linux/drivers/md/persistent-data/dm-space-map-metadata.c
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   1/*
   2 * Copyright (C) 2011 Red Hat, Inc.
   3 *
   4 * This file is released under the GPL.
   5 */
   6
   7#include "dm-space-map.h"
   8#include "dm-space-map-common.h"
   9#include "dm-space-map-metadata.h"
  10
  11#include <linux/list.h>
  12#include <linux/slab.h>
  13#include <linux/device-mapper.h>
  14#include <linux/kernel.h>
  15
  16#define DM_MSG_PREFIX "space map metadata"
  17
  18/*----------------------------------------------------------------*/
  19
  20/*
  21 * An edge triggered threshold.
  22 */
  23struct threshold {
  24        bool threshold_set;
  25        bool value_set;
  26        dm_block_t threshold;
  27        dm_block_t current_value;
  28        dm_sm_threshold_fn fn;
  29        void *context;
  30};
  31
  32static void threshold_init(struct threshold *t)
  33{
  34        t->threshold_set = false;
  35        t->value_set = false;
  36}
  37
  38static void set_threshold(struct threshold *t, dm_block_t value,
  39                          dm_sm_threshold_fn fn, void *context)
  40{
  41        t->threshold_set = true;
  42        t->threshold = value;
  43        t->fn = fn;
  44        t->context = context;
  45}
  46
  47static bool below_threshold(struct threshold *t, dm_block_t value)
  48{
  49        return t->threshold_set && value <= t->threshold;
  50}
  51
  52static bool threshold_already_triggered(struct threshold *t)
  53{
  54        return t->value_set && below_threshold(t, t->current_value);
  55}
  56
  57static void check_threshold(struct threshold *t, dm_block_t value)
  58{
  59        if (below_threshold(t, value) &&
  60            !threshold_already_triggered(t))
  61                t->fn(t->context);
  62
  63        t->value_set = true;
  64        t->current_value = value;
  65}
  66
  67/*----------------------------------------------------------------*/
  68
  69/*
  70 * Space map interface.
  71 *
  72 * The low level disk format is written using the standard btree and
  73 * transaction manager.  This means that performing disk operations may
  74 * cause us to recurse into the space map in order to allocate new blocks.
  75 * For this reason we have a pool of pre-allocated blocks large enough to
  76 * service any metadata_ll_disk operation.
  77 */
  78
  79/*
  80 * FIXME: we should calculate this based on the size of the device.
  81 * Only the metadata space map needs this functionality.
  82 */
  83#define MAX_RECURSIVE_ALLOCATIONS 1024
  84
  85enum block_op_type {
  86        BOP_INC,
  87        BOP_DEC
  88};
  89
  90struct block_op {
  91        enum block_op_type type;
  92        dm_block_t block;
  93};
  94
  95struct bop_ring_buffer {
  96        unsigned begin;
  97        unsigned end;
  98        struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
  99};
 100
 101static void brb_init(struct bop_ring_buffer *brb)
 102{
 103        brb->begin = 0;
 104        brb->end = 0;
 105}
 106
 107static bool brb_empty(struct bop_ring_buffer *brb)
 108{
 109        return brb->begin == brb->end;
 110}
 111
 112static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
 113{
 114        unsigned r = old + 1;
 115        return r >= ARRAY_SIZE(brb->bops) ? 0 : r;
 116}
 117
 118static int brb_push(struct bop_ring_buffer *brb,
 119                    enum block_op_type type, dm_block_t b)
 120{
 121        struct block_op *bop;
 122        unsigned next = brb_next(brb, brb->end);
 123
 124        /*
 125         * We don't allow the last bop to be filled, this way we can
 126         * differentiate between full and empty.
