cmd/zhack/zhack.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  24  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  25  */
  26
  27 /*
  28  * zhack is a debugging tool that can write changes to ZFS pool using libzpool
  29  * for testing purposes. Altering pools with zhack is unsupported and may
  30  * result in corrupted pools.
  31  */
  32
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <ctype.h>
  36 #include <sys/stat.h>
  37 #include <sys/zfs_context.h>
  38 #include <sys/spa.h>
  39 #include <sys/spa_impl.h>
  40 #include <sys/dmu.h>
  41 #include <sys/zap.h>
  42 #include <sys/zfs_znode.h>
  43 #include <sys/dsl_synctask.h>
  44 #include <sys/vdev.h>
  45 #include <sys/vdev_impl.h>
  46 #include <sys/fs/zfs.h>
  47 #include <sys/dmu_objset.h>
  48 #include <sys/dsl_pool.h>
  49 #include <sys/zio_checksum.h>
  50 #include <sys/zio_compress.h>
  51 #include <sys/zfeature.h>
  52 #include <sys/dmu_tx.h>
  53 #include <zfeature_common.h>
  54 #include <libzutil.h>
  55
  56 static importargs_t g_importargs;
  57 static char *g_pool;
  58 static boolean_t g_readonly;
  59
  60 static __attribute__((noreturn)) void
  61 usage(void)
  62 {
  63         (void) fprintf(stderr,
  64             "Usage: zhack [-c cachefile] [-d dir] <subcommand> <args> ...\n"
  65             "where <subcommand> <args> is one of the following:\n"
  66             "\n");
  67
  68         (void) fprintf(stderr,
  69             "    feature stat <pool>\n"
  70             "        print information about enabled features\n"
  71             "    feature enable [-r] [-d desc] <pool> <feature>\n"
  72             "        add a new enabled feature to the pool\n"
  73             "        -d <desc> sets the feature's description\n"
  74             "        -r set read-only compatible flag for feature\n"
  75             "    feature ref [-md] <pool> <feature>\n"
  76             "        change the refcount on the given feature\n"
  77             "        -d decrease instead of increase the refcount\n"
  78             "        -m add the feature to the label if increasing refcount\n"
  79             "\n"
  80             "    <feature> : should be a feature guid\n"
  81             "\n"
  82             "    label repair <device>\n"
  83             "        repair corrupted label checksums\n"
  84             "\n"
  85             "    <device> : path to vdev\n");
  86         exit(1);
  87 }
  88
  89
  90 static __attribute__((noreturn)) __attribute__((format(printf, 3, 4))) void
  91 fatal(spa_t *spa, void *tag, const char *fmt, ...)
  92 {
  93         va_list ap;
  94
  95         if (spa != NULL) {
  96                 spa_close(spa, tag);
  97                 (void) spa_export(g_pool, NULL, B_TRUE, B_FALSE);
  98         }
  99
 100         va_start(ap, fmt);
 101         (void) fputs("zhack: ", stderr);
 102         (void) vfprintf(stderr, fmt, ap);
 103         va_end(ap);
 104         (void) fputc('\n', stderr);
 105
 106         exit(1);
 107 }
 108
 109 static int
 110 space_delta_cb(dmu_object_type_t bonustype, const void *data,
 111     zfs_file_info_t *zoi)
 112 {
 113         (void) data, (void) zoi;
 114
 115         /*
 116          * Is it a valid type of object to track?
 117          */
 118         if (bonustype != DMU_OT_ZNODE && bonustype != DMU_OT_SA)
 119                 return (ENOENT);
 120         (void) fprintf(stderr, "modifying object that needs user accounting");
 121         abort();
 122 }
 123
 124 /*
 125  * Target is the dataset whose pool we want to open.
