1 /* 2 * Copyright (C) 2003 Sistina Software Limited. 3 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved. 4 * 5 * This file is released under the GPL. 6 */ 7 8 #include <linux/dm-dirty-log.h> 9 #include <linux/dm-region-hash.h> 10 11 #include <linux/ctype.h> 12 #include <linux/init.h> 13 #include <linux/module.h> 14 #include <linux/slab.h> 15 #include <linux/vmalloc.h> 16 17 #include "dm.h" 18 19 #define DM_MSG_PREFIX "region hash" 20 21 /*----------------------------------------------------------------- 22 * Region hash 23 * 24 * The mirror splits itself up into discrete regions. Each 25 * region can be in one of three states: clean, dirty, 26 * nosync. There is no need to put clean regions in the hash. 27 * 28 * In addition to being present in the hash table a region _may_ 29 * be present on one of three lists. 30 * 31 * clean_regions: Regions on this list have no io pending to 32 * them, they are in sync, we are no longer interested in them, 33 * they are dull. dm_rh_update_states() will remove them from the 34 * hash table. 35 * 36 * quiesced_regions: These regions have been spun down, ready 37 * for recovery. rh_recovery_start() will remove regions from 38 * this list and hand them to kmirrord, which will schedule the 39 * recovery io with kcopyd. 40 * 41 * recovered_regions: Regions that kcopyd has successfully 42 * recovered. dm_rh_update_states() will now schedule any delayed 43 * io, up the recovery_count, and remove the region from the 44 * hash. 45 * 46 * There are 2 locks: 47 * A rw spin lock 'hash_lock' protects just the hash table, 48 * this is never held in write mode from interrupt context, 49 * which I believe means that we only have to disable irqs when 50 * doing a write lock. 51 * 52 * An ordinary spin lock 'region_lock' that protects the three 53 * lists in the region_hash, with the 'state', 'list' and 54 * 'delayed_bios' fields of the regions. This is used from irq 55 * context, so all other uses will have to suspend local irqs. 56 *---------------------------------------------------------------*/ 57 struct dm_region_hash { 58 uint32_t region_size; 59 unsigned region_shift; 60 61 /* holds persistent region state */ 62 struct dm_dirty_log *log; 63 64 /* hash table */ 65 rwlock_t hash_lock; 66 mempool_t *region_pool; 67 unsigned mask; 68 unsigned nr_buckets; 69 unsigned prime; 70 unsigned shift; 71 struct list_head *buckets; 72 73 unsigned max_recovery; /* Max # of regions to recover in parallel */ 74 75 spinlock_t region_lock; 76 atomic_t recovery_in_flight; 77 struct semaphore recovery_count; 78 struct list_head clean_regions; 79 struct list_head quiesced_regions; 80 struct list_head recovered_regions; 81 struct list_head failed_recovered_regions; 82 83 /* 84 * If there was a flush failure no regions can be marked clean. 85 */ 86 int flush_failure; 87 88 void *context; 89 sector_t target_begin; 90 91 /* Callback function to schedule bios writes */ 92 void (*dispatch_bios)(void *context, struct bio_list *bios); 93 94 /* Callback function to wakeup callers worker thread. */ 95 void (*wakeup_workers)(void *context); 96 97 /* Callback function to wakeup callers recovery waiters. */ 98 void (*wakeup_all_recovery_waiters)(void *context); 99 }; 100 101 struct dm_region { 102 struct dm_region_hash *rh; /* FIXME: can we get rid of this ? */ 103 region_t key; 104 int state; 105 106 struct list_head