FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zfs/vdev.c

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    
    /*
     * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
     * Copyright (c) 2011, 2021 by Delphix. All rights reserved.
     * Copyright 2017 Nexenta Systems, Inc.
     * Copyright (c) 2014 Integros [integros.com]
     * Copyright 2016 Toomas Soome <tsoome@me.com>
     * Copyright 2017 Joyent, Inc.
     * Copyright (c) 2017, Intel Corporation.
     * Copyright (c) 2019, Datto Inc. All rights reserved.
     * Copyright (c) 2021, Klara Inc.
     * Copyright [2021] Hewlett Packard Enterprise Development LP
     */
    
    #include <sys/zfs_context.h>
    #include <sys/fm/fs/zfs.h>
    #include <sys/spa.h>
    #include <sys/spa_impl.h>
    #include <sys/bpobj.h>
    #include <sys/dmu.h>
    #include <sys/dmu_tx.h>
    #include <sys/dsl_dir.h>
    #include <sys/vdev_impl.h>
    #include <sys/vdev_rebuild.h>
    #include <sys/vdev_draid.h>
    #include <sys/uberblock_impl.h>
    #include <sys/metaslab.h>
    #include <sys/metaslab_impl.h>
    #include <sys/space_map.h>
    #include <sys/space_reftree.h>
    #include <sys/zio.h>
    #include <sys/zap.h>
    #include <sys/fs/zfs.h>
    #include <sys/arc.h>
    #include <sys/zil.h>
    #include <sys/dsl_scan.h>
    #include <sys/vdev_raidz.h>
    #include <sys/abd.h>
    #include <sys/vdev_initialize.h>
    #include <sys/vdev_trim.h>
    #include <sys/zvol.h>
    #include <sys/zfs_ratelimit.h>
    #include "zfs_prop.h"
    
    /*
     * One metaslab from each (normal-class) vdev is used by the ZIL.  These are
     * called "embedded slog metaslabs", are referenced by vdev_log_mg, and are
     * part of the spa_embedded_log_class.  The metaslab with the most free space
     * in each vdev is selected for this purpose when the pool is opened (or a
     * vdev is added).  See vdev_metaslab_init().
     *
     * Log blocks can be allocated from the following locations.  Each one is tried
     * in order until the allocation succeeds:
     * 1. dedicated log vdevs, aka "slog" (spa_log_class)
     * 2. embedded slog metaslabs (spa_embedded_log_class)
     * 3. other metaslabs in normal vdevs (spa_normal_class)
     *
     * zfs_embedded_slog_min_ms disables the embedded slog if there are fewer
     * than this number of metaslabs in the vdev.  This ensures that we don't set
     * aside an unreasonable amount of space for the ZIL.  If set to less than
     * 1 << (spa_slop_shift + 1), on small pools the usable space may be reduced
     * (by more than 1<<spa_slop_shift) due to the embedded slog metaslab.
     */
    static uint_t zfs_embedded_slog_min_ms = 64;
    
    /* default target for number of metaslabs per top-level vdev */
    static uint_t zfs_vdev_default_ms_count = 200;
    
    /* minimum number of metaslabs per top-level vdev */
    static uint_t zfs_vdev_min_ms_count = 16;
    
    /* practical upper limit of total metaslabs per top-level vdev */
    static uint_t zfs_vdev_ms_count_limit = 1ULL << 17;
    
    /* lower limit for metaslab size (512M) */
    static uint_t zfs_vdev_default_ms_shift = 29;
    
    /* upper limit for metaslab size (16G) */
    static const uint_t zfs_vdev_max_ms_shift = 34;
   
   int vdev_validate_skip = B_FALSE;
   
   /*
    * Since the DTL space map of a vdev is not expected to have a lot of
    * entries, we default its block size to 4K.
    */
   int zfs_vdev_dtl_sm_blksz = (1 << 12);
   
   /*
    * Rate limit slow IO (delay) events to this many per second.
    */
   static unsigned int zfs_slow_io_events_per_second = 20;
   
   /*
    * Rate limit checksum events after this many checksum errors per second.
    */
   static unsigned int zfs_checksum_events_per_second = 20;
   
   /*
    * Ignore errors during scrub/resilver.  Allows to work around resilver
    * upon import when there are pool errors.
    */
   static int zfs_scan_ignore_errors = 0;
   
   /*
    * vdev-wide space maps that have lots of entries written to them at
    * the end of each transaction can benefit from a higher I/O bandwidth
    * (e.g. vdev_obsolete_sm), thus we default their block size to 128K.
    */
   int zfs_vdev_standard_sm_blksz = (1 << 17);
   
   /*
    * Tunable parameter for debugging or performance analysis. Setting this
    * will cause pool corruption on power loss if a volatile out-of-order
    * write cache is enabled.
    */
   int zfs_nocacheflush = 0;
   
   /*
    * Maximum and minimum ashift values that can be automatically set based on
    * vdev's physical ashift (disk's physical sector size).  While ASHIFT_MAX
    * is higher than the maximum value, it is intentionally limited here to not
    * excessively impact pool space efficiency.  Higher ashift values may still
    * be forced by vdev logical ashift or by user via ashift property, but won't
    * be set automatically as a performance optimization.
    */
   uint_t zfs_vdev_max_auto_ashift = 14;
   uint_t zfs_vdev_min_auto_ashift = ASHIFT_MIN;
   
   void
   vdev_dbgmsg(vdev_t *vd, const char *fmt, ...)
   {
           va_list adx;
           char buf[256];
   
           va_start(adx, fmt);
           (void) vsnprintf(buf, sizeof (buf), fmt, adx);
           va_end(adx);
   
           if (vd->vdev_path != NULL) {
                   zfs_dbgmsg("%s vdev '%s': %s", vd->vdev_ops->vdev_op_type,
                       vd->vdev_path, buf);
           } else {
                   zfs_dbgmsg("%s-%llu vdev (guid %llu): %s",
                       vd->vdev_ops->vdev_op_type,
                       (u_longlong_t)vd->vdev_id,
                       (u_longlong_t)vd->vdev_guid, buf);
           }
   }
   
   void
   vdev_dbgmsg_print_tree(vdev_t *vd, int indent)
   {
           char state[20];
   
           if (vd->vdev_ishole || vd->vdev_ops == &vdev_missing_ops) {
                   zfs_dbgmsg("%*svdev %llu: %s", indent, "",
                       (u_longlong_t)vd->vdev_id,
                       vd->vdev_ops->vdev_op_type);
                   return;
           }
   
           switch (vd->vdev_state) {
           case VDEV_STATE_UNKNOWN:
                   (void) snprintf(state, sizeof (state), "unknown");
                   break;
           case VDEV_STATE_CLOSED:
                   (void) snprintf(state, sizeof (state), "closed");
                   break;
           case VDEV_STATE_OFFLINE:
                   (void) snprintf(state, sizeof (state), "offline");
                   break;
           case VDEV_STATE_REMOVED:
                   (void) snprintf(state, sizeof (state), "removed");
                   break;
           case VDEV_STATE_CANT_OPEN:
                   (void) snprintf(state, sizeof (state), "can't open");
                   break;
           case VDEV_STATE_FAULTED:
                   (void) snprintf(state, sizeof (state), "faulted");
                   break;
           case VDEV_STATE_DEGRADED:
                   (void) snprintf(state, sizeof (state), "degraded");
                   break;
           case VDEV_STATE_HEALTHY:
                   (void) snprintf(state, sizeof (state), "healthy");
                   break;
           default:
                   (void) snprintf(state, sizeof (state), "<state %u>",
                       (uint_t)vd->vdev_state);
           }
   
           zfs_dbgmsg("%*svdev %u: %s%s, guid: %llu, path: %s, %s", indent,
               "", (int)vd->vdev_id, vd->vdev_ops->vdev_op_type,
               vd->vdev_islog ? " (log)" : "",
               (u_longlong_t)vd->vdev_guid,
               vd->vdev_path ? vd->vdev_path : "N/A", state);
   
           for (uint64_t i = 0; i < vd->vdev_children; i++)
                   vdev_dbgmsg_print_tree(vd->vdev_child[i], indent + 2);
   }
   
   /*
    * Virtual device management.
    */
   
   static vdev_ops_t *const vdev_ops_table[] = {
           &vdev_root_ops,
           &vdev_raidz_ops,
           &vdev_draid_ops,
           &vdev_draid_spare_ops,
           &vdev_mirror_ops,
           &vdev_replacing_ops,
           &vdev_spare_ops,
           &vdev_disk_ops,
           &vdev_file_ops,
           &vdev_missing_ops,
           &vdev_hole_ops,
           &vdev_indirect_ops,
           NULL
   };
   
   /*
    * Given a vdev type, return the appropriate ops vector.
    */
   static vdev_ops_t *
   vdev_getops(const char *type)
   {
           vdev_ops_t *ops, *const *opspp;
   
           for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
                   if (strcmp(ops->vdev_op_type, type) == 0)
                           break;
   
           return (ops);
   }
   
   /*
    * Given a vdev and a metaslab class, find which metaslab group we're
    * interested in. All vdevs may belong to two different metaslab classes.
    * Dedicated slog devices use only the primary metaslab group, rather than a
    * separate log group. For embedded slogs, the vdev_log_mg will be non-NULL.
    */
   metaslab_group_t *
   vdev_get_mg(vdev_t *vd, metaslab_class_t *mc)
   {
           if (mc == spa_embedded_log_class(vd->vdev_spa) &&
               vd->vdev_log_mg != NULL)
                   return (vd->vdev_log_mg);
           else
                   return (vd->vdev_mg);
   }
   
   void
   vdev_default_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
       range_seg64_t *physical_rs, range_seg64_t *remain_rs)
   {
           (void) vd, (void) remain_rs;
   
           physical_rs->rs_start = logical_rs->rs_start;
           physical_rs->rs_end = logical_rs->rs_end;
   }
   
   /*
    * Derive the enumerated allocation bias from string input.
    * String origin is either the per-vdev zap or zpool(8).
    */
   static vdev_alloc_bias_t
   vdev_derive_alloc_bias(const char *bias)
   {
           vdev_alloc_bias_t alloc_bias = VDEV_BIAS_NONE;
   
           if (strcmp(bias, VDEV_ALLOC_BIAS_LOG) == 0)
                   alloc_bias = VDEV_BIAS_LOG;
           else if (strcmp(bias, VDEV_ALLOC_BIAS_SPECIAL) == 0)
                   alloc_bias = VDEV_BIAS_SPECIAL;
           else if (strcmp(bias, VDEV_ALLOC_BIAS_DEDUP) == 0)
                   alloc_bias = VDEV_BIAS_DEDUP;
   
           return (alloc_bias);
   }
   
   /*
    * Default asize function: return the MAX of psize with the asize of
    * all children.  This is what's used by anything other than RAID-Z.
    */
   uint64_t
   vdev_default_asize(vdev_t *vd, uint64_t psize)
   {
           uint64_t asize = P2ROUNDUP(psize, 1ULL << vd->vdev_top->vdev_ashift);
           uint64_t csize;
   
           for (int c = 0; c < vd->vdev_children; c++) {
                   csize = vdev_psize_to_asize(vd->vdev_child[c], psize);
                   asize = MAX(asize, csize);
           }
   
           return (asize);
   }
   
   uint64_t
   vdev_default_min_asize(vdev_t *vd)
   {
           return (vd->vdev_min_asize);
   }
   
   /*
    * Get the minimum allocatable size. We define the allocatable size as
    * the vdev's asize rounded to the nearest metaslab. This allows us to
    * replace or attach devices which don't have the same physical size but
    * can still satisfy the same number of allocations.
    */
   uint64_t
   vdev_get_min_asize(vdev_t *vd)
   {
           vdev_t *pvd = vd->vdev_parent;
   
           /*
            * If our parent is NULL (inactive spare or cache) or is the root,
            * just return our own asize.
            */
           if (pvd == NULL)
                   return (vd->vdev_asize);
   
           /*
            * The top-level vdev just returns the allocatable size rounded
            * to the nearest metaslab.
            */
           if (vd == vd->vdev_top)
                   return (P2ALIGN(vd->vdev_asize, 1ULL << vd->vdev_ms_shift));
   
           return (pvd->vdev_ops->vdev_op_min_asize(pvd));
   }
   
   void
   vdev_set_min_asize(vdev_t *vd)
   {
           vd->vdev_min_asize = vdev_get_min_asize(vd);
   
           for (int c = 0; c < vd->vdev_children; c++)
                   vdev_set_min_asize(vd->vdev_child[c]);
   }
   
   /*
    * Get the minimal allocation size for the top-level vdev.
    */
   uint64_t
   vdev_get_min_alloc(vdev_t *vd)
   {
           uint64_t min_alloc = 1ULL << vd->vdev_ashift;
   
           if (vd->vdev_ops->vdev_op_min_alloc != NULL)
                   min_alloc = vd->vdev_ops->vdev_op_min_alloc(vd);
   
           return (min_alloc);
   }
   
   /*
    * Get the parity level for a top-level vdev.
    */
   uint64_t
   vdev_get_nparity(vdev_t *vd)
   {
           uint64_t nparity = 0;
   
           if (vd->vdev_ops->vdev_op_nparity != NULL)
                   nparity = vd->vdev_ops->vdev_op_nparity(vd);
   
           return (nparity);
   }
   
   static int
   vdev_prop_get_int(vdev_t *vd, vdev_prop_t prop, uint64_t *value)
   {
           spa_t *spa = vd->vdev_spa;
           objset_t *mos = spa->spa_meta_objset;
           uint64_t objid;
           int err;
   
           if (vd->vdev_top_zap != 0) {
                   objid = vd->vdev_top_zap;
           } else if (vd->vdev_leaf_zap != 0) {
                   objid = vd->vdev_leaf_zap;
           } else {
                   return (EINVAL);
           }
   
           err = zap_lookup(mos, objid, vdev_prop_to_name(prop),
               sizeof (uint64_t), 1, value);
   
           if (err == ENOENT)
                   *value = vdev_prop_default_numeric(prop);
   
           return (err);
   }
   
   /*
    * Get the number of data disks for a top-level vdev.
    */
   uint64_t
   vdev_get_ndisks(vdev_t *vd)
   {
           uint64_t ndisks = 1;
   
           if (vd->vdev_ops->vdev_op_ndisks != NULL)
                   ndisks = vd->vdev_ops->vdev_op_ndisks(vd);
   
           return (ndisks);
   }
   
   vdev_t *
   vdev_lookup_top(spa_t *spa, uint64_t vdev)
   {
           vdev_t *rvd = spa->spa_root_vdev;
   
           ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
   
           if (vdev < rvd->vdev_children) {
                   ASSERT(rvd->vdev_child[vdev] != NULL);
                   return (rvd->vdev_child[vdev]);
           }
   
           return (NULL);
   }
   
   vdev_t *
   vdev_lookup_by_guid(vdev_t *vd, uint64_t guid)
   {
           vdev_t *mvd;
   
           if (vd->vdev_guid == guid)
                   return (vd);
   
           for (int c = 0; c < vd->vdev_children; c++)
                   if ((mvd = vdev_lookup_by_guid(vd->vdev_child[c], guid)) !=
                       NULL)
                           return (mvd);
   
           return (NULL);
   }
   
   static int
   vdev_count_leaves_impl(vdev_t *vd)
   {
           int n = 0;
   
           if (vd->vdev_ops->vdev_op_leaf)
                   return (1);
   
           for (int c = 0; c < vd->vdev_children; c++)
                   n += vdev_count_leaves_impl(vd->vdev_child[c]);
   
           return (n);
   }
   
   int
   vdev_count_leaves(spa_t *spa)
   {
           int rc;
   
           spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
           rc = vdev_count_leaves_impl(spa->spa_root_vdev);
           spa_config_exit(spa, SCL_VDEV, FTAG);
   
           return (rc);
   }
   
   void
   vdev_add_child(vdev_t *pvd, vdev_t *cvd)
   {
           size_t oldsize, newsize;
           uint64_t id = cvd->vdev_id;
           vdev_t **newchild;
   
           ASSERT(spa_config_held(cvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
           ASSERT(cvd->vdev_parent == NULL);
   
           cvd->vdev_parent = pvd;
   
           if (pvd == NULL)
                   return;
   
           ASSERT(id >= pvd->vdev_children || pvd->vdev_child[id] == NULL);
   
           oldsize = pvd->vdev_children * sizeof (vdev_t *);
           pvd->vdev_children = MAX(pvd->vdev_children, id + 1);
           newsize = pvd->vdev_children * sizeof (vdev_t *);
   
           newchild = kmem_alloc(newsize, KM_SLEEP);
           if (pvd->vdev_child != NULL) {
                   memcpy(newchild, pvd->vdev_child, oldsize);
                   kmem_free(pvd->vdev_child, oldsize);
           }
   
           pvd->vdev_child = newchild;
           pvd->vdev_child[id] = cvd;
   
           cvd->vdev_top = (pvd->vdev_top ? pvd->vdev_top: cvd);
           ASSERT(cvd->vdev_top->vdev_parent->vdev_parent == NULL);
   
           /*
            * Walk up all ancestors to update guid sum.
            */
           for (; pvd != NULL; pvd = pvd->vdev_parent)
                   pvd->vdev_guid_sum += cvd->vdev_guid_sum;
   
           if (cvd->vdev_ops->vdev_op_leaf) {
                   list_insert_head(&cvd->vdev_spa->spa_leaf_list, cvd);
                   cvd->vdev_spa->spa_leaf_list_gen++;
           }
   }
   
   void
   vdev_remove_child(vdev_t *pvd, vdev_t *cvd)
   {
           int c;
           uint_t id = cvd->vdev_id;
   
           ASSERT(cvd->vdev_parent == pvd);
   
           if (pvd == NULL)
                   return;
   
           ASSERT(id < pvd->vdev_children);
           ASSERT(pvd->vdev_child[id] == cvd);
   
           pvd->vdev_child[id] = NULL;
           cvd->vdev_parent = NULL;
   
           for (c = 0; c < pvd->vdev_children; c++)
                   if (pvd->vdev_child[c])
                           break;
   
           if (c == pvd->vdev_children) {
                   kmem_free(pvd->vdev_child, c * sizeof (vdev_t *));
                   pvd->vdev_child = NULL;
                   pvd->vdev_children = 0;
           }
   
           if (cvd->vdev_ops->vdev_op_leaf) {
                   spa_t *spa = cvd->vdev_spa;
                   list_remove(&spa->spa_leaf_list, cvd);
                   spa->spa_leaf_list_gen++;
           }
   
           /*
            * Walk up all ancestors to update guid sum.
            */
           for (; pvd != NULL; pvd = pvd->vdev_parent)
                   pvd->vdev_guid_sum -= cvd->vdev_guid_sum;
   }
   
   /*
    * Remove any holes in the child array.
    */
   void
   vdev_compact_children(vdev_t *pvd)
   {
           vdev_t **newchild, *cvd;
           int oldc = pvd->vdev_children;
           int newc;
   
           ASSERT(spa_config_held(pvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
   
           if (oldc == 0)
                   return;
   
           for (int c = newc = 0; c < oldc; c++)
                   if (pvd->vdev_child[c])
                           newc++;
   
           if (newc > 0) {
                   newchild = kmem_zalloc(newc * sizeof (vdev_t *), KM_SLEEP);
   
                   for (int c = newc = 0; c < oldc; c++) {
                           if ((cvd = pvd->vdev_child[c]) != NULL) {
                                   newchild[newc] = cvd;
                                   cvd->vdev_id = newc++;
                           }
                   }
           } else {
                   newchild = NULL;
           }
   
           kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));
           pvd->vdev_child = newchild;
           pvd->vdev_children = newc;
   }
   
   /*
    * Allocate and minimally initialize a vdev_t.
    */
   vdev_t *
   vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
   {
           vdev_t *vd;
           vdev_indirect_config_t *vic;
   
           vd = kmem_zalloc(sizeof (vdev_t), KM_SLEEP);
           vic = &vd->vdev_indirect_config;
   
           if (spa->spa_root_vdev == NULL) {
                   ASSERT(ops == &vdev_root_ops);
                   spa->spa_root_vdev = vd;
                   spa->spa_load_guid = spa_generate_guid(NULL);
           }
   
           if (guid == 0 && ops != &vdev_hole_ops) {
                   if (spa->spa_root_vdev == vd) {
                           /*
                            * The root vdev's guid will also be the pool guid,
                            * which must be unique among all pools.
                            */
                           guid = spa_generate_guid(NULL);
                   } else {
                           /*
                            * Any other vdev's guid must be unique within the pool.
                            */
                           guid = spa_generate_guid(spa);
                   }
                   ASSERT(!spa_guid_exists(spa_guid(spa), guid));
           }
   
           vd->vdev_spa = spa;
           vd->vdev_id = id;
           vd->vdev_guid = guid;
           vd->vdev_guid_sum = guid;
           vd->vdev_ops = ops;
           vd->vdev_state = VDEV_STATE_CLOSED;
           vd->vdev_ishole = (ops == &vdev_hole_ops);
           vic->vic_prev_indirect_vdev = UINT64_MAX;
   
           rw_init(&vd->vdev_indirect_rwlock, NULL, RW_DEFAULT, NULL);
           mutex_init(&vd->vdev_obsolete_lock, NULL, MUTEX_DEFAULT, NULL);
           vd->vdev_obsolete_segments = range_tree_create(NULL, RANGE_SEG64, NULL,
               0, 0);
   
           /*
            * Initialize rate limit structs for events.  We rate limit ZIO delay
            * and checksum events so that we don't overwhelm ZED with thousands
            * of events when a disk is acting up.
            */
           zfs_ratelimit_init(&vd->vdev_delay_rl, &zfs_slow_io_events_per_second,
               1);
           zfs_ratelimit_init(&vd->vdev_deadman_rl, &zfs_slow_io_events_per_second,
               1);
           zfs_ratelimit_init(&vd->vdev_checksum_rl,
               &zfs_checksum_events_per_second, 1);
   
           /*
            * Default Thresholds for tuning ZED
            */
           vd->vdev_checksum_n = vdev_prop_default_numeric(VDEV_PROP_CHECKSUM_N);
           vd->vdev_checksum_t = vdev_prop_default_numeric(VDEV_PROP_CHECKSUM_T);
           vd->vdev_io_n = vdev_prop_default_numeric(VDEV_PROP_IO_N);
           vd->vdev_io_t = vdev_prop_default_numeric(VDEV_PROP_IO_T);
   
           list_link_init(&vd->vdev_config_dirty_node);
           list_link_init(&vd->vdev_state_dirty_node);
           list_link_init(&vd->vdev_initialize_node);
           list_link_init(&vd->vdev_leaf_node);
           list_link_init(&vd->vdev_trim_node);
   
           mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_NOLOCKDEP, NULL);
           mutex_init(&vd->vdev_stat_lock, NULL, MUTEX_DEFAULT, NULL);
           mutex_init(&vd->vdev_probe_lock, NULL, MUTEX_DEFAULT, NULL);
           mutex_init(&vd->vdev_scan_io_queue_lock, NULL, MUTEX_DEFAULT, NULL);
   
           mutex_init(&vd->vdev_initialize_lock, NULL, MUTEX_DEFAULT, NULL);
           mutex_init(&vd->vdev_initialize_io_lock, NULL, MUTEX_DEFAULT, NULL);
           cv_init(&vd->vdev_initialize_cv, NULL, CV_DEFAULT, NULL);
           cv_init(&vd->vdev_initialize_io_cv, NULL, CV_DEFAULT, NULL);
   
           mutex_init(&vd->vdev_trim_lock, NULL, MUTEX_DEFAULT, NULL);
           mutex_init(&vd->vdev_autotrim_lock, NULL, MUTEX_DEFAULT, NULL);
           mutex_init(&vd->vdev_trim_io_lock, NULL, MUTEX_DEFAULT, NULL);
           cv_init(&vd->vdev_trim_cv, NULL, CV_DEFAULT, NULL);
           cv_init(&vd->vdev_autotrim_cv, NULL, CV_DEFAULT, NULL);
           cv_init(&vd->vdev_trim_io_cv, NULL, CV_DEFAULT, NULL);
   
           mutex_init(&vd->vdev_rebuild_lock, NULL, MUTEX_DEFAULT, NULL);
           cv_init(&vd->vdev_rebuild_cv, NULL, CV_DEFAULT, NULL);
   
           for (int t = 0; t < DTL_TYPES; t++) {
                   vd->vdev_dtl[t] = range_tree_create(NULL, RANGE_SEG64, NULL, 0,
                       0);
           }
   
           txg_list_create(&vd->vdev_ms_list, spa,
               offsetof(struct metaslab, ms_txg_node));
           txg_list_create(&vd->vdev_dtl_list, spa,
               offsetof(struct vdev, vdev_dtl_node));
           vd->vdev_stat.vs_timestamp = gethrtime();
           vdev_queue_init(vd);
           vdev_cache_init(vd);
   
           return (vd);
   }
   
   /*
    * Allocate a new vdev.  The 'alloctype' is used to control whether we are
    * creating a new vdev or loading an existing one - the behavior is slightly
    * different for each case.
    */
   int
   vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
       int alloctype)
   {
           vdev_ops_t *ops;
           char *type;
           uint64_t guid = 0, islog;
           vdev_t *vd;
           vdev_indirect_config_t *vic;
           char *tmp = NULL;
           int rc;
           vdev_alloc_bias_t alloc_bias = VDEV_BIAS_NONE;
           boolean_t top_level = (parent && !parent->vdev_parent);
   
           ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
   
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0)
                   return (SET_ERROR(EINVAL));
   
           if ((ops = vdev_getops(type)) == NULL)
                   return (SET_ERROR(EINVAL));
   
           /*
            * If this is a load, get the vdev guid from the nvlist.
            * Otherwise, vdev_alloc_common() will generate one for us.
            */
           if (alloctype == VDEV_ALLOC_LOAD) {
                   uint64_t label_id;
   
                   if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ID, &label_id) ||
                       label_id != id)
                           return (SET_ERROR(EINVAL));
   
                   if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
                           return (SET_ERROR(EINVAL));
           } else if (alloctype == VDEV_ALLOC_SPARE) {
                   if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
                           return (SET_ERROR(EINVAL));
           } else if (alloctype == VDEV_ALLOC_L2CACHE) {
                   if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
                           return (SET_ERROR(EINVAL));
           } else if (alloctype == VDEV_ALLOC_ROOTPOOL) {
                   if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
                           return (SET_ERROR(EINVAL));
           }
   
           /*
            * The first allocated vdev must be of type 'root'.
            */
           if (ops != &vdev_root_ops && spa->spa_root_vdev == NULL)
                   return (SET_ERROR(EINVAL));
   
           /*
            * Determine whether we're a log vdev.
            */
           islog = 0;
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_IS_LOG, &islog);
           if (islog && spa_version(spa) < SPA_VERSION_SLOGS)
                   return (SET_ERROR(ENOTSUP));
   
           if (ops == &vdev_hole_ops && spa_version(spa) < SPA_VERSION_HOLES)
                   return (SET_ERROR(ENOTSUP));
   
           if (top_level && alloctype == VDEV_ALLOC_ADD) {
                   char *bias;
   
                   /*
                    * If creating a top-level vdev, check for allocation
                    * classes input.
                    */
                   if (nvlist_lookup_string(nv, ZPOOL_CONFIG_ALLOCATION_BIAS,
                       &bias) == 0) {
                           alloc_bias = vdev_derive_alloc_bias(bias);
   
                           /* spa_vdev_add() expects feature to be enabled */
                           if (spa->spa_load_state != SPA_LOAD_CREATE &&
                               !spa_feature_is_enabled(spa,
                               SPA_FEATURE_ALLOCATION_CLASSES)) {
                                   return (SET_ERROR(ENOTSUP));
                           }
                   }
   
