1762 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2#include "dm.h"3#include "persistent-data/dm-transaction-manager.h"4#include "persistent-data/dm-bitset.h"5#include "persistent-data/dm-space-map.h"6 7#include <linux/dm-io.h>8#include <linux/dm-kcopyd.h>9#include <linux/init.h>10#include <linux/mempool.h>11#include <linux/module.h>12#include <linux/slab.h>13#include <linux/vmalloc.h>14 15#define DM_MSG_PREFIX "era"16 17#define SUPERBLOCK_LOCATION 018#define SUPERBLOCK_MAGIC 212657957919#define SUPERBLOCK_CSUM_XOR 14653838120#define MIN_ERA_VERSION 121#define MAX_ERA_VERSION 122#define INVALID_WRITESET_ROOT SUPERBLOCK_LOCATION23#define MIN_BLOCK_SIZE 824 25/*26 *--------------------------------------------------------------27 * Writeset28 *--------------------------------------------------------------29 */30struct writeset_metadata {31 uint32_t nr_bits;32 dm_block_t root;33};34 35struct writeset {36 struct writeset_metadata md;37 38 /*39 * An in core copy of the bits to save constantly doing look ups on40 * disk.41 */42 unsigned long *bits;43};44 45/*46 * This does not free off the on disk bitset as this will normally be done47 * after digesting into the era array.48 */49static void writeset_free(struct writeset *ws)50{51 vfree(ws->bits);52 ws->bits = NULL;53}54 55static int setup_on_disk_bitset(struct dm_disk_bitset *info,56 unsigned int nr_bits, dm_block_t *root)57{58 int r;59 60 r = dm_bitset_empty(info, root);61 if (r)62 return r;63 64 return dm_bitset_resize(info, *root, 0, nr_bits, false, root);65}66 67static size_t bitset_size(unsigned int nr_bits)68{69 return sizeof(unsigned long) * dm_div_up(nr_bits, BITS_PER_LONG);70}71 72/*73 * Allocates memory for the in core bitset.74 */75static int writeset_alloc(struct writeset *ws, dm_block_t nr_blocks)76{77 ws->bits = vzalloc(bitset_size(nr_blocks));78 if (!ws->bits) {79 DMERR("%s: couldn't allocate in memory bitset", __func__);80 return -ENOMEM;81 }82 83 return 0;84}85 86/*87 * Wipes the in-core bitset, and creates a new on disk bitset.88 */89static int writeset_init(struct dm_disk_bitset *info, struct writeset *ws,90 dm_block_t nr_blocks)91{92 int r;93 94 memset(ws->bits, 0, bitset_size(nr_blocks));95 96 ws->md.nr_bits = nr_blocks;97 r = setup_on_disk_bitset(info, ws->md.nr_bits, &ws->md.root);98 if (r) {99 DMERR("%s: setup_on_disk_bitset failed", __func__);100 return r;101 }102 103 return 0;104}105 106static bool writeset_marked(struct writeset *ws, dm_block_t block)107{108 return test_bit(block, ws->bits);109}110 111static int writeset_marked_on_disk(struct dm_disk_bitset *info,112 struct writeset_metadata *m, dm_block_t block,113 bool *result)114{115 int r;116 dm_block_t old = m->root;117 118 /*119 * The bitset was flushed when it was archived, so we know there'll120 * be no change to the root.121 */122 r = dm_bitset_test_bit(info, m->root, block, &m->root, result);123 if (r) {124 DMERR("%s: dm_bitset_test_bit failed", __func__);125 return r;126 }127 128 BUG_ON(m->root != old);129 130 return r;131}132 133/*134 * Returns < 0 on error, 0 if the bit wasn't previously set, 1 if it was.135 */136static int writeset_test_and_set(struct dm_disk_bitset *info,137 struct writeset *ws, uint32_t block)138{139 int r;140 141 if (!test_bit(block, ws->bits)) {142 r = dm_bitset_set_bit(info, ws->md.root, block, &ws->md.root);143 if (r) {144 /* FIXME: fail mode */145 return r;146 }147 148 return 0;149 }150 151 return 1;152}153 154/*155 *--------------------------------------------------------------156 * On disk metadata layout157 *--------------------------------------------------------------158 */159#define SPACE_MAP_ROOT_SIZE 128160#define UUID_LEN 16161 162struct writeset_disk {163 __le32 nr_bits;164 __le64 root;165} __packed;166 167struct superblock_disk {168 __le32 csum;169 __le32 flags;170 __le64 blocknr;171 172 __u8 uuid[UUID_LEN];173 __le64 magic;174 __le32 version;175 176 __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];177 178 __le32 data_block_size;179 __le32 metadata_block_size;180 __le32 nr_blocks;181 182 __le32 current_era;183 struct writeset_disk current_writeset;184 185 /*186 * Only these two fields are valid within the metadata snapshot.187 */188 __le64 writeset_tree_root;189 __le64 era_array_root;190 191 __le64 metadata_snap;192} __packed;193 194/*195 *--------------------------------------------------------------196 * Superblock validation197 *--------------------------------------------------------------198 */199static void sb_prepare_for_write(const struct dm_block_validator *v,200 struct dm_block *b,201 size_t sb_block_size)202{203 struct superblock_disk *disk = dm_block_data(b);204 205 disk->blocknr = cpu_to_le64(dm_block_location(b));206 disk->csum = cpu_to_le32(dm_bm_checksum(&disk->flags,207 sb_block_size - sizeof(__le32),208 SUPERBLOCK_CSUM_XOR));209}210 211static int check_metadata_version(struct superblock_disk *disk)212{213 uint32_t metadata_version = le32_to_cpu(disk->version);214 215 if (metadata_version < MIN_ERA_VERSION || metadata_version > MAX_ERA_VERSION) {216 DMERR("Era metadata version %u found, but only versions between %u and %u supported.",217 metadata_version, MIN_ERA_VERSION, MAX_ERA_VERSION);218 return -EINVAL;219 }220 221 return 0;222}223 224static int sb_check(const struct dm_block_validator *v,225 struct dm_block *b,226 size_t sb_block_size)227{228 struct superblock_disk *disk = dm_block_data(b);229 __le32 csum_le;230 231 if (dm_block_location(b) != le64_to_cpu(disk->blocknr)) {232 DMERR("%s failed: blocknr %llu: wanted %llu",233 __func__, le64_to_cpu(disk->blocknr),234 (unsigned long long)dm_block_location(b));235 return -ENOTBLK;236 }237 238 if (le64_to_cpu(disk->magic) != SUPERBLOCK_MAGIC) {239 DMERR("%s failed: magic %llu: wanted %llu",240 __func__, le64_to_cpu(disk->magic),241 (unsigned long long) SUPERBLOCK_MAGIC);242 return -EILSEQ;243 }244 245 csum_le = cpu_to_le32(dm_bm_checksum(&disk->flags,246 sb_block_size - sizeof(__le32),247 SUPERBLOCK_CSUM_XOR));248 if (csum_le != disk->csum) {249 DMERR("%s failed: csum %u: wanted %u",250 __func__, le32_to_cpu(csum_le), le32_to_cpu(disk->csum));251 return -EILSEQ;252 }253 254 return check_metadata_version(disk);255}256 257static const struct dm_block_validator sb_validator = {258 .name = "superblock",259 .prepare_for_write = sb_prepare_for_write,260 .check = sb_check261};262 263/*264 *--------------------------------------------------------------265 * Low level metadata handling266 *--------------------------------------------------------------267 */268#define DM_ERA_METADATA_BLOCK_SIZE 4096269#define ERA_MAX_CONCURRENT_LOCKS 5270 271struct era_metadata {272 struct block_device *bdev;273 struct dm_block_manager *bm;274 struct dm_space_map *sm;275 struct dm_transaction_manager *tm;276 277 dm_block_t block_size;278 uint32_t nr_blocks;279 280 uint32_t current_era;281 282 /*283 * We preallocate 2 writesets. When an era rolls over we284 * switch between them. This means the allocation is done at285 * preresume time, rather than on the io path.286 */287 struct writeset writesets[2];288 struct writeset *current_writeset;289 290 dm_block_t writeset_tree_root;291 dm_block_t era_array_root;292 293 struct dm_disk_bitset bitset_info;294 struct dm_btree_info writeset_tree_info;295 struct dm_array_info era_array_info;296 297 dm_block_t metadata_snap;298 299 /*300 * A flag that is set whenever a writeset has been archived.301 */302 bool archived_writesets;303 304 /*305 * Reading the space map root can fail, so we read it into this306 * buffer before the superblock is locked and updated.307 */308 __u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];309};310 311static int superblock_read_lock(struct era_metadata *md,312 struct dm_block **sblock)313{314 return dm_bm_read_lock(md->bm, SUPERBLOCK_LOCATION,315 &sb_validator, sblock);316}317 318static int superblock_lock_zero(struct era_metadata *md,319 struct dm_block **sblock)320{321 return dm_bm_write_lock_zero(md->bm, SUPERBLOCK_LOCATION,322 &sb_validator, sblock);323}324 325static int superblock_lock(struct era_metadata *md,326 struct dm_block **sblock)327{328 return dm_bm_write_lock(md->bm, SUPERBLOCK_LOCATION,329 &sb_validator, sblock);330}331 332/* FIXME: duplication with cache and thin */333static int superblock_all_zeroes(struct dm_block_manager *bm, bool *result)334{335 int r;336 unsigned int i;337 struct dm_block *b;338 __le64 *data_le, zero = cpu_to_le64(0);339 unsigned int sb_block_size = dm_bm_block_size(bm) / sizeof(__le64);340 341 /*342 * We can't use a validator here - it may be all zeroes.343 */344 r = dm_bm_read_lock(bm, SUPERBLOCK_LOCATION, NULL, &b);345 if (r)346 return r;347 348 data_le = dm_block_data(b);349 *result = true;350 for (i = 0; i < sb_block_size; i++) {351 if (data_le[i] != zero) {352 *result = false;353 break;354 }355 }356 357 dm_bm_unlock(b);358 359 return 0;360}361 362/*----------------------------------------------------------------*/363 364static void ws_pack(const struct writeset_metadata *core, struct writeset_disk *disk)365{366 disk->nr_bits = cpu_to_le32(core->nr_bits);367 disk->root = cpu_to_le64(core->root);368}369 370static void ws_unpack(const struct writeset_disk *disk, struct writeset_metadata *core)371{372 core->nr_bits = le32_to_cpu(disk->nr_bits);373 core->root = le64_to_cpu(disk->root);374}375 376static void ws_inc(void *context, const void *value, unsigned int count)377{378 struct era_metadata *md = context;379 struct writeset_disk ws_d;380 dm_block_t b;381 unsigned int i;382 383 for (i = 0; i < count; i++) {384 memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));385 b = le64_to_cpu(ws_d.root);386 dm_tm_inc(md->tm, b);387 }388}389 390static void ws_dec(void *context, const void *value, unsigned int count)391{392 struct era_metadata *md = context;393 struct writeset_disk ws_d;394 dm_block_t b;395 unsigned int i;396 397 for (i = 0; i < count; i++) {398 memcpy(&ws_d, value + (i * sizeof(ws_d)), sizeof(ws_d));399 b = le64_to_cpu(ws_d.root);400 dm_bitset_del(&md->bitset_info, b);401 }402}403 404static int ws_eq(void *context, const void *value1, const void *value2)405{406 return !memcmp(value1, value2, sizeof(struct writeset_disk));407}408 409/*----------------------------------------------------------------*/410 411static void setup_writeset_tree_info(struct era_metadata *md)412{413 struct dm_btree_value_type *vt = &md->writeset_tree_info.value_type;414 415 md->writeset_tree_info.tm = md->tm;416 md->writeset_tree_info.levels = 1;417 vt->context = md;418 vt->size = sizeof(struct writeset_disk);419 vt->inc = ws_inc;420 vt->dec = ws_dec;421 vt->equal = ws_eq;422}423 424static void setup_era_array_info(struct era_metadata *md)425{426 struct dm_btree_value_type vt;427 428 vt.context = NULL;429 vt.size = sizeof(__le32);430 vt.inc = NULL;431 vt.dec = NULL;432 vt.equal = NULL;433 434 dm_array_info_init(&md->era_array_info, md->tm, &vt);435}436 437static void setup_infos(struct era_metadata *md)438{439 dm_disk_bitset_init(md->tm, &md->bitset_info);440 setup_writeset_tree_info(md);441 setup_era_array_info(md);442}443 444/*----------------------------------------------------------------*/445 446static int create_fresh_metadata(struct era_metadata *md)447{448 int r;449 450 r = dm_tm_create_with_sm(md->bm, SUPERBLOCK_LOCATION,451 &md->tm, &md->sm);452 if (r < 0) {453 DMERR("dm_tm_create_with_sm failed");454 return r;455 }456 457 setup_infos(md);458 459 r = dm_btree_empty(&md->writeset_tree_info, &md->writeset_tree_root);460 if (r) {461 DMERR("couldn't create new writeset tree");462 goto bad;463 }464 465 r = dm_array_empty(&md->era_array_info, &md->era_array_root);466 if (r) {467 DMERR("couldn't create era array");468 goto bad;469 }470 471 return 0;472 473bad:474 dm_sm_destroy(md->sm);475 dm_tm_destroy(md->tm);476 477 return r;478}479 480static int save_sm_root(struct era_metadata *md)481{482 int r;483 size_t metadata_len;484 485 r = dm_sm_root_size(md->sm, &metadata_len);486 if (r < 0)487 return r;488 489 return dm_sm_copy_root(md->sm, &md->metadata_space_map_root,490 metadata_len);491}492 493static void copy_sm_root(struct era_metadata *md, struct superblock_disk *disk)494{495 memcpy(&disk->metadata_space_map_root,496 &md->metadata_space_map_root,497 sizeof(md->metadata_space_map_root));498}499 500/*501 * Writes a superblock, including the static fields that don't get updated502 * with every commit (possible optimisation here). 'md' should be fully503 * constructed when this is called.504 */505static void prepare_superblock(struct era_metadata *md, struct superblock_disk *disk)506{507 disk->magic = cpu_to_le64(SUPERBLOCK_MAGIC);508 disk->flags = cpu_to_le32(0ul);509 510 /* FIXME: can't keep blanking the uuid (uuid is currently unused though) */511 memset(disk->uuid, 0, sizeof(disk->uuid));512 disk->version = cpu_to_le32(MAX_ERA_VERSION);513 514 copy_sm_root(md, disk);515 516 disk->data_block_size = cpu_to_le32(md->block_size);517 disk->metadata_block_size = cpu_to_le32(DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT);518 disk->nr_blocks = cpu_to_le32(md->nr_blocks);519 disk->current_era = cpu_to_le32(md->current_era);520 521 ws_pack(&md->current_writeset->md, &disk->current_writeset);522 disk->writeset_tree_root = cpu_to_le64(md->writeset_tree_root);523 disk->era_array_root = cpu_to_le64(md->era_array_root);524 disk->metadata_snap = cpu_to_le64(md->metadata_snap);525}526 527static int write_superblock(struct era_metadata *md)528{529 int r;530 struct dm_block *sblock;531 struct superblock_disk *disk;532 533 r = save_sm_root(md);534 if (r) {535 DMERR("%s: save_sm_root failed", __func__);536 return r;537 }538 539 r = superblock_lock_zero(md, &sblock);540 if (r)541 return r;542 543 disk = dm_block_data(sblock);544 prepare_superblock(md, disk);545 546 return dm_tm_commit(md->tm, sblock);547}548 549/*550 * Assumes block_size and the infos are set.551 */552static int format_metadata(struct era_metadata *md)553{554 int r;555 556 r = create_fresh_metadata(md);557 if (r)558 return r;559 560 r = write_superblock(md);561 if (r) {562 dm_sm_destroy(md->sm);563 dm_tm_destroy(md->tm);564 return r;565 }566 567 return 0;568}569 570static int open_metadata(struct era_metadata *md)571{572 int r;573 struct dm_block *sblock;574 struct superblock_disk *disk;575 576 r = superblock_read_lock(md, &sblock);577 if (r) {578 DMERR("couldn't read_lock superblock");579 return r;580 }581 582 disk = dm_block_data(sblock);583 584 /* Verify the data block size hasn't changed */585 if (le32_to_cpu(disk->data_block_size) != md->block_size) {586 DMERR("changing the data block size (from %u to %llu) is not supported",587 le32_to_cpu(disk->data_block_size), md->block_size);588 r = -EINVAL;589 goto bad;590 }591 592 r = dm_tm_open_with_sm(md->bm, SUPERBLOCK_LOCATION,593 disk->metadata_space_map_root,594 sizeof(disk->metadata_space_map_root),595 &md->tm, &md->sm);596 if (r) {597 DMERR("dm_tm_open_with_sm failed");598 goto bad;599 }600 601 setup_infos(md);602 603 md->nr_blocks = le32_to_cpu(disk->nr_blocks);604 md->current_era = le32_to_cpu(disk->current_era);605 606 ws_unpack(&disk->current_writeset, &md->current_writeset->md);607 md->writeset_tree_root = le64_to_cpu(disk->writeset_tree_root);608 md->era_array_root = le64_to_cpu(disk->era_array_root);609 md->metadata_snap = le64_to_cpu(disk->metadata_snap);610 md->archived_writesets = true;611 612 dm_bm_unlock(sblock);613 614 return 0;615 616bad:617 dm_bm_unlock(sblock);618 return r;619}620 621static int open_or_format_metadata(struct era_metadata *md,622 bool may_format)623{624 int r;625 bool unformatted = false;626 627 r = superblock_all_zeroes(md->bm, &unformatted);628 if (r)629 return r;630 631 if (unformatted)632 return may_format ? format_metadata(md) : -EPERM;633 634 return open_metadata(md);635}636 637static int create_persistent_data_objects(struct era_metadata *md,638 bool may_format)639{640 int r;641 642 md->bm = dm_block_manager_create(md->bdev, DM_ERA_METADATA_BLOCK_SIZE,643 ERA_MAX_CONCURRENT_LOCKS);644 if (IS_ERR(md->bm)) {645 DMERR("could not create block manager");646 return PTR_ERR(md->bm);647 }648 649 r = open_or_format_metadata(md, may_format);650 if (r)651 dm_block_manager_destroy(md->bm);652 653 return r;654}655 