linux/drivers/md/dm-cache-target.c
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   1/*
   2 * Copyright (C) 2012 Red Hat. All rights reserved.
   3 *
   4 * This file is released under the GPL.
   5 */
   6
   7#include "dm.h"
   8#include "dm-bio-prison.h"
   9#include "dm-bio-record.h"
  10#include "dm-cache-metadata.h"
  11
  12#include <linux/dm-io.h>
  13#include <linux/dm-kcopyd.h>
  14#include <linux/init.h>
  15#include <linux/mempool.h>
  16#include <linux/module.h>
  17#include <linux/slab.h>
  18#include <linux/vmalloc.h>
  19
  20#define DM_MSG_PREFIX "cache"
  21
  22DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle,
  23        "A percentage of time allocated for copying to and/or from cache");
  24
  25/*----------------------------------------------------------------*/
  26
  27/*
  28 * Glossary:
  29 *
  30 * oblock: index of an origin block
  31 * cblock: index of a cache block
  32 * promotion: movement of a block from origin to cache
  33 * demotion: movement of a block from cache to origin
  34 * migration: movement of a block between the origin and cache device,
  35 *            either direction
  36 */
  37
  38/*----------------------------------------------------------------*/
  39
  40static size_t bitset_size_in_bytes(unsigned nr_entries)
  41{
  42        return sizeof(unsigned long) * dm_div_up(nr_entries, BITS_PER_LONG);
  43}
  44
  45static unsigned long *alloc_bitset(unsigned nr_entries)
  46{
  47        size_t s = bitset_size_in_bytes(nr_entries);
  48        return vzalloc(s);
  49}
  50
  51static void clear_bitset(void *bitset, unsigned nr_entries)
  52{
  53        size_t s = bitset_size_in_bytes(nr_entries);
  54        memset(bitset, 0, s);
  55}
  56
  57static void free_bitset(unsigned long *bits)
  58{
  59        vfree(bits);
  60}
  61
  62/*----------------------------------------------------------------*/
  63
  64#define PRISON_CELLS 1024
  65#define MIGRATION_POOL_SIZE 128
  66#define COMMIT_PERIOD HZ
  67#define MIGRATION_COUNT_WINDOW 10
  68
  69/*
  70 * The block size of the device holding cache data must be >= 32KB
  71 */
  72#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
  73
  74/*
  75 * FIXME: the cache is read/write for the time being.
  76 */
  77enum cache_mode {
  78        CM_WRITE,               /* metadata may be changed */
  79        CM_READ_ONLY,           /* metadata may not be changed */
  80};
  81
  82struct cache_features {
  83        enum cache_mode mode;
  84        bool write_through:1;
  85};
  86
  87struct cache_stats {
  88        atomic_t read_hit;
  89        atomic_t read_miss;
  90        atomic_t write_hit;
  91        atomic_t write_miss;
  92        atomic_t demotion;
  93        atomic_t promotion;
  94        atomic_t copies_avoided;
  95        atomic_t cache_cell_clash;
  96        atomic_t commit_count;
  97        atomic_t discard_count;
  98};
  99
 100struct cache {
 101        struct dm_target *ti;
 102        struct dm_target_callbacks callbacks;
 103
 104        /*
 105         * Metadata is written to this device.
 106         */
 107        struct dm_dev *metadata_dev;
 108
 109        /*
 110         * The slower of the two data devices.  Typically a spindle.
 111         */
 112        struct dm_dev *origin_dev;
 113
 114        /*
 115         * The faster of the two data devices.  Typically an SSD.
 116         */
 117        struct dm_dev *cache_dev;
 118
 119        /*
 120         * Cache features such as write-through.
 121         */
 122        struct cache_features features;
 123
 124        /*
 125         * Size of the origin device in _complete_ blocks and native sectors.
 126         */
 127        dm_oblock_t origin_blocks;
 128        sector_t origin_sectors;
 129
 130        /*
 131         * Size of the cache device in blocks.
 132         */
 133        dm_cblock_t cache_size;
 134
 135        /*
 136         * Fields for converting from sectors to blocks.
 137         */
 138        uint32_t sectors_per_block;
 139        int sectors_per_block_shift;
 140
 141        struct dm_cache_metadata *cmd;
 142
 143        spinlock_t lock;
 144        struct bio_list deferred_bios;
 145        struct bio_list deferred_flush_bios;
 146        struct bio_list deferred_writethrough_bios;
 147        struct list_head quiesced_migrations;
 148        struct list_head completed_migrations;
 149        struct list_head need_commit_migrations;
 150        sector_t migration_threshold;
 151        atomic_t nr_migrations;
 152        wait_queue_head_t migration_wait;
 153
 154        /*
 155         * cache_size entries, dirty if set
 156         */
 157        dm_cblock_t nr_dirty;
 158        unsigned long *dirty_bitset;
 159
 160        /*
 161         * origin_blocks entries, discarded if set.
 162         */
 163        uint32_t discard_block_size; /* a power of 2 times sectors per block */
 164        dm_dblock_t discard_nr_blocks;
 165        unsigned long *discard_bitset;
 166
 167        struct dm_kcopyd_client *copier;
 168        struct workqueue_struct *wq;
 169        struct work_struct worker;
 170
 171        struct delayed_work waker;
 172        unsigned long last_commit_jiffies;
 173
 174        struct dm_bio_prison *prison;
 175        struct dm_deferred_set *all_io_ds;
 176
 177        mempool_t *migration_pool;
 178        struct dm_cache_migration *next_migration;
 179
 180        struct dm_cache_policy *policy;
 181        unsigned policy_nr_args;
 182
 183        bool need_tick_bio:1;
 184        bool sized:1;
 185        bool quiescing:1;
 186        bool commit_requested:1;
 187        bool loaded_mappings:1;
 188        bool loaded_discards:1;
 189
 190        struct cache_stats stats;
 191
 192        /*
 193         * Rather than reconstructing the table line for the status we just
 194         * save it and regurgitate.
 195         */
 196        unsigned nr_ctr_args;
 197        const char **ctr_args;
 198};
 199
 200struct per_bio_data {
 201        bool tick:1;
 202        unsigned req_nr:2;
 203        struct dm_deferred_entry *all_io_entry;
 204
 205        /*
 206         * writethrough fields.  These MUST remain at the end of this
 207         * structure and the 'cache' member must be the first as it
 208         * is used to determine the offset of the writethrough fields.
 209         */
 210        struct cache *cache;
 211        dm_cblock_t cblock;
 212        bio_end_io_t *saved_bi_end_io;
 213        struct dm_bio_details bio_details;
 214};
 215
 216struct dm_cache_migration {
 217        struct list_head list;
 218        struct cache *cache;
 219
 220        unsigned long start_jiffies;
 221        dm_oblock_t old_oblock;
 222        dm_oblock_t new_oblock;
 223        dm_cblock_t cblock;
 224
 225        bool err:1;
 226        bool writeback:1;
 227        bool demote:1;
 228        bool promote:1;
 229
 230        struct dm_bio_prison_cell *old_ocell;
 231        struct dm_bio_prison_cell *new_ocell;
 232};
 233
 234/*
 235 * Processing a bio in the worker thread may require these memory
 236 * allocations.  We prealloc to avoid deadlocks (the same worker thread
 237 * frees them back to the mempool).