 126  */
 127 static void
 128 zhack_import(char *target, boolean_t readonly)
 129 {
 130         nvlist_t *config;
 131         nvlist_t *props;
 132         int error;
 133
 134         kernel_init(readonly ? SPA_MODE_READ :
 135             (SPA_MODE_READ | SPA_MODE_WRITE));
 136
 137         dmu_objset_register_type(DMU_OST_ZFS, space_delta_cb);
 138
 139         g_readonly = readonly;
 140         g_importargs.can_be_active = readonly;
 141         g_pool = strdup(target);
 142
 143         error = zpool_find_config(NULL, target, &config, &g_importargs,
 144             &libzpool_config_ops);
 145         if (error)
 146                 fatal(NULL, FTAG, "cannot import '%s'", target);
 147
 148         props = NULL;
 149         if (readonly) {
 150                 VERIFY(nvlist_alloc(&props, NV_UNIQUE_NAME, 0) == 0);
 151                 VERIFY(nvlist_add_uint64(props,
 152                     zpool_prop_to_name(ZPOOL_PROP_READONLY), 1) == 0);
 153         }
 154
 155         zfeature_checks_disable = B_TRUE;
 156         error = spa_import(target, config, props,
 157             (readonly ?  ZFS_IMPORT_SKIP_MMP : ZFS_IMPORT_NORMAL));
 158         fnvlist_free(config);
 159         zfeature_checks_disable = B_FALSE;
 160         if (error == EEXIST)
 161                 error = 0;
 162
 163         if (error)
 164                 fatal(NULL, FTAG, "can't import '%s': %s", target,
 165                     strerror(error));
 166 }
 167
 168 static void
 169 zhack_spa_open(char *target, boolean_t readonly, void *tag, spa_t **spa)
 170 {
 171         int err;
 172
 173         zhack_import(target, readonly);
 174
 175         zfeature_checks_disable = B_TRUE;
 176         err = spa_open(target, spa, tag);
 177         zfeature_checks_disable = B_FALSE;
 178
 179         if (err != 0)
 180                 fatal(*spa, FTAG, "cannot open '%s': %s", target,
 181                     strerror(err));
 182         if (spa_version(*spa) < SPA_VERSION_FEATURES) {
 183                 fatal(*spa, FTAG, "'%s' has version %d, features not enabled",
 184                     target, (int)spa_version(*spa));
 185         }
 186 }
 187
 188 static void
 189 dump_obj(objset_t *os, uint64_t obj, const char *name)
 190 {
 191         zap_cursor_t zc;
 192         zap_attribute_t za;
 193
 194         (void) printf("%s_obj:\n", name);
 195
 196         for (zap_cursor_init(&zc, os, obj);
 197             zap_cursor_retrieve(&zc, &za) == 0;
 198             zap_cursor_advance(&zc)) {
 199                 if (za.za_integer_length == 8) {
 200                         ASSERT(za.za_num_integers == 1);
 201                         (void) printf("\t%s = %llu\n",
 202                             za.za_name, (u_longlong_t)za.za_first_integer);
 203                 } else {
 204                         ASSERT(za.za_integer_length == 1);
 205                         char val[1024];
 206                         VERIFY(zap_lookup(os, obj, za.za_name,
 207                             1, sizeof (val), val) == 0);
 208                         (void) printf("\t%s = %s\n", za.za_name, val);
 209                 }
 210         }
 211         zap_cursor_fini(&zc);
 212 }
 213
 214 static void
 215 dump_mos(spa_t *spa)
 216 {
 217         nvlist_t *nv = spa->spa_label_features;
 218         nvpair_t *pair;
 219
 220         (void) printf("label config:\n");
 221         for (pair = nvlist_next_nvpair(nv, NULL);
 222             pair != NULL;
 223             pair = nvlist_next_nvpair(nv, pair)) {
 224                 (void) printf("\t%s\n", nvpair_name(pair));
 225         }
 226 }
 227
 228 static void
 229 zhack_do_feature_stat(int argc, char **argv)
 230 {
 231         spa_t *spa;
 232         objset_t *os;
 233         char *target;
 234
 235         argc--;
 236         argv++;
 237
 238         if (argc < 1) {
 239                 (void) fprintf(stderr, "error: missing pool name\n");
 240                 usage();
 241         }
 242         target = argv[0];
 243
 244         zhack_spa_open(target, B_TRUE, FTAG, &spa);
 245         os = spa->spa_meta_objset;
 246
 247         dump_obj(os, spa->spa_feat_for_read_obj, "for_read");
 248         dump_obj(os, spa->spa_feat_for_write_obj, "for_write");
 249         dump_obj(os, spa->spa_feat_desc_obj, "descriptions");
 250         if (spa_feature_is_active(spa, SPA_FEATURE_ENABLED_TXG)) {
 251                 dump_obj(os, spa->spa_feat_enabled_txg_obj, "enabled_txg");
 252         }
 253         dump_mos(spa);