656static void destroy_persistent_data_objects(struct era_metadata *md)657{658 dm_sm_destroy(md->sm);659 dm_tm_destroy(md->tm);660 dm_block_manager_destroy(md->bm);661}662 663/*664 * This waits until all era_map threads have picked up the new filter.665 */666static void swap_writeset(struct era_metadata *md, struct writeset *new_writeset)667{668 rcu_assign_pointer(md->current_writeset, new_writeset);669 synchronize_rcu();670}671 672/*673 *------------------------------------------------------------------------674 * Writesets get 'digested' into the main era array.675 *676 * We're using a coroutine here so the worker thread can do the digestion,677 * thus avoiding synchronisation of the metadata. Digesting a whole678 * writeset in one go would cause too much latency.679 *------------------------------------------------------------------------680 */681struct digest {682 uint32_t era;683 unsigned int nr_bits, current_bit;684 struct writeset_metadata writeset;685 __le32 value;686 struct dm_disk_bitset info;687 688 int (*step)(struct era_metadata *md, struct digest *d);689};690 691static int metadata_digest_lookup_writeset(struct era_metadata *md,692 struct digest *d);693 694static int metadata_digest_remove_writeset(struct era_metadata *md,695 struct digest *d)696{697 int r;698 uint64_t key = d->era;699 700 r = dm_btree_remove(&md->writeset_tree_info, md->writeset_tree_root,701 &key, &md->writeset_tree_root);702 if (r) {703 DMERR("%s: dm_btree_remove failed", __func__);704 return r;705 }706 707 d->step = metadata_digest_lookup_writeset;708 return 0;709}710 711#define INSERTS_PER_STEP 100712 713static int metadata_digest_transcribe_writeset(struct era_metadata *md,714 struct digest *d)715{716 int r;717 bool marked;718 unsigned int b, e = min(d->current_bit + INSERTS_PER_STEP, d->nr_bits);719 720 for (b = d->current_bit; b < e; b++) {721 r = writeset_marked_on_disk(&d->info, &d->writeset, b, &marked);722 if (r) {723 DMERR("%s: writeset_marked_on_disk failed", __func__);724 return r;725 }726 727 if (!marked)728 continue;729 730 __dm_bless_for_disk(&d->value);731 r = dm_array_set_value(&md->era_array_info, md->era_array_root,732 b, &d->value, &md->era_array_root);733 if (r) {734 DMERR("%s: dm_array_set_value failed", __func__);735 return r;736 }737 }738 739 if (b == d->nr_bits)740 d->step = metadata_digest_remove_writeset;741 else742 d->current_bit = b;743 744 return 0;745}746 747static int metadata_digest_lookup_writeset(struct era_metadata *md,748 struct digest *d)749{750 int r;751 uint64_t key;752 struct writeset_disk disk;753 754 r = dm_btree_find_lowest_key(&md->writeset_tree_info,755 md->writeset_tree_root, &key);756 if (r < 0)757 return r;758 759 d->era = key;760 761 r = dm_btree_lookup(&md->writeset_tree_info,762 md->writeset_tree_root, &key, &disk);763 if (r) {764 if (r == -ENODATA) {765 d->step = NULL;766 return 0;767 }768 769 DMERR("%s: dm_btree_lookup failed", __func__);770 return r;771 }772 773 ws_unpack(&disk, &d->writeset);774 d->value = cpu_to_le32(key);775 776 /*777 * We initialise another bitset info to avoid any caching side effects778 * with the previous one.779 */780 dm_disk_bitset_init(md->tm, &d->info);781 782 d->nr_bits = min(d->writeset.nr_bits, md->nr_blocks);783 d->current_bit = 0;784 d->step = metadata_digest_transcribe_writeset;785 786 return 0;787}788 789static int metadata_digest_start(struct era_metadata *md, struct digest *d)790{791 if (d->step)792 return 0;793 794 memset(d, 0, sizeof(*d));795 d->step = metadata_digest_lookup_writeset;796 797 return 0;798}799 800/*801 *-----------------------------------------------------------------802 * High level metadata interface. Target methods should use these,803 * and not the lower level ones.804 *-----------------------------------------------------------------805 */806static struct era_metadata *metadata_open(struct block_device *bdev,807 sector_t block_size,808 bool may_format)809{810 int r;811 struct era_metadata *md = kzalloc(sizeof(*md), GFP_KERNEL);812 813 if (!md)814 return NULL;815 816 md->bdev = bdev;817 md->block_size = block_size;818 819 md->writesets[0].md.root = INVALID_WRITESET_ROOT;820 md->writesets[1].md.root = INVALID_WRITESET_ROOT;821 md->current_writeset = &md->writesets[0];822 823 r = create_persistent_data_objects(md, may_format);824 if (r) {825 kfree(md);826 return ERR_PTR(r);827 }828 829 return md;830}831 832static void metadata_close(struct era_metadata *md)833{834 writeset_free(&md->writesets[0]);835 writeset_free(&md->writesets[1]);836 destroy_persistent_data_objects(md);837 kfree(md);838}839 840static bool valid_nr_blocks(dm_block_t n)841{842 /*843 * dm_bitset restricts us to 2^32. test_bit & co. restrict us844 * further to 2^31 - 1845 */846 return n < (1ull << 31);847}848 849static int metadata_resize(struct era_metadata *md, void *arg)850{851 int r;852 dm_block_t *new_size = arg;853 __le32 value;854 855 if (!valid_nr_blocks(*new_size)) {856 DMERR("Invalid number of origin blocks %llu",857 (unsigned long long) *new_size);858 return -EINVAL;859 }860 861 writeset_free(&md->writesets[0]);862 writeset_free(&md->writesets[1]);863 864 r = writeset_alloc(&md->writesets[0], *new_size);865 if (r) {866 DMERR("%s: writeset_alloc failed for writeset 0", __func__);867 return r;868 }869 870 r = writeset_alloc(&md->writesets[1], *new_size);871 if (r) {872 DMERR("%s: writeset_alloc failed for writeset 1", __func__);873 