 238 */
 239struct prealloc {
 240        struct dm_cache_migration *mg;
 241        struct dm_bio_prison_cell *cell1;
 242        struct dm_bio_prison_cell *cell2;
 243};
 244
 245static void wake_worker(struct cache *cache)
 246{
 247        queue_work(cache->wq, &cache->worker);
 248}
 249
 250/*----------------------------------------------------------------*/
 251
 252static struct dm_bio_prison_cell *alloc_prison_cell(struct cache *cache)
 253{
 254        /* FIXME: change to use a local slab. */
 255        return dm_bio_prison_alloc_cell(cache->prison, GFP_NOWAIT);
 256}
 257
 258static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell *cell)
 259{
 260        dm_bio_prison_free_cell(cache->prison, cell);
 261}
 262
 263static int prealloc_data_structs(struct cache *cache, struct prealloc *p)
 264{
 265        if (!p->mg) {
 266                p->mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT);
 267                if (!p->mg)
 268                        return -ENOMEM;
 269        }
 270
 271        if (!p->cell1) {
 272                p->cell1 = alloc_prison_cell(cache);
 273                if (!p->cell1)
 274                        return -ENOMEM;
 275        }
 276
 277        if (!p->cell2) {
 278                p->cell2 = alloc_prison_cell(cache);
 279                if (!p->cell2)
 280                        return -ENOMEM;
 281        }
 282
 283        return 0;
 284}
 285
 286static void prealloc_free_structs(struct cache *cache, struct prealloc *p)
 287{
 288        if (p->cell2)
 289                free_prison_cell(cache, p->cell2);
 290
 291        if (p->cell1)
 292                free_prison_cell(cache, p->cell1);
 293
 294        if (p->mg)
 295                mempool_free(p->mg, cache->migration_pool);
 296}
 297
 298static struct dm_cache_migration *prealloc_get_migration(struct prealloc *p)
 299{
 300        struct dm_cache_migration *mg = p->mg;
 301
 302        BUG_ON(!mg);
 303        p->mg = NULL;
 304
 305        return mg;
 306}
 307
 308/*
 309 * You must have a cell within the prealloc struct to return.  If not this
 310 * function will BUG() rather than returning NULL.
 311 */
 312static struct dm_bio_prison_cell *prealloc_get_cell(struct prealloc *p)
 313{
 314        struct dm_bio_prison_cell *r = NULL;
 315
 316        if (p->cell1) {
 317                r = p->cell1;
 318                p->cell1 = NULL;
 319
 320        } else if (p->cell2) {
 321                r = p->cell2;
 322                p->cell2 = NULL;
 323        } else
 324                BUG();
 325
 326        return r;
 327}
 328
 329/*
 330 * You can't have more than two cells in a prealloc struct.  BUG() will be
 331 * called if you try and overfill.
 332 */
 333static void prealloc_put_cell(struct prealloc *p, struct dm_bio_prison_cell *cell)
 334{
 335        if (!p->cell2)
 336                p->cell2 = cell;
 337
 338        else if (!p->cell1)
 339                p->cell1 = cell;
 340
 341        else
 342                BUG();
 343}
 344
 345/*----------------------------------------------------------------*/
 346
 347static void build_key(dm_oblock_t oblock, struct dm_cell_key *key)
 348{
 349        key->virtual = 0;
 350        key->dev = 0;
 351        key->block = from_oblock(oblock);
 352}
 353
 354/*
 355 * The caller hands in a preallocated cell, and a free function for it.
 356 * The cell will be freed if there's an error, or if it wasn't used because
 357 * a cell with that key already exists.
 358 */
 359typedef void (*cell_free_fn)(void *context, struct dm_bio_prison_cell *cell);
 360
 361static int bio_detain(struct cache *cache, dm_oblock_t oblock,
 362                      struct bio *bio, struct dm_bio_prison_cell *cell_prealloc,
 363                      cell_free_fn free_fn, void *free_context,
 364                      struct dm_bio_prison_cell **cell_result)
 365{
 366        int r;
 367        struct dm_cell_key key;
 368
 369        build_key(oblock, &key);
 370        r = dm_bio_detain(cache->prison, &key, bio, cell_prealloc, cell_result);
 371        if (r)
 372                free_fn(free_context, cell_prealloc);
 373
 374        return r;
 375}
 376
 377static int get_cell(struct cache *cache,
 378                    dm_oblock_t oblock,
 379                    struct prealloc *structs,
 380                    struct dm_bio_prison_cell **cell_result)
 381{
 382        int r;
 383        struct dm_cell_key key;
 384        struct dm_bio_prison_cell *cell_prealloc;
 385
 386        cell_prealloc = prealloc_get_cell(structs);
 387
 388        build_key(oblock, &key);
 389        r = dm_get_cell(cache->prison, &key, cell_prealloc, cell_result);
 390        if (r)
 391                prealloc_put_cell(structs, cell_prealloc);
 392
 393        return r;
 394}
 395
 396/*----------------------------------------------------------------*/
 397
 398static bool is_dirty(struct cache *cache, dm_cblock_t b)
 399{
 400        return test_bit(from_cblock(b), cache->dirty_bitset);
 401}
 402
 403static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
 404{
 405        if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
 406                cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1);
 407                policy_set_dirty(cache->policy, oblock);
 408        }
 409}
 410
 411static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
 412{
 413        if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
 414                policy_clear_dirty(cache->policy, oblock);
 415                cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1);
 416                if (!from_cblock(cache->nr_dirty))
 417                        dm_table_event(cache->ti->table);
 418        }
 419}
 420
 421/*----------------------------------------------------------------*/
 422
 423static bool block_size_is_power_of_two(struct cache *cache)
 424{
 425        return cache->sectors_per_block_shift >= 0;
 426}
 427
 428static dm_block_t block_div(dm_block_t b, uint32_t n)
 429{
 430        do_div(b, n);
 431
 432        return b;
 433}
 434
 435static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
 436{
 437        uint32_t discard_blocks = cache->discard_block_size;
 438        dm_block_t b = from_oblock(oblock);
 439
 440        if (!block_size_is_power_of_two(cache))
 441                discard_blocks = discard_blocks / cache->sectors_per_block;
 442        else
 443                discard_blocks >>= cache->sectors_per_block_shift;
 444
 445        b = block_div(b, discard_blocks);
 446
 447        return to_dblock(b);
 448}
 449
 450static void set_discard(struct cache *cache, dm_dblock_t b)
 451{
 452        unsigned long flags;
 453
 454        atomic_inc(&cache->stats.discard_count);
 455
 456        spin_lock_irqsave(&cache->lock, flags);
 457        set_bit(from_dblock(b), cache->discard_bitset);
 458        spin_unlock_irqrestore(&cache->lock, flags);
 459}
 460
 461static void clear_discard(struct cache *cache, dm_dblock_t b)
 462{
 463        unsigned long flags;
 464
 465        spin_lock_irqsave(&cache->lock, flags);
 466        clear_bit(from_dblock(b), cache->discard_bitset);
 467        spin_unlock_irqrestore(&cache->lock, flags);
 468}
 469
 470static bool is_discarded(struct cache *cache, dm_dblock_t b)
 471{
 472        int r;
 473        unsigned long flags;
 474
 475        spin_lock_irqsave(&cache->lock, flags);
 476        r = test_bit(from_dblock(b), cache->discard_bitset);
 477        spin_unlock_irqrestore(&cache->lock, flags);
 478
 479        return r;
 480}
 481
 482static bool is_discarded_oblock(struct cache *cache, dm_oblock_t b)
 483{
 484        int r;
 485        unsigned long flags;
 486
 487        spin_lock_irqsave(&cache->lock, flags);
 488        r = test_bit(from_dblock(oblock_to_dblock(cache, b)),
 489                     cache->discard_bitset);
 490        spin_unlock_irqrestore(&cache->lock, flags);
 491
 492        return r;
 493}
 494
 495/*----------------------------------------------------------------*/
 496
 497static void load_stats(struct cache *cache)
 498{
 499        struct dm_cache_statistics stats;
 500
 501        dm_cache_metadata_get_stats(cache->cmd, &stats);
 502        atomic_set(&cache->stats.read_hit, stats.read_hits);
 503        atomic_set(&cache->stats.read_miss, stats.read_misses);
 504        atomic_set(&cache->stats.write_hit, stats.write_hits);
 505        atomic_set(&cache->stats.write_miss, stats.write_misses);
 506}
 507
 508static void save_stats(struct cache *cache)
 509{
 510        struct dm_cache_statistics stats;
 511
 512        stats.read_hits = atomic_read(&cache->stats.read_hit);
 513        stats.read_misses = atomic_read(&cache->stats.read_miss);
 514        stats.write_hits = atomic_read(&cache->stats.write_hit);
 515        stats.write_misses = atomic_read(&cache->stats.write_miss);
 516
 517        dm_cache_metadata_set_stats(cache->cmd, &stats);
 518}
 519
 520/*----------------------------------------------------------------
 521 * Per bio data
 522 *--------------------------------------------------------------*/
 523
 524/*
 525 * If using writeback, leave out struct per_bio_data's writethrough fields.
