MFV r357163:

[FreeBSD/FreeBSD.git] / stand / libsa / zfs / zfsimpl.c

/*-
 * Copyright (c) 2007 Doug Rabson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 *      Stand-alone ZFS file reader.
 */

#include <sys/endian.h>
#include <sys/stat.h>
#include <sys/stdint.h>
#include <sys/list.h>
#include <machine/_inttypes.h>

#include "zfsimpl.h"
#include "zfssubr.c"


struct zfsmount {
        const spa_t     *spa;
        objset_phys_t   objset;
        uint64_t        rootobj;
};
static struct zfsmount zfsmount __unused;

/*
 * The indirect_child_t represents the vdev that we will read from, when we
 * need to read all copies of the data (e.g. for scrub or reconstruction).
 * For plain (non-mirror) top-level vdevs (i.e. is_vdev is not a mirror),
 * ic_vdev is the same as is_vdev.  However, for mirror top-level vdevs,
 * ic_vdev is a child of the mirror.
 */
typedef struct indirect_child {
        void *ic_data;
        vdev_t *ic_vdev;
} indirect_child_t;

/*
 * The indirect_split_t represents one mapped segment of an i/o to the
 * indirect vdev. For non-split (contiguously-mapped) blocks, there will be
 * only one indirect_split_t, with is_split_offset==0 and is_size==io_size.
 * For split blocks, there will be several of these.
 */
typedef struct indirect_split {
        list_node_t is_node; /* link on iv_splits */

        /*
         * is_split_offset is the offset into the i/o.
         * This is the sum of the previous splits' is_size's.
         */
        uint64_t is_split_offset;

        vdev_t *is_vdev; /* top-level vdev */
        uint64_t is_target_offset; /* offset on is_vdev */
        uint64_t is_size;
        int is_children; /* number of entries in is_child[] */

        /*
         * is_good_child is the child that we are currently using to
         * attempt reconstruction.
         */
        int is_good_child;

        indirect_child_t is_child[1]; /* variable-length */
} indirect_split_t;

/*
 * The indirect_vsd_t is associated with each i/o to the indirect vdev.
 * It is the "Vdev-Specific Data" in the zio_t's io_vsd.
 */
typedef struct indirect_vsd {
        boolean_t iv_split_block;
        boolean_t iv_reconstruct;

        list_t iv_splits; /* list of indirect_split_t's */
} indirect_vsd_t;

/*
 * List of all vdevs, chained through v_alllink.
 */
static vdev_list_t zfs_vdevs;

/*
 * List of ZFS features supported for read
 */
static const char *features_for_read[] = {
        "org.illumos:lz4_compress",
        "com.delphix:hole_birth",
        "com.delphix:extensible_dataset",
        "com.delphix:embedded_data",
        "org.open-zfs:large_blocks",
        "org.illumos:sha512",
        "org.illumos:skein",
        "org.zfsonlinux:large_dnode",
        "com.joyent:multi_vdev_crash_dump",
        "com.delphix:spacemap_histogram",
        "com.delphix:zpool_checkpoint",
        "com.delphix:spacemap_v2",
        "com.datto:encryption",
        "org.zfsonlinux:allocation_classes",
        "com.datto:resilver_defer",
        "com.delphix:device_removal",
        "com.delphix:obsolete_counts",
        "com.intel:allocation_classes",
        NULL
};

/*
 * List of all pools, chained through spa_link.
 */
static spa_list_t zfs_pools;

static const dnode_phys_t *dnode_cache_obj;
static uint64_t dnode_cache_bn;
static char *dnode_cache_buf;
static char *zap_scratch;
static char *zfs_temp_buf, *zfs_temp_end, *zfs_temp_ptr;

#define TEMP_SIZE       (1024 * 1024)

static int zio_read(const spa_t *spa, const blkptr_t *bp, void *buf);
static int zfs_get_root(const spa_t *spa, uint64_t *objid);
static int zfs_rlookup(const spa_t *spa, uint64_t objnum, char *result);
static int zap_lookup(const spa_t *spa, const dnode_phys_t *dnode,
    const char *name, uint64_t integer_size, uint64_t num_integers,
    void *value);
static int objset_get_dnode(const spa_t *, const objset_phys_t *, uint64_t,
    dnode_phys_t *);
static int dnode_read(const spa_t *, const dnode_phys_t *, off_t, void *,
    size_t);
static int vdev_indirect_read(vdev_t *, const blkptr_t *, void *, off_t,
    size_t);
static int vdev_mirror_read(vdev_t *, const blkptr_t *, void *, off_t, size_t);
vdev_indirect_mapping_t *vdev_indirect_mapping_open(spa_t *, objset_phys_t *,
    uint64_t);
vdev_indirect_mapping_entry_phys_t *
    vdev_indirect_mapping_duplicate_adjacent_entries(vdev_t *, uint64_t,
    uint64_t, uint64_t *);

static void
zfs_init(void)
{
        STAILQ_INIT(&zfs_vdevs);
        STAILQ_INIT(&zfs_pools);

        zfs_temp_buf = malloc(TEMP_SIZE);
        zfs_temp_end = zfs_temp_buf + TEMP_SIZE;
        zfs_temp_ptr = zfs_temp_buf;
        dnode_cache_buf = malloc(SPA_MAXBLOCKSIZE);
        zap_scratch = malloc(SPA_MAXBLOCKSIZE);

        zfs_init_crc();
}

static void *
zfs_alloc(size_t size)
{
        char *ptr;

        if (zfs_temp_ptr + size > zfs_temp_end) {
                panic("ZFS: out of temporary buffer space");
        }
        ptr = zfs_temp_ptr;
        zfs_temp_ptr += size;

        return (ptr);
}

static void
zfs_free(void *ptr, size_t size)
{

        zfs_temp_ptr -= size;
        if (zfs_temp_ptr != ptr) {
                panic("ZFS: zfs_alloc()/zfs_free() mismatch");
        }
}

static int
xdr_int(const unsigned char **xdr, int *ip)
{
        *ip = be32dec(*xdr);
        (*xdr) += 4;
        return (0);
}

static int
xdr_u_int(const unsigned char **xdr, u_int *ip)
{
        *ip = be32dec(*xdr);
        (*xdr) += 4;
        return (0);
}

static int
xdr_uint64_t(const unsigned char **xdr, uint64_t *lp)
{
        u_int hi, lo;

        xdr_u_int(xdr, &hi);
        xdr_u_int(xdr, &lo);
        *lp = (((uint64_t)hi) << 32) | lo;
        return (0);
}

static int
nvlist_find(const unsigned char *nvlist, const char *name, int type,
    int *elementsp, void *valuep)
{
        const unsigned char *p, *pair;
        int junk;
        int encoded_size, decoded_size;

        p = nvlist;
        xdr_int(&p, &junk);
        xdr_int(&p, &junk);

        pair = p;
        xdr_int(&p, &encoded_size);
        xdr_int(&p, &decoded_size);
        while (encoded_size && decoded_size) {
                int namelen, pairtype, elements;
                const char *pairname;

                xdr_int(&p, &namelen);
                pairname = (const char *)p;
                p += roundup(namelen, 4);
                xdr_int(&p, &pairtype);

                if (memcmp(name, pairname, namelen) == 0 && type == pairtype) {
                        xdr_int(&p, &elements);
                        if (elementsp)
                                *elementsp = elements;
                        if (type == DATA_TYPE_UINT64) {
                                xdr_uint64_t(&p, (uint64_t *)valuep);
                                return (0);
                        } else if (type == DATA_TYPE_STRING) {
                                int len;
                                xdr_int(&p, &len);
                                (*(const char **)valuep) = (const char *)p;
                                return (0);
                        } else if (type == DATA_TYPE_NVLIST ||
                            type == DATA_TYPE_NVLIST_ARRAY) {
                                (*(const unsigned char **)valuep) =
                                    (const unsigned char *)p;
                                return (0);
                        } else {
                                return (EIO);
                        }
                } else {
                        /*
                         * Not the pair we are looking for, skip to the
                         * next one.
                         */
                        p = pair + encoded_size;
                }

                pair = p;
                xdr_int(&p, &encoded_size);
                xdr_int(&p, &decoded_size);
        }

        return (EIO);
}

static int
nvlist_check_features_for_read(const unsigned char *nvlist)
{
        const unsigned char *p, *pair;
        int junk;
        int encoded_size, decoded_size;
        int rc;

        rc = 0;

        p = nvlist;
        xdr_int(&p, &junk);
        xdr_int(&p, &junk);

        pair = p;
        xdr_int(&p, &encoded_size);
        xdr_int(&p, &decoded_size);
        while (encoded_size && decoded_size) {
                int namelen, pairtype;
                const char *pairname;
                int i, found;

                found = 0;

                xdr_int(&p, &namelen);
                pairname = (const char *)p;
                p += roundup(namelen, 4);
                xdr_int(&p, &pairtype);

                for (i = 0; features_for_read[i] != NULL; i++) {
                        if (memcmp(pairname, features_for_read[i],
                            namelen) == 0) {
                                found = 1;
                                break;
                        }
                }

                if (!found) {
                        printf("ZFS: unsupported feature: %s\n", pairname);
                        rc = EIO;
                }

                p = pair + encoded_size;

                pair = p;
                xdr_int(&p, &encoded_size);
                xdr_int(&p, &decoded_size);
        }

        return (rc);
}

/*
 * Return the next nvlist in an nvlist array.
 */
static const unsigned char *
nvlist_next(const unsigned char *nvlist)
{
        const unsigned char *p, *pair;
        int junk;
        int encoded_size, decoded_size;

        p = nvlist;
        xdr_int(&p, &junk);
        xdr_int(&p, &junk);

        pair = p;
        xdr_int(&p, &encoded_size);
        xdr_int(&p, &decoded_size);
        while (encoded_size && decoded_size) {
                p = pair + encoded_size;

                pair = p;
                xdr_int(&p, &encoded_size);
                xdr_int(&p, &decoded_size);
        }

        return (p);
}

#ifdef TEST

static const unsigned char *
nvlist_print(const unsigned char *nvlist, unsigned int indent)
{
        static const char *typenames[] = {
                "DATA_TYPE_UNKNOWN",
                "DATA_TYPE_BOOLEAN",
                "DATA_TYPE_BYTE",
                "DATA_TYPE_INT16",
                "DATA_TYPE_UINT16",
                "DATA_TYPE_INT32",
                "DATA_TYPE_UINT32",
                "DATA_TYPE_INT64",
                "DATA_TYPE_UINT64",
                "DATA_TYPE_STRING",
                "DATA_TYPE_BYTE_ARRAY",
                "DATA_TYPE_INT16_ARRAY",
                "DATA_TYPE_UINT16_ARRAY",
                "DATA_TYPE_INT32_ARRAY",
                "DATA_TYPE_UINT32_ARRAY",
                "DATA_TYPE_INT64_ARRAY",
                "DATA_TYPE_UINT64_ARRAY",
                "DATA_TYPE_STRING_ARRAY",
                "DATA_TYPE_HRTIME",
                "DATA_TYPE_NVLIST",
                "DATA_TYPE_NVLIST_ARRAY",
                "DATA_TYPE_BOOLEAN_VALUE",
                "DATA_TYPE_INT8",
                "DATA_TYPE_UINT8",
                "DATA_TYPE_BOOLEAN_ARRAY",
                "DATA_TYPE_INT8_ARRAY",
                "DATA_TYPE_UINT8_ARRAY"
        };

        unsigned int i, j;
        const unsigned char *p, *pair;
        int junk;
        int encoded_size, decoded_size;

        p = nvlist;
        xdr_int(&p, &junk);
        xdr_int(&p, &junk);

        pair = p;
        xdr_int(&p, &encoded_size);
        xdr_int(&p, &decoded_size);
        while (encoded_size && decoded_size) {
                int namelen, pairtype, elements;
                const char *pairname;

                xdr_int(&p, &namelen);
                pairname = (const char *)p;
                p += roundup(namelen, 4);
                xdr_int(&p, &pairtype);

                for (i = 0; i < indent; i++)
                        printf(" ");
                printf("%s %s", typenames[pairtype], pairname);

                xdr_int(&p, &elements);
                switch (pairtype) {
                case DATA_TYPE_UINT64: {
                        uint64_t val;
                        xdr_uint64_t(&p, &val);
                        printf(" = 0x%jx\n", (uintmax_t)val);
                        break;
                }

                case DATA_TYPE_STRING: {
                        int len;
                        xdr_int(&p, &len);
                        printf(" = \"%s\"\n", p);
                        break;
                }

                case DATA_TYPE_NVLIST:
                        printf("\n");
                        nvlist_print(p, indent + 1);
                        break;

                case DATA_TYPE_NVLIST_ARRAY:
                        for (j = 0; j < elements; j++) {
                                printf("[%d]\n", j);
                                p = nvlist_print(p, indent + 1);
                                if (j != elements - 1) {
                                        for (i = 0; i < indent; i++)
                                                printf(" ");
                                        printf("%s %s", typenames[pairtype],
                                            pairname);
                                }
                        }
                        break;

                default:
                        printf("\n");
                }

                p = pair + encoded_size;

                pair = p;
                xdr_int(&p, &encoded_size);
                xdr_int(&p, &decoded_size);
        }

        return (p);
}

#endif

static int
vdev_read_phys(vdev_t *vdev, const blkptr_t *bp, void *buf,
    off_t offset, size_t size)
{
        size_t psize;
        int rc;

        if (!vdev->v_phys_read)
                return (EIO);

        if (bp) {
                psize = BP_GET_PSIZE(bp);
        } else {
                psize = size;
        }

        rc = vdev->v_phys_read(vdev, vdev->v_read_priv, offset, buf, psize);
        if (rc == 0) {
                if (bp != NULL)
                        rc = zio_checksum_verify(vdev->v_spa, bp, buf);
        }