 254
 255         spa_close(spa, FTAG);
 256 }
 257
 258 static void
 259 zhack_feature_enable_sync(void *arg, dmu_tx_t *tx)
 260 {
 261         spa_t *spa = dmu_tx_pool(tx)->dp_spa;
 262         zfeature_info_t *feature = arg;
 263
 264         feature_enable_sync(spa, feature, tx);
 265
 266         spa_history_log_internal(spa, "zhack enable feature", tx,
 267             "name=%s flags=%u",
 268             feature->fi_guid, feature->fi_flags);
 269 }
 270
 271 static void
 272 zhack_do_feature_enable(int argc, char **argv)
 273 {
 274         int c;
 275         char *desc, *target;
 276         spa_t *spa;
 277         objset_t *mos;
 278         zfeature_info_t feature;
 279         const spa_feature_t nodeps[] = { SPA_FEATURE_NONE };
 280
 281         /*
 282          * Features are not added to the pool's label until their refcounts
 283          * are incremented, so fi_mos can just be left as false for now.
 284          */
 285         desc = NULL;
 286         feature.fi_uname = "zhack";
 287         feature.fi_flags = 0;
 288         feature.fi_depends = nodeps;
 289         feature.fi_feature = SPA_FEATURE_NONE;
 290
 291         optind = 1;
 292         while ((c = getopt(argc, argv, "+rd:")) != -1) {
 293                 switch (c) {
 294                 case 'r':
 295                         feature.fi_flags |= ZFEATURE_FLAG_READONLY_COMPAT;
 296                         break;
 297                 case 'd':
 298                         desc = strdup(optarg);
 299                         break;
 300                 default:
 301                         usage();
 302                         break;
 303                 }
 304         }
 305
 306         if (desc == NULL)
 307                 desc = strdup("zhack injected");
 308         feature.fi_desc = desc;
 309
 310         argc -= optind;
 311         argv += optind;
 312
 313         if (argc < 2) {
 314                 (void) fprintf(stderr, "error: missing feature or pool name\n");
 315                 usage();
 316         }
 317         target = argv[0];
 318         feature.fi_guid = argv[1];
 319
 320         if (!zfeature_is_valid_guid(feature.fi_guid))
 321                 fatal(NULL, FTAG, "invalid feature guid: %s", feature.fi_guid);
 322
 323         zhack_spa_open(target, B_FALSE, FTAG, &spa);
 324         mos = spa->spa_meta_objset;
 325
 326         if (zfeature_is_supported(feature.fi_guid))
 327                 fatal(spa, FTAG, "'%s' is a real feature, will not enable",
 328                     feature.fi_guid);
 329         if (0 == zap_contains(mos, spa->spa_feat_desc_obj, feature.fi_guid))
 330                 fatal(spa, FTAG, "feature already enabled: %s",
 331                     feature.fi_guid);
 332
 333         VERIFY0(dsl_sync_task(spa_name(spa), NULL,
 334             zhack_feature_enable_sync, &feature, 5, ZFS_SPACE_CHECK_NORMAL));
 335
 336         spa_close(spa, FTAG);
 337
 338         free(desc);
 339 }
 340
 341 static void
 342 feature_incr_sync(void *arg, dmu_tx_t *tx)
 343 {
 344         spa_t *spa = dmu_tx_pool(tx)->dp_spa;
 345         zfeature_info_t *feature = arg;
 346         uint64_t refcount;
 347
 348         VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
 349         feature_sync(spa, feature, refcount + 1, tx);
 350         spa_history_log_internal(spa, "zhack feature incr", tx,
 351             "name=%s", feature->fi_guid);
 352 }
 353
 354 static void
 355 feature_decr_sync(void *arg, dmu_tx_t *tx)
 356 {
 357         spa_t *spa = dmu_tx_pool(tx)->dp_spa;
 358         zfeature_info_t *feature = arg;
 359         uint64_t refcount;
 360
 361         VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
 362         feature_sync(spa, feature, refcount - 1, tx);
 363         spa_history_log_internal(spa, "zhack feature decr", tx,
 364             "name=%s", feature->fi_guid);
 365 }
 366
 367 static void
 368 zhack_do_feature_ref(int argc, char **argv)
 369 {
 370         int c;
 371         char *target;
 372         boolean_t decr = B_FALSE;
 373         spa_t *spa;
 374         objset_t *mos;
 375         zfeature_info_t feature;
 376         const spa_feature_t nodeps[] = { SPA_FEATURE_NONE };
 377
 378         /*
 379          * fi_desc does not matter here because it was written to disk
 380          * when the feature was enabled, but we need to properly set the
 381          * feature for read or write based on the information we read off
 382          * disk later.
