvlist_t *config, nvlist_t *props, uint64_t flags)
        spa_t *spa;
        char *altroot = NULL;
        spa_load_state_t state = SPA_LOAD_IMPORT;
-       zpool_rewind_policy_t policy;
+       zpool_load_policy_t policy;
        uint64_t mode = spa_mode_global;
        uint64_t readonly = B_FALSE;
        int error;
@@ -4327,9 +5333,9 @@ spa_import(char *pool, nvlist_t *config, nvlist_t *props, uint64_t flags)
                if (props != NULL)
                        spa_configfile_set(spa, props, B_FALSE);
 
-               spa_config_sync(spa, B_FALSE, B_TRUE);
+               spa_write_cachefile(spa, B_FALSE, B_TRUE);
                spa_event_notify(spa, NULL, NULL, ESC_ZFS_POOL_IMPORT);
-
+               zfs_dbgmsg("spa_import: verbatim import of %s", pool);
                mutex_exit(&spa_namespace_lock);
                return (0);
        }
@@ -4341,20 +5347,20 @@ spa_import(char *pool, nvlist_t *config, nvlist_t *props, uint64_t flags)
         */
        spa_async_suspend(spa);
 
-       zpool_get_rewind_policy(config, &policy);
-       if (policy.zrp_request & ZPOOL_DO_REWIND)
+       zpool_get_load_policy(config, &policy);
+       if (policy.zlp_rewind & ZPOOL_DO_REWIND)
                state = SPA_LOAD_RECOVER;
 
-       /*
-        * Pass off the heavy lifting to spa_load().  Pass TRUE for mosconfig
-        * because the user-supplied config is actually the one to trust when
-        * doing an import.
-        */
-       if (state != SPA_LOAD_RECOVER)
-               spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
+       spa->spa_config_source = SPA_CONFIG_SRC_TRYIMPORT;
 
-       error = spa_load_best(spa, state, B_TRUE, policy.zrp_txg,
-           policy.zrp_request);
+       if (state != SPA_LOAD_RECOVER) {
+               spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
+               zfs_dbgmsg("spa_import: importing %s", pool);
+       } else {
+               zfs_dbgmsg("spa_import: importing %s, max_txg=%lld "
+                   "(RECOVERY MODE)", pool, (longlong_t)policy.zlp_txg);
+       }
+       error = spa_load_best(spa, state, policy.zlp_txg, policy.zlp_rewind);
 
        /*
         * Propagate anything learned while loading the pool and pass it
@@ -4468,10 +5474,11 @@ nvlist_t *
 spa_tryimport(nvlist_t *tryconfig)
 {
        nvlist_t *config = NULL;
-       char *poolname;
+       char *poolname, *cachefile;
        spa_t *spa;
        uint64_t state;
        int error;
+       zpool_load_policy_t policy;
 
        if (nvlist_lookup_string(tryconfig, ZPOOL_CONFIG_POOL_NAME, &poolname))
                return (NULL);
@@ -4487,11 +5494,27 @@ spa_tryimport(nvlist_t *tryconfig)
        spa_activate(spa, FREAD);
 
        /*
-        * Pass off the heavy lifting to spa_load().
-        * Pass TRUE for mosconfig because the user-supplied config
-        * is actually the one to trust when doing an import.
+        * Rewind pool if a max txg was provided.
         */
-       error = spa_load(spa, SPA_LOAD_TRYIMPORT, SPA_IMPORT_EXISTING, B_TRUE);
+       zpool_get_load_policy(spa->spa_config, &policy);
+       if (policy.zlp_txg != UINT64_MAX) {
+               spa->spa_load_max_txg = policy.zlp_txg;
+               spa->spa_extreme_rewind = B_TRUE;
+               zfs_dbgmsg("spa_tryimport: importing %s, max_txg=%lld",
+                   poolname, (longlong_t)policy.zlp_txg);
+       } else {
+               zfs_dbgmsg("spa_tryimport: importing %s", poolname);
+       }
+
+       if (nvlist_lookup_string(tryconfig, ZPOOL_CONFIG_CACHEFILE, &cachefile)
+           == 0) {
+               zfs_dbgmsg("spa_tryimport: using cachefile '%s'", cachefile);
+               spa->spa_config_source = SPA_CONFIG_SRC_CACHEFILE;
+       } else {
+               spa->spa_config_source = SPA_CONFIG_SRC_SCAN;
+       }
+
+       error = spa_load(spa, SPA_LOAD_TRYIMPORT, SPA_IMPORT_EXISTING);
 
        /*
         * If 'tryconfig' was at least parsable, return the current config.
@@ -4640,6 +5663,18 @@ spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
                        return (SET_ERROR(EXDEV));
                }
 
+               /*
+                * We're about to export or destroy this pool. Make sure
+                * we stop all initializtion activity here before we
+                * set the spa_final_txg. This will ensure that all
+                * dirty data resulting from the initialization is
+                * committed to disk before we unload the pool.
+                */
+               if (spa->spa_root_vdev != NULL) {
+                       vdev_initialize_stop_all(spa->spa_root_vdev,
+                           VDEV_INITIALIZE_ACTIVE);
+               }
+
                /*
                 * We want this to be reflected on every label,
                 * so mark them all dirty.  spa_unload() will do the
@@ -4671,7 +5706,7 @@ export_spa:
 
        if (new_state != POOL_STATE_UNINITIALIZED) {
                if (!hardforce)
-                       spa_config_sync(spa, B_TRUE, B_TRUE);
+                       spa_write_cachefile(spa, B_TRUE, B_TRUE);
                spa_remove(spa);
        }
        mutex_exit(&spa_namespace_lock);
@@ -4763,8 +5798,40 @@ spa_vdev_add(spa_t *spa, nvlist_t *nvroot)
                return (spa_vdev_exit(spa, vd, txg, error));
 
        /*
-        * Transfer each new top-level vdev from vd to rvd.
+        * If we are in the middle of a device removal, we can only add
+        * devices which match the existing devices in the pool.
+        * If we are in the middle of a removal, or have some indirect
+        * vdevs, we can not add raidz toplevels.
         */
+       if (spa->spa_vdev_removal != NULL ||
+           spa->spa_removing_phys.sr_prev_indirect_vdev != -1) {
+               for (int c = 0; c < vd->vdev_children; c++) {
+                       tvd = vd->vdev_child[c];
+                       if (spa->spa_vdev_removal != NULL &&
+                           tvd->vdev_ashift != spa->spa_max_ashift) {
+                               return (spa_vdev_exit(spa, vd, txg, EINVAL));
+                       }
+                       /* Fail if top level vdev is raidz */
+                       if (tvd->vdev_ops == &vdev_raidz_ops) {
+                               return (spa_vdev_exit(spa, vd, txg, EINVAL));
+                       }
+                       /*
+                        * Need the top level mirror to be
+                        * a mirror of leaf vdevs only
+                        */
+                       if (tvd->vdev_ops == &vdev_mirror_ops) {
+                               for (uint64_t cid = 0;
+                                   cid < tvd->vdev_children; cid++) {
+                                       vdev_t *cvd = tvd->vdev_child[cid];
+                                       if (!cvd->vdev_ops->vdev_op_leaf) {
+                                               return (spa_vdev_exit(spa, vd,
+                                                   txg, EINVAL));
+                                       }
+                               }
+                       }
+               }
+       }
+
        for (int c = 0; c < vd->vdev_children; c++) {
 
