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