1 /* 2 * dm-snapshot.c 3 * 4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited. 5 * 6 * This file is released under the GPL. 7 */ 8 9 #include <linux/blkdev.h> 10 #include <linux/device-mapper.h> 11 #include <linux/delay.h> 12 #include <linux/fs.h> 13 #include <linux/init.h> 14 #include <linux/kdev_t.h> 15 #include <linux/list.h> 16 #include <linux/mempool.h> 17 #include <linux/module.h> 18 #include <linux/slab.h> 19 #include <linux/vmalloc.h> 20 #include <linux/log2.h> 21 #include <linux/dm-kcopyd.h> 22 23 #include "dm.h" 24 25 #include "dm-exception-store.h" 26 27 #define DM_MSG_PREFIX "snapshots" 28 29 static const char dm_snapshot_merge_target_name[] = "snapshot-merge"; 30 31 #define dm_target_is_snapshot_merge(ti) \ 32 ((ti)->type->name == dm_snapshot_merge_target_name) 33 34 /* 35 * The size of the mempool used to track chunks in use. 36 */ 37 #define MIN_IOS 256 38 39 #define DM_TRACKED_CHUNK_HASH_SIZE 16 40 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ 41 (DM_TRACKED_CHUNK_HASH_SIZE - 1)) 42 43 struct dm_exception_table { 44 uint32_t hash_mask; 45 unsigned hash_shift; 46 struct list_head *table; 47 }; 48 49 struct dm_snapshot { 50 struct rw_semaphore lock; 51 52 struct dm_dev *origin; 53 struct dm_dev *cow; 54 55 struct dm_target *ti; 56 57 /* List of snapshots per Origin */ 58 struct list_head list; 59 60 /* 61 * You can't use a snapshot if this is 0 (e.g. if full). 62 * A snapshot-merge target never clears this. 63 */ 64 int valid; 65 66 /* 67 * The snapshot overflowed because of a write to the snapshot device. 68 * We don't have to invalidate the snapshot in this case, but we need 69 * to prevent further writes. 70 */ 71 int snapshot_overflowed; 72 73 /* Origin writes don't trigger exceptions until this is set */ 74 int active; 75 76 atomic_t pending_exceptions_count; 77 78 /* Protected by "lock" */ 79 sector_t exception_start_sequence; 80 81 /* Protected by kcopyd single-threaded callback */ 82 sector_t exception_complete_sequence; 83 84 /* 85 * A list of pending exceptions that completed out of order. 86 * Protected by kcopyd single-threaded callback. 87 */ 88 struct list_head out_of_order_list; 89 90 mempool_t *pending_pool; 91 92 struct dm_exception_table pending; 93 struct dm_exception_table complete; 94 95 /* 96 * pe_lock protects all pending_exception operations and access 97 * as well as the snapshot_bios list. 98 */ 99 spinlock_t pe_lock; 100 101 /* Chunks with outstanding reads */ 102 spinlock_t tracked_chunk_lock; 103 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; 104 105 /* The on disk metadata handler */ 106 struct dm_exception_store *store; 107 108 struct dm_kcopyd_client *kcopyd_client; 109 110 /* Wait for events based on state_bits */ 111 unsigned long state_bits; 112 113 /* Range of chunks currently being merged. */ 114 chunk_t first_merging_chunk; 115 int num_merging_chunks; 116 117 /* 118 * The merge operation failed if this flag is set. 119 * Failure modes are handled as follows: 120 * - I/O error reading the header 121 * => don't load the target; abort. 122 * - Header does not have "valid" flag set 123 * => use the origin; forget about the snapshot. 124 * - I/O error when reading exceptions 125 * => don't load the target; abort. 126 * (We can't use the intermediate origin state.) 127 * - I/O error while merging 128 * => stop merging; set merge_failed; process I/O normally. 129 */ 130 int merge_failed; 131 132 /* 133 * Incoming bios that overlap with chunks being merged must wait 134 * for them to be committed. 135 */ 136 struct bio_list bios_queued_during_merge; 137 }; 138 139 /* 140 * state_bits: 141 * RUNNING_MERGE - Merge operation is in progress. 142 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped; 143 * cleared afterwards. 144 */ 145 #define RUNNING_MERGE 0 146 #define SHUTDOWN_MERGE 1 147 148 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, 149 "A percentage of time allocated for copy on write"); 150 151 struct dm_dev *dm_snap_origin(struct dm_snapshot *s) 152 { 153 return s->origin; 154 } 155 EXPORT_SYMBOL(dm_snap_origin); 156 157 struct dm_dev *dm_snap_cow(struct dm_snapshot *s) 158 { 159 return s->cow; 160 } 161 EXPORT_SYMBOL(dm_snap_cow); 162 163 static sector_t chunk_to_sector(struct dm_exception_store *store, 164 chunk_t chunk) 165 { 166 return chunk << store->chunk_shift; 167 } 168 169 static int bdev_equal(struct block_device *lhs, struct block_device *rhs) 170 { 171 /* 172 * There is only ever one instance of a particular block 173 * device so we can compare pointers safely. 174 */ 175 return lhs == rhs; 176 } 177 178 struct dm_snap_pending_exception { 179 struct dm_exception e; 180 181 /* 182 * Origin buffers waiting for this to complete are held 183 * in a bio list 184 */ 185 struct bio_list origin_bios; 186 struct bio_list snapshot_bios; 187 188 /* Pointer back to snapshot context */ 189 struct dm_snapshot *snap; 190 191 /* 192 * 1 indicates the exception has already been sent to 193 * kcopyd. 194 */ 195 int started; 196 197 /* There was copying error. */ 198 int copy_error; 199 200 /* A sequence number, it is used for in-order completion. */ 201 sector_t exception_sequence; 202 203 struct list_head out_of_order_entry; 204 205 /* 206 * For writing a complete chunk, bypassing the copy. 207 */ 208 struct bio *full_bio; 209 bio_end_io_t *full_bio_end_io; 210 }; 211 212 /* 213 * Hash table mapping origin volumes to lists of snapshots and 214 * a lock to protect it 215 */ 216 static struct kmem_cache *exception_cache; 217 static struct kmem_cache *pending_cache; 218 219 struct dm_snap_tracked_chunk { 220 struct hlist_node node; 221 chunk_t chunk; 222 }; 223 224 static void init_tracked_chunk(struct bio *bio) 225 { 226 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); 227 INIT_HLIST_NODE(&c->node); 228 } 229 230 static bool is_bio_tracked(struct bio *bio) 231 { 232 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); 233 return !hlist_unhashed(&c->node); 234 } 235 236 static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk) 237 { 238 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); 239 240 c->chunk = chunk; 241 242 spin_lock_irq(&s->tracked_chunk_lock); 243 hlist_add_head(&c->node, 244 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]); 245 spin_unlock_irq(&s->tracked_chunk_lock); 246 } 247 248 static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio) 249 { 250 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); 251 unsigned long flags; 252 253 spin_lock_irqsave(&s->tracked_chunk_lock, flags); 254 hlist_del(&c->node); 255 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags); 256 } 257 258 static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk) 259 { 260 struct dm_snap_tracked_chunk *c; 261 int found = 0; 262 263 spin_lock_irq(&s->tracked_chunk_lock); 264 265 hlist_for_each_entry(c, 266 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) { 267 if (c->chunk == chunk) { 268 found = 1; 269 break; 270 } 271 } 272 273 spin_unlock_irq(&s->tracked_chunk_lock); 274 275 return found; 276 } 277 278 /* 279 * This conflicting I/O is extremely improbable in the caller, 280 * so msleep(1) is sufficient and there is no need for a wait queue. 281 */ 282 static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk) 283 { 284 while (__chunk_is_tracked(s, chunk)) 285 msleep(1); 286 } 287 288 /* 289 * One of these per registered origin, held in the snapshot_origins hash 290 */ 291 struct origin { 292 /* The origin device */ 293 struct block_device *bdev; 294 295 struct list_head hash_list; 296 297 /* List of snapshots for this origin */ 298 struct list_head snapshots; 299 }; 300 301 /* 302 * This structure is allocated for each origin target 303 */ 304 struct dm_origin { 305 struct dm_dev *dev; 306 struct dm_target *ti; 307 unsigned split_boundary; 308 struct list_head hash_list; 309 }; 310 311 /* 312 * Size of the hash table for origin volumes. If we make this 313 * the size of the minors list then it should be nearly perfect 314 */ 315 #define ORIGIN_HASH_SIZE 256 316 #define ORIGIN_MASK 0xFF 317 static struct list_head *_origins; 318 static struct list_head *_dm_origins; 319 static struct rw_semaphore _origins_lock; 320 321 static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done); 322 static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock); 323 static uint64_t _pending_exceptions_done_count; 324 325 static int init_origin_hash(void) 326 { 327 int i; 328 329 _origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head), 330 GFP_KERNEL); 331 if (!