[mirror_zfs-debian.git] / lib / libzfs / libzfs_import.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 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 2015 Nexenta Systems, Inc. All rights reserved.
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
 * Copyright 2015 RackTop Systems.
 * Copyright (c) 2016, Intel Corporation.
 */

/*
 * Pool import support functions.
 *
 * To import a pool, we rely on reading the configuration information from the
 * ZFS label of each device.  If we successfully read the label, then we
 * organize the configuration information in the following hierarchy:
 *
 *      pool guid -> toplevel vdev guid -> label txg
 *
 * Duplicate entries matching this same tuple will be discarded.  Once we have
 * examined every device, we pick the best label txg config for each toplevel
 * vdev.  We then arrange these toplevel vdevs into a complete pool config, and
 * update any paths that have changed.  Finally, we attempt to import the pool
 * using our derived config, and record the results.
 */

#include <ctype.h>
#include <devid.h>
#include <dirent.h>
#include <errno.h>
#include <libintl.h>
#ifdef HAVE_LIBUDEV
#include <libudev.h>
#include <sched.h>
#endif
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/vtoc.h>
#include <sys/dktp/fdisk.h>
#include <sys/efi_partition.h>
#include <sys/vdev_impl.h>
#include <blkid/blkid.h>
#include "libzfs.h"
#include "libzfs_impl.h"
#include <libzfs.h>

/*
 * Intermediate structures used to gather configuration information.
 */
typedef struct config_entry {
        uint64_t                ce_txg;
        nvlist_t                *ce_config;
        struct config_entry     *ce_next;
} config_entry_t;

typedef struct vdev_entry {
        uint64_t                ve_guid;
        config_entry_t          *ve_configs;
        struct vdev_entry       *ve_next;
} vdev_entry_t;

typedef struct pool_entry {
        uint64_t                pe_guid;
        vdev_entry_t            *pe_vdevs;
        struct pool_entry       *pe_next;
} pool_entry_t;

typedef struct name_entry {
        char                    *ne_name;
        uint64_t                ne_guid;
        uint64_t                ne_order;
        uint64_t                ne_num_labels;
        struct name_entry       *ne_next;
} name_entry_t;

typedef struct pool_list {
        pool_entry_t            *pools;
        name_entry_t            *names;
} pool_list_t;

#define DEV_BYID_PATH   "/dev/disk/by-id/"

/*
 * Linux persistent device strings for vdev labels
 *
 * based on libudev for consistency with libudev disk add/remove events
 */
#ifdef HAVE_LIBUDEV

typedef struct vdev_dev_strs {
        char    vds_devid[128];
        char    vds_devphys[128];
} vdev_dev_strs_t;

/*
 * Obtain the persistent device id string (describes what)
 *
 * used by ZED vdev matching for auto-{online,expand,replace}
 */
int
zfs_device_get_devid(struct udev_device *dev, char *bufptr, size_t buflen)
{
        struct udev_list_entry *entry;
        const char *bus;
        char devbyid[MAXPATHLEN];

        /* The bus based by-id path is preferred */
        bus = udev_device_get_property_value(dev, "ID_BUS");

        if (bus == NULL) {
                const char *dm_uuid;

                /*
                 * For multipath nodes use the persistent uuid based identifier
                 *
                 * Example: /dev/disk/by-id/dm-uuid-mpath-35000c5006304de3f
                 */
                dm_uuid = udev_device_get_property_value(dev, "DM_UUID");
                if (dm_uuid != NULL) {
                        (void) snprintf(bufptr, buflen, "dm-uuid-%s", dm_uuid);
                        return (0);
                }
                return (ENODATA);
        }

        /*
         * locate the bus specific by-id link
         */
        (void) snprintf(devbyid, sizeof (devbyid), "%s%s-", DEV_BYID_PATH, bus);
        entry = udev_device_get_devlinks_list_entry(dev);
        while (entry != NULL) {
                const char *name;

                name = udev_list_entry_get_name(entry);
                if (strncmp(name, devbyid, strlen(devbyid)) == 0) {
                        name += strlen(DEV_BYID_PATH);
                        (void) strlcpy(bufptr, name, buflen);
                        return (0);
                }
                entry = udev_list_entry_get_next(entry);
        }

        return (ENODATA);
}

/*
 * Obtain the persistent physical location string (describes where)
 *
 * used by ZED vdev matching for auto-{online,expand,replace}
 */
int
zfs_device_get_physical(struct udev_device *dev, char *bufptr, size_t buflen)
{
        const char *physpath = NULL;

        /*
         * Normal disks use ID_PATH for their physical path.  Device mapper
         * devices are virtual and don't have a physical path.  For them we
         * use ID_VDEV instead, which is setup via the /etc/vdev_id.conf file.
         * ID_VDEV provides a persistent path to a virtual device.  If you
         * don't have vdev_id.conf setup, you cannot use multipath autoreplace.
         */
        if (!((physpath = udev_device_get_property_value(dev, "ID_PATH")) &&
            physpath[0])) {
                if (!((physpath =
                    udev_device_get_property_value(dev, "ID_VDEV")) &&
                    physpath[0])) {
                        return (ENODATA);
                }
        }

        (void) strlcpy(bufptr, physpath, buflen);

        return (0);
}

boolean_t
udev_is_mpath(struct udev_device *dev)
{
        return udev_device_get_property_value(dev, "DM_UUID") &&
            udev_device_get_property_value(dev, "MPATH_SBIN_PATH");
}

/*
 * A disk is considered a multipath whole disk when:
 *      DEVNAME key value has "dm-"
 *      DM_NAME key value has "mpath" prefix
 *      DM_UUID key exists
 *      ID_PART_TABLE_TYPE key does not exist or is not gpt
 */
static boolean_t
udev_mpath_whole_disk(struct udev_device *dev)
{
        const char *devname, *type, *uuid;

        devname = udev_device_get_property_value(dev, "DEVNAME");
        type = udev_device_get_property_value(dev, "ID_PART_TABLE_TYPE");
        uuid = udev_device_get_property_value(dev, "DM_UUID");

        if ((devname != NULL && strncmp(devname, "/dev/dm-", 8) == 0) &&
            ((type == NULL) || (strcmp(type, "gpt") != 0)) &&
            (uuid != NULL)) {
                return (B_TRUE);
        }

        return (B_FALSE);
}

/*
 * Check if a disk is effectively a multipath whole disk
 */
boolean_t
is_mpath_whole_disk(const char *path)
{
        struct udev *udev;
        struct udev_device *dev = NULL;
        char nodepath[MAXPATHLEN];
        char *sysname;
        boolean_t wholedisk = B_FALSE;

        if (realpath(path, nodepath) == NULL)
                return (B_FALSE);
        sysname = strrchr(nodepath, '/') + 1;
        if (strncmp(sysname, "dm-", 3) != 0)
                return (B_FALSE);
        if ((udev = udev_new()) == NULL)
                return (B_FALSE);
        if ((dev = udev_device_new_from_subsystem_sysname(udev, "block",
            sysname)) == NULL) {
                udev_device_unref(dev);
                return (B_FALSE);
        }

        wholedisk = udev_mpath_whole_disk(dev);

        udev_device_unref(dev);
        return (wholedisk);
}

static int
udev_device_is_ready(struct udev_device *dev)
{
#ifdef HAVE_LIBUDEV_UDEV_DEVICE_GET_IS_INITIALIZED
        return (udev_device_get_is_initialized(dev));
#else
        /* wait for DEVLINKS property to be initialized */
        return (udev_device_get_property_value(dev, "DEVLINKS") != NULL);
#endif
}

/*
 * Wait up to timeout_ms for udev to set up the device node.  The device is
 * considered ready when libudev determines it has been initialized, all of
 * the device links have been verified to exist, and it has been allowed to
 * settle.  At this point the device the device can be accessed reliably.
 * Depending on the complexity of the udev rules this process could take
 * several seconds.
 */
int
zpool_label_disk_wait(char *path, int timeout_ms)
{
        struct udev *udev;
        struct udev_device *dev = NULL;
        char nodepath[MAXPATHLEN];
        char *sysname = NULL;
        int ret = ENODEV;
        int settle_ms = 50;
        long sleep_ms = 10;
        hrtime_t start, settle;

        if ((udev = udev_new()) == NULL)
                return (ENXIO);

        start = gethrtime();
        settle = 0;

        do {
                if (sysname == NULL) {
                        if (realpath(path, nodepath) != NULL) {
                                sysname = strrchr(nodepath, '/') + 1;
                        } else {
                                (void) usleep(sleep_ms * MILLISEC);
                                continue;
                        }
                }

                dev = udev_device_new_from_subsystem_sysname(udev,
                    "block", sysname);
                if ((dev != NULL) && udev_device_is_ready(dev)) {
                        struct udev_list_entry *links, *link;

                        ret = 0;
                        links = udev_device_get_devlinks_list_entry(dev);

                        udev_list_entry_foreach(link, links) {
                                struct stat64 statbuf;
                                const char *name;

                                name = udev_list_entry_get_name(link);
                                errno = 0;
                                if (stat64(name, &statbuf) == 0 && errno == 0)
                                        continue;

                                settle = 0;
                                ret = ENODEV;
                                break;
                        }

                        if (ret == 0) {
                                if (settle == 0) {
                                        settle = gethrtime();
                                } else if (NSEC2MSEC(gethrtime() - settle) >=
                                    settle_ms) {
                                        udev_device_unref(dev);
                                        break;
                                }
                        }
                }

                udev_device_unref(dev);
                (void) usleep(sleep_ms * MILLISEC);