 383          */
 384         feature.fi_uname = "zhack";
 385         feature.fi_flags = 0;
 386         feature.fi_desc = NULL;
 387         feature.fi_depends = nodeps;
 388         feature.fi_feature = SPA_FEATURE_NONE;
 389
 390         optind = 1;
 391         while ((c = getopt(argc, argv, "+md")) != -1) {
 392                 switch (c) {
 393                 case 'm':
 394                         feature.fi_flags |= ZFEATURE_FLAG_MOS;
 395                         break;
 396                 case 'd':
 397                         decr = B_TRUE;
 398                         break;
 399                 default:
 400                         usage();
 401                         break;
 402                 }
 403         }
 404         argc -= optind;
 405         argv += optind;
 406
 407         if (argc < 2) {
 408                 (void) fprintf(stderr, "error: missing feature or pool name\n");
 409                 usage();
 410         }
 411         target = argv[0];
 412         feature.fi_guid = argv[1];
 413
 414         if (!zfeature_is_valid_guid(feature.fi_guid))
 415                 fatal(NULL, FTAG, "invalid feature guid: %s", feature.fi_guid);
 416
 417         zhack_spa_open(target, B_FALSE, FTAG, &spa);
 418         mos = spa->spa_meta_objset;
 419
 420         if (zfeature_is_supported(feature.fi_guid)) {
 421                 fatal(spa, FTAG,
 422                     "'%s' is a real feature, will not change refcount",
 423                     feature.fi_guid);
 424         }
 425
 426         if (0 == zap_contains(mos, spa->spa_feat_for_read_obj,
 427             feature.fi_guid)) {
 428                 feature.fi_flags &= ~ZFEATURE_FLAG_READONLY_COMPAT;
 429         } else if (0 == zap_contains(mos, spa->spa_feat_for_write_obj,
 430             feature.fi_guid)) {
 431                 feature.fi_flags |= ZFEATURE_FLAG_READONLY_COMPAT;
 432         } else {
 433                 fatal(spa, FTAG, "feature is not enabled: %s", feature.fi_guid);
 434         }
 435
 436         if (decr) {
 437                 uint64_t count;
 438                 if (feature_get_refcount_from_disk(spa, &feature,
 439                     &count) == 0 && count == 0) {
 440                         fatal(spa, FTAG, "feature refcount already 0: %s",
 441                             feature.fi_guid);
 442                 }
 443         }
 444
 445         VERIFY0(dsl_sync_task(spa_name(spa), NULL,
 446             decr ? feature_decr_sync : feature_incr_sync, &feature,
 447             5, ZFS_SPACE_CHECK_NORMAL));
 448
 449         spa_close(spa, FTAG);
 450 }
 451
 452 static int
 453 zhack_do_feature(int argc, char **argv)
 454 {
 455         char *subcommand;
 456
 457         argc--;
 458         argv++;
 459         if (argc == 0) {
 460                 (void) fprintf(stderr,
 461                     "error: no feature operation specified\n");
 462                 usage();
 463         }
 464
 465         subcommand = argv[0];
 466         if (strcmp(subcommand, "stat") == 0) {
 467                 zhack_do_feature_stat(argc, argv);
 468         } else if (strcmp(subcommand, "enable") == 0) {
 469                 zhack_do_feature_enable(argc, argv);
 470         } else if (strcmp(subcommand, "ref") == 0) {
 471                 zhack_do_feature_ref(argc, argv);
 472         } else {
 473                 (void) fprintf(stderr, "error: unknown subcommand: %s\n",
 474                     subcommand);
 475                 usage();
 476         }
 477
 478         return (0);
 479 }
 480
 481 static int
 482 zhack_repair_label_cksum(int argc, char **argv)
 483 {
 484         zio_checksum_info_t *ci = &zio_checksum_table[ZIO_CHECKSUM_LABEL];
 485         const char *cfg_keys[] = { ZPOOL_CONFIG_VERSION,
 486             ZPOOL_CONFIG_POOL_STATE, ZPOOL_CONFIG_GUID };
 487         boolean_t labels_repaired[VDEV_LABELS];
