FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/cmd/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 https://opensource.org/licenses/CDDL-1.0.
     * 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, 2018 by Delphix. All rights reserved.
     * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
     * Copyright (c) 2013 Steven Hartland. All rights reserved.
     * Copyright (c) 2014 Integros [integros.com]
     * Copyright 2017 Joyent, Inc.
     * Copyright (c) 2017, Intel Corporation.
     */
    
    /*
     * 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 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/vdev_draid.h>
   #include <sys/vdev_impl.h>
   #include <sys/vdev_file.h>
   #include <sys/vdev_initialize.h>
   #include <sys/vdev_raidz.h>
   #include <sys/vdev_trim.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/zfs_refcount.h>
   #include <sys/zfeature.h>
   #include <sys/dsl_userhold.h>
   #include <sys/abd.h>
   #include <sys/blake3.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <unistd.h>
   #include <getopt.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>
   #include <libzutil.h>
   #include <sys/crypto/icp.h>
   #if (__GLIBC__ && !__UCLIBC__)
   #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;
   
   enum ztest_class_state {
           ZTEST_VDEV_CLASS_OFF,
           ZTEST_VDEV_CLASS_ON,
           ZTEST_VDEV_CLASS_RND
   };
   
   #define ZO_GVARS_MAX_ARGLEN     ((size_t)64)
   #define ZO_GVARS_MAX_COUNT      ((size_t)10)
   
   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_raid_children;
           int zo_raid_parity;
           char zo_raid_type[8];
           int zo_draid_data;
           int zo_draid_spares;
           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_force_ganging;
           int zo_mmp_test;
           int zo_special_vdevs;
           int zo_dump_dbgmsg;
           int zo_gvars_count;
           char zo_gvars[ZO_GVARS_MAX_COUNT][ZO_GVARS_MAX_ARGLEN];
   } ztest_shared_opts_t;
   
   /* Default values for command line options. */
   #define DEFAULT_POOL "ztest"
   #define DEFAULT_VDEV_DIR "/tmp"
   #define DEFAULT_VDEV_COUNT 5
   #define DEFAULT_VDEV_SIZE (SPA_MINDEVSIZE * 4)  /* 256m default size */
   #define DEFAULT_VDEV_SIZE_STR "256M"
   #define DEFAULT_ASHIFT SPA_MINBLOCKSHIFT
   #define DEFAULT_MIRRORS 2
   #define DEFAULT_RAID_CHILDREN 4
   #define DEFAULT_RAID_PARITY 1
   #define DEFAULT_DRAID_DATA 4
   #define DEFAULT_DRAID_SPARES 1
   #define DEFAULT_DATASETS_COUNT 7
   #define DEFAULT_THREADS 23
   #define DEFAULT_RUN_TIME 300 /* 300 seconds */
   #define DEFAULT_RUN_TIME_STR "300 sec"
   #define DEFAULT_PASS_TIME 60 /* 60 seconds */
   #define DEFAULT_PASS_TIME_STR "60 sec"
   #define DEFAULT_KILL_RATE 70 /* 70% kill rate */
   #define DEFAULT_KILLRATE_STR "70%"
   #define DEFAULT_INITS 1
   #define DEFAULT_MAX_LOOPS 50 /* 5 minutes */
   #define DEFAULT_FORCE_GANGING (64 << 10)
   #define DEFAULT_FORCE_GANGING_STR "64K"
   
   /* Simplifying assumption: -1 is not a valid default. */
   #define NO_DEFAULT -1
   
   static const ztest_shared_opts_t ztest_opts_defaults = {
           .zo_pool = DEFAULT_POOL,
           .zo_dir = DEFAULT_VDEV_DIR,
           .zo_alt_ztest = { '\0' },
           .zo_alt_libpath = { '\0' },
           .zo_vdevs = DEFAULT_VDEV_COUNT,
           .zo_ashift = DEFAULT_ASHIFT,
           .zo_mirrors = DEFAULT_MIRRORS,
           .zo_raid_children = DEFAULT_RAID_CHILDREN,
           .zo_raid_parity = DEFAULT_RAID_PARITY,
           .zo_raid_type = VDEV_TYPE_RAIDZ,
           .zo_vdev_size = DEFAULT_VDEV_SIZE,
           .zo_draid_data = DEFAULT_DRAID_DATA,    /* data drives */
           .zo_draid_spares = DEFAULT_DRAID_SPARES, /* distributed spares */
           .zo_datasets = DEFAULT_DATASETS_COUNT,
           .zo_threads = DEFAULT_THREADS,
           .zo_passtime = DEFAULT_PASS_TIME,
           .zo_killrate = DEFAULT_KILL_RATE,
           .zo_verbose = 0,
           .zo_mmp_test = 0,
           .zo_init = DEFAULT_INITS,
           .zo_time = DEFAULT_RUN_TIME,
           .zo_maxloops = DEFAULT_MAX_LOOPS, /* max loops during spa_freeze() */
           .zo_metaslab_force_ganging = DEFAULT_FORCE_GANGING,
           .zo_special_vdevs = ZTEST_VDEV_CLASS_RND,
           .zo_gvars_count = 0,
   };
   
   extern uint64_t metaslab_force_ganging;
   extern uint64_t metaslab_df_alloc_threshold;
   extern uint64_t zfs_deadman_synctime_ms;
   extern uint_t metaslab_preload_limit;
   extern int zfs_compressed_arc_enabled;
   extern int zfs_abd_scatter_enabled;
   extern uint_t dmu_object_alloc_chunk_shift;
   extern boolean_t zfs_force_some_double_word_sm_entries;
   extern unsigned long zio_decompress_fail_fraction;
   extern unsigned long zfs_reconstruct_indirect_damage_fraction;
   
   
   static ztest_shared_opts_t *ztest_shared_opts;
   static ztest_shared_opts_t ztest_opts;
   static const char *const ztest_wkeydata = "abcdefghijklmnopqrstuvwxyz012345";
   
   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(zs) \
           (MAX((zs)->zs_mirrors, 1) * (ztest_opts.zo_raid_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;
   
   /*
    * It would be better to use a rangelock_t per object.  Unfortunately
    * the rangelock_t is not a drop-in replacement for rl_t, because we
    * still need to map from object ID to rangelock_t.
    */
   typedef enum {
           RL_READER,
           RL_WRITER,
           RL_APPEND
   } rl_type_t;
   
   typedef struct rll {
           void            *rll_writer;
           int             rll_readers;
           kmutex_t        rll_lock;
           kcondvar_t      rll_cv;
   } rll_t;
   
   typedef struct rl {
           uint64_t        rl_object;
           uint64_t        rl_offset;
           uint64_t        rl_size;
           rll_t           *rl_lock;
   } rl_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;
           pthread_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];
           rll_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_object_next_chunk;
   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_dmu_snapshot_hold;
   ztest_func_t ztest_mmp_enable_disable;
   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_class_add;
   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_device_removal;
   ztest_func_t ztest_spa_checkpoint_create_discard;
   ztest_func_t ztest_initialize;
   ztest_func_t ztest_trim;
   ztest_func_t ztest_blake3;
   ztest_func_t ztest_fletcher;
   ztest_func_t ztest_fletcher_incr;
   ztest_func_t ztest_verify_dnode_bt;
   
   static uint64_t zopt_always = 0ULL * NANOSEC;           /* all the time */
   static uint64_t zopt_incessant = 1ULL * NANOSEC / 10;   /* every 1/10 second */
   static uint64_t zopt_often = 1ULL * NANOSEC;            /* every second */
   static uint64_t zopt_sometimes = 10ULL * NANOSEC;       /* every 10 seconds */
   static 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 }
   
   static 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_object_next_chunk, 1, &zopt_sometimes),
           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_sometimes),
           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_dmu_snapshot_hold, 1, &zopt_sometimes),
           ZTI_INIT(ztest_mmp_enable_disable, 1, &zopt_sometimes),
           ZTI_INIT(ztest_reguid, 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_class_add, 1, &ztest_opts.zo_vdevtime),
           ZTI_INIT(ztest_vdev_aux_add_remove, 1, &ztest_opts.zo_vdevtime),
           ZTI_INIT(ztest_device_removal, 1, &zopt_sometimes),
           ZTI_INIT(ztest_spa_checkpoint_create_discard, 1, &zopt_rarely),
           ZTI_INIT(ztest_initialize, 1, &zopt_sometimes),
           ZTI_INIT(ztest_trim, 1, &zopt_sometimes),
           ZTI_INIT(ztest_blake3, 1, &zopt_rarely),
           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";
   static ztest_shared_t *ztest_shared;
   
   static spa_t *ztest_spa = NULL;
   static ztest_ds_t *ztest_ds;
   
   static kmutex_t ztest_vdev_lock;
   static boolean_t ztest_device_removal_active = B_FALSE;
   static boolean_t ztest_pool_scrubbed = B_FALSE;
   static kmutex_t ztest_checkpoint_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 pthread_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)
   
   enum ztest_object {
           ZTEST_META_DNODE = 0,
           ZTEST_DIROBJ,
           ZTEST_OBJECTS
   };
   
   static __attribute__((noreturn)) void usage(boolean_t requested);
   static int ztest_scrub_impl(spa_t *spa);
   
   /*
    * 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 */
   }
   
   static void
   dump_debug_buffer(void)
   {
           ssize_t ret __attribute__((unused));
   
           if (!ztest_opts.zo_dump_dbgmsg)
                   return;
   
           /*
            * We use write() instead of printf() so that this function
            * is safe to call from a signal handler.
            */
           ret = write(STDOUT_FILENO, "\n", 1);
           zfs_dbgmsg_print("ztest");
   }
   
   #define BACKTRACE_SZ    100
   
   static void sig_handler(int signo)
   {
           struct sigaction action;
   #if (__GLIBC__ && !__UCLIBC__) /* backtrace() is a GNU extension */
           int nptrs;
           void *buffer[BACKTRACE_SZ];
   
           nptrs = backtrace(buffer, BACKTRACE_SZ);
           backtrace_symbols_fd(buffer, nptrs, STDERR_FILENO);
   #endif
           dump_debug_buffer();
   
           /*
            * 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
   
   static const char *fatal_msg;
   
   static __attribute__((format(printf, 2, 3))) __attribute__((noreturn)) void
   fatal(int do_perror, const char *message, ...)
   {
           va_list args;
           int save_errno = errno;
           char *buf;
   
           (void) fflush(stdout);
           buf = umem_alloc(FATAL_MSG_SZ, UMEM_NOFAIL);
           if (buf == NULL)
                   goto out;
   
           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 */
   
   out:
           if (ztest_dump_core)
                   abort();
           else
                   dump_debug_buffer();
   
           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);
   }
   
   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));
                   /*
                    * UINT64_MAX is not exactly representable as a double.
                    * The closest representation is UINT64_MAX + 1, so we
                    * use a >= comparison instead of > for the bounds check.
                    */
                   if (fval >= (double)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);
   }
   
   typedef struct ztest_option {
           const char      short_opt;
           const char      *long_opt;
           const char      *long_opt_param;
           const char      *comment;
           unsigned int    default_int;
           const char      *default_str;
   } ztest_option_t;
   
   /*
    * The following option_table is used for generating the usage info as well as
    * the long and short option information for calling getopt_long().
    */
   static ztest_option_t option_table[] = {
           { 'v',  "vdevs", "INTEGER", "Number of vdevs", DEFAULT_VDEV_COUNT,
               NULL},
           { 's',  "vdev-size", "INTEGER", "Size of each vdev",
               NO_DEFAULT, DEFAULT_VDEV_SIZE_STR},
           { 'a',  "alignment-shift", "INTEGER",
               "Alignment shift; use 0 for random", DEFAULT_ASHIFT, NULL},
           { 'm',  "mirror-copies", "INTEGER", "Number of mirror copies",
               DEFAULT_MIRRORS, NULL},
           { 'r',  "raid-disks", "INTEGER", "Number of raidz/draid disks",
               DEFAULT_RAID_CHILDREN, NULL},
           { 'R',  "raid-parity", "INTEGER", "Raid parity",
               DEFAULT_RAID_PARITY, NULL},
           { 'K',  "raid-kind", "raidz|draid|random", "Raid kind",
               NO_DEFAULT, "random"},
           { 'D',  "draid-data", "INTEGER", "Number of draid data drives",
               DEFAULT_DRAID_DATA, NULL},
           { 'S',  "draid-spares", "INTEGER", "Number of draid spares",
               DEFAULT_DRAID_SPARES, NULL},
           { 'd',  "datasets", "INTEGER", "Number of datasets",
               DEFAULT_DATASETS_COUNT, NULL},
           { 't',  "threads", "INTEGER", "Number of ztest threads",
               DEFAULT_THREADS, NULL},
           { 'g',  "gang-block-threshold", "INTEGER",
               "Metaslab gang block threshold",
               NO_DEFAULT, DEFAULT_FORCE_GANGING_STR},
           { 'i',  "init-count", "INTEGER", "Number of times to initialize pool",
               DEFAULT_INITS, NULL},
           { 'k',  "kill-percentage", "INTEGER", "Kill percentage",
               NO_DEFAULT, DEFAULT_KILLRATE_STR},
           { 'p',  "pool-name", "STRING", "Pool name",
               NO_DEFAULT, DEFAULT_POOL},
           { 'f',  "vdev-file-directory", "PATH", "File directory for vdev files",
               NO_DEFAULT, DEFAULT_VDEV_DIR},
           { 'M',  "multi-host", NULL,
               "Multi-host; simulate pool imported on remote host",
               NO_DEFAULT, NULL},
           { 'E',  "use-existing-pool", NULL,
               "Use existing pool instead of creating new one", NO_DEFAULT, NULL},
           { 'T',  "run-time", "INTEGER", "Total run time",
               NO_DEFAULT, DEFAULT_RUN_TIME_STR},
           { 'P',  "pass-time", "INTEGER", "Time per pass",
               NO_DEFAULT, DEFAULT_PASS_TIME_STR},
           { 'F',  "freeze-loops", "INTEGER", "Max loops in spa_freeze()",
               DEFAULT_MAX_LOOPS, NULL},
           { 'B',  "alt-ztest", "PATH", "Alternate ztest path",
               NO_DEFAULT, NULL},
           { 'C',  "vdev-class-state", "on|off|random", "vdev class state",
               NO_DEFAULT, "random"},
           { 'o',  "option", "\"OPTION=INTEGER\"",
               "Set global variable to an unsigned 32-bit integer value",
               NO_DEFAULT, NULL},
           { 'G',  "dump-debug-msg", NULL,
               "Dump zfs_dbgmsg buffer before exiting due to an error",
               NO_DEFAULT, NULL},
           { 'V',  "verbose", NULL,
               "Verbose (use multiple times for ever more verbosity)",
               NO_DEFAULT, NULL},
           { 'h',  "help", NULL, "Show this help",
               NO_DEFAULT, NULL},
           {0, 0, 0, 0, 0, 0}
   };
   
   static struct option *long_opts = NULL;
   static char *short_opts = NULL;
   
   static void
   init_options(void)
   {
           ASSERT3P(long_opts, ==, NULL);
           ASSERT3P(short_opts, ==, NULL);
   
           int count = sizeof (option_table) / sizeof (option_table[0]);
           long_opts = umem_alloc(sizeof (struct option) * count, UMEM_NOFAIL);
   
           short_opts = umem_alloc(sizeof (char) * 2 * count, UMEM_NOFAIL);
           int short_opt_index = 0;
   
           for (int i = 0; i < count; i++) {
                   long_opts[i].val = option_table[i].short_opt;
                   long_opts[i].name = option_table[i].long_opt;
                   long_opts[i].has_arg = option_table[i].long_opt_param != NULL
                       ? required_argument : no_argument;
                   long_opts[i].flag = NULL;
                   short_opts[short_opt_index++] = option_table[i].short_opt;
                   if (option_table[i].long_opt_param != NULL) {
                           short_opts[short_opt_index++] = ':';
                   }
           }
   }
   
   static void
   fini_options(void)
   {
           int count = sizeof (option_table) / sizeof (option_table[0]);
   
           umem_free(long_opts, sizeof (struct option) * count);
           umem_free(short_opts, sizeof (char) * 2 * count);
   
           long_opts = NULL;
           short_opts = NULL;
   }
   
   static __attribute__((noreturn)) void
   usage(boolean_t requested)
   {
           char option[80];
           FILE *fp = requested ? stdout : stderr;
   