_origins) { 332 DMERR("unable to allocate memory for _origins"); 333 return -ENOMEM; 334 } 335 for (i = 0; i < ORIGIN_HASH_SIZE; i++) 336 INIT_LIST_HEAD(_origins + i); 337 338 _dm_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head), 339 GFP_KERNEL); 340 if (!_dm_origins) { 341 DMERR("unable to allocate memory for _dm_origins"); 342 kfree(_origins); 343 return -ENOMEM; 344 } 345 for (i = 0; i < ORIGIN_HASH_SIZE; i++) 346 INIT_LIST_HEAD(_dm_origins + i); 347 348 init_rwsem(&_origins_lock); 349 350 return 0; 351 } 352 353 static void exit_origin_hash(void) 354 { 355 kfree(_origins); 356 kfree(_dm_origins); 357 } 358 359 static unsigned origin_hash(struct block_device *bdev) 360 { 361 return bdev->bd_dev & ORIGIN_MASK; 362 } 363 364 static struct origin *__lookup_origin(struct block_device *origin) 365 { 366 struct list_head *ol; 367 struct origin *o; 368 369 ol = &_origins[origin_hash(origin)]; 370 list_for_each_entry (o, ol, hash_list) 371 if (bdev_equal(o->bdev, origin)) 372 return o; 373 374 return NULL; 375 } 376 377 static void __insert_origin(struct origin *o) 378 { 379 struct list_head *sl = &_origins[origin_hash(o->bdev)]; 380 list_add_tail(&o->hash_list, sl); 381 } 382 383 static struct dm_origin *__lookup_dm_origin(struct block_device *origin) 384 { 385 struct list_head *ol; 386 struct dm_origin *o; 387 388 ol = &_dm_origins[origin_hash(origin)]; 389 list_for_each_entry (o, ol, hash_list) 390 if (bdev_equal(o->dev->bdev, origin)) 391 return o; 392 393 return NULL; 394 } 395 396 static void __insert_dm_origin(struct dm_origin *o) 397 { 398 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)]; 399 list_add_tail(&o->hash_list, sl); 400 } 401 402 static void __remove_dm_origin(struct dm_origin *o) 403 { 404 list_del(&o->hash_list); 405 } 406 407 /* 408 * _origins_lock must be held when calling this function. 409 * Returns number of snapshots registered using the supplied cow device, plus: 410 * snap_src - a snapshot suitable for use as a source of exception handover 411 * snap_dest - a snapshot capable of receiving exception handover. 412 * snap_merge - an existing snapshot-merge target linked to the same origin. 413 * There can be at most one snapshot-merge target. The parameter is optional. 414 * 415 * Possible return values and states of snap_src and snap_dest. 416 * 0: NULL, NULL - first new snapshot 417 * 1: snap_src, NULL - normal snapshot 418 * 2: snap_src, snap_dest - waiting for handover 419 * 2: snap_src, NULL - handed over, waiting for old to be deleted 420 * 1: NULL, snap_dest - source got destroyed without handover 421 */ 422 static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, 423 struct dm_snapshot **snap_src, 424 struct dm_snapshot **snap_dest, 425 struct dm_snapshot **snap_merge) 426 { 427 struct dm_snapshot *s; 428 struct origin *o; 429 int count = 0; 430 int active; 431 432 o = __lookup_origin(snap->origin->bdev); 433 if (!o) 434 goto out; 435 436 list_for_each_entry(s, &o->snapshots, list) { 437 if (dm_target_is_snapshot_merge(s->ti) && snap_merge) 438 *snap_merge = s; 439 if (!bdev_equal(s->cow->bdev, snap->cow->bdev)) 440 continue; 441 442 down_read(&s->lock); 443 active = s->active; 444 up_read(&s->lock); 445 446 if (active) { 447 if (snap_src) 448 *snap_src = s; 449 } else if (snap_dest) 450 *snap_dest = s; 451 452 count++; 453 } 454 455 out: 456 return count; 457 } 458 459 /* 460 * On success, returns 1 if this snapshot is a handover destination, 461 * otherwise returns 0. 462 */ 463 static int __validate_exception_handover(struct dm_snapshot *snap) 464 { 465 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; 466 struct dm_snapshot *snap_merge = NULL; 467 468 /* Does snapshot need exceptions handed over to it? */ 469 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, 470 &snap_merge) == 2) || 471 snap_dest) { 472 snap->ti->error = "Snapshot cow pairing for exception " 473 "table handover failed"; 474 return -EINVAL; 475 } 476 477 /* 478 * If no snap_src was found, snap cannot become a handover 479 * destination. 480 */ 481 if (!snap_src) 482 return 0; 483 484 /* 485 * Non-snapshot-merge handover? 486 */ 487 if (!dm_target_is_snapshot_merge(snap->ti)) 488 return 1; 489 490 /* 491 * Do not allow more than one merging snapshot. 492 */ 493 if (snap_merge) { 494 snap->ti->error = "A snapshot is already merging."; 495 return -EINVAL; 496 } 497 498 if (!snap_src->store->type->prepare_merge || 499 !snap_src->store->type->commit_merge) { 500 snap->ti->error = "Snapshot exception store does not " 501 "support snapshot-merge."; 502 return -EINVAL; 503 } 504 505 return 1; 506 } 507 508 static void __insert_snapshot(struct origin *o, struct dm_snapshot *s) 509 { 510 struct dm_snapshot *l; 511 512 /* Sort the list according to chunk size, largest-first smallest-last */ 513 list_for_each_entry(l, &o->snapshots, list) 514 if (l->store->chunk_size < s->store->chunk_size) 515 break; 516 list_add_tail(&s->list, &l->list); 517 } 518 519 /* 520 * Make a note of the snapshot and its origin so we can look it 521 * up when the origin has a write on it. 522 * 523 * Also validate snapshot exception store handovers. 524 * On success, returns 1 if this registration is a handover destination, 525 * otherwise returns 0. 526 */ 527 static int register_snapshot(struct dm_snapshot *snap) 528 { 529 struct origin *o, *new_o = NULL; 530 struct block_device *bdev = snap->origin->bdev; 531 int r = 0; 532 533 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL); 534 if (!new_o) 535 return -ENOMEM; 536 537 down_write(&_origins_lock); 538 539 r = __validate_exception_handover(snap); 540 if (r < 0) { 541 kfree(new_o); 542 goto out; 543 } 544 545 o = __lookup_origin(bdev); 546 if (o) 547 kfree(new_o); 548 else { 549 /* New origin */ 550 o = new_o; 551 552 /* Initialise the struct */ 553 INIT_LIST_HEAD(&o->snapshots); 554 o->bdev = bdev; 555 556 __insert_origin(o); 557 } 558 559 __insert_snapshot(o, snap); 560 561 out: 562 up_write(&_origins_lock); 563 564 return r; 565 } 566 567 /* 568 * Move snapshot to correct place in list according to chunk size. 569 */ 570 static void reregister_snapshot(struct dm_snapshot *s) 571 { 572 struct block_device *bdev = s->origin->bdev; 573 574 down_write(&_origins_lock); 575 576 list_del(&s->list); 577 __insert_snapshot(__lookup_origin(bdev), s); 578 579 up_write(&_origins_lock); 580 } 581 582 static void unregister_snapshot(struct dm_snapshot *s) 583 { 584 struct origin *o; 585 586 down_write(&_origins_lock); 587 o = __lookup_origin(s->origin->bdev); 588 589 list_del(&s->list); 590 if (o && list_empty(&o->snapshots)) { 591 list_del(&o->hash_list); 592 kfree(o); 593 } 594 595 up_write(&_origins_lock); 596 } 597 598 /* 599 * Implementation of the exception hash tables. 600 * The lowest hash_shift bits of the chunk number are ignored, allowing 601 * some consecutive chunks to be grouped together. 602 */ 603 static int dm_exception_table_init(struct dm_exception_table *et, 604 uint32_t size, unsigned hash_shift) 605 { 606 unsigned int i; 607 608 et->hash_shift = hash_shift; 609 et->hash_mask = size - 1; 610 et->table = dm_vcalloc(size, sizeof(struct list_head)); 611 if (!et->table) 612 return -ENOMEM; 613 614 for (i = 0; i < size; i++) 615 INIT_LIST_HEAD(et->table + i); 616 617 return 0; 618 } 619 620 static void dm_exception_table_exit(struct dm_exception_table *et, 621 struct kmem_cache *mem) 622 { 623 struct list_head *slot; 624 struct dm_exception *ex, *next; 625 int i, size; 626 627 size = et->hash_mask + 1; 628 for (i = 0; i < size; i++) { 629 slot = et->table + i; 630 631 list_for_each_entry_safe (ex, next, slot, hash_list) 632 kmem_cache_free(mem, ex); 633 } 634 635 vfree(et->table); 636 } 637 638 static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk) 639 { 640 return (chunk >> et->hash_shift) & et->hash_mask; 641 } 642 643 static void dm_remove_exception(struct dm_exception *e) 644 { 645 list_del(&e->hash_list); 646 } 647 648 /* 649 * Return the exception data for a sector, or NULL if not 650 * remapped. 