        return (rc);
}

typedef struct remap_segment {
        vdev_t *rs_vd;
        uint64_t rs_offset;
        uint64_t rs_asize;
        uint64_t rs_split_offset;
        list_node_t rs_node;
} remap_segment_t;

static remap_segment_t *
rs_alloc(vdev_t *vd, uint64_t offset, uint64_t asize, uint64_t split_offset)
{
        remap_segment_t *rs = malloc(sizeof (remap_segment_t));

        if (rs != NULL) {
                rs->rs_vd = vd;
                rs->rs_offset = offset;
                rs->rs_asize = asize;
                rs->rs_split_offset = split_offset;
        }

        return (rs);
}

vdev_indirect_mapping_t *
vdev_indirect_mapping_open(spa_t *spa, objset_phys_t *os,
    uint64_t mapping_object)
{
        vdev_indirect_mapping_t *vim;
        vdev_indirect_mapping_phys_t *vim_phys;
        int rc;

        vim = calloc(1, sizeof (*vim));
        if (vim == NULL)
                return (NULL);

        vim->vim_dn = calloc(1, sizeof (*vim->vim_dn));
        if (vim->vim_dn == NULL) {
                free(vim);
                return (NULL);
        }

        rc = objset_get_dnode(spa, os, mapping_object, vim->vim_dn);
        if (rc != 0) {
                free(vim->vim_dn);
                free(vim);
                return (NULL);
        }

        vim->vim_spa = spa;
        vim->vim_phys = malloc(sizeof (*vim->vim_phys));
        if (vim->vim_phys == NULL) {
                free(vim->vim_dn);
                free(vim);
                return (NULL);
        }

        vim_phys = (vdev_indirect_mapping_phys_t *)DN_BONUS(vim->vim_dn);
        *vim->vim_phys = *vim_phys;

        vim->vim_objset = os;
        vim->vim_object = mapping_object;
        vim->vim_entries = NULL;

        vim->vim_havecounts =
            (vim->vim_dn->dn_bonuslen > VDEV_INDIRECT_MAPPING_SIZE_V0);

        return (vim);
}

/*
 * Compare an offset with an indirect mapping entry; there are three
 * possible scenarios:
 *
 *     1. The offset is "less than" the mapping entry; meaning the
 *        offset is less than the source offset of the mapping entry. In
 *        this case, there is no overlap between the offset and the
 *        mapping entry and -1 will be returned.
 *
 *     2. The offset is "greater than" the mapping entry; meaning the
 *        offset is greater than the mapping entry's source offset plus
 *        the entry's size. In this case, there is no overlap between
 *        the offset and the mapping entry and 1 will be returned.
 *
 *        NOTE: If the offset is actually equal to the entry's offset
 *        plus size, this is considered to be "greater" than the entry,
 *        and this case applies (i.e. 1 will be returned). Thus, the
 *        entry's "range" can be considered to be inclusive at its
 *        start, but exclusive at its end: e.g. [src, src + size).
 *
 *     3. The last case to consider is if the offset actually falls
 *        within the mapping entry's range. If this is the case, the
 *        offset is considered to be "equal to" the mapping entry and
 *        0 will be returned.
 *
 *        NOTE: If the offset is equal to the entry's source offset,
 *        this case applies and 0 will be returned. If the offset is
 *        equal to the entry's source plus its size, this case does
 *        *not* apply (see "NOTE" above for scenario 2), and 1 will be
 *        returned.
 */
static int
dva_mapping_overlap_compare(const void *v_key, const void *v_array_elem)
{
        const uint64_t *key = v_key;
        const vdev_indirect_mapping_entry_phys_t *array_elem =
            v_array_elem;
        uint64_t src_offset = DVA_MAPPING_GET_SRC_OFFSET(array_elem);

        if (*key < src_offset) {
                return (-1);
        } else if (*key < src_offset + DVA_GET_ASIZE(&array_elem->vimep_dst)) {
                return (0);
        } else {
                return (1);
        }
}

/*
 * Return array entry.
 */
static vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_entry(vdev_indirect_mapping_t *vim, uint64_t index)
{
        uint64_t size;
        off_t offset = 0;
        int rc;

        if (vim->vim_phys->vimp_num_entries == 0)
                return (NULL);

        if (vim->vim_entries == NULL) {
                uint64_t bsize;

                bsize = vim->vim_dn->dn_datablkszsec << SPA_MINBLOCKSHIFT;
                size = vim->vim_phys->vimp_num_entries *
                    sizeof (*vim->vim_entries);
                if (size > bsize) {
                        size = bsize / sizeof (*vim->vim_entries);
                        size *= sizeof (*vim->vim_entries);
                }
                vim->vim_entries = malloc(size);
                if (vim->vim_entries == NULL)
                        return (NULL);
                vim->vim_num_entries = size / sizeof (*vim->vim_entries);
                offset = index * sizeof (*vim->vim_entries);
        }

        /* We have data in vim_entries */
        if (offset == 0) {
                if (index >= vim->vim_entry_offset &&
                    index <= vim->vim_entry_offset + vim->vim_num_entries) {
                        index -= vim->vim_entry_offset;
                        return (&vim->vim_entries[index]);
                }
                offset = index * sizeof (*vim->vim_entries);
        }

        vim->vim_entry_offset = index;
        size = vim->vim_num_entries * sizeof (*vim->vim_entries);
        rc = dnode_read(vim->vim_spa, vim->vim_dn, offset, vim->vim_entries,
            size);
        if (rc != 0) {
                /* Read error, invalidate vim_entries. */
                free(vim->vim_entries);
                vim->vim_entries = NULL;
                return (NULL);
        }
        index -= vim->vim_entry_offset;
        return (&vim->vim_entries[index]);
}

/*
 * Returns the mapping entry for the given offset.
 *
 * It's possible that the given offset will not be in the mapping table
 * (i.e. no mapping entries contain this offset), in which case, the
 * return value value depends on the "next_if_missing" parameter.
 *
 * If the offset is not found in the table and "next_if_missing" is
 * B_FALSE, then NULL will always be returned. The behavior is intended
 * to allow consumers to get the entry corresponding to the offset
 * parameter, iff the offset overlaps with an entry in the table.
 *
 * If the offset is not found in the table and "next_if_missing" is
 * B_TRUE, then the entry nearest to the given offset will be returned,
 * such that the entry's source offset is greater than the offset
 * passed in (i.e. the "next" mapping entry in the table is returned, if
 * the offset is missing from the table). If there are no entries whose
 * source offset is greater than the passed in offset, NULL is returned.
 */
static vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_entry_for_offset(vdev_indirect_mapping_t *vim,
    uint64_t offset)
{
        ASSERT(vim->vim_phys->vimp_num_entries > 0);

        vdev_indirect_mapping_entry_phys_t *entry;

        uint64_t last = vim->vim_phys->vimp_num_entries - 1;
        uint64_t base = 0;

        /*
         * We don't define these inside of the while loop because we use
         * their value in the case that offset isn't in the mapping.
         */
        uint64_t mid;
        int result;

        while (last >= base) {
                mid = base + ((last - base) >> 1);

                entry = vdev_indirect_mapping_entry(vim, mid);
                if (entry == NULL)
                        break;
                result = dva_mapping_overlap_compare(&offset, entry);

                if (result == 0) {
                        break;
                } else if (result < 0) {
                        last = mid - 1;
                } else {
                        base = mid + 1;
                }
        }
        return (entry);
}

/*
 * Given an indirect vdev and an extent on that vdev, it duplicates the
 * physical entries of the indirect mapping that correspond to the extent
 * to a new array and returns a pointer to it. In addition, copied_entries
 * is populated with the number of mapping entries that were duplicated.
 *
 * Finally, since we are doing an allocation, it is up to the caller to
 * free the array allocated in this function.
 */
vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_duplicate_adjacent_entries(vdev_t *vd, uint64_t offset,
    uint64_t asize, uint64_t *copied_entries)
{
        vdev_indirect_mapping_entry_phys_t *duplicate_mappings = NULL;
        vdev_indirect_mapping_t *vim = vd->v_mapping;
        uint64_t entries = 0;

        vdev_indirect_mapping_entry_phys_t *first_mapping =
            vdev_indirect_mapping_entry_for_offset(vim, offset);
        ASSERT3P(first_mapping, !=, NULL);

        vdev_indirect_mapping_entry_phys_t *m = first_mapping;
        while (asize > 0) {
                uint64_t size = DVA_GET_ASIZE(&m->vimep_dst);
                uint64_t inner_offset = offset - DVA_MAPPING_GET_SRC_OFFSET(m);
                uint64_t inner_size = MIN(asize, size - inner_offset);

                offset += inner_size;
                asize -= inner_size;
                entries++;
                m++;
        }

        size_t copy_length = entries * sizeof (*first_mapping);
        duplicate_mappings = malloc(copy_length);
        if (duplicate_mappings != NULL)
                bcopy(first_mapping, duplicate_mappings, copy_length);
        else
                entries = 0;

        *copied_entries = entries;

        return (duplicate_mappings);
}

static vdev_t *
vdev_lookup_top(spa_t *spa, uint64_t vdev)
{
        vdev_t *rvd;
        vdev_list_t *vlist;

        vlist = &spa->spa_root_vdev->v_children;
        STAILQ_FOREACH(rvd, vlist, v_childlink)
                if (rvd->v_id == vdev)
                        break;

        return (rvd);
}

/*
 * This is a callback for vdev_indirect_remap() which allocates an
 * indirect_split_t for each split segment and adds it to iv_splits.
 */
static void
vdev_indirect_gather_splits(uint64_t split_offset, vdev_t *vd, uint64_t offset,
    uint64_t size, void *arg)
{
        int n = 1;
        zio_t *zio = arg;
        indirect_vsd_t *iv = zio->io_vsd;

        if (vd->v_read == vdev_indirect_read)
                return;

        if (vd->v_read == vdev_mirror_read)
                n = vd->v_nchildren;

        indirect_split_t *is =
            malloc(offsetof(indirect_split_t, is_child[n]));
        if (is == NULL) {
                zio->io_error = ENOMEM;
                return;
        }
        bzero(is, offsetof(indirect_split_t, is_child[n]));

        is->is_children = n;
        is->is_size = size;
        is->is_split_offset = split_offset;
        is->is_target_offset = offset;
        is->is_vdev = vd;

        /*
         * Note that we only consider multiple copies of the data for
         * *mirror* vdevs.  We don't for "replacing" or "spare" vdevs, even
         * though they use the same ops as mirror, because there's only one
         * "good" copy under the replacing/spare.
         */
        if (vd->v_read == vdev_mirror_read) {
                int i = 0;
                vdev_t *kid;

                STAILQ_FOREACH(kid, &vd->v_children, v_childlink) {
                        is->is_child[i++].ic_vdev = kid;
                }
        } else {
                is->is_child[0].ic_vdev = vd;
        }

        list_insert_tail(&iv->iv_splits, is);
}

static void
vdev_indirect_remap(vdev_t *vd, uint64_t offset, uint64_t asize, void *arg)
{
        list_t stack;
        spa_t *spa = vd->v_spa;
        zio_t *zio = arg;
        remap_segment_t *rs;

        list_create(&stack, sizeof (remap_segment_t),
            offsetof(remap_segment_t, rs_node));

        rs = rs_alloc(vd, offset, asize, 0);
        if (rs == NULL) {
                printf("vdev_indirect_remap: out of memory.\n");
                zio->io_error = ENOMEM;
        }
        for (; rs != NULL; rs = list_remove_head(&stack)) {
                vdev_t *v = rs->rs_vd;
                uint64_t num_entries = 0;
                /* vdev_indirect_mapping_t *vim = v->v_mapping; */
                vdev_indirect_mapping_entry_phys_t *mapping =
                    vdev_indirect_mapping_duplicate_adjacent_entries(v,
                    rs->rs_offset, rs->rs_asize, &num_entries);

                if (num_entries == 0)
                        zio->io_error = ENOMEM;

                for (uint64_t i = 0; i < num_entries; i++) {
                        vdev_indirect_mapping_entry_phys_t *m = &mapping[i];
                        uint64_t size = DVA_GET_ASIZE(&m->vimep_dst);
                        uint64_t dst_offset = DVA_GET_OFFSET(&m->vimep_dst);
                        uint64_t dst_vdev = DVA_GET_VDEV(&m->vimep_dst);
                        uint64_t inner_offset = rs->rs_offset -
                            DVA_MAPPING_GET_SRC_OFFSET(m);
                        uint64_t inner_size =
                            MIN(rs->rs_asize, size - inner_offset);
                        vdev_t *dst_v = vdev_lookup_top(spa, dst_vdev);

                        if (dst_v->v_read == vdev_indirect_read) {
                                remap_segment_t *o;

                                o = rs_alloc(dst_v, dst_offset + inner_offset,
                                    inner_size, rs->rs_split_offset);
                                if (o == NULL) {
                                        printf("vdev_indirect_remap: "
                                            "out of memory.\n");
                                        zio->io_error = ENOMEM;
                                        break;
                                }

                                list_insert_head(&stack, o);
                        }
                        vdev_indirect_gather_splits(rs->rs_split_offset, dst_v,
                            dst_offset + inner_offset,
                            inner_size, arg);

