root/usr/src/cmd/mdb/common/modules/zfs/zfs.c
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
 * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
 * Copyright 2020 Joyent, Inc.
 * Copyright 2025 Oxide Computer Company
 */

/* Portions Copyright 2010 Robert Milkowski */

/*
 * ZFS_MDB lets dmu.h know that we don't have dmu_ot, and we will define our
 * own macros to access the target's dmu_ot.  Therefore it must be defined
 * before including any ZFS headers.  Note that we don't define
 * DMU_OT_IS_ENCRYPTED_IMPL() or DMU_OT_BYTESWAP_IMPL(), therefore using them
 * will result in a compilation error.  If they are needed in the future, we
 * can implement them similarly to mdb_dmu_ot_is_encrypted_impl().
 */
#define ZFS_MDB
#define DMU_OT_IS_ENCRYPTED_IMPL(ot) mdb_dmu_ot_is_encrypted_impl(ot)

#include <mdb/mdb_ctf.h>
#include <sys/zfs_context.h>
#include <sys/mdb_modapi.h>
#include <sys/dbuf.h>
#include <sys/dmu_objset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_pool.h>
#include <sys/metaslab_impl.h>
#include <sys/space_map.h>
#include <sys/list.h>
#include <sys/vdev_impl.h>
#include <sys/zap_leaf.h>
#include <sys/zap_impl.h>
#include <ctype.h>
#include <sys/zfs_acl.h>
#include <sys/sa_impl.h>
#include <sys/multilist.h>
#include <sys/btree.h>

#ifdef _KERNEL
#define ZFS_OBJ_NAME    "zfs"
#else
#define ZFS_OBJ_NAME    "libzpool.so.1"
#endif
extern int64_t mdb_gethrtime(void);

#define ZFS_STRUCT      "struct " ZFS_OBJ_NAME "`"

#ifndef _KERNEL
int aok;
#endif

enum spa_flags {
        SPA_FLAG_CONFIG                 = 1 << 0,
        SPA_FLAG_VDEVS                  = 1 << 1,
        SPA_FLAG_ERRORS                 = 1 << 2,
        SPA_FLAG_METASLAB_GROUPS        = 1 << 3,
        SPA_FLAG_METASLABS              = 1 << 4,
        SPA_FLAG_HISTOGRAMS             = 1 << 5
};

/*
 * If any of these flags are set, call spa_vdevs in spa_print
 */
#define SPA_FLAG_ALL_VDEV       \
        (SPA_FLAG_VDEVS | SPA_FLAG_ERRORS | SPA_FLAG_METASLAB_GROUPS | \
        SPA_FLAG_METASLABS)

static int
getmember(uintptr_t addr, const char *type, mdb_ctf_id_t *idp,
    const char *member, int len, void *buf)
{
        mdb_ctf_id_t id;
        ulong_t off;
        char name[64];

        if (idp == NULL) {
                if (mdb_ctf_lookup_by_name(type, &id) == -1) {
                        mdb_warn("couldn't find type %s", type);
                        return (DCMD_ERR);
                }
                idp = &id;
        } else {
                type = name;
                mdb_ctf_type_name(*idp, name, sizeof (name));
        }

        if (mdb_ctf_offsetof(*idp, member, &off) == -1) {
                mdb_warn("couldn't find member %s of type %s\n", member, type);
                return (DCMD_ERR);
        }
        if (off % 8 != 0) {
                mdb_warn("member %s of type %s is unsupported bitfield",
                    member, type);
                return (DCMD_ERR);
        }
        off /= 8;

        if (mdb_vread(buf, len, addr + off) == -1) {
                mdb_warn("failed to read %s from %s at %p",
                    member, type, addr + off);
                return (DCMD_ERR);
        }
        /* mdb_warn("read %s from %s at %p+%llx\n", member, type, addr, off); */

        return (0);
}

#define GETMEMB(addr, structname, member, dest) \
        getmember(addr, ZFS_STRUCT structname, NULL, #member, \
        sizeof (dest), &(dest))

#define GETMEMBID(addr, ctfid, member, dest) \
        getmember(addr, NULL, ctfid, #member, sizeof (dest), &(dest))

static boolean_t
strisprint(const char *cp)
{
        for (; *cp; cp++) {
                if (!isprint(*cp))
                        return (B_FALSE);
        }
        return (B_TRUE);
}

/*
 * <addr>::sm_entries <buffer length in bytes>
 *
 * Treat the buffer specified by the given address as a buffer that contains
 * space map entries. Iterate over the specified number of entries and print
 * them in both encoded and decoded form.
 */
/* ARGSUSED */
static int
sm_entries(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        uint64_t bufsz = 0;
        boolean_t preview = B_FALSE;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (argc < 1) {
                preview = B_TRUE;
                bufsz = 2;
        } else if (argc != 1) {
                return (DCMD_USAGE);
        } else {
                switch (argv[0].a_type) {
                case MDB_TYPE_STRING:
                        bufsz = mdb_strtoull(argv[0].a_un.a_str);
                        break;
                case MDB_TYPE_IMMEDIATE:
                        bufsz = argv[0].a_un.a_val;
                        break;
                default:
                        return (DCMD_USAGE);
                }
        }

        char *actions[] = { "ALLOC", "FREE", "INVALID" };
        for (uintptr_t bufend = addr + bufsz; addr < bufend;
            addr += sizeof (uint64_t)) {
                uint64_t nwords;
                uint64_t start_addr = addr;

                uint64_t word = 0;
                if (mdb_vread(&word, sizeof (word), addr) == -1) {
                        mdb_warn("failed to read space map entry %p", addr);
                        return (DCMD_ERR);
                }

                if (SM_PREFIX_DECODE(word) == SM_DEBUG_PREFIX) {
                        (void) mdb_printf("\t    [%6llu] %s: txg %llu, "
                            "pass %llu\n",
                            (u_longlong_t)(addr),
                            actions[SM_DEBUG_ACTION_DECODE(word)],
                            (u_longlong_t)SM_DEBUG_TXG_DECODE(word),
                            (u_longlong_t)SM_DEBUG_SYNCPASS_DECODE(word));
                        continue;
                }

                char entry_type;
                uint64_t raw_offset, raw_run, vdev_id = SM_NO_VDEVID;

                if (SM_PREFIX_DECODE(word) != SM2_PREFIX) {
                        entry_type = (SM_TYPE_DECODE(word) == SM_ALLOC) ?
                            'A' : 'F';
                        raw_offset = SM_OFFSET_DECODE(word);
                        raw_run = SM_RUN_DECODE(word);
                        nwords = 1;
                } else {
                        ASSERT3U(SM_PREFIX_DECODE(word), ==, SM2_PREFIX);

                        raw_run = SM2_RUN_DECODE(word);
                        vdev_id = SM2_VDEV_DECODE(word);

                        /* it is a two-word entry so we read another word */
                        addr += sizeof (uint64_t);
                        if (addr >= bufend) {
                                mdb_warn("buffer ends in the middle of a two "
                                    "word entry\n", addr);
                                return (DCMD_ERR);
                        }

                        if (mdb_vread(&word, sizeof (word), addr) == -1) {
                                mdb_warn("failed to read space map entry %p",
                                    addr);
                                return (DCMD_ERR);
                        }

                        entry_type = (SM2_TYPE_DECODE(word) == SM_ALLOC) ?
                            'A' : 'F';
                        raw_offset = SM2_OFFSET_DECODE(word);
                        nwords = 2;
                }

                (void) mdb_printf("\t    [%6llx]    %c  range:"
                    " %010llx-%010llx  size: %06llx vdev: %06llu words: %llu\n",
                    (u_longlong_t)start_addr,
                    entry_type, (u_longlong_t)raw_offset,
                    (u_longlong_t)(raw_offset + raw_run),
                    (u_longlong_t)raw_run,
                    (u_longlong_t)vdev_id, (u_longlong_t)nwords);

                if (preview)
                        break;
        }
        return (DCMD_OK);
}

static int
mdb_dsl_dir_name(uintptr_t addr, char *buf)
{
        static int gotid;
        static mdb_ctf_id_t dd_id;
        uintptr_t dd_parent;
        char dd_myname[ZFS_MAX_DATASET_NAME_LEN];

        if (!gotid) {
                if (mdb_ctf_lookup_by_name(ZFS_STRUCT "dsl_dir",
                    &dd_id) == -1) {
                        mdb_warn("couldn't find struct dsl_dir");
                        return (DCMD_ERR);
                }
                gotid = TRUE;
        }
        if (GETMEMBID(addr, &dd_id, dd_parent, dd_parent) ||
            GETMEMBID(addr, &dd_id, dd_myname, dd_myname)) {
                return (DCMD_ERR);
        }

        if (dd_parent) {
                if (mdb_dsl_dir_name(dd_parent, buf))
                        return (DCMD_ERR);
                strcat(buf, "/");
        }

        if (dd_myname[0])
                strcat(buf, dd_myname);
        else
                strcat(buf, "???");

        return (0);
}

static int
objset_name(uintptr_t addr, char *buf)
{
        static int gotid;
        static mdb_ctf_id_t os_id, ds_id;
        uintptr_t os_dsl_dataset;
        char ds_snapname[ZFS_MAX_DATASET_NAME_LEN];
        uintptr_t ds_dir;

        buf[0] = '\0';

        if (!gotid) {
                if (mdb_ctf_lookup_by_name(ZFS_STRUCT "objset",
                    &os_id) == -1) {
                        mdb_warn("couldn't find struct objset");
                        return (DCMD_ERR);
                }
                if (mdb_ctf_lookup_by_name(ZFS_STRUCT "dsl_dataset",
                    &ds_id) == -1) {
                        mdb_warn("couldn't find struct dsl_dataset");
                        return (DCMD_ERR);
                }

                gotid = TRUE;
        }

        if (GETMEMBID(addr, &os_id, os_dsl_dataset, os_dsl_dataset))
                return (DCMD_ERR);

        if (os_dsl_dataset == 0) {
                strcat(buf, "mos");
                return (0);
        }

        if (GETMEMBID(os_dsl_dataset, &ds_id, ds_snapname, ds_snapname) ||
            GETMEMBID(os_dsl_dataset, &ds_id, ds_dir, ds_dir)) {
                return (DCMD_ERR);
        }

        if (ds_dir && mdb_dsl_dir_name(ds_dir, buf))
                return (DCMD_ERR);

        if (ds_snapname[0]) {
                strcat(buf, "@");
                strcat(buf, ds_snapname);
        }
        return (0);
}

static int
enum_lookup(char *type, int val, const char *prefix, size_t size, char *out)
{
        const char *cp;
        size_t len = strlen(prefix);
        mdb_ctf_id_t enum_type;

        if (mdb_ctf_lookup_by_name(type, &enum_type) != 0) {
                mdb_warn("Could not find enum for %s", type);
                return (-1);
        }

        if ((cp = mdb_ctf_enum_name(enum_type, val)) != NULL) {
                if (strncmp(cp, prefix, len) == 0)
                        cp += len;
                (void) strncpy(out, cp, size);
        } else {
                mdb_snprintf(out, size, "? (%d)", val);
        }
        return (0);
}

/* ARGSUSED */
static int
zfs_params(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        /*
         * This table can be approximately generated by running:
         * egrep "^[a-z0-9_]+ [a-z0-9_]+( =.*)?;" *.c | cut -d ' ' -f 2
         */
        static const char *params[] = {
                "arc_lotsfree_percent",
                "arc_pages_pp_reserve",
                "arc_reduce_dnlc_percent",
                "arc_swapfs_reserve",
                "arc_zio_arena_free_shift",
                "dbuf_cache_hiwater_pct",
                "dbuf_cache_lowater_pct",
                "dbuf_cache_max_bytes",
                "dbuf_cache_max_shift",
                "ddt_zap_indirect_blockshift",
                "ddt_zap_leaf_blockshift",
                "ditto_same_vdev_distance_shift",
                "dmu_find_threads",
                "dmu_rescan_dnode_threshold",
                "dsl_scan_delay_completion",
                "fzap_default_block_shift",
                "l2arc_feed_again",
                "l2arc_feed_min_ms",
                "l2arc_feed_secs",
                "l2arc_headroom",
                "l2arc_headroom_boost",
                "l2arc_noprefetch",
                "l2arc_norw",
                "l2arc_write_boost",
                "l2arc_write_max",
                "metaslab_aliquot",
                "metaslab_bias_enabled",
                "metaslab_debug_load",
                "metaslab_debug_unload",
                "metaslab_df_alloc_threshold",
                "metaslab_df_free_pct",
                "metaslab_fragmentation_factor_enabled",
                "metaslab_force_ganging",
                "metaslab_lba_weighting_enabled",
                "metaslab_load_pct",
                "metaslab_min_alloc_size",
                "metaslab_ndf_clump_shift",
                "metaslab_preload_enabled",
                "metaslab_preload_limit",
                "metaslab_trace_enabled",
                "metaslab_trace_max_entries",
                "metaslab_unload_delay",
                "metaslabs_per_vdev",
                "reference_history",
                "reference_tracking_enable",
                "send_holes_without_birth_time",
                "spa_asize_inflation",
                "spa_load_verify_data",
                "spa_load_verify_maxinflight",
                "spa_load_verify_metadata",
                "spa_max_replication_override",
                "spa_min_slop",
                "spa_mode_global",
                "spa_slop_shift",
                "space_map_blksz",
                "vdev_mirror_shift",
                "zfetch_max_distance",
                "zfs_abd_chunk_size",
                "zfs_abd_scatter_enabled",
                "zfs_arc_average_blocksize",
                "zfs_arc_evict_batch_limit",
                "zfs_arc_grow_retry",
                "zfs_arc_max",
                "zfs_arc_meta_limit",
                "zfs_arc_meta_min",
                "zfs_arc_min",
                "zfs_arc_p_min_shift",
                "zfs_arc_shrink_shift",
                "zfs_async_block_max_blocks",
                "zfs_ccw_retry_interval",
                "zfs_commit_timeout_pct",
                "zfs_compressed_arc_enabled",
                "zfs_condense_indirect_commit_entry_delay_ticks",
                "zfs_condense_indirect_vdevs_enable",
                "zfs_condense_max_obsolete_bytes",
                "zfs_condense_min_mapping_bytes",
                "zfs_condense_pct",
                "zfs_dbgmsg_maxsize",
                "zfs_deadman_checktime_ms",
                "zfs_deadman_enabled",
                "zfs_deadman_synctime_ms",
                "zfs_dedup_prefetch",
                "zfs_default_bs",
                "zfs_default_ibs",
                "zfs_delay_max_ns",
                "zfs_delay_min_dirty_percent",
                "zfs_delay_resolution_ns",
                "zfs_delay_scale",
                "zfs_dirty_data_max",
                "zfs_dirty_data_max_max",
                "zfs_dirty_data_max_percent",
                "zfs_dirty_data_sync",
                "zfs_flags",
                "zfs_free_bpobj_enabled",
                "zfs_free_leak_on_eio",
                "zfs_free_min_time_ms",
                "zfs_immediate_write_sz",
                "zfs_indirect_condense_obsolete_pct",
                "zfs_lua_check_instrlimit_interval",
                "zfs_lua_max_instrlimit",
                "zfs_lua_max_memlimit",
                "zfs_max_recordsize",
                "zfs_mdcomp_disable",
                "zfs_metaslab_condense_block_threshold",
                "zfs_metaslab_fragmentation_threshold",
                "zfs_metaslab_segment_weight_enabled",
                "zfs_metaslab_switch_threshold",
                "zfs_mg_fragmentation_threshold",
                "zfs_mg_noalloc_threshold",
                "zfs_multilist_num_sublists",
                "zfs_no_scrub_io",
                "zfs_no_scrub_prefetch",
                "zfs_nocacheflush",
                "zfs_nopwrite_enabled",
                "zfs_object_remap_one_indirect_delay_ticks",
                "zfs_obsolete_min_time_ms",
                "zfs_pd_bytes_max",
                "zfs_per_txg_dirty_frees_percent",
                "zfs_prefetch_disable",
                "zfs_read_chunk_size",
                "zfs_recover",
                "zfs_recv_queue_length",
                "zfs_redundant_metadata_most_ditto_level",
                "zfs_remap_blkptr_enable",
                "zfs_remove_max_copy_bytes",
                "zfs_remove_max_segment",
                "zfs_resilver_min_time_ms",
                "zfs_scan_min_time_ms",
                "zfs_scrub_limit",
                "zfs_send_corrupt_data",
                "zfs_send_queue_length",
                "zfs_send_set_freerecords_bit",
                "zfs_sync_pass_deferred_free",
                "zfs_sync_pass_dont_compress",
                "zfs_sync_pass_rewrite",
                "zfs_sync_taskq_batch_pct",
                "zfs_top_maxinflight",
                "zfs_txg_timeout",
                "zfs_vdev_aggregation_limit",
                "zfs_vdev_async_read_max_active",
                "zfs_vdev_async_read_min_active",
                "zfs_vdev_async_write_active_max_dirty_percent",
                "zfs_vdev_async_write_active_min_dirty_percent",
                "zfs_vdev_async_write_max_active",
                "zfs_vdev_async_write_min_active",
                "zfs_vdev_cache_bshift",
                "zfs_vdev_cache_max",
                "zfs_vdev_cache_size",
                "zfs_vdev_max_active",
                "zfs_vdev_queue_depth_pct",
                "zfs_vdev_read_gap_limit",
                "zfs_vdev_removal_max_active",
                "zfs_vdev_removal_min_active",
                "zfs_vdev_scrub_max_active",
                "zfs_vdev_scrub_min_active",
                "zfs_vdev_sync_read_max_active",
                "zfs_vdev_sync_read_min_active",
                "zfs_vdev_sync_write_max_active",
                "zfs_vdev_sync_write_min_active",
                "zfs_vdev_write_gap_limit",
                "zfs_write_implies_delete_child",
                "zfs_zil_clean_taskq_maxalloc",
                "zfs_zil_clean_taskq_minalloc",
                "zfs_zil_clean_taskq_nthr_pct",
                "zil_replay_disable",
                "zil_slog_bulk",
                "zio_buf_debug_limit",
                "zio_dva_throttle_enabled",
                "zio_injection_enabled",
                "zvol_immediate_write_sz",
                "zvol_maxphys",
                "zvol_unmap_enabled",
                "zvol_unmap_sync_enabled",
                "zfs_max_dataset_nesting",
        };

        for (int i = 0; i < sizeof (params) / sizeof (params[0]); i++) {
                int sz;
                uint64_t val64;
                uint32_t *val32p = (uint32_t *)&val64;

                sz = mdb_readvar(&val64, params[i]);
                if (sz == 4) {
                        mdb_printf("%s = 0x%x\n", params[i], *val32p);
                } else if (sz == 8) {
                        mdb_printf("%s = 0x%llx\n", params[i], val64);
                } else {
                        mdb_warn("variable %s not found", params[i]);
                }
        }

        return (DCMD_OK);
}

/* ARGSUSED */
static int
dva(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        dva_t dva;
        if (mdb_vread(&dva, sizeof (dva_t), addr) == -1) {
                mdb_warn("failed to read dva_t");
                return (DCMD_ERR);
        }
        mdb_printf("<%llu:%llx:%llx>\n",
            (u_longlong_t)DVA_GET_VDEV(&dva),
            (u_longlong_t)DVA_GET_OFFSET(&dva),
            (u_longlong_t)DVA_GET_ASIZE(&dva));

        return (DCMD_OK);
}

typedef struct mdb_dmu_object_type_info {
        boolean_t ot_encrypt;
} mdb_dmu_object_type_info_t;

static boolean_t
mdb_dmu_ot_is_encrypted_impl(dmu_object_type_t ot)
{
        mdb_dmu_object_type_info_t mdoti;
        GElf_Sym sym;
        size_t sz = mdb_ctf_sizeof_by_name("dmu_object_type_info_t");

        if (mdb_lookup_by_obj(ZFS_OBJ_NAME, "dmu_ot", &sym)) {
                mdb_warn("failed to find " ZFS_OBJ_NAME "`dmu_ot");
                return (B_FALSE);
        }

        if (mdb_ctf_vread(&mdoti, "dmu_object_type_info_t",
            "mdb_dmu_object_type_info_t", sym.st_value + sz * ot, 0) != 0) {
                return (B_FALSE);
        }

        return (mdoti.ot_encrypt);
}

/* ARGSUSED */
static int
blkptr(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        char type[80], checksum[80], compress[80];
        blkptr_t blk, *bp = &blk;
        char buf[BP_SPRINTF_LEN];

        if (mdb_vread(&blk, sizeof (blkptr_t), addr) == -1) {
                mdb_warn("failed to read blkptr_t");
                return (DCMD_ERR);
        }

        if (enum_lookup("enum dmu_object_type", BP_GET_TYPE(bp), "DMU_OT_",
            sizeof (type), type) == -1 ||
            enum_lookup("enum zio_checksum", BP_GET_CHECKSUM(bp),
            "ZIO_CHECKSUM_", sizeof (checksum), checksum) == -1 ||
            enum_lookup("enum zio_compress", BP_GET_COMPRESS(bp),
            "ZIO_COMPRESS_", sizeof (compress), compress) == -1) {
                mdb_warn("Could not find blkptr enumerated types");
                return (DCMD_ERR);
        }