                   /* spa_vdev_add() expects feature to be enabled */
                   if (ops == &vdev_draid_ops &&
                       spa->spa_load_state != SPA_LOAD_CREATE &&
                       !spa_feature_is_enabled(spa, SPA_FEATURE_DRAID)) {
                           return (SET_ERROR(ENOTSUP));
                   }
           }
   
           /*
            * Initialize the vdev specific data.  This is done before calling
            * vdev_alloc_common() since it may fail and this simplifies the
            * error reporting and cleanup code paths.
            */
           void *tsd = NULL;
           if (ops->vdev_op_init != NULL) {
                   rc = ops->vdev_op_init(spa, nv, &tsd);
                   if (rc != 0) {
                           return (rc);
                   }
           }
   
           vd = vdev_alloc_common(spa, id, guid, ops);
           vd->vdev_tsd = tsd;
           vd->vdev_islog = islog;
   
           if (top_level && alloc_bias != VDEV_BIAS_NONE)
                   vd->vdev_alloc_bias = alloc_bias;
   
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &vd->vdev_path) == 0)
                   vd->vdev_path = spa_strdup(vd->vdev_path);
   
           /*
            * ZPOOL_CONFIG_AUX_STATE = "external" means we previously forced a
            * fault on a vdev and want it to persist across imports (like with
            * zpool offline -f).
            */
           rc = nvlist_lookup_string(nv, ZPOOL_CONFIG_AUX_STATE, &tmp);
           if (rc == 0 && tmp != NULL && strcmp(tmp, "external") == 0) {
                   vd->vdev_stat.vs_aux = VDEV_AUX_EXTERNAL;
                   vd->vdev_faulted = 1;
                   vd->vdev_label_aux = VDEV_AUX_EXTERNAL;
           }
   
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_DEVID, &vd->vdev_devid) == 0)
                   vd->vdev_devid = spa_strdup(vd->vdev_devid);
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PHYS_PATH,
               &vd->vdev_physpath) == 0)
                   vd->vdev_physpath = spa_strdup(vd->vdev_physpath);
   
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH,
               &vd->vdev_enc_sysfs_path) == 0)
                   vd->vdev_enc_sysfs_path = spa_strdup(vd->vdev_enc_sysfs_path);
   
           if (nvlist_lookup_string(nv, ZPOOL_CONFIG_FRU, &vd->vdev_fru) == 0)
                   vd->vdev_fru = spa_strdup(vd->vdev_fru);
   
           /*
            * Set the whole_disk property.  If it's not specified, leave the value
            * as -1.
            */
           if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
               &vd->vdev_wholedisk) != 0)
                   vd->vdev_wholedisk = -1ULL;
   
           vic = &vd->vdev_indirect_config;
   
           ASSERT0(vic->vic_mapping_object);
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_INDIRECT_OBJECT,
               &vic->vic_mapping_object);
           ASSERT0(vic->vic_births_object);
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_INDIRECT_BIRTHS,
               &vic->vic_births_object);
           ASSERT3U(vic->vic_prev_indirect_vdev, ==, UINT64_MAX);
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_PREV_INDIRECT_VDEV,
               &vic->vic_prev_indirect_vdev);
   
           /*
            * Look for the 'not present' flag.  This will only be set if the device
            * was not present at the time of import.
            */
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT,
               &vd->vdev_not_present);
   
           /*
            * Get the alignment requirement.
            */
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT, &vd->vdev_ashift);
   
           /*
            * Retrieve the vdev creation time.
            */
           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_CREATE_TXG,
               &vd->vdev_crtxg);
   
           /*
            * If we're a top-level vdev, try to load the allocation parameters.
            */
           if (top_level &&
               (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_SPLIT)) {
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
                       &vd->vdev_ms_array);
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
                       &vd->vdev_ms_shift);
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASIZE,
                       &vd->vdev_asize);
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NONALLOCATING,
                       &vd->vdev_noalloc);
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REMOVING,
                       &vd->vdev_removing);
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_VDEV_TOP_ZAP,
                       &vd->vdev_top_zap);
           } else {
                   ASSERT0(vd->vdev_top_zap);
           }
   
           if (top_level && alloctype != VDEV_ALLOC_ATTACH) {
                   ASSERT(alloctype == VDEV_ALLOC_LOAD ||
                       alloctype == VDEV_ALLOC_ADD ||
                       alloctype == VDEV_ALLOC_SPLIT ||
                       alloctype == VDEV_ALLOC_ROOTPOOL);
                   /* Note: metaslab_group_create() is now deferred */
           }
   
           if (vd->vdev_ops->vdev_op_leaf &&
               (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_SPLIT)) {
                   (void) nvlist_lookup_uint64(nv,
                       ZPOOL_CONFIG_VDEV_LEAF_ZAP, &vd->vdev_leaf_zap);
           } else {
                   ASSERT0(vd->vdev_leaf_zap);
           }
   
           /*
            * If we're a leaf vdev, try to load the DTL object and other state.
            */
   
           if (vd->vdev_ops->vdev_op_leaf &&
               (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_L2CACHE ||
               alloctype == VDEV_ALLOC_ROOTPOOL)) {
                   if (alloctype == VDEV_ALLOC_LOAD) {
                           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DTL,
                               &vd->vdev_dtl_object);
                           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_UNSPARE,
                               &vd->vdev_unspare);
                   }
   
                   if (alloctype == VDEV_ALLOC_ROOTPOOL) {
                           uint64_t spare = 0;
   
                           if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_IS_SPARE,
                               &spare) == 0 && spare)
                                   spa_spare_add(vd);
                   }
   
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE,
                       &vd->vdev_offline);
   
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_RESILVER_TXG,
                       &vd->vdev_resilver_txg);
   
                   (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REBUILD_TXG,
                       &vd->vdev_rebuild_txg);
   
                   if (nvlist_exists(nv, ZPOOL_CONFIG_RESILVER_DEFER))
                           vdev_defer_resilver(vd);
   
                   /*
                    * In general, when importing a pool we want to ignore the
                    * persistent fault state, as the diagnosis made on another
                    * system may not be valid in the current context.  The only
                    * exception is if we forced a vdev to a persistently faulted
                    * state with 'zpool offline -f'.  The persistent fault will
                    * remain across imports until cleared.
                    *
                    * Local vdevs will remain in the faulted state.
                    */
                   if (spa_load_state(spa) == SPA_LOAD_OPEN ||
                       spa_load_state(spa) == SPA_LOAD_IMPORT) {
                           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_FAULTED,
                               &vd->vdev_faulted);
                           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DEGRADED,
                               &vd->vdev_degraded);
                           (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REMOVED,
                               &vd->vdev_removed);
   
                           if (vd->vdev_faulted || vd->vdev_degraded) {
                                   char *aux;
   
                                   vd->vdev_label_aux =
                                       VDEV_AUX_ERR_EXCEEDED;
                                   if (nvlist_lookup_string(nv,
                                       ZPOOL_CONFIG_AUX_STATE, &aux) == 0 &&
                                       strcmp(aux, "external") == 0)
                                           vd->vdev_label_aux = VDEV_AUX_EXTERNAL;
                                  else
                                          vd->vdev_faulted = 0ULL;
                          }
                  }
          }
  
          /*
           * Add ourselves to the parent's list of children.
           */
          vdev_add_child(parent, vd);
  
          *vdp = vd;
  
          return (0);
  }
  
  void
  vdev_free(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT3P(vd->vdev_initialize_thread, ==, NULL);
          ASSERT3P(vd->vdev_trim_thread, ==, NULL);
          ASSERT3P(vd->vdev_autotrim_thread, ==, NULL);
          ASSERT3P(vd->vdev_rebuild_thread, ==, NULL);
  
          /*
           * Scan queues are normally destroyed at the end of a scan. If the
           * queue exists here, that implies the vdev is being removed while
           * the scan is still running.
           */
          if (vd->vdev_scan_io_queue != NULL) {
                  mutex_enter(&vd->vdev_scan_io_queue_lock);
                  dsl_scan_io_queue_destroy(vd->vdev_scan_io_queue);
                  vd->vdev_scan_io_queue = NULL;
                  mutex_exit(&vd->vdev_scan_io_queue_lock);
          }
  
          /*
           * vdev_free() implies closing the vdev first.  This is simpler than
           * trying to ensure complicated semantics for all callers.
           */
          vdev_close(vd);
  
          ASSERT(!list_link_active(&vd->vdev_config_dirty_node));
          ASSERT(!list_link_active(&vd->vdev_state_dirty_node));
  
          /*
           * Free all children.
           */
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_free(vd->vdev_child[c]);
  
          ASSERT(vd->vdev_child == NULL);
          ASSERT(vd->vdev_guid_sum == vd->vdev_guid);
  
          if (vd->vdev_ops->vdev_op_fini != NULL)
                  vd->vdev_ops->vdev_op_fini(vd);
  
          /*
           * Discard allocation state.
           */
          if (vd->vdev_mg != NULL) {
                  vdev_metaslab_fini(vd);
                  metaslab_group_destroy(vd->vdev_mg);
                  vd->vdev_mg = NULL;
          }
          if (vd->vdev_log_mg != NULL) {
                  ASSERT0(vd->vdev_ms_count);
                  metaslab_group_destroy(vd->vdev_log_mg);
                  vd->vdev_log_mg = NULL;
          }
  
          ASSERT0(vd->vdev_stat.vs_space);
          ASSERT0(vd->vdev_stat.vs_dspace);
          ASSERT0(vd->vdev_stat.vs_alloc);
  
          /*
           * Remove this vdev from its parent's child list.
           */
          vdev_remove_child(vd->vdev_parent, vd);
  
          ASSERT(vd->vdev_parent == NULL);
          ASSERT(!list_link_active(&vd->vdev_leaf_node));
  
          /*
           * Clean up vdev structure.
           */
          vdev_queue_fini(vd);
          vdev_cache_fini(vd);
  
          if (vd->vdev_path)
                  spa_strfree(vd->vdev_path);
          if (vd->vdev_devid)
                  spa_strfree(vd->vdev_devid);
          if (vd->vdev_physpath)
                  spa_strfree(vd->vdev_physpath);
  
          if (vd->vdev_enc_sysfs_path)
                  spa_strfree(vd->vdev_enc_sysfs_path);
  
          if (vd->vdev_fru)
                  spa_strfree(vd->vdev_fru);
  
          if (vd->vdev_isspare)
                  spa_spare_remove(vd);
          if (vd->vdev_isl2cache)
                  spa_l2cache_remove(vd);
  
          txg_list_destroy(&vd->vdev_ms_list);
          txg_list_destroy(&vd->vdev_dtl_list);
  
          mutex_enter(&vd->vdev_dtl_lock);
          space_map_close(vd->vdev_dtl_sm);
          for (int t = 0; t < DTL_TYPES; t++) {
                  range_tree_vacate(vd->vdev_dtl[t], NULL, NULL);
                  range_tree_destroy(vd->vdev_dtl[t]);
          }
          mutex_exit(&vd->vdev_dtl_lock);
  
          EQUIV(vd->vdev_indirect_births != NULL,
              vd->vdev_indirect_mapping != NULL);
          if (vd->vdev_indirect_births != NULL) {
                  vdev_indirect_mapping_close(vd->vdev_indirect_mapping);
                  vdev_indirect_births_close(vd->vdev_indirect_births);
          }
  
          if (vd->vdev_obsolete_sm != NULL) {
                  ASSERT(vd->vdev_removing ||
                      vd->vdev_ops == &vdev_indirect_ops);
                  space_map_close(vd->vdev_obsolete_sm);
                  vd->vdev_obsolete_sm = NULL;
          }
          range_tree_destroy(vd->vdev_obsolete_segments);
          rw_destroy(&vd->vdev_indirect_rwlock);
          mutex_destroy(&vd->vdev_obsolete_lock);
  
          mutex_destroy(&vd->vdev_dtl_lock);
          mutex_destroy(&vd->vdev_stat_lock);
          mutex_destroy(&vd->vdev_probe_lock);
          mutex_destroy(&vd->vdev_scan_io_queue_lock);
  
          mutex_destroy(&vd->vdev_initialize_lock);
          mutex_destroy(&vd->vdev_initialize_io_lock);
          cv_destroy(&vd->vdev_initialize_io_cv);
          cv_destroy(&vd->vdev_initialize_cv);
  
          mutex_destroy(&vd->vdev_trim_lock);
          mutex_destroy(&vd->vdev_autotrim_lock);
          mutex_destroy(&vd->vdev_trim_io_lock);
          cv_destroy(&vd->vdev_trim_cv);
          cv_destroy(&vd->vdev_autotrim_cv);
          cv_destroy(&vd->vdev_trim_io_cv);
  
          mutex_destroy(&vd->vdev_rebuild_lock);
          cv_destroy(&vd->vdev_rebuild_cv);
  
          zfs_ratelimit_fini(&vd->vdev_delay_rl);
          zfs_ratelimit_fini(&vd->vdev_deadman_rl);
          zfs_ratelimit_fini(&vd->vdev_checksum_rl);
  
          if (vd == spa->spa_root_vdev)
                  spa->spa_root_vdev = NULL;
  
          kmem_free(vd, sizeof (vdev_t));
  }
  
  /*
   * Transfer top-level vdev state from svd to tvd.
   */
  static void
  vdev_top_transfer(vdev_t *svd, vdev_t *tvd)
  {
          spa_t *spa = svd->vdev_spa;
          metaslab_t *msp;
          vdev_t *vd;
          int t;
  
          ASSERT(tvd == tvd->vdev_top);
  
          tvd->vdev_pending_fastwrite = svd->vdev_pending_fastwrite;
          tvd->vdev_ms_array = svd->vdev_ms_array;
          tvd->vdev_ms_shift = svd->vdev_ms_shift;
          tvd->vdev_ms_count = svd->vdev_ms_count;
          tvd->vdev_top_zap = svd->vdev_top_zap;
  
          svd->vdev_ms_array = 0;
          svd->vdev_ms_shift = 0;
          svd->vdev_ms_count = 0;
          svd->vdev_top_zap = 0;
  
          if (tvd->vdev_mg)
                  ASSERT3P(tvd->vdev_mg, ==, svd->vdev_mg);
          if (tvd->vdev_log_mg)
                  ASSERT3P(tvd->vdev_log_mg, ==, svd->vdev_log_mg);
          tvd->vdev_mg = svd->vdev_mg;
          tvd->vdev_log_mg = svd->vdev_log_mg;
          tvd->vdev_ms = svd->vdev_ms;
  
          svd->vdev_mg = NULL;
          svd->vdev_log_mg = NULL;
          svd->vdev_ms = NULL;
  
          if (tvd->vdev_mg != NULL)
                  tvd->vdev_mg->mg_vd = tvd;
          if (tvd->vdev_log_mg != NULL)
                  tvd->vdev_log_mg->mg_vd = tvd;
  
          tvd->vdev_checkpoint_sm = svd->vdev_checkpoint_sm;
          svd->vdev_checkpoint_sm = NULL;
  
          tvd->vdev_alloc_bias = svd->vdev_alloc_bias;
          svd->vdev_alloc_bias = VDEV_BIAS_NONE;
  
          tvd->vdev_stat.vs_alloc = svd->vdev_stat.vs_alloc;
          tvd->vdev_stat.vs_space = svd->vdev_stat.vs_space;
          tvd->vdev_stat.vs_dspace = svd->vdev_stat.vs_dspace;
  
          svd->vdev_stat.vs_alloc = 0;
          svd->vdev_stat.vs_space = 0;
          svd->vdev_stat.vs_dspace = 0;
  
          /*
           * State which may be set on a top-level vdev that's in the
           * process of being removed.
           */
          ASSERT0(tvd->vdev_indirect_config.vic_births_object);
          ASSERT0(tvd->vdev_indirect_config.vic_mapping_object);
          ASSERT3U(tvd->vdev_indirect_config.vic_prev_indirect_vdev, ==, -1ULL);
          ASSERT3P(tvd->vdev_indirect_mapping, ==, NULL);
          ASSERT3P(tvd->vdev_indirect_births, ==, NULL);
          ASSERT3P(tvd->vdev_obsolete_sm, ==, NULL);
          ASSERT0(tvd->vdev_noalloc);
          ASSERT0(tvd->vdev_removing);
          ASSERT0(tvd->vdev_rebuilding);
          tvd->vdev_noalloc = svd->vdev_noalloc;
          tvd->vdev_removing = svd->vdev_removing;
          tvd->vdev_rebuilding = svd->vdev_rebuilding;
          tvd->vdev_rebuild_config = svd->vdev_rebuild_config;
          tvd->vdev_indirect_config = svd->vdev_indirect_config;
          tvd->vdev_indirect_mapping = svd->vdev_indirect_mapping;
          tvd->vdev_indirect_births = svd->vdev_indirect_births;
          range_tree_swap(&svd->vdev_obsolete_segments,
              &tvd->vdev_obsolete_segments);
          tvd->vdev_obsolete_sm = svd->vdev_obsolete_sm;
          svd->vdev_indirect_config.vic_mapping_object = 0;
          svd->vdev_indirect_config.vic_births_object = 0;
          svd->vdev_indirect_config.vic_prev_indirect_vdev = -1ULL;
          svd->vdev_indirect_mapping = NULL;
          svd->vdev_indirect_births = NULL;
          svd->vdev_obsolete_sm = NULL;
          svd->vdev_noalloc = 0;
          svd->vdev_removing = 0;
          svd->vdev_rebuilding = 0;
  
          for (t = 0; t < TXG_SIZE; t++) {
                  while ((msp = txg_list_remove(&svd->vdev_ms_list, t)) != NULL)
                          (void) txg_list_add(&tvd->vdev_ms_list, msp, t);
                  while ((vd = txg_list_remove(&svd->vdev_dtl_list, t)) != NULL)
                          (void) txg_list_add(&tvd->vdev_dtl_list, vd, t);
                  if (txg_list_remove_this(&spa->spa_vdev_txg_list, svd, t))
                          (void) txg_list_add(&spa->spa_vdev_txg_list, tvd, t);
          }
  
          if (list_link_active(&svd->vdev_config_dirty_node)) {
                  vdev_config_clean(svd);
                  vdev_config_dirty(tvd);
          }
  
          if (list_link_active(&svd->vdev_state_dirty_node)) {
                  vdev_state_clean(svd);
                  vdev_state_dirty(tvd);
          }
  
          tvd->vdev_deflate_ratio = svd->vdev_deflate_ratio;
          svd->vdev_deflate_ratio = 0;
  
          tvd->vdev_islog = svd->vdev_islog;
          svd->vdev_islog = 0;
  
          dsl_scan_io_queue_vdev_xfer(svd, tvd);
  }
  
  static void
  vdev_top_update(vdev_t *tvd, vdev_t *vd)
  {
          if (vd == NULL)
                  return;
  
          vd->vdev_top = tvd;
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_top_update(tvd, vd->vdev_child[c]);
  }
  
  /*
   * Add a mirror/replacing vdev above an existing vdev.  There is no need to
   * call .vdev_op_init() since mirror/replacing vdevs do not have private state.
   */
  vdev_t *
  vdev_add_parent(vdev_t *cvd, vdev_ops_t *ops)
  {
          spa_t *spa = cvd->vdev_spa;
          vdev_t *pvd = cvd->vdev_parent;
          vdev_t *mvd;
  
          ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
  
          mvd = vdev_alloc_common(spa, cvd->vdev_id, 0, ops);
  
          mvd->vdev_asize = cvd->vdev_asize;
          mvd->vdev_min_asize = cvd->vdev_min_asize;
          mvd->vdev_max_asize = cvd->vdev_max_asize;
          mvd->vdev_psize = cvd->vdev_psize;
          mvd->vdev_ashift = cvd->vdev_ashift;
          mvd->vdev_logical_ashift = cvd->vdev_logical_ashift;
          mvd->vdev_physical_ashift = cvd->vdev_physical_ashift;
          mvd->vdev_state = cvd->vdev_state;
          mvd->vdev_crtxg = cvd->vdev_crtxg;
  
          vdev_remove_child(pvd, cvd);
          vdev_add_child(pvd, mvd);
          cvd->vdev_id = mvd->vdev_children;
          vdev_add_child(mvd, cvd);
          vdev_top_update(cvd->vdev_top, cvd->vdev_top);
  
          if (mvd == mvd->vdev_top)
                  vdev_top_transfer(cvd, mvd);
  
          return (mvd);
  }
  
  /*
   * Remove a 1-way mirror/replacing vdev from the tree.
   */
  void
  vdev_remove_parent(vdev_t *cvd)
  {
          vdev_t *mvd = cvd->vdev_parent;
          vdev_t *pvd = mvd->vdev_parent;
  
          ASSERT(spa_config_held(cvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
  
          ASSERT(mvd->vdev_children == 1);
          ASSERT(mvd->vdev_ops == &vdev_mirror_ops ||
              mvd->vdev_ops == &vdev_replacing_ops ||
              mvd->vdev_ops == &vdev_spare_ops);
          cvd->vdev_ashift = mvd->vdev_ashift;
          cvd->vdev_logical_ashift = mvd->vdev_logical_ashift;
          cvd->vdev_physical_ashift = mvd->vdev_physical_ashift;
          vdev_remove_child(mvd, cvd);
          vdev_remove_child(pvd, mvd);
  
          /*
           * If cvd will replace mvd as a top-level vdev, preserve mvd's guid.
           * Otherwise, we could have detached an offline device, and when we
           * go to import the pool we'll think we have two top-level vdevs,
           * instead of a different version of the same top-level vdev.
           */
          if (mvd->vdev_top == mvd) {
                  uint64_t guid_delta = mvd->vdev_guid - cvd->vdev_guid;
                  cvd->vdev_orig_guid = cvd->vdev_guid;
                  cvd->vdev_guid += guid_delta;
                  cvd->vdev_guid_sum += guid_delta;
  
                  /*
                   * If pool not set for autoexpand, we need to also preserve
                   * mvd's asize to prevent automatic expansion of cvd.
                   * Otherwise if we are adjusting the mirror by attaching and
                   * detaching children of non-uniform sizes, the mirror could
                   * autoexpand, unexpectedly requiring larger devices to
                   * re-establish the mirror.
                   */
                  if (!cvd->vdev_spa->spa_autoexpand)
                          cvd->vdev_asize = mvd->vdev_asize;
          }
          cvd->vdev_id = mvd->vdev_id;
          vdev_add_child(pvd, cvd);
          vdev_top_update(cvd->vdev_top, cvd->vdev_top);
  
          if (cvd == cvd->vdev_top)
                  vdev_top_transfer(mvd, cvd);
  
          ASSERT(mvd->vdev_children == 0);
          vdev_free(mvd);
  }
  
  void
  vdev_metaslab_group_create(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          /*
           * metaslab_group_create was delayed until allocation bias was available
           */
          if (vd->vdev_mg == NULL) {
                  metaslab_class_t *mc;
  
                  if (vd->vdev_islog && vd->vdev_alloc_bias == VDEV_BIAS_NONE)
                          vd->vdev_alloc_bias = VDEV_BIAS_LOG;
  
                  ASSERT3U(vd->vdev_islog, ==,
                      (vd->vdev_alloc_bias == VDEV_BIAS_LOG));
  
                  switch (vd->vdev_alloc_bias) {
                  case VDEV_BIAS_LOG:
                          mc = spa_log_class(spa);
                          break;
                  case VDEV_BIAS_SPECIAL:
                          mc = spa_special_class(spa);
                          break;
                  case VDEV_BIAS_DEDUP:
                          mc = spa_dedup_class(spa);
                          break;
                  default:
                          mc = spa_normal_class(spa);
                  }
  
                  vd->vdev_mg = metaslab_group_create(mc, vd,
                      spa->spa_alloc_count);
  
                  if (!vd->vdev_islog) {
                          vd->vdev_log_mg = metaslab_group_create(
                              spa_embedded_log_class(spa), vd, 1);
                  }
  
                  /*
                   * The spa ashift min/max only apply for the normal metaslab
                   * class. Class destination is late binding so ashift boundary
                   * setting had to wait until now.
                   */
                  if (vd->vdev_top == vd && vd->vdev_ashift != 0 &&
                      mc == spa_normal_class(spa) && vd->vdev_aux == NULL) {
                          if (vd->vdev_ashift > spa->spa_max_ashift)
                                  spa->spa_max_ashift = vd->vdev_ashift;
                          if (vd->vdev_ashift < spa->spa_min_ashift)
                                  spa->spa_min_ashift = vd->vdev_ashift;
  
                          uint64_t min_alloc = vdev_get_min_alloc(vd);
                          if (min_alloc < spa->spa_min_alloc)
                                  spa->spa_min_alloc = min_alloc;
                  }
          }
  }
  
  int
  vdev_metaslab_init(vdev_t *vd, uint64_t txg)
  {
          spa_t *spa = vd->vdev_spa;
          uint64_t oldc = vd->vdev_ms_count;
          uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
          metaslab_t **mspp;
          int error;
          boolean_t expanding = (oldc != 0);
  
          ASSERT(txg == 0 || spa_config_held(spa, SCL_ALLOC, RW_WRITER));
  
          /*
           * This vdev is not being allocated from yet or is a hole.
           */
          if (vd->vdev_ms_shift == 0)
                  return (0);
  
          ASSERT(!vd->vdev_ishole);
  
          ASSERT(oldc <= newc);
  
          mspp = vmem_zalloc(newc * sizeof (*mspp), KM_SLEEP);
  
          if (expanding) {
                  memcpy(mspp, vd->vdev_ms, oldc * sizeof (*mspp));
                  vmem_free(vd->vdev_ms, oldc * sizeof (*mspp));
          }
  
          vd->vdev_ms = mspp;
          vd->vdev_ms_count = newc;
  
          for (uint64_t m = oldc; m < newc; m++) {
                  uint64_t object = 0;
                  /*
                   * vdev_ms_array may be 0 if we are creating the "fake"
                   * metaslabs for an indirect vdev for zdb's leak detection.
                   * See zdb_leak_init().
                   */
                  if (txg == 0 && vd->vdev_ms_array != 0) {
                          error = dmu_read(spa->spa_meta_objset,
                              vd->vdev_ms_array,
                              m * sizeof (uint64_t), sizeof (uint64_t), &object,
                              DMU_READ_PREFETCH);
                          if (error != 0) {
                                  vdev_dbgmsg(vd, "unable to read the metaslab "
                                      "array [error=%d]", error);
                                  return (error);
                          }
                  }
  
                  error = metaslab_init(vd->vdev_mg, m, object, txg,
                      &(vd->vdev_ms[m]));
                  if (error != 0) {
                          vdev_dbgmsg(vd, "metaslab_init failed [error=%d]",
                              error);
                          return (error);
                  }
          }
  
          /*
           * Find the emptiest metaslab on the vdev and mark it for use for
           * embedded slog by moving it from the regular to the log metaslab
           * group.
           */
          if (vd->vdev_mg->mg_class == spa_normal_class(spa) &&
              vd->vdev_ms_count > zfs_embedded_slog_min_ms &&
              avl_is_empty(&vd->vdev_log_mg->mg_metaslab_tree)) {
                  uint64_t slog_msid = 0;
                  uint64_t smallest = UINT64_MAX;
  
                  /*
                   * Note, we only search the new metaslabs, because the old
                   * (pre-existing) ones may be active (e.g. have non-empty
                   * range_tree's), and we don't move them to the new
                   * metaslab_t.
                   */
                  for (uint64_t m = oldc; m < newc; m++) {
                          uint64_t alloc =
                              space_map_allocated(vd->vdev_ms[m]->ms_sm);
                          if (alloc < smallest) {
                                  slog_msid = m;
                                  smallest = alloc;
                          }
                  }
                  metaslab_t *slog_ms = vd->vdev_ms[slog_msid];
                  /*
                   * The metaslab was marked as dirty at the end of
                   * metaslab_init(). Remove it from the dirty list so that we
                   * can uninitialize and reinitialize it to the new class.
                   */
                  if (txg != 0) {
                          (void) txg_list_remove_this(&vd->vdev_ms_list,
                              slog_ms, txg);
                  }
                  uint64_t sm_obj = space_map_object(slog_ms->ms_sm);
                  metaslab_fini(slog_ms);
                  VERIFY0(metaslab_init(vd->vdev_log_mg, slog_msid, sm_obj, txg,
                      &vd->vdev_ms[slog_msid]));
          }
  
          if (txg == 0)
                  spa_config_enter(spa, SCL_ALLOC, FTAG, RW_WRITER);
  