 526 */
 527#define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
 528#define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
 529
 530static size_t get_per_bio_data_size(struct cache *cache)
 531{
 532        return cache->features.write_through ? PB_DATA_SIZE_WT : PB_DATA_SIZE_WB;
 533}
 534
 535static struct per_bio_data *get_per_bio_data(struct bio *bio, size_t data_size)
 536{
 537        struct per_bio_data *pb = dm_per_bio_data(bio, data_size);
 538        BUG_ON(!pb);
 539        return pb;
 540}
 541
 542static struct per_bio_data *init_per_bio_data(struct bio *bio, size_t data_size)
 543{
 544        struct per_bio_data *pb = get_per_bio_data(bio, data_size);
 545
 546        pb->tick = false;
 547        pb->req_nr = dm_bio_get_target_bio_nr(bio);
 548        pb->all_io_entry = NULL;
 549
 550        return pb;
 551}
 552
 553/*----------------------------------------------------------------
 554 * Remapping
 555 *--------------------------------------------------------------*/
 556static void remap_to_origin(struct cache *cache, struct bio *bio)
 557{
 558        bio->bi_bdev = cache->origin_dev->bdev;
 559}
 560
 561static void remap_to_cache(struct cache *cache, struct bio *bio,
 562                           dm_cblock_t cblock)
 563{
 564        sector_t bi_sector = bio->bi_sector;
 565
 566        bio->bi_bdev = cache->cache_dev->bdev;
 567        if (!block_size_is_power_of_two(cache))
 568                bio->bi_sector = (from_cblock(cblock) * cache->sectors_per_block) +
 569                                sector_div(bi_sector, cache->sectors_per_block);
 570        else
 571                bio->bi_sector = (from_cblock(cblock) << cache->sectors_per_block_shift) |
 572                                (bi_sector & (cache->sectors_per_block - 1));
 573}
 574
 575static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio)
 576{
 577        unsigned long flags;
 578        size_t pb_data_size = get_per_bio_data_size(cache);
 579        struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
 580
 581        spin_lock_irqsave(&cache->lock, flags);
 582        if (cache->need_tick_bio &&
 583            !(bio->bi_rw & (REQ_FUA | REQ_FLUSH | REQ_DISCARD))) {
 584                pb->tick = true;
 585                cache->need_tick_bio = false;
 586        }
 587        spin_unlock_irqrestore(&cache->lock, flags);
 588}
 589
 590static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio,
 591                                  dm_oblock_t oblock)
 592{
 593        check_if_tick_bio_needed(cache, bio);
 594        remap_to_origin(cache, bio);
 595        if (bio_data_dir(bio) == WRITE)
 596                clear_discard(cache, oblock_to_dblock(cache, oblock));
 597}
 598
 599static void remap_to_cache_dirty(struct cache *cache, struct bio *bio,
 600                                 dm_oblock_t oblock, dm_cblock_t cblock)
 601{
 602        remap_to_cache(cache, bio, cblock);
 603        if (bio_data_dir(bio) == WRITE) {
 604                set_dirty(cache, oblock, cblock);
 605                clear_discard(cache, oblock_to_dblock(cache, oblock));
 606        }
 607}
 608
 609static dm_oblock_t get_bio_block(struct cache *cache, struct bio *bio)
 610{
 611        sector_t block_nr = bio->bi_sector;
 612
 613        if (!block_size_is_power_of_two(cache))
 614                (void) sector_div(block_nr, cache->sectors_per_block);
 615        else
 616                block_nr >>= cache->sectors_per_block_shift;
 617
 618        return to_oblock(block_nr);
 619}
 620
 621static int bio_triggers_commit(struct cache *cache, struct bio *bio)
 622{
 623        return bio->bi_rw & (REQ_FLUSH | REQ_FUA);
 624}
 625
 626static void issue(struct cache *cache, struct bio *bio)
 627{
 628        unsigned long flags;
 629
 630        if (!bio_triggers_commit(cache, bio)) {
 631                generic_make_request(bio);
 632                return;
 633        }
 634
 635        /*
 636         * Batch together any bios that trigger commits and then issue a
 637         * single commit for them in do_worker().
 638         */
 639        spin_lock_irqsave(&cache->lock, flags);
 640        cache->commit_requested = true;
 641        bio_list_add(&cache->deferred_flush_bios, bio);
 642        spin_unlock_irqrestore(&cache->lock, flags);
 643}
 644
 645static void defer_writethrough_bio(struct cache *cache, struct bio *bio)
 646{
 647        unsigned long flags;
 648
 649        spin_lock_irqsave(&cache->lock, flags);
 650        bio_list_add(&cache->deferred_writethrough_bios, bio);
 651        spin_unlock_irqrestore(&cache->lock, flags);
 652
 653        wake_worker(cache);
 654}
 655
 656static void writethrough_endio(struct bio *bio, int err)
 657{
 658        struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
 659        bio->bi_end_io = pb->saved_bi_end_io;
 660
 661        if (err) {
 662                bio_endio(bio, err);
 663                return;
 664        }
 665
 666        dm_bio_restore(&pb->bio_details, bio);
 667        remap_to_cache(pb->cache, bio, pb->cblock);
 668
 669        /*
 670         * We can't issue this bio directly, since we're in interrupt
 671         * context.  So it gets put on a bio list for processing by the
 672         * worker thread.
 673         */
 674        defer_writethrough_bio(pb->cache, bio);
 675}
 676
 677/*
 678 * When running in writethrough mode we need to send writes to clean blocks
 679 * to both the cache and origin devices.  In future we'd like to clone the
 680 * bio and send them in parallel, but for now we're doing them in
 681 * series as this is easier.
 682 */
 683static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
 684                                       dm_oblock_t oblock, dm_cblock_t cblock)
 685{
 686        struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
 687
 688        pb->cache = cache;
 689        pb->cblock = cblock;
 690        pb->saved_bi_end_io = bio->bi_end_io;
 691        dm_bio_record(&pb->bio_details, bio);
 692        bio->bi_end_io = writethrough_endio;
 693
 694        remap_to_origin_clear_discard(pb->cache, bio, oblock);
 695}
 696
 697/*----------------------------------------------------------------
 698 * Migration processing
 699 *
 700 * Migration covers moving data from the origin device to the cache, or
 701 * vice versa.
 702 *--------------------------------------------------------------*/
 703static void free_migration(struct dm_cache_migration *mg)
 704{
 705        mempool_free(mg, mg->cache->migration_pool);
 706}
 707
 708static void inc_nr_migrations(struct cache *cache)
 709{
 710        atomic_inc(&cache->nr_migrations);
 711}
 712
 713static void dec_nr_migrations(struct cache *cache)
 714{
 715        atomic_dec(&cache->nr_migrations);
 716
 717        /*
 718         * Wake the worker in case we're suspending the target.
