1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * Copyright (C) 2003 Sistina Software Limited. 4 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved. 5 * 6 * This file is released under the GPL. 7 */ 8 9#include <linux/dm-dirty-log.h> 10#include <linux/dm-region-hash.h> 11 12#include <linux/ctype.h> 13#include <linux/init.h> 14#include <linux/module.h> 15#include <linux/slab.h> 16#include <linux/vmalloc.h> 17 18#include "dm.h" 19 20#define DM_MSG_PREFIX "region hash" 21 22/* 23 *------------------------------------------------------------------ 24 * Region hash 25 * 26 * The mirror splits itself up into discrete regions. Each 27 * region can be in one of three states: clean, dirty, 28 * nosync. There is no need to put clean regions in the hash. 29 * 30 * In addition to being present in the hash table a region _may_ 31 * be present on one of three lists. 32 * 33 * clean_regions: Regions on this list have no io pending to 34 * them, they are in sync, we are no longer interested in them, 35 * they are dull. dm_rh_update_states() will remove them from the 36 * hash table. 37 * 38 * quiesced_regions: These regions have been spun down, ready 39 * for recovery. rh_recovery_start() will remove regions from 40 * this list and hand them to kmirrord, which will schedule the 41 * recovery io with kcopyd. 42 * 43 * recovered_regions: Regions that kcopyd has successfully 44 * recovered. dm_rh_update_states() will now schedule any delayed 45 * io, up the recovery_count, and remove the region from the 46 * hash. 47 * 48 * There are 2 locks: 49 * A rw spin lock 'hash_lock' protects just the hash table, 50 * this is never held in write mode from interrupt context, 51 * which I believe means that we only have to disable irqs when 52 * doing a write lock. 53 * 54 * An ordinary spin lock 'region_lock' that protects the three 55 * lists in the region_hash, with the 'state', 'list' and 56 * 'delayed_bios' fields of the regions. This is used from irq 57 * context, so all other uses will have to suspend local irqs. 58 *------------------------------------------------------------------ 59 */ 60struct dm_region_hash { 61 uint32_t region_size; 62 unsigned int region_shift; 63 64 /* holds persistent region state */ 65 struct dm_dirty_log *log; 66 67 /* hash table */ 68 rwlock_t hash_lock; 69 unsigned int mask; 70 unsigned int nr_buckets; 71 unsigned int prime; 72 unsigned int shift; 73 struct list_head *buckets; 74 75 /* 76 * If there was a flush failure no regions can be marked clean. 77 */ 78 int flush_failure; 79 80 unsigned int max_recovery; /* Max # of regions to recover in parallel */ 81 82 spinlock_t region_lock; 83 atomic_t recovery_in_flight; 84 struct list_head clean_regions; 85 struct list_head quiesced_regions; 86 struct list_head recovered_regions; 87 struct list_head failed_recovered_regions; 88 struct semaphore recovery_count; 89 90 mempool_t region_pool; 91 92 void *context; 93 sector_t target_begin; 94 95 /* Callback function to schedule bios writes */ 96 void (*dispatch_bios)(void *context, struct bio_list *bios); 97 98 /* Callback function to wakeup callers worker thread. */ 99 void (*wakeup_workers)(void *context); 100 101 /* Callback function to wakeup callers recovery waiters. */ 102 void (*wakeup_all_recovery_waiters)(void *context); 103}; 104 105struct dm_region { 106 struct dm_region_hash *rh; /* FIXME: can we