                /*
@@ -4850,6 +5917,16 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
 
        oldvd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       if (spa_feature_is_active(spa, SPA_FEATURE_POOL_CHECKPOINT)) {
+               error = (spa_has_checkpoint(spa)) ?
+                   ZFS_ERR_CHECKPOINT_EXISTS : ZFS_ERR_DISCARDING_CHECKPOINT;
+               return (spa_vdev_exit(spa, NULL, txg, error));
+       }
+
+       if (spa->spa_vdev_removal != NULL)
+               return (spa_vdev_exit(spa, NULL, txg, EBUSY));
+
        if (oldvd == NULL)
                return (spa_vdev_exit(spa, NULL, txg, ENODEV));
 
@@ -5010,9 +6087,14 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
        /*
         * Schedule the resilver to restart in the future. We do this to
         * ensure that dmu_sync-ed blocks have been stitched into the
-        * respective datasets.
+        * respective datasets. We do not do this if resilvers have been
+        * deferred.
         */
-       dsl_resilver_restart(spa->spa_dsl_pool, dtl_max_txg);
+       if (dsl_scan_resilvering(spa_get_dsl(spa)) &&
+           spa_feature_is_enabled(spa, SPA_FEATURE_RESILVER_DEFER))
+               vdev_set_deferred_resilver(spa, newvd);
+       else
+               dsl_resilver_restart(spa->spa_dsl_pool, dtl_max_txg);
 
        if (spa->spa_bootfs)
                spa_event_notify(spa, newvd, NULL, ESC_ZFS_BOOTFS_VDEV_ATTACH);
@@ -5059,6 +6141,27 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid, int replace_done)
 
        vd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
+       /*
+        * Besides being called directly from the userland through the
+        * ioctl interface, spa_vdev_detach() can be potentially called
+        * at the end of spa_vdev_resilver_done().
+        *
+        * In the regular case, when we have a checkpoint this shouldn't
+        * happen as we never empty the DTLs of a vdev during the scrub
+        * [see comment in dsl_scan_done()]. Thus spa_vdev_resilvering_done()
+        * should never get here when we have a checkpoint.
+        *
+        * That said, even in a case when we checkpoint the pool exactly
+        * as spa_vdev_resilver_done() calls this function everything
+        * should be fine as the resilver will return right away.
+        */
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       if (spa_feature_is_active(spa, SPA_FEATURE_POOL_CHECKPOINT)) {
+               error = (spa_has_checkpoint(spa)) ?
+                   ZFS_ERR_CHECKPOINT_EXISTS : ZFS_ERR_DISCARDING_CHECKPOINT;
+               return (spa_vdev_exit(spa, NULL, txg, error));
+       }
+
        if (vd == NULL)
                return (spa_vdev_exit(spa, NULL, txg, ENODEV));
 
@@ -5276,6 +6379,117 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid, int replace_done)
        return (error);
 }
 
+static int
+spa_vdev_initialize_impl(spa_t *spa, uint64_t guid, uint64_t cmd_type,
+    list_t *vd_list)
+{
+       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);
+               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);
+               return (SET_ERROR(EINVAL));
+       } else if (!vdev_writeable(vd)) {
+               spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+               return (SET_ERROR(EROFS));
+       }
+       mutex_enter(&vd->vdev_initialize_lock);
+       spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+
+       /*
+        * When we activate an initialize action we check to see
+        * if the vdev_initialize_thread is NULL. We do this instead
+        * of using the vdev_initialize_state since there might be
+        * a previous initialization process which has completed but
+        * the thread is not exited.
+        */
+       if (cmd_type == POOL_INITIALIZE_DO &&
+           (vd->vdev_initialize_thread != NULL ||
+           vd->vdev_top->vdev_removing)) {
+               mutex_exit(&vd->vdev_initialize_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);
+               return (SET_ERROR(ESRCH));
+       } else if (cmd_type == POOL_INITIALIZE_SUSPEND &&
+           vd->vdev_initialize_state != VDEV_INITIALIZE_ACTIVE) {
+               mutex_exit(&vd->vdev_initialize_lock);
+               return (SET_ERROR(ESRCH));
+       }
+
+       switch (cmd_type) {
+       case POOL_INITIALIZE_DO:
+               vdev_initialize(vd);
+               break;
+       case POOL_INITIALIZE_CANCEL:
+               vdev_initialize_stop(vd, VDEV_INITIALIZE_CANCELED, vd_list);
+               break;
+       case POOL_INITIALIZE_SUSPEND:
+               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);
+
+       list_destroy(&vd_list);
+
+       return (total_errors);
+}
+
 /*
  * Split a set of devices from their mirrors, and create a new pool from them.
  */
@@ -5297,10 +6511,17 @@ spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
 
        txg = spa_vdev_enter(spa);
 
+       ASSERT(MUTEX_HELD(&spa_namespace_lock));
+       if (spa_feature_is_active(spa, SPA_FEATURE_POOL_CHECKPOINT)) {
+               error = (spa_has_checkpoint(spa)) ?
+                   ZFS_ERR_CHECKPOINT_EXISTS : ZFS_ERR_DISCARDING_CHECKPOINT;
+               return (spa_vdev_exit(spa, NULL, txg, error));
+       }
+
        /* clear the log and flush everything up to now */
        activate_slog = spa_passivate_log(spa);
        (void) spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);
-       error = spa_offline_log(spa);
+       error = spa_reset_logs(spa);
        txg = spa_vdev_config_enter(spa);
 
        if (activate_slog)
@@ -5328,7 +6549,7 @@ spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
                vdev_t *vd = rvd->vdev_child[c];
 
                /* don't count the holes & logs as children */
-               if (vd->vdev_islog || vd->vdev_ishole) {
+               if (vd->vdev_islog || !vdev_is_concrete(vd)) {
                        if (lastlog == 0)
                                lastlog = c;
                        continue;
@@ -5381,7 +6602,7 @@ spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
                /* make sure there's nothing stopping the split */
                if (vml[c]->vdev_parent->vdev_ops != &vdev_mirror_ops ||
                    vml[c]->vdev_islog ||
-                   vml[c]->vdev_ishole ||
+                   !vdev_is_concrete(vml[c]) ||
                    vml[c]->vdev_isspare ||
                    vml[c]->vdev_isl2cache ||
                    !vdev_writeable(vml[c]) ||
@@ -5392,7 +6613,8 @@ spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
                        break;
                }
 