           (void) fprintf(fp, "Usage: %s [OPTIONS...]\n", DEFAULT_POOL);
           for (int i = 0; option_table[i].short_opt != 0; i++) {
                   if (option_table[i].long_opt_param != NULL) {
                           (void) sprintf(option, "  -%c --%s=%s",
                               option_table[i].short_opt,
                               option_table[i].long_opt,
                               option_table[i].long_opt_param);
                   } else {
                           (void) sprintf(option, "  -%c --%s",
                               option_table[i].short_opt,
                               option_table[i].long_opt);
                   }
                   (void) fprintf(fp, "  %-40s%s", option,
                       option_table[i].comment);
   
                   if (option_table[i].long_opt_param != NULL) {
                           if (option_table[i].default_str != NULL) {
                                   (void) fprintf(fp, " (default: %s)",
                                       option_table[i].default_str);
                           } else if (option_table[i].default_int != NO_DEFAULT) {
                                   (void) fprintf(fp, " (default: %u)",
                                       option_table[i].default_int);
                           }
                   }
                   (void) fprintf(fp, "\n");
           }
           exit(requested ? 0 : 1);
   }
   
   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(B_TRUE, "short read from /dev/urandom");
   
           return (r % range);
   }
   
   static void
   ztest_parse_name_value(const char *input, ztest_shared_opts_t *zo)
   {
           char name[32];
           char *value;
           int state = ZTEST_VDEV_CLASS_RND;
   
           (void) strlcpy(name, input, sizeof (name));
   
           value = strchr(name, '=');
           if (value == NULL) {
                   (void) fprintf(stderr, "missing value in property=value "
                       "'-C' argument (%s)\n", input);
                   usage(B_FALSE);
           }
           *(value) = '\0';
           value++;
   
           if (strcmp(value, "on") == 0) {
                   state = ZTEST_VDEV_CLASS_ON;
           } else if (strcmp(value, "off") == 0) {
                   state = ZTEST_VDEV_CLASS_OFF;
           } else if (strcmp(value, "random") == 0) {
                   state = ZTEST_VDEV_CLASS_RND;
           } else {
                   (void) fprintf(stderr, "invalid property value '%s'\n", value);
                   usage(B_FALSE);
           }
   
           if (strcmp(name, "special") == 0) {
                   zo->zo_special_vdevs = state;
           } else {
                   (void) fprintf(stderr, "invalid property name '%s'\n", name);
                   usage(B_FALSE);
           }
           if (zo->zo_verbose >= 3)
                   (void) printf("%s vdev state is '%s'\n", name, value);
   }
   
   static void
   process_options(int argc, char **argv)
   {
           char *path;
           ztest_shared_opts_t *zo = &ztest_opts;
   
           int opt;
           uint64_t value;
           const char *raid_kind = "random";
   
           memcpy(zo, &ztest_opts_defaults, sizeof (*zo));
   
           init_options();
   
           while ((opt = getopt_long(argc, argv, short_opts, long_opts,
               NULL)) != EOF) {
                   value = 0;
                   switch (opt) {
                   case 'v':
                   case 's':
                   case 'a':
                   case 'm':
                   case 'r':
                   case 'R':
                   case 'D':
                   case 'S':
                   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_raid_children = MAX(1, value);
                           break;
                   case 'R':
                           zo->zo_raid_parity = MIN(MAX(value, 1), 3);
                           break;
                   case 'K':
                           raid_kind = optarg;
                           break;
                   case 'D':
                           zo->zo_draid_data = MAX(1, value);
                           break;
                   case 'S':
                           zo->zo_draid_spares = MAX(1, value);
                           break;
                   case 'd':
                           zo->zo_datasets = MAX(1, value);
                           break;
                   case 't':
                           zo->zo_threads = MAX(1, value);
                           break;
                   case 'g':
                           zo->zo_metaslab_force_ganging =
                               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 'M':
                          zo->zo_mmp_test = 1;
                          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(zo->zo_alt_ztest, optarg,
                              sizeof (zo->zo_alt_ztest));
                          break;
                  case 'C':
                          ztest_parse_name_value(optarg, zo);
                          break;
                  case 'o':
                          if (zo->zo_gvars_count >= ZO_GVARS_MAX_COUNT) {
                                  (void) fprintf(stderr,
                                      "max global var count (%zu) exceeded\n",
                                      ZO_GVARS_MAX_COUNT);
                                  usage(B_FALSE);
                          }
                          char *v = zo->zo_gvars[zo->zo_gvars_count];
                          if (strlcpy(v, optarg, ZO_GVARS_MAX_ARGLEN) >=
                              ZO_GVARS_MAX_ARGLEN) {
                                  (void) fprintf(stderr,
                                      "global var option '%s' is too long\n",
                                      optarg);
                                  usage(B_FALSE);
                          }
                          zo->zo_gvars_count++;
                          break;
                  case 'G':
                          zo->zo_dump_dbgmsg = 1;
                          break;
                  case 'h':
                          usage(B_TRUE);
                          break;
                  case '?':
                  default:
                          usage(B_FALSE);
                          break;
                  }
          }
  
          fini_options();
  
          /* When raid choice is 'random' add a draid pool 50% of the time */
          if (strcmp(raid_kind, "random") == 0) {
                  raid_kind = (ztest_random(2) == 0) ? "draid" : "raidz";
  
                  if (ztest_opts.zo_verbose >= 3)
                          (void) printf("choosing RAID type '%s'\n", raid_kind);
          }
  
          if (strcmp(raid_kind, "draid") == 0) {
                  uint64_t min_devsize;
  
                  /* With fewer disk use 256M, otherwise 128M is OK */
                  min_devsize = (ztest_opts.zo_raid_children < 16) ?
                      (256ULL << 20) : (128ULL << 20);
  
                  /* No top-level mirrors with dRAID for now */
                  zo->zo_mirrors = 0;
  
                  /* Use more appropriate defaults for dRAID */
                  if (zo->zo_vdevs == ztest_opts_defaults.zo_vdevs)
                          zo->zo_vdevs = 1;
                  if (zo->zo_raid_children ==
                      ztest_opts_defaults.zo_raid_children)
                          zo->zo_raid_children = 16;
                  if (zo->zo_ashift < 12)
                          zo->zo_ashift = 12;
                  if (zo->zo_vdev_size < min_devsize)
                          zo->zo_vdev_size = min_devsize;
  
                  if (zo->zo_draid_data + zo->zo_raid_parity >
                      zo->zo_raid_children - zo->zo_draid_spares) {
                          (void) fprintf(stderr, "error: too few draid "
                              "children (%d) for stripe width (%d)\n",
                              zo->zo_raid_children,
                              zo->zo_draid_data + zo->zo_raid_parity);
                          usage(B_FALSE);
                  }
  
                  (void) strlcpy(zo->zo_raid_type, VDEV_TYPE_DRAID,
                      sizeof (zo->zo_raid_type));
  
          } else /* using raidz */ {
                  ASSERT0(strcmp(raid_kind, "raidz"));
  
                  zo->zo_raid_parity = MIN(zo->zo_raid_parity,
                      zo->zo_raid_children - 1);
          }
  
          zo->zo_vdevtime =
              (zo->zo_vdevs > 0 ? zo->zo_time * NANOSEC / zo->zo_vdevs :
              UINT64_MAX >> 2);
  
          if (*zo->zo_alt_ztest) {
                  const char *invalid_what = "ztest";
                  char *val = zo->zo_alt_ztest;
                  if (0 != access(val, X_OK) ||
                      (strrchr(val, '/') == NULL && (errno == EINVAL)))
                          goto invalid;
  
                  int dirlen = strrchr(val, '/') - val;
                  strlcpy(zo->zo_alt_libpath, val,
                      MIN(sizeof (zo->zo_alt_libpath), dirlen + 1));
                  invalid_what = "library path", val = zo->zo_alt_libpath;
                  if (strrchr(val, '/') == NULL && (errno == EINVAL))
                          goto invalid;
                  *strrchr(val, '/') = '\0';
                  strlcat(val, "/lib", sizeof (zo->zo_alt_libpath));
  
                  if (0 != access(zo->zo_alt_libpath, X_OK))
                          goto invalid;
                  return;
  
  invalid:
                  ztest_dump_core = B_FALSE;
                  fatal(B_TRUE, "invalid alternate %s %s", invalid_what, val);
          }
  }
  
  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 ourselves, make sure that the config is updated.
           * See comment above spa_write_cachefile().
           */
          mutex_enter(&spa_namespace_lock);
          spa_write_cachefile(ztest_spa, B_FALSE, B_FALSE, B_FALSE);
          mutex_exit(&spa_namespace_lock);
  
          (void) raise(SIGKILL);
  }
  
  static void
  ztest_record_enospc(const char *s)
  {
          (void) 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 boolean_t
  ztest_is_draid_spare(const char *name)
  {
          uint64_t spare_id = 0, parity = 0, vdev_id = 0;
  
          if (sscanf(name, VDEV_TYPE_DRAID "%"PRIu64"-%"PRIu64"-%"PRIu64"",
              &parity, &vdev_id, &spare_id) == 3) {
                  return (B_TRUE);
          }
  
          return (B_FALSE);
  }
  
  static nvlist_t *
  make_vdev_file(const char *path, const char *aux, const char *pool,
      size_t size, uint64_t ashift)
  {
          char *pathbuf = NULL;
          uint64_t vdev;
          nvlist_t *file;
          boolean_t draid_spare = B_FALSE;
  
  
          if (ashift == 0)
                  ashift = ztest_get_ashift();
  
          if (path == NULL) {
                  pathbuf = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
                  path = pathbuf;
  
                  if (aux != NULL) {
                          vdev = ztest_shared->zs_vdev_aux;
                          (void) snprintf(pathbuf, 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(pathbuf, MAXPATHLEN,
                              ztest_dev_template, ztest_opts.zo_dir,
                              pool == NULL ? ztest_opts.zo_pool : pool, vdev);
                  }
          } else {
                  draid_spare = ztest_is_draid_spare(path);
          }
  
          if (size != 0 && !draid_spare) {
                  int fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0666);
                  if (fd == -1)
                          fatal(B_TRUE, "can't open %s", path);
                  if (ftruncate(fd, size) != 0)
                          fatal(B_TRUE, "can't ftruncate %s", path);
                  (void) close(fd);
          }
  
          file = fnvlist_alloc();
          fnvlist_add_string(file, ZPOOL_CONFIG_TYPE,
              draid_spare ? VDEV_TYPE_DRAID_SPARE : VDEV_TYPE_FILE);
          fnvlist_add_string(file, ZPOOL_CONFIG_PATH, path);
          fnvlist_add_uint64(file, ZPOOL_CONFIG_ASHIFT, ashift);
          umem_free(pathbuf, MAXPATHLEN);
  
          return (file);
  }
  
  static nvlist_t *
  make_vdev_raid(const char *path, const char *aux, const char *pool, size_t size,
      uint64_t ashift, int r)
  {
          nvlist_t *raid, **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);
  
          raid = fnvlist_alloc();
          fnvlist_add_string(raid, ZPOOL_CONFIG_TYPE,
              ztest_opts.zo_raid_type);
          fnvlist_add_uint64(raid, ZPOOL_CONFIG_NPARITY,
              ztest_opts.zo_raid_parity);
          fnvlist_add_nvlist_array(raid, ZPOOL_CONFIG_CHILDREN,
              (const nvlist_t **)child, r);
  
          if (strcmp(ztest_opts.zo_raid_type, VDEV_TYPE_DRAID) == 0) {
                  uint64_t ndata = ztest_opts.zo_draid_data;
                  uint64_t nparity = ztest_opts.zo_raid_parity;
                  uint64_t nspares = ztest_opts.zo_draid_spares;
                  uint64_t children = ztest_opts.zo_raid_children;
                  uint64_t ngroups = 1;
  
                  /*
                   * Calculate the minimum number of groups required to fill a
                   * slice. This is the LCM of the stripe width (data + parity)
                   * and the number of data drives (children - spares).
                   */
                  while (ngroups * (ndata + nparity) % (children - nspares) != 0)
                          ngroups++;
  
                  /* Store the basic dRAID configuration. */
                  fnvlist_add_uint64(raid, ZPOOL_CONFIG_DRAID_NDATA, ndata);
                  fnvlist_add_uint64(raid, ZPOOL_CONFIG_DRAID_NSPARES, nspares);
                  fnvlist_add_uint64(raid, ZPOOL_CONFIG_DRAID_NGROUPS, ngroups);
          }
  
          for (c = 0; c < r; c++)
                  fnvlist_free(child[c]);
  
          umem_free(child, r * sizeof (nvlist_t *));
  
          return (raid);
  }
  
  static nvlist_t *
  make_vdev_mirror(const char *path, const char *aux, const char *pool,
      size_t size, uint64_t ashift, int r, int m)
  {
          nvlist_t *mirror, **child;
          int c;
  
          if (m < 1)
                  return (make_vdev_raid(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_raid(path, aux, pool, size, ashift, r);
  
          mirror = fnvlist_alloc();
          fnvlist_add_string(mirror, ZPOOL_CONFIG_TYPE, VDEV_TYPE_MIRROR);
          fnvlist_add_nvlist_array(mirror, ZPOOL_CONFIG_CHILDREN,
              (const nvlist_t **)child, m);
  
          for (c = 0; c < m; c++)
                  fnvlist_free(child[c]);
  
          umem_free(child, m * sizeof (nvlist_t *));
  
          return (mirror);
  }
  
  static nvlist_t *
  make_vdev_root(const char *path, const char *aux, const char *pool, size_t size,
      uint64_t ashift, const char *class, int r, int m, int t)
  {
          nvlist_t *root, **child;
          int c;
          boolean_t log;
  
          ASSERT3S(t, >, 0);
  
          log = (class != NULL && strcmp(class, "log") == 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);
                  fnvlist_add_uint64(child[c], ZPOOL_CONFIG_IS_LOG, log);
  
                  if (class != NULL && class[0] != '\0') {
                          ASSERT(m > 1 || log);   /* expecting a mirror */
                          fnvlist_add_string(child[c],
                              ZPOOL_CONFIG_ALLOCATION_BIAS, class);
                  }
          }
  
          root = fnvlist_alloc();
          fnvlist_add_string(root, ZPOOL_CONFIG_TYPE, VDEV_TYPE_ROOT);
          fnvlist_add_nvlist_array(root, aux ? aux : ZPOOL_CONFIG_CHILDREN,
              (const nvlist_t **)child, t);
  
          for (c = 0; c < t; c++)
                  fnvlist_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)
  {
          ASSERT3U(ztest_spa->spa_max_ashift, !=, 0);
  
          /*
           * 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;
  
          ASSERT3U(spa_config_held(spa, SCL_ALL, RW_READER), !=, 0);
  
          do {
                  top = ztest_random(rvd->vdev_children);
                  tvd = rvd->vdev_child[top];
          } while (!vdev_is_concrete(tvd) || (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;
  
          props = fnvlist_alloc();
          fnvlist_add_uint64(props, zpool_prop_to_name(prop), value);
  
          error = spa_prop_set(spa, props);
  
          fnvlist_free(props);
  
          if (error == ENOSPC) {
                  ztest_record_enospc(FTAG);
                  return (error);
          }
          ASSERT0(error);
  
          return (error);
  }
  
  static int
  ztest_dmu_objset_own(const char *name, dmu_objset_type_t type,
      boolean_t readonly, boolean_t decrypt, const void *tag, objset_t **osp)
  {
          int err;
          char *cp = NULL;
          char ddname[ZFS_MAX_DATASET_NAME_LEN];
  
          strlcpy(ddname, name, sizeof (ddname));
          cp = strchr(ddname, '@');
          if (cp != NULL)
                  *cp = '\0';
  
          err = dmu_objset_own(name, type, readonly, decrypt, tag, osp);
          while (decrypt && err == EACCES) {
                  dsl_crypto_params_t *dcp;
                  nvlist_t *crypto_args = fnvlist_alloc();
  
                  fnvlist_add_uint8_array(crypto_args, "wkeydata",
                      (uint8_t *)ztest_wkeydata, WRAPPING_KEY_LEN);
                  VERIFY0(dsl_crypto_params_create_nvlist(DCP_CMD_NONE, NULL,
                      crypto_args, &dcp));
                  err = spa_keystore_load_wkey(ddname, dcp, B_FALSE);
                  /*
                   * Note: if there was an error loading, the wkey was not
                   * consumed, and needs to be freed.
                   */
                  dsl_crypto_params_free(dcp, (err != 0));
                  fnvlist_free(crypto_args);
  
                  if (err == EINVAL) {
                          /*
                           * We couldn't load a key for this dataset so try
                           * the parent. This loop will eventually hit the
                           * encryption root since ztest only makes clones
                           * as children of their origin datasets.
                           */
                          cp = strrchr(ddname, '/');
                          if (cp == NULL)
                                  return (err);
  