get rid of this ? */ 107 region_t key; 108 int state; 109 110 struct list_head hash_list; 111 struct list_head list; 112 113 atomic_t pending; 114 struct bio_list delayed_bios; 115}; 116 117/* 118 * Conversion fns 119 */ 120static region_t dm_rh_sector_to_region(struct dm_region_hash *rh, sector_t sector) 121{ 122 return sector >> rh->region_shift; 123} 124 125sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region) 126{ 127 return region << rh->region_shift; 128} 129EXPORT_SYMBOL_GPL(dm_rh_region_to_sector); 130 131region_t dm_rh_bio_to_region(struct dm_region_hash *rh, struct bio *bio) 132{ 133 return dm_rh_sector_to_region(rh, bio->bi_iter.bi_sector - 134 rh->target_begin); 135} 136EXPORT_SYMBOL_GPL(dm_rh_bio_to_region); 137 138void *dm_rh_region_context(struct dm_region *reg) 139{ 140 return reg->rh->context; 141} 142EXPORT_SYMBOL_GPL(dm_rh_region_context); 143 144region_t dm_rh_get_region_key(struct dm_region *reg) 145{ 146 return reg->key; 147} 148EXPORT_SYMBOL_GPL(dm_rh_get_region_key); 149 150sector_t dm_rh_get_region_size(struct dm_region_hash *rh) 151{ 152 return rh->region_size; 153} 154EXPORT_SYMBOL_GPL(dm_rh_get_region_size); 155 156/* 157 * FIXME: shall we pass in a structure instead of all these args to 158 * dm_region_hash_create()???? 159 */ 160#define RH_HASH_MULT 2654435387U 161#define RH_HASH_SHIFT 12 162 163#define MIN_REGIONS 64 164struct dm_region_hash *dm_region_hash_create( 165 void *context, void (*dispatch_bios)(void *context, 166 struct bio_list *bios), 167 void (*wakeup_workers)(void *context), 168 void (*wakeup_all_recovery_waiters)(void *context), 169 sector_t target_begin, unsigned int max_recovery, 170 struct dm_dirty_log *log, uint32_t region_size, 171 region_t nr_regions) 172{ 173 struct dm_region_hash *rh; 174 unsigned int nr_buckets, max_buckets; 175 size_t i; 176 int ret; 177 178 /* 179 * Calculate a suitable number of buckets for our hash 180 * table. 181 */ 182 max_buckets = nr_regions >> 6; 183 for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1) 184 ; 185 nr_buckets >>= 1; 186 187 rh = kzalloc(sizeof(*rh), GFP_KERNEL); 188 if (!rh) { 189 DMERR("unable to allocate region hash memory"); 190 return ERR_PTR(-ENOMEM); 191 } 192 193 rh->context = context; 194 rh->dispatch_bios = dispatch_bios; 195 rh->wakeup_workers = wakeup_workers; 196 rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters; 197 rh->target_begin = target_begin; 198 rh->max_recovery = max_recovery; 199 rh->log = log; 200 rh->region_size = region_size; 201 rh->region_shift = __ffs(region_size); 202 rwlock_init(&rh->hash_lock); 203 rh->mask = nr_buckets - 1; 204 rh->nr_buckets = nr_buckets; 205 206 rh->shift = RH_HASH_SHIFT; 207 rh->prime = RH_HASH_MULT; 208 209 rh->buckets = vmalloc(array_size(nr_buckets, sizeof(*rh->buckets))); 210 if (!rh->buckets) { 211 DMERR("unable to allocate region hash bucket memory"); 212 kfree(rh); 213 return ERR_PTR(-ENOMEM); 214 } 215 216 for (i = 0; i < nr_buckets; i++) 217 INIT_LIST_HEAD(rh->buckets + i); 218 219 spin_lock_init(&rh->region_lock); 220 sema_init(&rh->recovery_count, 0); 221 atomic_set(&rh->recovery_in_flight, 0); 222 INIT_LIST_HEAD(&rh->clean_regions); 223 INIT_LIST_HEAD(&rh->quiesced_regions); 224 INIT_LIST_HEAD(&rh->recovered_regions); 225 INIT_LIST_HEAD(&rh->failed_recovered_regions); 226 rh->flush_failure = 0; 227 228 ret = mempool_init_kmalloc_pool(&rh->region_pool, MIN_REGIONS, 