drivers/md/dm-era-target.c

   1 #include "dm.h"
   2 #include "persistent-data/dm-transaction-manager.h"
   3 #include "persistent-data/dm-bitset.h"
   4 #include "persistent-data/dm-space-map.h"
   5
   6 #include <linux/dm-io.h>
   7 #include <linux/dm-kcopyd.h>
   8 #include <linux/init.h>
   9 #include <linux/mempool.h>
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/vmalloc.h>
  13
  14 #define DM_MSG_PREFIX "era"
  15
  16 #define SUPERBLOCK_LOCATION 0
  17 #define SUPERBLOCK_MAGIC 2126579579
  18 #define SUPERBLOCK_CSUM_XOR 146538381
  19 #define MIN_ERA_VERSION 1
  20 #define MAX_ERA_VERSION 1
  21 #define INVALID_WRITESET_ROOT SUPERBLOCK_LOCATION
  22 #define MIN_BLOCK_SIZE 8
  23
  24 /*----------------------------------------------------------------
  25  * Writeset
  26  *--------------------------------------------------------------*/
  27 struct writeset_metadata {
  28         uint32_t nr_bits;
  29         dm_block_t root;
  30 };
  31
  32 struct writeset {
  33         struct writeset_metadata md;
  34
  35         /*
  36          * An in core copy of the bits to save constantly doing look ups on
  37          * disk.
  38          */
  39         unsigned long *bits;
  40 };
  41
  42 /*
  43  * This does not free off the on disk bitset as this will normally be done
  44  * after digesting into the era array.
  45  */
  46 static void writeset_free(struct writeset *ws)
  47 {
  48         vfree(ws->bits);
  49 }
  50
  51 static int setup_on_disk_bitset(struct dm_disk_bitset *info,
  52                                 unsigned nr_bits, dm_block_t *root)
  53 {
  54         int r;
  55
  56         r = dm_bitset_empty(info, root);
  57         if (r)
  58                 return r;
  59
  60         return dm_bitset_resize(info, *root, 0, nr_bits, false, root);
  61 }
  62
  63 static size_t bitset_size(unsigned nr_bits)
  64 {
  65         return sizeof(unsigned long) * dm_div_up(nr_bits, BITS_PER_LONG);
  66 }
  67
  68 /*
  69  * Allocates memory for the in core bitset.
  70  */
  71 static int writeset_alloc(struct writeset *ws, dm_block_t nr_blocks)
  72 {
  73         ws->md.nr_bits = nr_blocks;
  74         ws->md.root = INVALID_WRITESET_ROOT;
  75         ws->bits = vzalloc(bitset_size(nr_blocks));
  76         if (!ws->bits) {
  77                 DMERR("%s: couldn't allocate in memory bitset", __func__);
  78                 return -ENOMEM;
  79         }
  80
  81         return 0;
  82 }
  83
  84 /*
  85  * Wipes the in-core bitset, and creates a new on disk bitset.
  86  */
  87 static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws)
  88 {
  89         int r;
  90
  91         memset(ws->bits, 0, bitset_size(ws->md.nr_bits));
  92
  93         r = setup_on_disk_bitset(info, ws->md.nr_bits, &ws->md.root);
  94         if (r) {
  95                 DMERR("%s: setup_on_disk_bitset failed", __func__);
  96                 return r;
  97         }
  98
  99         return 0;
 100 }
 101
 102 static bool writeset_marked(struct writeset *ws, dm_block_t block)
 103 {
 104         return test_bit(block, ws->bits);
 105 }
 106
 107 static int writeset_marked_on_disk(struct dm_disk_bitset *info,
 108                                    struct writeset_metadata *m, dm_block_t block,
 109                                    bool *result)
 110 {
 111         dm_block_t old = m->root;
 112
 113         /*
 114          * The bitset was flushed when it was archived, so we know there'll
 115          * be no change to the root.
 116          */
 117         int r = dm_bitset_test_bit(info, m->root, block, &m->root, result);
 118         if (r) {
 119                 DMERR("%s: dm_bitset_test_bit failed", __func__);
 120                 return r;
 121         }
 122
 123         BUG_ON(m->root != old);
 124
 125         return r;
 126 }
 127
 128 /*
 129  * Returns < 0 on error, 0 if the bit wasn't previously set, 1 if it was.
 130  */
 131 static int writeset_test_and_set(struct dm_disk_bitset *info,
 132                                  struct writeset *ws, uint32_t block)
 133 {
 134         int r;
 135
 136         if (!test_and_set_bit(block, ws->bits)) {
 137                 r = dm_bitset_set_bit(info, ws->md.root, block, &ws->md.root);
 138                 if (r) {
 139                         /* FIXME: fail mode */
 140                         return r;
 141                 }
 142
 143                 return 0;
 144         }
 145
 146         return 1;
 147 }
 148
 149 /*----------------------------------------------------------------
 150  * On disk metadata layout
 151  *--------------------------------------------------------------*/
 152 #define SPACE_MAP_ROOT_SIZE 128
 153 #define UUID_LEN 16
 154
 155 struct writeset_disk {
 156         __le32 nr_bits;
 157         __le64 root;
 158 } __packed;
 159
 160 struct superblock_disk {
 161         __le32 csum;
 162         __le32 flags;
 163         __le64 blocknr;
 164
 165         __u8 uuid[UUID_LEN];
 166         __le64 magic;
 167         __le32 version;
 168
 169         __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
 170
 171         __le32 data_block_size;
 172         __le32 metadata_block_size;
 173         __le32 nr_blocks;
 174
 175         __le32 current_era;
 176         struct writeset_disk current_writeset;
 177
 178         /*
 179          * Only these two fields are valid within the metadata snapshot.