-               if (vdev_dtl_required(vml[c])) {
+               if (vdev_dtl_required(vml[c]) ||
+                   vdev_resilver_needed(vml[c], NULL, NULL)) {
                        error = SET_ERROR(EBUSY);
                        break;
                }
@@ -5476,8 +6698,30 @@ 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) {
+                       mutex_enter(&vml[c]->vdev_initialize_lock);
+                       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;
+
        /* create the new pool from the disks of the original pool */
-       error = spa_load(newspa, SPA_LOAD_IMPORT, SPA_IMPORT_ASSEMBLE, B_TRUE);
+       error = spa_load(newspa, SPA_LOAD_IMPORT, SPA_IMPORT_ASSEMBLE);
        if (error)
                goto out;
 
@@ -5561,6 +6805,10 @@ out:
                if (vml[c] != NULL)
                        vml[c]->vdev_offline = B_FALSE;
        }
+
+       /* restart initializing disks as necessary */
+       spa_async_request(spa, SPA_ASYNC_INITIALIZE_RESTART);
+
        vdev_reopen(spa->spa_root_vdev);
 
        nvlist_free(spa->spa_config_splitting);
@@ -5571,257 +6819,6 @@ out:
        return (error);
 }
 
-static nvlist_t *
-spa_nvlist_lookup_by_guid(nvlist_t **nvpp, int count, uint64_t target_guid)
-{
-       for (int i = 0; i < count; i++) {
-               uint64_t guid;
-
-               VERIFY(nvlist_lookup_uint64(nvpp[i], ZPOOL_CONFIG_GUID,
-                   &guid) == 0);
-
-               if (guid == target_guid)
-                       return (nvpp[i]);
-       }
-
-       return (NULL);
-}
-
-static void
-spa_vdev_remove_aux(nvlist_t *config, char *name, nvlist_t **dev, int count,
-    nvlist_t *dev_to_remove)
-{
-       nvlist_t **newdev = NULL;
-
-       if (count > 1)
-               newdev = kmem_alloc((count - 1) * sizeof (void *), KM_SLEEP);
-
-       for (int i = 0, j = 0; i < count; i++) {
-               if (dev[i] == dev_to_remove)
-                       continue;
-               VERIFY(nvlist_dup(dev[i], &newdev[j++], KM_SLEEP) == 0);
-       }
-
-       VERIFY(nvlist_remove(config, name, DATA_TYPE_NVLIST_ARRAY) == 0);
-       VERIFY(nvlist_add_nvlist_array(config, name, newdev, count - 1) == 0);
-
-       for (int i = 0; i < count - 1; i++)
-               nvlist_free(newdev[i]);
-
-       if (count > 1)
-               kmem_free(newdev, (count - 1) * sizeof (void *));
-}
-
-/*
- * Evacuate the device.
- */
-static int
-spa_vdev_remove_evacuate(spa_t *spa, vdev_t *vd)
-{
-       uint64_t txg;
-       int error = 0;
-
-       ASSERT(MUTEX_HELD(&spa_namespace_lock));
-       ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
-       ASSERT(vd == vd->vdev_top);
-
-       /*
-        * Evacuate the device.  We don't hold the config lock as writer
-        * since we need to do I/O but we do keep the
-        * spa_namespace_lock held.  Once this completes the device
-        * should no longer have any blocks allocated on it.
-        */
-       if (vd->vdev_islog) {
-               if (vd->vdev_stat.vs_alloc != 0)
-                       error = spa_offline_log(spa);
-       } else {
-               error = SET_ERROR(ENOTSUP);
-       }
-
-       if (error)
-               return (error);
-
-       /*
-        * The evacuation succeeded.  Remove any remaining MOS metadata
-        * associated with this vdev, and wait for these changes to sync.
-        */
-       ASSERT0(vd->vdev_stat.vs_alloc);
-       txg = spa_vdev_config_enter(spa);
-       vd->vdev_removing = B_TRUE;
-       vdev_dirty_leaves(vd, VDD_DTL, txg);
-       vdev_config_dirty(vd);
-       spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);
-
-       return (0);
-}
-
-/*
- * Complete the removal by cleaning up the namespace.
- */
-static void
-spa_vdev_remove_from_namespace(spa_t *spa, vdev_t *vd)
-{
-       vdev_t *rvd = spa->spa_root_vdev;
-       uint64_t id = vd->vdev_id;
-       boolean_t last_vdev = (id == (rvd->vdev_children - 1));
-
-       ASSERT(MUTEX_HELD(&spa_namespace_lock));
-       ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
-       ASSERT(vd == vd->vdev_top);
-
-       /*
-        * Only remove any devices which are empty.
-        */
-       if (vd->vdev_stat.vs_alloc != 0)
-               return;
-
-       (void) vdev_label_init(vd, 0, VDEV_LABEL_REMOVE);
-
-       if (list_link_active(&vd->vdev_state_dirty_node))
-               vdev_state_clean(vd);
-       if (list_link_active(&vd->vdev_config_dirty_node))
-               vdev_config_clean(vd);
-
-       vdev_free(vd);
-
-       if (last_vdev) {
-               vdev_compact_children(rvd);
-       } else {
-               vd = vdev_alloc_common(spa, id, 0, &vdev_hole_ops);
-               vdev_add_child(rvd, vd);
-       }
-       vdev_config_dirty(rvd);
-
-       /*
-        * Reassess the health of our root vdev.
-        */
-       vdev_reopen(rvd);
-}
-
-/*
- * Remove a device from the pool -
- *
- * Removing a device from the vdev namespace requires several steps
- * and can take a significant amount of time.  As a result we use
- * the spa_vdev_config_[enter/exit] functions which allow us to
- * grab and release the spa_config_lock while still holding the namespace
- * lock.  During each step the configuration is synced out.
- *
- * Currently, this supports removing only hot spares, slogs, and level 2 ARC
- * devices.
- */
-int
-spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
-{
-       vdev_t *vd;
-       sysevent_t *ev = NULL;
-       metaslab_group_t *mg;
-       nvlist_t **spares, **l2cache, *nv;
-       uint64_t txg = 0;
-       uint_t nspares, nl2cache;
-       int error = 0;
-       boolean_t locked = MUTEX_HELD(&spa_namespace_lock);
-
-       ASSERT(spa_writeable(spa));
-
-       if (!locked)
-               txg = spa_vdev_enter(spa);
-
-       vd = spa_lookup_by_guid(spa, guid, B_FALSE);
-
-       if (spa->spa_spares.sav_vdevs != NULL &&
-           nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
-           ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0 &&
-           (nv = spa_nvlist_lookup_by_guid(spares, nspares, guid)) != NULL) {
-               /*
-                * Only remove the hot spare if it's not currently in use
-                * in this pool.
-                */
-               if (vd == NULL || unspare) {
-                       if (vd == NULL)
-                               vd = spa_lookup_by_guid(spa, guid, B_TRUE);
-                       ev = spa_event_create(spa, vd, NULL,
-                           ESC_ZFS_VDEV_REMOVE_AUX);
-                       spa_vdev_remove_aux(spa->spa_spares.sav_config,
-                           ZPOOL_CONFIG_SPARES, spares, nspares, nv);
-                       spa_load_spares(spa);
-                       spa->spa_spares.sav_sync = B_TRUE;
-               } else {
-                       error = SET_ERROR(EBUSY);
-               }
-       } else if (spa->spa_l2cache.sav_vdevs != NULL &&
-           nvlist_lookup_nvlist_array(spa->spa_l2cache.sav_config,
-           ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0 &&
-           (nv = spa_nvlist_lookup_by_guid(l2cache, nl2cache, guid)) != NULL) {
-               /*
-                * Cache devices can always be removed.
-                */
-               vd = spa_lookup_by_guid(spa, guid, B_TRUE);
-               ev = spa_event_create(spa, vd, NULL, ESC_ZFS_VDEV_REMOVE_AUX);
-               spa_vdev_remove_aux(spa->spa_l2cache.sav_config,
-                   ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache, nv);
-               spa_load_l2cache(spa);
-               spa->spa_l2cache.sav_sync = B_TRUE;
-       } else if (vd != NULL && vd->vdev_islog) {
-               ASSERT(!locked);
-               ASSERT(vd == vd->vdev_top);
-
-               mg = vd->vdev_mg;
-
-               /*
-                * Stop allocating from this vdev.
-                */
-               metaslab_group_passivate(mg);
-
-               /*
-                * Wait for the youngest allocations and frees to sync,
-                * and then wait for the deferral of those frees to finish.
-                */
-               spa_vdev_config_exit(spa, NULL,
-                   txg + TXG_CONCURRENT_STATES + TXG_DEFER_SIZE, 0, FTAG);
-
-               /*
-                * Attempt to evacuate the vdev.
-                */
-               error = spa_vdev_remove_evacuate(spa, vd);
-
-               txg = spa_vdev_config_enter(spa);
-
-               /*
-                * If we couldn't evacuate the vdev, unwind.
-                */
-               if (error) {
-                       metaslab_group_activate(mg);
-                       return (spa_vdev_exit(spa, NULL, txg, error));
-               }
-
-               /*
-                * Clean up the vdev namespace.
-                */
-               ev = spa_event_create(spa, vd, NULL, ESC_ZFS_VDEV_REMOVE_DEV);
-               spa_vdev_remove_from_namespace(spa, vd);
-
-       } else if (vd != NULL) {
-               /*
-                * Normal vdevs cannot be removed (yet).
-                */
-               error = SET_ERROR(ENOTSUP);
-       } else {
-               /*
-                * There is no vdev of any kind with the specified guid.
-                */
-               error = SET_ERROR(ENOENT);
-       }
-
-       if (!locked)
-               error = spa_vdev_exit(spa, NULL, txg, error);
-
-       if (ev)
-               spa_event_post(ev);
-
-       return (error);
-}
-
 /*
  * Find any device that's done replacing, or a vdev marked 'unspare' that's
  * currently spared, so we can detach it.
@@ -5859,6 +6856,7 @@ spa_vdev_resilver_done_hunt(vdev_t *vd)
 
