Align mount options handling and type/function names with OpenZFS

[zfs] / cmd / ztest / ztest.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 (c) 2011, 2016 by Delphix. All rights reserved.
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 2013 Steven Hartland. All rights reserved.
 */

/*
 * The objective of this program is to provide a DMU/ZAP/SPA stress test
 * that runs entirely in userland, is easy to use, and easy to extend.
 *
 * The overall design of the ztest program is as follows:
 *
 * (1) For each major functional area (e.g. adding vdevs to a pool,
 *     creating and destroying datasets, reading and writing objects, etc)
 *     we have a simple routine to test that functionality.  These
 *     individual routines do not have to do anything "stressful".
 *
 * (2) We turn these simple functionality tests into a stress test by
 *     running them all in parallel, with as many threads as desired,
 *     and spread across as many datasets, objects, and vdevs as desired.
 *
 * (3) While all this is happening, we inject faults into the pool to
 *     verify that self-healing data really works.
 *
 * (4) Every time we open a dataset, we change its checksum and compression
 *     functions.  Thus even individual objects vary from block to block
 *     in which checksum they use and whether they're compressed.
 *
 * (5) To verify that we never lose on-disk consistency after a crash,
 *     we run the entire test in a child of the main process.
 *     At random times, the child self-immolates with a SIGKILL.
 *     This is the software equivalent of pulling the power cord.
 *     The parent then runs the test again, using the existing
 *     storage pool, as many times as desired. If backwards compatibility
 *     testing is enabled ztest will sometimes run the "older" version
 *     of ztest after a SIGKILL.
 *
 * (6) To verify that we don't have future leaks or temporal incursions,
 *     many of the functional tests record the transaction group number
 *     as part of their data.  When reading old data, they verify that
 *     the transaction group number is less than the current, open txg.
 *     If you add a new test, please do this if applicable.
 *
 * (7) Threads are created with a reduced stack size, for sanity checking.
 *     Therefore, it's important not to allocate huge buffers on the stack.
 *
 * When run with no arguments, ztest runs for about five minutes and
 * produces no output if successful.  To get a little bit of information,
 * specify -V.  To get more information, specify -VV, and so on.
 *
 * To turn this into an overnight stress test, use -T to specify run time.
 *
 * You can ask more more vdevs [-v], datasets [-d], or threads [-t]
 * to increase the pool capacity, fanout, and overall stress level.
 *
 * Use the -k option to set the desired frequency of kills.
 *
 * When ztest invokes itself it passes all relevant information through a
 * temporary file which is mmap-ed in the child process. This allows shared
 * memory to survive the exec syscall. The ztest_shared_hdr_t struct is always
 * stored at offset 0 of this file and contains information on the size and
 * number of shared structures in the file. The information stored in this file
 * must remain backwards compatible with older versions of ztest so that
 * ztest can invoke them during backwards compatibility testing (-B).
 */

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/dmu.h>
#include <sys/txg.h>
#include <sys/dbuf.h>
#include <sys/zap.h>
#include <sys/dmu_objset.h>
#include <sys/poll.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/zio.h>
#include <sys/zil.h>
#include <sys/zil_impl.h>
#include <sys/zfs_rlock.h>
#include <sys/vdev_impl.h>
#include <sys/vdev_file.h>
#include <sys/spa_impl.h>
#include <sys/metaslab_impl.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_destroy.h>
#include <sys/dsl_scan.h>
#include <sys/zio_checksum.h>
#include <sys/refcount.h>
#include <sys/zfeature.h>
#include <sys/dsl_userhold.h>
#include <sys/abd.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <umem.h>
#include <ctype.h>
#include <math.h>
#include <sys/fs/zfs.h>
#include <zfs_fletcher.h>
#include <libnvpair.h>
#ifdef __GLIBC__
#include <execinfo.h> /* for backtrace() */
#endif

static int ztest_fd_data = -1;
static int ztest_fd_rand = -1;

typedef struct ztest_shared_hdr {
        uint64_t        zh_hdr_size;
        uint64_t        zh_opts_size;
        uint64_t        zh_size;
        uint64_t        zh_stats_size;
        uint64_t        zh_stats_count;
        uint64_t        zh_ds_size;
        uint64_t        zh_ds_count;
} ztest_shared_hdr_t;

static ztest_shared_hdr_t *ztest_shared_hdr;

typedef struct ztest_shared_opts {
        char zo_pool[ZFS_MAX_DATASET_NAME_LEN];
        char zo_dir[ZFS_MAX_DATASET_NAME_LEN];
        char zo_alt_ztest[MAXNAMELEN];
        char zo_alt_libpath[MAXNAMELEN];
        uint64_t zo_vdevs;
        uint64_t zo_vdevtime;
        size_t zo_vdev_size;
        int zo_ashift;
        int zo_mirrors;
        int zo_raidz;
        int zo_raidz_parity;
        int zo_datasets;
        int zo_threads;
        uint64_t zo_passtime;
        uint64_t zo_killrate;
        int zo_verbose;
        int zo_init;
        uint64_t zo_time;
        uint64_t zo_maxloops;
        uint64_t zo_metaslab_gang_bang;
} ztest_shared_opts_t;

static const ztest_shared_opts_t ztest_opts_defaults = {
        .zo_pool = { 'z', 't', 'e', 's', 't', '\0' },
        .zo_dir = { '/', 't', 'm', 'p', '\0' },
        .zo_alt_ztest = { '\0' },
        .zo_alt_libpath = { '\0' },
        .zo_vdevs = 5,
        .zo_ashift = SPA_MINBLOCKSHIFT,
        .zo_mirrors = 2,
        .zo_raidz = 4,
        .zo_raidz_parity = 1,
        .zo_vdev_size = SPA_MINDEVSIZE * 4,     /* 256m default size */
        .zo_datasets = 7,
        .zo_threads = 23,
        .zo_passtime = 60,              /* 60 seconds */
        .zo_killrate = 70,              /* 70% kill rate */
        .zo_verbose = 0,
        .zo_init = 1,
        .zo_time = 300,                 /* 5 minutes */
        .zo_maxloops = 50,              /* max loops during spa_freeze() */
        .zo_metaslab_gang_bang = 32 << 10
};

extern uint64_t metaslab_gang_bang;
extern uint64_t metaslab_df_alloc_threshold;
extern int metaslab_preload_limit;
extern boolean_t zfs_compressed_arc_enabled;
extern int  zfs_abd_scatter_enabled;

static ztest_shared_opts_t *ztest_shared_opts;
static ztest_shared_opts_t ztest_opts;

typedef struct ztest_shared_ds {
        uint64_t        zd_seq;
} ztest_shared_ds_t;

static ztest_shared_ds_t *ztest_shared_ds;
#define ZTEST_GET_SHARED_DS(d) (&ztest_shared_ds[d])

#define BT_MAGIC        0x123456789abcdefULL
#define MAXFAULTS() \
        (MAX(zs->zs_mirrors, 1) * (ztest_opts.zo_raidz_parity + 1) - 1)

enum ztest_io_type {
        ZTEST_IO_WRITE_TAG,
        ZTEST_IO_WRITE_PATTERN,
        ZTEST_IO_WRITE_ZEROES,
        ZTEST_IO_TRUNCATE,
        ZTEST_IO_SETATTR,
        ZTEST_IO_REWRITE,
        ZTEST_IO_TYPES
};

typedef struct ztest_block_tag {
        uint64_t        bt_magic;
        uint64_t        bt_objset;
        uint64_t        bt_object;
        uint64_t        bt_dnodesize;
        uint64_t        bt_offset;
        uint64_t        bt_gen;
        uint64_t        bt_txg;
        uint64_t        bt_crtxg;
} ztest_block_tag_t;

typedef struct bufwad {
        uint64_t        bw_index;
        uint64_t        bw_txg;
        uint64_t        bw_data;
} bufwad_t;

typedef struct rll {
        void            *rll_writer;
        int             rll_readers;
        kmutex_t        rll_lock;
        kcondvar_t      rll_cv;
} rll_t;

typedef struct zll {
        list_t z_list;
        kmutex_t z_lock;
} zll_t;

#define ZTEST_RANGE_LOCKS       64
#define ZTEST_OBJECT_LOCKS      64

/*
 * Object descriptor.  Used as a template for object lookup/create/remove.
 */
typedef struct ztest_od {
        uint64_t        od_dir;
        uint64_t        od_object;
        dmu_object_type_t od_type;
        dmu_object_type_t od_crtype;
        uint64_t        od_blocksize;
        uint64_t        od_crblocksize;
        uint64_t        od_crdnodesize;
        uint64_t        od_gen;
        uint64_t        od_crgen;
        char            od_name[ZFS_MAX_DATASET_NAME_LEN];
} ztest_od_t;

/*
 * Per-dataset state.
 */
typedef struct ztest_ds {
        ztest_shared_ds_t *zd_shared;
        objset_t        *zd_os;
        rwlock_t        zd_zilog_lock;
        zilog_t         *zd_zilog;
        ztest_od_t      *zd_od;         /* debugging aid */
        char            zd_name[ZFS_MAX_DATASET_NAME_LEN];
        kmutex_t        zd_dirobj_lock;
        rll_t           zd_object_lock[ZTEST_OBJECT_LOCKS];
        zll_t           zd_range_lock[ZTEST_RANGE_LOCKS];
} ztest_ds_t;

/*
 * Per-iteration state.
 */
typedef void ztest_func_t(ztest_ds_t *zd, uint64_t id);

typedef struct ztest_info {
        ztest_func_t    *zi_func;       /* test function */
        uint64_t        zi_iters;       /* iterations per execution */
        uint64_t        *zi_interval;   /* execute every <interval> seconds */
        const char      *zi_funcname;   /* name of test function */
} ztest_info_t;

typedef struct ztest_shared_callstate {
        uint64_t        zc_count;       /* per-pass count */
        uint64_t        zc_time;        /* per-pass time */
        uint64_t        zc_next;        /* next time to call this function */
} ztest_shared_callstate_t;

static ztest_shared_callstate_t *ztest_shared_callstate;
#define ZTEST_GET_SHARED_CALLSTATE(c) (&ztest_shared_callstate[c])

ztest_func_t ztest_dmu_read_write;
ztest_func_t ztest_dmu_write_parallel;
ztest_func_t ztest_dmu_object_alloc_free;
ztest_func_t ztest_dmu_commit_callbacks;
ztest_func_t ztest_zap;
ztest_func_t ztest_zap_parallel;
ztest_func_t ztest_zil_commit;
ztest_func_t ztest_zil_remount;
ztest_func_t ztest_dmu_read_write_zcopy;
ztest_func_t ztest_dmu_objset_create_destroy;
ztest_func_t ztest_dmu_prealloc;
ztest_func_t ztest_fzap;
ztest_func_t ztest_dmu_snapshot_create_destroy;
ztest_func_t ztest_dsl_prop_get_set;
ztest_func_t ztest_spa_prop_get_set;
ztest_func_t ztest_spa_create_destroy;
ztest_func_t ztest_fault_inject;
ztest_func_t ztest_ddt_repair;
ztest_func_t ztest_dmu_snapshot_hold;
ztest_func_t ztest_spa_rename;
ztest_func_t ztest_scrub;
ztest_func_t ztest_dsl_dataset_promote_busy;
ztest_func_t ztest_vdev_attach_detach;
ztest_func_t ztest_vdev_LUN_growth;
ztest_func_t ztest_vdev_add_remove;
ztest_func_t ztest_vdev_aux_add_remove;
ztest_func_t ztest_split_pool;
ztest_func_t ztest_reguid;
ztest_func_t ztest_spa_upgrade;
ztest_func_t ztest_fletcher;
ztest_func_t ztest_fletcher_incr;
ztest_func_t ztest_verify_dnode_bt;

uint64_t zopt_always = 0ULL * NANOSEC;          /* all the time */
uint64_t zopt_incessant = 1ULL * NANOSEC / 10;  /* every 1/10 second */
uint64_t zopt_often = 1ULL * NANOSEC;           /* every second */
uint64_t zopt_sometimes = 10ULL * NANOSEC;      /* every 10 seconds */
uint64_t zopt_rarely = 60ULL * NANOSEC;         /* every 60 seconds */

#define ZTI_INIT(func, iters, interval) \
        {   .zi_func = (func), \
            .zi_iters = (iters), \
            .zi_interval = (interval), \
            .zi_funcname = # func }

ztest_info_t ztest_info[] = {
        ZTI_INIT(ztest_dmu_read_write, 1, &zopt_always),
        ZTI_INIT(ztest_dmu_write_parallel, 10, &zopt_always),
        ZTI_INIT(ztest_dmu_object_alloc_free, 1, &zopt_always),
        ZTI_INIT(ztest_dmu_commit_callbacks, 1, &zopt_always),
        ZTI_INIT(ztest_zap, 30, &zopt_always),
        ZTI_INIT(ztest_zap_parallel, 100, &zopt_always),
        ZTI_INIT(ztest_split_pool, 1, &zopt_always),
        ZTI_INIT(ztest_zil_commit, 1, &zopt_incessant),
        ZTI_INIT(ztest_zil_remount, 1, &zopt_sometimes),
        ZTI_INIT(ztest_dmu_read_write_zcopy, 1, &zopt_often),
        ZTI_INIT(ztest_dmu_objset_create_destroy, 1, &zopt_often),
        ZTI_INIT(ztest_dsl_prop_get_set, 1, &zopt_often),
        ZTI_INIT(ztest_spa_prop_get_set, 1, &zopt_sometimes),
#if 0
        ZTI_INIT(ztest_dmu_prealloc, 1, &zopt_sometimes),
#endif
        ZTI_INIT(ztest_fzap, 1, &zopt_sometimes),
        ZTI_INIT(ztest_dmu_snapshot_create_destroy, 1, &zopt_sometimes),
        ZTI_INIT(ztest_spa_create_destroy, 1, &zopt_sometimes),
        ZTI_INIT(ztest_fault_inject, 1, &zopt_sometimes),
        ZTI_INIT(ztest_ddt_repair, 1, &zopt_sometimes),
        ZTI_INIT(ztest_dmu_snapshot_hold, 1, &zopt_sometimes),
        ZTI_INIT(ztest_reguid, 1, &zopt_rarely),
        ZTI_INIT(ztest_spa_rename, 1, &zopt_rarely),
        ZTI_INIT(ztest_scrub, 1, &zopt_rarely),
        ZTI_INIT(ztest_spa_upgrade, 1, &zopt_rarely),
        ZTI_INIT(ztest_dsl_dataset_promote_busy, 1, &zopt_rarely),
        ZTI_INIT(ztest_vdev_attach_detach, 1, &zopt_sometimes),
        ZTI_INIT(ztest_vdev_LUN_growth, 1, &zopt_rarely),
        ZTI_INIT(ztest_vdev_add_remove, 1, &ztest_opts.zo_vdevtime),
        ZTI_INIT(ztest_vdev_aux_add_remove, 1, &ztest_opts.zo_vdevtime),
        ZTI_INIT(ztest_fletcher, 1, &zopt_rarely),
        ZTI_INIT(ztest_fletcher_incr, 1, &zopt_rarely),
        ZTI_INIT(ztest_verify_dnode_bt, 1, &zopt_sometimes),
};

#define ZTEST_FUNCS     (sizeof (ztest_info) / sizeof (ztest_info_t))

/*
 * The following struct is used to hold a list of uncalled commit callbacks.
 * The callbacks are ordered by txg number.
 */
typedef struct ztest_cb_list {
        kmutex_t        zcl_callbacks_lock;
        list_t          zcl_callbacks;
} ztest_cb_list_t;

/*
 * Stuff we need to share writably between parent and child.
 */
typedef struct ztest_shared {
        boolean_t       zs_do_init;
        hrtime_t        zs_proc_start;
        hrtime_t        zs_proc_stop;
        hrtime_t        zs_thread_start;
        hrtime_t        zs_thread_stop;
        hrtime_t        zs_thread_kill;
        uint64_t        zs_enospc_count;
        uint64_t        zs_vdev_next_leaf;
        uint64_t        zs_vdev_aux;
        uint64_t        zs_alloc;
        uint64_t        zs_space;
        uint64_t        zs_splits;
        uint64_t        zs_mirrors;
        uint64_t        zs_metaslab_sz;
        uint64_t        zs_metaslab_df_alloc_threshold;
        uint64_t        zs_guid;
} ztest_shared_t;

#define ID_PARALLEL     -1ULL

static char ztest_dev_template[] = "%s/%s.%llua";
static char ztest_aux_template[] = "%s/%s.%s.%llu";
ztest_shared_t *ztest_shared;

static spa_t *ztest_spa = NULL;
static ztest_ds_t *ztest_ds;

static kmutex_t ztest_vdev_lock;

/*
 * The ztest_name_lock protects the pool and dataset namespace used by
 * the individual tests. To modify the namespace, consumers must grab
 * this lock as writer. Grabbing the lock as reader will ensure that the
 * namespace does not change while the lock is held.
 */
static rwlock_t ztest_name_lock;

static boolean_t ztest_dump_core = B_TRUE;
static boolean_t ztest_exiting;

/* Global commit callback list */
static ztest_cb_list_t zcl;
/* Commit cb delay */
static uint64_t zc_min_txg_delay = UINT64_MAX;
static int zc_cb_counter = 0;

/*
 * Minimum number of commit callbacks that need to be registered for us to check
 * whether the minimum txg delay is acceptable.
 */
#define ZTEST_COMMIT_CB_MIN_REG 100

/*
 * If a number of txgs equal to this threshold have been created after a commit
 * callback has been registered but not called, then we assume there is an
 * implementation bug.
 */
#define ZTEST_COMMIT_CB_THRESH  (TXG_CONCURRENT_STATES + 1000)

extern uint64_t metaslab_gang_bang;
extern uint64_t metaslab_df_alloc_threshold;

enum ztest_object {
        ZTEST_META_DNODE = 0,
        ZTEST_DIROBJ,
        ZTEST_OBJECTS
};

static void usage(boolean_t) __NORETURN;

/*
 * These libumem hooks provide a reasonable set of defaults for the allocator's
 * debugging facilities.
 */
const char *
_umem_debug_init(void)
{
        return ("default,verbose"); /* $UMEM_DEBUG setting */
}

const char *
_umem_logging_init(void)
{
        return ("fail,contents"); /* $UMEM_LOGGING setting */
}

#define BACKTRACE_SZ    100

static void sig_handler(int signo)
{
        struct sigaction action;
#ifdef __GLIBC__ /* backtrace() is a GNU extension */
        int nptrs;
        void *buffer[BACKTRACE_SZ];

        nptrs = backtrace(buffer, BACKTRACE_SZ);
        backtrace_symbols_fd(buffer, nptrs, STDERR_FILENO);
#endif

        /*
         * Restore default action and re-raise signal so SIGSEGV and
         * SIGABRT can trigger a core dump.
         */
        action.sa_handler = SIG_DFL;
        sigemptyset(&action.sa_mask);
        action.sa_flags = 0;
        (void) sigaction(signo, &action, NULL);
        raise(signo);
}

#define FATAL_MSG_SZ    1024

char *fatal_msg;

static void
fatal(int do_perror, char *message, ...)
{
        va_list args;
        int save_errno = errno;
        char *buf;

        (void) fflush(stdout);
        buf = umem_alloc(FATAL_MSG_SZ, UMEM_NOFAIL);

        va_start(args, message);
        (void) sprintf(buf, "ztest: ");
        /* LINTED */
        (void) vsprintf(buf + strlen(buf), message, args);
        va_end(args);
        if (do_perror) {
                (void) snprintf(buf + strlen(buf), FATAL_MSG_SZ - strlen(buf),
                    ": %s", strerror(save_errno));
        }
        (void) fprintf(stderr, "%s\n", buf);
        fatal_msg = buf;                        /* to ease debugging */
        if (ztest_dump_core)
                abort();
        exit(3);
}

static int
str2shift(const char *buf)
{
        const char *ends = "BKMGTPEZ";
        int i;

        if (buf[0] == '\0')
                return (0);
        for (i = 0; i < strlen(ends); i++) {
                if (toupper(buf[0]) == ends[i])
                        break;
        }
        if (i == strlen(ends)) {
                (void) fprintf(stderr, "ztest: invalid bytes suffix: %s\n",
                    buf);
                usage(B_FALSE);
        }
        if (buf[1] == '\0' || (toupper(buf[1]) == 'B' && buf[2] == '\0')) {
                return (10*i);
        }
        (void) fprintf(stderr, "ztest: invalid bytes suffix: %s\n", buf);
        usage(B_FALSE);
        /* NOTREACHED */
}

static uint64_t
nicenumtoull(const char *buf)
{
        char *end;
        uint64_t val;

        val = strtoull(buf, &end, 0);
        if (end == buf) {
                (void) fprintf(stderr, "ztest: bad numeric value: %s\n", buf);
                usage(B_FALSE);
        } else if (end[0] == '.') {
                double fval = strtod(buf, &end);
                fval *= pow(2, str2shift(end));
                if (fval > UINT64_MAX) {
                        (void) fprintf(stderr, "ztest: value too large: %s\n",
                            buf);
                        usage(B_FALSE);
                }
                val = (uint64_t)fval;
        } else {
                int shift = str2shift(end);
                if (shift >= 64 || (val << shift) >> shift != val) {
                        (void) fprintf(stderr, "ztest: value too large: %s\n",
                            buf);
                        usage(B_FALSE);
                }
                val <<= shift;
        }
        return (val);
}

static void
usage(boolean_t requested)
{
        const ztest_shared_opts_t *zo = &ztest_opts_defaults;

        char nice_vdev_size[10];
        char nice_gang_bang[10];
        FILE *fp = requested ? stdout : stderr;

        nicenum(zo->zo_vdev_size, nice_vdev_size);
        nicenum(zo->zo_metaslab_gang_bang, nice_gang_bang);

        (void) fprintf(fp, "Usage: %s\n"
            "\t[-v vdevs (default: %llu)]\n"
            "\t[-s size_of_each_vdev (default: %s)]\n"
            "\t[-a alignment_shift (default: %d)] use 0 for random\n"
            "\t[-m mirror_copies (default: %d)]\n"
            "\t[-r raidz_disks (default: %d)]\n"
            "\t[-R raidz_parity (default: %d)]\n"
            "\t[-d datasets (default: %d)]\n"
            "\t[-t threads (default: %d)]\n"
            "\t[-g gang_block_threshold (default: %s)]\n"
            "\t[-i init_count (default: %d)] initialize pool i times\n"
            "\t[-k kill_percentage (default: %llu%%)]\n"
            "\t[-p pool_name (default: %s)]\n"
            "\t[-f dir (default: %s)] file directory for vdev files\n"
            "\t[-V] verbose (use multiple times for ever more blather)\n"
            "\t[-E] use existing pool instead of creating new one\n"
            "\t[-T time (default: %llu sec)] total run time\n"
            "\t[-F freezeloops (default: %llu)] max loops in spa_freeze()\n"
            "\t[-P passtime (default: %llu sec)] time per pass\n"
            "\t[-B alt_ztest (default: <none>)] alternate ztest path\n"
            "\t[-o variable=value] ... set global variable to an unsigned\n"
            "\t    32-bit integer value\n"
            "\t[-h] (print help)\n"
            "",
            zo->zo_pool,
            (u_longlong_t)zo->zo_vdevs,                 /* -v */
            nice_vdev_size,                             /* -s */
            zo->zo_ashift,                              /* -a */
            zo->zo_mirrors,                             /* -m */
            zo->zo_raidz,                               /* -r */
            zo->zo_raidz_parity,                        /* -R */
            zo->zo_datasets,                            /* -d */
            zo->zo_threads,                             /* -t */
            nice_gang_bang,                             /* -g */
            zo->zo_init,                                /* -i */
            (u_longlong_t)zo->zo_killrate,              /* -k */
            zo->zo_pool,                                /* -p */
            zo->zo_dir,                                 /* -f */
            (u_longlong_t)zo->zo_time,                  /* -T */
            (u_longlong_t)zo->zo_maxloops,              /* -F */
            (u_longlong_t)zo->zo_passtime);
        exit(requested ? 0 : 1);
}

static void
process_options(int argc, char **argv)
{
        char *path;
        ztest_shared_opts_t *zo = &ztest_opts;

        int opt;
        uint64_t value;
        char altdir[MAXNAMELEN] = { 0 };

        bcopy(&ztest_opts_defaults, zo, sizeof (*zo));

        while ((opt = getopt(argc, argv,
            "v:s:a:m:r:R:d:t:g:i:k:p:f:VET:P:hF:B:o:")) != EOF) {
                value = 0;
                switch (opt) {
                case 'v':
                case 's':
                case 'a':
                case 'm':
                case 'r':
                case 'R':
                case 'd':
                case 't':
                case 'g':
                case 'i':
                case 'k':
                case 'T':
                case 'P':
                case 'F':
                        value = nicenumtoull(optarg);
                }
                switch (opt) {
                case 'v':
                        zo->zo_vdevs = value;
                        break;
                case 's':
                        zo->zo_vdev_size = MAX(SPA_MINDEVSIZE, value);
                        break;
                case 'a':
                        zo->zo_ashift = value;
                        break;
                case 'm':
                        zo->zo_mirrors = value;
                        break;
                case 'r':
                        zo->zo_raidz = MAX(1, value);
                        break;
                case 'R':
                        zo->zo_raidz_parity = MIN(MAX(value, 1), 3);
                        break;
                case 'd':
                        zo->zo_datasets = MAX(1, value);
                        break;
                case 't':
                        zo->zo_threads = MAX(1, value);
                        break;
                case 'g':
                        zo->zo_metaslab_gang_bang = MAX(SPA_MINBLOCKSIZE << 1,
                            value);
                        break;
                case 'i':
                        zo->zo_init = value;
                        break;
                case 'k':
                        zo->zo_killrate = value;
                        break;
                case 'p':
                        (void) strlcpy(zo->zo_pool, optarg,
                            sizeof (zo->zo_pool));
                        break;
                case 'f':
                        path = realpath(optarg, NULL);
                        if (path == NULL) {
                                (void) fprintf(stderr, "error: %s: %s\n",
                                    optarg, strerror(errno));
                                usage(B_FALSE);
                        } else {
                                (void) strlcpy(zo->zo_dir, path,
                                    sizeof (zo->zo_dir));
                                free(path);
                        }
                        break;
                case 'V':
                        zo->zo_verbose++;
                        break;
                case 'E':
                        zo->zo_init = 0;
                        break;
                case 'T':
                        zo->zo_time = value;
                        break;
                case 'P':
                        zo->zo_passtime = MAX(1, value);
                        break;
                case 'F':
                        zo->zo_maxloops = MAX(1, value);
                        break;
                case 'B':
                        (void) strlcpy(altdir, optarg, sizeof (altdir));
                        break;
                case 'o':
                        if (set_global_var(optarg) != 0)
                                usage(B_FALSE);
                        break;
                case 'h':
                        usage(B_TRUE);
                        break;
                case '?':
                default:
                        usage(B_FALSE);
                        break;
                }
        }

        zo->zo_raidz_parity = MIN(zo->zo_raidz_parity, zo->zo_raidz - 1);

        zo->zo_vdevtime =
            (zo->zo_vdevs > 0 ? zo->zo_time * NANOSEC / zo->zo_vdevs :
            UINT64_MAX >> 2);

        if (strlen(altdir) > 0) {
                char *cmd;
                char *realaltdir;
                char *bin;
                char *ztest;
                char *isa;
                int isalen;

                cmd = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
                realaltdir = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);

                VERIFY(NULL != realpath(getexecname(), cmd));
                if (0 != access(altdir, F_OK)) {
                        ztest_dump_core = B_FALSE;
                        fatal(B_TRUE, "invalid alternate ztest path: %s",
                            altdir);
                }
                VERIFY(NULL != realpath(altdir, realaltdir));

                /*
                 * 'cmd' should be of the form "<anything>/usr/bin/<isa>/ztest".
                 * We want to extract <isa> to determine if we should use
                 * 32 or 64 bit binaries.
                 */
                bin = strstr(cmd, "/usr/bin/");
                ztest = strstr(bin, "/ztest");
                isa = bin + 9;
                isalen = ztest - isa;
                (void) snprintf(zo->zo_alt_ztest, sizeof (zo->zo_alt_ztest),
                    "%s/usr/bin/%.*s/ztest", realaltdir, isalen, isa);
                (void) snprintf(zo->zo_alt_libpath, sizeof (zo->zo_alt_libpath),
                    "%s/usr/lib/%.*s", realaltdir, isalen, isa);

                if (0 != access(zo->zo_alt_ztest, X_OK)) {
                        ztest_dump_core = B_FALSE;
                        fatal(B_TRUE, "invalid alternate ztest: %s",
                            zo->zo_alt_ztest);
                } else if (0 != access(zo->zo_alt_libpath, X_OK)) {
                        ztest_dump_core = B_FALSE;
                        fatal(B_TRUE, "invalid alternate lib directory %s",
                            zo->zo_alt_libpath);
                }

                umem_free(cmd, MAXPATHLEN);
                umem_free(realaltdir, MAXPATHLEN);
        }
}

static void
ztest_kill(ztest_shared_t *zs)
{
        zs->zs_alloc = metaslab_class_get_alloc(spa_normal_class(ztest_spa));
        zs->zs_space = metaslab_class_get_space(spa_normal_class(ztest_spa));