        } while (NSEC2MSEC(gethrtime() - start) < timeout_ms);

        udev_unref(udev);

        return (ret);
}


/*
 * Encode the persistent devices strings
 * used for the vdev disk label
 */
static int
encode_device_strings(const char *path, vdev_dev_strs_t *ds,
    boolean_t wholedisk)
{
        struct udev *udev;
        struct udev_device *dev = NULL;
        char nodepath[MAXPATHLEN];
        char *sysname;
        int ret = ENODEV;
        hrtime_t start;

        if ((udev = udev_new()) == NULL)
                return (ENXIO);

        /* resolve path to a runtime device node instance */
        if (realpath(path, nodepath) == NULL)
                goto no_dev;

        sysname = strrchr(nodepath, '/') + 1;

        /*
         * Wait up to 3 seconds for udev to set up the device node context
         */
        start = gethrtime();
        do {
                dev = udev_device_new_from_subsystem_sysname(udev, "block",
                    sysname);
                if (dev == NULL)
                        goto no_dev;
                if (udev_device_is_ready(dev))
                        break;  /* udev ready */

                udev_device_unref(dev);
                dev = NULL;

                if (NSEC2MSEC(gethrtime() - start) < 10)
                        (void) sched_yield();   /* yield/busy wait up to 10ms */
                else
                        (void) usleep(10 * MILLISEC);

        } while (NSEC2MSEC(gethrtime() - start) < (3 * MILLISEC));

        if (dev == NULL)
                goto no_dev;

        /*
         * Only whole disks require extra device strings
         */
        if (!wholedisk && !udev_mpath_whole_disk(dev))
                goto no_dev;

        ret = zfs_device_get_devid(dev, ds->vds_devid, sizeof (ds->vds_devid));
        if (ret != 0)
                goto no_dev_ref;

        /* physical location string (optional) */
        if (zfs_device_get_physical(dev, ds->vds_devphys,
            sizeof (ds->vds_devphys)) != 0) {
                ds->vds_devphys[0] = '\0'; /* empty string --> not available */
        }

no_dev_ref:
        udev_device_unref(dev);
no_dev:
        udev_unref(udev);

        return (ret);
}

/*
 * Update a leaf vdev's persistent device strings (Linux only)
 *
 * - only applies for a dedicated leaf vdev (aka whole disk)
 * - updated during pool create|add|attach|import
 * - used for matching device matching during auto-{online,expand,replace}
 * - stored in a leaf disk config label (i.e. alongside 'path' NVP)
 * - these strings are currently not used in kernel (i.e. for vdev_disk_open)
 *
 * single device node example:
 *      devid:          'scsi-MG03SCA300_350000494a8cb3d67-part1'
 *      phys_path:      'pci-0000:04:00.0-sas-0x50000394a8cb3d67-lun-0'
 *
 * multipath device node example:
 *      devid:          'dm-uuid-mpath-35000c5006304de3f'
 *
 * We also store the enclosure sysfs path for turning on enclosure LEDs
 * (if applicable):
 *      vdev_enc_sysfs_path: '/sys/class/enclosure/11:0:1:0/SLOT 4'
 */
void
update_vdev_config_dev_strs(nvlist_t *nv)
{
        vdev_dev_strs_t vds;
        char *env, *type, *path;
        uint64_t wholedisk = 0;
        char *upath, *spath;

        /*
         * For the benefit of legacy ZFS implementations, allow
         * for opting out of devid strings in the vdev label.
         *
         * example use:
         *      env ZFS_VDEV_DEVID_OPT_OUT=YES zpool import dozer
         *
         * explanation:
         * Older ZFS on Linux implementations had issues when attempting to
         * display pool config VDEV names if a "devid" NVP value is present
         * in the pool's config.
         *
         * For example, a pool that originated on illumos platform would
         * have a devid value in the config and "zpool status" would fail
         * when listing the config.
         *
         * A pool can be stripped of any "devid" values on import or
         * prevented from adding them on zpool create|add by setting
         * ZFS_VDEV_DEVID_OPT_OUT.
         */
        env = getenv("ZFS_VDEV_DEVID_OPT_OUT");
        if (env && (strtoul(env, NULL, 0) > 0 ||
            !strncasecmp(env, "YES", 3) || !strncasecmp(env, "ON", 2))) {
                (void) nvlist_remove_all(nv, ZPOOL_CONFIG_DEVID);
                (void) nvlist_remove_all(nv, ZPOOL_CONFIG_PHYS_PATH);
                return;
        }

        if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0 ||
            strcmp(type, VDEV_TYPE_DISK) != 0) {
                return;
        }
        if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &path) != 0)
                return;
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK, &wholedisk);

        /*
         * Update device string values in config nvlist
         */
        if (encode_device_strings(path, &vds, (boolean_t)wholedisk) == 0) {
                (void) nvlist_add_string(nv, ZPOOL_CONFIG_DEVID, vds.vds_devid);
                if (vds.vds_devphys[0] != '\0') {
                        (void) nvlist_add_string(nv, ZPOOL_CONFIG_PHYS_PATH,
                            vds.vds_devphys);
                }

                /* Add enclosure sysfs path (if disk is in an enclosure) */
                upath = zfs_get_underlying_path(path);
                spath = zfs_get_enclosure_sysfs_path(upath);
                if (spath)
                        nvlist_add_string(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH,
                            spath);
                else
                        nvlist_remove_all(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH);

                free(upath);
                free(spath);
        } else {
                /* clear out any stale entries */
                (void) nvlist_remove_all(nv, ZPOOL_CONFIG_DEVID);
                (void) nvlist_remove_all(nv, ZPOOL_CONFIG_PHYS_PATH);
                (void) nvlist_remove_all(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH);
        }
}
#else

boolean_t
is_mpath_whole_disk(const char *path)
{
        return (B_FALSE);
}

/*
 * Wait up to timeout_ms for udev to set up the device node.  The device is
 * considered ready when the provided path have been verified to exist and
 * it has been allowed to settle.  At this point the device the device can
 * be accessed reliably.  Depending on the complexity of the udev rules thisi
 * process could take several seconds.
 */
int
zpool_label_disk_wait(char *path, int timeout_ms)
{
        int settle_ms = 50;
        long sleep_ms = 10;
        hrtime_t start, settle;
        struct stat64 statbuf;

        start = gethrtime();
        settle = 0;

        do {
                errno = 0;
                if ((stat64(path, &statbuf) == 0) && (errno == 0)) {
                        if (settle == 0)
                                settle = gethrtime();
                        else if (NSEC2MSEC(gethrtime() - settle) >= settle_ms)
                                return (0);
                } else if (errno != ENOENT) {
                        return (errno);
                }

                usleep(sleep_ms * MILLISEC);
        } while (NSEC2MSEC(gethrtime() - start) < timeout_ms);

        return (ENODEV);
}

void
update_vdev_config_dev_strs(nvlist_t *nv)
{
}

#endif /* HAVE_LIBUDEV */

/*
 * Go through and fix up any path and/or devid information for the given vdev
 * configuration.
 */
static int
fix_paths(nvlist_t *nv, name_entry_t *names)
{
        nvlist_t **child;
        uint_t c, children;
        uint64_t guid;
        name_entry_t *ne, *best;
        char *path;

        if (nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
            &child, &children) == 0) {
                for (c = 0; c < children; c++)
                        if (fix_paths(child[c], names) != 0)
                                return (-1);
                return (0);
        }

        /*
         * This is a leaf (file or disk) vdev.  In either case, go through
         * the name list and see if we find a matching guid.  If so, replace
         * the path and see if we can calculate a new devid.
         *
         * There may be multiple names associated with a particular guid, in
         * which case we have overlapping partitions or multiple paths to the
         * same disk.  In this case we prefer to use the path name which
         * matches the ZPOOL_CONFIG_PATH.  If no matching entry is found we
         * use the lowest order device which corresponds to the first match
         * while traversing the ZPOOL_IMPORT_PATH search path.
         */
        verify(nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) == 0);
        if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &path) != 0)
                path = NULL;

        best = NULL;
        for (ne = names; ne != NULL; ne = ne->ne_next) {
                if (ne->ne_guid == guid) {
                        if (path == NULL) {
                                best = ne;
                                break;
                        }

                        if ((strlen(path) == strlen(ne->ne_name)) &&
                            strncmp(path, ne->ne_name, strlen(path)) == 0) {
                                best = ne;
                                break;
                        }

                        if (best == NULL) {
                                best = ne;
                                continue;
                        }

                        /* Prefer paths with move vdev labels. */
                        if (ne->ne_num_labels > best->ne_num_labels) {
                                best = ne;
                                continue;
                        }

                        /* Prefer paths earlier in the search order. */
                        if (ne->ne_num_labels == best->ne_num_labels &&
                            ne->ne_order < best->ne_order) {
                                best = ne;
                                continue;
                        }
                }
        }

        if (best == NULL)
                return (0);

        if (nvlist_add_string(nv, ZPOOL_CONFIG_PATH, best->ne_name) != 0)
                return (-1);

