drivers/md/dm-log.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software
   3  *
   4  * This file is released under the LGPL.
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/slab.h>
   9 #include <linux/module.h>
  10 #include <linux/vmalloc.h>
  11
  12 #include "dm-log.h"
  13 #include "dm-io.h"
  14
  15 #define DM_MSG_PREFIX "mirror log"
  16
  17 static LIST_HEAD(_log_types);
  18 static DEFINE_SPINLOCK(_lock);
  19
  20 int dm_register_dirty_log_type(struct dirty_log_type *type)
  21 {
  22         spin_lock(&_lock);
  23         type->use_count = 0;
  24         list_add(&type->list, &_log_types);
  25         spin_unlock(&_lock);
  26
  27         return 0;
  28 }
  29
  30 int dm_unregister_dirty_log_type(struct dirty_log_type *type)
  31 {
  32         spin_lock(&_lock);
  33
  34         if (type->use_count)
  35                 DMWARN("Unregister failed: log type '%s' still in use",
  36                        type->name);
  37         else
  38                 list_del(&type->list);
  39
  40         spin_unlock(&_lock);
  41
  42         return 0;
  43 }
  44
  45 static struct dirty_log_type *get_type(const char *type_name)
  46 {
  47         struct dirty_log_type *type;
  48
  49         spin_lock(&_lock);
  50         list_for_each_entry (type, &_log_types, list)
  51                 if (!strcmp(type_name, type->name)) {
  52                         if (!type->use_count && !try_module_get(type->module)){
  53                                 spin_unlock(&_lock);
  54                                 return NULL;
  55                         }
  56                         type->use_count++;
  57                         spin_unlock(&_lock);
  58                         return type;
  59                 }
  60
  61         spin_unlock(&_lock);
  62         return NULL;
  63 }
  64
  65 static void put_type(struct dirty_log_type *type)
  66 {
  67         spin_lock(&_lock);
  68         if (!--type->use_count)
  69                 module_put(type->module);
  70         spin_unlock(&_lock);
  71 }
  72
  73 struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
  74                                       unsigned int argc, char **argv)
  75 {
  76         struct dirty_log_type *type;
  77         struct dirty_log *log;
  78
  79         log = kmalloc(sizeof(*log), GFP_KERNEL);
  80         if (!log)
  81                 return NULL;
  82
  83         type = get_type(type_name);
  84         if (!type) {
  85                 kfree(log);
  86                 return NULL;
  87         }
  88
  89         log->type = type;
  90         if (type->ctr(log, ti, argc, argv)) {
  91                 kfree(log);
  92                 put_type(type);
  93                 return NULL;
  94         }
  95
  96         return log;
  97 }
  98
  99 void dm_destroy_dirty_log(struct dirty_log *log)
 100 {
 101         log->type->dtr(log);
 102         put_type(log->type);
 103         kfree(log);
 104 }
 105
 106 /*-----------------------------------------------------------------
 107  * Persistent and core logs share a lot of their implementation.
 108  * FIXME: need a reload method to be called from a resume
 109  *---------------------------------------------------------------*/
 110 /*
 111  * Magic for persistent mirrors: "MiRr"
 112  */
 113 #define MIRROR_MAGIC 0x4D695272
 114
 115 /*
 116  * The on-disk version of the metadata.
 117  */
 118 #define MIRROR_DISK_VERSION 2
 119 #define LOG_OFFSET 2
 120
 121 struct log_header {
 122         uint32_t magic;
 123
 124         /*
 125          * Simple, incrementing version. no backward
 126          * compatibility.
 127          */
 128         uint32_t version;
 129         sector_t nr_regions;
 130 };
 131
 132 struct log_c {
 133         struct dm_target *ti;
 134         int touched;
 135         uint32_t region_size;
 136         unsigned int region_count;
 137         region_t sync_count;
 138
 139         unsigned bitset_uint32_count;
 140         uint32_t *clean_bits;
 141         uint32_t *sync_bits;
 142         uint32_t *recovering_bits;
 143
 144         int sync_search;
 145
 146         /* Resync flag */
 147         enum sync {
 148                 DEFAULTSYNC,    /* Synchronize if necessary */
 149                 NOSYNC,         /* Devices known to be already in sync */
 150                 FORCESYNC,      /* Force a sync to happen */
 151         } sync;
 152
 153         int failure_response;
 154
 155         /*
 156          * Disk log fields
 157          */
 158         int log_dev_failed;
 159         struct dm_dev *log_dev;
 160         struct log_header header;
 161
 162         struct io_region header_location;
 163         struct log_header *disk_header;
 164 };
 165
 166 /*
 167  * The touched member needs to be updated every time we access
 168  * one of the bitsets.
