xref: /illumos-gate/usr/src/uts/common/fs/zfs/vdev.c (revision 4e93fb0f6383eaac21897dcdae56b87118131e4d)

/*
 * 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 http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

#include <sys/zfs_context.h>
#include <sys/fm/fs/zfs.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/vdev_impl.h>
#include <sys/uberblock_impl.h>
#include <sys/metaslab.h>
#include <sys/metaslab_impl.h>
#include <sys/space_map.h>
#include <sys/zio.h>
#include <sys/zap.h>
#include <sys/fs/zfs.h>

/*
 * Virtual device management.
 */

static vdev_ops_t *vdev_ops_table[] = {
	&vdev_root_ops,
	&vdev_raidz_ops,
	&vdev_mirror_ops,
	&vdev_replacing_ops,
	&vdev_spare_ops,
	&vdev_disk_ops,
	&vdev_file_ops,
	&vdev_missing_ops,
	NULL
};

/*
 * Given a vdev type, return the appropriate ops vector.
 */
static vdev_ops_t *
vdev_getops(const char *type)
{
	vdev_ops_t *ops, **opspp;

	for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
		if (strcmp(ops->vdev_op_type, type) == 0)
			break;

	return (ops);
}

/*
 * 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;
	uint64_t c;

	for (c = 0; c < vd->vdev_children; c++) {
		csize = vdev_psize_to_asize(vd->vdev_child[c], psize);
		asize = MAX(asize, csize);
	}

	return (asize);
}

/*
 * Get the replaceable or attachable device size.
 * If the parent is a mirror or raidz, the replaceable size is the minimum
 * psize of all its children. For the rest, just return our own psize.
 *
 * e.g.
 *			psize	rsize
 * root			-	-
 *	mirror/raidz	-	-
 *	    disk1	20g	20g
 *	    disk2 	40g	20g
 *	disk3 		80g	80g
 */
uint64_t
vdev_get_rsize(vdev_t *vd)
{
	vdev_t *pvd, *cvd;
	uint64_t c, rsize;

	pvd = vd->vdev_parent;

	/*
	 * If our parent is NULL or the root, just return our own psize.
	 */
	if (pvd == NULL || pvd->vdev_parent == NULL)
		return (vd->vdev_psize);

	rsize = 0;

	for (c = 0; c < pvd->vdev_children; c++) {
		cvd = pvd->vdev_child[c];
		rsize = MIN(rsize - 1, cvd->vdev_psize - 1) + 1;
	}

	return (rsize);
}

vdev_t *
vdev_lookup_top(spa_t *spa, uint64_t vdev)
{
	vdev_t *rvd = spa->spa_root_vdev;

	if (vdev < rvd->vdev_children)
		return (rvd->vdev_child[vdev]);

	return (NULL);
}

vdev_t *
vdev_lookup_by_guid(vdev_t *vd, uint64_t guid)
{
	int c;
	vdev_t *mvd;

	if (vd->vdev_guid == guid)
		return (vd);

	for (c = 0; c < vd->vdev_children; c++)
		if ((mvd = vdev_lookup_by_guid(vd->vdev_child[c], guid)) !=
		    NULL)
			return (mvd);

	return (NULL);
}

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, RW_WRITER));
	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_zalloc(newsize, KM_SLEEP);
	if (pvd->vdev_child != NULL) {
		bcopy(pvd->vdev_child, newchild, 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;
}

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;
	}

	/*
	 * 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, c;

	ASSERT(spa_config_held(pvd->vdev_spa, RW_WRITER));

	for (c = newc = 0; c < oldc; c++)
		if (pvd->vdev_child[c])
			newc++;

	newchild = kmem_alloc(newc * sizeof (vdev_t *), KM_SLEEP);

	for (c = newc = 0; c < oldc; c++) {
		if ((cvd = pvd->vdev_child[c]) != NULL) {
			newchild[newc] = cvd;
			cvd->vdev_id = newc++;
		}
	}

	kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));
	pvd->vdev_child = newchild;
	pvd->vdev_children = newc;
}

/*
 * Allocate and minimally initialize a vdev_t.
 */
static vdev_t *
vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
{
	vdev_t *vd;

	vd = kmem_zalloc(sizeof (vdev_t), KM_SLEEP);

	if (spa->spa_root_vdev == NULL) {
		ASSERT(ops == &vdev_root_ops);
		spa->spa_root_vdev = vd;
	}

	if (guid == 0) {
		if (spa->spa_root_vdev == vd) {
			/*
			 * The root vdev's guid will also be the pool guid,
			 * which must be unique among all pools.
			 */
			while (guid == 0 || spa_guid_exists(guid, 0))
				guid = spa_get_random(-1ULL);
		} else {
			/*
			 * Any other vdev's guid must be unique within the pool.
			 */
			while (guid == 0 ||
			    spa_guid_exists(spa_guid(spa), guid))
				guid = spa_get_random(-1ULL);
		}
		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;

	mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_DEFAULT, NULL);
	mutex_init(&vd->vdev_stat_lock, NULL, MUTEX_DEFAULT, NULL);
	space_map_create(&vd->vdev_dtl_map, 0, -1ULL, 0, &vd->vdev_dtl_lock);
	space_map_create(&vd->vdev_dtl_scrub, 0, -1ULL, 0, &vd->vdev_dtl_lock);
	txg_list_create(&vd->vdev_ms_list,
	    offsetof(struct metaslab, ms_txg_node));
	txg_list_create(&vd->vdev_dtl_list,
	    offsetof(struct vdev, vdev_dtl_node));
	vd->vdev_stat.vs_timestamp = gethrtime();