                          *cp = '\0';
                          err = EACCES;
                          continue;
                  } else if (err != 0) {
                          break;
                  }
  
                  err = dmu_objset_own(name, type, readonly, decrypt, tag, osp);
                  break;
          }
  
          return (err);
  }
  
  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)
  {
          ASSERT3P(rll->rll_writer, ==, NULL);
          ASSERT0(rll->rll_readers);
          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) {
                  ASSERT0(rll->rll_readers);
                  rll->rll_writer = NULL;
          } else {
                  ASSERT3S(rll->rll_readers, >, 0);
                  ASSERT3P(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 rl_t *
  ztest_range_lock(ztest_ds_t *zd, uint64_t object, uint64_t offset,
      uint64_t size, rl_type_t type)
  {
          uint64_t hash = object ^ (offset % (ZTEST_RANGE_LOCKS + 1));
          rll_t *rll = &zd->zd_range_lock[hash & (ZTEST_RANGE_LOCKS - 1)];
          rl_t *rl;
  
          rl = umem_alloc(sizeof (*rl), UMEM_NOFAIL);
          rl->rl_object = object;
          rl->rl_offset = offset;
          rl->rl_size = size;
          rl->rl_lock = rll;
  
          ztest_rll_lock(rll, type);
  
          return (rl);
  }
  
  static void
  ztest_range_unlock(rl_t *rl)
  {
          rll_t *rll = rl->rl_lock;
  
          ztest_rll_unlock(rll);
  
          umem_free(rl, sizeof (*rl));
  }
  
  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;
  
          VERIFY0(pthread_rwlock_init(&zd->zd_zilog_lock, NULL));
          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_rll_init(&zd->zd_range_lock[l]);
  }
  
  static void
  ztest_zd_fini(ztest_ds_t *zd)
  {
          int l;
  
          mutex_destroy(&zd->zd_dirobj_lock);
          (void) pthread_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_rll_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) {
                          ASSERT3U(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);
          ASSERT3U(txg, !=, 0);
          return (txg);
  }
  
  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.
   */
  static 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.
   */
  static 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);
          memcpy(&itx->itx_lr + 1, &lr->lr_common + 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);
          memcpy(&itx->itx_lr + 1, &lr->lr_common + 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(zd->zd_zilog))
                  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);
  
          memcpy(&itx->itx_lr + 1, &lr->lr_common + 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));
          memcpy(&itx->itx_lr + 1, &lr->lr_common + 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));
          memcpy(&itx->itx_lr + 1, &lr->lr_common + 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(void *arg1, void *arg2, boolean_t byteswap)
  {
          ztest_ds_t *zd = arg1;
          lr_create_t *lr = arg2;
          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));
  
          ASSERT3U(lr->lr_doid, ==, ZTEST_DIROBJ);
          ASSERT3S(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);
  
          ASSERT3U(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);
          }
  
          ASSERT3U(lr->lr_foid, !=, 0);
  
          if (lr->lrz_type != DMU_OT_ZAP_OTHER)
                  VERIFY0(dmu_object_set_blocksize(os, lr->lr_foid,
                      lr->lrz_blocksize, lr->lrz_ibshift, tx));
  
          VERIFY0(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);
  
          VERIFY0(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(void *arg1, void *arg2, boolean_t byteswap)
  {
          ztest_ds_t *zd = arg1;
          lr_remove_t *lr = arg2;
          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));
  
          ASSERT3U(lr->lr_doid, ==, ZTEST_DIROBJ);
          ASSERT3S(name[0], !=, '\0');
  
          VERIFY0(
              zap_lookup(os, lr->lr_doid, name, sizeof (object), 1, &object));
          ASSERT3U(object, !=, 0);
  
          ztest_object_lock(zd, object, RL_WRITER);
  
          VERIFY0(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) {
                  VERIFY0(zap_destroy(os, object, tx));
          } else {
                  VERIFY0(dmu_object_free(os, object, tx));
          }
  
          VERIFY0(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(void *arg1, void *arg2, boolean_t byteswap)
  {
          ztest_ds_t *zd = arg1;
          lr_write_t *lr = arg2;
          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;
          rl_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);
  
          VERIFY0(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(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(doi.doi_data_block_size);
                  ASSERT0(offset % doi.doi_data_block_size);
                  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 {
                  memcpy(abuf->b_data, data, length);
                  VERIFY0(dmu_assign_arcbuf_by_dbuf(db, offset, abuf, tx));
          }
  
          (void) ztest_log_write(zd, tx, lr);
  
          dmu_buf_rele(db, FTAG);
  
          dmu_tx_commit(tx);
  
          ztest_range_unlock(rl);
          ztest_object_unlock(zd, lr->lr_foid);
  
          return (0);
  }
  
  static int
  ztest_replay_truncate(void *arg1, void *arg2, boolean_t byteswap)
  {
          ztest_ds_t *zd = arg1;
          lr_truncate_t *lr = arg2;
          objset_t *os = zd->zd_os;
          dmu_tx_t *tx;
          uint64_t txg;
          rl_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(rl);
                  ztest_object_unlock(zd, lr->lr_foid);
                  return (ENOSPC);
          }
  
          VERIFY0(dmu_free_range(os, lr->lr_foid, lr->lr_offset,
              lr->lr_length, tx));
  
          (void) ztest_log_truncate(zd, tx, lr);
  
          dmu_tx_commit(tx);
  
          ztest_range_unlock(rl);
          ztest_object_unlock(zd, lr->lr_foid);
  
          return (0);
  }
  
  static int
  ztest_replay_setattr(void *arg1, void *arg2, boolean_t byteswap)
  {
          ztest_ds_t *zd = arg1;
          lr_setattr_t *lr = arg2;
          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);
  
          VERIFY0(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) {
                  ASSERT3U(lr->lr_size, !=, 0);
                  ASSERT3U(lr->lr_mode, !=, 0);
                  ASSERT3U(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;
                  ASSERT0(lrtxg);
          }
  
          /*
           * 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);
  }
  
  static zil_replay_func_t *ztest_replay_vector[TX_MAX_TYPE] = {
          NULL,                   /* 0 no such transaction type */
          ztest_replay_create,    /* TX_CREATE */
          NULL,                   /* TX_MKDIR */
          NULL,                   /* TX_MKXATTR */
          NULL,                   /* TX_SYMLINK */
          ztest_replay_remove,    /* TX_REMOVE */
          NULL,                   /* TX_RMDIR */
          NULL,                   /* TX_LINK */
          NULL,                   /* TX_RENAME */
          ztest_replay_write,     /* TX_WRITE */
          ztest_replay_truncate,  /* TX_TRUNCATE */
          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 */
          NULL,                   /* TX_SETSAXATTR */
          NULL,                   /* TX_RENAME_EXCHANGE */
          NULL,                   /* TX_RENAME_WHITEOUT */
  };
  
  /*
   * ZIL get_data callbacks
   */
  
  static void
  ztest_get_done(zgd_t *zgd, int error)
  {
          (void) error;
          ztest_ds_t *zd = zgd->zgd_private;
          uint64_t object = ((rl_t *)zgd->zgd_lr)->rl_object;
  
          if (zgd->zgd_db)
                  dmu_buf_rele(zgd->zgd_db, zgd);
  
          ztest_range_unlock((rl_t *)zgd->zgd_lr);
          ztest_object_unlock(zd, object);
  
          umem_free(zgd, sizeof (*zgd));
  }
  
  static int
  ztest_get_data(void *arg, uint64_t arg2, lr_write_t *lr, char *buf,
      struct lwb *lwb, zio_t *zio)
  {
          (void) arg2;
          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;
          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;
  
          ASSERT3P(lwb, !=, NULL);
          ASSERT3P(zio, !=, NULL);
          ASSERT3U(size, !=, 0);
  
          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_lwb = lwb;
          zgd->zgd_private = zd;
  
          if (buf != NULL) {      /* immediate write */
                  zgd->zgd_lr = (struct zfs_locked_range *)ztest_range_lock(zd,
                      object, offset, size, RL_READER);
  
                  error = dmu_read(os, object, offset, size, buf,
                      DMU_READ_NO_PREFETCH);
                  ASSERT0(error);
          } else {
                  size = doi.doi_data_block_size;
                  if (ISP2(size)) {
                          offset = P2ALIGN(offset, size);
                  } else {
                          ASSERT3U(offset, <, size);
                          offset = 0;
                  }
  
                  zgd->zgd_lr = (struct zfs_locked_range *)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 *bp = &lr->lr_blkptr;
  
                          zgd->zgd_db = db;
                          zgd->zgd_bp = bp;
  
                          ASSERT3U(db->db_offset, ==, offset);
                          ASSERT3U(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)
                  memcpy(lr + lrsize, name, namesize);
  
          return (lr);
  }
  
  static 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) {
                          ASSERT3S(error, ==, ENOENT);
                          ASSERT0(od->od_object);
                          missing++;
                  } else {
                          dmu_buf_t *db;
                          ztest_block_tag_t *bbt;
                          dmu_object_info_t doi;
  
                          ASSERT3U(od->od_object, !=, 0);
                          ASSERT0(missing);       /* there should be no gaps */
  
                          ztest_object_lock(zd, od->od_object, RL_READER);
                          VERIFY0(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) {
                          ASSERT0(missing);
                          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;
                          ASSERT3U(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);
  
          memcpy(lr + 1, data, 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;
          rl_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(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;
  
          VERIFY0(dmu_object_info(zd->zd_os, object, &doi));
          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) pthread_rwlock_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:
                  memset(data, 0, 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) pthread_rwlock_rdlock(&ztest_name_lock);
                  err = ztest_dsl_prop_set_uint64(zd->zd_name,
                      ZFS_PROP_CHECKSUM, spa_dedup_checksum(ztest_spa),
                      B_FALSE);
                  ASSERT(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);
                  ASSERT(err == 0 || err == ENOSPC);
                  (void) pthread_rwlock_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) pthread_rwlock_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, const 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(%"PRId64")[%"PRIu64"]",
              tag, id, 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);
  }
  
  void
  ztest_zil_commit(ztest_ds_t *zd, uint64_t id)
  {
          (void) id;
          zilog_t *zilog = zd->zd_zilog;
  
          (void) pthread_rwlock_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);
          ASSERT3P(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) pthread_rwlock_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.
   */
  void
  ztest_zil_remount(ztest_ds_t *zd, uint64_t id)
  {
          (void) id;
          objset_t *os = zd->zd_os;
  
          /*
           * We hold the ztest_vdev_lock so we don't cause problems with
           * other threads that wish to remove a log device, such as
           * ztest_device_removal().
           */
          mutex_enter(&ztest_vdev_lock);
  
          /*
           * 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) pthread_rwlock_wrlock(&zd->zd_zilog_lock);
  
          /* zfsvfs_teardown() */
          zil_close(zd->zd_zilog);
  
          /* zfsvfs_setup() */
          VERIFY3P(zil_open(os, ztest_get_data, NULL), ==, zd->zd_zilog);
          zil_replay(os, zd, ztest_replay_vector);
  
          (void) pthread_rwlock_unlock(&zd->zd_zilog_lock);
          mutex_exit(&zd->zd_dirobj_lock);
          mutex_exit(&ztest_vdev_lock);
  }
  
  /*
   * Verify that we can't destroy an active pool, create an existing pool,
   * or create a pool with a bad vdev spec.
   */
  void
  ztest_spa_create_destroy(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          ztest_shared_opts_t *zo = &ztest_opts;
          spa_t *spa;
          nvlist_t *nvroot;
  
          if (zo->zo_mmp_test)
                  return;
  
          /*
           * Attempt to create using a bad file.
           */
          nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, NULL, 0, 0, 1);
          VERIFY3U(ENOENT, ==,
              spa_create("ztest_bad_file", nvroot, NULL, NULL, NULL));
          fnvlist_free(nvroot);
  
          /*
           * Attempt to create using a bad mirror.
           */
          nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, NULL, 0, 2, 1);
          VERIFY3U(ENOENT, ==,
              spa_create("ztest_bad_mirror", nvroot, NULL, NULL, NULL));
          fnvlist_free(nvroot);
  
          /*
           * Attempt to create an existing pool.  It shouldn't matter
           * what's in the nvroot; we should fail with EEXIST.
           */
          (void) pthread_rwlock_rdlock(&ztest_name_lock);
          nvroot = make_vdev_root("/dev/bogus", NULL, NULL, 0, 0, NULL, 0, 0, 1);
          VERIFY3U(EEXIST, ==,
              spa_create(zo->zo_pool, nvroot, NULL, NULL, NULL));
          fnvlist_free(nvroot);
  
          /*
           * We open a reference to the spa and then we try to export it
           * expecting one of the following errors:
           *
           * EBUSY
           *      Because of the reference we just opened.
           *
           * ZFS_ERR_EXPORT_IN_PROGRESS
           *      For the case that there is another ztest thread doing
           *      an export concurrently.
           */
          VERIFY0(spa_open(zo->zo_pool, &spa, FTAG));
          int error = spa_destroy(zo->zo_pool);
          if (error != EBUSY && error != ZFS_ERR_EXPORT_IN_PROGRESS) {
                  fatal(B_FALSE, "spa_destroy(%s) returned unexpected value %d",
                      spa->spa_name, error);
          }
          spa_close(spa, FTAG);
  
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  }
  
  /*
   * Start and then stop the MMP threads to ensure the startup and shutdown code
   * works properly.  Actual protection and property-related code tested via ZTS.
   */
  void
  ztest_mmp_enable_disable(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          ztest_shared_opts_t *zo = &ztest_opts;
          spa_t *spa = ztest_spa;
  
          if (zo->zo_mmp_test)
                  return;
  
          /*
           * Since enabling MMP involves setting a property, it could not be done
           * while the pool is suspended.
           */
          if (spa_suspended(spa))
                  return;
  
          spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
          mutex_enter(&spa->spa_props_lock);
  
          zfs_multihost_fail_intervals = 0;
  
          if (!spa_multihost(spa)) {
                  spa->spa_multihost = B_TRUE;
                  mmp_thread_start(spa);
          }
  
          mutex_exit(&spa->spa_props_lock);
          spa_config_exit(spa, SCL_CONFIG, FTAG);
  
          txg_wait_synced(spa_get_dsl(spa), 0);
          mmp_signal_all_threads();
          txg_wait_synced(spa_get_dsl(spa), 0);
  
          spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
          mutex_enter(&spa->spa_props_lock);
  
          if (spa_multihost(spa)) {
                  mmp_thread_stop(spa);
                  spa->spa_multihost = B_FALSE;
          }
  
          mutex_exit(&spa->spa_props_lock);
          spa_config_exit(spa, SCL_CONFIG, FTAG);
  }
  
  void
  ztest_spa_upgrade(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa;
          uint64_t initial_version = SPA_VERSION_INITIAL;
          uint64_t version, newversion;
          nvlist_t *nvroot, *props;
          char *name;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          /* dRAID added after feature flags, skip upgrade test. */
          if (strcmp(ztest_opts.zo_raid_type, VDEV_TYPE_DRAID) == 0)
                  return;
  
          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,
              NULL, ztest_opts.zo_raid_children, ztest_opts.zo_mirrors, 1);
  
          /*
           * If we're configuring a RAIDZ device then make sure that the
           * initial version is capable of supporting that feature.
           */
          switch (ztest_opts.zo_raid_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);
          VERIFY0(spa_create(name, nvroot, props, NULL, NULL));
          fnvlist_free(nvroot);
          fnvlist_free(props);
  
          VERIFY0(spa_open(name, &spa, FTAG));
          VERIFY3U(spa_version(spa), ==, version);
          newversion = ztest_random_spa_version(version + 1);
  
          if (ztest_opts.zo_verbose >= 4) {
                  (void) printf("upgrading spa version from "
                      "%"PRIu64" to %"PRIu64"\n",
                      version, 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);
  
          kmem_strfree(name);
          mutex_exit(&ztest_vdev_lock);
  }
  
  static void
  ztest_spa_checkpoint(spa_t *spa)
  {
          ASSERT(MUTEX_HELD(&ztest_checkpoint_lock));
  
          int error = spa_checkpoint(spa->spa_name);
  
          switch (error) {
          case 0:
          case ZFS_ERR_DEVRM_IN_PROGRESS:
          case ZFS_ERR_DISCARDING_CHECKPOINT:
          case ZFS_ERR_CHECKPOINT_EXISTS:
                  break;
          case ENOSPC:
                  ztest_record_enospc(FTAG);
                  break;
          default:
                  fatal(B_FALSE, "spa_checkpoint(%s) = %d", spa->spa_name, error);
          }
  }
  
  static void
  ztest_spa_discard_checkpoint(spa_t *spa)
  {
          ASSERT(MUTEX_HELD(&ztest_checkpoint_lock));
  
          int error = spa_checkpoint_discard(spa->spa_name);
  
          switch (error) {
          case 0:
          case ZFS_ERR_DISCARDING_CHECKPOINT:
          case ZFS_ERR_NO_CHECKPOINT:
                  break;
          default:
                  fatal(B_FALSE, "spa_discard_checkpoint(%s) = %d",
                      spa->spa_name, error);
          }
  