229 sizeof(struct dm_region)); 230 if (ret) { 231 vfree(rh->buckets); 232 kfree(rh); 233 rh = ERR_PTR(-ENOMEM); 234 } 235 236 return rh; 237} 238EXPORT_SYMBOL_GPL(dm_region_hash_create); 239 240void dm_region_hash_destroy(struct dm_region_hash *rh) 241{ 242 unsigned int h; 243 struct dm_region *reg, *nreg; 244 245 BUG_ON(!list_empty(&rh->quiesced_regions)); 246 for (h = 0; h < rh->nr_buckets; h++) { 247 list_for_each_entry_safe(reg, nreg, rh->buckets + h, 248 hash_list) { 249 BUG_ON(atomic_read(®->pending)); 250 mempool_free(reg, &rh->region_pool); 251 } 252 } 253 254 if (rh->log) 255 dm_dirty_log_destroy(rh->log); 256 257 mempool_exit(&rh->region_pool); 258 vfree(rh->buckets); 259 kfree(rh); 260} 261EXPORT_SYMBOL_GPL(dm_region_hash_destroy); 262 263struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh) 264{ 265 return rh->log; 266} 267EXPORT_SYMBOL_GPL(dm_rh_dirty_log); 268 269static unsigned int rh_hash(struct dm_region_hash *rh, region_t region) 270{ 271 return (unsigned int) ((region * rh->prime) >> rh->shift) & rh->mask; 272} 273 274static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region) 275{ 276 struct dm_region *reg; 277 struct list_head *bucket = rh->buckets + rh_hash(rh, region); 278 279 list_for_each_entry(reg, bucket, hash_list) 280 if (reg->key == region) 281 return reg; 282 283 return NULL; 284} 285 286static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg) 287{ 288 list_add(®->hash_list, rh->buckets + rh_hash(rh, reg->key)); 289} 290 291static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region) 292{ 293 struct dm_region *reg, *nreg; 294 295 nreg = mempool_alloc(&rh->region_pool, GFP_ATOMIC); 296 if (unlikely(!nreg)) 297 nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL); 298 299 nreg->state = rh->log->type->in_sync(rh->log, region, 1) ? 300 DM_RH_CLEAN : DM_RH_NOSYNC; 301 nreg->rh = rh; 302 nreg->key = region; 303 INIT_LIST_HEAD(&nreg->list); 304 atomic_set(&nreg->pending, 0); 305 bio_list_init(&nreg->delayed_bios); 306 307 write_lock_irq(&rh->hash_lock); 308 reg = __rh_lookup(rh, region); 309 if (reg) 310 /* We lost the race. */ 311 mempool_free(nreg, &rh->region_pool); 312 else { 313 __rh_insert(rh, nreg); 314 if (nreg->state == DM_RH_CLEAN) { 315 spin_lock(&rh->region_lock); 316 list_add(&nreg->list, &rh->clean_regions); 317 spin_unlock(&rh->region_lock); 318 } 319 320 reg = nreg; 321 } 322 write_unlock_irq(&rh->hash_lock); 323 324 return reg; 325} 326 327static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region) 328{ 329 struct dm_region *reg; 330 331 reg = __rh_lookup(rh, region); 332 if (!reg) { 333 read_unlock(&rh->hash_lock); 334 reg = __rh_alloc(rh, region); 335 read_lock(&rh->hash_lock); 336 } 337 338 return reg; 339} 340 341int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block) 342{ 343 int r; 344 struct dm_region *reg; 345 346 read_lock(&rh->hash_lock); 347 reg = __rh_lookup(rh, region); 348 read_unlock(&rh->hash_lock); 349 350 if (reg) 351 return reg->state; 352 353 /* 354 * The region wasn't in the hash, so we fall back to the 355 * dirty log. 356 */ 357 r = rh->log->type->in_sync(rh->log, region, may_block); 358 359 /* 360 * Any error from the dirty log (eg. -EWOULDBLOCK) gets 361 * taken as a DM_RH_NOSYNC 362 */ 363 return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC; 364} 365EXPORT_SYMBOL_GPL(dm_rh_get_state); 366 367static void complete_resync_work(struct dm_region *reg, int success) 368{ 369 struct dm_region_hash *rh = reg->rh; 370 371 rh->log->type->set_region_sync(rh->log, reg->key, success); 372 373 /* 374 * Dispatch the bios before we call 'wake_up_all'. 