        SNPRINTF_BLKPTR(mdb_snprintf, '\n', buf, sizeof (buf), bp, type,
            checksum, compress);

        mdb_printf("%s\n", buf);

        return (DCMD_OK);
}

typedef struct mdb_dmu_buf_impl {
        struct {
                uint64_t db_object;
                uintptr_t db_data;
        } db;
        uintptr_t db_objset;
        uint64_t db_level;
        uint64_t db_blkid;
        struct {
                uint64_t rc_count;
        } db_holds;
} mdb_dmu_buf_impl_t;

/* ARGSUSED */
static int
dbuf(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_dmu_buf_impl_t db;
        char objectname[32];
        char blkidname[32];
        char path[ZFS_MAX_DATASET_NAME_LEN];
        int ptr_width = (int)(sizeof (void *)) * 2;

        if (DCMD_HDRSPEC(flags))
                mdb_printf("%*s %8s %3s %9s %5s %s\n",
                    ptr_width, "addr", "object", "lvl", "blkid", "holds", "os");

        if (mdb_ctf_vread(&db, ZFS_STRUCT "dmu_buf_impl", "mdb_dmu_buf_impl_t",
            addr, 0) == -1)
                return (DCMD_ERR);

        if (db.db.db_object == DMU_META_DNODE_OBJECT)
                (void) strcpy(objectname, "mdn");
        else
                (void) mdb_snprintf(objectname, sizeof (objectname), "%llx",
                    (u_longlong_t)db.db.db_object);

        if (db.db_blkid == DMU_BONUS_BLKID)
                (void) strcpy(blkidname, "bonus");
        else
                (void) mdb_snprintf(blkidname, sizeof (blkidname), "%llx",
                    (u_longlong_t)db.db_blkid);

        if (objset_name(db.db_objset, path)) {
                return (DCMD_ERR);
        }

        mdb_printf("%*p %8s %3u %9s %5llu %s\n", ptr_width, addr,
            objectname, (int)db.db_level, blkidname,
            db.db_holds.rc_count, path);

        return (DCMD_OK);
}

/* ARGSUSED */
static int
dbuf_stats(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
#define HISTOSZ 32
        uintptr_t dbp;
        dmu_buf_impl_t db;
        dbuf_hash_table_t ht;
        uint64_t bucket, ndbufs;
        uint64_t histo[HISTOSZ];
        uint64_t histo2[HISTOSZ];
        int i, maxidx;

        if (mdb_readvar(&ht, "dbuf_hash_table") == -1) {
                mdb_warn("failed to read 'dbuf_hash_table'");
                return (DCMD_ERR);
        }

        for (i = 0; i < HISTOSZ; i++) {
                histo[i] = 0;
                histo2[i] = 0;
        }

        ndbufs = 0;
        for (bucket = 0; bucket < ht.hash_table_mask+1; bucket++) {
                int len;

                if (mdb_vread(&dbp, sizeof (void *),
                    (uintptr_t)(ht.hash_table+bucket)) == -1) {
                        mdb_warn("failed to read hash bucket %u at %p",
                            bucket, ht.hash_table+bucket);
                        return (DCMD_ERR);
                }

                len = 0;
                while (dbp != 0) {
                        if (mdb_vread(&db, sizeof (dmu_buf_impl_t),
                            dbp) == -1) {
                                mdb_warn("failed to read dbuf at %p", dbp);
                                return (DCMD_ERR);
                        }
                        dbp = (uintptr_t)db.db_hash_next;
                        for (i = MIN(len, HISTOSZ - 1); i >= 0; i--)
                                histo2[i]++;
                        len++;
                        ndbufs++;
                }

                if (len >= HISTOSZ)
                        len = HISTOSZ-1;
                histo[len]++;
        }

        mdb_printf("hash table has %llu buckets, %llu dbufs "
            "(avg %llu buckets/dbuf)\n",
            ht.hash_table_mask+1, ndbufs,
            (ht.hash_table_mask+1)/ndbufs);

        mdb_printf("\n");
        maxidx = 0;
        for (i = 0; i < HISTOSZ; i++)
                if (histo[i] > 0)
                        maxidx = i;
        mdb_printf("hash chain length   number of buckets\n");
        for (i = 0; i <= maxidx; i++)
                mdb_printf("%u                  %llu\n", i, histo[i]);

        mdb_printf("\n");
        maxidx = 0;
        for (i = 0; i < HISTOSZ; i++)
                if (histo2[i] > 0)
                        maxidx = i;
        mdb_printf("hash chain depth    number of dbufs\n");
        for (i = 0; i <= maxidx; i++)
                mdb_printf("%u or more          %llu    %llu%%\n",
                    i, histo2[i], histo2[i]*100/ndbufs);


        return (DCMD_OK);
}

#define CHAIN_END 0xffff
/*
 * ::zap_leaf [-v]
 *
 * Print a zap_leaf_phys_t, assumed to be 16k
 */
/* ARGSUSED */
static int
zap_leaf(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        char buf[16*1024];
        int verbose = B_FALSE;
        int four = B_FALSE;
        dmu_buf_t l_dbuf;
        zap_leaf_t l;
        zap_leaf_phys_t *zlp = (void *)buf;
        int i;

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, TRUE, &verbose,
            '4', MDB_OPT_SETBITS, TRUE, &four,
            NULL) != argc)
                return (DCMD_USAGE);

        l_dbuf.db_data = zlp;
        l.l_dbuf = &l_dbuf;
        l.l_bs = 14; /* assume 16k blocks */
        if (four)
                l.l_bs = 12;

        if (!(flags & DCMD_ADDRSPEC)) {
                return (DCMD_USAGE);
        }

        if (mdb_vread(buf, sizeof (buf), addr) == -1) {
                mdb_warn("failed to read zap_leaf_phys_t at %p", addr);
                return (DCMD_ERR);
        }

        if (zlp->l_hdr.lh_block_type != ZBT_LEAF ||
            zlp->l_hdr.lh_magic != ZAP_LEAF_MAGIC) {
                mdb_warn("This does not appear to be a zap_leaf_phys_t");
                return (DCMD_ERR);
        }

        mdb_printf("zap_leaf_phys_t at %p:\n", addr);
        mdb_printf("    lh_prefix_len = %u\n", zlp->l_hdr.lh_prefix_len);
        mdb_printf("    lh_prefix = %llx\n", zlp->l_hdr.lh_prefix);
        mdb_printf("    lh_nentries = %u\n", zlp->l_hdr.lh_nentries);
        mdb_printf("    lh_nfree = %u\n", zlp->l_hdr.lh_nfree,
            zlp->l_hdr.lh_nfree * 100 / (ZAP_LEAF_NUMCHUNKS(&l)));
        mdb_printf("    lh_freelist = %u\n", zlp->l_hdr.lh_freelist);
        mdb_printf("    lh_flags = %x (%s)\n", zlp->l_hdr.lh_flags,
            zlp->l_hdr.lh_flags & ZLF_ENTRIES_CDSORTED ?
            "ENTRIES_CDSORTED" : "");

        if (verbose) {
                mdb_printf(" hash table:\n");
                for (i = 0; i < ZAP_LEAF_HASH_NUMENTRIES(&l); i++) {
                        if (zlp->l_hash[i] != CHAIN_END)
                                mdb_printf("    %u: %u\n", i, zlp->l_hash[i]);
                }
        }

        mdb_printf(" chunks:\n");
        for (i = 0; i < ZAP_LEAF_NUMCHUNKS(&l); i++) {
                /* LINTED: alignment */
                zap_leaf_chunk_t *zlc = &ZAP_LEAF_CHUNK(&l, i);
                switch (zlc->l_entry.le_type) {
                case ZAP_CHUNK_FREE:
                        if (verbose) {
                                mdb_printf("    %u: free; lf_next = %u\n",
                                    i, zlc->l_free.lf_next);
                        }
                        break;
                case ZAP_CHUNK_ENTRY:
                        mdb_printf("    %u: entry\n", i);
                        if (verbose) {
                                mdb_printf("        le_next = %u\n",
                                    zlc->l_entry.le_next);
                        }
                        mdb_printf("        le_name_chunk = %u\n",
                            zlc->l_entry.le_name_chunk);
                        mdb_printf("        le_name_numints = %u\n",
                            zlc->l_entry.le_name_numints);
                        mdb_printf("        le_value_chunk = %u\n",
                            zlc->l_entry.le_value_chunk);
                        mdb_printf("        le_value_intlen = %u\n",
                            zlc->l_entry.le_value_intlen);
                        mdb_printf("        le_value_numints = %u\n",
                            zlc->l_entry.le_value_numints);
                        mdb_printf("        le_cd = %u\n",
                            zlc->l_entry.le_cd);
                        mdb_printf("        le_hash = %llx\n",
                            zlc->l_entry.le_hash);
                        break;
                case ZAP_CHUNK_ARRAY:
                        mdb_printf("    %u: array", i);
                        if (strisprint((char *)zlc->l_array.la_array))
                                mdb_printf(" \"%s\"", zlc->l_array.la_array);
                        mdb_printf("\n");
                        if (verbose) {
                                int j;
                                mdb_printf("        ");
                                for (j = 0; j < ZAP_LEAF_ARRAY_BYTES; j++) {
                                        mdb_printf("%02x ",
                                            zlc->l_array.la_array[j]);
                                }
                                mdb_printf("\n");
                        }
                        if (zlc->l_array.la_next != CHAIN_END) {
                                mdb_printf("        lf_next = %u\n",
                                    zlc->l_array.la_next);
                        }
                        break;
                default:
                        mdb_printf("    %u: undefined type %u\n",
                            zlc->l_entry.le_type);
                }
        }

        return (DCMD_OK);
}

typedef struct dbufs_data {
        mdb_ctf_id_t id;
        uint64_t objset;
        uint64_t object;
        uint64_t level;
        uint64_t blkid;
        char *osname;
} dbufs_data_t;

#define DBUFS_UNSET     (0xbaddcafedeadbeefULL)

/* ARGSUSED */
static int
dbufs_cb(uintptr_t addr, const void *unknown, void *arg)
{
        dbufs_data_t *data = arg;
        uintptr_t objset;
        dmu_buf_t db;
        uint8_t level;
        uint64_t blkid;
        char osname[ZFS_MAX_DATASET_NAME_LEN];

        if (GETMEMBID(addr, &data->id, db_objset, objset) ||
            GETMEMBID(addr, &data->id, db, db) ||
            GETMEMBID(addr, &data->id, db_level, level) ||
            GETMEMBID(addr, &data->id, db_blkid, blkid)) {
                return (WALK_ERR);
        }

        if ((data->objset == DBUFS_UNSET || data->objset == objset) &&
            (data->osname == NULL || (objset_name(objset, osname) == 0 &&
            strcmp(data->osname, osname) == 0)) &&
            (data->object == DBUFS_UNSET || data->object == db.db_object) &&
            (data->level == DBUFS_UNSET || data->level == level) &&
            (data->blkid == DBUFS_UNSET || data->blkid == blkid)) {
                mdb_printf("%#lr\n", addr);
        }
        return (WALK_NEXT);
}

/* ARGSUSED */
static int
dbufs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        dbufs_data_t data;
        char *object = NULL;
        char *blkid = NULL;

        data.objset = data.object = data.level = data.blkid = DBUFS_UNSET;
        data.osname = NULL;

        if (mdb_getopts(argc, argv,
            'O', MDB_OPT_UINT64, &data.objset,
            'n', MDB_OPT_STR, &data.osname,
            'o', MDB_OPT_STR, &object,
            'l', MDB_OPT_UINT64, &data.level,
            'b', MDB_OPT_STR, &blkid,
            NULL) != argc) {
                return (DCMD_USAGE);
        }

        if (object) {
                if (strcmp(object, "mdn") == 0) {
                        data.object = DMU_META_DNODE_OBJECT;
                } else {
                        data.object = mdb_strtoull(object);
                }
        }

        if (blkid) {
                if (strcmp(blkid, "bonus") == 0) {
                        data.blkid = DMU_BONUS_BLKID;
                } else {
                        data.blkid = mdb_strtoull(blkid);
                }
        }

        if (mdb_ctf_lookup_by_name(ZFS_STRUCT "dmu_buf_impl", &data.id) == -1) {
                mdb_warn("couldn't find struct dmu_buf_impl_t");
                return (DCMD_ERR);
        }

        if (mdb_walk("dmu_buf_impl_t", dbufs_cb, &data) != 0) {
                mdb_warn("can't walk dbufs");
                return (DCMD_ERR);
        }

        return (DCMD_OK);
}

typedef struct abuf_find_data {
        dva_t dva;
        mdb_ctf_id_t id;
} abuf_find_data_t;

/* ARGSUSED */
static int
abuf_find_cb(uintptr_t addr, const void *unknown, void *arg)
{
        abuf_find_data_t *data = arg;
        dva_t dva;

        if (GETMEMBID(addr, &data->id, b_dva, dva)) {
                return (WALK_ERR);
        }

        if (dva.dva_word[0] == data->dva.dva_word[0] &&
            dva.dva_word[1] == data->dva.dva_word[1]) {
                mdb_printf("%#lr\n", addr);
        }
        return (WALK_NEXT);
}

typedef struct mdb_arc_state {
        uintptr_t       arcs_list[ARC_BUFC_NUMTYPES];
} mdb_arc_state_t;

/* ARGSUSED */
static int
abuf_find(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        abuf_find_data_t data;
        GElf_Sym sym;
        int i, j;
        const char *syms[] = {
                "ARC_mru",
                "ARC_mru_ghost",
                "ARC_mfu",
                "ARC_mfu_ghost",
        };

        if (argc != 2)
                return (DCMD_USAGE);

        for (i = 0; i < 2; i ++) {
                switch (argv[i].a_type) {
                case MDB_TYPE_STRING:
                        data.dva.dva_word[i] = mdb_strtoull(argv[i].a_un.a_str);
                        break;
                case MDB_TYPE_IMMEDIATE:
                        data.dva.dva_word[i] = argv[i].a_un.a_val;
                        break;
                default:
                        return (DCMD_USAGE);
                }
        }

        if (mdb_ctf_lookup_by_name(ZFS_STRUCT "arc_buf_hdr", &data.id) == -1) {
                mdb_warn("couldn't find struct arc_buf_hdr");
                return (DCMD_ERR);
        }

        for (i = 0; i < sizeof (syms) / sizeof (syms[0]); i++) {
                mdb_arc_state_t mas;

                if (mdb_lookup_by_obj(ZFS_OBJ_NAME, syms[i], &sym)) {
                        mdb_warn("can't find symbol %s", syms[i]);
                        return (DCMD_ERR);
                }

                if (mdb_ctf_vread(&mas, "arc_state_t", "mdb_arc_state_t",
                    sym.st_value, 0) != 0) {
                        mdb_warn("can't read arcs_list of %s", syms[i]);
                        return (DCMD_ERR);
                }

                for (j = 0; j < ARC_BUFC_NUMTYPES; j++) {
                        uintptr_t addr = mas.arcs_list[j];

                        if (addr == 0)
                                continue;

                        if (mdb_pwalk("multilist", abuf_find_cb, &data,
                            addr) != 0) {
                                mdb_warn("can't walk %s", syms[i]);
                                return (DCMD_ERR);
                        }
                }
        }

        return (DCMD_OK);
}

typedef struct dbgmsg_arg {
        boolean_t da_address;
        boolean_t da_hrtime;
        boolean_t da_timedelta;
        boolean_t da_time;
        boolean_t da_whatis;

        hrtime_t da_curtime;
} dbgmsg_arg_t;

static int
dbgmsg_cb(uintptr_t addr, const void *unknown __unused, void *arg)
{
        static mdb_ctf_id_t id;
        static boolean_t gotid;
        static ulong_t off;

        dbgmsg_arg_t *da = arg;
        time_t timestamp;
        hrtime_t hrtime;
        char buf[1024];

        if (!gotid) {
                if (mdb_ctf_lookup_by_name(ZFS_STRUCT "zfs_dbgmsg", &id) ==
                    -1) {
                        mdb_warn("couldn't find struct zfs_dbgmsg");
                        return (WALK_ERR);
                }
                gotid = TRUE;
                if (mdb_ctf_offsetof(id, "zdm_msg", &off) == -1) {
                        mdb_warn("couldn't find zdm_msg");
                        return (WALK_ERR);
                }
                off /= 8;
        }

        if (GETMEMBID(addr, &id, zdm_timestamp, timestamp)) {
                return (WALK_ERR);
        }

        if (da->da_hrtime || da->da_timedelta) {
                if (GETMEMBID(addr, &id, zdm_hrtime, hrtime)) {
                        return (WALK_ERR);
                }
        }

        if (mdb_readstr(buf, sizeof (buf), addr + off) == -1) {
                mdb_warn("failed to read zdm_msg at %p\n", addr + off);
                return (DCMD_ERR);
        }

        if (da->da_address)
                mdb_printf("%p ", addr);

        if (da->da_timedelta) {
                int64_t         diff;
                char            dbuf[32] = { 0 };

                if (da->da_curtime == 0)
                        da->da_curtime = mdb_gethrtime();

                diff = (int64_t)hrtime - da->da_curtime;
                mdb_nicetime(diff, dbuf, sizeof (dbuf));
                mdb_printf("%-20s ", dbuf);
        } else if (da->da_hrtime) {
                mdb_printf("%016x ", hrtime);
        } else if (da->da_time) {
                mdb_printf("%Y ", timestamp);
        }

        mdb_printf("%s\n", buf);

        if (da->da_whatis)
                (void) mdb_call_dcmd("whatis", addr, DCMD_ADDRSPEC, 0, NULL);

        return (WALK_NEXT);
}

static int
dbgmsg(uintptr_t addr, uint_t flags __unused, int argc, const mdb_arg_t *argv)
{
        GElf_Sym sym;
        dbgmsg_arg_t da = { 0 };
        boolean_t verbose = B_FALSE;

        if (mdb_getopts(argc, argv,
            'a', MDB_OPT_SETBITS, B_TRUE, &da.da_address,
            'r', MDB_OPT_SETBITS, B_TRUE, &da.da_hrtime,
            't', MDB_OPT_SETBITS, B_TRUE, &da.da_timedelta,
            'T', MDB_OPT_SETBITS, B_TRUE, &da.da_time,
            'v', MDB_OPT_SETBITS, B_TRUE, &verbose,
            'w', MDB_OPT_SETBITS, B_TRUE, &da.da_whatis,
            NULL) != argc) {
                return (DCMD_USAGE);
        }

        if (verbose)
                da.da_address = da.da_time = B_TRUE;

        if (mdb_lookup_by_obj(ZFS_OBJ_NAME, "zfs_dbgmsgs", &sym)) {
                mdb_warn("can't find zfs_dbgmsgs");
                return (DCMD_ERR);
        }

        if (mdb_pwalk("list", dbgmsg_cb, &da, sym.st_value) != 0) {
                mdb_warn("can't walk zfs_dbgmsgs");
                return (DCMD_ERR);
        }

        return (DCMD_OK);
}


static void
dbgmsg_help(void)
{
        mdb_printf("Print entries from the ZFS debug log.\n\n"
            "%<b>OPTIONS%</b>\n"
            "\t-a\tInclude the address of each zfs_dbgmsg_t.\n"
            "\t-r\tDisplay high-resolution timestamps.\n"
            "\t-t\tInclude the age of the message.\n"
            "\t-T\tInclude the date/time of the message.\n"
            "\t-v\tEquivalent to -aT.\n"
            "\t-w\tRun ::whatis on each zfs_dbgmsg_t. Useful in DEBUG kernels\n"
            "\t\tto show the origin of the message.\n");
}

/*ARGSUSED*/
static int
arc_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        kstat_named_t *stats;
        GElf_Sym sym;
        int nstats, i;
        uint_t opt_a = FALSE;
        uint_t opt_b = FALSE;
        uint_t shift = 0;
        const char *suffix;

        static const char *bytestats[] = {
                "p", "c", "c_min", "c_max", "size", "duplicate_buffers_size",
                "arc_meta_used", "arc_meta_limit", "arc_meta_max",
                "arc_meta_min", "hdr_size", "data_size", "metadata_size",
                "other_size", "anon_size", "anon_evictable_data",
                "anon_evictable_metadata", "mru_size", "mru_evictable_data",
                "mru_evictable_metadata", "mru_ghost_size",
                "mru_ghost_evictable_data", "mru_ghost_evictable_metadata",
                "mfu_size", "mfu_evictable_data", "mfu_evictable_metadata",
                "mfu_ghost_size", "mfu_ghost_evictable_data",
                "mfu_ghost_evictable_metadata", "evict_l2_cached",
                "evict_l2_eligible", "evict_l2_ineligible", "l2_read_bytes",
                "l2_write_bytes", "l2_size", "l2_asize", "l2_hdr_size",
                "compressed_size", "uncompressed_size", "overhead_size",
                NULL
        };

        static const char *extras[] = {
                "arc_no_grow", "arc_tempreserve",
                NULL
        };

        if (mdb_lookup_by_obj(ZFS_OBJ_NAME, "arc_stats", &sym) == -1) {
                mdb_warn("failed to find 'arc_stats'");
                return (DCMD_ERR);
        }

        stats = mdb_zalloc(sym.st_size, UM_SLEEP | UM_GC);

        if (mdb_vread(stats, sym.st_size, sym.st_value) == -1) {
                mdb_warn("couldn't read 'arc_stats' at %p", sym.st_value);
                return (DCMD_ERR);
        }

        nstats = sym.st_size / sizeof (kstat_named_t);