651 */ 652 static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et, 653 chunk_t chunk) 654 { 655 struct list_head *slot; 656 struct dm_exception *e; 657 658 slot = &et->table[exception_hash(et, chunk)]; 659 list_for_each_entry (e, slot, hash_list) 660 if (chunk >= e->old_chunk && 661 chunk <= e->old_chunk + dm_consecutive_chunk_count(e)) 662 return e; 663 664 return NULL; 665 } 666 667 static struct dm_exception *alloc_completed_exception(gfp_t gfp) 668 { 669 struct dm_exception *e; 670 671 e = kmem_cache_alloc(exception_cache, gfp); 672 if (!e && gfp == GFP_NOIO) 673 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC); 674 675 return e; 676 } 677 678 static void free_completed_exception(struct dm_exception *e) 679 { 680 kmem_cache_free(exception_cache, e); 681 } 682 683 static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s) 684 { 685 struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool, 686 GFP_NOIO); 687 688 atomic_inc(&s->pending_exceptions_count); 689 pe->snap = s; 690 691 return pe; 692 } 693 694 static void free_pending_exception(struct dm_snap_pending_exception *pe) 695 { 696 struct dm_snapshot *s = pe->snap; 697 698 mempool_free(pe, s->pending_pool); 699 smp_mb__before_atomic(); 700 atomic_dec(&s->pending_exceptions_count); 701 } 702 703 static void dm_insert_exception(struct dm_exception_table *eh, 704 struct dm_exception *new_e) 705 { 706 struct list_head *l; 707 struct dm_exception *e = NULL; 708 709 l = &eh->table[exception_hash(eh, new_e->old_chunk)]; 710 711 /* Add immediately if this table doesn't support consecutive chunks */ 712 if (!eh->hash_shift) 713 goto out; 714 715 /* List is ordered by old_chunk */ 716 list_for_each_entry_reverse(e, l, hash_list) { 717 /* Insert after an existing chunk? */ 718 if (new_e->old_chunk == (e->old_chunk + 719 dm_consecutive_chunk_count(e) + 1) && 720 new_e->new_chunk == (dm_chunk_number(e->new_chunk) + 721 dm_consecutive_chunk_count(e) + 1)) { 722 dm_consecutive_chunk_count_inc(e); 723 free_completed_exception(new_e); 724 return; 725 } 726 727 /* Insert before an existing chunk? */ 728 if (new_e->old_chunk == (e->old_chunk - 1) && 729 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) { 730 dm_consecutive_chunk_count_inc(e); 731 e->old_chunk--; 732 e->new_chunk--; 733 free_completed_exception(new_e); 734 return; 735 } 736 737 if (new_e->old_chunk > e->old_chunk) 738 break; 739 } 740 741 out: 742 list_add(&new_e->hash_list, e ? &e->hash_list : l); 743 } 744 745 /* 746 * Callback used by the exception stores to load exceptions when 747 * initialising. 748 */ 749 static int dm_add_exception(void *context, chunk_t old, chunk_t new) 750 { 751 struct dm_snapshot *s = context; 752 struct dm_exception *e; 753 754 e = alloc_completed_exception(GFP_KERNEL); 755 if (!e) 756 return -ENOMEM; 757 758 e->old_chunk = old; 759 760 /* Consecutive_count is implicitly initialised to zero */ 761 e->new_chunk = new; 762 763 dm_insert_exception(&s->complete, e); 764 765 return 0; 766 } 767 768 /* 769 * Return a minimum chunk size of all snapshots that have the specified origin. 770 * Return zero if the origin has no snapshots. 771 */ 772 static uint32_t __minimum_chunk_size(struct origin *o) 773 { 774 struct dm_snapshot *snap; 775 unsigned chunk_size = 0; 776 777 if (o) 778 list_for_each_entry(snap, &o->snapshots, list) 779 chunk_size = min_not_zero(chunk_size, 780 snap->store->chunk_size); 781 782 return (uint32_t) chunk_size; 783 } 784 785 /* 786 * Hard coded magic. 787 */ 788 static int calc_max_buckets(void) 789 { 790 /* use a fixed size of 2MB */ 791 unsigned long mem = 2 * 1024 * 1024; 792 mem /= sizeof(struct list_head); 793 794 return mem; 795 } 796 797 /* 798 * Allocate room for a suitable hash table. 799 */ 800 static int init_hash_tables(struct dm_snapshot *s) 801 { 802 sector_t hash_size, cow_dev_size, max_buckets; 803 804 /* 805 * Calculate based on the size of the original volume or 806 * the COW volume... 807 */ 808 cow_dev_size = get_dev_size(s->cow->bdev); 809 max_buckets = calc_max_buckets(); 810 811 hash_size = cow_dev_size >> s->store->chunk_shift; 812 hash_size = min(hash_size, max_buckets); 813 814 if (hash_size < 64) 815 hash_size = 64; 816 hash_size = rounddown_pow_of_two(hash_size); 817 if (dm_exception_table_init(&s->complete, hash_size, 818 DM_CHUNK_CONSECUTIVE_BITS)) 819 return -ENOMEM; 820 821 /* 822 * Allocate hash table for in-flight exceptions 823 * Make this smaller than the real hash table 824 */ 825 hash_size >>= 3; 826 if (hash_size < 64) 827 hash_size = 64; 828 829 if (dm_exception_table_init(&s->pending, hash_size, 0)) { 830 dm_exception_table_exit(&s->complete, exception_cache); 831 return -ENOMEM; 832 } 833 834 return 0; 835 } 836 837 static void merge_shutdown(struct dm_snapshot *s) 838 { 839 clear_bit_unlock(RUNNING_MERGE, &s->state_bits); 840 smp_mb__after_atomic(); 841 wake_up_bit(&s->state_bits, RUNNING_MERGE); 842 } 843 844 static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s) 845 { 846 s->first_merging_chunk = 0; 847 s->num_merging_chunks = 0; 848 849 return bio_list_get(&s->bios_queued_during_merge); 850 } 851 852 /* 853 * Remove one chunk from the index of completed exceptions. 854 */ 855 static int __remove_single_exception_chunk(struct dm_snapshot *s, 856 chunk_t old_chunk) 857 { 858 struct dm_exception *e; 859 860 e = dm_lookup_exception(&s->complete, old_chunk); 861 if (!e) { 862 DMERR("Corruption detected: exception for block %llu is " 863 "on disk but not in memory", 864 (unsigned long long)old_chunk); 865 return -EINVAL; 866 } 867 868 /* 869 * If this is the only chunk using this exception, remove exception. 870 */ 871 if (!dm_consecutive_chunk_count(e)) { 872 dm_remove_exception(e); 873 free_completed_exception(e); 874 return 0; 875 } 876 877 /* 878 * The chunk may be either at the beginning or the end of a 879 * group of consecutive chunks - never in the middle. We are 880 * removing chunks in the opposite order to that in which they 881 * were added, so this should always be true. 882 * Decrement the consecutive chunk counter and adjust the 883 * starting point if necessary. 884 */ 885 if (old_chunk == e->old_chunk) { 886 e->old_chunk++; 887 e->new_chunk++; 888 } else if (old_chunk != e->old_chunk + 889 dm_consecutive_chunk_count(e)) { 890 DMERR("Attempt to merge block %llu from the " 891 "middle of a chunk range [%llu - %llu]", 892 (unsigned long long)old_chunk, 893 (unsigned long long)e->old_chunk, 894 (unsigned long long) 895 e->old_chunk + dm_consecutive_chunk_count(e)); 896 return -EINVAL; 897 } 898 899 dm_consecutive_chunk_count_dec(e); 900 901 return 0; 902 } 903 904 static void flush_bios(struct bio *bio); 905 906 static int remove_single_exception_chunk(struct dm_snapshot *s) 907 { 908 struct bio *b = NULL; 909 int r; 910 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1; 911 912 down_write(&s->lock); 913 914 /* 915 * Process chunks (and associated exceptions) in reverse order 916 * so that dm_consecutive_chunk_count_dec() accounting works. 917 */ 918 do { 919 r = __remove_single_exception_chunk(s, old_chunk); 920 if (r) 921 goto out; 922 } while (old_chunk-- > s->first_merging_chunk); 923 924 b = __release_queued_bios_after_merge(s); 925 926 out: 927 up_write(&s->lock); 928 if (b) 929 flush_bios(b); 930 931 return r; 932 } 933 934 static int origin_write_extent(struct dm_snapshot *merging_snap, 935 sector_t sector, unsigned chunk_size); 936 937 static void merge_callback(int read_err, unsigned long write_err, 938 void *context); 939 940 static uint64_t read_pending_exceptions_done_count(void) 941 { 942 uint64_t pending_exceptions_done; 943 944 spin_lock(&_pending_exceptions_done_spinlock); 945 pending_exceptions_done = _pending_exceptions_done_count; 946 spin_unlock(&_pending_exceptions_done_spinlock); 947 948 return pending_exceptions_done; 949 } 950 951 static void increment_pending_exceptions_done_count(void) 952 { 953 spin_lock(&_pending_exceptions_done_spinlock); 954 _pending_exceptions_done_count++; 955 spin_unlock(&_pending_exceptions_done_spinlock); 956 957 wake_up_all(&_pending_exceptions_done); 958 } 959 960 static void snapshot_merge_next_chunks(struct dm_snapshot *s) 961 { 962 int i, linear_chunks; 963 chunk_t old_chunk, new_chunk; 964 struct dm_io_region src, dest; 965 sector_t io_size; 966 uint64_t previous_count; 967 968 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits)); 969 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits))) 970 goto shut; 971 972 /* 973 * valid flag never changes during merge, so no lock required. 