                        /*
                         * vdev_indirect_gather_splits can have memory
                         * allocation error, we can not recover from it.
                         */
                        if (zio->io_error != 0)
                                break;
                        rs->rs_offset += inner_size;
                        rs->rs_asize -= inner_size;
                        rs->rs_split_offset += inner_size;
                }

                free(mapping);
                free(rs);
                if (zio->io_error != 0)
                        break;
        }

        list_destroy(&stack);
}

static void
vdev_indirect_map_free(zio_t *zio)
{
        indirect_vsd_t *iv = zio->io_vsd;
        indirect_split_t *is;

        while ((is = list_head(&iv->iv_splits)) != NULL) {
                for (int c = 0; c < is->is_children; c++) {
                        indirect_child_t *ic = &is->is_child[c];
                        free(ic->ic_data);
                }
                list_remove(&iv->iv_splits, is);
                free(is);
        }
        free(iv);
}

static int
vdev_indirect_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
    off_t offset, size_t bytes)
{
        zio_t zio;
        spa_t *spa = vdev->v_spa;
        indirect_vsd_t *iv;
        indirect_split_t *first;
        int rc = EIO;

        iv = calloc(1, sizeof(*iv));
        if (iv == NULL)
                return (ENOMEM);

        list_create(&iv->iv_splits,
            sizeof (indirect_split_t), offsetof(indirect_split_t, is_node));

        bzero(&zio, sizeof(zio));
        zio.io_spa = spa;
        zio.io_bp = (blkptr_t *)bp;
        zio.io_data = buf;
        zio.io_size = bytes;
        zio.io_offset = offset;
        zio.io_vd = vdev;
        zio.io_vsd = iv;

        if (vdev->v_mapping == NULL) {
                vdev_indirect_config_t *vic;

                vic = &vdev->vdev_indirect_config;
                vdev->v_mapping = vdev_indirect_mapping_open(spa,
                    &spa->spa_mos, vic->vic_mapping_object);
        }

        vdev_indirect_remap(vdev, offset, bytes, &zio);
        if (zio.io_error != 0)
                return (zio.io_error);

        first = list_head(&iv->iv_splits);
        if (first->is_size == zio.io_size) {
                /*
                 * This is not a split block; we are pointing to the entire
                 * data, which will checksum the same as the original data.
                 * Pass the BP down so that the child i/o can verify the
                 * checksum, and try a different location if available
                 * (e.g. on a mirror).
                 *
                 * While this special case could be handled the same as the
                 * general (split block) case, doing it this way ensures
                 * that the vast majority of blocks on indirect vdevs
                 * (which are not split) are handled identically to blocks
                 * on non-indirect vdevs.  This allows us to be less strict
                 * about performance in the general (but rare) case.
                 */
                rc = first->is_vdev->v_read(first->is_vdev, zio.io_bp,
                    zio.io_data, first->is_target_offset, bytes);
        } else {
                iv->iv_split_block = B_TRUE;
                /*
                 * Read one copy of each split segment, from the
                 * top-level vdev.  Since we don't know the
                 * checksum of each split individually, the child
                 * zio can't ensure that we get the right data.
                 * E.g. if it's a mirror, it will just read from a
                 * random (healthy) leaf vdev.  We have to verify
                 * the checksum in vdev_indirect_io_done().
                 */
                for (indirect_split_t *is = list_head(&iv->iv_splits);
                    is != NULL; is = list_next(&iv->iv_splits, is)) {
                        char *ptr = zio.io_data;

                        rc = is->is_vdev->v_read(is->is_vdev, zio.io_bp,
                            ptr + is->is_split_offset, is->is_target_offset,
                            is->is_size);
                }
                if (zio_checksum_verify(spa, zio.io_bp, zio.io_data))
                        rc = ECKSUM;
                else
                        rc = 0;
        }

        vdev_indirect_map_free(&zio);
        if (rc == 0)
                rc = zio.io_error;

        return (rc);
}

static int
vdev_disk_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
    off_t offset, size_t bytes)
{

        return (vdev_read_phys(vdev, bp, buf,
            offset + VDEV_LABEL_START_SIZE, bytes));
}


static int
vdev_mirror_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
    off_t offset, size_t bytes)
{
        vdev_t *kid;
        int rc;

        rc = EIO;
        STAILQ_FOREACH(kid, &vdev->v_children, v_childlink) {
                if (kid->v_state != VDEV_STATE_HEALTHY)
                        continue;
                rc = kid->v_read(kid, bp, buf, offset, bytes);
                if (!rc)
                        return (0);
        }

        return (rc);
}

static int
vdev_replacing_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
    off_t offset, size_t bytes)
{
        vdev_t *kid;

        /*
         * Here we should have two kids:
         * First one which is the one we are replacing and we can trust
         * only this one to have valid data, but it might not be present.
         * Second one is that one we are replacing with. It is most likely
         * healthy, but we can't trust it has needed data, so we won't use it.
         */
        kid = STAILQ_FIRST(&vdev->v_children);
        if (kid == NULL)
                return (EIO);
        if (kid->v_state != VDEV_STATE_HEALTHY)
                return (EIO);
        return (kid->v_read(kid, bp, buf, offset, bytes));
}

static vdev_t *
vdev_find(uint64_t guid)
{
        vdev_t *vdev;

        STAILQ_FOREACH(vdev, &zfs_vdevs, v_alllink)
                if (vdev->v_guid == guid)
                        return (vdev);

        return (0);
}

static vdev_t *
vdev_create(uint64_t guid, vdev_read_t *_read)
{
        vdev_t *vdev;
        vdev_indirect_config_t *vic;

        vdev = calloc(1, sizeof(vdev_t));
        if (vdev != NULL) {
                STAILQ_INIT(&vdev->v_children);
                vdev->v_guid = guid;
                vdev->v_read = _read;

                /*
                 * root vdev has no read function, we use this fact to
                 * skip setting up data we do not need for root vdev.
                 * We only point root vdev from spa.
                 */
                if (_read != NULL) {
                        vic = &vdev->vdev_indirect_config;
                        vic->vic_prev_indirect_vdev = UINT64_MAX;
                        STAILQ_INSERT_TAIL(&zfs_vdevs, vdev, v_alllink);
                }
        }

        return (vdev);
}

static void
vdev_set_initial_state(vdev_t *vdev, const unsigned char *nvlist)
{
        uint64_t is_offline, is_faulted, is_degraded, is_removed, isnt_present;
        uint64_t is_log;

        is_offline = is_removed = is_faulted = is_degraded = isnt_present = 0;
        is_log = 0;
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_OFFLINE, DATA_TYPE_UINT64, NULL,
            &is_offline);
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_REMOVED, DATA_TYPE_UINT64, NULL,
            &is_removed);
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_FAULTED, DATA_TYPE_UINT64, NULL,
            &is_faulted);
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_DEGRADED, DATA_TYPE_UINT64,
            NULL, &is_degraded);
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_NOT_PRESENT, DATA_TYPE_UINT64,
            NULL, &isnt_present);
        (void) nvlist_find(nvlist, ZPOOL_CONFIG_IS_LOG, DATA_TYPE_UINT64, NULL,
            &is_log);

        if (is_offline != 0)
                vdev->v_state = VDEV_STATE_OFFLINE;
        else if (is_removed != 0)
                vdev->v_state = VDEV_STATE_REMOVED;
        else if (is_faulted != 0)
                vdev->v_state = VDEV_STATE_FAULTED;
        else if (is_degraded != 0)
                vdev->v_state = VDEV_STATE_DEGRADED;
        else if (isnt_present != 0)
                vdev->v_state = VDEV_STATE_CANT_OPEN;

        vdev->v_islog = is_log != 0;
}

static int
vdev_init(uint64_t guid, const unsigned char *nvlist, vdev_t **vdevp)
{
        uint64_t id, ashift, asize, nparity;
        const char *path;
        const char *type;
        vdev_t *vdev;

        if (nvlist_find(nvlist, ZPOOL_CONFIG_ID, DATA_TYPE_UINT64, NULL, &id) ||
            nvlist_find(nvlist, ZPOOL_CONFIG_TYPE, DATA_TYPE_STRING,
            NULL, &type)) {
                return (ENOENT);
        }

        if (strcmp(type, VDEV_TYPE_MIRROR) != 0 &&
            strcmp(type, VDEV_TYPE_DISK) != 0 &&
#ifdef ZFS_TEST
            strcmp(type, VDEV_TYPE_FILE) != 0 &&
#endif
            strcmp(type, VDEV_TYPE_RAIDZ) != 0 &&
            strcmp(type, VDEV_TYPE_INDIRECT) != 0 &&
            strcmp(type, VDEV_TYPE_REPLACING) != 0) {
                printf("ZFS: can only boot from disk, mirror, raidz1, "
                    "raidz2 and raidz3 vdevs\n");
                return (EIO);
        }

        if (strcmp(type, VDEV_TYPE_MIRROR) == 0)
                vdev = vdev_create(guid, vdev_mirror_read);
        else if (strcmp(type, VDEV_TYPE_RAIDZ) == 0)
                vdev = vdev_create(guid, vdev_raidz_read);
        else if (strcmp(type, VDEV_TYPE_REPLACING) == 0)
                vdev = vdev_create(guid, vdev_replacing_read);
        else if (strcmp(type, VDEV_TYPE_INDIRECT) == 0) {
                vdev_indirect_config_t *vic;

                vdev = vdev_create(guid, vdev_indirect_read);
                if (vdev != NULL) {
                        vdev->v_state = VDEV_STATE_HEALTHY;
                        vic = &vdev->vdev_indirect_config;

                        nvlist_find(nvlist,
                            ZPOOL_CONFIG_INDIRECT_OBJECT,
                            DATA_TYPE_UINT64,
                            NULL, &vic->vic_mapping_object);
                        nvlist_find(nvlist,
                            ZPOOL_CONFIG_INDIRECT_BIRTHS,
                            DATA_TYPE_UINT64,
                            NULL, &vic->vic_births_object);
                        nvlist_find(nvlist,
                            ZPOOL_CONFIG_PREV_INDIRECT_VDEV,
                            DATA_TYPE_UINT64,
                            NULL, &vic->vic_prev_indirect_vdev);
                }
        } else {
                vdev = vdev_create(guid, vdev_disk_read);
        }

        if (vdev == NULL)
                return (ENOMEM);

        vdev_set_initial_state(vdev, nvlist);
        vdev->v_id = id;
        if (nvlist_find(nvlist, ZPOOL_CONFIG_ASHIFT,
            DATA_TYPE_UINT64, NULL, &ashift) == 0)
                vdev->v_ashift = ashift;

        if (nvlist_find(nvlist, ZPOOL_CONFIG_ASIZE,
            DATA_TYPE_UINT64, NULL, &asize) == 0) {
                vdev->v_psize = asize +
                    VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE;
        }

        if (nvlist_find(nvlist, ZPOOL_CONFIG_NPARITY,
            DATA_TYPE_UINT64, NULL, &nparity) == 0)
                vdev->v_nparity = nparity;

        if (nvlist_find(nvlist, ZPOOL_CONFIG_PATH,
            DATA_TYPE_STRING, NULL, &path) == 0) {
                if (strncmp(path, "/dev/", 5) == 0)
                        path += 5;
                vdev->v_name = strdup(path);
        } else {
                char *name;

                name = NULL;
                if (strcmp(type, "raidz") == 0) {
                        if (vdev->v_nparity < 1 ||
                            vdev->v_nparity > 3) {
                                printf("ZFS: invalid raidz parity: %d\n",
                                    vdev->v_nparity);
                                return (EIO);
                        }
                        (void) asprintf(&name, "%s%d-%" PRIu64, type,
                            vdev->v_nparity, id);
                } else {
                        (void) asprintf(&name, "%s-%" PRIu64, type, id);
                }
                vdev->v_name = name;
        }
        *vdevp = vdev;
        return (0);
}

/*
 * Find slot for vdev. We return either NULL to signal to use
 * STAILQ_INSERT_HEAD, or we return link element to be used with
 * STAILQ_INSERT_AFTER.
 */
static vdev_t *
vdev_find_previous(vdev_t *top_vdev, vdev_t *vdev)
{
        vdev_t *v, *previous;

        if (STAILQ_EMPTY(&top_vdev->v_children))
                return (NULL);

        previous = NULL;
        STAILQ_FOREACH(v, &top_vdev->v_children, v_childlink) {
                if (v->v_id > vdev->v_id)
                        return (previous);

                if (v->v_id == vdev->v_id)
                        return (v);

                if (v->v_id < vdev->v_id)
                        previous = v;
        }
        return (previous);
}

static size_t
vdev_child_count(vdev_t *vdev)
{
        vdev_t *v;
        size_t count;

        count = 0;
        STAILQ_FOREACH(v, &vdev->v_children, v_childlink) {
                count++;
        }
        return (count);
}

/*
 * Insert vdev into top_vdev children list. List is ordered by v_id.
 */
static void
vdev_insert(vdev_t *top_vdev, vdev_t *vdev)
{
        vdev_t *previous;
        size_t count;

        /*
         * The top level vdev can appear in random order, depending how
         * the firmware is presenting the disk devices.
         * However, we will insert vdev to create list ordered by v_id,
         * so we can use either STAILQ_INSERT_HEAD or STAILQ_INSERT_AFTER
         * as STAILQ does not have insert before.
         */
        previous = vdev_find_previous(top_vdev, vdev);

        if (previous == NULL) {
                STAILQ_INSERT_HEAD(&top_vdev->v_children, vdev, v_childlink);
        } else if (previous->v_id == vdev->v_id) {
                /*
                 * This vdev was configured from label config,
                 * do not insert duplicate.
                 */
                return;
        } else {
                STAILQ_INSERT_AFTER(&top_vdev->v_children, previous, vdev,
                    v_childlink);
        }

        count = vdev_child_count(top_vdev);
        if (top_vdev->v_nchildren < count)
                top_vdev->v_nchildren = count;
}

static int
vdev_from_nvlist(spa_t *spa, uint64_t top_guid, const unsigned char *nvlist)
{
        vdev_t *top_vdev, *vdev;
        const unsigned char *kids;
        int rc, nkids;