 169  */
 170 static  inline int log_test_bit(uint32_t *bs, unsigned bit)
 171 {
 172         return ext2_test_bit(bit, (unsigned long *) bs) ? 1 : 0;
 173 }
 174
 175 static inline void log_set_bit(struct log_c *l,
 176                                uint32_t *bs, unsigned bit)
 177 {
 178         ext2_set_bit(bit, (unsigned long *) bs);
 179         l->touched = 1;
 180 }
 181
 182 static inline void log_clear_bit(struct log_c *l,
 183                                  uint32_t *bs, unsigned bit)
 184 {
 185         ext2_clear_bit(bit, (unsigned long *) bs);
 186         l->touched = 1;
 187 }
 188
 189 /*----------------------------------------------------------------
 190  * Header IO
 191  *--------------------------------------------------------------*/
 192 static void header_to_disk(struct log_header *core, struct log_header *disk)
 193 {
 194         disk->magic = cpu_to_le32(core->magic);
 195         disk->version = cpu_to_le32(core->version);
 196         disk->nr_regions = cpu_to_le64(core->nr_regions);
 197 }
 198
 199 static void header_from_disk(struct log_header *core, struct log_header *disk)
 200 {
 201         core->magic = le32_to_cpu(disk->magic);
 202         core->version = le32_to_cpu(disk->version);
 203         core->nr_regions = le64_to_cpu(disk->nr_regions);
 204 }
 205
 206 static int read_header(struct log_c *log)
 207 {
 208         int r;
 209         unsigned long ebits;
 210
 211         r = dm_io_sync_vm(1, &log->header_location, READ,
 212                           log->disk_header, &ebits);
 213         if (r)
 214                 return r;
 215
 216         header_from_disk(&log->header, log->disk_header);
 217
 218         /* New log required? */
 219         if (log->sync != DEFAULTSYNC || log->header.magic != MIRROR_MAGIC) {
 220                 log->header.magic = MIRROR_MAGIC;
 221                 log->header.version = MIRROR_DISK_VERSION;
 222                 log->header.nr_regions = 0;
 223         }
 224
 225 #ifdef __LITTLE_ENDIAN
 226         if (log->header.version == 1)
 227                 log->header.version = 2;
 228 #endif
 229
 230         if (log->header.version != MIRROR_DISK_VERSION) {
 231                 DMWARN("incompatible disk log version");
 232                 return -EINVAL;
 233         }
 234
 235         return 0;
 236 }
 237
 238 static inline int write_header(struct log_c *log)
 239 {
 240         unsigned long ebits;
 241
 242         header_to_disk(&log->header, log->disk_header);
 243         return dm_io_sync_vm(1, &log->header_location, WRITE,
 244                              log->disk_header, &ebits);
 245 }
 246
 247 /*----------------------------------------------------------------
 248  * core log constructor/destructor
 249  *
 250  * argv contains 1 - 3 arguments:
 251  *   <region_size> [[no]sync] [block_on_error]
 252  *--------------------------------------------------------------*/
 253 #define BYTE_SHIFT 3
 254 static int create_log_context(struct dirty_log *log, struct dm_target *ti,
 255                               unsigned int argc, char **argv,
 256                               struct dm_dev *dev)
 257 {
 258         int i;
 259         enum sync sync = DEFAULTSYNC;
 260         int failure_response = DMLOG_IOERR_IGNORE;
 261         struct log_c *lc;
 262         uint32_t region_size;
 263         unsigned int region_count;
 264         size_t bitset_size, buf_size;
 265
 266         if (argc < 1 || argc > 3) {
 267                 DMWARN("wrong number of arguments to mirror log");
 268                 return -EINVAL;
 269         }
 270
 271         for (i = 1; i < argc; i++) {
 272                 if (!strcmp(argv[i], "sync"))
 273                         sync = FORCESYNC;
 274                 else if (!strcmp(argv[i], "nosync"))
 275                         sync = NOSYNC;
 276                 else if (!strcmp(argv[i], "block_on_error"))
 277                         failure_response = DMLOG_IOERR_BLOCK;
 278                 else {
 279                         DMWARN("unrecognised sync argument to mirror log: %s",
 280                                argv[i]);
 281                         return -EINVAL;
 282                 }
 283         }
 284
 285         if (sscanf(argv[0], "%u", &region_size) != 1) {
 286                 DMWARN("invalid region size string");
 287                 return -EINVAL;
 288         }
 289
 290         region_count = dm_sector_div_up(ti->len, region_size);
 291
 292         lc = kmalloc(sizeof(*lc), GFP_KERNEL);
 293         if (!lc) {
 294                 DMWARN("couldn't allocate core log");
 295                 return -ENOMEM;
 296         }
 297
 298         lc->ti = ti;
 299         lc->touched = 0;
 300         lc->region_size = region_size;
 301         lc->region_count = region_count;
 302         lc->sync = sync;
 303         lc->failure_response = failure_response;
 304
 305         /*
 306          * Work out how many "unsigned long"s we need to hold the bitset.