        /* NB: -a / opt_a are ignored for backwards compatability */
        if (mdb_getopts(argc, argv,
            'a', MDB_OPT_SETBITS, TRUE, &opt_a,
            'b', MDB_OPT_SETBITS, TRUE, &opt_b,
            'k', MDB_OPT_SETBITS, 10, &shift,
            'm', MDB_OPT_SETBITS, 20, &shift,
            'g', MDB_OPT_SETBITS, 30, &shift,
            NULL) != argc)
                return (DCMD_USAGE);

        if (!opt_b && !shift)
                shift = 20;

        switch (shift) {
        case 0:
                suffix = "B";
                break;
        case 10:
                suffix = "KB";
                break;
        case 20:
                suffix = "MB";
                break;
        case 30:
                suffix = "GB";
                break;
        default:
                suffix = "XX";
        }

        for (i = 0; i < nstats; i++) {
                int j;
                boolean_t bytes = B_FALSE;

                for (j = 0; bytestats[j]; j++) {
                        if (strcmp(stats[i].name, bytestats[j]) == 0) {
                                bytes = B_TRUE;
                                break;
                        }
                }

                if (bytes) {
                        mdb_printf("%-25s = %9llu %s\n", stats[i].name,
                            stats[i].value.ui64 >> shift, suffix);
                } else {
                        mdb_printf("%-25s = %9llu\n", stats[i].name,
                            stats[i].value.ui64);
                }
        }

        for (i = 0; extras[i]; i++) {
                uint64_t buf;

                if (mdb_lookup_by_obj(ZFS_OBJ_NAME, extras[i], &sym) == -1) {
                        mdb_warn("failed to find '%s'", extras[i]);
                        return (DCMD_ERR);
                }

                if (sym.st_size != sizeof (uint64_t) &&
                    sym.st_size != sizeof (uint32_t)) {
                        mdb_warn("expected scalar for variable '%s'\n",
                            extras[i]);
                        return (DCMD_ERR);
                }

                if (mdb_vread(&buf, sym.st_size, sym.st_value) == -1) {
                        mdb_warn("couldn't read '%s'", extras[i]);
                        return (DCMD_ERR);
                }

                mdb_printf("%-25s = ", extras[i]);

                /* NB: all the 64-bit extras happen to be byte counts */
                if (sym.st_size == sizeof (uint64_t))
                        mdb_printf("%9llu %s\n", buf >> shift, suffix);

                if (sym.st_size == sizeof (uint32_t))
                        mdb_printf("%9d\n", *((uint32_t *)&buf));
        }
        return (DCMD_OK);
}

typedef struct mdb_spa_print {
        pool_state_t spa_state;
        char spa_name[ZFS_MAX_DATASET_NAME_LEN];
        uintptr_t spa_normal_class;
} mdb_spa_print_t;


const char histo_stars[] = "****************************************";
const int histo_width = sizeof (histo_stars) - 1;

static void
dump_histogram(const uint64_t *histo, int size, int offset)
{
        int i;
        int minidx = size - 1;
        int maxidx = 0;
        uint64_t max = 0;

        for (i = 0; i < size; i++) {
                if (histo[i] > max)
                        max = histo[i];
                if (histo[i] > 0 && i > maxidx)
                        maxidx = i;
                if (histo[i] > 0 && i < minidx)
                        minidx = i;
        }

        if (max < histo_width)
                max = histo_width;

        for (i = minidx; i <= maxidx; i++) {
                mdb_printf("%3u: %6llu %s\n",
                    i + offset, (u_longlong_t)histo[i],
                    &histo_stars[(max - histo[i]) * histo_width / max]);
        }
}

typedef struct mdb_metaslab_class {
        uint64_t mc_histogram[RANGE_TREE_HISTOGRAM_SIZE];
} mdb_metaslab_class_t;

/*
 * spa_class_histogram(uintptr_t class_addr)
 *
 * Prints free space histogram for a device class
 *
 * Returns DCMD_OK, or DCMD_ERR.
 */
static int
spa_class_histogram(uintptr_t class_addr)
{
        mdb_metaslab_class_t mc;
        if (mdb_ctf_vread(&mc, "metaslab_class_t",
            "mdb_metaslab_class_t", class_addr, 0) == -1)
                return (DCMD_ERR);

        mdb_inc_indent(4);
        dump_histogram(mc.mc_histogram, RANGE_TREE_HISTOGRAM_SIZE, 0);
        mdb_dec_indent(4);
        return (DCMD_OK);
}

/*
 * ::spa
 *
 *      -c      Print configuration information as well
 *      -v      Print vdev state
 *      -e      Print vdev error stats
 *      -m      Print vdev metaslab info
 *      -M      print vdev metaslab group info
 *      -h      Print histogram info (must be combined with -m or -M)
 *
 * Print a summarized spa_t.  When given no arguments, prints out a table of all
 * active pools on the system.
 */
/* ARGSUSED */
static int
spa_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        const char *statetab[] = { "ACTIVE", "EXPORTED", "DESTROYED",
                "SPARE", "L2CACHE", "UNINIT", "UNAVAIL", "POTENTIAL" };
        const char *state;
        int spa_flags = 0;

        if (mdb_getopts(argc, argv,
            'c', MDB_OPT_SETBITS, SPA_FLAG_CONFIG, &spa_flags,
            'v', MDB_OPT_SETBITS, SPA_FLAG_VDEVS, &spa_flags,
            'e', MDB_OPT_SETBITS, SPA_FLAG_ERRORS, &spa_flags,
            'M', MDB_OPT_SETBITS, SPA_FLAG_METASLAB_GROUPS, &spa_flags,
            'm', MDB_OPT_SETBITS, SPA_FLAG_METASLABS, &spa_flags,
            'h', MDB_OPT_SETBITS, SPA_FLAG_HISTOGRAMS, &spa_flags,
            NULL) != argc)
                return (DCMD_USAGE);

        if (!(flags & DCMD_ADDRSPEC)) {
                if (mdb_walk_dcmd("spa", "spa", argc, argv) == -1) {
                        mdb_warn("can't walk spa");
                        return (DCMD_ERR);
                }

                return (DCMD_OK);
        }

        if (flags & DCMD_PIPE_OUT) {
                mdb_printf("%#lr\n", addr);
                return (DCMD_OK);
        }

        if (DCMD_HDRSPEC(flags))
                mdb_printf("%<u>%-?s %9s %-*s%</u>\n", "ADDR", "STATE",
                    sizeof (uintptr_t) == 4 ? 60 : 52, "NAME");

        mdb_spa_print_t spa;
        if (mdb_ctf_vread(&spa, "spa_t", "mdb_spa_print_t", addr, 0) == -1)
                return (DCMD_ERR);

        if (spa.spa_state < 0 || spa.spa_state > POOL_STATE_UNAVAIL)
                state = "UNKNOWN";
        else
                state = statetab[spa.spa_state];

        mdb_printf("%0?p %9s %s\n", addr, state, spa.spa_name);
        if (spa_flags & SPA_FLAG_HISTOGRAMS)
                spa_class_histogram(spa.spa_normal_class);

        if (spa_flags & SPA_FLAG_CONFIG) {
                mdb_printf("\n");
                mdb_inc_indent(4);
                if (mdb_call_dcmd("spa_config", addr, flags, 0,
                    NULL) != DCMD_OK)
                        return (DCMD_ERR);
                mdb_dec_indent(4);
        }

        if (spa_flags & SPA_FLAG_ALL_VDEV) {
                mdb_arg_t v;
                char opts[100] = "-";
                int args =
                    (spa_flags | SPA_FLAG_VDEVS) == SPA_FLAG_VDEVS ? 0 : 1;

                if (spa_flags & SPA_FLAG_ERRORS)
                        strcat(opts, "e");
                if (spa_flags & SPA_FLAG_METASLABS)
                        strcat(opts, "m");
                if (spa_flags & SPA_FLAG_METASLAB_GROUPS)
                        strcat(opts, "M");
                if (spa_flags & SPA_FLAG_HISTOGRAMS)
                        strcat(opts, "h");

                v.a_type = MDB_TYPE_STRING;
                v.a_un.a_str = opts;

                mdb_printf("\n");
                mdb_inc_indent(4);
                if (mdb_call_dcmd("spa_vdevs", addr, flags, args,
                    &v) != DCMD_OK)
                        return (DCMD_ERR);
                mdb_dec_indent(4);
        }

        return (DCMD_OK);
}

typedef struct mdb_spa_config_spa {
        uintptr_t spa_config;
} mdb_spa_config_spa_t;

/*
 * ::spa_config
 *
 * Given a spa_t, print the configuration information stored in spa_config.
 * Since it's just an nvlist, format it as an indented list of name=value pairs.
 * We simply read the value of spa_config and pass off to ::nvlist.
 */
/* ARGSUSED */
static int
spa_print_config(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_spa_config_spa_t spa;

        if (argc != 0 || !(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_ctf_vread(&spa, ZFS_STRUCT "spa", "mdb_spa_config_spa_t",
            addr, 0) == -1)
                return (DCMD_ERR);

        if (spa.spa_config == 0) {
                mdb_printf("(none)\n");
                return (DCMD_OK);
        }

        return (mdb_call_dcmd("nvlist", spa.spa_config, flags,
            0, NULL));
}

typedef struct mdb_range_tree {
        struct {
                uint64_t bt_num_elems;
                uint64_t bt_num_nodes;
        } rt_root;
        uint64_t rt_space;
        range_seg_type_t rt_type;
        uint8_t         rt_shift;
        uint64_t        rt_start;
} mdb_range_tree_t;

typedef struct mdb_metaslab_group {
        uint64_t mg_fragmentation;
        uint64_t mg_histogram[RANGE_TREE_HISTOGRAM_SIZE];
        uintptr_t mg_vd;
} mdb_metaslab_group_t;

typedef struct mdb_metaslab {
        uint64_t ms_id;
        uint64_t ms_start;
        uint64_t ms_size;
        int64_t ms_deferspace;
        uint64_t ms_fragmentation;
        uint64_t ms_weight;
        uintptr_t ms_allocating[TXG_SIZE];
        uintptr_t ms_checkpointing;
        uintptr_t ms_freeing;
        uintptr_t ms_freed;
        uintptr_t ms_allocatable;
        uintptr_t ms_unflushed_frees;
        uintptr_t ms_unflushed_allocs;
        uintptr_t ms_sm;
} mdb_metaslab_t;

typedef struct mdb_space_map_phys_t {
        int64_t smp_alloc;
        uint64_t smp_histogram[SPACE_MAP_HISTOGRAM_SIZE];
} mdb_space_map_phys_t;

typedef struct mdb_space_map {
        uint64_t sm_size;
        uint8_t sm_shift;
        uintptr_t sm_phys;
} mdb_space_map_t;

typedef struct mdb_vdev {
        uint64_t vdev_id;
        uint64_t vdev_state;
        uintptr_t vdev_ops;
        struct {
                uint64_t vs_aux;
                uint64_t vs_ops[VS_ZIO_TYPES];
                uint64_t vs_bytes[VS_ZIO_TYPES];
                uint64_t vs_read_errors;
                uint64_t vs_write_errors;
                uint64_t vs_checksum_errors;
        } vdev_stat;
        uintptr_t vdev_child;
        uint64_t vdev_children;
        uint64_t vdev_ms_count;
        uintptr_t vdev_mg;
        uintptr_t vdev_ms;
        uintptr_t vdev_path;
} mdb_vdev_t;

typedef struct mdb_vdev_ops {
        char vdev_op_type[16];
} mdb_vdev_ops_t;

static int
metaslab_stats(mdb_vdev_t *vd, int spa_flags)
{
        mdb_inc_indent(4);
        mdb_printf("%<u>%-?s %6s %20s %10s %10s %10s%</u>\n", "ADDR", "ID",
            "OFFSET", "FREE", "FRAG", "UCMU");

        uintptr_t *vdev_ms = mdb_alloc(vd->vdev_ms_count * sizeof (vdev_ms),
            UM_SLEEP | UM_GC);
        if (mdb_vread(vdev_ms, vd->vdev_ms_count * sizeof (uintptr_t),
            vd->vdev_ms) == -1) {
                mdb_warn("failed to read vdev_ms at %p\n", vd->vdev_ms);
                return (DCMD_ERR);
        }

        for (int m = 0; m < vd->vdev_ms_count; m++) {
                mdb_metaslab_t ms;
                mdb_space_map_t sm = { 0 };
                mdb_space_map_phys_t smp = { 0 };
                mdb_range_tree_t rt;
                uint64_t uallocs, ufrees, raw_free, raw_uchanges_mem;
                char free[MDB_NICENUM_BUFLEN];
                char uchanges_mem[MDB_NICENUM_BUFLEN];

                if (mdb_ctf_vread(&ms, "metaslab_t", "mdb_metaslab_t",
                    vdev_ms[m], 0) == -1)
                        return (DCMD_ERR);

                if (ms.ms_sm != 0 &&
                    mdb_ctf_vread(&sm, "space_map_t", "mdb_space_map_t",
                    ms.ms_sm, 0) == -1)
                        return (DCMD_ERR);

                if (mdb_ctf_vread(&rt, "range_tree_t", "mdb_range_tree_t",
                    ms.ms_unflushed_frees, 0) == -1)
                        return (DCMD_ERR);
                ufrees = rt.rt_space;
                raw_uchanges_mem = rt.rt_root.bt_num_nodes * BTREE_LEAF_SIZE;

                if (mdb_ctf_vread(&rt, "range_tree_t", "mdb_range_tree_t",
                    ms.ms_unflushed_allocs, 0) == -1)
                        return (DCMD_ERR);
                uallocs = rt.rt_space;
                raw_uchanges_mem += rt.rt_root.bt_num_nodes * BTREE_LEAF_SIZE;
                mdb_nicenum(raw_uchanges_mem, uchanges_mem);

                raw_free = ms.ms_size;
                if (ms.ms_sm != 0 && sm.sm_phys != 0) {
                        (void) mdb_ctf_vread(&smp, "space_map_phys_t",
                            "mdb_space_map_phys_t", sm.sm_phys, 0);
                        raw_free -= smp.smp_alloc;
                }
                raw_free += ufrees - uallocs;
                mdb_nicenum(raw_free, free);

                mdb_printf("%0?p %6llu %20llx %10s ", vdev_ms[m], ms.ms_id,
                    ms.ms_start, free);
                if (ms.ms_fragmentation == ZFS_FRAG_INVALID)
                        mdb_printf("%9s ", "-");
                else
                        mdb_printf("%9llu%% ", ms.ms_fragmentation);
                mdb_printf("%10s\n", uchanges_mem);

                if ((spa_flags & SPA_FLAG_HISTOGRAMS) && ms.ms_sm != 0 &&
                    sm.sm_phys != 0) {
                        dump_histogram(smp.smp_histogram,
                            SPACE_MAP_HISTOGRAM_SIZE, sm.sm_shift);
                }
        }
        mdb_dec_indent(4);
        return (DCMD_OK);
}

static int
metaslab_group_stats(mdb_vdev_t *vd, int spa_flags)
{
        mdb_metaslab_group_t mg;
        if (mdb_ctf_vread(&mg, "metaslab_group_t", "mdb_metaslab_group_t",
            vd->vdev_mg, 0) == -1) {
                mdb_warn("failed to read vdev_mg at %p\n", vd->vdev_mg);
                return (DCMD_ERR);
        }

        mdb_inc_indent(4);
        mdb_printf("%<u>%-?s %7s %9s%</u>\n", "ADDR", "FRAG", "UCMU");

        if (mg.mg_fragmentation == ZFS_FRAG_INVALID)
                mdb_printf("%0?p %6s\n", vd->vdev_mg, "-");
        else
                mdb_printf("%0?p %6llu%%", vd->vdev_mg, mg.mg_fragmentation);


        uintptr_t *vdev_ms = mdb_alloc(vd->vdev_ms_count * sizeof (vdev_ms),
            UM_SLEEP | UM_GC);
        if (mdb_vread(vdev_ms, vd->vdev_ms_count * sizeof (uintptr_t),
            vd->vdev_ms) == -1) {
                mdb_warn("failed to read vdev_ms at %p\n", vd->vdev_ms);
                return (DCMD_ERR);
        }

        uint64_t raw_uchanges_mem = 0;
        char uchanges_mem[MDB_NICENUM_BUFLEN];
        for (int m = 0; m < vd->vdev_ms_count; m++) {
                mdb_metaslab_t ms;
                mdb_range_tree_t rt;

                if (mdb_ctf_vread(&ms, "metaslab_t", "mdb_metaslab_t",
                    vdev_ms[m], 0) == -1)
                        return (DCMD_ERR);

                if (mdb_ctf_vread(&rt, "range_tree_t", "mdb_range_tree_t",
                    ms.ms_unflushed_frees, 0) == -1)
                        return (DCMD_ERR);
                raw_uchanges_mem += rt.rt_root.bt_num_nodes * BTREE_LEAF_SIZE;

                if (mdb_ctf_vread(&rt, "range_tree_t", "mdb_range_tree_t",
                    ms.ms_unflushed_allocs, 0) == -1)
                        return (DCMD_ERR);
                raw_uchanges_mem += rt.rt_root.bt_num_nodes * BTREE_LEAF_SIZE;
        }
        mdb_nicenum(raw_uchanges_mem, uchanges_mem);
        mdb_printf("%10s\n", uchanges_mem);

        if (spa_flags & SPA_FLAG_HISTOGRAMS)
                dump_histogram(mg.mg_histogram, RANGE_TREE_HISTOGRAM_SIZE, 0);
        mdb_dec_indent(4);
        return (DCMD_OK);
}

/*
 * ::vdev
 *
 * Print out a summarized vdev_t, in the following form:
 *
 * ADDR             STATE       AUX            DESC
 * fffffffbcde23df0 HEALTHY     -              /dev/dsk/c0t0d0
 *
 * If '-r' is specified, recursively visit all children.
 *
 * With '-e', the statistics associated with the vdev are printed as well.
 */
static int
do_print_vdev(uintptr_t addr, int flags, int depth, boolean_t recursive,
    int spa_flags)
{
        mdb_vdev_t vd;
        if (mdb_ctf_vread(&vd, "vdev_t", "mdb_vdev_t",
            (uintptr_t)addr, 0) == -1)
                return (DCMD_ERR);

        if (flags & DCMD_PIPE_OUT) {
                mdb_printf("%#lr\n", addr);
        } else {
                char desc[MAXNAMELEN];
                if (vd.vdev_path != 0) {
                        if (mdb_readstr(desc, sizeof (desc),
                            (uintptr_t)vd.vdev_path) == -1) {
                                mdb_warn("failed to read vdev_path at %p\n",
                                    vd.vdev_path);
                                return (DCMD_ERR);
                        }
                } else if (vd.vdev_ops != 0) {
                        vdev_ops_t ops;
                        if (mdb_vread(&ops, sizeof (ops),
                            (uintptr_t)vd.vdev_ops) == -1) {
                                mdb_warn("failed to read vdev_ops at %p\n",
                                    vd.vdev_ops);
                                return (DCMD_ERR);
                        }
                        (void) strcpy(desc, ops.vdev_op_type);
                } else {
                        (void) strcpy(desc, "<unknown>");
                }

                if (depth == 0 && DCMD_HDRSPEC(flags))
                        mdb_printf("%<u>%-?s %-9s %-12s %-*s%</u>\n",
                            "ADDR", "STATE", "AUX",
                            sizeof (uintptr_t) == 4 ? 43 : 35,
                            "DESCRIPTION");

                mdb_printf("%0?p ", addr);

                const char *state, *aux;
                switch (vd.vdev_state) {
                case VDEV_STATE_CLOSED:
                        state = "CLOSED";
                        break;
                case VDEV_STATE_OFFLINE:
                        state = "OFFLINE";
                        break;
                case VDEV_STATE_CANT_OPEN:
                        state = "CANT_OPEN";
                        break;
                case VDEV_STATE_DEGRADED:
                        state = "DEGRADED";
                        break;
                case VDEV_STATE_HEALTHY:
                        state = "HEALTHY";
                        break;
                case VDEV_STATE_REMOVED:
                        state = "REMOVED";
                        break;
                case VDEV_STATE_FAULTED:
                        state = "FAULTED";
                        break;
                default:
                        state = "UNKNOWN";
                        break;
                }

                switch (vd.vdev_stat.vs_aux) {
                case VDEV_AUX_NONE:
                        aux = "-";
                        break;
                case VDEV_AUX_OPEN_FAILED:
                        aux = "OPEN_FAILED";
                        break;
                case VDEV_AUX_CORRUPT_DATA:
                        aux = "CORRUPT_DATA";
                        break;
                case VDEV_AUX_NO_REPLICAS:
                        aux = "NO_REPLICAS";
                        break;
                case VDEV_AUX_BAD_GUID_SUM:
                        aux = "BAD_GUID_SUM";
                        break;
                case VDEV_AUX_TOO_SMALL:
                        aux = "TOO_SMALL";
                        break;
                case VDEV_AUX_BAD_LABEL:
                        aux = "BAD_LABEL";
                        break;
                case VDEV_AUX_VERSION_NEWER:
                        aux = "VERS_NEWER";
                        break;
                case VDEV_AUX_VERSION_OLDER:
                        aux = "VERS_OLDER";
                        break;
                case VDEV_AUX_UNSUP_FEAT:
                        aux = "UNSUP_FEAT";
                        break;
                case VDEV_AUX_SPARED:
                        aux = "SPARED";
                        break;
                case VDEV_AUX_ERR_EXCEEDED:
                        aux = "ERR_EXCEEDED";
                        break;
                case VDEV_AUX_IO_FAILURE:
                        aux = "IO_FAILURE";
                        break;
                case VDEV_AUX_BAD_LOG:
                        aux = "BAD_LOG";
                        break;
                case VDEV_AUX_EXTERNAL:
                        aux = "EXTERNAL";
                        break;
                case VDEV_AUX_SPLIT_POOL:
                        aux = "SPLIT_POOL";
                        break;
                case VDEV_AUX_CHILDREN_OFFLINE:
                        aux = "CHILDREN_OFFLINE";
                        break;
                default:
                        aux = "UNKNOWN";
                        break;
                }

                mdb_printf("%-9s %-12s %*s%s\n", state, aux, depth, "", desc);

                if (spa_flags & SPA_FLAG_ERRORS) {
                        int i;