  }
  
  void
  ztest_spa_checkpoint_create_discard(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
  
          mutex_enter(&ztest_checkpoint_lock);
          if (ztest_random(2) == 0) {
                  ztest_spa_checkpoint(spa);
          } else {
                  ztest_spa_discard_checkpoint(spa);
          }
          mutex_exit(&ztest_checkpoint_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);
  }
  
  static int
  spa_num_top_vdevs(spa_t *spa)
  {
          vdev_t *rvd = spa->spa_root_vdev;
          ASSERT3U(spa_config_held(spa, SCL_VDEV, RW_READER), ==, SCL_VDEV);
          return (rvd->vdev_children);
  }
  
  /*
   * Verify that vdev_add() works as expected.
   */
  void
  ztest_vdev_add_remove(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          ztest_shared_t *zs = ztest_shared;
          spa_t *spa = ztest_spa;
          uint64_t leaves;
          uint64_t guid;
          nvlist_t *nvroot;
          int error;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          mutex_enter(&ztest_vdev_lock);
          leaves = MAX(zs->zs_mirrors + zs->zs_splits, 1) *
              ztest_opts.zo_raid_children;
  
          spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
  
          ztest_shared->zs_vdev_next_leaf = spa_num_top_vdevs(spa) * leaves;
  
          /*
           * If we have slogs then remove them 1/4 of the time.
           */
          if (spa_has_slogs(spa) && ztest_random(4) == 0) {
                  metaslab_group_t *mg;
  
                  /*
                   * find the first real slog in log allocation class
                   */
                  mg =  spa_log_class(spa)->mc_allocator[0].mca_rotor;
                  while (!mg->mg_vd->vdev_islog)
                          mg = mg->mg_next;
  
                  guid = mg->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.
                   */
                  pthread_rwlock_wrlock(&ztest_name_lock);
                  error = spa_vdev_remove(spa, guid, B_FALSE);
                  pthread_rwlock_unlock(&ztest_name_lock);
  
                  switch (error) {
                  case 0:
                  case EEXIST:    /* Generic zil_reset() error */
                  case EBUSY:     /* Replay required */
                  case EACCES:    /* Crypto key not loaded */
                  case ZFS_ERR_CHECKPOINT_EXISTS:
                  case ZFS_ERR_DISCARDING_CHECKPOINT:
                          break;
                  default:
                          fatal(B_FALSE, "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) ?
                      "log" : NULL, ztest_opts.zo_raid_children, zs->zs_mirrors,
                      1);
  
                  error = spa_vdev_add(spa, nvroot);
                  fnvlist_free(nvroot);
  
                  switch (error) {
                  case 0:
                          break;
                  case ENOSPC:
                          ztest_record_enospc("spa_vdev_add");
                          break;
                  default:
                          fatal(B_FALSE, "spa_vdev_add() = %d", error);
                  }
          }
  
          mutex_exit(&ztest_vdev_lock);
  }
  
  void
  ztest_vdev_class_add(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          ztest_shared_t *zs = ztest_shared;
          spa_t *spa = ztest_spa;
          uint64_t leaves;
          nvlist_t *nvroot;
          const char *class = (ztest_random(2) == 0) ?
              VDEV_ALLOC_BIAS_SPECIAL : VDEV_ALLOC_BIAS_DEDUP;
          int error;
  
          /*
           * By default add a special vdev 50% of the time
           */
          if ((ztest_opts.zo_special_vdevs == ZTEST_VDEV_CLASS_OFF) ||
              (ztest_opts.zo_special_vdevs == ZTEST_VDEV_CLASS_RND &&
              ztest_random(2) == 0)) {
                  return;
          }
  
          mutex_enter(&ztest_vdev_lock);
  
          /* Only test with mirrors */
          if (zs->zs_mirrors < 2) {
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          /* requires feature@allocation_classes */
          if (!spa_feature_is_enabled(spa, SPA_FEATURE_ALLOCATION_CLASSES)) {
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          leaves = MAX(zs->zs_mirrors + zs->zs_splits, 1) *
              ztest_opts.zo_raid_children;
  
          spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
          ztest_shared->zs_vdev_next_leaf = spa_num_top_vdevs(spa) * leaves;
          spa_config_exit(spa, SCL_VDEV, FTAG);
  
          nvroot = make_vdev_root(NULL, NULL, NULL, ztest_opts.zo_vdev_size, 0,
              class, ztest_opts.zo_raid_children, zs->zs_mirrors, 1);
  
          error = spa_vdev_add(spa, nvroot);
          fnvlist_free(nvroot);
  
          if (error == ENOSPC)
                  ztest_record_enospc("spa_vdev_add");
          else if (error != 0)
                  fatal(B_FALSE, "spa_vdev_add() = %d", error);
  
          /*
           * 50% of the time allow small blocks in the special class
           */
          if (error == 0 &&
              spa_special_class(spa)->mc_groups == 1 && ztest_random(2) == 0) {
                  if (ztest_opts.zo_verbose >= 3)
                          (void) printf("Enabling special VDEV small blocks\n");
                  error = ztest_dsl_prop_set_uint64(zd->zd_name,
                      ZFS_PROP_SPECIAL_SMALL_BLOCKS, 32768, B_FALSE);
                  ASSERT(error == 0 || error == ENOSPC);
          }
  
          mutex_exit(&ztest_vdev_lock);
  
          if (ztest_opts.zo_verbose >= 3) {
                  metaslab_class_t *mc;
  
                  if (strcmp(class, VDEV_ALLOC_BIAS_SPECIAL) == 0)
                          mc = spa_special_class(spa);
                  else
                          mc = spa_dedup_class(spa);
                  (void) printf("Added a %s mirrored vdev (of %d)\n",
                      class, (int)mc->mc_groups);
          }
  }
  
  /*
   * Verify that adding/removing aux devices (l2arc, hot spare) works as expected.
   */
  void
  ztest_vdev_aux_add_remove(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          ztest_shared_t *zs = ztest_shared;
          spa_t *spa = ztest_spa;
          vdev_t *rvd = spa->spa_root_vdev;
          spa_aux_vdev_t *sav;
          const char *aux;
          char *path;
          uint64_t guid = 0;
          int error, ignore_err = 0;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          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.
                   */
                  vdev_t *svd = sav->sav_vdevs[ztest_random(sav->sav_count)];
  
                  /* dRAID spares cannot be removed; try anyways to see ENOTSUP */
                  if (strstr(svd->vdev_path, VDEV_TYPE_DRAID) != NULL)
                          ignore_err = ENOTSUP;
  
                  guid = svd->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, NULL, 0, 0, 1);
                  error = spa_vdev_add(spa, nvroot);
  
                  switch (error) {
                  case 0:
                          break;
                  default:
                          fatal(B_FALSE, "spa_vdev_add(%p) = %d", nvroot, error);
                  }
                  fnvlist_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);
  
                  switch (error) {
                  case 0:
                  case EBUSY:
                  case ZFS_ERR_CHECKPOINT_EXISTS:
                  case ZFS_ERR_DISCARDING_CHECKPOINT:
                          break;
                  default:
                          if (error != ignore_err)
                                  fatal(B_FALSE,
                                      "spa_vdev_remove(%"PRIu64") = %d",
                                      guid, error);
                  }
          }
  
          mutex_exit(&ztest_vdev_lock);
  
          umem_free(path, MAXPATHLEN);
  }
  
  /*
   * split a pool if it has mirror tlvdevs
   */
  void
  ztest_split_pool(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) 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;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          mutex_enter(&ztest_vdev_lock);
  
          /* ensure we have a usable config; mirrors of raidz aren't supported */
          if (zs->zs_mirrors < 3 || ztest_opts.zo_raid_children > 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);
          tree = fnvlist_lookup_nvlist(spa->spa_config, ZPOOL_CONFIG_VDEV_TREE);
          mutex_exit(&spa->spa_props_lock);
  
          VERIFY0(nvlist_lookup_nvlist_array(tree, ZPOOL_CONFIG_CHILDREN,
              &child, &children));
  
          schild = umem_alloc(rvd->vdev_children * sizeof (nvlist_t *),
              UMEM_NOFAIL);
          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) {
                          schild[schildren] = fnvlist_alloc();
                          fnvlist_add_string(schild[schildren],
                              ZPOOL_CONFIG_TYPE, VDEV_TYPE_HOLE);
                          fnvlist_add_uint64(schild[schildren],
                              ZPOOL_CONFIG_IS_HOLE, 1);
                          if (lastlogid == 0)
                                  lastlogid = schildren;
                          ++schildren;
                          continue;
                  }
                  lastlogid = 0;
                  VERIFY0(nvlist_lookup_nvlist_array(child[c],
                      ZPOOL_CONFIG_CHILDREN, &mchild, &mchildren));
                  schild[schildren++] = fnvlist_dup(mchild[0]);
          }
  
          /* OK, create a config that can be used to split */
          split = fnvlist_alloc();
          fnvlist_add_string(split, ZPOOL_CONFIG_TYPE, VDEV_TYPE_ROOT);
          fnvlist_add_nvlist_array(split, ZPOOL_CONFIG_CHILDREN,
              (const nvlist_t **)schild, lastlogid != 0 ? lastlogid : schildren);
  
          config = fnvlist_alloc();
          fnvlist_add_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, split);
  
          for (c = 0; c < schildren; c++)
                  fnvlist_free(schild[c]);
          umem_free(schild, rvd->vdev_children * sizeof (nvlist_t *));
          fnvlist_free(split);
  
          spa_config_exit(spa, SCL_VDEV, FTAG);
  
          (void) pthread_rwlock_wrlock(&ztest_name_lock);
          error = spa_vdev_split_mirror(spa, "splitp", config, NULL, B_FALSE);
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  
          fnvlist_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.
   */
  void
  ztest_vdev_attach_detach(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) 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 newvd_is_dspare = B_FALSE;
          int oldvd_is_log;
          int oldvd_is_special;
          int error, expected_error;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          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_raid_children;
  
          spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
  
          /*
           * If a vdev is in the process of being removed, its removal may
           * finish while we are in progress, leading to an unexpected error
           * value.  Don't bother trying to attach while we are in the middle
           * of removal.
           */
          if (ztest_device_removal_active) {
                  spa_config_exit(spa, SCL_ALL, FTAG);
                  goto out;
          }
  
          /*
           * 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];
  
          /* pick a child from the mirror */
          if (zs->zs_mirrors >= 1) {
                  ASSERT3P(oldvd->vdev_ops, ==, &vdev_mirror_ops);
                  ASSERT3U(oldvd->vdev_children, >=, zs->zs_mirrors);
                  oldvd = oldvd->vdev_child[leaf / ztest_opts.zo_raid_children];
          }
  
          /* pick a child out of the raidz group */
          if (ztest_opts.zo_raid_children > 1) {
                  if (strcmp(oldvd->vdev_ops->vdev_op_type, "raidz") == 0)
                          ASSERT3P(oldvd->vdev_ops, ==, &vdev_raidz_ops);
                  else
                          ASSERT3P(oldvd->vdev_ops, ==, &vdev_draid_ops);
                  ASSERT3U(oldvd->vdev_children, ==, ztest_opts.zo_raid_children);
                  oldvd = oldvd->vdev_child[leaf % ztest_opts.zo_raid_children];
          }
  
          /*
           * 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;
                  ASSERT3U(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;
          oldvd_is_special =
              oldvd->vdev_top->vdev_alloc_bias == VDEV_BIAS_SPECIAL ||
              oldvd->vdev_top->vdev_alloc_bias == VDEV_BIAS_DEDUP;
          (void) strlcpy(oldpath, oldvd->vdev_path, MAXPATHLEN);
          pvd = oldvd->vdev_parent;
          pguid = pvd->vdev_guid;
  
          /*
           * If oldvd has siblings, then half of the time, detach it.  Prior
           * to the detach the pool is scrubbed in order to prevent creating
           * unrepairable blocks as a result of the data corruption injection.
           */
          if (oldvd_has_siblings && ztest_random(2) == 0) {
                  spa_config_exit(spa, SCL_ALL, FTAG);
  
                  error = ztest_scrub_impl(spa);
                  if (error)
                          goto out;
  
                  error = spa_vdev_detach(spa, oldguid, pguid, B_FALSE);
                  if (error != 0 && error != ENODEV && error != EBUSY &&
                      error != ENOTSUP && error != ZFS_ERR_CHECKPOINT_EXISTS &&
                      error != ZFS_ERR_DISCARDING_CHECKPOINT)
                          fatal(B_FALSE, "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;
  
                  if (newvd->vdev_ops == &vdev_draid_spare_ops)
                          newvd_is_dspare = B_TRUE;
  
                  (void) strlcpy(newpath, newvd->vdev_path, MAXPATHLEN);
          } 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) {
                  /*
                   * Reopen to ensure the vdev's asize field isn't stale.
                   */
                  vdev_reopen(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 newvd is a distributed spare and it's being attached to a
           * dRAID which is not its parent it should fail with EINVAL.
           */
          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 || oldvd_is_special))
                  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 (!newvd_is_dspare && newsize < oldsize)
                  expected_error = EOVERFLOW;
          else if (ashift > oldvd->vdev_top->vdev_ashift)
                  expected_error = EDOM;
          else if (newvd_is_dspare && pvd != vdev_draid_spare_get_parent(newvd))
                  expected_error = ENOTSUP;
          else
                  expected_error = 0;
  
          spa_config_exit(spa, SCL_ALL, FTAG);
  
          /*
           * Build the nvlist describing newpath.
           */
          root = make_vdev_root(newpath, NULL, NULL, newvd == NULL ? newsize : 0,
              ashift, NULL, 0, 0, 1);
  
          /*
           * When supported select either a healing or sequential resilver.
           */
          boolean_t rebuilding = B_FALSE;
          if (pvd->vdev_ops == &vdev_mirror_ops ||
              pvd->vdev_ops ==  &vdev_root_ops) {
                  rebuilding = !!ztest_random(2);
          }
  
          error = spa_vdev_attach(spa, oldguid, root, replacing, rebuilding);
  
          fnvlist_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;
  
          if (error == ZFS_ERR_CHECKPOINT_EXISTS ||
              error == ZFS_ERR_DISCARDING_CHECKPOINT ||
              error == ZFS_ERR_RESILVER_IN_PROGRESS ||
              error == ZFS_ERR_REBUILD_IN_PROGRESS)
                  expected_error = error;
  
          if (error != expected_error && expected_error != EBUSY) {
                  fatal(B_FALSE, "attach (%s %"PRIu64", %s %"PRIu64", %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);
  }
  
  void
  ztest_device_removal(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
          vdev_t *vd;
          uint64_t guid;
          int error;
  
          mutex_enter(&ztest_vdev_lock);
  
          if (ztest_device_removal_active) {
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          /*
           * Remove a random top-level vdev and wait for removal to finish.
           */
          spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
          vd = vdev_lookup_top(spa, ztest_random_vdev_top(spa, B_FALSE));
          guid = vd->vdev_guid;
          spa_config_exit(spa, SCL_VDEV, FTAG);
  
          error = spa_vdev_remove(spa, guid, B_FALSE);
          if (error == 0) {
                  ztest_device_removal_active = B_TRUE;
                  mutex_exit(&ztest_vdev_lock);
  
                  /*
                   * spa->spa_vdev_removal is created in a sync task that
                   * is initiated via dsl_sync_task_nowait(). Since the
                   * task may not run before spa_vdev_remove() returns, we
                   * must wait at least 1 txg to ensure that the removal
                   * struct has been created.
                   */
                  txg_wait_synced(spa_get_dsl(spa), 0);
  
                  while (spa->spa_removing_phys.sr_state == DSS_SCANNING)
                          txg_wait_synced(spa_get_dsl(spa), 0);
          } else {
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          /*
           * The pool needs to be scrubbed after completing device removal.
           * Failure to do so may result in checksum errors due to the
           * strategy employed by ztest_fault_inject() when selecting which
           * offset are redundant and can be damaged.
           */
          error = spa_scan(spa, POOL_SCAN_SCRUB);
          if (error == 0) {
                  while (dsl_scan_scrubbing(spa_get_dsl(spa)))
                          txg_wait_synced(spa_get_dsl(spa), 0);
          }
  
          mutex_enter(&ztest_vdev_lock);
          ztest_device_removal_active = B_FALSE;
          mutex_exit(&ztest_vdev_lock);
  }
  