 307          */
 308         bitset_size = dm_round_up(region_count,
 309                                   sizeof(*lc->clean_bits) << BYTE_SHIFT);
 310         bitset_size >>= BYTE_SHIFT;
 311
 312         lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);
 313
 314         /*
 315          * Disk log?
 316          */
 317         if (!dev) {
 318                 lc->clean_bits = vmalloc(bitset_size);
 319                 if (!lc->clean_bits) {
 320                         DMWARN("couldn't allocate clean bitset");
 321                         kfree(lc);
 322                         return -ENOMEM;
 323                 }
 324                 lc->disk_header = NULL;
 325         } else {
 326                 lc->log_dev = dev;
 327                 lc->log_dev_failed = 0;
 328                 lc->header_location.bdev = lc->log_dev->bdev;
 329                 lc->header_location.sector = 0;
 330
 331                 /*
 332                  * Buffer holds both header and bitset.
 333                  */
 334                 buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
 335                                        bitset_size, ti->limits.hardsect_size);
 336                 lc->header_location.count = buf_size >> SECTOR_SHIFT;
 337
 338                 lc->disk_header = vmalloc(buf_size);
 339                 if (!lc->disk_header) {
 340                         DMWARN("couldn't allocate disk log buffer");
 341                         kfree(lc);
 342                         return -ENOMEM;
 343                 }
 344
 345                 lc->clean_bits = (void *)lc->disk_header +
 346                                  (LOG_OFFSET << SECTOR_SHIFT);
 347         }
 348
 349         memset(lc->clean_bits, -1, bitset_size);
 350
 351         lc->sync_bits = vmalloc(bitset_size);
 352         if (!lc->sync_bits) {
 353                 DMWARN("couldn't allocate sync bitset");
 354                 if (!dev)
 355                         vfree(lc->clean_bits);
 356                 vfree(lc->disk_header);
 357                 kfree(lc);
 358                 return -ENOMEM;
 359         }
 360         memset(lc->sync_bits, (sync == NOSYNC) ? -1 : 0, bitset_size);
 361         lc->sync_count = (sync == NOSYNC) ? region_count : 0;
 362
 363         lc->recovering_bits = vmalloc(bitset_size);
 364         if (!lc->recovering_bits) {
 365                 DMWARN("couldn't allocate recovering bitset");
 366                 vfree(lc->sync_bits);
 367                 if (!dev)
 368                         vfree(lc->clean_bits);
 369                 vfree(lc->disk_header);
 370                 kfree(lc);
 371                 return -ENOMEM;
 372         }
 373         memset(lc->recovering_bits, 0, bitset_size);
 374         lc->sync_search = 0;
 375         log->context = lc;
 376
 377         return 0;
 378 }
 379
 380 static int core_ctr(struct dirty_log *log, struct dm_target *ti,
 381                     unsigned int argc, char **argv)
 382 {
 383         return create_log_context(log, ti, argc, argv, NULL);
 384 }
 385
 386 static void destroy_log_context(struct log_c *lc)
 387 {
 388         vfree(lc->sync_bits);
 389         vfree(lc->recovering_bits);
 390         kfree(lc);
 391 }
 392
 393 static void core_dtr(struct dirty_log *log)
 394 {
 395         struct log_c *lc = (struct log_c *) log->context;
 396
 397         vfree(lc->clean_bits);
 398         destroy_log_context(lc);
 399 }
 400
 401 /*----------------------------------------------------------------
 402  * disk log constructor/destructor
 403  *
 404  * argv contains 2 - 4 arguments:
 405  *      <log_device> <region_size> [[no]sync] [block_on_error]
 406  *--------------------------------------------------------------*/
 407 static int disk_ctr(struct dirty_log *log, struct dm_target *ti,
 408                     unsigned int argc, char **argv)
 409 {
 410         int r;
 411         struct dm_dev *dev;
 412