          /*
           * If the vdev is marked as non-allocating then don't
           * activate the metaslabs since we want to ensure that
           * no allocations are performed on this device.
           */
          if (vd->vdev_noalloc) {
                  /* track non-allocating vdev space */
                  spa->spa_nonallocating_dspace += spa_deflate(spa) ?
                      vd->vdev_stat.vs_dspace : vd->vdev_stat.vs_space;
          } else if (!expanding) {
                  metaslab_group_activate(vd->vdev_mg);
                  if (vd->vdev_log_mg != NULL)
                          metaslab_group_activate(vd->vdev_log_mg);
          }
  
          if (txg == 0)
                  spa_config_exit(spa, SCL_ALLOC, FTAG);
  
          return (0);
  }
  
  void
  vdev_metaslab_fini(vdev_t *vd)
  {
          if (vd->vdev_checkpoint_sm != NULL) {
                  ASSERT(spa_feature_is_active(vd->vdev_spa,
                      SPA_FEATURE_POOL_CHECKPOINT));
                  space_map_close(vd->vdev_checkpoint_sm);
                  /*
                   * Even though we close the space map, we need to set its
                   * pointer to NULL. The reason is that vdev_metaslab_fini()
                   * may be called multiple times for certain operations
                   * (i.e. when destroying a pool) so we need to ensure that
                   * this clause never executes twice. This logic is similar
                   * to the one used for the vdev_ms clause below.
                   */
                  vd->vdev_checkpoint_sm = NULL;
          }
  
          if (vd->vdev_ms != NULL) {
                  metaslab_group_t *mg = vd->vdev_mg;
  
                  metaslab_group_passivate(mg);
                  if (vd->vdev_log_mg != NULL) {
                          ASSERT(!vd->vdev_islog);
                          metaslab_group_passivate(vd->vdev_log_mg);
                  }
  
                  uint64_t count = vd->vdev_ms_count;
                  for (uint64_t m = 0; m < count; m++) {
                          metaslab_t *msp = vd->vdev_ms[m];
                          if (msp != NULL)
                                  metaslab_fini(msp);
                  }
                  vmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
                  vd->vdev_ms = NULL;
                  vd->vdev_ms_count = 0;
  
                  for (int i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
                          ASSERT0(mg->mg_histogram[i]);
                          if (vd->vdev_log_mg != NULL)
                                  ASSERT0(vd->vdev_log_mg->mg_histogram[i]);
                  }
          }
          ASSERT0(vd->vdev_ms_count);
          ASSERT3U(vd->vdev_pending_fastwrite, ==, 0);
  }
  
  typedef struct vdev_probe_stats {
          boolean_t       vps_readable;
          boolean_t       vps_writeable;
          int             vps_flags;
  } vdev_probe_stats_t;
  
  static void
  vdev_probe_done(zio_t *zio)
  {
          spa_t *spa = zio->io_spa;
          vdev_t *vd = zio->io_vd;
          vdev_probe_stats_t *vps = zio->io_private;
  
          ASSERT(vd->vdev_probe_zio != NULL);
  
          if (zio->io_type == ZIO_TYPE_READ) {
                  if (zio->io_error == 0)
                          vps->vps_readable = 1;
                  if (zio->io_error == 0 && spa_writeable(spa)) {
                          zio_nowait(zio_write_phys(vd->vdev_probe_zio, vd,
                              zio->io_offset, zio->io_size, zio->io_abd,
                              ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
                              ZIO_PRIORITY_SYNC_WRITE, vps->vps_flags, B_TRUE));
                  } else {
                          abd_free(zio->io_abd);
                  }
          } else if (zio->io_type == ZIO_TYPE_WRITE) {
                  if (zio->io_error == 0)
                          vps->vps_writeable = 1;
                  abd_free(zio->io_abd);
          } else if (zio->io_type == ZIO_TYPE_NULL) {
                  zio_t *pio;
                  zio_link_t *zl;
  
                  vd->vdev_cant_read |= !vps->vps_readable;
                  vd->vdev_cant_write |= !vps->vps_writeable;
  
                  if (vdev_readable(vd) &&
                      (vdev_writeable(vd) || !spa_writeable(spa))) {
                          zio->io_error = 0;
                  } else {
                          ASSERT(zio->io_error != 0);
                          vdev_dbgmsg(vd, "failed probe");
                          (void) zfs_ereport_post(FM_EREPORT_ZFS_PROBE_FAILURE,
                              spa, vd, NULL, NULL, 0);
                          zio->io_error = SET_ERROR(ENXIO);
                  }
  
                  mutex_enter(&vd->vdev_probe_lock);
                  ASSERT(vd->vdev_probe_zio == zio);
                  vd->vdev_probe_zio = NULL;
                  mutex_exit(&vd->vdev_probe_lock);
  
                  zl = NULL;
                  while ((pio = zio_walk_parents(zio, &zl)) != NULL)
                          if (!vdev_accessible(vd, pio))
                                  pio->io_error = SET_ERROR(ENXIO);
  
                  kmem_free(vps, sizeof (*vps));
          }
  }
  
  /*
   * Determine whether this device is accessible.
   *
   * Read and write to several known locations: the pad regions of each
   * vdev label but the first, which we leave alone in case it contains
   * a VTOC.
   */
  zio_t *
  vdev_probe(vdev_t *vd, zio_t *zio)
  {
          spa_t *spa = vd->vdev_spa;
          vdev_probe_stats_t *vps = NULL;
          zio_t *pio;
  
          ASSERT(vd->vdev_ops->vdev_op_leaf);
  
          /*
           * Don't probe the probe.
           */
          if (zio && (zio->io_flags & ZIO_FLAG_PROBE))
                  return (NULL);
  
          /*
           * To prevent 'probe storms' when a device fails, we create
           * just one probe i/o at a time.  All zios that want to probe
           * this vdev will become parents of the probe io.
           */
          mutex_enter(&vd->vdev_probe_lock);
  
          if ((pio = vd->vdev_probe_zio) == NULL) {
                  vps = kmem_zalloc(sizeof (*vps), KM_SLEEP);
  
                  vps->vps_flags = ZIO_FLAG_CANFAIL | ZIO_FLAG_PROBE |
                      ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_AGGREGATE |
                      ZIO_FLAG_TRYHARD;
  
                  if (spa_config_held(spa, SCL_ZIO, RW_WRITER)) {
                          /*
                           * vdev_cant_read and vdev_cant_write can only
                           * transition from TRUE to FALSE when we have the
                           * SCL_ZIO lock as writer; otherwise they can only
                           * transition from FALSE to TRUE.  This ensures that
                           * any zio looking at these values can assume that
                           * failures persist for the life of the I/O.  That's
                           * important because when a device has intermittent
                           * connectivity problems, we want to ensure that
                           * they're ascribed to the device (ENXIO) and not
                           * the zio (EIO).
                           *
                           * Since we hold SCL_ZIO as writer here, clear both
                           * values so the probe can reevaluate from first
                           * principles.
                           */
                          vps->vps_flags |= ZIO_FLAG_CONFIG_WRITER;
                          vd->vdev_cant_read = B_FALSE;
                          vd->vdev_cant_write = B_FALSE;
                  }
  
                  vd->vdev_probe_zio = pio = zio_null(NULL, spa, vd,
                      vdev_probe_done, vps,
                      vps->vps_flags | ZIO_FLAG_DONT_PROPAGATE);
  
                  /*
                   * We can't change the vdev state in this context, so we
                   * kick off an async task to do it on our behalf.
                   */
                  if (zio != NULL) {
                          vd->vdev_probe_wanted = B_TRUE;
                          spa_async_request(spa, SPA_ASYNC_PROBE);
                  }
          }
  
          if (zio != NULL)
                  zio_add_child(zio, pio);
  
          mutex_exit(&vd->vdev_probe_lock);
  
          if (vps == NULL) {
                  ASSERT(zio != NULL);
                  return (NULL);
          }
  
          for (int l = 1; l < VDEV_LABELS; l++) {
                  zio_nowait(zio_read_phys(pio, vd,
                      vdev_label_offset(vd->vdev_psize, l,
                      offsetof(vdev_label_t, vl_be)), VDEV_PAD_SIZE,
                      abd_alloc_for_io(VDEV_PAD_SIZE, B_TRUE),
                      ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
                      ZIO_PRIORITY_SYNC_READ, vps->vps_flags, B_TRUE));
          }
  
          if (zio == NULL)
                  return (pio);
  
          zio_nowait(pio);
          return (NULL);
  }
  
  static void
  vdev_load_child(void *arg)
  {
          vdev_t *vd = arg;
  
          vd->vdev_load_error = vdev_load(vd);
  }
  
  static void
  vdev_open_child(void *arg)
  {
          vdev_t *vd = arg;
  
          vd->vdev_open_thread = curthread;
          vd->vdev_open_error = vdev_open(vd);
          vd->vdev_open_thread = NULL;
  }
  
  static boolean_t
  vdev_uses_zvols(vdev_t *vd)
  {
  #ifdef _KERNEL
          if (zvol_is_zvol(vd->vdev_path))
                  return (B_TRUE);
  #endif
  
          for (int c = 0; c < vd->vdev_children; c++)
                  if (vdev_uses_zvols(vd->vdev_child[c]))
                          return (B_TRUE);
  
          return (B_FALSE);
  }
  
  /*
   * Returns B_TRUE if the passed child should be opened.
   */
  static boolean_t
  vdev_default_open_children_func(vdev_t *vd)
  {
          (void) vd;
          return (B_TRUE);
  }
  
  /*
   * Open the requested child vdevs.  If any of the leaf vdevs are using
   * a ZFS volume then do the opens in a single thread.  This avoids a
   * deadlock when the current thread is holding the spa_namespace_lock.
   */
  static void
  vdev_open_children_impl(vdev_t *vd, vdev_open_children_func_t *open_func)
  {
          int children = vd->vdev_children;
  
          taskq_t *tq = taskq_create("vdev_open", children, minclsyspri,
              children, children, TASKQ_PREPOPULATE);
          vd->vdev_nonrot = B_TRUE;
  
          for (int c = 0; c < children; c++) {
                  vdev_t *cvd = vd->vdev_child[c];
  
                  if (open_func(cvd) == B_FALSE)
                          continue;
  
                  if (tq == NULL || vdev_uses_zvols(vd)) {
                          cvd->vdev_open_error = vdev_open(cvd);
                  } else {
                          VERIFY(taskq_dispatch(tq, vdev_open_child,
                              cvd, TQ_SLEEP) != TASKQID_INVALID);
                  }
  
                  vd->vdev_nonrot &= cvd->vdev_nonrot;
          }
  
          if (tq != NULL) {
                  taskq_wait(tq);
                  taskq_destroy(tq);
          }
  }
  
  /*
   * Open all child vdevs.
   */
  void
  vdev_open_children(vdev_t *vd)
  {
          vdev_open_children_impl(vd, vdev_default_open_children_func);
  }
  
  /*
   * Conditionally open a subset of child vdevs.
   */
  void
  vdev_open_children_subset(vdev_t *vd, vdev_open_children_func_t *open_func)
  {
          vdev_open_children_impl(vd, open_func);
  }
  
  /*
   * Compute the raidz-deflation ratio.  Note, we hard-code
   * in 128k (1 << 17) because it is the "typical" blocksize.
   * Even though SPA_MAXBLOCKSIZE changed, this algorithm can not change,
   * otherwise it would inconsistently account for existing bp's.
   */
  static void
  vdev_set_deflate_ratio(vdev_t *vd)
  {
          if (vd == vd->vdev_top && !vd->vdev_ishole && vd->vdev_ashift != 0) {
                  vd->vdev_deflate_ratio = (1 << 17) /
                      (vdev_psize_to_asize(vd, 1 << 17) >> SPA_MINBLOCKSHIFT);
          }
  }
  
  /*
   * Choose the best of two ashifts, preferring one between logical ashift
   * (absolute minimum) and administrator defined maximum, otherwise take
   * the biggest of the two.
   */
  uint64_t
  vdev_best_ashift(uint64_t logical, uint64_t a, uint64_t b)
  {
          if (a > logical && a <= zfs_vdev_max_auto_ashift) {
                  if (b <= logical || b > zfs_vdev_max_auto_ashift)
                          return (a);
                  else
                          return (MAX(a, b));
          } else if (b <= logical || b > zfs_vdev_max_auto_ashift)
                  return (MAX(a, b));
          return (b);
  }
  
  /*
   * Maximize performance by inflating the configured ashift for top level
   * vdevs to be as close to the physical ashift as possible while maintaining
   * administrator defined limits and ensuring it doesn't go below the
   * logical ashift.
   */
  static void
  vdev_ashift_optimize(vdev_t *vd)
  {
          ASSERT(vd == vd->vdev_top);
  
          if (vd->vdev_ashift < vd->vdev_physical_ashift &&
              vd->vdev_physical_ashift <= zfs_vdev_max_auto_ashift) {
                  vd->vdev_ashift = MIN(
                      MAX(zfs_vdev_max_auto_ashift, vd->vdev_ashift),
                      MAX(zfs_vdev_min_auto_ashift,
                      vd->vdev_physical_ashift));
          } else {
                  /*
                   * If the logical and physical ashifts are the same, then
                   * we ensure that the top-level vdev's ashift is not smaller
                   * than our minimum ashift value. For the unusual case
                   * where logical ashift > physical ashift, we can't cap
                   * the calculated ashift based on max ashift as that
                   * would cause failures.
                   * We still check if we need to increase it to match
                   * the min ashift.
                   */
                  vd->vdev_ashift = MAX(zfs_vdev_min_auto_ashift,
                      vd->vdev_ashift);
          }
  }
  
  /*
   * Prepare a virtual device for access.
   */
  int
  vdev_open(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          int error;
          uint64_t osize = 0;
          uint64_t max_osize = 0;
          uint64_t asize, max_asize, psize;
          uint64_t logical_ashift = 0;
          uint64_t physical_ashift = 0;
  
          ASSERT(vd->vdev_open_thread == curthread ||
              spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
          ASSERT(vd->vdev_state == VDEV_STATE_CLOSED ||
              vd->vdev_state == VDEV_STATE_CANT_OPEN ||
              vd->vdev_state == VDEV_STATE_OFFLINE);
  
          vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
          vd->vdev_cant_read = B_FALSE;
          vd->vdev_cant_write = B_FALSE;
          vd->vdev_min_asize = vdev_get_min_asize(vd);
  
          /*
           * If this vdev is not removed, check its fault status.  If it's
           * faulted, bail out of the open.
           */
          if (!vd->vdev_removed && vd->vdev_faulted) {
                  ASSERT(vd->vdev_children == 0);
                  ASSERT(vd->vdev_label_aux == VDEV_AUX_ERR_EXCEEDED ||
                      vd->vdev_label_aux == VDEV_AUX_EXTERNAL);
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
                      vd->vdev_label_aux);
                  return (SET_ERROR(ENXIO));
          } else if (vd->vdev_offline) {
                  ASSERT(vd->vdev_children == 0);
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE, VDEV_AUX_NONE);
                  return (SET_ERROR(ENXIO));
          }
  
          error = vd->vdev_ops->vdev_op_open(vd, &osize, &max_osize,
              &logical_ashift, &physical_ashift);
  
          /* Keep the device in removed state if unplugged */
          if (error == ENOENT && vd->vdev_removed) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_REMOVED,
                      VDEV_AUX_NONE);
                  return (error);
          }
  
          /*
           * Physical volume size should never be larger than its max size, unless
           * the disk has shrunk while we were reading it or the device is buggy
           * or damaged: either way it's not safe for use, bail out of the open.
           */
          if (osize > max_osize) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_OPEN_FAILED);
                  return (SET_ERROR(ENXIO));
          }
  
          /*
           * Reset the vdev_reopening flag so that we actually close
           * the vdev on error.
           */
          vd->vdev_reopening = B_FALSE;
          if (zio_injection_enabled && error == 0)
                  error = zio_handle_device_injection(vd, NULL, SET_ERROR(ENXIO));
  
          if (error) {
                  if (vd->vdev_removed &&
                      vd->vdev_stat.vs_aux != VDEV_AUX_OPEN_FAILED)
                          vd->vdev_removed = B_FALSE;
  
                  if (vd->vdev_stat.vs_aux == VDEV_AUX_CHILDREN_OFFLINE) {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE,
                              vd->vdev_stat.vs_aux);
                  } else {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                              vd->vdev_stat.vs_aux);
                  }
                  return (error);
          }
  
          vd->vdev_removed = B_FALSE;
  
          /*
           * Recheck the faulted flag now that we have confirmed that
           * the vdev is accessible.  If we're faulted, bail.
           */
          if (vd->vdev_faulted) {
                  ASSERT(vd->vdev_children == 0);
                  ASSERT(vd->vdev_label_aux == VDEV_AUX_ERR_EXCEEDED ||
                      vd->vdev_label_aux == VDEV_AUX_EXTERNAL);
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
                      vd->vdev_label_aux);
                  return (SET_ERROR(ENXIO));
          }
  
          if (vd->vdev_degraded) {
                  ASSERT(vd->vdev_children == 0);
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
                      VDEV_AUX_ERR_EXCEEDED);
          } else {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_HEALTHY, 0);
          }
  
          /*
           * For hole or missing vdevs we just return success.
           */
          if (vd->vdev_ishole || vd->vdev_ops == &vdev_missing_ops)
                  return (0);
  
          for (int c = 0; c < vd->vdev_children; c++) {
                  if (vd->vdev_child[c]->vdev_state != VDEV_STATE_HEALTHY) {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
                              VDEV_AUX_NONE);
                          break;
                  }
          }
  
          osize = P2ALIGN(osize, (uint64_t)sizeof (vdev_label_t));
          max_osize = P2ALIGN(max_osize, (uint64_t)sizeof (vdev_label_t));
  
          if (vd->vdev_children == 0) {
                  if (osize < SPA_MINDEVSIZE) {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_TOO_SMALL);
                          return (SET_ERROR(EOVERFLOW));
                  }
                  psize = osize;
                  asize = osize - (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE);
                  max_asize = max_osize - (VDEV_LABEL_START_SIZE +
                      VDEV_LABEL_END_SIZE);
          } else {
                  if (vd->vdev_parent != NULL && osize < SPA_MINDEVSIZE -
                      (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE)) {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_TOO_SMALL);
                          return (SET_ERROR(EOVERFLOW));
                  }
                  psize = 0;
                  asize = osize;
                  max_asize = max_osize;
          }
  
          /*
           * If the vdev was expanded, record this so that we can re-create the
           * uberblock rings in labels {2,3}, during the next sync.
           */
          if ((psize > vd->vdev_psize) && (vd->vdev_psize != 0))
                  vd->vdev_copy_uberblocks = B_TRUE;
  
          vd->vdev_psize = psize;
  
          /*
           * Make sure the allocatable size hasn't shrunk too much.
           */
          if (asize < vd->vdev_min_asize) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_BAD_LABEL);
                  return (SET_ERROR(EINVAL));
          }
  
          /*
           * We can always set the logical/physical ashift members since
           * their values are only used to calculate the vdev_ashift when
           * the device is first added to the config. These values should
           * not be used for anything else since they may change whenever
           * the device is reopened and we don't store them in the label.
           */
          vd->vdev_physical_ashift =
              MAX(physical_ashift, vd->vdev_physical_ashift);
          vd->vdev_logical_ashift = MAX(logical_ashift,
              vd->vdev_logical_ashift);
  
          if (vd->vdev_asize == 0) {
                  /*
                   * This is the first-ever open, so use the computed values.
                   * For compatibility, a different ashift can be requested.
                   */
                  vd->vdev_asize = asize;
                  vd->vdev_max_asize = max_asize;
  
                  /*
                   * If the vdev_ashift was not overridden at creation time,
                   * then set it the logical ashift and optimize the ashift.
                   */
                  if (vd->vdev_ashift == 0) {
                          vd->vdev_ashift = vd->vdev_logical_ashift;
  
                          if (vd->vdev_logical_ashift > ASHIFT_MAX) {
                                  vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                                      VDEV_AUX_ASHIFT_TOO_BIG);
                                  return (SET_ERROR(EDOM));
                          }
  
                          if (vd->vdev_top == vd) {
                                  vdev_ashift_optimize(vd);
                          }
                  }
                  if (vd->vdev_ashift != 0 && (vd->vdev_ashift < ASHIFT_MIN ||
                      vd->vdev_ashift > ASHIFT_MAX)) {
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_BAD_ASHIFT);
                          return (SET_ERROR(EDOM));
                  }
          } else {
                  /*
                   * Make sure the alignment required hasn't increased.
                   */
                  if (vd->vdev_ashift > vd->vdev_top->vdev_ashift &&
                      vd->vdev_ops->vdev_op_leaf) {
                          (void) zfs_ereport_post(
                              FM_EREPORT_ZFS_DEVICE_BAD_ASHIFT,
                              spa, vd, NULL, NULL, 0);
                          vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_BAD_LABEL);
                          return (SET_ERROR(EDOM));
                  }
                  vd->vdev_max_asize = max_asize;
          }
  
          /*
           * If all children are healthy we update asize if either:
           * The asize has increased, due to a device expansion caused by dynamic
           * LUN growth or vdev replacement, and automatic expansion is enabled;
           * making the additional space available.
           *
           * The asize has decreased, due to a device shrink usually caused by a
           * vdev replace with a smaller device. This ensures that calculations
           * based of max_asize and asize e.g. esize are always valid. It's safe
           * to do this as we've already validated that asize is greater than
           * vdev_min_asize.
           */
          if (vd->vdev_state == VDEV_STATE_HEALTHY &&
              ((asize > vd->vdev_asize &&
              (vd->vdev_expanding || spa->spa_autoexpand)) ||
              (asize < vd->vdev_asize)))
                  vd->vdev_asize = asize;
  
          vdev_set_min_asize(vd);
  
          /*
           * Ensure we can issue some IO before declaring the
           * vdev open for business.
           */
          if (vd->vdev_ops->vdev_op_leaf &&
              (error = zio_wait(vdev_probe(vd, NULL))) != 0) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
                      VDEV_AUX_ERR_EXCEEDED);
                  return (error);
          }
  
          /*
           * Track the minimum allocation size.
           */
          if (vd->vdev_top == vd && vd->vdev_ashift != 0 &&
              vd->vdev_islog == 0 && vd->vdev_aux == NULL) {
                  uint64_t min_alloc = vdev_get_min_alloc(vd);
                  if (min_alloc < spa->spa_min_alloc)
                          spa->spa_min_alloc = min_alloc;
          }
  
          /*
           * If this is a leaf vdev, assess whether a resilver is needed.
           * But don't do this if we are doing a reopen for a scrub, since
           * this would just restart the scrub we are already doing.
           */
          if (vd->vdev_ops->vdev_op_leaf && !spa->spa_scrub_reopen)
                  dsl_scan_assess_vdev(spa->spa_dsl_pool, vd);
  
          return (0);
  }
  
  static void
  vdev_validate_child(void *arg)
  {
          vdev_t *vd = arg;
  
          vd->vdev_validate_thread = curthread;
          vd->vdev_validate_error = vdev_validate(vd);
          vd->vdev_validate_thread = NULL;
  }
  
  /*
   * Called once the vdevs are all opened, this routine validates the label
   * contents. This needs to be done before vdev_load() so that we don't
   * inadvertently do repair I/Os to the wrong device.
   *
   * This function will only return failure if one of the vdevs indicates that it
   * has since been destroyed or exported.  This is only possible if
   * /etc/zfs/zpool.cache was readonly at the time.  Otherwise, the vdev state
   * will be updated but the function will return 0.
   */
  int
  vdev_validate(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          taskq_t *tq = NULL;
          nvlist_t *label;
          uint64_t guid = 0, aux_guid = 0, top_guid;
          uint64_t state;
          nvlist_t *nvl;
          uint64_t txg;
          int children = vd->vdev_children;
  
          if (vdev_validate_skip)
                  return (0);
  
          if (children > 0) {
                  tq = taskq_create("vdev_validate", children, minclsyspri,
                      children, children, TASKQ_PREPOPULATE);
          }
  
          for (uint64_t c = 0; c < children; c++) {
                  vdev_t *cvd = vd->vdev_child[c];
  
                  if (tq == NULL || vdev_uses_zvols(cvd)) {
                          vdev_validate_child(cvd);
                  } else {
                          VERIFY(taskq_dispatch(tq, vdev_validate_child, cvd,
                              TQ_SLEEP) != TASKQID_INVALID);
                  }
          }
          if (tq != NULL) {
                  taskq_wait(tq);
                  taskq_destroy(tq);
          }
          for (int c = 0; c < children; c++) {
                  int error = vd->vdev_child[c]->vdev_validate_error;
  
                  if (error != 0)
                          return (SET_ERROR(EBADF));
          }
  
  
          /*
           * If the device has already failed, or was marked offline, don't do
           * any further validation.  Otherwise, label I/O will fail and we will
           * overwrite the previous state.
           */
          if (!vd->vdev_ops->vdev_op_leaf || !vdev_readable(vd))
                  return (0);
  
          /*
           * If we are performing an extreme rewind, we allow for a label that
           * was modified at a point after the current txg.
           * If config lock is not held do not check for the txg. spa_sync could
           * be updating the vdev's label before updating spa_last_synced_txg.
           */
          if (spa->spa_extreme_rewind || spa_last_synced_txg(spa) == 0 ||
              spa_config_held(spa, SCL_CONFIG, RW_WRITER) != SCL_CONFIG)
                  txg = UINT64_MAX;
          else
                  txg = spa_last_synced_txg(spa);
  
          if ((label = vdev_label_read_config(vd, txg)) == NULL) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_BAD_LABEL);
                  vdev_dbgmsg(vd, "vdev_validate: failed reading config for "
                      "txg %llu", (u_longlong_t)txg);
                  return (0);
          }
  
          /*
           * Determine if this vdev has been split off into another
           * pool.  If so, then refuse to open it.
           */
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_SPLIT_GUID,
              &aux_guid) == 0 && aux_guid == spa_guid(spa)) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_SPLIT_POOL);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: vdev split into other pool");
                  return (0);
          }
  
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &guid) != 0) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
                      ZPOOL_CONFIG_POOL_GUID);
                  return (0);
          }
  
          /*
           * If config is not trusted then ignore the spa guid check. This is
           * necessary because if the machine crashed during a re-guid the new
           * guid might have been written to all of the vdev labels, but not the
           * cached config. The check will be performed again once we have the
           * trusted config from the MOS.
           */
          if (spa->spa_trust_config && guid != spa_guid(spa)) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: vdev label pool_guid doesn't "
                      "match config (%llu != %llu)", (u_longlong_t)guid,
                      (u_longlong_t)spa_guid(spa));
                  return (0);
          }
  
          if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_VDEV_TREE, &nvl)
              != 0 || nvlist_lookup_uint64(nvl, ZPOOL_CONFIG_ORIG_GUID,
              &aux_guid) != 0)
                  aux_guid = 0;
  
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid) != 0) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
                      ZPOOL_CONFIG_GUID);
                  return (0);
          }
  
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_TOP_GUID, &top_guid)
              != 0) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
                      ZPOOL_CONFIG_TOP_GUID);
                  return (0);
          }
  