        /*
         * Before we kill off ztest, make sure that the config is updated.
         * See comment above spa_config_sync().
         */
        mutex_enter(&spa_namespace_lock);
        spa_config_sync(ztest_spa, B_FALSE, B_FALSE);
        mutex_exit(&spa_namespace_lock);

        (void) kill(getpid(), SIGKILL);
}

static uint64_t
ztest_random(uint64_t range)
{
        uint64_t r;

        ASSERT3S(ztest_fd_rand, >=, 0);

        if (range == 0)
                return (0);

        if (read(ztest_fd_rand, &r, sizeof (r)) != sizeof (r))
                fatal(1, "short read from /dev/urandom");

        return (r % range);
}

/* ARGSUSED */
static void
ztest_record_enospc(const char *s)
{
        ztest_shared->zs_enospc_count++;
}

static uint64_t
ztest_get_ashift(void)
{
        if (ztest_opts.zo_ashift == 0)
                return (SPA_MINBLOCKSHIFT + ztest_random(5));
        return (ztest_opts.zo_ashift);
}

static nvlist_t *
make_vdev_file(char *path, char *aux, char *pool, size_t size, uint64_t ashift)
{
        char *pathbuf;
        uint64_t vdev;
        nvlist_t *file;

        pathbuf = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);

        if (ashift == 0)
                ashift = ztest_get_ashift();

        if (path == NULL) {
                path = pathbuf;

                if (aux != NULL) {
                        vdev = ztest_shared->zs_vdev_aux;
                        (void) snprintf(path, MAXPATHLEN,
                            ztest_aux_template, ztest_opts.zo_dir,
                            pool == NULL ? ztest_opts.zo_pool : pool,
                            aux, vdev);
                } else {
                        vdev = ztest_shared->zs_vdev_next_leaf++;
                        (void) snprintf(path, MAXPATHLEN,
                            ztest_dev_template, ztest_opts.zo_dir,
                            pool == NULL ? ztest_opts.zo_pool : pool, vdev);
                }
        }

        if (size != 0) {
                int fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0666);
                if (fd == -1)
                        fatal(1, "can't open %s", path);
                if (ftruncate(fd, size) != 0)
                        fatal(1, "can't ftruncate %s", path);
                (void) close(fd);
        }

        VERIFY(nvlist_alloc(&file, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_string(file, ZPOOL_CONFIG_TYPE, VDEV_TYPE_FILE) == 0);
        VERIFY(nvlist_add_string(file, ZPOOL_CONFIG_PATH, path) == 0);
        VERIFY(nvlist_add_uint64(file, ZPOOL_CONFIG_ASHIFT, ashift) == 0);
        umem_free(pathbuf, MAXPATHLEN);

        return (file);
}

static nvlist_t *
make_vdev_raidz(char *path, char *aux, char *pool, size_t size,
    uint64_t ashift, int r)
{
        nvlist_t *raidz, **child;
        int c;

        if (r < 2)
                return (make_vdev_file(path, aux, pool, size, ashift));
        child = umem_alloc(r * sizeof (nvlist_t *), UMEM_NOFAIL);

        for (c = 0; c < r; c++)
                child[c] = make_vdev_file(path, aux, pool, size, ashift);

        VERIFY(nvlist_alloc(&raidz, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_string(raidz, ZPOOL_CONFIG_TYPE,
            VDEV_TYPE_RAIDZ) == 0);
        VERIFY(nvlist_add_uint64(raidz, ZPOOL_CONFIG_NPARITY,
            ztest_opts.zo_raidz_parity) == 0);
        VERIFY(nvlist_add_nvlist_array(raidz, ZPOOL_CONFIG_CHILDREN,
            child, r) == 0);

        for (c = 0; c < r; c++)
                nvlist_free(child[c]);

        umem_free(child, r * sizeof (nvlist_t *));

        return (raidz);
}

static nvlist_t *
make_vdev_mirror(char *path, char *aux, char *pool, size_t size,
    uint64_t ashift, int r, int m)
{
        nvlist_t *mirror, **child;
        int c;

        if (m < 1)
                return (make_vdev_raidz(path, aux, pool, size, ashift, r));

        child = umem_alloc(m * sizeof (nvlist_t *), UMEM_NOFAIL);

        for (c = 0; c < m; c++)
                child[c] = make_vdev_raidz(path, aux, pool, size, ashift, r);

        VERIFY(nvlist_alloc(&mirror, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_string(mirror, ZPOOL_CONFIG_TYPE,
            VDEV_TYPE_MIRROR) == 0);
        VERIFY(nvlist_add_nvlist_array(mirror, ZPOOL_CONFIG_CHILDREN,
            child, m) == 0);

        for (c = 0; c < m; c++)
                nvlist_free(child[c]);

        umem_free(child, m * sizeof (nvlist_t *));

        return (mirror);
}

static nvlist_t *
make_vdev_root(char *path, char *aux, char *pool, size_t size, uint64_t ashift,
    int log, int r, int m, int t)
{
        nvlist_t *root, **child;
        int c;

        ASSERT(t > 0);

        child = umem_alloc(t * sizeof (nvlist_t *), UMEM_NOFAIL);

        for (c = 0; c < t; c++) {
                child[c] = make_vdev_mirror(path, aux, pool, size, ashift,
                    r, m);
                VERIFY(nvlist_add_uint64(child[c], ZPOOL_CONFIG_IS_LOG,
                    log) == 0);
        }

        VERIFY(nvlist_alloc(&root, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_string(root, ZPOOL_CONFIG_TYPE, VDEV_TYPE_ROOT) == 0);
        VERIFY(nvlist_add_nvlist_array(root, aux ? aux : ZPOOL_CONFIG_CHILDREN,
            child, t) == 0);

        for (c = 0; c < t; c++)
                nvlist_free(child[c]);

        umem_free(child, t * sizeof (nvlist_t *));

        return (root);
}

/*
 * Find a random spa version. Returns back a random spa version in the
 * range [initial_version, SPA_VERSION_FEATURES].
 */
static uint64_t
ztest_random_spa_version(uint64_t initial_version)
{
        uint64_t version = initial_version;

        if (version <= SPA_VERSION_BEFORE_FEATURES) {
                version = version +
                    ztest_random(SPA_VERSION_BEFORE_FEATURES - version + 1);
        }

        if (version > SPA_VERSION_BEFORE_FEATURES)
                version = SPA_VERSION_FEATURES;

        ASSERT(SPA_VERSION_IS_SUPPORTED(version));
        return (version);
}

static int
ztest_random_blocksize(void)
{
        /*
         * Choose a block size >= the ashift.
         * If the SPA supports new MAXBLOCKSIZE, test up to 1MB blocks.
         */
        int maxbs = SPA_OLD_MAXBLOCKSHIFT;
        if (spa_maxblocksize(ztest_spa) == SPA_MAXBLOCKSIZE)
                maxbs = 20;
        uint64_t block_shift =
            ztest_random(maxbs - ztest_spa->spa_max_ashift + 1);
        return (1 << (SPA_MINBLOCKSHIFT + block_shift));
}

static int
ztest_random_dnodesize(void)
{
        int slots;
        int max_slots = spa_maxdnodesize(ztest_spa) >> DNODE_SHIFT;

        if (max_slots == DNODE_MIN_SLOTS)
                return (DNODE_MIN_SIZE);

        /*
         * Weight the random distribution more heavily toward smaller
         * dnode sizes since that is more likely to reflect real-world
         * usage.
         */
        ASSERT3U(max_slots, >, 4);
        switch (ztest_random(10)) {
        case 0:
                slots = 5 + ztest_random(max_slots - 4);
                break;
        case 1 ... 4:
                slots = 2 + ztest_random(3);
                break;
        default:
                slots = 1;
                break;
        }

        return (slots << DNODE_SHIFT);
}

static int
ztest_random_ibshift(void)
{
        return (DN_MIN_INDBLKSHIFT +
            ztest_random(DN_MAX_INDBLKSHIFT - DN_MIN_INDBLKSHIFT + 1));
}

static uint64_t
ztest_random_vdev_top(spa_t *spa, boolean_t log_ok)
{
        uint64_t top;
        vdev_t *rvd = spa->spa_root_vdev;
        vdev_t *tvd;

        ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);

        do {
                top = ztest_random(rvd->vdev_children);
                tvd = rvd->vdev_child[top];
        } while (tvd->vdev_ishole || (tvd->vdev_islog && !log_ok) ||
            tvd->vdev_mg == NULL || tvd->vdev_mg->mg_class == NULL);

        return (top);
}

static uint64_t
ztest_random_dsl_prop(zfs_prop_t prop)
{
        uint64_t value;

        do {
                value = zfs_prop_random_value(prop, ztest_random(-1ULL));
        } while (prop == ZFS_PROP_CHECKSUM && value == ZIO_CHECKSUM_OFF);

        return (value);
}

static int
ztest_dsl_prop_set_uint64(char *osname, zfs_prop_t prop, uint64_t value,
    boolean_t inherit)
{
        const char *propname = zfs_prop_to_name(prop);
        const char *valname;
        char *setpoint;
        uint64_t curval;
        int error;

        error = dsl_prop_set_int(osname, propname,
            (inherit ? ZPROP_SRC_NONE : ZPROP_SRC_LOCAL), value);

        if (error == ENOSPC) {
                ztest_record_enospc(FTAG);
                return (error);
        }
        ASSERT0(error);

        setpoint = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
        VERIFY0(dsl_prop_get_integer(osname, propname, &curval, setpoint));

        if (ztest_opts.zo_verbose >= 6) {
                int err;

                err = zfs_prop_index_to_string(prop, curval, &valname);
                if (err)
                        (void) printf("%s %s = %llu at '%s'\n", osname,
                            propname, (unsigned long long)curval, setpoint);
                else
                        (void) printf("%s %s = %s at '%s'\n",
                            osname, propname, valname, setpoint);
        }
        umem_free(setpoint, MAXPATHLEN);

        return (error);
}

static int
ztest_spa_prop_set_uint64(zpool_prop_t prop, uint64_t value)
{
        spa_t *spa = ztest_spa;
        nvlist_t *props = NULL;
        int error;

        VERIFY(nvlist_alloc(&props, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_uint64(props, zpool_prop_to_name(prop), value) == 0);

        error = spa_prop_set(spa, props);

        nvlist_free(props);

        if (error == ENOSPC) {
                ztest_record_enospc(FTAG);
                return (error);
        }
        ASSERT0(error);

        return (error);
}


/*
 * Object and range lock mechanics
 */
typedef struct {
        list_node_t z_lnode;
        refcount_t z_refcnt;
        uint64_t z_object;
        zfs_rlock_t z_range_lock;
} ztest_znode_t;

typedef struct {
        rl_t *z_rl;
        ztest_znode_t *z_ztznode;
} ztest_zrl_t;

static ztest_znode_t *
ztest_znode_init(uint64_t object)
{
        ztest_znode_t *zp = umem_alloc(sizeof (*zp), UMEM_NOFAIL);

        list_link_init(&zp->z_lnode);
        refcount_create(&zp->z_refcnt);
        zp->z_object = object;
        zfs_rlock_init(&zp->z_range_lock);

        return (zp);
}

static void
ztest_znode_fini(ztest_znode_t *zp)
{
        ASSERT(refcount_is_zero(&zp->z_refcnt));
        zfs_rlock_destroy(&zp->z_range_lock);
        zp->z_object = 0;
        refcount_destroy(&zp->z_refcnt);
        list_link_init(&zp->z_lnode);
        umem_free(zp, sizeof (*zp));
}

static void
ztest_zll_init(zll_t *zll)
{
        mutex_init(&zll->z_lock, NULL, MUTEX_DEFAULT, NULL);
        list_create(&zll->z_list, sizeof (ztest_znode_t),
            offsetof(ztest_znode_t, z_lnode));
}

static void
ztest_zll_destroy(zll_t *zll)
{
        list_destroy(&zll->z_list);
        mutex_destroy(&zll->z_lock);
}

#define RL_TAG "range_lock"
static ztest_znode_t *
ztest_znode_get(ztest_ds_t *zd, uint64_t object)
{
        zll_t *zll = &zd->zd_range_lock[object & (ZTEST_OBJECT_LOCKS - 1)];
        ztest_znode_t *zp = NULL;
        mutex_enter(&zll->z_lock);
        for (zp = list_head(&zll->z_list); (zp);
            zp = list_next(&zll->z_list, zp)) {
                if (zp->z_object == object) {
                        refcount_add(&zp->z_refcnt, RL_TAG);
                        break;
                }
        }
        if (zp == NULL) {
                zp = ztest_znode_init(object);
                refcount_add(&zp->z_refcnt, RL_TAG);
                list_insert_head(&zll->z_list, zp);
        }
        mutex_exit(&zll->z_lock);
        return (zp);
}

static void
ztest_znode_put(ztest_ds_t *zd, ztest_znode_t *zp)
{
        zll_t *zll = NULL;
        ASSERT3U(zp->z_object, !=, 0);
        zll = &zd->zd_range_lock[zp->z_object & (ZTEST_OBJECT_LOCKS - 1)];
        mutex_enter(&zll->z_lock);
        refcount_remove(&zp->z_refcnt, RL_TAG);
        if (refcount_is_zero(&zp->z_refcnt)) {
                list_remove(&zll->z_list, zp);
                ztest_znode_fini(zp);
        }
        mutex_exit(&zll->z_lock);
}


static void
ztest_rll_init(rll_t *rll)
{
        rll->rll_writer = NULL;
        rll->rll_readers = 0;
        mutex_init(&rll->rll_lock, NULL, MUTEX_DEFAULT, NULL);
        cv_init(&rll->rll_cv, NULL, CV_DEFAULT, NULL);
}

static void
ztest_rll_destroy(rll_t *rll)
{
        ASSERT(rll->rll_writer == NULL);
        ASSERT(rll->rll_readers == 0);
        mutex_destroy(&rll->rll_lock);
        cv_destroy(&rll->rll_cv);
}

static void
ztest_rll_lock(rll_t *rll, rl_type_t type)
{
        mutex_enter(&rll->rll_lock);

        if (type == RL_READER) {
                while (rll->rll_writer != NULL)
                        (void) cv_wait(&rll->rll_cv, &rll->rll_lock);
                rll->rll_readers++;
        } else {
                while (rll->rll_writer != NULL || rll->rll_readers)
                        (void) cv_wait(&rll->rll_cv, &rll->rll_lock);
                rll->rll_writer = curthread;
        }

        mutex_exit(&rll->rll_lock);
}

static void
ztest_rll_unlock(rll_t *rll)
{
        mutex_enter(&rll->rll_lock);

        if (rll->rll_writer) {
                ASSERT(rll->rll_readers == 0);
                rll->rll_writer = NULL;
        } else {
                ASSERT(rll->rll_readers != 0);
                ASSERT(rll->rll_writer == NULL);
                rll->rll_readers--;
        }

        if (rll->rll_writer == NULL && rll->rll_readers == 0)
                cv_broadcast(&rll->rll_cv);

        mutex_exit(&rll->rll_lock);
}

static void
ztest_object_lock(ztest_ds_t *zd, uint64_t object, rl_type_t type)
{
        rll_t *rll = &zd->zd_object_lock[object & (ZTEST_OBJECT_LOCKS - 1)];

        ztest_rll_lock(rll, type);
}

static void
ztest_object_unlock(ztest_ds_t *zd, uint64_t object)
{
        rll_t *rll = &zd->zd_object_lock[object & (ZTEST_OBJECT_LOCKS - 1)];

        ztest_rll_unlock(rll);
}

static ztest_zrl_t *
ztest_zrl_init(rl_t *rl, ztest_znode_t *zp)
{
        ztest_zrl_t *zrl = umem_alloc(sizeof (*zrl), UMEM_NOFAIL);
        zrl->z_rl = rl;
        zrl->z_ztznode = zp;
        return (zrl);
}

static void
ztest_zrl_fini(ztest_zrl_t *zrl)
{
        umem_free(zrl, sizeof (*zrl));
}

static ztest_zrl_t *
ztest_range_lock(ztest_ds_t *zd, uint64_t object, uint64_t offset,
    uint64_t size, rl_type_t type)
{
        ztest_znode_t *zp = ztest_znode_get(zd, object);
        rl_t *rl = zfs_range_lock(&zp->z_range_lock, offset,
            size, type);
        return (ztest_zrl_init(rl, zp));
}

static void
ztest_range_unlock(ztest_ds_t *zd, ztest_zrl_t *zrl)
{
        zfs_range_unlock(zrl->z_rl);
        ztest_znode_put(zd, zrl->z_ztznode);
        ztest_zrl_fini(zrl);
}

static void
ztest_zd_init(ztest_ds_t *zd, ztest_shared_ds_t *szd, objset_t *os)
{
        zd->zd_os = os;
        zd->zd_zilog = dmu_objset_zil(os);
        zd->zd_shared = szd;
        dmu_objset_name(os, zd->zd_name);
        int l;

        if (zd->zd_shared != NULL)
                zd->zd_shared->zd_seq = 0;

        VERIFY(rwlock_init(&zd->zd_zilog_lock, USYNC_THREAD, NULL) == 0);
        mutex_init(&zd->zd_dirobj_lock, NULL, MUTEX_DEFAULT, NULL);

        for (l = 0; l < ZTEST_OBJECT_LOCKS; l++)
                ztest_rll_init(&zd->zd_object_lock[l]);

        for (l = 0; l < ZTEST_RANGE_LOCKS; l++)
                ztest_zll_init(&zd->zd_range_lock[l]);
}

static void
ztest_zd_fini(ztest_ds_t *zd)
{
        int l;

        mutex_destroy(&zd->zd_dirobj_lock);
        (void) rwlock_destroy(&zd->zd_zilog_lock);

        for (l = 0; l < ZTEST_OBJECT_LOCKS; l++)
                ztest_rll_destroy(&zd->zd_object_lock[l]);

        for (l = 0; l < ZTEST_RANGE_LOCKS; l++)
                ztest_zll_destroy(&zd->zd_range_lock[l]);
}

#define TXG_MIGHTWAIT   (ztest_random(10) == 0 ? TXG_NOWAIT : TXG_WAIT)

static uint64_t
ztest_tx_assign(dmu_tx_t *tx, uint64_t txg_how, const char *tag)
{
        uint64_t txg;
        int error;

        /*
         * Attempt to assign tx to some transaction group.
         */
        error = dmu_tx_assign(tx, txg_how);
        if (error) {
                if (error == ERESTART) {
                        ASSERT(txg_how == TXG_NOWAIT);
                        dmu_tx_wait(tx);
                } else {
                        ASSERT3U(error, ==, ENOSPC);
                        ztest_record_enospc(tag);
                }
                dmu_tx_abort(tx);
                return (0);
        }
        txg = dmu_tx_get_txg(tx);
        ASSERT(txg != 0);
        return (txg);
}

static void
ztest_pattern_set(void *buf, uint64_t size, uint64_t value)
{
        uint64_t *ip = buf;
        uint64_t *ip_end = (uint64_t *)((uintptr_t)buf + (uintptr_t)size);

        while (ip < ip_end)
                *ip++ = value;
}

#ifndef NDEBUG
static boolean_t
ztest_pattern_match(void *buf, uint64_t size, uint64_t value)
{
        uint64_t *ip = buf;
        uint64_t *ip_end = (uint64_t *)((uintptr_t)buf + (uintptr_t)size);
        uint64_t diff = 0;

        while (ip < ip_end)
                diff |= (value - *ip++);

        return (diff == 0);
}
#endif

static void
ztest_bt_generate(ztest_block_tag_t *bt, objset_t *os, uint64_t object,
    uint64_t dnodesize, uint64_t offset, uint64_t gen, uint64_t txg,
    uint64_t crtxg)
{
        bt->bt_magic = BT_MAGIC;
        bt->bt_objset = dmu_objset_id(os);
        bt->bt_object = object;
        bt->bt_dnodesize = dnodesize;
        bt->bt_offset = offset;
        bt->bt_gen = gen;
        bt->bt_txg = txg;
        bt->bt_crtxg = crtxg;
}

static void
ztest_bt_verify(ztest_block_tag_t *bt, objset_t *os, uint64_t object,
    uint64_t dnodesize, uint64_t offset, uint64_t gen, uint64_t txg,
    uint64_t crtxg)
{
        ASSERT3U(bt->bt_magic, ==, BT_MAGIC);
        ASSERT3U(bt->bt_objset, ==, dmu_objset_id(os));
        ASSERT3U(bt->bt_object, ==, object);
        ASSERT3U(bt->bt_dnodesize, ==, dnodesize);
        ASSERT3U(bt->bt_offset, ==, offset);
        ASSERT3U(bt->bt_gen, <=, gen);
        ASSERT3U(bt->bt_txg, <=, txg);
        ASSERT3U(bt->bt_crtxg, ==, crtxg);
}

static ztest_block_tag_t *
ztest_bt_bonus(dmu_buf_t *db)
{
        dmu_object_info_t doi;
        ztest_block_tag_t *bt;

        dmu_object_info_from_db(db, &doi);
        ASSERT3U(doi.doi_bonus_size, <=, db->db_size);
        ASSERT3U(doi.doi_bonus_size, >=, sizeof (*bt));
        bt = (void *)((char *)db->db_data + doi.doi_bonus_size - sizeof (*bt));

        return (bt);
}

/*
 * Generate a token to fill up unused bonus buffer space.  Try to make
 * it unique to the object, generation, and offset to verify that data
 * is not getting overwritten by data from other dnodes.
 */
#define ZTEST_BONUS_FILL_TOKEN(obj, ds, gen, offset) \
        (((ds) << 48) | ((gen) << 32) | ((obj) << 8) | (offset))

/*
 * Fill up the unused bonus buffer region before the block tag with a
 * verifiable pattern. Filling the whole bonus area with non-zero data
 * helps ensure that all dnode traversal code properly skips the
 * interior regions of large dnodes.
 */
void
ztest_fill_unused_bonus(dmu_buf_t *db, void *end, uint64_t obj,
    objset_t *os, uint64_t gen)
{
        uint64_t *bonusp;

        ASSERT(IS_P2ALIGNED((char *)end - (char *)db->db_data, 8));

        for (bonusp = db->db_data; bonusp < (uint64_t *)end; bonusp++) {
                uint64_t token = ZTEST_BONUS_FILL_TOKEN(obj, dmu_objset_id(os),
                    gen, bonusp - (uint64_t *)db->db_data);
                *bonusp = token;
        }
}

/*
 * Verify that the unused area of a bonus buffer is filled with the
 * expected tokens.
 */
void
ztest_verify_unused_bonus(dmu_buf_t *db, void *end, uint64_t obj,
    objset_t *os, uint64_t gen)
{
        uint64_t *bonusp;

        for (bonusp = db->db_data; bonusp < (uint64_t *)end; bonusp++) {
                uint64_t token = ZTEST_BONUS_FILL_TOKEN(obj, dmu_objset_id(os),
                    gen, bonusp - (uint64_t *)db->db_data);
                VERIFY3U(*bonusp, ==, token);
        }
}

/*
 * ZIL logging ops
 */

#define lrz_type        lr_mode
#define lrz_blocksize   lr_uid
#define lrz_ibshift     lr_gid
#define lrz_bonustype   lr_rdev
#define lrz_dnodesize   lr_crtime[1]

static void
ztest_log_create(ztest_ds_t *zd, dmu_tx_t *tx, lr_create_t *lr)
{
        char *name = (void *)(lr + 1);          /* name follows lr */
        size_t namesize = strlen(name) + 1;
        itx_t *itx;

        if (zil_replaying(zd->zd_zilog, tx))
                return;

        itx = zil_itx_create(TX_CREATE, sizeof (*lr) + namesize);
        bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
            sizeof (*lr) + namesize - sizeof (lr_t));

        zil_itx_assign(zd->zd_zilog, itx, tx);
}

static void
ztest_log_remove(ztest_ds_t *zd, dmu_tx_t *tx, lr_remove_t *lr, uint64_t object)
{
        char *name = (void *)(lr + 1);          /* name follows lr */
        size_t namesize = strlen(name) + 1;
        itx_t *itx;

        if (zil_replaying(zd->zd_zilog, tx))
                return;

        itx = zil_itx_create(TX_REMOVE, sizeof (*lr) + namesize);
        bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
            sizeof (*lr) + namesize - sizeof (lr_t));

        itx->itx_oid = object;
        zil_itx_assign(zd->zd_zilog, itx, tx);
}

static void
ztest_log_write(ztest_ds_t *zd, dmu_tx_t *tx, lr_write_t *lr)
{
        itx_t *itx;
        itx_wr_state_t write_state = ztest_random(WR_NUM_STATES);

        if (zil_replaying(zd->zd_zilog, tx))
                return;

        if (lr->lr_length > ZIL_MAX_LOG_DATA)
                write_state = WR_INDIRECT;

        itx = zil_itx_create(TX_WRITE,
            sizeof (*lr) + (write_state == WR_COPIED ? lr->lr_length : 0));

        if (write_state == WR_COPIED &&
            dmu_read(zd->zd_os, lr->lr_foid, lr->lr_offset, lr->lr_length,
            ((lr_write_t *)&itx->itx_lr) + 1, DMU_READ_NO_PREFETCH) != 0) {
                zil_itx_destroy(itx);
                itx = zil_itx_create(TX_WRITE, sizeof (*lr));
                write_state = WR_NEED_COPY;
        }
        itx->itx_private = zd;
        itx->itx_wr_state = write_state;
        itx->itx_sync = (ztest_random(8) == 0);
        itx->itx_sod += (write_state == WR_NEED_COPY ? lr->lr_length : 0);

        bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
            sizeof (*lr) - sizeof (lr_t));

        zil_itx_assign(zd->zd_zilog, itx, tx);
}

static void
ztest_log_truncate(ztest_ds_t *zd, dmu_tx_t *tx, lr_truncate_t *lr)
{
        itx_t *itx;

        if (zil_replaying(zd->zd_zilog, tx))
                return;

        itx = zil_itx_create(TX_TRUNCATE, sizeof (*lr));
        bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
            sizeof (*lr) - sizeof (lr_t));

        itx->itx_sync = B_FALSE;
        zil_itx_assign(zd->zd_zilog, itx, tx);
}

static void
ztest_log_setattr(ztest_ds_t *zd, dmu_tx_t *tx, lr_setattr_t *lr)
{
        itx_t *itx;

        if (zil_replaying(zd->zd_zilog, tx))
                return;

        itx = zil_itx_create(TX_SETATTR, sizeof (*lr));
        bcopy(&lr->lr_common + 1, &itx->itx_lr + 1,
            sizeof (*lr) - sizeof (lr_t));

        itx->itx_sync = B_FALSE;
        zil_itx_assign(zd->zd_zilog, itx, tx);
}

/*
 * ZIL replay ops
 */
static int
ztest_replay_create(ztest_ds_t *zd, lr_create_t *lr, boolean_t byteswap)
{
        char *name = (void *)(lr + 1);          /* name follows lr */
        objset_t *os = zd->zd_os;
        ztest_block_tag_t *bbt;
        dmu_buf_t *db;
        dmu_tx_t *tx;
        uint64_t txg;
        int error = 0;
        int bonuslen;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        ASSERT(lr->lr_doid == ZTEST_DIROBJ);
        ASSERT(name[0] != '\0');

        tx = dmu_tx_create(os);

        dmu_tx_hold_zap(tx, lr->lr_doid, B_TRUE, name);

        if (lr->lrz_type == DMU_OT_ZAP_OTHER) {
                dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
        } else {
                dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
        }

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0)
                return (ENOSPC);

        ASSERT(dmu_objset_zil(os)->zl_replay == !!lr->lr_foid);
        bonuslen = DN_BONUS_SIZE(lr->lrz_dnodesize);

        if (lr->lrz_type == DMU_OT_ZAP_OTHER) {
                if (lr->lr_foid == 0) {
                        lr->lr_foid = zap_create_dnsize(os,
                            lr->lrz_type, lr->lrz_bonustype,
                            bonuslen, lr->lrz_dnodesize, tx);
                } else {
                        error = zap_create_claim_dnsize(os, lr->lr_foid,
                            lr->lrz_type, lr->lrz_bonustype,
                            bonuslen, lr->lrz_dnodesize, tx);
                }
        } else {
                if (lr->lr_foid == 0) {
                        lr->lr_foid = dmu_object_alloc_dnsize(os,
                            lr->lrz_type, 0, lr->lrz_bonustype,
                            bonuslen, lr->lrz_dnodesize, tx);
                } else {
                        error = dmu_object_claim_dnsize(os, lr->lr_foid,
                            lr->lrz_type, 0, lr->lrz_bonustype,
                            bonuslen, lr->lrz_dnodesize, tx);
                }
        }

        if (error) {
                ASSERT3U(error, ==, EEXIST);
                ASSERT(zd->zd_zilog->zl_replay);
                dmu_tx_commit(tx);
                return (error);
        }

