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_iter.bi_sector -
 130                                      rh->target_begin);
 131}
 132EXPORT_SYMBOL_GPL(dm_rh_bio_to_region);
 133
 134void *dm_rh_region_context(struct dm_region *reg)
 135{
 136        return reg->rh->context;
 137}
 138EXPORT_SYMBOL_GPL(dm_rh_region_context);
 139
 140region_t dm_rh_get_region_key(struct dm_region *reg)
 141{
 142        return reg->key;
 143}
 144EXPORT_SYMBOL_GPL(dm_rh_get_region_key);
 145
 146sector_t dm_rh_get_region_size(struct dm_region_hash *rh)
 147{
 148        return rh->region_size;
 149}
 150EXPORT_SYMBOL_GPL(dm_rh_get_region_size);
 151
 152/*
 153 * FIXME: shall we pass in a structure instead of all these args to
 154 * dm_region_hash_create()????
 155 */
 156#define RH_HASH_MULT 2654435387U
 157#define RH_HASH_SHIFT 12
 158
 159#define MIN_REGIONS 64
 160struct dm_region_hash *dm_region_hash_create(
 161                void *context, void (*dispatch_bios)(void *context,
 162                                                     struct bio_list *bios),
 163                void (*wakeup_workers)(void *context),
 164                void (*wakeup_all_recovery_waiters)(void *context),
 165                sector_t target_begin, unsigned max_recovery,
 166                struct dm_dirty_log *log, uint32_t region_size,
 167                region_t nr_regions)
 168{
 169        struct dm_region_hash *rh;
 170        unsigned nr_buckets, max_buckets;
 171        size_t i;
 172
 173        /*
 174         * Calculate a suitable number of buckets for our hash
 175         * table.
 176         */
 177        max_buckets = nr_regions >> 6;
 178        for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1)
 179                ;
 180        nr_buckets >>= 1;
 181
 182        rh = kmalloc(sizeof(*rh), GFP_KERNEL);
 183        if (!rh) {
 184                DMERR("unable to allocate region hash memory");
 185                return ERR_PTR(-ENOMEM);
 186        }
 187
 188        rh->context = context;
 189        rh->dispatch_bios = dispatch_bios;
 190        rh->wakeup_workers = wakeup_workers;
 191        rh->wakeup_all_recovery_waiters = wakeup_all_recovery_waiters;
 192        rh->target_begin = target_begin;
 193        rh->max_recovery = max_recovery;
 194        rh->log = log;
 195        rh->region_size = region_size;
 196        rh->region_shift = ffs(region_size) - 1;
 197        rwlock_init(&rh->hash_lock);
 198        rh->mask = nr_buckets - 1;
 199        rh->nr_buckets = nr_buckets;
 200
 201        rh->shift = RH_HASH_SHIFT;
 202        rh->prime = RH_HASH_MULT;
 203
 204        rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets));
 205        if (!rh->buckets) {
 206                DMERR("unable to allocate region hash bucket memory");
 207                kfree(rh);
 208                return ERR_PTR(-ENOMEM);
 209        }
 210
 211        for (i = 0; i < nr_buckets; i++)
 212                INIT_LIST_HEAD(rh->buckets + i);
 213
 214        spin_lock_init(&rh->region_lock);
 215        sema_init(&rh->recovery_count, 0);
 216        atomic_set(&rh->recovery_in_flight, 0);
 217        INIT_LIST_HEAD(&rh->clean_regions);
 218        INIT_LIST_HEAD(&rh->quiesced_regions);
 219        INIT_LIST_HEAD(&rh->recovered_regions);
 220        INIT_LIST_HEAD(&rh->failed_recovered_regions);
 221        rh->flush_failure = 0;
 222
 223        rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
 224                                                      sizeof(struct dm_region));
 225        if (!rh->region_pool) {
 226                vfree(rh->buckets);
 227                kfree(rh);
 228                rh = ERR_PTR(-ENOMEM);
 229        }
 230
 231        return rh;
 232}
 233EXPORT_SYMBOL_GPL(dm_region_hash_create);
 234
 235void dm_region_hash_destroy(struct dm_region_hash *rh)
 236{
 237        unsigned h;
 238        struct dm_region *reg, *nreg;
 239
 240        BUG_ON(!list_empty(&rh->quiesced_regions));
 241        for (h = 0; h < rh->nr_buckets; h++) {
 242                list_for_each_entry_safe(reg, nreg, rh->buckets + h,
