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