          /*
           * If this vdev just became a top-level vdev because its sibling was
           * detached, it will have adopted the parent's vdev guid -- but the
           * label may or may not be on disk yet. Fortunately, either version
           * of the label will have the same top guid, so if we're a top-level
           * vdev, we can safely compare to that instead.
           * However, if the config comes from a cachefile that failed to update
           * after the detach, a top-level vdev will appear as a non top-level
           * vdev in the config. Also relax the constraints if we perform an
           * extreme rewind.
           *
           * If we split this vdev off instead, then we also check the
           * original pool's guid. We don't want to consider the vdev
           * corrupt if it is partway through a split operation.
           */
          if (vd->vdev_guid != guid && vd->vdev_guid != aux_guid) {
                  boolean_t mismatch = B_FALSE;
                  if (spa->spa_trust_config && !spa->spa_extreme_rewind) {
                          if (vd != vd->vdev_top || vd->vdev_guid != top_guid)
                                  mismatch = B_TRUE;
                  } else {
                          if (vd->vdev_guid != top_guid &&
                              vd->vdev_top->vdev_guid != guid)
                                  mismatch = B_TRUE;
                  }
  
                  if (mismatch) {
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          nvlist_free(label);
                          vdev_dbgmsg(vd, "vdev_validate: config guid "
                              "doesn't match label guid");
                          vdev_dbgmsg(vd, "CONFIG: guid %llu, top_guid %llu",
                              (u_longlong_t)vd->vdev_guid,
                              (u_longlong_t)vd->vdev_top->vdev_guid);
                          vdev_dbgmsg(vd, "LABEL: guid %llu, top_guid %llu, "
                              "aux_guid %llu", (u_longlong_t)guid,
                              (u_longlong_t)top_guid, (u_longlong_t)aux_guid);
                          return (0);
                  }
          }
  
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
              &state) != 0) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
                      ZPOOL_CONFIG_POOL_STATE);
                  return (0);
          }
  
          nvlist_free(label);
  
          /*
           * If this is a verbatim import, no need to check the
           * state of the pool.
           */
          if (!(spa->spa_import_flags & ZFS_IMPORT_VERBATIM) &&
              spa_load_state(spa) == SPA_LOAD_OPEN &&
              state != POOL_STATE_ACTIVE) {
                  vdev_dbgmsg(vd, "vdev_validate: invalid pool state (%llu) "
                      "for spa %s", (u_longlong_t)state, spa->spa_name);
                  return (SET_ERROR(EBADF));
          }
  
          /*
           * If we were able to open and validate a vdev that was
           * previously marked permanently unavailable, clear that state
           * now.
           */
          if (vd->vdev_not_present)
                  vd->vdev_not_present = 0;
  
          return (0);
  }
  
  static void
  vdev_copy_path_impl(vdev_t *svd, vdev_t *dvd)
  {
          char *old, *new;
          if (svd->vdev_path != NULL && dvd->vdev_path != NULL) {
                  if (strcmp(svd->vdev_path, dvd->vdev_path) != 0) {
                          zfs_dbgmsg("vdev_copy_path: vdev %llu: path changed "
                              "from '%s' to '%s'", (u_longlong_t)dvd->vdev_guid,
                              dvd->vdev_path, svd->vdev_path);
                          spa_strfree(dvd->vdev_path);
                          dvd->vdev_path = spa_strdup(svd->vdev_path);
                  }
          } else if (svd->vdev_path != NULL) {
                  dvd->vdev_path = spa_strdup(svd->vdev_path);
                  zfs_dbgmsg("vdev_copy_path: vdev %llu: path set to '%s'",
                      (u_longlong_t)dvd->vdev_guid, dvd->vdev_path);
          }
  
          /*
           * Our enclosure sysfs path may have changed between imports
           */
          old = dvd->vdev_enc_sysfs_path;
          new = svd->vdev_enc_sysfs_path;
          if ((old != NULL && new == NULL) ||
              (old == NULL && new != NULL) ||
              ((old != NULL && new != NULL) && strcmp(new, old) != 0)) {
                  zfs_dbgmsg("vdev_copy_path: vdev %llu: vdev_enc_sysfs_path "
                      "changed from '%s' to '%s'", (u_longlong_t)dvd->vdev_guid,
                      old, new);
  
                  if (dvd->vdev_enc_sysfs_path)
                          spa_strfree(dvd->vdev_enc_sysfs_path);
  
                  if (svd->vdev_enc_sysfs_path) {
                          dvd->vdev_enc_sysfs_path = spa_strdup(
                              svd->vdev_enc_sysfs_path);
                  } else {
                          dvd->vdev_enc_sysfs_path = NULL;
                  }
          }
  }
  
  /*
   * Recursively copy vdev paths from one vdev to another. Source and destination
   * vdev trees must have same geometry otherwise return error. Intended to copy
   * paths from userland config into MOS config.
   */
  int
  vdev_copy_path_strict(vdev_t *svd, vdev_t *dvd)
  {
          if ((svd->vdev_ops == &vdev_missing_ops) ||
              (svd->vdev_ishole && dvd->vdev_ishole) ||
              (dvd->vdev_ops == &vdev_indirect_ops))
                  return (0);
  
          if (svd->vdev_ops != dvd->vdev_ops) {
                  vdev_dbgmsg(svd, "vdev_copy_path: vdev type mismatch: %s != %s",
                      svd->vdev_ops->vdev_op_type, dvd->vdev_ops->vdev_op_type);
                  return (SET_ERROR(EINVAL));
          }
  
          if (svd->vdev_guid != dvd->vdev_guid) {
                  vdev_dbgmsg(svd, "vdev_copy_path: guids mismatch (%llu != "
                      "%llu)", (u_longlong_t)svd->vdev_guid,
                      (u_longlong_t)dvd->vdev_guid);
                  return (SET_ERROR(EINVAL));
          }
  
          if (svd->vdev_children != dvd->vdev_children) {
                  vdev_dbgmsg(svd, "vdev_copy_path: children count mismatch: "
                      "%llu != %llu", (u_longlong_t)svd->vdev_children,
                      (u_longlong_t)dvd->vdev_children);
                  return (SET_ERROR(EINVAL));
          }
  
          for (uint64_t i = 0; i < svd->vdev_children; i++) {
                  int error = vdev_copy_path_strict(svd->vdev_child[i],
                      dvd->vdev_child[i]);
                  if (error != 0)
                          return (error);
          }
  
          if (svd->vdev_ops->vdev_op_leaf)
                  vdev_copy_path_impl(svd, dvd);
  
          return (0);
  }
  
  static void
  vdev_copy_path_search(vdev_t *stvd, vdev_t *dvd)
  {
          ASSERT(stvd->vdev_top == stvd);
          ASSERT3U(stvd->vdev_id, ==, dvd->vdev_top->vdev_id);
  
          for (uint64_t i = 0; i < dvd->vdev_children; i++) {
                  vdev_copy_path_search(stvd, dvd->vdev_child[i]);
          }
  
          if (!dvd->vdev_ops->vdev_op_leaf || !vdev_is_concrete(dvd))
                  return;
  
          /*
           * The idea here is that while a vdev can shift positions within
           * a top vdev (when replacing, attaching mirror, etc.) it cannot
           * step outside of it.
           */
          vdev_t *vd = vdev_lookup_by_guid(stvd, dvd->vdev_guid);
  
          if (vd == NULL || vd->vdev_ops != dvd->vdev_ops)
                  return;
  
          ASSERT(vd->vdev_ops->vdev_op_leaf);
  
          vdev_copy_path_impl(vd, dvd);
  }
  
  /*
   * Recursively copy vdev paths from one root vdev to another. Source and
   * destination vdev trees may differ in geometry. For each destination leaf
   * vdev, search a vdev with the same guid and top vdev id in the source.
   * Intended to copy paths from userland config into MOS config.
   */
  void
  vdev_copy_path_relaxed(vdev_t *srvd, vdev_t *drvd)
  {
          uint64_t children = MIN(srvd->vdev_children, drvd->vdev_children);
          ASSERT(srvd->vdev_ops == &vdev_root_ops);
          ASSERT(drvd->vdev_ops == &vdev_root_ops);
  
          for (uint64_t i = 0; i < children; i++) {
                  vdev_copy_path_search(srvd->vdev_child[i],
                      drvd->vdev_child[i]);
          }
  }
  
  /*
   * Close a virtual device.
   */
  void
  vdev_close(vdev_t *vd)
  {
          vdev_t *pvd = vd->vdev_parent;
          spa_t *spa __maybe_unused = vd->vdev_spa;
  
          ASSERT(vd != NULL);
          ASSERT(vd->vdev_open_thread == curthread ||
              spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
  
          /*
           * If our parent is reopening, then we are as well, unless we are
           * going offline.
           */
          if (pvd != NULL && pvd->vdev_reopening)
                  vd->vdev_reopening = (pvd->vdev_reopening && !vd->vdev_offline);
  
          vd->vdev_ops->vdev_op_close(vd);
  
          vdev_cache_purge(vd);
  
          /*
           * We record the previous state before we close it, so that if we are
           * doing a reopen(), we don't generate FMA ereports if we notice that
           * it's still faulted.
           */
          vd->vdev_prevstate = vd->vdev_state;
  
          if (vd->vdev_offline)
                  vd->vdev_state = VDEV_STATE_OFFLINE;
          else
                  vd->vdev_state = VDEV_STATE_CLOSED;
          vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
  }
  
  void
  vdev_hold(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(spa_is_root(spa));
          if (spa->spa_state == POOL_STATE_UNINITIALIZED)
                  return;
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_hold(vd->vdev_child[c]);
  
          if (vd->vdev_ops->vdev_op_leaf && vd->vdev_ops->vdev_op_hold != NULL)
                  vd->vdev_ops->vdev_op_hold(vd);
  }
  
  void
  vdev_rele(vdev_t *vd)
  {
          ASSERT(spa_is_root(vd->vdev_spa));
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_rele(vd->vdev_child[c]);
  
          if (vd->vdev_ops->vdev_op_leaf && vd->vdev_ops->vdev_op_rele != NULL)
                  vd->vdev_ops->vdev_op_rele(vd);
  }
  
  /*
   * Reopen all interior vdevs and any unopened leaves.  We don't actually
   * reopen leaf vdevs which had previously been opened as they might deadlock
   * on the spa_config_lock.  Instead we only obtain the leaf's physical size.
   * If the leaf has never been opened then open it, as usual.
   */
  void
  vdev_reopen(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
  
          /* set the reopening flag unless we're taking the vdev offline */
          vd->vdev_reopening = !vd->vdev_offline;
          vdev_close(vd);
          (void) vdev_open(vd);
  
          /*
           * Call vdev_validate() here to make sure we have the same device.
           * Otherwise, a device with an invalid label could be successfully
           * opened in response to vdev_reopen().
           */
          if (vd->vdev_aux) {
                  (void) vdev_validate_aux(vd);
                  if (vdev_readable(vd) && vdev_writeable(vd) &&
                      vd->vdev_aux == &spa->spa_l2cache) {
                          /*
                           * In case the vdev is present we should evict all ARC
                           * buffers and pointers to log blocks and reclaim their
                           * space before restoring its contents to L2ARC.
                           */
                          if (l2arc_vdev_present(vd)) {
                                  l2arc_rebuild_vdev(vd, B_TRUE);
                          } else {
                                  l2arc_add_vdev(spa, vd);
                          }
                          spa_async_request(spa, SPA_ASYNC_L2CACHE_REBUILD);
                          spa_async_request(spa, SPA_ASYNC_L2CACHE_TRIM);
                  }
          } else {
                  (void) vdev_validate(vd);
          }
  
          /*
           * Reassess parent vdev's health.
           */
          vdev_propagate_state(vd);
  }
  
  int
  vdev_create(vdev_t *vd, uint64_t txg, boolean_t isreplacing)
  {
          int error;
  
          /*
           * Normally, partial opens (e.g. of a mirror) are allowed.
           * For a create, however, we want to fail the request if
           * there are any components we can't open.
           */
          error = vdev_open(vd);
  
          if (error || vd->vdev_state != VDEV_STATE_HEALTHY) {
                  vdev_close(vd);
                  return (error ? error : SET_ERROR(ENXIO));
          }
  
          /*
           * Recursively load DTLs and initialize all labels.
           */
          if ((error = vdev_dtl_load(vd)) != 0 ||
              (error = vdev_label_init(vd, txg, isreplacing ?
              VDEV_LABEL_REPLACE : VDEV_LABEL_CREATE)) != 0) {
                  vdev_close(vd);
                  return (error);
          }
  
          return (0);
  }
  
  void
  vdev_metaslab_set_size(vdev_t *vd)
  {
          uint64_t asize = vd->vdev_asize;
          uint64_t ms_count = asize >> zfs_vdev_default_ms_shift;
          uint64_t ms_shift;
  
          /*
           * There are two dimensions to the metaslab sizing calculation:
           * the size of the metaslab and the count of metaslabs per vdev.
           *
           * The default values used below are a good balance between memory
           * usage (larger metaslab size means more memory needed for loaded
           * metaslabs; more metaslabs means more memory needed for the
           * metaslab_t structs), metaslab load time (larger metaslabs take
           * longer to load), and metaslab sync time (more metaslabs means
           * more time spent syncing all of them).
           *
           * In general, we aim for zfs_vdev_default_ms_count (200) metaslabs.
           * The range of the dimensions are as follows:
           *
           *      2^29 <= ms_size  <= 2^34
           *        16 <= ms_count <= 131,072
           *
           * On the lower end of vdev sizes, we aim for metaslabs sizes of
           * at least 512MB (2^29) to minimize fragmentation effects when
           * testing with smaller devices.  However, the count constraint
           * of at least 16 metaslabs will override this minimum size goal.
           *
           * On the upper end of vdev sizes, we aim for a maximum metaslab
           * size of 16GB.  However, we will cap the total count to 2^17
           * metaslabs to keep our memory footprint in check and let the
           * metaslab size grow from there if that limit is hit.
           *
           * The net effect of applying above constrains is summarized below.
           *
           *   vdev size       metaslab count
           *  --------------|-----------------
           *      < 8GB        ~16
           *  8GB   - 100GB   one per 512MB
           *  100GB - 3TB     ~200
           *  3TB   - 2PB     one per 16GB
           *      > 2PB       ~131,072
           *  --------------------------------
           *
           *  Finally, note that all of the above calculate the initial
           *  number of metaslabs. Expanding a top-level vdev will result
           *  in additional metaslabs being allocated making it possible
           *  to exceed the zfs_vdev_ms_count_limit.
           */
  
          if (ms_count < zfs_vdev_min_ms_count)
                  ms_shift = highbit64(asize / zfs_vdev_min_ms_count);
          else if (ms_count > zfs_vdev_default_ms_count)
                  ms_shift = highbit64(asize / zfs_vdev_default_ms_count);
          else
                  ms_shift = zfs_vdev_default_ms_shift;
  
          if (ms_shift < SPA_MAXBLOCKSHIFT) {
                  ms_shift = SPA_MAXBLOCKSHIFT;
          } else if (ms_shift > zfs_vdev_max_ms_shift) {
                  ms_shift = zfs_vdev_max_ms_shift;
                  /* cap the total count to constrain memory footprint */
                  if ((asize >> ms_shift) > zfs_vdev_ms_count_limit)
                          ms_shift = highbit64(asize / zfs_vdev_ms_count_limit);
          }
  
          vd->vdev_ms_shift = ms_shift;
          ASSERT3U(vd->vdev_ms_shift, >=, SPA_MAXBLOCKSHIFT);
  }
  
  void
  vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg)
  {
          ASSERT(vd == vd->vdev_top);
          /* indirect vdevs don't have metaslabs or dtls */
          ASSERT(vdev_is_concrete(vd) || flags == 0);
          ASSERT(ISP2(flags));
          ASSERT(spa_writeable(vd->vdev_spa));
  
          if (flags & VDD_METASLAB)
                  (void) txg_list_add(&vd->vdev_ms_list, arg, txg);
  
          if (flags & VDD_DTL)
                  (void) txg_list_add(&vd->vdev_dtl_list, arg, txg);
  
          (void) txg_list_add(&vd->vdev_spa->spa_vdev_txg_list, vd, txg);
  }
  
  void
  vdev_dirty_leaves(vdev_t *vd, int flags, uint64_t txg)
  {
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_dirty_leaves(vd->vdev_child[c], flags, txg);
  
          if (vd->vdev_ops->vdev_op_leaf)
                  vdev_dirty(vd->vdev_top, flags, vd, txg);
  }
  
  /*
   * DTLs.
   *
   * A vdev's DTL (dirty time log) is the set of transaction groups for which
   * the vdev has less than perfect replication.  There are four kinds of DTL:
   *
   * DTL_MISSING: txgs for which the vdev has no valid copies of the data
   *
   * DTL_PARTIAL: txgs for which data is available, but not fully replicated
   *
   * DTL_SCRUB: the txgs that could not be repaired by the last scrub; upon
   *      scrub completion, DTL_SCRUB replaces DTL_MISSING in the range of
   *      txgs that was scrubbed.
   *
   * DTL_OUTAGE: txgs which cannot currently be read, whether due to
   *      persistent errors or just some device being offline.
   *      Unlike the other three, the DTL_OUTAGE map is not generally
   *      maintained; it's only computed when needed, typically to
   *      determine whether a device can be detached.
   *
   * For leaf vdevs, DTL_MISSING and DTL_PARTIAL are identical: the device
   * either has the data or it doesn't.
   *
   * For interior vdevs such as mirror and RAID-Z the picture is more complex.
   * A vdev's DTL_PARTIAL is the union of its children's DTL_PARTIALs, because
   * if any child is less than fully replicated, then so is its parent.
   * A vdev's DTL_MISSING is a modified union of its children's DTL_MISSINGs,
   * comprising only those txgs which appear in 'maxfaults' or more children;
   * those are the txgs we don't have enough replication to read.  For example,
   * double-parity RAID-Z can tolerate up to two missing devices (maxfaults == 2);
   * thus, its DTL_MISSING consists of the set of txgs that appear in more than
   * two child DTL_MISSING maps.
   *
   * It should be clear from the above that to compute the DTLs and outage maps
   * for all vdevs, it suffices to know just the leaf vdevs' DTL_MISSING maps.
   * Therefore, that is all we keep on disk.  When loading the pool, or after
   * a configuration change, we generate all other DTLs from first principles.
   */
  void
  vdev_dtl_dirty(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
  {
          range_tree_t *rt = vd->vdev_dtl[t];
  
          ASSERT(t < DTL_TYPES);
          ASSERT(vd != vd->vdev_spa->spa_root_vdev);
          ASSERT(spa_writeable(vd->vdev_spa));
  
          mutex_enter(&vd->vdev_dtl_lock);
          if (!range_tree_contains(rt, txg, size))
                  range_tree_add(rt, txg, size);
          mutex_exit(&vd->vdev_dtl_lock);
  }
  
  boolean_t
  vdev_dtl_contains(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
  {
          range_tree_t *rt = vd->vdev_dtl[t];
          boolean_t dirty = B_FALSE;
  
          ASSERT(t < DTL_TYPES);
          ASSERT(vd != vd->vdev_spa->spa_root_vdev);
  
          /*
           * While we are loading the pool, the DTLs have not been loaded yet.
           * This isn't a problem but it can result in devices being tried
           * which are known to not have the data.  In which case, the import
           * is relying on the checksum to ensure that we get the right data.
           * Note that while importing we are only reading the MOS, which is
           * always checksummed.
           */
          mutex_enter(&vd->vdev_dtl_lock);
          if (!range_tree_is_empty(rt))
                  dirty = range_tree_contains(rt, txg, size);
          mutex_exit(&vd->vdev_dtl_lock);
  
          return (dirty);
  }
  
  boolean_t
  vdev_dtl_empty(vdev_t *vd, vdev_dtl_type_t t)
  {
          range_tree_t *rt = vd->vdev_dtl[t];
          boolean_t empty;
  
          mutex_enter(&vd->vdev_dtl_lock);
          empty = range_tree_is_empty(rt);
          mutex_exit(&vd->vdev_dtl_lock);
  
          return (empty);
  }
  
  /*
   * Check if the txg falls within the range which must be
   * resilvered.  DVAs outside this range can always be skipped.
   */
  boolean_t
  vdev_default_need_resilver(vdev_t *vd, const dva_t *dva, size_t psize,
      uint64_t phys_birth)
  {
          (void) dva, (void) psize;
  
          /* Set by sequential resilver. */
          if (phys_birth == TXG_UNKNOWN)
                  return (B_TRUE);
  
          return (vdev_dtl_contains(vd, DTL_PARTIAL, phys_birth, 1));
  }
  
  /*
   * Returns B_TRUE if the vdev determines the DVA needs to be resilvered.
   */
  boolean_t
  vdev_dtl_need_resilver(vdev_t *vd, const dva_t *dva, size_t psize,
      uint64_t phys_birth)
  {
          ASSERT(vd != vd->vdev_spa->spa_root_vdev);
  
          if (vd->vdev_ops->vdev_op_need_resilver == NULL ||
              vd->vdev_ops->vdev_op_leaf)
                  return (B_TRUE);
  
          return (vd->vdev_ops->vdev_op_need_resilver(vd, dva, psize,
              phys_birth));
  }
  
  /*
   * Returns the lowest txg in the DTL range.
   */
  static uint64_t
  vdev_dtl_min(vdev_t *vd)
  {
          ASSERT(MUTEX_HELD(&vd->vdev_dtl_lock));
          ASSERT3U(range_tree_space(vd->vdev_dtl[DTL_MISSING]), !=, 0);
          ASSERT0(vd->vdev_children);
  
          return (range_tree_min(vd->vdev_dtl[DTL_MISSING]) - 1);
  }
  
  /*
   * Returns the highest txg in the DTL.
   */
  static uint64_t
  vdev_dtl_max(vdev_t *vd)
  {
          ASSERT(MUTEX_HELD(&vd->vdev_dtl_lock));
          ASSERT3U(range_tree_space(vd->vdev_dtl[DTL_MISSING]), !=, 0);
          ASSERT0(vd->vdev_children);
  
          return (range_tree_max(vd->vdev_dtl[DTL_MISSING]));
  }
  
  /*
   * Determine if a resilvering vdev should remove any DTL entries from
   * its range. If the vdev was resilvering for the entire duration of the
   * scan then it should excise that range from its DTLs. Otherwise, this
   * vdev is considered partially resilvered and should leave its DTL
   * entries intact. The comment in vdev_dtl_reassess() describes how we
   * excise the DTLs.
   */
  static boolean_t
  vdev_dtl_should_excise(vdev_t *vd, boolean_t rebuild_done)
  {
          ASSERT0(vd->vdev_children);
  
          if (vd->vdev_state < VDEV_STATE_DEGRADED)
                  return (B_FALSE);
  
          if (vd->vdev_resilver_deferred)
                  return (B_FALSE);
  
          if (range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]))
                  return (B_TRUE);
  
          if (rebuild_done) {
                  vdev_rebuild_t *vr = &vd->vdev_top->vdev_rebuild_config;
                  vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
  
                  /* Rebuild not initiated by attach */
                  if (vd->vdev_rebuild_txg == 0)
                          return (B_TRUE);
  
                  /*
                   * When a rebuild completes without error then all missing data
                   * up to the rebuild max txg has been reconstructed and the DTL
                   * is eligible for excision.
                   */
                  if (vrp->vrp_rebuild_state == VDEV_REBUILD_COMPLETE &&
                      vdev_dtl_max(vd) <= vrp->vrp_max_txg) {
                          ASSERT3U(vrp->vrp_min_txg, <=, vdev_dtl_min(vd));
                          ASSERT3U(vrp->vrp_min_txg, <, vd->vdev_rebuild_txg);
                          ASSERT3U(vd->vdev_rebuild_txg, <=, vrp->vrp_max_txg);
                          return (B_TRUE);
                  }
          } else {
                  dsl_scan_t *scn = vd->vdev_spa->spa_dsl_pool->dp_scan;
                  dsl_scan_phys_t *scnp __maybe_unused = &scn->scn_phys;
  
                  /* Resilver not initiated by attach */
                  if (vd->vdev_resilver_txg == 0)
                          return (B_TRUE);
  
                  /*
                   * When a resilver is initiated the scan will assign the
                   * scn_max_txg value to the highest txg value that exists
                   * in all DTLs. If this device's max DTL is not part of this
                   * scan (i.e. it is not in the range (scn_min_txg, scn_max_txg]
                   * then it is not eligible for excision.
                   */
                  if (vdev_dtl_max(vd) <= scn->scn_phys.scn_max_txg) {
                          ASSERT3U(scnp->scn_min_txg, <=, vdev_dtl_min(vd));
                          ASSERT3U(scnp->scn_min_txg, <, vd->vdev_resilver_txg);
                          ASSERT3U(vd->vdev_resilver_txg, <=, scnp->scn_max_txg);
                          return (B_TRUE);
                  }
          }
  
          return (B_FALSE);
  }
  
  /*
   * Reassess DTLs after a config change or scrub completion. If txg == 0 no
   * write operations will be issued to the pool.
   */
  void
  vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg,
      boolean_t scrub_done, boolean_t rebuild_done)
  {
          spa_t *spa = vd->vdev_spa;
          avl_tree_t reftree;
          int minref;
  
          ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_dtl_reassess(vd->vdev_child[c], txg,
                      scrub_txg, scrub_done, rebuild_done);
  
          if (vd == spa->spa_root_vdev || !vdev_is_concrete(vd) || vd->vdev_aux)
                  return;
  
          if (vd->vdev_ops->vdev_op_leaf) {
                  dsl_scan_t *scn = spa->spa_dsl_pool->dp_scan;
                  vdev_rebuild_t *vr = &vd->vdev_top->vdev_rebuild_config;
                  boolean_t check_excise = B_FALSE;
                  boolean_t wasempty = B_TRUE;
  
                  mutex_enter(&vd->vdev_dtl_lock);
  
                  /*
                   * If requested, pretend the scan or rebuild completed cleanly.
                   */
                  if (zfs_scan_ignore_errors) {
                          if (scn != NULL)
                                  scn->scn_phys.scn_errors = 0;
                          if (vr != NULL)
                                  vr->vr_rebuild_phys.vrp_errors = 0;
                  }
  
                  if (scrub_txg != 0 &&
                      !range_tree_is_empty(vd->vdev_dtl[DTL_MISSING])) {
                          wasempty = B_FALSE;
                          zfs_dbgmsg("guid:%llu txg:%llu scrub:%llu started:%d "
                              "dtl:%llu/%llu errors:%llu",
                              (u_longlong_t)vd->vdev_guid, (u_longlong_t)txg,
                              (u_longlong_t)scrub_txg, spa->spa_scrub_started,
                              (u_longlong_t)vdev_dtl_min(vd),
                              (u_longlong_t)vdev_dtl_max(vd),
                              (u_longlong_t)(scn ? scn->scn_phys.scn_errors : 0));
                  }
  
                  /*
                   * If we've completed a scrub/resilver or a rebuild cleanly
                   * then determine if this vdev should remove any DTLs. We
                   * only want to excise regions on vdevs that were available
                   * during the entire duration of this scan.
                   */
                  if (rebuild_done &&
                      vr != NULL && vr->vr_rebuild_phys.vrp_errors == 0) {
                          check_excise = B_TRUE;
                  } else {
                          if (spa->spa_scrub_started ||
                              (scn != NULL && scn->scn_phys.scn_errors == 0)) {
                                  check_excise = B_TRUE;
                          }
                  }
  
                  if (scrub_txg && check_excise &&
                      vdev_dtl_should_excise(vd, rebuild_done)) {
                          /*
                           * We completed a scrub, resilver or rebuild up to
                           * scrub_txg.  If we did it without rebooting, then
                           * the scrub dtl will be valid, so excise the old
                           * region and fold in the scrub dtl.  Otherwise,
                           * leave the dtl as-is if there was an error.
                           *
                           * There's little trick here: to excise the beginning
                           * of the DTL_MISSING map, we put it into a reference
                           * tree and then add a segment with refcnt -1 that
                           * covers the range [0, scrub_txg).  This means
                           * that each txg in that range has refcnt -1 or 0.
                           * We then add DTL_SCRUB with a refcnt of 2, so that
                           * entries in the range [0, scrub_txg) will have a
                           * positive refcnt -- either 1 or 2.  We then convert
                           * the reference tree into the new DTL_MISSING map.
                           */
                          space_reftree_create(&reftree);
                          space_reftree_add_map(&reftree,
                              vd->vdev_dtl[DTL_MISSING], 1);
                          space_reftree_add_seg(&reftree, 0, scrub_txg, -1);
                          space_reftree_add_map(&reftree,
                              vd->vdev_dtl[DTL_SCRUB], 2);
                          space_reftree_generate_map(&reftree,
                              vd->vdev_dtl[DTL_MISSING], 1);
                          space_reftree_destroy(&reftree);
  