writeset_free(&md->writesets[0]);874 return r;875 }876 877 value = cpu_to_le32(0u);878 __dm_bless_for_disk(&value);879 r = dm_array_resize(&md->era_array_info, md->era_array_root,880 md->nr_blocks, *new_size,881 &value, &md->era_array_root);882 if (r) {883 DMERR("%s: dm_array_resize failed", __func__);884 writeset_free(&md->writesets[0]);885 writeset_free(&md->writesets[1]);886 return r;887 }888 889 md->nr_blocks = *new_size;890 return 0;891}892 893static int metadata_era_archive(struct era_metadata *md)894{895 int r;896 uint64_t keys[1];897 struct writeset_disk value;898 899 r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,900 &md->current_writeset->md.root);901 if (r) {902 DMERR("%s: dm_bitset_flush failed", __func__);903 return r;904 }905 906 ws_pack(&md->current_writeset->md, &value);907 908 keys[0] = md->current_era;909 __dm_bless_for_disk(&value);910 r = dm_btree_insert(&md->writeset_tree_info, md->writeset_tree_root,911 keys, &value, &md->writeset_tree_root);912 if (r) {913 DMERR("%s: couldn't insert writeset into btree", __func__);914 /* FIXME: fail mode */915 return r;916 }917 918 md->current_writeset->md.root = INVALID_WRITESET_ROOT;919 md->archived_writesets = true;920 921 return 0;922}923 924static struct writeset *next_writeset(struct era_metadata *md)925{926 return (md->current_writeset == &md->writesets[0]) ?927 &md->writesets[1] : &md->writesets[0];928}929 930static int metadata_new_era(struct era_metadata *md)931{932 int r;933 struct writeset *new_writeset = next_writeset(md);934 935 r = writeset_init(&md->bitset_info, new_writeset, md->nr_blocks);936 if (r) {937 DMERR("%s: writeset_init failed", __func__);938 return r;939 }940 941 swap_writeset(md, new_writeset);942 md->current_era++;943 944 return 0;945}946 947static int metadata_era_rollover(struct era_metadata *md)948{949 int r;950 951 if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {952 r = metadata_era_archive(md);953 if (r) {954 DMERR("%s: metadata_archive_era failed", __func__);955 /* FIXME: fail mode? */956 return r;957 }958 }959 960 r = metadata_new_era(md);961 if (r) {962 DMERR("%s: new era failed", __func__);963 /* FIXME: fail mode */964 return r;965 }966 967 return 0;968}969 970static bool metadata_current_marked(struct era_metadata *md, dm_block_t block)971{972 bool r;973 struct writeset *ws;974 975 rcu_read_lock();976 ws = rcu_dereference(md->current_writeset);977 r = writeset_marked(ws, block);978 rcu_read_unlock();979 980 return r;981}982 983static int metadata_commit(struct era_metadata *md)984{985 int r;986 struct dm_block *sblock;987 988 if (md->current_writeset->md.root != INVALID_WRITESET_ROOT) {989 r = dm_bitset_flush(&md->bitset_info, md->current_writeset->md.root,990 &md->current_writeset->md.root);991 if (r) {992 DMERR("%s: bitset flush failed", __func__);993 return r;994 }995 }996 997 r = dm_tm_pre_commit(md->tm);998 if (r) {999 DMERR("%s: pre commit failed", __func__);1000 return r;1001 }1002 1003 r = save_sm_root(md);1004 if (r) {1005 DMERR("%s: save_sm_root failed", __func__);1006 return r;1007 }1008 1009 r = superblock_lock(md, &sblock);1010 if (r) {1011 DMERR("%s: superblock lock failed", __func__);1012 return r;1013 }1014 1015 prepare_superblock(md, dm_block_data(sblock));1016 1017 return dm_tm_commit(md->tm, sblock);1018}1019 1020static int metadata_checkpoint(struct era_metadata *md)1021{1022 /*1023 * For now we just rollover, but later I want to put a check in to1024 * avoid this if the filter is still pretty fresh.1025 */1026 return metadata_era_rollover(md);1027}1028 1029/*1030 * Metadata snapshots allow userland to access era data.1031 */1032static int metadata_take_snap(struct era_metadata *md)1033{1034 int r, inc;1035 struct dm_block *clone;1036 1037 if (md->metadata_snap != SUPERBLOCK_LOCATION) {1038 DMERR("%s: metadata snapshot already exists", __func__);1039 return -EINVAL;1040 }1041 1042 r = metadata_era_rollover(md);1043 if (r) {1044 DMERR("%s: era rollover failed", __func__);1045 return r;1046 }1047 1048 r = metadata_commit(md);1049 if (r) {1050 DMERR("%s: pre commit failed", __func__);1051 return r;1052 }1053 1054 r = dm_sm_inc_block(md->sm, SUPERBLOCK_LOCATION);1055 if (r) {1056 DMERR("%s: couldn't increment superblock", __func__);1057 return r;1058 }1059 1060 r = dm_tm_shadow_block(md->tm, SUPERBLOCK_LOCATION,1061 &sb_validator, &clone, &inc);1062 if (r) {1063 DMERR("%s: couldn't shadow superblock", __func__);1064 dm_sm_dec_block(md->sm, SUPERBLOCK_LOCATION);1065 return r;1066 }1067 BUG_ON(!inc);1068 1069 r = dm_sm_inc_block(md->sm, md->writeset_tree_root);1070 if (r) {1071 DMERR("%s: couldn't inc writeset tree root", __func__);1072 dm_tm_unlock(md->tm, clone);1073 return r;1074 }1075 1076 r = dm_sm_inc_block(md->sm, md->era_array_root);1077 if (r) {1078 DMERR("%s: couldn't inc era tree root", __func__);1079 dm_sm_dec_block(md->sm, md->writeset_tree_root);1080 dm_tm_unlock(md->tm, clone);1081 return r;1082 }1083 1084 md->metadata_snap = dm_block_location(clone);1085 1086 dm_tm_unlock(md->tm, clone);1087 1088 return 0;1089}1090 1091static int metadata_drop_snap(struct era_metadata *md)1092{1093 int r;1094 dm_block_t location;1095 struct dm_block *clone;1096 struct superblock_disk *disk;1097 1098 if (md->metadata_snap == SUPERBLOCK_LOCATION) {1099 DMERR("%s: no snap to drop", __func__);1100 return -EINVAL;1101 }1102 1103 r = dm_tm_read_lock(md->tm, md->metadata_snap, &sb_validator, &clone);1104 if (r) {1105 DMERR("%s: couldn't read lock superblock clone", __func__);1106 return r;1107 }1108 1109 /*1110 * Whatever happens now we'll commit with no record of the metadata1111 * snap.1112 */1113 md->metadata_snap = SUPERBLOCK_LOCATION;1114 1115 disk = dm_block_data(clone);1116 r = dm_btree_del(&md->writeset_tree_info,1117 le64_to_cpu(disk->writeset_tree_root));1118 if (r) {1119 DMERR("%s: error deleting writeset tree clone", __func__);1120 dm_tm_unlock(md->tm, clone);1121 return r;1122 }1123 1124 r = dm_array_del(&md->era_array_info, le64_to_cpu(disk->era_array_root));1125 if (r) {1126 DMERR("%s: error deleting era array clone", __func__);1127 dm_tm_unlock(md->tm, clone);1128 return r;1129 }1130 1131 location = dm_block_location(clone);1132 dm_tm_unlock(md->tm, clone);1133 1134 return dm_sm_dec_block(md->sm, location);1135}1136 1137struct metadata_stats {1138 dm_block_t used;1139 dm_block_t total;1140 dm_block_t snap;1141 uint32_t era;1142};1143 1144static int metadata_get_stats(struct era_metadata *md, void *ptr)1145{1146 int r;1147 struct metadata_stats *s = ptr;1148 dm_block_t nr_free, nr_total;1149 1150 r = dm_sm_get_nr_free(md->sm, &nr_free);1151 if (r) {1152 DMERR("dm_sm_get_nr_free returned %d", r);1153 return r;1154 }1155 1156 r = dm_sm_get_nr_blocks(md->sm, &nr_total);1157 if (r) {1158 DMERR("dm_pool_get_metadata_dev_size returned %d", r);1159 return r;1160 }1161 1162 s->used = nr_total - nr_free;1163 s->total = nr_total;1164 s->snap = md->metadata_snap;1165 s->era = md->current_era;1166 1167 return 0;1168}1169 1170/*----------------------------------------------------------------*/1171 1172struct era {1173 struct dm_target *ti;1174 1175 struct dm_dev *metadata_dev;1176 struct dm_dev *origin_dev;1177 1178 dm_block_t nr_blocks;1179 uint32_t sectors_per_block;1180 int sectors_per_block_shift;1181 struct era_metadata *md;1182 1183 struct workqueue_struct *wq;1184 struct work_struct worker;1185 1186 spinlock_t deferred_lock;1187 struct bio_list deferred_bios;1188 1189 spinlock_t rpc_lock;1190 struct list_head rpc_calls;1191 1192 struct digest digest;1193 atomic_t suspended;1194};1195 1196struct rpc {1197 struct list_head list;1198 1199 int (*fn0)(struct era_metadata *md);1200 int (*fn1)(struct era_metadata *md, void *ref);1201 void *arg;1202 int result;1203 1204 struct completion complete;1205};1206 1207/*1208 *---------------------------------------------------------------1209 * Remapping.1210 *---------------------------------------------------------------1211 */1212static bool block_size_is_power_of_two(struct era *era)1213{1214 return era->sectors_per_block_shift >= 0;1215}1216 1217static dm_block_t get_block(struct era *era, struct bio *bio)1218{1219 sector_t block_nr = bio->bi_iter.bi_sector;1220 1221 if (!block_size_is_power_of_two(era))1222 (void) sector_div(block_nr, era->sectors_per_block);1223 else1224 block_nr >>= era->sectors_per_block_shift;1225 1226 return block_nr;1227}1228 1229static void remap_to_origin(struct era *era, struct bio *bio)1230{1231 bio_set_dev(bio, era->origin_dev->bdev);1232}1233 1234/*1235 *--------------------------------------------------------------1236 * Worker thread1237 *--------------------------------------------------------------1238 */1239static void wake_worker(struct era *era)1240{1241 if (!atomic_read(&era->suspended))1242 queue_work(era->wq, &era->worker);1243}1244 1245static void process_old_eras(struct era *era)1246{1247 int r;1248 1249 if (!era->digest.step)1250 return;1251 1252 r = era->digest.step(era->md, &era->digest);1253 if (r < 0) {1254 DMERR("%s: digest step failed, stopping digestion", __func__);1255 era->digest.step = NULL;1256 1257 } else if (era->digest.step)1258 wake_worker(era);1259}1260 1261static void process_deferred_bios(struct era *era)1262{1263 int r;1264 struct bio_list deferred_bios, marked_bios;1265 struct bio *bio;1266 struct blk_plug plug;1267 bool commit_needed = false;1268 bool failed = false;1269 struct writeset *ws = era->md->current_writeset;1270 1271 bio_list_init(&deferred_bios);1272 bio_list_init(&marked_bios);1273 1274 spin_lock(&era->deferred_lock);1275 bio_list_merge_init(&deferred_bios, &era->deferred_bios);1276 spin_unlock(&era->deferred_lock);1277 1278 if (bio_list_empty(&deferred_bios))1279 return;1280 1281 while ((bio = bio_list_pop(&deferred_bios))) {1282 r = writeset_test_and_set(&era->md->bitset_info, ws,1283 get_block(era, bio));1284 if (r < 0) {1285 /*1286 * This is bad news, we need to rollback.1287 * FIXME: finish.1288 */1289 failed = true;1290 } else if (r == 0)1291 commit_needed = true;1292 1293 bio_list_add(&marked_bios, bio);1294 }1295 1296 if (commit_needed) {1297 r = metadata_commit(era->md);1298 if (r)1299 failed = true;1300 }1301 1302 if (failed)1303 while ((bio = bio_list_pop(&marked_bios)))1304 bio_io_error(bio);1305 else {1306 blk_start_plug(&plug);1307 while ((bio = bio_list_pop(&marked_bios))) {1308 /*1309 * Only update the in-core writeset if the on-disk one1310 * was updated too.1311 */1312 if (commit_needed)1313 set_bit(get_block(era, bio), ws->bits);1314 submit_bio_noacct(bio);1315 }1316 blk_finish_plug(&plug);1317 }1318}1319 1320static void process_rpc_calls(struct era *era)1321{1322 int r;1323 bool need_commit = false;1324 struct list_head calls;1325 struct rpc *rpc, *tmp;1326 1327 INIT_LIST_HEAD(&calls);1328 spin_lock(&era->rpc_lock);1329 