 127         */
 128        if (next == brb->begin)
 129                return -ENOMEM;
 130
 131        bop = brb->bops + brb->end;
 132        bop->type = type;
 133        bop->block = b;
 134
 135        brb->end = next;
 136
 137        return 0;
 138}
 139
 140static int brb_peek(struct bop_ring_buffer *brb, struct block_op *result)
 141{
 142        struct block_op *bop;
 143
 144        if (brb_empty(brb))
 145                return -ENODATA;
 146
 147        bop = brb->bops + brb->begin;
 148        result->type = bop->type;
 149        result->block = bop->block;
 150
 151        return 0;
 152}
 153
 154static int brb_pop(struct bop_ring_buffer *brb)
 155{
 156        if (brb_empty(brb))
 157                return -ENODATA;
 158
 159        brb->begin = brb_next(brb, brb->begin);
 160
 161        return 0;
 162}
 163
 164/*----------------------------------------------------------------*/
 165
 166struct sm_metadata {
 167        struct dm_space_map sm;
 168
 169        struct ll_disk ll;
 170        struct ll_disk old_ll;
 171
 172        dm_block_t begin;
 173
 174        unsigned recursion_count;
 175        unsigned allocated_this_transaction;
 176        struct bop_ring_buffer uncommitted;
 177
 178        struct threshold threshold;
 179};
 180
 181static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
 182{
 183        int r = brb_push(&smm->uncommitted, type, b);
 184
 185        if (r) {
 186                DMERR("too many recursive allocations");
 187                return -ENOMEM;
 188        }
 189
 190        return 0;
 191}
 192
 193static int commit_bop(struct sm_metadata *smm, struct block_op *op)
 194{
 195        int r = 0;
 196        enum allocation_event ev;
 197
 198        switch (op->type) {
 199        case BOP_INC:
 200                r = sm_ll_inc(&smm->ll, op->block, &ev);
 201                break;
 202
 203        case BOP_DEC:
 204                r = sm_ll_dec(&smm->ll, op->block, &ev);
 205                break;
 206        }
 207
 208        return r;
 209}
 210
 211static void in(struct sm_metadata *smm)
 212{
 213        smm->recursion_count++;
 214}
 215
 216static int apply_bops(struct sm_metadata *smm)
 217{
 218        int r = 0;
 219
 220        while (!brb_empty(&smm->uncommitted)) {
 221                struct block_op bop;
 222
 223                r = brb_peek(&smm->uncommitted, &bop);
 224                if (r) {
 225                        DMERR("bug in bop ring buffer");
 226                        break;
 227                }
 228
 229                r = commit_bop(smm, &bop);
 230                if (r)
 231                        break;
 232
 233                brb_pop(&smm->uncommitted);
 234        }
 235
 236        return r;
 237}
 238
 239static int out(struct sm_metadata *smm)
 240{
 241        int r = 0;
 242
 243        /*
 244         * If we're not recursing then very bad things are happening.
 245         */
 246        if (!smm->recursion_count) {
 247                DMERR("lost track of recursion depth");
 248                return -ENOMEM;
 249        }
 250
 251        if (smm->recursion_count == 1)
 252                apply_bops(smm);
 253
 254        smm->recursion_count--;
 255
 256        return r;
 257}
 258
 259/*
 260 * When using the out() function above, we often want to combine an error
 261 * code for the operation run in the recursive context with that from
 262 * out().
 263 */
 264static int combine_errors(int r1, int r2)
 265{
 266        return r1 ? r1 : r2;
 267}
 268
 269static int recursing(struct sm_metadata *smm)
 270{
 271        return smm->recursion_count;
 272}
 273
 274static void sm_metadata_destroy(struct dm_space_map *sm)
 275{
 276        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 277
 278        kfree(smm);
 279}
 280
 281static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
 282{
 283        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 284
 285        *count = smm->ll.nr_blocks;
 286
 287        return 0;
 288}
 289
 290static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
 291{
 292        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 293
 294        *count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
 295                 smm->allocated_this_transaction;
 296
 297        return 0;
 298}
 299
 300static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
 301                                 uint32_t *result)
 302{
 303        int r;
 304        unsigned i;
 305        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 306        unsigned adjustment = 0;
 307
 308        /*
 309         * We may have some uncommitted adjustments to add.  This list
 310         * should always be really short.