 719         */
 720        wake_up(&cache->migration_wait);
 721}
 722
 723static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
 724                         bool holder)
 725{
 726        (holder ? dm_cell_release : dm_cell_release_no_holder)
 727                (cache->prison, cell, &cache->deferred_bios);
 728        free_prison_cell(cache, cell);
 729}
 730
 731static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
 732                       bool holder)
 733{
 734        unsigned long flags;
 735
 736        spin_lock_irqsave(&cache->lock, flags);
 737        __cell_defer(cache, cell, holder);
 738        spin_unlock_irqrestore(&cache->lock, flags);
 739
 740        wake_worker(cache);
 741}
 742
 743static void cleanup_migration(struct dm_cache_migration *mg)
 744{
 745        dec_nr_migrations(mg->cache);
 746        free_migration(mg);
 747}
 748
 749static void migration_failure(struct dm_cache_migration *mg)
 750{
 751        struct cache *cache = mg->cache;
 752
 753        if (mg->writeback) {
 754                DMWARN_LIMIT("writeback failed; couldn't copy block");
 755                set_dirty(cache, mg->old_oblock, mg->cblock);
 756                cell_defer(cache, mg->old_ocell, false);
 757
 758        } else if (mg->demote) {
 759                DMWARN_LIMIT("demotion failed; couldn't copy block");
 760                policy_force_mapping(cache->policy, mg->new_oblock, mg->old_oblock);
 761
 762                cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
 763                if (mg->promote)
 764                        cell_defer(cache, mg->new_ocell, 1);
 765        } else {
 766                DMWARN_LIMIT("promotion failed; couldn't copy block");
 767                policy_remove_mapping(cache->policy, mg->new_oblock);
 768                cell_defer(cache, mg->new_ocell, 1);
 769        }
 770
 771        cleanup_migration(mg);
 772}
 773
 774static void migration_success_pre_commit(struct dm_cache_migration *mg)
 775{
 776        unsigned long flags;
 777        struct cache *cache = mg->cache;
 778
 779        if (mg->writeback) {
 780                cell_defer(cache, mg->old_ocell, false);
 781                clear_dirty(cache, mg->old_oblock, mg->cblock);
 782                cleanup_migration(mg);
 783                return;
 784
 785        } else if (mg->demote) {
 786                if (dm_cache_remove_mapping(cache->cmd, mg->cblock)) {
 787                        DMWARN_LIMIT("demotion failed; couldn't update on disk metadata");
 788                        policy_force_mapping(cache->policy, mg->new_oblock,
 789                                             mg->old_oblock);
 790                        if (mg->promote)
 791                                cell_defer(cache, mg->new_ocell, true);
 792                        cleanup_migration(mg);
 793                        return;
 794                }
 795        } else {
 796                if (dm_cache_insert_mapping(cache->cmd, mg->cblock, mg->new_oblock)) {
 797                        DMWARN_LIMIT("promotion failed; couldn't update on disk metadata");
 798                        policy_remove_mapping(cache->policy, mg->new_oblock);
 799                        cleanup_migration(mg);
 800                        return;
 801                }
 802        }
 803
 804        spin_lock_irqsave(&cache->lock, flags);
 805        list_add_tail(&mg->list, &cache->need_commit_migrations);
 806        cache->commit_requested = true;
 807        spin_unlock_irqrestore(&cache->lock, flags);
 808}
 809
 810static void migration_success_post_commit(struct dm_cache_migration *mg)
 811{
 812        unsigned long flags;
 813        struct cache *cache = mg->cache;
 814
 815        if (mg->writeback) {
 816                DMWARN("writeback unexpectedly triggered commit");
 817                return;
 818
 819        } else if (mg->demote) {
 820                cell_defer(cache, mg->old_ocell, mg->promote ? 0 : 1);
 821
 822                if (mg->promote) {
 823                        mg->demote = false;
 824
 825                        spin_lock_irqsave(&cache->lock, flags);
 826                        list_add_tail(&mg->list, &cache->quiesced_migrations);
 827                        spin_unlock_irqrestore(&cache->lock, flags);
 828
 829                } else
 830                        cleanup_migration(mg);
 831
 832        } else {
 833                cell_defer(cache, mg->new_ocell, true);
 834                clear_dirty(cache, mg->new_oblock, mg->cblock);
 835                cleanup_migration(mg);
 836        }
 837}
 838
 839static void copy_complete(int read_err, unsigned long write_err, void *context)
 840{
 841        unsigned long flags;
 842        struct dm_cache_migration *mg = (struct dm_cache_migration *) context;
 843        struct cache *cache = mg->cache;
 844
 845        if (read_err || write_err)
 846                mg->err = true;
 847
 848        spin_lock_irqsave(&cache->lock, flags);
 849        list_add_tail(&mg->list, &cache->completed_migrations);
 850        spin_unlock_irqrestore(&cache->lock, flags);
 851
 852        wake_worker(cache);
 853}
 854
 855static void issue_copy_real(struct dm_cache_migration *mg)
 856{
 857        int r;
 858        struct dm_io_region o_region, c_region;
 859        struct cache *cache = mg->cache;
 860
 861        o_region.bdev = cache->origin_dev->bdev;
 862        o_region.count = cache->sectors_per_block;
 863
 864        c_region.bdev = cache->cache_dev->bdev;
 865        c_region.sector = from_cblock(mg->cblock) * cache->sectors_per_block;
 866        c_region.count = cache->sectors_per_block;
 867
 868        if (mg->writeback || mg->demote) {
 869                /* demote */
 870                o_region.sector = from_oblock(mg->old_oblock) * cache->sectors_per_block;
 871                r = dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, mg);
 872        } else {
 873                /* promote */
 874                o_region.sector = from_oblock(mg->new_oblock) * cache->sectors_per_block;
 875                r = dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, mg);
 876        }
 877
 878        if (r < 0)
 879                migration_failure(mg);
 880}
 881
 882static void avoid_copy(struct dm_cache_migration *mg)
 883{
 884        atomic_inc(&mg->cache->stats.copies_avoided);
 885        migration_success_pre_commit(mg);
 886}
 887
 888static void issue_copy(struct dm_cache_migration *mg)
 889{
 890        bool avoid;
 891        struct cache *cache = mg->cache;
 892
 893        if (mg->writeback || mg->demote)
 894                avoid = !is_dirty(cache, mg->cblock) ||
 895                        is_discarded_oblock(cache, mg->old_oblock);
 896        else
 897                avoid = is_discarded_oblock(cache, mg->new_oblock);
 898
 899        avoid ? avoid_copy(mg) : issue_copy_real(mg);
 900}
 901
 902static void complete_migration(struct dm_cache_migration *mg)
 903{
 904        if (mg->err)
 905                migration_failure(mg);
 906        else
 907                migration_success_pre_commit(mg);
 908}
 909
 910static void process_migrations(struct cache *cache, struct list_head *head,
 911                               void (*fn)(struct dm_cache_migration *))
 912{
 913        unsigned long flags;
 914        struct list_head list;
 915        struct dm_cache_migration *mg, *tmp;
 916
 917        INIT_LIST_HEAD(&list);
 918        spin_lock_irqsave(&cache->lock, flags);
 919        list_splice_init(head, &list);
 920        spin_unlock_irqrestore(&cache->lock, flags);
 921
 922        list_for_each_entry_safe(mg, tmp, &list, list)
 923                fn(mg);
 924}
 925
 926static void __queue_quiesced_migration(struct dm_cache_migration *mg)