        /* Linux only - update ZPOOL_CONFIG_DEVID and ZPOOL_CONFIG_PHYS_PATH */
        update_vdev_config_dev_strs(nv);

        return (0);
}

/*
 * Add the given configuration to the list of known devices.
 */
static int
add_config(libzfs_handle_t *hdl, pool_list_t *pl, const char *path,
    int order, int num_labels, nvlist_t *config)
{
        uint64_t pool_guid, vdev_guid, top_guid, txg, state;
        pool_entry_t *pe;
        vdev_entry_t *ve;
        config_entry_t *ce;
        name_entry_t *ne;

        /*
         * If this is a hot spare not currently in use or level 2 cache
         * device, add it to the list of names to translate, but don't do
         * anything else.
         */
        if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_STATE,
            &state) == 0 &&
            (state == POOL_STATE_SPARE || state == POOL_STATE_L2CACHE) &&
            nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID, &vdev_guid) == 0) {
                if ((ne = zfs_alloc(hdl, sizeof (name_entry_t))) == NULL) {
                        nvlist_free(config);
                        return (-1);
                }

                if ((ne->ne_name = zfs_strdup(hdl, path)) == NULL) {
                        free(ne);
                        nvlist_free(config);
                        return (-1);
                }
                ne->ne_guid = vdev_guid;
                ne->ne_order = order;
                ne->ne_num_labels = num_labels;
                ne->ne_next = pl->names;
                pl->names = ne;
                nvlist_free(config);
                return (0);
        }

        /*
         * If we have a valid config but cannot read any of these fields, then
         * it means we have a half-initialized label.  In vdev_label_init()
         * we write a label with txg == 0 so that we can identify the device
         * in case the user refers to the same disk later on.  If we fail to
         * create the pool, we'll be left with a label in this state
         * which should not be considered part of a valid pool.
         */
        if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
            &pool_guid) != 0 ||
            nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID,
            &vdev_guid) != 0 ||
            nvlist_lookup_uint64(config, ZPOOL_CONFIG_TOP_GUID,
            &top_guid) != 0 ||
            nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG,
            &txg) != 0 || txg == 0) {
                nvlist_free(config);
                return (0);
        }

        /*
         * First, see if we know about this pool.  If not, then add it to the
         * list of known pools.
         */
        for (pe = pl->pools; pe != NULL; pe = pe->pe_next) {
                if (pe->pe_guid == pool_guid)
                        break;
        }

        if (pe == NULL) {
                if ((pe = zfs_alloc(hdl, sizeof (pool_entry_t))) == NULL) {
                        nvlist_free(config);
                        return (-1);
                }
                pe->pe_guid = pool_guid;
                pe->pe_next = pl->pools;
                pl->pools = pe;
        }

        /*
         * Second, see if we know about this toplevel vdev.  Add it if its
         * missing.
         */
        for (ve = pe->pe_vdevs; ve != NULL; ve = ve->ve_next) {
                if (ve->ve_guid == top_guid)
                        break;
        }

        if (ve == NULL) {
                if ((ve = zfs_alloc(hdl, sizeof (vdev_entry_t))) == NULL) {
                        nvlist_free(config);
                        return (-1);
                }
                ve->ve_guid = top_guid;
                ve->ve_next = pe->pe_vdevs;
                pe->pe_vdevs = ve;
        }

        /*
         * Third, see if we have a config with a matching transaction group.  If
         * so, then we do nothing.  Otherwise, add it to the list of known
         * configs.
         */
        for (ce = ve->ve_configs; ce != NULL; ce = ce->ce_next) {
                if (ce->ce_txg == txg)
                        break;
        }

        if (ce == NULL) {
                if ((ce = zfs_alloc(hdl, sizeof (config_entry_t))) == NULL) {
                        nvlist_free(config);
                        return (-1);
                }
                ce->ce_txg = txg;
                ce->ce_config = config;
                ce->ce_next = ve->ve_configs;
                ve->ve_configs = ce;
        } else {
                nvlist_free(config);
        }

        /*
         * At this point we've successfully added our config to the list of
         * known configs.  The last thing to do is add the vdev guid -> path
         * mappings so that we can fix up the configuration as necessary before
         * doing the import.
         */
        if ((ne = zfs_alloc(hdl, sizeof (name_entry_t))) == NULL)
                return (-1);

        if ((ne->ne_name = zfs_strdup(hdl, path)) == NULL) {
                free(ne);
                return (-1);
        }

        ne->ne_guid = vdev_guid;
        ne->ne_order = order;
        ne->ne_num_labels = num_labels;
        ne->ne_next = pl->names;
        pl->names = ne;

        return (0);
}

/*
 * Returns true if the named pool matches the given GUID.
 */
static int
pool_active(libzfs_handle_t *hdl, const char *name, uint64_t guid,
    boolean_t *isactive)
{
        zpool_handle_t *zhp;
        uint64_t theguid;

        if (zpool_open_silent(hdl, name, &zhp) != 0)
                return (-1);

        if (zhp == NULL) {
                *isactive = B_FALSE;
                return (0);
        }

        verify(nvlist_lookup_uint64(zhp->zpool_config, ZPOOL_CONFIG_POOL_GUID,
            &theguid) == 0);

        zpool_close(zhp);

        *isactive = (theguid == guid);
        return (0);
}

static nvlist_t *
refresh_config(libzfs_handle_t *hdl, nvlist_t *config)
{
        nvlist_t *nvl;
        zfs_cmd_t zc = {"\0"};
        int err, dstbuf_size;

        if (zcmd_write_conf_nvlist(hdl, &zc, config) != 0)
                return (NULL);

        dstbuf_size = MAX(CONFIG_BUF_MINSIZE, zc.zc_nvlist_conf_size * 4);

        if (zcmd_alloc_dst_nvlist(hdl, &zc, dstbuf_size) != 0) {
                zcmd_free_nvlists(&zc);
                return (NULL);
        }

        while ((err = ioctl(hdl->libzfs_fd, ZFS_IOC_POOL_TRYIMPORT,
            &zc)) != 0 && errno == ENOMEM) {
                if (zcmd_expand_dst_nvlist(hdl, &zc) != 0) {
                        zcmd_free_nvlists(&zc);
                        return (NULL);
                }
        }

        if (err) {
                zcmd_free_nvlists(&zc);
                return (NULL);
        }

        if (zcmd_read_dst_nvlist(hdl, &zc, &nvl) != 0) {
                zcmd_free_nvlists(&zc);
                return (NULL);
        }

        zcmd_free_nvlists(&zc);
        return (nvl);
}

/*
 * Determine if the vdev id is a hole in the namespace.
 */
boolean_t
vdev_is_hole(uint64_t *hole_array, uint_t holes, uint_t id)
{
        int c;

        for (c = 0; c < holes; c++) {

                /* Top-level is a hole */
                if (hole_array[c] == id)
                        return (B_TRUE);
        }
        return (B_FALSE);
}

/*
 * Convert our list of pools into the definitive set of configurations.  We
 * start by picking the best config for each toplevel vdev.  Once that's done,
 * we assemble the toplevel vdevs into a full config for the pool.  We make a
 * pass to fix up any incorrect paths, and then add it to the main list to
 * return to the user.
 */
static nvlist_t *
get_configs(libzfs_handle_t *hdl, pool_list_t *pl, boolean_t active_ok)
{
        pool_entry_t *pe;
        vdev_entry_t *ve;
        config_entry_t *ce;
        nvlist_t *ret = NULL, *config = NULL, *tmp = NULL, *nvtop, *nvroot;
        nvlist_t **spares, **l2cache;
        uint_t i, nspares, nl2cache;
        boolean_t config_seen;
        uint64_t best_txg;
        char *name, *hostname = NULL;
        uint64_t guid;
        uint_t children = 0;
        nvlist_t **child = NULL;
        uint_t holes;
        uint64_t *hole_array, max_id;
        uint_t c;
        boolean_t isactive;
        uint64_t hostid;
        nvlist_t *nvl;
        boolean_t valid_top_config = B_FALSE;

        if (nvlist_alloc(&ret, 0, 0) != 0)
                goto nomem;

        for (pe = pl->pools; pe != NULL; pe = pe->pe_next) {
                uint64_t id, max_txg = 0;

                if (nvlist_alloc(&config, NV_UNIQUE_NAME, 0) != 0)
                        goto nomem;
                config_seen = B_FALSE;

                /*
                 * Iterate over all toplevel vdevs.  Grab the pool configuration
                 * from the first one we find, and then go through the rest and
                 * add them as necessary to the 'vdevs' member of the config.
                 */
                for (ve = pe->pe_vdevs; ve != NULL; ve = ve->ve_next) {

                        /*
                         * Determine the best configuration for this vdev by
                         * selecting the config with the latest transaction
                         * group.
                         */
                        best_txg = 0;
                        for (ce = ve->ve_configs; ce != NULL;
                            ce = ce->ce_next) {

                                if (ce->ce_txg > best_txg) {
                                        tmp = ce->ce_config;
                                        best_txg = ce->ce_txg;
                                }
                        }

                        /*
                         * We rely on the fact that the max txg for the
                         * pool will contain the most up-to-date information
                         * about the valid top-levels in the vdev namespace.
                         */
                        if (best_txg > max_txg) {
                                (void) nvlist_remove(config,
                                    ZPOOL_CONFIG_VDEV_CHILDREN,
                                    DATA_TYPE_UINT64);
                                (void) nvlist_remove(config,
                                    ZPOOL_CONFIG_HOLE_ARRAY,
                                    DATA_TYPE_UINT64_ARRAY);

                                max_txg = best_txg;
                                hole_array = NULL;
                                holes = 0;
                                max_id = 0;
                                valid_top_config = B_FALSE;