 243                                         hash_list) {
 244                        BUG_ON(atomic_read(&reg->pending));
 245                        mempool_free(reg, rh->region_pool);
 246                }
 247        }
 248
 249        if (rh->log)
 250                dm_dirty_log_destroy(rh->log);
 251
 252        if (rh->region_pool)
 253                mempool_destroy(rh->region_pool);
 254
 255        vfree(rh->buckets);
 256        kfree(rh);
 257}
 258EXPORT_SYMBOL_GPL(dm_region_hash_destroy);
 259
 260struct dm_dirty_log *dm_rh_dirty_log(struct dm_region_hash *rh)
 261{
 262        return rh->log;
 263}
 264EXPORT_SYMBOL_GPL(dm_rh_dirty_log);
 265
 266static unsigned rh_hash(struct dm_region_hash *rh, region_t region)
 267{
 268        return (unsigned) ((region * rh->prime) >> rh->shift) & rh->mask;
 269}
 270
 271static struct dm_region *__rh_lookup(struct dm_region_hash *rh, region_t region)
 272{
 273        struct dm_region *reg;
 274        struct list_head *bucket = rh->buckets + rh_hash(rh, region);
 275
 276        list_for_each_entry(reg, bucket, hash_list)
 277                if (reg->key == region)
 278                        return reg;
 279
 280        return NULL;
 281}
 282
 283static void __rh_insert(struct dm_region_hash *rh, struct dm_region *reg)
 284{
 285        list_add(&reg->hash_list, rh->buckets + rh_hash(rh, reg->key));
 286}
 287
 288static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
 289{
 290        struct dm_region *reg, *nreg;
 291
 292        nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC);
 293        if (unlikely(!nreg))
 294                nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
 295
 296        nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
 297                      DM_RH_CLEAN : DM_RH_NOSYNC;
 298        nreg->rh = rh;
 299        nreg->key = region;
 300        INIT_LIST_HEAD(&nreg->list);
 301        atomic_set(&nreg->pending, 0);
 302        bio_list_init(&nreg->delayed_bios);
 303
 304        write_lock_irq(&rh->hash_lock);
 305        reg = __rh_lookup(rh, region);
 306        if (reg)
 307                /* We lost the race. */
 308                mempool_free(nreg, rh->region_pool);
 309        else {
 310                __rh_insert(rh, nreg);
 311                if (nreg->state == DM_RH_CLEAN) {
 312                        spin_lock(&rh->region_lock);
 313                        list_add(&nreg->list, &rh->clean_regions);
 314                        spin_unlock(&rh->region_lock);
 315                }
 316
 317                reg = nreg;
 318        }
 319        write_unlock_irq(&rh->hash_lock);
 320
 321        return reg;
 322}
 323
 324static struct dm_region *__rh_find(struct dm_region_hash *rh, region_t region)
 325{
 326        struct dm_region *reg;
 327
 328        reg = __rh_lookup(rh, region);
 329        if (!reg) {
 330                read_unlock(&rh->hash_lock);
 331                reg = __rh_alloc(rh, region);
 332                read_lock(&rh->hash_lock);
 333        }
 334
 335        return reg;
 336}
 337
 338int dm_rh_get_state(struct dm_region_hash *rh, region_t region, int may_block)
 339{
 340        int r;
 341        struct dm_region *reg;
 342
 343        read_lock(&rh->hash_lock);
 344        reg = __rh_lookup(rh, region);
 345        read_unlock(&rh->hash_lock);
 346
 347        if (reg)
 348                return reg->state;
 349
 350        /*
 351         * The region wasn't in the hash, so we fall back to the
 352         * dirty log.
 353         */
 354        r = rh->log->type->in_sync(rh->log, region, may_block);
 355
 356        /*
 357         * Any error from the dirty log (eg. -EWOULDBLOCK) gets
 358         * taken as a DM_RH_NOSYNC
 359         */
 360        return r == 1 ? DM_RH_CLEAN : DM_RH_NOSYNC;
 361}
 362EXPORT_SYMBOL_GPL(dm_rh_get_state);
 363
 364static void complete_resync_work(struct dm_region *reg, int success)
 365{
 366        struct dm_region_hash *rh = reg->rh;
 367
 368        rh->log->type->set_region_sync(rh->log, reg->key, success);
 369
 370        /*
 371         * Dispatch the bios before we call 'wake_up_all'.