 927{
 928        list_add_tail(&mg->list, &mg->cache->quiesced_migrations);
 929}
 930
 931static void queue_quiesced_migration(struct dm_cache_migration *mg)
 932{
 933        unsigned long flags;
 934        struct cache *cache = mg->cache;
 935
 936        spin_lock_irqsave(&cache->lock, flags);
 937        __queue_quiesced_migration(mg);
 938        spin_unlock_irqrestore(&cache->lock, flags);
 939
 940        wake_worker(cache);
 941}
 942
 943static void queue_quiesced_migrations(struct cache *cache, struct list_head *work)
 944{
 945        unsigned long flags;
 946        struct dm_cache_migration *mg, *tmp;
 947
 948        spin_lock_irqsave(&cache->lock, flags);
 949        list_for_each_entry_safe(mg, tmp, work, list)
 950                __queue_quiesced_migration(mg);
 951        spin_unlock_irqrestore(&cache->lock, flags);
 952
 953        wake_worker(cache);
 954}
 955
 956static void check_for_quiesced_migrations(struct cache *cache,
 957                                          struct per_bio_data *pb)
 958{
 959        struct list_head work;
 960
 961        if (!pb->all_io_entry)
 962                return;
 963
 964        INIT_LIST_HEAD(&work);
 965        if (pb->all_io_entry)
 966                dm_deferred_entry_dec(pb->all_io_entry, &work);
 967
 968        if (!list_empty(&work))
 969                queue_quiesced_migrations(cache, &work);
 970}
 971
 972static void quiesce_migration(struct dm_cache_migration *mg)
 973{
 974        if (!dm_deferred_set_add_work(mg->cache->all_io_ds, &mg->list))
 975                queue_quiesced_migration(mg);
 976}
 977
 978static void promote(struct cache *cache, struct prealloc *structs,
 979                    dm_oblock_t oblock, dm_cblock_t cblock,
 980                    struct dm_bio_prison_cell *cell)
 981{
 982        struct dm_cache_migration *mg = prealloc_get_migration(structs);
 983
 984        mg->err = false;
 985        mg->writeback = false;
 986        mg->demote = false;
 987        mg->promote = true;
 988        mg->cache = cache;
 989        mg->new_oblock = oblock;
 990        mg->cblock = cblock;
 991        mg->old_ocell = NULL;
 992        mg->new_ocell = cell;
 993        mg->start_jiffies = jiffies;
 994
 995        inc_nr_migrations(cache);
 996        quiesce_migration(mg);
 997}
 998
 999static void writeback(struct cache *cache, struct prealloc *structs,
1000                      dm_oblock_t oblock, dm_cblock_t cblock,
1001                      struct dm_bio_prison_cell *cell)
1002{
1003        struct dm_cache_migration *mg = prealloc_get_migration(structs);
1004
1005        mg->err = false;
1006        mg->writeback = true;
1007        mg->demote = false;
1008        mg->promote = false;
1009        mg->cache = cache;
1010        mg->old_oblock = oblock;
1011        mg->cblock = cblock;
1012        mg->old_ocell = cell;
1013        mg->new_ocell = NULL;
1014        mg->start_jiffies = jiffies;
1015
1016        inc_nr_migrations(cache);
1017        quiesce_migration(mg);
1018}
1019
1020static void demote_then_promote(struct cache *cache, struct prealloc *structs,
1021                                dm_oblock_t old_oblock, dm_oblock_t new_oblock,
1022                                dm_cblock_t cblock,
1023                                struct dm_bio_prison_cell *old_ocell,
1024                                struct dm_bio_prison_cell *new_ocell)
1025{
1026        struct dm_cache_migration *mg = prealloc_get_migration(structs);
1027
1028        mg->err = false;
1029        mg->writeback = false;
1030        mg->demote = true;
1031        mg->promote = true;
1032        mg->cache = cache;
1033        mg->old_oblock = old_oblock;
1034        mg->new_oblock = new_oblock;
1035        mg->cblock = cblock;
1036        mg->old_ocell = old_ocell;
1037        mg->new_ocell = new_ocell;
1038        mg->start_jiffies = jiffies;
1039
1040        inc_nr_migrations(cache);
1041        quiesce_migration(mg);
1042}
1043
1044/*----------------------------------------------------------------
1045 * bio processing
1046 *--------------------------------------------------------------*/
1047static void defer_bio(struct cache *cache, struct bio *bio)
1048{
1049        unsigned long flags;
1050
1051        spin_lock_irqsave(&cache->lock, flags);
1052        bio_list_add(&cache->deferred_bios, bio);
1053        spin_unlock_irqrestore(&cache->lock, flags);
1054
1055        wake_worker(cache);
1056}
1057
1058static void process_flush_bio(struct cache *cache, struct bio *bio)
1059{
1060        size_t pb_data_size = get_per_bio_data_size(cache);
1061        struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1062
1063        BUG_ON(bio->bi_size);
1064        if (!pb->req_nr)
1065                remap_to_origin(cache, bio);
1066        else
1067                remap_to_cache(cache, bio, 0);
1068
1069        issue(cache, bio);
1070}
1071
1072/*
1073 * People generally discard large parts of a device, eg, the whole device
1074 * when formatting.  Splitting these large discards up into cache block
1075 * sized ios and then quiescing (always neccessary for discard) takes too
1076 * long.
1077 *
1078 * We keep it simple, and allow any size of discard to come in, and just
1079 * mark off blocks on the discard bitset.  No passdown occurs!
1080 *
1081 * To implement passdown we need to change the bio_prison such that a cell
1082 * can have a key that spans many blocks.
1083 */
1084static void process_discard_bio(struct cache *cache, struct bio *bio)
1085{
1086        dm_block_t start_block = dm_sector_div_up(bio->bi_sector,
1087                                                  cache->discard_block_size);
1088        dm_block_t end_block = bio->bi_sector + bio_sectors(bio);
1089        dm_block_t b;
1090
1091        end_block = block_div(end_block, cache->discard_block_size);
1092
1093        for (b = start_block; b < end_block; b++)
1094                set_discard(cache, to_dblock(b));
1095
1096        bio_endio(bio, 0);
1097}
1098
1099static bool spare_migration_bandwidth(struct cache *cache)
1100{
1101        sector_t current_volume = (atomic_read(&cache->nr_migrations) + 1) *
1102                cache->sectors_per_block;
1103        return current_volume < cache->migration_threshold;
1104}
1105
1106static bool is_writethrough_io(struct cache *cache, struct bio *bio,
1107                               dm_cblock_t cblock)
1108{
1109        return bio_data_dir(bio) == WRITE &&
1110                cache->features.write_through && !is_dirty(cache, cblock);
1111}
1112
1113static void inc_hit_counter(struct cache *cache, struct bio *bio)
1114{
1115        atomic_inc(bio_data_dir(bio) == READ ?
1116                   &cache->stats.read_hit : &cache->stats.write_hit);
1117}
1118
1119static void inc_miss_counter(struct cache *cache, struct bio *bio)
1120{
1121        atomic_inc(bio_data_dir(bio) == READ ?
1122                   &cache->stats.read_miss : &cache->stats.write_miss);
1123}
1124
1125static void process_bio(struct cache *cache, struct prealloc *structs,
1126                        struct bio *bio)
1127{
1128        int r;
1129        bool release_cell = true;
1130        dm_oblock_t block = get_bio_block(cache, bio);
1131        struct dm_bio_prison_cell *cell_prealloc, *old_ocell, *new_ocell;
1132        struct policy_result lookup_result;
1133        size_t pb_data_size = get_per_bio_data_size(cache);
1134        struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1135        bool discarded_block = is_discarded_oblock(cache, block);
1136        bool can_migrate = discarded_block || spare_migration_bandwidth(cache);
1137
1138        /*
1139         * Check to see if that block is currently migrating.