        /*
         * Check for a completed resilver with the 'unspare' flag set.
+        * Also potentially update faulted state.
         */
        if (vd->vdev_ops == &vdev_spare_ops) {
                vdev_t *first = vd->vdev_child[0];
@@ -5880,6 +6878,8 @@ spa_vdev_resilver_done_hunt(vdev_t *vd)
                    !vdev_dtl_required(oldvd))
                        return (oldvd);
 
+               vdev_propagate_state(vd);
+
                /*
                 * If there are more than two spares attached to a disk,
                 * and those spares are not required, then we want to
@@ -6101,6 +7101,7 @@ static void
 spa_async_thread(void *arg)
 {
        spa_t *spa = (spa_t *)arg;
+       dsl_pool_t *dp = spa->spa_dsl_pool;
        int tasks;
 
        ASSERT(spa->spa_sync_on);
@@ -6118,8 +7119,14 @@ spa_async_thread(void *arg)
 
                mutex_enter(&spa_namespace_lock);
                old_space = metaslab_class_get_space(spa_normal_class(spa));
+               old_space += metaslab_class_get_space(spa_special_class(spa));
+               old_space += metaslab_class_get_space(spa_dedup_class(spa));
+
                spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
+
                new_space = metaslab_class_get_space(spa_normal_class(spa));
+               new_space += metaslab_class_get_space(spa_special_class(spa));
+               new_space += metaslab_class_get_space(spa_dedup_class(spa));
                mutex_exit(&spa_namespace_lock);
 
                /*
@@ -6170,8 +7177,18 @@ spa_async_thread(void *arg)
        /*
         * Kick off a resilver.
         */
-       if (tasks & SPA_ASYNC_RESILVER)
-               dsl_resilver_restart(spa->spa_dsl_pool, 0);
+       if (tasks & SPA_ASYNC_RESILVER &&
+           (!dsl_scan_resilvering(dp) ||
+           !spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_RESILVER_DEFER)))
+               dsl_resilver_restart(dp, 0);
+
+       if (tasks & SPA_ASYNC_INITIALIZE_RESTART) {
+               mutex_enter(&spa_namespace_lock);
+               spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+               vdev_initialize_restart(spa->spa_root_vdev);
+               spa_config_exit(spa, SCL_CONFIG, FTAG);
+               mutex_exit(&spa_namespace_lock);
+       }
 