                        mdb_inc_indent(4);
                        mdb_printf("\n");
                        mdb_printf("%<u>       %12s %12s %12s %12s "
                            "%12s%</u>\n", "READ", "WRITE", "FREE", "CLAIM",
                            "IOCTL");
                        mdb_printf("OPS     ");
                        for (i = 1; i < VS_ZIO_TYPES; i++)
                                mdb_printf("%11#llx%s",
                                    vd.vdev_stat.vs_ops[i],
                                    i == VS_ZIO_TYPES - 1 ? "" : "  ");
                        mdb_printf("\n");
                        mdb_printf("BYTES   ");
                        for (i = 1; i < VS_ZIO_TYPES; i++)
                                mdb_printf("%11#llx%s",
                                    vd.vdev_stat.vs_bytes[i],
                                    i == VS_ZIO_TYPES - 1 ? "" : "  ");


                        mdb_printf("\n");
                        mdb_printf("EREAD    %10#llx\n",
                            vd.vdev_stat.vs_read_errors);
                        mdb_printf("EWRITE   %10#llx\n",
                            vd.vdev_stat.vs_write_errors);
                        mdb_printf("ECKSUM   %10#llx\n",
                            vd.vdev_stat.vs_checksum_errors);
                        mdb_dec_indent(4);
                        mdb_printf("\n");
                }

                if ((spa_flags & SPA_FLAG_METASLAB_GROUPS) &&
                    vd.vdev_mg != 0) {
                        metaslab_group_stats(&vd, spa_flags);
                }
                if ((spa_flags & SPA_FLAG_METASLABS) && vd.vdev_ms != 0) {
                        metaslab_stats(&vd, spa_flags);
                }
        }

        uint64_t children = vd.vdev_children;
        if (children == 0 || !recursive)
                return (DCMD_OK);

        uintptr_t *child = mdb_alloc(children * sizeof (child),
            UM_SLEEP | UM_GC);
        if (mdb_vread(child, children * sizeof (void *), vd.vdev_child) == -1) {
                mdb_warn("failed to read vdev children at %p", vd.vdev_child);
                return (DCMD_ERR);
        }

        for (uint64_t c = 0; c < children; c++) {
                if (do_print_vdev(child[c], flags, depth + 2, recursive,
                    spa_flags)) {
                        return (DCMD_ERR);
                }
        }

        return (DCMD_OK);
}

static int
vdev_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        uint64_t depth = 0;
        boolean_t recursive = B_FALSE;
        int spa_flags = 0;

        if (mdb_getopts(argc, argv,
            'e', MDB_OPT_SETBITS, SPA_FLAG_ERRORS, &spa_flags,
            'm', MDB_OPT_SETBITS, SPA_FLAG_METASLABS, &spa_flags,
            'M', MDB_OPT_SETBITS, SPA_FLAG_METASLAB_GROUPS, &spa_flags,
            'h', MDB_OPT_SETBITS, SPA_FLAG_HISTOGRAMS, &spa_flags,
            'r', MDB_OPT_SETBITS, TRUE, &recursive,
            'd', MDB_OPT_UINT64, &depth, NULL) != argc)
                return (DCMD_USAGE);

        if (!(flags & DCMD_ADDRSPEC)) {
                mdb_warn("no vdev_t address given\n");
                return (DCMD_ERR);
        }

        return (do_print_vdev(addr, flags, (int)depth, recursive, spa_flags));
}

typedef struct mdb_metaslab_alloc_trace {
        uintptr_t mat_mg;
        uintptr_t mat_msp;
        uint64_t mat_size;
        uint64_t mat_weight;
        uint64_t mat_offset;
        uint32_t mat_dva_id;
        int mat_allocator;
} mdb_metaslab_alloc_trace_t;

static void
metaslab_print_weight(uint64_t weight)
{
        char buf[100];

        if (WEIGHT_IS_SPACEBASED(weight)) {
                mdb_nicenum(
                    weight & ~(METASLAB_ACTIVE_MASK | METASLAB_WEIGHT_TYPE),
                    buf);
        } else {
                char size[MDB_NICENUM_BUFLEN];
                mdb_nicenum(1ULL << WEIGHT_GET_INDEX(weight), size);
                (void) mdb_snprintf(buf, sizeof (buf), "%llu x %s",
                    WEIGHT_GET_COUNT(weight), size);
        }
        mdb_printf("%11s ", buf);
}

/* ARGSUSED */
static int
metaslab_weight(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        uint64_t weight = 0;
        char active;

        if (argc == 0 && (flags & DCMD_ADDRSPEC)) {
                if (mdb_vread(&weight, sizeof (uint64_t), addr) == -1) {
                        mdb_warn("failed to read weight at %p\n", addr);
                        return (DCMD_ERR);
                }
        } else if (argc == 1 && !(flags & DCMD_ADDRSPEC)) {
                weight = (uint64_t)mdb_argtoull(&argv[0]);
        } else {
                return (DCMD_USAGE);
        }

        if (DCMD_HDRSPEC(flags)) {
                mdb_printf("%<u>%-6s %9s %9s%</u>\n",
                    "ACTIVE", "ALGORITHM", "WEIGHT");
        }

        if (weight & METASLAB_WEIGHT_PRIMARY)
                active = 'P';
        else if (weight & METASLAB_WEIGHT_SECONDARY)
                active = 'S';
        else
                active = '-';
        mdb_printf("%6c %8s ", active,
            WEIGHT_IS_SPACEBASED(weight) ? "SPACE" : "SEGMENT");
        metaslab_print_weight(weight);
        mdb_printf("\n");

        return (DCMD_OK);
}

/* ARGSUSED */
static int
metaslab_trace(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_metaslab_alloc_trace_t mat;
        mdb_metaslab_group_t mg = { 0 };
        char result_type[100];

        if (mdb_ctf_vread(&mat, "metaslab_alloc_trace_t",
            "mdb_metaslab_alloc_trace_t", addr, 0) == -1) {
                return (DCMD_ERR);
        }

        if (!(flags & DCMD_PIPE_OUT) && DCMD_HDRSPEC(flags)) {
                mdb_printf("%<u>%6s %6s %8s %11s %11s %18s %18s%</u>\n",
                    "MSID", "DVA", "ASIZE", "ALLOCATOR", "WEIGHT", "RESULT",
                    "VDEV");
        }

        if (mat.mat_msp != 0) {
                mdb_metaslab_t ms;

                if (mdb_ctf_vread(&ms, "metaslab_t", "mdb_metaslab_t",
                    mat.mat_msp, 0) == -1) {
                        return (DCMD_ERR);
                }
                mdb_printf("%6llu ", ms.ms_id);
        } else {
                mdb_printf("%6s ", "-");
        }

        mdb_printf("%6d %8llx %11llx ", mat.mat_dva_id, mat.mat_size,
            mat.mat_allocator);

        metaslab_print_weight(mat.mat_weight);

        if ((int64_t)mat.mat_offset < 0) {
                if (enum_lookup("enum trace_alloc_type", mat.mat_offset,
                    "TRACE_", sizeof (result_type), result_type) == -1) {
                        mdb_warn("Could not find enum for trace_alloc_type");
                        return (DCMD_ERR);
                }
                mdb_printf("%18s ", result_type);
        } else {
                mdb_printf("%<b>%18llx%</b> ", mat.mat_offset);
        }

        if (mat.mat_mg != 0 &&
            mdb_ctf_vread(&mg, "metaslab_group_t", "mdb_metaslab_group_t",
            mat.mat_mg, 0) == -1) {
                return (DCMD_ERR);
        }

        if (mg.mg_vd != 0) {
                mdb_vdev_t vdev;
                char desc[MAXNAMELEN];

                if (mdb_ctf_vread(&vdev, "vdev_t", "mdb_vdev_t",
                    mg.mg_vd, 0) == -1) {
                        return (DCMD_ERR);
                }

                if (vdev.vdev_path != 0) {
                        char path[MAXNAMELEN];

                        if (mdb_readstr(path, sizeof (path),
                            vdev.vdev_path) == -1) {
                                mdb_warn("failed to read vdev_path at %p\n",
                                    vdev.vdev_path);
                                return (DCMD_ERR);
                        }
                        char *slash;
                        if ((slash = strrchr(path, '/')) != NULL) {
                                strcpy(desc, slash + 1);
                        } else {
                                strcpy(desc, path);
                        }
                } else if (vdev.vdev_ops != 0) {
                        mdb_vdev_ops_t ops;
                        if (mdb_ctf_vread(&ops, "vdev_ops_t", "mdb_vdev_ops_t",
                            vdev.vdev_ops, 0) == -1) {
                                mdb_warn("failed to read vdev_ops at %p\n",
                                    vdev.vdev_ops);
                                return (DCMD_ERR);
                        }
                        (void) mdb_snprintf(desc, sizeof (desc),
                            "%s-%llu", ops.vdev_op_type, vdev.vdev_id);
                } else {
                        (void) strcpy(desc, "<unknown>");
                }
                mdb_printf("%18s\n", desc);
        }

        return (DCMD_OK);
}

typedef struct metaslab_walk_data {
        uint64_t mw_numvdevs;
        uintptr_t *mw_vdevs;
        int mw_curvdev;
        uint64_t mw_nummss;
        uintptr_t *mw_mss;
        int mw_curms;
} metaslab_walk_data_t;

static int
metaslab_walk_step(mdb_walk_state_t *wsp)
{
        metaslab_walk_data_t *mw = wsp->walk_data;
        metaslab_t ms;
        uintptr_t msp;

        if (mw->mw_curvdev >= mw->mw_numvdevs)
                return (WALK_DONE);

        if (mw->mw_mss == NULL) {
                uintptr_t mssp;
                uintptr_t vdevp;

                ASSERT(mw->mw_curms == 0);
                ASSERT(mw->mw_nummss == 0);

                vdevp = mw->mw_vdevs[mw->mw_curvdev];
                if (GETMEMB(vdevp, "vdev", vdev_ms, mssp) ||
                    GETMEMB(vdevp, "vdev", vdev_ms_count, mw->mw_nummss)) {
                        return (WALK_ERR);
                }

                mw->mw_mss = mdb_alloc(mw->mw_nummss * sizeof (void*),
                    UM_SLEEP | UM_GC);
                if (mdb_vread(mw->mw_mss, mw->mw_nummss * sizeof (void*),
                    mssp) == -1) {
                        mdb_warn("failed to read vdev_ms at %p", mssp);
                        return (WALK_ERR);
                }
        }

        if (mw->mw_curms >= mw->mw_nummss) {
                mw->mw_mss = NULL;
                mw->mw_curms = 0;
                mw->mw_nummss = 0;
                mw->mw_curvdev++;
                return (WALK_NEXT);
        }

        msp = mw->mw_mss[mw->mw_curms];
        if (mdb_vread(&ms, sizeof (metaslab_t), msp) == -1) {
                mdb_warn("failed to read metaslab_t at %p", msp);
                return (WALK_ERR);
        }

        mw->mw_curms++;

        return (wsp->walk_callback(msp, &ms, wsp->walk_cbdata));
}

static int
metaslab_walk_init(mdb_walk_state_t *wsp)
{
        metaslab_walk_data_t *mw;
        uintptr_t root_vdevp;
        uintptr_t childp;

        if (wsp->walk_addr == 0) {
                mdb_warn("must supply address of spa_t\n");
                return (WALK_ERR);
        }

        mw = mdb_zalloc(sizeof (metaslab_walk_data_t), UM_SLEEP | UM_GC);

        if (GETMEMB(wsp->walk_addr, "spa", spa_root_vdev, root_vdevp) ||
            GETMEMB(root_vdevp, "vdev", vdev_children, mw->mw_numvdevs) ||
            GETMEMB(root_vdevp, "vdev", vdev_child, childp)) {
                return (DCMD_ERR);
        }

        mw->mw_vdevs = mdb_alloc(mw->mw_numvdevs * sizeof (void *),
            UM_SLEEP | UM_GC);
        if (mdb_vread(mw->mw_vdevs, mw->mw_numvdevs * sizeof (void *),
            childp) == -1) {
                mdb_warn("failed to read root vdev children at %p", childp);
                return (DCMD_ERR);
        }

        wsp->walk_data = mw;

        return (WALK_NEXT);
}

typedef struct mdb_spa {
        uintptr_t spa_dsl_pool;
        uintptr_t spa_root_vdev;
} mdb_spa_t;

typedef struct mdb_dsl_pool {
        uintptr_t dp_root_dir;
} mdb_dsl_pool_t;

typedef struct mdb_dsl_dir {
        uintptr_t dd_dbuf;
        int64_t dd_space_towrite[TXG_SIZE];
} mdb_dsl_dir_t;

typedef struct mdb_dsl_dir_phys {
        uint64_t dd_used_bytes;
        uint64_t dd_compressed_bytes;
        uint64_t dd_uncompressed_bytes;
} mdb_dsl_dir_phys_t;

typedef struct space_data {
        uint64_t ms_allocating[TXG_SIZE];
        uint64_t ms_checkpointing;
        uint64_t ms_freeing;
        uint64_t ms_freed;
        uint64_t ms_unflushed_frees;
        uint64_t ms_unflushed_allocs;
        uint64_t ms_allocatable;
        int64_t ms_deferspace;
        uint64_t avail;
} space_data_t;

/* ARGSUSED */
static int
space_cb(uintptr_t addr, const void *unknown, void *arg)
{
        space_data_t *sd = arg;
        mdb_metaslab_t ms;
        mdb_range_tree_t rt;
        mdb_space_map_t sm = { 0 };
        mdb_space_map_phys_t smp = { 0 };
        uint64_t uallocs, ufrees;
        int i;

        if (mdb_ctf_vread(&ms, "metaslab_t", "mdb_metaslab_t",
            addr, 0) == -1)
                return (WALK_ERR);

        for (i = 0; i < TXG_SIZE; i++) {
                if (mdb_ctf_vread(&rt, "range_tree_t",
                    "mdb_range_tree_t", ms.ms_allocating[i], 0) == -1)
                        return (WALK_ERR);
                sd->ms_allocating[i] += rt.rt_space;
        }

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_checkpointing, 0) == -1)
                return (WALK_ERR);
        sd->ms_checkpointing += rt.rt_space;

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_freeing, 0) == -1)
                return (WALK_ERR);
        sd->ms_freeing += rt.rt_space;

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_freed, 0) == -1)
                return (WALK_ERR);
        sd->ms_freed += rt.rt_space;

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_allocatable, 0) == -1)
                return (WALK_ERR);
        sd->ms_allocatable += rt.rt_space;

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_unflushed_frees, 0) == -1)
                return (WALK_ERR);
        sd->ms_unflushed_frees += rt.rt_space;
        ufrees = rt.rt_space;

        if (mdb_ctf_vread(&rt, "range_tree_t",
            "mdb_range_tree_t", ms.ms_unflushed_allocs, 0) == -1)
                return (WALK_ERR);
        sd->ms_unflushed_allocs += rt.rt_space;
        uallocs = rt.rt_space;

        if (ms.ms_sm != 0 &&
            mdb_ctf_vread(&sm, "space_map_t",
            "mdb_space_map_t", ms.ms_sm, 0) == -1)
                return (WALK_ERR);

        if (sm.sm_phys != 0) {
                (void) mdb_ctf_vread(&smp, "space_map_phys_t",
                    "mdb_space_map_phys_t", sm.sm_phys, 0);
        }

        sd->ms_deferspace += ms.ms_deferspace;
        sd->avail += sm.sm_size - smp.smp_alloc + ufrees - uallocs;

        return (WALK_NEXT);
}

/*
 * ::spa_space [-b]
 *
 * Given a spa_t, print out it's on-disk space usage and in-core
 * estimates of future usage.  If -b is given, print space in bytes.
 * Otherwise print in megabytes.
 */
/* ARGSUSED */
static int
spa_space(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_spa_t spa;
        mdb_dsl_pool_t dp;
        mdb_dsl_dir_t dd;
        mdb_dmu_buf_impl_t db;
        mdb_dsl_dir_phys_t dsp;
        space_data_t sd;
        int shift = 20;
        char *suffix = "M";
        int bytes = B_FALSE;

        if (mdb_getopts(argc, argv, 'b', MDB_OPT_SETBITS, TRUE, &bytes, NULL) !=
            argc)
                return (DCMD_USAGE);
        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (bytes) {
                shift = 0;
                suffix = "";
        }

        if (mdb_ctf_vread(&spa, ZFS_STRUCT "spa", "mdb_spa_t",
            addr, 0) == -1 ||
            mdb_ctf_vread(&dp, ZFS_STRUCT "dsl_pool", "mdb_dsl_pool_t",
            spa.spa_dsl_pool, 0) == -1 ||
            mdb_ctf_vread(&dd, ZFS_STRUCT "dsl_dir", "mdb_dsl_dir_t",
            dp.dp_root_dir, 0) == -1 ||
            mdb_ctf_vread(&db, ZFS_STRUCT "dmu_buf_impl", "mdb_dmu_buf_impl_t",
            dd.dd_dbuf, 0) == -1 ||
            mdb_ctf_vread(&dsp, ZFS_STRUCT "dsl_dir_phys",
            "mdb_dsl_dir_phys_t", db.db.db_data, 0) == -1) {
                return (DCMD_ERR);
        }

        mdb_printf("dd_space_towrite = %llu%s %llu%s %llu%s %llu%s\n",
            dd.dd_space_towrite[0] >> shift, suffix,
            dd.dd_space_towrite[1] >> shift, suffix,
            dd.dd_space_towrite[2] >> shift, suffix,
            dd.dd_space_towrite[3] >> shift, suffix);

        mdb_printf("dd_phys.dd_used_bytes = %llu%s\n",
            dsp.dd_used_bytes >> shift, suffix);
        mdb_printf("dd_phys.dd_compressed_bytes = %llu%s\n",
            dsp.dd_compressed_bytes >> shift, suffix);
        mdb_printf("dd_phys.dd_uncompressed_bytes = %llu%s\n",
            dsp.dd_uncompressed_bytes >> shift, suffix);

        bzero(&sd, sizeof (sd));
        if (mdb_pwalk("metaslab", space_cb, &sd, addr) != 0) {
                mdb_warn("can't walk metaslabs");
                return (DCMD_ERR);
        }

        mdb_printf("ms_allocmap = %llu%s %llu%s %llu%s %llu%s\n",
            sd.ms_allocating[0] >> shift, suffix,
            sd.ms_allocating[1] >> shift, suffix,
            sd.ms_allocating[2] >> shift, suffix,
            sd.ms_allocating[3] >> shift, suffix);
        mdb_printf("ms_checkpointing = %llu%s\n",
            sd.ms_checkpointing >> shift, suffix);
        mdb_printf("ms_freeing = %llu%s\n",
            sd.ms_freeing >> shift, suffix);
        mdb_printf("ms_freed = %llu%s\n",
            sd.ms_freed >> shift, suffix);
        mdb_printf("ms_unflushed_frees = %llu%s\n",
            sd.ms_unflushed_frees >> shift, suffix);
        mdb_printf("ms_unflushed_allocs = %llu%s\n",
            sd.ms_unflushed_allocs >> shift, suffix);
        mdb_printf("ms_allocatable = %llu%s\n",
            sd.ms_allocatable >> shift, suffix);
        mdb_printf("ms_deferspace = %llu%s\n",
            sd.ms_deferspace >> shift, suffix);
        mdb_printf("current avail = %llu%s\n",
            sd.avail >> shift, suffix);

        return (DCMD_OK);
}

typedef struct mdb_spa_aux_vdev {
        int sav_count;
        uintptr_t sav_vdevs;
} mdb_spa_aux_vdev_t;

typedef struct mdb_spa_vdevs {
        uintptr_t spa_root_vdev;
        mdb_spa_aux_vdev_t spa_l2cache;
        mdb_spa_aux_vdev_t spa_spares;
} mdb_spa_vdevs_t;

static int
spa_print_aux(mdb_spa_aux_vdev_t *sav, uint_t flags, mdb_arg_t *v,
    const char *name)
{
        uintptr_t *aux;
        size_t len;
        int ret, i;