 180          */
 181         __le64 writeset_tree_root;
 182         __le64 era_array_root;
 183
 184         __le64 metadata_snap;
 185 } __packed;
 186
 187 /*----------------------------------------------------------------
 188  * Superblock validation
 189  *--------------------------------------------------------------*/
 190 static void sb_prepare_for_write(struct dm_block_validator *v,
 191                                  struct dm_block *b,
 192                                  size_t sb_block_size)
 193 {
 194         struct superblock_disk *disk = dm_block_data(b);
 195
 196         disk->blocknr = cpu_to_le64(dm_block_location(b));
 197         disk->csum = cpu_to_le32(dm_bm_checksum(&disk->flags,
 198                                                 sb_block_size - sizeof(__le32),
 199                                                 SUPERBLOCK_CSUM_XOR));
 200 }
 201
 202 static int check_metadata_version(struct superblock_disk *disk)
 203 {
 204         uint32_t metadata_version = le32_to_cpu(disk->version);
 205         if (metadata_version < MIN_ERA_VERSION || metadata_version > MAX_ERA_VERSION) {
 206                 DMERR("Era metadata version %u found, but only versions between %u and %u supported.",
 207                       metadata_version, MIN_ERA_VERSION, MAX_ERA_VERSION);
 208                 return -EINVAL;
 209         }
 210
 211         return 0;
 212 }
 213
 214 static int sb_check(struct dm_block_validator *v,
 215                     struct dm_block *b,
 216                     size_t sb_block_size)
 217 {
 218         struct superblock_disk *disk = dm_block_data(b);
 219         __le32 csum_le;
 220
 221         if (dm_block_location(b) != le64_to_cpu(disk->blocknr)) {
 222                 DMERR("sb_check failed: blocknr %llu: wanted %llu",
 223                       le64_to_cpu(disk->blocknr),
 224                       (unsigned long long)dm_block_location(b));
 225                 return -ENOTBLK;
 226         }
 227
 228         if (le64_to_cpu(disk->magic) != SUPERBLOCK_MAGIC) {
 229                 DMERR("sb_check failed: magic %llu: wanted %llu",
 230                       le64_to_cpu(disk->magic),
 231                       (unsigned long long) SUPERBLOCK_MAGIC);
 232                 return -EILSEQ;
 233         }
 234
 235         csum_le = cpu_to_le32(dm_bm_checksum(&disk->flags,
 236                                              sb_block_size - sizeof(__le32),
 237                                              SUPERBLOCK_CSUM_XOR));
 238         if (csum_le != disk->csum) {
 239                 DMERR("sb_check failed: csum %u: wanted %u",
 240                       le32_to_cpu(csum_le), le32_to_cpu(disk->csum));
 241                 return -EILSEQ;
 242         }
 243
 244         return check_metadata_version(disk);
 245 }
 246
 247 static struct dm_block_validator sb_validator = {
 248         .name = "superblock",
 249         .prepare_for_write = sb_prepare_for_write,
 250         .check = sb_check
 251 };
 252
 253 /*----------------------------------------------------------------
 254  * Low level metadata handling
 255  *--------------------------------------------------------------*/
 256 #define DM_ERA_METADATA_BLOCK_SIZE 4096
 257 #define DM_ERA_METADATA_CACHE_SIZE 64
 258 #define ERA_MAX_CONCURRENT_LOCKS 5
 259
 260 struct era_metadata {
 261         struct block_device *bdev;
 262         struct dm_block_manager *bm;
 263         struct dm_space_map *sm;
 264         struct dm_transaction_manager *tm;
 265
 266         dm_block_t block_size;
 267         uint32_t nr_blocks;
 268
 269         uint32_t current_era;
 270
 271         /*
 272          * We preallocate 2 writesets.  When an era rolls over we
 273          * switch between them. This means the allocation is done at
 274          * preresume time, rather than on the io path.
 275          */
 276         struct writeset writesets[2];
 277         struct writeset *current_writeset;
 278
 279         dm_block_t writeset_tree_root;
 280         dm_block_t era_array_root;
 281
 282         struct dm_disk_bitset bitset_info;
 283         struct dm_btree_info writeset_tree_info;
 284         struct dm_array_info era_array_info;
 285
 286         dm_block_t metadata_snap;
 287
 288         /*
 289          * A flag that is set whenever a writeset has been archived.
 290          */
 291         bool archived_writesets;
 292
 293         /*
 294          * Reading the space map root can fail, so we read it into this
 295          * buffer before the superblock is locked and updated.
 296          */
 297         __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
 298 };
 299
 300 static int superblock_read_lock(struct era_metadata *md,
 301                                 struct dm_block **sblock)
 302 {
 303         return dm_bm_read_lock(md->bm, SUPERBLOCK_LOCATION,
 304                                &sb_validator, sblock);
 305 }
 306
 307 static int superblock_lock_zero(struct era_metadata *md,
 308                                 struct dm_block **sblock)
 309 {
 310         return dm_bm_write_lock_zero(md->bm, SUPERBLOCK_LOCATION,
 311                                      &sb_validator, sblock);
 312 }
 313
 314 static int superblock_lock(struct era_metadata *md,
 315                            struct dm_block **sblock)
 316 {
 317         return dm_bm_write_lock(md->bm, SUPERBLOCK_LOCATION,
 318                                 &sb_validator, sblock);
 319 }
 320
 321 /* FIXME: duplication with cache and thin */
 322 static int superblock_all_zeroes(struct dm_block_manager *bm, bool *result)
 323 {
 324         int r;
 325         unsigned i;
 326         struct dm_block *b;
 327         __le64 *data_le, zero = cpu_to_le64(0);
 328         unsigned sb_block_size = dm_bm_block_size(bm) / sizeof(__le64);
 329
 330         /*
 331          * We can't use a validator here - it may be all zeroes.
 332          */
 333         r = dm_bm_read_lock(bm, SUPERBLOCK_LOCATION, NULL, &b);
 334         if (r)
 335                 return r;
 336
 337         data_le = dm_block_data(b);
 338         *result = true;
 339         for (i = 0; i < sb_block_size; i++) {
 340                 if (data_le[i] != zero) {
 341                         *result = false;
 342                         break;
 343                 }
 344         }
 345
 346         return dm_bm_unlock(b);
 347 }
 348
 349 /*----------------------------------------------------------------*/
 350
 351 static void ws_pack(const struct writeset_metadata *core, struct writeset_disk *disk)
 352 {
 353         disk->nr_bits = cpu_to_le32(core->nr_bits);
 354         disk->root = cpu_to_le64(core->root);
 355 }
 356
 357 static void ws_unpack(const struct writeset_disk *disk, struct writeset_metadata *core)
 358 {
 359         core->nr_bits = le32_to_cpu(disk->nr_bits);
 360         core->root = le64_to_cpu(disk->root);
 361 }
 362
 363 static void ws_inc(void *context, const void *value)
 364 {
 365         struct era_metadata *md = context;
 366         struct writeset_disk ws_d;
 367         dm_block_t b;
 368
 369         memcpy(&ws_d, value, sizeof(ws_d));
 370         b = le64_to_cpu(ws_d.root);
 371
 372         dm_tm_inc(md->tm, b);
 373 }
 374
 375 static void ws_dec(void *context, const void *value)
 376 {
 377         struct era_metadata *md = context;
 378         struct writeset_disk ws_d;
 379         dm_block_t b;
 380
 381         memcpy(&ws_d, value, sizeof(ws_d));
 382         b = le64_to_cpu(ws_d.root);
 383
 384         dm_bitset_del(&md->bitset_info, b);
 385 }
 386
 387 static int ws_eq(void *context, const void *value1, const void *value2)
 388 {
 389         return !memcmp(value1, value2, sizeof(struct writeset_metadata));
 390 }
 391
 392 /*----------------------------------------------------------------*/
 393
 394 static void setup_writeset_tree_info(struct era_metadata *md)
 395 {
 396         struct dm_btree_value_type *vt = &md->writeset_tree_info.value_type;
 397         md->writeset_tree_info.tm = md->tm;
 398         md->writeset_tree_info.levels = 1;
 399         vt->context = md;
 400         vt->size = sizeof(struct writeset_disk);
 401         vt->inc = ws_inc;
 402         vt->dec = ws_dec;
 403         vt->equal = ws_eq;
 404 }
 405
 406 static void setup_era_array_info(struct era_metadata *md)
 407
 408 {
 409         struct dm_btree_value_type vt;
 410         vt.context = NULL;
 411         vt.size = sizeof(__le32);
 412         vt.inc = NULL;
 413         vt.dec = NULL;
 414         vt.equal = NULL;
 415
 416         dm_array_info_init(&md->era_array_info, md->tm, &vt);
 417 }
 418
 419 static void setup_infos(struct era_metadata *md)
 420 {
 421         dm_disk_bitset_init(md->tm, &md->bitset_info);
 422         setup_writeset_tree_info(md);
 423         setup_era_array_info(md);
 424 }
 425
 426 /*----------------------------------------------------------------*/
 427
 428 static int create_fresh_metadata(struct era_metadata *md)
 429 {
 430         int r;
 431
 432         r = dm_tm_create_with_sm(md->bm, SUPERBLOCK_LOCATION,
 433                                  &md->tm, &md->sm);
 434         if (r < 0) {
 435                 DMERR("dm_tm_create_with_sm failed");
 436                 return r;
 437         }
 438
 439         setup_infos(md);
 440
 441         r = dm_btree_empty(&md->writeset_tree_info, &md->writeset_tree_root);
 442         if (r) {
 443                 DMERR("couldn't create new writeset tree");
 444                 goto bad;
 445         }
 446
 447         r = dm_array_empty(&md->era_array_info, &md->era_array_root);
 448         if (r) {
 449                 DMERR("couldn't create era array");
 450                 goto bad;
 451         }
 452
 453         return 0;
 454
 455 bad:
 456         dm_sm_destroy(md->sm);
 457         dm_tm_destroy(md->tm);
 458
 459         return r;
 460 }
 461
 462 static int save_sm_root(struct era_metadata *md)
 463 {
 464         int r;
 465         size_t metadata_len;
 466
 467         r = dm_sm_root_size(md->sm, &metadata_len);
 468         if (r < 0)
 469                 return r;
 470
 471         return dm_sm_copy_root(md->sm, &md->metadata_space_map_root,
 472                                metadata_len);
 473 }
 474
 475 static void copy_sm_root(struct era_metadata *md, struct superblock_disk *disk)
 476 {
 477         memcpy(&disk->metadata_space_map_root,
 478                &md->metadata_space_map_root,
 479                sizeof(md->metadata_space_map_root));
 480 }
 481
 482 /*
 483  * Writes a superblock, including the static fields that don't get updated
 484  * with every commit (possible optimisation here).  'md' should be fully
 485  * constructed when this is called.