  /*
   * Callback function which expands the physical size of the vdev.
   */
  static vdev_t *
  grow_vdev(vdev_t *vd, void *arg)
  {
          spa_t *spa __maybe_unused = vd->vdev_spa;
          size_t *newsize = arg;
          size_t fsize;
          int fd;
  
          ASSERT3S(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);
          VERIFY0(ftruncate(fd, *newsize));
  
          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().
   */
  static vdev_t *
  online_vdev(vdev_t *vd, void *arg)
  {
          (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;
  
          ASSERT3S(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 %u, "
                              "error %d\n", 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 %"PRIu64", state %"PRIu64", "
                              "expected gen %"PRIu64", got gen %"PRIu64"\n",
                              guid,
                              tvd->vdev_state,
                              generation,
                              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.
   */
  static 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.
   */
  void
  ztest_vdev_LUN_growth(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) 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_checkpoint_lock);
          mutex_enter(&ztest_vdev_lock);
          spa_config_enter(spa, SCL_STATE, spa, RW_READER);
  
          /*
           * If there is a vdev removal in progress, it could complete while
           * we are running, in which case we would not be able to verify
           * that the metaslab_class space increased (because it decreases
           * when the device removal completes).
           */
          if (ztest_device_removal_active) {
                  spa_config_exit(spa, SCL_STATE, spa);
                  mutex_exit(&ztest_vdev_lock);
                  mutex_exit(&ztest_checkpoint_lock);
                  return;
          }
  
          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);
                  mutex_exit(&ztest_checkpoint_lock);
                  return;
          }
          ASSERT3U(psize, >, 0);
          newsize = psize + MAX(psize / 8, SPA_MAXBLOCKSIZE);
          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);
                  mutex_exit(&ztest_checkpoint_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);
                  mutex_exit(&ztest_checkpoint_lock);
                  return;
          }
  
          /*
           * Make sure we were able to grow the vdev.
           */
          if (new_ms_count <= old_ms_count) {
                  fatal(B_FALSE,
                      "LUN expansion failed: ms_count %"PRIu64" < %"PRIu64"\n",
                      old_ms_count, new_ms_count);
          }
  
          /*
           * Make sure we were able to grow the pool.
           */
          if (new_class_space <= old_class_space) {
                  fatal(B_FALSE,
                      "LUN expansion failed: class_space %"PRIu64" < %"PRIu64"\n",
                      old_class_space, new_class_space);
          }
  
          if (ztest_opts.zo_verbose >= 5) {
                  char oldnumbuf[NN_NUMBUF_SZ], newnumbuf[NN_NUMBUF_SZ];
  
                  nicenum(old_class_space, oldnumbuf, sizeof (oldnumbuf));
                  nicenum(new_class_space, newnumbuf, sizeof (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);
          mutex_exit(&ztest_checkpoint_lock);
  }
  
  /*
   * Verify that dmu_objset_{create,destroy,open,close} work as expected.
   */
  static void
  ztest_objset_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx)
  {
          (void) arg, (void) cr;
  
          /*
           * Create the objects common to all ztest datasets.
           */
          VERIFY0(zap_create_claim(os, ZTEST_DIROBJ,
              DMU_OT_ZAP_OTHER, DMU_OT_NONE, 0, tx));
  }
  
  static int
  ztest_dataset_create(char *dsname)
  {
          int err;
          uint64_t rand;
          dsl_crypto_params_t *dcp = NULL;
  
          /*
           * 50% of the time, we create encrypted datasets
           * using a random cipher suite and a hard-coded
           * wrapping key.
           */
          rand = ztest_random(2);
          if (rand != 0) {
                  nvlist_t *crypto_args = fnvlist_alloc();
                  nvlist_t *props = fnvlist_alloc();
  
                  /* slight bias towards the default cipher suite */
                  rand = ztest_random(ZIO_CRYPT_FUNCTIONS);
                  if (rand < ZIO_CRYPT_AES_128_CCM)
                          rand = ZIO_CRYPT_ON;
  
                  fnvlist_add_uint64(props,
                      zfs_prop_to_name(ZFS_PROP_ENCRYPTION), rand);
                  fnvlist_add_uint8_array(crypto_args, "wkeydata",
                      (uint8_t *)ztest_wkeydata, WRAPPING_KEY_LEN);
  
                  /*
                   * These parameters aren't really used by the kernel. They
                   * are simply stored so that userspace knows how to load
                   * the wrapping key.
                   */
                  fnvlist_add_uint64(props,
                      zfs_prop_to_name(ZFS_PROP_KEYFORMAT), ZFS_KEYFORMAT_RAW);
                  fnvlist_add_string(props,
                      zfs_prop_to_name(ZFS_PROP_KEYLOCATION), "prompt");
                  fnvlist_add_uint64(props,
                      zfs_prop_to_name(ZFS_PROP_PBKDF2_SALT), 0ULL);
                  fnvlist_add_uint64(props,
                      zfs_prop_to_name(ZFS_PROP_PBKDF2_ITERS), 0ULL);
  
                  VERIFY0(dsl_crypto_params_create_nvlist(DCP_CMD_NONE, props,
                      crypto_args, &dcp));
  
                  /*
                   * Cycle through all available encryption implementations
                   * to verify interoperability.
                   */
                  VERIFY0(gcm_impl_set("cycle"));
                  VERIFY0(aes_impl_set("cycle"));
  
                  fnvlist_free(crypto_args);
                  fnvlist_free(props);
          }
  
          err = dmu_objset_create(dsname, DMU_OST_OTHER, 0, dcp,
              ztest_objset_create_cb, NULL);
          dsl_crypto_params_free(dcp, !!err);
  
          rand = ztest_random(100);
          if (err || rand < 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));
  }
  
  static int
  ztest_objset_destroy_cb(const char *name, void *arg)
  {
          (void) arg;
          objset_t *os;
          dmu_object_info_t doi;
          int error;
  
          /*
           * Verify that the dataset contains a directory object.
           */
          VERIFY0(ztest_dmu_objset_own(name, DMU_OST_OTHER, B_TRUE,
              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, B_TRUE, FTAG);
  
          /*
           * Destroy the dataset.
           */
          if (strchr(name, '@') != NULL) {
                  error = dsl_destroy_snapshot(name, B_TRUE);
                  if (error != ECHRNG) {
                          /*
                           * The program was executed, but encountered a runtime
                           * error, such as insufficient slop, or a hold on the
                           * dataset.
                           */
                          ASSERT0(error);
                  }
          } else {
                  error = dsl_destroy_head(name);
                  if (error == ENOSPC) {
                          /* There could be checkpoint or insufficient slop */
                          ztest_record_enospc(FTAG);
                  } else if (error != EBUSY) {
                          /* There could be a hold on this dataset */
                          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), "%"PRIu64"", id);
  
          error = dmu_objset_snapshot_one(osname, snapname);
          if (error == ENOSPC) {
                  ztest_record_enospc(FTAG);
                  return (B_FALSE);
          }
          if (error != 0 && error != EEXIST && error != ECHRNG) {
                  fatal(B_FALSE, "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@%"PRIu64"",
              osname, id);
  
          error = dsl_destroy_snapshot(snapname, B_FALSE);
          if (error != 0 && error != ENOENT && error != ECHRNG)
                  fatal(B_FALSE, "ztest_snapshot_destroy(%s) = %d",
                      snapname, error);
          return (B_TRUE);
  }
  
  void
  ztest_dmu_objset_create_destroy(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd;
          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) pthread_rwlock_rdlock(&ztest_name_lock);
  
          (void) snprintf(name, sizeof (name), "%s/temp_%"PRIu64"",
              ztest_opts.zo_pool, 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 &&
              ztest_dmu_objset_own(name, DMU_OST_OTHER, B_FALSE,
              B_TRUE, FTAG, &os) == 0) {
                  ztest_zd_init(zdtmp, NULL, os);
                  zil_replay(os, zdtmp, ztest_replay_vector);
                  ztest_zd_fini(zdtmp);
                  dmu_objset_disown(os, B_TRUE, 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.
           * It may still be present if the destroy above fails with ENOSPC.
           */
          error = ztest_dmu_objset_own(name, DMU_OST_OTHER, B_TRUE, B_TRUE,
              FTAG, &os);
          if (error == 0) {
                  dmu_objset_disown(os, B_TRUE, FTAG);
                  ztest_record_enospc(FTAG);
                  goto out;
          }
          VERIFY3U(ENOENT, ==, error);
  
          /*
           * 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(B_FALSE, "dmu_objset_create(%s) = %d", name, error);
          }
  
          VERIFY0(ztest_dmu_objset_own(name, DMU_OST_OTHER, B_FALSE, B_TRUE,
              FTAG, &os));
  
          ztest_zd_init(zdtmp, NULL, os);
  
          /*
           * Open the intent log for it.
           */
          zilog = zil_open(os, ztest_get_data, NULL);
  
          /*
           * 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, NULL));
  
          /*
           * Verify that we can hold an objset that is also owned.
           */
          VERIFY0(dmu_objset_hold(name, FTAG, &os2));
          dmu_objset_rele(os2, FTAG);
  
          /*
           * Verify that we cannot own an objset that is already owned.
           */
          VERIFY3U(EBUSY, ==, ztest_dmu_objset_own(name, DMU_OST_OTHER,
              B_FALSE, B_TRUE, FTAG, &os2));
  
          zil_close(zilog);
          dmu_objset_disown(os, B_TRUE, FTAG);
          ztest_zd_fini(zdtmp);
  out:
          (void) pthread_rwlock_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) pthread_rwlock_rdlock(&ztest_name_lock);
          (void) ztest_snapshot_destroy(zd->zd_name, id);
          (void) ztest_snapshot_create(zd->zd_name, id);
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  }
  
  /*
   * Cleanup non-standard snapshots and clones.
   */
  static 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_%"PRIu64"",
              osname, id);
          (void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN, "%s/c1_%"PRIu64"",
              osname, id);
          (void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN, "%s@s2_%"PRIu64"",
              clone1name, id);
          (void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN, "%s/c2_%"PRIu64"",
              osname, id);
          (void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN, "%s@s3_%"PRIu64"",
              clone1name, id);
  
          error = dsl_destroy_head(clone2name);
          if (error && error != ENOENT)
                  fatal(B_FALSE, "dsl_destroy_head(%s) = %d", clone2name, error);
          error = dsl_destroy_snapshot(snap3name, B_FALSE);
          if (error && error != ENOENT)
                  fatal(B_FALSE, "dsl_destroy_snapshot(%s) = %d",
                      snap3name, error);
          error = dsl_destroy_snapshot(snap2name, B_FALSE);
          if (error && error != ENOENT)
                  fatal(B_FALSE, "dsl_destroy_snapshot(%s) = %d",
                      snap2name, error);
          error = dsl_destroy_head(clone1name);
          if (error && error != ENOENT)
                  fatal(B_FALSE, "dsl_destroy_head(%s) = %d", clone1name, error);
          error = dsl_destroy_snapshot(snap1name, B_FALSE);
          if (error && error != ENOENT)
                  fatal(B_FALSE, "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) pthread_rwlock_rdlock(&ztest_name_lock);
  
          ztest_dsl_dataset_cleanup(osname, id);
  
          (void) snprintf(snap1name, ZFS_MAX_DATASET_NAME_LEN, "%s@s1_%"PRIu64"",
              osname, id);
          (void) snprintf(clone1name, ZFS_MAX_DATASET_NAME_LEN, "%s/c1_%"PRIu64"",
              osname, id);
          (void) snprintf(snap2name, ZFS_MAX_DATASET_NAME_LEN, "%s@s2_%"PRIu64"",
              clone1name, id);
          (void) snprintf(clone2name, ZFS_MAX_DATASET_NAME_LEN, "%s/c2_%"PRIu64"",
              osname, id);
          (void) snprintf(snap3name, ZFS_MAX_DATASET_NAME_LEN, "%s@s3_%"PRIu64"",
              clone1name, id);
  
          error = dmu_objset_snapshot_one(osname, strchr(snap1name, '@') + 1);
          if (error && error != EEXIST) {
                  if (error == ENOSPC) {
                          ztest_record_enospc(FTAG);
                          goto out;
                  }
                  fatal(B_FALSE, "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(B_FALSE, "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(B_FALSE, "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(B_FALSE, "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(B_FALSE, "dmu_objset_create(%s) = %d", clone2name, error);
          }
  
          error = ztest_dmu_objset_own(snap2name, DMU_OST_ANY, B_TRUE, B_TRUE,
              FTAG, &os);
          if (error)
                  fatal(B_FALSE, "dmu_objset_own(%s) = %d", snap2name, error);
          error = dsl_dataset_promote(clone2name, NULL);
          if (error == ENOSPC) {
                  dmu_objset_disown(os, B_TRUE, FTAG);
                  ztest_record_enospc(FTAG);
                  goto out;
          }
          if (error != EBUSY)
                  fatal(B_FALSE, "dsl_dataset_promote(%s), %d, not EBUSY",
                      clone2name, error);
          dmu_objset_disown(os, B_TRUE, FTAG);
  
  out:
          ztest_dsl_dataset_cleanup(osname, id);
  
          (void) pthread_rwlock_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);
  }
  
  /*
   * Rewind the global allocator to verify object allocation backfilling.
   */
  void
  ztest_dmu_object_next_chunk(ztest_ds_t *zd, uint64_t id)
  {
          (void) id;
          objset_t *os = zd->zd_os;
          uint_t dnodes_per_chunk = 1 << dmu_object_alloc_chunk_shift;
          uint64_t object;
  
          /*
           * Rewind the global allocator randomly back to a lower object number
           * to force backfilling and reclamation of recently freed dnodes.
           */
          mutex_enter(&os->os_obj_lock);
          object = ztest_random(os->os_obj_next_chunk);
          os->os_obj_next_chunk = P2ALIGN(object, dnodes_per_chunk);
          mutex_exit(&os->os_obj_lock);
  }
  
  #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 freeit, error;
          uint64_t i, 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;
          ASSERT3U(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;
  
                  ASSERT3U((uintptr_t)bigH - (uintptr_t)bigbuf, <, bigsize);
                  ASSERT3U((uintptr_t)bigT - (uintptr_t)bigbuf, <, bigsize);
  
                  if (pack->bw_txg > txg)
                          fatal(B_FALSE,
                              "future leak: got %"PRIx64", open txg is %"PRIx64"",
                              pack->bw_txg, txg);
  
                  if (pack->bw_data != 0 && pack->bw_index != n + i)
                          fatal(B_FALSE, "wrong index: "
                              "got %"PRIx64", wanted %"PRIx64"+%"PRIx64"",
                              pack->bw_index, n, i);
  
                  if (memcmp(pack, bigH, sizeof (bufwad_t)) != 0)
                          fatal(B_FALSE, "pack/bigH mismatch in %p/%p",
                              pack, bigH);
  
                  if (memcmp(pack, bigT, sizeof (bufwad_t)) != 0)
                          fatal(B_FALSE, "pack/bigT mismatch in %p/%p",
                              pack, bigT);
  
                  if (freeit) {
                          memset(pack, 0, 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 %"PRIx64" size %"PRIx64""
                              " txg %"PRIx64"\n",
                              bigoff, bigsize, txg);
                  }
                  VERIFY0(dmu_free_range(os, bigobj, bigoff, bigsize, tx));
          } else {
                  if (ztest_opts.zo_verbose >= 7) {
                          (void) printf("writing offset %"PRIx64" size %"PRIx64""
                              " txg %"PRIx64"\n",
                              bigoff, bigsize, 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);
  
                  VERIFY0(dmu_read(os, packobj, packoff,
                      packsize, packcheck, DMU_READ_PREFETCH));
                  VERIFY0(dmu_read(os, bigobj, bigoff,
                      bigsize, bigcheck, DMU_READ_PREFETCH));
  
                  ASSERT0(memcmp(packbuf, packcheck, packsize));
                  ASSERT0(memcmp(bigbuf, bigcheck, bigsize));
  
                  umem_free(packcheck, packsize);
                  umem_free(bigcheck, bigsize);
          }
  
          umem_free(packbuf, packsize);
          umem_free(bigbuf, bigsize);
          umem_free(od, size);
  }
  
  static 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;
  