        /*
         * Iterate over aux vdevs and print those out as well.  This is a
         * little annoying because we don't have a root vdev to pass to ::vdev.
         * Instead, we print a single line and then call it for each child
         * vdev.
         */
        if (sav->sav_count != 0) {
                v[1].a_type = MDB_TYPE_STRING;
                v[1].a_un.a_str = "-d";
                v[2].a_type = MDB_TYPE_IMMEDIATE;
                v[2].a_un.a_val = 2;

                len = sav->sav_count * sizeof (uintptr_t);
                aux = mdb_alloc(len, UM_SLEEP);
                if (mdb_vread(aux, len, sav->sav_vdevs) == -1) {
                        mdb_free(aux, len);
                        mdb_warn("failed to read l2cache vdevs at %p",
                            sav->sav_vdevs);
                        return (DCMD_ERR);
                }

                mdb_printf("%-?s %-9s %-12s %s\n", "-", "-", "-", name);

                for (i = 0; i < sav->sav_count; i++) {
                        ret = mdb_call_dcmd("vdev", aux[i], flags, 3, v);
                        if (ret != DCMD_OK) {
                                mdb_free(aux, len);
                                return (ret);
                        }
                }

                mdb_free(aux, len);
        }

        return (0);
}

/*
 * ::spa_vdevs
 *
 *      -e      Include error stats
 *      -m      Include metaslab information
 *      -M      Include metaslab group information
 *      -h      Include histogram information (requires -m or -M)
 *
 * Print out a summarized list of vdevs for the given spa_t.
 * This is accomplished by invoking "::vdev -re" on the root vdev, as well as
 * iterating over the cache devices.
 */
/* ARGSUSED */
static int
spa_vdevs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_arg_t v[3];
        int ret;
        char opts[100] = "-r";
        int spa_flags = 0;

        if (mdb_getopts(argc, argv,
            'e', MDB_OPT_SETBITS, SPA_FLAG_ERRORS, &spa_flags,
            'm', MDB_OPT_SETBITS, SPA_FLAG_METASLABS, &spa_flags,
            'M', MDB_OPT_SETBITS, SPA_FLAG_METASLAB_GROUPS, &spa_flags,
            'h', MDB_OPT_SETBITS, SPA_FLAG_HISTOGRAMS, &spa_flags,
            NULL) != argc)
                return (DCMD_USAGE);

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        mdb_spa_vdevs_t spa;
        if (mdb_ctf_vread(&spa, "spa_t", "mdb_spa_vdevs_t", addr, 0) == -1)
                return (DCMD_ERR);

        /*
         * Unitialized spa_t structures can have a NULL root vdev.
         */
        if (spa.spa_root_vdev == 0) {
                mdb_printf("no associated vdevs\n");
                return (DCMD_OK);
        }

        if (spa_flags & SPA_FLAG_ERRORS)
                strcat(opts, "e");
        if (spa_flags & SPA_FLAG_METASLABS)
                strcat(opts, "m");
        if (spa_flags & SPA_FLAG_METASLAB_GROUPS)
                strcat(opts, "M");
        if (spa_flags & SPA_FLAG_HISTOGRAMS)
                strcat(opts, "h");

        v[0].a_type = MDB_TYPE_STRING;
        v[0].a_un.a_str = opts;

        ret = mdb_call_dcmd("vdev", (uintptr_t)spa.spa_root_vdev,
            flags, 1, v);
        if (ret != DCMD_OK)
                return (ret);

        if (spa_print_aux(&spa.spa_l2cache, flags, v, "cache") != 0 ||
            spa_print_aux(&spa.spa_spares, flags, v, "spares") != 0)
                return (DCMD_ERR);

        return (DCMD_OK);
}

/*
 * ::zio
 *
 * Print a summary of zio_t and all its children.  This is intended to display a
 * zio tree, and hence we only pick the most important pieces of information for
 * the main summary.  More detailed information can always be found by doing a
 * '::print zio' on the underlying zio_t.  The columns we display are:
 *
 *      ADDRESS  TYPE  STAGE  WAITER  TIME_ELAPSED
 *
 * The 'address' column is indented by one space for each depth level as we
 * descend down the tree.
 */

#define ZIO_MAXINDENT   7
#define ZIO_MAXWIDTH    (sizeof (uintptr_t) * 2 + ZIO_MAXINDENT)
#define ZIO_WALK_SELF   0
#define ZIO_WALK_CHILD  1
#define ZIO_WALK_PARENT 2

typedef struct zio_print_args {
        int     zpa_current_depth;
        int     zpa_min_depth;
        int     zpa_max_depth;
        int     zpa_type;
        uint_t  zpa_flags;
} zio_print_args_t;

typedef struct mdb_zio {
        enum zio_type io_type;
        enum zio_stage io_stage;
        uintptr_t io_waiter;
        uintptr_t io_spa;
        struct {
                struct {
                        uintptr_t list_next;
                } list_head;
        } io_parent_list;
        int io_error;
} mdb_zio_t;

typedef struct mdb_zio_timestamp {
        hrtime_t io_timestamp;
} mdb_zio_timestamp_t;

static int zio_child_cb(uintptr_t addr, const void *unknown, void *arg);

static int
zio_print_cb(uintptr_t addr, zio_print_args_t *zpa)
{
        mdb_ctf_id_t type_enum, stage_enum;
        int indent = zpa->zpa_current_depth;
        const char *type, *stage;
        uintptr_t laddr;
        mdb_zio_t zio;
        mdb_zio_timestamp_t zio_timestamp = { 0 };

        if (mdb_ctf_vread(&zio, ZFS_STRUCT "zio", "mdb_zio_t", addr, 0) == -1)
                return (WALK_ERR);
        (void) mdb_ctf_vread(&zio_timestamp, ZFS_STRUCT "zio",
            "mdb_zio_timestamp_t", addr, MDB_CTF_VREAD_QUIET);

        if (indent > ZIO_MAXINDENT)
                indent = ZIO_MAXINDENT;

        if (mdb_ctf_lookup_by_name("enum zio_type", &type_enum) == -1 ||
            mdb_ctf_lookup_by_name("enum zio_stage", &stage_enum) == -1) {
                mdb_warn("failed to lookup zio enums");
                return (WALK_ERR);
        }

        if ((type = mdb_ctf_enum_name(type_enum, zio.io_type)) != NULL)
                type += sizeof ("ZIO_TYPE_") - 1;
        else
                type = "?";

        if (zio.io_error == 0) {
                stage = mdb_ctf_enum_name(stage_enum, zio.io_stage);
                if (stage != NULL)
                        stage += sizeof ("ZIO_STAGE_") - 1;
                else
                        stage = "?";
        } else {
                stage = "FAILED";
        }

        if (zpa->zpa_current_depth >= zpa->zpa_min_depth) {
                if (zpa->zpa_flags & DCMD_PIPE_OUT) {
                        mdb_printf("%?p\n", addr);
                } else {
                        mdb_printf("%*s%-*p %-5s %-16s ", indent, "",
                            ZIO_MAXWIDTH - indent, addr, type, stage);
                        if (zio.io_waiter != 0)
                                mdb_printf("%-16lx ", zio.io_waiter);
                        else
                                mdb_printf("%-16s ", "-");
#ifdef _KERNEL
                        if (zio_timestamp.io_timestamp != 0) {
                                mdb_printf("%llums", (mdb_gethrtime() -
                                    zio_timestamp.io_timestamp) /
                                    1000000);
                        } else {
                                mdb_printf("%-12s ", "-");
                        }
#else
                        mdb_printf("%-12s ", "-");
#endif
                        mdb_printf("\n");
                }
        }

        if (zpa->zpa_current_depth >= zpa->zpa_max_depth)
                return (WALK_NEXT);

        if (zpa->zpa_type == ZIO_WALK_PARENT)
                laddr = addr + mdb_ctf_offsetof_by_name(ZFS_STRUCT "zio",
                    "io_parent_list");
        else
                laddr = addr + mdb_ctf_offsetof_by_name(ZFS_STRUCT "zio",
                    "io_child_list");

        zpa->zpa_current_depth++;
        if (mdb_pwalk("list", zio_child_cb, zpa, laddr) != 0) {
                mdb_warn("failed to walk zio_t children at %p\n", laddr);
                return (WALK_ERR);
        }
        zpa->zpa_current_depth--;

        return (WALK_NEXT);
}

/* ARGSUSED */
static int
zio_child_cb(uintptr_t addr, const void *unknown, void *arg)
{
        zio_link_t zl;
        uintptr_t ziop;
        zio_print_args_t *zpa = arg;

        if (mdb_vread(&zl, sizeof (zl), addr) == -1) {
                mdb_warn("failed to read zio_link_t at %p", addr);
                return (WALK_ERR);
        }

        if (zpa->zpa_type == ZIO_WALK_PARENT)
                ziop = (uintptr_t)zl.zl_parent;
        else
                ziop = (uintptr_t)zl.zl_child;

        return (zio_print_cb(ziop, zpa));
}

/* ARGSUSED */
static int
zio_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        zio_print_args_t zpa = { 0 };

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_getopts(argc, argv,
            'r', MDB_OPT_SETBITS, INT_MAX, &zpa.zpa_max_depth,
            'c', MDB_OPT_SETBITS, ZIO_WALK_CHILD, &zpa.zpa_type,
            'p', MDB_OPT_SETBITS, ZIO_WALK_PARENT, &zpa.zpa_type,
            NULL) != argc)
                return (DCMD_USAGE);

        zpa.zpa_flags = flags;
        if (zpa.zpa_max_depth != 0) {
                if (zpa.zpa_type == ZIO_WALK_SELF)
                        zpa.zpa_type = ZIO_WALK_CHILD;
        } else if (zpa.zpa_type != ZIO_WALK_SELF) {
                zpa.zpa_min_depth = 1;
                zpa.zpa_max_depth = 1;
        }

        if (!(flags & DCMD_PIPE_OUT) && DCMD_HDRSPEC(flags)) {
                mdb_printf("%<u>%-*s %-5s %-16s %-16s %-12s%</u>\n",
                    ZIO_MAXWIDTH, "ADDRESS", "TYPE", "STAGE", "WAITER",
                    "TIME_ELAPSED");
        }

        if (zio_print_cb(addr, &zpa) != WALK_NEXT)
                return (DCMD_ERR);

        return (DCMD_OK);
}

/*
 * [addr]::zio_state
 *
 * Print a summary of all zio_t structures on the system, or for a particular
 * pool.  This is equivalent to '::walk zio_root | ::zio'.
 */
/*ARGSUSED*/
static int
zio_state(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        /*
         * MDB will remember the last address of the pipeline, so if we don't
         * zero this we'll end up trying to walk zio structures for a
         * non-existent spa_t.
         */
        if (!(flags & DCMD_ADDRSPEC))
                addr = 0;

        return (mdb_pwalk_dcmd("zio_root", "zio", argc, argv, addr));
}


typedef struct mdb_zfs_btree_hdr {
        uintptr_t               bth_parent;
        boolean_t               bth_core;
        /*
         * For both leaf and core nodes, represents the number of elements in
         * the node. For core nodes, they will have bth_count + 1 children.
         */
        uint32_t                bth_count;
} mdb_zfs_btree_hdr_t;

typedef struct mdb_zfs_btree_core {
        mdb_zfs_btree_hdr_t     btc_hdr;
        uintptr_t               btc_children[BTREE_CORE_ELEMS + 1];
        uint8_t                 btc_elems[];
} mdb_zfs_btree_core_t;

typedef struct mdb_zfs_btree_leaf {
        mdb_zfs_btree_hdr_t     btl_hdr;
        uint8_t                 btl_elems[];
} mdb_zfs_btree_leaf_t;

typedef struct mdb_zfs_btree {
        uintptr_t               bt_root;
        size_t                  bt_elem_size;
} mdb_zfs_btree_t;

typedef struct btree_walk_data {
        mdb_zfs_btree_t         bwd_btree;
        mdb_zfs_btree_hdr_t     *bwd_node;
        uint64_t                bwd_offset; // In units of bt_node_size
} btree_walk_data_t;

static uintptr_t
btree_leftmost_child(uintptr_t addr, mdb_zfs_btree_hdr_t *buf)
{
        size_t size = offsetof(zfs_btree_core_t, btc_children) +
            sizeof (uintptr_t);
        for (;;) {
                if (mdb_vread(buf, size, addr) == -1) {
                        mdb_warn("failed to read at %p\n", addr);
                        return ((uintptr_t)0ULL);
                }
                if (!buf->bth_core)
                        return (addr);
                mdb_zfs_btree_core_t *node = (mdb_zfs_btree_core_t *)buf;
                addr = node->btc_children[0];
        }
}

static int
btree_walk_step(mdb_walk_state_t *wsp)
{
        btree_walk_data_t *bwd = wsp->walk_data;
        size_t elem_size = bwd->bwd_btree.bt_elem_size;
        if (wsp->walk_addr == 0ULL)
                return (WALK_DONE);

        if (!bwd->bwd_node->bth_core) {
                /*
                 * For the first element in a leaf node, read in the full
                 * leaf, since we only had part of it read in before.
                 */
                if (bwd->bwd_offset == 0) {
                        if (mdb_vread(bwd->bwd_node, BTREE_LEAF_SIZE,
                            wsp->walk_addr) == -1) {
                                mdb_warn("failed to read at %p\n",
                                    wsp->walk_addr);
                                return (WALK_ERR);
                        }
                }

                int status = wsp->walk_callback((uintptr_t)(wsp->walk_addr +
                    offsetof(mdb_zfs_btree_leaf_t, btl_elems) +
                    bwd->bwd_offset * elem_size), bwd->bwd_node,
                    wsp->walk_cbdata);
                if (status != WALK_NEXT)
                        return (status);
                bwd->bwd_offset++;

                /* Find the next element, if we're at the end of the leaf. */
                while (bwd->bwd_offset == bwd->bwd_node->bth_count) {
                        uintptr_t par = bwd->bwd_node->bth_parent;
                        uintptr_t cur = wsp->walk_addr;
                        wsp->walk_addr = par;
                        if (par == 0ULL)
                                return (WALK_NEXT);

                        size_t size = sizeof (zfs_btree_core_t) +
                            BTREE_CORE_ELEMS * elem_size;
                        if (mdb_vread(bwd->bwd_node, size, wsp->walk_addr) ==
                            -1) {
                                mdb_warn("failed to read at %p\n",
                                    wsp->walk_addr);
                                return (WALK_ERR);
                        }
                        mdb_zfs_btree_core_t *node =
                            (mdb_zfs_btree_core_t *)bwd->bwd_node;
                        int i;
                        for (i = 0; i <= bwd->bwd_node->bth_count; i++) {
                                if (node->btc_children[i] == cur)
                                        break;
                        }
                        if (i > bwd->bwd_node->bth_count) {
                                mdb_warn("btree parent/child mismatch at "
                                    "%#lx\n", cur);
                                return (WALK_ERR);
                        }
                        bwd->bwd_offset = i;
                }
                return (WALK_NEXT);
        }

        if (!bwd->bwd_node->bth_core) {
                mdb_warn("Invalid btree node at %#lx\n", wsp->walk_addr);
                return (WALK_ERR);
        }
        mdb_zfs_btree_core_t *node = (mdb_zfs_btree_core_t *)bwd->bwd_node;
        int status = wsp->walk_callback((uintptr_t)(wsp->walk_addr +
            offsetof(mdb_zfs_btree_core_t, btc_elems) + bwd->bwd_offset *
            elem_size), bwd->bwd_node, wsp->walk_cbdata);
        if (status != WALK_NEXT)
                return (status);

        uintptr_t new_child = node->btc_children[bwd->bwd_offset + 1];
        wsp->walk_addr = btree_leftmost_child(new_child, bwd->bwd_node);
        if (wsp->walk_addr == 0ULL)
                return (WALK_ERR);

        bwd->bwd_offset = 0;
        return (WALK_NEXT);
}

static int
btree_walk_init(mdb_walk_state_t *wsp)
{
        btree_walk_data_t *bwd;

        if (wsp->walk_addr == 0ULL) {
                mdb_warn("must supply address of zfs_btree_t\n");
                return (WALK_ERR);
        }

        bwd = mdb_zalloc(sizeof (btree_walk_data_t), UM_SLEEP);
        if (mdb_ctf_vread(&bwd->bwd_btree, "zfs_btree_t", "mdb_zfs_btree_t",
            wsp->walk_addr, 0) == -1) {
                mdb_free(bwd, sizeof (*bwd));
                return (WALK_ERR);
        }

        if (bwd->bwd_btree.bt_elem_size == 0) {
                mdb_warn("invalid or uninitialized btree at %#lx\n",
                    wsp->walk_addr);
                mdb_free(bwd, sizeof (*bwd));
                return (WALK_ERR);
        }

        size_t size = MAX(BTREE_LEAF_SIZE, sizeof (zfs_btree_core_t) +
            BTREE_CORE_ELEMS * bwd->bwd_btree.bt_elem_size);
        bwd->bwd_node = mdb_zalloc(size, UM_SLEEP);

        uintptr_t node = (uintptr_t)bwd->bwd_btree.bt_root;
        if (node == 0ULL) {
                wsp->walk_addr = 0ULL;
                wsp->walk_data = bwd;
                return (WALK_NEXT);
        }
        node = btree_leftmost_child(node, bwd->bwd_node);
        if (node == 0ULL) {
                mdb_free(bwd->bwd_node, size);
                mdb_free(bwd, sizeof (*bwd));
                return (WALK_ERR);
        }
        bwd->bwd_offset = 0;

        wsp->walk_addr = node;
        wsp->walk_data = bwd;
        return (WALK_NEXT);
}

static void
btree_walk_fini(mdb_walk_state_t *wsp)
{
        btree_walk_data_t *bwd = (btree_walk_data_t *)wsp->walk_data;

        if (bwd == NULL)
                return;

        size_t size = MAX(BTREE_LEAF_SIZE, sizeof (zfs_btree_core_t) +
            BTREE_CORE_ELEMS * bwd->bwd_btree.bt_elem_size);
        if (bwd->bwd_node != NULL)
                mdb_free(bwd->bwd_node, size);

        mdb_free(bwd, sizeof (*bwd));
}

typedef struct mdb_multilist {
        uint64_t ml_num_sublists;
        uintptr_t ml_sublists;
} mdb_multilist_t;

static int
multilist_walk_step(mdb_walk_state_t *wsp)
{
        return (wsp->walk_callback(wsp->walk_addr, wsp->walk_layer,
            wsp->walk_cbdata));
}

static int
multilist_walk_init(mdb_walk_state_t *wsp)
{
        mdb_multilist_t ml;
        ssize_t sublist_sz;
        int list_offset;
        size_t i;

        if (wsp->walk_addr == 0) {
                mdb_warn("must supply address of multilist_t\n");
                return (WALK_ERR);
        }

        if (mdb_ctf_vread(&ml, "multilist_t", "mdb_multilist_t",
            wsp->walk_addr, 0) == -1) {
                return (WALK_ERR);
        }

        if (ml.ml_num_sublists == 0 || ml.ml_sublists == 0) {
                mdb_warn("invalid or uninitialized multilist at %#lx\n",
                    wsp->walk_addr);
                return (WALK_ERR);
        }

        /* mdb_ctf_sizeof_by_name() will print an error for us */
        sublist_sz = mdb_ctf_sizeof_by_name("multilist_sublist_t");
        if (sublist_sz == -1)
                return (WALK_ERR);