 486  */
 487 static void prepare_superblock(struct era_metadata *md, struct superblock_disk *disk)
 488 {
 489         disk->magic = cpu_to_le64(SUPERBLOCK_MAGIC);
 490         disk->flags = cpu_to_le32(0ul);
 491
 492         /* FIXME: can't keep blanking the uuid (uuid is currently unused though) */
 493         memset(disk->uuid, 0, sizeof(disk->uuid));
 494         disk->version = cpu_to_le32(MAX_ERA_VERSION);
 495
 496         copy_sm_root(md, disk);
 497
 498         disk->data_block_size = cpu_to_le32(md->block_size);
 499         disk->metadata_block_size = cpu_to_le32(DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);
 500         disk->nr_blocks = cpu_to_le32(md->nr_blocks);
 501         disk->current_era = cpu_to_le32(md->current_era);
 502
 503         ws_pack(&md->current_writeset->md, &disk->current_writeset);
 504         disk->writeset_tree_root = cpu_to_le64(md->writeset_tree_root);
 505         disk->era_array_root = cpu_to_le64(md->era_array_root);
 506         disk->metadata_snap = cpu_to_le64(md->metadata_snap);
 507 }
 508
 509 static int write_superblock(struct era_metadata *md)
 510 {
 511         int r;
 512         struct dm_block *sblock;
 513         struct superblock_disk *disk;
 514
 515         r = save_sm_root(md);
 516         if (r) {
 517                 DMERR("%s: save_sm_root failed", __func__);
 518                 return r;
 519         }
 520
 521         r = superblock_lock_zero(md, &sblock);
 522         if (r)
 523                 return r;
 524
 525         disk = dm_block_data(sblock);
 526         prepare_superblock(md, disk);
 527
 528         return dm_tm_commit(md->tm, sblock);
 529 }
 530
 531 /*
 532  * Assumes block_size and the infos are set.
 533  */
 534 static int format_metadata(struct era_metadata *md)
 535 {
 536         int r;
 537
 538         r = create_fresh_metadata(md);
 539         if (r)
 540                 return r;
 541
 542         r = write_superblock(md);
 543         if (r) {
 544                 dm_sm_destroy(md->sm);
 545                 dm_tm_destroy(md->tm);
 546                 return r;
 547         }
 548
 549         return 0;
 550 }
 551
 552 static int open_metadata(struct era_metadata *md)
 553 {
 554         int r;
 555         struct dm_block *sblock;
 556         struct superblock_disk *disk;
 557
 558         r = superblock_read_lock(md, &sblock);
 559         if (r) {
 560                 DMERR("couldn't read_lock superblock");
 561                 return r;
 562         }
 563
 564         disk = dm_block_data(sblock);
 565         r = dm_tm_open_with_sm(md->bm, SUPERBLOCK_LOCATION,
 566                                disk->metadata_space_map_root,
 567                                sizeof(disk->metadata_space_map_root),
 568                                &md->tm, &md->sm);
 569         if (r) {
 570                 DMERR("dm_tm_open_with_sm failed");
 571                 goto bad;
 572         }
 573
 574         setup_infos(md);
 575
 576         md->block_size = le32_to_cpu(disk->data_block_size);
 577         md->nr_blocks = le32_to_cpu(disk->nr_blocks);
 578         md->current_era = le32_to_cpu(disk->current_era);
 579
 580         md->writeset_tree_root = le64_to_cpu(disk->writeset_tree_root);
 581         md->era_array_root = le64_to_cpu(disk->era_array_root);
 582         md->metadata_snap = le64_to_cpu(disk->metadata_snap);
 583         md->archived_writesets = true;
 584
 585         return dm_bm_unlock(sblock);
 586
 587 bad:
 588         dm_bm_unlock(sblock);
 589         return r;
 590 }
 591
 592 static int open_or_format_metadata(struct era_metadata *md,
 593                                    bool may_format)
 594 {
 595         int r;
 596         bool unformatted = false;
 597
 598         r = superblock_all_zeroes(md->bm, &unformatted);
 599         if (r)
 600                 return r;
 601
 602         if (unformatted)
 603                 return may_format ? format_metadata(md) : -EPERM;
 604
 605         return open_metadata(md);
 606 }
 607
 608 static int create_persistent_data_objects(struct era_metadata *md,
 609                                           bool may_format)
 610 {
 611         int r;
 612
 613         md->bm = dm_block_manager_create(md->bdev, DM_ERA_METADATA_BLOCK_SIZE,
 614                                          DM_ERA_METADATA_CACHE_SIZE,
 615                                          ERA_MAX_CONCURRENT_LOCKS);
 616         if (IS_ERR(md->bm)) {
 617                 DMERR("could not create block manager");
 618                 return PTR_ERR(md->bm);
 619         }
 620
 621         r = open_or_format_metadata(md, may_format);
 622         if (r)
 623                 dm_block_manager_destroy(md->bm);
 624
 625         return r;
 626 }
 627
 628 static void destroy_persistent_data_objects(struct era_metadata *md)
 629 {
 630         dm_sm_destroy(md->sm);
 631         dm_tm_destroy(md->tm);
 632         dm_block_manager_destroy(md->bm);
 633 }
 634
 635 /*
 636  * This waits until all era_map threads have picked up the new filter.