 311         */
 312        for (i = smm->uncommitted.begin;
 313             i != smm->uncommitted.end;
 314             i = brb_next(&smm->uncommitted, i)) {
 315                struct block_op *op = smm->uncommitted.bops + i;
 316
 317                if (op->block != b)
 318                        continue;
 319
 320                switch (op->type) {
 321                case BOP_INC:
 322                        adjustment++;
 323                        break;
 324
 325                case BOP_DEC:
 326                        adjustment--;
 327                        break;
 328                }
 329        }
 330
 331        r = sm_ll_lookup(&smm->ll, b, result);
 332        if (r)
 333                return r;
 334
 335        *result += adjustment;
 336
 337        return 0;
 338}
 339
 340static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
 341                                              dm_block_t b, int *result)
 342{
 343        int r, adjustment = 0;
 344        unsigned i;
 345        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 346        uint32_t rc;
 347
 348        /*
 349         * We may have some uncommitted adjustments to add.  This list
 350         * should always be really short.
 351         */
 352        for (i = smm->uncommitted.begin;
 353             i != smm->uncommitted.end;
 354             i = brb_next(&smm->uncommitted, i)) {
 355
 356                struct block_op *op = smm->uncommitted.bops + i;
 357
 358                if (op->block != b)
 359                        continue;
 360
 361                switch (op->type) {
 362                case BOP_INC:
 363                        adjustment++;
 364                        break;
 365
 366                case BOP_DEC:
 367                        adjustment--;
 368                        break;
 369                }
 370        }
 371
 372        if (adjustment > 1) {
 373                *result = 1;
 374                return 0;
 375        }
 376
 377        r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
 378        if (r)
 379                return r;
 380
 381        if (rc == 3)
 382                /*
 383                 * We err on the side of caution, and always return true.
 384                 */
 385                *result = 1;
 386        else
 387                *result = rc + adjustment > 1;
 388
 389        return 0;
 390}
 391
 392static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
 393                                 uint32_t count)
 394{
 395        int r, r2;
 396        enum allocation_event ev;
 397        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 398
 399        if (smm->recursion_count) {
 400                DMERR("cannot recurse set_count()");
 401                return -EINVAL;
 402        }
 403
 404        in(smm);
 405        r = sm_ll_insert(&smm->ll, b, count, &ev);
 406        r2 = out(smm);
 407
 408        return combine_errors(r, r2);
 409}
 410
 411static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
 412{
 413        int r, r2 = 0;
 414        enum allocation_event ev;
 415        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 416
 417        if (recursing(smm))
 418                r = add_bop(smm, BOP_INC, b);
 419        else {
 420                in(smm);
 421                r = sm_ll_inc(&smm->ll, b, &ev);
 422                r2 = out(smm);
 423        }
 424
 425        return combine_errors(r, r2);
 426}
 427
 428static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
 429{
 430        int r, r2 = 0;
 431        enum allocation_event ev;
 432        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 433
 434        if (recursing(smm))
 435                r = add_bop(smm, BOP_DEC, b);
 436        else {
 437                in(smm);
 438                r = sm_ll_dec(&smm->ll, b, &ev);
 439                r2 = out(smm);
 440        }
 441
 442        return combine_errors(r, r2);
 443}
 444
 445static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
 446{
 447        int r, r2 = 0;
 448        enum allocation_event ev;
 449        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 450
 451        r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
 452        if (r)
 453                return r;
 454
 455        smm->begin = *b + 1;
 456
 457        if (recursing(smm))
 458                r = add_bop(smm, BOP_INC, *b);
 459        else {
 460                in(smm);
 461                r = sm_ll_inc(&smm->ll, *b, &ev);
 462                r2 = out(smm);
 463        }
 464
 465        if (!r)
 466                smm->allocated_this_transaction++;
 467
 468        return combine_errors(r, r2);
 469}
 470
 471static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
 472{
 473        dm_block_t count;
 474        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 475
 476        int r = sm_metadata_new_block_(sm, b);
 477        if (r) {
 478                DMERR_LIMIT("unable to allocate new metadata block");
 479                return r;
 480        }
 481
 482        r = sm_metadata_get_nr_free(sm, &count);
 483        if (r) {
 484                DMERR_LIMIT("couldn't get free block count");
 485                return r;
 486        }
 487
 488        check_threshold(&smm->threshold, count);
 489
 490        return r;
 491}
 492
 493static int sm_metadata_commit(struct dm_space_map *sm)
 494{
 495        int r;
 496        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 497
 498        r = sm_ll_commit(&smm->ll);
 499        if (r)
 500                return r;
 501
 502        memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
 503        smm->begin = 0;
 504        smm->allocated_this_transaction = 0;
 505
 506        return 0;
 507}
 508
 509static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
 510                                                   dm_block_t threshold,
 511                                                   dm_sm_threshold_fn fn,