 488         boolean_t repaired = B_FALSE;
 489         vdev_label_t labels[VDEV_LABELS];
 490         struct stat st;
 491         int fd;
 492
 493         bzero(labels_repaired, sizeof (labels_repaired));
 494         bzero(labels, sizeof (labels));
 495
 496         abd_init();
 497
 498         argc -= 1;
 499         argv += 1;
 500
 501         if (argc < 1) {
 502                 (void) fprintf(stderr, "error: missing device\n");
 503                 usage();
 504         }
 505
 506         if ((fd = open(argv[0], O_RDWR)) == -1)
 507                 fatal(NULL, FTAG, "cannot open '%s': %s", argv[0],
 508                     strerror(errno));
 509
 510         if (stat(argv[0], &st) != 0)
 511                 fatal(NULL, FTAG, "cannot stat '%s': %s", argv[0],
 512                     strerror(errno));
 513
 514         for (int l = 0; l < VDEV_LABELS; l++) {
 515                 uint64_t label_offset, offset;
 516                 zio_cksum_t expected_cksum;
 517                 zio_cksum_t actual_cksum;
 518                 zio_cksum_t verifier;
 519                 zio_eck_t *eck;
 520                 nvlist_t *cfg;
 521                 int byteswap;
 522                 uint64_t val;
 523                 ssize_t err;
 524
 525                 vdev_label_t *vl = &labels[l];
 526
 527                 label_offset = vdev_label_offset(st.st_size, l, 0);
 528                 err = pread64(fd, vl, sizeof (vdev_label_t), label_offset);
 529                 if (err == -1) {
 530                         (void) fprintf(stderr, "error: cannot read "
 531                             "label %d: %s\n", l, strerror(errno));
 532                         continue;
 533                 } else if (err != sizeof (vdev_label_t)) {
 534                         (void) fprintf(stderr, "error: bad label %d read size "
 535                             "\n", l);
 536                         continue;
 537                 }
 538
 539                 err = nvlist_unpack(vl->vl_vdev_phys.vp_nvlist,
 540                     VDEV_PHYS_SIZE - sizeof (zio_eck_t), &cfg, 0);
 541                 if (err) {
 542                         (void) fprintf(stderr, "error: cannot unpack nvlist "
 543                             "label %d\n", l);
 544                         continue;
 545                 }
 546
 547                 for (int i = 0; i < ARRAY_SIZE(cfg_keys); i++) {
 548                         err = nvlist_lookup_uint64(cfg, cfg_keys[i], &val);
 549                         if (err) {
 550                                 (void) fprintf(stderr, "error: label %d: "
 551                                     "cannot find nvlist key %s\n",
 552                                     l, cfg_keys[i]);
 553                                 continue;
 554                         }
 555                 }
 556
 557                 void *data = (char *)vl + offsetof(vdev_label_t, vl_vdev_phys);
 558                 eck = (zio_eck_t *)((char *)(data) + VDEV_PHYS_SIZE) - 1;
 559
 560                 offset = label_offset + offsetof(vdev_label_t, vl_vdev_phys);
 561                 ZIO_SET_CHECKSUM(&verifier, offset, 0, 0, 0);
 562
 563                 byteswap = (eck->zec_magic == BSWAP_64(ZEC_MAGIC));
 564                 if (byteswap)
 565                         byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));
 566
 567                 expected_cksum = eck->zec_cksum;
 568                 eck->zec_cksum = verifier;
 569
 570                 abd_t *abd = abd_get_from_buf(data, VDEV_PHYS_SIZE);
 571                 ci->ci_func[byteswap](abd, VDEV_PHYS_SIZE, NULL, &actual_cksum);
 572                 abd_free(abd);
 573
 574                 if (byteswap)
 575                         byteswap_uint64_array(&expected_cksum,
 576                             sizeof (zio_cksum_t));
 577
 578                 if (ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum))