	return (vd);
}

/*
 * Free a vdev_t that has been removed from service.
 */
static void
vdev_free_common(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	if (vd->vdev_path)
		spa_strfree(vd->vdev_path);
	if (vd->vdev_devid)
		spa_strfree(vd->vdev_devid);

	if (vd->vdev_isspare)
		spa_spare_remove(vd);

	txg_list_destroy(&vd->vdev_ms_list);
	txg_list_destroy(&vd->vdev_dtl_list);
	mutex_enter(&vd->vdev_dtl_lock);
	space_map_unload(&vd->vdev_dtl_map);
	space_map_destroy(&vd->vdev_dtl_map);
	space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
	space_map_destroy(&vd->vdev_dtl_scrub);
	mutex_exit(&vd->vdev_dtl_lock);
	mutex_destroy(&vd->vdev_dtl_lock);
	mutex_destroy(&vd->vdev_stat_lock);

	if (vd == spa->spa_root_vdev)
		spa->spa_root_vdev = NULL;

	kmem_free(vd, sizeof (vdev_t));
}

/*
 * 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;
	vdev_t *vd;

	ASSERT(spa_config_held(spa, RW_WRITER));

	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0)
		return (EINVAL);

	if ((ops = vdev_getops(type)) == NULL)
		return (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 (EINVAL);

		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
			return (EINVAL);
	} else if (alloctype == VDEV_ALLOC_SPARE) {
		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
			return (EINVAL);
	}

	/*
	 * The first allocated vdev must be of type 'root'.
	 */
	if (ops != &vdev_root_ops && spa->spa_root_vdev == NULL)
		return (EINVAL);

	vd = vdev_alloc_common(spa, id, guid, ops);

	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &vd->vdev_path) == 0)
		vd->vdev_path = spa_strdup(vd->vdev_path);
	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_DEVID, &vd->vdev_devid) == 0)
		vd->vdev_devid = spa_strdup(vd->vdev_devid);

	/*
	 * Set the nparity propery for RAID-Z vdevs.
	 */
	if (ops == &vdev_raidz_ops) {
		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NPARITY,
		    &vd->vdev_nparity) == 0) {
			/*
			 * Currently, we can only support 2 parity devices.
			 */
			if (vd->vdev_nparity > 2)
				return (EINVAL);
			/*
			 * Older versions can only support 1 parity device.
			 */
			if (vd->vdev_nparity == 2 &&
			    spa_version(spa) < ZFS_VERSION_RAID6)
				return (ENOTSUP);

		} else {
			/*
			 * We require the parity to be specified for SPAs that
			 * support multiple parity levels.
			 */
			if (spa_version(spa) >= ZFS_VERSION_RAID6)
				return (EINVAL);

			/*
			 * Otherwise, we default to 1 parity device for RAID-Z.
			 */
			vd->vdev_nparity = 1;
		}
	} else {
		vd->vdev_nparity = 0;
	}

	/*
	 * 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;

	/*
	 * 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);

	/*
	 * If we're a top-level vdev, try to load the allocation parameters.
	 */
	if (parent && !parent->vdev_parent && alloctype == VDEV_ALLOC_LOAD) {
		(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);
	}

	/*
	 * If we're a leaf vdev, try to load the DTL object and offline state.
	 */
	if (vd->vdev_ops->vdev_op_leaf && alloctype == VDEV_ALLOC_LOAD) {
		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DTL,
		    &vd->vdev_dtl.smo_object);
		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE,
		    &vd->vdev_offline);
	}

	/*
	 * Add ourselves to the parent's list of children.
	 */
	vdev_add_child(parent, vd);

	*vdp = vd;

	return (0);
}

void
vdev_free(vdev_t *vd)
{
	int c;

	/*
	 * 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_dirty_node));

	/*
	 * Free all children.
	 */
	for (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);

	/*
	 * Discard allocation state.
	 */
	if (vd == vd->vdev_top)
		vdev_metaslab_fini(vd);

	ASSERT3U(vd->vdev_stat.vs_space, ==, 0);
	ASSERT3U(vd->vdev_stat.vs_dspace, ==, 0);
	ASSERT3U(vd->vdev_stat.vs_alloc, ==, 0);

	/*
	 * Remove this vdev from its parent's child list.
	 */
	vdev_remove_child(vd->vdev_parent, vd);

	ASSERT(vd->vdev_parent == NULL);

	vdev_free_common(vd);
}

/*
 * 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_ms_array = svd->vdev_ms_array;
	tvd->vdev_ms_shift = svd->vdev_ms_shift;
	tvd->vdev_ms_count = svd->vdev_ms_count;

	svd->vdev_ms_array = 0;
	svd->vdev_ms_shift = 0;
	svd->vdev_ms_count = 0;

	tvd->vdev_mg = svd->vdev_mg;
	tvd->vdev_ms = svd->vdev_ms;

	svd->vdev_mg = NULL;
	svd->vdev_ms = NULL;

	if (tvd->vdev_mg != NULL)
		tvd->vdev_mg->mg_vd = tvd;

	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;