        /* Get top vdev. */
        top_vdev = vdev_find(top_guid);
        if (top_vdev == NULL) {
                rc = vdev_init(top_guid, nvlist, &top_vdev);
                if (rc != 0)
                        return (rc);
                top_vdev->v_spa = spa;
                top_vdev->v_top = top_vdev;
                vdev_insert(spa->spa_root_vdev, top_vdev);
        }

        /* Add children if there are any. */
        rc = nvlist_find(nvlist, ZPOOL_CONFIG_CHILDREN, DATA_TYPE_NVLIST_ARRAY,
            &nkids, &kids);
        if (rc == 0) {
                for (int i = 0; i < nkids; i++) {
                        uint64_t guid;

                        rc = nvlist_find(kids, ZPOOL_CONFIG_GUID,
                            DATA_TYPE_UINT64, NULL, &guid);
                        if (rc != 0)
                                return (rc);
                        rc = vdev_init(guid, kids, &vdev);
                        if (rc != 0)
                                return (rc);

                        vdev->v_spa = spa;
                        vdev->v_top = top_vdev;
                        vdev_insert(top_vdev, vdev);

                        kids = nvlist_next(kids);
                }
        } else {
                /*
                 * When there are no children, nvlist_find() does return
                 * error, reset it because leaf devices have no children.
                 */
                rc = 0;
        }

        return (rc);
}

static int
vdev_init_from_label(spa_t *spa, const unsigned char *nvlist)
{
        uint64_t pool_guid, top_guid;
        const unsigned char *vdevs;

        if (nvlist_find(nvlist, ZPOOL_CONFIG_POOL_GUID, DATA_TYPE_UINT64,
            NULL, &pool_guid) ||
            nvlist_find(nvlist, ZPOOL_CONFIG_TOP_GUID, DATA_TYPE_UINT64,
            NULL, &top_guid) ||
            nvlist_find(nvlist, ZPOOL_CONFIG_VDEV_TREE, DATA_TYPE_NVLIST,
            NULL, &vdevs)) {
                printf("ZFS: can't find vdev details\n");
                return (ENOENT);
        }

        return (vdev_from_nvlist(spa, top_guid, vdevs));
}

static void
vdev_set_state(vdev_t *vdev)
{
        vdev_t *kid;
        int good_kids;
        int bad_kids;

        STAILQ_FOREACH(kid, &vdev->v_children, v_childlink) {
                vdev_set_state(kid);
        }

        /*
         * A mirror or raidz is healthy if all its kids are healthy. A
         * mirror is degraded if any of its kids is healthy; a raidz
         * is degraded if at most nparity kids are offline.
         */
        if (STAILQ_FIRST(&vdev->v_children)) {
                good_kids = 0;
                bad_kids = 0;
                STAILQ_FOREACH(kid, &vdev->v_children, v_childlink) {
                        if (kid->v_state == VDEV_STATE_HEALTHY)
                                good_kids++;
                        else
                                bad_kids++;
                }
                if (bad_kids == 0) {
                        vdev->v_state = VDEV_STATE_HEALTHY;
                } else {
                        if (vdev->v_read == vdev_mirror_read) {
                                if (good_kids) {
                                        vdev->v_state = VDEV_STATE_DEGRADED;
                                } else {
                                        vdev->v_state = VDEV_STATE_OFFLINE;
                                }
                        } else if (vdev->v_read == vdev_raidz_read) {
                                if (bad_kids > vdev->v_nparity) {
                                        vdev->v_state = VDEV_STATE_OFFLINE;
                                } else {
                                        vdev->v_state = VDEV_STATE_DEGRADED;
                                }
                        }
                }
        }
}

static int
vdev_update_from_nvlist(uint64_t top_guid, const unsigned char *nvlist)
{
        vdev_t *vdev;
        const unsigned char *kids;
        int rc, nkids;

        /* Update top vdev. */
        vdev = vdev_find(top_guid);
        if (vdev != NULL)
                vdev_set_initial_state(vdev, nvlist);

        /* Update children if there are any. */
        rc = nvlist_find(nvlist, ZPOOL_CONFIG_CHILDREN, DATA_TYPE_NVLIST_ARRAY,
            &nkids, &kids);
        if (rc == 0) {
                for (int i = 0; i < nkids; i++) {
                        uint64_t guid;

                        rc = nvlist_find(kids, ZPOOL_CONFIG_GUID,
                            DATA_TYPE_UINT64, NULL, &guid);
                        if (rc != 0)
                                break;

                        vdev = vdev_find(guid);
                        if (vdev != NULL)
                                vdev_set_initial_state(vdev, kids);

                        kids = nvlist_next(kids);
                }
        } else {
                rc = 0;
        }

        return (rc);
}

static int
vdev_init_from_nvlist(spa_t *spa, const unsigned char *nvlist)
{
        uint64_t pool_guid, vdev_children;
        const unsigned char *vdevs, *kids;
        int rc, nkids;

        if (nvlist_find(nvlist, ZPOOL_CONFIG_POOL_GUID, DATA_TYPE_UINT64,
            NULL, &pool_guid) ||
            nvlist_find(nvlist, ZPOOL_CONFIG_VDEV_CHILDREN, DATA_TYPE_UINT64,
            NULL, &vdev_children) ||
            nvlist_find(nvlist, ZPOOL_CONFIG_VDEV_TREE, DATA_TYPE_NVLIST,
            NULL, &vdevs)) {
                printf("ZFS: can't find vdev details\n");
                return (ENOENT);
        }

        /* Wrong guid?! */
        if (spa->spa_guid != pool_guid)
                return (EINVAL);

        spa->spa_root_vdev->v_nchildren = vdev_children;

        rc = nvlist_find(vdevs, ZPOOL_CONFIG_CHILDREN, DATA_TYPE_NVLIST_ARRAY,
            &nkids, &kids);

        /*
         * MOS config has at least one child for root vdev.
         */
        if (rc != 0)
                return (rc);

        for (int i = 0; i < nkids; i++) {
                uint64_t guid;
                vdev_t *vdev;

                rc = nvlist_find(kids, ZPOOL_CONFIG_GUID, DATA_TYPE_UINT64,
                    NULL, &guid);
                if (rc != 0)
                        break;
                vdev = vdev_find(guid);
                /*
                 * Top level vdev is missing, create it.
                 */
                if (vdev == NULL)
                        rc = vdev_from_nvlist(spa, guid, kids);
                else
                        rc = vdev_update_from_nvlist(guid, kids);
                if (rc != 0)
                        break;
                kids = nvlist_next(kids);
        }

        /*
         * Re-evaluate top-level vdev state.
         */
        vdev_set_state(spa->spa_root_vdev);

        return (rc);
}

static spa_t *
spa_find_by_guid(uint64_t guid)
{
        spa_t *spa;

        STAILQ_FOREACH(spa, &zfs_pools, spa_link)
                if (spa->spa_guid == guid)
                        return (spa);

        return (NULL);
}

static spa_t *
spa_find_by_name(const char *name)
{
        spa_t *spa;

        STAILQ_FOREACH(spa, &zfs_pools, spa_link)
                if (strcmp(spa->spa_name, name) == 0)
                        return (spa);

        return (NULL);
}

#ifdef BOOT2
static spa_t *
spa_get_primary(void)
{

        return (STAILQ_FIRST(&zfs_pools));
}

static vdev_t *
spa_get_primary_vdev(const spa_t *spa)
{
        vdev_t *vdev;
        vdev_t *kid;

        if (spa == NULL)
                spa = spa_get_primary();
        if (spa == NULL)
                return (NULL);
        vdev = spa->spa_root_vdev;
        if (vdev == NULL)
                return (NULL);
        for (kid = STAILQ_FIRST(&vdev->v_children); kid != NULL;
            kid = STAILQ_FIRST(&vdev->v_children))
                vdev = kid;
        return (vdev);
}
#endif

static spa_t *
spa_create(uint64_t guid, const char *name)
{
        spa_t *spa;

        if ((spa = calloc(1, sizeof(spa_t))) == NULL)
                return (NULL);
        if ((spa->spa_name = strdup(name)) == NULL) {
                free(spa);
                return (NULL);
        }
        spa->spa_guid = guid;
        spa->spa_root_vdev = vdev_create(guid, NULL);
        if (spa->spa_root_vdev == NULL) {
                free(spa->spa_name);
                free(spa);
                return (NULL);
        }
        spa->spa_root_vdev->v_name = strdup("root");
        STAILQ_INSERT_TAIL(&zfs_pools, spa, spa_link);

        return (spa);
}

static const char *
state_name(vdev_state_t state)
{
        static const char *names[] = {
                "UNKNOWN",
                "CLOSED",
                "OFFLINE",
                "REMOVED",
                "CANT_OPEN",
                "FAULTED",
                "DEGRADED",
                "ONLINE"
        };
        return (names[state]);
}

#ifdef BOOT2

#define pager_printf printf

#else

static int
pager_printf(const char *fmt, ...)
{
        char line[80];
        va_list args;

        va_start(args, fmt);
        vsnprintf(line, sizeof(line), fmt, args);
        va_end(args);
        return (pager_output(line));
}

#endif

#define STATUS_FORMAT   "        %s %s\n"

static int
print_state(int indent, const char *name, vdev_state_t state)
{
        int i;
        char buf[512];

        buf[0] = 0;
        for (i = 0; i < indent; i++)
                strcat(buf, "  ");
        strcat(buf, name);
        return (pager_printf(STATUS_FORMAT, buf, state_name(state)));
}

static int
vdev_status(vdev_t *vdev, int indent)
{
        vdev_t *kid;
        int ret;

        if (vdev->v_islog) {
                (void) pager_output("        logs\n");
                indent++;
        }

        ret = print_state(indent, vdev->v_name, vdev->v_state);
        if (ret != 0)
                return (ret);

        STAILQ_FOREACH(kid, &vdev->v_children, v_childlink) {
                ret = vdev_status(kid, indent + 1);
                if (ret != 0)
                        return (ret);
        }
        return (ret);
}

static int
spa_status(spa_t *spa)
{
        static char bootfs[ZFS_MAXNAMELEN];
        uint64_t rootid;
        vdev_list_t *vlist;
        vdev_t *vdev;
        int good_kids, bad_kids, degraded_kids, ret;
        vdev_state_t state;

        ret = pager_printf("  pool: %s\n", spa->spa_name);
        if (ret != 0)
                return (ret);

        if (zfs_get_root(spa, &rootid) == 0 &&
            zfs_rlookup(spa, rootid, bootfs) == 0) {
                if (bootfs[0] == '\0')
                        ret = pager_printf("bootfs: %s\n", spa->spa_name);
                else
                        ret = pager_printf("bootfs: %s/%s\n", spa->spa_name,
                            bootfs);
                if (ret != 0)
                        return (ret);
        }
        ret = pager_printf("config:\n\n");
        if (ret != 0)
                return (ret);
        ret = pager_printf(STATUS_FORMAT, "NAME", "STATE");
        if (ret != 0)
                return (ret);

        good_kids = 0;
        degraded_kids = 0;
        bad_kids = 0;
        vlist = &spa->spa_root_vdev->v_children;
        STAILQ_FOREACH(vdev, vlist, v_childlink) {
                if (vdev->v_state == VDEV_STATE_HEALTHY)
                        good_kids++;
                else if (vdev->v_state == VDEV_STATE_DEGRADED)
                        degraded_kids++;
                else
                        bad_kids++;
        }

        state = VDEV_STATE_CLOSED;
        if (good_kids > 0 && (degraded_kids + bad_kids) == 0)
                state = VDEV_STATE_HEALTHY;
        else if ((good_kids + degraded_kids) > 0)
                state = VDEV_STATE_DEGRADED;

        ret = print_state(0, spa->spa_name, state);
        if (ret != 0)
                return (ret);

        STAILQ_FOREACH(vdev, vlist, v_childlink) {
                ret = vdev_status(vdev, 1);
                if (ret != 0)
                        return (ret);
        }
        return (ret);
}

static int
spa_all_status(void)
{
        spa_t *spa;
        int first = 1, ret = 0;

        STAILQ_FOREACH(spa, &zfs_pools, spa_link) {
                if (!first) {
                        ret = pager_printf("\n");
                        if (ret != 0)
                                return (ret);
                }
                first = 0;
                ret = spa_status(spa);
                if (ret != 0)
                        return (ret);
        }
        return (ret);
}

static uint64_t
vdev_label_offset(uint64_t psize, int l, uint64_t offset)
{
        uint64_t label_offset;

        if (l < VDEV_LABELS / 2)
                label_offset = 0;
        else
                label_offset = psize - VDEV_LABELS * sizeof (vdev_label_t);

        return (offset + l * sizeof (vdev_label_t) + label_offset);
}

static int
vdev_uberblock_compare(const uberblock_t *ub1, const uberblock_t *ub2)
{
        unsigned int seq1 = 0;
        unsigned int seq2 = 0;
        int cmp = AVL_CMP(ub1->ub_txg, ub2->ub_txg);

        if (cmp != 0)
                return (cmp);

        cmp = AVL_CMP(ub1->ub_timestamp, ub2->ub_timestamp);
        if (cmp != 0)
                return (cmp);

        if (MMP_VALID(ub1) && MMP_SEQ_VALID(ub1))
                seq1 = MMP_SEQ(ub1);

        if (MMP_VALID(ub2) && MMP_SEQ_VALID(ub2))
                seq2 = MMP_SEQ(ub2);

        return (AVL_CMP(seq1, seq2));
}

static int
uberblock_verify(uberblock_t *ub)
{
        if (ub->ub_magic == BSWAP_64((uint64_t)UBERBLOCK_MAGIC)) {
                byteswap_uint64_array(ub, sizeof (uberblock_t));
        }

        if (ub->ub_magic != UBERBLOCK_MAGIC ||
            !SPA_VERSION_IS_SUPPORTED(ub->ub_version))
                return (EINVAL);

        return (0);
}

static int
vdev_label_read(vdev_t *vd, int l, void *buf, uint64_t offset,
    size_t size)
{
        blkptr_t bp;
        off_t off;

        off = vdev_label_offset(vd->v_psize, l, offset);