hash_list; 107 struct list_head list; 108 109 atomic_t pending; 110 struct bio_list delayed_bios; 111 }; 112 113 /* 114 * Conversion fns 115 */ 116 static region_t dm_rh_sector_to_region(struct dm_region_hash *rh, sector_t sector) 117 { 118 return sector >> rh->region_shift; 119 } 120 121 sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region) 122 { 123 return region << rh->region_shift; 124 } 125 EXPORT_SYMBOL_GPL(dm_rh_region_to_sector); 126 127 region_t dm_rh_bio_to_region(struct dm_region_hash *rh, struct bio *bio) 128 { 129 return dm_rh_sector_to_region(rh, bio->bi_iter.bi_sector - 130 rh->target_begin); 131 } 132 EXPORT_SYMBOL_GPL(dm_rh_bio_to_region); 133 134 void *dm_rh_region_context(struct dm_region *reg) 135 { 136 return reg->rh->context; 137 } 138 EXPORT_SYMBOL_GPL(dm_rh_region_context); 139 140 region_t dm_rh_get_region_key(struct dm_region *reg) 141 { 142 return reg->key; 143 } 144 EXPORT_SYMBOL_GPL(dm_rh_get_region_key); 145 146 sector_t dm_rh_get_region_size(struct dm_region_hash *rh) 147 { 148 return rh->region_size; 149 } 150 EXPORT_SYMBOL_GPL(dm_rh_get_region_size); 151 152 /* 153 * FIXME: shall we pass in a structure instead of all these args to 154 * dm_region_hash_create()???? 155 */ 156 #define RH_HASH_MULT 2654435387U 157 #define RH_HASH_SHIFT 12 158 159 #define MIN_REGIONS 64 160 struct dm_region_hash *dm_region_hash_create( 161 void *context, void (*dispatch_bios)(void *context, 162 struct bio_list *bios), 163 void (*wakeup_workers)(void *context), 164 void (*wakeup_all_recovery_waiters)(void *context), 165 sector_t target_begin, unsigned max_recovery, 166 struct dm_dirty_log *log, uint32_t region_size, 167 region_t nr_regions) 168 { 169 struct dm_region_hash *rh; 170 unsigned nr_buckets, max_buckets; 171 size_t i; 172 173 /* 174 * Calculate a suitable number of buckets for our hash 175 * table. 176 */ 177 max_buckets = nr_regions >> 6; 178 for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1) 179 ; 180 nr_buckets >>= 1; 181 182 rh = kmalloc(sizeof(*rh), GFP_KERNEL); 183 if (!rh) { 184 DMERR("unable to allocate region hash memory"); 185 return ERR_PTR(-ENOMEM); 186 } 187 188 rh->context = context; 189 rh->dispatch_bios = dispatch_bios; 190 rh->wakeup_workers = wakeup_workers; 191 rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters; 192 rh->target_begin = target_begin; 193 rh->max_recovery = max_recovery; 194 rh->log = log; 195 rh->region_size = region_size; 196 rh->region_shift = ffs(region_size) - 1; 197 rwlock_init(&rh->hash_lock); 198 rh->mask = nr_buckets - 1; 199 rh->nr_buckets = nr_buckets; 200 201 rh->shift = RH_HASH_SHIFT; 202 rh->prime = RH_HASH_MULT; 203 204 rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets)); 205 if (!rh->buckets) { 206 DMERR("unable to allocate region hash bucket memory"); 207 kfree(rh); 208 return ERR_PTR(-ENOMEM); 209 } 210 211 for (i = 0; i < nr_buckets; i++) 212 INIT_LIST_HEAD(rh->buckets + i); 213 214 spin_lock_init(&rh->region_lock); 215 sema_init(&rh->recovery_count, 0); 216 atomic_set(&rh->recovery_in_flight, 0); 217 INIT_LIST_HEAD(&rh->clean_regions); 218 INIT_LIST_HEAD(&rh->quiesced_regions); 219 INIT_LIST_HEAD(&rh->recovered_regions); 220 INIT_LIST_HEAD(&rh->failed_recovered_regions); 221 rh->flush_failure = 0; 222 223 rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS, 224 sizeof(struct dm_region)); 225 if (!rh->region_pool) { 226 