        ASSERT(lr->lr_foid != 0);

        if (lr->lrz_type != DMU_OT_ZAP_OTHER)
                VERIFY3U(0, ==, dmu_object_set_blocksize(os, lr->lr_foid,
                    lr->lrz_blocksize, lr->lrz_ibshift, tx));

        VERIFY3U(0, ==, dmu_bonus_hold(os, lr->lr_foid, FTAG, &db));
        bbt = ztest_bt_bonus(db);
        dmu_buf_will_dirty(db, tx);
        ztest_bt_generate(bbt, os, lr->lr_foid, lr->lrz_dnodesize, -1ULL,
            lr->lr_gen, txg, txg);
        ztest_fill_unused_bonus(db, bbt, lr->lr_foid, os, lr->lr_gen);
        dmu_buf_rele(db, FTAG);

        VERIFY3U(0, ==, zap_add(os, lr->lr_doid, name, sizeof (uint64_t), 1,
            &lr->lr_foid, tx));

        (void) ztest_log_create(zd, tx, lr);

        dmu_tx_commit(tx);

        return (0);
}

static int
ztest_replay_remove(ztest_ds_t *zd, lr_remove_t *lr, boolean_t byteswap)
{
        char *name = (void *)(lr + 1);          /* name follows lr */
        objset_t *os = zd->zd_os;
        dmu_object_info_t doi;
        dmu_tx_t *tx;
        uint64_t object, txg;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        ASSERT(lr->lr_doid == ZTEST_DIROBJ);
        ASSERT(name[0] != '\0');

        VERIFY3U(0, ==,
            zap_lookup(os, lr->lr_doid, name, sizeof (object), 1, &object));
        ASSERT(object != 0);

        ztest_object_lock(zd, object, RL_WRITER);

        VERIFY3U(0, ==, dmu_object_info(os, object, &doi));

        tx = dmu_tx_create(os);

        dmu_tx_hold_zap(tx, lr->lr_doid, B_FALSE, name);
        dmu_tx_hold_free(tx, object, 0, DMU_OBJECT_END);

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0) {
                ztest_object_unlock(zd, object);
                return (ENOSPC);
        }

        if (doi.doi_type == DMU_OT_ZAP_OTHER) {
                VERIFY3U(0, ==, zap_destroy(os, object, tx));
        } else {
                VERIFY3U(0, ==, dmu_object_free(os, object, tx));
        }

        VERIFY3U(0, ==, zap_remove(os, lr->lr_doid, name, tx));

        (void) ztest_log_remove(zd, tx, lr, object);

        dmu_tx_commit(tx);

        ztest_object_unlock(zd, object);

        return (0);
}

static int
ztest_replay_write(ztest_ds_t *zd, lr_write_t *lr, boolean_t byteswap)
{
        objset_t *os = zd->zd_os;
        void *data = lr + 1;                    /* data follows lr */
        uint64_t offset, length;
        ztest_block_tag_t *bt = data;
        ztest_block_tag_t *bbt;
        uint64_t gen, txg, lrtxg, crtxg;
        dmu_object_info_t doi;
        dmu_tx_t *tx;
        dmu_buf_t *db;
        arc_buf_t *abuf = NULL;
        ztest_zrl_t *rl;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        offset = lr->lr_offset;
        length = lr->lr_length;

        /* If it's a dmu_sync() block, write the whole block */
        if (lr->lr_common.lrc_reclen == sizeof (lr_write_t)) {
                uint64_t blocksize = BP_GET_LSIZE(&lr->lr_blkptr);
                if (length < blocksize) {
                        offset -= offset % blocksize;
                        length = blocksize;
                }
        }

        if (bt->bt_magic == BSWAP_64(BT_MAGIC))
                byteswap_uint64_array(bt, sizeof (*bt));

        if (bt->bt_magic != BT_MAGIC)
                bt = NULL;

        ztest_object_lock(zd, lr->lr_foid, RL_READER);
        rl = ztest_range_lock(zd, lr->lr_foid, offset, length, RL_WRITER);

        VERIFY3U(0, ==, dmu_bonus_hold(os, lr->lr_foid, FTAG, &db));

        dmu_object_info_from_db(db, &doi);

        bbt = ztest_bt_bonus(db);
        ASSERT3U(bbt->bt_magic, ==, BT_MAGIC);
        gen = bbt->bt_gen;
        crtxg = bbt->bt_crtxg;
        lrtxg = lr->lr_common.lrc_txg;

        tx = dmu_tx_create(os);

        dmu_tx_hold_write(tx, lr->lr_foid, offset, length);

        if (ztest_random(8) == 0 && length == doi.doi_data_block_size &&
            P2PHASE(offset, length) == 0)
                abuf = dmu_request_arcbuf(db, length);

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0) {
                if (abuf != NULL)
                        dmu_return_arcbuf(abuf);
                dmu_buf_rele(db, FTAG);
                ztest_range_unlock(zd, rl);
                ztest_object_unlock(zd, lr->lr_foid);
                return (ENOSPC);
        }

        if (bt != NULL) {
                /*
                 * Usually, verify the old data before writing new data --
                 * but not always, because we also want to verify correct
                 * behavior when the data was not recently read into cache.
                 */
                ASSERT(offset % doi.doi_data_block_size == 0);
                if (ztest_random(4) != 0) {
                        int prefetch = ztest_random(2) ?
                            DMU_READ_PREFETCH : DMU_READ_NO_PREFETCH;
                        ztest_block_tag_t rbt;

                        VERIFY(dmu_read(os, lr->lr_foid, offset,
                            sizeof (rbt), &rbt, prefetch) == 0);
                        if (rbt.bt_magic == BT_MAGIC) {
                                ztest_bt_verify(&rbt, os, lr->lr_foid, 0,
                                    offset, gen, txg, crtxg);
                        }
                }

                /*
                 * Writes can appear to be newer than the bonus buffer because
                 * the ztest_get_data() callback does a dmu_read() of the
                 * open-context data, which may be different than the data
                 * as it was when the write was generated.
                 */
                if (zd->zd_zilog->zl_replay) {
                        ztest_bt_verify(bt, os, lr->lr_foid, 0, offset,
                            MAX(gen, bt->bt_gen), MAX(txg, lrtxg),
                            bt->bt_crtxg);
                }

                /*
                 * Set the bt's gen/txg to the bonus buffer's gen/txg
                 * so that all of the usual ASSERTs will work.
                 */
                ztest_bt_generate(bt, os, lr->lr_foid, 0, offset, gen, txg,
                    crtxg);
        }

        if (abuf == NULL) {
                dmu_write(os, lr->lr_foid, offset, length, data, tx);
        } else {
                bcopy(data, abuf->b_data, length);
                dmu_assign_arcbuf(db, offset, abuf, tx);
        }

        (void) ztest_log_write(zd, tx, lr);

        dmu_buf_rele(db, FTAG);

        dmu_tx_commit(tx);

        ztest_range_unlock(zd, rl);
        ztest_object_unlock(zd, lr->lr_foid);

        return (0);
}

static int
ztest_replay_truncate(ztest_ds_t *zd, lr_truncate_t *lr, boolean_t byteswap)
{
        objset_t *os = zd->zd_os;
        dmu_tx_t *tx;
        uint64_t txg;
        ztest_zrl_t *rl;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        ztest_object_lock(zd, lr->lr_foid, RL_READER);
        rl = ztest_range_lock(zd, lr->lr_foid, lr->lr_offset, lr->lr_length,
            RL_WRITER);

        tx = dmu_tx_create(os);

        dmu_tx_hold_free(tx, lr->lr_foid, lr->lr_offset, lr->lr_length);

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0) {
                ztest_range_unlock(zd, rl);
                ztest_object_unlock(zd, lr->lr_foid);
                return (ENOSPC);
        }

        VERIFY(dmu_free_range(os, lr->lr_foid, lr->lr_offset,
            lr->lr_length, tx) == 0);

        (void) ztest_log_truncate(zd, tx, lr);

        dmu_tx_commit(tx);

        ztest_range_unlock(zd, rl);
        ztest_object_unlock(zd, lr->lr_foid);

        return (0);
}

static int
ztest_replay_setattr(ztest_ds_t *zd, lr_setattr_t *lr, boolean_t byteswap)
{
        objset_t *os = zd->zd_os;
        dmu_tx_t *tx;
        dmu_buf_t *db;
        ztest_block_tag_t *bbt;
        uint64_t txg, lrtxg, crtxg, dnodesize;

        if (byteswap)
                byteswap_uint64_array(lr, sizeof (*lr));

        ztest_object_lock(zd, lr->lr_foid, RL_WRITER);

        VERIFY3U(0, ==, dmu_bonus_hold(os, lr->lr_foid, FTAG, &db));

        tx = dmu_tx_create(os);
        dmu_tx_hold_bonus(tx, lr->lr_foid);

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0) {
                dmu_buf_rele(db, FTAG);
                ztest_object_unlock(zd, lr->lr_foid);
                return (ENOSPC);
        }

        bbt = ztest_bt_bonus(db);
        ASSERT3U(bbt->bt_magic, ==, BT_MAGIC);
        crtxg = bbt->bt_crtxg;
        lrtxg = lr->lr_common.lrc_txg;
        dnodesize = bbt->bt_dnodesize;

        if (zd->zd_zilog->zl_replay) {
                ASSERT(lr->lr_size != 0);
                ASSERT(lr->lr_mode != 0);
                ASSERT(lrtxg != 0);
        } else {
                /*
                 * Randomly change the size and increment the generation.
                 */
                lr->lr_size = (ztest_random(db->db_size / sizeof (*bbt)) + 1) *
                    sizeof (*bbt);
                lr->lr_mode = bbt->bt_gen + 1;
                ASSERT(lrtxg == 0);
        }

        /*
         * Verify that the current bonus buffer is not newer than our txg.
         */
        ztest_bt_verify(bbt, os, lr->lr_foid, dnodesize, -1ULL, lr->lr_mode,
            MAX(txg, lrtxg), crtxg);

        dmu_buf_will_dirty(db, tx);

        ASSERT3U(lr->lr_size, >=, sizeof (*bbt));
        ASSERT3U(lr->lr_size, <=, db->db_size);
        VERIFY0(dmu_set_bonus(db, lr->lr_size, tx));
        bbt = ztest_bt_bonus(db);

        ztest_bt_generate(bbt, os, lr->lr_foid, dnodesize, -1ULL, lr->lr_mode,
            txg, crtxg);
        ztest_fill_unused_bonus(db, bbt, lr->lr_foid, os, bbt->bt_gen);
        dmu_buf_rele(db, FTAG);

        (void) ztest_log_setattr(zd, tx, lr);

        dmu_tx_commit(tx);

        ztest_object_unlock(zd, lr->lr_foid);

        return (0);
}

zil_replay_func_t ztest_replay_vector[TX_MAX_TYPE] = {
        NULL,                           /* 0 no such transaction type */
        (zil_replay_func_t)ztest_replay_create,         /* TX_CREATE */
        NULL,                                           /* TX_MKDIR */
        NULL,                                           /* TX_MKXATTR */
        NULL,                                           /* TX_SYMLINK */
        (zil_replay_func_t)ztest_replay_remove,         /* TX_REMOVE */
        NULL,                                           /* TX_RMDIR */
        NULL,                                           /* TX_LINK */
        NULL,                                           /* TX_RENAME */
        (zil_replay_func_t)ztest_replay_write,          /* TX_WRITE */
        (zil_replay_func_t)ztest_replay_truncate,       /* TX_TRUNCATE */
        (zil_replay_func_t)ztest_replay_setattr,        /* TX_SETATTR */
        NULL,                                           /* TX_ACL */
        NULL,                                           /* TX_CREATE_ACL */
        NULL,                                           /* TX_CREATE_ATTR */
        NULL,                                           /* TX_CREATE_ACL_ATTR */
        NULL,                                           /* TX_MKDIR_ACL */
        NULL,                                           /* TX_MKDIR_ATTR */
        NULL,                                           /* TX_MKDIR_ACL_ATTR */
        NULL,                                           /* TX_WRITE2 */
};

/*
 * ZIL get_data callbacks
 */
typedef struct ztest_zgd_private {
        ztest_ds_t *z_zd;
        ztest_zrl_t *z_rl;
        uint64_t z_object;
} ztest_zgd_private_t;

static void
ztest_get_done(zgd_t *zgd, int error)
{
        ztest_zgd_private_t *zzp = zgd->zgd_private;
        ztest_ds_t *zd = zzp->z_zd;
        uint64_t object = zzp->z_object;

        if (zgd->zgd_db)
                dmu_buf_rele(zgd->zgd_db, zgd);

        ztest_range_unlock(zd, zzp->z_rl);
        ztest_object_unlock(zd, object);

        if (error == 0 && zgd->zgd_bp)
                zil_add_block(zgd->zgd_zilog, zgd->zgd_bp);

        umem_free(zgd, sizeof (*zgd));
        umem_free(zzp, sizeof (*zzp));
}

static int
ztest_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio)
{
        ztest_ds_t *zd = arg;
        objset_t *os = zd->zd_os;
        uint64_t object = lr->lr_foid;
        uint64_t offset = lr->lr_offset;
        uint64_t size = lr->lr_length;
        blkptr_t *bp = &lr->lr_blkptr;
        uint64_t txg = lr->lr_common.lrc_txg;
        uint64_t crtxg;
        dmu_object_info_t doi;
        dmu_buf_t *db;
        zgd_t *zgd;
        int error;
        ztest_zgd_private_t *zgd_private;

        ztest_object_lock(zd, object, RL_READER);
        error = dmu_bonus_hold(os, object, FTAG, &db);
        if (error) {
                ztest_object_unlock(zd, object);
                return (error);
        }

        crtxg = ztest_bt_bonus(db)->bt_crtxg;

        if (crtxg == 0 || crtxg > txg) {
                dmu_buf_rele(db, FTAG);
                ztest_object_unlock(zd, object);
                return (ENOENT);
        }

        dmu_object_info_from_db(db, &doi);
        dmu_buf_rele(db, FTAG);
        db = NULL;

        zgd = umem_zalloc(sizeof (*zgd), UMEM_NOFAIL);
        zgd->zgd_zilog = zd->zd_zilog;
        zgd_private = umem_zalloc(sizeof (ztest_zgd_private_t), UMEM_NOFAIL);
        zgd_private->z_zd = zd;
        zgd_private->z_object = object;
        zgd->zgd_private = zgd_private;

        if (buf != NULL) {      /* immediate write */
                zgd_private->z_rl = ztest_range_lock(zd, object, offset, size,
                    RL_READER);

                error = dmu_read(os, object, offset, size, buf,
                    DMU_READ_NO_PREFETCH);
                ASSERT(error == 0);
        } else {
                size = doi.doi_data_block_size;
                if (ISP2(size)) {
                        offset = P2ALIGN(offset, size);
                } else {
                        ASSERT(offset < size);
                        offset = 0;
                }

                zgd_private->z_rl = ztest_range_lock(zd, object, offset, size,
                    RL_READER);

                error = dmu_buf_hold(os, object, offset, zgd, &db,
                    DMU_READ_NO_PREFETCH);

                if (error == 0) {
                        blkptr_t *obp = dmu_buf_get_blkptr(db);
                        if (obp) {
                                ASSERT(BP_IS_HOLE(bp));
                                *bp = *obp;
                        }

                        zgd->zgd_db = db;
                        zgd->zgd_bp = bp;

                        ASSERT(db->db_offset == offset);
                        ASSERT(db->db_size == size);

                        error = dmu_sync(zio, lr->lr_common.lrc_txg,
                            ztest_get_done, zgd);

                        if (error == 0)
                                return (0);
                }
        }

        ztest_get_done(zgd, error);

        return (error);
}

static void *
ztest_lr_alloc(size_t lrsize, char *name)
{
        char *lr;
        size_t namesize = name ? strlen(name) + 1 : 0;

        lr = umem_zalloc(lrsize + namesize, UMEM_NOFAIL);

        if (name)
                bcopy(name, lr + lrsize, namesize);

        return (lr);
}

void
ztest_lr_free(void *lr, size_t lrsize, char *name)
{
        size_t namesize = name ? strlen(name) + 1 : 0;

        umem_free(lr, lrsize + namesize);
}

/*
 * Lookup a bunch of objects.  Returns the number of objects not found.
 */
static int
ztest_lookup(ztest_ds_t *zd, ztest_od_t *od, int count)
{
        int missing = 0;
        int error;
        int i;

        ASSERT(mutex_held(&zd->zd_dirobj_lock));

        for (i = 0; i < count; i++, od++) {
                od->od_object = 0;
                error = zap_lookup(zd->zd_os, od->od_dir, od->od_name,
                    sizeof (uint64_t), 1, &od->od_object);
                if (error) {
                        ASSERT(error == ENOENT);
                        ASSERT(od->od_object == 0);
                        missing++;
                } else {
                        dmu_buf_t *db;
                        ztest_block_tag_t *bbt;
                        dmu_object_info_t doi;

                        ASSERT(od->od_object != 0);
                        ASSERT(missing == 0);   /* there should be no gaps */

                        ztest_object_lock(zd, od->od_object, RL_READER);
                        VERIFY3U(0, ==, dmu_bonus_hold(zd->zd_os,
                            od->od_object, FTAG, &db));
                        dmu_object_info_from_db(db, &doi);
                        bbt = ztest_bt_bonus(db);
                        ASSERT3U(bbt->bt_magic, ==, BT_MAGIC);
                        od->od_type = doi.doi_type;
                        od->od_blocksize = doi.doi_data_block_size;
                        od->od_gen = bbt->bt_gen;
                        dmu_buf_rele(db, FTAG);
                        ztest_object_unlock(zd, od->od_object);
                }
        }

        return (missing);
}

static int
ztest_create(ztest_ds_t *zd, ztest_od_t *od, int count)
{
        int missing = 0;
        int i;

        ASSERT(mutex_held(&zd->zd_dirobj_lock));

        for (i = 0; i < count; i++, od++) {
                if (missing) {
                        od->od_object = 0;
                        missing++;
                        continue;
                }

                lr_create_t *lr = ztest_lr_alloc(sizeof (*lr), od->od_name);

                lr->lr_doid = od->od_dir;
                lr->lr_foid = 0;        /* 0 to allocate, > 0 to claim */
                lr->lrz_type = od->od_crtype;
                lr->lrz_blocksize = od->od_crblocksize;
                lr->lrz_ibshift = ztest_random_ibshift();
                lr->lrz_bonustype = DMU_OT_UINT64_OTHER;
                lr->lrz_dnodesize = od->od_crdnodesize;
                lr->lr_gen = od->od_crgen;
                lr->lr_crtime[0] = time(NULL);

                if (ztest_replay_create(zd, lr, B_FALSE) != 0) {
                        ASSERT(missing == 0);
                        od->od_object = 0;
                        missing++;
                } else {
                        od->od_object = lr->lr_foid;
                        od->od_type = od->od_crtype;
                        od->od_blocksize = od->od_crblocksize;
                        od->od_gen = od->od_crgen;
                        ASSERT(od->od_object != 0);
                }

                ztest_lr_free(lr, sizeof (*lr), od->od_name);
        }

        return (missing);
}

static int
ztest_remove(ztest_ds_t *zd, ztest_od_t *od, int count)
{
        int missing = 0;
        int error;
        int i;

        ASSERT(mutex_held(&zd->zd_dirobj_lock));

        od += count - 1;

        for (i = count - 1; i >= 0; i--, od--) {
                if (missing) {
                        missing++;
                        continue;
                }

                /*
                 * No object was found.
                 */
                if (od->od_object == 0)
                        continue;

                lr_remove_t *lr = ztest_lr_alloc(sizeof (*lr), od->od_name);

                lr->lr_doid = od->od_dir;

                if ((error = ztest_replay_remove(zd, lr, B_FALSE)) != 0) {
                        ASSERT3U(error, ==, ENOSPC);
                        missing++;
                } else {
                        od->od_object = 0;
                }
                ztest_lr_free(lr, sizeof (*lr), od->od_name);
        }

        return (missing);
}

static int
ztest_write(ztest_ds_t *zd, uint64_t object, uint64_t offset, uint64_t size,
    void *data)
{
        lr_write_t *lr;
        int error;

        lr = ztest_lr_alloc(sizeof (*lr) + size, NULL);

        lr->lr_foid = object;
        lr->lr_offset = offset;
        lr->lr_length = size;
        lr->lr_blkoff = 0;
        BP_ZERO(&lr->lr_blkptr);

        bcopy(data, lr + 1, size);

        error = ztest_replay_write(zd, lr, B_FALSE);

        ztest_lr_free(lr, sizeof (*lr) + size, NULL);

        return (error);
}

static int
ztest_truncate(ztest_ds_t *zd, uint64_t object, uint64_t offset, uint64_t size)
{
        lr_truncate_t *lr;
        int error;

        lr = ztest_lr_alloc(sizeof (*lr), NULL);

        lr->lr_foid = object;
        lr->lr_offset = offset;
        lr->lr_length = size;

        error = ztest_replay_truncate(zd, lr, B_FALSE);

        ztest_lr_free(lr, sizeof (*lr), NULL);

        return (error);
}

static int
ztest_setattr(ztest_ds_t *zd, uint64_t object)
{
        lr_setattr_t *lr;
        int error;

        lr = ztest_lr_alloc(sizeof (*lr), NULL);

        lr->lr_foid = object;
        lr->lr_size = 0;
        lr->lr_mode = 0;

        error = ztest_replay_setattr(zd, lr, B_FALSE);

        ztest_lr_free(lr, sizeof (*lr), NULL);

        return (error);
}

static void
ztest_prealloc(ztest_ds_t *zd, uint64_t object, uint64_t offset, uint64_t size)
{
        objset_t *os = zd->zd_os;
        dmu_tx_t *tx;
        uint64_t txg;
        ztest_zrl_t *rl;

        txg_wait_synced(dmu_objset_pool(os), 0);

        ztest_object_lock(zd, object, RL_READER);
        rl = ztest_range_lock(zd, object, offset, size, RL_WRITER);

        tx = dmu_tx_create(os);

        dmu_tx_hold_write(tx, object, offset, size);

        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);

        if (txg != 0) {
                dmu_prealloc(os, object, offset, size, tx);
                dmu_tx_commit(tx);
                txg_wait_synced(dmu_objset_pool(os), txg);
        } else {
                (void) dmu_free_long_range(os, object, offset, size);
        }

        ztest_range_unlock(zd, rl);
        ztest_object_unlock(zd, object);
}

static void
ztest_io(ztest_ds_t *zd, uint64_t object, uint64_t offset)
{
        int err;
        ztest_block_tag_t wbt;
        dmu_object_info_t doi;
        enum ztest_io_type io_type;
        uint64_t blocksize;
        void *data;

        VERIFY(dmu_object_info(zd->zd_os, object, &doi) == 0);
        blocksize = doi.doi_data_block_size;
        data = umem_alloc(blocksize, UMEM_NOFAIL);

        /*
         * Pick an i/o type at random, biased toward writing block tags.
         */
        io_type = ztest_random(ZTEST_IO_TYPES);
        if (ztest_random(2) == 0)
                io_type = ZTEST_IO_WRITE_TAG;

        (void) rw_rdlock(&zd->zd_zilog_lock);

        switch (io_type) {

        case ZTEST_IO_WRITE_TAG:
                ztest_bt_generate(&wbt, zd->zd_os, object, doi.doi_dnodesize,
                    offset, 0, 0, 0);
                (void) ztest_write(zd, object, offset, sizeof (wbt), &wbt);
                break;

        case ZTEST_IO_WRITE_PATTERN:
                (void) memset(data, 'a' + (object + offset) % 5, blocksize);
                if (ztest_random(2) == 0) {
                        /*
                         * Induce fletcher2 collisions to ensure that
                         * zio_ddt_collision() detects and resolves them
                         * when using fletcher2-verify for deduplication.
                         */
                        ((uint64_t *)data)[0] ^= 1ULL << 63;
                        ((uint64_t *)data)[4] ^= 1ULL << 63;
                }
                (void) ztest_write(zd, object, offset, blocksize, data);
                break;

        case ZTEST_IO_WRITE_ZEROES:
                bzero(data, blocksize);
                (void) ztest_write(zd, object, offset, blocksize, data);
                break;

        case ZTEST_IO_TRUNCATE:
                (void) ztest_truncate(zd, object, offset, blocksize);
                break;

        case ZTEST_IO_SETATTR:
                (void) ztest_setattr(zd, object);
                break;
        default:
                break;

        case ZTEST_IO_REWRITE:
                (void) rw_rdlock(&ztest_name_lock);
                err = ztest_dsl_prop_set_uint64(zd->zd_name,
                    ZFS_PROP_CHECKSUM, spa_dedup_checksum(ztest_spa),
                    B_FALSE);
                VERIFY(err == 0 || err == ENOSPC);
                err = ztest_dsl_prop_set_uint64(zd->zd_name,
                    ZFS_PROP_COMPRESSION,
                    ztest_random_dsl_prop(ZFS_PROP_COMPRESSION),
                    B_FALSE);
                VERIFY(err == 0 || err == ENOSPC);
                (void) rw_unlock(&ztest_name_lock);

                VERIFY0(dmu_read(zd->zd_os, object, offset, blocksize, data,
                    DMU_READ_NO_PREFETCH));

                (void) ztest_write(zd, object, offset, blocksize, data);
                break;
        }

        (void) rw_unlock(&zd->zd_zilog_lock);

        umem_free(data, blocksize);
}

/*
 * Initialize an object description template.
 */
static void
ztest_od_init(ztest_od_t *od, uint64_t id, char *tag, uint64_t index,
    dmu_object_type_t type, uint64_t blocksize, uint64_t dnodesize,
    uint64_t gen)
{
        od->od_dir = ZTEST_DIROBJ;
        od->od_object = 0;

        od->od_crtype = type;
        od->od_crblocksize = blocksize ? blocksize : ztest_random_blocksize();
        od->od_crdnodesize = dnodesize ? dnodesize : ztest_random_dnodesize();
        od->od_crgen = gen;

        od->od_type = DMU_OT_NONE;
        od->od_blocksize = 0;
        od->od_gen = 0;

        (void) snprintf(od->od_name, sizeof (od->od_name), "%s(%lld)[%llu]",
            tag, (longlong_t)id, (u_longlong_t)index);
}

/*
 * Lookup or create the objects for a test using the od template.
 * If the objects do not all exist, or if 'remove' is specified,
 * remove any existing objects and create new ones.  Otherwise,
 * use the existing objects.
 */
static int
ztest_object_init(ztest_ds_t *zd, ztest_od_t *od, size_t size, boolean_t remove)
{
        int count = size / sizeof (*od);
        int rv = 0;

        mutex_enter(&zd->zd_dirobj_lock);
        if ((ztest_lookup(zd, od, count) != 0 || remove) &&
            (ztest_remove(zd, od, count) != 0 ||
            ztest_create(zd, od, count) != 0))
                rv = -1;
        zd->zd_od = od;
        mutex_exit(&zd->zd_dirobj_lock);

        return (rv);
}

/* ARGSUSED */
void
ztest_zil_commit(ztest_ds_t *zd, uint64_t id)
{
        zilog_t *zilog = zd->zd_zilog;

        (void) rw_rdlock(&zd->zd_zilog_lock);

        zil_commit(zilog, ztest_random(ZTEST_OBJECTS));

        /*
         * Remember the committed values in zd, which is in parent/child
         * shared memory.  If we die, the next iteration of ztest_run()
         * will verify that the log really does contain this record.
         */
        mutex_enter(&zilog->zl_lock);
        ASSERT(zd->zd_shared != NULL);
        ASSERT3U(zd->zd_shared->zd_seq, <=, zilog->zl_commit_lr_seq);
        zd->zd_shared->zd_seq = zilog->zl_commit_lr_seq;
        mutex_exit(&zilog->zl_lock);

        (void) rw_unlock(&zd->zd_zilog_lock);
}

/*
 * This function is designed to simulate the operations that occur during a
 * mount/unmount operation.  We hold the dataset across these operations in an
 * attempt to expose any implicit assumptions about ZIL management.
 */
/* ARGSUSED */
void
ztest_zil_remount(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;

        /*
         * We grab the zd_dirobj_lock to ensure that no other thread is
         * updating the zil (i.e. adding in-memory log records) and the
         * zd_zilog_lock to block any I/O.
         */
        mutex_enter(&zd->zd_dirobj_lock);
        (void) rw_wrlock(&zd->zd_zilog_lock);

        /* zfsvfs_teardown() */
        zil_close(zd->zd_zilog);

        /* zfsvfs_setup() */
        VERIFY(zil_open(os, ztest_get_data) == zd->zd_zilog);
        zil_replay(os, zd, ztest_replay_vector);

        (void) rw_unlock(&zd->zd_zilog_lock);
        mutex_exit(&zd->zd_dirobj_lock);
}

/*
 * Verify that we can't destroy an active pool, create an existing pool,
 * or create a pool with a bad vdev spec.
 */
/* ARGSUSED */
void
ztest_spa_create_destroy(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_opts_t *zo = &ztest_opts;
        spa_t *spa;
        nvlist_t *nvroot;

        /*
         * Attempt to create using a bad file.
         */
        nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, 0, 0, 0, 1);
        VERIFY3U(ENOENT, ==,
            spa_create("ztest_bad_file", nvroot, NULL, NULL));
        nvlist_free(nvroot);