        BP_ZERO(&bp);
        BP_SET_LSIZE(&bp, size);
        BP_SET_PSIZE(&bp, size);
        BP_SET_CHECKSUM(&bp, ZIO_CHECKSUM_LABEL);
        BP_SET_COMPRESS(&bp, ZIO_COMPRESS_OFF);
        DVA_SET_OFFSET(BP_IDENTITY(&bp), off);
        ZIO_SET_CHECKSUM(&bp.blk_cksum, off, 0, 0, 0);

        return (vdev_read_phys(vd, &bp, buf, off, size));
}

static unsigned char *
vdev_label_read_config(vdev_t *vd, uint64_t txg)
{
        vdev_phys_t *label;
        uint64_t best_txg = 0;
        uint64_t label_txg = 0;
        uint64_t asize;
        unsigned char *nvl;
        size_t nvl_size;
        int error;

        label = malloc(sizeof (vdev_phys_t));
        if (label == NULL)
                return (NULL);

        nvl_size = VDEV_PHYS_SIZE - sizeof (zio_eck_t) - 4;
        nvl = malloc(nvl_size);
        if (nvl == NULL)
                goto done;

        for (int l = 0; l < VDEV_LABELS; l++) {
                const unsigned char *nvlist;

                if (vdev_label_read(vd, l, label,
                    offsetof(vdev_label_t, vl_vdev_phys),
                    sizeof (vdev_phys_t)))
                        continue;

                if (label->vp_nvlist[0] != NV_ENCODE_XDR)
                        continue;

                nvlist = (const unsigned char *) label->vp_nvlist + 4;
                error = nvlist_find(nvlist, ZPOOL_CONFIG_POOL_TXG,
                    DATA_TYPE_UINT64, NULL, &label_txg);
                if (error != 0 || label_txg == 0) {
                        memcpy(nvl, nvlist, nvl_size);
                        goto done;
                }

                if (label_txg <= txg && label_txg > best_txg) {
                        best_txg = label_txg;
                        memcpy(nvl, nvlist, nvl_size);

                        /*
                         * Use asize from pool config. We need this
                         * because we can get bad value from BIOS.
                         */
                        if (nvlist_find(nvlist, ZPOOL_CONFIG_ASIZE,
                            DATA_TYPE_UINT64, NULL, &asize) == 0) {
                                vd->v_psize = asize +
                                    VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE;
                        }
                }
        }

        if (best_txg == 0) {
                free(nvl);
                nvl = NULL;
        }
done:
        free(label);
        return (nvl);
}

static void
vdev_uberblock_load(vdev_t *vd, uberblock_t *ub)
{
        uberblock_t *buf;

        buf = malloc(VDEV_UBERBLOCK_SIZE(vd));
        if (buf == NULL)
                return;

        for (int l = 0; l < VDEV_LABELS; l++) {
                for (int n = 0; n < VDEV_UBERBLOCK_COUNT(vd); n++) {
                        if (vdev_label_read(vd, l, buf,
                            VDEV_UBERBLOCK_OFFSET(vd, n),
                            VDEV_UBERBLOCK_SIZE(vd)))
                                continue;
                        if (uberblock_verify(buf) != 0)
                                continue;

                        if (vdev_uberblock_compare(buf, ub) > 0)
                                *ub = *buf;
                }
        }
        free(buf);
}

static int
vdev_probe(vdev_phys_read_t *_read, void *read_priv, spa_t **spap)
{
        vdev_t vtmp;
        spa_t *spa;
        vdev_t *vdev;
        unsigned char *nvlist;
        uint64_t val;
        uint64_t guid, vdev_children;
        uint64_t pool_txg, pool_guid;
        const char *pool_name;
        const unsigned char *features;
        int rc;

        /*
         * Load the vdev label and figure out which
         * uberblock is most current.
         */
        memset(&vtmp, 0, sizeof(vtmp));
        vtmp.v_phys_read = _read;
        vtmp.v_read_priv = read_priv;
        vtmp.v_psize = P2ALIGN(ldi_get_size(read_priv),
            (uint64_t)sizeof (vdev_label_t));

        /* Test for minimum device size. */
        if (vtmp.v_psize < SPA_MINDEVSIZE)
                return (EIO);

        nvlist = vdev_label_read_config(&vtmp, UINT64_MAX);
        if (nvlist == NULL)
                return (EIO);

        if (nvlist_find(nvlist, ZPOOL_CONFIG_VERSION, DATA_TYPE_UINT64,
            NULL, &val) != 0) {
                free(nvlist);
                return (EIO);
        }

        if (!SPA_VERSION_IS_SUPPORTED(val)) {
                printf("ZFS: unsupported ZFS version %u (should be %u)\n",
                    (unsigned)val, (unsigned)SPA_VERSION);
                free(nvlist);
                return (EIO);
        }

        /* Check ZFS features for read */
        if (nvlist_find(nvlist, ZPOOL_CONFIG_FEATURES_FOR_READ,
            DATA_TYPE_NVLIST, NULL, &features) == 0 &&
            nvlist_check_features_for_read(features) != 0) {
                free(nvlist);
                return (EIO);
        }

        if (nvlist_find(nvlist, ZPOOL_CONFIG_POOL_STATE, DATA_TYPE_UINT64,
            NULL, &val) != 0) {
                free(nvlist);
                return (EIO);
        }

        if (val == POOL_STATE_DESTROYED) {
                /* We don't boot only from destroyed pools. */
                free(nvlist);
                return (EIO);
        }

        if (nvlist_find(nvlist, ZPOOL_CONFIG_POOL_TXG, DATA_TYPE_UINT64,
            NULL, &pool_txg) != 0 ||
            nvlist_find(nvlist, ZPOOL_CONFIG_POOL_GUID, DATA_TYPE_UINT64,
            NULL, &pool_guid) != 0 ||
            nvlist_find(nvlist, ZPOOL_CONFIG_POOL_NAME, DATA_TYPE_STRING,
            NULL, &pool_name) != 0) {
                /*
                 * Cache and spare devices end up here - just ignore
                 * them.
                 */
                free(nvlist);
                return (EIO);
        }

        /*
         * Create the pool if this is the first time we've seen it.
         */
        spa = spa_find_by_guid(pool_guid);
        if (spa == NULL) {
                nvlist_find(nvlist, ZPOOL_CONFIG_VDEV_CHILDREN,
                    DATA_TYPE_UINT64, NULL, &vdev_children);
                spa = spa_create(pool_guid, pool_name);
                if (spa == NULL) {
                        free(nvlist);
                        return (ENOMEM);
                }
                spa->spa_root_vdev->v_nchildren = vdev_children;
        }
        if (pool_txg > spa->spa_txg)
                spa->spa_txg = pool_txg;

        /*
         * Get the vdev tree and create our in-core copy of it.
         * If we already have a vdev with this guid, this must
         * be some kind of alias (overlapping slices, dangerously dedicated
         * disks etc).
         */
        if (nvlist_find(nvlist, ZPOOL_CONFIG_GUID, DATA_TYPE_UINT64,
            NULL, &guid) != 0) {
                free(nvlist);
                return (EIO);
        }
        vdev = vdev_find(guid);
        /* Has this vdev already been inited? */
        if (vdev && vdev->v_phys_read) {
                free(nvlist);
                return (EIO);
        }

        rc = vdev_init_from_label(spa, nvlist);
        free(nvlist);
        if (rc != 0)
                return (rc);

        /*
         * We should already have created an incomplete vdev for this
         * vdev. Find it and initialise it with our read proc.
         */
        vdev = vdev_find(guid);
        if (vdev != NULL) {
                vdev->v_phys_read = _read;
                vdev->v_read_priv = read_priv;
                vdev->v_psize = vtmp.v_psize;
                /*
                 * If no other state is set, mark vdev healthy.
                 */
                if (vdev->v_state == VDEV_STATE_UNKNOWN)
                        vdev->v_state = VDEV_STATE_HEALTHY;
        } else {
                printf("ZFS: inconsistent nvlist contents\n");
                return (EIO);
        }

        if (vdev->v_islog)
                spa->spa_with_log = vdev->v_islog;

        /*
         * Re-evaluate top-level vdev state.
         */
        vdev_set_state(vdev->v_top);

        /*
         * Ok, we are happy with the pool so far. Lets find
         * the best uberblock and then we can actually access
         * the contents of the pool.
         */
        vdev_uberblock_load(vdev, &spa->spa_uberblock);

        if (spap != NULL)
                *spap = spa;
        return (0);
}

static int
ilog2(int n)
{
        int v;

        for (v = 0; v < 32; v++)
                if (n == (1 << v))
                        return (v);
        return (-1);
}

static int
zio_read_gang(const spa_t *spa, const blkptr_t *bp, void *buf)
{
        blkptr_t gbh_bp;
        zio_gbh_phys_t zio_gb;
        char *pbuf;
        int i;

        /* Artificial BP for gang block header. */
        gbh_bp = *bp;
        BP_SET_PSIZE(&gbh_bp, SPA_GANGBLOCKSIZE);
        BP_SET_LSIZE(&gbh_bp, SPA_GANGBLOCKSIZE);
        BP_SET_CHECKSUM(&gbh_bp, ZIO_CHECKSUM_GANG_HEADER);
        BP_SET_COMPRESS(&gbh_bp, ZIO_COMPRESS_OFF);
        for (i = 0; i < SPA_DVAS_PER_BP; i++)
                DVA_SET_GANG(&gbh_bp.blk_dva[i], 0);

        /* Read gang header block using the artificial BP. */
        if (zio_read(spa, &gbh_bp, &zio_gb))
                return (EIO);

        pbuf = buf;
        for (i = 0; i < SPA_GBH_NBLKPTRS; i++) {
                blkptr_t *gbp = &zio_gb.zg_blkptr[i];

                if (BP_IS_HOLE(gbp))
                        continue;
                if (zio_read(spa, gbp, pbuf))
                        return (EIO);
                pbuf += BP_GET_PSIZE(gbp);
        }

        if (zio_checksum_verify(spa, bp, buf))
                return (EIO);
        return (0);
}

static int
zio_read(const spa_t *spa, const blkptr_t *bp, void *buf)
{
        int cpfunc = BP_GET_COMPRESS(bp);
        uint64_t align, size;
        void *pbuf;
        int i, error;

        /*
         * Process data embedded in block pointer
         */
        if (BP_IS_EMBEDDED(bp)) {
                ASSERT(BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);

                size = BPE_GET_PSIZE(bp);
                ASSERT(size <= BPE_PAYLOAD_SIZE);

                if (cpfunc != ZIO_COMPRESS_OFF)
                        pbuf = zfs_alloc(size);
                else
                        pbuf = buf;

                decode_embedded_bp_compressed(bp, pbuf);
                error = 0;

                if (cpfunc != ZIO_COMPRESS_OFF) {
                        error = zio_decompress_data(cpfunc, pbuf,
                            size, buf, BP_GET_LSIZE(bp));
                        zfs_free(pbuf, size);
                }
                if (error != 0)
                        printf("ZFS: i/o error - unable to decompress "
                            "block pointer data, error %d\n", error);
                return (error);
        }

        error = EIO;

        for (i = 0; i < SPA_DVAS_PER_BP; i++) {
                const dva_t *dva = &bp->blk_dva[i];
                vdev_t *vdev;
                vdev_list_t *vlist;
                uint64_t vdevid;
                off_t offset;

                if (!dva->dva_word[0] && !dva->dva_word[1])
                        continue;

                vdevid = DVA_GET_VDEV(dva);
                offset = DVA_GET_OFFSET(dva);
                vlist = &spa->spa_root_vdev->v_children;
                STAILQ_FOREACH(vdev, vlist, v_childlink) {
                        if (vdev->v_id == vdevid)
                                break;
                }
                if (!vdev || !vdev->v_read)
                        continue;

                size = BP_GET_PSIZE(bp);
                if (vdev->v_read == vdev_raidz_read) {
                        align = 1ULL << vdev->v_ashift;
                        if (P2PHASE(size, align) != 0)
                                size = P2ROUNDUP(size, align);
                }
                if (size != BP_GET_PSIZE(bp) || cpfunc != ZIO_COMPRESS_OFF)
                        pbuf = zfs_alloc(size);
                else
                        pbuf = buf;

                if (DVA_GET_GANG(dva))
                        error = zio_read_gang(spa, bp, pbuf);
                else
                        error = vdev->v_read(vdev, bp, pbuf, offset, size);
                if (error == 0) {
                        if (cpfunc != ZIO_COMPRESS_OFF)
                                error = zio_decompress_data(cpfunc, pbuf,
                                    BP_GET_PSIZE(bp), buf, BP_GET_LSIZE(bp));
                        else if (size != BP_GET_PSIZE(bp))
                                bcopy(pbuf, buf, BP_GET_PSIZE(bp));
                }
                if (buf != pbuf)
                        zfs_free(pbuf, size);
                if (error == 0)
                        break;
        }
        if (error != 0)
                printf("ZFS: i/o error - all block copies unavailable\n");
        return (error);
}

static int
dnode_read(const spa_t *spa, const dnode_phys_t *dnode, off_t offset,
    void *buf, size_t buflen)
{
        int ibshift = dnode->dn_indblkshift - SPA_BLKPTRSHIFT;
        int bsize = dnode->dn_datablkszsec << SPA_MINBLOCKSHIFT;
        int nlevels = dnode->dn_nlevels;
        int i, rc;

        if (bsize > SPA_MAXBLOCKSIZE) {
                printf("ZFS: I/O error - blocks larger than %llu are not "
                    "supported\n", SPA_MAXBLOCKSIZE);
                return (EIO);
        }