                          if (!range_tree_is_empty(vd->vdev_dtl[DTL_MISSING])) {
                                  zfs_dbgmsg("update DTL_MISSING:%llu/%llu",
                                      (u_longlong_t)vdev_dtl_min(vd),
                                      (u_longlong_t)vdev_dtl_max(vd));
                          } else if (!wasempty) {
                                  zfs_dbgmsg("DTL_MISSING is now empty");
                          }
                  }
                  range_tree_vacate(vd->vdev_dtl[DTL_PARTIAL], NULL, NULL);
                  range_tree_walk(vd->vdev_dtl[DTL_MISSING],
                      range_tree_add, vd->vdev_dtl[DTL_PARTIAL]);
                  if (scrub_done)
                          range_tree_vacate(vd->vdev_dtl[DTL_SCRUB], NULL, NULL);
                  range_tree_vacate(vd->vdev_dtl[DTL_OUTAGE], NULL, NULL);
                  if (!vdev_readable(vd))
                          range_tree_add(vd->vdev_dtl[DTL_OUTAGE], 0, -1ULL);
                  else
                          range_tree_walk(vd->vdev_dtl[DTL_MISSING],
                              range_tree_add, vd->vdev_dtl[DTL_OUTAGE]);
  
                  /*
                   * If the vdev was resilvering or rebuilding and no longer
                   * has any DTLs then reset the appropriate flag and dirty
                   * the top level so that we persist the change.
                   */
                  if (txg != 0 &&
                      range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]) &&
                      range_tree_is_empty(vd->vdev_dtl[DTL_OUTAGE])) {
                          if (vd->vdev_rebuild_txg != 0) {
                                  vd->vdev_rebuild_txg = 0;
                                  vdev_config_dirty(vd->vdev_top);
                          } else if (vd->vdev_resilver_txg != 0) {
                                  vd->vdev_resilver_txg = 0;
                                  vdev_config_dirty(vd->vdev_top);
                          }
                  }
  
                  mutex_exit(&vd->vdev_dtl_lock);
  
                  if (txg != 0)
                          vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
                  return;
          }
  
          mutex_enter(&vd->vdev_dtl_lock);
          for (int t = 0; t < DTL_TYPES; t++) {
                  /* account for child's outage in parent's missing map */
                  int s = (t == DTL_MISSING) ? DTL_OUTAGE: t;
                  if (t == DTL_SCRUB)
                          continue;                       /* leaf vdevs only */
                  if (t == DTL_PARTIAL)
                          minref = 1;                     /* i.e. non-zero */
                  else if (vdev_get_nparity(vd) != 0)
                          minref = vdev_get_nparity(vd) + 1; /* RAID-Z, dRAID */
                  else
                          minref = vd->vdev_children;     /* any kind of mirror */
                  space_reftree_create(&reftree);
                  for (int c = 0; c < vd->vdev_children; c++) {
                          vdev_t *cvd = vd->vdev_child[c];
                          mutex_enter(&cvd->vdev_dtl_lock);
                          space_reftree_add_map(&reftree, cvd->vdev_dtl[s], 1);
                          mutex_exit(&cvd->vdev_dtl_lock);
                  }
                  space_reftree_generate_map(&reftree, vd->vdev_dtl[t], minref);
                  space_reftree_destroy(&reftree);
          }
          mutex_exit(&vd->vdev_dtl_lock);
  }
  
  /*
   * Iterate over all the vdevs except spare, and post kobj events
   */
  void
  vdev_post_kobj_evt(vdev_t *vd)
  {
          if (vd->vdev_ops->vdev_op_kobj_evt_post &&
              vd->vdev_kobj_flag == B_FALSE) {
                  vd->vdev_kobj_flag = B_TRUE;
                  vd->vdev_ops->vdev_op_kobj_evt_post(vd);
          }
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_post_kobj_evt(vd->vdev_child[c]);
  }
  
  /*
   * Iterate over all the vdevs except spare, and clear kobj events
   */
  void
  vdev_clear_kobj_evt(vdev_t *vd)
  {
          vd->vdev_kobj_flag = B_FALSE;
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_clear_kobj_evt(vd->vdev_child[c]);
  }
  
  int
  vdev_dtl_load(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          objset_t *mos = spa->spa_meta_objset;
          range_tree_t *rt;
          int error = 0;
  
          if (vd->vdev_ops->vdev_op_leaf && vd->vdev_dtl_object != 0) {
                  ASSERT(vdev_is_concrete(vd));
  
                  /*
                   * If the dtl cannot be sync'd there is no need to open it.
                   */
                  if (spa->spa_mode == SPA_MODE_READ && !spa->spa_read_spacemaps)
                          return (0);
  
                  error = space_map_open(&vd->vdev_dtl_sm, mos,
                      vd->vdev_dtl_object, 0, -1ULL, 0);
                  if (error)
                          return (error);
                  ASSERT(vd->vdev_dtl_sm != NULL);
  
                  rt = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
                  error = space_map_load(vd->vdev_dtl_sm, rt, SM_ALLOC);
                  if (error == 0) {
                          mutex_enter(&vd->vdev_dtl_lock);
                          range_tree_walk(rt, range_tree_add,
                              vd->vdev_dtl[DTL_MISSING]);
                          mutex_exit(&vd->vdev_dtl_lock);
                  }
  
                  range_tree_vacate(rt, NULL, NULL);
                  range_tree_destroy(rt);
  
                  return (error);
          }
  
          for (int c = 0; c < vd->vdev_children; c++) {
                  error = vdev_dtl_load(vd->vdev_child[c]);
                  if (error != 0)
                          break;
          }
  
          return (error);
  }
  
  static void
  vdev_zap_allocation_data(vdev_t *vd, dmu_tx_t *tx)
  {
          spa_t *spa = vd->vdev_spa;
          objset_t *mos = spa->spa_meta_objset;
          vdev_alloc_bias_t alloc_bias = vd->vdev_alloc_bias;
          const char *string;
  
          ASSERT(alloc_bias != VDEV_BIAS_NONE);
  
          string =
              (alloc_bias == VDEV_BIAS_LOG) ? VDEV_ALLOC_BIAS_LOG :
              (alloc_bias == VDEV_BIAS_SPECIAL) ? VDEV_ALLOC_BIAS_SPECIAL :
              (alloc_bias == VDEV_BIAS_DEDUP) ? VDEV_ALLOC_BIAS_DEDUP : NULL;
  
          ASSERT(string != NULL);
          VERIFY0(zap_add(mos, vd->vdev_top_zap, VDEV_TOP_ZAP_ALLOCATION_BIAS,
              1, strlen(string) + 1, string, tx));
  
          if (alloc_bias == VDEV_BIAS_SPECIAL || alloc_bias == VDEV_BIAS_DEDUP) {
                  spa_activate_allocation_classes(spa, tx);
          }
  }
  
  void
  vdev_destroy_unlink_zap(vdev_t *vd, uint64_t zapobj, dmu_tx_t *tx)
  {
          spa_t *spa = vd->vdev_spa;
  
          VERIFY0(zap_destroy(spa->spa_meta_objset, zapobj, tx));
          VERIFY0(zap_remove_int(spa->spa_meta_objset, spa->spa_all_vdev_zaps,
              zapobj, tx));
  }
  
  uint64_t
  vdev_create_link_zap(vdev_t *vd, dmu_tx_t *tx)
  {
          spa_t *spa = vd->vdev_spa;
          uint64_t zap = zap_create(spa->spa_meta_objset, DMU_OTN_ZAP_METADATA,
              DMU_OT_NONE, 0, tx);
  
          ASSERT(zap != 0);
          VERIFY0(zap_add_int(spa->spa_meta_objset, spa->spa_all_vdev_zaps,
              zap, tx));
  
          return (zap);
  }
  
  void
  vdev_construct_zaps(vdev_t *vd, dmu_tx_t *tx)
  {
          if (vd->vdev_ops != &vdev_hole_ops &&
              vd->vdev_ops != &vdev_missing_ops &&
              vd->vdev_ops != &vdev_root_ops &&
              !vd->vdev_top->vdev_removing) {
                  if (vd->vdev_ops->vdev_op_leaf && vd->vdev_leaf_zap == 0) {
                          vd->vdev_leaf_zap = vdev_create_link_zap(vd, tx);
                  }
                  if (vd == vd->vdev_top && vd->vdev_top_zap == 0) {
                          vd->vdev_top_zap = vdev_create_link_zap(vd, tx);
                          if (vd->vdev_alloc_bias != VDEV_BIAS_NONE)
                                  vdev_zap_allocation_data(vd, tx);
                  }
          }
  
          for (uint64_t i = 0; i < vd->vdev_children; i++) {
                  vdev_construct_zaps(vd->vdev_child[i], tx);
          }
  }
  
  static void
  vdev_dtl_sync(vdev_t *vd, uint64_t txg)
  {
          spa_t *spa = vd->vdev_spa;
          range_tree_t *rt = vd->vdev_dtl[DTL_MISSING];
          objset_t *mos = spa->spa_meta_objset;
          range_tree_t *rtsync;
          dmu_tx_t *tx;
          uint64_t object = space_map_object(vd->vdev_dtl_sm);
  
          ASSERT(vdev_is_concrete(vd));
          ASSERT(vd->vdev_ops->vdev_op_leaf);
  
          tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
  
          if (vd->vdev_detached || vd->vdev_top->vdev_removing) {
                  mutex_enter(&vd->vdev_dtl_lock);
                  space_map_free(vd->vdev_dtl_sm, tx);
                  space_map_close(vd->vdev_dtl_sm);
                  vd->vdev_dtl_sm = NULL;
                  mutex_exit(&vd->vdev_dtl_lock);
  
                  /*
                   * We only destroy the leaf ZAP for detached leaves or for
                   * removed log devices. Removed data devices handle leaf ZAP
                   * cleanup later, once cancellation is no longer possible.
                   */
                  if (vd->vdev_leaf_zap != 0 && (vd->vdev_detached ||
                      vd->vdev_top->vdev_islog)) {
                          vdev_destroy_unlink_zap(vd, vd->vdev_leaf_zap, tx);
                          vd->vdev_leaf_zap = 0;
                  }
  
                  dmu_tx_commit(tx);
                  return;
          }
  
          if (vd->vdev_dtl_sm == NULL) {
                  uint64_t new_object;
  
                  new_object = space_map_alloc(mos, zfs_vdev_dtl_sm_blksz, tx);
                  VERIFY3U(new_object, !=, 0);
  
                  VERIFY0(space_map_open(&vd->vdev_dtl_sm, mos, new_object,
                      0, -1ULL, 0));
                  ASSERT(vd->vdev_dtl_sm != NULL);
          }
  
          rtsync = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
  
          mutex_enter(&vd->vdev_dtl_lock);
          range_tree_walk(rt, range_tree_add, rtsync);
          mutex_exit(&vd->vdev_dtl_lock);
  
          space_map_truncate(vd->vdev_dtl_sm, zfs_vdev_dtl_sm_blksz, tx);
          space_map_write(vd->vdev_dtl_sm, rtsync, SM_ALLOC, SM_NO_VDEVID, tx);
          range_tree_vacate(rtsync, NULL, NULL);
  
          range_tree_destroy(rtsync);
  
          /*
           * If the object for the space map has changed then dirty
           * the top level so that we update the config.
           */
          if (object != space_map_object(vd->vdev_dtl_sm)) {
                  vdev_dbgmsg(vd, "txg %llu, spa %s, DTL old object %llu, "
                      "new object %llu", (u_longlong_t)txg, spa_name(spa),
                      (u_longlong_t)object,
                      (u_longlong_t)space_map_object(vd->vdev_dtl_sm));
                  vdev_config_dirty(vd->vdev_top);
          }
  
          dmu_tx_commit(tx);
  }
  
  /*
   * Determine whether the specified vdev can be offlined/detached/removed
   * without losing data.
   */
  boolean_t
  vdev_dtl_required(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          vdev_t *tvd = vd->vdev_top;
          uint8_t cant_read = vd->vdev_cant_read;
          boolean_t required;
  
          ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
  
          if (vd == spa->spa_root_vdev || vd == tvd)
                  return (B_TRUE);
  
          /*
           * Temporarily mark the device as unreadable, and then determine
           * whether this results in any DTL outages in the top-level vdev.
           * If not, we can safely offline/detach/remove the device.
           */
          vd->vdev_cant_read = B_TRUE;
          vdev_dtl_reassess(tvd, 0, 0, B_FALSE, B_FALSE);
          required = !vdev_dtl_empty(tvd, DTL_OUTAGE);
          vd->vdev_cant_read = cant_read;
          vdev_dtl_reassess(tvd, 0, 0, B_FALSE, B_FALSE);
  
          if (!required && zio_injection_enabled) {
                  required = !!zio_handle_device_injection(vd, NULL,
                      SET_ERROR(ECHILD));
          }
  
          return (required);
  }
  
  /*
   * Determine if resilver is needed, and if so the txg range.
   */
  boolean_t
  vdev_resilver_needed(vdev_t *vd, uint64_t *minp, uint64_t *maxp)
  {
          boolean_t needed = B_FALSE;
          uint64_t thismin = UINT64_MAX;
          uint64_t thismax = 0;
  
          if (vd->vdev_children == 0) {
                  mutex_enter(&vd->vdev_dtl_lock);
                  if (!range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]) &&
                      vdev_writeable(vd)) {
  
                          thismin = vdev_dtl_min(vd);
                          thismax = vdev_dtl_max(vd);
                          needed = B_TRUE;
                  }
                  mutex_exit(&vd->vdev_dtl_lock);
          } else {
                  for (int c = 0; c < vd->vdev_children; c++) {
                          vdev_t *cvd = vd->vdev_child[c];
                          uint64_t cmin, cmax;
  
                          if (vdev_resilver_needed(cvd, &cmin, &cmax)) {
                                  thismin = MIN(thismin, cmin);
                                  thismax = MAX(thismax, cmax);
                                  needed = B_TRUE;
                          }
                  }
          }
  
          if (needed && minp) {
                  *minp = thismin;
                  *maxp = thismax;
          }
          return (needed);
  }
  
  /*
   * Gets the checkpoint space map object from the vdev's ZAP.  On success sm_obj
   * will contain either the checkpoint spacemap object or zero if none exists.
   * All other errors are returned to the caller.
   */
  int
  vdev_checkpoint_sm_object(vdev_t *vd, uint64_t *sm_obj)
  {
          ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
  
          if (vd->vdev_top_zap == 0) {
                  *sm_obj = 0;
                  return (0);
          }
  
          int error = zap_lookup(spa_meta_objset(vd->vdev_spa), vd->vdev_top_zap,
              VDEV_TOP_ZAP_POOL_CHECKPOINT_SM, sizeof (uint64_t), 1, sm_obj);
          if (error == ENOENT) {
                  *sm_obj = 0;
                  error = 0;
          }
  
          return (error);
  }
  
  int
  vdev_load(vdev_t *vd)
  {
          int children = vd->vdev_children;
          int error = 0;
          taskq_t *tq = NULL;
  
          /*
           * It's only worthwhile to use the taskq for the root vdev, because the
           * slow part is metaslab_init, and that only happens for top-level
           * vdevs.
           */
          if (vd->vdev_ops == &vdev_root_ops && vd->vdev_children > 0) {
                  tq = taskq_create("vdev_load", children, minclsyspri,
                      children, children, TASKQ_PREPOPULATE);
          }
  
          /*
           * Recursively load all children.
           */
          for (int c = 0; c < vd->vdev_children; c++) {
                  vdev_t *cvd = vd->vdev_child[c];
  
                  if (tq == NULL || vdev_uses_zvols(cvd)) {
                          cvd->vdev_load_error = vdev_load(cvd);
                  } else {
                          VERIFY(taskq_dispatch(tq, vdev_load_child,
                              cvd, TQ_SLEEP) != TASKQID_INVALID);
                  }
          }
  
          if (tq != NULL) {
                  taskq_wait(tq);
                  taskq_destroy(tq);
          }
  
          for (int c = 0; c < vd->vdev_children; c++) {
                  int error = vd->vdev_child[c]->vdev_load_error;
  
                  if (error != 0)
                          return (error);
          }
  
          vdev_set_deflate_ratio(vd);
  
          /*
           * On spa_load path, grab the allocation bias from our zap
           */
          if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
                  spa_t *spa = vd->vdev_spa;
                  char bias_str[64];
  
                  error = zap_lookup(spa->spa_meta_objset, vd->vdev_top_zap,
                      VDEV_TOP_ZAP_ALLOCATION_BIAS, 1, sizeof (bias_str),
                      bias_str);
                  if (error == 0) {
                          ASSERT(vd->vdev_alloc_bias == VDEV_BIAS_NONE);
                          vd->vdev_alloc_bias = vdev_derive_alloc_bias(bias_str);
                  } else if (error != ENOENT) {
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          vdev_dbgmsg(vd, "vdev_load: zap_lookup(top_zap=%llu) "
                              "failed [error=%d]",
                              (u_longlong_t)vd->vdev_top_zap, error);
                          return (error);
                  }
          }
  
          if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
                  spa_t *spa = vd->vdev_spa;
                  uint64_t failfast;
  
                  error = zap_lookup(spa->spa_meta_objset, vd->vdev_top_zap,
                      vdev_prop_to_name(VDEV_PROP_FAILFAST), sizeof (failfast),
                      1, &failfast);
                  if (error == 0) {
                          vd->vdev_failfast = failfast & 1;
                  } else if (error == ENOENT) {
                          vd->vdev_failfast = vdev_prop_default_numeric(
                              VDEV_PROP_FAILFAST);
                  } else {
                          vdev_dbgmsg(vd,
                              "vdev_load: zap_lookup(top_zap=%llu) "
                              "failed [error=%d]",
                              (u_longlong_t)vd->vdev_top_zap, error);
                  }
          }
  
          /*
           * Load any rebuild state from the top-level vdev zap.
           */
          if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
                  error = vdev_rebuild_load(vd);
                  if (error && error != ENOTSUP) {
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          vdev_dbgmsg(vd, "vdev_load: vdev_rebuild_load "
                              "failed [error=%d]", error);
                          return (error);
                  }
          }
  
          if (vd->vdev_top_zap != 0 || vd->vdev_leaf_zap != 0) {
                  uint64_t zapobj;
  
                  if (vd->vdev_top_zap != 0)
                          zapobj = vd->vdev_top_zap;
                  else
                          zapobj = vd->vdev_leaf_zap;
  
                  error = vdev_prop_get_int(vd, VDEV_PROP_CHECKSUM_N,
                      &vd->vdev_checksum_n);
                  if (error && error != ENOENT)
                          vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
                              "failed [error=%d]", (u_longlong_t)zapobj, error);
  
                  error = vdev_prop_get_int(vd, VDEV_PROP_CHECKSUM_T,
                      &vd->vdev_checksum_t);
                  if (error && error != ENOENT)
                          vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
                              "failed [error=%d]", (u_longlong_t)zapobj, error);
  
                  error = vdev_prop_get_int(vd, VDEV_PROP_IO_N,
                      &vd->vdev_io_n);
                  if (error && error != ENOENT)
                          vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
                              "failed [error=%d]", (u_longlong_t)zapobj, error);
  
                  error = vdev_prop_get_int(vd, VDEV_PROP_IO_T,
                      &vd->vdev_io_t);
                  if (error && error != ENOENT)
                          vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
                              "failed [error=%d]", (u_longlong_t)zapobj, error);
          }
  
          /*
           * If this is a top-level vdev, initialize its metaslabs.
           */
          if (vd == vd->vdev_top && vdev_is_concrete(vd)) {
                  vdev_metaslab_group_create(vd);
  
                  if (vd->vdev_ashift == 0 || vd->vdev_asize == 0) {
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          vdev_dbgmsg(vd, "vdev_load: invalid size. ashift=%llu, "
                              "asize=%llu", (u_longlong_t)vd->vdev_ashift,
                              (u_longlong_t)vd->vdev_asize);
                          return (SET_ERROR(ENXIO));
                  }
  
                  error = vdev_metaslab_init(vd, 0);
                  if (error != 0) {
                          vdev_dbgmsg(vd, "vdev_load: metaslab_init failed "
                              "[error=%d]", error);
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          return (error);
                  }
  
                  uint64_t checkpoint_sm_obj;
                  error = vdev_checkpoint_sm_object(vd, &checkpoint_sm_obj);
                  if (error == 0 && checkpoint_sm_obj != 0) {
                          objset_t *mos = spa_meta_objset(vd->vdev_spa);
                          ASSERT(vd->vdev_asize != 0);
                          ASSERT3P(vd->vdev_checkpoint_sm, ==, NULL);
  
                          error = space_map_open(&vd->vdev_checkpoint_sm,
                              mos, checkpoint_sm_obj, 0, vd->vdev_asize,
                              vd->vdev_ashift);
                          if (error != 0) {
                                  vdev_dbgmsg(vd, "vdev_load: space_map_open "
                                      "failed for checkpoint spacemap (obj %llu) "
                                      "[error=%d]",
                                      (u_longlong_t)checkpoint_sm_obj, error);
                                  return (error);
                          }
                          ASSERT3P(vd->vdev_checkpoint_sm, !=, NULL);
  
                          /*
                           * Since the checkpoint_sm contains free entries
                           * exclusively we can use space_map_allocated() to
                           * indicate the cumulative checkpointed space that
                           * has been freed.
                           */
                          vd->vdev_stat.vs_checkpoint_space =
                              -space_map_allocated(vd->vdev_checkpoint_sm);
                          vd->vdev_spa->spa_checkpoint_info.sci_dspace +=
                              vd->vdev_stat.vs_checkpoint_space;
                  } else if (error != 0) {
                          vdev_dbgmsg(vd, "vdev_load: failed to retrieve "
                              "checkpoint space map object from vdev ZAP "
                              "[error=%d]", error);
                          return (error);
                  }
          }
  
          /*
           * If this is a leaf vdev, load its DTL.
           */
          if (vd->vdev_ops->vdev_op_leaf && (error = vdev_dtl_load(vd)) != 0) {
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  vdev_dbgmsg(vd, "vdev_load: vdev_dtl_load failed "
                      "[error=%d]", error);
                  return (error);
          }
  
          uint64_t obsolete_sm_object;
          error = vdev_obsolete_sm_object(vd, &obsolete_sm_object);
          if (error == 0 && obsolete_sm_object != 0) {
                  objset_t *mos = vd->vdev_spa->spa_meta_objset;
                  ASSERT(vd->vdev_asize != 0);
                  ASSERT3P(vd->vdev_obsolete_sm, ==, NULL);
  
                  if ((error = space_map_open(&vd->vdev_obsolete_sm, mos,
                      obsolete_sm_object, 0, vd->vdev_asize, 0))) {
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
                          vdev_dbgmsg(vd, "vdev_load: space_map_open failed for "
                              "obsolete spacemap (obj %llu) [error=%d]",
                              (u_longlong_t)obsolete_sm_object, error);
                          return (error);
                  }
          } else if (error != 0) {
                  vdev_dbgmsg(vd, "vdev_load: failed to retrieve obsolete "
                      "space map object from vdev ZAP [error=%d]", error);
                  return (error);
          }
  
          return (0);
  }
  
  /*
   * The special vdev case is used for hot spares and l2cache devices.  Its
   * sole purpose it to set the vdev state for the associated vdev.  To do this,
   * we make sure that we can open the underlying device, then try to read the
   * label, and make sure that the label is sane and that it hasn't been
   * repurposed to another pool.
   */
  int
  vdev_validate_aux(vdev_t *vd)
  {
          nvlist_t *label;
          uint64_t guid, version;
          uint64_t state;
  
          if (!vdev_readable(vd))
                  return (0);
  
          if ((label = vdev_label_read_config(vd, -1ULL)) == NULL) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  return (-1);
          }
  
          if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_VERSION, &version) != 0 ||
              !SPA_VERSION_IS_SUPPORTED(version) ||
              nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid) != 0 ||
              guid != vd->vdev_guid ||
              nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE, &state) != 0) {
                  vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  nvlist_free(label);
                  return (-1);
          }
  
          /*
           * We don't actually check the pool state here.  If it's in fact in
           * use by another pool, we update this fact on the fly when requested.
           */
          nvlist_free(label);
          return (0);
  }
  
  static void
  vdev_destroy_ms_flush_data(vdev_t *vd, dmu_tx_t *tx)
  {
          objset_t *mos = spa_meta_objset(vd->vdev_spa);
  
          if (vd->vdev_top_zap == 0)
                  return;
  
          uint64_t object = 0;
          int err = zap_lookup(mos, vd->vdev_top_zap,
              VDEV_TOP_ZAP_MS_UNFLUSHED_PHYS_TXGS, sizeof (uint64_t), 1, &object);
          if (err == ENOENT)
                  return;
          VERIFY0(err);
  
          VERIFY0(dmu_object_free(mos, object, tx));
          VERIFY0(zap_remove(mos, vd->vdev_top_zap,
              VDEV_TOP_ZAP_MS_UNFLUSHED_PHYS_TXGS, tx));
  }
  
  /*
   * Free the objects used to store this vdev's spacemaps, and the array
   * that points to them.
   */
  void
  vdev_destroy_spacemaps(vdev_t *vd, dmu_tx_t *tx)
  {
          if (vd->vdev_ms_array == 0)
                  return;
  
          objset_t *mos = vd->vdev_spa->spa_meta_objset;
          uint64_t array_count = vd->vdev_asize >> vd->vdev_ms_shift;
          size_t array_bytes = array_count * sizeof (uint64_t);
          uint64_t *smobj_array = kmem_alloc(array_bytes, KM_SLEEP);
          VERIFY0(dmu_read(mos, vd->vdev_ms_array, 0,
              array_bytes, smobj_array, 0));
  
          for (uint64_t i = 0; i < array_count; i++) {
                  uint64_t smobj = smobj_array[i];
                  if (smobj == 0)
                          continue;
  
                  space_map_free_obj(mos, smobj, tx);
          }
  
          kmem_free(smobj_array, array_bytes);
          VERIFY0(dmu_object_free(mos, vd->vdev_ms_array, tx));
          vdev_destroy_ms_flush_data(vd, tx);
          vd->vdev_ms_array = 0;
  }
  
  static void
  vdev_remove_empty_log(vdev_t *vd, uint64_t txg)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(vd->vdev_islog);
          ASSERT(vd == vd->vdev_top);
          ASSERT3U(txg, ==, spa_syncing_txg(spa));
  
          dmu_tx_t *tx = dmu_tx_create_assigned(spa_get_dsl(spa), txg);
  
          vdev_destroy_spacemaps(vd, tx);
          if (vd->vdev_top_zap != 0) {
                  vdev_destroy_unlink_zap(vd, vd->vdev_top_zap, tx);
                  vd->vdev_top_zap = 0;
          }
  
          dmu_tx_commit(tx);
  }
  
  void
  vdev_sync_done(vdev_t *vd, uint64_t txg)
  {
          metaslab_t *msp;
          boolean_t reassess = !txg_list_empty(&vd->vdev_ms_list, TXG_CLEAN(txg));
  