                  ASSERT3U((uintptr_t)bigH - (uintptr_t)bigbuf, <, bigsize);
                  ASSERT3U((uintptr_t)bigT - (uintptr_t)bigbuf, <, bigsize);
  
                  if (pack->bw_txg > txg)
                          fatal(B_FALSE,
                              "future leak: got %"PRIx64", open txg is %"PRIx64"",
                              pack->bw_txg, txg);
  
                  if (pack->bw_data != 0 && pack->bw_index != n + i)
                          fatal(B_FALSE, "wrong index: "
                              "got %"PRIx64", wanted %"PRIx64"+%"PRIx64"",
                              pack->bw_index, n, i);
  
                  if (memcmp(pack, bigH, sizeof (bufwad_t)) != 0)
                          fatal(B_FALSE, "pack/bigH mismatch in %p/%p",
                              pack, bigH);
  
                  if (memcmp(pack, bigT, sizeof (bufwad_t)) != 0)
                          fatal(B_FALSE, "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_by_dbuf() 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;
          ASSERT3U(chunksize, ==, od[1].od_gen);
  
          VERIFY0(dmu_object_info(os, bigobj, &doi));
          VERIFY(ISP2(doi.doi_data_block_size));
          VERIFY3U(chunksize, ==, doi.doi_data_block_size);
          VERIFY3U(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);
  
          VERIFY0(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_by_dbuf() 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_by_dbuf() for the case when there are
                   * 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 %"PRIx64" size %"PRIx64""
                              " txg %"PRIx64"\n",
                              bigoff, bigsize, txg);
                  }
                  for (off = bigoff, j = 0; j < s; j++, off += chunksize) {
                          dmu_buf_t *dbt;
                          if (i != 5 || chunksize < (SPA_MINBLOCKSIZE * 2)) {
                                  memcpy(bigbuf_arcbufs[j]->b_data,
                                      (caddr_t)bigbuf + (off - bigoff),
                                      chunksize);
                          } else {
                                  memcpy(bigbuf_arcbufs[2 * j]->b_data,
                                      (caddr_t)bigbuf + (off - bigoff),
                                      chunksize / 2);
                                  memcpy(bigbuf_arcbufs[2 * j + 1]->b_data,
                                      (caddr_t)bigbuf + (off - bigoff) +
                                      chunksize / 2,
                                      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)) {
                                  VERIFY0(dmu_assign_arcbuf_by_dbuf(bonus_db,
                                      off, bigbuf_arcbufs[j], tx));
                          } else {
                                  VERIFY0(dmu_assign_arcbuf_by_dbuf(bonus_db,
                                      off, bigbuf_arcbufs[2 * j], tx));
                                  VERIFY0(dmu_assign_arcbuf_by_dbuf(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);
  
                          VERIFY0(dmu_read(os, packobj, packoff,
                              packsize, packcheck, DMU_READ_PREFETCH));
                          VERIFY0(dmu_read(os, bigobj, bigoff,
                              bigsize, bigcheck, DMU_READ_PREFETCH));
  
                          ASSERT0(memcmp(packbuf, packcheck, packsize));
                          ASSERT0(memcmp(bigbuf, bigcheck, bigsize));
  
                          umem_free(packcheck, packsize);
                          umem_free(bigcheck, bigsize);
                  }
                  if (i == 2) {
                          txg_wait_open(dmu_objset_pool(os), 0, B_TRUE);
                  } 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);
  }
  
  void
  ztest_dmu_write_parallel(ztest_ds_t *zd, uint64_t id)
  {
          (void) 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;
          const char *const 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;
                  VERIFY0(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));
                  VERIFY0(
                      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++) {
                  VERIFY0(zap_remove(os, object, hc[i], tx));
          }
          dmu_tx_commit(tx);
  
          /*
           * Generate a bunch 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_%"PRIu64"", prop);
          (void) sprintf(txgname, "txg_%"PRIu64"", prop);
          memset(value, 0, 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);
  
                  VERIFY0(zap_lookup(os, object, txgname, zl_intsize,
                      zl_ints, &last_txg));
  
                  VERIFY0(zap_length(os, object, propname, &zl_intsize,
                      &zl_ints));
  
                  ASSERT3U(zl_intsize, ==, sizeof (uint64_t));
                  ASSERT3U(zl_ints, ==, ints);
  
                  VERIFY0(zap_lookup(os, object, propname, zl_intsize,
                      zl_ints, value));
  
                  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(B_FALSE, "zap future leak: old %"PRIu64" new %"PRIu64"",
                      last_txg, txg);
  
          for (i = 0; i < ints; i++)
                  value[i] = txg + object + i;
  
          VERIFY0(zap_update(os, object, txgname, sizeof (uint64_t),
              1, &txg, tx));
          VERIFY0(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_%"PRIu64"", prop);
          (void) sprintf(txgname, "txg_%"PRIu64"", 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;
          VERIFY0(zap_remove(os, object, txgname, tx));
          VERIFY0(zap_remove(os, object, propname, tx));
          dmu_tx_commit(tx);
  out:
          umem_free(od, sizeof (ztest_od_t));
  }
  
  /*
   * Test case 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, value;
  
          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 (value = 0; value < 2050; value++) {
                  char name[ZFS_MAX_DATASET_NAME_LEN];
                  dmu_tx_t *tx;
                  int error;
  
                  (void) snprintf(name, sizeof (name), "fzap-%"PRIu64"-%"PRIu64"",
                      id, 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));
  }
  
  void
  ztest_zap_parallel(ztest_ds_t *zd, uint64_t id)
  {
          (void) 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));
          ASSERT3S(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;
                  }
                  memcpy(string_value, name, namelen);
          } else {
                  tx = NULL;
                  txg = 0;
                  memset(string_value, 0, 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 &&
                              memcmp(name, data, namelen) != 0)
                                  fatal(B_FALSE, "name '%s' != val '%s' len %d",
                                      name, (char *)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:
                  VERIFY0(zap_update(os, object, name, wsize, wc, data, tx));
                  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;
  
          VERIFY3P(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(B_FALSE,
                      "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.
           */
          VERIFY0(dmu_read(os, od->od_object, 0, sizeof (uint64_t),
              &old_txg, DMU_READ_PREFETCH));
  
          if (old_txg > txg)
                  fatal(B_FALSE,
                      "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(B_FALSE,
                      "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)
  {
          (void) 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;
  
                  ztest_object_lock(zd, obj, RL_READER);
                  if (dmu_bonus_hold(os, obj, FTAG, &db) != 0) {
                          ztest_object_unlock(zd, obj);
                          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);
                  ztest_object_unlock(zd, obj);
          }
  }
  
  void
  ztest_dsl_prop_get_set(ztest_ds_t *zd, uint64_t id)
  {
          (void) id;
          zfs_prop_t proplist[] = {
                  ZFS_PROP_CHECKSUM,
                  ZFS_PROP_COMPRESSION,
                  ZFS_PROP_COPIES,
                  ZFS_PROP_DEDUP
          };
  
          (void) pthread_rwlock_rdlock(&ztest_name_lock);
  
          for (int p = 0; p < sizeof (proplist) / sizeof (proplist[0]); p++) {
                  int error = ztest_dsl_prop_set_uint64(zd->zd_name, proplist[p],
                      ztest_random_dsl_prop(proplist[p]), (int)ztest_random(2));
                  ASSERT(error == 0 || error == ENOSPC);
          }
  
          int error = ztest_dsl_prop_set_uint64(zd->zd_name, ZFS_PROP_RECORDSIZE,
              ztest_random_blocksize(), (int)ztest_random(2));
          ASSERT(error == 0 || error == ENOSPC);
  
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  }
  
  void
  ztest_spa_prop_get_set(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          nvlist_t *props = NULL;
  
          (void) pthread_rwlock_rdlock(&ztest_name_lock);
  
          (void) ztest_spa_prop_set_uint64(ZPOOL_PROP_AUTOTRIM, ztest_random(2));
  
          VERIFY0(spa_prop_get(ztest_spa, &props));
  
          if (ztest_opts.zo_verbose >= 6)
                  dump_nvlist(props, 4);
  
          fnvlist_free(props);
  
          (void) pthread_rwlock_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) pthread_rwlock_rdlock(&ztest_name_lock);
  
          dmu_objset_name(os, osname);
  
          (void) snprintf(snapname, sizeof (snapname), "sh1_%"PRIu64"", id);
          (void) snprintf(fullname, sizeof (fullname), "%s@%s", osname, snapname);
          (void) snprintf(clonename, sizeof (clonename), "%s/ch1_%"PRIu64"",
              osname, id);
          (void) snprintf(tag, sizeof (tag), "tag_%"PRIu64"", 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(B_FALSE, "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(B_FALSE, "dmu_objset_clone(%s) = %d", clonename, error);
          }
  
          error = dsl_destroy_snapshot(fullname, B_TRUE);
          if (error) {
                  fatal(B_FALSE, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
                      fullname, error);
          }
  
          error = dsl_destroy_head(clonename);
          if (error)
                  fatal(B_FALSE, "dsl_destroy_head(%s) = %d", clonename, error);
  
          error = dmu_objset_hold(fullname, FTAG, &origin);
          if (error != ENOENT)
                  fatal(B_FALSE, "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(B_FALSE, "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(B_FALSE, "dsl_dataset_user_hold(%s, %s) = %u",
                      fullname, tag, error);
          }
  
          error = dsl_destroy_snapshot(fullname, B_FALSE);
          if (error != EBUSY) {
                  fatal(B_FALSE, "dsl_destroy_snapshot(%s, B_FALSE) = %d",
                      fullname, error);
          }
  
          error = dsl_destroy_snapshot(fullname, B_TRUE);
          if (error) {
                  fatal(B_FALSE, "dsl_destroy_snapshot(%s, B_TRUE) = %d",
                      fullname, error);
          }
  
          error = user_release_one(fullname, tag);
          if (error)
                  fatal(B_FALSE, "user_release_one(%s, %s) = %d",
                      fullname, tag, error);
  
          VERIFY3U(dmu_objset_hold(fullname, FTAG, &origin), ==, ENOENT);
  
  out:
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  }
  
  /*
   * Inject random faults into the on-disk data.
   */
  void
  ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) 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);
  
          /*
           * Device removal is in progress, fault injection must be disabled
           * until it completes and the pool is scrubbed.  The fault injection
           * strategy for damaging blocks does not take in to account evacuated
           * blocks which may have already been damaged.
           */
          if (ztest_device_removal_active) {
                  mutex_exit(&ztest_vdev_lock);
                  goto out;
          }
  
          maxfaults = MAXFAULTS(zs);
          leaves = MAX(zs->zs_mirrors, 1) * ztest_opts.zo_raid_children;
          mirror_save = zs->zs_mirrors;
          mutex_exit(&ztest_vdev_lock);
  
          ASSERT3U(leaves, >=, 1);
  
          /*
           * While ztest is running the number of leaves will not change.  This
           * is critical for the fault injection logic as it determines where
           * errors can be safely injected such that they are always repairable.
           *
           * When restarting ztest a different number of leaves may be requested
           * which will shift the regions to be damaged.  This is fine as long
           * as the pool has been scrubbed prior to using the new mapping.
           * Failure to do can result in non-repairable damage being injected.
           */
          if (ztest_pool_scrubbed == B_FALSE)
                  goto out;
  
          /*
           * 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) pthread_rwlock_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 unwritable, 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;
  
                          zfs_dbgmsg("injecting fault to vdev %llu; maxfaults=%d",
                              (long long)vd0->vdev_id, (int)maxfaults);
  
                          if (vf != NULL && ztest_random(3) == 0) {
                                  (void) close(vf->vf_file->f_fd);
                                  vf->vf_file->f_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) pthread_rwlock_unlock(&ztest_name_lock);
                          goto out;
                  }
                  vd0 = sav->sav_vdevs[ztest_random(sav->sav_count)];
                  guid0 = vd0->vdev_guid;
                  (void) strlcpy(path0, vd0->vdev_path, MAXPATHLEN);
                  (void) strlcpy(pathrand, vd0->vdev_path, MAXPATHLEN);
  
                  leaf = 0;
                  leaves = 1;
                  maxfaults = INT_MAX;    /* no limit on cache devices */
          }
  
          spa_config_exit(spa, SCL_STATE, FTAG);
          (void) pthread_rwlock_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) pthread_rwlock_wrlock(&ztest_name_lock);
  
                          VERIFY3U(vdev_offline(spa, guid0, flags), !=, EBUSY);
  
                          if (islog)
                                  (void) pthread_rwlock_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).
                   *
                   * To achieve this we divide each leaf device into
                   * chunks of size (# leaves * SPA_MAXBLOCKSIZE * 4).
                   * Each chunk is further divided into error-injection
                   * ranges (can accept errors) and clear ranges (we do
                   * not inject errors in those). Each error-injection
                   * range can accept errors only for a single leaf vdev.
                   * Error-injection ranges are separated by clear ranges.
                   *
                   * For example, with 3 leaves, each chunk looks like:
                   *    0 to  32M: injection range for leaf 0
                   *  32M to  64M: clear range - no injection allowed
                   *  64M to  96M: injection range for leaf 1
                   *  96M to 128M: clear range - no injection allowed
                   * 128M to 160M: injection range for leaf 2
                   * 160M to 192M: clear range - no injection allowed
                   *
                   * Each clear range must be large enough such that a
                   * single block cannot straddle it. This way a block
                   * can't be a target in two different injection ranges
                   * (on different leaf vdevs).
                   */
                  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(B_TRUE,
                              "can't inject bad word at 0x%"PRIx64" in %s",
                              offset, pathrand);
  
                  mutex_exit(&ztest_vdev_lock);
  
                  if (ztest_opts.zo_verbose >= 7)
                          (void) printf("injected bad word into %s,"
                              " offset 0x%"PRIx64"\n", pathrand, offset);
          }
  
          (void) close(fd);
  out:
          umem_free(path0, MAXPATHLEN);
          umem_free(pathrand, MAXPATHLEN);
  }
  
  /*
   * By design ztest will never inject uncorrectable damage in to the pool.
   * Issue a scrub, wait for it to complete, and verify there is never any
   * persistent damage.
   *
   * Only after a full scrub has been completed is it safe to start injecting
   * data corruption.  See the comment in zfs_fault_inject().
   */
  static int
  ztest_scrub_impl(spa_t *spa)
  {
          int error = spa_scan(spa, POOL_SCAN_SCRUB);
          if (error)
                  return (error);
  
          while (dsl_scan_scrubbing(spa_get_dsl(spa)))
                  txg_wait_synced(spa_get_dsl(spa), 0);
  
          if (spa_approx_errlog_size(spa) > 0)
                  return (ECKSUM);
  
          ztest_pool_scrubbed = B_TRUE;
  
          return (0);
  }
  
  /*
   * Scrub the pool.
   */
  void
  ztest_scrub(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
          int error;
  
          /*
           * Scrub in progress by device removal.
           */
          if (ztest_device_removal_active)
                  return;
  
          /*
           * Start a scrub, wait a moment, then force a restart.
           */
          (void) spa_scan(spa, POOL_SCAN_SCRUB);
          (void) poll(NULL, 0, 100);
  
          error = ztest_scrub_impl(spa);
          if (error == EBUSY)
                  error = 0;
          ASSERT0(error);
  }
  
  /*
   * Change the guid for the pool.
   */
  void
  ztest_reguid(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
          uint64_t orig, load;
          int error;
  
          if (ztest_opts.zo_mmp_test)
                  return;
  
          orig = spa_guid(spa);
          load = spa_load_guid(spa);
  
          (void) pthread_rwlock_wrlock(&ztest_name_lock);
          error = spa_change_guid(spa);
          (void) pthread_rwlock_unlock(&ztest_name_lock);
  
          if (error != 0)
                  return;
  
          if (ztest_opts.zo_verbose >= 4) {
                  (void) printf("Changed guid old %"PRIu64" -> %"PRIu64"\n",
                      orig, spa_guid(spa));
          }
  
          VERIFY3U(orig, !=, spa_guid(spa));
          VERIFY3U(load, ==, spa_load_guid(spa));
  }
  
  void
  ztest_blake3(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          hrtime_t end = gethrtime() + NANOSEC;
          zio_cksum_salt_t salt;
          void *salt_ptr = &salt.zcs_bytes;
          struct abd *abd_data, *abd_meta;
          void *buf, *templ;
          int i, *ptr;
          uint32_t size;
          BLAKE3_CTX ctx;
  