 413         if (argc < 2 || argc > 4) {
 414                 DMWARN("wrong number of arguments to disk mirror log");
 415                 return -EINVAL;
 416         }
 417
 418         r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
 419                           FMODE_READ | FMODE_WRITE, &dev);
 420         if (r)
 421                 return r;
 422
 423         r = create_log_context(log, ti, argc - 1, argv + 1, dev);
 424         if (r) {
 425                 dm_put_device(ti, dev);
 426                 return r;
 427         }
 428
 429         return 0;
 430 }
 431
 432 static void disk_dtr(struct dirty_log *log)
 433 {
 434         struct log_c *lc = (struct log_c *) log->context;
 435
 436         dm_put_device(lc->ti, lc->log_dev);
 437         vfree(lc->disk_header);
 438         destroy_log_context(lc);
 439 }
 440
 441 static int count_bits32(uint32_t *addr, unsigned size)
 442 {
 443         int count = 0, i;
 444
 445         for (i = 0; i < size; i++) {
 446                 count += hweight32(*(addr+i));
 447         }
 448         return count;
 449 }
 450
 451 static void fail_log_device(struct log_c *lc)
 452 {
 453         if (lc->log_dev_failed)
 454                 return;
 455
 456         lc->log_dev_failed = 1;
 457         if (lc->failure_response == DMLOG_IOERR_BLOCK)
 458                 dm_table_event(lc->ti->table);
 459 }
 460
 461 static void restore_log_device(struct log_c *lc)
 462 {
 463         lc->log_dev_failed = 0;
 464 }
 465
 466 static int disk_resume(struct dirty_log *log)
 467 {
 468         int r;
 469         unsigned i;
 470         struct log_c *lc = (struct log_c *) log->context;
 471         size_t size = lc->bitset_uint32_count * sizeof(uint32_t);
 472
 473         /*
 474          * Read the disk header, but only if we know it is good.
 475          * Assume the worst in the event of failure.
 476          */
 477         if (!lc->log_dev_failed && read_header(lc)) {
 478                 DMWARN("Failed to read header on mirror log device, %s",
 479                        lc->log_dev->name);
 480                 fail_log_device(lc);
 481                 lc->header.nr_regions = 0;
 482         }
 483
 484         /* set or clear any new bits -- device has grown */
 485         if (lc->sync == NOSYNC)
 486                 for (i = lc->header.nr_regions; i < lc->region_count; i++)
 487                         /* FIXME: amazingly inefficient */
 488                         log_set_bit(lc, lc->clean_bits, i);
 489         else
 490                 for (i = lc->header.nr_regions; i < lc->region_count; i++)
 491                         /* FIXME: amazingly inefficient */
 492                         log_clear_bit(lc, lc->clean_bits, i);
 493
 494         /* clear any old bits -- device has shrunk */
 495         for (i = lc->region_count; i % (sizeof(*lc->clean_bits) << BYTE_SHIFT); i++)
 496                 log_clear_bit(lc, lc->clean_bits, i);
 497
 498         /* copy clean across to sync */
 499         memcpy(lc->sync_bits, lc->clean_bits, size);
 500         lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
 501         lc->sync_search = 0;
 502
 503         /* set the correct number of regions in the header */
 504         lc->header.nr_regions = lc->region_count;
 505
 506         /* write the new header */
 507         r = write_header(lc);
 508         if (r) {
 509                 DMWARN("Failed to write header on mirror log device, %s",
 510                        lc->log_dev->name);
 511                 fail_log_device(lc);
 512         } else
 513                 restore_log_device(lc);
 514
 515         return r;
 516 }
 517
 518 static uint32_t core_get_region_size(struct dirty_log *log)
 519 {
 520         struct log_c *lc = (struct log_c *) log->context;
 521         return lc->region_size;
 522 }
 523
 524 static int core_resume(struct dirty_log *log)
 525 {
 526         struct log_c *lc = (struct log_c *) log->context;