 637  */
 638 static void swap_writeset(struct era_metadata *md, struct writeset *new_writeset)
 639 {
 640         rcu_assign_pointer(md->current_writeset, new_writeset);
 641         synchronize_rcu();
 642 }
 643
 644 /*----------------------------------------------------------------
 645  * Writesets get 'digested' into the main era array.
 646  *
 647  * We're using a coroutine here so the worker thread can do the digestion,
 648  * thus avoiding synchronisation of the metadata.  Digesting a whole
 649  * writeset in one go would cause too much latency.
 650  *--------------------------------------------------------------*/
 651 struct digest {
 652         uint32_t era;
 653         unsigned nr_bits, current_bit;
 654         struct writeset_metadata writeset;
 655         __le32 value;
 656         struct dm_disk_bitset info;
 657
 658         int (*step)(struct era_metadata *, struct digest *);
 659 };
 660
 661 static int metadata_digest_lookup_writeset(struct era_metadata *md,
 662                                            struct digest *d);
 663
 664 static int metadata_digest_remove_writeset(struct era_metadata *md,
 665                                            struct digest *d)
 666 {
 667         int r;
 668         uint64_t key = d->era;
 669
 670         r = dm_btree_remove(&md->writeset_tree_info, md->writeset_tree_root,
 671                             &key, &md->writeset_tree_root);
 672         if (r) {
 673                 DMERR("%s: dm_btree_remove failed", __func__);
 674                 return r;
 675         }
 676
 677         d->step = metadata_digest_lookup_writeset;
 678         return 0;
 679 }
 680
 681 #define INSERTS_PER_STEP 100
 682
 683 static int metadata_digest_transcribe_writeset(struct era_metadata *md,
 684                                                struct digest *d)
 685 {
 686         int r;
 687         bool marked;
 688         unsigned b, e = min(d->current_bit + INSERTS_PER_STEP, d->nr_bits);
 689
 690         for (b = d->current_bit; b < e; b++) {
 691                 r = writeset_marked_on_disk(&d->info, &d->writeset, b, &marked);
 692                 if (r) {
 693                         DMERR("%s: writeset_marked_on_disk failed", __func__);
 694                         return r;
 695                 }
 696
 697                 if (!marked)
 698                         continue;
 699
 700                 __dm_bless_for_disk(&d->value);
 701                 r = dm_array_set_value(&md->era_array_info, md->era_array_root,
 702                                        b, &d->value, &md->era_array_root);
 703                 if (r) {
 704                         DMERR("%s: dm_array_set_value failed", __func__);
 705                         return r;
 706                 }
 707         }
 708
 709         if (b == d->nr_bits)
 710                 d->step = metadata_digest_remove_writeset;
 711         else
 712                 d->current_bit = b;
 713
 714         return 0;
 715 }
 716
 717 static int metadata_digest_lookup_writeset(struct era_metadata *md,
 718                                            struct digest *d)
 719 {
 720         int r;
 721         uint64_t key;
 722         struct writeset_disk disk;
 723
 724         r = dm_btree_find_lowest_key(&md->writeset_tree_info,
 725                                      md->writeset_tree_root, &key);
 726         if (r < 0)
 727                 return r;
 728
 729         d->era = key;
 730
 731         r = dm_btree_lookup(&md->writeset_tree_info,
 732                             md->writeset_tree_root, &key, &disk);
 733         if (r) {
 734                 if (r == -ENODATA) {
 735                         d->step = NULL;
 736                         return 0;
 737                 }
 738
 739                 DMERR("%s: dm_btree_lookup failed", __func__);
 740                 return r;
 741         }
 742
 743         ws_unpack(&disk, &d->writeset);
 744         d->value = cpu_to_le32(key);
 745
 746         d->nr_bits = min(d->writeset.nr_bits, md->nr_blocks);
 747         d->current_bit = 0;
 748         d->step = metadata_digest_transcribe_writeset;
 749
 750         return 0;
 751 }
 752
 753 static int metadata_digest_start(struct era_metadata *md, struct digest *d)
 754 {
 755         if (d->step)
 756                 return 0;
 757
 758         memset(d, 0, sizeof(*d));
 759
 760         /*
 761          * We initialise another bitset info to avoid any caching side
 762          * effects with the previous one.
 763          */
 764         dm_disk_bitset_init(md->tm, &d->info);
 765         d->step = metadata_digest_lookup_writeset;
 766
 767         return 0;
 768 }
 769
 770 /*----------------------------------------------------------------
 771  * High level metadata interface.  Target methods should use these, and not
 772  * the lower level ones.
 773  *--------------------------------------------------------------*/
 774 static struct era_metadata *metadata_open(struct block_device *bdev,
 775                                           sector_t block_size,
 776                                           bool may_format)
 777 {
 778         int r;
 779         struct era_metadata *md = kzalloc(sizeof(*md), GFP_KERNEL);
 780
 781         if (!md)
 782                 return NULL;
 783
 784         md->bdev = bdev;
 785         md->block_size = block_size;
 786
 787         md->writesets[0].md.root = INVALID_WRITESET_ROOT;
 788         md->writesets[1].md.root = INVALID_WRITESET_ROOT;
 789         md->current_writeset = &md->writesets[0];
 790
 791         r = create_persistent_data_objects(md, may_format);
 792         if (r) {
 793                 kfree(md);
 794                 return ERR_PTR(r);
 795         }
 796
 797         return md;
 798 }
 799
 800 static void metadata_close(struct era_metadata *md)
 801 {
 802         destroy_persistent_data_objects(md);
 803         kfree(md);
 804 }
 805
 806 static bool valid_nr_blocks(dm_block_t n)
 807 {
 808         /*
 809          * dm_bitset restricts us to 2^32.  test_bit & co. restrict us
 810          * further to 2^31 - 1
 811          */
 812         return n < (1ull << 31);
 813 }
 814
 815 static int metadata_resize(struct era_metadata *md, void *arg)
 816 {
 817         int r;
 818         dm_block_t *new_size = arg;
 819         __le32 value;
 820
 821         if (!valid_nr_blocks(*new_size)) {
 822                 DMERR("Invalid number of origin blocks %llu",
 823                       (unsigned long long) *new_size);
 824                 return -EINVAL;
 825         }
 826
 827         writeset_free(&md->writesets[0]);
 828         writeset_free(&md->writesets[1]);
 829
 830         r = writeset_alloc(&md->writesets[0], *new_size);
 831         if (r) {
 832                 DMERR("%s: writeset_alloc failed for writeset 0", __func__);
 833                 return r;
 834         }
 835
 836         r = writeset_alloc(&md->writesets[1], *new_size);
 837         if (r) {
 838                 DMERR("%s: writeset_alloc failed for writeset 1", __func__);
 839                 return r;
 840         }
 841
 842         value = cpu_to_le32(0u);
 843         __dm_bless_for_disk(&value);
 844         r = dm_array_resize(&md->era_array_info, md->era_array_root,
 845                             md->nr_blocks, *new_size,
 846                             &value, &md->era_array_root);
 847         if (r) {
 848                 DMERR("%s: dm_array_resize failed", __func__);
 849                 return r;
 850         }
 851
 852         md->nr_blocks = *new_size;
 853         return 0;
 854 }
 855
 856 static int metadata_era_archive(struct era_metadata *md)
 857 {
 858         int r;
 859         uint64_t keys[1];
 860         struct writeset_disk value;
 861
 862         r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
 863                             &md->current_writeset->md.root);
 864         if (r) {
 865                 DMERR("%s: dm_bitset_flush failed", __func__);
 866                 return r;
 867         }
 868
 869         ws_pack(&md->current_writeset->md, &value);
 870         md->current_writeset->md.root = INVALID_WRITESET_ROOT;
 871
 872         keys[0] = md->current_era;
 873         __dm_bless_for_disk(&value);
 874         r = dm_btree_insert(&md->writeset_tree_info, md->writeset_tree_root,
 875                             keys, &value, &md->writeset_tree_root);
 876         if (r) {
 877                 DMERR("%s: couldn't insert writeset into btree", __func__);
 878                 /* FIXME: fail mode */
 879                 return r;
 880         }
 881
 882         md->archived_writesets = true;
 883
 884         return 0;
 885 }
 886
 887 static struct writeset *next_writeset(struct era_metadata *md)
 888 {
 889         return (md->current_writeset == &md->writesets[0]) ?