          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);
          memset(salt_ptr, 'A', 32);
  
          abd_copy_from_buf_off(abd_data, buf, 0, size);
          abd_copy_from_buf_off(abd_meta, buf, 0, size);
  
          while (gethrtime() <= end) {
                  int run_count = 100;
                  zio_cksum_t zc_ref1, zc_ref2;
                  zio_cksum_t zc_res1, zc_res2;
  
                  void *ref1 = &zc_ref1;
                  void *ref2 = &zc_ref2;
                  void *res1 = &zc_res1;
                  void *res2 = &zc_res2;
  
                  /* BLAKE3_KEY_LEN = 32 */
                  VERIFY0(blake3_impl_setname("generic"));
                  templ = abd_checksum_blake3_tmpl_init(&salt);
                  Blake3_InitKeyed(&ctx, salt_ptr);
                  Blake3_Update(&ctx, buf, size);
                  Blake3_Final(&ctx, ref1);
                  zc_ref2 = zc_ref1;
                  ZIO_CHECKSUM_BSWAP(&zc_ref2);
                  abd_checksum_blake3_tmpl_free(templ);
  
                  VERIFY0(blake3_impl_setname("cycle"));
                  while (run_count-- > 0) {
  
                          /* Test current implementation */
                          Blake3_InitKeyed(&ctx, salt_ptr);
                          Blake3_Update(&ctx, buf, size);
                          Blake3_Final(&ctx, res1);
                          zc_res2 = zc_res1;
                          ZIO_CHECKSUM_BSWAP(&zc_res2);
  
                          VERIFY0(memcmp(ref1, res1, 32));
                          VERIFY0(memcmp(ref2, res2, 32));
  
                          /* Test ABD - data */
                          templ = abd_checksum_blake3_tmpl_init(&salt);
                          abd_checksum_blake3_native(abd_data, size,
                              templ, &zc_res1);
                          abd_checksum_blake3_byteswap(abd_data, size,
                              templ, &zc_res2);
  
                          VERIFY0(memcmp(ref1, res1, 32));
                          VERIFY0(memcmp(ref2, res2, 32));
  
                          /* Test ABD - metadata */
                          abd_checksum_blake3_native(abd_meta, size,
                              templ, &zc_res1);
                          abd_checksum_blake3_byteswap(abd_meta, size,
                              templ, &zc_res2);
                          abd_checksum_blake3_tmpl_free(templ);
  
                          VERIFY0(memcmp(ref1, res1, 32));
                          VERIFY0(memcmp(ref2, res2, 32));
  
                  }
          }
  
          abd_free(abd_data);
          abd_free(abd_meta);
          umem_free(buf, size);
  }
  
  void
  ztest_fletcher(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) 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(memcmp(&zc, &zc_ref, sizeof (zc)));
                          VERIFY0(memcmp(&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(memcmp(&zc, &zc_ref, sizeof (zc)));
                          VERIFY0(memcmp(&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(memcmp(&zc, &zc_ref, sizeof (zc)));
                          VERIFY0(memcmp(&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) zd, (void) 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_set_global_vars(void)
  {
          for (size_t i = 0; i < ztest_opts.zo_gvars_count; i++) {
                  char *kv = ztest_opts.zo_gvars[i];
                  VERIFY3U(strlen(kv), <=, ZO_GVARS_MAX_ARGLEN);
                  VERIFY3U(strlen(kv), >, 0);
                  int err = set_global_var(kv);
                  if (ztest_opts.zo_verbose > 0) {
                          (void) printf("setting global var %s ... %s\n", kv,
                              err ? "failed" : "ok");
                  }
                  if (err != 0) {
                          (void) fprintf(stderr,
                              "failed to set global var '%s'\n", kv);
                          return (err);
                  }
          }
          return (0);
  }
  
  static char **
  ztest_global_vars_to_zdb_args(void)
  {
          char **args = calloc(2*ztest_opts.zo_gvars_count + 1, sizeof (char *));
          char **cur = args;
          if (args == NULL)
                  return (NULL);
          for (size_t i = 0; i < ztest_opts.zo_gvars_count; i++) {
                  *cur++ = (char *)"-o";
                  *cur++ = ztest_opts.zo_gvars[i];
          }
          ASSERT3P(cur, ==, &args[2*ztest_opts.zo_gvars_count]);
          *cur = NULL;
          return (args);
  }
  
  /* The end of strings is indicated by a NULL element */
  static char *
  join_strings(char **strings, const char *sep)
  {
          size_t totallen = 0;
          for (char **sp = strings; *sp != NULL; sp++) {
                  totallen += strlen(*sp);
                  totallen += strlen(sep);
          }
          if (totallen > 0) {
                  ASSERT(totallen >= strlen(sep));
                  totallen -= strlen(sep);
          }
  
          size_t buflen = totallen + 1;
          char *o = umem_alloc(buflen, UMEM_NOFAIL); /* trailing 0 byte */
          o[0] = '\0';
          for (char **sp = strings; *sp != NULL; sp++) {
                  size_t would;
                  would = strlcat(o, *sp, buflen);
                  VERIFY3U(would, <, buflen);
                  if (*(sp+1) == NULL) {
                          break;
                  }
                  would = strlcat(o, sep, buflen);
                  VERIFY3U(would, <, buflen);
          }
          ASSERT3S(strlen(o), ==, totallen);
          return (o);
  }
  
  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 and in-tree zdb path. If not successful, just
           * let popen to search through PATH.
           */
          if ((zdb_path = getenv("ZDB"))) {
                  strlcpy(bin, zdb_path, len); /* In env */
                  if (!ztest_check_path(bin)) {
                          ztest_dump_core = 0;
                          fatal(B_TRUE, "invalid ZDB '%s'", bin);
                  }
                  return;
          }
  
          VERIFY3P(realpath(getexecname(), bin), !=, NULL);
          if (strstr(bin, ".libs/ztest")) {
                  strstr(bin, ".libs/ztest")[0] = '\0'; /* In-tree */
                  strcat(bin, "zdb");
                  if (ztest_check_path(bin))
                          return;
          }
          strcpy(bin, "zdb");
  }
  
  static vdev_t *
  ztest_random_concrete_vdev_leaf(vdev_t *vd)
  {
          if (vd == NULL)
                  return (NULL);
  
          if (vd->vdev_children == 0)
                  return (vd);
  
          vdev_t *eligible[vd->vdev_children];
          int eligible_idx = 0, i;
          for (i = 0; i < vd->vdev_children; i++) {
                  vdev_t *cvd = vd->vdev_child[i];
                  if (cvd->vdev_top->vdev_removing)
                          continue;
                  if (cvd->vdev_children > 0 ||
                      (vdev_is_concrete(cvd) && !cvd->vdev_detached)) {
                          eligible[eligible_idx++] = cvd;
                  }
          }
          VERIFY3S(eligible_idx, >, 0);
  
          uint64_t child_no = ztest_random(eligible_idx);
          return (ztest_random_concrete_vdev_leaf(eligible[child_no]));
  }
  
  void
  ztest_initialize(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
          int error = 0;
  
          mutex_enter(&ztest_vdev_lock);
  
          spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
  
          /* Random leaf vdev */
          vdev_t *rand_vd = ztest_random_concrete_vdev_leaf(spa->spa_root_vdev);
          if (rand_vd == NULL) {
                  spa_config_exit(spa, SCL_VDEV, FTAG);
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          /*
           * The random vdev we've selected may change as soon as we
           * drop the spa_config_lock. We create local copies of things
           * we're interested in.
           */
          uint64_t guid = rand_vd->vdev_guid;
          char *path = strdup(rand_vd->vdev_path);
          boolean_t active = rand_vd->vdev_initialize_thread != NULL;
  
          zfs_dbgmsg("vd %px, guid %llu", rand_vd, (u_longlong_t)guid);
          spa_config_exit(spa, SCL_VDEV, FTAG);
  
          uint64_t cmd = ztest_random(POOL_INITIALIZE_FUNCS);
  
          nvlist_t *vdev_guids = fnvlist_alloc();
          nvlist_t *vdev_errlist = fnvlist_alloc();
          fnvlist_add_uint64(vdev_guids, path, guid);
          error = spa_vdev_initialize(spa, vdev_guids, cmd, vdev_errlist);
          fnvlist_free(vdev_guids);
          fnvlist_free(vdev_errlist);
  
          switch (cmd) {
          case POOL_INITIALIZE_CANCEL:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Cancel initialize %s", path);
                          if (!active)
                                  (void) printf(" failed (no initialize active)");
                          (void) printf("\n");
                  }
                  break;
          case POOL_INITIALIZE_START:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Start initialize %s", path);
                          if (active && error == 0)
                                  (void) printf(" failed (already active)");
                          else if (error != 0)
                                  (void) printf(" failed (error %d)", error);
                          (void) printf("\n");
                  }
                  break;
          case POOL_INITIALIZE_SUSPEND:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Suspend initialize %s", path);
                          if (!active)
                                  (void) printf(" failed (no initialize active)");
                          (void) printf("\n");
                  }
                  break;
          }
          free(path);
          mutex_exit(&ztest_vdev_lock);
  }
  
  void
  ztest_trim(ztest_ds_t *zd, uint64_t id)
  {
          (void) zd, (void) id;
          spa_t *spa = ztest_spa;
          int error = 0;
  
          mutex_enter(&ztest_vdev_lock);
  
          spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
  
          /* Random leaf vdev */
          vdev_t *rand_vd = ztest_random_concrete_vdev_leaf(spa->spa_root_vdev);
          if (rand_vd == NULL) {
                  spa_config_exit(spa, SCL_VDEV, FTAG);
                  mutex_exit(&ztest_vdev_lock);
                  return;
          }
  
          /*
           * The random vdev we've selected may change as soon as we
           * drop the spa_config_lock. We create local copies of things
           * we're interested in.
           */
          uint64_t guid = rand_vd->vdev_guid;
          char *path = strdup(rand_vd->vdev_path);
          boolean_t active = rand_vd->vdev_trim_thread != NULL;
  
          zfs_dbgmsg("vd %p, guid %llu", rand_vd, (u_longlong_t)guid);
          spa_config_exit(spa, SCL_VDEV, FTAG);
  
          uint64_t cmd = ztest_random(POOL_TRIM_FUNCS);
          uint64_t rate = 1 << ztest_random(30);
          boolean_t partial = (ztest_random(5) > 0);
          boolean_t secure = (ztest_random(5) > 0);
  
          nvlist_t *vdev_guids = fnvlist_alloc();
          nvlist_t *vdev_errlist = fnvlist_alloc();
          fnvlist_add_uint64(vdev_guids, path, guid);
          error = spa_vdev_trim(spa, vdev_guids, cmd, rate, partial,
              secure, vdev_errlist);
          fnvlist_free(vdev_guids);
          fnvlist_free(vdev_errlist);
  
          switch (cmd) {
          case POOL_TRIM_CANCEL:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Cancel TRIM %s", path);
                          if (!active)
                                  (void) printf(" failed (no TRIM active)");
                          (void) printf("\n");
                  }
                  break;
          case POOL_TRIM_START:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Start TRIM %s", path);
                          if (active && error == 0)
                                  (void) printf(" failed (already active)");
                          else if (error != 0)
                                  (void) printf(" failed (error %d)", error);
                          (void) printf("\n");
                  }
                  break;
          case POOL_TRIM_SUSPEND:
                  if (ztest_opts.zo_verbose >= 4) {
                          (void) printf("Suspend TRIM %s", path);
                          if (!active)
                                  (void) printf(" failed (no TRIM active)");
                          (void) printf("\n");
                  }
                  break;
          }
          free(path);
          mutex_exit(&ztest_vdev_lock);
  }
  
  /*
   * Verify pool integrity by running zdb.
   */
  static void
  ztest_run_zdb(const 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);
  
          char **set_gvars_args = ztest_global_vars_to_zdb_args();
          if (set_gvars_args == NULL) {
                  fatal(B_FALSE, "Failed to allocate memory in "
                      "ztest_global_vars_to_zdb_args(). Cannot run zdb.\n");
          }
          char *set_gvars_args_joined = join_strings(set_gvars_args, " ");
          free(set_gvars_args);
  
          size_t would = snprintf(zdb, len,
              "%s -bcc%s%s -G -d -Y -e -y %s -p %s %s",
              bin,
              ztest_opts.zo_verbose >= 3 ? "s" : "",
              ztest_opts.zo_verbose >= 4 ? "v" : "",
              set_gvars_args_joined,
              ztest_opts.zo_dir,
              pool);
          ASSERT3U(would, <, len);
  
          umem_free(set_gvars_args_joined, strlen(set_gvars_args_joined) + 1);
  
          if (ztest_opts.zo_verbose >= 5)
                  (void) printf("Executing %s\n", 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(B_FALSE, "'%s' exit code %d", zdb, WEXITSTATUS(status));
          else
                  fatal(B_FALSE, "'%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(const char *header)
  {
          spa_t *spa = NULL;
  
          if (ztest_opts.zo_verbose >= 6)
                  (void) puts(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.
           */
          VERIFY0(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.
           */
          VERIFY0(spa_export(oldname, &config, B_FALSE, B_FALSE));
  
          ztest_walk_pool_directory("pools after export");
  
          /*
           * Try to import it.
           */
          newconfig = spa_tryimport(config);
          ASSERT3P(newconfig, !=, NULL);
          fnvlist_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.
           */
          VERIFY0(spa_open(newname, &spa, FTAG));
          ASSERT3U(pool_guid, ==, spa_guid(spa));
          spa_close(spa, FTAG);
  
          fnvlist_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 __attribute__((noreturn)) 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();
  }
  
  static __attribute__((noreturn)) void
  ztest_deadman_thread(void *arg)
  {
          ztest_shared_t *zs = arg;
          spa_t *spa = ztest_spa;
          hrtime_t delay, overdue, last_run = gethrtime();
  
          delay = (zs->zs_thread_stop - zs->zs_thread_start) +
              MSEC2NSEC(zfs_deadman_synctime_ms);
  
          while (!ztest_exiting) {
                  /*
                   * Wait for the delay timer while checking occasionally
                   * if we should stop.
                   */
                  if (gethrtime() < last_run + delay) {
                          (void) poll(NULL, 0, 1000);
                          continue;
                  }
  
                  /*
                   * If the pool is suspended then fail immediately. Otherwise,
                   * check to see if the pool is making any progress. If
                   * vdev_deadman() discovers that there hasn't been any recent
                   * I/Os then it will end up aborting the tests.
                   */
                  if (spa_suspended(spa) || spa->spa_root_vdev == NULL) {
                          fatal(B_FALSE,
                              "aborting test after %llu seconds because "
                              "pool has transitioned to a suspended state.",
                              (u_longlong_t)zfs_deadman_synctime_ms / 1000);
                  }
                  vdev_deadman(spa->spa_root_vdev, FTAG);
  
                  /*
                   * If the process doesn't complete within a grace period of
                   * zfs_deadman_synctime_ms over the expected finish time,
                   * then it may be hung and is terminated.
                   */
                  overdue = zs->zs_proc_stop + MSEC2NSEC(zfs_deadman_synctime_ms);
                  if (gethrtime() > overdue) {
                          fatal(B_FALSE,
                              "aborting test after %llu seconds because "
                              "the process is overdue for termination.",
                              (gethrtime() - zs->zs_proc_start) / NANOSEC);
                  }
  
                  (void) printf("ztest has been running for %lld seconds\n",
                      (gethrtime() - zs->zs_proc_start) / NANOSEC);
  
                  last_run = gethrtime();
                  delay = MSEC2NSEC(zfs_deadman_checktime_ms);
          }
  
          thread_exit();
  }
  
  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 __attribute__((noreturn)) 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();
  }
  
  static void
  ztest_dataset_name(char *dsname, const 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.
           */
          VERIFY0(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) pthread_rwlock_rdlock(&ztest_name_lock);
  
          error = ztest_dataset_create(name);
          if (error == ENOSPC) {
                  (void) pthread_rwlock_unlock(&ztest_name_lock);
                  ztest_record_enospc(FTAG);
                  return (error);
          }
          ASSERT(error == 0 || error == EEXIST);
  
          VERIFY0(ztest_dmu_objset_own(name, DMU_OST_OTHER, B_FALSE,
              B_TRUE, zd, &os));
          (void) pthread_rwlock_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(B_FALSE, "missing log records: "
                      "claimed %"PRIu64" < committed %"PRIu64"",
                      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 %"PRIu64" blocks, "
                      "%"PRIu64" records, seq %"PRIu64"\n",
                      zd->zd_name,
                      zilog->zl_parse_blk_count,
                      zilog->zl_parse_lr_count,
                      zilog->zl_replaying_seq);
  
          zilog = zil_open(os, ztest_get_data, NULL);
  
          if (zilog->zl_replaying_seq != 0 &&
              zilog->zl_replaying_seq < committed_seq)
                  fatal(B_FALSE, "missing log records: "
                      "replayed %"PRIu64" < committed %"PRIu64"",
                      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, B_TRUE, zd);
  
          ztest_zd_fini(zd);
  }
  
  static int
  ztest_replay_zil_cb(const char *name, void *arg)
  {
          (void) arg;
          objset_t *os;
          ztest_ds_t *zdtmp;
  