        /* mdb_ctf_offsetof_by_name will print an error for us */
        list_offset = mdb_ctf_offsetof_by_name("multilist_sublist_t",
            "mls_list");
        if (list_offset == -1)
                return (WALK_ERR);

        for (i = 0; i < ml.ml_num_sublists; i++) {
                wsp->walk_addr = ml.ml_sublists + i * sublist_sz + list_offset;

                if (mdb_layered_walk("list", wsp) == -1) {
                        mdb_warn("can't walk multilist sublist");
                        return (WALK_ERR);
                }
        }

        return (WALK_NEXT);
}

typedef struct mdb_txg_list {
        size_t          tl_offset;
        uintptr_t       tl_head[TXG_SIZE];
} mdb_txg_list_t;

typedef struct txg_list_walk_data {
        uintptr_t lw_head[TXG_SIZE];
        int     lw_txgoff;
        int     lw_maxoff;
        size_t  lw_offset;
        void    *lw_obj;
} txg_list_walk_data_t;

static int
txg_list_walk_init_common(mdb_walk_state_t *wsp, int txg, int maxoff)
{
        txg_list_walk_data_t *lwd;
        mdb_txg_list_t list;
        int i;

        lwd = mdb_alloc(sizeof (txg_list_walk_data_t), UM_SLEEP | UM_GC);
        if (mdb_ctf_vread(&list, "txg_list_t", "mdb_txg_list_t", wsp->walk_addr,
            0) == -1) {
                mdb_warn("failed to read txg_list_t at %#lx", wsp->walk_addr);
                return (WALK_ERR);
        }

        for (i = 0; i < TXG_SIZE; i++)
                lwd->lw_head[i] = list.tl_head[i];
        lwd->lw_offset = list.tl_offset;
        lwd->lw_obj = mdb_alloc(lwd->lw_offset + sizeof (txg_node_t),
            UM_SLEEP | UM_GC);
        lwd->lw_txgoff = txg;
        lwd->lw_maxoff = maxoff;

        wsp->walk_addr = lwd->lw_head[lwd->lw_txgoff];
        wsp->walk_data = lwd;

        return (WALK_NEXT);
}

static int
txg_list_walk_init(mdb_walk_state_t *wsp)
{
        return (txg_list_walk_init_common(wsp, 0, TXG_SIZE-1));
}

static int
txg_list0_walk_init(mdb_walk_state_t *wsp)
{
        return (txg_list_walk_init_common(wsp, 0, 0));
}

static int
txg_list1_walk_init(mdb_walk_state_t *wsp)
{
        return (txg_list_walk_init_common(wsp, 1, 1));
}

static int
txg_list2_walk_init(mdb_walk_state_t *wsp)
{
        return (txg_list_walk_init_common(wsp, 2, 2));
}

static int
txg_list3_walk_init(mdb_walk_state_t *wsp)
{
        return (txg_list_walk_init_common(wsp, 3, 3));
}

static int
txg_list_walk_step(mdb_walk_state_t *wsp)
{
        txg_list_walk_data_t *lwd = wsp->walk_data;
        uintptr_t addr;
        txg_node_t *node;
        int status;

        while (wsp->walk_addr == 0 && lwd->lw_txgoff < lwd->lw_maxoff) {
                lwd->lw_txgoff++;
                wsp->walk_addr = lwd->lw_head[lwd->lw_txgoff];
        }

        if (wsp->walk_addr == 0)
                return (WALK_DONE);

        addr = wsp->walk_addr - lwd->lw_offset;

        if (mdb_vread(lwd->lw_obj,
            lwd->lw_offset + sizeof (txg_node_t), addr) == -1) {
                mdb_warn("failed to read list element at %#lx", addr);
                return (WALK_ERR);
        }

        status = wsp->walk_callback(addr, lwd->lw_obj, wsp->walk_cbdata);
        node = (txg_node_t *)((uintptr_t)lwd->lw_obj + lwd->lw_offset);
        wsp->walk_addr = (uintptr_t)node->tn_next[lwd->lw_txgoff];

        return (status);
}

/*
 * ::walk spa
 *
 * Walk all named spa_t structures in the namespace.  This is nothing more than
 * a layered avl walk.
 */
static int
spa_walk_init(mdb_walk_state_t *wsp)
{
        GElf_Sym sym;

        if (wsp->walk_addr != 0) {
                mdb_warn("spa walk only supports global walks\n");
                return (WALK_ERR);
        }

        if (mdb_lookup_by_obj(ZFS_OBJ_NAME, "spa_namespace_avl", &sym) == -1) {
                mdb_warn("failed to find symbol 'spa_namespace_avl'");
                return (WALK_ERR);
        }

        wsp->walk_addr = (uintptr_t)sym.st_value;

        if (mdb_layered_walk("avl", wsp) == -1) {
                mdb_warn("failed to walk 'avl'\n");
                return (WALK_ERR);
        }

        return (WALK_NEXT);
}

static int
spa_walk_step(mdb_walk_state_t *wsp)
{
        return (wsp->walk_callback(wsp->walk_addr, NULL, wsp->walk_cbdata));
}

/*
 * [addr]::walk zio
 *
 * Walk all active zio_t structures on the system.  This is simply a layered
 * walk on top of ::walk zio_cache, with the optional ability to limit the
 * structures to a particular pool.
 */
static int
zio_walk_init(mdb_walk_state_t *wsp)
{
        wsp->walk_data = (void *)wsp->walk_addr;

        if (mdb_layered_walk("zio_cache", wsp) == -1) {
                mdb_warn("failed to walk 'zio_cache'\n");
                return (WALK_ERR);
        }

        return (WALK_NEXT);
}

static int
zio_walk_step(mdb_walk_state_t *wsp)
{
        mdb_zio_t zio;
        uintptr_t spa = (uintptr_t)wsp->walk_data;

        if (mdb_ctf_vread(&zio, ZFS_STRUCT "zio", "mdb_zio_t",
            wsp->walk_addr, 0) == -1)
                return (WALK_ERR);

        if (spa != 0 && spa != zio.io_spa)
                return (WALK_NEXT);

        return (wsp->walk_callback(wsp->walk_addr, &zio, wsp->walk_cbdata));
}

/*
 * [addr]::walk zio_root
 *
 * Walk only root zio_t structures, optionally for a particular spa_t.
 */
static int
zio_walk_root_step(mdb_walk_state_t *wsp)
{
        mdb_zio_t zio;
        uintptr_t spa = (uintptr_t)wsp->walk_data;

        if (mdb_ctf_vread(&zio, ZFS_STRUCT "zio", "mdb_zio_t",
            wsp->walk_addr, 0) == -1)
                return (WALK_ERR);

        if (spa != 0 && spa != zio.io_spa)
                return (WALK_NEXT);

        /* If the parent list is not empty, ignore */
        if (zio.io_parent_list.list_head.list_next !=
            wsp->walk_addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "zio", "io_parent_list") +
            mdb_ctf_offsetof_by_name("struct list", "list_head"))
                return (WALK_NEXT);

        return (wsp->walk_callback(wsp->walk_addr, &zio, wsp->walk_cbdata));
}

/*
 * ::zfs_blkstats
 *
 *      -v      print verbose per-level information
 *
 */
static int
zfs_blkstats(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        boolean_t verbose = B_FALSE;
        zfs_all_blkstats_t stats;
        dmu_object_type_t t;
        zfs_blkstat_t *tzb;
        uint64_t ditto;

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, TRUE, &verbose,
            NULL) != argc)
                return (DCMD_USAGE);

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (GETMEMB(addr, "spa", spa_dsl_pool, addr) ||
            GETMEMB(addr, "dsl_pool", dp_blkstats, addr) ||
            mdb_vread(&stats, sizeof (zfs_all_blkstats_t), addr) == -1) {
                mdb_warn("failed to read data at %p;", addr);
                mdb_printf("maybe no stats? run \"zpool scrub\" first.");
                return (DCMD_ERR);
        }

        tzb = &stats.zab_type[DN_MAX_LEVELS][DMU_OT_TOTAL];
        if (tzb->zb_gangs != 0) {
                mdb_printf("Ganged blocks: %llu\n",
                    (longlong_t)tzb->zb_gangs);
        }

        ditto = tzb->zb_ditto_2_of_2_samevdev + tzb->zb_ditto_2_of_3_samevdev +
            tzb->zb_ditto_3_of_3_samevdev;
        if (ditto != 0) {
                mdb_printf("Dittoed blocks on same vdev: %llu\n",
                    (longlong_t)ditto);
        }

        mdb_printf("\nBlocks\tLSIZE\tPSIZE\tASIZE"
            "\t  avg\t comp\t%%Total\tType\n");

        for (t = 0; t <= DMU_OT_TOTAL; t++) {
                char csize[MDB_NICENUM_BUFLEN], lsize[MDB_NICENUM_BUFLEN];
                char psize[MDB_NICENUM_BUFLEN], asize[MDB_NICENUM_BUFLEN];
                char avg[MDB_NICENUM_BUFLEN];
                char comp[MDB_NICENUM_BUFLEN], pct[MDB_NICENUM_BUFLEN];
                char typename[64];
                int l;


                if (t == DMU_OT_DEFERRED)
                        strcpy(typename, "deferred free");
                else if (t == DMU_OT_OTHER)
                        strcpy(typename, "other");
                else if (t == DMU_OT_TOTAL)
                        strcpy(typename, "Total");
                else if (enum_lookup("enum dmu_object_type",
                    t, "DMU_OT_", sizeof (typename), typename) == -1) {
                        mdb_warn("failed to read type name");
                        return (DCMD_ERR);
                }

                if (stats.zab_type[DN_MAX_LEVELS][t].zb_asize == 0)
                        continue;

                for (l = -1; l < DN_MAX_LEVELS; l++) {
                        int level = (l == -1 ? DN_MAX_LEVELS : l);
                        zfs_blkstat_t *zb = &stats.zab_type[level][t];

                        if (zb->zb_asize == 0)
                                continue;

                        /*
                         * Don't print each level unless requested.
                         */
                        if (!verbose && level != DN_MAX_LEVELS)
                                continue;

                        /*
                         * If all the space is level 0, don't print the
                         * level 0 separately.
                         */
                        if (level == 0 && zb->zb_asize ==
                            stats.zab_type[DN_MAX_LEVELS][t].zb_asize)
                                continue;

                        mdb_nicenum(zb->zb_count, csize);
                        mdb_nicenum(zb->zb_lsize, lsize);
                        mdb_nicenum(zb->zb_psize, psize);
                        mdb_nicenum(zb->zb_asize, asize);
                        mdb_nicenum(zb->zb_asize / zb->zb_count, avg);
                        (void) mdb_snprintfrac(comp, MDB_NICENUM_BUFLEN,
                            zb->zb_lsize, zb->zb_psize, 2);
                        (void) mdb_snprintfrac(pct, MDB_NICENUM_BUFLEN,
                            100 * zb->zb_asize, tzb->zb_asize, 2);

                        mdb_printf("%6s\t%5s\t%5s\t%5s\t%5s"
                            "\t%5s\t%6s\t",
                            csize, lsize, psize, asize, avg, comp, pct);

                        if (level == DN_MAX_LEVELS)
                                mdb_printf("%s\n", typename);
                        else
                                mdb_printf("  L%d %s\n",
                                    level, typename);
                }
        }

        return (DCMD_OK);
}

typedef struct mdb_reference {
        uintptr_t ref_holder;
        uintptr_t ref_removed;
        uint64_t ref_number;
} mdb_reference_t;

/* ARGSUSED */
static int
reference_cb(uintptr_t addr, const void *ignored, void *arg)
{
        mdb_reference_t ref;
        boolean_t holder_is_str = B_FALSE;
        char holder_str[128];
        boolean_t removed = (boolean_t)arg;

        if (mdb_ctf_vread(&ref, "reference_t", "mdb_reference_t", addr,
            0) == -1)
                return (DCMD_ERR);

        if (mdb_readstr(holder_str, sizeof (holder_str),
            ref.ref_holder) != -1)
                holder_is_str = strisprint(holder_str);

        if (removed)
                mdb_printf("removed ");
        mdb_printf("reference ");
        if (ref.ref_number != 1)
                mdb_printf("with count=%llu ", ref.ref_number);
        mdb_printf("with tag %lx", ref.ref_holder);
        if (holder_is_str)
                mdb_printf(" \"%s\"", holder_str);
        mdb_printf(", held at:\n");

        (void) mdb_call_dcmd("whatis", addr, DCMD_ADDRSPEC, 0, NULL);

        if (removed) {
                mdb_printf("removed at:\n");
                (void) mdb_call_dcmd("whatis", ref.ref_removed,
                    DCMD_ADDRSPEC, 0, NULL);
        }

        mdb_printf("\n");

        return (WALK_NEXT);
}

typedef struct mdb_zfs_refcount {
        uint64_t rc_count;
} mdb_zfs_refcount_t;

typedef struct mdb_zfs_refcount_removed {
        uint_t rc_removed_count;
} mdb_zfs_refcount_removed_t;

typedef struct mdb_zfs_refcount_tracked {
        boolean_t rc_tracked;
} mdb_zfs_refcount_tracked_t;

/* ARGSUSED */
static int
zfs_refcount(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_zfs_refcount_t rc;
        mdb_zfs_refcount_removed_t rcr;
        mdb_zfs_refcount_tracked_t rct;
        int off;
        boolean_t released = B_FALSE;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_getopts(argc, argv,
            'r', MDB_OPT_SETBITS, B_TRUE, &released,
            NULL) != argc)
                return (DCMD_USAGE);

        if (mdb_ctf_vread(&rc, "zfs_refcount_t", "mdb_zfs_refcount_t", addr,
            0) == -1)
                return (DCMD_ERR);

        if (mdb_ctf_vread(&rcr, "zfs_refcount_t", "mdb_zfs_refcount_removed_t",
            addr, MDB_CTF_VREAD_QUIET) == -1) {
                mdb_printf("zfs_refcount_t at %p has %llu holds (untracked)\n",
                    addr, (longlong_t)rc.rc_count);
                return (DCMD_OK);
        }

        if (mdb_ctf_vread(&rct, "zfs_refcount_t", "mdb_zfs_refcount_tracked_t",
            addr, MDB_CTF_VREAD_QUIET) == -1) {
                /* If this is an old target, it might be tracked. */
                rct.rc_tracked = B_TRUE;
        }

        mdb_printf("zfs_refcount_t at %p has %llu current holds, "
            "%llu recently released holds\n",
            addr, (longlong_t)rc.rc_count, (longlong_t)rcr.rc_removed_count);

        if (rct.rc_tracked && rc.rc_count > 0)
                mdb_printf("current holds:\n");
        off = mdb_ctf_offsetof_by_name("zfs_refcount_t", "rc_tree");
        if (off == -1)
                return (DCMD_ERR);
        mdb_pwalk("avl", reference_cb, (void *)B_FALSE, addr + off);

        if (released && rcr.rc_removed_count > 0) {
                mdb_printf("released holds:\n");

                off = mdb_ctf_offsetof_by_name("zfs_refcount_t", "rc_removed");
                if (off == -1)
                        return (DCMD_ERR);
                mdb_pwalk("list", reference_cb, (void *)B_TRUE, addr + off);
        }

        return (DCMD_OK);
}

/* ARGSUSED */
static int
sa_attr_table(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        sa_attr_table_t *table;
        sa_os_t sa_os;
        char *name;
        int i;

        if (mdb_vread(&sa_os, sizeof (sa_os_t), addr) == -1) {
                mdb_warn("failed to read sa_os at %p", addr);
                return (DCMD_ERR);
        }

        table = mdb_alloc(sizeof (sa_attr_table_t) * sa_os.sa_num_attrs,
            UM_SLEEP | UM_GC);
        name = mdb_alloc(MAXPATHLEN, UM_SLEEP | UM_GC);

        if (mdb_vread(table, sizeof (sa_attr_table_t) * sa_os.sa_num_attrs,
            (uintptr_t)sa_os.sa_attr_table) == -1) {
                mdb_warn("failed to read sa_os at %p", addr);
                return (DCMD_ERR);
        }

        mdb_printf("%<u>%-10s %-10s %-10s %-10s %s%</u>\n",
            "ATTR ID", "REGISTERED", "LENGTH", "BSWAP", "NAME");
        for (i = 0; i != sa_os.sa_num_attrs; i++) {
                mdb_readstr(name, MAXPATHLEN, (uintptr_t)table[i].sa_name);
                mdb_printf("%5x   %8x %8x %8x          %-s\n",
                    (int)table[i].sa_attr, (int)table[i].sa_registered,
                    (int)table[i].sa_length, table[i].sa_byteswap, name);
        }

        return (DCMD_OK);
}

static int
sa_get_off_table(uintptr_t addr, uint32_t **off_tab, int attr_count)
{
        uintptr_t idx_table;

        if (GETMEMB(addr, "sa_idx_tab", sa_idx_tab, idx_table)) {
                mdb_printf("can't find offset table in sa_idx_tab\n");
                return (-1);
        }

        *off_tab = mdb_alloc(attr_count * sizeof (uint32_t),
            UM_SLEEP | UM_GC);

        if (mdb_vread(*off_tab,
            attr_count * sizeof (uint32_t), idx_table) == -1) {
                mdb_warn("failed to attribute offset table %p", idx_table);
                return (-1);
        }

        return (DCMD_OK);
}

/*ARGSUSED*/
static int
sa_attr_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        uint32_t *offset_tab;
        int attr_count;
        uint64_t attr_id;
        uintptr_t attr_addr;
        uintptr_t bonus_tab, spill_tab;
        uintptr_t db_bonus, db_spill;
        uintptr_t os, os_sa;
        uintptr_t db_data;

        if (argc != 1)
                return (DCMD_USAGE);

        if (argv[0].a_type == MDB_TYPE_STRING)
                attr_id = mdb_strtoull(argv[0].a_un.a_str);
        else
                return (DCMD_USAGE);

        if (GETMEMB(addr, "sa_handle", sa_bonus_tab, bonus_tab) ||
            GETMEMB(addr, "sa_handle", sa_spill_tab, spill_tab) ||
            GETMEMB(addr, "sa_handle", sa_os, os) ||
            GETMEMB(addr, "sa_handle", sa_bonus, db_bonus) ||
            GETMEMB(addr, "sa_handle", sa_spill, db_spill)) {
                mdb_printf("Can't find necessary information in sa_handle "
                    "in sa_handle\n");
                return (DCMD_ERR);
        }

        if (GETMEMB(os, "objset", os_sa, os_sa)) {
                mdb_printf("Can't find os_sa in objset\n");
                return (DCMD_ERR);
        }

        if (GETMEMB(os_sa, "sa_os", sa_num_attrs, attr_count)) {
                mdb_printf("Can't find sa_num_attrs\n");
                return (DCMD_ERR);
        }

        if (attr_id > attr_count) {
                mdb_printf("attribute id number is out of range\n");
                return (DCMD_ERR);
        }

        if (bonus_tab) {
                if (sa_get_off_table(bonus_tab, &offset_tab,
                    attr_count) == -1) {
                        return (DCMD_ERR);
                }

                if (GETMEMB(db_bonus, "dmu_buf", db_data, db_data)) {
                        mdb_printf("can't find db_data in bonus dbuf\n");
                        return (DCMD_ERR);
                }
        }

        if (bonus_tab && !TOC_ATTR_PRESENT(offset_tab[attr_id]) &&
            spill_tab == 0) {
                mdb_printf("Attribute does not exist\n");
                return (DCMD_ERR);
        } else if (!TOC_ATTR_PRESENT(offset_tab[attr_id]) && spill_tab) {
                if (sa_get_off_table(spill_tab, &offset_tab,
                    attr_count) == -1) {
                        return (DCMD_ERR);
                }
                if (GETMEMB(db_spill, "dmu_buf", db_data, db_data)) {
                        mdb_printf("can't find db_data in spill dbuf\n");
                        return (DCMD_ERR);
                }
                if (!TOC_ATTR_PRESENT(offset_tab[attr_id])) {
                        mdb_printf("Attribute does not exist\n");
                        return (DCMD_ERR);
                }
        }
        attr_addr = db_data + TOC_OFF(offset_tab[attr_id]);
        mdb_printf("%p\n", attr_addr);
        return (DCMD_OK);
}

/* ARGSUSED */
static int
zfs_ace_print_common(uintptr_t addr, uint_t flags,
    uint64_t id, uint32_t access_mask, uint16_t ace_flags,
    uint16_t ace_type, int verbose)
{
        if (DCMD_HDRSPEC(flags) && !verbose)
                mdb_printf("%<u>%-?s %-8s %-8s %-8s %s%</u>\n",
                    "ADDR", "FLAGS", "MASK", "TYPE", "ID");

        if (!verbose) {
                mdb_printf("%0?p %-8x %-8x %-8x %-llx\n", addr,
                    ace_flags, access_mask, ace_type, id);
                return (DCMD_OK);
        }

        switch (ace_flags & ACE_TYPE_FLAGS) {
        case ACE_OWNER:
                mdb_printf("owner@:");
                break;
        case (ACE_IDENTIFIER_GROUP | ACE_GROUP):
                mdb_printf("group@:");
                break;
        case ACE_EVERYONE:
                mdb_printf("everyone@:");
                break;
        case ACE_IDENTIFIER_GROUP:
                mdb_printf("group:%llx:", (u_longlong_t)id);
                break;
        case 0: /* User entry */
                mdb_printf("user:%llx:", (u_longlong_t)id);
                break;
        }