 372         * This is important because if we are suspending,
 373         * we want to know that recovery is complete and
 374         * the work queue is flushed.  If we wake_up_all
 375         * before we dispatch_bios (queue bios and call wake()),
 376         * then we risk suspending before the work queue
 377         * has been properly flushed.
 378         */
 379        rh->dispatch_bios(rh->context, &reg->delayed_bios);
 380        if (atomic_dec_and_test(&rh->recovery_in_flight))
 381                rh->wakeup_all_recovery_waiters(rh->context);
 382        up(&rh->recovery_count);
 383}
 384
 385/* dm_rh_mark_nosync
 386 * @ms
 387 * @bio
 388 *
 389 * The bio was written on some mirror(s) but failed on other mirror(s).
 390 * We can successfully endio the bio but should avoid the region being
 391 * marked clean by setting the state DM_RH_NOSYNC.
 392 *
 393 * This function is _not_ safe in interrupt context!
 394 */
 395void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio)
 396{
 397        unsigned long flags;
 398        struct dm_dirty_log *log = rh->log;
 399        struct dm_region *reg;
 400        region_t region = dm_rh_bio_to_region(rh, bio);
 401        int recovering = 0;
 402
 403        if (bio->bi_rw & REQ_FLUSH) {
 404                rh->flush_failure = 1;
 405                return;
 406        }
 407
 408        if (bio->bi_rw & REQ_DISCARD)
 409                return;
 410
 411        /* We must inform the log that the sync count has changed. */
 412        log->type->set_region_sync(log, region, 0);
 413
 414        read_lock(&rh->hash_lock);
 415        reg = __rh_find(rh, region);
 416        read_unlock(&rh->hash_lock);
 417
 418        /* region hash entry should exist because write was in-flight */
 419        BUG_ON(!reg);
 420        BUG_ON(!list_empty(&reg->list));
 421
 422        spin_lock_irqsave(&rh->region_lock, flags);
 423        /*
 424         * Possible cases:
 425         *   1) DM_RH_DIRTY
 426         *   2) DM_RH_NOSYNC: was dirty, other preceding writes failed
 427         *   3) DM_RH_RECOVERING: flushing pending writes
 428         * Either case, the region should have not been connected to list.
 429         */
 430        recovering = (reg->state == DM_RH_RECOVERING);
 431        reg->state = DM_RH_NOSYNC;
 432        BUG_ON(!list_empty(&reg->list));
 433        spin_unlock_irqrestore(&rh->region_lock, flags);
 434
 435        if (recovering)
 436                complete_resync_work(reg, 0);
 437}
 438EXPORT_SYMBOL_GPL(dm_rh_mark_nosync);
 439
 440void dm_rh_update_states(struct dm_region_hash *rh, int errors_handled)
 441{
 442        struct dm_region *reg, *next;
 443
 444        LIST_HEAD(clean);
 445        LIST_HEAD(recovered);
 446        LIST_HEAD(failed_recovered);
 447
 448        /*
 449         * Quickly grab the lists.
 450         */
 451        write_lock_irq(&rh->hash_lock);
 452        spin_lock(&rh->region_lock);
 453        if (!list_empty(&rh->clean_regions)) {
 454                list_splice_init(&rh->clean_regions, &clean);
 455
 456                list_for_each_entry(reg, &clean, list)
 457                        list_del(&reg->hash_list);
 458        }
 459
 460        if (!list_empty(&rh->recovered_regions)) {
 461                list_splice_init(&rh->recovered_regions, &recovered);
 462
 463                list_for_each_entry(reg, &recovered, list)
 464                        list_del(&reg->hash_list);
 465        }
 466
 467        if (!list_empty(&rh->failed_recovered_regions)) {
 468                list_splice_init(&rh->failed_recovered_regions,
 469                                 &failed_recovered);
 470
 471                list_for_each_entry(reg, &failed_recovered, list)
 472                        list_del(&reg->hash_list);
 473        }
 474
 475        spin_unlock(&rh->region_lock);
 476        write_unlock_irq(&rh->hash_lock);
 477
 478        /*
 479         * All the regions on the recovered and clean lists have
 480         * now been pulled out of the system, so no need to do
 481         * any more locking.
