linux/drivers/md/dm-region-hash.c
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   1/*
   2 * Copyright (C) 2003 Sistina Software Limited.
   3 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
   4 *
   5 * This file is released under the GPL.
   6 */
   7
   8#include <linux/dm-dirty-log.h>
   9#include <linux/dm-region-hash.h>
  10
  11#include <linux/ctype.h>
  12#include <linux/init.h>
  13#include <linux/module.h>
  14#include <linux/slab.h>
  15#include <linux/vmalloc.h>
  16
  17#include "dm.h"
  18
  19#define DM_MSG_PREFIX   "region hash"
  20
  21/*-----------------------------------------------------------------
  22 * Region hash
  23 *
  24 * The mirror splits itself up into discrete regions.  Each
  25 * region can be in one of three states: clean, dirty,
  26 * nosync.  There is no need to put clean regions in the hash.
  27 *
  28 * In addition to being present in the hash table a region _may_
  29 * be present on one of three lists.
  30 *
  31 *   clean_regions: Regions on this list have no io pending to
  32 *   them, they are in sync, we are no longer interested in them,
  33 *   they are dull.  dm_rh_update_states() will remove them from the
  34 *   hash table.
  35 *
  36 *   quiesced_regions: These regions have been spun down, ready
  37 *   for recovery.  rh_recovery_start() will remove regions from
  38 *   this list and hand them to kmirrord, which will schedule the
  39 *   recovery io with kcopyd.
  40 *
  41 *   recovered_regions: Regions that kcopyd has successfully
  42 *   recovered.  dm_rh_update_states() will now schedule any delayed
  43 *   io, up the recovery_count, and remove the region from the
  44 *   hash.
  45 *
  46 * There are 2 locks:
  47 *   A rw spin lock 'hash_lock' protects just the hash table,
  48 *   this is never held in write mode from interrupt context,
  49 *   which I believe means that we only have to disable irqs when
  50 *   doing a write lock.
  51 *
  52 *   An ordinary spin lock 'region_lock' that protects the three
  53 *   lists in the region_hash, with the 'state', 'list' and
  54 *   'delayed_bios' fields of the regions.  This is used from irq
  55 *   context, so all other uses will have to suspend local irqs.
  56 *---------------------------------------------------------------*/
  57struct dm_region_hash {
  58        uint32_t region_size;
  59        unsigned region_shift;
  60
  61        /* holds persistent region state */
  62        struct dm_dirty_log *log;
  63
  64        /* hash table */
  65        rwlock_t hash_lock;
  66        mempool_t *region_pool;
  67        unsigned mask;
  68        unsigned nr_buckets;
  69        unsigned prime;
  70        unsigned shift;
  71        struct list_head *buckets;
  72
  73        unsigned max_recovery; /* Max # of regions to recover in parallel */
  74
  75        spinlock_t region_lock;
  76        atomic_t recovery_in_flight;
  77        struct semaphore recovery_count;
  78        struct list_head clean_regions;
  79        struct list_head quiesced_regions;
  80        struct list_head recovered_regions;
  81        struct list_head failed_recovered_regions;
  82
  83        /*
  84         * If there was a flush failure no regions can be marked clean.