                                if (nvlist_lookup_uint64(tmp,
                                    ZPOOL_CONFIG_VDEV_CHILDREN, &max_id) == 0) {
                                        verify(nvlist_add_uint64(config,
                                            ZPOOL_CONFIG_VDEV_CHILDREN,
                                            max_id) == 0);
                                        valid_top_config = B_TRUE;
                                }

                                if (nvlist_lookup_uint64_array(tmp,
                                    ZPOOL_CONFIG_HOLE_ARRAY, &hole_array,
                                    &holes) == 0) {
                                        verify(nvlist_add_uint64_array(config,
                                            ZPOOL_CONFIG_HOLE_ARRAY,
                                            hole_array, holes) == 0);
                                }
                        }

                        if (!config_seen) {
                                /*
                                 * Copy the relevant pieces of data to the pool
                                 * configuration:
                                 *
                                 *      version
                                 *      pool guid
                                 *      name
                                 *      comment (if available)
                                 *      pool state
                                 *      hostid (if available)
                                 *      hostname (if available)
                                 */
                                uint64_t state, version;
                                char *comment = NULL;

                                version = fnvlist_lookup_uint64(tmp,
                                    ZPOOL_CONFIG_VERSION);
                                fnvlist_add_uint64(config,
                                    ZPOOL_CONFIG_VERSION, version);
                                guid = fnvlist_lookup_uint64(tmp,
                                    ZPOOL_CONFIG_POOL_GUID);
                                fnvlist_add_uint64(config,
                                    ZPOOL_CONFIG_POOL_GUID, guid);
                                name = fnvlist_lookup_string(tmp,
                                    ZPOOL_CONFIG_POOL_NAME);
                                fnvlist_add_string(config,
                                    ZPOOL_CONFIG_POOL_NAME, name);

                                if (nvlist_lookup_string(tmp,
                                    ZPOOL_CONFIG_COMMENT, &comment) == 0)
                                        fnvlist_add_string(config,
                                            ZPOOL_CONFIG_COMMENT, comment);

                                state = fnvlist_lookup_uint64(tmp,
                                    ZPOOL_CONFIG_POOL_STATE);
                                fnvlist_add_uint64(config,
                                    ZPOOL_CONFIG_POOL_STATE, state);

                                hostid = 0;
                                if (nvlist_lookup_uint64(tmp,
                                    ZPOOL_CONFIG_HOSTID, &hostid) == 0) {
                                        fnvlist_add_uint64(config,
                                            ZPOOL_CONFIG_HOSTID, hostid);
                                        hostname = fnvlist_lookup_string(tmp,
                                            ZPOOL_CONFIG_HOSTNAME);
                                        fnvlist_add_string(config,
                                            ZPOOL_CONFIG_HOSTNAME, hostname);
                                }

                                config_seen = B_TRUE;
                        }

                        /*
                         * Add this top-level vdev to the child array.
                         */
                        verify(nvlist_lookup_nvlist(tmp,
                            ZPOOL_CONFIG_VDEV_TREE, &nvtop) == 0);
                        verify(nvlist_lookup_uint64(nvtop, ZPOOL_CONFIG_ID,
                            &id) == 0);

                        if (id >= children) {
                                nvlist_t **newchild;

                                newchild = zfs_alloc(hdl, (id + 1) *
                                    sizeof (nvlist_t *));
                                if (newchild == NULL)
                                        goto nomem;

                                for (c = 0; c < children; c++)
                                        newchild[c] = child[c];

                                free(child);
                                child = newchild;
                                children = id + 1;
                        }
                        if (nvlist_dup(nvtop, &child[id], 0) != 0)
                                goto nomem;

                }

                /*
                 * If we have information about all the top-levels then
                 * clean up the nvlist which we've constructed. This
                 * means removing any extraneous devices that are
                 * beyond the valid range or adding devices to the end
                 * of our array which appear to be missing.
                 */
                if (valid_top_config) {
                        if (max_id < children) {
                                for (c = max_id; c < children; c++)
                                        nvlist_free(child[c]);
                                children = max_id;
                        } else if (max_id > children) {
                                nvlist_t **newchild;

                                newchild = zfs_alloc(hdl, (max_id) *
                                    sizeof (nvlist_t *));
                                if (newchild == NULL)
                                        goto nomem;

                                for (c = 0; c < children; c++)
                                        newchild[c] = child[c];

                                free(child);
                                child = newchild;
                                children = max_id;
                        }
                }

                verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
                    &guid) == 0);

                /*
                 * The vdev namespace may contain holes as a result of
                 * device removal. We must add them back into the vdev
                 * tree before we process any missing devices.
                 */
                if (holes > 0) {
                        ASSERT(valid_top_config);

                        for (c = 0; c < children; c++) {
                                nvlist_t *holey;

                                if (child[c] != NULL ||
                                    !vdev_is_hole(hole_array, holes, c))
                                        continue;

                                if (nvlist_alloc(&holey, NV_UNIQUE_NAME,
                                    0) != 0)
                                        goto nomem;

                                /*
                                 * Holes in the namespace are treated as
                                 * "hole" top-level vdevs and have a
                                 * special flag set on them.
                                 */
                                if (nvlist_add_string(holey,
                                    ZPOOL_CONFIG_TYPE,
                                    VDEV_TYPE_HOLE) != 0 ||
                                    nvlist_add_uint64(holey,
                                    ZPOOL_CONFIG_ID, c) != 0 ||
                                    nvlist_add_uint64(holey,
                                    ZPOOL_CONFIG_GUID, 0ULL) != 0) {
                                        nvlist_free(holey);
                                        goto nomem;
                                }
                                child[c] = holey;
                        }
                }

                /*
                 * Look for any missing top-level vdevs.  If this is the case,
                 * create a faked up 'missing' vdev as a placeholder.  We cannot
                 * simply compress the child array, because the kernel performs
                 * certain checks to make sure the vdev IDs match their location
                 * in the configuration.
                 */
                for (c = 0; c < children; c++) {
                        if (child[c] == NULL) {
                                nvlist_t *missing;
                                if (nvlist_alloc(&missing, NV_UNIQUE_NAME,
                                    0) != 0)
                                        goto nomem;
                                if (nvlist_add_string(missing,
                                    ZPOOL_CONFIG_TYPE,
                                    VDEV_TYPE_MISSING) != 0 ||
                                    nvlist_add_uint64(missing,
                                    ZPOOL_CONFIG_ID, c) != 0 ||
                                    nvlist_add_uint64(missing,
                                    ZPOOL_CONFIG_GUID, 0ULL) != 0) {
                                        nvlist_free(missing);
                                        goto nomem;
                                }
                                child[c] = missing;
                        }
                }

                /*
                 * Put all of this pool's top-level vdevs into a root vdev.
                 */
                if (nvlist_alloc(&nvroot, NV_UNIQUE_NAME, 0) != 0)
                        goto nomem;
                if (nvlist_add_string(nvroot, ZPOOL_CONFIG_TYPE,
                    VDEV_TYPE_ROOT) != 0 ||
                    nvlist_add_uint64(nvroot, ZPOOL_CONFIG_ID, 0ULL) != 0 ||
                    nvlist_add_uint64(nvroot, ZPOOL_CONFIG_GUID, guid) != 0 ||
                    nvlist_add_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
                    child, children) != 0) {
                        nvlist_free(nvroot);
                        goto nomem;
                }

                for (c = 0; c < children; c++)
                        nvlist_free(child[c]);
                free(child);
                children = 0;
                child = NULL;

                /*
                 * Go through and fix up any paths and/or devids based on our
                 * known list of vdev GUID -> path mappings.
                 */
                if (fix_paths(nvroot, pl->names) != 0) {
                        nvlist_free(nvroot);
                        goto nomem;
                }

                /*
                 * Add the root vdev to this pool's configuration.
                 */
                if (nvlist_add_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
                    nvroot) != 0) {
                        nvlist_free(nvroot);
                        goto nomem;
                }
                nvlist_free(nvroot);

                /*
                 * zdb uses this path to report on active pools that were
                 * imported or created using -R.
                 */
                if (active_ok)
                        goto add_pool;

                /*
                 * Determine if this pool is currently active, in which case we
                 * can't actually import it.
                 */
                verify(nvlist_lookup_string(config, ZPOOL_CONFIG_POOL_NAME,
                    &name) == 0);
                verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
                    &guid) == 0);

                if (pool_active(hdl, name, guid, &isactive) != 0)
                        goto error;

                if (isactive) {
                        nvlist_free(config);
                        config = NULL;
                        continue;
                }

                if ((nvl = refresh_config(hdl, config)) == NULL) {
                        nvlist_free(config);
                        config = NULL;
                        continue;
                }

                nvlist_free(config);
                config = nvl;

                /*
                 * Go through and update the paths for spares, now that we have
                 * them.
                 */
                verify(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
                    &nvroot) == 0);
                if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
                    &spares, &nspares) == 0) {
                        for (i = 0; i < nspares; i++) {
                                if (fix_paths(spares[i], pl->names) != 0)
                                        goto nomem;
                        }
                }

                /*
                 * Update the paths for l2cache devices.
                 */
                if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE,
                    &l2cache, &nl2cache) == 0) {
                        for (i = 0; i < nl2cache; i++) {
                                if (fix_paths(l2cache[i], pl->names) != 0)
                                        goto nomem;
                        }
                }