vfree(rh->buckets); 227 kfree(rh); 228 rh = ERR_PTR(-ENOMEM); 229 } 230 231 return rh; 232 } 233 EXPORT_SYMBOL_GPL(dm_region_hash_create); 234 235 void dm_region_hash_destroy(struct dm_region_hash *rh) 236 { 237 unsigned h; 238 struct dm_region *reg, *nreg; 239 240 BUG_ON(!list_empty(&rh->quiesced_regions)); 241 for (h = 0; h < rh->nr_buckets; h++) { 242 list_for_each_entry_safe(reg, nreg, rh->buckets + h, 243 hash_list) { 244 BUG_ON(atomic_read(®->pending)); 245 mempool_free(reg, rh->region_pool); 246 } 247 } 248 249 if (rh->log) 250 dm_dirty_log_destroy(rh->log); 251 252 if (rh->region_pool) 253 mempool_destroy(rh->region_pool); 254 255 vfree(rh->buckets); 256 kfree(rh); 257 } 258 EXPORT_SYMBOL_GPL(dm_region_hash_destroy); 259 260 struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh) 261 { 262 return rh->log; 263 } 264 EXPORT_SYMBOL_GPL(dm_rh_dirty_log); 265 266 static unsigned rh_hash(struct dm_region_hash *rh, region_t region) 267 { 268 return (unsigned) ((region * rh->prime) >> rh->shift) & rh->mask; 269 } 270 271 static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region) 272 { 273 struct dm_region *reg; 274 struct list_head *bucket = rh->buckets + rh_hash(rh, region); 275 276 list_for_each_entry(reg, bucket, hash_list) 277 if (reg->key == region) 278 return reg; 279 280 return NULL; 281 } 282 283 static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg) 284 { 285 list_add(®->hash_list, rh->buckets + rh_hash(rh, reg->key)); 286 } 287 288 static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region) 289 { 290 struct dm_region *reg, *nreg; 291 292 nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC); 293 if (unlikely(!nreg)) 294 nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL); 295 296 nreg->state = rh->log->type->in_sync(rh->log, region, 1) ? 297 DM_RH_CLEAN : DM_RH_NOSYNC; 298 nreg->rh = rh; 299 nreg->key = region; 300 INIT_LIST_HEAD(&nreg->list); 301 atomic_set(&nreg->pending, 0); 302 bio_list_init(&nreg->delayed_bios); 303 304 write_lock_irq(&rh->hash_lock); 305 reg = __rh_lookup(rh, region); 306 if (reg) 307 /* We lost the race. */ 308 mempool_free(nreg, rh->region_pool); 309 else { 310 __rh_insert(rh, nreg); 311 if (nreg->state == DM_RH_CLEAN) { 312 spin_lock(&rh->region_lock); 313 list_add(&nreg->list, &rh->clean_regions); 314 spin_unlock(&rh->region_lock); 315 } 316 317 reg = nreg; 318 } 319 write_unlock_irq(&rh->hash_lock); 320 321 return reg; 322 } 323 324 static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region) 325 { 326 struct dm_region *reg; 327 328 reg = __rh_lookup(rh, region); 329 if (!reg) { 330 read_unlock(&rh->hash_lock); 331 reg = __rh_alloc(rh, region); 332 read_lock(&rh->hash_lock); 333 } 334 335 return reg; 336 } 337 338 int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block) 339 { 340 int r; 341 struct dm_region *reg; 342 343 read_lock(&rh->hash_lock); 344 reg = __rh_lookup(rh, region); 345 read_unlock(&rh->hash_lock); 346 347 if (reg) 348 return reg->state; 349 350 /* 351 * The region wasn't in the hash, so we fall back to the 352 * dirty log. 353 */ 354 r = rh->log->type->in_sync(rh->log, region, may_block); 355 356 /* 357 * Any error from the dirty log (eg. -EWOULDBLOCK) gets 358 * taken as a DM_RH_NOSYNC 359 */ 360 return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC; 361 } 362 EXPORT_SYMBOL_GPL(dm_rh_get_state); 363 364 static void complete_resync_work(struct dm_region *reg, int success) 365 { 366 struct dm_region_hash *rh = reg->rh; 367 368 rh->log->type->set_region_sync(rh->log, reg->key, success); 369 370 /* 371 * Dispatch the bios before we call 'wake_up_all'. 