375 * This is important because if we are suspending, 376 * we want to know that recovery is complete and 377 * the work queue is flushed. If we wake_up_all 378 * before we dispatch_bios (queue bios and call wake()), 379 * then we risk suspending before the work queue 380 * has been properly flushed. 381 */ 382 rh->dispatch_bios(rh->context, ®->delayed_bios); 383 if (atomic_dec_and_test(&rh->recovery_in_flight)) 384 rh->wakeup_all_recovery_waiters(rh->context); 385 up(&rh->recovery_count); 386} 387 388/* dm_rh_mark_nosync 389 * @ms 390 * @bio 391 * 392 * The bio was written on some mirror(s) but failed on other mirror(s). 393 * We can successfully endio the bio but should avoid the region being 394 * marked clean by setting the state DM_RH_NOSYNC. 395 * 396 * This function is _not_ safe in interrupt context! 397 */ 398void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio) 399{ 400 unsigned long flags; 401 struct dm_dirty_log *log = rh->log; 402 struct dm_region *reg; 403 region_t region = dm_rh_bio_to_region(rh, bio); 404 int recovering = 0; 405 406 if (bio->bi_opf & REQ_PREFLUSH) { 407 rh->flush_failure = 1; 408 return; 409 } 410 411 if (bio_op(bio) == REQ_OP_DISCARD) 412 return; 413 414 /* We must inform the log that the sync count has changed. */ 415 log->type->set_region_sync(log, region, 0); 416 417 read_lock(&rh->hash_lock); 418 reg = __rh_find(rh, region); 419 read_unlock(&rh->hash_lock); 420 421 /* region hash entry should exist because write was in-flight */ 422 BUG_ON(!reg); 423 BUG_ON(!list_empty(®->list)); 424 425 spin_lock_irqsave(&rh->region_lock, flags); 426 /* 427 * Possible cases: 428 * 1) DM_RH_DIRTY 429 * 2) DM_RH_NOSYNC: was dirty, other preceding writes failed 430 * 3) DM_RH_RECOVERING: flushing pending writes 431 * Either case, the region should have not been connected to list. 432 */ 433 recovering = (reg->state == DM_RH_RECOVERING); 434 reg->state = DM_RH_NOSYNC; 435 BUG_ON(!list_empty(®->list)); 436 spin_unlock_irqrestore(&rh->region_lock, flags); 437 438 if (recovering) 439 complete_resync_work(reg, 0); 440} 441EXPORT_SYMBOL_GPL(dm_rh_mark_nosync); 442 443void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled) 444{ 445 struct dm_region *reg, *next; 446 447 LIST_HEAD(clean); 448 LIST_HEAD(recovered); 449 LIST_HEAD(failed_recovered); 450 451 /* 452 * Quickly grab the lists. 453 */ 454 write_lock_irq(&rh->hash_lock); 455 spin_lock(&rh->region_lock); 456 if (!list_empty(&rh->clean_regions)) { 457 list_splice_init(&rh->clean_regions, &clean); 458 459 list_for_each_entry(reg, &clean, list) 460 list_del(®->hash_list); 461 } 462 463 if (!list_empty(&rh->recovered_regions)) { 464 list_splice_init(&rh->recovered_regions, &recovered); 465 466 list_for_each_entry(reg, &recovered, list) 467 list_del(®->hash_list); 468 } 469 470 if (!list_empty(&rh->failed_recovered_regions)) { 471 list_splice_init(&rh->failed_recovered_regions, 472 &failed_recovered); 473 474 list_for_each_entry(reg, &failed_recovered, list) 475 list_del(®->hash_list); 476 } 477 478 spin_unlock(&rh->region_lock); 479 write_unlock_irq(&rh->hash_lock); 480 481 /* 482 * All the regions on the recovered and clean lists have 483 * now been pulled out of the system, so no need to do 484 * any more locking. 