        /*
         * Let the world know that we're done.
@@ -6191,6 +7208,16 @@ spa_async_suspend(spa_t *spa)
        while (spa->spa_async_thread != NULL)
                cv_wait(&spa->spa_async_cv, &spa->spa_async_lock);
        mutex_exit(&spa->spa_async_lock);
+
+       spa_vdev_remove_suspend(spa);
+
+       zthr_t *condense_thread = spa->spa_condense_zthr;
+       if (condense_thread != NULL)
+               zthr_cancel(condense_thread);
+
+       zthr_t *discard_thread = spa->spa_checkpoint_discard_zthr;
+       if (discard_thread != NULL)
+               zthr_cancel(discard_thread);
 }
 
 void
@@ -6200,6 +7227,15 @@ spa_async_resume(spa_t *spa)
        ASSERT(spa->spa_async_suspended != 0);
        spa->spa_async_suspended--;
        mutex_exit(&spa->spa_async_lock);
+       spa_restart_removal(spa);
+
+       zthr_t *condense_thread = spa->spa_condense_zthr;
+       if (condense_thread != NULL)
+               zthr_resume(condense_thread);
+
+       zthr_t *discard_thread = spa->spa_checkpoint_discard_zthr;
+       if (discard_thread != NULL)
+               zthr_resume(discard_thread);
 }
 
 static boolean_t
@@ -6287,6 +7323,9 @@ spa_sync_frees(spa_t *spa, bplist_t *bpl, dmu_tx_t *tx)
 static void
 spa_sync_deferred_frees(spa_t *spa, dmu_tx_t *tx)
 {
+       if (spa_sync_pass(spa) != 1)
+               return;
+
        zio_t *zio = zio_root(spa, NULL, NULL, 0);
        VERIFY3U(bpobj_iterate(&spa->spa_deferred_bpobj,
            spa_free_sync_cb, zio, tx), ==, 0);
@@ -6682,10 +7721,10 @@ spa_sync_props(void *arg, dmu_tx_t *tx)
 static void
 spa_sync_upgrades(spa_t *spa, dmu_tx_t *tx)
 {
-       dsl_pool_t *dp = spa->spa_dsl_pool;
-
-       ASSERT(spa->spa_sync_pass == 1);
+       if (spa_sync_pass(spa) != 1)
+               return;
 
+       dsl_pool_t *dp = spa->spa_dsl_pool;
        rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
 
        if (spa->spa_ubsync.ub_version < SPA_VERSION_ORIGIN &&
@@ -6746,103 +7785,67 @@ spa_sync_upgrades(spa_t *spa, dmu_tx_t *tx)
        rrw_exit(&dp->dp_config_rwlock, FTAG);
 }
 
-/*
- * Sync the specified transaction group.  New blocks may be dirtied as
- * part of the process, so we iterate until it converges.
- */
-void
-spa_sync(spa_t *spa, uint64_t txg)
+static void
+vdev_indirect_state_sync_verify(vdev_t *vd)
 {
-       dsl_pool_t *dp = spa->spa_dsl_pool;
-       objset_t *mos = spa->spa_meta_objset;
-       bplist_t *free_bpl = &spa->spa_free_bplist[txg & TXG_MASK];
-       vdev_t *rvd = spa->spa_root_vdev;
-       vdev_t *vd;
-       dmu_tx_t *tx;
-       int error;
-       uint32_t max_queue_depth = zfs_vdev_async_write_max_active *
-           zfs_vdev_queue_depth_pct / 100;
-
-       VERIFY(spa_writeable(spa));
-
-       /*
-        * Lock out configuration changes.
-        */
-       spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+       ASSERTV(vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping);
+       ASSERTV(vdev_indirect_births_t *vib = vd->vdev_indirect_births);
 
-       spa->spa_syncing_txg = txg;
-       spa->spa_sync_pass = 0;
-
-       mutex_enter(&spa->spa_alloc_lock);
-       VERIFY0(avl_numnodes(&spa->spa_alloc_tree));
-       mutex_exit(&spa->spa_alloc_lock);
-
-       /*
-        * If there are any pending vdev state changes, convert them
-        * into config changes that go out with this transaction group.
-        */
-       spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
-       while (list_head(&spa->spa_state_dirty_list) != NULL) {
-               /*
-                * We need the write lock here because, for aux vdevs,
-                * calling vdev_config_dirty() modifies sav_config.
-                * This is ugly and will become unnecessary when we
-                * eliminate the aux vdev wart by integrating all vdevs
-                * into the root vdev tree.
-                */
-               spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
-               spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_WRITER);
-               while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
-                       vdev_state_clean(vd);
-                       vdev_config_dirty(vd);
-               }
-               spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
-               spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
+       if (vd->vdev_ops == &vdev_indirect_ops) {
+               ASSERT(vim != NULL);
+               ASSERT(vib != NULL);
        }
-       spa_config_exit(spa, SCL_STATE, FTAG);
-
-       tx = dmu_tx_create_assigned(dp, txg);
 
-       spa->spa_sync_starttime = gethrtime();
-       taskq_cancel_id(system_delay_taskq, spa->spa_deadman_tqid);
-       spa->spa_deadman_tqid = taskq_dispatch_delay(system_delay_taskq,
-           spa_deadman, spa, TQ_SLEEP, ddi_get_lbolt() +
-           NSEC_TO_TICK(spa->spa_deadman_synctime));
+       uint64_t obsolete_sm_object = 0;
+       ASSERT0(vdev_obsolete_sm_object(vd, &obsolete_sm_object));
+       if (obsolete_sm_object != 0) {
+               ASSERT(vd->vdev_obsolete_sm != NULL);
+               ASSERT(vd->vdev_removing ||
+                   vd->vdev_ops == &vdev_indirect_ops);
+               ASSERT(vdev_indirect_mapping_num_entries(vim) > 0);
+               ASSERT(vdev_indirect_mapping_bytes_mapped(vim) > 0);
+               ASSERT3U(obsolete_sm_object, ==,
+                   space_map_object(vd->vdev_obsolete_sm));
+               ASSERT3U(vdev_indirect_mapping_bytes_mapped(vim), >=,
+                   space_map_allocated(vd->vdev_obsolete_sm));
+       }
+       ASSERT(vd->vdev_obsolete_segments != NULL);
 
        /*
-        * If we are upgrading to SPA_VERSION_RAIDZ_DEFLATE this txg,
-        * set spa_deflate if we have no raid-z vdevs.
+        * Since frees / remaps to an indirect vdev can only
+        * happen in syncing context, the obsolete segments
+        * tree must be empty when we start syncing.
         */
-       if (spa->spa_ubsync.ub_version < SPA_VERSION_RAIDZ_DEFLATE &&
-           spa->spa_uberblock.ub_version >= SPA_VERSION_RAIDZ_DEFLATE) {
-               int i;
+       ASSERT0(range_tree_space(vd->vdev_obsolete_segments));
+}
 
-               for (i = 0; i < rvd->vdev_children; i++) {
-                       vd = rvd->vdev_child[i];
-                       if (vd->vdev_deflate_ratio != SPA_MINBLOCKSIZE)
-                               break;
-               }
-               if (i == rvd->vdev_children) {
-                       spa->spa_deflate = TRUE;
-                       VERIFY(0 == zap_add(spa->spa_meta_objset,
-                           DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
-                           sizeof (uint64_t), 1, &spa->spa_deflate, tx));
-               }
-       }
+/*
+ * Set the top-level vdev's max queue depth. Evaluate each top-level's
+ * async write queue depth in case it changed. The max queue depth will
+ * not change in the middle of syncing out this txg.
+ */
+static void
+spa_sync_adjust_vdev_max_queue_depth(spa_t *spa)
+{
+       ASSERT(spa_writeable(spa));
 