 512                                                   void *context)
 513{
 514        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 515
 516        set_threshold(&smm->threshold, threshold, fn, context);
 517
 518        return 0;
 519}
 520
 521static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
 522{
 523        *result = sizeof(struct disk_sm_root);
 524
 525        return 0;
 526}
 527
 528static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
 529{
 530        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 531        struct disk_sm_root root_le;
 532
 533        root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
 534        root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
 535        root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
 536        root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);
 537
 538        if (max < sizeof(root_le))
 539                return -ENOSPC;
 540
 541        memcpy(where_le, &root_le, sizeof(root_le));
 542
 543        return 0;
 544}
 545
 546static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);
 547
 548static const struct dm_space_map ops = {
 549        .destroy = sm_metadata_destroy,
 550        .extend = sm_metadata_extend,
 551        .get_nr_blocks = sm_metadata_get_nr_blocks,
 552        .get_nr_free = sm_metadata_get_nr_free,
 553        .get_count = sm_metadata_get_count,
 554        .count_is_more_than_one = sm_metadata_count_is_more_than_one,
 555        .set_count = sm_metadata_set_count,
 556        .inc_block = sm_metadata_inc_block,
 557        .dec_block = sm_metadata_dec_block,
 558        .new_block = sm_metadata_new_block,
 559        .commit = sm_metadata_commit,
 560        .root_size = sm_metadata_root_size,
 561        .copy_root = sm_metadata_copy_root,
 562        .register_threshold_callback = sm_metadata_register_threshold_callback
 563};
 564
 565/*----------------------------------------------------------------*/
 566
 567/*
 568 * When a new space map is created that manages its own space.  We use
 569 * this tiny bootstrap allocator.
 570 */
 571static void sm_bootstrap_destroy(struct dm_space_map *sm)
 572{
 573}
 574
 575static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 576{
 577        DMERR("bootstrap doesn't support extend");
 578
 579        return -EINVAL;
 580}
 581
 582static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
 583{
 584        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 585
 586        *count = smm->ll.nr_blocks;
 587
 588        return 0;
 589}
 590
 591static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
 592{
 593        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 594
 595        *count = smm->ll.nr_blocks - smm->begin;
 596
 597        return 0;
 598}
 599
 600static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
 601                                  uint32_t *result)
 602{
 603        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 604
 605        *result = (b < smm->begin) ? 1 : 0;
 606
 607        return 0;
 608}
 609
 610static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
 611                                               dm_block_t b, int *result)
 612{
 613        *result = 0;
 614
 615        return 0;
 616}
 617
 618static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
 619                                  uint32_t count)
 620{
 621        DMERR("bootstrap doesn't support set_count");
 622
 623        return -EINVAL;
 624}
 625
 626static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
 627{
 628        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 629
 630        /*
 631         * We know the entire device is unused.
 632         */
 633        if (smm->begin == smm->ll.nr_blocks)
 634                return -ENOSPC;
 635
 636        *b = smm->begin++;
 637
 638        return 0;
 639}
 640
 641static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
 642{
 643        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 644
 645        return add_bop(smm, BOP_INC, b);
 646}
 647
 648static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
 649{
 650        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 651
 652        return add_bop(smm, BOP_DEC, b);
 653}
 654
 655static int sm_bootstrap_commit(struct dm_space_map *sm)
 656{
 657        return 0;
 658}
 659
 660static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
 661{
 662        DMERR("bootstrap doesn't support root_size");
 663
 664        return -EINVAL;
 665}
 666
 667static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
 668                                  size_t max)
 669{
 670        DMERR("bootstrap doesn't support copy_root");
 671
 672        return -EINVAL;
 673}
 674
 675static const struct dm_space_map bootstrap_ops = {
 676        .destroy = sm_bootstrap_destroy,
 677        .extend = sm_bootstrap_extend,
 678        .get_nr_blocks = sm_bootstrap_get_nr_blocks,
 679        .get_nr_free = sm_bootstrap_get_nr_free,
 680        .get_count = sm_bootstrap_get_count,
 681        .count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
 682        .set_count = sm_bootstrap_set_count,
 683        .inc_block = sm_bootstrap_inc_block,
 684        .dec_block = sm_bootstrap_dec_block,
 685        .new_block = sm_bootstrap_new_block,
 686        .commit = sm_bootstrap_commit,
 687        .root_size = sm_bootstrap_root_size,
 688        .copy_root = sm_bootstrap_copy_root,
 689        .register_threshold_callback = NULL
 690};
 691
 692/*----------------------------------------------------------------*/
 693
 694static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 695{
 696        int r, i;
 697        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 698        dm_block_t old_len = smm->ll.nr_blocks;
 699
 700        /*
 701         * Flick into a mode where all blocks get allocated in the new area.