  85         */
  86        int flush_failure;
  87
  88        void *context;
  89        sector_t target_begin;
  90
  91        /* Callback function to schedule bios writes */
  92        void (*dispatch_bios)(void *context, struct bio_list *bios);
  93
  94        /* Callback function to wakeup callers worker thread. */
  95        void (*wakeup_workers)(void *context);
  96
  97        /* Callback function to wakeup callers recovery waiters. */
  98        void (*wakeup_all_recovery_waiters)(void *context);
  99};
 100
 101struct dm_region {
 102        struct dm_region_hash *rh;      /* FIXME: can we get rid of this ? */
 103        region_t key;
 104        int state;
 105
 106        struct list_head hash_list;
 107        struct list_head list;
 108
 109        atomic_t pending;
 110        struct bio_list delayed_bios;
 111};
 112
 113/*
 114 * Conversion fns
 115 */
 116static region_t dm_rh_sector_to_region(struct dm_region_hash *rh, sector_t sector)
 117{
 118        return sector >> rh->region_shift;
 119}
 120
 121sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region)
 122{
 123        return region << rh->region_shift;
 124}
 125EXPORT_SYMBOL_GPL(dm_rh_region_to_sector);
 126
 127region_t dm_rh_bio_to_region(struct dm_region_hash *rh, struct bio *bio)
 128{
 129        return dm_rh_sector_to_region(rh, bio->bi_sector - rh->target_begin);
 130}
 131EXPORT_SYMBOL_GPL(dm_rh_bio_to_region);
 132
 133void *dm_rh_region_context(struct dm_region *reg)
 134{
 135        return reg->rh->context;
 136}
 137EXPORT_SYMBOL_GPL(dm_rh_region_context);
 138
 139region_t dm_rh_get_region_key(struct dm_region *reg)
 140{
 141        return reg->key;
 142}
 143EXPORT_SYMBOL_GPL(dm_rh_get_region_key);
 144
 145sector_t dm_rh_get_region_size(struct dm_region_hash *rh)
 146{
 147        return rh->region_size;
 148}
 149EXPORT_SYMBOL_GPL(dm_rh_get_region_size);
 150
 151/*
 152 * FIXME: shall we pass in a structure instead of all these args to
 153 * dm_region_hash_create()????
 154 */
 155#define RH_HASH_MULT 2654435387U
 156#define RH_HASH_SHIFT 12
 157
 158#define MIN_REGIONS 64
 159struct dm_region_hash *dm_region_hash_create(
 160                void *context, void (*dispatch_bios)(void *context,
 161                                                     struct bio_list *bios),
 162                void (*wakeup_workers)(void *context),
 163                void (*wakeup_all_recovery_waiters)(void *context),
 164                sector_t target_begin, unsigned max_recovery,
 165                struct dm_dirty_log *log, uint32_t region_size,
 166                region_t nr_regions)
 167{
 168        struct dm_region_hash *rh;
 169        unsigned nr_buckets, max_buckets;
 170        size_t i;
 171
 172        /*
 173         * Calculate a suitable number of buckets for our hash
 174         * table.
 175         */
 176        max_buckets = nr_regions >> 6;
 177        for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1)
 178                ;
 179        nr_buckets >>= 1;
 180
 181        rh = kmalloc(sizeof(*rh), GFP_KERNEL);
 182        if (!rh) {
 183                DMERR("unable to allocate region hash memory");
 184                return ERR_PTR(-ENOMEM);
 185        }
 186
 187        rh->context = context;
 188        rh->dispatch_bios = dispatch_bios;
 189        rh->wakeup_workers = wakeup_workers;
 190        rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters;
 191        rh->target_begin = target_begin;
 192        rh->max_recovery = max_recovery;
 193        rh->log = log;
 194        rh->region_size = region_size;
 195        rh->region_shift = ffs(region_size) - 1;
 196        rwlock_init(&rh->hash_lock);
 197        rh->mask = nr_buckets - 1;
 198        rh->nr_buckets = nr_buckets;
 199
 200        rh->shift = RH_HASH_SHIFT;
 201        rh->prime = RH_HASH_MULT;
 202
 203        rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets));
 204        if (!rh->buckets) {
 205                DMERR("unable to allocate region hash bucket memory");
 206                kfree(rh);
 207                return ERR_PTR(-ENOMEM);
 208        }
 209
 210        for (i = 0; i < nr_buckets; i++)
 211                INIT_LIST_HEAD(rh->buckets + i);
 212
 213        spin_lock_init(&rh->region_lock);
 214        sema_init(&rh->recovery_count, 0);
 215        atomic_set(&rh->recovery_in_flight, 0);
 216        INIT_LIST_HEAD(&rh->clean_regions);
 217        INIT_LIST_HEAD(&rh->quiesced_regions);
 218        INIT_LIST_HEAD(&rh->recovered_regions);
 219        INIT_LIST_HEAD(&rh->failed_recovered_regions);
 220        rh->flush_failure = 0;
 221
 222        rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