974 */ 975 if (!s->valid) { 976 DMERR("Snapshot is invalid: can't merge"); 977 goto shut; 978 } 979 980 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk, 981 &new_chunk); 982 if (linear_chunks <= 0) { 983 if (linear_chunks < 0) { 984 DMERR("Read error in exception store: " 985 "shutting down merge"); 986 down_write(&s->lock); 987 s->merge_failed = 1; 988 up_write(&s->lock); 989 } 990 goto shut; 991 } 992 993 /* Adjust old_chunk and new_chunk to reflect start of linear region */ 994 old_chunk = old_chunk + 1 - linear_chunks; 995 new_chunk = new_chunk + 1 - linear_chunks; 996 997 /* 998 * Use one (potentially large) I/O to copy all 'linear_chunks' 999 * from the exception store to the origin 1000 */ 1001 io_size = linear_chunks * s->store->chunk_size; 1002 1003 dest.bdev = s->origin->bdev; 1004 dest.sector = chunk_to_sector(s->store, old_chunk); 1005 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector); 1006 1007 src.bdev = s->cow->bdev; 1008 src.sector = chunk_to_sector(s->store, new_chunk); 1009 src.count = dest.count; 1010 1011 /* 1012 * Reallocate any exceptions needed in other snapshots then 1013 * wait for the pending exceptions to complete. 1014 * Each time any pending exception (globally on the system) 1015 * completes we are woken and repeat the process to find out 1016 * if we can proceed. While this may not seem a particularly 1017 * efficient algorithm, it is not expected to have any 1018 * significant impact on performance. 1019 */ 1020 previous_count = read_pending_exceptions_done_count(); 1021 while (origin_write_extent(s, dest.sector, io_size)) { 1022 wait_event(_pending_exceptions_done, 1023 (read_pending_exceptions_done_count() != 1024 previous_count)); 1025 /* Retry after the wait, until all exceptions are done. */ 1026 previous_count = read_pending_exceptions_done_count(); 1027 } 1028 1029 down_write(&s->lock); 1030 s->first_merging_chunk = old_chunk; 1031 s->num_merging_chunks = linear_chunks; 1032 up_write(&s->lock); 1033 1034 /* Wait until writes to all 'linear_chunks' drain */ 1035 for (i = 0; i < linear_chunks; i++) 1036 __check_for_conflicting_io(s, old_chunk + i); 1037 1038 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s); 1039 return; 1040 1041 shut: 1042 merge_shutdown(s); 1043 } 1044 1045 static void error_bios(struct bio *bio); 1046 1047 static void merge_callback(int read_err, unsigned long write_err, void *context) 1048 { 1049 struct dm_snapshot *s = context; 1050 struct bio *b = NULL; 1051 1052 if (read_err || write_err) { 1053 if (read_err) 1054 DMERR("Read error: shutting down merge."); 1055 else 1056 DMERR("Write error: shutting down merge."); 1057 goto shut; 1058 } 1059 1060 if (s->store->type->commit_merge(s->store, 1061 s->num_merging_chunks) < 0) { 1062 DMERR("Write error in exception store: shutting down merge"); 1063 goto shut; 1064 } 1065 1066 if (remove_single_exception_chunk(s) < 0) 1067 goto shut; 1068 1069 snapshot_merge_next_chunks(s); 1070 1071 return; 1072 1073 shut: 1074 down_write(&s->lock); 1075 s->merge_failed = 1; 1076 b = __release_queued_bios_after_merge(s); 1077 up_write(&s->lock); 1078 error_bios(b); 1079 1080 merge_shutdown(s); 1081 } 1082 1083 static void start_merge(struct dm_snapshot *s) 1084 { 1085 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits)) 1086 snapshot_merge_next_chunks(s); 1087 } 1088 1089 /* 1090 * Stop the merging process and wait until it finishes. 1091 */ 1092 static void stop_merge(struct dm_snapshot *s) 1093 { 1094 set_bit(SHUTDOWN_MERGE, &s->state_bits); 1095 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE); 1096 clear_bit(SHUTDOWN_MERGE, &s->state_bits); 1097 } 1098 1099 /* 1100 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size> 1101 */ 1102 static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) 1103 { 1104 struct dm_snapshot *s; 1105 int i; 1106 int r = -EINVAL; 1107 char *origin_path, *cow_path; 1108 dev_t origin_dev, cow_dev; 1109 unsigned args_used, num_flush_bios = 1; 1110 fmode_t origin_mode = FMODE_READ; 1111 1112 if (argc != 4) { 1113 ti->error = "requires exactly 4 arguments"; 1114 r = -EINVAL; 1115 goto bad; 1116 } 1117 1118 if (dm_target_is_snapshot_merge(ti)) { 1119 num_flush_bios = 2; 1120 origin_mode = FMODE_WRITE; 1121 } 1122 1123 s = kmalloc(sizeof(*s), GFP_KERNEL); 1124 if (!s) { 1125 ti->error = "Cannot allocate private snapshot structure"; 1126 r = -ENOMEM; 1127 goto bad; 1128 } 1129 1130 origin_path = argv[0]; 1131 argv++; 1132 argc--; 1133 1134 r = dm_get_device(ti, origin_path, origin_mode, &s->origin); 1135 if (r) { 1136 ti->error = "Cannot get origin device"; 1137 goto bad_origin; 1138 } 1139 origin_dev = s->origin->bdev->bd_dev; 1140 1141 cow_path = argv[0]; 1142 argv++; 1143 argc--; 1144 1145 cow_dev = dm_get_dev_t(cow_path); 1146 if (cow_dev && cow_dev == origin_dev) { 1147 ti->error = "COW device cannot be the same as origin device"; 1148 r = -EINVAL; 1149 goto bad_cow; 1150 } 1151 1152 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow); 1153 if (r) { 1154 ti->error = "Cannot get COW device"; 1155 goto bad_cow; 1156 } 1157 1158 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store); 1159 if (r) { 1160 ti->error = "Couldn't create exception store"; 1161 r = -EINVAL; 1162 goto bad_store; 1163 } 1164 1165 argv += args_used; 1166 argc -= args_used; 1167 1168 s->ti = ti; 1169 s->valid = 1; 1170 s->snapshot_overflowed = 0; 1171 s->active = 0; 1172 atomic_set(&s->pending_exceptions_count, 0); 1173 s->exception_start_sequence = 0; 1174 s->exception_complete_sequence = 0; 1175 INIT_LIST_HEAD(&s->out_of_order_list); 1176 init_rwsem(&s->lock); 1177 INIT_LIST_HEAD(&s->list); 1178 spin_lock_init(&s->pe_lock); 1179 s->state_bits = 0; 1180 s->merge_failed = 0; 1181 s->first_merging_chunk = 0; 1182 s->num_merging_chunks = 0; 1183 bio_list_init(&s->bios_queued_during_merge); 1184 1185 /* Allocate hash table for COW data */ 1186 if (init_hash_tables(s)) { 1187 ti->error = "Unable to allocate hash table space"; 1188 r = -ENOMEM; 1189 goto bad_hash_tables; 1190 } 1191 1192 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); 1193 if (IS_ERR(s->kcopyd_client)) { 1194 r = PTR_ERR(s->kcopyd_client); 1195 ti->error = "Could not create kcopyd client"; 1196 goto bad_kcopyd; 1197 } 1198 1199 s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache); 1200 if (!s->pending_pool) { 1201 ti->error = "Could not allocate mempool for pending exceptions"; 1202 r = -ENOMEM; 1203 goto bad_pending_pool; 1204 } 1205 1206 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) 1207 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]); 1208 1209 spin_lock_init(&s->tracked_chunk_lock); 1210 1211 ti->private = s; 1212 ti->num_flush_bios = num_flush_bios; 1213 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk); 1214 1215 /* Add snapshot to the list of snapshots for this origin */ 1216 /* Exceptions aren't triggered till snapshot_resume() is called */ 1217 r = register_snapshot(s); 1218 if (r == -ENOMEM) { 1219 ti->error = "Snapshot origin struct allocation failed"; 1220 goto bad_load_and_register; 1221 } else if (r < 0) { 1222 /* invalid handover, register_snapshot has set ti->error */ 1223 goto bad_load_and_register; 1224 } 1225 1226 /* 1227 * Metadata must only be loaded into one table at once, so skip this 1228 * if metadata will be handed over during resume. 1229 * Chunk size will be set during the handover - set it to zero to 1230 * ensure it's ignored. 