	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_dirty_node)) {
		vdev_config_clean(svd);
		vdev_config_dirty(tvd);
	}

	tvd->vdev_reopen_wanted = svd->vdev_reopen_wanted;
	svd->vdev_reopen_wanted = 0;

	tvd->vdev_deflate_ratio = svd->vdev_deflate_ratio;
	svd->vdev_deflate_ratio = 0;
}

static void
vdev_top_update(vdev_t *tvd, vdev_t *vd)
{
	int c;

	if (vd == NULL)
		return;

	vd->vdev_top = tvd;

	for (c = 0; c < vd->vdev_children; c++)
		vdev_top_update(tvd, vd->vdev_child[c]);
}

/*
 * Add a mirror/replacing vdev above an existing vdev.
 */
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, RW_WRITER));

	mvd = vdev_alloc_common(spa, cvd->vdev_id, 0, ops);

	mvd->vdev_asize = cvd->vdev_asize;
	mvd->vdev_ashift = cvd->vdev_ashift;
	mvd->vdev_state = cvd->vdev_state;

	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, RW_WRITER));

	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;

	vdev_remove_child(mvd, cvd);
	vdev_remove_child(pvd, mvd);
	cvd->vdev_id = mvd->vdev_id;
	vdev_add_child(pvd, cvd);
	/*
	 * If we created a new toplevel vdev, then we need to change the child's
	 * vdev GUID to match the old toplevel vdev.  Otherwise, we could have
	 * detached an offline device, and when we go to import the pool we'll
	 * think we have two toplevel vdevs, instead of a different version of
	 * the same toplevel vdev.
	 */
	if (cvd->vdev_top == cvd) {
		pvd->vdev_guid_sum -= cvd->vdev_guid;
		cvd->vdev_guid_sum -= cvd->vdev_guid;
		cvd->vdev_guid = mvd->vdev_guid;
		cvd->vdev_guid_sum += mvd->vdev_guid;
		pvd->vdev_guid_sum += cvd->vdev_guid;
	}
	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);
}

int
vdev_metaslab_init(vdev_t *vd, uint64_t txg)
{
	spa_t *spa = vd->vdev_spa;
	objset_t *mos = spa->spa_meta_objset;
	metaslab_class_t *mc = spa_metaslab_class_select(spa);
	uint64_t m;
	uint64_t oldc = vd->vdev_ms_count;
	uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
	metaslab_t **mspp;
	int error;

	if (vd->vdev_ms_shift == 0)	/* not being allocated from yet */
		return (0);

	dprintf("%s oldc %llu newc %llu\n", vdev_description(vd), oldc, newc);

	ASSERT(oldc <= newc);

	if (vd->vdev_mg == NULL)
		vd->vdev_mg = metaslab_group_create(mc, vd);

	mspp = kmem_zalloc(newc * sizeof (*mspp), KM_SLEEP);

	if (oldc != 0) {
		bcopy(vd->vdev_ms, mspp, oldc * sizeof (*mspp));
		kmem_free(vd->vdev_ms, oldc * sizeof (*mspp));
	}

	vd->vdev_ms = mspp;
	vd->vdev_ms_count = newc;

	for (m = oldc; m < newc; m++) {
		space_map_obj_t smo = { 0, 0, 0 };
		if (txg == 0) {
			uint64_t object = 0;
			error = dmu_read(mos, vd->vdev_ms_array,
			    m * sizeof (uint64_t), sizeof (uint64_t), &object);
			if (error)
				return (error);
			if (object != 0) {
				dmu_buf_t *db;
				error = dmu_bonus_hold(mos, object, FTAG, &db);
				if (error)
					return (error);
				ASSERT3U(db->db_size, ==, sizeof (smo));
				bcopy(db->db_data, &smo, db->db_size);
				ASSERT3U(smo.smo_object, ==, object);
				dmu_buf_rele(db, FTAG);
			}
		}
		vd->vdev_ms[m] = metaslab_init(vd->vdev_mg, &smo,
		    m << vd->vdev_ms_shift, 1ULL << vd->vdev_ms_shift, txg);
	}

	return (0);
}

void
vdev_metaslab_fini(vdev_t *vd)
{
	uint64_t m;
	uint64_t count = vd->vdev_ms_count;

	if (vd->vdev_ms != NULL) {
		for (m = 0; m < count; m++)
			if (vd->vdev_ms[m] != NULL)
				metaslab_fini(vd->vdev_ms[m]);
		kmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
		vd->vdev_ms = NULL;
	}
}

/*
 * Prepare a virtual device for access.
 */
int
vdev_open(vdev_t *vd)
{
	int error;
	int c;
	uint64_t osize = 0;
	uint64_t asize, psize;
	uint64_t ashift = 0;

	ASSERT(vd->vdev_state == VDEV_STATE_CLOSED ||
	    vd->vdev_state == VDEV_STATE_CANT_OPEN ||
	    vd->vdev_state == VDEV_STATE_OFFLINE);

	if (vd->vdev_fault_mode == VDEV_FAULT_COUNT)
		vd->vdev_fault_arg >>= 1;
	else
		vd->vdev_fault_mode = VDEV_FAULT_NONE;

	vd->vdev_stat.vs_aux = VDEV_AUX_NONE;

	if (vd->vdev_ops->vdev_op_leaf) {
		vdev_cache_init(vd);
		vdev_queue_init(vd);
		vd->vdev_cache_active = B_TRUE;
	}

	if (vd->vdev_offline) {
		ASSERT(vd->vdev_children == 0);
		vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE, VDEV_AUX_NONE);
		return (ENXIO);
	}

	error = vd->vdev_ops->vdev_op_open(vd, &osize, &ashift);

	if (zio_injection_enabled && error == 0)
		error = zio_handle_device_injection(vd, ENXIO);