list_splice_init(&era->rpc_calls, &calls);1330 spin_unlock(&era->rpc_lock);1331 1332 list_for_each_entry_safe(rpc, tmp, &calls, list) {1333 rpc->result = rpc->fn0 ? rpc->fn0(era->md) : rpc->fn1(era->md, rpc->arg);1334 need_commit = true;1335 }1336 1337 if (need_commit) {1338 r = metadata_commit(era->md);1339 if (r)1340 list_for_each_entry_safe(rpc, tmp, &calls, list)1341 rpc->result = r;1342 }1343 1344 list_for_each_entry_safe(rpc, tmp, &calls, list)1345 complete(&rpc->complete);1346}1347 1348static void kick_off_digest(struct era *era)1349{1350 if (era->md->archived_writesets) {1351 era->md->archived_writesets = false;1352 metadata_digest_start(era->md, &era->digest);1353 }1354}1355 1356static void do_work(struct work_struct *ws)1357{1358 struct era *era = container_of(ws, struct era, worker);1359 1360 kick_off_digest(era);1361 process_old_eras(era);1362 process_deferred_bios(era);1363 process_rpc_calls(era);1364}1365 1366static void defer_bio(struct era *era, struct bio *bio)1367{1368 spin_lock(&era->deferred_lock);1369 bio_list_add(&era->deferred_bios, bio);1370 spin_unlock(&era->deferred_lock);1371 1372 wake_worker(era);1373}1374 1375/*1376 * Make an rpc call to the worker to change the metadata.1377 */1378static int perform_rpc(struct era *era, struct rpc *rpc)1379{1380 rpc->result = 0;1381 init_completion(&rpc->complete);1382 1383 spin_lock(&era->rpc_lock);1384 list_add(&rpc->list, &era->rpc_calls);1385 spin_unlock(&era->rpc_lock);1386 1387 wake_worker(era);1388 wait_for_completion(&rpc->complete);1389 1390 return rpc->result;1391}1392 1393static int in_worker0(struct era *era, int (*fn)(struct era_metadata *md))1394{1395 struct rpc rpc;1396 1397 rpc.fn0 = fn;1398 rpc.fn1 = NULL;1399 1400 return perform_rpc(era, &rpc);1401}1402 1403static int in_worker1(struct era *era,1404 int (*fn)(struct era_metadata *md, void *ref), void *arg)1405{1406 struct rpc rpc;1407 1408 rpc.fn0 = NULL;1409 rpc.fn1 = fn;1410 rpc.arg = arg;1411 1412 return perform_rpc(era, &rpc);1413}1414 1415static void start_worker(struct era *era)1416{1417 atomic_set(&era->suspended, 0);1418}1419 1420static void stop_worker(struct era *era)1421{1422 atomic_set(&era->suspended, 1);1423 drain_workqueue(era->wq);1424}1425 1426/*1427 *--------------------------------------------------------------1428 * Target methods1429 *--------------------------------------------------------------1430 */1431static void era_destroy(struct era *era)1432{1433 if (era->md)1434 metadata_close(era->md);1435 1436 if (era->wq)1437 destroy_workqueue(era->wq);1438 1439 if (era->origin_dev)1440 dm_put_device(era->ti, era->origin_dev);1441 1442 if (era->metadata_dev)1443 dm_put_device(era->ti, era->metadata_dev);1444 1445 kfree(era);1446}1447 1448static dm_block_t calc_nr_blocks(struct era *era)1449{1450 return dm_sector_div_up(era->ti->len, era->sectors_per_block);1451}1452 1453static bool valid_block_size(dm_block_t block_size)1454{1455 bool greater_than_zero = block_size > 0;1456 bool multiple_of_min_block_size = (block_size & (MIN_BLOCK_SIZE - 1)) == 0;1457 1458 return greater_than_zero && multiple_of_min_block_size;1459}1460 1461/*1462 * <metadata dev> <data dev> <data block size (sectors)>1463 */1464static int era_ctr(struct dm_target *ti, unsigned int argc, char **argv)1465{1466 int r;1467 char dummy;1468 struct era *era;1469 struct era_metadata *md;1470 1471 if (argc != 3) {1472 ti->error = "Invalid argument count";1473 return -EINVAL;1474 }1475 1476 era = kzalloc(sizeof(*era), GFP_KERNEL);1477 if (!era) {1478 ti->error = "Error allocating era structure";1479 return -ENOMEM;1480 }1481 1482 era->ti = ti;1483 1484 r = dm_get_device(ti, argv[0], BLK_OPEN_READ | BLK_OPEN_WRITE,1485 &era->metadata_dev);1486 if (r) {1487 ti->error = "Error opening metadata device";1488 era_destroy(era);1489 return -EINVAL;1490 }1491 1492 r = dm_get_device(ti, argv[1], BLK_OPEN_READ | BLK_OPEN_WRITE,1493 &era->origin_dev);1494 if (r) {1495 ti->error = "Error opening data device";1496 era_destroy(era);1497 return -EINVAL;1498 }1499 1500 r = sscanf(argv[2], "%u%c", &era->sectors_per_block, &dummy);1501 if (r != 1) {1502 ti->error = "Error parsing block size";1503 era_destroy(era);1504 return -EINVAL;1505 }1506 1507 r = dm_set_target_max_io_len(ti, era->sectors_per_block);1508 if (r) {1509 ti->error = "could not set max io len";1510 era_destroy(era);1511 return -EINVAL;1512 }1513 1514 if (!valid_block_size(era->sectors_per_block)) {1515 ti->error = "Invalid block size";1516 era_destroy(era);1517 return -EINVAL;1518 }1519 if (era->sectors_per_block & (era->sectors_per_block - 1))1520 era->sectors_per_block_shift = -1;1521 else1522 era->sectors_per_block_shift = __ffs(era->sectors_per_block);1523 1524 md = metadata_open(era->metadata_dev->bdev, era->sectors_per_block, true);1525 if (IS_ERR(md)) {1526 ti->error = "Error reading metadata";1527 era_destroy(era);1528 return PTR_ERR(md);1529 }1530 era->md = md;1531 1532 era->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);1533 if (!era->wq) {1534 ti->error = "could not create workqueue for metadata object";1535 era_destroy(era);1536 return -ENOMEM;1537 }1538 INIT_WORK(&era->worker, do_work);1539 1540 spin_lock_init(&era->deferred_lock);1541 bio_list_init(&era->deferred_bios);1542 1543 spin_lock_init(&era->rpc_lock);1544 INIT_LIST_HEAD(&era->rpc_calls);1545 1546 ti->private = era;1547 ti->num_flush_bios = 1;1548 ti->flush_supported = true;1549 1550 ti->num_discard_bios = 1;1551 1552 return 0;1553}1554 1555static void era_dtr(struct dm_target *ti)1556{1557 era_destroy(ti->private);1558}1559 1560static int era_map(struct dm_target *ti, struct bio *bio)1561{1562 struct era *era = ti->private;1563 dm_block_t block = get_block(era, bio);1564 1565 /*1566 * All bios get remapped to the origin device. We do this now, but1567 * it may not get issued until later. Depending on whether the1568 * block is marked in this era.1569 */1570 remap_to_origin(era, bio);1571 1572 /*1573 * REQ_PREFLUSH bios carry no data, so we're not interested in them.1574 */1575 if (!