        /* print out permission mask */
        if (access_mask & ACE_READ_DATA)
                mdb_printf("r");
        else
                mdb_printf("-");
        if (access_mask & ACE_WRITE_DATA)
                mdb_printf("w");
        else
                mdb_printf("-");
        if (access_mask & ACE_EXECUTE)
                mdb_printf("x");
        else
                mdb_printf("-");
        if (access_mask & ACE_APPEND_DATA)
                mdb_printf("p");
        else
                mdb_printf("-");
        if (access_mask & ACE_DELETE)
                mdb_printf("d");
        else
                mdb_printf("-");
        if (access_mask & ACE_DELETE_CHILD)
                mdb_printf("D");
        else
                mdb_printf("-");
        if (access_mask & ACE_READ_ATTRIBUTES)
                mdb_printf("a");
        else
                mdb_printf("-");
        if (access_mask & ACE_WRITE_ATTRIBUTES)
                mdb_printf("A");
        else
                mdb_printf("-");
        if (access_mask & ACE_READ_NAMED_ATTRS)
                mdb_printf("R");
        else
                mdb_printf("-");
        if (access_mask & ACE_WRITE_NAMED_ATTRS)
                mdb_printf("W");
        else
                mdb_printf("-");
        if (access_mask & ACE_READ_ACL)
                mdb_printf("c");
        else
                mdb_printf("-");
        if (access_mask & ACE_WRITE_ACL)
                mdb_printf("C");
        else
                mdb_printf("-");
        if (access_mask & ACE_WRITE_OWNER)
                mdb_printf("o");
        else
                mdb_printf("-");
        if (access_mask & ACE_SYNCHRONIZE)
                mdb_printf("s");
        else
                mdb_printf("-");

        mdb_printf(":");

        /* Print out inheritance flags */
        if (ace_flags & ACE_FILE_INHERIT_ACE)
                mdb_printf("f");
        else
                mdb_printf("-");
        if (ace_flags & ACE_DIRECTORY_INHERIT_ACE)
                mdb_printf("d");
        else
                mdb_printf("-");
        if (ace_flags & ACE_INHERIT_ONLY_ACE)
                mdb_printf("i");
        else
                mdb_printf("-");
        if (ace_flags & ACE_NO_PROPAGATE_INHERIT_ACE)
                mdb_printf("n");
        else
                mdb_printf("-");
        if (ace_flags & ACE_SUCCESSFUL_ACCESS_ACE_FLAG)
                mdb_printf("S");
        else
                mdb_printf("-");
        if (ace_flags & ACE_FAILED_ACCESS_ACE_FLAG)
                mdb_printf("F");
        else
                mdb_printf("-");
        if (ace_flags & ACE_INHERITED_ACE)
                mdb_printf("I");
        else
                mdb_printf("-");

        switch (ace_type) {
        case ACE_ACCESS_ALLOWED_ACE_TYPE:
                mdb_printf(":allow\n");
                break;
        case ACE_ACCESS_DENIED_ACE_TYPE:
                mdb_printf(":deny\n");
                break;
        case ACE_SYSTEM_AUDIT_ACE_TYPE:
                mdb_printf(":audit\n");
                break;
        case ACE_SYSTEM_ALARM_ACE_TYPE:
                mdb_printf(":alarm\n");
                break;
        default:
                mdb_printf(":?\n");
        }
        return (DCMD_OK);
}

/* ARGSUSED */
static int
zfs_ace_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        zfs_ace_t zace;
        int verbose = FALSE;
        uint64_t id;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, TRUE, &verbose, TRUE, NULL) != argc)
                return (DCMD_USAGE);

        if (mdb_vread(&zace, sizeof (zfs_ace_t), addr) == -1) {
                mdb_warn("failed to read zfs_ace_t");
                return (DCMD_ERR);
        }

        if ((zace.z_hdr.z_flags & ACE_TYPE_FLAGS) == 0 ||
            (zace.z_hdr.z_flags & ACE_TYPE_FLAGS) == ACE_IDENTIFIER_GROUP)
                id = zace.z_fuid;
        else
                id = -1;

        return (zfs_ace_print_common(addr, flags, id, zace.z_hdr.z_access_mask,
            zace.z_hdr.z_flags, zace.z_hdr.z_type, verbose));
}

/* ARGSUSED */
static int
zfs_ace0_print(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        ace_t ace;
        uint64_t id;
        int verbose = FALSE;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, TRUE, &verbose, TRUE, NULL) != argc)
                return (DCMD_USAGE);

        if (mdb_vread(&ace, sizeof (ace_t), addr) == -1) {
                mdb_warn("failed to read ace_t");
                return (DCMD_ERR);
        }

        if ((ace.a_flags & ACE_TYPE_FLAGS) == 0 ||
            (ace.a_flags & ACE_TYPE_FLAGS) == ACE_IDENTIFIER_GROUP)
                id = ace.a_who;
        else
                id = -1;

        return (zfs_ace_print_common(addr, flags, id, ace.a_access_mask,
            ace.a_flags, ace.a_type, verbose));
}

typedef struct acl_dump_args {
        int a_argc;
        const mdb_arg_t *a_argv;
        uint16_t a_version;
        int a_flags;
} acl_dump_args_t;

/* ARGSUSED */
static int
acl_aces_cb(uintptr_t addr, const void *unknown, void *arg)
{
        acl_dump_args_t *acl_args = (acl_dump_args_t *)arg;

        if (acl_args->a_version == 1) {
                if (mdb_call_dcmd("zfs_ace", addr,
                    DCMD_ADDRSPEC|acl_args->a_flags, acl_args->a_argc,
                    acl_args->a_argv) != DCMD_OK) {
                        return (WALK_ERR);
                }
        } else {
                if (mdb_call_dcmd("zfs_ace0", addr,
                    DCMD_ADDRSPEC|acl_args->a_flags, acl_args->a_argc,
                    acl_args->a_argv) != DCMD_OK) {
                        return (WALK_ERR);
                }
        }
        acl_args->a_flags = DCMD_LOOP;
        return (WALK_NEXT);
}

/* ARGSUSED */
static int
acl_cb(uintptr_t addr, const void *unknown, void *arg)
{
        acl_dump_args_t *acl_args = (acl_dump_args_t *)arg;

        if (acl_args->a_version == 1) {
                if (mdb_pwalk("zfs_acl_node_aces", acl_aces_cb,
                    arg, addr) != 0) {
                        mdb_warn("can't walk ACEs");
                        return (DCMD_ERR);
                }
        } else {
                if (mdb_pwalk("zfs_acl_node_aces0", acl_aces_cb,
                    arg, addr) != 0) {
                        mdb_warn("can't walk ACEs");
                        return (DCMD_ERR);
                }
        }
        return (WALK_NEXT);
}

/* ARGSUSED */
static int
zfs_acl_dump(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        zfs_acl_t zacl;
        int verbose = FALSE;
        acl_dump_args_t acl_args;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, TRUE, &verbose, NULL) != argc)
                return (DCMD_USAGE);

        if (mdb_vread(&zacl, sizeof (zfs_acl_t), addr) == -1) {
                mdb_warn("failed to read zfs_acl_t");
                return (DCMD_ERR);
        }

        acl_args.a_argc = argc;
        acl_args.a_argv = argv;
        acl_args.a_version = zacl.z_version;
        acl_args.a_flags = DCMD_LOOPFIRST;

        if (mdb_pwalk("zfs_acl_node", acl_cb, &acl_args, addr) != 0) {
                mdb_warn("can't walk ACL");
                return (DCMD_ERR);
        }

        return (DCMD_OK);
}

/* ARGSUSED */
static int
zfs_acl_node_walk_init(mdb_walk_state_t *wsp)
{
        if (wsp->walk_addr == 0) {
                mdb_warn("must supply address of zfs_acl_node_t\n");
                return (WALK_ERR);
        }

        wsp->walk_addr +=
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "zfs_acl", "z_acl");

        if (mdb_layered_walk("list", wsp) == -1) {
                mdb_warn("failed to walk 'list'\n");
                return (WALK_ERR);
        }

        return (WALK_NEXT);
}

static int
zfs_acl_node_walk_step(mdb_walk_state_t *wsp)
{
        zfs_acl_node_t  aclnode;

        if (mdb_vread(&aclnode, sizeof (zfs_acl_node_t),
            wsp->walk_addr) == -1) {
                mdb_warn("failed to read zfs_acl_node at %p", wsp->walk_addr);
                return (WALK_ERR);
        }

        return (wsp->walk_callback(wsp->walk_addr, &aclnode, wsp->walk_cbdata));
}

typedef struct ace_walk_data {
        int             ace_count;
        int             ace_version;
} ace_walk_data_t;

static int
zfs_aces_walk_init_common(mdb_walk_state_t *wsp, int version,
    int ace_count, uintptr_t ace_data)
{
        ace_walk_data_t *ace_walk_data;

        if (wsp->walk_addr == 0) {
                mdb_warn("must supply address of zfs_acl_node_t\n");
                return (WALK_ERR);
        }

        ace_walk_data = mdb_alloc(sizeof (ace_walk_data_t), UM_SLEEP | UM_GC);

        ace_walk_data->ace_count = ace_count;
        ace_walk_data->ace_version = version;

        wsp->walk_addr = ace_data;
        wsp->walk_data = ace_walk_data;

        return (WALK_NEXT);
}

static int
zfs_acl_node_aces_walk_init_common(mdb_walk_state_t *wsp, int version)
{
        static int gotid;
        static mdb_ctf_id_t acl_id;
        int z_ace_count;
        uintptr_t z_acldata;

        if (!gotid) {
                if (mdb_ctf_lookup_by_name("struct zfs_acl_node",
                    &acl_id) == -1) {
                        mdb_warn("couldn't find struct zfs_acl_node");
                        return (DCMD_ERR);
                }
                gotid = TRUE;
        }

        if (GETMEMBID(wsp->walk_addr, &acl_id, z_ace_count, z_ace_count)) {
                return (DCMD_ERR);
        }
        if (GETMEMBID(wsp->walk_addr, &acl_id, z_acldata, z_acldata)) {
                return (DCMD_ERR);
        }

        return (zfs_aces_walk_init_common(wsp, version,
            z_ace_count, z_acldata));
}

/* ARGSUSED */
static int
zfs_acl_node_aces_walk_init(mdb_walk_state_t *wsp)
{
        return (zfs_acl_node_aces_walk_init_common(wsp, 1));
}

/* ARGSUSED */
static int
zfs_acl_node_aces0_walk_init(mdb_walk_state_t *wsp)
{
        return (zfs_acl_node_aces_walk_init_common(wsp, 0));
}

static int
zfs_aces_walk_step(mdb_walk_state_t *wsp)
{
        ace_walk_data_t *ace_data = wsp->walk_data;
        zfs_ace_t zace;
        ace_t *acep;
        int status;
        int entry_type;
        int allow_type;
        uintptr_t ptr;

        if (ace_data->ace_count == 0)
                return (WALK_DONE);

        if (mdb_vread(&zace, sizeof (zfs_ace_t), wsp->walk_addr) == -1) {
                mdb_warn("failed to read zfs_ace_t at %#lx",
                    wsp->walk_addr);
                return (WALK_ERR);
        }

        switch (ace_data->ace_version) {
        case 0:
                acep = (ace_t *)&zace;
                entry_type = acep->a_flags & ACE_TYPE_FLAGS;
                allow_type = acep->a_type;
                break;
        case 1:
                entry_type = zace.z_hdr.z_flags & ACE_TYPE_FLAGS;
                allow_type = zace.z_hdr.z_type;
                break;
        default:
                return (WALK_ERR);
        }

        ptr = (uintptr_t)wsp->walk_addr;
        switch (entry_type) {
        case ACE_OWNER:
        case ACE_EVERYONE:
        case (ACE_IDENTIFIER_GROUP | ACE_GROUP):
                ptr += ace_data->ace_version == 0 ?
                    sizeof (ace_t) : sizeof (zfs_ace_hdr_t);
                break;
        case ACE_IDENTIFIER_GROUP:
        default:
                switch (allow_type) {
                case ACE_ACCESS_ALLOWED_OBJECT_ACE_TYPE:
                case ACE_ACCESS_DENIED_OBJECT_ACE_TYPE:
                case ACE_SYSTEM_AUDIT_OBJECT_ACE_TYPE:
                case ACE_SYSTEM_ALARM_OBJECT_ACE_TYPE:
                        ptr += ace_data->ace_version == 0 ?
                            sizeof (ace_t) : sizeof (zfs_object_ace_t);
                        break;
                default:
                        ptr += ace_data->ace_version == 0 ?
                            sizeof (ace_t) : sizeof (zfs_ace_t);
                        break;
                }
        }

        ace_data->ace_count--;
        status = wsp->walk_callback(wsp->walk_addr,
            (void *)(uintptr_t)&zace, wsp->walk_cbdata);

        wsp->walk_addr = ptr;
        return (status);
}

typedef struct mdb_zfs_rrwlock {
        uintptr_t       rr_writer;
        boolean_t       rr_writer_wanted;
} mdb_zfs_rrwlock_t;

static uint_t rrw_key;

/* ARGSUSED */
static int
rrwlock(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        mdb_zfs_rrwlock_t rrw;

        if (rrw_key == 0) {
                if (mdb_ctf_readsym(&rrw_key, "uint_t", "rrw_tsd_key", 0) == -1)
                        return (DCMD_ERR);
        }

        if (mdb_ctf_vread(&rrw, "rrwlock_t", "mdb_zfs_rrwlock_t", addr,
            0) == -1)
                return (DCMD_ERR);

        if (rrw.rr_writer != 0) {
                mdb_printf("write lock held by thread %lx\n", rrw.rr_writer);
                return (DCMD_OK);
        }

        if (rrw.rr_writer_wanted) {
                mdb_printf("writer wanted\n");
        }

        mdb_printf("anonymous references:\n");
        (void) mdb_call_dcmd("zfs_refcount", addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "rrwlock", "rr_anon_rcount"),
            DCMD_ADDRSPEC, 0, NULL);

        mdb_printf("linked references:\n");
        (void) mdb_call_dcmd("zfs_refcount", addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "rrwlock", "rr_linked_rcount"),
            DCMD_ADDRSPEC, 0, NULL);

        /*
         * XXX This should find references from
         * "::walk thread | ::tsd -v <rrw_key>", but there is no support
         * for programmatic consumption of dcmds, so this would be
         * difficult, potentially requiring reimplementing ::tsd (both
         * user and kernel versions) in this MDB module.
         */

        return (DCMD_OK);
}

typedef struct mdb_arc_buf_hdr_t {
        uint16_t b_psize;
        uint16_t b_lsize;
        struct {
                uint32_t        b_bufcnt;
                uintptr_t       b_state;
        } b_l1hdr;
} mdb_arc_buf_hdr_t;

enum arc_cflags {
        ARC_CFLAG_VERBOSE               = 1 << 0,
        ARC_CFLAG_ANON                  = 1 << 1,
        ARC_CFLAG_MRU                   = 1 << 2,
        ARC_CFLAG_MFU                   = 1 << 3,
        ARC_CFLAG_BUFS                  = 1 << 4,
};

typedef struct arc_compression_stats_data {
        GElf_Sym anon_sym;      /* ARC_anon symbol */
        GElf_Sym mru_sym;       /* ARC_mru symbol */
        GElf_Sym mrug_sym;      /* ARC_mru_ghost symbol */
        GElf_Sym mfu_sym;       /* ARC_mfu symbol */
        GElf_Sym mfug_sym;      /* ARC_mfu_ghost symbol */
        GElf_Sym l2c_sym;       /* ARC_l2c_only symbol */
        uint64_t *anon_c_hist;  /* histogram of compressed sizes in anon */
        uint64_t *anon_u_hist;  /* histogram of uncompressed sizes in anon */
        uint64_t *anon_bufs;    /* histogram of buffer counts in anon state */
        uint64_t *mru_c_hist;   /* histogram of compressed sizes in mru */
        uint64_t *mru_u_hist;   /* histogram of uncompressed sizes in mru */
        uint64_t *mru_bufs;     /* histogram of buffer counts in mru */
        uint64_t *mfu_c_hist;   /* histogram of compressed sizes in mfu */
        uint64_t *mfu_u_hist;   /* histogram of uncompressed sizes in mfu */
        uint64_t *mfu_bufs;     /* histogram of buffer counts in mfu */
        uint64_t *all_c_hist;   /* histogram of compressed anon + mru + mfu */
        uint64_t *all_u_hist;   /* histogram of uncompressed anon + mru + mfu */
        uint64_t *all_bufs;     /* histogram of buffer counts in all states  */
        int arc_cflags;         /* arc compression flags, specified by user */
        int hist_nbuckets;      /* number of buckets in each histogram */

        ulong_t l1hdr_off;      /* offset of b_l1hdr in arc_buf_hdr_t */
} arc_compression_stats_data_t;

int
highbit64(uint64_t i)
{
        int h = 1;

        if (i == 0)
                return (0);
        if (i & 0xffffffff00000000ULL) {
                h += 32; i >>= 32;
        }
        if (i & 0xffff0000) {
                h += 16; i >>= 16;
        }
        if (i & 0xff00) {
                h += 8; i >>= 8;
        }
        if (i & 0xf0) {
                h += 4; i >>= 4;
        }
        if (i & 0xc) {
                h += 2; i >>= 2;
        }
        if (i & 0x2) {
                h += 1;
        }
        return (h);
}

/* ARGSUSED */
static int
arc_compression_stats_cb(uintptr_t addr, const void *unknown, void *arg)
{
        arc_compression_stats_data_t *data = arg;
        arc_flags_t flags;
        mdb_arc_buf_hdr_t hdr;
        int cbucket, ubucket, bufcnt;

        /*
         * mdb_ctf_vread() uses the sizeof the target type (e.g.
         * sizeof (arc_buf_hdr_t) in the target) to read in the entire contents
         * of the target type into a buffer and then copy the values of the
         * desired members from the mdb typename (e.g. mdb_arc_buf_hdr_t) from
         * this buffer. Unfortunately, the way arc_buf_hdr_t is used by zfs,
         * the actual size allocated by the kernel for arc_buf_hdr_t is often
         * smaller than `sizeof (arc_buf_hdr_t)` (see the definitions of
         * l1arc_buf_hdr_t and arc_buf_hdr_t in
         * usr/src/uts/common/fs/zfs/arc.c). Attempting to read the entire
         * contents of arc_buf_hdr_t from the target (as mdb_ctf_vread() does)
         * can cause an error if the allocated size is indeed smaller--it's
         * possible that the 'missing' trailing members of arc_buf_hdr_t
         * (l1arc_buf_hdr_t and/or arc_buf_hdr_crypt_t) may fall into unmapped
         * memory.
         *
         * We use the GETMEMB macro instead which performs an mdb_vread()
         * but only reads enough of the target to retrieve the desired struct
         * member instead of the entire struct.
         */
        if (GETMEMB(addr, "arc_buf_hdr", b_flags, flags) == -1)
                return (WALK_ERR);

        /*
         * We only count headers that have data loaded in the kernel.
         * This means an L1 header must be present as well as the data
         * that corresponds to the L1 header. If there's no L1 header,
         * we can skip the arc_buf_hdr_t completely. If it's present, we
         * must look at the ARC state (b_l1hdr.b_state) to determine if
         * the data is present.
         */
        if ((flags & ARC_FLAG_HAS_L1HDR) == 0)
                return (WALK_NEXT);

        if (GETMEMB(addr, "arc_buf_hdr", b_psize, hdr.b_psize) == -1 ||
            GETMEMB(addr, "arc_buf_hdr", b_lsize, hdr.b_lsize) == -1 ||
            GETMEMB(addr + data->l1hdr_off, "l1arc_buf_hdr", b_bufcnt,
            hdr.b_l1hdr.b_bufcnt) == -1 ||
            GETMEMB(addr + data->l1hdr_off, "l1arc_buf_hdr", b_state,
            hdr.b_l1hdr.b_state) == -1)
                return (WALK_ERR);

        /*
         * Headers in the ghost states, or the l2c_only state don't have
         * arc buffers linked off of them. Thus, their compressed size
         * is meaningless, so we skip these from the stats.
         */
        if (hdr.b_l1hdr.b_state == data->mrug_sym.st_value ||
            hdr.b_l1hdr.b_state == data->mfug_sym.st_value ||
            hdr.b_l1hdr.b_state == data->l2c_sym.st_value) {
                return (WALK_NEXT);
        }