 890                 &md->writesets[1] : &md->writesets[0];
 891 }
 892
 893 static int metadata_new_era(struct era_metadata *md)
 894 {
 895         int r;
 896         struct writeset *new_writeset = next_writeset(md);
 897
 898         r = writeset_init(&md->bitset_info, new_writeset);
 899         if (r) {
 900                 DMERR("%s: writeset_init failed", __func__);
 901                 return r;
 902         }
 903
 904         swap_writeset(md, new_writeset);
 905         md->current_era++;
 906
 907         return 0;
 908 }
 909
 910 static int metadata_era_rollover(struct era_metadata *md)
 911 {
 912         int r;
 913
 914         if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {
 915                 r = metadata_era_archive(md);
 916                 if (r) {
 917                         DMERR("%s: metadata_archive_era failed", __func__);
 918                         /* FIXME: fail mode? */
 919                         return r;
 920                 }
 921         }
 922
 923         r = metadata_new_era(md);
 924         if (r) {
 925                 DMERR("%s: new era failed", __func__);
 926                 /* FIXME: fail mode */
 927                 return r;
 928         }
 929
 930         return 0;
 931 }
 932
 933 static bool metadata_current_marked(struct era_metadata *md, dm_block_t block)
 934 {
 935         bool r;
 936         struct writeset *ws;
 937
 938         rcu_read_lock();
 939         ws = rcu_dereference(md->current_writeset);
 940         r = writeset_marked(ws, block);
 941         rcu_read_unlock();
 942
 943         return r;
 944 }
 945
 946 static int metadata_commit(struct era_metadata *md)
 947 {
 948         int r;
 949         struct dm_block *sblock;
 950
 951         if (md->current_writeset->md.root != SUPERBLOCK_LOCATION) {
 952                 r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,
 953                                     &md->current_writeset->md.root);
 954                 if (r) {
 955                         DMERR("%s: bitset flush failed", __func__);
 956                         return r;
 957                 }
 958         }
 959
 960         r = save_sm_root(md);
 961         if (r) {
 962                 DMERR("%s: save_sm_root failed", __func__);
 963                 return r;
 964         }
 965
 966         r = dm_tm_pre_commit(md->tm);
 967         if (r) {
 968                 DMERR("%s: pre commit failed", __func__);
 969                 return r;
 970         }
 971
 972         r = superblock_lock(md, &sblock);
 973         if (r) {
 974                 DMERR("%s: superblock lock failed", __func__);
 975                 return r;
 976         }
 977
 978         prepare_superblock(md, dm_block_data(sblock));
 979
 980         return dm_tm_commit(md->tm, sblock);
 981 }
 982
 983 static int metadata_checkpoint(struct era_metadata *md)
 984 {
 985         /*
 986          * For now we just rollover, but later I want to put a check in to
 987          * avoid this if the filter is still pretty fresh.
 988          */
 989         return metadata_era_rollover(md);
 990 }
 991
 992 /*
 993  * Metadata snapshots allow userland to access era data.
 994  */
 995 static int metadata_take_snap(struct era_metadata *md)
 996 {
 997         int r, inc;
 998         struct dm_block *clone;
 999
1000         if (md->metadata_snap != SUPERBLOCK_LOCATION) {
1001                 DMERR("%s: metadata snapshot already exists", __func__);
1002                 return -EINVAL;
1003         }
1004
1005         r = metadata_era_rollover(md);
1006         if (r) {
1007                 DMERR("%s: era rollover failed", __func__);
1008                 return r;
1009         }
1010
1011         r = metadata_commit(md);
1012         if (r) {
1013                 DMERR("%s: pre commit failed", __func__);
1014                 return r;
1015         }
1016
1017         r = dm_sm_inc_block(md->sm, SUPERBLOCK_LOCATION);
1018         if (r) {
1019                 DMERR("%s: couldn't increment superblock", __func__);
1020                 return r;
1021         }
1022
1023         r = dm_tm_shadow_block(md->tm, SUPERBLOCK_LOCATION,
1024                                &sb_validator, &clone, &inc);
1025         if (r) {
1026                 DMERR("%s: couldn't shadow superblock", __func__);
1027                 dm_sm_dec_block(md->sm, SUPERBLOCK_LOCATION);
1028                 return r;
1029         }
1030         BUG_ON(!inc);
1031
1032         r = dm_sm_inc_block(md->sm, md->writeset_tree_root);
1033         if (r) {
1034                 DMERR("%s: couldn't inc writeset tree root", __func__);
1035                 dm_tm_unlock(md->tm, clone);
1036                 return r;
1037         }
1038
1039         r = dm_sm_inc_block(md->sm, md->era_array_root);
1040         if (r) {
1041                 DMERR("%s: couldn't inc era tree root", __func__);
1042                 dm_sm_dec_block(md->sm, md->writeset_tree_root);
1043                 dm_tm_unlock(md->tm, clone);
1044                 return r;
1045         }
1046
1047         md->metadata_snap = dm_block_location(clone);
1048
1049         r = dm_tm_unlock(md->tm, clone);
1050         if (r) {
1051                 DMERR("%s: couldn't unlock clone", __func__);
1052                 md->metadata_snap = SUPERBLOCK_LOCATION;
1053                 return r;
1054         }
1055
1056         return 0;
1057 }
1058
1059 static int metadata_drop_snap(struct era_metadata *md)
1060 {
1061         int r;
1062         dm_block_t location;
1063         struct dm_block *clone;
1064         struct superblock_disk *disk;
1065
1066         if (md->metadata_snap == SUPERBLOCK_LOCATION) {
1067                 DMERR("%s: no snap to drop", __func__);
1068                 return -EINVAL;
1069         }
1070
1071         r = dm_tm_read_lock(md->tm, md->metadata_snap, &sb_validator, &clone);
1072         if (r) {
1073                 DMERR("%s: couldn't read lock superblock clone", __func__);
1074                 return r;
1075         }
1076
1077         /*
1078          * Whatever happens now we'll commit with no record of the metadata
1079          * snap.