        /*
         * Attempt to create using a bad mirror.
         */
        nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, 0, 0, 2, 1);
        VERIFY3U(ENOENT, ==,
            spa_create("ztest_bad_mirror", nvroot, NULL, NULL));
        nvlist_free(nvroot);

        /*
         * Attempt to create an existing pool.  It shouldn't matter
         * what's in the nvroot; we should fail with EEXIST.
         */
        (void) rw_rdlock(&ztest_name_lock);
        nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, 0, 0, 0, 1);
        VERIFY3U(EEXIST, ==, spa_create(zo->zo_pool, nvroot, NULL, NULL));
        nvlist_free(nvroot);
        VERIFY3U(0, ==, spa_open(zo->zo_pool, &spa, FTAG));
        VERIFY3U(EBUSY, ==, spa_destroy(zo->zo_pool));
        spa_close(spa, FTAG);

        (void) rw_unlock(&ztest_name_lock);
}

/* ARGSUSED */
void
ztest_spa_upgrade(ztest_ds_t *zd, uint64_t id)
{
        spa_t *spa;
        uint64_t initial_version = SPA_VERSION_INITIAL;
        uint64_t version, newversion;
        nvlist_t *nvroot, *props;
        char *name;

        mutex_enter(&ztest_vdev_lock);
        name = kmem_asprintf("%s_upgrade", ztest_opts.zo_pool);

        /*
         * Clean up from previous runs.
         */
        (void) spa_destroy(name);

        nvroot = make_vdev_root(NULL, NULL, name, ztest_opts.zo_vdev_size, 0,
            0, ztest_opts.zo_raidz, ztest_opts.zo_mirrors, 1);

        /*
         * If we're configuring a RAIDZ device then make sure that the
         * the initial version is capable of supporting that feature.
         */
        switch (ztest_opts.zo_raidz_parity) {
        case 0:
        case 1:
                initial_version = SPA_VERSION_INITIAL;
                break;
        case 2:
                initial_version = SPA_VERSION_RAIDZ2;
                break;
        case 3:
                initial_version = SPA_VERSION_RAIDZ3;
                break;
        }

        /*
         * Create a pool with a spa version that can be upgraded. Pick
         * a value between initial_version and SPA_VERSION_BEFORE_FEATURES.
         */
        do {
                version = ztest_random_spa_version(initial_version);
        } while (version > SPA_VERSION_BEFORE_FEATURES);

        props = fnvlist_alloc();
        fnvlist_add_uint64(props,
            zpool_prop_to_name(ZPOOL_PROP_VERSION), version);
        VERIFY3S(spa_create(name, nvroot, props, NULL), ==, 0);
        fnvlist_free(nvroot);
        fnvlist_free(props);

        VERIFY3S(spa_open(name, &spa, FTAG), ==, 0);
        VERIFY3U(spa_version(spa), ==, version);
        newversion = ztest_random_spa_version(version + 1);

        if (ztest_opts.zo_verbose >= 4) {
                (void) printf("upgrading spa version from %llu to %llu\n",
                    (u_longlong_t)version, (u_longlong_t)newversion);
        }

        spa_upgrade(spa, newversion);
        VERIFY3U(spa_version(spa), >, version);
        VERIFY3U(spa_version(spa), ==, fnvlist_lookup_uint64(spa->spa_config,
            zpool_prop_to_name(ZPOOL_PROP_VERSION)));
        spa_close(spa, FTAG);

        strfree(name);
        mutex_exit(&ztest_vdev_lock);
}

static vdev_t *
vdev_lookup_by_path(vdev_t *vd, const char *path)
{
        vdev_t *mvd;
        int c;

        if (vd->vdev_path != NULL && strcmp(path, vd->vdev_path) == 0)
                return (vd);

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

        return (NULL);
}

/*
 * Find the first available hole which can be used as a top-level.
 */
int
find_vdev_hole(spa_t *spa)
{
        vdev_t *rvd = spa->spa_root_vdev;
        int c;

        ASSERT(spa_config_held(spa, SCL_VDEV, RW_READER) == SCL_VDEV);

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

                if (cvd->vdev_ishole)
                        break;
        }
        return (c);
}

/*
 * Verify that vdev_add() works as expected.
 */
/* ARGSUSED */
void
ztest_vdev_add_remove(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        uint64_t leaves;
        uint64_t guid;
        nvlist_t *nvroot;
        int error;

        mutex_enter(&ztest_vdev_lock);
        leaves = MAX(zs->zs_mirrors + zs->zs_splits, 1) * ztest_opts.zo_raidz;

        spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);

        ztest_shared->zs_vdev_next_leaf = find_vdev_hole(spa) * leaves;

        /*
         * If we have slogs then remove them 1/4 of the time.
         */
        if (spa_has_slogs(spa) && ztest_random(4) == 0) {
                /*
                 * Grab the guid from the head of the log class rotor.
                 */
                guid = spa_log_class(spa)->mc_rotor->mg_vd->vdev_guid;

                spa_config_exit(spa, SCL_VDEV, FTAG);

                /*
                 * We have to grab the zs_name_lock as writer to
                 * prevent a race between removing a slog (dmu_objset_find)
                 * and destroying a dataset. Removing the slog will
                 * grab a reference on the dataset which may cause
                 * dsl_destroy_head() to fail with EBUSY thus
                 * leaving the dataset in an inconsistent state.
                 */
                rw_wrlock(&ztest_name_lock);
                error = spa_vdev_remove(spa, guid, B_FALSE);
                rw_unlock(&ztest_name_lock);

                if (error && error != EEXIST)
                        fatal(0, "spa_vdev_remove() = %d", error);
        } else {
                spa_config_exit(spa, SCL_VDEV, FTAG);

                /*
                 * Make 1/4 of the devices be log devices.
                 */
                nvroot = make_vdev_root(NULL, NULL, NULL,
                    ztest_opts.zo_vdev_size, 0,
                    ztest_random(4) == 0, ztest_opts.zo_raidz,
                    zs->zs_mirrors, 1);

                error = spa_vdev_add(spa, nvroot);
                nvlist_free(nvroot);

                if (error == ENOSPC)
                        ztest_record_enospc("spa_vdev_add");
                else if (error != 0)
                        fatal(0, "spa_vdev_add() = %d", error);
        }

        mutex_exit(&ztest_vdev_lock);
}

/*
 * Verify that adding/removing aux devices (l2arc, hot spare) works as expected.
 */
/* ARGSUSED */
void
ztest_vdev_aux_add_remove(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        vdev_t *rvd = spa->spa_root_vdev;
        spa_aux_vdev_t *sav;
        char *aux;
        char *path;
        uint64_t guid = 0;
        int error;

        path = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);

        if (ztest_random(2) == 0) {
                sav = &spa->spa_spares;
                aux = ZPOOL_CONFIG_SPARES;
        } else {
                sav = &spa->spa_l2cache;
                aux = ZPOOL_CONFIG_L2CACHE;
        }

        mutex_enter(&ztest_vdev_lock);

        spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);

        if (sav->sav_count != 0 && ztest_random(4) == 0) {
                /*
                 * Pick a random device to remove.
                 */
                guid = sav->sav_vdevs[ztest_random(sav->sav_count)]->vdev_guid;
        } else {
                /*
                 * Find an unused device we can add.
                 */
                zs->zs_vdev_aux = 0;
                for (;;) {
                        int c;
                        (void) snprintf(path, MAXPATHLEN, ztest_aux_template,
                            ztest_opts.zo_dir, ztest_opts.zo_pool, aux,
                            zs->zs_vdev_aux);
                        for (c = 0; c < sav->sav_count; c++)
                                if (strcmp(sav->sav_vdevs[c]->vdev_path,
                                    path) == 0)
                                        break;
                        if (c == sav->sav_count &&
                            vdev_lookup_by_path(rvd, path) == NULL)
                                break;
                        zs->zs_vdev_aux++;
                }
        }

        spa_config_exit(spa, SCL_VDEV, FTAG);

        if (guid == 0) {
                /*
                 * Add a new device.
                 */
                nvlist_t *nvroot = make_vdev_root(NULL, aux, NULL,
                    (ztest_opts.zo_vdev_size * 5) / 4, 0, 0, 0, 0, 1);
                error = spa_vdev_add(spa, nvroot);
                if (error != 0)
                        fatal(0, "spa_vdev_add(%p) = %d", nvroot, error);
                nvlist_free(nvroot);
        } else {
                /*
                 * Remove an existing device.  Sometimes, dirty its
                 * vdev state first to make sure we handle removal
                 * of devices that have pending state changes.
                 */
                if (ztest_random(2) == 0)
                        (void) vdev_online(spa, guid, 0, NULL);

                error = spa_vdev_remove(spa, guid, B_FALSE);
                if (error != 0 && error != EBUSY)
                        fatal(0, "spa_vdev_remove(%llu) = %d", guid, error);
        }

        mutex_exit(&ztest_vdev_lock);

        umem_free(path, MAXPATHLEN);
}

/*
 * split a pool if it has mirror tlvdevs
 */
/* ARGSUSED */
void
ztest_split_pool(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        vdev_t *rvd = spa->spa_root_vdev;
        nvlist_t *tree, **child, *config, *split, **schild;
        uint_t c, children, schildren = 0, lastlogid = 0;
        int error = 0;

        mutex_enter(&ztest_vdev_lock);

        /* ensure we have a useable config; mirrors of raidz aren't supported */
        if (zs->zs_mirrors < 3 || ztest_opts.zo_raidz > 1) {
                mutex_exit(&ztest_vdev_lock);
                return;
        }

        /* clean up the old pool, if any */
        (void) spa_destroy("splitp");

        spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);

        /* generate a config from the existing config */
        mutex_enter(&spa->spa_props_lock);
        VERIFY(nvlist_lookup_nvlist(spa->spa_config, ZPOOL_CONFIG_VDEV_TREE,
            &tree) == 0);
        mutex_exit(&spa->spa_props_lock);

        VERIFY(nvlist_lookup_nvlist_array(tree, ZPOOL_CONFIG_CHILDREN, &child,
            &children) == 0);

        schild = malloc(rvd->vdev_children * sizeof (nvlist_t *));
        for (c = 0; c < children; c++) {
                vdev_t *tvd = rvd->vdev_child[c];
                nvlist_t **mchild;
                uint_t mchildren;

                if (tvd->vdev_islog || tvd->vdev_ops == &vdev_hole_ops) {
                        VERIFY(nvlist_alloc(&schild[schildren], NV_UNIQUE_NAME,
                            0) == 0);
                        VERIFY(nvlist_add_string(schild[schildren],
                            ZPOOL_CONFIG_TYPE, VDEV_TYPE_HOLE) == 0);
                        VERIFY(nvlist_add_uint64(schild[schildren],
                            ZPOOL_CONFIG_IS_HOLE, 1) == 0);
                        if (lastlogid == 0)
                                lastlogid = schildren;
                        ++schildren;
                        continue;
                }
                lastlogid = 0;
                VERIFY(nvlist_lookup_nvlist_array(child[c],
                    ZPOOL_CONFIG_CHILDREN, &mchild, &mchildren) == 0);
                VERIFY(nvlist_dup(mchild[0], &schild[schildren++], 0) == 0);
        }

        /* OK, create a config that can be used to split */
        VERIFY(nvlist_alloc(&split, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_string(split, ZPOOL_CONFIG_TYPE,
            VDEV_TYPE_ROOT) == 0);
        VERIFY(nvlist_add_nvlist_array(split, ZPOOL_CONFIG_CHILDREN, schild,
            lastlogid != 0 ? lastlogid : schildren) == 0);

        VERIFY(nvlist_alloc(&config, NV_UNIQUE_NAME, 0) == 0);
        VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, split) == 0);

        for (c = 0; c < schildren; c++)
                nvlist_free(schild[c]);
        free(schild);
        nvlist_free(split);

        spa_config_exit(spa, SCL_VDEV, FTAG);

        (void) rw_wrlock(&ztest_name_lock);
        error = spa_vdev_split_mirror(spa, "splitp", config, NULL, B_FALSE);
        (void) rw_unlock(&ztest_name_lock);

        nvlist_free(config);

        if (error == 0) {
                (void) printf("successful split - results:\n");
                mutex_enter(&spa_namespace_lock);
                show_pool_stats(spa);
                show_pool_stats(spa_lookup("splitp"));
                mutex_exit(&spa_namespace_lock);
                ++zs->zs_splits;
                --zs->zs_mirrors;
        }
        mutex_exit(&ztest_vdev_lock);

}

/*
 * Verify that we can attach and detach devices.
 */
/* ARGSUSED */
void
ztest_vdev_attach_detach(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        spa_aux_vdev_t *sav = &spa->spa_spares;
        vdev_t *rvd = spa->spa_root_vdev;
        vdev_t *oldvd, *newvd, *pvd;
        nvlist_t *root;
        uint64_t leaves;
        uint64_t leaf, top;
        uint64_t ashift = ztest_get_ashift();
        uint64_t oldguid, pguid;
        uint64_t oldsize, newsize;
        char *oldpath, *newpath;
        int replacing;
        int oldvd_has_siblings = B_FALSE;
        int newvd_is_spare = B_FALSE;
        int oldvd_is_log;
        int error, expected_error;

        oldpath = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
        newpath = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);

        mutex_enter(&ztest_vdev_lock);
        leaves = MAX(zs->zs_mirrors, 1) * ztest_opts.zo_raidz;

        spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);

        /*
         * Decide whether to do an attach or a replace.
         */
        replacing = ztest_random(2);

        /*
         * Pick a random top-level vdev.
         */
        top = ztest_random_vdev_top(spa, B_TRUE);

        /*
         * Pick a random leaf within it.
         */
        leaf = ztest_random(leaves);

        /*
         * Locate this vdev.
         */
        oldvd = rvd->vdev_child[top];
        if (zs->zs_mirrors >= 1) {
                ASSERT(oldvd->vdev_ops == &vdev_mirror_ops);
                ASSERT(oldvd->vdev_children >= zs->zs_mirrors);
                oldvd = oldvd->vdev_child[leaf / ztest_opts.zo_raidz];
        }
        if (ztest_opts.zo_raidz > 1) {
                ASSERT(oldvd->vdev_ops == &vdev_raidz_ops);
                ASSERT(oldvd->vdev_children == ztest_opts.zo_raidz);
                oldvd = oldvd->vdev_child[leaf % ztest_opts.zo_raidz];
        }

        /*
         * If we're already doing an attach or replace, oldvd may be a
         * mirror vdev -- in which case, pick a random child.
         */
        while (oldvd->vdev_children != 0) {
                oldvd_has_siblings = B_TRUE;
                ASSERT(oldvd->vdev_children >= 2);
                oldvd = oldvd->vdev_child[ztest_random(oldvd->vdev_children)];
        }

        oldguid = oldvd->vdev_guid;
        oldsize = vdev_get_min_asize(oldvd);
        oldvd_is_log = oldvd->vdev_top->vdev_islog;
        (void) strcpy(oldpath, oldvd->vdev_path);
        pvd = oldvd->vdev_parent;
        pguid = pvd->vdev_guid;

        /*
         * If oldvd has siblings, then half of the time, detach it.
         */
        if (oldvd_has_siblings && ztest_random(2) == 0) {
                spa_config_exit(spa, SCL_VDEV, FTAG);
                error = spa_vdev_detach(spa, oldguid, pguid, B_FALSE);
                if (error != 0 && error != ENODEV && error != EBUSY &&
                    error != ENOTSUP)
                        fatal(0, "detach (%s) returned %d", oldpath, error);
                goto out;
        }

        /*
         * For the new vdev, choose with equal probability between the two
         * standard paths (ending in either 'a' or 'b') or a random hot spare.
         */
        if (sav->sav_count != 0 && ztest_random(3) == 0) {
                newvd = sav->sav_vdevs[ztest_random(sav->sav_count)];
                newvd_is_spare = B_TRUE;
                (void) strcpy(newpath, newvd->vdev_path);
        } else {
                (void) snprintf(newpath, MAXPATHLEN, ztest_dev_template,
                    ztest_opts.zo_dir, ztest_opts.zo_pool,
                    top * leaves + leaf);
                if (ztest_random(2) == 0)
                        newpath[strlen(newpath) - 1] = 'b';
                newvd = vdev_lookup_by_path(rvd, newpath);
        }

        if (newvd) {
                newsize = vdev_get_min_asize(newvd);
        } else {
                /*
                 * Make newsize a little bigger or smaller than oldsize.
                 * If it's smaller, the attach should fail.
                 * If it's larger, and we're doing a replace,
                 * we should get dynamic LUN growth when we're done.
                 */
                newsize = 10 * oldsize / (9 + ztest_random(3));
        }

        /*
         * If pvd is not a mirror or root, the attach should fail with ENOTSUP,
         * unless it's a replace; in that case any non-replacing parent is OK.
         *
         * If newvd is already part of the pool, it should fail with EBUSY.
         *
         * If newvd is too small, it should fail with EOVERFLOW.
         */
        if (pvd->vdev_ops != &vdev_mirror_ops &&
            pvd->vdev_ops != &vdev_root_ops && (!replacing ||
            pvd->vdev_ops == &vdev_replacing_ops ||
            pvd->vdev_ops == &vdev_spare_ops))
                expected_error = ENOTSUP;
        else if (newvd_is_spare && (!replacing || oldvd_is_log))
                expected_error = ENOTSUP;
        else if (newvd == oldvd)
                expected_error = replacing ? 0 : EBUSY;
        else if (vdev_lookup_by_path(rvd, newpath) != NULL)
                expected_error = EBUSY;
        else if (newsize < oldsize)
                expected_error = EOVERFLOW;
        else if (ashift > oldvd->vdev_top->vdev_ashift)
                expected_error = EDOM;
        else
                expected_error = 0;

        spa_config_exit(spa, SCL_VDEV, FTAG);

        /*
         * Build the nvlist describing newpath.
         */
        root = make_vdev_root(newpath, NULL, NULL, newvd == NULL ? newsize : 0,
            ashift, 0, 0, 0, 1);

        error = spa_vdev_attach(spa, oldguid, root, replacing);

        nvlist_free(root);

        /*
         * If our parent was the replacing vdev, but the replace completed,
         * then instead of failing with ENOTSUP we may either succeed,
         * fail with ENODEV, or fail with EOVERFLOW.
         */
        if (expected_error == ENOTSUP &&
            (error == 0 || error == ENODEV || error == EOVERFLOW))
                expected_error = error;

        /*
         * If someone grew the LUN, the replacement may be too small.
         */
        if (error == EOVERFLOW || error == EBUSY)
                expected_error = error;

        /* XXX workaround 6690467 */
        if (error != expected_error && expected_error != EBUSY) {
                fatal(0, "attach (%s %llu, %s %llu, %d) "
                    "returned %d, expected %d",
                    oldpath, oldsize, newpath,
                    newsize, replacing, error, expected_error);
        }
out:
        mutex_exit(&ztest_vdev_lock);

        umem_free(oldpath, MAXPATHLEN);
        umem_free(newpath, MAXPATHLEN);
}

/*
 * Callback function which expands the physical size of the vdev.
 */
vdev_t *
grow_vdev(vdev_t *vd, void *arg)
{
        ASSERTV(spa_t *spa = vd->vdev_spa);
        size_t *newsize = arg;
        size_t fsize;
        int fd;

        ASSERT(spa_config_held(spa, SCL_STATE, RW_READER) == SCL_STATE);
        ASSERT(vd->vdev_ops->vdev_op_leaf);

        if ((fd = open(vd->vdev_path, O_RDWR)) == -1)
                return (vd);

        fsize = lseek(fd, 0, SEEK_END);
        VERIFY(ftruncate(fd, *newsize) == 0);

        if (ztest_opts.zo_verbose >= 6) {
                (void) printf("%s grew from %lu to %lu bytes\n",
                    vd->vdev_path, (ulong_t)fsize, (ulong_t)*newsize);
        }
        (void) close(fd);
        return (NULL);
}

/*
 * Callback function which expands a given vdev by calling vdev_online().
 */
/* ARGSUSED */
vdev_t *
online_vdev(vdev_t *vd, void *arg)
{
        spa_t *spa = vd->vdev_spa;
        vdev_t *tvd = vd->vdev_top;
        uint64_t guid = vd->vdev_guid;
        uint64_t generation = spa->spa_config_generation + 1;
        vdev_state_t newstate = VDEV_STATE_UNKNOWN;
        int error;

        ASSERT(spa_config_held(spa, SCL_STATE, RW_READER) == SCL_STATE);
        ASSERT(vd->vdev_ops->vdev_op_leaf);

        /* Calling vdev_online will initialize the new metaslabs */
        spa_config_exit(spa, SCL_STATE, spa);
        error = vdev_online(spa, guid, ZFS_ONLINE_EXPAND, &newstate);
        spa_config_enter(spa, SCL_STATE, spa, RW_READER);

        /*
         * If vdev_online returned an error or the underlying vdev_open
         * failed then we abort the expand. The only way to know that
         * vdev_open fails is by checking the returned newstate.
         */
        if (error || newstate != VDEV_STATE_HEALTHY) {
                if (ztest_opts.zo_verbose >= 5) {
                        (void) printf("Unable to expand vdev, state %llu, "
                            "error %d\n", (u_longlong_t)newstate, error);
                }
                return (vd);
        }
        ASSERT3U(newstate, ==, VDEV_STATE_HEALTHY);

        /*
         * Since we dropped the lock we need to ensure that we're
         * still talking to the original vdev. It's possible this
         * vdev may have been detached/replaced while we were
         * trying to online it.
         */
        if (generation != spa->spa_config_generation) {
                if (ztest_opts.zo_verbose >= 5) {
                        (void) printf("vdev configuration has changed, "
                            "guid %llu, state %llu, expected gen %llu, "
                            "got gen %llu\n",
                            (u_longlong_t)guid,
                            (u_longlong_t)tvd->vdev_state,
                            (u_longlong_t)generation,
                            (u_longlong_t)spa->spa_config_generation);
                }
                return (vd);
        }
        return (NULL);
}

/*
 * Traverse the vdev tree calling the supplied function.
 * We continue to walk the tree until we either have walked all
 * children or we receive a non-NULL return from the callback.
 * If a NULL callback is passed, then we just return back the first
 * leaf vdev we encounter.
 */
vdev_t *
vdev_walk_tree(vdev_t *vd, vdev_t *(*func)(vdev_t *, void *), void *arg)
{
        uint_t c;

        if (vd->vdev_ops->vdev_op_leaf) {
                if (func == NULL)
                        return (vd);
                else
                        return (func(vd, arg));
        }

        for (c = 0; c < vd->vdev_children; c++) {
                vdev_t *cvd = vd->vdev_child[c];
                if ((cvd = vdev_walk_tree(cvd, func, arg)) != NULL)
                        return (cvd);
        }
        return (NULL);
}

/*
 * Verify that dynamic LUN growth works as expected.
 */
/* ARGSUSED */
void
ztest_vdev_LUN_growth(ztest_ds_t *zd, uint64_t id)
{
        spa_t *spa = ztest_spa;
        vdev_t *vd, *tvd;
        metaslab_class_t *mc;
        metaslab_group_t *mg;
        size_t psize, newsize;
        uint64_t top;
        uint64_t old_class_space, new_class_space, old_ms_count, new_ms_count;

        mutex_enter(&ztest_vdev_lock);
        spa_config_enter(spa, SCL_STATE, spa, RW_READER);

        top = ztest_random_vdev_top(spa, B_TRUE);

        tvd = spa->spa_root_vdev->vdev_child[top];
        mg = tvd->vdev_mg;
        mc = mg->mg_class;
        old_ms_count = tvd->vdev_ms_count;
        old_class_space = metaslab_class_get_space(mc);

        /*
         * Determine the size of the first leaf vdev associated with
         * our top-level device.
         */
        vd = vdev_walk_tree(tvd, NULL, NULL);
        ASSERT3P(vd, !=, NULL);
        ASSERT(vd->vdev_ops->vdev_op_leaf);

        psize = vd->vdev_psize;

        /*
         * We only try to expand the vdev if it's healthy, less than 4x its
         * original size, and it has a valid psize.
         */
        if (tvd->vdev_state != VDEV_STATE_HEALTHY ||
            psize == 0 || psize >= 4 * ztest_opts.zo_vdev_size) {
                spa_config_exit(spa, SCL_STATE, spa);
                mutex_exit(&ztest_vdev_lock);
                return;
        }
        ASSERT(psize > 0);
        newsize = psize + psize / 8;
        ASSERT3U(newsize, >, psize);

        if (ztest_opts.zo_verbose >= 6) {
                (void) printf("Expanding LUN %s from %lu to %lu\n",
                    vd->vdev_path, (ulong_t)psize, (ulong_t)newsize);
        }

        /*
         * Growing the vdev is a two step process:
         *      1). expand the physical size (i.e. relabel)
         *      2). online the vdev to create the new metaslabs
         */
        if (vdev_walk_tree(tvd, grow_vdev, &newsize) != NULL ||
            vdev_walk_tree(tvd, online_vdev, NULL) != NULL ||
            tvd->vdev_state != VDEV_STATE_HEALTHY) {
                if (ztest_opts.zo_verbose >= 5) {
                        (void) printf("Could not expand LUN because "
                            "the vdev configuration changed.\n");
                }
                spa_config_exit(spa, SCL_STATE, spa);
                mutex_exit(&ztest_vdev_lock);
                return;
        }

        spa_config_exit(spa, SCL_STATE, spa);

        /*
         * Expanding the LUN will update the config asynchronously,
         * thus we must wait for the async thread to complete any
         * pending tasks before proceeding.
         */
        for (;;) {
                boolean_t done;
                mutex_enter(&spa->spa_async_lock);
                done = (spa->spa_async_thread == NULL && !spa->spa_async_tasks);
                mutex_exit(&spa->spa_async_lock);
                if (done)
                        break;
                txg_wait_synced(spa_get_dsl(spa), 0);
                (void) poll(NULL, 0, 100);
        }

        spa_config_enter(spa, SCL_STATE, spa, RW_READER);

        tvd = spa->spa_root_vdev->vdev_child[top];
        new_ms_count = tvd->vdev_ms_count;
        new_class_space = metaslab_class_get_space(mc);

        if (tvd->vdev_mg != mg || mg->mg_class != mc) {
                if (ztest_opts.zo_verbose >= 5) {
                        (void) printf("Could not verify LUN expansion due to "
                            "intervening vdev offline or remove.\n");
                }
                spa_config_exit(spa, SCL_STATE, spa);
                mutex_exit(&ztest_vdev_lock);
                return;
        }

        /*
         * Make sure we were able to grow the vdev.
         */
        if (new_ms_count <= old_ms_count)
                fatal(0, "LUN expansion failed: ms_count %llu <= %llu\n",
                    old_ms_count, new_ms_count);

        /*
         * Make sure we were able to grow the pool.
         */
        if (new_class_space <= old_class_space)
                fatal(0, "LUN expansion failed: class_space %llu <= %llu\n",
                    old_class_space, new_class_space);

        if (ztest_opts.zo_verbose >= 5) {
                char oldnumbuf[6], newnumbuf[6];

                nicenum(old_class_space, oldnumbuf);
                nicenum(new_class_space, newnumbuf);
                (void) printf("%s grew from %s to %s\n",
                    spa->spa_name, oldnumbuf, newnumbuf);
        }

        spa_config_exit(spa, SCL_STATE, spa);
        mutex_exit(&ztest_vdev_lock);
}

/*
 * Verify that dmu_objset_{create,destroy,open,close} work as expected.
 */
/* ARGSUSED */
static void
ztest_objset_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx)
{
        /*
         * Create the objects common to all ztest datasets.
         */
        VERIFY(zap_create_claim(os, ZTEST_DIROBJ,
            DMU_OT_ZAP_OTHER, DMU_OT_NONE, 0, tx) == 0);
}

static int
ztest_dataset_create(char *dsname)
{
        uint64_t zilset = ztest_random(100);
        int err = dmu_objset_create(dsname, DMU_OST_OTHER, 0,
            ztest_objset_create_cb, NULL);

        if (err || zilset < 80)
                return (err);

        if (ztest_opts.zo_verbose >= 5)
                (void) printf("Setting dataset %s to sync always\n", dsname);
        return (ztest_dsl_prop_set_uint64(dsname, ZFS_PROP_SYNC,
            ZFS_SYNC_ALWAYS, B_FALSE));
}

/* ARGSUSED */
static int
ztest_objset_destroy_cb(const char *name, void *arg)
{
        objset_t *os;
        dmu_object_info_t doi;
        int error;

        /*
         * Verify that the dataset contains a directory object.
         */
        VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_TRUE, FTAG, &os));
        error = dmu_object_info(os, ZTEST_DIROBJ, &doi);
        if (error != ENOENT) {
                /* We could have crashed in the middle of destroying it */
                ASSERT0(error);
                ASSERT3U(doi.doi_type, ==, DMU_OT_ZAP_OTHER);
                ASSERT3S(doi.doi_physical_blocks_512, >=, 0);
        }
        dmu_objset_disown(os, FTAG);