 482         */
 483        list_for_each_entry_safe(reg, next, &recovered, list) {
 484                rh->log->type->clear_region(rh->log, reg->key);
 485                complete_resync_work(reg, 1);
 486                mempool_free(reg, rh->region_pool);
 487        }
 488
 489        list_for_each_entry_safe(reg, next, &failed_recovered, list) {
 490                complete_resync_work(reg, errors_handled ? 0 : 1);
 491                mempool_free(reg, rh->region_pool);
 492        }
 493
 494        list_for_each_entry_safe(reg, next, &clean, list) {
 495                rh->log->type->clear_region(rh->log, reg->key);
 496                mempool_free(reg, rh->region_pool);
 497        }
 498
 499        rh->log->type->flush(rh->log);
 500}
 501EXPORT_SYMBOL_GPL(dm_rh_update_states);
 502
 503static void rh_inc(struct dm_region_hash *rh, region_t region)
 504{
 505        struct dm_region *reg;
 506
 507        read_lock(&rh->hash_lock);
 508        reg = __rh_find(rh, region);
 509
 510        spin_lock_irq(&rh->region_lock);
 511        atomic_inc(&reg->pending);
 512
 513        if (reg->state == DM_RH_CLEAN) {
 514                reg->state = DM_RH_DIRTY;
 515                list_del_init(&reg->list);      /* take off the clean list */
 516                spin_unlock_irq(&rh->region_lock);
 517
 518                rh->log->type->mark_region(rh->log, reg->key);
 519        } else
 520                spin_unlock_irq(&rh->region_lock);
 521
 522
 523        read_unlock(&rh->hash_lock);
 524}
 525
 526void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios)
 527{
 528        struct bio *bio;
 529
 530        for (bio = bios->head; bio; bio = bio->bi_next) {
 531                if (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD))
 532                        continue;
 533                rh_inc(rh, dm_rh_bio_to_region(rh, bio));
 534        }
 535}
 536EXPORT_SYMBOL_GPL(dm_rh_inc_pending);
 537
 538void dm_rh_dec(struct dm_region_hash *rh, region_t region)
 539{
 540        unsigned long flags;
 541        struct dm_region *reg;
 542        int should_wake = 0;
 543
 544        read_lock(&rh->hash_lock);
 545        reg = __rh_lookup(rh, region);
 546        read_unlock(&rh->hash_lock);
 547
 548        spin_lock_irqsave(&rh->region_lock, flags);
 549        if (atomic_dec_and_test(&reg->pending)) {
 550                /*
 551                 * There is no pending I/O for this region.
 552                 * We can move the region to corresponding list for next action.
 553                 * At this point, the region is not yet connected to any list.
 554                 *
 555                 * If the state is DM_RH_NOSYNC, the region should be kept off
 556                 * from clean list.
 557                 * The hash entry for DM_RH_NOSYNC will remain in memory
 558                 * until the region is recovered or the map is reloaded.
 559                 */
 560
 561                /* do nothing for DM_RH_NOSYNC */
 562                if (unlikely(rh->flush_failure)) {
 563                        /*
 564                         * If a write flush failed some time ago, we
 565                         * don't know whether or not this write made it
 566                         * to the disk, so we must resync the device.
 567                         */
 568                        reg->state = DM_RH_NOSYNC;
 569                } else if (reg->state == DM_RH_RECOVERING) {
 570                        list_add_tail(&reg->list, &rh->quiesced_regions);
 571                } else if (reg->state == DM_RH_DIRTY) {
 572                        reg->state = DM_RH_CLEAN;
 573                        list_add(&reg->list, &rh->clean_regions);
 574                }
 575                should_wake = 1;
 576        }
 577        spin_unlock_irqrestore(&rh->region_lock, flags);
 578
 579        if (should_wake)
 580                rh->wakeup_workers(rh->context);
 581}
 582EXPORT_SYMBOL_GPL(dm_rh_dec);
 583
 584/*
 585 * Starts quiescing a region in preparation for recovery.
 586 */
 587static int __rh_recovery_prepare(struct dm_region_hash *rh)
 588{
 589        int r;
 590        region_t region;
 591        struct dm_region *reg;
 592
 593        /*
 594         * Ask the dirty log what's next.
 595         */
 596        r = rh->log->type->get_resync_work(rh->log, &region);
 597        if (r <= 0)
 598                return r;
 599
 600        /*
 601         * Get this region, and start it quiescing by setting the
 602         * recovering flag.