1231 */ 1232 if (r > 0) { 1233 s->store->chunk_size = 0; 1234 return 0; 1235 } 1236 1237 r = s->store->type->read_metadata(s->store, dm_add_exception, 1238 (void *)s); 1239 if (r < 0) { 1240 ti->error = "Failed to read snapshot metadata"; 1241 goto bad_read_metadata; 1242 } else if (r > 0) { 1243 s->valid = 0; 1244 DMWARN("Snapshot is marked invalid."); 1245 } 1246 1247 if (!s->store->chunk_size) { 1248 ti->error = "Chunk size not set"; 1249 goto bad_read_metadata; 1250 } 1251 1252 r = dm_set_target_max_io_len(ti, s->store->chunk_size); 1253 if (r) 1254 goto bad_read_metadata; 1255 1256 return 0; 1257 1258 bad_read_metadata: 1259 unregister_snapshot(s); 1260 1261 bad_load_and_register: 1262 mempool_destroy(s->pending_pool); 1263 1264 bad_pending_pool: 1265 dm_kcopyd_client_destroy(s->kcopyd_client); 1266 1267 bad_kcopyd: 1268 dm_exception_table_exit(&s->pending, pending_cache); 1269 dm_exception_table_exit(&s->complete, exception_cache); 1270 1271 bad_hash_tables: 1272 dm_exception_store_destroy(s->store); 1273 1274 bad_store: 1275 dm_put_device(ti, s->cow); 1276 1277 bad_cow: 1278 dm_put_device(ti, s->origin); 1279 1280 bad_origin: 1281 kfree(s); 1282 1283 bad: 1284 return r; 1285 } 1286 1287 static void __free_exceptions(struct dm_snapshot *s) 1288 { 1289 dm_kcopyd_client_destroy(s->kcopyd_client); 1290 s->kcopyd_client = NULL; 1291 1292 dm_exception_table_exit(&s->pending, pending_cache); 1293 dm_exception_table_exit(&s->complete, exception_cache); 1294 } 1295 1296 static void __handover_exceptions(struct dm_snapshot *snap_src, 1297 struct dm_snapshot *snap_dest) 1298 { 1299 union { 1300 struct dm_exception_table table_swap; 1301 struct dm_exception_store *store_swap; 1302 } u; 1303 1304 /* 1305 * Swap all snapshot context information between the two instances. 1306 */ 1307 u.table_swap = snap_dest->complete; 1308 snap_dest->complete = snap_src->complete; 1309 snap_src->complete = u.table_swap; 1310 1311 u.store_swap = snap_dest->store; 1312 snap_dest->store = snap_src->store; 1313 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow; 1314 snap_src->store = u.store_swap; 1315 1316 snap_dest->store->snap = snap_dest; 1317 snap_src->store->snap = snap_src; 1318 1319 snap_dest->ti->max_io_len = snap_dest->store->chunk_size; 1320 snap_dest->valid = snap_src->valid; 1321 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed; 1322 1323 /* 1324 * Set source invalid to ensure it receives no further I/O. 1325 */ 1326 snap_src->valid = 0; 1327 } 1328 1329 static void snapshot_dtr(struct dm_target *ti) 1330 { 1331 #ifdef CONFIG_DM_DEBUG 1332 int i; 1333 #endif 1334 struct dm_snapshot *s = ti->private; 1335 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; 1336 1337 down_read(&_origins_lock); 1338 /* Check whether exception handover must be cancelled */ 1339 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); 1340 if (snap_src && snap_dest && (s == snap_src)) { 1341 down_write(&snap_dest->lock); 1342 snap_dest->valid = 0; 1343 up_write(&snap_dest->lock); 1344 DMERR("Cancelling snapshot handover."); 1345 } 1346 up_read(&_origins_lock); 1347 1348 if (dm_target_is_snapshot_merge(ti)) 1349 stop_merge(s); 1350 1351 /* Prevent further origin writes from using this snapshot. */ 1352 /* After this returns there can be no new kcopyd jobs. */ 1353 unregister_snapshot(s); 1354 1355 while (atomic_read(&s->pending_exceptions_count)) 1356 msleep(1); 1357 /* 1358 * Ensure instructions in mempool_destroy aren't reordered 1359 * before atomic_read. 1360 */ 1361 smp_mb(); 1362 1363 #ifdef CONFIG_DM_DEBUG 1364 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) 1365 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i])); 1366 #endif 1367 1368 __free_exceptions(s); 1369 1370 mempool_destroy(s->pending_pool); 1371 1372 dm_exception_store_destroy(s->store); 1373 1374 dm_put_device(ti, s->cow); 1375 1376 dm_put_device(ti, s->origin); 1377 1378 kfree(s); 1379 } 1380 1381 /* 1382 * Flush a list of buffers. 1383 */ 1384 static void flush_bios(struct bio *bio) 1385 { 1386 struct bio *n; 1387 1388 while (bio) { 1389 n = bio->bi_next; 1390 bio->bi_next = NULL; 1391 generic_make_request(bio); 1392 bio = n; 1393 } 1394 } 1395 1396 static int do_origin(struct dm_dev *origin, struct bio *bio); 1397 1398 /* 1399 * Flush a list of buffers. 1400 */ 1401 static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) 1402 { 1403 struct bio *n; 1404 int r; 1405 1406 while (bio) { 1407 n = bio->bi_next; 1408 bio->bi_next = NULL; 1409 r = do_origin(s->origin, bio); 1410 if (r == DM_MAPIO_REMAPPED) 1411 generic_make_request(bio); 1412 bio = n; 1413 } 1414 } 1415 1416 /* 1417 * Error a list of buffers. 1418 */ 1419 static void error_bios(struct bio *bio) 1420 { 1421 struct bio *n; 1422 1423 while (bio) { 1424 n = bio->bi_next; 1425 bio->bi_next = NULL; 1426 bio_io_error(bio); 1427 bio = n; 1428 } 1429 } 1430 1431 static void __invalidate_snapshot(struct dm_snapshot *s, int err) 1432 { 1433 if (!s->valid) 1434 return; 1435 1436 if (err == -EIO) 1437 DMERR("Invalidating snapshot: Error reading/writing."); 1438 else if (err == -ENOMEM) 1439 DMERR("Invalidating snapshot: Unable to allocate exception."); 1440 1441 if (s->store->type->drop_snapshot) 1442 s->store->type->drop_snapshot(s->store); 1443 1444 s->valid = 0; 1445 1446 dm_table_event(s->ti->table); 1447 } 1448 1449 static void pending_complete(void *context, int success) 1450 { 1451 struct dm_snap_pending_exception *pe = context; 1452 struct dm_exception *e; 1453 struct dm_snapshot *s = pe->snap; 1454 struct bio *origin_bios = NULL; 1455 struct bio *snapshot_bios = NULL; 1456 struct bio *full_bio = NULL; 1457 int error = 0; 1458 1459 if (!success) { 1460 /* Read/write error - snapshot is unusable */ 1461 down_write(&s->lock); 1462 __invalidate_snapshot(s, -EIO); 1463 error = 1; 1464 goto out; 1465 } 1466 1467 e = alloc_completed_exception(GFP_NOIO); 1468 if (!e) { 1469 down_write(&s->lock); 1470 __invalidate_snapshot(s, -ENOMEM); 1471 error = 1; 1472 goto out; 1473 } 1474 *e = pe->e; 1475 1476 down_write(&s->lock); 1477 if (!s->valid) { 1478 free_completed_exception(e); 1479 error = 1; 1480 goto out; 1481 } 1482 1483 /* Check for conflicting reads */ 1484 __check_for_conflicting_io(s, pe->e.old_chunk); 1485 1486 /* 1487 * Add a proper exception, and remove the 1488 * in-flight exception from the list. 1489 */ 1490 dm_insert_exception(&s->complete, e); 1491 1492 out: 1493 dm_remove_exception(&pe->e); 1494 snapshot_bios = bio_list_get(&pe->snapshot_bios); 1495 origin_bios = bio_list_get(&pe->origin_bios); 1496 full_bio = pe->full_bio; 1497 if (full_bio) 1498 full_bio->bi_end_io = pe->full_bio_end_io; 1499 increment_pending_exceptions_done_count(); 1500 1501 up_write(&s->lock); 1502 1503 /* Submit any pending write bios */ 1504 if (error) { 1505 if (full_bio) 1506 bio_io_error(full_bio); 1507 error_bios(snapshot_bios); 1508 } else { 1509 if (full_bio) 1510 bio_endio(full_bio); 1511 flush_bios(snapshot_bios); 1512 } 1513 1514 retry_origin_bios(s, origin_bios); 1515 1516 free_pending_exception(pe); 1517 } 1518 1519 static void complete_exception(struct dm_snap_pending_exception *pe) 1520 { 1521 struct dm_snapshot *s = pe->snap; 1522 1523 /* Update the metadata if we are persistent */ 1524 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error, 1525 pending_complete, pe); 1526 } 1527 1528 /* 1529 * Called when the copy I/O has finished. kcopyd actually runs 1530 * this code so don't block. 1531 */ 1532 static void copy_callback(int read_err, unsigned long write_err, void *context) 1533 { 1534 struct dm_snap_pending_exception *pe = context; 1535 struct dm_snapshot *s = pe->snap; 1536 1537 pe->copy_error = read_err || write_err; 1538 1539 if (pe->exception_sequence == s->exception_complete_sequence) { 1540 s->exception_complete_sequence++; 1541 complete_exception(pe); 1542 1543 while (!list_empty(&s->out_of_order_list)) { 1544 pe = list_entry(s->out_of_order_list.next, 1545 struct dm_snap_pending_exception, out_of_order_entry); 1546 if (pe->exception_sequence != s->exception_complete_sequence) 1547 break; 1548 s->exception_complete_sequence++; 1549 list_del(&pe->out_of_order_entry); 1550 complete_exception(pe); 1551 } 1552 } else { 1553 struct list_head *lh; 1554 struct dm_snap_pending_exception *pe2; 1555 1556 list_for_each_prev(lh, &s->out_of_order_list) { 1557 pe2 = list_entry(lh, struct dm_snap_pending_exception, out_of_order_entry); 1558 if (pe2->exception_sequence < pe->exception_sequence) 1559 break; 1560 } 1561 list_add(&pe->out_of_order_entry, lh); 1562 } 1563 } 1564 1565 /* 1566 * Dispatches the copy operation to kcopyd. 