-       /*
-        * Set the top-level vdev's max queue depth. Evaluate each
-        * top-level's async write queue depth in case it changed.
-        * The max queue depth will not change in the middle of syncing
-        * out this txg.
-        */
-       uint64_t queue_depth_total = 0;
+       vdev_t *rvd = spa->spa_root_vdev;
+       uint32_t max_queue_depth = zfs_vdev_async_write_max_active *
+           zfs_vdev_queue_depth_pct / 100;
+       metaslab_class_t *normal = spa_normal_class(spa);
+       metaslab_class_t *special = spa_special_class(spa);
+       metaslab_class_t *dedup = spa_dedup_class(spa);
+
+       uint64_t slots_per_allocator = 0;
        for (int c = 0; c < rvd->vdev_children; c++) {
                vdev_t *tvd = rvd->vdev_child[c];
+
                metaslab_group_t *mg = tvd->vdev_mg;
+               if (mg == NULL || !metaslab_group_initialized(mg))
+                       continue;
 
-               if (mg == NULL || mg->mg_class != spa_normal_class(spa) ||
-                   !metaslab_group_initialized(mg))
+               metaslab_class_t *mc = mg->mg_class;
+               if (mc != normal && mc != special && mc != dedup)
                        continue;
 
                /*
@@ -6850,21 +7853,56 @@ spa_sync(spa_t *spa, uint64_t txg)
                 * allocations look at mg_max_alloc_queue_depth, and async
                 * allocations all happen from spa_sync().
                 */
-               ASSERT0(refcount_count(&mg->mg_alloc_queue_depth));
+               for (int i = 0; i < spa->spa_alloc_count; i++)
+                       ASSERT0(zfs_refcount_count(
+                           &(mg->mg_alloc_queue_depth[i])));
                mg->mg_max_alloc_queue_depth = max_queue_depth;
-               queue_depth_total += mg->mg_max_alloc_queue_depth;
+
+               for (int i = 0; i < spa->spa_alloc_count; i++) {
+                       mg->mg_cur_max_alloc_queue_depth[i] =
+                           zfs_vdev_def_queue_depth;
+               }
+               slots_per_allocator += zfs_vdev_def_queue_depth;
        }
-       metaslab_class_t *mc = spa_normal_class(spa);
-       ASSERT0(refcount_count(&mc->mc_alloc_slots));
-       mc->mc_alloc_max_slots = queue_depth_total;
-       mc->mc_alloc_throttle_enabled = zio_dva_throttle_enabled;
 
-       ASSERT3U(mc->mc_alloc_max_slots, <=,
-           max_queue_depth * rvd->vdev_children);
+       for (int i = 0; i < spa->spa_alloc_count; i++) {
+               ASSERT0(zfs_refcount_count(&normal->mc_alloc_slots[i]));
+               ASSERT0(zfs_refcount_count(&special->mc_alloc_slots[i]));
+               ASSERT0(zfs_refcount_count(&dedup->mc_alloc_slots[i]));
+               normal->mc_alloc_max_slots[i] = slots_per_allocator;
+               special->mc_alloc_max_slots[i] = slots_per_allocator;
+               dedup->mc_alloc_max_slots[i] = slots_per_allocator;
+       }
+       normal->mc_alloc_throttle_enabled = zio_dva_throttle_enabled;
+       special->mc_alloc_throttle_enabled = zio_dva_throttle_enabled;
+       dedup->mc_alloc_throttle_enabled = zio_dva_throttle_enabled;
+}
+
+static void
+spa_sync_condense_indirect(spa_t *spa, dmu_tx_t *tx)
+{
+       ASSERT(spa_writeable(spa));
+
+       vdev_t *rvd = spa->spa_root_vdev;
+       for (int c = 0; c < rvd->vdev_children; c++) {
+               vdev_t *vd = rvd->vdev_child[c];
+               vdev_indirect_state_sync_verify(vd);
+
+               if (vdev_indirect_should_condense(vd)) {
+                       spa_condense_indirect_start_sync(vd, tx);
+                       break;
+               }
+       }
+}
+
+static void
+spa_sync_iterate_to_convergence(spa_t *spa, dmu_tx_t *tx)
+{
+       objset_t *mos = spa->spa_meta_objset;
+       dsl_pool_t *dp = spa->spa_dsl_pool;
+       uint64_t txg = tx->tx_txg;
+       bplist_t *free_bpl = &spa->spa_free_bplist[txg & TXG_MASK];
 
-       /*
-        * Iterate to convergence.
-        */
        do {
                int pass = ++spa->spa_sync_pass;
 
@@ -6890,71 +7928,60 @@ spa_sync(spa_t *spa, uint64_t txg)
 
                ddt_sync(spa, txg);
                dsl_scan_sync(dp, tx);
+               svr_sync(spa, tx);
+               spa_sync_upgrades(spa, tx);
 
-               while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, txg)))
+               vdev_t *vd = NULL;
+               while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, txg))
+                   != NULL)
                        vdev_sync(vd, txg);
 
-               if (pass == 1) {
-                       spa_sync_upgrades(spa, tx);
-                       ASSERT3U(txg, >=,
-                           spa->spa_uberblock.ub_rootbp.blk_birth);
+               /*
+                * Note: We need to check if the MOS is dirty because we could
+                * have marked the MOS dirty without updating the uberblock
+                * (e.g. if we have sync tasks but no dirty user data). We need
+                * to check the uberblock's rootbp because it is updated if we
+                * have synced out dirty data (though in this case the MOS will
+                * most likely also be dirty due to second order effects, we
+                * don't want to rely on that here).
+                */
+               if (pass == 1 &&
+                   spa->spa_uberblock.ub_rootbp.blk_birth < txg &&
+                   !dmu_objset_is_dirty(mos, txg)) {
                        /*
-                        * Note: We need to check if the MOS is dirty
-                        * because we could have marked the MOS dirty
-                        * without updating the uberblock (e.g. if we
-                        * have sync tasks but no dirty user data).  We
-                        * need to check the uberblock's rootbp because
-                        * it is updated if we have synced out dirty
-                        * data (though in this case the MOS will most
-                        * likely also be dirty due to second order
-                        * effects, we don't want to rely on that here).
+                        * Nothing changed on the first pass, therefore this
+                        * TXG is a no-op. Avoid syncing deferred frees, so
+                        * that we can keep this TXG as a no-op.
                         */
-                       if (spa->spa_uberblock.ub_rootbp.blk_birth < txg &&
-                           !dmu_objset_is_dirty(mos, txg)) {
-                               /*
-                                * Nothing changed on the first pass,
-                                * therefore this TXG is a no-op.  Avoid
-                                * syncing deferred frees, so that we
-                                * can keep this TXG as a no-op.
-                                */
-                               ASSERT(txg_list_empty(&dp->dp_dirty_datasets,
-                                   txg));
-                               ASSERT(txg_list_empty(&dp->dp_dirty_dirs, txg));
-                               ASSERT(txg_list_empty(&dp->dp_sync_tasks, txg));
-                               break;
-                       }
-                       spa_sync_deferred_frees(spa, tx);
+                       ASSERT(txg_list_empty(&dp->dp_dirty_datasets, txg));
+                       ASSERT(txg_list_empty(&dp->dp_dirty_dirs, txg));
+                       ASSERT(txg_list_empty(&dp->dp_sync_tasks, txg));
+                       ASSERT(txg_list_empty(&dp->dp_early_sync_tasks, txg));
+                       break;
                }
 