	dprintf("%s = %d, osize %llu, state = %d\n",
	    vdev_description(vd), error, osize, vd->vdev_state);

	if (error) {
		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
		    vd->vdev_stat.vs_aux);
		return (error);
	}

	vd->vdev_state = VDEV_STATE_HEALTHY;

	for (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));

	if (vd->vdev_children == 0) {
		if (osize < SPA_MINDEVSIZE) {
			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_TOO_SMALL);
			return (EOVERFLOW);
		}
		psize = osize;
		asize = 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 (EOVERFLOW);
		}
		psize = 0;
		asize = osize;
	}

	vd->vdev_psize = psize;

	if (vd->vdev_asize == 0) {
		/*
		 * This is the first-ever open, so use the computed values.
		 * For testing purposes, a higher ashift can be requested.
		 */
		vd->vdev_asize = asize;
		vd->vdev_ashift = MAX(ashift, vd->vdev_ashift);
	} else {
		/*
		 * Make sure the alignment requirement hasn't increased.
		 */
		if (ashift > vd->vdev_top->vdev_ashift) {
			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_BAD_LABEL);
			return (EINVAL);
		}

		/*
		 * Make sure the device hasn't shrunk.
		 */
		if (asize < vd->vdev_asize) {
			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_BAD_LABEL);
			return (EINVAL);
		}

		/*
		 * If all children are healthy and the asize has increased,
		 * then we've experienced dynamic LUN growth.
		 */
		if (vd->vdev_state == VDEV_STATE_HEALTHY &&
		    asize > vd->vdev_asize) {
			vd->vdev_asize = asize;
		}
	}

	/*
	 * If this is a top-level vdev, compute the raidz-deflation
	 * ratio.  Note, we hard-code in 128k (1<<17) because it is the
	 * current "typical" blocksize.  Even if SPA_MAXBLOCKSIZE
	 * changes, this algorithm must never change, or we will
	 * inconsistently account for existing bp's.
	 */
	if (vd->vdev_top == vd) {
		vd->vdev_deflate_ratio = (1<<17) /
		    (vdev_psize_to_asize(vd, 1<<17) >> SPA_MINBLOCKSHIFT);
	}

	/*
	 * This allows the ZFS DE to close cases appropriately.  If a device
	 * goes away and later returns, we want to close the associated case.
	 * But it's not enough to simply post this only when a device goes from
	 * CANT_OPEN -> HEALTHY.  If we reboot the system and the device is
	 * back, we also need to close the case (otherwise we will try to replay
	 * it).  So we have to post this notifier every time.  Since this only
	 * occurs during pool open or error recovery, this should not be an
	 * issue.
	 */
	zfs_post_ok(vd->vdev_spa, vd);

	return (0);
}

/*
 * 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, and so that vdev_reopen()
 * won't succeed if the device has been changed underneath.
 *
 * 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;
	int c;
	nvlist_t *label;
	uint64_t guid;
	uint64_t state;

	for (c = 0; c < vd->vdev_children; c++)
		if (vdev_validate(vd->vdev_child[c]) != 0)
			return (-1);

	/*
	 * 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_is_dead(vd)) {

		if ((label = vdev_label_read_config(vd)) == NULL) {
			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_BAD_LABEL);
			return (0);
		}

		if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
		    &guid) != 0 || guid != spa_guid(spa)) {
			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_CORRUPT_DATA);
			nvlist_free(label);
			return (0);
		}

		if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID,
		    &guid) != 0 || guid != vd->vdev_guid) {
			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
			    VDEV_AUX_CORRUPT_DATA);
			nvlist_free(label);
			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);
			return (0);
		}

		nvlist_free(label);

		if (spa->spa_load_state == SPA_LOAD_OPEN &&
		    state != POOL_STATE_ACTIVE)
			return (-1);
	}

	/*
	 * 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);
}

/*
 * Close a virtual device.
 */
void
vdev_close(vdev_t *vd)
{
	vd->vdev_ops->vdev_op_close(vd);

	if (vd->vdev_cache_active) {
		vdev_cache_fini(vd);
		vdev_queue_fini(vd);
		vd->vdev_cache_active = B_FALSE;
	}

	/*
	 * 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_reopen(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	ASSERT(spa_config_held(spa, RW_WRITER));

	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().
	 *
	 * The downside to this is that if the user is simply experimenting by
	 * overwriting an entire disk, we'll fault the device rather than
	 * demonstrate self-healing capabilities.  On the other hand, with
	 * proper FMA integration, the series of errors we'd see from the device
	 * would result in a faulted device anyway.  Given that this doesn't
	 * model any real-world corruption, it's better to catch this here and
	 * correctly identify that the device has either changed beneath us, or
	 * is corrupted beyond recognition.
	 */
	(void) vdev_validate(vd);

	/*
	 * Reassess root vdev's health.
	 */
	vdev_propagate_state(spa->spa_root_vdev);
}

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 : ENXIO);
	}

	/*
	 * Recursively initialize all labels.
	 */
	if ((error = vdev_label_init(vd, txg, isreplacing ?
	    VDEV_LABEL_REPLACE : VDEV_LABEL_CREATE)) != 0) {
		vdev_close(vd);
		return (error);
	}

	return (0);
}

/*
 * The is the latter half of vdev_create().  It is distinct because it
 * involves initiating transactions in order to do metaslab creation.
 * For creation, we want to try to create all vdevs at once and then undo it
 * if anything fails; this is much harder if we have pending transactions.
 */
void
vdev_init(vdev_t *vd, uint64_t txg)
{
	/*
	 * Aim for roughly 200 metaslabs per vdev.
	 */
	vd->vdev_ms_shift = highbit(vd->vdev_asize / 200);
	vd->vdev_ms_shift = MAX(vd->vdev_ms_shift, SPA_MAXBLOCKSHIFT);