        /*
         * Note: bsize may not be a power of two here so we need to do an
         * actual divide rather than a bitshift.
         */
        while (buflen > 0) {
                uint64_t bn = offset / bsize;
                int boff = offset % bsize;
                int ibn;
                const blkptr_t *indbp;
                blkptr_t bp;

                if (bn > dnode->dn_maxblkid)
                        return (EIO);

                if (dnode == dnode_cache_obj && bn == dnode_cache_bn)
                        goto cached;

                indbp = dnode->dn_blkptr;
                for (i = 0; i < nlevels; i++) {
                        /*
                         * Copy the bp from the indirect array so that
                         * we can re-use the scratch buffer for multi-level
                         * objects.
                         */
                        ibn = bn >> ((nlevels - i - 1) * ibshift);
                        ibn &= ((1 << ibshift) - 1);
                        bp = indbp[ibn];
                        if (BP_IS_HOLE(&bp)) {
                                memset(dnode_cache_buf, 0, bsize);
                                break;
                        }
                        rc = zio_read(spa, &bp, dnode_cache_buf);
                        if (rc)
                                return (rc);
                        indbp = (const blkptr_t *) dnode_cache_buf;
                }
                dnode_cache_obj = dnode;
                dnode_cache_bn = bn;
        cached:

                /*
                 * The buffer contains our data block. Copy what we
                 * need from it and loop.
                 */
                i = bsize - boff;
                if (i > buflen) i = buflen;
                memcpy(buf, &dnode_cache_buf[boff], i);
                buf = ((char *)buf) + i;
                offset += i;
                buflen -= i;
        }

        return (0);
}

/*
 * Lookup a value in a microzap directory. Assumes that the zap
 * scratch buffer contains the directory contents.
 */
static int
mzap_lookup(const dnode_phys_t *dnode, const char *name, uint64_t *value)
{
        const mzap_phys_t *mz;
        const mzap_ent_phys_t *mze;
        size_t size;
        int chunks, i;

        /*
         * Microzap objects use exactly one block. Read the whole
         * thing.
         */
        size = dnode->dn_datablkszsec * 512;

        mz = (const mzap_phys_t *) zap_scratch;
        chunks = size / MZAP_ENT_LEN - 1;

        for (i = 0; i < chunks; i++) {
                mze = &mz->mz_chunk[i];
                if (strcmp(mze->mze_name, name) == 0) {
                        *value = mze->mze_value;
                        return (0);
                }
        }

        return (ENOENT);
}

/*
 * Compare a name with a zap leaf entry. Return non-zero if the name
 * matches.
 */
static int
fzap_name_equal(const zap_leaf_t *zl, const zap_leaf_chunk_t *zc,
    const char *name)
{
        size_t namelen;
        const zap_leaf_chunk_t *nc;
        const char *p;

        namelen = zc->l_entry.le_name_numints;

        nc = &ZAP_LEAF_CHUNK(zl, zc->l_entry.le_name_chunk);
        p = name;
        while (namelen > 0) {
                size_t len;

                len = namelen;
                if (len > ZAP_LEAF_ARRAY_BYTES)
                        len = ZAP_LEAF_ARRAY_BYTES;
                if (memcmp(p, nc->l_array.la_array, len))
                        return (0);
                p += len;
                namelen -= len;
                nc = &ZAP_LEAF_CHUNK(zl, nc->l_array.la_next);
        }

        return (1);
}

/*
 * Extract a uint64_t value from a zap leaf entry.
 */
static uint64_t
fzap_leaf_value(const zap_leaf_t *zl, const zap_leaf_chunk_t *zc)
{
        const zap_leaf_chunk_t *vc;
        int i;
        uint64_t value;
        const uint8_t *p;

        vc = &ZAP_LEAF_CHUNK(zl, zc->l_entry.le_value_chunk);
        for (i = 0, value = 0, p = vc->l_array.la_array; i < 8; i++) {
                value = (value << 8) | p[i];
        }

        return (value);
}

static void
stv(int len, void *addr, uint64_t value)
{
        switch (len) {
        case 1:
                *(uint8_t *)addr = value;
                return;
        case 2:
                *(uint16_t *)addr = value;
                return;
        case 4:
                *(uint32_t *)addr = value;
                return;
        case 8:
                *(uint64_t *)addr = value;
                return;
        }
}

/*
 * Extract a array from a zap leaf entry.
 */
static void
fzap_leaf_array(const zap_leaf_t *zl, const zap_leaf_chunk_t *zc,
    uint64_t integer_size, uint64_t num_integers, void *buf)
{
        uint64_t array_int_len = zc->l_entry.le_value_intlen;
        uint64_t value = 0;
        uint64_t *u64 = buf;
        char *p = buf;
        int len = MIN(zc->l_entry.le_value_numints, num_integers);
        int chunk = zc->l_entry.le_value_chunk;
        int byten = 0;

        if (integer_size == 8 && len == 1) {
                *u64 = fzap_leaf_value(zl, zc);
                return;
        }

        while (len > 0) {
                struct zap_leaf_array *la = &ZAP_LEAF_CHUNK(zl, chunk).l_array;
                int i;

                ASSERT3U(chunk, <, ZAP_LEAF_NUMCHUNKS(zl));
                for (i = 0; i < ZAP_LEAF_ARRAY_BYTES && len > 0; i++) {
                        value = (value << 8) | la->la_array[i];
                        byten++;
                        if (byten == array_int_len) {
                                stv(integer_size, p, value);
                                byten = 0;
                                len--;
                                if (len == 0)
                                        return;
                                p += integer_size;
                        }
                }
                chunk = la->la_next;
        }
}

static int
fzap_check_size(uint64_t integer_size, uint64_t num_integers)
{

        switch (integer_size) {
        case 1:
        case 2:
        case 4:
        case 8:
                break;
        default:
                return (EINVAL);
        }

        if (integer_size * num_integers > ZAP_MAXVALUELEN)
                return (E2BIG);

        return (0);
}

/*
 * Lookup a value in a fatzap directory. Assumes that the zap scratch
 * buffer contains the directory header.
 */
static int
fzap_lookup(const spa_t *spa, const dnode_phys_t *dnode, const char *name,
    uint64_t integer_size, uint64_t num_integers, void *value)
{
        int bsize = dnode->dn_datablkszsec << SPA_MINBLOCKSHIFT;
        zap_phys_t zh = *(zap_phys_t *)zap_scratch;
        fat_zap_t z;
        uint64_t *ptrtbl;
        uint64_t hash;
        int rc;

        if (zh.zap_magic != ZAP_MAGIC)
                return (EIO);

        if ((rc = fzap_check_size(integer_size, num_integers)) != 0)
                return (rc);

        z.zap_block_shift = ilog2(bsize);
        z.zap_phys = (zap_phys_t *)zap_scratch;

        /*
         * Figure out where the pointer table is and read it in if necessary.
         */
        if (zh.zap_ptrtbl.zt_blk) {
                rc = dnode_read(spa, dnode, zh.zap_ptrtbl.zt_blk * bsize,
                    zap_scratch, bsize);
                if (rc)
                        return (rc);
                ptrtbl = (uint64_t *)zap_scratch;
        } else {
                ptrtbl = &ZAP_EMBEDDED_PTRTBL_ENT(&z, 0);
        }

        hash = zap_hash(zh.zap_salt, name);

        zap_leaf_t zl;
        zl.l_bs = z.zap_block_shift;

        off_t off = ptrtbl[hash >> (64 - zh.zap_ptrtbl.zt_shift)] << zl.l_bs;
        zap_leaf_chunk_t *zc;

        rc = dnode_read(spa, dnode, off, zap_scratch, bsize);
        if (rc)
                return (rc);

        zl.l_phys = (zap_leaf_phys_t *)zap_scratch;

        /*
         * Make sure this chunk matches our hash.
         */
        if (zl.l_phys->l_hdr.lh_prefix_len > 0 &&
            zl.l_phys->l_hdr.lh_prefix !=
            hash >> (64 - zl.l_phys->l_hdr.lh_prefix_len))
                return (ENOENT);

        /*
         * Hash within the chunk to find our entry.
         */
        int shift = (64 - ZAP_LEAF_HASH_SHIFT(&zl) -
            zl.l_phys->l_hdr.lh_prefix_len);
        int h = (hash >> shift) & ((1 << ZAP_LEAF_HASH_SHIFT(&zl)) - 1);
        h = zl.l_phys->l_hash[h];
        if (h == 0xffff)
                return (ENOENT);
        zc = &ZAP_LEAF_CHUNK(&zl, h);
        while (zc->l_entry.le_hash != hash) {
                if (zc->l_entry.le_next == 0xffff)
                        return (ENOENT);
                zc = &ZAP_LEAF_CHUNK(&zl, zc->l_entry.le_next);
        }
        if (fzap_name_equal(&zl, zc, name)) {
                if (zc->l_entry.le_value_intlen * zc->l_entry.le_value_numints >
                    integer_size * num_integers)
                        return (E2BIG);
                fzap_leaf_array(&zl, zc, integer_size, num_integers, value);
                return (0);
        }

        return (ENOENT);
}

/*
 * Lookup a name in a zap object and return its value as a uint64_t.
 */
static int
zap_lookup(const spa_t *spa, const dnode_phys_t *dnode, const char *name,
    uint64_t integer_size, uint64_t num_integers, void *value)
{
        int rc;
        uint64_t zap_type;
        size_t size = dnode->dn_datablkszsec << SPA_MINBLOCKSHIFT;

        rc = dnode_read(spa, dnode, 0, zap_scratch, size);
        if (rc)
                return (rc);

        zap_type = *(uint64_t *)zap_scratch;
        if (zap_type == ZBT_MICRO)
                return (mzap_lookup(dnode, name, value));
        else if (zap_type == ZBT_HEADER) {
                return (fzap_lookup(spa, dnode, name, integer_size,
                    num_integers, value));
        }
        printf("ZFS: invalid zap_type=%d\n", (int)zap_type);
        return (EIO);
}

/*
 * List a microzap directory. Assumes that the zap scratch buffer contains
 * the directory contents.
 */
static int
mzap_list(const dnode_phys_t *dnode, int (*callback)(const char *, uint64_t))
{
        const mzap_phys_t *mz;
        const mzap_ent_phys_t *mze;
        size_t size;
        int chunks, i, rc;

        /*
         * Microzap objects use exactly one block. Read the whole
         * thing.
         */
        size = dnode->dn_datablkszsec * 512;
        mz = (const mzap_phys_t *) zap_scratch;
        chunks = size / MZAP_ENT_LEN - 1;

        for (i = 0; i < chunks; i++) {
                mze = &mz->mz_chunk[i];
                if (mze->mze_name[0]) {
                        rc = callback(mze->mze_name, mze->mze_value);
                        if (rc != 0)
                                return (rc);
                }
        }

        return (0);
}

/*
 * List a fatzap directory. Assumes that the zap scratch buffer contains
 * the directory header.
 */
static int
fzap_list(const spa_t *spa, const dnode_phys_t *dnode,
    int (*callback)(const char *, uint64_t))
{
        int bsize = dnode->dn_datablkszsec << SPA_MINBLOCKSHIFT;
        zap_phys_t zh = *(zap_phys_t *)zap_scratch;
        fat_zap_t z;
        int i, j, rc;

        if (zh.zap_magic != ZAP_MAGIC)
                return (EIO);

        z.zap_block_shift = ilog2(bsize);
        z.zap_phys = (zap_phys_t *)zap_scratch;

        /*
         * This assumes that the leaf blocks start at block 1. The
         * documentation isn't exactly clear on this.
         */
        zap_leaf_t zl;
        zl.l_bs = z.zap_block_shift;
        for (i = 0; i < zh.zap_num_leafs; i++) {
                off_t off = ((off_t)(i + 1)) << zl.l_bs;
                char name[256], *p;
                uint64_t value;

                if (dnode_read(spa, dnode, off, zap_scratch, bsize))
                        return (EIO);

                zl.l_phys = (zap_leaf_phys_t *)zap_scratch;

                for (j = 0; j < ZAP_LEAF_NUMCHUNKS(&zl); j++) {
                        zap_leaf_chunk_t *zc, *nc;
                        int namelen;

                        zc = &ZAP_LEAF_CHUNK(&zl, j);
                        if (zc->l_entry.le_type != ZAP_CHUNK_ENTRY)
                                continue;
                        namelen = zc->l_entry.le_name_numints;
                        if (namelen > sizeof(name))
                                namelen = sizeof(name);

                        /*
                         * Paste the name back together.
                         */
                        nc = &ZAP_LEAF_CHUNK(&zl, zc->l_entry.le_name_chunk);
                        p = name;
                        while (namelen > 0) {
                                int len;
                                len = namelen;
                                if (len > ZAP_LEAF_ARRAY_BYTES)
                                        len = ZAP_LEAF_ARRAY_BYTES;
                                memcpy(p, nc->l_array.la_array, len);
                                p += len;
                                namelen -= len;
                                nc = &ZAP_LEAF_CHUNK(&zl, nc->l_array.la_next);
                        }

                        /*
                         * Assume the first eight bytes of the value are
                         * a uint64_t.
                         */
                        value = fzap_leaf_value(&zl, zc);