(bio->bi_opf & REQ_PREFLUSH) &&1576 (bio_data_dir(bio) == WRITE) &&1577 !metadata_current_marked(era->md, block)) {1578 defer_bio(era, bio);1579 return DM_MAPIO_SUBMITTED;1580 }1581 1582 return DM_MAPIO_REMAPPED;1583}1584 1585static void era_postsuspend(struct dm_target *ti)1586{1587 int r;1588 struct era *era = ti->private;1589 1590 r = in_worker0(era, metadata_era_archive);1591 if (r) {1592 DMERR("%s: couldn't archive current era", __func__);1593 /* FIXME: fail mode */1594 }1595 1596 stop_worker(era);1597 1598 r = metadata_commit(era->md);1599 if (r) {1600 DMERR("%s: metadata_commit failed", __func__);1601 /* FIXME: fail mode */1602 }1603}1604 1605static int era_preresume(struct dm_target *ti)1606{1607 int r;1608 struct era *era = ti->private;1609 dm_block_t new_size = calc_nr_blocks(era);1610 1611 if (era->nr_blocks != new_size) {1612 r = metadata_resize(era->md, &new_size);1613 if (r) {1614 DMERR("%s: metadata_resize failed", __func__);1615 return r;1616 }1617 1618 r = metadata_commit(era->md);1619 if (r) {1620 DMERR("%s: metadata_commit failed", __func__);1621 return r;1622 }1623 1624 era->nr_blocks = new_size;1625 }1626 1627 start_worker(era);1628 1629 r = in_worker0(era, metadata_era_rollover);1630 if (r) {1631 DMERR("%s: metadata_era_rollover failed", __func__);1632 return r;1633 }1634 1635 return 0;1636}1637 1638/*1639 * Status format:1640 *1641 * <metadata block size> <#used metadata blocks>/<#total metadata blocks>1642 * <current era> <held metadata root | '-'>1643 */1644static void era_status(struct dm_target *ti, status_type_t type,1645 unsigned int status_flags, char *result, unsigned int maxlen)1646{1647 int r;1648 struct era *era = ti->private;1649 ssize_t sz = 0;1650 struct metadata_stats stats;1651 char buf[BDEVNAME_SIZE];1652 1653 switch (type) {1654 case STATUSTYPE_INFO:1655 r = in_worker1(era, metadata_get_stats, &stats);1656 if (r)1657 goto err;1658 1659 DMEMIT("%u %llu/%llu %u",1660 (unsigned int) (DM_ERA_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),1661 (unsigned long long) stats.used,1662 (unsigned long long) stats.total,1663 (unsigned int) stats.era);1664 1665 if (stats.snap != SUPERBLOCK_LOCATION)1666 DMEMIT(" %llu", stats.snap);1667 else1668 DMEMIT(" -");1669 break;1670 1671 case STATUSTYPE_TABLE:1672 format_dev_t(buf, era->metadata_dev->bdev->bd_dev);1673 DMEMIT("%s ", buf);1674 format_dev_t(buf, era->origin_dev->bdev->bd_dev);1675 DMEMIT("%s %u", buf, era->sectors_per_block);1676 break;1677 1678 case STATUSTYPE_IMA:1679 *result = '\0';1680 break;1681 }1682 1683 return;1684 1685err:1686 DMEMIT("Error");1687}1688 1689static int era_message(struct dm_target *ti, unsigned int argc, char **argv,1690 char *result, unsigned int maxlen)1691{1692 struct era *era = ti->private;1693 1694 if (argc != 1) {1695 DMERR("incorrect number of message arguments");1696 return -EINVAL;1697 }1698 1699 if (!strcasecmp(argv[0], "checkpoint"))1700 return in_worker0(era, metadata_checkpoint);1701 1702 if (!strcasecmp(argv[0], "take_metadata_snap"))1703 return in_worker0(era, metadata_take_snap);1704 1705 if (!strcasecmp(argv[0], "drop_metadata_snap"))1706 return in_worker0(era, metadata_drop_snap);1707 1708 DMERR("unsupported message '%s'", argv[0]);1709 return -EINVAL;1710}1711 1712static sector_t get_dev_size(struct dm_dev *dev)1713{1714 return bdev_nr_sectors(dev->bdev);1715}1716 1717static int era_iterate_devices(struct dm_target *ti,1718 iterate_devices_callout_fn fn, void *data)1719{1720 struct era *era = ti->private;1721 1722 return fn(ti, era->origin_dev, 0, get_dev_size(era->origin_dev), data);1723}1724 1725static void era_io_hints(struct dm_target *ti, struct queue_limits *limits)1726{1727 struct era *era = ti->private;1728 uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;1729 1730 /*1731 * If the system-determined stacked limits are compatible with the1732 * era device's blocksize (io_opt is a factor) do not override them.1733 */1734 if (io_opt_sectors < era->sectors_per_block ||1735 do_div(io_opt_sectors, era->sectors_per_block)) {1736 limits->io_min = 0;1737 limits->io_opt = era->sectors_per_block << SECTOR_SHIFT;1738 }1739}1740 1741/*----------------------------------------------------------------*/1742 1743static struct target_type era_target = {1744 .name = "era",1745 .version = {1, 0, 0},1746 .module = THIS_MODULE,1747 .ctr = era_ctr,1748 .dtr = era_dtr,1749 .map = era_map,1750 .postsuspend = era_postsuspend,1751 .preresume = era_preresume,1752 .status = era_status,1753 .message = era_message,1754 .iterate_devices = era_iterate_devices,1755 .io_hints = era_io_hints1756};1757module_dm(era);1758 1759MODULE_DESCRIPTION(DM_NAME " era target");1760MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");1761MODULE_LICENSE("GPL");1762