	/*
	 * Initialize the vdev's metaslabs.  This can't fail because
	 * there's nothing to read when creating all new metaslabs.
	 */
	VERIFY(vdev_metaslab_init(vd, txg) == 0);
}

void
vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg)
{
	ASSERT(vd == vd->vdev_top);
	ASSERT(ISP2(flags));

	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_dtl_dirty(space_map_t *sm, uint64_t txg, uint64_t size)
{
	mutex_enter(sm->sm_lock);
	if (!space_map_contains(sm, txg, size))
		space_map_add(sm, txg, size);
	mutex_exit(sm->sm_lock);
}

int
vdev_dtl_contains(space_map_t *sm, uint64_t txg, uint64_t size)
{
	int dirty;

	/*
	 * Quick test without the lock -- covers the common case that
	 * there are no dirty time segments.
	 */
	if (sm->sm_space == 0)
		return (0);

	mutex_enter(sm->sm_lock);
	dirty = space_map_contains(sm, txg, size);
	mutex_exit(sm->sm_lock);

	return (dirty);
}

/*
 * Reassess DTLs after a config change or scrub completion.
 */
void
vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg, int scrub_done)
{
	spa_t *spa = vd->vdev_spa;
	int c;

	ASSERT(spa_config_held(spa, RW_WRITER));

	if (vd->vdev_children == 0) {
		mutex_enter(&vd->vdev_dtl_lock);
		/*
		 * We're successfully scrubbed everything up to scrub_txg.
		 * Therefore, excise all old DTLs up to that point, then
		 * fold in the DTLs for everything we couldn't scrub.
		 */
		if (scrub_txg != 0) {
			space_map_excise(&vd->vdev_dtl_map, 0, scrub_txg);
			space_map_union(&vd->vdev_dtl_map, &vd->vdev_dtl_scrub);
		}
		if (scrub_done)
			space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
		mutex_exit(&vd->vdev_dtl_lock);
		if (txg != 0)
			vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
		return;
	}

	/*
	 * Make sure the DTLs are always correct under the scrub lock.
	 */
	if (vd == spa->spa_root_vdev)
		mutex_enter(&spa->spa_scrub_lock);

	mutex_enter(&vd->vdev_dtl_lock);
	space_map_vacate(&vd->vdev_dtl_map, NULL, NULL);
	space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
	mutex_exit(&vd->vdev_dtl_lock);

	for (c = 0; c < vd->vdev_children; c++) {
		vdev_t *cvd = vd->vdev_child[c];
		vdev_dtl_reassess(cvd, txg, scrub_txg, scrub_done);
		mutex_enter(&vd->vdev_dtl_lock);
		space_map_union(&vd->vdev_dtl_map, &cvd->vdev_dtl_map);
		space_map_union(&vd->vdev_dtl_scrub, &cvd->vdev_dtl_scrub);
		mutex_exit(&vd->vdev_dtl_lock);
	}

	if (vd == spa->spa_root_vdev)
		mutex_exit(&spa->spa_scrub_lock);
}

static int
vdev_dtl_load(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;
	space_map_obj_t *smo = &vd->vdev_dtl;
	objset_t *mos = spa->spa_meta_objset;
	dmu_buf_t *db;
	int error;

	ASSERT(vd->vdev_children == 0);

	if (smo->smo_object == 0)
		return (0);

	if ((error = dmu_bonus_hold(mos, smo->smo_object, FTAG, &db)) != 0)
		return (error);

	ASSERT3U(db->db_size, ==, sizeof (*smo));
	bcopy(db->db_data, smo, db->db_size);
	dmu_buf_rele(db, FTAG);

	mutex_enter(&vd->vdev_dtl_lock);
	error = space_map_load(&vd->vdev_dtl_map, NULL, SM_ALLOC, smo, mos);
	mutex_exit(&vd->vdev_dtl_lock);

	return (error);
}

void
vdev_dtl_sync(vdev_t *vd, uint64_t txg)
{
	spa_t *spa = vd->vdev_spa;
	space_map_obj_t *smo = &vd->vdev_dtl;
	space_map_t *sm = &vd->vdev_dtl_map;
	objset_t *mos = spa->spa_meta_objset;
	space_map_t smsync;
	kmutex_t smlock;
	dmu_buf_t *db;
	dmu_tx_t *tx;

	dprintf("%s in txg %llu pass %d\n",
	    vdev_description(vd), (u_longlong_t)txg, spa_sync_pass(spa));

	tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);

	if (vd->vdev_detached) {
		if (smo->smo_object != 0) {
			int err = dmu_object_free(mos, smo->smo_object, tx);
			ASSERT3U(err, ==, 0);
			smo->smo_object = 0;
		}
		dmu_tx_commit(tx);
		dprintf("detach %s committed in txg %llu\n",
		    vdev_description(vd), txg);
		return;
	}