          ASSERT(vdev_is_concrete(vd));
  
          while ((msp = txg_list_remove(&vd->vdev_ms_list, TXG_CLEAN(txg)))
              != NULL)
                  metaslab_sync_done(msp, txg);
  
          if (reassess) {
                  metaslab_sync_reassess(vd->vdev_mg);
                  if (vd->vdev_log_mg != NULL)
                          metaslab_sync_reassess(vd->vdev_log_mg);
          }
  }
  
  void
  vdev_sync(vdev_t *vd, uint64_t txg)
  {
          spa_t *spa = vd->vdev_spa;
          vdev_t *lvd;
          metaslab_t *msp;
  
          ASSERT3U(txg, ==, spa->spa_syncing_txg);
          dmu_tx_t *tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
          if (range_tree_space(vd->vdev_obsolete_segments) > 0) {
                  ASSERT(vd->vdev_removing ||
                      vd->vdev_ops == &vdev_indirect_ops);
  
                  vdev_indirect_sync_obsolete(vd, tx);
  
                  /*
                   * If the vdev is indirect, it can't have dirty
                   * metaslabs or DTLs.
                   */
                  if (vd->vdev_ops == &vdev_indirect_ops) {
                          ASSERT(txg_list_empty(&vd->vdev_ms_list, txg));
                          ASSERT(txg_list_empty(&vd->vdev_dtl_list, txg));
                          dmu_tx_commit(tx);
                          return;
                  }
          }
  
          ASSERT(vdev_is_concrete(vd));
  
          if (vd->vdev_ms_array == 0 && vd->vdev_ms_shift != 0 &&
              !vd->vdev_removing) {
                  ASSERT(vd == vd->vdev_top);
                  ASSERT0(vd->vdev_indirect_config.vic_mapping_object);
                  vd->vdev_ms_array = dmu_object_alloc(spa->spa_meta_objset,
                      DMU_OT_OBJECT_ARRAY, 0, DMU_OT_NONE, 0, tx);
                  ASSERT(vd->vdev_ms_array != 0);
                  vdev_config_dirty(vd);
          }
  
          while ((msp = txg_list_remove(&vd->vdev_ms_list, txg)) != NULL) {
                  metaslab_sync(msp, txg);
                  (void) txg_list_add(&vd->vdev_ms_list, msp, TXG_CLEAN(txg));
          }
  
          while ((lvd = txg_list_remove(&vd->vdev_dtl_list, txg)) != NULL)
                  vdev_dtl_sync(lvd, txg);
  
          /*
           * If this is an empty log device being removed, destroy the
           * metadata associated with it.
           */
          if (vd->vdev_islog && vd->vdev_stat.vs_alloc == 0 && vd->vdev_removing)
                  vdev_remove_empty_log(vd, txg);
  
          (void) txg_list_add(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg));
          dmu_tx_commit(tx);
  }
  
  uint64_t
  vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
  {
          return (vd->vdev_ops->vdev_op_asize(vd, psize));
  }
  
  /*
   * Mark the given vdev faulted.  A faulted vdev behaves as if the device could
   * not be opened, and no I/O is attempted.
   */
  int
  vdev_fault(spa_t *spa, uint64_t guid, vdev_aux_t aux)
  {
          vdev_t *vd, *tvd;
  
          spa_vdev_state_enter(spa, SCL_NONE);
  
          if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
  
          if (!vd->vdev_ops->vdev_op_leaf)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
  
          tvd = vd->vdev_top;
  
          /*
           * If user did a 'zpool offline -f' then make the fault persist across
           * reboots.
           */
          if (aux == VDEV_AUX_EXTERNAL_PERSIST) {
                  /*
                   * There are two kinds of forced faults: temporary and
                   * persistent.  Temporary faults go away at pool import, while
                   * persistent faults stay set.  Both types of faults can be
                   * cleared with a zpool clear.
                   *
                   * We tell if a vdev is persistently faulted by looking at the
                   * ZPOOL_CONFIG_AUX_STATE nvpair.  If it's set to "external" at
                   * import then it's a persistent fault.  Otherwise, it's
                   * temporary.  We get ZPOOL_CONFIG_AUX_STATE set to "external"
                   * by setting vd.vdev_stat.vs_aux to VDEV_AUX_EXTERNAL.  This
                   * tells vdev_config_generate() (which gets run later) to set
                   * ZPOOL_CONFIG_AUX_STATE to "external" in the nvlist.
                   */
                  vd->vdev_stat.vs_aux = VDEV_AUX_EXTERNAL;
                  vd->vdev_tmpoffline = B_FALSE;
                  aux = VDEV_AUX_EXTERNAL;
          } else {
                  vd->vdev_tmpoffline = B_TRUE;
          }
  
          /*
           * We don't directly use the aux state here, but if we do a
           * vdev_reopen(), we need this value to be present to remember why we
           * were faulted.
           */
          vd->vdev_label_aux = aux;
  
          /*
           * Faulted state takes precedence over degraded.
           */
          vd->vdev_delayed_close = B_FALSE;
          vd->vdev_faulted = 1ULL;
          vd->vdev_degraded = 0ULL;
          vdev_set_state(vd, B_FALSE, VDEV_STATE_FAULTED, aux);
  
          /*
           * If this device has the only valid copy of the data, then
           * back off and simply mark the vdev as degraded instead.
           */
          if (!tvd->vdev_islog && vd->vdev_aux == NULL && vdev_dtl_required(vd)) {
                  vd->vdev_degraded = 1ULL;
                  vd->vdev_faulted = 0ULL;
  
                  /*
                   * If we reopen the device and it's not dead, only then do we
                   * mark it degraded.
                   */
                  vdev_reopen(tvd);
  
                  if (vdev_readable(vd))
                          vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, aux);
          }
  
          return (spa_vdev_state_exit(spa, vd, 0));
  }
  
  /*
   * Mark the given vdev degraded.  A degraded vdev is purely an indication to the
   * user that something is wrong.  The vdev continues to operate as normal as far
   * as I/O is concerned.
   */
  int
  vdev_degrade(spa_t *spa, uint64_t guid, vdev_aux_t aux)
  {
          vdev_t *vd;
  
          spa_vdev_state_enter(spa, SCL_NONE);
  
          if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
  
          if (!vd->vdev_ops->vdev_op_leaf)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
  
          /*
           * If the vdev is already faulted, then don't do anything.
           */
          if (vd->vdev_faulted || vd->vdev_degraded)
                  return (spa_vdev_state_exit(spa, NULL, 0));
  
          vd->vdev_degraded = 1ULL;
          if (!vdev_is_dead(vd))
                  vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED,
                      aux);
  
          return (spa_vdev_state_exit(spa, vd, 0));
  }
  
  int
  vdev_remove_wanted(spa_t *spa, uint64_t guid)
  {
          vdev_t *vd;
  
          spa_vdev_state_enter(spa, SCL_NONE);
  
          if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
  
          /*
           * If the vdev is already removed, then don't do anything.
           */
          if (vd->vdev_removed)
                  return (spa_vdev_state_exit(spa, NULL, 0));
  
          vd->vdev_remove_wanted = B_TRUE;
          spa_async_request(spa, SPA_ASYNC_REMOVE);
  
          return (spa_vdev_state_exit(spa, vd, 0));
  }
  
  
  /*
   * Online the given vdev.
   *
   * If 'ZFS_ONLINE_UNSPARE' is set, it implies two things.  First, any attached
   * spare device should be detached when the device finishes resilvering.
   * Second, the online should be treated like a 'test' online case, so no FMA
   * events are generated if the device fails to open.
   */
  int
  vdev_online(spa_t *spa, uint64_t guid, uint64_t flags, vdev_state_t *newstate)
  {
          vdev_t *vd, *tvd, *pvd, *rvd = spa->spa_root_vdev;
          boolean_t wasoffline;
          vdev_state_t oldstate;
  
          spa_vdev_state_enter(spa, SCL_NONE);
  
          if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
  
          if (!vd->vdev_ops->vdev_op_leaf)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
  
          wasoffline = (vd->vdev_offline || vd->vdev_tmpoffline);
          oldstate = vd->vdev_state;
  
          tvd = vd->vdev_top;
          vd->vdev_offline = B_FALSE;
          vd->vdev_tmpoffline = B_FALSE;
          vd->vdev_checkremove = !!(flags & ZFS_ONLINE_CHECKREMOVE);
          vd->vdev_forcefault = !!(flags & ZFS_ONLINE_FORCEFAULT);
  
          /* XXX - L2ARC 1.0 does not support expansion */
          if (!vd->vdev_aux) {
                  for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
                          pvd->vdev_expanding = !!((flags & ZFS_ONLINE_EXPAND) ||
                              spa->spa_autoexpand);
                  vd->vdev_expansion_time = gethrestime_sec();
          }
  
          vdev_reopen(tvd);
          vd->vdev_checkremove = vd->vdev_forcefault = B_FALSE;
  
          if (!vd->vdev_aux) {
                  for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
                          pvd->vdev_expanding = B_FALSE;
          }
  
          if (newstate)
                  *newstate = vd->vdev_state;
          if ((flags & ZFS_ONLINE_UNSPARE) &&
              !vdev_is_dead(vd) && vd->vdev_parent &&
              vd->vdev_parent->vdev_ops == &vdev_spare_ops &&
              vd->vdev_parent->vdev_child[0] == vd)
                  vd->vdev_unspare = B_TRUE;
  
          if ((flags & ZFS_ONLINE_EXPAND) || spa->spa_autoexpand) {
  
                  /* XXX - L2ARC 1.0 does not support expansion */
                  if (vd->vdev_aux)
                          return (spa_vdev_state_exit(spa, vd, ENOTSUP));
                  spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
          }
  
          /* Restart initializing if necessary */
          mutex_enter(&vd->vdev_initialize_lock);
          if (vdev_writeable(vd) &&
              vd->vdev_initialize_thread == NULL &&
              vd->vdev_initialize_state == VDEV_INITIALIZE_ACTIVE) {
                  (void) vdev_initialize(vd);
          }
          mutex_exit(&vd->vdev_initialize_lock);
  
          /*
           * Restart trimming if necessary. We do not restart trimming for cache
           * devices here. This is triggered by l2arc_rebuild_vdev()
           * asynchronously for the whole device or in l2arc_evict() as it evicts
           * space for upcoming writes.
           */
          mutex_enter(&vd->vdev_trim_lock);
          if (vdev_writeable(vd) && !vd->vdev_isl2cache &&
              vd->vdev_trim_thread == NULL &&
              vd->vdev_trim_state == VDEV_TRIM_ACTIVE) {
                  (void) vdev_trim(vd, vd->vdev_trim_rate, vd->vdev_trim_partial,
                      vd->vdev_trim_secure);
          }
          mutex_exit(&vd->vdev_trim_lock);
  
          if (wasoffline ||
              (oldstate < VDEV_STATE_DEGRADED &&
              vd->vdev_state >= VDEV_STATE_DEGRADED))
                  spa_event_notify(spa, vd, NULL, ESC_ZFS_VDEV_ONLINE);
  
          return (spa_vdev_state_exit(spa, vd, 0));
  }
  
  static int
  vdev_offline_locked(spa_t *spa, uint64_t guid, uint64_t flags)
  {
          vdev_t *vd, *tvd;
          int error = 0;
          uint64_t generation;
          metaslab_group_t *mg;
  
  top:
          spa_vdev_state_enter(spa, SCL_ALLOC);
  
          if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
  
          if (!vd->vdev_ops->vdev_op_leaf)
                  return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
  
          if (vd->vdev_ops == &vdev_draid_spare_ops)
                  return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
  
          tvd = vd->vdev_top;
          mg = tvd->vdev_mg;
          generation = spa->spa_config_generation + 1;
  
          /*
           * If the device isn't already offline, try to offline it.
           */
          if (!vd->vdev_offline) {
                  /*
                   * If this device has the only valid copy of some data,
                   * don't allow it to be offlined. Log devices are always
                   * expendable.
                   */
                  if (!tvd->vdev_islog && vd->vdev_aux == NULL &&
                      vdev_dtl_required(vd))
                          return (spa_vdev_state_exit(spa, NULL,
                              SET_ERROR(EBUSY)));
  
                  /*
                   * If the top-level is a slog and it has had allocations
                   * then proceed.  We check that the vdev's metaslab group
                   * is not NULL since it's possible that we may have just
                   * added this vdev but not yet initialized its metaslabs.
                   */
                  if (tvd->vdev_islog && mg != NULL) {
                          /*
                           * Prevent any future allocations.
                           */
                          ASSERT3P(tvd->vdev_log_mg, ==, NULL);
                          metaslab_group_passivate(mg);
                          (void) spa_vdev_state_exit(spa, vd, 0);
  
                          error = spa_reset_logs(spa);
  
                          /*
                           * If the log device was successfully reset but has
                           * checkpointed data, do not offline it.
                           */
                          if (error == 0 &&
                              tvd->vdev_checkpoint_sm != NULL) {
                                  ASSERT3U(space_map_allocated(
                                      tvd->vdev_checkpoint_sm), !=, 0);
                                  error = ZFS_ERR_CHECKPOINT_EXISTS;
                          }
  
                          spa_vdev_state_enter(spa, SCL_ALLOC);
  
                          /*
                           * Check to see if the config has changed.
                           */
                          if (error || generation != spa->spa_config_generation) {
                                  metaslab_group_activate(mg);
                                  if (error)
                                          return (spa_vdev_state_exit(spa,
                                              vd, error));
                                  (void) spa_vdev_state_exit(spa, vd, 0);
                                  goto top;
                          }
                          ASSERT0(tvd->vdev_stat.vs_alloc);
                  }
  
                  /*
                   * Offline this device and reopen its top-level vdev.
                   * If the top-level vdev is a log device then just offline
                   * it. Otherwise, if this action results in the top-level
                   * vdev becoming unusable, undo it and fail the request.
                   */
                  vd->vdev_offline = B_TRUE;
                  vdev_reopen(tvd);
  
                  if (!tvd->vdev_islog && vd->vdev_aux == NULL &&
                      vdev_is_dead(tvd)) {
                          vd->vdev_offline = B_FALSE;
                          vdev_reopen(tvd);
                          return (spa_vdev_state_exit(spa, NULL,
                              SET_ERROR(EBUSY)));
                  }
  
                  /*
                   * Add the device back into the metaslab rotor so that
                   * once we online the device it's open for business.
                   */
                  if (tvd->vdev_islog && mg != NULL)
                          metaslab_group_activate(mg);
          }
  
          vd->vdev_tmpoffline = !!(flags & ZFS_OFFLINE_TEMPORARY);
  
          return (spa_vdev_state_exit(spa, vd, 0));
  }
  
  int
  vdev_offline(spa_t *spa, uint64_t guid, uint64_t flags)
  {
          int error;
  
          mutex_enter(&spa->spa_vdev_top_lock);
          error = vdev_offline_locked(spa, guid, flags);
          mutex_exit(&spa->spa_vdev_top_lock);
  
          return (error);
  }
  
  /*
   * Clear the error counts associated with this vdev.  Unlike vdev_online() and
   * vdev_offline(), we assume the spa config is locked.  We also clear all
   * children.  If 'vd' is NULL, then the user wants to clear all vdevs.
   */
  void
  vdev_clear(spa_t *spa, vdev_t *vd)
  {
          vdev_t *rvd = spa->spa_root_vdev;
  
          ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
  
          if (vd == NULL)
                  vd = rvd;
  
          vd->vdev_stat.vs_read_errors = 0;
          vd->vdev_stat.vs_write_errors = 0;
          vd->vdev_stat.vs_checksum_errors = 0;
          vd->vdev_stat.vs_slow_ios = 0;
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_clear(spa, vd->vdev_child[c]);
  
          /*
           * It makes no sense to "clear" an indirect  or removed vdev.
           */
          if (!vdev_is_concrete(vd) || vd->vdev_removed)
                  return;
  
          /*
           * If we're in the FAULTED state or have experienced failed I/O, then
           * clear the persistent state and attempt to reopen the device.  We
           * also mark the vdev config dirty, so that the new faulted state is
           * written out to disk.
           */
          if (vd->vdev_faulted || vd->vdev_degraded ||
              !vdev_readable(vd) || !vdev_writeable(vd)) {
                  /*
                   * When reopening in response to a clear event, it may be due to
                   * a fmadm repair request.  In this case, if the device is
                   * still broken, we want to still post the ereport again.
                   */
                  vd->vdev_forcefault = B_TRUE;
  
                  vd->vdev_faulted = vd->vdev_degraded = 0ULL;
                  vd->vdev_cant_read = B_FALSE;
                  vd->vdev_cant_write = B_FALSE;
                  vd->vdev_stat.vs_aux = 0;
  
                  vdev_reopen(vd == rvd ? rvd : vd->vdev_top);
  
                  vd->vdev_forcefault = B_FALSE;
  
                  if (vd != rvd && vdev_writeable(vd->vdev_top))
                          vdev_state_dirty(vd->vdev_top);
  
                  /* If a resilver isn't required, check if vdevs can be culled */
                  if (vd->vdev_aux == NULL && !vdev_is_dead(vd) &&
                      !dsl_scan_resilvering(spa->spa_dsl_pool) &&
                      !dsl_scan_resilver_scheduled(spa->spa_dsl_pool))
                          spa_async_request(spa, SPA_ASYNC_RESILVER_DONE);
  
                  spa_event_notify(spa, vd, NULL, ESC_ZFS_VDEV_CLEAR);
          }
  
          /*
           * When clearing a FMA-diagnosed fault, we always want to
           * unspare the device, as we assume that the original spare was
           * done in response to the FMA fault.
           */
          if (!vdev_is_dead(vd) && vd->vdev_parent != NULL &&
              vd->vdev_parent->vdev_ops == &vdev_spare_ops &&
              vd->vdev_parent->vdev_child[0] == vd)
                  vd->vdev_unspare = B_TRUE;
  
          /* Clear recent error events cache (i.e. duplicate events tracking) */
          zfs_ereport_clear(spa, vd);
  }
  
  boolean_t
  vdev_is_dead(vdev_t *vd)
  {
          /*
           * Holes and missing devices are always considered "dead".
           * This simplifies the code since we don't have to check for
           * these types of devices in the various code paths.
           * Instead we rely on the fact that we skip over dead devices
           * before issuing I/O to them.
           */
          return (vd->vdev_state < VDEV_STATE_DEGRADED ||
              vd->vdev_ops == &vdev_hole_ops ||
              vd->vdev_ops == &vdev_missing_ops);
  }
  
  boolean_t
  vdev_readable(vdev_t *vd)
  {
          return (!vdev_is_dead(vd) && !vd->vdev_cant_read);
  }
  
  boolean_t
  vdev_writeable(vdev_t *vd)
  {
          return (!vdev_is_dead(vd) && !vd->vdev_cant_write &&
              vdev_is_concrete(vd));
  }
  
  boolean_t
  vdev_allocatable(vdev_t *vd)
  {
          uint64_t state = vd->vdev_state;
  
          /*
           * We currently allow allocations from vdevs which may be in the
           * process of reopening (i.e. VDEV_STATE_CLOSED). If the device
           * fails to reopen then we'll catch it later when we're holding
           * the proper locks.  Note that we have to get the vdev state
           * in a local variable because although it changes atomically,
           * we're asking two separate questions about it.
           */
          return (!(state < VDEV_STATE_DEGRADED && state != VDEV_STATE_CLOSED) &&
              !vd->vdev_cant_write && vdev_is_concrete(vd) &&
              vd->vdev_mg->mg_initialized);
  }
  
  boolean_t
  vdev_accessible(vdev_t *vd, zio_t *zio)
  {
          ASSERT(zio->io_vd == vd);
  
          if (vdev_is_dead(vd) || vd->vdev_remove_wanted)
                  return (B_FALSE);
  
          if (zio->io_type == ZIO_TYPE_READ)
                  return (!vd->vdev_cant_read);
  
          if (zio->io_type == ZIO_TYPE_WRITE)
                  return (!vd->vdev_cant_write);
  
          return (B_TRUE);
  }
  
  static void
  vdev_get_child_stat(vdev_t *cvd, vdev_stat_t *vs, vdev_stat_t *cvs)
  {
          /*
           * Exclude the dRAID spare when aggregating to avoid double counting
           * the ops and bytes.  These IOs are counted by the physical leaves.
           */
          if (cvd->vdev_ops == &vdev_draid_spare_ops)
                  return;
  
          for (int t = 0; t < VS_ZIO_TYPES; t++) {
                  vs->vs_ops[t] += cvs->vs_ops[t];
                  vs->vs_bytes[t] += cvs->vs_bytes[t];
          }
  
          cvs->vs_scan_removing = cvd->vdev_removing;
  }
  
  /*
   * Get extended stats
   */
  static void
  vdev_get_child_stat_ex(vdev_t *cvd, vdev_stat_ex_t *vsx, vdev_stat_ex_t *cvsx)
  {
          (void) cvd;
  
          int t, b;
          for (t = 0; t < ZIO_TYPES; t++) {
                  for (b = 0; b < ARRAY_SIZE(vsx->vsx_disk_histo[0]); b++)
                          vsx->vsx_disk_histo[t][b] += cvsx->vsx_disk_histo[t][b];
  
                  for (b = 0; b < ARRAY_SIZE(vsx->vsx_total_histo[0]); b++) {
                          vsx->vsx_total_histo[t][b] +=
                              cvsx->vsx_total_histo[t][b];
                  }
          }
  
          for (t = 0; t < ZIO_PRIORITY_NUM_QUEUEABLE; t++) {
                  for (b = 0; b < ARRAY_SIZE(vsx->vsx_queue_histo[0]); b++) {
                          vsx->vsx_queue_histo[t][b] +=
                              cvsx->vsx_queue_histo[t][b];
                  }
                  vsx->vsx_active_queue[t] += cvsx->vsx_active_queue[t];
                  vsx->vsx_pend_queue[t] += cvsx->vsx_pend_queue[t];
  
                  for (b = 0; b < ARRAY_SIZE(vsx->vsx_ind_histo[0]); b++)
                          vsx->vsx_ind_histo[t][b] += cvsx->vsx_ind_histo[t][b];
  
                  for (b = 0; b < ARRAY_SIZE(vsx->vsx_agg_histo[0]); b++)
                          vsx->vsx_agg_histo[t][b] += cvsx->vsx_agg_histo[t][b];
          }
  
  }
  
  boolean_t
  vdev_is_spacemap_addressable(vdev_t *vd)
  {
          if (spa_feature_is_active(vd->vdev_spa, SPA_FEATURE_SPACEMAP_V2))
                  return (B_TRUE);
  
          /*
           * If double-word space map entries are not enabled we assume
           * 47 bits of the space map entry are dedicated to the entry's
           * offset (see SM_OFFSET_BITS in space_map.h). We then use that
           * to calculate the maximum address that can be described by a
           * space map entry for the given device.
           */
          uint64_t shift = vd->vdev_ashift + SM_OFFSET_BITS;
  
          if (shift >= 63) /* detect potential overflow */
                  return (B_TRUE);
  
          return (vd->vdev_asize < (1ULL << shift));
  }
  
  /*
   * Get statistics for the given vdev.
   */
  static void
  vdev_get_stats_ex_impl(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
  {
          int t;
          /*
           * If we're getting stats on the root vdev, aggregate the I/O counts
           * over all top-level vdevs (i.e. the direct children of the root).
           */
          if (!vd->vdev_ops->vdev_op_leaf) {
                  if (vs) {
                          memset(vs->vs_ops, 0, sizeof (vs->vs_ops));
                          memset(vs->vs_bytes, 0, sizeof (vs->vs_bytes));
                  }
                  if (vsx)
                          memset(vsx, 0, sizeof (*vsx));
  
                  for (int c = 0; c < vd->vdev_children; c++) {
                          vdev_t *cvd = vd->vdev_child[c];
                          vdev_stat_t *cvs = &cvd->vdev_stat;
                          vdev_stat_ex_t *cvsx = &cvd->vdev_stat_ex;
  
                          vdev_get_stats_ex_impl(cvd, cvs, cvsx);
                          if (vs)
                                  vdev_get_child_stat(cvd, vs, cvs);
                          if (vsx)
                                  vdev_get_child_stat_ex(cvd, vsx, cvsx);
                  }
          } else {
                  /*
                   * We're a leaf.  Just copy our ZIO active queue stats in.  The
                   * other leaf stats are updated in vdev_stat_update().
                   */
                  if (!vsx)
                          return;
  
                  memcpy(vsx, &vd->vdev_stat_ex, sizeof (vd->vdev_stat_ex));
  
                  for (t = 0; t < ARRAY_SIZE(vd->vdev_queue.vq_class); t++) {
                          vsx->vsx_active_queue[t] =
                              vd->vdev_queue.vq_class[t].vqc_active;
                          vsx->vsx_pend_queue[t] = avl_numnodes(
                              &vd->vdev_queue.vq_class[t].vqc_queued_tree);
                  }
          }
  }
  
  void
  vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
  {
          vdev_t *tvd = vd->vdev_top;
          mutex_enter(&vd->vdev_stat_lock);
          if (vs) {
                  memcpy(vs, &vd->vdev_stat, sizeof (*vs));
                  vs->vs_timestamp = gethrtime() - vs->vs_timestamp;
                  vs->vs_state = vd->vdev_state;
                  vs->vs_rsize = vdev_get_min_asize(vd);
  
                  if (vd->vdev_ops->vdev_op_leaf) {
                          vs->vs_pspace = vd->vdev_psize;
                          vs->vs_rsize += VDEV_LABEL_START_SIZE +
                              VDEV_LABEL_END_SIZE;
                          /*
                           * Report initializing progress. Since we don't
                           * have the initializing locks held, this is only
                           * an estimate (although a fairly accurate one).
                           */
                          vs->vs_initialize_bytes_done =
                              vd->vdev_initialize_bytes_done;
                          vs->vs_initialize_bytes_est =
                              vd->vdev_initialize_bytes_est;
                          vs->vs_initialize_state = vd->vdev_initialize_state;
                          vs->vs_initialize_action_time =
                              vd->vdev_initialize_action_time;
  
                          /*
                           * Report manual TRIM progress. Since we don't have
                           * the manual TRIM locks held, this is only an
                           * estimate (although fairly accurate one).
                           */
                          vs->vs_trim_notsup = !vd->vdev_has_trim;
                          vs->vs_trim_bytes_done = vd->vdev_trim_bytes_done;
                          vs->vs_trim_bytes_est = vd->vdev_trim_bytes_est;
                          vs->vs_trim_state = vd->vdev_trim_state;
                          vs->vs_trim_action_time = vd->vdev_trim_action_time;
  
                          /* Set when there is a deferred resilver. */
                          vs->vs_resilver_deferred = vd->vdev_resilver_deferred;
                  }
  
                  /*
                   * Report expandable space on top-level, non-auxiliary devices
                   * only. The expandable space is reported in terms of metaslab
                   * sized units since that determines how much space the pool
                   * can expand.
                   */
                  if (vd->vdev_aux == NULL && tvd != NULL) {
                          vs->vs_esize = P2ALIGN(
                              vd->vdev_max_asize - vd->vdev_asize,
                              1ULL << tvd->vdev_ms_shift);
                  }
  
                  vs->vs_configured_ashift = vd->vdev_top != NULL
                      ? vd->vdev_top->vdev_ashift : vd->vdev_ashift;
                  vs->vs_logical_ashift = vd->vdev_logical_ashift;
                  if (vd->vdev_physical_ashift <= ASHIFT_MAX)
                          vs->vs_physical_ashift = vd->vdev_physical_ashift;
                  else
                          vs->vs_physical_ashift = 0;
  