 223                                                      sizeof(struct dm_region));
 224        if (!rh->region_pool) {
 225                vfree(rh->buckets);
 226                kfree(rh);
 227                rh = ERR_PTR(-ENOMEM);
 228        }
 229
 230        return rh;
 231}
 232EXPORT_SYMBOL_GPL(dm_region_hash_create);
 233
 234void dm_region_hash_destroy(struct dm_region_hash *rh)
 235{
 236        unsigned h;
 237        struct dm_region *reg, *nreg;
 238
 239        BUG_ON(!list_empty(&rh->quiesced_regions));
 240        for (h = 0; h < rh->nr_buckets; h++) {
 241                list_for_each_entry_safe(reg, nreg, rh->buckets + h,
 242                                         hash_list) {
 243                        BUG_ON(atomic_read(&reg->pending));
 244                        mempool_free(reg, rh->region_pool);
 245                }
 246        }
 247
 248        if (rh->log)
 249                dm_dirty_log_destroy(rh->log);
 250
 251        if (rh->region_pool)
 252                mempool_destroy(rh->region_pool);
 253
 254        vfree(rh->buckets);
 255        kfree(rh);
 256}
 257EXPORT_SYMBOL_GPL(dm_region_hash_destroy);
 258
 259struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh)
 260{
 261        return rh->log;
 262}
 263EXPORT_SYMBOL_GPL(dm_rh_dirty_log);
 264
 265static unsigned rh_hash(struct dm_region_hash *rh, region_t region)
 266{
 267        return (unsigned) ((region * rh->prime) >> rh->shift) & rh->mask;
 268}
 269
 270static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region)
 271{
 272        struct dm_region *reg;
 273        struct list_head *bucket = rh->buckets + rh_hash(rh, region);
 274
 275        list_for_each_entry(reg, bucket, hash_list)
 276                if (reg->key == region)
 277                        return reg;
 278
 279        return NULL;
 280}
 281
 282static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg)
 283{
 284        list_add(&reg->hash_list, rh->buckets + rh_hash(rh, reg->key));
 285}
 286
 287static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
 288{
 289        struct dm_region *reg, *nreg;
 290
 291        nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC);
 292        if (unlikely(!nreg))
 293                nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
 294
 295        nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
 296                      DM_RH_CLEAN : DM_RH_NOSYNC;
 297        nreg->rh = rh;
 298        nreg->key = region;
 299        INIT_LIST_HEAD(&nreg->list);
 300        atomic_set(&nreg->pending, 0);
 301        bio_list_init(&nreg->delayed_bios);
 302
 303        write_lock_irq(&rh->hash_lock);
 304        reg = __rh_lookup(rh, region);
 305        if (reg)
 306                /* We lost the race. */
 307                mempool_free(nreg, rh->region_pool);
 308        else {
 309                __rh_insert(rh, nreg);
 310                if (nreg->state == DM_RH_CLEAN) {
 311                        spin_lock(&rh->region_lock);
 312                        list_add(&nreg->list, &rh->clean_regions);
 313                        spin_unlock(&rh->region_lock);
 314                }
 315
 316                reg = nreg;
 317        }
 318        write_unlock_irq(&rh->hash_lock);
 319
 320        return reg;
 321}
 322
 323static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region)
 324{
 325        struct dm_region *reg;
 326
 327        reg = __rh_lookup(rh, region);
 328        if (!reg) {
 329                read_unlock(&rh->hash_lock);
 330                reg = __rh_alloc(rh, region);
 331                read_lock(&rh->hash_lock);
 332        }
 333
 334        return reg;
 335}
 336
 337int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block)
 338{
 339        int r;
 340        struct dm_region *reg;
 341
 342        read_lock(&rh->hash_lock);
 343        reg = __rh_lookup(rh, region);
 344        read_unlock(&rh->hash_lock);
 345
 346        if (reg)
 347                return reg->state;
 348
 349        /*
 350         * The region wasn't in the hash, so we fall back to the
 351         * dirty log.
 352         */
 353        r = rh->log->type->in_sync(rh->log, region, may_block);
 354
 355        /*
 356         * Any error from the dirty log (eg. -EWOULDBLOCK) gets
 357         * taken as a DM_RH_NOSYNC
 358         */
 359        return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC;
 360}
 361EXPORT_SYMBOL_GPL(dm_rh_get_state);
 362
 363static void complete_resync_work(struct dm_region *reg, int success)
 364{
 365        struct dm_region_hash *rh = reg->rh;
 366
 367        rh->log->type->set_region_sync(rh->log, reg->key, success);
 368
 369        /*
 370         * Dispatch the bios before we call 'wake_up_all'.