485 */ 486 list_for_each_entry_safe(reg, next, &recovered, list) { 487 rh->log->type->clear_region(rh->log, reg->key); 488 complete_resync_work(reg, 1); 489 mempool_free(reg, &rh->region_pool); 490 } 491 492 list_for_each_entry_safe(reg, next, &failed_recovered, list) { 493 complete_resync_work(reg, errors_handled ? 0 : 1); 494 mempool_free(reg, &rh->region_pool); 495 } 496 497 list_for_each_entry_safe(reg, next, &clean, list) { 498 rh->log->type->clear_region(rh->log, reg->key); 499 mempool_free(reg, &rh->region_pool); 500 } 501 502 rh->log->type->flush(rh->log); 503} 504EXPORT_SYMBOL_GPL(dm_rh_update_states); 505 506static void rh_inc(struct dm_region_hash *rh, region_t region) 507{ 508 struct dm_region *reg; 509 510 read_lock(&rh->hash_lock); 511 reg = __rh_find(rh, region); 512 513 spin_lock_irq(&rh->region_lock); 514 atomic_inc(®->pending); 515 516 if (reg->state == DM_RH_CLEAN) { 517 reg->state = DM_RH_DIRTY; 518 list_del_init(®->list); /* take off the clean list */ 519 spin_unlock_irq(&rh->region_lock); 520 521 rh->log->type->mark_region(rh->log, reg->key); 522 } else 523 spin_unlock_irq(&rh->region_lock); 524 525 526 read_unlock(&rh->hash_lock); 527} 528 529void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios) 530{ 531 struct bio *bio; 532 533 for (bio = bios->head; bio; bio = bio->bi_next) { 534 if (bio->bi_opf & REQ_PREFLUSH || bio_op(bio) == REQ_OP_DISCARD) 535 continue; 536 rh_inc(rh, dm_rh_bio_to_region(rh, bio)); 537 } 538} 539EXPORT_SYMBOL_GPL(dm_rh_inc_pending); 540 541void dm_rh_dec(struct dm_region_hash *rh, region_t region) 542{ 543 unsigned long flags; 544 struct dm_region *reg; 545 int should_wake = 0; 546 547 read_lock(&rh->hash_lock); 548 reg = __rh_lookup(rh, region); 549 read_unlock(&rh->hash_lock); 550 551 spin_lock_irqsave(&rh->region_lock, flags); 552 if (atomic_dec_and_test(®->pending)) { 553 /* 554 * There is no pending I/O for this region. 555 * We can move the region to corresponding list for next action. 556 * At this point, the region is not yet connected to any list. 557 * 558 * If the state is DM_RH_NOSYNC, the region should be kept off 559 * from clean list. 560 * The hash entry for DM_RH_NOSYNC will remain in memory 561 * until the region is recovered or the map is reloaded. 562 */ 563 564 /* do nothing for DM_RH_NOSYNC */ 565 if (unlikely(rh->flush_failure)) { 566 /* 567 * If a write flush failed some time ago, we 568 * don't know whether or not this write made it 569 * to the disk, so we must resync the device. 570 */ 571 reg->state = DM_RH_NOSYNC; 572 } else if (reg->state == DM_RH_RECOVERING) { 573 list_add_tail(®->list, &rh->quiesced_regions); 574 } else if (reg->state == DM_RH_DIRTY) { 575 reg->state = DM_RH_CLEAN; 576 list_add(®->list, &rh->clean_regions); 577 } 578 should_wake = 1; 579 } 580 spin_unlock_irqrestore(&rh->region_lock, flags); 581 582 if (should_wake) 583 rh->wakeup_workers(rh->context); 584} 585EXPORT_SYMBOL_GPL(dm_rh_dec); 586 587/* 588 * Starts quiescing a region in preparation for recovery. 