                /*
                 * Restore the original information read from the actual label.
                 */
                (void) nvlist_remove(config, ZPOOL_CONFIG_HOSTID,
                    DATA_TYPE_UINT64);
                (void) nvlist_remove(config, ZPOOL_CONFIG_HOSTNAME,
                    DATA_TYPE_STRING);
                if (hostid != 0) {
                        verify(nvlist_add_uint64(config, ZPOOL_CONFIG_HOSTID,
                            hostid) == 0);
                        verify(nvlist_add_string(config, ZPOOL_CONFIG_HOSTNAME,
                            hostname) == 0);
                }

add_pool:
                /*
                 * Add this pool to the list of configs.
                 */
                verify(nvlist_lookup_string(config, ZPOOL_CONFIG_POOL_NAME,
                    &name) == 0);
                if (nvlist_add_nvlist(ret, name, config) != 0)
                        goto nomem;

                nvlist_free(config);
                config = NULL;
        }

        return (ret);

nomem:
        (void) no_memory(hdl);
error:
        nvlist_free(config);
        nvlist_free(ret);
        for (c = 0; c < children; c++)
                nvlist_free(child[c]);
        free(child);

        return (NULL);
}

/*
 * Return the offset of the given label.
 */
static uint64_t
label_offset(uint64_t size, int l)
{
        ASSERT(P2PHASE_TYPED(size, sizeof (vdev_label_t), uint64_t) == 0);
        return (l * sizeof (vdev_label_t) + (l < VDEV_LABELS / 2 ?
            0 : size - VDEV_LABELS * sizeof (vdev_label_t)));
}

/*
 * Given a file descriptor, read the label information and return an nvlist
 * describing the configuration, if there is one.  The number of valid
 * labels found will be returned in num_labels when non-NULL.
 */
int
zpool_read_label(int fd, nvlist_t **config, int *num_labels)
{
        struct stat64 statbuf;
        int l, count = 0;
        vdev_label_t *label;
        nvlist_t *expected_config = NULL;
        uint64_t expected_guid = 0, size;
        int error;

        *config = NULL;

        if (fstat64_blk(fd, &statbuf) == -1)
                return (0);
        size = P2ALIGN_TYPED(statbuf.st_size, sizeof (vdev_label_t), uint64_t);

        error = posix_memalign((void **)&label, PAGESIZE, sizeof (*label));
        if (error)
                return (-1);

        for (l = 0; l < VDEV_LABELS; l++) {
                uint64_t state, guid, txg;

                if (pread64(fd, label, sizeof (vdev_label_t),
                    label_offset(size, l)) != sizeof (vdev_label_t))
                        continue;

                if (nvlist_unpack(label->vl_vdev_phys.vp_nvlist,
                    sizeof (label->vl_vdev_phys.vp_nvlist), config, 0) != 0)
                        continue;

                if (nvlist_lookup_uint64(*config, ZPOOL_CONFIG_GUID,
                    &guid) != 0 || guid == 0) {
                        nvlist_free(*config);
                        continue;
                }

                if (nvlist_lookup_uint64(*config, ZPOOL_CONFIG_POOL_STATE,
                    &state) != 0 || state > POOL_STATE_L2CACHE) {
                        nvlist_free(*config);
                        continue;
                }

                if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
                    (nvlist_lookup_uint64(*config, ZPOOL_CONFIG_POOL_TXG,
                    &txg) != 0 || txg == 0)) {
                        nvlist_free(*config);
                        continue;
                }

                if (expected_guid) {
                        if (expected_guid == guid)
                                count++;

                        nvlist_free(*config);
                } else {
                        expected_config = *config;
                        expected_guid = guid;
                        count++;
                }
        }

        if (num_labels != NULL)
                *num_labels = count;

        free(label);
        *config = expected_config;

        return (0);
}

typedef struct rdsk_node {
        char *rn_name;                  /* Full path to device */
        int rn_order;                   /* Preferred order (low to high) */
        int rn_num_labels;              /* Number of valid labels */
        uint64_t rn_vdev_guid;          /* Expected vdev guid when set */
        libzfs_handle_t *rn_hdl;
        nvlist_t *rn_config;            /* Label config */
        avl_tree_t *rn_avl;
        avl_node_t rn_node;
        kmutex_t *rn_lock;
        boolean_t rn_labelpaths;
} rdsk_node_t;

/*
 * Sorted by vdev guid and full path to allow for multiple entries with
 * the same full path name.  This is required because it's possible to
 * have multiple block devices with labels that refer to the same
 * ZPOOL_CONFIG_PATH yet have different vdev guids.  In this case both
 * entries need to be added to the cache.  Scenarios where this can occur
 * include overwritten pool labels, devices which are visible from multiple
 * hosts and multipath devices.
 */
static int
slice_cache_compare(const void *arg1, const void *arg2)
{
        const char  *nm1 = ((rdsk_node_t *)arg1)->rn_name;
        const char  *nm2 = ((rdsk_node_t *)arg2)->rn_name;
        uint64_t guid1 = ((rdsk_node_t *)arg1)->rn_vdev_guid;
        uint64_t guid2 = ((rdsk_node_t *)arg2)->rn_vdev_guid;
        int rv;

        rv = AVL_CMP(guid1, guid2);
        if (rv)
                return (rv);

        return (AVL_ISIGN(strcmp(nm1, nm2)));
}

static boolean_t
is_watchdog_dev(char *dev)
{
        /* For 'watchdog' dev */
        if (strcmp(dev, "watchdog") == 0)
                return (B_TRUE);

        /* For 'watchdog<digit><whatever> */
        if (strstr(dev, "watchdog") == dev && isdigit(dev[8]))
                return (B_TRUE);

        return (B_FALSE);
}

static int
label_paths_impl(libzfs_handle_t *hdl, nvlist_t *nvroot, uint64_t pool_guid,
    uint64_t vdev_guid, char **path, char **devid)
{
        nvlist_t **child;
        uint_t c, children;
        uint64_t guid;
        char *val;
        int error;

        if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
            &child, &children) == 0) {
                for (c = 0; c < children; c++) {
                        error  = label_paths_impl(hdl, child[c],
                            pool_guid, vdev_guid, path, devid);
                        if (error)
                                return (error);
                }
                return (0);
        }

        if (nvroot == NULL)
                return (0);

        error = nvlist_lookup_uint64(nvroot, ZPOOL_CONFIG_GUID, &guid);
        if ((error != 0) || (guid != vdev_guid))
                return (0);

        error = nvlist_lookup_string(nvroot, ZPOOL_CONFIG_PATH, &val);
        if (error == 0)
                *path = val;

        error = nvlist_lookup_string(nvroot, ZPOOL_CONFIG_DEVID, &val);
        if (error == 0)
                *devid = val;

        return (0);
}

/*
 * Given a disk label fetch the ZPOOL_CONFIG_PATH and ZPOOL_CONFIG_DEVID
 * and store these strings as config_path and devid_path respectively.
 * The returned pointers are only valid as long as label remains valid.
 */
static int
label_paths(libzfs_handle_t *hdl, nvlist_t *label, char **path, char **devid)
{
        nvlist_t *nvroot;
        uint64_t pool_guid;
        uint64_t vdev_guid;

        *path = NULL;
        *devid = NULL;

        if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_VDEV_TREE, &nvroot) ||
            nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &pool_guid) ||
            nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &vdev_guid))
                return (ENOENT);

        return (label_paths_impl(hdl, nvroot, pool_guid, vdev_guid, path,
            devid));
}

static void
zpool_open_func(void *arg)
{
        rdsk_node_t *rn = arg;
        libzfs_handle_t *hdl = rn->rn_hdl;
        struct stat64 statbuf;
        nvlist_t *config;
        char *bname, *dupname;
        uint64_t vdev_guid = 0;
        int error;
        int num_labels;
        int fd;

        /*
         * Skip devices with well known prefixes there can be side effects
         * when opening devices which need to be avoided.
         *
         * hpet     - High Precision Event Timer
         * watchdog - Watchdog must be closed in a special way.
         */
        dupname = zfs_strdup(hdl, rn->rn_name);
        bname = basename(dupname);
        error = ((strcmp(bname, "hpet") == 0) || is_watchdog_dev(bname));
        free(dupname);
        if (error)
                return;

        /*
         * Ignore failed stats.  We only want regular files and block devices.
         */
        if (stat64(rn->rn_name, &statbuf) != 0 ||
            (!S_ISREG(statbuf.st_mode) && !S_ISBLK(statbuf.st_mode)))
                return;

        /*
         * Preferentially open using O_DIRECT to bypass the block device
         * cache which may be stale for multipath devices.  An EINVAL errno
         * indicates O_DIRECT is unsupported so fallback to just O_RDONLY.
         */
        fd = open(rn->rn_name, O_RDONLY | O_DIRECT);
        if ((fd < 0) && (errno == EINVAL))
                fd = open(rn->rn_name, O_RDONLY);

        if (fd < 0)
                return;

        /*
         * This file is too small to hold a zpool
         */
        if (S_ISREG(statbuf.st_mode) && statbuf.st_size < SPA_MINDEVSIZE) {
                (void) close(fd);
                return;
        }

        error = zpool_read_label(fd, &config, &num_labels);
        if (error != 0) {
                (void) close(fd);
                return;
        }

        if (num_labels == 0) {
                (void) close(fd);
                nvlist_free(config);
                return;
        }