                  /*
                   * Report fragmentation and rebuild progress for top-level,
                   * non-auxiliary, concrete devices.
                   */
                  if (vd->vdev_aux == NULL && vd == vd->vdev_top &&
                      vdev_is_concrete(vd)) {
                          /*
                           * The vdev fragmentation rating doesn't take into
                           * account the embedded slog metaslab (vdev_log_mg).
                           * Since it's only one metaslab, it would have a tiny
                           * impact on the overall fragmentation.
                           */
                          vs->vs_fragmentation = (vd->vdev_mg != NULL) ?
                              vd->vdev_mg->mg_fragmentation : 0;
                  }
                  vs->vs_noalloc = MAX(vd->vdev_noalloc,
                      tvd ? tvd->vdev_noalloc : 0);
          }
  
          vdev_get_stats_ex_impl(vd, vs, vsx);
          mutex_exit(&vd->vdev_stat_lock);
  }
  
  void
  vdev_get_stats(vdev_t *vd, vdev_stat_t *vs)
  {
          return (vdev_get_stats_ex(vd, vs, NULL));
  }
  
  void
  vdev_clear_stats(vdev_t *vd)
  {
          mutex_enter(&vd->vdev_stat_lock);
          vd->vdev_stat.vs_space = 0;
          vd->vdev_stat.vs_dspace = 0;
          vd->vdev_stat.vs_alloc = 0;
          mutex_exit(&vd->vdev_stat_lock);
  }
  
  void
  vdev_scan_stat_init(vdev_t *vd)
  {
          vdev_stat_t *vs = &vd->vdev_stat;
  
          for (int c = 0; c < vd->vdev_children; c++)
                  vdev_scan_stat_init(vd->vdev_child[c]);
  
          mutex_enter(&vd->vdev_stat_lock);
          vs->vs_scan_processed = 0;
          mutex_exit(&vd->vdev_stat_lock);
  }
  
  void
  vdev_stat_update(zio_t *zio, uint64_t psize)
  {
          spa_t *spa = zio->io_spa;
          vdev_t *rvd = spa->spa_root_vdev;
          vdev_t *vd = zio->io_vd ? zio->io_vd : rvd;
          vdev_t *pvd;
          uint64_t txg = zio->io_txg;
          vdev_stat_t *vs = vd ? &vd->vdev_stat : NULL;
          vdev_stat_ex_t *vsx = vd ? &vd->vdev_stat_ex : NULL;
          zio_type_t type = zio->io_type;
          int flags = zio->io_flags;
  
          /*
           * If this i/o is a gang leader, it didn't do any actual work.
           */
          if (zio->io_gang_tree)
                  return;
  
          if (zio->io_error == 0) {
                  /*
                   * If this is a root i/o, don't count it -- we've already
                   * counted the top-level vdevs, and vdev_get_stats() will
                   * aggregate them when asked.  This reduces contention on
                   * the root vdev_stat_lock and implicitly handles blocks
                   * that compress away to holes, for which there is no i/o.
                   * (Holes never create vdev children, so all the counters
                   * remain zero, which is what we want.)
                   *
                   * Note: this only applies to successful i/o (io_error == 0)
                   * because unlike i/o counts, errors are not additive.
                   * When reading a ditto block, for example, failure of
                   * one top-level vdev does not imply a root-level error.
                   */
                  if (vd == rvd)
                          return;
  
                  ASSERT(vd == zio->io_vd);
  
                  if (flags & ZIO_FLAG_IO_BYPASS)
                          return;
  
                  mutex_enter(&vd->vdev_stat_lock);
  
                  if (flags & ZIO_FLAG_IO_REPAIR) {
                          /*
                           * Repair is the result of a resilver issued by the
                           * scan thread (spa_sync).
                           */
                          if (flags & ZIO_FLAG_SCAN_THREAD) {
                                  dsl_scan_t *scn = spa->spa_dsl_pool->dp_scan;
                                  dsl_scan_phys_t *scn_phys = &scn->scn_phys;
                                  uint64_t *processed = &scn_phys->scn_processed;
  
                                  if (vd->vdev_ops->vdev_op_leaf)
                                          atomic_add_64(processed, psize);
                                  vs->vs_scan_processed += psize;
                          }
  
                          /*
                           * Repair is the result of a rebuild issued by the
                           * rebuild thread (vdev_rebuild_thread).  To avoid
                           * double counting repaired bytes the virtual dRAID
                           * spare vdev is excluded from the processed bytes.
                           */
                          if (zio->io_priority == ZIO_PRIORITY_REBUILD) {
                                  vdev_t *tvd = vd->vdev_top;
                                  vdev_rebuild_t *vr = &tvd->vdev_rebuild_config;
                                  vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
                                  uint64_t *rebuilt = &vrp->vrp_bytes_rebuilt;
  
                                  if (vd->vdev_ops->vdev_op_leaf &&
                                      vd->vdev_ops != &vdev_draid_spare_ops) {
                                          atomic_add_64(rebuilt, psize);
                                  }
                                  vs->vs_rebuild_processed += psize;
                          }
  
                          if (flags & ZIO_FLAG_SELF_HEAL)
                                  vs->vs_self_healed += psize;
                  }
  
                  /*
                   * The bytes/ops/histograms are recorded at the leaf level and
                   * aggregated into the higher level vdevs in vdev_get_stats().
                   */
                  if (vd->vdev_ops->vdev_op_leaf &&
                      (zio->io_priority < ZIO_PRIORITY_NUM_QUEUEABLE)) {
                          zio_type_t vs_type = type;
                          zio_priority_t priority = zio->io_priority;
  
                          /*
                           * TRIM ops and bytes are reported to user space as
                           * ZIO_TYPE_IOCTL.  This is done to preserve the
                           * vdev_stat_t structure layout for user space.
                           */
                          if (type == ZIO_TYPE_TRIM)
                                  vs_type = ZIO_TYPE_IOCTL;
  
                          /*
                           * Solely for the purposes of 'zpool iostat -lqrw'
                           * reporting use the priority to categorize the IO.
                           * Only the following are reported to user space:
                           *
                           *   ZIO_PRIORITY_SYNC_READ,
                           *   ZIO_PRIORITY_SYNC_WRITE,
                           *   ZIO_PRIORITY_ASYNC_READ,
                           *   ZIO_PRIORITY_ASYNC_WRITE,
                           *   ZIO_PRIORITY_SCRUB,
                           *   ZIO_PRIORITY_TRIM,
                           *   ZIO_PRIORITY_REBUILD.
                           */
                          if (priority == ZIO_PRIORITY_INITIALIZING) {
                                  ASSERT3U(type, ==, ZIO_TYPE_WRITE);
                                  priority = ZIO_PRIORITY_ASYNC_WRITE;
                          } else if (priority == ZIO_PRIORITY_REMOVAL) {
                                  priority = ((type == ZIO_TYPE_WRITE) ?
                                      ZIO_PRIORITY_ASYNC_WRITE :
                                      ZIO_PRIORITY_ASYNC_READ);
                          }
  
                          vs->vs_ops[vs_type]++;
                          vs->vs_bytes[vs_type] += psize;
  
                          if (flags & ZIO_FLAG_DELEGATED) {
                                  vsx->vsx_agg_histo[priority]
                                      [RQ_HISTO(zio->io_size)]++;
                          } else {
                                  vsx->vsx_ind_histo[priority]
                                      [RQ_HISTO(zio->io_size)]++;
                          }
  
                          if (zio->io_delta && zio->io_delay) {
                                  vsx->vsx_queue_histo[priority]
                                      [L_HISTO(zio->io_delta - zio->io_delay)]++;
                                  vsx->vsx_disk_histo[type]
                                      [L_HISTO(zio->io_delay)]++;
                                  vsx->vsx_total_histo[type]
                                      [L_HISTO(zio->io_delta)]++;
                          }
                  }
  
                  mutex_exit(&vd->vdev_stat_lock);
                  return;
          }
  
          if (flags & ZIO_FLAG_SPECULATIVE)
                  return;
  
          /*
           * If this is an I/O error that is going to be retried, then ignore the
           * error.  Otherwise, the user may interpret B_FAILFAST I/O errors as
           * hard errors, when in reality they can happen for any number of
           * innocuous reasons (bus resets, MPxIO link failure, etc).
           */
          if (zio->io_error == EIO &&
              !(zio->io_flags & ZIO_FLAG_IO_RETRY))
                  return;
  
          /*
           * Intent logs writes won't propagate their error to the root
           * I/O so don't mark these types of failures as pool-level
           * errors.
           */
          if (zio->io_vd == NULL && (zio->io_flags & ZIO_FLAG_DONT_PROPAGATE))
                  return;
  
          if (type == ZIO_TYPE_WRITE && txg != 0 &&
              (!(flags & ZIO_FLAG_IO_REPAIR) ||
              (flags & ZIO_FLAG_SCAN_THREAD) ||
              spa->spa_claiming)) {
                  /*
                   * This is either a normal write (not a repair), or it's
                   * a repair induced by the scrub thread, or it's a repair
                   * made by zil_claim() during spa_load() in the first txg.
                   * In the normal case, we commit the DTL change in the same
                   * txg as the block was born.  In the scrub-induced repair
                   * case, we know that scrubs run in first-pass syncing context,
                   * so we commit the DTL change in spa_syncing_txg(spa).
                   * In the zil_claim() case, we commit in spa_first_txg(spa).
                   *
                   * We currently do not make DTL entries for failed spontaneous
                   * self-healing writes triggered by normal (non-scrubbing)
                   * reads, because we have no transactional context in which to
                   * do so -- and it's not clear that it'd be desirable anyway.
                   */
                  if (vd->vdev_ops->vdev_op_leaf) {
                          uint64_t commit_txg = txg;
                          if (flags & ZIO_FLAG_SCAN_THREAD) {
                                  ASSERT(flags & ZIO_FLAG_IO_REPAIR);
                                  ASSERT(spa_sync_pass(spa) == 1);
                                  vdev_dtl_dirty(vd, DTL_SCRUB, txg, 1);
                                  commit_txg = spa_syncing_txg(spa);
                          } else if (spa->spa_claiming) {
                                  ASSERT(flags & ZIO_FLAG_IO_REPAIR);
                                  commit_txg = spa_first_txg(spa);
                          }
                          ASSERT(commit_txg >= spa_syncing_txg(spa));
                          if (vdev_dtl_contains(vd, DTL_MISSING, txg, 1))
                                  return;
                          for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
                                  vdev_dtl_dirty(pvd, DTL_PARTIAL, txg, 1);
                          vdev_dirty(vd->vdev_top, VDD_DTL, vd, commit_txg);
                  }
                  if (vd != rvd)
                          vdev_dtl_dirty(vd, DTL_MISSING, txg, 1);
          }
  }
  
  int64_t
  vdev_deflated_space(vdev_t *vd, int64_t space)
  {
          ASSERT((space & (SPA_MINBLOCKSIZE-1)) == 0);
          ASSERT(vd->vdev_deflate_ratio != 0 || vd->vdev_isl2cache);
  
          return ((space >> SPA_MINBLOCKSHIFT) * vd->vdev_deflate_ratio);
  }
  
  /*
   * Update the in-core space usage stats for this vdev, its metaslab class,
   * and the root vdev.
   */
  void
  vdev_space_update(vdev_t *vd, int64_t alloc_delta, int64_t defer_delta,
      int64_t space_delta)
  {
          (void) defer_delta;
          int64_t dspace_delta;
          spa_t *spa = vd->vdev_spa;
          vdev_t *rvd = spa->spa_root_vdev;
  
          ASSERT(vd == vd->vdev_top);
  
          /*
           * Apply the inverse of the psize-to-asize (ie. RAID-Z) space-expansion
           * factor.  We must calculate this here and not at the root vdev
           * because the root vdev's psize-to-asize is simply the max of its
           * children's, thus not accurate enough for us.
           */
          dspace_delta = vdev_deflated_space(vd, space_delta);
  
          mutex_enter(&vd->vdev_stat_lock);
          /* ensure we won't underflow */
          if (alloc_delta < 0) {
                  ASSERT3U(vd->vdev_stat.vs_alloc, >=, -alloc_delta);
          }
  
          vd->vdev_stat.vs_alloc += alloc_delta;
          vd->vdev_stat.vs_space += space_delta;
          vd->vdev_stat.vs_dspace += dspace_delta;
          mutex_exit(&vd->vdev_stat_lock);
  
          /* every class but log contributes to root space stats */
          if (vd->vdev_mg != NULL && !vd->vdev_islog) {
                  ASSERT(!vd->vdev_isl2cache);
                  mutex_enter(&rvd->vdev_stat_lock);
                  rvd->vdev_stat.vs_alloc += alloc_delta;
                  rvd->vdev_stat.vs_space += space_delta;
                  rvd->vdev_stat.vs_dspace += dspace_delta;
                  mutex_exit(&rvd->vdev_stat_lock);
          }
          /* Note: metaslab_class_space_update moved to metaslab_space_update */
  }
  
  /*
   * Mark a top-level vdev's config as dirty, placing it on the dirty list
   * so that it will be written out next time the vdev configuration is synced.
   * If the root vdev is specified (vdev_top == NULL), dirty all top-level vdevs.
   */
  void
  vdev_config_dirty(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          vdev_t *rvd = spa->spa_root_vdev;
          int c;
  
          ASSERT(spa_writeable(spa));
  
          /*
           * If this is an aux vdev (as with l2cache and spare devices), then we
           * update the vdev config manually and set the sync flag.
           */
          if (vd->vdev_aux != NULL) {
                  spa_aux_vdev_t *sav = vd->vdev_aux;
                  nvlist_t **aux;
                  uint_t naux;
  
                  for (c = 0; c < sav->sav_count; c++) {
                          if (sav->sav_vdevs[c] == vd)
                                  break;
                  }
  
                  if (c == sav->sav_count) {
                          /*
                           * We're being removed.  There's nothing more to do.
                           */
                          ASSERT(sav->sav_sync == B_TRUE);
                          return;
                  }
  
                  sav->sav_sync = B_TRUE;
  
                  if (nvlist_lookup_nvlist_array(sav->sav_config,
                      ZPOOL_CONFIG_L2CACHE, &aux, &naux) != 0) {
                          VERIFY(nvlist_lookup_nvlist_array(sav->sav_config,
                              ZPOOL_CONFIG_SPARES, &aux, &naux) == 0);
                  }
  
                  ASSERT(c < naux);
  
                  /*
                   * Setting the nvlist in the middle if the array is a little
                   * sketchy, but it will work.
                   */
                  nvlist_free(aux[c]);
                  aux[c] = vdev_config_generate(spa, vd, B_TRUE, 0);
  
                  return;
          }
  
          /*
           * The dirty list is protected by the SCL_CONFIG lock.  The caller
           * must either hold SCL_CONFIG as writer, or must be the sync thread
           * (which holds SCL_CONFIG as reader).  There's only one sync thread,
           * so this is sufficient to ensure mutual exclusion.
           */
          ASSERT(spa_config_held(spa, SCL_CONFIG, RW_WRITER) ||
              (dsl_pool_sync_context(spa_get_dsl(spa)) &&
              spa_config_held(spa, SCL_CONFIG, RW_READER)));
  
          if (vd == rvd) {
                  for (c = 0; c < rvd->vdev_children; c++)
                          vdev_config_dirty(rvd->vdev_child[c]);
          } else {
                  ASSERT(vd == vd->vdev_top);
  
                  if (!list_link_active(&vd->vdev_config_dirty_node) &&
                      vdev_is_concrete(vd)) {
                          list_insert_head(&spa->spa_config_dirty_list, vd);
                  }
          }
  }
  
  void
  vdev_config_clean(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(spa_config_held(spa, SCL_CONFIG, RW_WRITER) ||
              (dsl_pool_sync_context(spa_get_dsl(spa)) &&
              spa_config_held(spa, SCL_CONFIG, RW_READER)));
  
          ASSERT(list_link_active(&vd->vdev_config_dirty_node));
          list_remove(&spa->spa_config_dirty_list, vd);
  }
  
  /*
   * Mark a top-level vdev's state as dirty, so that the next pass of
   * spa_sync() can convert this into vdev_config_dirty().  We distinguish
   * the state changes from larger config changes because they require
   * much less locking, and are often needed for administrative actions.
   */
  void
  vdev_state_dirty(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(spa_writeable(spa));
          ASSERT(vd == vd->vdev_top);
  
          /*
           * The state list is protected by the SCL_STATE lock.  The caller
           * must either hold SCL_STATE as writer, or must be the sync thread
           * (which holds SCL_STATE as reader).  There's only one sync thread,
           * so this is sufficient to ensure mutual exclusion.
           */
          ASSERT(spa_config_held(spa, SCL_STATE, RW_WRITER) ||
              (dsl_pool_sync_context(spa_get_dsl(spa)) &&
              spa_config_held(spa, SCL_STATE, RW_READER)));
  
          if (!list_link_active(&vd->vdev_state_dirty_node) &&
              vdev_is_concrete(vd))
                  list_insert_head(&spa->spa_state_dirty_list, vd);
  }
  
  void
  vdev_state_clean(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
  
          ASSERT(spa_config_held(spa, SCL_STATE, RW_WRITER) ||
              (dsl_pool_sync_context(spa_get_dsl(spa)) &&
              spa_config_held(spa, SCL_STATE, RW_READER)));
  
          ASSERT(list_link_active(&vd->vdev_state_dirty_node));
          list_remove(&spa->spa_state_dirty_list, vd);
  }
  
  /*
   * Propagate vdev state up from children to parent.
   */
  void
  vdev_propagate_state(vdev_t *vd)
  {
          spa_t *spa = vd->vdev_spa;
          vdev_t *rvd = spa->spa_root_vdev;
          int degraded = 0, faulted = 0;
          int corrupted = 0;
          vdev_t *child;
  
          if (vd->vdev_children > 0) {
                  for (int c = 0; c < vd->vdev_children; c++) {
                          child = vd->vdev_child[c];
  
                          /*
                           * Don't factor holes or indirect vdevs into the
                           * decision.
                           */
                          if (!vdev_is_concrete(child))
                                  continue;
  
                          if (!vdev_readable(child) ||
                              (!vdev_writeable(child) && spa_writeable(spa))) {
                                  /*
                                   * Root special: if there is a top-level log
                                   * device, treat the root vdev as if it were
                                   * degraded.
                                   */
                                  if (child->vdev_islog && vd == rvd)
                                          degraded++;
                                  else
                                          faulted++;
                          } else if (child->vdev_state <= VDEV_STATE_DEGRADED) {
                                  degraded++;
                          }
  
                          if (child->vdev_stat.vs_aux == VDEV_AUX_CORRUPT_DATA)
                                  corrupted++;
                  }
  
                  vd->vdev_ops->vdev_op_state_change(vd, faulted, degraded);
  
                  /*
                   * Root special: if there is a top-level vdev that cannot be
                   * opened due to corrupted metadata, then propagate the root
                   * vdev's aux state as 'corrupt' rather than 'insufficient
                   * replicas'.
                   */
                  if (corrupted && vd == rvd &&
                      rvd->vdev_state == VDEV_STATE_CANT_OPEN)
                          vdev_set_state(rvd, B_FALSE, VDEV_STATE_CANT_OPEN,
                              VDEV_AUX_CORRUPT_DATA);
          }
  
          if (vd->vdev_parent)
                  vdev_propagate_state(vd->vdev_parent);
  }
  
  /*
   * Set a vdev's state.  If this is during an open, we don't update the parent
   * state, because we're in the process of opening children depth-first.
   * Otherwise, we propagate the change to the parent.
   *
   * If this routine places a device in a faulted state, an appropriate ereport is
   * generated.
   */
  void
  vdev_set_state(vdev_t *vd, boolean_t isopen, vdev_state_t state, vdev_aux_t aux)
  {
          uint64_t save_state;
          spa_t *spa = vd->vdev_spa;
  
          if (state == vd->vdev_state) {
                  /*
                   * Since vdev_offline() code path is already in an offline
                   * state we can miss a statechange event to OFFLINE. Check
                   * the previous state to catch this condition.
                   */
                  if (vd->vdev_ops->vdev_op_leaf &&
                      (state == VDEV_STATE_OFFLINE) &&
                      (vd->vdev_prevstate >= VDEV_STATE_FAULTED)) {
                          /* post an offline state change */
                          zfs_post_state_change(spa, vd, vd->vdev_prevstate);
                  }
                  vd->vdev_stat.vs_aux = aux;
                  return;
          }
  
          save_state = vd->vdev_state;
  
          vd->vdev_state = state;
          vd->vdev_stat.vs_aux = aux;
  
          /*
           * If we are setting the vdev state to anything but an open state, then
           * always close the underlying device unless the device has requested
           * a delayed close (i.e. we're about to remove or fault the device).
           * Otherwise, we keep accessible but invalid devices open forever.
           * We don't call vdev_close() itself, because that implies some extra
           * checks (offline, etc) that we don't want here.  This is limited to
           * leaf devices, because otherwise closing the device will affect other
           * children.
           */
          if (!vd->vdev_delayed_close && vdev_is_dead(vd) &&
              vd->vdev_ops->vdev_op_leaf)
                  vd->vdev_ops->vdev_op_close(vd);
  
          if (vd->vdev_removed &&
              state == VDEV_STATE_CANT_OPEN &&
              (aux == VDEV_AUX_OPEN_FAILED || vd->vdev_checkremove)) {
                  /*
                   * If the previous state is set to VDEV_STATE_REMOVED, then this
                   * device was previously marked removed and someone attempted to
                   * reopen it.  If this failed due to a nonexistent device, then
                   * keep the device in the REMOVED state.  We also let this be if
                   * it is one of our special test online cases, which is only
                   * attempting to online the device and shouldn't generate an FMA
                   * fault.
                   */
                  vd->vdev_state = VDEV_STATE_REMOVED;
                  vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
          } else if (state == VDEV_STATE_REMOVED) {
                  vd->vdev_removed = B_TRUE;
          } else if (state == VDEV_STATE_CANT_OPEN) {
                  /*
                   * If we fail to open a vdev during an import or recovery, we
                   * mark it as "not available", which signifies that it was
                   * never there to begin with.  Failure to open such a device
                   * is not considered an error.
                   */
                  if ((spa_load_state(spa) == SPA_LOAD_IMPORT ||
                      spa_load_state(spa) == SPA_LOAD_RECOVER) &&
                      vd->vdev_ops->vdev_op_leaf)
                          vd->vdev_not_present = 1;
  
                  /*
                   * Post the appropriate ereport.  If the 'prevstate' field is
                   * set to something other than VDEV_STATE_UNKNOWN, it indicates
                   * that this is part of a vdev_reopen().  In this case, we don't
                   * want to post the ereport if the device was already in the
                   * CANT_OPEN state beforehand.
                   *
                   * If the 'checkremove' flag is set, then this is an attempt to
                   * online the device in response to an insertion event.  If we
                   * hit this case, then we have detected an insertion event for a
                   * faulted or offline device that wasn't in the removed state.
                   * In this scenario, we don't post an ereport because we are
                   * about to replace the device, or attempt an online with
                   * vdev_forcefault, which will generate the fault for us.
                   */
                  if ((vd->vdev_prevstate != state || vd->vdev_forcefault) &&
                      !vd->vdev_not_present && !vd->vdev_checkremove &&
                      vd != spa->spa_root_vdev) {
                          const char *class;
  
                          switch (aux) {
                          case VDEV_AUX_OPEN_FAILED:
                                  class = FM_EREPORT_ZFS_DEVICE_OPEN_FAILED;
                                  break;
                          case VDEV_AUX_CORRUPT_DATA:
                                  class = FM_EREPORT_ZFS_DEVICE_CORRUPT_DATA;
                                  break;
                          case VDEV_AUX_NO_REPLICAS:
                                  class = FM_EREPORT_ZFS_DEVICE_NO_REPLICAS;
                                  break;
                          case VDEV_AUX_BAD_GUID_SUM:
                                  class = FM_EREPORT_ZFS_DEVICE_BAD_GUID_SUM;
                                  break;
                          case VDEV_AUX_TOO_SMALL:
                                  class = FM_EREPORT_ZFS_DEVICE_TOO_SMALL;
                                  break;
                          case VDEV_AUX_BAD_LABEL:
                                  class = FM_EREPORT_ZFS_DEVICE_BAD_LABEL;
                                  break;
                          case VDEV_AUX_BAD_ASHIFT:
                                  class = FM_EREPORT_ZFS_DEVICE_BAD_ASHIFT;
                                  break;
                          default:
                                  class = FM_EREPORT_ZFS_DEVICE_UNKNOWN;
                          }
  
                          (void) zfs_ereport_post(class, spa, vd, NULL, NULL,
                              save_state);
                  }
  
                  /* Erase any notion of persistent removed state */
                  vd->vdev_removed = B_FALSE;
          } else {
                  vd->vdev_removed = B_FALSE;
          }
  
          /*
           * Notify ZED of any significant state-change on a leaf vdev.
           *
           */
          if (vd->vdev_ops->vdev_op_leaf) {
                  /* preserve original state from a vdev_reopen() */
                  if ((vd->vdev_prevstate != VDEV_STATE_UNKNOWN) &&
                      (vd->vdev_prevstate != vd->vdev_state) &&
                      (save_state <= VDEV_STATE_CLOSED))
                          save_state = vd->vdev_prevstate;
  
                  /* filter out state change due to initial vdev_open */
                  if (save_state > VDEV_STATE_CLOSED)
                          zfs_post_state_change(spa, vd, save_state);
          }
  
          if (!isopen && vd->vdev_parent)
                  vdev_propagate_state(vd->vdev_parent);
  }
  
  boolean_t
  vdev_children_are_offline(vdev_t *vd)
  {
          ASSERT(!vd->vdev_ops->vdev_op_leaf);
  
          for (uint64_t i = 0; i < vd->vdev_children; i++) {
                  if (vd->vdev_child[i]->vdev_state != VDEV_STATE_OFFLINE)
                          return (B_FALSE);
          }
  
          return (B_TRUE);
  }
  
  /*
   * Check the vdev configuration to ensure that it's capable of supporting
   * a root pool. We do not support partial configuration.
   */
  boolean_t
  vdev_is_bootable(vdev_t *vd)
  {
          if (!vd->vdev_ops->vdev_op_leaf) {
                  const char *vdev_type = vd->vdev_ops->vdev_op_type;
  
                  if (strcmp(vdev_type, VDEV_TYPE_MISSING) == 0)
                          return (B_FALSE);
          }
  
          for (int c = 0; c < vd->vdev_children; c++) {
                  if (!vdev_is_bootable(vd->vdev_child[c]))
                          return (B_FALSE);
          }
          return (B_TRUE);
  }
  
  boolean_t
  vdev_is_concrete(vdev_t *vd)
  {
          vdev_ops_t *ops = vd->vdev_ops;
          if (ops == &vdev_indirect_ops || ops == &vdev_hole_ops ||
              ops == &vdev_missing_ops || ops == &vdev_root_ops) {
                  return (B_FALSE);
          } else {
                  return (B_TRUE);
          }
  }
  
  /*
   * Determine if a log device has valid content.  If the vdev was
   * removed or faulted in the MOS config then we know that
   * the content on the log device has already been written to the pool.
   */
  boolean_t
  vdev_log_state_valid(vdev_t *vd)
  {
          if (vd->vdev_ops->vdev_op_leaf && !vd->vdev_faulted &&
              !vd->vdev_removed)
                  return (B_TRUE);
  
          for (int c = 0; c < vd->vdev_children; c++)
                  if (vdev_log_state_valid(vd->vdev_child[c]))
                          return (B_TRUE);
  
          return (B_FALSE);
  }
  
  /*
   * Expand a vdev if possible.
   */
  void
  vdev_expand(vdev_t *vd, uint64_t txg)
  {
          ASSERT(vd->vdev_top == vd);
          ASSERT(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
          ASSERT(vdev_is_concrete(vd));
  
          vdev_set_deflate_ratio(vd);
  
          if ((vd->vdev_asize >> vd->vdev_ms_shift) > vd->vdev_ms_count &&
              vdev_is_concrete(vd)) {
                  vdev_metaslab_group_create(vd);
                  VERIFY(vdev_metaslab_init(vd, txg) == 0);
                  vdev_config_dirty(vd);
          }
  }
  