589 */ 590static int __rh_recovery_prepare(struct dm_region_hash *rh) 591{ 592 int r; 593 region_t region; 594 struct dm_region *reg; 595 596 /* 597 * Ask the dirty log what's next. 598 */ 599 r = rh->log->type->get_resync_work(rh->log, ®ion); 600 if (r <= 0) 601 return r; 602 603 /* 604 * Get this region, and start it quiescing by setting the 605 * recovering flag. 606 */ 607 read_lock(&rh->hash_lock); 608 reg = __rh_find(rh, region); 609 read_unlock(&rh->hash_lock); 610 611 spin_lock_irq(&rh->region_lock); 612 reg->state = DM_RH_RECOVERING; 613 614 /* Already quiesced ? */ 615 if (atomic_read(®->pending)) 616 list_del_init(®->list); 617 else 618 list_move(®->list, &rh->quiesced_regions); 619 620 spin_unlock_irq(&rh->region_lock); 621 622 return 1; 623} 624 625void dm_rh_recovery_prepare(struct dm_region_hash *rh) 626{ 627 /* Extra reference to avoid race with dm_rh_stop_recovery */ 628 atomic_inc(&rh->recovery_in_flight); 629 630 while (!down_trylock(&rh->recovery_count)) { 631 atomic_inc(&rh->recovery_in_flight); 632 if (__rh_recovery_prepare(rh) <= 0) { 633 atomic_dec(&rh->recovery_in_flight); 634 up(&rh->recovery_count); 635 break; 636 } 637 } 638 639 /* Drop the extra reference */ 640 if (atomic_dec_and_test(&rh->recovery_in_flight)) 641 rh->wakeup_all_recovery_waiters(rh->context); 642} 643EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare); 644 645/* 646 * Returns any quiesced regions. 647 */ 648struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh) 649{ 650 struct dm_region *reg = NULL; 651 652 spin_lock_irq(&rh->region_lock); 653 if (!list_empty(&rh->quiesced_regions)) { 654 reg = list_entry(rh->quiesced_regions.next, 655 struct dm_region, list); 656 list_del_init(®->list); /* remove from the quiesced list */ 657 } 658 spin_unlock_irq(&rh->region_lock); 659 660 return reg; 661} 662EXPORT_SYMBOL_GPL(dm_rh_recovery_start); 663 664void dm_rh_recovery_end(struct dm_region *reg, int success) 665{ 666 struct dm_region_hash *rh = reg->rh; 667 668 spin_lock_irq(&rh->region_lock); 669 if (success) 670 list_add(®->list, ®->rh->recovered_regions); 671 else 672 list_add(®->list, ®->rh->failed_recovered_regions); 673 674 spin_unlock_irq(&rh->region_lock); 675 676 rh->wakeup_workers(rh->context); 677} 678EXPORT_SYMBOL_GPL(dm_rh_recovery_end); 679 680/* Return recovery in flight count. */ 681int dm_rh_recovery_in_flight(struct dm_region_hash *rh) 682{ 683 return atomic_read(&rh->recovery_in_flight); 684} 685EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight); 686 687int dm_rh_flush(struct dm_region_hash *rh) 688{ 689 return rh->log->type->flush(rh->log); 690} 691EXPORT_SYMBOL_GPL(dm_rh_flush); 692 693void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio) 694{ 695 struct dm_region *reg; 696 697 read_lock(&rh->hash_lock); 698 reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio)); 699 bio_list_add(®->delayed_bios, bio); 700 read_unlock(&rh->hash_lock); 701} 702EXPORT_SYMBOL_GPL(dm_rh_delay); 703 704void dm_rh_stop_recovery(struct dm_region_hash *rh) 705{ 706 int i; 707 708 /* wait for any recovering regions */ 709 for (i = 0; i < rh->max_recovery; i++) 710 down(&rh->recovery_count); 711} 712EXPORT_SYMBOL_GPL(dm_rh_stop_recovery); 713 714void dm_rh_start_recovery(struct dm_region_hash *rh) 715{ 716 int i; 717 718 for (i = 0; i < rh->max_recovery; i++) 719 up(&rh->recovery_count); 720 721 rh->wakeup_workers(rh->context); 722} 723EXPORT_SYMBOL_GPL(dm_rh_start_recovery); 724 725MODULE_DESCRIPTION(DM_NAME " region hash"); 726MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@lists.linux.dev>"); 727MODULE_LICENSE("GPL"); 728