 702         */
 703        smm->begin = old_len;
 704        memcpy(sm, &bootstrap_ops, sizeof(*sm));
 705
 706        /*
 707         * Extend.
 708         */
 709        r = sm_ll_extend(&smm->ll, extra_blocks);
 710        if (r)
 711                goto out;
 712
 713        /*
 714         * We repeatedly increment then commit until the commit doesn't
 715         * allocate any new blocks.
 716         */
 717        do {
 718                for (i = old_len; !r && i < smm->begin; i++)
 719                        r = add_bop(smm, BOP_INC, i);
 720
 721                if (r)
 722                        goto out;
 723
 724                old_len = smm->begin;
 725
 726                r = apply_bops(smm);
 727                if (r) {
 728                        DMERR("%s: apply_bops failed", __func__);
 729                        goto out;
 730                }
 731
 732                r = sm_ll_commit(&smm->ll);
 733                if (r)
 734                        goto out;
 735
 736        } while (old_len != smm->begin);
 737
 738out:
 739        /*
 740         * Switch back to normal behaviour.
 741         */
 742        memcpy(sm, &ops, sizeof(*sm));
 743        return r;
 744}
 745
 746/*----------------------------------------------------------------*/
 747
 748struct dm_space_map *dm_sm_metadata_init(void)
 749{
 750        struct sm_metadata *smm;
 751
 752        smm = kmalloc(sizeof(*smm), GFP_KERNEL);
 753        if (!smm)
 754                return ERR_PTR(-ENOMEM);
 755
 756        memcpy(&smm->sm, &ops, sizeof(smm->sm));
 757
 758        return &smm->sm;
 759}
 760
 761int dm_sm_metadata_create(struct dm_space_map *sm,
 762                          struct dm_transaction_manager *tm,
 763                          dm_block_t nr_blocks,
 764                          dm_block_t superblock)
 765{
 766        int r;
 767        dm_block_t i;
 768        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 769
 770        smm->begin = superblock + 1;
 771        smm->recursion_count = 0;
 772        smm->allocated_this_transaction = 0;
 773        brb_init(&smm->uncommitted);
 774        threshold_init(&smm->threshold);
 775
 776        memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
 777
 778        r = sm_ll_new_metadata(&smm->ll, tm);
 779        if (!r) {
 780                if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
 781                        nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
 782                r = sm_ll_extend(&smm->ll, nr_blocks);
 783        }
 784        memcpy(&smm->sm, &ops, sizeof(smm->sm));
 785        if (r)
 786                return r;
 787
 788        /*
 789         * Now we need to update the newly created data structures with the
 790         * allocated blocks that they were built from.
 791         */
 792        for (i = superblock; !r && i < smm->begin; i++)
 793                r = add_bop(smm, BOP_INC, i);
 794
 795        if (r)
 796                return r;
 797
 798        r = apply_bops(smm);
 799        if (r) {
 800                DMERR("%s: apply_bops failed", __func__);
 801                return r;
 802        }
 803
 804        return sm_metadata_commit(sm);
 805}
 806
 807int dm_sm_metadata_open(struct dm_space_map *sm,
 808                        struct dm_transaction_manager *tm,
 809                        void *root_le, size_t len)
 810{
 811        int r;
 812        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
 813
 814        r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
 815        if (r)
 816                return r;
 817
 818        smm->begin = 0;
 819        smm->recursion_count = 0;
 820        smm->allocated_this_transaction = 0;
 821        brb_init(&smm->uncommitted);
 822        threshold_init(&smm->threshold);
 823
 824        memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
 825        return 0;
 826}
 827