 371         * This is important because if we are suspending,
 372         * we want to know that recovery is complete and
 373         * the work queue is flushed.  If we wake_up_all
 374         * before we dispatch_bios (queue bios and call wake()),
 375         * then we risk suspending before the work queue
 376         * has been properly flushed.
 377         */
 378        rh->dispatch_bios(rh->context, &reg->delayed_bios);
 379        if (atomic_dec_and_test(&rh->recovery_in_flight))
 380                rh->wakeup_all_recovery_waiters(rh->context);
 381        up(&rh->recovery_count);
 382}
 383
 384/* dm_rh_mark_nosync
 385 * @ms
 386 * @bio
 387 *
 388 * The bio was written on some mirror(s) but failed on other mirror(s).
 389 * We can successfully endio the bio but should avoid the region being
 390 * marked clean by setting the state DM_RH_NOSYNC.
 391 *
 392 * This function is _not_ safe in interrupt context!
 393 */
 394void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio)
 395{
 396        unsigned long flags;
 397        struct dm_dirty_log *log = rh->log;
 398        struct dm_region *reg;
 399        region_t region = dm_rh_bio_to_region(rh, bio);
 400        int recovering = 0;
 401
 402        if (bio->bi_rw & REQ_FLUSH) {
 403                rh->flush_failure = 1;
 404                return;
 405        }
 406
 407        if (bio->bi_rw & REQ_DISCARD)
 408                return;
 409
 410        /* We must inform the log that the sync count has changed. */
 411        log->type->set_region_sync(log, region, 0);
 412
 413        read_lock(&rh->hash_lock);
 414        reg = __rh_find(rh, region);
 415        read_unlock(&rh->hash_lock);
 416
 417        /* region hash entry should exist because write was in-flight */
 418        BUG_ON(!reg);
 419        BUG_ON(!list_empty(&reg->list));
 420
 421        spin_lock_irqsave(&rh->region_lock, flags);
 422        /*
 423         * Possible cases:
 424         *   1) DM_RH_DIRTY
 425         *   2) DM_RH_NOSYNC: was dirty, other preceding writes failed
 426         *   3) DM_RH_RECOVERING: flushing pending writes
 427         * Either case, the region should have not been connected to list.
 428         */
 429        recovering = (reg->state == DM_RH_RECOVERING);
 430        reg->state = DM_RH_NOSYNC;
 431        BUG_ON(!list_empty(&reg->list));
 432        spin_unlock_irqrestore(&rh->region_lock, flags);
 433
 434        if (recovering)
 435                complete_resync_work(reg, 0);
 436}
 437EXPORT_SYMBOL_GPL(dm_rh_mark_nosync);
 438
 439void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled)
 440{
 441        struct dm_region *reg, *next;
 442
 443        LIST_HEAD(clean);
 444        LIST_HEAD(recovered);
 445        LIST_HEAD(failed_recovered);
 446
 447        /*
 448         * Quickly grab the lists.
 449         */
 450        write_lock_irq(&rh->hash_lock);
 451        spin_lock(&rh->region_lock);
 452        if (!list_empty(&rh->clean_regions)) {
 453                list_splice_init(&rh->clean_regions, &clean);
 454
 455                list_for_each_entry(reg, &clean, list)
 456                        list_del(&reg->hash_list);
 457        }
 458
 459        if (!list_empty(&rh->recovered_regions)) {
 460                list_splice_init(&rh->recovered_regions, &recovered);
 461
 462                list_for_each_entry(reg, &recovered, list)
 463                        list_del(&reg->hash_list);
 464        }
 465
 466        if (!list_empty(&rh->failed_recovered_regions)) {
 467                list_splice_init(&rh->failed_recovered_regions,
 468                                 &failed_recovered);
 469
 470                list_for_each_entry(reg, &failed_recovered, list)
 471                        list_del(&reg->hash_list);
 472        }
 473
 474        spin_unlock(&rh->region_lock);
 475        write_unlock_irq(&rh->hash_lock);
 476
 477        /*
 478         * All the regions on the recovered and clean lists have
 479         * now been pulled out of the system, so no need to do
 480         * any more locking.