        /*
         * Destroy the dataset.
         */
        if (strchr(name, '@') != NULL) {
                VERIFY0(dsl_destroy_snapshot(name, B_TRUE));
        } else {
                error = dsl_destroy_head(name);
                /* There could be a hold on this dataset */
                if (error != EBUSY)
                        ASSERT0(error);
        }
        return (0);
}

static boolean_t
ztest_snapshot_create(char *osname, uint64_t id)
{
        char snapname[ZFS_MAX_DATASET_NAME_LEN];
        int error;

        (void) snprintf(snapname, sizeof (snapname), "%llu", (u_longlong_t)id);

        error = dmu_objset_snapshot_one(osname, snapname);
        if (error == ENOSPC) {
                ztest_record_enospc(FTAG);
                return (B_FALSE);
        }
        if (error != 0 && error != EEXIST) {
                fatal(0, "ztest_snapshot_create(%s@%s) = %d", osname,
                    snapname, error);
        }
        return (B_TRUE);
}

static boolean_t
ztest_snapshot_destroy(char *osname, uint64_t id)
{
        char snapname[ZFS_MAX_DATASET_NAME_LEN];
        int error;

        (void) snprintf(snapname, sizeof (snapname), "%s@%llu", osname,
            (u_longlong_t)id);

        error = dsl_destroy_snapshot(snapname, B_FALSE);
        if (error != 0 && error != ENOENT)
                fatal(0, "ztest_snapshot_destroy(%s) = %d", snapname, error);
        return (B_TRUE);
}

/* ARGSUSED */
void
ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
{
        ztest_ds_t *zdtmp;
        int iters;
        int error;
        objset_t *os, *os2;
        char name[ZFS_MAX_DATASET_NAME_LEN];
        zilog_t *zilog;
        int i;

        zdtmp = umem_alloc(sizeof (ztest_ds_t), UMEM_NOFAIL);

        (void) rw_rdlock(&ztest_name_lock);

        (void) snprintf(name, sizeof (name), "%s/temp_%llu",
            ztest_opts.zo_pool, (u_longlong_t)id);

        /*
         * If this dataset exists from a previous run, process its replay log
         * half of the time.  If we don't replay it, then dsl_destroy_head()
         * (invoked from ztest_objset_destroy_cb()) should just throw it away.
         */
        if (ztest_random(2) == 0 &&
            dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, FTAG, &os) == 0) {
                ztest_zd_init(zdtmp, NULL, os);
                zil_replay(os, zdtmp, ztest_replay_vector);
                ztest_zd_fini(zdtmp);
                dmu_objset_disown(os, FTAG);
        }

        /*
         * There may be an old instance of the dataset we're about to
         * create lying around from a previous run.  If so, destroy it
         * and all of its snapshots.
         */
        (void) dmu_objset_find(name, ztest_objset_destroy_cb, NULL,
            DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);

        /*
         * Verify that the destroyed dataset is no longer in the namespace.
         */
        VERIFY3U(ENOENT, ==, dmu_objset_own(name, DMU_OST_OTHER, B_TRUE,
            FTAG, &os));

        /*
         * Verify that we can create a new dataset.
         */
        error = ztest_dataset_create(name);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_objset_create(%s) = %d", name, error);
        }

        VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, FTAG, &os));

        ztest_zd_init(zdtmp, NULL, os);

        /*
         * Open the intent log for it.
         */
        zilog = zil_open(os, ztest_get_data);

        /*
         * Put some objects in there, do a little I/O to them,
         * and randomly take a couple of snapshots along the way.
         */
        iters = ztest_random(5);
        for (i = 0; i < iters; i++) {
                ztest_dmu_object_alloc_free(zdtmp, id);
                if (ztest_random(iters) == 0)
                        (void) ztest_snapshot_create(name, i);
        }

        /*
         * Verify that we cannot create an existing dataset.
         */
        VERIFY3U(EEXIST, ==,
            dmu_objset_create(name, DMU_OST_OTHER, 0, NULL, NULL));

        /*
         * Verify that we can hold an objset that is also owned.
         */
        VERIFY3U(0, ==, dmu_objset_hold(name, FTAG, &os2));
        dmu_objset_rele(os2, FTAG);

        /*
         * Verify that we cannot own an objset that is already owned.
         */
        VERIFY3U(EBUSY, ==,
            dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, FTAG, &os2));

        zil_close(zilog);
        dmu_objset_disown(os, FTAG);
        ztest_zd_fini(zdtmp);
out:
        (void) rw_unlock(&ztest_name_lock);

        umem_free(zdtmp, sizeof (ztest_ds_t));
}

/*
 * Verify that dmu_snapshot_{create,destroy,open,close} work as expected.
 */
void
ztest_dmu_snapshot_create_destroy(ztest_ds_t *zd, uint64_t id)
{
        (void) rw_rdlock(&ztest_name_lock);
        (void) ztest_snapshot_destroy(zd->zd_name, id);
        (void) ztest_snapshot_create(zd->zd_name, id);
        (void) rw_unlock(&ztest_name_lock);
}

/*
 * Cleanup non-standard snapshots and clones.
 */
void
ztest_dsl_dataset_cleanup(char *osname, uint64_t id)
{
        char *snap1name;
        char *clone1name;
        char *snap2name;
        char *clone2name;
        char *snap3name;
        int error;

        snap1name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        clone1name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        snap2name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        clone2name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        snap3name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);

        (void) snprintf(snap1name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s1_%llu", osname, (u_longlong_t)id);
        (void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN,
            "%s/c1_%llu", osname, (u_longlong_t)id);
        (void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s2_%llu", clone1name, (u_longlong_t)id);
        (void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN,
            "%s/c2_%llu", osname, (u_longlong_t)id);
        (void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s3_%llu", clone1name, (u_longlong_t)id);

        error = dsl_destroy_head(clone2name);
        if (error && error != ENOENT)
                fatal(0, "dsl_destroy_head(%s) = %d", clone2name, error);
        error = dsl_destroy_snapshot(snap3name, B_FALSE);
        if (error && error != ENOENT)
                fatal(0, "dsl_destroy_snapshot(%s) = %d", snap3name, error);
        error = dsl_destroy_snapshot(snap2name, B_FALSE);
        if (error && error != ENOENT)
                fatal(0, "dsl_destroy_snapshot(%s) = %d", snap2name, error);
        error = dsl_destroy_head(clone1name);
        if (error && error != ENOENT)
                fatal(0, "dsl_destroy_head(%s) = %d", clone1name, error);
        error = dsl_destroy_snapshot(snap1name, B_FALSE);
        if (error && error != ENOENT)
                fatal(0, "dsl_destroy_snapshot(%s) = %d", snap1name, error);

        umem_free(snap1name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(clone1name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(snap2name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(clone2name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(snap3name, ZFS_MAX_DATASET_NAME_LEN);
}

/*
 * Verify dsl_dataset_promote handles EBUSY
 */
void
ztest_dsl_dataset_promote_busy(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os;
        char *snap1name;
        char *clone1name;
        char *snap2name;
        char *clone2name;
        char *snap3name;
        char *osname = zd->zd_name;
        int error;

        snap1name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        clone1name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        snap2name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        clone2name = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);
        snap3name  = umem_alloc(ZFS_MAX_DATASET_NAME_LEN, UMEM_NOFAIL);

        (void) rw_rdlock(&ztest_name_lock);

        ztest_dsl_dataset_cleanup(osname, id);

        (void) snprintf(snap1name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s1_%llu", osname, (u_longlong_t)id);
        (void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN,
            "%s/c1_%llu", osname, (u_longlong_t)id);
        (void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s2_%llu", clone1name, (u_longlong_t)id);
        (void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN,
            "%s/c2_%llu", osname, (u_longlong_t)id);
        (void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN,
            "%s@s3_%llu", clone1name, (u_longlong_t)id);

        error = dmu_objset_snapshot_one(osname, strchr(snap1name, '@') + 1);
        if (error && error != EEXIST) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_take_snapshot(%s) = %d", snap1name, error);
        }

        error = dmu_objset_clone(clone1name, snap1name);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_objset_create(%s) = %d", clone1name, error);
        }

        error = dmu_objset_snapshot_one(clone1name, strchr(snap2name, '@') + 1);
        if (error && error != EEXIST) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_open_snapshot(%s) = %d", snap2name, error);
        }

        error = dmu_objset_snapshot_one(clone1name, strchr(snap3name, '@') + 1);
        if (error && error != EEXIST) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_open_snapshot(%s) = %d", snap3name, error);
        }

        error = dmu_objset_clone(clone2name, snap3name);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc(FTAG);
                        goto out;
                }
                fatal(0, "dmu_objset_create(%s) = %d", clone2name, error);
        }

        error = dmu_objset_own(snap2name, DMU_OST_ANY, B_TRUE, FTAG, &os);
        if (error)
                fatal(0, "dmu_objset_own(%s) = %d", snap2name, error);
        error = dsl_dataset_promote(clone2name, NULL);
        if (error == ENOSPC) {
                dmu_objset_disown(os, FTAG);
                ztest_record_enospc(FTAG);
                goto out;
        }
        if (error != EBUSY)
                fatal(0, "dsl_dataset_promote(%s), %d, not EBUSY", clone2name,
                    error);
        dmu_objset_disown(os, FTAG);

out:
        ztest_dsl_dataset_cleanup(osname, id);

        (void) rw_unlock(&ztest_name_lock);

        umem_free(snap1name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(clone1name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(snap2name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(clone2name, ZFS_MAX_DATASET_NAME_LEN);
        umem_free(snap3name, ZFS_MAX_DATASET_NAME_LEN);
}

#undef OD_ARRAY_SIZE
#define OD_ARRAY_SIZE   4

/*
 * Verify that dmu_object_{alloc,free} work as expected.
 */
void
ztest_dmu_object_alloc_free(ztest_ds_t *zd, uint64_t id)
{
        ztest_od_t *od;
        int batchsize;
        int size;
        int b;

        size = sizeof (ztest_od_t) * OD_ARRAY_SIZE;
        od = umem_alloc(size, UMEM_NOFAIL);
        batchsize = OD_ARRAY_SIZE;

        for (b = 0; b < batchsize; b++)
                ztest_od_init(od + b, id, FTAG, b, DMU_OT_UINT64_OTHER,
                    0, 0, 0);

        /*
         * Destroy the previous batch of objects, create a new batch,
         * and do some I/O on the new objects.
         */
        if (ztest_object_init(zd, od, size, B_TRUE) != 0)
                return;

        while (ztest_random(4 * batchsize) != 0)
                ztest_io(zd, od[ztest_random(batchsize)].od_object,
                    ztest_random(ZTEST_RANGE_LOCKS) << SPA_MAXBLOCKSHIFT);

        umem_free(od, size);
}

#undef OD_ARRAY_SIZE
#define OD_ARRAY_SIZE   2

/*
 * Verify that dmu_{read,write} work as expected.
 */
void
ztest_dmu_read_write(ztest_ds_t *zd, uint64_t id)
{
        int size;
        ztest_od_t *od;

        objset_t *os = zd->zd_os;
        size = sizeof (ztest_od_t) * OD_ARRAY_SIZE;
        od = umem_alloc(size, UMEM_NOFAIL);
        dmu_tx_t *tx;
        int i, freeit, error;
        uint64_t n, s, txg;
        bufwad_t *packbuf, *bigbuf, *pack, *bigH, *bigT;
        uint64_t packobj, packoff, packsize, bigobj, bigoff, bigsize;
        uint64_t chunksize = (1000 + ztest_random(1000)) * sizeof (uint64_t);
        uint64_t regions = 997;
        uint64_t stride = 123456789ULL;
        uint64_t width = 40;
        int free_percent = 5;

        /*
         * This test uses two objects, packobj and bigobj, that are always
         * updated together (i.e. in the same tx) so that their contents are
         * in sync and can be compared.  Their contents relate to each other
         * in a simple way: packobj is a dense array of 'bufwad' structures,
         * while bigobj is a sparse array of the same bufwads.  Specifically,
         * for any index n, there are three bufwads that should be identical:
         *
         *      packobj, at offset n * sizeof (bufwad_t)
         *      bigobj, at the head of the nth chunk
         *      bigobj, at the tail of the nth chunk
         *
         * The chunk size is arbitrary. It doesn't have to be a power of two,
         * and it doesn't have any relation to the object blocksize.
         * The only requirement is that it can hold at least two bufwads.
         *
         * Normally, we write the bufwad to each of these locations.
         * However, free_percent of the time we instead write zeroes to
         * packobj and perform a dmu_free_range() on bigobj.  By comparing
         * bigobj to packobj, we can verify that the DMU is correctly
         * tracking which parts of an object are allocated and free,
         * and that the contents of the allocated blocks are correct.
         */

        /*
         * Read the directory info.  If it's the first time, set things up.
         */
        ztest_od_init(od, id, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0, chunksize);
        ztest_od_init(od + 1, id, FTAG, 1, DMU_OT_UINT64_OTHER, 0, 0,
            chunksize);

        if (ztest_object_init(zd, od, size, B_FALSE) != 0) {
                umem_free(od, size);
                return;
        }

        bigobj = od[0].od_object;
        packobj = od[1].od_object;
        chunksize = od[0].od_gen;
        ASSERT(chunksize == od[1].od_gen);

        /*
         * Prefetch a random chunk of the big object.
         * Our aim here is to get some async reads in flight
         * for blocks that we may free below; the DMU should
         * handle this race correctly.
         */
        n = ztest_random(regions) * stride + ztest_random(width);
        s = 1 + ztest_random(2 * width - 1);
        dmu_prefetch(os, bigobj, 0, n * chunksize, s * chunksize,
            ZIO_PRIORITY_SYNC_READ);

        /*
         * Pick a random index and compute the offsets into packobj and bigobj.
         */
        n = ztest_random(regions) * stride + ztest_random(width);
        s = 1 + ztest_random(width - 1);

        packoff = n * sizeof (bufwad_t);
        packsize = s * sizeof (bufwad_t);

        bigoff = n * chunksize;
        bigsize = s * chunksize;

        packbuf = umem_alloc(packsize, UMEM_NOFAIL);
        bigbuf = umem_alloc(bigsize, UMEM_NOFAIL);

        /*
         * free_percent of the time, free a range of bigobj rather than
         * overwriting it.
         */
        freeit = (ztest_random(100) < free_percent);

        /*
         * Read the current contents of our objects.
         */
        error = dmu_read(os, packobj, packoff, packsize, packbuf,
            DMU_READ_PREFETCH);
        ASSERT0(error);
        error = dmu_read(os, bigobj, bigoff, bigsize, bigbuf,
            DMU_READ_PREFETCH);
        ASSERT0(error);

        /*
         * Get a tx for the mods to both packobj and bigobj.
         */
        tx = dmu_tx_create(os);

        dmu_tx_hold_write(tx, packobj, packoff, packsize);

        if (freeit)
                dmu_tx_hold_free(tx, bigobj, bigoff, bigsize);
        else
                dmu_tx_hold_write(tx, bigobj, bigoff, bigsize);

        /* This accounts for setting the checksum/compression. */
        dmu_tx_hold_bonus(tx, bigobj);

        txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
        if (txg == 0) {
                umem_free(packbuf, packsize);
                umem_free(bigbuf, bigsize);
                umem_free(od, size);
                return;
        }

        enum zio_checksum cksum;
        do {
                cksum = (enum zio_checksum)
                    ztest_random_dsl_prop(ZFS_PROP_CHECKSUM);
        } while (cksum >= ZIO_CHECKSUM_LEGACY_FUNCTIONS);
        dmu_object_set_checksum(os, bigobj, cksum, tx);

        enum zio_compress comp;
        do {
                comp = (enum zio_compress)
                    ztest_random_dsl_prop(ZFS_PROP_COMPRESSION);
        } while (comp >= ZIO_COMPRESS_LEGACY_FUNCTIONS);
        dmu_object_set_compress(os, bigobj, comp, tx);

        /*
         * For each index from n to n + s, verify that the existing bufwad
         * in packobj matches the bufwads at the head and tail of the
         * corresponding chunk in bigobj.  Then update all three bufwads
         * with the new values we want to write out.
         */
        for (i = 0; i < s; i++) {
                /* LINTED */
                pack = (bufwad_t *)((char *)packbuf + i * sizeof (bufwad_t));
                /* LINTED */
                bigH = (bufwad_t *)((char *)bigbuf + i * chunksize);
                /* LINTED */
                bigT = (bufwad_t *)((char *)bigH + chunksize) - 1;

                ASSERT((uintptr_t)bigH - (uintptr_t)bigbuf < bigsize);
                ASSERT((uintptr_t)bigT - (uintptr_t)bigbuf < bigsize);

                if (pack->bw_txg > txg)
                        fatal(0, "future leak: got %llx, open txg is %llx",
                            pack->bw_txg, txg);

                if (pack->bw_data != 0 && pack->bw_index != n + i)
                        fatal(0, "wrong index: got %llx, wanted %llx+%llx",
                            pack->bw_index, n, i);

                if (bcmp(pack, bigH, sizeof (bufwad_t)) != 0)
                        fatal(0, "pack/bigH mismatch in %p/%p", pack, bigH);

                if (bcmp(pack, bigT, sizeof (bufwad_t)) != 0)
                        fatal(0, "pack/bigT mismatch in %p/%p", pack, bigT);

                if (freeit) {
                        bzero(pack, sizeof (bufwad_t));
                } else {
                        pack->bw_index = n + i;
                        pack->bw_txg = txg;
                        pack->bw_data = 1 + ztest_random(-2ULL);
                }
                *bigH = *pack;
                *bigT = *pack;
        }

        /*
         * We've verified all the old bufwads, and made new ones.
         * Now write them out.
         */
        dmu_write(os, packobj, packoff, packsize, packbuf, tx);

        if (freeit) {
                if (ztest_opts.zo_verbose >= 7) {
                        (void) printf("freeing offset %llx size %llx"
                            " txg %llx\n",
                            (u_longlong_t)bigoff,
                            (u_longlong_t)bigsize,
                            (u_longlong_t)txg);
                }
                VERIFY(0 == dmu_free_range(os, bigobj, bigoff, bigsize, tx));
        } else {
                if (ztest_opts.zo_verbose >= 7) {
                        (void) printf("writing offset %llx size %llx"
                            " txg %llx\n",
                            (u_longlong_t)bigoff,
                            (u_longlong_t)bigsize,
                            (u_longlong_t)txg);
                }
                dmu_write(os, bigobj, bigoff, bigsize, bigbuf, tx);
        }

        dmu_tx_commit(tx);

        /*
         * Sanity check the stuff we just wrote.
         */
        {
                void *packcheck = umem_alloc(packsize, UMEM_NOFAIL);
                void *bigcheck = umem_alloc(bigsize, UMEM_NOFAIL);

                VERIFY(0 == dmu_read(os, packobj, packoff,
                    packsize, packcheck, DMU_READ_PREFETCH));
                VERIFY(0 == dmu_read(os, bigobj, bigoff,
                    bigsize, bigcheck, DMU_READ_PREFETCH));

                ASSERT(bcmp(packbuf, packcheck, packsize) == 0);
                ASSERT(bcmp(bigbuf, bigcheck, bigsize) == 0);

                umem_free(packcheck, packsize);
                umem_free(bigcheck, bigsize);
        }

        umem_free(packbuf, packsize);
        umem_free(bigbuf, bigsize);
        umem_free(od, size);
}

void
compare_and_update_pbbufs(uint64_t s, bufwad_t *packbuf, bufwad_t *bigbuf,
    uint64_t bigsize, uint64_t n, uint64_t chunksize, uint64_t txg)
{
        uint64_t i;
        bufwad_t *pack;
        bufwad_t *bigH;
        bufwad_t *bigT;

        /*
         * For each index from n to n + s, verify that the existing bufwad
         * in packobj matches the bufwads at the head and tail of the
         * corresponding chunk in bigobj.  Then update all three bufwads
         * with the new values we want to write out.
         */
        for (i = 0; i < s; i++) {
                /* LINTED */
                pack = (bufwad_t *)((char *)packbuf + i * sizeof (bufwad_t));
                /* LINTED */
                bigH = (bufwad_t *)((char *)bigbuf + i * chunksize);
                /* LINTED */
                bigT = (bufwad_t *)((char *)bigH + chunksize) - 1;

                ASSERT((uintptr_t)bigH - (uintptr_t)bigbuf < bigsize);
                ASSERT((uintptr_t)bigT - (uintptr_t)bigbuf < bigsize);

                if (pack->bw_txg > txg)
                        fatal(0, "future leak: got %llx, open txg is %llx",
                            pack->bw_txg, txg);

                if (pack->bw_data != 0 && pack->bw_index != n + i)
                        fatal(0, "wrong index: got %llx, wanted %llx+%llx",
                            pack->bw_index, n, i);

                if (bcmp(pack, bigH, sizeof (bufwad_t)) != 0)
                        fatal(0, "pack/bigH mismatch in %p/%p", pack, bigH);

                if (bcmp(pack, bigT, sizeof (bufwad_t)) != 0)
                        fatal(0, "pack/bigT mismatch in %p/%p", pack, bigT);

                pack->bw_index = n + i;
                pack->bw_txg = txg;
                pack->bw_data = 1 + ztest_random(-2ULL);

                *bigH = *pack;
                *bigT = *pack;
        }
}

#undef OD_ARRAY_SIZE
#define OD_ARRAY_SIZE   2

void
ztest_dmu_read_write_zcopy(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        dmu_tx_t *tx;
        uint64_t i;
        int error;
        int size;
        uint64_t n, s, txg;
        bufwad_t *packbuf, *bigbuf;
        uint64_t packobj, packoff, packsize, bigobj, bigoff, bigsize;
        uint64_t blocksize = ztest_random_blocksize();
        uint64_t chunksize = blocksize;
        uint64_t regions = 997;
        uint64_t stride = 123456789ULL;
        uint64_t width = 9;
        dmu_buf_t *bonus_db;
        arc_buf_t **bigbuf_arcbufs;
        dmu_object_info_t doi;

        size = sizeof (ztest_od_t) * OD_ARRAY_SIZE;
        od = umem_alloc(size, UMEM_NOFAIL);

        /*
         * This test uses two objects, packobj and bigobj, that are always
         * updated together (i.e. in the same tx) so that their contents are
         * in sync and can be compared.  Their contents relate to each other
         * in a simple way: packobj is a dense array of 'bufwad' structures,
         * while bigobj is a sparse array of the same bufwads.  Specifically,
         * for any index n, there are three bufwads that should be identical:
         *
         *      packobj, at offset n * sizeof (bufwad_t)
         *      bigobj, at the head of the nth chunk
         *      bigobj, at the tail of the nth chunk
         *
         * The chunk size is set equal to bigobj block size so that
         * dmu_assign_arcbuf() can be tested for object updates.
         */

        /*
         * Read the directory info.  If it's the first time, set things up.
         */
        ztest_od_init(od, id, FTAG, 0, DMU_OT_UINT64_OTHER, blocksize, 0, 0);
        ztest_od_init(od + 1, id, FTAG, 1, DMU_OT_UINT64_OTHER, 0, 0,
            chunksize);


        if (ztest_object_init(zd, od, size, B_FALSE) != 0) {
                umem_free(od, size);
                return;
        }

        bigobj = od[0].od_object;
        packobj = od[1].od_object;
        blocksize = od[0].od_blocksize;
        chunksize = blocksize;
        ASSERT(chunksize == od[1].od_gen);

        VERIFY(dmu_object_info(os, bigobj, &doi) == 0);
        VERIFY(ISP2(doi.doi_data_block_size));
        VERIFY(chunksize == doi.doi_data_block_size);
        VERIFY(chunksize >= 2 * sizeof (bufwad_t));

        /*
         * Pick a random index and compute the offsets into packobj and bigobj.
         */
        n = ztest_random(regions) * stride + ztest_random(width);
        s = 1 + ztest_random(width - 1);

        packoff = n * sizeof (bufwad_t);
        packsize = s * sizeof (bufwad_t);

        bigoff = n * chunksize;
        bigsize = s * chunksize;

        packbuf = umem_zalloc(packsize, UMEM_NOFAIL);
        bigbuf = umem_zalloc(bigsize, UMEM_NOFAIL);

        VERIFY3U(0, ==, dmu_bonus_hold(os, bigobj, FTAG, &bonus_db));

        bigbuf_arcbufs = umem_zalloc(2 * s * sizeof (arc_buf_t *), UMEM_NOFAIL);

        /*
         * Iteration 0 test zcopy for DB_UNCACHED dbufs.
         * Iteration 1 test zcopy to already referenced dbufs.
         * Iteration 2 test zcopy to dirty dbuf in the same txg.
         * Iteration 3 test zcopy to dbuf dirty in previous txg.
         * Iteration 4 test zcopy when dbuf is no longer dirty.
         * Iteration 5 test zcopy when it can't be done.
         * Iteration 6 one more zcopy write.
         */
        for (i = 0; i < 7; i++) {
                uint64_t j;
                uint64_t off;

                /*
                 * In iteration 5 (i == 5) use arcbufs
                 * that don't match bigobj blksz to test
                 * dmu_assign_arcbuf() when it can't directly
                 * assign an arcbuf to a dbuf.
                 */
                for (j = 0; j < s; j++) {
                        if (i != 5 || chunksize < (SPA_MINBLOCKSIZE * 2)) {
                                bigbuf_arcbufs[j] =
                                    dmu_request_arcbuf(bonus_db, chunksize);
                        } else {
                                bigbuf_arcbufs[2 * j] =
                                    dmu_request_arcbuf(bonus_db, chunksize / 2);
                                bigbuf_arcbufs[2 * j + 1] =
                                    dmu_request_arcbuf(bonus_db, chunksize / 2);
                        }
                }

                /*
                 * Get a tx for the mods to both packobj and bigobj.
                 */
                tx = dmu_tx_create(os);

                dmu_tx_hold_write(tx, packobj, packoff, packsize);
                dmu_tx_hold_write(tx, bigobj, bigoff, bigsize);

                txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
                if (txg == 0) {
                        umem_free(packbuf, packsize);
                        umem_free(bigbuf, bigsize);
                        for (j = 0; j < s; j++) {
                                if (i != 5 ||
                                    chunksize < (SPA_MINBLOCKSIZE * 2)) {
                                        dmu_return_arcbuf(bigbuf_arcbufs[j]);
                                } else {
                                        dmu_return_arcbuf(
                                            bigbuf_arcbufs[2 * j]);
                                        dmu_return_arcbuf(
                                            bigbuf_arcbufs[2 * j + 1]);
                                }
                        }
                        umem_free(bigbuf_arcbufs, 2 * s * sizeof (arc_buf_t *));
                        umem_free(od, size);
                        dmu_buf_rele(bonus_db, FTAG);
                        return;
                }

                /*
                 * 50% of the time don't read objects in the 1st iteration to
                 * test dmu_assign_arcbuf() for the case when there're no
                 * existing dbufs for the specified offsets.
                 */
                if (i != 0 || ztest_random(2) != 0) {
                        error = dmu_read(os, packobj, packoff,
                            packsize, packbuf, DMU_READ_PREFETCH);
                        ASSERT0(error);
                        error = dmu_read(os, bigobj, bigoff, bigsize,
                            bigbuf, DMU_READ_PREFETCH);
                        ASSERT0(error);
                }
                compare_and_update_pbbufs(s, packbuf, bigbuf, bigsize,
                    n, chunksize, txg);

                /*
                 * We've verified all the old bufwads, and made new ones.
                 * Now write them out.
                 */
                dmu_write(os, packobj, packoff, packsize, packbuf, tx);
                if (ztest_opts.zo_verbose >= 7) {
                        (void) printf("writing offset %llx size %llx"
                            " txg %llx\n",
                            (u_longlong_t)bigoff,
                            (u_longlong_t)bigsize,
                            (u_longlong_t)txg);
                }
                for (off = bigoff, j = 0; j < s; j++, off += chunksize) {
                        dmu_buf_t *dbt;
                        if (i != 5 || chunksize < (SPA_MINBLOCKSIZE * 2)) {
                                bcopy((caddr_t)bigbuf + (off - bigoff),
                                    bigbuf_arcbufs[j]->b_data, chunksize);
                        } else {
                                bcopy((caddr_t)bigbuf + (off - bigoff),
                                    bigbuf_arcbufs[2 * j]->b_data,
                                    chunksize / 2);
                                bcopy((caddr_t)bigbuf + (off - bigoff) +
                                    chunksize / 2,
                                    bigbuf_arcbufs[2 * j + 1]->b_data,
                                    chunksize / 2);
                        }

                        if (i == 1) {
                                VERIFY(dmu_buf_hold(os, bigobj, off,
                                    FTAG, &dbt, DMU_READ_NO_PREFETCH) == 0);
                        }
                        if (i != 5 || chunksize < (SPA_MINBLOCKSIZE * 2)) {
                                dmu_assign_arcbuf(bonus_db, off,
                                    bigbuf_arcbufs[j], tx);
                        } else {
                                dmu_assign_arcbuf(bonus_db, off,
                                    bigbuf_arcbufs[2 * j], tx);
                                dmu_assign_arcbuf(bonus_db,
                                    off + chunksize / 2,
                                    bigbuf_arcbufs[2 * j + 1], tx);
                        }
                        if (i == 1) {
                                dmu_buf_rele(dbt, FTAG);
                        }
                }
                dmu_tx_commit(tx);