1567 */ 1568 static void start_copy(struct dm_snap_pending_exception *pe) 1569 { 1570 struct dm_snapshot *s = pe->snap; 1571 struct dm_io_region src, dest; 1572 struct block_device *bdev = s->origin->bdev; 1573 sector_t dev_size; 1574 1575 dev_size = get_dev_size(bdev); 1576 1577 src.bdev = bdev; 1578 src.sector = chunk_to_sector(s->store, pe->e.old_chunk); 1579 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector); 1580 1581 dest.bdev = s->cow->bdev; 1582 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk); 1583 dest.count = src.count; 1584 1585 /* Hand over to kcopyd */ 1586 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe); 1587 } 1588 1589 static void full_bio_end_io(struct bio *bio) 1590 { 1591 void *callback_data = bio->bi_private; 1592 1593 dm_kcopyd_do_callback(callback_data, 0, bio->bi_error ? 1 : 0); 1594 } 1595 1596 static void start_full_bio(struct dm_snap_pending_exception *pe, 1597 struct bio *bio) 1598 { 1599 struct dm_snapshot *s = pe->snap; 1600 void *callback_data; 1601 1602 pe->full_bio = bio; 1603 pe->full_bio_end_io = bio->bi_end_io; 1604 1605 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client, 1606 copy_callback, pe); 1607 1608 bio->bi_end_io = full_bio_end_io; 1609 bio->bi_private = callback_data; 1610 1611 generic_make_request(bio); 1612 } 1613 1614 static struct dm_snap_pending_exception * 1615 __lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) 1616 { 1617 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk); 1618 1619 if (!e) 1620 return NULL; 1621 1622 return container_of(e, struct dm_snap_pending_exception, e); 1623 } 1624 1625 /* 1626 * Looks to see if this snapshot already has a pending exception 1627 * for this chunk, otherwise it allocates a new one and inserts 1628 * it into the pending table. 1629 * 1630 * NOTE: a write lock must be held on snap->lock before calling 1631 * this. 1632 */ 1633 static struct dm_snap_pending_exception * 1634 __find_pending_exception(struct dm_snapshot *s, 1635 struct dm_snap_pending_exception *pe, chunk_t chunk) 1636 { 1637 struct dm_snap_pending_exception *pe2; 1638 1639 pe2 = __lookup_pending_exception(s, chunk); 1640 if (pe2) { 1641 free_pending_exception(pe); 1642 return pe2; 1643 } 1644 1645 pe->e.old_chunk = chunk; 1646 bio_list_init(&pe->origin_bios); 1647 bio_list_init(&pe->snapshot_bios); 1648 pe->started = 0; 1649 pe->full_bio = NULL; 1650 1651 if (s->store->type->prepare_exception(s->store, &pe->e)) { 1652 free_pending_exception(pe); 1653 return NULL; 1654 } 1655 1656 pe->exception_sequence = s->exception_start_sequence++; 1657 1658 dm_insert_exception(&s->pending, &pe->e); 1659 1660 return pe; 1661 } 1662 1663 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e, 1664 struct bio *bio, chunk_t chunk) 1665 { 1666 bio->bi_bdev = s->cow->bdev; 1667 bio->bi_iter.bi_sector = 1668 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) + 1669 (chunk - e->old_chunk)) + 1670 (bio->bi_iter.bi_sector & s->store->chunk_mask); 1671 } 1672 1673 static int snapshot_map(struct dm_target *ti, struct bio *bio) 1674 { 1675 struct dm_exception *e; 1676 struct dm_snapshot *s = ti->private; 1677 int r = DM_MAPIO_REMAPPED; 1678 chunk_t chunk; 1679 struct dm_snap_pending_exception *pe = NULL; 1680 1681 init_tracked_chunk(bio); 1682 1683 if (bio->bi_rw & REQ_FLUSH) { 1684 bio->bi_bdev = s->cow->bdev; 1685 return DM_MAPIO_REMAPPED; 1686 } 1687 1688 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); 1689 1690 /* Full snapshots are not usable */ 1691 /* To get here the table must be live so s->active is always set. */ 1692 if (!s->valid) 1693 return -EIO; 1694 1695 /* FIXME: should only take write lock if we need 1696 * to copy an exception */ 1697 down_write(&s->lock); 1698 1699 if (!s->valid || (unlikely(s->snapshot_overflowed) && bio_rw(bio) == WRITE)) { 1700 r = -EIO; 1701 goto out_unlock; 1702 } 1703 1704 /* If the block is already remapped - use that, else remap it */ 1705 e = dm_lookup_exception(&s->complete, chunk); 1706 if (e) { 1707 remap_exception(s, e, bio, chunk); 1708 goto out_unlock; 1709 } 1710 1711 /* 1712 * Write to snapshot - higher level takes care of RW/RO 1713 * flags so we should only get this if we are 1714 * writeable. 1715 */ 1716 if (bio_rw(bio) == WRITE) { 1717 pe = __lookup_pending_exception(s, chunk); 1718 if (!pe) { 1719 up_write(&s->lock); 1720 pe = alloc_pending_exception(s); 1721 down_write(&s->lock); 1722 1723 if (!s->valid || s->snapshot_overflowed) { 1724 free_pending_exception(pe); 1725 r = -EIO; 1726 goto out_unlock; 1727 } 1728 1729 e = dm_lookup_exception(&s->complete, chunk); 1730 if (e) { 1731 free_pending_exception(pe); 1732 remap_exception(s, e, bio, chunk); 1733 goto out_unlock; 1734 } 1735 1736 pe = __find_pending_exception(s, pe, chunk); 1737 if (!pe) { 1738 if (s->store->userspace_supports_overflow) { 1739 s->snapshot_overflowed = 1; 1740 DMERR("Snapshot overflowed: Unable to allocate exception."); 1741 } else 1742 __invalidate_snapshot(s, -ENOMEM); 1743 r = -EIO; 1744 goto out_unlock; 1745 } 1746 } 1747 1748 remap_exception(s, &pe->e, bio, chunk); 1749 1750 r = DM_MAPIO_SUBMITTED; 1751 1752 if (!pe->started && 1753 bio->bi_iter.bi_size == 1754 (s->store->chunk_size << SECTOR_SHIFT)) { 1755 pe->started = 1; 1756 up_write(&s->lock); 1757 start_full_bio(pe, bio); 1758 goto out; 1759 } 1760 1761 bio_list_add(&pe->snapshot_bios, bio); 1762 1763 if (!pe->started) { 1764 /* this is protected by snap->lock */ 1765 pe->started = 1; 1766 up_write(&s->lock); 1767 start_copy(pe); 1768 goto out; 1769 } 1770 } else { 1771 bio->bi_bdev = s->origin->bdev; 1772 track_chunk(s, bio, chunk); 1773 } 1774 1775 out_unlock: 1776 up_write(&s->lock); 1777 out: 1778 return r; 1779 } 1780 1781 /* 1782 * A snapshot-merge target behaves like a combination of a snapshot 1783 * target and a snapshot-origin target. It only generates new 1784 * exceptions in other snapshots and not in the one that is being 1785 * merged. 1786 * 1787 * For each chunk, if there is an existing exception, it is used to 1788 * redirect I/O to the cow device. Otherwise I/O is sent to the origin, 1789 * which in turn might generate exceptions in other snapshots. 1790 * If merging is currently taking place on the chunk in question, the 1791 * I/O is deferred by adding it to s->bios_queued_during_merge. 1792 */ 1793 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) 1794 { 1795 struct dm_exception *e; 1796 struct dm_snapshot *s = ti->private; 1797 int r = DM_MAPIO_REMAPPED; 1798 chunk_t chunk; 1799 1800 init_tracked_chunk(bio); 1801 1802 if (bio->bi_rw & REQ_FLUSH) { 1803 if (!dm_bio_get_target_bio_nr(bio)) 1804 bio->bi_bdev = s->origin->bdev; 1805 else 1806 bio->bi_bdev = s->cow->bdev; 1807 return DM_MAPIO_REMAPPED; 1808 } 1809 1810 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); 1811 1812 down_write(&s->lock); 1813 1814 /* Full merging snapshots are redirected to the origin */ 1815 if (!s->valid) 1816 goto redirect_to_origin; 1817 1818 /* If the block is already remapped - use that */ 1819 e = dm_lookup_exception(&s->complete, chunk); 1820 if (e) { 1821 /* Queue writes overlapping with chunks being merged */ 1822 if (bio_rw(bio) == WRITE && 1823 chunk >= s->first_merging_chunk && 1824 chunk < (s->first_merging_chunk + 1825 s->num_merging_chunks)) { 1826 bio->bi_bdev = s->origin->bdev; 1827 bio_list_add(&s->bios_queued_during_merge, bio); 1828 r = DM_MAPIO_SUBMITTED; 1829 goto out_unlock; 1830 } 1831 1832 remap_exception(s, e, bio, chunk); 1833 1834 if (bio_rw(bio) == WRITE) 1835 track_chunk(s, bio, chunk); 1836 goto out_unlock; 1837 } 1838 1839 redirect_to_origin: 1840 bio->bi_bdev = s->origin->bdev; 1841 1842 if (bio_rw(bio) == WRITE) { 1843 up_write(&s->lock); 1844 return do_origin(s->origin, bio); 1845 } 1846 1847 out_unlock: 1848 up_write(&s->lock); 1849 1850 return r; 1851 } 1852 1853 static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error) 1854 { 1855 struct dm_snapshot *s = ti->private; 1856 1857 if (is_bio_tracked(bio)) 1858 stop_tracking_chunk(s, bio); 1859 1860 return 0; 1861 } 1862 1863 static void