 527         lc->sync_search = 0;
 528         return 0;
 529 }
 530
 531 static int core_is_clean(struct dirty_log *log, region_t region)
 532 {
 533         struct log_c *lc = (struct log_c *) log->context;
 534         return log_test_bit(lc->clean_bits, region);
 535 }
 536
 537 static int core_in_sync(struct dirty_log *log, region_t region, int block)
 538 {
 539         struct log_c *lc = (struct log_c *) log->context;
 540         return log_test_bit(lc->sync_bits, region);
 541 }
 542
 543 static int core_flush(struct dirty_log *log)
 544 {
 545         /* no op */
 546         return 0;
 547 }
 548
 549 static int disk_presuspend(struct dirty_log *log)
 550 {
 551         return 0;
 552 }
 553
 554 static int disk_flush(struct dirty_log *log)
 555 {
 556         int r;
 557         struct log_c *lc = (struct log_c *) log->context;
 558
 559         /* only write if the log has changed */
 560         if (!lc->touched)
 561                 return 0;
 562
 563         r = write_header(lc);
 564         if (r)
 565                 fail_log_device(lc);
 566         else {
 567                 lc->touched = 0;
 568                 restore_log_device(lc);
 569         }
 570         return r;
 571 }
 572
 573 static void core_mark_region(struct dirty_log *log, region_t region)
 574 {
 575         struct log_c *lc = (struct log_c *) log->context;
 576         log_clear_bit(lc, lc->clean_bits, region);
 577 }
 578
 579 static void core_clear_region(struct dirty_log *log, region_t region)
 580 {
 581         struct log_c *lc = (struct log_c *) log->context;
 582         log_set_bit(lc, lc->clean_bits, region);
 583 }
 584
 585 static int core_get_resync_work(struct dirty_log *log, region_t *region)
 586 {
 587         struct log_c *lc = (struct log_c *) log->context;
 588
 589         if (lc->sync_search >= lc->region_count)
 590                 return 0;
 591
 592         do {
 593                 *region = ext2_find_next_zero_bit(
 594                                              (unsigned long *) lc->sync_bits,
 595                                              lc->region_count,
 596                                              lc->sync_search);
 597                 lc->sync_search = *region + 1;
 598
 599                 if (*region >= lc->region_count)
 600                         return 0;
 601
 602         } while (log_test_bit(lc->recovering_bits, *region));
 603
 604         log_set_bit(lc, lc->recovering_bits, *region);
 605         return 1;
 606 }
 607
 608 static void core_set_region_sync(struct dirty_log *log, region_t region,
 609                                  int in_sync)
 610 {
 611         struct log_c *lc = (struct log_c *) log->context;
 612
 613         log_clear_bit(lc, lc->recovering_bits, region);
 614         if (in_sync) {
 615                 log_set_bit(lc, lc->sync_bits, region);
 616                 lc->sync_count++;
 617         } else if (log_test_bit(lc->sync_bits, region)) {
 618                 lc->sync_count--;
 619                 log_clear_bit(lc, lc->sync_bits, region);
 620         }
 621 }
 622
 623 static region_t core_get_sync_count(struct dirty_log *log)
 624 {
 625         struct log_c *lc = (struct log_c *) log->context;
 626
 627         return lc->sync_count;
 628 }
 629
 630 #define DMEMIT_SYNC \
 631         if (lc->sync != DEFAULTSYNC) \
 632                 DMEMIT("%ssync ", lc->sync == NOSYNC ? "no" : "")
 633
 634 static int core_status(struct dirty_log *log, status_type_t status,
 635                        char *result, unsigned int maxlen)
 636 {
 637         int sz = 0;
 638         int params;
 639         struct log_c *lc = log->context;
 640
 641         switch(status) {
 642         case STATUSTYPE_INFO:
 643                 DMEMIT("1 core");
 644                 break;
 645
 646         case STATUSTYPE_TABLE:
 647                 params = (lc->sync == DEFAULTSYNC) ? 1 : 2;
 648                 params += (lc->failure_response == DMLOG_IOERR_BLOCK) ? 1 : 0;