372 * This is important because if we are suspending, 373 * we want to know that recovery is complete and 374 * the work queue is flushed. If we wake_up_all 375 * before we dispatch_bios (queue bios and call wake()), 376 * then we risk suspending before the work queue 377 * has been properly flushed. 378 */ 379 rh->dispatch_bios(rh->context, ®->delayed_bios); 380 if (atomic_dec_and_test(&rh->recovery_in_flight)) 381 rh->wakeup_all_recovery_waiters(rh->context); 382 up(&rh->recovery_count); 383 } 384 385 /* dm_rh_mark_nosync 386 * @ms 387 * @bio 388 * 389 * The bio was written on some mirror(s) but failed on other mirror(s). 390 * We can successfully endio the bio but should avoid the region being 391 * marked clean by setting the state DM_RH_NOSYNC. 392 * 393 * This function is _not_ safe in interrupt context! 394 */ 395 void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio) 396 { 397 unsigned long flags; 398 struct dm_dirty_log *log = rh->log; 399 struct dm_region *reg; 400 region_t region = dm_rh_bio_to_region(rh, bio); 401 int recovering = 0; 402 403 if (bio->bi_rw & REQ_FLUSH) { 404 rh->flush_failure = 1; 405 return; 406 } 407 408 if (bio->bi_rw & REQ_DISCARD) 409 return; 410 411 /* We must inform the log that the sync count has changed. */ 412 log->type->set_region_sync(log, region, 0); 413 414 read_lock(&rh->hash_lock); 415 reg = __rh_find(rh, region); 416 read_unlock(&rh->hash_lock); 417 418 /* region hash entry should exist because write was in-flight */ 419 BUG_ON(!reg); 420 BUG_ON(!list_empty(®->list)); 421 422 spin_lock_irqsave(&rh->region_lock, flags); 423 /* 424 * Possible cases: 425 * 1) DM_RH_DIRTY 426 * 2) DM_RH_NOSYNC: was dirty, other preceding writes failed 427 * 3) DM_RH_RECOVERING: flushing pending writes 428 * Either case, the region should have not been connected to list. 429 */ 430 recovering = (reg->state == DM_RH_RECOVERING); 431 reg->state = DM_RH_NOSYNC; 432 BUG_ON(!list_empty(®->list)); 433 spin_unlock_irqrestore(&rh->region_lock, flags); 434 435 if (recovering) 436 complete_resync_work(reg, 0); 437 } 438 EXPORT_SYMBOL_GPL(dm_rh_mark_nosync); 439 440 void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled) 441 { 442 struct dm_region *reg, *next; 443 444 LIST_HEAD(clean); 445 LIST_HEAD(recovered); 446 LIST_HEAD(failed_recovered); 447 448 /* 449 * Quickly grab the lists. 450 */ 451 write_lock_irq(&rh->hash_lock); 452 spin_lock(&rh->region_lock); 453 if (!list_empty(&rh->clean_regions)) { 454 list_splice_init(&rh->clean_regions, &clean); 455 456 list_for_each_entry(reg, &clean, list) 457 list_del(®->hash_list); 458 } 459 460 if (!list_empty(&rh->recovered_regions)) { 461 list_splice_init(&rh->recovered_regions, &recovered); 462 463 list_for_each_entry(reg, &recovered, list) 464 list_del(®->hash_list); 465 } 466 467 if (!list_empty(&rh->failed_recovered_regions)) { 468 list_splice_init(&rh->failed_recovered_regions, 469 &failed_recovered); 470 471 list_for_each_entry(reg, &failed_recovered, list) 472 list_del(®->hash_list); 473 } 474 475 spin_unlock(&rh->region_lock); 476 write_unlock_irq(&rh->hash_lock); 477 478 /* 479 * All the regions on the recovered and clean lists have 480 * now been pulled out of the system, so no need to do 481 * any more locking. 