1140         */
1141        cell_prealloc = prealloc_get_cell(structs);
1142        r = bio_detain(cache, block, bio, cell_prealloc,
1143                       (cell_free_fn) prealloc_put_cell,
1144                       structs, &new_ocell);
1145        if (r > 0)
1146                return;
1147
1148        r = policy_map(cache->policy, block, true, can_migrate, discarded_block,
1149                       bio, &lookup_result);
1150
1151        if (r == -EWOULDBLOCK)
1152                /* migration has been denied */
1153                lookup_result.op = POLICY_MISS;
1154
1155        switch (lookup_result.op) {
1156        case POLICY_HIT:
1157                inc_hit_counter(cache, bio);
1158                pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1159
1160                if (is_writethrough_io(cache, bio, lookup_result.cblock))
1161                        remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
1162                else
1163                        remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
1164
1165                issue(cache, bio);
1166                break;
1167
1168        case POLICY_MISS:
1169                inc_miss_counter(cache, bio);
1170                pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1171                remap_to_origin_clear_discard(cache, bio, block);
1172                issue(cache, bio);
1173                break;
1174
1175        case POLICY_NEW:
1176                atomic_inc(&cache->stats.promotion);
1177                promote(cache, structs, block, lookup_result.cblock, new_ocell);
1178                release_cell = false;
1179                break;
1180
1181        case POLICY_REPLACE:
1182                cell_prealloc = prealloc_get_cell(structs);
1183                r = bio_detain(cache, lookup_result.old_oblock, bio, cell_prealloc,
1184                               (cell_free_fn) prealloc_put_cell,
1185                               structs, &old_ocell);
1186                if (r > 0) {
1187                        /*
1188                         * We have to be careful to avoid lock inversion of
1189                         * the cells.  So we back off, and wait for the
1190                         * old_ocell to become free.
1191                         */
1192                        policy_force_mapping(cache->policy, block,
1193                                             lookup_result.old_oblock);
1194                        atomic_inc(&cache->stats.cache_cell_clash);
1195                        break;
1196                }
1197                atomic_inc(&cache->stats.demotion);
1198                atomic_inc(&cache->stats.promotion);
1199
1200                demote_then_promote(cache, structs, lookup_result.old_oblock,
1201                                    block, lookup_result.cblock,
1202                                    old_ocell, new_ocell);
1203                release_cell = false;
1204                break;
1205
1206        default:
1207                DMERR_LIMIT("%s: erroring bio, unknown policy op: %u", __func__,
1208                            (unsigned) lookup_result.op);
1209                bio_io_error(bio);
1210        }
1211
1212        if (release_cell)
1213                cell_defer(cache, new_ocell, false);
1214}
1215
1216static int need_commit_due_to_time(struct cache *cache)
1217{
1218        return jiffies < cache->last_commit_jiffies ||
1219               jiffies > cache->last_commit_jiffies + COMMIT_PERIOD;
1220}
1221
1222static int commit_if_needed(struct cache *cache)
1223{
1224        if (dm_cache_changed_this_transaction(cache->cmd) &&
1225            (cache->commit_requested || need_commit_due_to_time(cache))) {
1226                atomic_inc(&cache->stats.commit_count);
1227                cache->last_commit_jiffies = jiffies;
1228                cache->commit_requested = false;
1229                return dm_cache_commit(cache->cmd, false);
1230        }
1231
1232        return 0;
1233}
1234
1235static void process_deferred_bios(struct cache *cache)
1236{
1237        unsigned long flags;
1238        struct bio_list bios;
1239        struct bio *bio;
1240        struct prealloc structs;
1241
1242        memset(&structs, 0, sizeof(structs));
1243        bio_list_init(&bios);
1244
1245        spin_lock_irqsave(&cache->lock, flags);
1246        bio_list_merge(&bios, &cache->deferred_bios);
1247        bio_list_init(&cache->deferred_bios);
1248        spin_unlock_irqrestore(&cache->lock, flags);
1249
1250        while (!bio_list_empty(&bios)) {
1251                /*
1252                 * If we've got no free migration structs, and processing
1253                 * this bio might require one, we pause until there are some
1254                 * prepared mappings to process.
1255                 */
1256                if (prealloc_data_structs(cache, &structs)) {
1257                        spin_lock_irqsave(&cache->lock, flags);
1258                        bio_list_merge(&cache->deferred_bios, &bios);
1259                        spin_unlock_irqrestore(&cache->lock, flags);
1260                        break;
1261                }
1262
1263                bio = bio_list_pop(&bios);
1264
1265                if (bio->bi_rw & REQ_FLUSH)
1266                        process_flush_bio(cache, bio);
1267                else if (bio->bi_rw & REQ_DISCARD)
1268                        process_discard_bio(cache, bio);
1269                else
1270                        process_bio(cache, &structs, bio);
1271        }
1272
1273        prealloc_free_structs(cache, &structs);
1274}
1275
1276static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
1277{
1278        unsigned long flags;
1279        struct bio_list bios;
1280        struct bio *bio;
1281
1282        bio_list_init(&bios);
1283
1284        spin_lock_irqsave(&cache->lock, flags);
1285        bio_list_merge(&bios, &cache->deferred_flush_bios);
1286        bio_list_init(&cache->deferred_flush_bios);
1287        spin_unlock_irqrestore(&cache->lock, flags);
1288
1289        while ((bio = bio_list_pop(&bios)))
1290                submit_bios ? generic_make_request(bio) : bio_io_error(bio);
1291}
1292
1293static void process_deferred_writethrough_bios(struct cache *cache)
1294{
1295        unsigned long flags;
1296        struct bio_list bios;
1297        struct bio *bio;
1298
1299        bio_list_init(&bios);
1300
1301        spin_lock_irqsave(&cache->lock, flags);
1302        bio_list_merge(&bios, &cache->deferred_writethrough_bios);
1303        bio_list_init(&cache->deferred_writethrough_bios);
1304        spin_unlock_irqrestore(&cache->lock, flags);
1305
1306        while ((bio = bio_list_pop(&bios)))
1307                generic_make_request(bio);
1308}
1309
1310static void writeback_some_dirty_blocks(struct cache *cache)
1311{
1312        int r = 0;
1313        dm_oblock_t oblock;
1314        dm_cblock_t cblock;
1315        struct prealloc structs;
1316        struct dm_bio_prison_cell *old_ocell;
1317
1318        memset(&structs, 0, sizeof(structs));
1319
1320        while (spare_migration_bandwidth(cache)) {
1321                if (prealloc_data_structs(cache, &structs))
1322                        break;
1323
1324                r = policy_writeback_work(cache->policy, &oblock, &cblock);
1325                if (r)
1326                        break;
1327
1328                r = get_cell(cache, oblock, &structs, &old_ocell);
1329                if (r) {
1330                        policy_set_dirty(cache->policy, oblock);
1331                        break;
1332                }
1333
1334                writeback(cache, &structs, oblock, cblock, old_ocell);
1335        }
1336
1337        prealloc_free_structs(cache, &structs);
1338}
1339
1340/*----------------------------------------------------------------
1341 * Main worker loop
1342 *--------------------------------------------------------------*/
1343static void start_quiescing(struct cache *cache)
1344{
1345        unsigned long flags;
1346
1347        spin_lock_irqsave(&cache->lock, flags);