                        /* printf("%s 0x%jx\n", name, (uintmax_t)value); */
                        rc = callback((const char *)name, value);
                        if (rc != 0)
                                return (rc);
                }
        }

        return (0);
}

static int zfs_printf(const char *name, uint64_t value __unused)
{

        printf("%s\n", name);

        return (0);
}

/*
 * List a zap directory.
 */
static int
zap_list(const spa_t *spa, const dnode_phys_t *dnode)
{
        uint64_t zap_type;
        size_t size = dnode->dn_datablkszsec * 512;

        if (dnode_read(spa, dnode, 0, zap_scratch, size))
                return (EIO);

        zap_type = *(uint64_t *)zap_scratch;
        if (zap_type == ZBT_MICRO)
                return (mzap_list(dnode, zfs_printf));
        else
                return (fzap_list(spa, dnode, zfs_printf));
}

static int
objset_get_dnode(const spa_t *spa, const objset_phys_t *os, uint64_t objnum,
    dnode_phys_t *dnode)
{
        off_t offset;

        offset = objnum * sizeof(dnode_phys_t);
        return dnode_read(spa, &os->os_meta_dnode, offset,
                dnode, sizeof(dnode_phys_t));
}

static int
mzap_rlookup(const spa_t *spa, const dnode_phys_t *dnode, char *name,
    uint64_t value)
{
        const mzap_phys_t *mz;
        const mzap_ent_phys_t *mze;
        size_t size;
        int chunks, i;

        /*
         * Microzap objects use exactly one block. Read the whole
         * thing.
         */
        size = dnode->dn_datablkszsec * 512;

        mz = (const mzap_phys_t *)zap_scratch;
        chunks = size / MZAP_ENT_LEN - 1;

        for (i = 0; i < chunks; i++) {
                mze = &mz->mz_chunk[i];
                if (value == mze->mze_value) {
                        strcpy(name, mze->mze_name);
                        return (0);
                }
        }

        return (ENOENT);
}

static void
fzap_name_copy(const zap_leaf_t *zl, const zap_leaf_chunk_t *zc, char *name)
{
        size_t namelen;
        const zap_leaf_chunk_t *nc;
        char *p;

        namelen = zc->l_entry.le_name_numints;

        nc = &ZAP_LEAF_CHUNK(zl, zc->l_entry.le_name_chunk);
        p = name;
        while (namelen > 0) {
                size_t len;
                len = namelen;
                if (len > ZAP_LEAF_ARRAY_BYTES)
                        len = ZAP_LEAF_ARRAY_BYTES;
                memcpy(p, nc->l_array.la_array, len);
                p += len;
                namelen -= len;
                nc = &ZAP_LEAF_CHUNK(zl, nc->l_array.la_next);
        }

        *p = '\0';
}

static int
fzap_rlookup(const spa_t *spa, const dnode_phys_t *dnode, char *name,
    uint64_t value)
{
        int bsize = dnode->dn_datablkszsec << SPA_MINBLOCKSHIFT;
        zap_phys_t zh = *(zap_phys_t *)zap_scratch;
        fat_zap_t z;
        int i, j;

        if (zh.zap_magic != ZAP_MAGIC)
                return (EIO);

        z.zap_block_shift = ilog2(bsize);
        z.zap_phys = (zap_phys_t *)zap_scratch;

        /*
         * This assumes that the leaf blocks start at block 1. The
         * documentation isn't exactly clear on this.
         */
        zap_leaf_t zl;
        zl.l_bs = z.zap_block_shift;
        for (i = 0; i < zh.zap_num_leafs; i++) {
                off_t off = ((off_t)(i + 1)) << zl.l_bs;

                if (dnode_read(spa, dnode, off, zap_scratch, bsize))
                        return (EIO);

                zl.l_phys = (zap_leaf_phys_t *)zap_scratch;

                for (j = 0; j < ZAP_LEAF_NUMCHUNKS(&zl); j++) {
                        zap_leaf_chunk_t *zc;

                        zc = &ZAP_LEAF_CHUNK(&zl, j);
                        if (zc->l_entry.le_type != ZAP_CHUNK_ENTRY)
                                continue;
                        if (zc->l_entry.le_value_intlen != 8 ||
                            zc->l_entry.le_value_numints != 1)
                                continue;

                        if (fzap_leaf_value(&zl, zc) == value) {
                                fzap_name_copy(&zl, zc, name);
                                return (0);
                        }
                }
        }

        return (ENOENT);
}

static int
zap_rlookup(const spa_t *spa, const dnode_phys_t *dnode, char *name,
    uint64_t value)
{
        int rc;
        uint64_t zap_type;
        size_t size = dnode->dn_datablkszsec * 512;

        rc = dnode_read(spa, dnode, 0, zap_scratch, size);
        if (rc)
                return (rc);

        zap_type = *(uint64_t *)zap_scratch;
        if (zap_type == ZBT_MICRO)
                return (mzap_rlookup(spa, dnode, name, value));
        else
                return (fzap_rlookup(spa, dnode, name, value));
}

static int
zfs_rlookup(const spa_t *spa, uint64_t objnum, char *result)
{
        char name[256];
        char component[256];
        uint64_t dir_obj, parent_obj, child_dir_zapobj;
        dnode_phys_t child_dir_zap, dataset, dir, parent;
        dsl_dir_phys_t *dd;
        dsl_dataset_phys_t *ds;
        char *p;
        int len;

        p = &name[sizeof(name) - 1];
        *p = '\0';

        if (objset_get_dnode(spa, &spa->spa_mos, objnum, &dataset)) {
                printf("ZFS: can't find dataset %ju\n", (uintmax_t)objnum);
                return (EIO);
        }
        ds = (dsl_dataset_phys_t *)&dataset.dn_bonus;
        dir_obj = ds->ds_dir_obj;

        for (;;) {
                if (objset_get_dnode(spa, &spa->spa_mos, dir_obj, &dir) != 0)
                        return (EIO);
                dd = (dsl_dir_phys_t *)&dir.dn_bonus;

                /* Actual loop condition. */
                parent_obj = dd->dd_parent_obj;
                if (parent_obj == 0)
                        break;

                if (objset_get_dnode(spa, &spa->spa_mos, parent_obj,
                    &parent) != 0)
                        return (EIO);
                dd = (dsl_dir_phys_t *)&parent.dn_bonus;
                child_dir_zapobj = dd->dd_child_dir_zapobj;
                if (objset_get_dnode(spa, &spa->spa_mos, child_dir_zapobj,
                    &child_dir_zap) != 0)
                        return (EIO);
                if (zap_rlookup(spa, &child_dir_zap, component, dir_obj) != 0)
                        return (EIO);

                len = strlen(component);
                p -= len;
                memcpy(p, component, len);
                --p;
                *p = '/';

                /* Actual loop iteration. */
                dir_obj = parent_obj;
        }

        if (*p != '\0')
                ++p;
        strcpy(result, p);

        return (0);
}

static int
zfs_lookup_dataset(const spa_t *spa, const char *name, uint64_t *objnum)
{
        char element[256];
        uint64_t dir_obj, child_dir_zapobj;
        dnode_phys_t child_dir_zap, dir;
        dsl_dir_phys_t *dd;
        const char *p, *q;

        if (objset_get_dnode(spa, &spa->spa_mos,
            DMU_POOL_DIRECTORY_OBJECT, &dir))
                return (EIO);
        if (zap_lookup(spa, &dir, DMU_POOL_ROOT_DATASET, sizeof (dir_obj),
            1, &dir_obj))
                return (EIO);

        p = name;
        for (;;) {
                if (objset_get_dnode(spa, &spa->spa_mos, dir_obj, &dir))
                        return (EIO);
                dd = (dsl_dir_phys_t *)&dir.dn_bonus;

                while (*p == '/')
                        p++;
                /* Actual loop condition #1. */
                if (*p == '\0')
                        break;

                q = strchr(p, '/');
                if (q) {
                        memcpy(element, p, q - p);
                        element[q - p] = '\0';
                        p = q + 1;
                } else {
                        strcpy(element, p);
                        p += strlen(p);
                }

                child_dir_zapobj = dd->dd_child_dir_zapobj;
                if (objset_get_dnode(spa, &spa->spa_mos, child_dir_zapobj,
                    &child_dir_zap) != 0)
                        return (EIO);

                /* Actual loop condition #2. */
                if (zap_lookup(spa, &child_dir_zap, element, sizeof (dir_obj),
                    1, &dir_obj) != 0)
                        return (ENOENT);
        }

        *objnum = dd->dd_head_dataset_obj;
        return (0);
}

#ifndef BOOT2
static int
zfs_list_dataset(const spa_t *spa, uint64_t objnum/*, int pos, char *entry*/)
{
        uint64_t dir_obj, child_dir_zapobj;
        dnode_phys_t child_dir_zap, dir, dataset;
        dsl_dataset_phys_t *ds;
        dsl_dir_phys_t *dd;

        if (objset_get_dnode(spa, &spa->spa_mos, objnum, &dataset)) {
                printf("ZFS: can't find dataset %ju\n", (uintmax_t)objnum);
                return (EIO);
        }
        ds = (dsl_dataset_phys_t *)&dataset.dn_bonus;
        dir_obj = ds->ds_dir_obj;

        if (objset_get_dnode(spa, &spa->spa_mos, dir_obj, &dir)) {
                printf("ZFS: can't find dirobj %ju\n", (uintmax_t)dir_obj);
                return (EIO);
        }
        dd = (dsl_dir_phys_t *)&dir.dn_bonus;

        child_dir_zapobj = dd->dd_child_dir_zapobj;
        if (objset_get_dnode(spa, &spa->spa_mos, child_dir_zapobj,
            &child_dir_zap) != 0) {
                printf("ZFS: can't find child zap %ju\n", (uintmax_t)dir_obj);
                return (EIO);
        }

        return (zap_list(spa, &child_dir_zap) != 0);
}

int
zfs_callback_dataset(const spa_t *spa, uint64_t objnum,
    int (*callback)(const char *, uint64_t))
{
        uint64_t dir_obj, child_dir_zapobj, zap_type;
        dnode_phys_t child_dir_zap, dir, dataset;
        dsl_dataset_phys_t *ds;
        dsl_dir_phys_t *dd;
        int err;

        err = objset_get_dnode(spa, &spa->spa_mos, objnum, &dataset);
        if (err != 0) {
                printf("ZFS: can't find dataset %ju\n", (uintmax_t)objnum);
                return (err);
        }
        ds = (dsl_dataset_phys_t *)&dataset.dn_bonus;
        dir_obj = ds->ds_dir_obj;

        err = objset_get_dnode(spa, &spa->spa_mos, dir_obj, &dir);
        if (err != 0) {
                printf("ZFS: can't find dirobj %ju\n", (uintmax_t)dir_obj);
                return (err);
        }
        dd = (dsl_dir_phys_t *)&dir.dn_bonus;

        child_dir_zapobj = dd->dd_child_dir_zapobj;
        err = objset_get_dnode(spa, &spa->spa_mos, child_dir_zapobj,
            &child_dir_zap);
        if (err != 0) {
                printf("ZFS: can't find child zap %ju\n", (uintmax_t)dir_obj);
                return (err);
        }

        err = dnode_read(spa, &child_dir_zap, 0, zap_scratch,
            child_dir_zap.dn_datablkszsec * 512);
        if (err != 0)
                return (err);

        zap_type = *(uint64_t *)zap_scratch;
        if (zap_type == ZBT_MICRO)
                return (mzap_list(&child_dir_zap, callback));
        else
                return (fzap_list(spa, &child_dir_zap, callback));
}
#endif

/*
 * Find the object set given the object number of its dataset object
 * and return its details in *objset
 */
static int
zfs_mount_dataset(const spa_t *spa, uint64_t objnum, objset_phys_t *objset)
{
        dnode_phys_t dataset;
        dsl_dataset_phys_t *ds;

        if (objset_get_dnode(spa, &spa->spa_mos, objnum, &dataset)) {
                printf("ZFS: can't find dataset %ju\n", (uintmax_t)objnum);
                return (EIO);
        }

        ds = (dsl_dataset_phys_t *)&dataset.dn_bonus;
        if (zio_read(spa, &ds->ds_bp, objset)) {
                printf("ZFS: can't read object set for dataset %ju\n",
                    (uintmax_t)objnum);
                return (EIO);
        }

        return (0);
}

/*
 * Find the object set pointed to by the BOOTFS property or the root
 * dataset if there is none and return its details in *objset
 */
static int
zfs_get_root(const spa_t *spa, uint64_t *objid)
{
        dnode_phys_t dir, propdir;
        uint64_t props, bootfs, root;

        *objid = 0;

        /*
         * Start with the MOS directory object.
         */
        if (objset_get_dnode(spa, &spa->spa_mos,
            DMU_POOL_DIRECTORY_OBJECT, &dir)) {
                printf("ZFS: can't read MOS object directory\n");
                return (EIO);
        }

        /*
         * Lookup the pool_props and see if we can find a bootfs.
         */
        if (zap_lookup(spa, &dir, DMU_POOL_PROPS,
            sizeof(props), 1, &props) == 0 &&
            objset_get_dnode(spa, &spa->spa_mos, props, &propdir) == 0 &&
            zap_lookup(spa, &propdir, "bootfs",
            sizeof(bootfs), 1, &bootfs) == 0 && bootfs != 0) {
                *objid = bootfs;
                return (0);
        }
        /*
         * Lookup the root dataset directory
         */
        if (zap_lookup(spa, &dir, DMU_POOL_ROOT_DATASET,
            sizeof(root), 1, &root) ||
            objset_get_dnode(spa, &spa->spa_mos, root, &dir)) {
                printf("ZFS: can't find root dsl_dir\n");
                return (EIO);
        }

        /*
         * Use the information from the dataset directory's bonus buffer
         * to find the dataset object and from that the object set itself.
         */
        dsl_dir_phys_t *dd = (dsl_dir_phys_t *)&dir.dn_bonus;
        *objid = dd->dd_head_dataset_obj;
        return (0);
}

static int
zfs_mount(const spa_t *spa, uint64_t rootobj, struct zfsmount *mount)
{

        mount->spa = spa;