482 */ 483 list_for_each_entry_safe(reg, next, &recovered, list) { 484 rh->log->type->clear_region(rh->log, reg->key); 485 complete_resync_work(reg, 1); 486 mempool_free(reg, rh->region_pool); 487 } 488 489 list_for_each_entry_safe(reg, next, &failed_recovered, list) { 490 complete_resync_work(reg, errors_handled ? 0 : 1); 491 mempool_free(reg, rh->region_pool); 492 } 493 494 list_for_each_entry_safe(reg, next, &clean, list) { 495 rh->log->type->clear_region(rh->log, reg->key); 496 mempool_free(reg, rh->region_pool); 497 } 498 499 rh->log->type->flush(rh->log); 500 } 501 EXPORT_SYMBOL_GPL(dm_rh_update_states); 502 503 static void rh_inc(struct dm_region_hash *rh, region_t region) 504 { 505 struct dm_region *reg; 506 507 read_lock(&rh->hash_lock); 508 reg = __rh_find(rh, region); 509 510 spin_lock_irq(&rh->region_lock); 511 atomic_inc(®->pending); 512 513 if (reg->state == DM_RH_CLEAN) { 514 reg->state = DM_RH_DIRTY; 515 list_del_init(®->list); /* take off the clean list */ 516 spin_unlock_irq(&rh->region_lock); 517 518 rh->log->type->mark_region(rh->log, reg->key); 519 } else 520 spin_unlock_irq(&rh->region_lock); 521 522 523 read_unlock(&rh->hash_lock); 524 } 525 526 void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios) 527 { 528 struct bio *bio; 529 530 for (bio = bios->head; bio; bio = bio->bi_next) { 531 if (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD)) 532 continue; 533 rh_inc(rh, dm_rh_bio_to_region(rh, bio)); 534 } 535 } 536 EXPORT_SYMBOL_GPL(dm_rh_inc_pending); 537 538 void dm_rh_dec(struct dm_region_hash *rh, region_t region) 539 { 540 unsigned long flags; 541 struct dm_region *reg; 542 int should_wake = 0; 543 544 read_lock(&rh->hash_lock); 545 reg = __rh_lookup(rh, region); 546 read_unlock(&rh->hash_lock); 547 548 spin_lock_irqsave(&rh->region_lock, flags); 549 if (atomic_dec_and_test(®->pending)) { 550 /* 551 * There is no pending I/O for this region. 552 * We can move the region to corresponding list for next action. 553 * At this point, the region is not yet connected to any list. 554 * 555 * If the state is DM_RH_NOSYNC, the region should be kept off 556 * from clean list. 557 * The hash entry for DM_RH_NOSYNC will remain in memory 558 * until the region is recovered or the map is reloaded. 559 */ 560 561 /* do nothing for DM_RH_NOSYNC */ 562 if (unlikely(rh->flush_failure)) { 563 /* 564 * If a write flush failed some time ago, we 565 * don't know whether or not this write made it 566 * to the disk, so we must resync the device. 567 */ 568 reg->state = DM_RH_NOSYNC; 569 } else if (reg->state == DM_RH_RECOVERING) { 570 list_add_tail(®->list, &rh->quiesced_regions); 571 } else if (reg->state == DM_RH_DIRTY) { 572 reg->state = DM_RH_CLEAN; 573 list_add(®->list, &rh->clean_regions); 574 } 575 should_wake = 1; 576 } 577 spin_unlock_irqrestore(&rh->region_lock, flags); 578 579 if (should_wake) 580 rh->wakeup_workers(rh->context); 581 } 582 EXPORT_SYMBOL_GPL(dm_rh_dec); 583 584 /* 585 * Starts quiescing a region in preparation for recovery. 