+               spa_sync_deferred_frees(spa, tx);
        } while (dmu_objset_is_dirty(mos, txg));
+}
 
-#ifdef ZFS_DEBUG
-       if (!list_is_empty(&spa->spa_config_dirty_list)) {
-               /*
-                * Make sure that the number of ZAPs for all the vdevs matches
-                * the number of ZAPs in the per-vdev ZAP list. This only gets
-                * called if the config is dirty; otherwise there may be
-                * outstanding AVZ operations that weren't completed in
-                * spa_sync_config_object.
-                */
-               uint64_t all_vdev_zap_entry_count;
-               ASSERT0(zap_count(spa->spa_meta_objset,
-                   spa->spa_all_vdev_zaps, &all_vdev_zap_entry_count));
-               ASSERT3U(vdev_count_verify_zaps(spa->spa_root_vdev), ==,
-                   all_vdev_zap_entry_count);
-       }
-#endif
+/*
+ * Rewrite the vdev configuration (which includes the uberblock) to
+ * commit the transaction group.
+ *
+ * If there are no dirty vdevs, we sync the uberblock to a few random
+ * top-level vdevs that are known to be visible in the config cache
+ * (see spa_vdev_add() for a complete description). If there *are* dirty
+ * vdevs, sync the uberblock to all vdevs.
+ */
+static void
+spa_sync_rewrite_vdev_config(spa_t *spa, dmu_tx_t *tx)
+{
+       vdev_t *rvd = spa->spa_root_vdev;
+       uint64_t txg = tx->tx_txg;
 
-       /*
-        * Rewrite the vdev configuration (which includes the uberblock)
-        * to commit the transaction group.
-        *
-        * If there are no dirty vdevs, we sync the uberblock to a few
-        * random top-level vdevs that are known to be visible in the
-        * config cache (see spa_vdev_add() for a complete description).
-        * If there *are* dirty vdevs, sync the uberblock to all vdevs.
-        */
        for (;;) {
+               int error = 0;
+
                /*
                 * We hold SCL_STATE to prevent vdev open/close/etc.
                 * while we're attempting to write the vdev labels.
@@ -6962,17 +7989,26 @@ spa_sync(spa_t *spa, uint64_t txg)
                spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
 
                if (list_is_empty(&spa->spa_config_dirty_list)) {
-                       vdev_t *svd[SPA_DVAS_PER_BP];
+                       vdev_t *svd[SPA_SYNC_MIN_VDEVS] = { NULL };
                        int svdcount = 0;
                        int children = rvd->vdev_children;
                        int c0 = spa_get_random(children);
 
                        for (int c = 0; c < children; c++) {
-                               vd = rvd->vdev_child[(c0 + c) % children];
-                               if (vd->vdev_ms_array == 0 || vd->vdev_islog)
+                               vdev_t *vd =
+                                   rvd->vdev_child[(c0 + c) % children];
+
+                               /* Stop when revisiting the first vdev */
+                               if (c > 0 && svd[0] == vd)
+                                       break;
+
+                               if (vd->vdev_ms_array == 0 ||
+                                   vd->vdev_islog ||
+                                   !vdev_is_concrete(vd))
                                        continue;
+
                                svd[svdcount++] = vd;
-                               if (svdcount == SPA_DVAS_PER_BP)
+                               if (svdcount == SPA_SYNC_MIN_VDEVS)
                                        break;
                        }
                        error = vdev_config_sync(svd, svdcount, txg);
@@ -6991,6 +8027,124 @@ spa_sync(spa_t *spa, uint64_t txg)
                zio_suspend(spa, NULL, ZIO_SUSPEND_IOERR);
                zio_resume_wait(spa);
        }
+}
+
+/*
+ * Sync the specified transaction group.  New blocks may be dirtied as
+ * part of the process, so we iterate until it converges.
+ */
+void
+spa_sync(spa_t *spa, uint64_t txg)
+{
+       vdev_t *vd = NULL;
+
+       VERIFY(spa_writeable(spa));
+
+       /*
+        * Wait for i/os issued in open context that need to complete
+        * before this txg syncs.
+        */
+       (void) zio_wait(spa->spa_txg_zio[txg & TXG_MASK]);
+       spa->spa_txg_zio[txg & TXG_MASK] = zio_root(spa, NULL, NULL,
+           ZIO_FLAG_CANFAIL);
+
+       /*
+        * Lock out configuration changes.
+        */
+       spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+
+       spa->spa_syncing_txg = txg;
+       spa->spa_sync_pass = 0;
+
+       for (int i = 0; i < spa->spa_alloc_count; i++) {
+               mutex_enter(&spa->spa_alloc_locks[i]);
+               VERIFY0(avl_numnodes(&spa->spa_alloc_trees[i]));
+               mutex_exit(&spa->spa_alloc_locks[i]);
+       }
+
+       /*
+        * If there are any pending vdev state changes, convert them
+        * into config changes that go out with this transaction group.
+        */
+       spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
+       while (list_head(&spa->spa_state_dirty_list) != NULL) {
+               /*
+                * We need the write lock here because, for aux vdevs,
+                * calling vdev_config_dirty() modifies sav_config.
+                * This is ugly and will become unnecessary when we
+                * eliminate the aux vdev wart by integrating all vdevs
+                * into the root vdev tree.
+                */
+               spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+               spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_WRITER);
+               while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
+                       vdev_state_clean(vd);
+                       vdev_config_dirty(vd);
+               }
+               spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+               spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
+       }
+       spa_config_exit(spa, SCL_STATE, FTAG);
+
+       dsl_pool_t *dp = spa->spa_dsl_pool;
+       dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg);
+
+       spa->spa_sync_starttime = gethrtime();
+       taskq_cancel_id(system_delay_taskq, spa->spa_deadman_tqid);
+       spa->spa_deadman_tqid = taskq_dispatch_delay(system_delay_taskq,
+           spa_deadman, spa, TQ_SLEEP, ddi_get_lbolt() +
+           NSEC_TO_TICK(spa->spa_deadman_synctime));
+
+       /*
+        * If we are upgrading to SPA_VERSION_RAIDZ_DEFLATE this txg,
+        * set spa_deflate if we have no raid-z vdevs.
+        */
+       if (spa->spa_ubsync.ub_version < SPA_VERSION_RAIDZ_DEFLATE &&
+           spa->spa_uberblock.ub_version >= SPA_VERSION_RAIDZ_DEFLATE) {
+               vdev_t *rvd = spa->spa_root_vdev;
+
+               int i;
+               for (i = 0; i < rvd->vdev_children; i++) {
+                       vd = rvd->vdev_child[i];
+                       if (vd->vdev_deflate_ratio != SPA_MINBLOCKSIZE)
+                               break;
+               }
+               if (i == rvd->vdev_children) {
+                       spa->spa_deflate = TRUE;
+                       VERIFY0(zap_add(spa->spa_meta_objset,
+                           DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
+                           sizeof (uint64_t), 1, &spa->spa_deflate, tx));
+               }
+       }
+
+       spa_sync_adjust_vdev_max_queue_depth(spa);
+
+       spa_sync_condense_indirect(spa, tx);
+
+       spa_sync_iterate_to_convergence(spa, tx);
+
+#ifdef ZFS_DEBUG
+       if (!list_is_empty(&spa->spa_config_dirty_list)) {
+       /*
+        * Make sure that the number of ZAPs for all the vdevs matches
+        * the number of ZAPs in the per-vdev ZAP list. This only gets
+        * called if the config is dirty; otherwise there may be
+        * outstanding AVZ operations that weren't completed in
+        * spa_sync_config_object.
+        */
+               uint64_t all_vdev_zap_entry_count;
+               ASSERT0(zap_count(spa->spa_meta_objset,
+                   spa->spa_all_vdev_zaps, &all_vdev_zap_entry_count));
+               ASSERT3U(vdev_count_verify_zaps(spa->spa_root_vdev), ==,
+                   all_vdev_zap_entry_count);
+       }
+#endif
+
+       if (spa->spa_vdev_removal != NULL) {
+               ASSERT0(spa->spa_vdev_removal->svr_bytes_done[txg & TXG_MASK]);
+       }
+
+       spa_sync_rewrite_vdev_config(spa, tx);
        dmu_tx_commit(tx);
 