	if (smo->smo_object == 0) {
		ASSERT(smo->smo_objsize == 0);
		ASSERT(smo->smo_alloc == 0);
		smo->smo_object = dmu_object_alloc(mos,
		    DMU_OT_SPACE_MAP, 1 << SPACE_MAP_BLOCKSHIFT,
		    DMU_OT_SPACE_MAP_HEADER, sizeof (*smo), tx);
		ASSERT(smo->smo_object != 0);
		vdev_config_dirty(vd->vdev_top);
	}

	mutex_init(&smlock, NULL, MUTEX_DEFAULT, NULL);

	space_map_create(&smsync, sm->sm_start, sm->sm_size, sm->sm_shift,
	    &smlock);

	mutex_enter(&smlock);

	mutex_enter(&vd->vdev_dtl_lock);
	space_map_walk(sm, space_map_add, &smsync);
	mutex_exit(&vd->vdev_dtl_lock);

	space_map_truncate(smo, mos, tx);
	space_map_sync(&smsync, SM_ALLOC, smo, mos, tx);

	space_map_destroy(&smsync);

	mutex_exit(&smlock);
	mutex_destroy(&smlock);

	VERIFY(0 == dmu_bonus_hold(mos, smo->smo_object, FTAG, &db));
	dmu_buf_will_dirty(db, tx);
	ASSERT3U(db->db_size, ==, sizeof (*smo));
	bcopy(smo, db->db_data, db->db_size);
	dmu_buf_rele(db, FTAG);

	dmu_tx_commit(tx);
}

void
vdev_load(vdev_t *vd)
{
	int c;

	/*
	 * Recursively load all children.
	 */
	for (c = 0; c < vd->vdev_children; c++)
		vdev_load(vd->vdev_child[c]);

	/*
	 * If this is a top-level vdev, initialize its metaslabs.
	 */
	if (vd == vd->vdev_top &&
	    (vd->vdev_ashift == 0 || vd->vdev_asize == 0 ||
	    vdev_metaslab_init(vd, 0) != 0))
		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
		    VDEV_AUX_CORRUPT_DATA);

	/*
	 * If this is a leaf vdev, load its DTL.
	 */
	if (vd->vdev_ops->vdev_op_leaf && vdev_dtl_load(vd) != 0)
		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
		    VDEV_AUX_CORRUPT_DATA);
}

/*
 * This special case of vdev_spare() is used for hot spares.  It's 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_spare(vdev_t *vd)
{
	nvlist_t *label;
	uint64_t guid, version;
	uint64_t state;

	if ((label = vdev_label_read_config(vd)) == 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 ||
	    version > ZFS_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);
	}

	spa_spare_add(vd);

	/*
	 * 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);
}

void
vdev_sync_done(vdev_t *vd, uint64_t txg)
{
	metaslab_t *msp;

	dprintf("%s txg %llu\n", vdev_description(vd), txg);

	while (msp = txg_list_remove(&vd->vdev_ms_list, TXG_CLEAN(txg)))
		metaslab_sync_done(msp, txg);
}

void
vdev_sync(vdev_t *vd, uint64_t txg)
{
	spa_t *spa = vd->vdev_spa;
	vdev_t *lvd;
	metaslab_t *msp;
	dmu_tx_t *tx;

	dprintf("%s txg %llu pass %d\n",
	    vdev_description(vd), (u_longlong_t)txg, spa_sync_pass(spa));

	if (vd->vdev_ms_array == 0 && vd->vdev_ms_shift != 0) {
		ASSERT(vd == vd->vdev_top);
		tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
		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);
		dmu_tx_commit(tx);
	}

	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);

	(void) txg_list_add(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg));
}

uint64_t
vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
{
	return (vd->vdev_ops->vdev_op_asize(vd, psize));
}

void
vdev_io_start(zio_t *zio)
{
	zio->io_vd->vdev_ops->vdev_op_io_start(zio);
}

void
vdev_io_done(zio_t *zio)
{
	zio->io_vd->vdev_ops->vdev_op_io_done(zio);
}

const char *
vdev_description(vdev_t *vd)
{
	if (vd == NULL || vd->vdev_ops == NULL)
		return ("<unknown>");

	if (vd->vdev_path != NULL)
		return (vd->vdev_path);

	if (vd->vdev_parent == NULL)
		return (spa_name(vd->vdev_spa));

	return (vd->vdev_ops->vdev_op_type);
}

int
vdev_online(spa_t *spa, uint64_t guid)
{
	vdev_t *rvd, *vd;
	uint64_t txg;

	txg = spa_vdev_enter(spa);

	rvd = spa->spa_root_vdev;

	if ((vd = vdev_lookup_by_guid(rvd, guid)) == NULL)
		return (spa_vdev_exit(spa, NULL, txg, ENODEV));

	if (!vd->vdev_ops->vdev_op_leaf)
		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));

	dprintf("ONLINE: %s\n", vdev_description(vd));

	vd->vdev_offline = B_FALSE;
	vd->vdev_tmpoffline = B_FALSE;
	vdev_reopen(vd->vdev_top);

	vdev_config_dirty(vd->vdev_top);

	(void) spa_vdev_exit(spa, NULL, txg, 0);

	VERIFY(spa_scrub(spa, POOL_SCRUB_RESILVER, B_TRUE) == 0);

	return (0);
}

int
vdev_offline(spa_t *spa, uint64_t guid, int istmp)
{
	vdev_t *rvd, *vd;
	uint64_t txg;

	txg = spa_vdev_enter(spa);

	rvd = spa->spa_root_vdev;

	if ((vd = vdev_lookup_by_guid(rvd, guid)) == NULL)
		return (spa_vdev_exit(spa, NULL, txg, ENODEV));

	if (!vd->vdev_ops->vdev_op_leaf)
		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));

	dprintf("OFFLINE: %s\n", vdev_description(vd));