586 */ 587 static int __rh_recovery_prepare(struct dm_region_hash *rh) 588 { 589 int r; 590 region_t region; 591 struct dm_region *reg; 592 593 /* 594 * Ask the dirty log what's next. 595 */ 596 r = rh->log->type->get_resync_work(rh->log, ®ion); 597 if (r <= 0) 598 return r; 599 600 /* 601 * Get this region, and start it quiescing by setting the 602 * recovering flag. 603 */ 604 read_lock(&rh->hash_lock); 605 reg = __rh_find(rh, region); 606 read_unlock(&rh->hash_lock); 607 608 spin_lock_irq(&rh->region_lock); 609 reg->state = DM_RH_RECOVERING; 610 611 /* Already quiesced ? */ 612 if (atomic_read(®->pending)) 613 list_del_init(®->list); 614 else 615 list_move(®->list, &rh->quiesced_regions); 616 617 spin_unlock_irq(&rh->region_lock); 618 619 return 1; 620 } 621 622 void dm_rh_recovery_prepare(struct dm_region_hash *rh) 623 { 624 /* Extra reference to avoid race with dm_rh_stop_recovery */ 625 atomic_inc(&rh->recovery_in_flight); 626 627 while (!down_trylock(&rh->recovery_count)) { 628 atomic_inc(&rh->recovery_in_flight); 629 if (__rh_recovery_prepare(rh) <= 0) { 630 atomic_dec(&rh->recovery_in_flight); 631 up(&rh->recovery_count); 632 break; 633 } 634 } 635 636 /* Drop the extra reference */ 637 if (atomic_dec_and_test(&rh->recovery_in_flight)) 638 rh->wakeup_all_recovery_waiters(rh->context); 639 } 640 EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare); 641 642 /* 643 * Returns any quiesced regions. 644 */ 645 struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh) 646 { 647 struct dm_region *reg = NULL; 648 649 spin_lock_irq(&rh->region_lock); 650 if (!list_empty(&rh->quiesced_regions)) { 651 reg = list_entry(rh->quiesced_regions.next, 652 struct dm_region, list); 653 list_del_init(®->list); /* remove from the quiesced list */ 654 } 655 spin_unlock_irq(&rh->region_lock); 656 657 return reg; 658 } 659 EXPORT_SYMBOL_GPL(dm_rh_recovery_start); 660 661 void dm_rh_recovery_end(struct dm_region *reg, int success) 662 { 663 struct dm_region_hash *rh = reg->rh; 664 665 spin_lock_irq(&rh->region_lock); 666 if (success) 667 list_add(®->list, ®->rh->recovered_regions); 668 else 669 list_add(®->list, ®->rh->failed_recovered_regions); 670 671 spin_unlock_irq(&rh->region_lock); 672 673 rh->wakeup_workers(rh->context); 674 } 675 EXPORT_SYMBOL_GPL(dm_rh_recovery_end); 676 677 /* Return recovery in flight count. */ 678 int dm_rh_recovery_in_flight(struct dm_region_hash *rh) 679 { 680 return atomic_read(&rh->recovery_in_flight); 681 } 682 EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight); 683 684 int dm_rh_flush(struct dm_region_hash *rh) 685 { 686 return rh->log->type->flush(rh->log); 687 } 688 EXPORT_SYMBOL_GPL(dm_rh_flush); 689 690 void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio) 691 { 692 struct dm_region *reg; 693 694 read_lock(&rh->hash_lock); 695 reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio)); 696 bio_list_add(®->delayed_bios, bio); 697 read_unlock(&rh->hash_lock); 698 } 699 EXPORT_SYMBOL_GPL(dm_rh_delay); 700 701 void dm_rh_stop_recovery(struct dm_region_hash *rh) 702 { 703 int i; 704 705 /* wait for any recovering regions */ 706 for (i = 0; i < rh->max_recovery; i++) 707 down(&rh->recovery_count); 708 } 709 EXPORT_SYMBOL_GPL(dm_rh_stop_recovery); 710 711 void dm_rh_start_recovery(struct dm_region_hash *rh) 712 { 713 int i; 714 715 for (i = 0; i < rh->max_recovery; i++) 716 up(&rh->recovery_count); 717 718 rh->wakeup_workers(rh->context); 719 } 720 EXPORT_SYMBOL_GPL(dm_rh_start_recovery); 721 722 MODULE_DESCRIPTION(DM_NAME " region hash"); 723 MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@redhat.com>"); 724 MODULE_LICENSE("GPL"); 725