1348        cache->quiescing = 1;
1349        spin_unlock_irqrestore(&cache->lock, flags);
1350}
1351
1352static void stop_quiescing(struct cache *cache)
1353{
1354        unsigned long flags;
1355
1356        spin_lock_irqsave(&cache->lock, flags);
1357        cache->quiescing = 0;
1358        spin_unlock_irqrestore(&cache->lock, flags);
1359}
1360
1361static bool is_quiescing(struct cache *cache)
1362{
1363        int r;
1364        unsigned long flags;
1365
1366        spin_lock_irqsave(&cache->lock, flags);
1367        r = cache->quiescing;
1368        spin_unlock_irqrestore(&cache->lock, flags);
1369
1370        return r;
1371}
1372
1373static void wait_for_migrations(struct cache *cache)
1374{
1375        wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations));
1376}
1377
1378static void stop_worker(struct cache *cache)
1379{
1380        cancel_delayed_work(&cache->waker);
1381        flush_workqueue(cache->wq);
1382}
1383
1384static void requeue_deferred_io(struct cache *cache)
1385{
1386        struct bio *bio;
1387        struct bio_list bios;
1388
1389        bio_list_init(&bios);
1390        bio_list_merge(&bios, &cache->deferred_bios);
1391        bio_list_init(&cache->deferred_bios);
1392
1393        while ((bio = bio_list_pop(&bios)))
1394                bio_endio(bio, DM_ENDIO_REQUEUE);
1395}
1396
1397static int more_work(struct cache *cache)
1398{
1399        if (is_quiescing(cache))
1400                return !list_empty(&cache->quiesced_migrations) ||
1401                        !list_empty(&cache->completed_migrations) ||
1402                        !list_empty(&cache->need_commit_migrations);
1403        else
1404                return !bio_list_empty(&cache->deferred_bios) ||
1405                        !bio_list_empty(&cache->deferred_flush_bios) ||
1406                        !bio_list_empty(&cache->deferred_writethrough_bios) ||
1407                        !list_empty(&cache->quiesced_migrations) ||
1408                        !list_empty(&cache->completed_migrations) ||
1409                        !list_empty(&cache->need_commit_migrations);
1410}
1411
1412static void do_worker(struct work_struct *ws)
1413{
1414        struct cache *cache = container_of(ws, struct cache, worker);
1415
1416        do {
1417                if (!is_quiescing(cache))
1418                        process_deferred_bios(cache);
1419
1420                process_migrations(cache, &cache->quiesced_migrations, issue_copy);
1421                process_migrations(cache, &cache->completed_migrations, complete_migration);
1422
1423                writeback_some_dirty_blocks(cache);
1424
1425                process_deferred_writethrough_bios(cache);
1426
1427                if (commit_if_needed(cache)) {
1428                        process_deferred_flush_bios(cache, false);
1429
1430                        /*
1431                         * FIXME: rollback metadata or just go into a
1432                         * failure mode and error everything
1433                         */
1434                } else {
1435                        process_deferred_flush_bios(cache, true);
1436                        process_migrations(cache, &cache->need_commit_migrations,
1437                                           migration_success_post_commit);
1438                }
1439        } while (more_work(cache));
1440}
1441
1442/*
1443 * We want to commit periodically so that not too much
1444 * unwritten metadata builds up.
1445 */
1446static void do_waker(struct work_struct *ws)
1447{
1448        struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);
1449        policy_tick(cache->policy);
1450        wake_worker(cache);
1451        queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
1452}
1453
1454/*----------------------------------------------------------------*/
1455
1456static int is_congested(struct dm_dev *dev, int bdi_bits)
1457{
1458        struct request_queue *q = bdev_get_queue(dev->bdev);
1459        return bdi_congested(&q->backing_dev_info, bdi_bits);
1460}
1461
1462static int cache_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
1463{
1464        struct cache *cache = container_of(cb, struct cache, callbacks);
1465
1466        return is_congested(cache->origin_dev, bdi_bits) ||
1467                is_congested(cache->cache_dev, bdi_bits);
1468}
1469
1470/*----------------------------------------------------------------
1471 * Target methods
1472 *--------------------------------------------------------------*/
1473
1474/*
1475 * This function gets called on the error paths of the constructor, so we
1476 * have to cope with a partially initialised struct.
1477 */
1478static void destroy(struct cache *cache)
1479{
1480        unsigned i;
1481
1482        if (cache->next_migration)
1483                mempool_free(cache->next_migration, cache->migration_pool);
1484
1485        if (cache->migration_pool)
1486                mempool_destroy(cache->migration_pool);
1487
1488        if (cache->all_io_ds)
1489                dm_deferred_set_destroy(cache->all_io_ds);
1490
1491        if (cache->prison)
1492                dm_bio_prison_destroy(cache->prison);
1493
1494        if (cache->wq)
1495                destroy_workqueue(cache->wq);
1496
1497        if (cache->dirty_bitset)
1498                free_bitset(cache->dirty_bitset);
1499
1500        if (cache->discard_bitset)
1501                free_bitset(cache->discard_bitset);
1502
1503        if (cache->copier)
1504                dm_kcopyd_client_destroy(cache->copier);
1505
1506        if (cache->cmd)
1507                dm_cache_metadata_close(cache->cmd);
1508
1509        if (cache->metadata_dev)
1510                dm_put_device(cache->ti, cache->metadata_dev);
1511
1512        if (cache->origin_dev)
1513                dm_put_device(cache->ti, cache->origin_dev);
1514
1515        if (cache->cache_dev)
1516                dm_put_device(cache->ti, cache->cache_dev);
1517
1518        if (cache->policy)
1519                dm_cache_policy_destroy(cache->policy);
1520
1521        for (i = 0; i < cache->nr_ctr_args ; i++)
1522                kfree(cache->ctr_args[i]);
1523        kfree(cache->ctr_args);
1524
1525        kfree(cache);
1526}
1527
1528static void cache_dtr(struct dm_target *ti)
1529{
1530        struct cache *cache = ti->private;
1531
1532        destroy(cache);
1533}
1534
1535static sector_t get_dev_size(struct dm_dev *dev)
1536{
1537        return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
1538}
1539
1540/*----------------------------------------------------------------*/
1541
1542/*
1543 * Construct a cache device mapping.
1544 *
1545 * cache <metadata dev> <cache dev> <origin dev> <block size>
1546 *       <#feature args> [<feature arg>]*
1547 *       <policy> <#policy args> [<policy arg>]*
1548 *
1549 * metadata dev    : fast device holding the persistent metadata
1550 * cache dev       : fast device holding cached data blocks
1551 * origin dev      : slow device holding original data blocks
1552 * block size      : cache unit size in sectors
1553 *
1554 * #feature args   : number of feature arguments passed
1555 * feature args    : writethrough.  (The default is writeback.)
1556 *
1557 * policy          : the replacement policy to use
1558 * #policy args    : an even number of policy arguments corresponding
1559 *                   to key/value pairs passed to the policy
1560 * policy args     : key/value pairs passed to the policy
1561 *                   E.g. 'sequential_threshold 1024'
1562 *                   See cache-policies.txt for details.
1563 *
1564 * Optional feature arguments are:
1565 *   writethrough  : write through caching that prohibits cache block
1566 *                   content from being different from origin block content.
1567 *                   Without this argument, the default behaviour is to write
1568 *                   back cache block contents later for performance reasons,
1569 *                   so they may differ from the corresponding origin blocks.