                /*
                 * Sanity check the stuff we just wrote.
                 */
                {
                        void *packcheck = umem_alloc(packsize, UMEM_NOFAIL);
                        void *bigcheck = umem_alloc(bigsize, UMEM_NOFAIL);

                        VERIFY(0 == dmu_read(os, packobj, packoff,
                            packsize, packcheck, DMU_READ_PREFETCH));
                        VERIFY(0 == dmu_read(os, bigobj, bigoff,
                            bigsize, bigcheck, DMU_READ_PREFETCH));

                        ASSERT(bcmp(packbuf, packcheck, packsize) == 0);
                        ASSERT(bcmp(bigbuf, bigcheck, bigsize) == 0);

                        umem_free(packcheck, packsize);
                        umem_free(bigcheck, bigsize);
                }
                if (i == 2) {
                        txg_wait_open(dmu_objset_pool(os), 0);
                } else if (i == 3) {
                        txg_wait_synced(dmu_objset_pool(os), 0);
                }
        }

        dmu_buf_rele(bonus_db, FTAG);
        umem_free(packbuf, packsize);
        umem_free(bigbuf, bigsize);
        umem_free(bigbuf_arcbufs, 2 * s * sizeof (arc_buf_t *));
        umem_free(od, size);
}

/* ARGSUSED */
void
ztest_dmu_write_parallel(ztest_ds_t *zd, uint64_t id)
{
        ztest_od_t *od;

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        uint64_t offset = (1ULL << (ztest_random(20) + 43)) +
            (ztest_random(ZTEST_RANGE_LOCKS) << SPA_MAXBLOCKSHIFT);

        /*
         * Have multiple threads write to large offsets in an object
         * to verify that parallel writes to an object -- even to the
         * same blocks within the object -- doesn't cause any trouble.
         */
        ztest_od_init(od, ID_PARALLEL, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t), B_FALSE) != 0)
                return;

        while (ztest_random(10) != 0)
                ztest_io(zd, od->od_object, offset);

        umem_free(od, sizeof (ztest_od_t));
}

void
ztest_dmu_prealloc(ztest_ds_t *zd, uint64_t id)
{
        ztest_od_t *od;
        uint64_t offset = (1ULL << (ztest_random(4) + SPA_MAXBLOCKSHIFT)) +
            (ztest_random(ZTEST_RANGE_LOCKS) << SPA_MAXBLOCKSHIFT);
        uint64_t count = ztest_random(20) + 1;
        uint64_t blocksize = ztest_random_blocksize();
        void *data;

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);

        ztest_od_init(od, id, FTAG, 0, DMU_OT_UINT64_OTHER, blocksize, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t),
            !ztest_random(2)) != 0) {
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        if (ztest_truncate(zd, od->od_object, offset, count * blocksize) != 0) {
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        ztest_prealloc(zd, od->od_object, offset, count * blocksize);

        data = umem_zalloc(blocksize, UMEM_NOFAIL);

        while (ztest_random(count) != 0) {
                uint64_t randoff = offset + (ztest_random(count) * blocksize);
                if (ztest_write(zd, od->od_object, randoff, blocksize,
                    data) != 0)
                        break;
                while (ztest_random(4) != 0)
                        ztest_io(zd, od->od_object, randoff);
        }

        umem_free(data, blocksize);
        umem_free(od, sizeof (ztest_od_t));
}

/*
 * Verify that zap_{create,destroy,add,remove,update} work as expected.
 */
#define ZTEST_ZAP_MIN_INTS      1
#define ZTEST_ZAP_MAX_INTS      4
#define ZTEST_ZAP_MAX_PROPS     1000

void
ztest_zap(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        uint64_t object;
        uint64_t txg, last_txg;
        uint64_t value[ZTEST_ZAP_MAX_INTS];
        uint64_t zl_ints, zl_intsize, prop;
        int i, ints;
        dmu_tx_t *tx;
        char propname[100], txgname[100];
        int error;
        char *hc[2] = { "s.acl.h", ".s.open.h.hyLZlg" };

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        ztest_od_init(od, id, FTAG, 0, DMU_OT_ZAP_OTHER, 0, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t),
            !ztest_random(2)) != 0)
                goto out;

        object = od->od_object;

        /*
         * Generate a known hash collision, and verify that
         * we can lookup and remove both entries.
         */
        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, object, B_TRUE, NULL);
        txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
        if (txg == 0)
                goto out;
        for (i = 0; i < 2; i++) {
                value[i] = i;
                VERIFY3U(0, ==, zap_add(os, object, hc[i], sizeof (uint64_t),
                    1, &value[i], tx));
        }
        for (i = 0; i < 2; i++) {
                VERIFY3U(EEXIST, ==, zap_add(os, object, hc[i],
                    sizeof (uint64_t), 1, &value[i], tx));
                VERIFY3U(0, ==,
                    zap_length(os, object, hc[i], &zl_intsize, &zl_ints));
                ASSERT3U(zl_intsize, ==, sizeof (uint64_t));
                ASSERT3U(zl_ints, ==, 1);
        }
        for (i = 0; i < 2; i++) {
                VERIFY3U(0, ==, zap_remove(os, object, hc[i], tx));
        }
        dmu_tx_commit(tx);

        /*
         * Generate a buch of random entries.
         */
        ints = MAX(ZTEST_ZAP_MIN_INTS, object % ZTEST_ZAP_MAX_INTS);

        prop = ztest_random(ZTEST_ZAP_MAX_PROPS);
        (void) sprintf(propname, "prop_%llu", (u_longlong_t)prop);
        (void) sprintf(txgname, "txg_%llu", (u_longlong_t)prop);
        bzero(value, sizeof (value));
        last_txg = 0;

        /*
         * If these zap entries already exist, validate their contents.
         */
        error = zap_length(os, object, txgname, &zl_intsize, &zl_ints);
        if (error == 0) {
                ASSERT3U(zl_intsize, ==, sizeof (uint64_t));
                ASSERT3U(zl_ints, ==, 1);

                VERIFY(zap_lookup(os, object, txgname, zl_intsize,
                    zl_ints, &last_txg) == 0);

                VERIFY(zap_length(os, object, propname, &zl_intsize,
                    &zl_ints) == 0);

                ASSERT3U(zl_intsize, ==, sizeof (uint64_t));
                ASSERT3U(zl_ints, ==, ints);

                VERIFY(zap_lookup(os, object, propname, zl_intsize,
                    zl_ints, value) == 0);

                for (i = 0; i < ints; i++) {
                        ASSERT3U(value[i], ==, last_txg + object + i);
                }
        } else {
                ASSERT3U(error, ==, ENOENT);
        }

        /*
         * Atomically update two entries in our zap object.
         * The first is named txg_%llu, and contains the txg
         * in which the property was last updated.  The second
         * is named prop_%llu, and the nth element of its value
         * should be txg + object + n.
         */
        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, object, B_TRUE, NULL);
        txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
        if (txg == 0)
                goto out;

        if (last_txg > txg)
                fatal(0, "zap future leak: old %llu new %llu", last_txg, txg);

        for (i = 0; i < ints; i++)
                value[i] = txg + object + i;

        VERIFY3U(0, ==, zap_update(os, object, txgname, sizeof (uint64_t),
            1, &txg, tx));
        VERIFY3U(0, ==, zap_update(os, object, propname, sizeof (uint64_t),
            ints, value, tx));

        dmu_tx_commit(tx);

        /*
         * Remove a random pair of entries.
         */
        prop = ztest_random(ZTEST_ZAP_MAX_PROPS);
        (void) sprintf(propname, "prop_%llu", (u_longlong_t)prop);
        (void) sprintf(txgname, "txg_%llu", (u_longlong_t)prop);

        error = zap_length(os, object, txgname, &zl_intsize, &zl_ints);

        if (error == ENOENT)
                goto out;

        ASSERT0(error);

        tx = dmu_tx_create(os);
        dmu_tx_hold_zap(tx, object, B_TRUE, NULL);
        txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
        if (txg == 0)
                goto out;
        VERIFY3U(0, ==, zap_remove(os, object, txgname, tx));
        VERIFY3U(0, ==, zap_remove(os, object, propname, tx));
        dmu_tx_commit(tx);
out:
        umem_free(od, sizeof (ztest_od_t));
}

/*
 * Testcase to test the upgrading of a microzap to fatzap.
 */
void
ztest_fzap(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        uint64_t object, txg;
        int i;

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        ztest_od_init(od, id, FTAG, 0, DMU_OT_ZAP_OTHER, 0, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t),
            !ztest_random(2)) != 0)
                goto out;
        object = od->od_object;

        /*
         * Add entries to this ZAP and make sure it spills over
         * and gets upgraded to a fatzap. Also, since we are adding
         * 2050 entries we should see ptrtbl growth and leaf-block split.
         */
        for (i = 0; i < 2050; i++) {
                char name[ZFS_MAX_DATASET_NAME_LEN];
                uint64_t value = i;
                dmu_tx_t *tx;
                int error;

                (void) snprintf(name, sizeof (name), "fzap-%llu-%llu",
                    (u_longlong_t)id, (u_longlong_t)value);

                tx = dmu_tx_create(os);
                dmu_tx_hold_zap(tx, object, B_TRUE, name);
                txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
                if (txg == 0)
                        goto out;
                error = zap_add(os, object, name, sizeof (uint64_t), 1,
                    &value, tx);
                ASSERT(error == 0 || error == EEXIST);
                dmu_tx_commit(tx);
        }
out:
        umem_free(od, sizeof (ztest_od_t));
}

/* ARGSUSED */
void
ztest_zap_parallel(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        uint64_t txg, object, count, wsize, wc, zl_wsize, zl_wc;
        dmu_tx_t *tx;
        int i, namelen, error;
        int micro = ztest_random(2);
        char name[20], string_value[20];
        void *data;

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        ztest_od_init(od, ID_PARALLEL, FTAG, micro, DMU_OT_ZAP_OTHER, 0, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t), B_FALSE) != 0) {
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        object = od->od_object;

        /*
         * Generate a random name of the form 'xxx.....' where each
         * x is a random printable character and the dots are dots.
         * There are 94 such characters, and the name length goes from
         * 6 to 20, so there are 94^3 * 15 = 12,458,760 possible names.
         */
        namelen = ztest_random(sizeof (name) - 5) + 5 + 1;

        for (i = 0; i < 3; i++)
                name[i] = '!' + ztest_random('~' - '!' + 1);
        for (; i < namelen - 1; i++)
                name[i] = '.';
        name[i] = '\0';

        if ((namelen & 1) || micro) {
                wsize = sizeof (txg);
                wc = 1;
                data = &txg;
        } else {
                wsize = 1;
                wc = namelen;
                data = string_value;
        }

        count = -1ULL;
        VERIFY0(zap_count(os, object, &count));
        ASSERT(count != -1ULL);

        /*
         * Select an operation: length, lookup, add, update, remove.
         */
        i = ztest_random(5);

        if (i >= 2) {
                tx = dmu_tx_create(os);
                dmu_tx_hold_zap(tx, object, B_TRUE, NULL);
                txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
                if (txg == 0) {
                        umem_free(od, sizeof (ztest_od_t));
                        return;
                }
                bcopy(name, string_value, namelen);
        } else {
                tx = NULL;
                txg = 0;
                bzero(string_value, namelen);
        }

        switch (i) {

        case 0:
                error = zap_length(os, object, name, &zl_wsize, &zl_wc);
                if (error == 0) {
                        ASSERT3U(wsize, ==, zl_wsize);
                        ASSERT3U(wc, ==, zl_wc);
                } else {
                        ASSERT3U(error, ==, ENOENT);
                }
                break;

        case 1:
                error = zap_lookup(os, object, name, wsize, wc, data);
                if (error == 0) {
                        if (data == string_value &&
                            bcmp(name, data, namelen) != 0)
                                fatal(0, "name '%s' != val '%s' len %d",
                                    name, data, namelen);
                } else {
                        ASSERT3U(error, ==, ENOENT);
                }
                break;

        case 2:
                error = zap_add(os, object, name, wsize, wc, data, tx);
                ASSERT(error == 0 || error == EEXIST);
                break;

        case 3:
                VERIFY(zap_update(os, object, name, wsize, wc, data, tx) == 0);
                break;

        case 4:
                error = zap_remove(os, object, name, tx);
                ASSERT(error == 0 || error == ENOENT);
                break;
        }

        if (tx != NULL)
                dmu_tx_commit(tx);

        umem_free(od, sizeof (ztest_od_t));
}

/*
 * Commit callback data.
 */
typedef struct ztest_cb_data {
        list_node_t             zcd_node;
        uint64_t                zcd_txg;
        int                     zcd_expected_err;
        boolean_t               zcd_added;
        boolean_t               zcd_called;
        spa_t                   *zcd_spa;
} ztest_cb_data_t;

/* This is the actual commit callback function */
static void
ztest_commit_callback(void *arg, int error)
{
        ztest_cb_data_t *data = arg;
        uint64_t synced_txg;

        VERIFY(data != NULL);
        VERIFY3S(data->zcd_expected_err, ==, error);
        VERIFY(!data->zcd_called);

        synced_txg = spa_last_synced_txg(data->zcd_spa);
        if (data->zcd_txg > synced_txg)
                fatal(0, "commit callback of txg %" PRIu64 " called prematurely"
                    ", last synced txg = %" PRIu64 "\n", data->zcd_txg,
                    synced_txg);

        data->zcd_called = B_TRUE;

        if (error == ECANCELED) {
                ASSERT0(data->zcd_txg);
                ASSERT(!data->zcd_added);

                /*
                 * The private callback data should be destroyed here, but
                 * since we are going to check the zcd_called field after
                 * dmu_tx_abort(), we will destroy it there.
                 */
                return;
        }

        ASSERT(data->zcd_added);
        ASSERT3U(data->zcd_txg, !=, 0);

        (void) mutex_enter(&zcl.zcl_callbacks_lock);

        /* See if this cb was called more quickly */
        if ((synced_txg - data->zcd_txg) < zc_min_txg_delay)
                zc_min_txg_delay = synced_txg - data->zcd_txg;

        /* Remove our callback from the list */
        list_remove(&zcl.zcl_callbacks, data);

        (void) mutex_exit(&zcl.zcl_callbacks_lock);

        umem_free(data, sizeof (ztest_cb_data_t));
}

/* Allocate and initialize callback data structure */
static ztest_cb_data_t *
ztest_create_cb_data(objset_t *os, uint64_t txg)
{
        ztest_cb_data_t *cb_data;

        cb_data = umem_zalloc(sizeof (ztest_cb_data_t), UMEM_NOFAIL);

        cb_data->zcd_txg = txg;
        cb_data->zcd_spa = dmu_objset_spa(os);
        list_link_init(&cb_data->zcd_node);

        return (cb_data);
}

/*
 * Commit callback test.
 */
void
ztest_dmu_commit_callbacks(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        dmu_tx_t *tx;
        ztest_cb_data_t *cb_data[3], *tmp_cb;
        uint64_t old_txg, txg;
        int i, error = 0;

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        ztest_od_init(od, id, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t), B_FALSE) != 0) {
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        tx = dmu_tx_create(os);

        cb_data[0] = ztest_create_cb_data(os, 0);
        dmu_tx_callback_register(tx, ztest_commit_callback, cb_data[0]);

        dmu_tx_hold_write(tx, od->od_object, 0, sizeof (uint64_t));

        /* Every once in a while, abort the transaction on purpose */
        if (ztest_random(100) == 0)
                error = -1;

        if (!error)
                error = dmu_tx_assign(tx, TXG_NOWAIT);

        txg = error ? 0 : dmu_tx_get_txg(tx);

        cb_data[0]->zcd_txg = txg;
        cb_data[1] = ztest_create_cb_data(os, txg);
        dmu_tx_callback_register(tx, ztest_commit_callback, cb_data[1]);

        if (error) {
                /*
                 * It's not a strict requirement to call the registered
                 * callbacks from inside dmu_tx_abort(), but that's what
                 * it's supposed to happen in the current implementation
                 * so we will check for that.
                 */
                for (i = 0; i < 2; i++) {
                        cb_data[i]->zcd_expected_err = ECANCELED;
                        VERIFY(!cb_data[i]->zcd_called);
                }

                dmu_tx_abort(tx);

                for (i = 0; i < 2; i++) {
                        VERIFY(cb_data[i]->zcd_called);
                        umem_free(cb_data[i], sizeof (ztest_cb_data_t));
                }

                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        cb_data[2] = ztest_create_cb_data(os, txg);
        dmu_tx_callback_register(tx, ztest_commit_callback, cb_data[2]);

        /*
         * Read existing data to make sure there isn't a future leak.
         */
        VERIFY(0 == dmu_read(os, od->od_object, 0, sizeof (uint64_t),
            &old_txg, DMU_READ_PREFETCH));

        if (old_txg > txg)
                fatal(0, "future leak: got %" PRIu64 ", open txg is %" PRIu64,
                    old_txg, txg);

        dmu_write(os, od->od_object, 0, sizeof (uint64_t), &txg, tx);

        (void) mutex_enter(&zcl.zcl_callbacks_lock);

        /*
         * Since commit callbacks don't have any ordering requirement and since
         * it is theoretically possible for a commit callback to be called
         * after an arbitrary amount of time has elapsed since its txg has been
         * synced, it is difficult to reliably determine whether a commit
         * callback hasn't been called due to high load or due to a flawed
         * implementation.
         *
         * In practice, we will assume that if after a certain number of txgs a
         * commit callback hasn't been called, then most likely there's an
         * implementation bug..
         */
        tmp_cb = list_head(&zcl.zcl_callbacks);
        if (tmp_cb != NULL &&
            tmp_cb->zcd_txg + ZTEST_COMMIT_CB_THRESH < txg) {
                fatal(0, "Commit callback threshold exceeded, oldest txg: %"
                    PRIu64 ", open txg: %" PRIu64 "\n", tmp_cb->zcd_txg, txg);
        }

        /*
         * Let's find the place to insert our callbacks.
         *
         * Even though the list is ordered by txg, it is possible for the
         * insertion point to not be the end because our txg may already be
         * quiescing at this point and other callbacks in the open txg
         * (from other objsets) may have sneaked in.
         */
        tmp_cb = list_tail(&zcl.zcl_callbacks);
        while (tmp_cb != NULL && tmp_cb->zcd_txg > txg)
                tmp_cb = list_prev(&zcl.zcl_callbacks, tmp_cb);

        /* Add the 3 callbacks to the list */
        for (i = 0; i < 3; i++) {
                if (tmp_cb == NULL)
                        list_insert_head(&zcl.zcl_callbacks, cb_data[i]);
                else
                        list_insert_after(&zcl.zcl_callbacks, tmp_cb,
                            cb_data[i]);

                cb_data[i]->zcd_added = B_TRUE;
                VERIFY(!cb_data[i]->zcd_called);

                tmp_cb = cb_data[i];
        }

        zc_cb_counter += 3;

        (void) mutex_exit(&zcl.zcl_callbacks_lock);

        dmu_tx_commit(tx);

        umem_free(od, sizeof (ztest_od_t));
}

/*
 * Visit each object in the dataset. Verify that its properties
 * are consistent what was stored in the block tag when it was created,
 * and that its unused bonus buffer space has not been overwritten.
 */
void
ztest_verify_dnode_bt(ztest_ds_t *zd, uint64_t id)
{
        objset_t *os = zd->zd_os;
        uint64_t obj;
        int err = 0;

        for (obj = 0; err == 0; err = dmu_object_next(os, &obj, FALSE, 0)) {
                ztest_block_tag_t *bt = NULL;
                dmu_object_info_t doi;
                dmu_buf_t *db;

                if (dmu_bonus_hold(os, obj, FTAG, &db) != 0)
                        continue;

                dmu_object_info_from_db(db, &doi);
                if (doi.doi_bonus_size >= sizeof (*bt))
                        bt = ztest_bt_bonus(db);

                if (bt && bt->bt_magic == BT_MAGIC) {
                        ztest_bt_verify(bt, os, obj, doi.doi_dnodesize,
                            bt->bt_offset, bt->bt_gen, bt->bt_txg,
                            bt->bt_crtxg);
                        ztest_verify_unused_bonus(db, bt, obj, os, bt->bt_gen);
                }

                dmu_buf_rele(db, FTAG);
        }
}

/* ARGSUSED */
void
ztest_dsl_prop_get_set(ztest_ds_t *zd, uint64_t id)
{
        zfs_prop_t proplist[] = {
                ZFS_PROP_CHECKSUM,
                ZFS_PROP_COMPRESSION,
                ZFS_PROP_COPIES,
                ZFS_PROP_DEDUP
        };
        int p;

        (void) rw_rdlock(&ztest_name_lock);

        for (p = 0; p < sizeof (proplist) / sizeof (proplist[0]); p++)
                (void) ztest_dsl_prop_set_uint64(zd->zd_name, proplist[p],
                    ztest_random_dsl_prop(proplist[p]), (int)ztest_random(2));

        VERIFY0(ztest_dsl_prop_set_uint64(zd->zd_name, ZFS_PROP_RECORDSIZE,
            ztest_random_blocksize(), (int)ztest_random(2)));

        (void) rw_unlock(&ztest_name_lock);
}

/* ARGSUSED */
void
ztest_spa_prop_get_set(ztest_ds_t *zd, uint64_t id)
{
        nvlist_t *props = NULL;

        (void) rw_rdlock(&ztest_name_lock);

        (void) ztest_spa_prop_set_uint64(ZPOOL_PROP_DEDUPDITTO,
            ZIO_DEDUPDITTO_MIN + ztest_random(ZIO_DEDUPDITTO_MIN));

        VERIFY0(spa_prop_get(ztest_spa, &props));

        if (ztest_opts.zo_verbose >= 6)
                dump_nvlist(props, 4);

        nvlist_free(props);

        (void) rw_unlock(&ztest_name_lock);
}

static int
user_release_one(const char *snapname, const char *holdname)
{
        nvlist_t *snaps, *holds;
        int error;

        snaps = fnvlist_alloc();
        holds = fnvlist_alloc();
        fnvlist_add_boolean(holds, holdname);
        fnvlist_add_nvlist(snaps, snapname, holds);
        fnvlist_free(holds);
        error = dsl_dataset_user_release(snaps, NULL);
        fnvlist_free(snaps);
        return (error);
}

/*
 * Test snapshot hold/release and deferred destroy.
 */
void
ztest_dmu_snapshot_hold(ztest_ds_t *zd, uint64_t id)
{
        int error;
        objset_t *os = zd->zd_os;
        objset_t *origin;
        char snapname[100];
        char fullname[100];
        char clonename[100];
        char tag[100];
        char osname[ZFS_MAX_DATASET_NAME_LEN];
        nvlist_t *holds;

        (void) rw_rdlock(&ztest_name_lock);

        dmu_objset_name(os, osname);

        (void) snprintf(snapname, sizeof (snapname), "sh1_%llu",
            (u_longlong_t)id);
        (void) snprintf(fullname, sizeof (fullname), "%s@%s", osname, snapname);
        (void) snprintf(clonename, sizeof (clonename),
            "%s/ch1_%llu", osname, (u_longlong_t)id);
        (void) snprintf(tag, sizeof (tag), "tag_%llu", (u_longlong_t)id);

        /*
         * Clean up from any previous run.
         */
        error = dsl_destroy_head(clonename);
        if (error != ENOENT)
                ASSERT0(error);
        error = user_release_one(fullname, tag);
        if (error != ESRCH && error != ENOENT)
                ASSERT0(error);
        error = dsl_destroy_snapshot(fullname, B_FALSE);
        if (error != ENOENT)
                ASSERT0(error);

        /*
         * Create snapshot, clone it, mark snap for deferred destroy,
         * destroy clone, verify snap was also destroyed.
         */
        error = dmu_objset_snapshot_one(osname, snapname);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc("dmu_objset_snapshot");
                        goto out;
                }
                fatal(0, "dmu_objset_snapshot(%s) = %d", fullname, error);
        }

        error = dmu_objset_clone(clonename, fullname);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc("dmu_objset_clone");
                        goto out;
                }
                fatal(0, "dmu_objset_clone(%s) = %d", clonename, error);
        }

        error = dsl_destroy_snapshot(fullname, B_TRUE);
        if (error) {
                fatal(0, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
                    fullname, error);
        }

        error = dsl_destroy_head(clonename);
        if (error)
                fatal(0, "dsl_destroy_head(%s) = %d", clonename, error);

        error = dmu_objset_hold(fullname, FTAG, &origin);
        if (error != ENOENT)
                fatal(0, "dmu_objset_hold(%s) = %d", fullname, error);

        /*
         * Create snapshot, add temporary hold, verify that we can't
         * destroy a held snapshot, mark for deferred destroy,
         * release hold, verify snapshot was destroyed.
         */
        error = dmu_objset_snapshot_one(osname, snapname);
        if (error) {
                if (error == ENOSPC) {
                        ztest_record_enospc("dmu_objset_snapshot");
                        goto out;
                }
                fatal(0, "dmu_objset_snapshot(%s) = %d", fullname, error);
        }

        holds = fnvlist_alloc();
        fnvlist_add_string(holds, fullname, tag);
        error = dsl_dataset_user_hold(holds, 0, NULL);
        fnvlist_free(holds);

        if (error == ENOSPC) {
                ztest_record_enospc("dsl_dataset_user_hold");
                goto out;
        } else if (error) {
                fatal(0, "dsl_dataset_user_hold(%s, %s) = %u",
                    fullname, tag, error);
        }

        error = dsl_destroy_snapshot(fullname, B_FALSE);
        if (error != EBUSY) {
                fatal(0, "dsl_destroy_snapshot(%s, B_FALSE) = %d",
                    fullname, error);
        }

        error = dsl_destroy_snapshot(fullname, B_TRUE);
        if (error) {
                fatal(0, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
                    fullname, error);
        }

        error = user_release_one(fullname, tag);
        if (error)
                fatal(0, "user_release_one(%s, %s) = %d", fullname, tag, error);

        VERIFY3U(dmu_objset_hold(fullname, FTAG, &origin), ==, ENOENT);

out:
        (void) rw_unlock(&ztest_name_lock);
}

/*
 * Inject random faults into the on-disk data.
 */
/* ARGSUSED */
void
ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        int fd;
        uint64_t offset;
        uint64_t leaves;
        uint64_t bad = 0x1990c0ffeedecadeull;
        uint64_t top, leaf;
        char *path0;
        char *pathrand;
        size_t fsize;
        int bshift = SPA_MAXBLOCKSHIFT + 2;
        int iters = 1000;
        int maxfaults;
        int mirror_save;
        vdev_t *vd0 = NULL;
        uint64_t guid0 = 0;
        boolean_t islog = B_FALSE;

        path0 = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
        pathrand = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);

        mutex_enter(&ztest_vdev_lock);
        maxfaults = MAXFAULTS();
        leaves = MAX(zs->zs_mirrors, 1) * ztest_opts.zo_raidz;
        mirror_save = zs->zs_mirrors;
        mutex_exit(&ztest_vdev_lock);

        ASSERT(leaves >= 1);

        /*
         * Grab the name lock as reader. There are some operations
         * which don't like to have their vdevs changed while
         * they are in progress (i.e. spa_change_guid). Those
         * operations will have grabbed the name lock as writer.
         */
        (void) rw_rdlock(&ztest_name_lock);

        /*
         * We need SCL_STATE here because we're going to look at vd0->vdev_tsd.
         */
        spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);

        if (ztest_random(2) == 0) {
                /*
                 * Inject errors on a normal data device or slog device.
                 */
                top = ztest_random_vdev_top(spa, B_TRUE);
                leaf = ztest_random(leaves) + zs->zs_splits;

                /*
                 * Generate paths to the first leaf in this top-level vdev,
                 * and to the random leaf we selected.  We'll induce transient
                 * write failures and random online/offline activity on leaf 0,
                 * and we'll write random garbage to the randomly chosen leaf.
                 */
                (void) snprintf(path0, MAXPATHLEN, ztest_dev_template,
                    ztest_opts.zo_dir, ztest_opts.zo_pool,
                    top * leaves + zs->zs_splits);
                (void) snprintf(pathrand, MAXPATHLEN, ztest_dev_template,
                    ztest_opts.zo_dir, ztest_opts.zo_pool,
                    top * leaves + leaf);

                vd0 = vdev_lookup_by_path(spa->spa_root_vdev, path0);
                if (vd0 != NULL && vd0->vdev_top->vdev_islog)
                        islog = B_TRUE;

                /*
                 * If the top-level vdev needs to be resilvered
                 * then we only allow faults on the device that is
                 * resilvering.
                 */
                if (vd0 != NULL && maxfaults != 1 &&
                    (!vdev_resilver_needed(vd0->vdev_top, NULL, NULL) ||
                    vd0->vdev_resilver_txg != 0)) {
                        /*
                         * Make vd0 explicitly claim to be unreadable,
                         * or unwriteable, or reach behind its back
                         * and close the underlying fd.  We can do this if
                         * maxfaults == 0 because we'll fail and reexecute,
                         * and we can do it if maxfaults >= 2 because we'll
                         * have enough redundancy.  If maxfaults == 1, the
                         * combination of this with injection of random data
                         * corruption below exceeds the pool's fault tolerance.
                         */
                        vdev_file_t *vf = vd0->vdev_tsd;