snapshot_merge_presuspend(struct dm_target *ti) 1864 { 1865 struct dm_snapshot *s = ti->private; 1866 1867 stop_merge(s); 1868 } 1869 1870 static int snapshot_preresume(struct dm_target *ti) 1871 { 1872 int r = 0; 1873 struct dm_snapshot *s = ti->private; 1874 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; 1875 1876 down_read(&_origins_lock); 1877 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); 1878 if (snap_src && snap_dest) { 1879 down_read(&snap_src->lock); 1880 if (s == snap_src) { 1881 DMERR("Unable to resume snapshot source until " 1882 "handover completes."); 1883 r = -EINVAL; 1884 } else if (!dm_suspended(snap_src->ti)) { 1885 DMERR("Unable to perform snapshot handover until " 1886 "source is suspended."); 1887 r = -EINVAL; 1888 } 1889 up_read(&snap_src->lock); 1890 } 1891 up_read(&_origins_lock); 1892 1893 return r; 1894 } 1895 1896 static void snapshot_resume(struct dm_target *ti) 1897 { 1898 struct dm_snapshot *s = ti->private; 1899 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL; 1900 struct dm_origin *o; 1901 struct mapped_device *origin_md = NULL; 1902 bool must_restart_merging = false; 1903 1904 down_read(&_origins_lock); 1905 1906 o = __lookup_dm_origin(s->origin->bdev); 1907 if (o) 1908 origin_md = dm_table_get_md(o->ti->table); 1909 if (!origin_md) { 1910 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging); 1911 if (snap_merging) 1912 origin_md = dm_table_get_md(snap_merging->ti->table); 1913 } 1914 if (origin_md == dm_table_get_md(ti->table)) 1915 origin_md = NULL; 1916 if (origin_md) { 1917 if (dm_hold(origin_md)) 1918 origin_md = NULL; 1919 } 1920 1921 up_read(&_origins_lock); 1922 1923 if (origin_md) { 1924 dm_internal_suspend_fast(origin_md); 1925 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) { 1926 must_restart_merging = true; 1927 stop_merge(snap_merging); 1928 } 1929 } 1930 1931 down_read(&_origins_lock); 1932 1933 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); 1934 if (snap_src && snap_dest) { 1935 down_write(&snap_src->lock); 1936 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING); 1937 __handover_exceptions(snap_src, snap_dest); 1938 up_write(&snap_dest->lock); 1939 up_write(&snap_src->lock); 1940 } 1941 1942 up_read(&_origins_lock); 1943 1944 if (origin_md) { 1945 if (must_restart_merging) 1946 start_merge(snap_merging); 1947 dm_internal_resume_fast(origin_md); 1948 dm_put(origin_md); 1949 } 1950 1951 /* Now we have correct chunk size, reregister */ 1952 reregister_snapshot(s); 1953 1954 down_write(&s->lock); 1955 s->active = 1; 1956 up_write(&s->lock); 1957 } 1958 1959 static uint32_t get_origin_minimum_chunksize(struct block_device *bdev) 1960 { 1961 uint32_t min_chunksize; 1962 1963 down_read(&_origins_lock); 1964 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev)); 1965 up_read(&_origins_lock); 1966 1967 return min_chunksize; 1968 } 1969 1970 static void snapshot_merge_resume(struct dm_target *ti) 1971 { 1972 struct dm_snapshot *s = ti->private; 1973 1974 /* 1975 * Handover exceptions from existing snapshot. 1976 */ 1977 snapshot_resume(ti); 1978 1979 /* 1980 * snapshot-merge acts as an origin, so set ti->max_io_len 1981 */ 1982 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev); 1983 1984 start_merge(s); 1985 } 1986 1987 static void snapshot_status(struct dm_target *ti, status_type_t type, 1988 unsigned status_flags, char *result, unsigned maxlen) 1989 { 1990 unsigned sz = 0; 1991 struct dm_snapshot *snap = ti->private; 1992 1993 switch (type) { 1994 case STATUSTYPE_INFO: 1995 1996 down_write(&snap->lock); 1997 1998 if (!snap->valid) 1999 DMEMIT("Invalid"); 2000 else if (snap->merge_failed) 2001 DMEMIT("Merge failed"); 2002 else if (snap->snapshot_overflowed) 2003 DMEMIT("Overflow"); 2004 else { 2005 if (snap->store->type->usage) { 2006 sector_t total_sectors, sectors_allocated, 2007 metadata_sectors; 2008 snap->store->type->usage(snap->store, 2009 &total_sectors, 2010 §ors_allocated, 2011 &metadata_sectors); 2012 DMEMIT("%llu/%llu %llu", 2013 (unsigned long long)sectors_allocated, 2014 (unsigned long long)total_sectors, 2015 (unsigned long long)metadata_sectors); 2016 } 2017 else 2018 DMEMIT("Unknown"); 2019 } 2020 2021 up_write(&snap->lock); 2022 2023 break; 2024 2025 case STATUSTYPE_TABLE: 2026 /* 2027 * kdevname returns a static pointer so we need 2028 * to make private copies if the output is to 2029 * make sense. 2030 */ 2031 DMEMIT("%s %s", snap->origin->name, snap->cow->name); 2032 snap->store->type->status(snap->store, type, result + sz, 2033 maxlen - sz); 2034 break; 2035 } 2036 } 2037 2038 static int snapshot_iterate_devices(struct dm_target *ti, 2039 iterate_devices_callout_fn fn, void *data) 2040 { 2041 struct dm_snapshot *snap = ti->private; 2042 int r; 2043 2044 r = fn(ti, snap->origin, 0, ti->len, data); 2045 2046 if (!r) 2047 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data); 2048 2049 return r; 2050 } 2051 2052 2053 /*----------------------------------------------------------------- 2054 * Origin methods 2055 *---------------------------------------------------------------*/ 2056 2057 /* 2058 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any 2059 * supplied bio was ignored. The caller may submit it immediately. 2060 * (No remapping actually occurs as the origin is always a direct linear 2061 * map.) 2062 * 2063 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned 2064 * and any supplied bio is added to a list to be submitted once all 2065 * the necessary exceptions exist. 2066 */ 2067 static int __origin_write(struct list_head *snapshots, sector_t sector, 2068 struct bio *bio) 2069 { 2070 int r = DM_MAPIO_REMAPPED; 2071 struct dm_snapshot *snap; 2072 struct dm_exception *e; 2073 struct dm_snap_pending_exception *pe; 2074 struct dm_snap_pending_exception *pe_to_start_now = NULL; 2075 struct dm_snap_pending_exception *pe_to_start_last = NULL; 2076 chunk_t chunk; 2077 2078 /* Do all the snapshots on this origin */ 2079 list_for_each_entry (snap, snapshots, list) { 2080 /* 2081 * Don't make new exceptions in a merging snapshot 2082 * because it has effectively been deleted 2083 */ 2084 if (dm_target_is_snapshot_merge(snap->ti)) 2085 continue; 2086 2087 down_write(&snap->lock); 2088 2089 /* Only deal with valid and active snapshots */ 2090 if (!snap->valid || !snap->active) 2091 goto next_snapshot; 2092 2093 /* Nothing to do if writing beyond end of snapshot */ 2094 if (sector >= dm_table_get_size(snap->ti->table)) 2095 goto next_snapshot; 2096 2097 /* 2098 * Remember, different snapshots can have 2099 * different chunk sizes. 2100 */ 2101 chunk = sector_to_chunk(snap->store, sector); 2102 2103 /* 2104 * Check exception table to see if block 2105 * is already remapped in this snapshot 2106 * and trigger an exception if not. 2107 */ 2108 e = dm_lookup_exception(&snap->complete, chunk); 2109 if (e) 2110 goto next_snapshot; 2111 2112 pe = __lookup_pending_exception(snap, chunk); 2113 if (!pe) { 2114 up_write(&snap->lock); 2115 pe = alloc_pending_exception(snap); 2116 down_write(&snap->lock); 2117 2118 if (!snap->valid) { 2119 free_pending_exception(pe); 2120 goto next_snapshot; 2121 } 2122 2123 e = dm_lookup_exception(&snap->complete, chunk); 2124 if (e) { 2125 free_pending_exception(pe); 2126 goto next_snapshot; 2127 } 2128 2129 pe = __find_pending_exception(snap, pe, chunk); 2130 if (!pe) { 2131 __invalidate_snapshot(snap, -ENOMEM); 2132 goto next_snapshot; 2133 } 2134 } 2135 2136 r = DM_MAPIO_SUBMITTED; 2137 2138 /* 2139 * If an origin bio was supplied, queue it to wait for the 2140 * completion of this exception, and start this one last, 2141 * at the end of the function. 2142 */ 2143 if (bio) { 2144 bio_list_add(&pe->origin_bios, bio); 2145 bio = NULL; 2146 2147 if (!pe->started) { 2148 pe->started = 1; 2149 pe_to_start_last = pe; 2150 } 2151 } 2152 2153 if (!pe->started) { 2154 pe->started = 1; 2155 pe_to_start_now = pe; 2156 } 2157 2158 next_snapshot: 2159 up_write(&snap->lock); 2160 2161 if (pe_to_start_now) { 2162 start_copy(pe_to_start_now); 2163 pe_to_start_now = NULL; 2164 } 2165 } 2166 2167 /* 2168 * Submit the exception against which the bio is queued last, 2169 * to give the other exceptions a head start. 