        /*
         * The physical size (compressed) and logical size
         * (uncompressed) are in units of SPA_MINBLOCKSIZE. By default,
         * we use the log2 of this value (rounded down to the nearest
         * integer) to determine the bucket to assign this header to.
         * Thus, the histogram is logarithmic with respect to the size
         * of the header. For example, the following is a mapping of the
         * bucket numbers and the range of header sizes they correspond to:
         *
         *      0: 0 byte headers
         *      1: 512 byte headers
         *      2: [1024 - 2048) byte headers
         *      3: [2048 - 4096) byte headers
         *      4: [4096 - 8192) byte headers
         *      5: [8192 - 16394) byte headers
         *      6: [16384 - 32768) byte headers
         *      7: [32768 - 65536) byte headers
         *      8: [65536 - 131072) byte headers
         *      9: 131072 byte headers
         *
         * If the ARC_CFLAG_VERBOSE flag was specified, we use the
         * physical and logical sizes directly. Thus, the histogram will
         * no longer be logarithmic; instead it will be linear with
         * respect to the size of the header. The following is a mapping
         * of the first many bucket numbers and the header size they
         * correspond to:
         *
         *      0: 0 byte headers
         *      1: 512 byte headers
         *      2: 1024 byte headers
         *      3: 1536 byte headers
         *      4: 2048 byte headers
         *      5: 2560 byte headers
         *      6: 3072 byte headers
         *
         * And so on. Keep in mind that a range of sizes isn't used in
         * the case of linear scale because the headers can only
         * increment or decrement in sizes of 512 bytes. So, it's not
         * possible for a header to be sized in between whats listed
         * above.
         *
         * Also, the above mapping values were calculated assuming a
         * SPA_MINBLOCKSHIFT of 512 bytes and a SPA_MAXBLOCKSIZE of 128K.
         */

        if (data->arc_cflags & ARC_CFLAG_VERBOSE) {
                cbucket = hdr.b_psize;
                ubucket = hdr.b_lsize;
        } else {
                cbucket = highbit64(hdr.b_psize);
                ubucket = highbit64(hdr.b_lsize);
        }

        bufcnt = hdr.b_l1hdr.b_bufcnt;
        if (bufcnt >= data->hist_nbuckets)
                bufcnt = data->hist_nbuckets - 1;

        /* Ensure we stay within the bounds of the histogram array */
        ASSERT3U(cbucket, <, data->hist_nbuckets);
        ASSERT3U(ubucket, <, data->hist_nbuckets);

        if (hdr.b_l1hdr.b_state == data->anon_sym.st_value) {
                data->anon_c_hist[cbucket]++;
                data->anon_u_hist[ubucket]++;
                data->anon_bufs[bufcnt]++;
        } else if (hdr.b_l1hdr.b_state == data->mru_sym.st_value) {
                data->mru_c_hist[cbucket]++;
                data->mru_u_hist[ubucket]++;
                data->mru_bufs[bufcnt]++;
        } else if (hdr.b_l1hdr.b_state == data->mfu_sym.st_value) {
                data->mfu_c_hist[cbucket]++;
                data->mfu_u_hist[ubucket]++;
                data->mfu_bufs[bufcnt]++;
        }

        data->all_c_hist[cbucket]++;
        data->all_u_hist[ubucket]++;
        data->all_bufs[bufcnt]++;

        return (WALK_NEXT);
}

/* ARGSUSED */
static int
arc_compression_stats(uintptr_t addr, uint_t flags, int argc,
    const mdb_arg_t *argv)
{
        arc_compression_stats_data_t data = { 0 };
        unsigned int max_shifted = SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT;
        unsigned int hist_size;
        char range[32];
        int rc = DCMD_OK;
        int off;

        if (mdb_getopts(argc, argv,
            'v', MDB_OPT_SETBITS, ARC_CFLAG_VERBOSE, &data.arc_cflags,
            'a', MDB_OPT_SETBITS, ARC_CFLAG_ANON, &data.arc_cflags,
            'b', MDB_OPT_SETBITS, ARC_CFLAG_BUFS, &data.arc_cflags,
            'r', MDB_OPT_SETBITS, ARC_CFLAG_MRU, &data.arc_cflags,
            'f', MDB_OPT_SETBITS, ARC_CFLAG_MFU, &data.arc_cflags,
            NULL) != argc)
                return (DCMD_USAGE);

        if (mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_anon", &data.anon_sym) ||
            mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_mru", &data.mru_sym) ||
            mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_mru_ghost", &data.mrug_sym) ||
            mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_mfu", &data.mfu_sym) ||
            mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_mfu_ghost", &data.mfug_sym) ||
            mdb_lookup_by_obj(ZFS_OBJ_NAME, "ARC_l2c_only", &data.l2c_sym)) {
                mdb_warn("can't find arc state symbol");
                return (DCMD_ERR);
        }

        /*
         * Determine the maximum expected size for any header, and use
         * this to determine the number of buckets needed for each
         * histogram. If ARC_CFLAG_VERBOSE is specified, this value is
         * used directly; otherwise the log2 of the maximum size is
         * used. Thus, if using a log2 scale there's a maximum of 10
         * possible buckets, while the linear scale (when using
         * ARC_CFLAG_VERBOSE) has a maximum of 257 buckets.
         */
        if (data.arc_cflags & ARC_CFLAG_VERBOSE)
                data.hist_nbuckets = max_shifted + 1;
        else
                data.hist_nbuckets = highbit64(max_shifted) + 1;

        hist_size = sizeof (uint64_t) * data.hist_nbuckets;

        data.anon_c_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.anon_u_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.anon_bufs = mdb_zalloc(hist_size, UM_SLEEP);

        data.mru_c_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.mru_u_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.mru_bufs = mdb_zalloc(hist_size, UM_SLEEP);

        data.mfu_c_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.mfu_u_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.mfu_bufs = mdb_zalloc(hist_size, UM_SLEEP);

        data.all_c_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.all_u_hist = mdb_zalloc(hist_size, UM_SLEEP);
        data.all_bufs = mdb_zalloc(hist_size, UM_SLEEP);

        if ((off = mdb_ctf_offsetof_by_name(ZFS_STRUCT "arc_buf_hdr",
            "b_l1hdr")) == -1) {
                mdb_warn("could not get offset of b_l1hdr from arc_buf_hdr_t");
                rc = DCMD_ERR;
                goto out;
        }
        data.l1hdr_off = off;

        if (mdb_walk("arc_buf_hdr_t_full", arc_compression_stats_cb,
            &data) != 0) {
                mdb_warn("can't walk arc_buf_hdr's");
                rc = DCMD_ERR;
                goto out;
        }

        if (data.arc_cflags & ARC_CFLAG_VERBOSE) {
                rc = mdb_snprintf(range, sizeof (range),
                    "[n*%llu, (n+1)*%llu)", SPA_MINBLOCKSIZE,
                    SPA_MINBLOCKSIZE);
        } else {
                rc = mdb_snprintf(range, sizeof (range),
                    "[2^(n-1)*%llu, 2^n*%llu)", SPA_MINBLOCKSIZE,
                    SPA_MINBLOCKSIZE);
        }

        if (rc < 0) {
                /* snprintf failed, abort the dcmd */
                rc = DCMD_ERR;
                goto out;
        } else {
                /* snprintf succeeded above, reset return code */
                rc = DCMD_OK;
        }

        if (data.arc_cflags & ARC_CFLAG_ANON) {
                if (data.arc_cflags & ARC_CFLAG_BUFS) {
                        mdb_printf("Histogram of the number of anon buffers "
                            "that are associated with an arc hdr.\n");
                        dump_histogram(data.anon_bufs, data.hist_nbuckets, 0);
                        mdb_printf("\n");
                }
                mdb_printf("Histogram of compressed anon buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.anon_c_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");

                mdb_printf("Histogram of uncompressed anon buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.anon_u_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");
        }

        if (data.arc_cflags & ARC_CFLAG_MRU) {
                if (data.arc_cflags & ARC_CFLAG_BUFS) {
                        mdb_printf("Histogram of the number of mru buffers "
                            "that are associated with an arc hdr.\n");
                        dump_histogram(data.mru_bufs, data.hist_nbuckets, 0);
                        mdb_printf("\n");
                }
                mdb_printf("Histogram of compressed mru buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.mru_c_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");

                mdb_printf("Histogram of uncompressed mru buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.mru_u_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");
        }

        if (data.arc_cflags & ARC_CFLAG_MFU) {
                if (data.arc_cflags & ARC_CFLAG_BUFS) {
                        mdb_printf("Histogram of the number of mfu buffers "
                            "that are associated with an arc hdr.\n");
                        dump_histogram(data.mfu_bufs, data.hist_nbuckets, 0);
                        mdb_printf("\n");
                }

                mdb_printf("Histogram of compressed mfu buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.mfu_c_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");

                mdb_printf("Histogram of uncompressed mfu buffers.\n"
                    "Each bucket represents buffers of size: %s.\n", range);
                dump_histogram(data.mfu_u_hist, data.hist_nbuckets, 0);
                mdb_printf("\n");
        }

        if (data.arc_cflags & ARC_CFLAG_BUFS) {
                mdb_printf("Histogram of all buffers that "
                    "are associated with an arc hdr.\n");
                dump_histogram(data.all_bufs, data.hist_nbuckets, 0);
                mdb_printf("\n");
        }

        mdb_printf("Histogram of all compressed buffers.\n"
            "Each bucket represents buffers of size: %s.\n", range);
        dump_histogram(data.all_c_hist, data.hist_nbuckets, 0);
        mdb_printf("\n");

        mdb_printf("Histogram of all uncompressed buffers.\n"
            "Each bucket represents buffers of size: %s.\n", range);
        dump_histogram(data.all_u_hist, data.hist_nbuckets, 0);

out:
        mdb_free(data.anon_c_hist, hist_size);
        mdb_free(data.anon_u_hist, hist_size);
        mdb_free(data.anon_bufs, hist_size);

        mdb_free(data.mru_c_hist, hist_size);
        mdb_free(data.mru_u_hist, hist_size);
        mdb_free(data.mru_bufs, hist_size);

        mdb_free(data.mfu_c_hist, hist_size);
        mdb_free(data.mfu_u_hist, hist_size);
        mdb_free(data.mfu_bufs, hist_size);

        mdb_free(data.all_c_hist, hist_size);
        mdb_free(data.all_u_hist, hist_size);
        mdb_free(data.all_bufs, hist_size);

        return (rc);
}

typedef struct mdb_range_seg64 {
        uint64_t rs_start;
        uint64_t rs_end;
} mdb_range_seg64_t;

typedef struct mdb_range_seg32 {
        uint32_t rs_start;
        uint32_t rs_end;
} mdb_range_seg32_t;

/* ARGSUSED */
static int
range_tree_cb(uintptr_t addr, const void *unknown, void *arg)
{
        mdb_range_tree_t *rt = (mdb_range_tree_t *)arg;
        uint64_t start, end;

        if (rt->rt_type == RANGE_SEG64) {
                mdb_range_seg64_t rs;

                if (mdb_ctf_vread(&rs, ZFS_STRUCT "range_seg64",
                    "mdb_range_seg64_t", addr, 0) == -1)
                        return (DCMD_ERR);
                start = rs.rs_start;
                end = rs.rs_end;
        } else {
                ASSERT3U(rt->rt_type, ==, RANGE_SEG32);
                mdb_range_seg32_t rs;

                if (mdb_ctf_vread(&rs, ZFS_STRUCT "range_seg32",
                    "mdb_range_seg32_t", addr, 0) == -1)
                        return (DCMD_ERR);
                start = ((uint64_t)rs.rs_start << rt->rt_shift) + rt->rt_start;
                end = ((uint64_t)rs.rs_end << rt->rt_shift) + rt->rt_start;
        }

        mdb_printf("\t[%llx %llx) (length %llx)\n", start, end, end - start);

        return (0);
}

/* ARGSUSED */
static int
range_tree(uintptr_t addr, uint_t flags, int argc,
    const mdb_arg_t *argv)
{
        mdb_range_tree_t rt;
        uintptr_t btree_addr;

        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        if (mdb_ctf_vread(&rt, ZFS_STRUCT "range_tree", "mdb_range_tree_t",
            addr, 0) == -1)
                return (DCMD_ERR);

        mdb_printf("%p: range tree of %llu entries, %llu bytes\n",
            addr, rt.rt_root.bt_num_elems, rt.rt_space);

        btree_addr = addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "range_tree", "rt_root");

        if (mdb_pwalk("zfs_btree", range_tree_cb, &rt, btree_addr) != 0) {
                mdb_warn("can't walk range_tree segments");
                return (DCMD_ERR);
        }
        return (DCMD_OK);
}

typedef struct mdb_spa_log_sm {
        uint64_t sls_sm_obj;
        uint64_t sls_txg;
        uint64_t sls_nblocks;
        uint64_t sls_mscount;
} mdb_spa_log_sm_t;

/* ARGSUSED */
static int
logsm_stats_cb(uintptr_t addr, const void *unknown, void *arg)
{
        mdb_spa_log_sm_t sls;
        if (mdb_ctf_vread(&sls, ZFS_STRUCT "spa_log_sm", "mdb_spa_log_sm_t",
            addr, 0) == -1)
                return (WALK_ERR);

        mdb_printf("%7lld %7lld %7lld %7lld\n",
            sls.sls_txg, sls.sls_nblocks, sls.sls_mscount, sls.sls_sm_obj);

        return (WALK_NEXT);
}
typedef struct mdb_log_summary_entry {
        uint64_t lse_start;
        uint64_t lse_blkcount;
        uint64_t lse_mscount;
} mdb_log_summary_entry_t;

/* ARGSUSED */
static int
logsm_summary_cb(uintptr_t addr, const void *unknown, void *arg)
{
        mdb_log_summary_entry_t lse;
        if (mdb_ctf_vread(&lse, ZFS_STRUCT "log_summary_entry",
            "mdb_log_summary_entry_t", addr, 0) == -1)
                return (WALK_ERR);

        mdb_printf("%7lld %7lld %7lld\n",
            lse.lse_start, lse.lse_blkcount, lse.lse_mscount);
        return (WALK_NEXT);
}

/* ARGSUSED */
static int
logsm_stats(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
        if (!(flags & DCMD_ADDRSPEC))
                return (DCMD_USAGE);

        uintptr_t sls_avl_addr = addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "spa", "spa_sm_logs_by_txg");
        uintptr_t summary_addr = addr +
            mdb_ctf_offsetof_by_name(ZFS_STRUCT "spa", "spa_log_summary");

        mdb_printf("Log Entries:\n");
        mdb_printf("%7s %7s %7s %7s\n", "txg", "blk", "ms", "obj");
        if (mdb_pwalk("avl", logsm_stats_cb, NULL, sls_avl_addr) != 0)
                return (DCMD_ERR);

        mdb_printf("\nSummary Entries:\n");
        mdb_printf("%7s %7s %7s\n", "txg", "blk", "ms");
        if (mdb_pwalk("list", logsm_summary_cb, NULL, summary_addr) != 0)
                return (DCMD_ERR);

        return (DCMD_OK);
}

/*
 * MDB module linkage information:
 *
 * We declare a list of structures describing our dcmds, and a function
 * named _mdb_init to return a pointer to our module information.
 */

static const mdb_dcmd_t dcmds[] = {
        { "arc", "[-bkmg]", "print ARC variables", arc_print },
        { "blkptr", ":", "print blkptr_t", blkptr },
        { "dva", ":", "print dva_t", dva },
        { "dbuf", ":", "print dmu_buf_impl_t", dbuf },
        { "dbuf_stats", ":", "dbuf stats", dbuf_stats },
        { "dbufs",
            "\t[-O objset_t*] [-n objset_name | \"mos\"] "
            "[-o object | \"mdn\"] \n"
            "\t[-l level] [-b blkid | \"bonus\"]",
            "find dmu_buf_impl_t's that match specified criteria", dbufs },
        { "abuf_find", "dva_word[0] dva_word[1]",
            "find arc_buf_hdr_t of a specified DVA",
            abuf_find },
        { "logsm_stats", ":", "print log space map statistics of a spa_t",
            logsm_stats},
        { "spa", "?[-cevmMh]\n"
            "\t-c display spa config\n"
            "\t-e display vdev statistics\n"
            "\t-v display vdev information\n"
            "\t-m display metaslab statistics\n"
            "\t-M display metaslab group statistics\n"
            "\t-h display histogram (requires -m or -M)\n",
            "spa_t summary", spa_print },
        { "spa_config", ":", "print spa_t configuration", spa_print_config },
        { "spa_space", ":[-b]", "print spa_t on-disk space usage", spa_space },
        { "spa_vdevs", ":[-emMh]\n"
            "\t-e display vdev statistics\n"
            "\t-m dispaly metaslab statistics\n"
            "\t-M display metaslab group statistic\n"
            "\t-h display histogram (requires -m or -M)\n",
            "given a spa_t, print vdev summary", spa_vdevs },
        { "sm_entries", "<buffer length in bytes>",
            "print out space map entries from a buffer decoded",
            sm_entries},
        { "vdev", ":[-remMh]\n"
            "\t-r display recursively\n"
            "\t-e display statistics\n"
            "\t-m display metaslab statistics (top level vdev only)\n"
            "\t-M display metaslab group statistics (top level vdev only)\n"
            "\t-h display histogram (requires -m or -M)\n",
            "vdev_t summary", vdev_print },
        { "zio", ":[-cpr]\n"
            "\t-c display children\n"
            "\t-p display parents\n"
            "\t-r display recursively",
            "zio_t summary", zio_print },
        { "zio_state", "?", "print out all zio_t structures on system or "
            "for a particular pool", zio_state },
        { "zfs_blkstats", ":[-v]",
            "given a spa_t, print block type stats from last scrub",
            zfs_blkstats },
        { "zfs_params", "", "print zfs tunable parameters", zfs_params },
        { "zfs_refcount", ":[-r]\n"
            "\t-r display recently removed references",
            "print zfs_refcount_t holders", zfs_refcount },
        { "zap_leaf", "", "print zap_leaf_phys_t", zap_leaf },
        { "zfs_aces", ":[-v]", "print all ACEs from a zfs_acl_t",
            zfs_acl_dump },
        { "zfs_ace", ":[-v]", "print zfs_ace", zfs_ace_print },
        { "zfs_ace0", ":[-v]", "print zfs_ace0", zfs_ace0_print },
        { "sa_attr_table", ":", "print SA attribute table from sa_os_t",
            sa_attr_table},
        { "sa_attr", ": attr_id",
            "print SA attribute address when given sa_handle_t", sa_attr_print},
        { "zfs_dbgmsg", ":[-artTvw]",
            "print zfs debug log", dbgmsg, dbgmsg_help},
        { "rrwlock", ":",
            "print rrwlock_t, including readers", rrwlock},
        { "metaslab_weight", "weight",
            "print metaslab weight", metaslab_weight},
        { "metaslab_trace", ":",
            "print metaslab allocation trace records", metaslab_trace},
        { "arc_compression_stats", ":[-vabrf]\n"
            "\t-v verbose, display a linearly scaled histogram\n"
            "\t-a display ARC_anon state statistics individually\n"
            "\t-r display ARC_mru state statistics individually\n"
            "\t-f display ARC_mfu state statistics individually\n"
            "\t-b display histogram of buffer counts\n",
            "print a histogram of compressed arc buffer sizes",
            arc_compression_stats},
        { "range_tree", ":",
            "print entries in range_tree_t", range_tree},
        { NULL }
};

static const mdb_walker_t walkers[] = {
        { "txg_list", "given any txg_list_t *, walk all entries in all txgs",
            txg_list_walk_init, txg_list_walk_step, NULL },
        { "txg_list0", "given any txg_list_t *, walk all entries in txg 0",
            txg_list0_walk_init, txg_list_walk_step, NULL },
        { "txg_list1", "given any txg_list_t *, walk all entries in txg 1",
            txg_list1_walk_init, txg_list_walk_step, NULL },
        { "txg_list2", "given any txg_list_t *, walk all entries in txg 2",
            txg_list2_walk_init, txg_list_walk_step, NULL },
        { "txg_list3", "given any txg_list_t *, walk all entries in txg 3",
            txg_list3_walk_init, txg_list_walk_step, NULL },
        { "zio", "walk all zio structures, optionally for a particular spa_t",
            zio_walk_init, zio_walk_step, NULL },
        { "zio_root",
            "walk all root zio_t structures, optionally for a particular spa_t",
            zio_walk_init, zio_walk_root_step, NULL },
        { "spa", "walk all spa_t entries in the namespace",
            spa_walk_init, spa_walk_step, NULL },
        { "metaslab", "given a spa_t *, walk all metaslab_t structures",
            metaslab_walk_init, metaslab_walk_step, NULL },
        { "multilist", "given a multilist_t *, walk all list_t structures",
            multilist_walk_init, multilist_walk_step, NULL },
        { "zfs_acl_node", "given a zfs_acl_t, walk all zfs_acl_nodes",
            zfs_acl_node_walk_init, zfs_acl_node_walk_step, NULL },
        { "zfs_acl_node_aces", "given a zfs_acl_node_t, walk all ACEs",
            zfs_acl_node_aces_walk_init, zfs_aces_walk_step, NULL },
        { "zfs_acl_node_aces0",
            "given a zfs_acl_node_t, walk all ACEs as ace_t",
            zfs_acl_node_aces0_walk_init, zfs_aces_walk_step, NULL },
        { "zfs_btree", "given a zfs_btree_t *, walk all entries",
            btree_walk_init, btree_walk_step, btree_walk_fini },
        { NULL }
};

static const mdb_modinfo_t modinfo = {
        MDB_API_VERSION, dcmds, walkers
};

const mdb_modinfo_t *
_mdb_init(void)
{
        return (&modinfo);
}