1080          */
1081         md->metadata_snap = SUPERBLOCK_LOCATION;
1082
1083         disk = dm_block_data(clone);
1084         r = dm_btree_del(&md->writeset_tree_info,
1085                          le64_to_cpu(disk->writeset_tree_root));
1086         if (r) {
1087                 DMERR("%s: error deleting writeset tree clone", __func__);
1088                 dm_tm_unlock(md->tm, clone);
1089                 return r;
1090         }
1091
1092         r = dm_array_del(&md->era_array_info, le64_to_cpu(disk->era_array_root));
1093         if (r) {
1094                 DMERR("%s: error deleting era array clone", __func__);
1095                 dm_tm_unlock(md->tm, clone);
1096                 return r;
1097         }
1098
1099         location = dm_block_location(clone);
1100         dm_tm_unlock(md->tm, clone);
1101
1102         return dm_sm_dec_block(md->sm, location);
1103 }
1104
1105 struct metadata_stats {
1106         dm_block_t used;
1107         dm_block_t total;
1108         dm_block_t snap;
1109         uint32_t era;
1110 };
1111
1112 static int metadata_get_stats(struct era_metadata *md, void *ptr)
1113 {
1114         int r;
1115         struct metadata_stats *s = ptr;
1116         dm_block_t nr_free, nr_total;
1117
1118         r = dm_sm_get_nr_free(md->sm, &nr_free);
1119         if (r) {
1120                 DMERR("dm_sm_get_nr_free returned %d", r);
1121                 return r;
1122         }
1123
1124         r = dm_sm_get_nr_blocks(md->sm, &nr_total);
1125         if (r) {
1126                 DMERR("dm_pool_get_metadata_dev_size returned %d", r);
1127                 return r;
1128         }
1129
1130         s->used = nr_total - nr_free;
1131         s->total = nr_total;
1132         s->snap = md->metadata_snap;
1133         s->era = md->current_era;
1134
1135         return 0;
1136 }
1137
1138 /*----------------------------------------------------------------*/
1139
1140 struct era {
1141         struct dm_target *ti;
1142         struct dm_target_callbacks callbacks;
1143
1144         struct dm_dev *metadata_dev;
1145         struct dm_dev *origin_dev;
1146
1147         dm_block_t nr_blocks;
1148         uint32_t sectors_per_block;
1149         int sectors_per_block_shift;
1150         struct era_metadata *md;
1151
1152         struct workqueue_struct *wq;
1153         struct work_struct worker;
1154
1155         spinlock_t deferred_lock;
1156         struct bio_list deferred_bios;
1157
1158         spinlock_t rpc_lock;
1159         struct list_head rpc_calls;
1160
1161         struct digest digest;
1162         atomic_t suspended;
1163 };
1164
1165 struct rpc {
1166         struct list_head list;
1167
1168         int (*fn0)(struct era_metadata *);
1169         int (*fn1)(struct era_metadata *, void *);
1170         void *arg;
1171         int result;
1172
1173         struct completion complete;
1174 };
1175
1176 /*----------------------------------------------------------------
1177  * Remapping.
1178  *---------------------------------------------------------------*/
1179 static bool block_size_is_power_of_two(struct era *era)
1180 {
1181         return era->sectors_per_block_shift >= 0;
1182 }
1183
1184 static dm_block_t get_block(struct era *era, struct bio *bio)
1185 {
1186         sector_t block_nr = bio->bi_iter.bi_sector;
1187
1188         if (!block_size_is_power_of_two(era))
1189                 (void) sector_div(block_nr, era->sectors_per_block);
1190         else
1191                 block_nr >>= era->sectors_per_block_shift;
1192
1193         return block_nr;
1194 }
1195
1196 static void remap_to_origin(struct era *era, struct bio *bio)
1197 {
1198         bio->bi_bdev = era->origin_dev->bdev;
1199 }
1200
1201 /*----------------------------------------------------------------
1202  * Worker thread
1203  *--------------------------------------------------------------*/
1204 static void wake_worker(struct era *era)
1205 {
1206         if (!atomic_read(&era->suspended))
1207                 queue_work(era->wq, &era->worker);
1208 }
1209
1210 static void process_old_eras(struct era *era)
1211 {
1212         int r;
1213
1214         if (!era->digest.step)
1215                 return;
1216
1217         r = era->digest.step(era->md, &era->digest);
1218         if (r < 0) {
1219                 DMERR("%s: digest step failed, stopping digestion", __func__);
1220                 era->digest.step = NULL;
1221
1222         } else if (era->digest.step)
1223                 wake_worker(era);
1224 }
1225
1226 static void process_deferred_bios(struct era *era)
1227 {
1228         int r;
1229         struct bio_list deferred_bios, marked_bios;
1230         struct bio *bio;
1231         bool commit_needed = false;
1232         bool failed = false;
1233
1234         bio_list_init(&deferred_bios);
1235         bio_list_init(&marked_bios);
1236
1237         spin_lock(&era->deferred_lock);
1238         bio_list_merge(&deferred_bios, &era->deferred_bios);
1239         bio_list_init(&era->deferred_bios);
1240         spin_unlock(&era->deferred_lock);
1241
1242         while ((bio = bio_list_pop(&deferred_bios))) {
1243                 r = writeset_test_and_set(&era->md->bitset_info,
1244                                           era->md->current_writeset,
1245                                           get_block(era, bio));
1246                 if (r < 0) {
1247                         /*
1248                          * This is bad news, we need to rollback.
1249                          * FIXME: finish.
1250                          */
1251                         failed = true;
1252
1253                 } else if (r == 0)
1254                         commit_needed = true;
1255
1256                 bio_list_add(&marked_bios, bio);
1257         }
1258
1259         if (commit_needed) {
1260                 r = metadata_commit(era->md);
1261                 if (r)
1262                         failed = true;
1263         }
1264
1265         if (failed)
1266                 while ((bio = bio_list_pop(&marked_bios)))
1267                         bio_io_error(bio);
1268         else
1269                 while ((bio = bio_list_pop(&marked_bios)))
1270                         generic_make_request(bio);
1271 }
1272
1273 static void process_rpc_calls(struct era *era)
1274 {
1275         int r;
1276         bool need_commit = false;
1277         struct list_head calls;
1278         struct rpc *rpc, *tmp;
1279
1280         INIT_LIST_HEAD(&calls);
1281         spin_lock(&era->rpc_lock);
1282         list_splice_init(&era->rpc_calls, &calls);
1283         spin_unlock(&era->rpc_lock);
1284
1285         list_for_each_entry_safe(rpc, tmp, &calls, list) {
1286                 rpc->result = rpc->fn0 ? rpc->fn0(era->md) : rpc->fn1(era->md, rpc->arg);
1287                 need_commit = true;
1288         }
1289
1290         if (need_commit) {
1291                 r = metadata_commit(era->md);
1292                 if (r)
1293                         list_for_each_entry_safe(rpc, tmp, &calls, list)
1294                                 rpc->result = r;
1295         }
1296
1297         list_for_each_entry_safe(rpc, tmp, &calls, list)
1298                 complete(&rpc->complete);
1299 }
1300
1301 static void kick_off_digest(struct era *era)
1302 {
1303         if (era->md->archived_writesets) {
1304                 era->md->archived_writesets = false;
1305                 metadata_digest_start(era->md, &era->digest);
1306         }
1307 }
1308
1309 static void do_work(struct work_struct *ws)
1310 {
1311         struct era *era = container_of(ws, struct era, worker);
1312
1313         kick_off_digest(era);
1314         process_old_eras(era);
1315         process_deferred_bios(era);
1316         process_rpc_calls(era);
1317 }
1318
1319 static void defer_bio(struct era *era, struct bio *bio)
1320 {
1321         spin_lock(&era->deferred_lock);
1322         bio_list_add(&era->deferred_bios, bio);
1323         spin_unlock(&era->deferred_lock);
1324
1325         wake_worker(era);
1326 }
1327
1328 /*
1329  * Make an rpc call to the worker to change the metadata.