2170 */ 2171 if (pe_to_start_last) 2172 start_copy(pe_to_start_last); 2173 2174 return r; 2175 } 2176 2177 /* 2178 * Called on a write from the origin driver. 2179 */ 2180 static int do_origin(struct dm_dev *origin, struct bio *bio) 2181 { 2182 struct origin *o; 2183 int r = DM_MAPIO_REMAPPED; 2184 2185 down_read(&_origins_lock); 2186 o = __lookup_origin(origin->bdev); 2187 if (o) 2188 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); 2189 up_read(&_origins_lock); 2190 2191 return r; 2192 } 2193 2194 /* 2195 * Trigger exceptions in all non-merging snapshots. 2196 * 2197 * The chunk size of the merging snapshot may be larger than the chunk 2198 * size of some other snapshot so we may need to reallocate multiple 2199 * chunks in other snapshots. 2200 * 2201 * We scan all the overlapping exceptions in the other snapshots. 2202 * Returns 1 if anything was reallocated and must be waited for, 2203 * otherwise returns 0. 2204 * 2205 * size must be a multiple of merging_snap's chunk_size. 2206 */ 2207 static int origin_write_extent(struct dm_snapshot *merging_snap, 2208 sector_t sector, unsigned size) 2209 { 2210 int must_wait = 0; 2211 sector_t n; 2212 struct origin *o; 2213 2214 /* 2215 * The origin's __minimum_chunk_size() got stored in max_io_len 2216 * by snapshot_merge_resume(). 2217 */ 2218 down_read(&_origins_lock); 2219 o = __lookup_origin(merging_snap->origin->bdev); 2220 for (n = 0; n < size; n += merging_snap->ti->max_io_len) 2221 if (__origin_write(&o->snapshots, sector + n, NULL) == 2222 DM_MAPIO_SUBMITTED) 2223 must_wait = 1; 2224 up_read(&_origins_lock); 2225 2226 return must_wait; 2227 } 2228 2229 /* 2230 * Origin: maps a linear range of a device, with hooks for snapshotting. 2231 */ 2232 2233 /* 2234 * Construct an origin mapping: <dev_path> 2235 * The context for an origin is merely a 'struct dm_dev *' 2236 * pointing to the real device. 2237 */ 2238 static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv) 2239 { 2240 int r; 2241 struct dm_origin *o; 2242 2243 if (argc != 1) { 2244 ti->error = "origin: incorrect number of arguments"; 2245 return -EINVAL; 2246 } 2247 2248 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL); 2249 if (!o) { 2250 ti->error = "Cannot allocate private origin structure"; 2251 r = -ENOMEM; 2252 goto bad_alloc; 2253 } 2254 2255 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev); 2256 if (r) { 2257 ti->error = "Cannot get target device"; 2258 goto bad_open; 2259 } 2260 2261 o->ti = ti; 2262 ti->private = o; 2263 ti->num_flush_bios = 1; 2264 2265 return 0; 2266 2267 bad_open: 2268 kfree(o); 2269 bad_alloc: 2270 return r; 2271 } 2272 2273 static void origin_dtr(struct dm_target *ti) 2274 { 2275 struct dm_origin *o = ti->private; 2276 2277 dm_put_device(ti, o->dev); 2278 kfree(o); 2279 } 2280 2281 static int origin_map(struct dm_target *ti, struct bio *bio) 2282 { 2283 struct dm_origin *o = ti->private; 2284 unsigned available_sectors; 2285 2286 bio->bi_bdev = o->dev->bdev; 2287 2288 if (unlikely(bio->bi_rw & REQ_FLUSH)) 2289 return DM_MAPIO_REMAPPED; 2290 2291 if (bio_rw(bio) != WRITE) 2292 return DM_MAPIO_REMAPPED; 2293 2294 available_sectors = o->split_boundary - 2295 ((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1)); 2296 2297 if (bio_sectors(bio) > available_sectors) 2298 dm_accept_partial_bio(bio, available_sectors); 2299 2300 /* Only tell snapshots if this is a write */ 2301 return do_origin(o->dev, bio); 2302 } 2303 2304 /* 2305 * Set the target "max_io_len" field to the minimum of all the snapshots' 2306 * chunk sizes. 2307 */ 2308 static void origin_resume(struct dm_target *ti) 2309 { 2310 struct dm_origin *o = ti->private; 2311 2312 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev); 2313 2314 down_write(&_origins_lock); 2315 __insert_dm_origin(o); 2316 up_write(&_origins_lock); 2317 } 2318 2319 static void origin_postsuspend(struct dm_target *ti) 2320 { 2321 struct dm_origin *o = ti->private; 2322 2323 down_write(&_origins_lock); 2324 __remove_dm_origin(o); 2325 up_write(&_origins_lock); 2326 } 2327 2328 static void origin_status(struct dm_target *ti, status_type_t type, 2329 unsigned status_flags, char *result, unsigned maxlen) 2330 { 2331 struct dm_origin *o = ti->private; 2332 2333 switch (type) { 2334 case STATUSTYPE_INFO: 2335 result[0] = '\0'; 2336 break; 2337 2338 case STATUSTYPE_TABLE: 2339 snprintf(result, maxlen, "%s", o->dev->name); 2340 break; 2341 } 2342 } 2343 2344 static int origin_iterate_devices(struct dm_target *ti, 2345 iterate_devices_callout_fn fn, void *data) 2346 { 2347 struct dm_origin *o = ti->private; 2348 2349 return fn(ti, o->dev, 0, ti->len, data); 2350 } 2351 2352 static struct target_type origin_target = { 2353 .name = "snapshot-origin", 2354 .version = {1, 9, 0}, 2355 .module = THIS_MODULE, 2356 .ctr = origin_ctr, 2357 .dtr = origin_dtr, 2358 .map = origin_map, 2359 .resume = origin_resume, 2360 .postsuspend = origin_postsuspend, 2361 .status = origin_status, 2362 .iterate_devices = origin_iterate_devices, 2363 }; 2364 2365 static struct target_type snapshot_target = { 2366 .name = "snapshot", 2367 .version = {1, 15, 0}, 2368 .module = THIS_MODULE, 2369 .ctr = snapshot_ctr, 2370 .dtr = snapshot_dtr, 2371 .map = snapshot_map, 2372 .end_io = snapshot_end_io, 2373 .preresume = snapshot_preresume, 2374 .resume = snapshot_resume, 2375 .status = snapshot_status, 2376 .iterate_devices = snapshot_iterate_devices, 2377 }; 2378 2379 static struct target_type merge_target = { 2380 .name = dm_snapshot_merge_target_name, 2381 .version = {1, 4, 0}, 2382 .module = THIS_MODULE, 2383 .ctr = snapshot_ctr, 2384 .dtr = snapshot_dtr, 2385 .map = snapshot_merge_map, 2386 .end_io = snapshot_end_io, 2387 .presuspend = snapshot_merge_presuspend, 2388 .preresume = snapshot_preresume, 2389 .resume = snapshot_merge_resume, 2390 .status = snapshot_status, 2391 .iterate_devices = snapshot_iterate_devices, 2392 }; 2393 2394 static int __init dm_snapshot_init(void) 2395 { 2396 int r; 2397 2398 r = dm_exception_store_init(); 2399 if (r) { 2400 DMERR("Failed to initialize exception stores"); 2401 return r; 2402 } 2403 2404 r = dm_register_target(&snapshot_target); 2405 if (r < 0) { 2406 DMERR("snapshot target register failed %d", r); 2407 goto bad_register_snapshot_target; 2408 } 2409 2410 r = dm_register_target(&origin_target); 2411 if (r < 0) { 2412 DMERR("Origin target register failed %d", r); 2413 goto bad_register_origin_target; 2414 } 2415 2416 r = dm_register_target(&merge_target); 2417 if (r < 0) { 2418 DMERR("Merge target register failed %d", r); 2419 goto bad_register_merge_target; 2420 } 2421 2422 r = init_origin_hash(); 2423 if (r) { 2424 DMERR("init_origin_hash failed."); 2425 goto bad_origin_hash; 2426 } 2427 2428 exception_cache = KMEM_CACHE(dm_exception, 0); 2429 if (!exception_cache) { 2430 DMERR("Couldn't create exception cache."); 2431 r = -ENOMEM; 2432 goto bad_exception_cache; 2433 } 2434 2435 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0); 2436 if (!pending_cache) { 2437 DMERR("Couldn't create pending cache."); 2438 r = -ENOMEM; 2439 goto bad_pending_cache; 2440 } 2441 2442 return 0; 2443 2444 bad_pending_cache: 2445 kmem_cache_destroy(exception_cache); 2446 bad_exception_cache: 2447 exit_origin_hash(); 2448 bad_origin_hash: 2449 dm_unregister_target(&merge_target); 2450 bad_register_merge_target: 2451 dm_unregister_target(&origin_target); 2452 bad_register_origin_target: 2453 dm_unregister_target(&snapshot_target); 2454 bad_register_snapshot_target: 2455 dm_exception_store_exit(); 2456 2457 return r; 2458 } 2459 2460 static void __exit dm_snapshot_exit(void) 2461 { 2462 dm_unregister_target(&snapshot_target); 2463 dm_unregister_target(&origin_target); 2464 dm_unregister_target(&merge_target); 2465 2466 exit_origin_hash(); 2467 kmem_cache_destroy(pending_cache); 2468 kmem_cache_destroy(exception_cache); 2469 2470 dm_exception_store_exit(); 2471 } 2472 2473 /* Module hooks */ 2474 module_init(dm_snapshot_init); 2475 module_exit(dm_snapshot_exit); 2476 2477 MODULE_DESCRIPTION(DM_NAME " snapshot target"); 2478 MODULE_AUTHOR("Joe Thornber"); 2479 MODULE_LICENSE("GPL"); 2480 MODULE_ALIAS("dm-snapshot-origin"); 2481 MODULE_ALIAS("dm-snapshot-merge"); 2482