 649
 650                 DMEMIT("%s %d %u ", log->type->name, params, lc->region_size);
 651                 DMEMIT_SYNC;
 652                 if (lc->failure_response == DMLOG_IOERR_BLOCK)
 653                         DMEMIT("block_on_error ");
 654         }
 655
 656         return sz;
 657 }
 658
 659 static int disk_status(struct dirty_log *log, status_type_t status,
 660                        char *result, unsigned int maxlen)
 661 {
 662         int sz = 0;
 663         int params;
 664         struct log_c *lc = log->context;
 665
 666         switch(status) {
 667         case STATUSTYPE_INFO:
 668                 DMEMIT("3 disk %s %c", lc->log_dev->name,
 669                        lc->log_dev_failed ? 'D' : 'A');
 670                 break;
 671
 672         case STATUSTYPE_TABLE:
 673                 params = (lc->sync == DEFAULTSYNC) ? 2 : 3;
 674                 params += (lc->failure_response == DMLOG_IOERR_BLOCK) ? 1 : 0;
 675
 676                 DMEMIT("%s %d %s %u ", log->type->name,
 677                        params,
 678                        lc->log_dev->name,
 679                        lc->region_size);
 680                 DMEMIT_SYNC;
 681                 if (lc->failure_response == DMLOG_IOERR_BLOCK)
 682                         DMEMIT("block_on_error ");
 683         }
 684
 685         return sz;
 686 }
 687
 688 static int core_get_failure_response(struct dirty_log *log)
 689 {
 690         struct log_c *lc = log->context;
 691
 692         return lc->failure_response;
 693 }
 694
 695 static struct dirty_log_type _core_type = {
 696         .name = "core",
 697         .module = THIS_MODULE,
 698         .ctr = core_ctr,
 699         .dtr = core_dtr,
 700         .resume = core_resume,
 701         .get_region_size = core_get_region_size,
 702         .is_clean = core_is_clean,
 703         .in_sync = core_in_sync,
 704         .flush = core_flush,
 705         .mark_region = core_mark_region,
 706         .clear_region = core_clear_region,
 707         .get_resync_work = core_get_resync_work,
 708         .set_region_sync = core_set_region_sync,
 709         .get_sync_count = core_get_sync_count,
 710         .status = core_status,
 711         .get_failure_response = core_get_failure_response,
 712 };
 713
 714 static struct dirty_log_type _disk_type = {
 715         .name = "disk",
 716         .module = THIS_MODULE,
 717         .ctr = disk_ctr,
 718         .dtr = disk_dtr,
 719         .presuspend = disk_presuspend,
 720         .postsuspend = disk_flush,
 721         .resume = disk_resume,
 722         .get_region_size = core_get_region_size,
 723         .is_clean = core_is_clean,
 724         .in_sync = core_in_sync,
 725         .flush = disk_flush,
 726         .mark_region = core_mark_region,
 727         .clear_region = core_clear_region,
 728         .get_resync_work = core_get_resync_work,
 729         .set_region_sync = core_set_region_sync,
 730         .get_sync_count = core_get_sync_count,
 731         .status = disk_status,
 732         .get_failure_response = core_get_failure_response,
 733 };
 734
 735 int __init dm_dirty_log_init(void)
 736 {
 737         int r;
 738
 739         r = dm_register_dirty_log_type(&_core_type);
 740         if (r)
 741                 DMWARN("couldn't register core log");
 742
 743         r = dm_register_dirty_log_type(&_disk_type);
 744         if (r) {
 745                 DMWARN("couldn't register disk type");
 746                 dm_unregister_dirty_log_type(&_core_type);
 747         }
 748
 749         return r;
 750 }
 751
 752 void dm_dirty_log_exit(void)
 753 {
 754         dm_unregister_dirty_log_type(&_disk_type);
 755         dm_unregister_dirty_log_type(&_core_type);
 756 }
 757
 758 EXPORT_SYMBOL(dm_register_dirty_log_type);
 759 EXPORT_SYMBOL(dm_unregister_dirty_log_type);
 760 EXPORT_SYMBOL(dm_create_dirty_log);
 761 EXPORT_SYMBOL(dm_destroy_dirty_log);