1330  */
1331 static int perform_rpc(struct era *era, struct rpc *rpc)
1332 {
1333         rpc->result = 0;
1334         init_completion(&rpc->complete);
1335
1336         spin_lock(&era->rpc_lock);
1337         list_add(&rpc->list, &era->rpc_calls);
1338         spin_unlock(&era->rpc_lock);
1339
1340         wake_worker(era);
1341         wait_for_completion(&rpc->complete);
1342
1343         return rpc->result;
1344 }
1345
1346 static int in_worker0(struct era *era, int (*fn)(struct era_metadata *))
1347 {
1348         struct rpc rpc;
1349         rpc.fn0 = fn;
1350         rpc.fn1 = NULL;
1351
1352         return perform_rpc(era, &rpc);
1353 }
1354
1355 static int in_worker1(struct era *era,
1356                       int (*fn)(struct era_metadata *, void *), void *arg)
1357 {
1358         struct rpc rpc;
1359         rpc.fn0 = NULL;
1360         rpc.fn1 = fn;
1361         rpc.arg = arg;
1362
1363         return perform_rpc(era, &rpc);
1364 }
1365
1366 static void start_worker(struct era *era)
1367 {
1368         atomic_set(&era->suspended, 0);
1369 }
1370
1371 static void stop_worker(struct era *era)
1372 {
1373         atomic_set(&era->suspended, 1);
1374         flush_workqueue(era->wq);
1375 }
1376
1377 /*----------------------------------------------------------------
1378  * Target methods
1379  *--------------------------------------------------------------*/
1380 static int dev_is_congested(struct dm_dev *dev, int bdi_bits)
1381 {
1382         struct request_queue *q = bdev_get_queue(dev->bdev);
1383         return bdi_congested(&q->backing_dev_info, bdi_bits);
1384 }
1385
1386 static int era_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
1387 {
1388         struct era *era = container_of(cb, struct era, callbacks);
1389         return dev_is_congested(era->origin_dev, bdi_bits);
1390 }
1391
1392 static void era_destroy(struct era *era)
1393 {
1394         if (era->md)
1395                 metadata_close(era->md);
1396
1397         if (era->wq)
1398                 destroy_workqueue(era->wq);
1399
1400         if (era->origin_dev)
1401                 dm_put_device(era->ti, era->origin_dev);
1402
1403         if (era->metadata_dev)
1404                 dm_put_device(era->ti, era->metadata_dev);
1405
1406         kfree(era);
1407 }
1408
1409 static dm_block_t calc_nr_blocks(struct era *era)
1410 {
1411         return dm_sector_div_up(era->ti->len, era->sectors_per_block);
1412 }
1413
1414 static bool valid_block_size(dm_block_t block_size)
1415 {
1416         bool greater_than_zero = block_size > 0;
1417         bool multiple_of_min_block_size = (block_size & (MIN_BLOCK_SIZE - 1)) == 0;
1418
1419         return greater_than_zero && multiple_of_min_block_size;
1420 }
1421
1422 /*
1423  * <metadata dev> <data dev> <data block size (sectors)>
1424  */
1425 static int era_ctr(struct dm_target *ti, unsigned argc, char **argv)
1426 {
1427         int r;
1428         char dummy;
1429         struct era *era;
1430         struct era_metadata *md;
1431
1432         if (argc != 3) {
1433                 ti->error = "Invalid argument count";
1434                 return -EINVAL;
1435         }
1436
1437         era = kzalloc(sizeof(*era), GFP_KERNEL);
1438         if (!era) {
1439                 ti->error = "Error allocating era structure";
1440                 return -ENOMEM;
1441         }
1442
1443         era->ti = ti;
1444
1445         r = dm_get_device(ti, argv[0], FMODE_READ | FMODE_WRITE, &era->metadata_dev);
1446         if (r) {
1447                 ti->error = "Error opening metadata device";
1448                 era_destroy(era);
1449                 return -EINVAL;
1450         }
1451
1452         r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &era->origin_dev);
1453         if (r) {
1454                 ti->error = "Error opening data device";
1455                 era_destroy(era);
1456                 return -EINVAL;
1457         }
1458
1459         r = sscanf(argv[2], "%u%c", &era->sectors_per_block, &dummy);
1460         if (r != 1) {
1461                 ti->error = "Error parsing block size";
1462                 era_destroy(era);
1463                 return -EINVAL;
1464         }
1465
1466         r = dm_set_target_max_io_len(ti, era->sectors_per_block);
1467         if (r) {
1468                 ti->error = "could not set max io len";
1469                 era_destroy(era);
1470                 return -EINVAL;
1471         }
1472
1473         if (!valid_block_size(era->sectors_per_block)) {
1474                 ti->error = "Invalid block size";
1475                 era_destroy(era);
1476                 return -EINVAL;
1477         }
1478         if (era->sectors_per_block & (era->sectors_per_block - 1))
1479                 era->sectors_per_block_shift = -1;
1480         else
1481                 era->sectors_per_block_shift = __ffs(era->sectors_per_block);
1482
1483         md = metadata_open(era->metadata_dev->bdev, era->sectors_per_block, true);
1484         if (IS_ERR(md)) {
1485                 ti->error = "Error reading metadata";
1486                 era_destroy(era);
1487                 return PTR_ERR(md);
1488         }
1489         era->md = md;
1490
1491         era->nr_blocks = calc_nr_blocks(era);
1492
1493         r = metadata_resize(era->md, &era->nr_blocks);
1494         if (r) {
1495                 ti->error = "couldn't resize metadata";
1496                 era_destroy(era);
1497                 return -ENOMEM;
1498         }
1499
1500         era->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
1501         if (!era->wq) {
1502                 ti->error = "could not create workqueue for metadata object";
1503                 era_destroy(era);
1504                 return -ENOMEM;
1505         }
1506         INIT_WORK(&era->worker, do_work);
1507
1508         spin_lock_init(&era->deferred_lock);
1509         bio_list_init(&era->deferred_bios);
1510
1511         spin_lock_init(&era->rpc_lock);
1512         INIT_LIST_HEAD(&era->rpc_calls);
1513
1514         ti->private = era;
1515         ti->num_flush_bios = 1;
1516         ti->flush_supported = true;
1517
1518         ti->num_discard_bios = 1;
1519         ti->discards_supported = true;
1520         era->callbacks.congested_fn = era_is_congested;
1521         dm_table_add_target_callbacks(ti->table, &era->callbacks);
1522
1523         return 0;
1524 }
1525
1526 static void era_dtr(struct dm_target *ti)
1527 {
1528         era_destroy(ti->private);
1529 }
1530
1531 static int era_map(struct dm_target *ti, struct bio *bio)
1532 {
1533         struct era *era = ti->private;
1534         dm_block_t block = get_block(era, bio);
1535
1536         /*
1537          * All bios get remapped to the origin device.  We do this now, but
1538          * it may not get issued until later.  Depending on whether the
1539          * block is marked in this era.