                        if (vf != NULL && ztest_random(3) == 0) {
                                (void) close(vf->vf_vnode->v_fd);
                                vf->vf_vnode->v_fd = -1;
                        } else if (ztest_random(2) == 0) {
                                vd0->vdev_cant_read = B_TRUE;
                        } else {
                                vd0->vdev_cant_write = B_TRUE;
                        }
                        guid0 = vd0->vdev_guid;
                }
        } else {
                /*
                 * Inject errors on an l2cache device.
                 */
                spa_aux_vdev_t *sav = &spa->spa_l2cache;

                if (sav->sav_count == 0) {
                        spa_config_exit(spa, SCL_STATE, FTAG);
                        (void) rw_unlock(&ztest_name_lock);
                        goto out;
                }
                vd0 = sav->sav_vdevs[ztest_random(sav->sav_count)];
                guid0 = vd0->vdev_guid;
                (void) strcpy(path0, vd0->vdev_path);
                (void) strcpy(pathrand, vd0->vdev_path);

                leaf = 0;
                leaves = 1;
                maxfaults = INT_MAX;    /* no limit on cache devices */
        }

        spa_config_exit(spa, SCL_STATE, FTAG);
        (void) rw_unlock(&ztest_name_lock);

        /*
         * If we can tolerate two or more faults, or we're dealing
         * with a slog, randomly online/offline vd0.
         */
        if ((maxfaults >= 2 || islog) && guid0 != 0) {
                if (ztest_random(10) < 6) {
                        int flags = (ztest_random(2) == 0 ?
                            ZFS_OFFLINE_TEMPORARY : 0);

                        /*
                         * We have to grab the zs_name_lock as writer to
                         * prevent a race between offlining a slog and
                         * destroying a dataset. Offlining the slog will
                         * grab a reference on the dataset which may cause
                         * dsl_destroy_head() to fail with EBUSY thus
                         * leaving the dataset in an inconsistent state.
                         */
                        if (islog)
                                (void) rw_wrlock(&ztest_name_lock);

                        VERIFY(vdev_offline(spa, guid0, flags) != EBUSY);

                        if (islog)
                                (void) rw_unlock(&ztest_name_lock);
                } else {
                        /*
                         * Ideally we would like to be able to randomly
                         * call vdev_[on|off]line without holding locks
                         * to force unpredictable failures but the side
                         * effects of vdev_[on|off]line prevent us from
                         * doing so. We grab the ztest_vdev_lock here to
                         * prevent a race between injection testing and
                         * aux_vdev removal.
                         */
                        mutex_enter(&ztest_vdev_lock);
                        (void) vdev_online(spa, guid0, 0, NULL);
                        mutex_exit(&ztest_vdev_lock);
                }
        }

        if (maxfaults == 0)
                goto out;

        /*
         * We have at least single-fault tolerance, so inject data corruption.
         */
        fd = open(pathrand, O_RDWR);

        if (fd == -1)   /* we hit a gap in the device namespace */
                goto out;

        fsize = lseek(fd, 0, SEEK_END);

        while (--iters != 0) {
                /*
                 * The offset must be chosen carefully to ensure that
                 * we do not inject a given logical block with errors
                 * on two different leaf devices, because ZFS can not
                 * tolerate that (if maxfaults==1).
                 *
                 * We divide each leaf into chunks of size
                 * (# leaves * SPA_MAXBLOCKSIZE * 4).  Within each chunk
                 * there is a series of ranges to which we can inject errors.
                 * Each range can accept errors on only a single leaf vdev.
                 * The error injection ranges are separated by ranges
                 * which we will not inject errors on any device (DMZs).
                 * Each DMZ must be large enough such that a single block
                 * can not straddle it, so that a single block can not be
                 * a target in two different injection ranges (on different
                 * leaf vdevs).
                 *
                 * For example, with 3 leaves, each chunk looks like:
                 *    0 to  32M: injection range for leaf 0
                 *  32M to  64M: DMZ - no injection allowed
                 *  64M to  96M: injection range for leaf 1
                 *  96M to 128M: DMZ - no injection allowed
                 * 128M to 160M: injection range for leaf 2
                 * 160M to 192M: DMZ - no injection allowed
                 */
                offset = ztest_random(fsize / (leaves << bshift)) *
                    (leaves << bshift) + (leaf << bshift) +
                    (ztest_random(1ULL << (bshift - 1)) & -8ULL);

                /*
                 * Only allow damage to the labels at one end of the vdev.
                 *
                 * If all labels are damaged, the device will be totally
                 * inaccessible, which will result in loss of data,
                 * because we also damage (parts of) the other side of
                 * the mirror/raidz.
                 *
                 * Additionally, we will always have both an even and an
                 * odd label, so that we can handle crashes in the
                 * middle of vdev_config_sync().
                 */
                if ((leaf & 1) == 0 && offset < VDEV_LABEL_START_SIZE)
                        continue;

                /*
                 * The two end labels are stored at the "end" of the disk, but
                 * the end of the disk (vdev_psize) is aligned to
                 * sizeof (vdev_label_t).
                 */
                uint64_t psize = P2ALIGN(fsize, sizeof (vdev_label_t));
                if ((leaf & 1) == 1 &&
                    offset + sizeof (bad) > psize - VDEV_LABEL_END_SIZE)
                        continue;

                mutex_enter(&ztest_vdev_lock);
                if (mirror_save != zs->zs_mirrors) {
                        mutex_exit(&ztest_vdev_lock);
                        (void) close(fd);
                        goto out;
                }

                if (pwrite(fd, &bad, sizeof (bad), offset) != sizeof (bad))
                        fatal(1, "can't inject bad word at 0x%llx in %s",
                            offset, pathrand);

                mutex_exit(&ztest_vdev_lock);

                if (ztest_opts.zo_verbose >= 7)
                        (void) printf("injected bad word into %s,"
                            " offset 0x%llx\n", pathrand, (u_longlong_t)offset);
        }

        (void) close(fd);
out:
        umem_free(path0, MAXPATHLEN);
        umem_free(pathrand, MAXPATHLEN);
}

/*
 * Verify that DDT repair works as expected.
 */
void
ztest_ddt_repair(ztest_ds_t *zd, uint64_t id)
{
        ztest_shared_t *zs = ztest_shared;
        spa_t *spa = ztest_spa;
        objset_t *os = zd->zd_os;
        ztest_od_t *od;
        uint64_t object, blocksize, txg, pattern, psize;
        enum zio_checksum checksum = spa_dedup_checksum(spa);
        dmu_buf_t *db;
        dmu_tx_t *tx;
        abd_t *abd;
        blkptr_t blk;
        int copies = 2 * ZIO_DEDUPDITTO_MIN;
        int i;

        blocksize = ztest_random_blocksize();
        blocksize = MIN(blocksize, 2048);       /* because we write so many */

        od = umem_alloc(sizeof (ztest_od_t), UMEM_NOFAIL);
        ztest_od_init(od, id, FTAG, 0, DMU_OT_UINT64_OTHER, blocksize, 0, 0);

        if (ztest_object_init(zd, od, sizeof (ztest_od_t), B_FALSE) != 0) {
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        /*
         * Take the name lock as writer to prevent anyone else from changing
         * the pool and dataset properies we need to maintain during this test.
         */
        (void) rw_wrlock(&ztest_name_lock);

        if (ztest_dsl_prop_set_uint64(zd->zd_name, ZFS_PROP_DEDUP, checksum,
            B_FALSE) != 0 ||
            ztest_dsl_prop_set_uint64(zd->zd_name, ZFS_PROP_COPIES, 1,
            B_FALSE) != 0) {
                (void) rw_unlock(&ztest_name_lock);
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        dmu_objset_stats_t dds;
        dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
        dmu_objset_fast_stat(os, &dds);
        dsl_pool_config_exit(dmu_objset_pool(os), FTAG);

        object = od[0].od_object;
        blocksize = od[0].od_blocksize;
        pattern = zs->zs_guid ^ dds.dds_guid;

        ASSERT(object != 0);

        tx = dmu_tx_create(os);
        dmu_tx_hold_write(tx, object, 0, copies * blocksize);
        txg = ztest_tx_assign(tx, TXG_WAIT, FTAG);
        if (txg == 0) {
                (void) rw_unlock(&ztest_name_lock);
                umem_free(od, sizeof (ztest_od_t));
                return;
        }

        /*
         * Write all the copies of our block.
         */
        for (i = 0; i < copies; i++) {
                uint64_t offset = i * blocksize;
                int error = dmu_buf_hold(os, object, offset, FTAG, &db,
                    DMU_READ_NO_PREFETCH);
                if (error != 0) {
                        fatal(B_FALSE, "dmu_buf_hold(%p, %llu, %llu) = %u",
                            os, (long long)object, (long long) offset, error);
                }
                ASSERT(db->db_offset == offset);
                ASSERT(db->db_size == blocksize);
                ASSERT(ztest_pattern_match(db->db_data, db->db_size, pattern) ||
                    ztest_pattern_match(db->db_data, db->db_size, 0ULL));
                dmu_buf_will_fill(db, tx);
                ztest_pattern_set(db->db_data, db->db_size, pattern);
                dmu_buf_rele(db, FTAG);
        }

        dmu_tx_commit(tx);
        txg_wait_synced(spa_get_dsl(spa), txg);

        /*
         * Find out what block we got.
         */
        VERIFY0(dmu_buf_hold(os, object, 0, FTAG, &db,
            DMU_READ_NO_PREFETCH));
        blk = *((dmu_buf_impl_t *)db)->db_blkptr;
        dmu_buf_rele(db, FTAG);

        /*
         * Damage the block.  Dedup-ditto will save us when we read it later.
         */
        psize = BP_GET_PSIZE(&blk);
        abd = abd_alloc_linear(psize, B_TRUE);
        ztest_pattern_set(abd_to_buf(abd), psize, ~pattern);

        (void) zio_wait(zio_rewrite(NULL, spa, 0, &blk,
            abd, psize, NULL, NULL, ZIO_PRIORITY_SYNC_WRITE,
            ZIO_FLAG_CANFAIL | ZIO_FLAG_INDUCE_DAMAGE, NULL));

        abd_free(abd);

        (void) rw_unlock(&ztest_name_lock);
        umem_free(od, sizeof (ztest_od_t));
}

/*
 * Scrub the pool.
 */
/* ARGSUSED */
void
ztest_scrub(ztest_ds_t *zd, uint64_t id)
{
        spa_t *spa = ztest_spa;

        (void) spa_scan(spa, POOL_SCAN_SCRUB);
        (void) poll(NULL, 0, 100); /* wait a moment, then force a restart */
        (void) spa_scan(spa, POOL_SCAN_SCRUB);
}

/*
 * Change the guid for the pool.
 */
/* ARGSUSED */
void
ztest_reguid(ztest_ds_t *zd, uint64_t id)
{
        spa_t *spa = ztest_spa;
        uint64_t orig, load;
        int error;

        orig = spa_guid(spa);
        load = spa_load_guid(spa);

        (void) rw_wrlock(&ztest_name_lock);
        error = spa_change_guid(spa);
        (void) rw_unlock(&ztest_name_lock);

        if (error != 0)
                return;

        if (ztest_opts.zo_verbose >= 4) {
                (void) printf("Changed guid old %llu -> %llu\n",
                    (u_longlong_t)orig, (u_longlong_t)spa_guid(spa));
        }

        VERIFY3U(orig, !=, spa_guid(spa));
        VERIFY3U(load, ==, spa_load_guid(spa));
}

/*
 * Rename the pool to a different name and then rename it back.
 */
/* ARGSUSED */
void
ztest_spa_rename(ztest_ds_t *zd, uint64_t id)
{
        char *oldname, *newname;
        spa_t *spa;

        (void) rw_wrlock(&ztest_name_lock);

        oldname = ztest_opts.zo_pool;
        newname = umem_alloc(strlen(oldname) + 5, UMEM_NOFAIL);
        (void) strcpy(newname, oldname);
        (void) strcat(newname, "_tmp");

        /*
         * Do the rename
         */
        VERIFY3U(0, ==, spa_rename(oldname, newname));

        /*
         * Try to open it under the old name, which shouldn't exist
         */
        VERIFY3U(ENOENT, ==, spa_open(oldname, &spa, FTAG));

        /*
         * Open it under the new name and make sure it's still the same spa_t.
         */
        VERIFY3U(0, ==, spa_open(newname, &spa, FTAG));

        ASSERT(spa == ztest_spa);
        spa_close(spa, FTAG);

        /*
         * Rename it back to the original
         */
        VERIFY3U(0, ==, spa_rename(newname, oldname));

        /*
         * Make sure it can still be opened
         */
        VERIFY3U(0, ==, spa_open(oldname, &spa, FTAG));

        ASSERT(spa == ztest_spa);
        spa_close(spa, FTAG);

        umem_free(newname, strlen(newname) + 1);

        (void) rw_unlock(&ztest_name_lock);
}

void
ztest_fletcher(ztest_ds_t *zd, uint64_t id)
{
        hrtime_t end = gethrtime() + NANOSEC;

        while (gethrtime() <= end) {
                int run_count = 100;
                void *buf;
                struct abd *abd_data, *abd_meta;
                uint32_t size;
                int *ptr;
                int i;
                zio_cksum_t zc_ref;
                zio_cksum_t zc_ref_byteswap;

                size = ztest_random_blocksize();

                buf = umem_alloc(size, UMEM_NOFAIL);
                abd_data = abd_alloc(size, B_FALSE);
                abd_meta = abd_alloc(size, B_TRUE);

                for (i = 0, ptr = buf; i < size / sizeof (*ptr); i++, ptr++)
                        *ptr = ztest_random(UINT_MAX);

                abd_copy_from_buf_off(abd_data, buf, 0, size);
                abd_copy_from_buf_off(abd_meta, buf, 0, size);

                VERIFY0(fletcher_4_impl_set("scalar"));
                fletcher_4_native(buf, size, NULL, &zc_ref);
                fletcher_4_byteswap(buf, size, NULL, &zc_ref_byteswap);

                VERIFY0(fletcher_4_impl_set("cycle"));
                while (run_count-- > 0) {
                        zio_cksum_t zc;
                        zio_cksum_t zc_byteswap;

                        fletcher_4_byteswap(buf, size, NULL, &zc_byteswap);
                        fletcher_4_native(buf, size, NULL, &zc);

                        VERIFY0(bcmp(&zc, &zc_ref, sizeof (zc)));
                        VERIFY0(bcmp(&zc_byteswap, &zc_ref_byteswap,
                            sizeof (zc_byteswap)));

                        /* Test ABD - data */
                        abd_fletcher_4_byteswap(abd_data, size, NULL,
                            &zc_byteswap);
                        abd_fletcher_4_native(abd_data, size, NULL, &zc);

                        VERIFY0(bcmp(&zc, &zc_ref, sizeof (zc)));
                        VERIFY0(bcmp(&zc_byteswap, &zc_ref_byteswap,
                            sizeof (zc_byteswap)));

                        /* Test ABD - metadata */
                        abd_fletcher_4_byteswap(abd_meta, size, NULL,
                            &zc_byteswap);
                        abd_fletcher_4_native(abd_meta, size, NULL, &zc);

                        VERIFY0(bcmp(&zc, &zc_ref, sizeof (zc)));
                        VERIFY0(bcmp(&zc_byteswap, &zc_ref_byteswap,
                            sizeof (zc_byteswap)));

                }

                umem_free(buf, size);
                abd_free(abd_data);
                abd_free(abd_meta);
        }
}

void
ztest_fletcher_incr(ztest_ds_t *zd, uint64_t id)
{
        void *buf;
        size_t size;
        int *ptr;
        int i;
        zio_cksum_t zc_ref;
        zio_cksum_t zc_ref_bswap;

        hrtime_t end = gethrtime() + NANOSEC;

        while (gethrtime() <= end) {
                int run_count = 100;

                size = ztest_random_blocksize();
                buf = umem_alloc(size, UMEM_NOFAIL);

                for (i = 0, ptr = buf; i < size / sizeof (*ptr); i++, ptr++)
                        *ptr = ztest_random(UINT_MAX);

                VERIFY0(fletcher_4_impl_set("scalar"));
                fletcher_4_native(buf, size, NULL, &zc_ref);
                fletcher_4_byteswap(buf, size, NULL, &zc_ref_bswap);

                VERIFY0(fletcher_4_impl_set("cycle"));

                while (run_count-- > 0) {
                        zio_cksum_t zc;
                        zio_cksum_t zc_bswap;
                        size_t pos = 0;

                        ZIO_SET_CHECKSUM(&zc, 0, 0, 0, 0);
                        ZIO_SET_CHECKSUM(&zc_bswap, 0, 0, 0, 0);

                        while (pos < size) {
                                size_t inc = 64 * ztest_random(size / 67);
                                /* sometimes add few bytes to test non-simd */
                                if (ztest_random(100) < 10)
                                        inc += P2ALIGN(ztest_random(64),
                                            sizeof (uint32_t));

                                if (inc > (size - pos))
                                        inc = size - pos;

                                fletcher_4_incremental_native(buf + pos, inc,
                                    &zc);
                                fletcher_4_incremental_byteswap(buf + pos, inc,
                                    &zc_bswap);

                                pos += inc;
                        }

                        VERIFY3U(pos, ==, size);

                        VERIFY(ZIO_CHECKSUM_EQUAL(zc, zc_ref));
                        VERIFY(ZIO_CHECKSUM_EQUAL(zc_bswap, zc_ref_bswap));

                        /*
                         * verify if incremental on the whole buffer is
                         * equivalent to non-incremental version
                         */
                        ZIO_SET_CHECKSUM(&zc, 0, 0, 0, 0);
                        ZIO_SET_CHECKSUM(&zc_bswap, 0, 0, 0, 0);

                        fletcher_4_incremental_native(buf, size, &zc);
                        fletcher_4_incremental_byteswap(buf, size, &zc_bswap);

                        VERIFY(ZIO_CHECKSUM_EQUAL(zc, zc_ref));
                        VERIFY(ZIO_CHECKSUM_EQUAL(zc_bswap, zc_ref_bswap));
                }

                umem_free(buf, size);
        }
}

static int
ztest_check_path(char *path)
{
        struct stat s;
        /* return true on success */
        return (!stat(path, &s));
}

static void
ztest_get_zdb_bin(char *bin, int len)
{
        char *zdb_path;
        /*
         * Try to use ZDB_PATH and in-tree zdb path. If not successful, just
         * let popen to search through PATH.
         */
        if ((zdb_path = getenv("ZDB_PATH"))) {
                strlcpy(bin, zdb_path, len); /* In env */
                if (!ztest_check_path(bin)) {
                        ztest_dump_core = 0;
                        fatal(1, "invalid ZDB_PATH '%s'", bin);
                }
                return;
        }

        VERIFY(realpath(getexecname(), bin) != NULL);
        if (strstr(bin, "/ztest/")) {
                strstr(bin, "/ztest/")[0] = '\0'; /* In-tree */
                strcat(bin, "/zdb/zdb");
                if (ztest_check_path(bin))
                        return;
        }
        strcpy(bin, "zdb");
}

/*
 * Verify pool integrity by running zdb.
 */
static void
ztest_run_zdb(char *pool)
{
        int status;
        char *bin;
        char *zdb;
        char *zbuf;
        const int len = MAXPATHLEN + MAXNAMELEN + 20;
        FILE *fp;

        bin = umem_alloc(len, UMEM_NOFAIL);
        zdb = umem_alloc(len, UMEM_NOFAIL);
        zbuf = umem_alloc(1024, UMEM_NOFAIL);

        ztest_get_zdb_bin(bin, len);

        (void) sprintf(zdb,
            "%s -bcc%s%s -G -d -U %s %s",
            bin,
            ztest_opts.zo_verbose >= 3 ? "s" : "",
            ztest_opts.zo_verbose >= 4 ? "v" : "",
            spa_config_path,
            pool);

        if (ztest_opts.zo_verbose >= 5)
                (void) printf("Executing %s\n", strstr(zdb, "zdb "));

        fp = popen(zdb, "r");

        while (fgets(zbuf, 1024, fp) != NULL)
                if (ztest_opts.zo_verbose >= 3)
                        (void) printf("%s", zbuf);

        status = pclose(fp);

        if (status == 0)
                goto out;

        ztest_dump_core = 0;
        if (WIFEXITED(status))
                fatal(0, "'%s' exit code %d", zdb, WEXITSTATUS(status));
        else
                fatal(0, "'%s' died with signal %d", zdb, WTERMSIG(status));
out:
        umem_free(bin, len);
        umem_free(zdb, len);
        umem_free(zbuf, 1024);
}

static void
ztest_walk_pool_directory(char *header)
{
        spa_t *spa = NULL;

        if (ztest_opts.zo_verbose >= 6)
                (void) printf("%s\n", header);

        mutex_enter(&spa_namespace_lock);
        while ((spa = spa_next(spa)) != NULL)
                if (ztest_opts.zo_verbose >= 6)
                        (void) printf("\t%s\n", spa_name(spa));
        mutex_exit(&spa_namespace_lock);
}

static void
ztest_spa_import_export(char *oldname, char *newname)
{
        nvlist_t *config, *newconfig;
        uint64_t pool_guid;
        spa_t *spa;
        int error;

        if (ztest_opts.zo_verbose >= 4) {
                (void) printf("import/export: old = %s, new = %s\n",
                    oldname, newname);
        }

        /*
         * Clean up from previous runs.
         */
        (void) spa_destroy(newname);

        /*
         * Get the pool's configuration and guid.
         */
        VERIFY3U(0, ==, spa_open(oldname, &spa, FTAG));

        /*
         * Kick off a scrub to tickle scrub/export races.
         */
        if (ztest_random(2) == 0)
                (void) spa_scan(spa, POOL_SCAN_SCRUB);

        pool_guid = spa_guid(spa);
        spa_close(spa, FTAG);

        ztest_walk_pool_directory("pools before export");

        /*
         * Export it.
         */
        VERIFY3U(0, ==, spa_export(oldname, &config, B_FALSE, B_FALSE));

        ztest_walk_pool_directory("pools after export");

        /*
         * Try to import it.
         */
        newconfig = spa_tryimport(config);
        ASSERT(newconfig != NULL);
        nvlist_free(newconfig);

        /*
         * Import it under the new name.
         */
        error = spa_import(newname, config, NULL, 0);
        if (error != 0) {
                dump_nvlist(config, 0);
                fatal(B_FALSE, "couldn't import pool %s as %s: error %u",
                    oldname, newname, error);
        }

        ztest_walk_pool_directory("pools after import");

        /*
         * Try to import it again -- should fail with EEXIST.
         */
        VERIFY3U(EEXIST, ==, spa_import(newname, config, NULL, 0));

        /*
         * Try to import it under a different name -- should fail with EEXIST.
         */
        VERIFY3U(EEXIST, ==, spa_import(oldname, config, NULL, 0));

        /*
         * Verify that the pool is no longer visible under the old name.
         */
        VERIFY3U(ENOENT, ==, spa_open(oldname, &spa, FTAG));

        /*
         * Verify that we can open and close the pool using the new name.
         */
        VERIFY3U(0, ==, spa_open(newname, &spa, FTAG));
        ASSERT(pool_guid == spa_guid(spa));
        spa_close(spa, FTAG);

        nvlist_free(config);
}

static void
ztest_resume(spa_t *spa)
{
        if (spa_suspended(spa) && ztest_opts.zo_verbose >= 6)
                (void) printf("resuming from suspended state\n");
        spa_vdev_state_enter(spa, SCL_NONE);
        vdev_clear(spa, NULL);
        (void) spa_vdev_state_exit(spa, NULL, 0);
        (void) zio_resume(spa);
}

static void *
ztest_resume_thread(void *arg)
{
        spa_t *spa = arg;

        while (!ztest_exiting) {
                if (spa_suspended(spa))
                        ztest_resume(spa);
                (void) poll(NULL, 0, 100);

                /*
                 * Periodically change the zfs_compressed_arc_enabled setting.
                 */
                if (ztest_random(10) == 0)
                        zfs_compressed_arc_enabled = ztest_random(2);

                /*
                 * Periodically change the zfs_abd_scatter_enabled setting.
                 */
                if (ztest_random(10) == 0)
                        zfs_abd_scatter_enabled = ztest_random(2);
        }

        thread_exit();

        return (NULL);
}

#define GRACE   300

#if 0
static void
ztest_deadman_alarm(int sig)
{
        fatal(0, "failed to complete within %d seconds of deadline", GRACE);
}
#endif

static void
ztest_execute(int test, ztest_info_t *zi, uint64_t id)
{
        ztest_ds_t *zd = &ztest_ds[id % ztest_opts.zo_datasets];
        ztest_shared_callstate_t *zc = ZTEST_GET_SHARED_CALLSTATE(test);
        hrtime_t functime = gethrtime();
        int i;

        for (i = 0; i < zi->zi_iters; i++)
                zi->zi_func(zd, id);

        functime = gethrtime() - functime;

        atomic_add_64(&zc->zc_count, 1);
        atomic_add_64(&zc->zc_time, functime);

        if (ztest_opts.zo_verbose >= 4)
                (void) printf("%6.2f sec in %s\n",
                    (double)functime / NANOSEC, zi->zi_funcname);
}

static void *
ztest_thread(void *arg)
{
        int rand;
        uint64_t id = (uintptr_t)arg;
        ztest_shared_t *zs = ztest_shared;
        uint64_t call_next;
        hrtime_t now;
        ztest_info_t *zi;
        ztest_shared_callstate_t *zc;

        while ((now = gethrtime()) < zs->zs_thread_stop) {
                /*
                 * See if it's time to force a crash.
                 */
                if (now > zs->zs_thread_kill)
                        ztest_kill(zs);

                /*
                 * If we're getting ENOSPC with some regularity, stop.
                 */
                if (zs->zs_enospc_count > 10)
                        break;

                /*
                 * Pick a random function to execute.
                 */
                rand = ztest_random(ZTEST_FUNCS);
                zi = &ztest_info[rand];
                zc = ZTEST_GET_SHARED_CALLSTATE(rand);
                call_next = zc->zc_next;

                if (now >= call_next &&
                    atomic_cas_64(&zc->zc_next, call_next, call_next +
                    ztest_random(2 * zi->zi_interval[0] + 1)) == call_next) {
                        ztest_execute(rand, zi, id);
                }
        }

        thread_exit();

        return (NULL);
}

static void
ztest_dataset_name(char *dsname, char *pool, int d)
{
        (void) snprintf(dsname, ZFS_MAX_DATASET_NAME_LEN, "%s/ds_%d", pool, d);
}

static void
ztest_dataset_destroy(int d)
{
        char name[ZFS_MAX_DATASET_NAME_LEN];
        int t;

        ztest_dataset_name(name, ztest_opts.zo_pool, d);

        if (ztest_opts.zo_verbose >= 3)
                (void) printf("Destroying %s to free up space\n", name);

        /*
         * Cleanup any non-standard clones and snapshots.  In general,
         * ztest thread t operates on dataset (t % zopt_datasets),
         * so there may be more than one thing to clean up.
         */
        for (t = d; t < ztest_opts.zo_threads;
            t += ztest_opts.zo_datasets)
                ztest_dsl_dataset_cleanup(name, t);

        (void) dmu_objset_find(name, ztest_objset_destroy_cb, NULL,
            DS_FIND_SNAPSHOTS | DS_FIND_CHILDREN);
}

static void
ztest_dataset_dirobj_verify(ztest_ds_t *zd)
{
        uint64_t usedobjs, dirobjs, scratch;

        /*
         * ZTEST_DIROBJ is the object directory for the entire dataset.
         * Therefore, the number of objects in use should equal the
         * number of ZTEST_DIROBJ entries, +1 for ZTEST_DIROBJ itself.
         * If not, we have an object leak.
         *
         * Note that we can only check this in ztest_dataset_open(),
         * when the open-context and syncing-context values agree.
         * That's because zap_count() returns the open-context value,
         * while dmu_objset_space() returns the rootbp fill count.
         */
        VERIFY3U(0, ==, zap_count(zd->zd_os, ZTEST_DIROBJ, &dirobjs));
        dmu_objset_space(zd->zd_os, &scratch, &scratch, &usedobjs, &scratch);
        ASSERT3U(dirobjs + 1, ==, usedobjs);
}

static int
ztest_dataset_open(int d)
{
        ztest_ds_t *zd = &ztest_ds[d];
        uint64_t committed_seq = ZTEST_GET_SHARED_DS(d)->zd_seq;
        objset_t *os;
        zilog_t *zilog;
        char name[ZFS_MAX_DATASET_NAME_LEN];
        int error;

        ztest_dataset_name(name, ztest_opts.zo_pool, d);