        taskq_cancel_id(system_delay_taskq, spa->spa_deadman_tqid);
@@ -7014,14 +8168,17 @@ spa_sync(spa_t *spa, uint64_t txg)
 
        dsl_pool_sync_done(dp, txg);
 
-       mutex_enter(&spa->spa_alloc_lock);
-       VERIFY0(avl_numnodes(&spa->spa_alloc_tree));
-       mutex_exit(&spa->spa_alloc_lock);
+       for (int i = 0; i < spa->spa_alloc_count; i++) {
+               mutex_enter(&spa->spa_alloc_locks[i]);
+               VERIFY0(avl_numnodes(&spa->spa_alloc_trees[i]));
+               mutex_exit(&spa->spa_alloc_locks[i]);
+       }
 
        /*
         * Update usable space statistics.
         */
-       while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, TXG_CLEAN(txg))))
+       while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)))
+           != NULL)
                vdev_sync_done(vd, txg);
 
        spa_update_dspace(spa);
@@ -7034,6 +8191,9 @@ spa_sync(spa_t *spa, uint64_t txg)
        ASSERT(txg_list_empty(&dp->dp_dirty_dirs, txg));
        ASSERT(txg_list_empty(&spa->spa_vdev_txg_list, txg));
 
+       while (zfs_pause_spa_sync)
+               delay(1);
+
        spa->spa_sync_pass = 0;
 
        /*
@@ -7206,7 +8366,7 @@ spa_has_active_shared_spare(spa_t *spa)
        return (B_FALSE);
 }
 
-static sysevent_t *
+sysevent_t *
 spa_event_create(spa_t *spa, vdev_t *vd, nvlist_t *hist_nvl, const char *name)
 {
        sysevent_t *ev = NULL;
@@ -7222,7 +8382,7 @@ spa_event_create(spa_t *spa, vdev_t *vd, nvlist_t *hist_nvl, const char *name)
        return (ev);
 }
 
-static void
+void
 spa_event_post(sysevent_t *ev)
 {
 #ifdef _KERNEL
@@ -7246,7 +8406,7 @@ spa_event_notify(spa_t *spa, vdev_t *vd, nvlist_t *hist_nvl, const char *name)
        spa_event_post(spa_event_create(spa, vd, hist_nvl, name));
 }
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 /* state manipulation functions */
 EXPORT_SYMBOL(spa_open);
 EXPORT_SYMBOL(spa_open_rewind);
@@ -7269,7 +8429,6 @@ EXPORT_SYMBOL(spa_scan_get_stats);
 EXPORT_SYMBOL(spa_vdev_add);
 EXPORT_SYMBOL(spa_vdev_attach);
 EXPORT_SYMBOL(spa_vdev_detach);
-EXPORT_SYMBOL(spa_vdev_remove);
 EXPORT_SYMBOL(spa_vdev_setpath);
 EXPORT_SYMBOL(spa_vdev_setfru);
 EXPORT_SYMBOL(spa_vdev_split_mirror);
@@ -7304,7 +8463,7 @@ EXPORT_SYMBOL(spa_prop_clear_bootfs);
 EXPORT_SYMBOL(spa_event_notify);
 #endif
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 module_param(spa_load_verify_maxinflight, int, 0644);
 MODULE_PARM_DESC(spa_load_verify_maxinflight,
        "Max concurrent traversal I/Os while verifying pool during import -X");
@@ -7317,9 +8476,20 @@ module_param(spa_load_verify_data, int, 0644);
 MODULE_PARM_DESC(spa_load_verify_data,
        "Set to traverse data on pool import");
 
+module_param(spa_load_print_vdev_tree, int, 0644);
+MODULE_PARM_DESC(spa_load_print_vdev_tree,
+       "Print vdev tree to zfs_dbgmsg during pool import");
+
 /* CSTYLED */
 module_param(zio_taskq_batch_pct, uint, 0444);
 MODULE_PARM_DESC(zio_taskq_batch_pct,
        "Percentage of CPUs to run an IO worker thread");
 
+/* BEGIN CSTYLED */
+module_param(zfs_max_missing_tvds, ulong, 0644);
+MODULE_PARM_DESC(zfs_max_missing_tvds,
+       "Allow importing pool with up to this number of missing top-level vdevs"
+       " (in read-only mode)");
+/* END CSTYLED */
+
 #endif