	/*
	 * If the device isn't already offline, try to offline it.
	 */
	if (!vd->vdev_offline) {
		/*
		 * If this device's top-level vdev has a non-empty DTL,
		 * don't allow the device to be offlined.
		 *
		 * XXX -- make this more precise by allowing the offline
		 * as long as the remaining devices don't have any DTL holes.
		 */
		if (vd->vdev_top->vdev_dtl_map.sm_space != 0)
			return (spa_vdev_exit(spa, NULL, txg, EBUSY));

		/*
		 * Offline this device and reopen its top-level vdev.
		 * If this action results in the top-level vdev becoming
		 * unusable, undo it and fail the request.
		 */
		vd->vdev_offline = B_TRUE;
		vdev_reopen(vd->vdev_top);
		if (vdev_is_dead(vd->vdev_top)) {
			vd->vdev_offline = B_FALSE;
			vdev_reopen(vd->vdev_top);
			return (spa_vdev_exit(spa, NULL, txg, EBUSY));
		}
	}

	vd->vdev_tmpoffline = istmp;

	vdev_config_dirty(vd->vdev_top);

	return (spa_vdev_exit(spa, NULL, txg, 0));
}

/*
 * 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)
{
	int c;

	if (vd == NULL)
		vd = spa->spa_root_vdev;

	vd->vdev_stat.vs_read_errors = 0;
	vd->vdev_stat.vs_write_errors = 0;
	vd->vdev_stat.vs_checksum_errors = 0;

	for (c = 0; c < vd->vdev_children; c++)
		vdev_clear(spa, vd->vdev_child[c]);
}

int
vdev_is_dead(vdev_t *vd)
{
	return (vd->vdev_state <= VDEV_STATE_CANT_OPEN);
}

int
vdev_error_inject(vdev_t *vd, zio_t *zio)
{
	int error = 0;

	if (vd->vdev_fault_mode == VDEV_FAULT_NONE)
		return (0);

	if (((1ULL << zio->io_type) & vd->vdev_fault_mask) == 0)
		return (0);

	switch (vd->vdev_fault_mode) {
	case VDEV_FAULT_RANDOM:
		if (spa_get_random(vd->vdev_fault_arg) == 0)
			error = EIO;
		break;

	case VDEV_FAULT_COUNT:
		if ((int64_t)--vd->vdev_fault_arg <= 0)
			vd->vdev_fault_mode = VDEV_FAULT_NONE;
		error = EIO;
		break;
	}

	if (error != 0) {
		dprintf("returning %d for type %d on %s state %d offset %llx\n",
		    error, zio->io_type, vdev_description(vd),
		    vd->vdev_state, zio->io_offset);
	}

	return (error);
}

/*
 * Get statistics for the given vdev.
 */
void
vdev_get_stats(vdev_t *vd, vdev_stat_t *vs)
{
	vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
	int c, t;

	mutex_enter(&vd->vdev_stat_lock);
	bcopy(&vd->vdev_stat, vs, sizeof (*vs));
	vs->vs_timestamp = gethrtime() - vs->vs_timestamp;
	vs->vs_state = vd->vdev_state;
	vs->vs_rsize = vdev_get_rsize(vd);
	mutex_exit(&vd->vdev_stat_lock);

	/*
	 * 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 == rvd) {
		for (c = 0; c < rvd->vdev_children; c++) {
			vdev_t *cvd = rvd->vdev_child[c];
			vdev_stat_t *cvs = &cvd->vdev_stat;

			mutex_enter(&vd->vdev_stat_lock);
			for (t = 0; t < ZIO_TYPES; t++) {
				vs->vs_ops[t] += cvs->vs_ops[t];
				vs->vs_bytes[t] += cvs->vs_bytes[t];
			}
			vs->vs_read_errors += cvs->vs_read_errors;
			vs->vs_write_errors += cvs->vs_write_errors;
			vs->vs_checksum_errors += cvs->vs_checksum_errors;
			vs->vs_scrub_examined += cvs->vs_scrub_examined;
			vs->vs_scrub_errors += cvs->vs_scrub_errors;
			mutex_exit(&vd->vdev_stat_lock);
		}
	}
}

void
vdev_stat_update(zio_t *zio)
{
	vdev_t *vd = zio->io_vd;
	vdev_t *pvd;
	uint64_t txg = zio->io_txg;
	vdev_stat_t *vs = &vd->vdev_stat;
	zio_type_t type = zio->io_type;
	int flags = zio->io_flags;

	if (zio->io_error == 0) {
		if (!(flags & ZIO_FLAG_IO_BYPASS)) {
			mutex_enter(&vd->vdev_stat_lock);
			vs->vs_ops[type]++;
			vs->vs_bytes[type] += zio->io_size;
			mutex_exit(&vd->vdev_stat_lock);
		}
		if ((flags & ZIO_FLAG_IO_REPAIR) &&
		    zio->io_delegate_list == NULL) {
			mutex_enter(&vd->vdev_stat_lock);
			if (flags & ZIO_FLAG_SCRUB_THREAD)
				vs->vs_scrub_repaired += zio->io_size;
			else
				vs->vs_self_healed += zio->io_size;
			mutex_exit(&vd->vdev_stat_lock);
		}
		return;
	}

	if (flags & ZIO_FLAG_SPECULATIVE)
		return;