        /*
         * Find the root object set if not explicitly provided
         */
        if (rootobj == 0 && zfs_get_root(spa, &rootobj)) {
                printf("ZFS: can't find root filesystem\n");
                return (EIO);
        }

        if (zfs_mount_dataset(spa, rootobj, &mount->objset)) {
                printf("ZFS: can't open root filesystem\n");
                return (EIO);
        }

        mount->rootobj = rootobj;

        return (0);
}

/*
 * callback function for feature name checks.
 */
static int
check_feature(const char *name, uint64_t value)
{
        int i;

        if (value == 0)
                return (0);
        if (name[0] == '\0')
                return (0);

        for (i = 0; features_for_read[i] != NULL; i++) {
                if (strcmp(name, features_for_read[i]) == 0)
                        return (0);
        }
        printf("ZFS: unsupported feature: %s\n", name);
        return (EIO);
}

/*
 * Checks whether the MOS features that are active are supported.
 */
static int
check_mos_features(const spa_t *spa)
{
        dnode_phys_t dir;
        uint64_t objnum, zap_type;
        size_t size;
        int rc;

        if ((rc = objset_get_dnode(spa, &spa->spa_mos, DMU_OT_OBJECT_DIRECTORY,
            &dir)) != 0)
                return (rc);
        if ((rc = zap_lookup(spa, &dir, DMU_POOL_FEATURES_FOR_READ,
            sizeof (objnum), 1, &objnum)) != 0) {
                /*
                 * It is older pool without features. As we have already
                 * tested the label, just return without raising the error.
                 */
                return (0);
        }

        if ((rc = objset_get_dnode(spa, &spa->spa_mos, objnum, &dir)) != 0)
                return (rc);

        if (dir.dn_type != DMU_OTN_ZAP_METADATA)
                return (EIO);

        size = dir.dn_datablkszsec * 512;
        if (dnode_read(spa, &dir, 0, zap_scratch, size))
                return (EIO);

        zap_type = *(uint64_t *)zap_scratch;
        if (zap_type == ZBT_MICRO)
                rc = mzap_list(&dir, check_feature);
        else
                rc = fzap_list(spa, &dir, check_feature);

        return (rc);
}

static int
load_nvlist(spa_t *spa, uint64_t obj, unsigned char **value)
{
        dnode_phys_t dir;
        size_t size;
        int rc;
        unsigned char *nv;

        *value = NULL;
        if ((rc = objset_get_dnode(spa, &spa->spa_mos, obj, &dir)) != 0)
                return (rc);
        if (dir.dn_type != DMU_OT_PACKED_NVLIST &&
            dir.dn_bonustype != DMU_OT_PACKED_NVLIST_SIZE) {
                return (EIO);
        }

        if (dir.dn_bonuslen != sizeof (uint64_t))
                return (EIO);

        size = *(uint64_t *)DN_BONUS(&dir);
        nv = malloc(size);
        if (nv == NULL)
                return (ENOMEM);

        rc = dnode_read(spa, &dir, 0, nv, size);
        if (rc != 0) {
                free(nv);
                nv = NULL;
                return (rc);
        }
        *value = nv;
        return (rc);
}

static int
zfs_spa_init(spa_t *spa)
{
        dnode_phys_t dir;
        uint64_t config_object;
        unsigned char *nvlist;
        int rc;

        if (zio_read(spa, &spa->spa_uberblock.ub_rootbp, &spa->spa_mos)) {
                printf("ZFS: can't read MOS of pool %s\n", spa->spa_name);
                return (EIO);
        }
        if (spa->spa_mos.os_type != DMU_OST_META) {
                printf("ZFS: corrupted MOS of pool %s\n", spa->spa_name);
                return (EIO);
        }

        if (objset_get_dnode(spa, &spa->spa_mos, DMU_POOL_DIRECTORY_OBJECT,
            &dir)) {
                printf("ZFS: failed to read pool %s directory object\n",
                    spa->spa_name);
                return (EIO);
        }
        /* this is allowed to fail, older pools do not have salt */
        rc = zap_lookup(spa, &dir, DMU_POOL_CHECKSUM_SALT, 1,
            sizeof (spa->spa_cksum_salt.zcs_bytes),
            spa->spa_cksum_salt.zcs_bytes);

        rc = check_mos_features(spa);
        if (rc != 0) {
                printf("ZFS: pool %s is not supported\n", spa->spa_name);
                return (rc);
        }

        rc = zap_lookup(spa, &dir, DMU_POOL_CONFIG,
            sizeof (config_object), 1, &config_object);
        if (rc != 0) {
                printf("ZFS: can not read MOS %s\n", DMU_POOL_CONFIG);
                return (EIO);
        }
        rc = load_nvlist(spa, config_object, &nvlist);
        if (rc != 0)
                return (rc);

        /*
         * Update vdevs from MOS config. Note, we do skip encoding bytes
         * here. See also vdev_label_read_config().
         */
        rc = vdev_init_from_nvlist(spa, nvlist + 4);
        free(nvlist);
        return (rc);
}

static int
zfs_dnode_stat(const spa_t *spa, dnode_phys_t *dn, struct stat *sb)
{

        if (dn->dn_bonustype != DMU_OT_SA) {
                znode_phys_t *zp = (znode_phys_t *)dn->dn_bonus;

                sb->st_mode = zp->zp_mode;
                sb->st_uid = zp->zp_uid;
                sb->st_gid = zp->zp_gid;
                sb->st_size = zp->zp_size;
        } else {
                sa_hdr_phys_t *sahdrp;
                int hdrsize;
                size_t size = 0;
                void *buf = NULL;

                if (dn->dn_bonuslen != 0)
                        sahdrp = (sa_hdr_phys_t *)DN_BONUS(dn);
                else {
                        if ((dn->dn_flags & DNODE_FLAG_SPILL_BLKPTR) != 0) {
                                blkptr_t *bp = DN_SPILL_BLKPTR(dn);
                                int error;

                                size = BP_GET_LSIZE(bp);
                                buf = zfs_alloc(size);
                                error = zio_read(spa, bp, buf);
                                if (error != 0) {
                                        zfs_free(buf, size);
                                        return (error);
                                }
                                sahdrp = buf;
                        } else {
                                return (EIO);
                        }
                }
                hdrsize = SA_HDR_SIZE(sahdrp);
                sb->st_mode = *(uint64_t *)((char *)sahdrp + hdrsize +
                    SA_MODE_OFFSET);
                sb->st_uid = *(uint64_t *)((char *)sahdrp + hdrsize +
                    SA_UID_OFFSET);
                sb->st_gid = *(uint64_t *)((char *)sahdrp + hdrsize +
                    SA_GID_OFFSET);
                sb->st_size = *(uint64_t *)((char *)sahdrp + hdrsize +
                    SA_SIZE_OFFSET);
                if (buf != NULL)
                        zfs_free(buf, size);
        }

        return (0);
}

static int
zfs_dnode_readlink(const spa_t *spa, dnode_phys_t *dn, char *path, size_t psize)
{
        int rc = 0;

        if (dn->dn_bonustype == DMU_OT_SA) {
                sa_hdr_phys_t *sahdrp = NULL;
                size_t size = 0;
                void *buf = NULL;
                int hdrsize;
                char *p;

                if (dn->dn_bonuslen != 0)
                        sahdrp = (sa_hdr_phys_t *)DN_BONUS(dn);
                else {
                        blkptr_t *bp;

                        if ((dn->dn_flags & DNODE_FLAG_SPILL_BLKPTR) == 0)
                                return (EIO);
                        bp = DN_SPILL_BLKPTR(dn);

                        size = BP_GET_LSIZE(bp);
                        buf = zfs_alloc(size);
                        rc = zio_read(spa, bp, buf);
                        if (rc != 0) {
                                zfs_free(buf, size);
                                return (rc);
                        }
                        sahdrp = buf;
                }
                hdrsize = SA_HDR_SIZE(sahdrp);
                p = (char *)((uintptr_t)sahdrp + hdrsize + SA_SYMLINK_OFFSET);
                memcpy(path, p, psize);
                if (buf != NULL)
                        zfs_free(buf, size);
                return (0);
        }
        /*
         * Second test is purely to silence bogus compiler
         * warning about accessing past the end of dn_bonus.
         */
        if (psize + sizeof(znode_phys_t) <= dn->dn_bonuslen &&
            sizeof(znode_phys_t) <= sizeof(dn->dn_bonus)) {
                memcpy(path, &dn->dn_bonus[sizeof(znode_phys_t)], psize);
        } else {
                rc = dnode_read(spa, dn, 0, path, psize);
        }
        return (rc);
}

struct obj_list {
        uint64_t                objnum;
        STAILQ_ENTRY(obj_list)  entry;
};

/*
 * Lookup a file and return its dnode.
 */
static int
zfs_lookup(const struct zfsmount *mount, const char *upath, dnode_phys_t *dnode)
{
        int rc;
        uint64_t objnum;
        const spa_t *spa;
        dnode_phys_t dn;
        const char *p, *q;
        char element[256];
        char path[1024];
        int symlinks_followed = 0;
        struct stat sb;
        struct obj_list *entry, *tentry;
        STAILQ_HEAD(, obj_list) on_cache = STAILQ_HEAD_INITIALIZER(on_cache);

        spa = mount->spa;
        if (mount->objset.os_type != DMU_OST_ZFS) {
                printf("ZFS: unexpected object set type %ju\n",
                    (uintmax_t)mount->objset.os_type);
                return (EIO);
        }

        if ((entry = malloc(sizeof(struct obj_list))) == NULL)
                return (ENOMEM);

        /*
         * Get the root directory dnode.
         */
        rc = objset_get_dnode(spa, &mount->objset, MASTER_NODE_OBJ, &dn);
        if (rc) {
                free(entry);
                return (rc);
        }

        rc = zap_lookup(spa, &dn, ZFS_ROOT_OBJ, sizeof(objnum), 1, &objnum);
        if (rc) {
                free(entry);
                return (rc);
        }
        entry->objnum = objnum;
        STAILQ_INSERT_HEAD(&on_cache, entry, entry);

        rc = objset_get_dnode(spa, &mount->objset, objnum, &dn);
        if (rc != 0)
                goto done;

        p = upath;
        while (p && *p) {
                rc = objset_get_dnode(spa, &mount->objset, objnum, &dn);
                if (rc != 0)
                        goto done;

                while (*p == '/')
                        p++;
                if (*p == '\0')
                        break;
                q = p;
                while (*q != '\0' && *q != '/')
                        q++;

                /* skip dot */
                if (p + 1 == q && p[0] == '.') {
                        p++;
                        continue;
                }
                /* double dot */
                if (p + 2 == q && p[0] == '.' && p[1] == '.') {
                        p += 2;
                        if (STAILQ_FIRST(&on_cache) ==
                            STAILQ_LAST(&on_cache, obj_list, entry)) {
                                rc = ENOENT;
                                goto done;
                        }
                        entry = STAILQ_FIRST(&on_cache);
                        STAILQ_REMOVE_HEAD(&on_cache, entry);
                        free(entry);
                        objnum = (STAILQ_FIRST(&on_cache))->objnum;
                        continue;
                }
                if (q - p + 1 > sizeof(element)) {
                        rc = ENAMETOOLONG;
                        goto done;
                }
                memcpy(element, p, q - p);
                element[q - p] = 0;
                p = q;

                if ((rc = zfs_dnode_stat(spa, &dn, &sb)) != 0)
                        goto done;
                if (!S_ISDIR(sb.st_mode)) {
                        rc = ENOTDIR;
                        goto done;
                }

                rc = zap_lookup(spa, &dn, element, sizeof (objnum), 1, &objnum);
                if (rc)
                        goto done;
                objnum = ZFS_DIRENT_OBJ(objnum);

                if ((entry = malloc(sizeof(struct obj_list))) == NULL) {
                        rc = ENOMEM;
                        goto done;
                }
                entry->objnum = objnum;
                STAILQ_INSERT_HEAD(&on_cache, entry, entry);
                rc = objset_get_dnode(spa, &mount->objset, objnum, &dn);
                if (rc)
                        goto done;

                /*
                 * Check for symlink.
                 */
                rc = zfs_dnode_stat(spa, &dn, &sb);
                if (rc)
                        goto done;
                if (S_ISLNK(sb.st_mode)) {
                        if (symlinks_followed > 10) {
                                rc = EMLINK;
                                goto done;
                        }
                        symlinks_followed++;

                        /*
                         * Read the link value and copy the tail of our
                         * current path onto the end.
                         */
                        if (sb.st_size + strlen(p) + 1 > sizeof(path)) {
                                rc = ENAMETOOLONG;
                                goto done;
                        }
                        strcpy(&path[sb.st_size], p);

                        rc = zfs_dnode_readlink(spa, &dn, path, sb.st_size);
                        if (rc != 0)
                                goto done;

                        /*
                         * Restart with the new path, starting either at
                         * the root or at the parent depending whether or
                         * not the link is relative.
                         */
                        p = path;
                        if (*p == '/') {
                                while (STAILQ_FIRST(&on_cache) !=
                                    STAILQ_LAST(&on_cache, obj_list, entry)) {
                                        entry = STAILQ_FIRST(&on_cache);
                                        STAILQ_REMOVE_HEAD(&on_cache, entry);
                                        free(entry);
                                }
                        } else {
                                entry = STAILQ_FIRST(&on_cache);
                                STAILQ_REMOVE_HEAD(&on_cache, entry);
                                free(entry);
                        }
                        objnum = (STAILQ_FIRST(&on_cache))->objnum;
                }
        }

        *dnode = dn;
done:
        STAILQ_FOREACH_SAFE(entry, &on_cache, entry, tentry)
                free(entry);
        return (rc);
}