  /*
   * Split a vdev.
   */
  void
  vdev_split(vdev_t *vd)
  {
          vdev_t *cvd, *pvd = vd->vdev_parent;
  
          vdev_remove_child(pvd, vd);
          vdev_compact_children(pvd);
  
          cvd = pvd->vdev_child[0];
          if (pvd->vdev_children == 1) {
                  vdev_remove_parent(cvd);
                  cvd->vdev_splitting = B_TRUE;
          }
          vdev_propagate_state(cvd);
  }
  
  void
  vdev_deadman(vdev_t *vd, const char *tag)
  {
          for (int c = 0; c < vd->vdev_children; c++) {
                  vdev_t *cvd = vd->vdev_child[c];
  
                  vdev_deadman(cvd, tag);
          }
  
          if (vd->vdev_ops->vdev_op_leaf) {
                  vdev_queue_t *vq = &vd->vdev_queue;
  
                  mutex_enter(&vq->vq_lock);
                  if (avl_numnodes(&vq->vq_active_tree) > 0) {
                          spa_t *spa = vd->vdev_spa;
                          zio_t *fio;
                          uint64_t delta;
  
                          zfs_dbgmsg("slow vdev: %s has %lu active IOs",
                              vd->vdev_path, avl_numnodes(&vq->vq_active_tree));
  
                          /*
                           * Look at the head of all the pending queues,
                           * if any I/O has been outstanding for longer than
                           * the spa_deadman_synctime invoke the deadman logic.
                           */
                          fio = avl_first(&vq->vq_active_tree);
                          delta = gethrtime() - fio->io_timestamp;
                          if (delta > spa_deadman_synctime(spa))
                                  zio_deadman(fio, tag);
                  }
                  mutex_exit(&vq->vq_lock);
          }
  }
  
  void
  vdev_defer_resilver(vdev_t *vd)
  {
          ASSERT(vd->vdev_ops->vdev_op_leaf);
  
          vd->vdev_resilver_deferred = B_TRUE;
          vd->vdev_spa->spa_resilver_deferred = B_TRUE;
  }
  
  /*
   * Clears the resilver deferred flag on all leaf devs under vd. Returns
   * B_TRUE if we have devices that need to be resilvered and are available to
   * accept resilver I/Os.
   */
  boolean_t
  vdev_clear_resilver_deferred(vdev_t *vd, dmu_tx_t *tx)
  {
          boolean_t resilver_needed = B_FALSE;
          spa_t *spa = vd->vdev_spa;
  
          for (int c = 0; c < vd->vdev_children; c++) {
                  vdev_t *cvd = vd->vdev_child[c];
                  resilver_needed |= vdev_clear_resilver_deferred(cvd, tx);
          }
  
          if (vd == spa->spa_root_vdev &&
              spa_feature_is_active(spa, SPA_FEATURE_RESILVER_DEFER)) {
                  spa_feature_decr(spa, SPA_FEATURE_RESILVER_DEFER, tx);
                  vdev_config_dirty(vd);
                  spa->spa_resilver_deferred = B_FALSE;
                  return (resilver_needed);
          }
  
          if (!vdev_is_concrete(vd) || vd->vdev_aux ||
              !vd->vdev_ops->vdev_op_leaf)
                  return (resilver_needed);
  
          vd->vdev_resilver_deferred = B_FALSE;
  
          return (!vdev_is_dead(vd) && !vd->vdev_offline &&
              vdev_resilver_needed(vd, NULL, NULL));
  }
  
  boolean_t
  vdev_xlate_is_empty(range_seg64_t *rs)
  {
          return (rs->rs_start == rs->rs_end);
  }
  
  /*
   * Translate a logical range to the first contiguous physical range for the
   * specified vdev_t.  This function is initially called with a leaf vdev and
   * will walk each parent vdev until it reaches a top-level vdev. Once the
   * top-level is reached the physical range is initialized and the recursive
   * function begins to unwind. As it unwinds it calls the parent's vdev
   * specific translation function to do the real conversion.
   */
  void
  vdev_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
      range_seg64_t *physical_rs, range_seg64_t *remain_rs)
  {
          /*
           * Walk up the vdev tree
           */
          if (vd != vd->vdev_top) {
                  vdev_xlate(vd->vdev_parent, logical_rs, physical_rs,
                      remain_rs);
          } else {
                  /*
                   * We've reached the top-level vdev, initialize the physical
                   * range to the logical range and set an empty remaining
                   * range then start to unwind.
                   */
                  physical_rs->rs_start = logical_rs->rs_start;
                  physical_rs->rs_end = logical_rs->rs_end;
  
                  remain_rs->rs_start = logical_rs->rs_start;
                  remain_rs->rs_end = logical_rs->rs_start;
  
                  return;
          }
  
          vdev_t *pvd = vd->vdev_parent;
          ASSERT3P(pvd, !=, NULL);
          ASSERT3P(pvd->vdev_ops->vdev_op_xlate, !=, NULL);
  
          /*
           * As this recursive function unwinds, translate the logical
           * range into its physical and any remaining components by calling
           * the vdev specific translate function.
           */
          range_seg64_t intermediate = { 0 };
          pvd->vdev_ops->vdev_op_xlate(vd, physical_rs, &intermediate, remain_rs);
  
          physical_rs->rs_start = intermediate.rs_start;
          physical_rs->rs_end = intermediate.rs_end;
  }
  
  void
  vdev_xlate_walk(vdev_t *vd, const range_seg64_t *logical_rs,
      vdev_xlate_func_t *func, void *arg)
  {
          range_seg64_t iter_rs = *logical_rs;
          range_seg64_t physical_rs;
          range_seg64_t remain_rs;
  
          while (!vdev_xlate_is_empty(&iter_rs)) {
  
                  vdev_xlate(vd, &iter_rs, &physical_rs, &remain_rs);
  
                  /*
                   * With raidz and dRAID, it's possible that the logical range
                   * does not live on this leaf vdev. Only when there is a non-
                   * zero physical size call the provided function.
                   */
                  if (!vdev_xlate_is_empty(&physical_rs))
                          func(arg, &physical_rs);
  
                  iter_rs = remain_rs;
          }
  }
  
  static char *
  vdev_name(vdev_t *vd, char *buf, int buflen)
  {
          if (vd->vdev_path == NULL) {
                  if (strcmp(vd->vdev_ops->vdev_op_type, "root") == 0) {
                          strlcpy(buf, vd->vdev_spa->spa_name, buflen);
                  } else if (!vd->vdev_ops->vdev_op_leaf) {
                          snprintf(buf, buflen, "%s-%llu",
                              vd->vdev_ops->vdev_op_type,
                              (u_longlong_t)vd->vdev_id);
                  }
          } else {
                  strlcpy(buf, vd->vdev_path, buflen);
          }
          return (buf);
  }
  
  /*
   * Look at the vdev tree and determine whether any devices are currently being
   * replaced.
   */
  boolean_t
  vdev_replace_in_progress(vdev_t *vdev)
  {
          ASSERT(spa_config_held(vdev->vdev_spa, SCL_ALL, RW_READER) != 0);
  
          if (vdev->vdev_ops == &vdev_replacing_ops)
                  return (B_TRUE);
  
          /*
           * A 'spare' vdev indicates that we have a replace in progress, unless
           * it has exactly two children, and the second, the hot spare, has
           * finished being resilvered.
           */
          if (vdev->vdev_ops == &vdev_spare_ops && (vdev->vdev_children > 2 ||
              !vdev_dtl_empty(vdev->vdev_child[1], DTL_MISSING)))
                  return (B_TRUE);
  
          for (int i = 0; i < vdev->vdev_children; i++) {
                  if (vdev_replace_in_progress(vdev->vdev_child[i]))
                          return (B_TRUE);
          }
  
          return (B_FALSE);
  }
  
  /*
   * Add a (source=src, propname=propval) list to an nvlist.
   */
  static void
  vdev_prop_add_list(nvlist_t *nvl, const char *propname, char *strval,
      uint64_t intval, zprop_source_t src)
  {
          nvlist_t *propval;
  
          propval = fnvlist_alloc();
          fnvlist_add_uint64(propval, ZPROP_SOURCE, src);
  
          if (strval != NULL)
                  fnvlist_add_string(propval, ZPROP_VALUE, strval);
          else
                  fnvlist_add_uint64(propval, ZPROP_VALUE, intval);
  
          fnvlist_add_nvlist(nvl, propname, propval);
          nvlist_free(propval);
  }
  
  static void
  vdev_props_set_sync(void *arg, dmu_tx_t *tx)
  {
          vdev_t *vd;
          nvlist_t *nvp = arg;
          spa_t *spa = dmu_tx_pool(tx)->dp_spa;
          objset_t *mos = spa->spa_meta_objset;
          nvpair_t *elem = NULL;
          uint64_t vdev_guid;
          nvlist_t *nvprops;
  
          vdev_guid = fnvlist_lookup_uint64(nvp, ZPOOL_VDEV_PROPS_SET_VDEV);
          nvprops = fnvlist_lookup_nvlist(nvp, ZPOOL_VDEV_PROPS_SET_PROPS);
          vd = spa_lookup_by_guid(spa, vdev_guid, B_TRUE);
  
          /* this vdev could get removed while waiting for this sync task */
          if (vd == NULL)
                  return;
  
          mutex_enter(&spa->spa_props_lock);
  
          while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
                  uint64_t intval, objid = 0;
                  char *strval;
                  vdev_prop_t prop;
                  const char *propname = nvpair_name(elem);
                  zprop_type_t proptype;
  
                  /*
                   * Set vdev property values in the vdev props mos object.
                   */
                  if (vd->vdev_top_zap != 0) {
                          objid = vd->vdev_top_zap;
                  } else if (vd->vdev_leaf_zap != 0) {
                          objid = vd->vdev_leaf_zap;
                  } else {
                          panic("vdev not top or leaf");
                  }
  
                  switch (prop = vdev_name_to_prop(propname)) {
                  case VDEV_PROP_USERPROP:
                          if (vdev_prop_user(propname)) {
                                  strval = fnvpair_value_string(elem);
                                  if (strlen(strval) == 0) {
                                          /* remove the property if value == "" */
                                          (void) zap_remove(mos, objid, propname,
                                              tx);
                                  } else {
                                          VERIFY0(zap_update(mos, objid, propname,
                                              1, strlen(strval) + 1, strval, tx));
                                  }
                                  spa_history_log_internal(spa, "vdev set", tx,
                                      "vdev_guid=%llu: %s=%s",
                                      (u_longlong_t)vdev_guid, nvpair_name(elem),
                                      strval);
                          }
                          break;
                  default:
                          /* normalize the property name */
                          propname = vdev_prop_to_name(prop);
                          proptype = vdev_prop_get_type(prop);
  
                          if (nvpair_type(elem) == DATA_TYPE_STRING) {
                                  ASSERT(proptype == PROP_TYPE_STRING);
                                  strval = fnvpair_value_string(elem);
                                  VERIFY0(zap_update(mos, objid, propname,
                                      1, strlen(strval) + 1, strval, tx));
                                  spa_history_log_internal(spa, "vdev set", tx,
                                      "vdev_guid=%llu: %s=%s",
                                      (u_longlong_t)vdev_guid, nvpair_name(elem),
                                      strval);
                          } else if (nvpair_type(elem) == DATA_TYPE_UINT64) {
                                  intval = fnvpair_value_uint64(elem);
  
                                  if (proptype == PROP_TYPE_INDEX) {
                                          const char *unused;
                                          VERIFY0(vdev_prop_index_to_string(
                                              prop, intval, &unused));
                                  }
                                  VERIFY0(zap_update(mos, objid, propname,
                                      sizeof (uint64_t), 1, &intval, tx));
                                  spa_history_log_internal(spa, "vdev set", tx,
                                      "vdev_guid=%llu: %s=%lld",
                                      (u_longlong_t)vdev_guid,
                                      nvpair_name(elem), (longlong_t)intval);
                          } else {
                                  panic("invalid vdev property type %u",
                                      nvpair_type(elem));
                          }
                  }
  
          }
  
          mutex_exit(&spa->spa_props_lock);
  }
  
  int
  vdev_prop_set(vdev_t *vd, nvlist_t *innvl, nvlist_t *outnvl)
  {
          spa_t *spa = vd->vdev_spa;
          nvpair_t *elem = NULL;
          uint64_t vdev_guid;
          nvlist_t *nvprops;
          int error = 0;
  
          ASSERT(vd != NULL);
  
          if (nvlist_lookup_uint64(innvl, ZPOOL_VDEV_PROPS_SET_VDEV,
              &vdev_guid) != 0)
                  return (SET_ERROR(EINVAL));
  
          if (nvlist_lookup_nvlist(innvl, ZPOOL_VDEV_PROPS_SET_PROPS,
              &nvprops) != 0)
                  return (SET_ERROR(EINVAL));
  
          if ((vd = spa_lookup_by_guid(spa, vdev_guid, B_TRUE)) == NULL)
                  return (SET_ERROR(EINVAL));
  
          while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
                  char *propname = nvpair_name(elem);
                  vdev_prop_t prop = vdev_name_to_prop(propname);
                  uint64_t intval = 0;
                  char *strval = NULL;
  
                  if (prop == VDEV_PROP_USERPROP && !vdev_prop_user(propname)) {
                          error = EINVAL;
                          goto end;
                  }
  
                  if (vdev_prop_readonly(prop)) {
                          error = EROFS;
                          goto end;
                  }
  
                  /* Special Processing */
                  switch (prop) {
                  case VDEV_PROP_PATH:
                          if (vd->vdev_path == NULL) {
                                  error = EROFS;
                                  break;
                          }
                          if (nvpair_value_string(elem, &strval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          /* New path must start with /dev/ */
                          if (strncmp(strval, "/dev/", 5)) {
                                  error = EINVAL;
                                  break;
                          }
                          error = spa_vdev_setpath(spa, vdev_guid, strval);
                          break;
                  case VDEV_PROP_ALLOCATING:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          if (intval != vd->vdev_noalloc)
                                  break;
                          if (intval == 0)
                                  error = spa_vdev_noalloc(spa, vdev_guid);
                          else
                                  error = spa_vdev_alloc(spa, vdev_guid);
                          break;
                  case VDEV_PROP_FAILFAST:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          vd->vdev_failfast = intval & 1;
                          break;
                  case VDEV_PROP_CHECKSUM_N:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          vd->vdev_checksum_n = intval;
                          break;
                  case VDEV_PROP_CHECKSUM_T:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          vd->vdev_checksum_t = intval;
                          break;
                  case VDEV_PROP_IO_N:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          vd->vdev_io_n = intval;
                          break;
                  case VDEV_PROP_IO_T:
                          if (nvpair_value_uint64(elem, &intval) != 0) {
                                  error = EINVAL;
                                  break;
                          }
                          vd->vdev_io_t = intval;
                          break;
                  default:
                          /* Most processing is done in vdev_props_set_sync */
                          break;
                  }
  end:
                  if (error != 0) {
                          intval = error;
                          vdev_prop_add_list(outnvl, propname, strval, intval, 0);
                          return (error);
                  }
          }
  
          return (dsl_sync_task(spa->spa_name, NULL, vdev_props_set_sync,
              innvl, 6, ZFS_SPACE_CHECK_EXTRA_RESERVED));
  }
  
  int
  vdev_prop_get(vdev_t *vd, nvlist_t *innvl, nvlist_t *outnvl)
  {
          spa_t *spa = vd->vdev_spa;
          objset_t *mos = spa->spa_meta_objset;
          int err = 0;
          uint64_t objid;
          uint64_t vdev_guid;
          nvpair_t *elem = NULL;
          nvlist_t *nvprops = NULL;
          uint64_t intval = 0;
          char *strval = NULL;
          const char *propname = NULL;
          vdev_prop_t prop;
  
          ASSERT(vd != NULL);
          ASSERT(mos != NULL);
  
          if (nvlist_lookup_uint64(innvl, ZPOOL_VDEV_PROPS_GET_VDEV,
              &vdev_guid) != 0)
                  return (SET_ERROR(EINVAL));
  
          nvlist_lookup_nvlist(innvl, ZPOOL_VDEV_PROPS_GET_PROPS, &nvprops);
  
          if (vd->vdev_top_zap != 0) {
                  objid = vd->vdev_top_zap;
          } else if (vd->vdev_leaf_zap != 0) {
                  objid = vd->vdev_leaf_zap;
          } else {
                  return (SET_ERROR(EINVAL));
          }
          ASSERT(objid != 0);
  
          mutex_enter(&spa->spa_props_lock);
  
          if (nvprops != NULL) {
                  char namebuf[64] = { 0 };
  
                  while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
                          intval = 0;
                          strval = NULL;
                          propname = nvpair_name(elem);
                          prop = vdev_name_to_prop(propname);
                          zprop_source_t src = ZPROP_SRC_DEFAULT;
                          uint64_t integer_size, num_integers;
  
                          switch (prop) {
                          /* Special Read-only Properties */
                          case VDEV_PROP_NAME:
                                  strval = vdev_name(vd, namebuf,
                                      sizeof (namebuf));
                                  if (strval == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname, strval, 0,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_CAPACITY:
                                  /* percent used */
                                  intval = (vd->vdev_stat.vs_dspace == 0) ? 0 :
                                      (vd->vdev_stat.vs_alloc * 100 /
                                      vd->vdev_stat.vs_dspace);
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      intval, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_STATE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_state, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_GUID:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_guid, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_ASIZE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_asize, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_PSIZE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_psize, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_ASHIFT:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_ashift, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_SIZE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_dspace, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_FREE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_dspace -
                                      vd->vdev_stat.vs_alloc, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_ALLOCATED:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_alloc, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_EXPANDSZ:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_esize, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_FRAGMENTATION:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_fragmentation,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_PARITY:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vdev_get_nparity(vd), ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_PATH:
                                  if (vd->vdev_path == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname,
                                      vd->vdev_path, 0, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_DEVID:
                                  if (vd->vdev_devid == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname,
                                      vd->vdev_devid, 0, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_PHYS_PATH:
                                  if (vd->vdev_physpath == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname,
                                      vd->vdev_physpath, 0, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_ENC_PATH:
                                  if (vd->vdev_enc_sysfs_path == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname,
                                      vd->vdev_enc_sysfs_path, 0, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_FRU:
                                  if (vd->vdev_fru == NULL)
                                          continue;
                                  vdev_prop_add_list(outnvl, propname,
                                      vd->vdev_fru, 0, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_PARENT:
                                  if (vd->vdev_parent != NULL) {
                                          strval = vdev_name(vd->vdev_parent,
                                              namebuf, sizeof (namebuf));
                                          vdev_prop_add_list(outnvl, propname,
                                              strval, 0, ZPROP_SRC_NONE);
                                  }
                                  continue;
                          case VDEV_PROP_CHILDREN:
                                  if (vd->vdev_children > 0)
                                          strval = kmem_zalloc(ZAP_MAXVALUELEN,
                                              KM_SLEEP);
                                  for (uint64_t i = 0; i < vd->vdev_children;
                                      i++) {
                                          const char *vname;
  
                                          vname = vdev_name(vd->vdev_child[i],
                                              namebuf, sizeof (namebuf));
                                          if (vname == NULL)
                                                  vname = "(unknown)";
                                          if (strlen(strval) > 0)
                                                  strlcat(strval, ",",
                                                      ZAP_MAXVALUELEN);
                                          strlcat(strval, vname, ZAP_MAXVALUELEN);
                                  }
                                  if (strval != NULL) {
                                          vdev_prop_add_list(outnvl, propname,
                                              strval, 0, ZPROP_SRC_NONE);
                                          kmem_free(strval, ZAP_MAXVALUELEN);
                                  }
                                  continue;
                          case VDEV_PROP_NUMCHILDREN:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_children, ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_READ_ERRORS:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_read_errors,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_WRITE_ERRORS:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_write_errors,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_CHECKSUM_ERRORS:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_checksum_errors,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_INITIALIZE_ERRORS:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_initialize_errors,
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_NULL:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_NULL],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_READ:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_READ],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_WRITE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_WRITE],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_FREE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_FREE],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_CLAIM:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_CLAIM],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_OPS_TRIM:
                                  /*
                                   * TRIM ops and bytes are reported to user
                                   * space as ZIO_TYPE_IOCTL.  This is done to
                                   * preserve the vdev_stat_t structure layout
                                   * for user space.
                                   */
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_ops[ZIO_TYPE_IOCTL],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_NULL:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_NULL],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_READ:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_READ],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_WRITE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_WRITE],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_FREE:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_FREE],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_CLAIM:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_CLAIM],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_BYTES_TRIM:
                                  /*
                                   * TRIM ops and bytes are reported to user
                                   * space as ZIO_TYPE_IOCTL.  This is done to
                                   * preserve the vdev_stat_t structure layout
                                   * for user space.
                                   */
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_stat.vs_bytes[ZIO_TYPE_IOCTL],
                                      ZPROP_SRC_NONE);
                                  continue;
                          case VDEV_PROP_REMOVING:
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      vd->vdev_removing, ZPROP_SRC_NONE);
                                  continue;
                          /* Numeric Properites */
                          case VDEV_PROP_ALLOCATING:
                                  /* Leaf vdevs cannot have this property */
                                  if (vd->vdev_mg == NULL &&
                                      vd->vdev_top != NULL) {
                                          src = ZPROP_SRC_NONE;
                                          intval = ZPROP_BOOLEAN_NA;
                                  } else {
                                          err = vdev_prop_get_int(vd, prop,
                                              &intval);
                                          if (err && err != ENOENT)
                                                  break;
  
                                          if (intval ==
                                              vdev_prop_default_numeric(prop))
                                                  src = ZPROP_SRC_DEFAULT;
                                          else
                                                  src = ZPROP_SRC_LOCAL;
                                  }
  
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      intval, src);
                                  break;
                          case VDEV_PROP_FAILFAST:
                                  src = ZPROP_SRC_LOCAL;
                                  strval = NULL;
  
                                  err = zap_lookup(mos, objid, nvpair_name(elem),
                                      sizeof (uint64_t), 1, &intval);
                                  if (err == ENOENT) {
                                          intval = vdev_prop_default_numeric(
                                              prop);
                                          err = 0;
                                  } else if (err) {
                                          break;
                                  }
                                  if (intval == vdev_prop_default_numeric(prop))
                                          src = ZPROP_SRC_DEFAULT;
  
                                  vdev_prop_add_list(outnvl, propname, strval,
                                      intval, src);
                                  break;
                          case VDEV_PROP_CHECKSUM_N:
                          case VDEV_PROP_CHECKSUM_T:
                          case VDEV_PROP_IO_N:
                          case VDEV_PROP_IO_T:
                                  err = vdev_prop_get_int(vd, prop, &intval);
                                  if (err && err != ENOENT)
                                          break;
  
                                  if (intval == vdev_prop_default_numeric(prop))
                                          src = ZPROP_SRC_DEFAULT;
                                  else
                                          src = ZPROP_SRC_LOCAL;
  
                                  vdev_prop_add_list(outnvl, propname, NULL,
                                      intval, src);
                                  break;
                          /* Text Properties */
                          case VDEV_PROP_COMMENT:
                                  /* Exists in the ZAP below */
                                  /* FALLTHRU */
                          case VDEV_PROP_USERPROP:
                                  /* User Properites */
                                  src = ZPROP_SRC_LOCAL;
  
                                  err = zap_length(mos, objid, nvpair_name(elem),
                                      &integer_size, &num_integers);
                                  if (err)
                                          break;
  
                                  switch (integer_size) {
                                  case 8:
                                          /* User properties cannot be integers */
                                          err = EINVAL;
                                          break;
                                  case 1:
                                          /* string property */
                                          strval = kmem_alloc(num_integers,
                                              KM_SLEEP);
                                          err = zap_lookup(mos, objid,
                                              nvpair_name(elem), 1,
                                              num_integers, strval);
                                          if (err) {
                                                  kmem_free(strval,
                                                      num_integers);
                                                  break;
                                          }
                                          vdev_prop_add_list(outnvl, propname,
                                              strval, 0, src);
                                          kmem_free(strval, num_integers);
                                          break;
                                  }
                                  break;
                          default:
                                  err = ENOENT;
                                  break;
                          }
                          if (err)
                                  break;
                  }
          } else {
                  /*
                   * Get all properties from the MOS vdev property object.
                   */
                  zap_cursor_t zc;
                  zap_attribute_t za;
                  for (zap_cursor_init(&zc, mos, objid);
                      (err = zap_cursor_retrieve(&zc, &za)) == 0;
                      zap_cursor_advance(&zc)) {
                          intval = 0;
                          strval = NULL;
                          zprop_source_t src = ZPROP_SRC_DEFAULT;
                          propname = za.za_name;
  
                          switch (za.za_integer_length) {
                          case 8:
                                  /* We do not allow integer user properties */
                                  /* This is likely an internal value */
                                  break;
                          case 1:
                                  /* string property */
                                  strval = kmem_alloc(za.za_num_integers,
                                      KM_SLEEP);
                                  err = zap_lookup(mos, objid, za.za_name, 1,
                                      za.za_num_integers, strval);
                                  if (err) {
                                          kmem_free(strval, za.za_num_integers);
                                          break;
                                  }
                                  vdev_prop_add_list(outnvl, propname, strval, 0,
                                      src);
                                  kmem_free(strval, za.za_num_integers);
                                  break;
  
                          default:
                                  break;
                          }
                  }
                  zap_cursor_fini(&zc);
          }
  
          mutex_exit(&spa->spa_props_lock);
          if (err && err != ENOENT) {
                  return (err);
          }
  
          return (0);
  }
  
  EXPORT_SYMBOL(vdev_fault);
  EXPORT_SYMBOL(vdev_degrade);
  EXPORT_SYMBOL(vdev_online);
  EXPORT_SYMBOL(vdev_offline);
  EXPORT_SYMBOL(vdev_clear);
  
  ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_count, UINT, ZMOD_RW,
          "Target number of metaslabs per top-level vdev");
  
  ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_shift, UINT, ZMOD_RW,
          "Default limit for metaslab size");
  
  ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, min_ms_count, UINT, ZMOD_RW,
          "Minimum number of metaslabs per top-level vdev");
  
  ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, ms_count_limit, UINT, ZMOD_RW,
          "Practical upper limit of total metaslabs per top-level vdev");
  
  ZFS_MODULE_PARAM(zfs, zfs_, slow_io_events_per_second, UINT, ZMOD_RW,
          "Rate limit slow IO (delay) events to this many per second");
  
  /* BEGIN CSTYLED */
  ZFS_MODULE_PARAM(zfs, zfs_, checksum_events_per_second, UINT, ZMOD_RW,
          "Rate limit checksum events to this many checksum errors per second "
          "(do not set below ZED threshold).");
  /* END CSTYLED */
  
  ZFS_MODULE_PARAM(zfs, zfs_, scan_ignore_errors, INT, ZMOD_RW,
          "Ignore errors during resilver/scrub");
  
  ZFS_MODULE_PARAM(zfs_vdev, vdev_, validate_skip, INT, ZMOD_RW,
          "Bypass vdev_validate()");
  
  ZFS_MODULE_PARAM(zfs, zfs_, nocacheflush, INT, ZMOD_RW,
          "Disable cache flushes");
  
  ZFS_MODULE_PARAM(zfs, zfs_, embedded_slog_min_ms, UINT, ZMOD_RW,
          "Minimum number of metaslabs required to dedicate one for log blocks");
  
  /* BEGIN CSTYLED */
  ZFS_MODULE_PARAM_CALL(zfs_vdev, zfs_vdev_, min_auto_ashift,
          param_set_min_auto_ashift, param_get_uint, ZMOD_RW,
          "Minimum ashift used when creating new top-level vdevs");
  
  ZFS_MODULE_PARAM_CALL(zfs_vdev, zfs_vdev_, max_auto_ashift,
          param_set_max_auto_ashift, param_get_uint, ZMOD_RW,
          "Maximum ashift used when optimizing for logical -> physical sector "
          "size on new top-level vdevs");
  /* END CSTYLED */