1540          */
1541         remap_to_origin(era, bio);
1542
1543         /*
1544          * REQ_FLUSH bios carry no data, so we're not interested in them.
1545          */
1546         if (!(bio->bi_rw & REQ_FLUSH) &&
1547             (bio_data_dir(bio) == WRITE) &&
1548             !metadata_current_marked(era->md, block)) {
1549                 defer_bio(era, bio);
1550                 return DM_MAPIO_SUBMITTED;
1551         }
1552
1553         return DM_MAPIO_REMAPPED;
1554 }
1555
1556 static void era_postsuspend(struct dm_target *ti)
1557 {
1558         int r;
1559         struct era *era = ti->private;
1560
1561         r = in_worker0(era, metadata_era_archive);
1562         if (r) {
1563                 DMERR("%s: couldn't archive current era", __func__);
1564                 /* FIXME: fail mode */
1565         }
1566
1567         stop_worker(era);
1568 }
1569
1570 static int era_preresume(struct dm_target *ti)
1571 {
1572         int r;
1573         struct era *era = ti->private;
1574         dm_block_t new_size = calc_nr_blocks(era);
1575
1576         if (era->nr_blocks != new_size) {
1577                 r = in_worker1(era, metadata_resize, &new_size);
1578                 if (r)
1579                         return r;
1580
1581                 era->nr_blocks = new_size;
1582         }
1583
1584         start_worker(era);
1585
1586         r = in_worker0(era, metadata_new_era);
1587         if (r) {
1588                 DMERR("%s: metadata_era_rollover failed", __func__);
1589                 return r;
1590         }
1591
1592         return 0;
1593 }
1594
1595 /*
1596  * Status format:
1597  *
1598  * <metadata block size> <#used metadata blocks>/<#total metadata blocks>
1599  * <current era> <held metadata root | '-'>
1600  */
1601 static void era_status(struct dm_target *ti, status_type_t type,
1602                        unsigned status_flags, char *result, unsigned maxlen)
1603 {
1604         int r;
1605         struct era *era = ti->private;
1606         ssize_t sz = 0;
1607         struct metadata_stats stats;
1608         char buf[BDEVNAME_SIZE];
1609
1610         switch (type) {
1611         case STATUSTYPE_INFO:
1612                 r = in_worker1(era, metadata_get_stats, &stats);
1613                 if (r)
1614                         goto err;
1615
1616                 DMEMIT("%u %llu/%llu %u",
1617                        (unsigned) (DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
1618                        (unsigned long long) stats.used,
1619                        (unsigned long long) stats.total,
1620                        (unsigned) stats.era);
1621
1622                 if (stats.snap != SUPERBLOCK_LOCATION)
1623                         DMEMIT(" %llu", stats.snap);
1624                 else
1625                         DMEMIT(" -");
1626                 break;
1627
1628         case STATUSTYPE_TABLE:
1629                 format_dev_t(buf, era->metadata_dev->bdev->bd_dev);
1630                 DMEMIT("%s ", buf);
1631                 format_dev_t(buf, era->origin_dev->bdev->bd_dev);
1632                 DMEMIT("%s %u", buf, era->sectors_per_block);
1633                 break;
1634         }
1635
1636         return;
1637
1638 err:
1639         DMEMIT("Error");
1640 }
1641
1642 static int era_message(struct dm_target *ti, unsigned argc, char **argv)
1643 {
1644         struct era *era = ti->private;
1645
1646         if (argc != 1) {
1647                 DMERR("incorrect number of message arguments");
1648                 return -EINVAL;
1649         }
1650
1651         if (!strcasecmp(argv[0], "checkpoint"))
1652                 return in_worker0(era, metadata_checkpoint);
1653
1654         if (!strcasecmp(argv[0], "take_metadata_snap"))
1655                 return in_worker0(era, metadata_take_snap);
1656
1657         if (!strcasecmp(argv[0], "drop_metadata_snap"))
1658                 return in_worker0(era, metadata_drop_snap);
1659
1660         DMERR("unsupported message '%s'", argv[0]);
1661         return -EINVAL;
1662 }
1663
1664 static sector_t get_dev_size(struct dm_dev *dev)
1665 {
1666         return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
1667 }
1668
1669 static int era_iterate_devices(struct dm_target *ti,
1670                                iterate_devices_callout_fn fn, void *data)
1671 {
1672         struct era *era = ti->private;
1673         return fn(ti, era->origin_dev, 0, get_dev_size(era->origin_dev), data);
1674 }
1675
1676 static int era_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
1677                      struct bio_vec *biovec, int max_size)
1678 {
1679         struct era *era = ti->private;
1680         struct request_queue *q = bdev_get_queue(era->origin_dev->bdev);
1681
1682         if (!q->merge_bvec_fn)
1683                 return max_size;
1684
1685         bvm->bi_bdev = era->origin_dev->bdev;
1686
1687         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
1688 }
1689
1690 static void era_io_hints(struct dm_target *ti, struct queue_limits *limits)
1691 {
1692         struct era *era = ti->private;
1693         uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
1694
1695         /*
1696          * If the system-determined stacked limits are compatible with the
1697          * era device's blocksize (io_opt is a factor) do not override them.
1698          */
1699         if (io_opt_sectors < era->sectors_per_block ||
1700             do_div(io_opt_sectors, era->sectors_per_block)) {
1701                 blk_limits_io_min(limits, 0);
1702                 blk_limits_io_opt(limits, era->sectors_per_block << SECTOR_SHIFT);
1703         }
1704 }
1705
1706 /*----------------------------------------------------------------*/
1707
1708 static struct target_type era_target = {
1709         .name = "era",
1710         .version = {1, 0, 0},
1711         .module = THIS_MODULE,
1712         .ctr = era_ctr,
1713         .dtr = era_dtr,
1714         .map = era_map,
1715         .postsuspend = era_postsuspend,
1716         .preresume = era_preresume,
1717         .status = era_status,
1718         .message = era_message,
1719         .iterate_devices = era_iterate_devices,
1720         .merge = era_merge,
1721         .io_hints = era_io_hints
1722 };
1723
1724 static int __init dm_era_init(void)
1725 {
1726         int r;
1727
1728         r = dm_register_target(&era_target);
1729         if (r) {
1730                 DMERR("era target registration failed: %d", r);
1731                 return r;
1732         }
1733
1734         return 0;
1735 }
1736
1737 static void __exit dm_era_exit(void)
1738 {
1739         dm_unregister_target(&era_target);
1740 }
1741
1742 module_init(dm_era_init);
1743 module_exit(dm_era_exit);
1744
1745 MODULE_DESCRIPTION(DM_NAME " era target");
1746 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
1747 MODULE_LICENSE("GPL");