 481         */
 482        list_for_each_entry_safe(reg, next, &recovered, list) {
 483                rh->log->type->clear_region(rh->log, reg->key);
 484                complete_resync_work(reg, 1);
 485                mempool_free(reg, rh->region_pool);
 486        }
 487
 488        list_for_each_entry_safe(reg, next, &failed_recovered, list) {
 489                complete_resync_work(reg, errors_handled ? 0 : 1);
 490                mempool_free(reg, rh->region_pool);
 491        }
 492
 493        list_for_each_entry_safe(reg, next, &clean, list) {
 494                rh->log->type->clear_region(rh->log, reg->key);
 495                mempool_free(reg, rh->region_pool);
 496        }
 497
 498        rh->log->type->flush(rh->log);
 499}
 500EXPORT_SYMBOL_GPL(dm_rh_update_states);
 501
 502static void rh_inc(struct dm_region_hash *rh, region_t region)
 503{
 504        struct dm_region *reg;
 505
 506        read_lock(&rh->hash_lock);
 507        reg = __rh_find(rh, region);
 508
 509        spin_lock_irq(&rh->region_lock);
 510        atomic_inc(&reg->pending);
 511
 512        if (reg->state == DM_RH_CLEAN) {
 513                reg->state = DM_RH_DIRTY;
 514                list_del_init(&reg->list);      /* take off the clean list */
 515                spin_unlock_irq(&rh->region_lock);
 516
 517                rh->log->type->mark_region(rh->log, reg->key);
 518        } else
 519                spin_unlock_irq(&rh->region_lock);
 520
 521
 522        read_unlock(&rh->hash_lock);
 523}
 524
 525void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios)
 526{
 527        struct bio *bio;
 528
 529        for (bio = bios->head; bio; bio = bio->bi_next) {
 530                if (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD))
 531                        continue;
 532                rh_inc(rh, dm_rh_bio_to_region(rh, bio));
 533        }
 534}
 535EXPORT_SYMBOL_GPL(dm_rh_inc_pending);
 536
 537void dm_rh_dec(struct dm_region_hash *rh, region_t region)
 538{
 539        unsigned long flags;
 540        struct dm_region *reg;
 541        int should_wake = 0;
 542
 543        read_lock(&rh->hash_lock);
 544        reg = __rh_lookup(rh, region);
 545        read_unlock(&rh->hash_lock);
 546
 547        spin_lock_irqsave(&rh->region_lock, flags);
 548        if (atomic_dec_and_test(&reg->pending)) {
 549                /*
 550                 * There is no pending I/O for this region.
 551                 * We can move the region to corresponding list for next action.
 552                 * At this point, the region is not yet connected to any list.
 553                 *
 554                 * If the state is DM_RH_NOSYNC, the region should be kept off
 555                 * from clean list.
 556                 * The hash entry for DM_RH_NOSYNC will remain in memory
 557                 * until the region is recovered or the map is reloaded.
 558                 */
 559
 560                /* do nothing for DM_RH_NOSYNC */
 561                if (unlikely(rh->flush_failure)) {
 562                        /*
 563                         * If a write flush failed some time ago, we
 564                         * don't know whether or not this write made it
 565                         * to the disk, so we must resync the device.
 566                         */
 567                        reg->state = DM_RH_NOSYNC;
 568                } else if (reg->state == DM_RH_RECOVERING) {
 569                        list_add_tail(&reg->list, &rh->quiesced_regions);
 570                } else if (reg->state == DM_RH_DIRTY) {
 571                        reg->state = DM_RH_CLEAN;
 572                        list_add(&reg->list, &rh->clean_regions);
 573                }
 574                should_wake = 1;
 575        }
 576        spin_unlock_irqrestore(&rh->region_lock, flags);
 577
 578        if (should_wake)
 579                rh->wakeup_workers(rh->context);
 580}
 581EXPORT_SYMBOL_GPL(dm_rh_dec);
 582
 583/*
 584 * Starts quiescing a region in preparation for recovery.
 585 */
 586static int __rh_recovery_prepare(struct dm_region_hash *rh)
 587{
 588        int r;
 589        region_t region;
 590        struct dm_region *reg;
 591
 592        /*
 593         * Ask the dirty log what's next.
 594         */
 595        r = rh->log->type->get_resync_work(rh->log, &region);
 596        if (r <= 0)
 597                return r;
 598
 599        /*
 600         * Get this region, and start it quiescing by setting the
 601         * recovering flag.