 579                         continue;
 580
 581                 eck->zec_cksum = actual_cksum;
 582
 583                 err = pwrite64(fd, data, VDEV_PHYS_SIZE, offset);
 584                 if (err == -1) {
 585                         (void) fprintf(stderr, "error: cannot write "
 586                             "label %d: %s\n", l, strerror(errno));
 587                         continue;
 588                 } else if (err != VDEV_PHYS_SIZE) {
 589                         (void) fprintf(stderr, "error: bad write size "
 590                             "label %d\n", l);
 591                         continue;
 592                 }
 593
 594                 fsync(fd);
 595
 596                 labels_repaired[l] = B_TRUE;
 597         }
 598
 599         close(fd);
 600
 601         abd_fini();
 602
 603         for (int l = 0; l < VDEV_LABELS; l++) {
 604                 (void) printf("label %d: %s\n", l,
 605                     labels_repaired[l] ? "repaired" : "skipped");
 606                 repaired |= labels_repaired[l];
 607         }
 608
 609         if (repaired)
 610                 return (0);
 611
 612         return (1);
 613 }
 614
 615 static int
 616 zhack_do_label(int argc, char **argv)
 617 {
 618         char *subcommand;
 619         int err;
 620
 621         argc--;
 622         argv++;
 623         if (argc == 0) {
 624                 (void) fprintf(stderr,
 625                     "error: no label operation specified\n");
 626                 usage();
 627         }
 628
 629         subcommand = argv[0];
 630         if (strcmp(subcommand, "repair") == 0) {
 631                 err = zhack_repair_label_cksum(argc, argv);
 632         } else {
 633                 (void) fprintf(stderr, "error: unknown subcommand: %s\n",
 634                     subcommand);
 635                 usage();
 636         }
 637
 638         return (err);
 639 }
 640
 641 #define MAX_NUM_PATHS 1024
 642
 643 int
 644 main(int argc, char **argv)
 645 {
 646         extern void zfs_prop_init(void);
 647
 648         char *path[MAX_NUM_PATHS];
 649         const char *subcommand;
 650         int rv = 0;
 651         int c;
 652
 653         g_importargs.path = path;
 654
 655         dprintf_setup(&argc, argv);
 656         zfs_prop_init();
 657
 658         while ((c = getopt(argc, argv, "+c:d:")) != -1) {
 659                 switch (c) {
 660                 case 'c':
 661                         g_importargs.cachefile = optarg;
 662                         break;
 663                 case 'd':
 664                         assert(g_importargs.paths < MAX_NUM_PATHS);
 665                         g_importargs.path[g_importargs.paths++] = optarg;
 666                         break;
 667                 default:
 668                         usage();
 669                         break;
 670                 }
 671         }
 672
 673         argc -= optind;
 674         argv += optind;
 675         optind = 1;
 676
 677         if (argc == 0) {
 678                 (void) fprintf(stderr, "error: no command specified\n");
 679                 usage();
 680         }
 681
 682         subcommand = argv[0];
 683
 684         if (strcmp(subcommand, "feature") == 0) {
 685                 rv = zhack_do_feature(argc, argv);
 686         } else if (strcmp(subcommand, "label") == 0) {
 687                 return (zhack_do_label(argc, argv));
 688         } else {
 689                 (void) fprintf(stderr, "error: unknown subcommand: %s\n",
 690                     subcommand);
 691                 usage();
 692         }
 693
 694         if (!g_readonly && spa_export(g_pool, NULL, B_TRUE, B_FALSE) != 0) {
 695                 fatal(NULL, FTAG, "pool export failed; "
 696                     "changes may not be committed to disk\n");
 697         }
 698
 699         kernel_fini();
 700
 701         return (rv);
 702 }