        (void) rw_rdlock(&ztest_name_lock);

        error = ztest_dataset_create(name);
        if (error == ENOSPC) {
                (void) rw_unlock(&ztest_name_lock);
                ztest_record_enospc(FTAG);
                return (error);
        }
        ASSERT(error == 0 || error == EEXIST);

        VERIFY0(dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, zd, &os));
        (void) rw_unlock(&ztest_name_lock);

        ztest_zd_init(zd, ZTEST_GET_SHARED_DS(d), os);

        zilog = zd->zd_zilog;

        if (zilog->zl_header->zh_claim_lr_seq != 0 &&
            zilog->zl_header->zh_claim_lr_seq < committed_seq)
                fatal(0, "missing log records: claimed %llu < committed %llu",
                    zilog->zl_header->zh_claim_lr_seq, committed_seq);

        ztest_dataset_dirobj_verify(zd);

        zil_replay(os, zd, ztest_replay_vector);

        ztest_dataset_dirobj_verify(zd);

        if (ztest_opts.zo_verbose >= 6)
                (void) printf("%s replay %llu blocks, %llu records, seq %llu\n",
                    zd->zd_name,
                    (u_longlong_t)zilog->zl_parse_blk_count,
                    (u_longlong_t)zilog->zl_parse_lr_count,
                    (u_longlong_t)zilog->zl_replaying_seq);

        zilog = zil_open(os, ztest_get_data);

        if (zilog->zl_replaying_seq != 0 &&
            zilog->zl_replaying_seq < committed_seq)
                fatal(0, "missing log records: replayed %llu < committed %llu",
                    zilog->zl_replaying_seq, committed_seq);

        return (0);
}

static void
ztest_dataset_close(int d)
{
        ztest_ds_t *zd = &ztest_ds[d];

        zil_close(zd->zd_zilog);
        dmu_objset_disown(zd->zd_os, zd);

        ztest_zd_fini(zd);
}

/*
 * Kick off threads to run tests on all datasets in parallel.
 */
static void
ztest_run(ztest_shared_t *zs)
{
        kt_did_t *tid;
        spa_t *spa;
        objset_t *os;
        kthread_t *resume_thread;
        uint64_t object;
        int error;
        int t, d;

        ztest_exiting = B_FALSE;

        /*
         * Initialize parent/child shared state.
         */
        mutex_init(&ztest_vdev_lock, NULL, MUTEX_DEFAULT, NULL);
        VERIFY(rwlock_init(&ztest_name_lock, USYNC_THREAD, NULL) == 0);

        zs->zs_thread_start = gethrtime();
        zs->zs_thread_stop =
            zs->zs_thread_start + ztest_opts.zo_passtime * NANOSEC;
        zs->zs_thread_stop = MIN(zs->zs_thread_stop, zs->zs_proc_stop);
        zs->zs_thread_kill = zs->zs_thread_stop;
        if (ztest_random(100) < ztest_opts.zo_killrate) {
                zs->zs_thread_kill -=
                    ztest_random(ztest_opts.zo_passtime * NANOSEC);
        }

        mutex_init(&zcl.zcl_callbacks_lock, NULL, MUTEX_DEFAULT, NULL);

        list_create(&zcl.zcl_callbacks, sizeof (ztest_cb_data_t),
            offsetof(ztest_cb_data_t, zcd_node));

        /*
         * Open our pool.
         */
        kernel_init(FREAD | FWRITE);
        VERIFY0(spa_open(ztest_opts.zo_pool, &spa, FTAG));
        spa->spa_debug = B_TRUE;
        metaslab_preload_limit = ztest_random(20) + 1;
        ztest_spa = spa;

        dmu_objset_stats_t dds;
        VERIFY0(dmu_objset_own(ztest_opts.zo_pool,
            DMU_OST_ANY, B_TRUE, FTAG, &os));
        dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
        dmu_objset_fast_stat(os, &dds);
        dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
        zs->zs_guid = dds.dds_guid;
        dmu_objset_disown(os, FTAG);

        spa->spa_dedup_ditto = 2 * ZIO_DEDUPDITTO_MIN;

        /*
         * We don't expect the pool to suspend unless maxfaults == 0,
         * in which case ztest_fault_inject() temporarily takes away
         * the only valid replica.
         */
        if (MAXFAULTS() == 0)
                spa->spa_failmode = ZIO_FAILURE_MODE_WAIT;
        else
                spa->spa_failmode = ZIO_FAILURE_MODE_PANIC;

        /*
         * Create a thread to periodically resume suspended I/O.
         */
        VERIFY3P((resume_thread = zk_thread_create(NULL, 0,
            (thread_func_t)ztest_resume_thread, spa, 0, NULL, TS_RUN, 0,
            PTHREAD_CREATE_JOINABLE)), !=, NULL);

#if 0
        /*
         * Set a deadman alarm to abort() if we hang.
         */
        signal(SIGALRM, ztest_deadman_alarm);
        alarm((zs->zs_thread_stop - zs->zs_thread_start) / NANOSEC + GRACE);
#endif

        /*
         * Verify that we can safely inquire about about any object,
         * whether it's allocated or not.  To make it interesting,
         * we probe a 5-wide window around each power of two.
         * This hits all edge cases, including zero and the max.
         */
        for (t = 0; t < 64; t++) {
                for (d = -5; d <= 5; d++) {
                        error = dmu_object_info(spa->spa_meta_objset,
                            (1ULL << t) + d, NULL);
                        ASSERT(error == 0 || error == ENOENT ||
                            error == EINVAL);
                }
        }

        /*
         * If we got any ENOSPC errors on the previous run, destroy something.
         */
        if (zs->zs_enospc_count != 0) {
                int d = ztest_random(ztest_opts.zo_datasets);
                ztest_dataset_destroy(d);
        }
        zs->zs_enospc_count = 0;

        tid = umem_zalloc(ztest_opts.zo_threads * sizeof (kt_did_t),
            UMEM_NOFAIL);

        if (ztest_opts.zo_verbose >= 4)
                (void) printf("starting main threads...\n");

        /*
         * Kick off all the tests that run in parallel.
         */
        for (t = 0; t < ztest_opts.zo_threads; t++) {
                kthread_t *thread;

                if (t < ztest_opts.zo_datasets &&
                    ztest_dataset_open(t) != 0) {
                        umem_free(tid,
                            ztest_opts.zo_threads * sizeof (kt_did_t));
                        return;
                }

                VERIFY3P(thread = zk_thread_create(NULL, 0,
                    (thread_func_t)ztest_thread,
                    (void *)(uintptr_t)t, 0, NULL, TS_RUN, 0,
                    PTHREAD_CREATE_JOINABLE), !=, NULL);
                tid[t] = thread->t_tid;
        }

        /*
         * Wait for all of the tests to complete.  We go in reverse order
         * so we don't close datasets while threads are still using them.
         */
        for (t = ztest_opts.zo_threads - 1; t >= 0; t--) {
                thread_join(tid[t]);
                if (t < ztest_opts.zo_datasets)
                        ztest_dataset_close(t);
        }

        txg_wait_synced(spa_get_dsl(spa), 0);

        zs->zs_alloc = metaslab_class_get_alloc(spa_normal_class(spa));
        zs->zs_space = metaslab_class_get_space(spa_normal_class(spa));

        umem_free(tid, ztest_opts.zo_threads * sizeof (kt_did_t));

        /* Kill the resume thread */
        ztest_exiting = B_TRUE;
        thread_join(resume_thread->t_tid);
        ztest_resume(spa);

        /*
         * Right before closing the pool, kick off a bunch of async I/O;
         * spa_close() should wait for it to complete.
         */
        for (object = 1; object < 50; object++) {
                dmu_prefetch(spa->spa_meta_objset, object, 0, 0, 1ULL << 20,
                    ZIO_PRIORITY_SYNC_READ);
        }

        /* Verify that at least one commit cb was called in a timely fashion */
        if (zc_cb_counter >= ZTEST_COMMIT_CB_MIN_REG)
                VERIFY0(zc_min_txg_delay);

        spa_close(spa, FTAG);

        /*
         * Verify that we can loop over all pools.
         */
        mutex_enter(&spa_namespace_lock);
        for (spa = spa_next(NULL); spa != NULL; spa = spa_next(spa))
                if (ztest_opts.zo_verbose > 3)
                        (void) printf("spa_next: found %s\n", spa_name(spa));
        mutex_exit(&spa_namespace_lock);

        /*
         * Verify that we can export the pool and reimport it under a
         * different name.
         */
        if (ztest_random(2) == 0) {
                char name[ZFS_MAX_DATASET_NAME_LEN];
                (void) snprintf(name, sizeof (name), "%s_import",
                    ztest_opts.zo_pool);
                ztest_spa_import_export(ztest_opts.zo_pool, name);
                ztest_spa_import_export(name, ztest_opts.zo_pool);
        }

        kernel_fini();

        list_destroy(&zcl.zcl_callbacks);
        mutex_destroy(&zcl.zcl_callbacks_lock);
        (void) rwlock_destroy(&ztest_name_lock);
        mutex_destroy(&ztest_vdev_lock);
}

static void
ztest_freeze(void)
{
        ztest_ds_t *zd = &ztest_ds[0];
        spa_t *spa;
        int numloops = 0;

        if (ztest_opts.zo_verbose >= 3)
                (void) printf("testing spa_freeze()...\n");

        kernel_init(FREAD | FWRITE);
        VERIFY3U(0, ==, spa_open(ztest_opts.zo_pool, &spa, FTAG));
        VERIFY3U(0, ==, ztest_dataset_open(0));
        spa->spa_debug = B_TRUE;
        ztest_spa = spa;

        /*
         * Force the first log block to be transactionally allocated.
         * We have to do this before we freeze the pool -- otherwise
         * the log chain won't be anchored.
         */
        while (BP_IS_HOLE(&zd->zd_zilog->zl_header->zh_log)) {
                ztest_dmu_object_alloc_free(zd, 0);
                zil_commit(zd->zd_zilog, 0);
        }

        txg_wait_synced(spa_get_dsl(spa), 0);

        /*
         * Freeze the pool.  This stops spa_sync() from doing anything,
         * so that the only way to record changes from now on is the ZIL.
         */
        spa_freeze(spa);

        /*
         * Because it is hard to predict how much space a write will actually
         * require beforehand, we leave ourselves some fudge space to write over
         * capacity.
         */
        uint64_t capacity = metaslab_class_get_space(spa_normal_class(spa)) / 2;

        /*
         * Run tests that generate log records but don't alter the pool config
         * or depend on DSL sync tasks (snapshots, objset create/destroy, etc).
         * We do a txg_wait_synced() after each iteration to force the txg
         * to increase well beyond the last synced value in the uberblock.
         * The ZIL should be OK with that.
         *
         * Run a random number of times less than zo_maxloops and ensure we do
         * not run out of space on the pool.
         */
        while (ztest_random(10) != 0 &&
            numloops++ < ztest_opts.zo_maxloops &&
            metaslab_class_get_alloc(spa_normal_class(spa)) < capacity) {
                ztest_od_t od;
                ztest_od_init(&od, 0, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0, 0);
                VERIFY0(ztest_object_init(zd, &od, sizeof (od), B_FALSE));
                ztest_io(zd, od.od_object,
                    ztest_random(ZTEST_RANGE_LOCKS) << SPA_MAXBLOCKSHIFT);
                txg_wait_synced(spa_get_dsl(spa), 0);
        }

        /*
         * Commit all of the changes we just generated.
         */
        zil_commit(zd->zd_zilog, 0);
        txg_wait_synced(spa_get_dsl(spa), 0);

        /*
         * Close our dataset and close the pool.
         */
        ztest_dataset_close(0);
        spa_close(spa, FTAG);
        kernel_fini();

        /*
         * Open and close the pool and dataset to induce log replay.
         */
        kernel_init(FREAD | FWRITE);
        VERIFY3U(0, ==, spa_open(ztest_opts.zo_pool, &spa, FTAG));
        ASSERT(spa_freeze_txg(spa) == UINT64_MAX);
        VERIFY3U(0, ==, ztest_dataset_open(0));
        ztest_dataset_close(0);

        spa->spa_debug = B_TRUE;
        ztest_spa = spa;
        txg_wait_synced(spa_get_dsl(spa), 0);
        ztest_reguid(NULL, 0);

        spa_close(spa, FTAG);
        kernel_fini();
}

void
print_time(hrtime_t t, char *timebuf)
{
        hrtime_t s = t / NANOSEC;
        hrtime_t m = s / 60;
        hrtime_t h = m / 60;
        hrtime_t d = h / 24;

        s -= m * 60;
        m -= h * 60;
        h -= d * 24;

        timebuf[0] = '\0';

        if (d)
                (void) sprintf(timebuf,
                    "%llud%02lluh%02llum%02llus", d, h, m, s);
        else if (h)
                (void) sprintf(timebuf, "%lluh%02llum%02llus", h, m, s);
        else if (m)
                (void) sprintf(timebuf, "%llum%02llus", m, s);
        else
                (void) sprintf(timebuf, "%llus", s);
}

static nvlist_t *
make_random_props(void)
{
        nvlist_t *props;

        VERIFY(nvlist_alloc(&props, NV_UNIQUE_NAME, 0) == 0);
        if (ztest_random(2) == 0)
                return (props);
        VERIFY(nvlist_add_uint64(props, "autoreplace", 1) == 0);

        return (props);
}

/*
 * Create a storage pool with the given name and initial vdev size.
 * Then test spa_freeze() functionality.
 */
static void
ztest_init(ztest_shared_t *zs)
{
        spa_t *spa;
        nvlist_t *nvroot, *props;
        int i;

        mutex_init(&ztest_vdev_lock, NULL, MUTEX_DEFAULT, NULL);
        VERIFY(rwlock_init(&ztest_name_lock, USYNC_THREAD, NULL) == 0);

        kernel_init(FREAD | FWRITE);

        /*
         * Create the storage pool.
         */
        (void) spa_destroy(ztest_opts.zo_pool);
        ztest_shared->zs_vdev_next_leaf = 0;
        zs->zs_splits = 0;
        zs->zs_mirrors = ztest_opts.zo_mirrors;
        nvroot = make_vdev_root(NULL, NULL, NULL, ztest_opts.zo_vdev_size, 0,
            0, ztest_opts.zo_raidz, zs->zs_mirrors, 1);
        props = make_random_props();
        for (i = 0; i < SPA_FEATURES; i++) {
                char *buf;
                VERIFY3S(-1, !=, asprintf(&buf, "feature@%s",
                    spa_feature_table[i].fi_uname));
                VERIFY3U(0, ==, nvlist_add_uint64(props, buf, 0));
                free(buf);
        }
        VERIFY3U(0, ==, spa_create(ztest_opts.zo_pool, nvroot, props, NULL));
        nvlist_free(nvroot);
        nvlist_free(props);

        VERIFY3U(0, ==, spa_open(ztest_opts.zo_pool, &spa, FTAG));
        zs->zs_metaslab_sz =
            1ULL << spa->spa_root_vdev->vdev_child[0]->vdev_ms_shift;
        spa_close(spa, FTAG);

        kernel_fini();

        ztest_run_zdb(ztest_opts.zo_pool);

        ztest_freeze();

        ztest_run_zdb(ztest_opts.zo_pool);

        (void) rwlock_destroy(&ztest_name_lock);
        mutex_destroy(&ztest_vdev_lock);
}

static void
setup_data_fd(void)
{
        static char ztest_name_data[] = "/tmp/ztest.data.XXXXXX";

        ztest_fd_data = mkstemp(ztest_name_data);
        ASSERT3S(ztest_fd_data, >=, 0);
        (void) unlink(ztest_name_data);
}

static int
shared_data_size(ztest_shared_hdr_t *hdr)
{
        int size;

        size = hdr->zh_hdr_size;
        size += hdr->zh_opts_size;
        size += hdr->zh_size;
        size += hdr->zh_stats_size * hdr->zh_stats_count;
        size += hdr->zh_ds_size * hdr->zh_ds_count;

        return (size);
}

static void
setup_hdr(void)
{
        int size;
        ztest_shared_hdr_t *hdr;

        hdr = (void *)mmap(0, P2ROUNDUP(sizeof (*hdr), getpagesize()),
            PROT_READ | PROT_WRITE, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);

        VERIFY3U(0, ==, ftruncate(ztest_fd_data, sizeof (ztest_shared_hdr_t)));

        hdr->zh_hdr_size = sizeof (ztest_shared_hdr_t);
        hdr->zh_opts_size = sizeof (ztest_shared_opts_t);
        hdr->zh_size = sizeof (ztest_shared_t);
        hdr->zh_stats_size = sizeof (ztest_shared_callstate_t);
        hdr->zh_stats_count = ZTEST_FUNCS;
        hdr->zh_ds_size = sizeof (ztest_shared_ds_t);
        hdr->zh_ds_count = ztest_opts.zo_datasets;

        size = shared_data_size(hdr);
        VERIFY3U(0, ==, ftruncate(ztest_fd_data, size));

        (void) munmap((caddr_t)hdr, P2ROUNDUP(sizeof (*hdr), getpagesize()));
}

static void
setup_data(void)
{
        int size, offset;
        ztest_shared_hdr_t *hdr;
        uint8_t *buf;

        hdr = (void *)mmap(0, P2ROUNDUP(sizeof (*hdr), getpagesize()),
            PROT_READ, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);

        size = shared_data_size(hdr);

        (void) munmap((caddr_t)hdr, P2ROUNDUP(sizeof (*hdr), getpagesize()));
        hdr = ztest_shared_hdr = (void *)mmap(0, P2ROUNDUP(size, getpagesize()),
            PROT_READ | PROT_WRITE, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);
        buf = (uint8_t *)hdr;

        offset = hdr->zh_hdr_size;
        ztest_shared_opts = (void *)&buf[offset];
        offset += hdr->zh_opts_size;
        ztest_shared = (void *)&buf[offset];
        offset += hdr->zh_size;
        ztest_shared_callstate = (void *)&buf[offset];
        offset += hdr->zh_stats_size * hdr->zh_stats_count;
        ztest_shared_ds = (void *)&buf[offset];
}

static boolean_t
exec_child(char *cmd, char *libpath, boolean_t ignorekill, int *statusp)
{
        pid_t pid;
        int status;
        char *cmdbuf = NULL;

        pid = fork();

        if (cmd == NULL) {
                cmdbuf = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
                (void) strlcpy(cmdbuf, getexecname(), MAXPATHLEN);
                cmd = cmdbuf;
        }

        if (pid == -1)
                fatal(1, "fork failed");

        if (pid == 0) { /* child */
                char *emptyargv[2] = { cmd, NULL };
                char fd_data_str[12];

                struct rlimit rl = { 1024, 1024 };
                (void) setrlimit(RLIMIT_NOFILE, &rl);

                (void) close(ztest_fd_rand);
                VERIFY(11 >= snprintf(fd_data_str, 12, "%d", ztest_fd_data));
                VERIFY(0 == setenv("ZTEST_FD_DATA", fd_data_str, 1));

                (void) enable_extended_FILE_stdio(-1, -1);
                if (libpath != NULL)
                        VERIFY(0 == setenv("LD_LIBRARY_PATH", libpath, 1));
                (void) execv(cmd, emptyargv);
                ztest_dump_core = B_FALSE;
                fatal(B_TRUE, "exec failed: %s", cmd);
        }

        if (cmdbuf != NULL) {
                umem_free(cmdbuf, MAXPATHLEN);
                cmd = NULL;
        }

        while (waitpid(pid, &status, 0) != pid)
                continue;
        if (statusp != NULL)
                *statusp = status;

        if (WIFEXITED(status)) {
                if (WEXITSTATUS(status) != 0) {
                        (void) fprintf(stderr, "child exited with code %d\n",
                            WEXITSTATUS(status));
                        exit(2);
                }
                return (B_FALSE);
        } else if (WIFSIGNALED(status)) {
                if (!ignorekill || WTERMSIG(status) != SIGKILL) {
                        (void) fprintf(stderr, "child died with signal %d\n",
                            WTERMSIG(status));
                        exit(3);
                }
                return (B_TRUE);
        } else {
                (void) fprintf(stderr, "something strange happened to child\n");
                exit(4);
                /* NOTREACHED */
        }
}

static void
ztest_run_init(void)
{
        int i;

        ztest_shared_t *zs = ztest_shared;

        ASSERT(ztest_opts.zo_init != 0);

        /*
         * Blow away any existing copy of zpool.cache
         */
        (void) remove(spa_config_path);

        /*
         * Create and initialize our storage pool.
         */
        for (i = 1; i <= ztest_opts.zo_init; i++) {
                bzero(zs, sizeof (ztest_shared_t));
                if (ztest_opts.zo_verbose >= 3 &&
                    ztest_opts.zo_init != 1) {
                        (void) printf("ztest_init(), pass %d\n", i);
                }
                ztest_init(zs);
        }
}

int
main(int argc, char **argv)
{
        int kills = 0;
        int iters = 0;
        int older = 0;
        int newer = 0;
        ztest_shared_t *zs;
        ztest_info_t *zi;
        ztest_shared_callstate_t *zc;
        char timebuf[100];
        char numbuf[6];
        spa_t *spa;
        char *cmd;
        boolean_t hasalt;
        int f;
        char *fd_data_str = getenv("ZTEST_FD_DATA");
        struct sigaction action;

        (void) setvbuf(stdout, NULL, _IOLBF, 0);

        dprintf_setup(&argc, argv);

        action.sa_handler = sig_handler;
        sigemptyset(&action.sa_mask);
        action.sa_flags = 0;

        if (sigaction(SIGSEGV, &action, NULL) < 0) {
                (void) fprintf(stderr, "ztest: cannot catch SIGSEGV: %s.\n",
                    strerror(errno));
                exit(EXIT_FAILURE);
        }

        if (sigaction(SIGABRT, &action, NULL) < 0) {
                (void) fprintf(stderr, "ztest: cannot catch SIGABRT: %s.\n",
                    strerror(errno));
                exit(EXIT_FAILURE);
        }

        ztest_fd_rand = open("/dev/urandom", O_RDONLY);
        ASSERT3S(ztest_fd_rand, >=, 0);

        if (!fd_data_str) {
                process_options(argc, argv);

                setup_data_fd();
                setup_hdr();
                setup_data();
                bcopy(&ztest_opts, ztest_shared_opts,
                    sizeof (*ztest_shared_opts));
        } else {
                ztest_fd_data = atoi(fd_data_str);
                setup_data();
                bcopy(ztest_shared_opts, &ztest_opts, sizeof (ztest_opts));
        }
        ASSERT3U(ztest_opts.zo_datasets, ==, ztest_shared_hdr->zh_ds_count);

        /* Override location of zpool.cache */
        VERIFY(asprintf((char **)&spa_config_path, "%s/zpool.cache",
            ztest_opts.zo_dir) != -1);

        ztest_ds = umem_alloc(ztest_opts.zo_datasets * sizeof (ztest_ds_t),
            UMEM_NOFAIL);
        zs = ztest_shared;

        if (fd_data_str) {
                metaslab_gang_bang = ztest_opts.zo_metaslab_gang_bang;
                metaslab_df_alloc_threshold =
                    zs->zs_metaslab_df_alloc_threshold;

                if (zs->zs_do_init)
                        ztest_run_init();
                else
                        ztest_run(zs);
                exit(0);
        }

        hasalt = (strlen(ztest_opts.zo_alt_ztest) != 0);

        if (ztest_opts.zo_verbose >= 1) {
                (void) printf("%llu vdevs, %d datasets, %d threads,"
                    " %llu seconds...\n",
                    (u_longlong_t)ztest_opts.zo_vdevs,
                    ztest_opts.zo_datasets,
                    ztest_opts.zo_threads,
                    (u_longlong_t)ztest_opts.zo_time);
        }

        cmd = umem_alloc(MAXNAMELEN, UMEM_NOFAIL);
        (void) strlcpy(cmd, getexecname(), MAXNAMELEN);

        zs->zs_do_init = B_TRUE;
        if (strlen(ztest_opts.zo_alt_ztest) != 0) {
                if (ztest_opts.zo_verbose >= 1) {
                        (void) printf("Executing older ztest for "
                            "initialization: %s\n", ztest_opts.zo_alt_ztest);
                }
                VERIFY(!exec_child(ztest_opts.zo_alt_ztest,
                    ztest_opts.zo_alt_libpath, B_FALSE, NULL));
        } else {
                VERIFY(!exec_child(NULL, NULL, B_FALSE, NULL));
        }
        zs->zs_do_init = B_FALSE;

        zs->zs_proc_start = gethrtime();
        zs->zs_proc_stop = zs->zs_proc_start + ztest_opts.zo_time * NANOSEC;

        for (f = 0; f < ZTEST_FUNCS; f++) {
                zi = &ztest_info[f];
                zc = ZTEST_GET_SHARED_CALLSTATE(f);
                if (zs->zs_proc_start + zi->zi_interval[0] > zs->zs_proc_stop)
                        zc->zc_next = UINT64_MAX;
                else
                        zc->zc_next = zs->zs_proc_start +
                            ztest_random(2 * zi->zi_interval[0] + 1);
        }

        /*
         * Run the tests in a loop.  These tests include fault injection
         * to verify that self-healing data works, and forced crashes
         * to verify that we never lose on-disk consistency.
         */
        while (gethrtime() < zs->zs_proc_stop) {
                int status;
                boolean_t killed;

                /*
                 * Initialize the workload counters for each function.
                 */
                for (f = 0; f < ZTEST_FUNCS; f++) {
                        zc = ZTEST_GET_SHARED_CALLSTATE(f);
                        zc->zc_count = 0;
                        zc->zc_time = 0;
                }

                /* Set the allocation switch size */
                zs->zs_metaslab_df_alloc_threshold =
                    ztest_random(zs->zs_metaslab_sz / 4) + 1;

                if (!hasalt || ztest_random(2) == 0) {
                        if (hasalt && ztest_opts.zo_verbose >= 1) {
                                (void) printf("Executing newer ztest: %s\n",
                                    cmd);
                        }
                        newer++;
                        killed = exec_child(cmd, NULL, B_TRUE, &status);
                } else {
                        if (hasalt && ztest_opts.zo_verbose >= 1) {
                                (void) printf("Executing older ztest: %s\n",
                                    ztest_opts.zo_alt_ztest);
                        }
                        older++;
                        killed = exec_child(ztest_opts.zo_alt_ztest,
                            ztest_opts.zo_alt_libpath, B_TRUE, &status);
                }

                if (killed)
                        kills++;
                iters++;

                if (ztest_opts.zo_verbose >= 1) {
                        hrtime_t now = gethrtime();

                        now = MIN(now, zs->zs_proc_stop);
                        print_time(zs->zs_proc_stop - now, timebuf);
                        nicenum(zs->zs_space, numbuf);

                        (void) printf("Pass %3d, %8s, %3llu ENOSPC, "
                            "%4.1f%% of %5s used, %3.0f%% done, %8s to go\n",
                            iters,
                            WIFEXITED(status) ? "Complete" : "SIGKILL",
                            (u_longlong_t)zs->zs_enospc_count,
                            100.0 * zs->zs_alloc / zs->zs_space,
                            numbuf,
                            100.0 * (now - zs->zs_proc_start) /
                            (ztest_opts.zo_time * NANOSEC), timebuf);
                }

                if (ztest_opts.zo_verbose >= 2) {
                        (void) printf("\nWorkload summary:\n\n");
                        (void) printf("%7s %9s   %s\n",
                            "Calls", "Time", "Function");
                        (void) printf("%7s %9s   %s\n",
                            "-----", "----", "--------");
                        for (f = 0; f < ZTEST_FUNCS; f++) {
                                zi = &ztest_info[f];
                                zc = ZTEST_GET_SHARED_CALLSTATE(f);
                                print_time(zc->zc_time, timebuf);
                                (void) printf("%7llu %9s   %s\n",
                                    (u_longlong_t)zc->zc_count, timebuf,
                                    zi->zi_funcname);
                        }
                        (void) printf("\n");
                }

                /*
                 * It's possible that we killed a child during a rename test,
                 * in which case we'll have a 'ztest_tmp' pool lying around
                 * instead of 'ztest'.  Do a blind rename in case this happened.
                 */
                kernel_init(FREAD);
                if (spa_open(ztest_opts.zo_pool, &spa, FTAG) == 0) {
                        spa_close(spa, FTAG);
                } else {
                        char tmpname[ZFS_MAX_DATASET_NAME_LEN];
                        kernel_fini();
                        kernel_init(FREAD | FWRITE);
                        (void) snprintf(tmpname, sizeof (tmpname), "%s_tmp",
                            ztest_opts.zo_pool);
                        (void) spa_rename(tmpname, ztest_opts.zo_pool);
                }
                kernel_fini();

                ztest_run_zdb(ztest_opts.zo_pool);
        }

        if (ztest_opts.zo_verbose >= 1) {
                if (hasalt) {
                        (void) printf("%d runs of older ztest: %s\n", older,
                            ztest_opts.zo_alt_ztest);
                        (void) printf("%d runs of newer ztest: %s\n", newer,
                            cmd);
                }
                (void) printf("%d killed, %d completed, %.0f%% kill rate\n",
                    kills, iters - kills, (100.0 * kills) / MAX(1, iters));
        }

        umem_free(cmd, MAXNAMELEN);

        return (0);
}