          VERIFY0(ztest_dmu_objset_own(name, DMU_OST_ANY, B_TRUE,
              B_TRUE, FTAG, &os));
  
          zdtmp = umem_alloc(sizeof (ztest_ds_t), UMEM_NOFAIL);
  
          ztest_zd_init(zdtmp, NULL, os);
          zil_replay(os, zdtmp, ztest_replay_vector);
          ztest_zd_fini(zdtmp);
  
          if (dmu_objset_zil(os)->zl_parse_lr_count != 0 &&
              ztest_opts.zo_verbose >= 6) {
                  zilog_t *zilog = dmu_objset_zil(os);
  
                  (void) printf("%s replay %"PRIu64" blocks, "
                      "%"PRIu64" records, seq %"PRIu64"\n",
                      name,
                      zilog->zl_parse_blk_count,
                      zilog->zl_parse_lr_count,
                      zilog->zl_replaying_seq);
          }
  
          umem_free(zdtmp, sizeof (ztest_ds_t));
  
          dmu_objset_disown(os, B_TRUE, FTAG);
          return (0);
  }
  
  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(SPA_MODE_READ | SPA_MODE_WRITE);
          VERIFY0(spa_open(ztest_opts.zo_pool, &spa, FTAG));
          VERIFY0(ztest_dataset_open(0));
          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(SPA_MODE_READ | SPA_MODE_WRITE);
          VERIFY0(spa_open(ztest_opts.zo_pool, &spa, FTAG));
          ASSERT3U(spa_freeze_txg(spa), ==, UINT64_MAX);
          VERIFY0(ztest_dataset_open(0));
          ztest_spa = spa;
          txg_wait_synced(spa_get_dsl(spa), 0);
          ztest_dataset_close(0);
          ztest_reguid(NULL, 0);
  
          spa_close(spa, FTAG);
          kernel_fini();
  }
  
  static void
  ztest_import_impl(void)
  {
          importargs_t args = { 0 };
          nvlist_t *cfg = NULL;
          int nsearch = 1;
          char *searchdirs[nsearch];
          int flags = ZFS_IMPORT_MISSING_LOG;
  
          searchdirs[0] = ztest_opts.zo_dir;
          args.paths = nsearch;
          args.path = searchdirs;
          args.can_be_active = B_FALSE;
  
          libpc_handle_t lpch = {
                  .lpc_lib_handle = NULL,
                  .lpc_ops = &libzpool_config_ops,
                  .lpc_printerr = B_TRUE
          };
          VERIFY0(zpool_find_config(&lpch, ztest_opts.zo_pool, &cfg, &args));
          VERIFY0(spa_import(ztest_opts.zo_pool, cfg, NULL, flags));
          fnvlist_free(cfg);
  }
  
  /*
   * Import a storage pool with the given name.
   */
  static void
  ztest_import(ztest_shared_t *zs)
  {
          spa_t *spa;
  
          mutex_init(&ztest_vdev_lock, NULL, MUTEX_DEFAULT, NULL);
          mutex_init(&ztest_checkpoint_lock, NULL, MUTEX_DEFAULT, NULL);
          VERIFY0(pthread_rwlock_init(&ztest_name_lock, NULL));
  
          kernel_init(SPA_MODE_READ | SPA_MODE_WRITE);
  
          ztest_import_impl();
  
          VERIFY0(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();
  
          if (!ztest_opts.zo_mmp_test) {
                  ztest_run_zdb(ztest_opts.zo_pool);
                  ztest_freeze();
                  ztest_run_zdb(ztest_opts.zo_pool);
          }
  
          (void) pthread_rwlock_destroy(&ztest_name_lock);
          mutex_destroy(&ztest_vdev_lock);
          mutex_destroy(&ztest_checkpoint_lock);
  }
  
  /*
   * Kick off threads to run tests on all datasets in parallel.
   */
  static void
  ztest_run(ztest_shared_t *zs)
  {
          spa_t *spa;
          objset_t *os;
          kthread_t *resume_thread, *deadman_thread;
          kthread_t **run_threads;
          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);
          mutex_init(&ztest_checkpoint_lock, NULL, MUTEX_DEFAULT, NULL);
          VERIFY0(pthread_rwlock_init(&ztest_name_lock, NULL));
  
          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.  It may need to be imported first depending on
           * what tests were running when the previous pass was terminated.
           */
          kernel_init(SPA_MODE_READ | SPA_MODE_WRITE);
          error = spa_open(ztest_opts.zo_pool, &spa, FTAG);
          if (error) {
                  VERIFY3S(error, ==, ENOENT);
                  ztest_import_impl();
                  VERIFY0(spa_open(ztest_opts.zo_pool, &spa, FTAG));
                  zs->zs_metaslab_sz =
                      1ULL << spa->spa_root_vdev->vdev_child[0]->vdev_ms_shift;
          }
  
          metaslab_preload_limit = ztest_random(20) + 1;
          ztest_spa = spa;
  
          VERIFY0(vdev_raidz_impl_set("cycle"));
  
          dmu_objset_stats_t dds;
          VERIFY0(ztest_dmu_objset_own(ztest_opts.zo_pool,
              DMU_OST_ANY, B_TRUE, 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, B_TRUE, FTAG);
  
          /*
           * Create a thread to periodically resume suspended I/O.
           */
          resume_thread = thread_create(NULL, 0, ztest_resume_thread,
              spa, 0, NULL, TS_RUN | TS_JOINABLE, defclsyspri);
  
          /*
           * Create a deadman thread and set to panic if we hang.
           */
          deadman_thread = thread_create(NULL, 0, ztest_deadman_thread,
              zs, 0, NULL, TS_RUN | TS_JOINABLE, defclsyspri);
  
          spa->spa_deadman_failmode = ZIO_FAILURE_MODE_PANIC;
  
          /*
           * Verify that we can safely inquire 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;
  
          /*
           * If we were in the middle of ztest_device_removal() and were killed
           * we need to ensure the removal and scrub complete before running
           * any tests that check ztest_device_removal_active. The removal will
           * be restarted automatically when the spa is opened, but we need to
           * initiate the scrub manually if it is not already in progress. Note
           * that we always run the scrub whenever an indirect vdev exists
           * because we have no way of knowing for sure if ztest_device_removal()
           * fully completed its scrub before the pool was reimported.
           */
          if (spa->spa_removing_phys.sr_state == DSS_SCANNING ||
              spa->spa_removing_phys.sr_prev_indirect_vdev != -1) {
                  while (spa->spa_removing_phys.sr_state == DSS_SCANNING)
                          txg_wait_synced(spa_get_dsl(spa), 0);
  
                  error = ztest_scrub_impl(spa);
                  if (error == EBUSY)
                          error = 0;
                  ASSERT0(error);
          }
  
          run_threads = umem_zalloc(ztest_opts.zo_threads * sizeof (kthread_t *),
              UMEM_NOFAIL);
  
          if (ztest_opts.zo_verbose >= 4)
                  (void) printf("starting main threads...\n");
  
          /*
           * Replay all logs of all datasets in the pool. This is primarily for
           * temporary datasets which wouldn't otherwise get replayed, which
           * can trigger failures when attempting to offline a SLOG in
           * ztest_fault_inject().
           */
          (void) dmu_objset_find(ztest_opts.zo_pool, ztest_replay_zil_cb,
              NULL, DS_FIND_CHILDREN);
  
          /*
           * Kick off all the tests that run in parallel.
           */
          for (t = 0; t < ztest_opts.zo_threads; t++) {
                  if (t < ztest_opts.zo_datasets && ztest_dataset_open(t) != 0) {
                          umem_free(run_threads, ztest_opts.zo_threads *
                              sizeof (kthread_t *));
                          return;
                  }
  
                  run_threads[t] = thread_create(NULL, 0, ztest_thread,
                      (void *)(uintptr_t)t, 0, NULL, TS_RUN | TS_JOINABLE,
                      defclsyspri);
          }
  
          /*
           * Wait for all of the tests to complete.
           */
          for (t = 0; t < ztest_opts.zo_threads; t++)
                  VERIFY0(thread_join(run_threads[t]));
  
          /*
           * Close all datasets. This must be done after all the threads
           * are joined so we can be sure none of the datasets are in-use
           * by any of the threads.
           */
          for (t = 0; t < ztest_opts.zo_threads; 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(run_threads, ztest_opts.zo_threads * sizeof (kthread_t *));
  
          /* Kill the resume and deadman threads */
          ztest_exiting = B_TRUE;
          VERIFY0(thread_join(resume_thread));
          VERIFY0(thread_join(deadman_thread));
          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) && !ztest_opts.zo_mmp_test) {
                  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) pthread_rwlock_destroy(&ztest_name_lock);
          mutex_destroy(&ztest_vdev_lock);
          mutex_destroy(&ztest_checkpoint_lock);
  }
  
  static 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;
  
          props = fnvlist_alloc();
  
          if (ztest_random(2) == 0)
                  return (props);
  
          fnvlist_add_uint64(props,
              zpool_prop_to_name(ZPOOL_PROP_AUTOREPLACE), 1);
  
          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);
          mutex_init(&ztest_checkpoint_lock, NULL, MUTEX_DEFAULT, NULL);
          VERIFY0(pthread_rwlock_init(&ztest_name_lock, NULL));
  
          kernel_init(SPA_MODE_READ | SPA_MODE_WRITE);
  
          /*
           * 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,
              NULL, ztest_opts.zo_raid_children, zs->zs_mirrors, 1);
          props = make_random_props();
  
          /*
           * We don't expect the pool to suspend unless maxfaults == 0,
           * in which case ztest_fault_inject() temporarily takes away
           * the only valid replica.
           */
          fnvlist_add_uint64(props,
              zpool_prop_to_name(ZPOOL_PROP_FAILUREMODE),
              MAXFAULTS(zs) ? ZIO_FAILURE_MODE_PANIC : ZIO_FAILURE_MODE_WAIT);
  
          for (i = 0; i < SPA_FEATURES; i++) {
                  char *buf;
  
                  if (!spa_feature_table[i].fi_zfs_mod_supported)
                          continue;
  
                  /*
                   * 75% chance of using the log space map feature. We want ztest
                   * to exercise both the code paths that use the log space map
                   * feature and the ones that don't.
                   */
                  if (i == SPA_FEATURE_LOG_SPACEMAP && ztest_random(4) == 0)
                          continue;
  
                  VERIFY3S(-1, !=, asprintf(&buf, "feature@%s",
                      spa_feature_table[i].fi_uname));
                  fnvlist_add_uint64(props, buf, 0);
                  free(buf);
          }
  
          VERIFY0(spa_create(ztest_opts.zo_pool, nvroot, props, NULL, NULL));
          fnvlist_free(nvroot);
          fnvlist_free(props);
  
          VERIFY0(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();
  
          if (!ztest_opts.zo_mmp_test) {
                  ztest_run_zdb(ztest_opts.zo_pool);
                  ztest_freeze();
                  ztest_run_zdb(ztest_opts.zo_pool);
          }
  
          (void) pthread_rwlock_destroy(&ztest_name_lock);
          mutex_destroy(&ztest_vdev_lock);
          mutex_destroy(&ztest_checkpoint_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);
          ASSERT3P(hdr, !=, MAP_FAILED);
  
          VERIFY0(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);
          VERIFY0(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);
          ASSERT3P(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);
          ASSERT3P(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(B_TRUE, "fork failed");
  
          if (pid == 0) { /* child */
                  char fd_data_str[12];
  
                  VERIFY3S(11, >=,
                      snprintf(fd_data_str, 12, "%d", ztest_fd_data));
                  VERIFY0(setenv("ZTEST_FD_DATA", fd_data_str, 1));
  
                  if (libpath != NULL) {
                          const char *curlp = getenv("LD_LIBRARY_PATH");
                          if (curlp == NULL)
                                  VERIFY0(setenv("LD_LIBRARY_PATH", libpath, 1));
                          else {
                                  char *newlp = NULL;
                                  VERIFY3S(-1, !=,
                                      asprintf(&newlp, "%s:%s", libpath, curlp));
                                  VERIFY0(setenv("LD_LIBRARY_PATH", newlp, 1));
                                  free(newlp);
                          }
                  }
                  (void) execl(cmd, cmd, (char *)NULL);
                  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);
          }
  }
  
  static void
  ztest_run_init(void)
  {
          int i;
  
          ztest_shared_t *zs = ztest_shared;
  
          /*
           * Blow away any existing copy of zpool.cache
           */
          (void) remove(spa_config_path);
  
          if (ztest_opts.zo_init == 0) {
                  if (ztest_opts.zo_verbose >= 1)
                          (void) printf("Importing pool %s\n",
                              ztest_opts.zo_pool);
                  ztest_import(zs);
                  return;
          }
  
          /*
           * Create and initialize our storage pool.
           */
          for (i = 1; i <= ztest_opts.zo_init; i++) {
                  memset(zs, 0, sizeof (*zs));
                  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[NN_NUMBUF_SZ];
          char *cmd;
          boolean_t hasalt;
          int f, err;
          char *fd_data_str = getenv("ZTEST_FD_DATA");
          struct sigaction action;
  
          (void) setvbuf(stdout, NULL, _IOLBF, 0);
  
          dprintf_setup(&argc, argv);
          zfs_deadman_synctime_ms = 300000;
          zfs_deadman_checktime_ms = 30000;
          /*
           * As two-word space map entries may not come up often (especially
           * if pool and vdev sizes are small) we want to force at least some
           * of them so the feature get tested.
           */
          zfs_force_some_double_word_sm_entries = B_TRUE;
  
          /*
           * Verify that even extensively damaged split blocks with many
           * segments can be reconstructed in a reasonable amount of time
           * when reconstruction is known to be possible.
           *
           * Note: the lower this value is, the more damage we inflict, and
           * the more time ztest spends in recovering that damage. We chose
           * to induce damage 1/100th of the time so recovery is tested but
           * not so frequently that ztest doesn't get to test other code paths.
           */
          zfs_reconstruct_indirect_damage_fraction = 100;
  
          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);
          }
  
          /*
           * Force random_get_bytes() to use /dev/urandom in order to prevent
           * ztest from needlessly depleting the system entropy pool.
           */
          random_path = "/dev/urandom";
          ztest_fd_rand = open(random_path, O_RDONLY | O_CLOEXEC);
          ASSERT3S(ztest_fd_rand, >=, 0);
  
          if (!fd_data_str) {
                  process_options(argc, argv);
  
                  setup_data_fd();
                  setup_hdr();
                  setup_data();
                  memcpy(ztest_shared_opts, &ztest_opts,
                      sizeof (*ztest_shared_opts));
          } else {
                  ztest_fd_data = atoi(fd_data_str);
                  setup_data();
                  memcpy(&ztest_opts, ztest_shared_opts, sizeof (ztest_opts));
          }
          ASSERT3U(ztest_opts.zo_datasets, ==, ztest_shared_hdr->zh_ds_count);
  
          err = ztest_set_global_vars();
          if (err != 0 && !fd_data_str) {
                  /* error message done by ztest_set_global_vars */
                  exit(EXIT_FAILURE);
          } else {
                  /* children should not be spawned if setting gvars fails */
                  VERIFY3S(err, ==, 0);
          }
  
          /* Override location of zpool.cache */
          VERIFY3S(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_force_ganging = ztest_opts.zo_metaslab_force_ganging;
                  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("%"PRIu64" vdevs, %d datasets, %d threads,"
                      "%d %s disks, %"PRIu64" seconds...\n\n",
                      ztest_opts.zo_vdevs,
                      ztest_opts.zo_datasets,
                      ztest_opts.zo_threads,
                      ztest_opts.zo_raid_children,
                      ztest_opts.zo_raid_type,
                      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, sizeof (numbuf));
  
                          (void) printf("Pass %3d, %8s, %3"PRIu64" ENOSPC, "
                              "%4.1f%% of %5s used, %3.0f%% done, %8s to go\n",
                              iters,
                              WIFEXITED(status) ? "Complete" : "SIGKILL",
                              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("%7"PRIu64" %9s   %s\n",
                                      zc->zc_count, timebuf,
                                      zi->zi_funcname);
                          }
                          (void) printf("\n");
                  }
  
                  if (!ztest_opts.zo_mmp_test)
                          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);
  }