	if (!vdev_is_dead(vd)) {
		mutex_enter(&vd->vdev_stat_lock);
		if (type == ZIO_TYPE_READ) {
			if (zio->io_error == ECKSUM)
				vs->vs_checksum_errors++;
			else
				vs->vs_read_errors++;
		}
		if (type == ZIO_TYPE_WRITE)
			vs->vs_write_errors++;
		mutex_exit(&vd->vdev_stat_lock);
	}

	if (type == ZIO_TYPE_WRITE) {
		if (txg == 0 || vd->vdev_children != 0)
			return;
		if (flags & ZIO_FLAG_SCRUB_THREAD) {
			ASSERT(flags & ZIO_FLAG_IO_REPAIR);
			for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
				vdev_dtl_dirty(&pvd->vdev_dtl_scrub, txg, 1);
		}
		if (!(flags & ZIO_FLAG_IO_REPAIR)) {
			if (vdev_dtl_contains(&vd->vdev_dtl_map, txg, 1))
				return;
			vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
			for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
				vdev_dtl_dirty(&pvd->vdev_dtl_map, txg, 1);
		}
	}
}

void
vdev_scrub_stat_update(vdev_t *vd, pool_scrub_type_t type, boolean_t complete)
{
	int c;
	vdev_stat_t *vs = &vd->vdev_stat;

	for (c = 0; c < vd->vdev_children; c++)
		vdev_scrub_stat_update(vd->vdev_child[c], type, complete);

	mutex_enter(&vd->vdev_stat_lock);

	if (type == POOL_SCRUB_NONE) {
		/*
		 * Update completion and end time.  Leave everything else alone
		 * so we can report what happened during the previous scrub.
		 */
		vs->vs_scrub_complete = complete;
		vs->vs_scrub_end = gethrestime_sec();
	} else {
		vs->vs_scrub_type = type;
		vs->vs_scrub_complete = 0;
		vs->vs_scrub_examined = 0;
		vs->vs_scrub_repaired = 0;
		vs->vs_scrub_errors = 0;
		vs->vs_scrub_start = gethrestime_sec();
		vs->vs_scrub_end = 0;
	}

	mutex_exit(&vd->vdev_stat_lock);
}

/*
 * Update the in-core space usage stats for this vdev and the root vdev.
 */
void
vdev_space_update(vdev_t *vd, int64_t space_delta, int64_t alloc_delta)
{
	ASSERT(vd == vd->vdev_top);
	int64_t dspace_delta = space_delta;

	do {
		if (vd->vdev_ms_count) {
			/*
			 * If this is a top-level vdev, apply the
			 * inverse of its 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 childrens', thus not accurate
			 * enough for us.
			 */
			ASSERT((dspace_delta & (SPA_MINBLOCKSIZE-1)) == 0);
			dspace_delta = (dspace_delta >> SPA_MINBLOCKSHIFT) *
			    vd->vdev_deflate_ratio;
		}

		mutex_enter(&vd->vdev_stat_lock);
		vd->vdev_stat.vs_space += space_delta;
		vd->vdev_stat.vs_alloc += alloc_delta;
		vd->vdev_stat.vs_dspace += dspace_delta;
		mutex_exit(&vd->vdev_stat_lock);
	} while ((vd = vd->vdev_parent) != NULL);
}

/*
 * 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;

	/*
	 * The dirty list is protected by the config lock.  The caller must
	 * either hold the config lock as writer, or must be the sync thread
	 * (which holds the lock as reader).  There's only one sync thread,
	 * so this is sufficient to ensure mutual exclusion.
	 */
	ASSERT(spa_config_held(spa, RW_WRITER) ||
	    dsl_pool_sync_context(spa_get_dsl(spa)));

	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_dirty_node))
			list_insert_head(&spa->spa_dirty_list, vd);
	}
}

void
vdev_config_clean(vdev_t *vd)
{
	spa_t *spa = vd->vdev_spa;

	ASSERT(spa_config_held(spa, RW_WRITER) ||
	    dsl_pool_sync_context(spa_get_dsl(spa)));

	ASSERT(list_link_active(&vd->vdev_dirty_node));
	list_remove(&spa->spa_dirty_list, vd);
}

void
vdev_propagate_state(vdev_t *vd)
{
	vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
	int degraded = 0, faulted = 0;
	int corrupted = 0;
	int c;
	vdev_t *child;

	for (c = 0; c < vd->vdev_children; c++) {
		child = vd->vdev_child[c];
		if (child->vdev_state <= VDEV_STATE_CANT_OPEN)
			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 toplevel 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);
}

/*
 * 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;

	if (state == vd->vdev_state) {
		vd->vdev_stat.vs_aux = aux;
		return;
	}

	save_state = vd->vdev_state;

	vd->vdev_state = state;
	vd->vdev_stat.vs_aux = aux;

	if (state == VDEV_STATE_CANT_OPEN) {
		/*
		 * If we fail to open a vdev during an import, 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 (vd->vdev_spa->spa_load_state == SPA_LOAD_IMPORT &&
		    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 (vd->vdev_prevstate != state && !vd->vdev_not_present &&
		    vd != vd->vdev_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;
			default:
				class = FM_EREPORT_ZFS_DEVICE_UNKNOWN;
			}

			zfs_ereport_post(class, vd->vdev_spa,
			    vd, NULL, save_state, 0);
		}
	}

	if (isopen)
		return;

	if (vd->vdev_parent != NULL)
		vdev_propagate_state(vd->vdev_parent);
}