        /*
         * Check that the vdev is for the expected guid.  Additional entries
         * are speculatively added based on the paths stored in the labels.
         * Entries with valid paths but incorrect guids must be removed.
         */
        error = nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID, &vdev_guid);
        if (error || (rn->rn_vdev_guid && rn->rn_vdev_guid != vdev_guid)) {
                (void) close(fd);
                nvlist_free(config);
                return;
        }

        (void) close(fd);

        rn->rn_config = config;
        rn->rn_num_labels = num_labels;

        /*
         * Add additional entries for paths described by this label.
         */
        if (rn->rn_labelpaths) {
                char *path = NULL;
                char *devid = NULL;
                rdsk_node_t *slice;
                avl_index_t where;
                int error;

                if (label_paths(rn->rn_hdl, rn->rn_config, &path, &devid))
                        return;

                /*
                 * Allow devlinks to stabilize so all paths are available.
                 */
                zpool_label_disk_wait(rn->rn_name, DISK_LABEL_WAIT);

                if (path != NULL) {
                        slice = zfs_alloc(hdl, sizeof (rdsk_node_t));
                        slice->rn_name = zfs_strdup(hdl, path);
                        slice->rn_vdev_guid = vdev_guid;
                        slice->rn_avl = rn->rn_avl;
                        slice->rn_hdl = hdl;
                        slice->rn_order = IMPORT_ORDER_PREFERRED_1;
                        slice->rn_labelpaths = B_FALSE;
                        mutex_enter(rn->rn_lock);
                        if (avl_find(rn->rn_avl, slice, &where)) {
                        mutex_exit(rn->rn_lock);
                                free(slice->rn_name);
                                free(slice);
                        } else {
                                avl_insert(rn->rn_avl, slice, where);
                                mutex_exit(rn->rn_lock);
                                zpool_open_func(slice);
                        }
                }

                if (devid != NULL) {
                        slice = zfs_alloc(hdl, sizeof (rdsk_node_t));
                        error = asprintf(&slice->rn_name, "%s%s",
                            DEV_BYID_PATH, devid);
                        if (error == -1) {
                                free(slice);
                                return;
                        }

                        slice->rn_vdev_guid = vdev_guid;
                        slice->rn_avl = rn->rn_avl;
                        slice->rn_hdl = hdl;
                        slice->rn_order = IMPORT_ORDER_PREFERRED_2;
                        slice->rn_labelpaths = B_FALSE;
                        mutex_enter(rn->rn_lock);
                        if (avl_find(rn->rn_avl, slice, &where)) {
                                mutex_exit(rn->rn_lock);
                                free(slice->rn_name);
                                free(slice);
                        } else {
                                avl_insert(rn->rn_avl, slice, where);
                                mutex_exit(rn->rn_lock);
                                zpool_open_func(slice);
                        }
                }
        }
}

/*
 * Given a file descriptor, clear (zero) the label information.  This function
 * is used in the appliance stack as part of the ZFS sysevent module and
 * to implement the "zpool labelclear" command.
 */
int
zpool_clear_label(int fd)
{
        struct stat64 statbuf;
        int l;
        vdev_label_t *label;
        uint64_t size;

        if (fstat64_blk(fd, &statbuf) == -1)
                return (0);
        size = P2ALIGN_TYPED(statbuf.st_size, sizeof (vdev_label_t), uint64_t);

        if ((label = calloc(sizeof (vdev_label_t), 1)) == NULL)
                return (-1);

        for (l = 0; l < VDEV_LABELS; l++) {
                if (pwrite64(fd, label, sizeof (vdev_label_t),
                    label_offset(size, l)) != sizeof (vdev_label_t)) {
                        free(label);
                        return (-1);
                }
        }

        free(label);
        return (0);
}

/*
 * Scan a list of directories for zfs devices.
 */
static int
zpool_find_import_scan(libzfs_handle_t *hdl, kmutex_t *lock,
    avl_tree_t **slice_cache, char **dir, int dirs)
{
        avl_tree_t *cache;
        rdsk_node_t *slice;
        void *cookie;
        int i, error;

        *slice_cache = NULL;
        cache = zfs_alloc(hdl, sizeof (avl_tree_t));
        avl_create(cache, slice_cache_compare, sizeof (rdsk_node_t),
            offsetof(rdsk_node_t, rn_node));

        for (i = 0; i < dirs; i++) {
                char path[MAXPATHLEN];
                struct dirent64 *dp;
                DIR *dirp;

                if (realpath(dir[i], path) == NULL) {
                        error = errno;
                        if (error == ENOENT)
                                continue;

                        zfs_error_aux(hdl, strerror(error));
                        (void) zfs_error_fmt(hdl, EZFS_BADPATH, dgettext(
                            TEXT_DOMAIN, "cannot resolve path '%s'"), dir[i]);
                        goto error;
                }

                dirp = opendir(path);
                if (dirp == NULL) {
                        error = errno;
                        zfs_error_aux(hdl, strerror(error));
                        (void) zfs_error_fmt(hdl, EZFS_BADPATH,
                            dgettext(TEXT_DOMAIN, "cannot open '%s'"), path);
                        goto error;
                }

                while ((dp = readdir64(dirp)) != NULL) {
                        const char *name = dp->d_name;
                        if (name[0] == '.' &&
                            (name[1] == 0 || (name[1] == '.' && name[2] == 0)))
                                continue;

                        slice = zfs_alloc(hdl, sizeof (rdsk_node_t));
                        error = asprintf(&slice->rn_name, "%s/%s", path, name);
                        if (error == -1) {
                                free(slice);
                                continue;
                        }
                        slice->rn_vdev_guid = 0;
                        slice->rn_lock = lock;
                        slice->rn_avl = cache;
                        slice->rn_hdl = hdl;
                        slice->rn_order = i + IMPORT_ORDER_SCAN_OFFSET;
                        slice->rn_labelpaths = B_FALSE;
                        mutex_enter(lock);
                        avl_add(cache, slice);
                        mutex_exit(lock);
                }

                (void) closedir(dirp);
        }

        *slice_cache = cache;
        return (0);

error:
        cookie = NULL;
        while ((slice = avl_destroy_nodes(cache, &cookie)) != NULL) {
                free(slice->rn_name);
                free(slice);
        }
        free(cache);

        return (error);
}

/*
 * Use libblkid to quickly enumerate all known zfs devices.
 */
static int
zpool_find_import_blkid(libzfs_handle_t *hdl, kmutex_t *lock,
    avl_tree_t **slice_cache)
{
        rdsk_node_t *slice;
        blkid_cache cache;
        blkid_dev_iterate iter;
        blkid_dev dev;
        avl_index_t where;
        int error;

        *slice_cache = NULL;

        error = blkid_get_cache(&cache, NULL);
        if (error != 0)
                return (error);

        error = blkid_probe_all_new(cache);
        if (error != 0) {
                blkid_put_cache(cache);
                return (error);
        }

        iter = blkid_dev_iterate_begin(cache);
        if (iter == NULL) {
                blkid_put_cache(cache);
                return (EINVAL);
        }

        error = blkid_dev_set_search(iter, "TYPE", "zfs_member");
        if (error != 0) {
                blkid_dev_iterate_end(iter);
                blkid_put_cache(cache);
                return (error);
        }

        *slice_cache = zfs_alloc(hdl, sizeof (avl_tree_t));
        avl_create(*slice_cache, slice_cache_compare, sizeof (rdsk_node_t),
            offsetof(rdsk_node_t, rn_node));

        while (blkid_dev_next(iter, &dev) == 0) {
                slice = zfs_alloc(hdl, sizeof (rdsk_node_t));
                slice->rn_name = zfs_strdup(hdl, blkid_dev_devname(dev));
                slice->rn_vdev_guid = 0;
                slice->rn_lock = lock;
                slice->rn_avl = *slice_cache;
                slice->rn_hdl = hdl;
                slice->rn_labelpaths = B_TRUE;

                error = zfs_path_order(slice->rn_name, &slice->rn_order);
                if (error == 0)
                        slice->rn_order += IMPORT_ORDER_SCAN_OFFSET;
                else
                        slice->rn_order = IMPORT_ORDER_DEFAULT;

                mutex_enter(lock);
                if (avl_find(*slice_cache, slice, &where)) {
                        free(slice->rn_name);
                        free(slice);
                } else {
                        avl_insert(*slice_cache, slice, where);
                }
                mutex_exit(lock);
        }

        blkid_dev_iterate_end(iter);
        blkid_put_cache(cache);

        return (0);
}

char *
zpool_default_import_path[DEFAULT_IMPORT_PATH_SIZE] = {
        "/dev/disk/by-vdev",    /* Custom rules, use first if they exist */
        "/dev/mapper",          /* Use multipath devices before components */
        "/dev/disk/by-partlabel", /* Single unique entry set by user */
        "/dev/disk/by-partuuid", /* Generated partition uuid */
        "/dev/disk/by-label",   /* Custom persistent labels */
        "/dev/disk/by-uuid",    /* Single unique entry and persistent */
        "/dev/disk/by-id",      /* May be multiple entries and persistent */
        "/dev/disk/by-path",    /* Encodes physical location and persistent */
        "/dev"                  /* UNSAFE device names will change */
};