 602         */
 603        read_lock(&rh->hash_lock);
 604        reg = __rh_find(rh, region);
 605        read_unlock(&rh->hash_lock);
 606
 607        spin_lock_irq(&rh->region_lock);
 608        reg->state = DM_RH_RECOVERING;
 609
 610        /* Already quiesced ? */
 611        if (atomic_read(&reg->pending))
 612                list_del_init(&reg->list);
 613        else
 614                list_move(&reg->list, &rh->quiesced_regions);
 615
 616        spin_unlock_irq(&rh->region_lock);
 617
 618        return 1;
 619}
 620
 621void dm_rh_recovery_prepare(struct dm_region_hash *rh)
 622{
 623        /* Extra reference to avoid race with dm_rh_stop_recovery */
 624        atomic_inc(&rh->recovery_in_flight);
 625
 626        while (!down_trylock(&rh->recovery_count)) {
 627                atomic_inc(&rh->recovery_in_flight);
 628                if (__rh_recovery_prepare(rh) <= 0) {
 629                        atomic_dec(&rh->recovery_in_flight);
 630                        up(&rh->recovery_count);
 631                        break;
 632                }
 633        }
 634
 635        /* Drop the extra reference */
 636        if (atomic_dec_and_test(&rh->recovery_in_flight))
 637                rh->wakeup_all_recovery_waiters(rh->context);
 638}
 639EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare);
 640
 641/*
 642 * Returns any quiesced regions.
 643 */
 644struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh)
 645{
 646        struct dm_region *reg = NULL;
 647
 648        spin_lock_irq(&rh->region_lock);
 649        if (!list_empty(&rh->quiesced_regions)) {
 650                reg = list_entry(rh->quiesced_regions.next,
 651                                 struct dm_region, list);
 652                list_del_init(&reg->list);  /* remove from the quiesced list */
 653        }
 654        spin_unlock_irq(&rh->region_lock);
 655
 656        return reg;
 657}
 658EXPORT_SYMBOL_GPL(dm_rh_recovery_start);
 659
 660void dm_rh_recovery_end(struct dm_region *reg, int success)
 661{
 662        struct dm_region_hash *rh = reg->rh;
 663
 664        spin_lock_irq(&rh->region_lock);
 665        if (success)
 666                list_add(&reg->list, &reg->rh->recovered_regions);
 667        else
 668                list_add(&reg->list, &reg->rh->failed_recovered_regions);
 669
 670        spin_unlock_irq(&rh->region_lock);
 671
 672        rh->wakeup_workers(rh->context);
 673}
 674EXPORT_SYMBOL_GPL(dm_rh_recovery_end);
 675
 676/* Return recovery in flight count. */
 677int dm_rh_recovery_in_flight(struct dm_region_hash *rh)
 678{
 679        return atomic_read(&rh->recovery_in_flight);
 680}
 681EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight);
 682
 683int dm_rh_flush(struct dm_region_hash *rh)
 684{
 685        return rh->log->type->flush(rh->log);
 686}
 687EXPORT_SYMBOL_GPL(dm_rh_flush);
 688
 689void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio)
 690{
 691        struct dm_region *reg;
 692
 693        read_lock(&rh->hash_lock);
 694        reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio));
 695        bio_list_add(&reg->delayed_bios, bio);
 696        read_unlock(&rh->hash_lock);
 697}
 698EXPORT_SYMBOL_GPL(dm_rh_delay);
 699
 700void dm_rh_stop_recovery(struct dm_region_hash *rh)
 701{
 702        int i;
 703
 704        /* wait for any recovering regions */
 705        for (i = 0; i < rh->max_recovery; i++)
 706                down(&rh->recovery_count);
 707}
 708EXPORT_SYMBOL_GPL(dm_rh_stop_recovery);
 709
 710void dm_rh_start_recovery(struct dm_region_hash *rh)
 711{
 712        int i;
 713
 714        for (i = 0; i < rh->max_recovery; i++)
 715                up(&rh->recovery_count);
 716
 717        rh->wakeup_workers(rh->context);
 718}
 719EXPORT_SYMBOL_GPL(dm_rh_start_recovery);
 720
 721MODULE_DESCRIPTION(DM_NAME " region hash");
 722MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@redhat.com>");
 723MODULE_LICENSE("GPL");
 724
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