 603         */
 604        read_lock(&rh->hash_lock);
 605        reg = __rh_find(rh, region);
 606        read_unlock(&rh->hash_lock);
 607
 608        spin_lock_irq(&rh->region_lock);
 609        reg->state = DM_RH_RECOVERING;
 610
 611        /* Already quiesced ? */
 612        if (atomic_read(&reg->pending))
 613                list_del_init(&reg->list);
 614        else
 615                list_move(&reg->list, &rh->quiesced_regions);
 616
 617        spin_unlock_irq(&rh->region_lock);
 618
 619        return 1;
 620}
 621
 622void dm_rh_recovery_prepare(struct dm_region_hash *rh)
 623{
 624        /* Extra reference to avoid race with dm_rh_stop_recovery */
 625        atomic_inc(&rh->recovery_in_flight);
 626
 627        while (!down_trylock(&rh->recovery_count)) {
 628                atomic_inc(&rh->recovery_in_flight);
 629                if (__rh_recovery_prepare(rh) <= 0) {
 630                        atomic_dec(&rh->recovery_in_flight);
 631                        up(&rh->recovery_count);
 632                        break;
 633                }
 634        }
 635
 636        /* Drop the extra reference */
 637        if (atomic_dec_and_test(&rh->recovery_in_flight))
 638                rh->wakeup_all_recovery_waiters(rh->context);
 639}
 640EXPORT_SYMBOL_GPL(dm_rh_recovery_prepare);
 641
 642/*
 643 * Returns any quiesced regions.
 644 */
 645struct dm_region *dm_rh_recovery_start(struct dm_region_hash *rh)
 646{
 647        struct dm_region *reg = NULL;
 648
 649        spin_lock_irq(&rh->region_lock);
 650        if (!list_empty(&rh->quiesced_regions)) {
 651                reg = list_entry(rh->quiesced_regions.next,
 652                                 struct dm_region, list);
 653                list_del_init(&reg->list);  /* remove from the quiesced list */
 654        }
 655        spin_unlock_irq(&rh->region_lock);
 656
 657        return reg;
 658}
 659EXPORT_SYMBOL_GPL(dm_rh_recovery_start);
 660
 661void dm_rh_recovery_end(struct dm_region *reg, int success)
 662{
 663        struct dm_region_hash *rh = reg->rh;
 664
 665        spin_lock_irq(&rh->region_lock);
 666        if (success)
 667                list_add(&reg->list, &reg->rh->recovered_regions);
 668        else
 669                list_add(&reg->list, &reg->rh->failed_recovered_regions);
 670
 671        spin_unlock_irq(&rh->region_lock);
 672
 673        rh->wakeup_workers(rh->context);
 674}
 675EXPORT_SYMBOL_GPL(dm_rh_recovery_end);
 676
 677/* Return recovery in flight count. */
 678int dm_rh_recovery_in_flight(struct dm_region_hash *rh)
 679{
 680        return atomic_read(&rh->recovery_in_flight);
 681}
 682EXPORT_SYMBOL_GPL(dm_rh_recovery_in_flight);
 683
 684int dm_rh_flush(struct dm_region_hash *rh)
 685{
 686        return rh->log->type->flush(rh->log);
 687}
 688EXPORT_SYMBOL_GPL(dm_rh_flush);
 689
 690void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio)
 691{
 692        struct dm_region *reg;
 693
 694        read_lock(&rh->hash_lock);
 695        reg = __rh_find(rh, dm_rh_bio_to_region(rh, bio));
 696        bio_list_add(&reg->delayed_bios, bio);
 697        read_unlock(&rh->hash_lock);
 698}
 699EXPORT_SYMBOL_GPL(dm_rh_delay);
 700
 701void dm_rh_stop_recovery(struct dm_region_hash *rh)
 702{
 703        int i;
 704
 705        /* wait for any recovering regions */
 706        for (i = 0; i < rh->max_recovery; i++)
 707                down(&rh->recovery_count);
 708}
 709EXPORT_SYMBOL_GPL(dm_rh_stop_recovery);
 710
 711void dm_rh_start_recovery(struct dm_region_hash *rh)
 712{
 713        int i;
 714
 715        for (i = 0; i < rh->max_recovery; i++)
 716                up(&rh->recovery_count);
 717
 718        rh->wakeup_workers(rh->context);
 719}
 720EXPORT_SYMBOL_GPL(dm_rh_start_recovery);
 721
 722MODULE_DESCRIPTION(DM_NAME " region hash");
 723MODULE_AUTHOR("Joe Thornber/Heinz Mauelshagen <dm-devel@redhat.com>");
 724MODULE_LICENSE("GPL");
 725