/*
 * Given a list of directories to search, find all pools stored on disk.  This
 * includes partial pools which are not available to import.  If no args are
 * given (argc is 0), then the default directory (/dev/dsk) is searched.
 * poolname or guid (but not both) are provided by the caller when trying
 * to import a specific pool.
 */
static nvlist_t *
zpool_find_import_impl(libzfs_handle_t *hdl, importargs_t *iarg)
{
        nvlist_t *ret = NULL;
        pool_list_t pools = { 0 };
        pool_entry_t *pe, *penext;
        vdev_entry_t *ve, *venext;
        config_entry_t *ce, *cenext;
        name_entry_t *ne, *nenext;
        kmutex_t lock;
        avl_tree_t *cache;
        rdsk_node_t *slice;
        void *cookie;
        taskq_t *t;

        verify(iarg->poolname == NULL || iarg->guid == 0);
        mutex_init(&lock, NULL, MUTEX_DEFAULT, NULL);

        /*
         * Locate pool member vdevs using libblkid or by directory scanning.
         * On success a newly allocated AVL tree which is populated with an
         * entry for each discovered vdev will be returned as the cache.
         * It's the callers responsibility to consume and destroy this tree.
         */
        if (iarg->scan || iarg->paths != 0) {
                int dirs = iarg->paths;
                char **dir = iarg->path;

                if (dirs == 0) {
                        dir = zpool_default_import_path;
                        dirs = DEFAULT_IMPORT_PATH_SIZE;
                }

                if (zpool_find_import_scan(hdl, &lock, &cache, dir,  dirs) != 0)
                        return (NULL);
        } else {
                if (zpool_find_import_blkid(hdl, &lock, &cache) != 0)
                        return (NULL);
        }

        /*
         * Create a thread pool to parallelize the process of reading and
         * validating labels, a large number of threads can be used due to
         * minimal contention.
         */
        t = taskq_create("z_import", 2 * boot_ncpus, defclsyspri,
            2 * boot_ncpus, INT_MAX, TASKQ_PREPOPULATE);

        for (slice = avl_first(cache); slice;
            (slice = avl_walk(cache, slice, AVL_AFTER)))
                (void) taskq_dispatch(t, zpool_open_func, slice, TQ_SLEEP);

        taskq_wait(t);
        taskq_destroy(t);

        /*
         * Process the cache filtering out any entries which are not
         * for the specificed pool then adding matching label configs.
         */
        cookie = NULL;
        while ((slice = avl_destroy_nodes(cache, &cookie)) != NULL) {
                if (slice->rn_config != NULL) {
                        nvlist_t *config = slice->rn_config;
                        boolean_t matched = B_TRUE;
                        boolean_t aux = B_FALSE;
                        int fd;

                        /*
                         * Check if it's a spare or l2cache device. If it is,
                         * we need to skip the name and guid check since they
                         * don't exist on aux device label.
                         */
                        if (iarg->poolname != NULL || iarg->guid != 0) {
                                uint64_t state;
                                aux = nvlist_lookup_uint64(config,
                                    ZPOOL_CONFIG_POOL_STATE, &state) == 0 &&
                                    (state == POOL_STATE_SPARE ||
                                    state == POOL_STATE_L2CACHE);
                        }

                        if (iarg->poolname != NULL && !aux) {
                                char *pname;

                                matched = nvlist_lookup_string(config,
                                    ZPOOL_CONFIG_POOL_NAME, &pname) == 0 &&
                                    strcmp(iarg->poolname, pname) == 0;
                        } else if (iarg->guid != 0 && !aux) {
                                uint64_t this_guid;

                                matched = nvlist_lookup_uint64(config,
                                    ZPOOL_CONFIG_POOL_GUID, &this_guid) == 0 &&
                                    iarg->guid == this_guid;
                        }
                        if (!matched) {
                                nvlist_free(config);
                        } else {
                                /*
                                 * Verify all remaining entries can be opened
                                 * exclusively. This will prune all underlying
                                 * multipath devices which otherwise could
                                 * result in the vdev appearing as UNAVAIL.
                                 *
                                 * Under zdb, this step isn't required and
                                 * would prevent a zdb -e of active pools with
                                 * no cachefile.
                                 */
                                fd = open(slice->rn_name, O_RDONLY | O_EXCL);
                                if (fd >= 0 || iarg->can_be_active) {
                                        if (fd >= 0)
                                                close(fd);
                                        add_config(hdl, &pools,
                                            slice->rn_name, slice->rn_order,
                                            slice->rn_num_labels, config);
                                } else {
                                        nvlist_free(config);
                                }
                        }
                }
                free(slice->rn_name);
                free(slice);
        }
        avl_destroy(cache);
        free(cache);
        mutex_destroy(&lock);

        ret = get_configs(hdl, &pools, iarg->can_be_active);

        for (pe = pools.pools; pe != NULL; pe = penext) {
                penext = pe->pe_next;
                for (ve = pe->pe_vdevs; ve != NULL; ve = venext) {
                        venext = ve->ve_next;
                        for (ce = ve->ve_configs; ce != NULL; ce = cenext) {
                                cenext = ce->ce_next;
                                nvlist_free(ce->ce_config);
                                free(ce);
                        }
                        free(ve);
                }
                free(pe);
        }

        for (ne = pools.names; ne != NULL; ne = nenext) {
                nenext = ne->ne_next;
                free(ne->ne_name);
                free(ne);
        }

        return (ret);
}

nvlist_t *
zpool_find_import(libzfs_handle_t *hdl, int argc, char **argv)
{
        importargs_t iarg = { 0 };

        iarg.paths = argc;
        iarg.path = argv;

        return (zpool_find_import_impl(hdl, &iarg));
}

/*
 * Given a cache file, return the contents as a list of importable pools.
 * poolname or guid (but not both) are provided by the caller when trying
 * to import a specific pool.
 */
nvlist_t *
zpool_find_import_cached(libzfs_handle_t *hdl, const char *cachefile,
    char *poolname, uint64_t guid)
{
        char *buf;
        int fd;
        struct stat64 statbuf;
        nvlist_t *raw, *src, *dst;
        nvlist_t *pools;
        nvpair_t *elem;
        char *name;
        uint64_t this_guid;
        boolean_t active;

        verify(poolname == NULL || guid == 0);

        if ((fd = open(cachefile, O_RDONLY)) < 0) {
                zfs_error_aux(hdl, "%s", strerror(errno));
                (void) zfs_error(hdl, EZFS_BADCACHE,
                    dgettext(TEXT_DOMAIN, "failed to open cache file"));
                return (NULL);
        }

        if (fstat64(fd, &statbuf) != 0) {
                zfs_error_aux(hdl, "%s", strerror(errno));
                (void) close(fd);
                (void) zfs_error(hdl, EZFS_BADCACHE,
                    dgettext(TEXT_DOMAIN, "failed to get size of cache file"));
                return (NULL);
        }

        if ((buf = zfs_alloc(hdl, statbuf.st_size)) == NULL) {
                (void) close(fd);
                return (NULL);
        }

        if (read(fd, buf, statbuf.st_size) != statbuf.st_size) {
                (void) close(fd);
                free(buf);
                (void) zfs_error(hdl, EZFS_BADCACHE,
                    dgettext(TEXT_DOMAIN,
                    "failed to read cache file contents"));
                return (NULL);
        }

        (void) close(fd);

        if (nvlist_unpack(buf, statbuf.st_size, &raw, 0) != 0) {
                free(buf);
                (void) zfs_error(hdl, EZFS_BADCACHE,
                    dgettext(TEXT_DOMAIN,
                    "invalid or corrupt cache file contents"));
                return (NULL);
        }

        free(buf);

        /*
         * Go through and get the current state of the pools and refresh their
         * state.
         */
        if (nvlist_alloc(&pools, 0, 0) != 0) {
                (void) no_memory(hdl);
                nvlist_free(raw);
                return (NULL);
        }

        elem = NULL;
        while ((elem = nvlist_next_nvpair(raw, elem)) != NULL) {
                src = fnvpair_value_nvlist(elem);

                name = fnvlist_lookup_string(src, ZPOOL_CONFIG_POOL_NAME);
                if (poolname != NULL && strcmp(poolname, name) != 0)
                        continue;

                this_guid = fnvlist_lookup_uint64(src, ZPOOL_CONFIG_POOL_GUID);
                if (guid != 0 && guid != this_guid)
                        continue;

                if (pool_active(hdl, name, this_guid, &active) != 0) {
                        nvlist_free(raw);
                        nvlist_free(pools);
                        return (NULL);
                }

                if (active)
                        continue;

                if ((dst = refresh_config(hdl, src)) == NULL) {
                        nvlist_free(raw);
                        nvlist_free(pools);
                        return (NULL);
                }

                if (nvlist_add_nvlist(pools, nvpair_name(elem), dst) != 0) {
                        (void) no_memory(hdl);
                        nvlist_free(dst);
                        nvlist_free(raw);
                        nvlist_free(pools);
                        return (NULL);
                }
                nvlist_free(dst);
        }

        nvlist_free(raw);
        return (pools);
}

static int
name_or_guid_exists(zpool_handle_t *zhp, void *data)
{
        importargs_t *import = data;
        int found = 0;

        if (import->poolname != NULL) {
                char *pool_name;

                verify(nvlist_lookup_string(zhp->zpool_config,
                    ZPOOL_CONFIG_POOL_NAME, &pool_name) == 0);
                if (strcmp(pool_name, import->poolname) == 0)
                        found = 1;
        } else {
                uint64_t pool_guid;

                verify(nvlist_lookup_uint64(zhp->zpool_config,
                    ZPOOL_CONFIG_POOL_GUID, &pool_guid) == 0);
                if (pool_guid == import->guid)
                        found = 1;
        }

        zpool_close(zhp);
        return (found);
}

nvlist_t *
zpool_search_import(libzfs_handle_t *hdl, importargs_t *import)
{
        verify(import->poolname == NULL || import->guid == 0);

        if (import->unique)
                import->exists = zpool_iter(hdl, name_or_guid_exists, import);

        if (import->cachefile != NULL)
                return (zpool_find_import_cached(hdl, import->cachefile,
                    import->poolname, import->guid));

        return (zpool_find_import_impl(hdl, import));
}

static boolean_t
pool_match(nvlist_t *cfg, char *tgt)
{
        uint64_t v, guid = strtoull(tgt, NULL, 0);
        char *s;

        if (guid != 0) {
                if (nvlist_lookup_uint64(cfg, ZPOOL_CONFIG_POOL_GUID, &v) == 0)
                        return (v == guid);
        } else {
                if (nvlist_lookup_string(cfg, ZPOOL_CONFIG_POOL_NAME, &s) == 0)
                        return (strcmp(s, tgt) == 0);
        }
        return (B_FALSE);
}

int
zpool_tryimport(libzfs_handle_t *hdl, char *target, nvlist_t **configp,
    importargs_t *args)
{
        nvlist_t *pools;
        nvlist_t *match = NULL;
        nvlist_t *config = NULL;
        char *name = NULL, *sepp = NULL;
        char sep = '\0';
        int count = 0;
        char *targetdup = strdup(target);

        *configp = NULL;

        if ((sepp = strpbrk(targetdup, "/@")) != NULL) {
                sep = *sepp;
                *sepp = '\0';
        }

        pools = zpool_search_import(hdl, args);

        if (pools != NULL) {
                nvpair_t *elem = NULL;
                while ((elem = nvlist_next_nvpair(pools, elem)) != NULL) {
                        VERIFY0(nvpair_value_nvlist(elem, &config));
                        if (pool_match(config, targetdup)) {
                                count++;
                                if (match != NULL) {
                                        /* multiple matches found */
                                        continue;
                                } else {
                                        match = config;
                                        name = nvpair_name(elem);
                                }
                        }
                }
        }

        if (count == 0) {
                (void) zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
                    "no pools found"));
                free(targetdup);
                return (ENOENT);
        }

        if (count > 1) {
                (void) zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
                    "%d pools found, use pool GUID\n"), count);
                free(targetdup);
                return (EINVAL);
        }

        *configp = match;
        free(targetdup);

        return (0);
}

boolean_t
find_guid(nvlist_t *nv, uint64_t guid)
{
        uint64_t tmp;
        nvlist_t **child;
        uint_t c, children;

        verify(nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &tmp) == 0);
        if (tmp == guid)
                return (B_TRUE);

        if (nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
            &child, &children) == 0) {
                for (c = 0; c < children; c++)
                        if (find_guid(child[c], guid))
                                return (B_TRUE);
        }

        return (B_FALSE);
}

typedef struct aux_cbdata {
        const char      *cb_type;
        uint64_t        cb_guid;
        zpool_handle_t  *cb_zhp;
} aux_cbdata_t;

static int
find_aux(zpool_handle_t *zhp, void *data)
{
        aux_cbdata_t *cbp = data;
        nvlist_t **list;
        uint_t i, count;
        uint64_t guid;
        nvlist_t *nvroot;

        verify(nvlist_lookup_nvlist(zhp->zpool_config, ZPOOL_CONFIG_VDEV_TREE,
            &nvroot) == 0);

        if (nvlist_lookup_nvlist_array(nvroot, cbp->cb_type,
            &list, &count) == 0) {
                for (i = 0; i < count; i++) {
                        verify(nvlist_lookup_uint64(list[i],
                            ZPOOL_CONFIG_GUID, &guid) == 0);
                        if (guid == cbp->cb_guid) {
                                cbp->cb_zhp = zhp;
                                return (1);
                        }
                }
        }

        zpool_close(zhp);
        return (0);
}

/*
 * Determines if the pool is in use.  If so, it returns true and the state of
 * the pool as well as the name of the pool.  Name string is allocated and
 * must be freed by the caller.
 */
int
zpool_in_use(libzfs_handle_t *hdl, int fd, pool_state_t *state, char **namestr,
    boolean_t *inuse)
{
        nvlist_t *config;
        char *name;
        boolean_t ret;
        uint64_t guid, vdev_guid;
        zpool_handle_t *zhp;
        nvlist_t *pool_config;
        uint64_t stateval, isspare;
        aux_cbdata_t cb = { 0 };
        boolean_t isactive;

        *inuse = B_FALSE;

        if (zpool_read_label(fd, &config, NULL) != 0) {
                (void) no_memory(hdl);
                return (-1);
        }

        if (config == NULL)
                return (0);

        verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_STATE,
            &stateval) == 0);
        verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID,
            &vdev_guid) == 0);

        if (stateval != POOL_STATE_SPARE && stateval != POOL_STATE_L2CACHE) {
                verify(nvlist_lookup_string(config, ZPOOL_CONFIG_POOL_NAME,
                    &name) == 0);
                verify(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
                    &guid) == 0);
        }

        switch (stateval) {
        case POOL_STATE_EXPORTED:
                /*
                 * A pool with an exported state may in fact be imported
                 * read-only, so check the in-core state to see if it's
                 * active and imported read-only.  If it is, set
                 * its state to active.
                 */
                if (pool_active(hdl, name, guid, &isactive) == 0 && isactive &&
                    (zhp = zpool_open_canfail(hdl, name)) != NULL) {
                        if (zpool_get_prop_int(zhp, ZPOOL_PROP_READONLY, NULL))
                                stateval = POOL_STATE_ACTIVE;

                        /*
                         * All we needed the zpool handle for is the
                         * readonly prop check.
                         */
                        zpool_close(zhp);
                }

                ret = B_TRUE;
                break;

        case POOL_STATE_ACTIVE:
                /*
                 * For an active pool, we have to determine if it's really part
                 * of a currently active pool (in which case the pool will exist
                 * and the guid will be the same), or whether it's part of an
                 * active pool that was disconnected without being explicitly
                 * exported.
                 */
                if (pool_active(hdl, name, guid, &isactive) != 0) {
                        nvlist_free(config);
                        return (-1);
                }

                if (isactive) {
                        /*
                         * Because the device may have been removed while
                         * offlined, we only report it as active if the vdev is
                         * still present in the config.  Otherwise, pretend like
                         * it's not in use.
                         */
                        if ((zhp = zpool_open_canfail(hdl, name)) != NULL &&
                            (pool_config = zpool_get_config(zhp, NULL))
                            != NULL) {
                                nvlist_t *nvroot;

                                verify(nvlist_lookup_nvlist(pool_config,
                                    ZPOOL_CONFIG_VDEV_TREE, &nvroot) == 0);
                                ret = find_guid(nvroot, vdev_guid);
                        } else {
                                ret = B_FALSE;
                        }

                        /*
                         * If this is an active spare within another pool, we
                         * treat it like an unused hot spare.  This allows the
                         * user to create a pool with a hot spare that currently
                         * in use within another pool.  Since we return B_TRUE,
                         * libdiskmgt will continue to prevent generic consumers
                         * from using the device.
                         */
                        if (ret && nvlist_lookup_uint64(config,
                            ZPOOL_CONFIG_IS_SPARE, &isspare) == 0 && isspare)
                                stateval = POOL_STATE_SPARE;

                        if (zhp != NULL)
                                zpool_close(zhp);
                } else {
                        stateval = POOL_STATE_POTENTIALLY_ACTIVE;
                        ret = B_TRUE;
                }
                break;

        case POOL_STATE_SPARE:
                /*
                 * For a hot spare, it can be either definitively in use, or
                 * potentially active.  To determine if it's in use, we iterate
                 * over all pools in the system and search for one with a spare
                 * with a matching guid.
                 *
                 * Due to the shared nature of spares, we don't actually report
                 * the potentially active case as in use.  This means the user
                 * can freely create pools on the hot spares of exported pools,
                 * but to do otherwise makes the resulting code complicated, and
                 * we end up having to deal with this case anyway.
                 */
                cb.cb_zhp = NULL;
                cb.cb_guid = vdev_guid;
                cb.cb_type = ZPOOL_CONFIG_SPARES;
                if (zpool_iter(hdl, find_aux, &cb) == 1) {
                        name = (char *)zpool_get_name(cb.cb_zhp);
                        ret = B_TRUE;
                } else {
                        ret = B_FALSE;
                }
                break;

        case POOL_STATE_L2CACHE:

                /*
                 * Check if any pool is currently using this l2cache device.
                 */
                cb.cb_zhp = NULL;
                cb.cb_guid = vdev_guid;
                cb.cb_type = ZPOOL_CONFIG_L2CACHE;
                if (zpool_iter(hdl, find_aux, &cb) == 1) {
                        name = (char *)zpool_get_name(cb.cb_zhp);
                        ret = B_TRUE;
                } else {
                        ret = B_FALSE;
                }
                break;

        default:
                ret = B_FALSE;
        }


        if (ret) {
                if ((*namestr = zfs_strdup(hdl, name)) == NULL) {
                        if (cb.cb_zhp)
                                zpool_close(cb.cb_zhp);
                        nvlist_free(config);
                        return (-1);
                }
                *state = (pool_state_t)stateval;
        }

        if (cb.cb_zhp)
                zpool_close(cb.cb_zhp);

        nvlist_free(config);
        *inuse = ret;
        return (0);
}