1570 */
1571struct cache_args {
1572        struct dm_target *ti;
1573
1574        struct dm_dev *metadata_dev;
1575
1576        struct dm_dev *cache_dev;
1577        sector_t cache_sectors;
1578
1579        struct dm_dev *origin_dev;
1580        sector_t origin_sectors;
1581
1582        uint32_t block_size;
1583
1584        const char *policy_name;
1585        int policy_argc;
1586        const char **policy_argv;
1587
1588        struct cache_features features;
1589};
1590
1591static void destroy_cache_args(struct cache_args *ca)
1592{
1593        if (ca->metadata_dev)
1594                dm_put_device(ca->ti, ca->metadata_dev);
1595
1596        if (ca->cache_dev)
1597                dm_put_device(ca->ti, ca->cache_dev);
1598
1599        if (ca->origin_dev)
1600                dm_put_device(ca->ti, ca->origin_dev);
1601
1602        kfree(ca);
1603}
1604
1605static bool at_least_one_arg(struct dm_arg_set *as, char **error)
1606{
1607        if (!as->argc) {
1608                *error = "Insufficient args";
1609                return false;
1610        }
1611
1612        return true;
1613}
1614
1615static int parse_metadata_dev(struct cache_args *ca, struct dm_arg_set *as,
1616                              char **error)
1617{
1618        int r;
1619        sector_t metadata_dev_size;
1620        char b[BDEVNAME_SIZE];
1621
1622        if (!at_least_one_arg(as, error))
1623                return -EINVAL;
1624
1625        r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1626                          &ca->metadata_dev);
1627        if (r) {
1628                *error = "Error opening metadata device";
1629                return r;
1630        }
1631
1632        metadata_dev_size = get_dev_size(ca->metadata_dev);
1633        if (metadata_dev_size > DM_CACHE_METADATA_MAX_SECTORS_WARNING)
1634                DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
1635                       bdevname(ca->metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);
1636
1637        return 0;
1638}
1639
1640static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as,
1641                           char **error)
1642{
1643        int r;
1644
1645        if (!at_least_one_arg(as, error))
1646                return -EINVAL;
1647
1648        r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1649                          &ca->cache_dev);
1650        if (r) {
1651                *error = "Error opening cache device";
1652                return r;
1653        }
1654        ca->cache_sectors = get_dev_size(ca->cache_dev);
1655
1656        return 0;
1657}
1658
1659static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
1660                            char **error)
1661{
1662        int r;
1663
1664        if (!at_least_one_arg(as, error))
1665                return -EINVAL;
1666
1667        r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1668                          &ca->origin_dev);
1669        if (r) {
1670                *error = "Error opening origin device";
1671                return r;
1672        }
1673
1674        ca->origin_sectors = get_dev_size(ca->origin_dev);
1675        if (ca->ti->len > ca->origin_sectors) {
1676                *error = "Device size larger than cached device";
1677                return -EINVAL;
1678        }
1679
1680        return 0;
1681}
1682
1683static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
1684                            char **error)
1685{
1686        unsigned long tmp;
1687
1688        if (!at_least_one_arg(as, error))
1689                return -EINVAL;
1690
1691        if (kstrtoul(dm_shift_arg(as), 10, &tmp) || !tmp ||
1692            tmp < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
1693            tmp & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
1694                *error = "Invalid data block size";
1695                return -EINVAL;
1696        }
1697
1698        if (tmp > ca->cache_sectors) {
1699                *error = "Data block size is larger than the cache device";
1700                return -EINVAL;
1701        }
1702
1703        ca->block_size = tmp;
1704
1705        return 0;
1706}
1707
1708static void init_features(struct cache_features *cf)
1709{
1710        cf->mode = CM_WRITE;
1711        cf->write_through = false;
1712}
1713
1714static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
1715                          char **error)
1716{
1717        static struct dm_arg _args[] = {
1718                {0, 1, "Invalid number of cache feature arguments"},
1719        };
1720
1721        int r;
1722        unsigned argc;
1723        const char *arg;
1724        struct cache_features *cf = &ca->features;
1725
1726        init_features(cf);
1727
1728        r = dm_read_arg_group(_args, as, &argc, error);
1729        if (r)
1730                return -EINVAL;
1731
1732        while (argc--) {
1733                arg = dm_shift_arg(as);
1734
1735                if (!strcasecmp(arg, "writeback"))
1736                        cf->write_through = false;
1737
1738                else if (!strcasecmp(arg, "writethrough"))
1739                        cf->write_through = true;
1740
1741                else {
1742                        *error = "Unrecognised cache feature requested";
1743                        return -EINVAL;
1744                }
1745        }
1746
1747        return 0;
1748}
1749
1750static int parse_policy(struct cache_args *ca, struct dm_arg_set *as,
1751                        char **error)
1752{
1753        static struct dm_arg _args[] = {
1754                {0, 1024, "Invalid number of policy arguments"},
1755        };
1756
1757        int r;
1758
1759        if (!at_least_one_arg(as, error))
1760                return -EINVAL;
1761
1762        ca->policy_name = dm_shift_arg(as);
1763
1764        r = dm_read_arg_group(_args, as, &ca->policy_argc, error);
1765        if (r)
1766                return -EINVAL;
1767
1768        ca->policy_argv = (const char **)as->argv;
1769        dm_consume_args(as, ca->policy_argc);
1770
1771        return 0;
1772}
1773
1774static int parse_cache_args(struct cache_args *ca, int argc, char **argv,
1775                            char **error)
1776{
1777        int r;
1778        struct dm_arg_set as;
1779
1780        as.argc = argc;
1781        as.argv = argv;
1782
1783        r = parse_metadata_dev(ca, &as, error);
1784        if (r)
1785                return r;
1786
1787        r = parse_cache_dev(ca, &as, error);
1788        if (r)
1789                return r;
1790
1791        r = parse_origin_dev(ca, &as, error);
1792        if (r)
1793                return r;
1794
1795        r = parse_block_size(ca, &as, error);
1796        if (r)
1797                return r;
1798
1799        r = parse_features(ca, &as, error);
1800        if (r)
1801                return r;
1802
1803        r = parse_policy(ca, &as, error);
1804        if (r)
1805                return r;
1806
1807        return 0;
1808}
1809
1810/*----------------------------------------------------------------*/
1811
1812static struct kmem_cache *migration_cache;
1813
1814#define NOT_CORE_OPTION 1
1815
1816static int process_config_option(struct cache *cache, const char *key, const char *value)
1817{
1818        unsigned long tmp;
1819
1820        if (!strcasecmp(key, "migration_threshold")) {
1821                if (kstrtoul(value, 10, &tmp))
1822                        return -EINVAL;
1823
1824                cache->migration_threshold = tmp;
1825                return 0;
1826        }
1827
1828        return NOT_CORE_OPTION;
1829}
1830
1831static int set_config_value(struct cache *cache, const char *key, const char *value)
1832{
1833        int r = process_config_option(cache, key, value);
1834
1835        if (r == NOT_CORE_OPTION)
1836                r = policy_set_config_value(cache->policy, key, value);
1837
1838        if (r)
1839                DMWARN("bad config value for %s: %s", key, value);
1840
1841        return r;
1842}
1843
1844static int set_config_values(struct cache *cache, int argc, const char **argv)
1845{
1846        int r = 0;
1847
1848        if (argc & 1) {
1849                DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
1850                return -EINVAL;
1851        }
1852
1853        while (argc) {
1854                r = set_config_value(cache, argv[0], argv[1]);
1855                if (r)
1856                        break;
1857
1858                argc -= 2;
1859                argv += 2;
1860        }
1861
1862        return r;
1863}
1864
1865static int create_cache_policy(struct cache *cache, struct cache_args *ca,
1866                               char **error)
1867{
1868        cache->policy = dm_cache_policy_create(ca->policy_name,
1869                                               cache->cache_size,
1870                                               cache->origin_sectors,
1871                                               cache->sectors_per_block);
1872        if (!cache->policy) {
1873                *error = "Error creating cache's policy";
1874                return -ENOMEM;
1875        }
1876
1877        return 0;
1878}
1879
1880/*
1881 * We want the discard block size to be a power of two, at least the size
1882 * of the cache block size, and have no more than 2^14 discard blocks
1883 * across the origin.
1884 */
1885#define MAX_DISCARD_BLOCKS (1 << 14)
1886
1887static bool too_many_discard_blocks(sector_t discard_block_size,
1888                                    sector_t origin_size)
1889{
1890        (void) sector_div(origin_size, discard_block_size);
1891
1892        return origin_size > MAX_DISCARD_BLOCKS;
1893}
1894
1895static sector_t calculate_discard_block_size(sector_t cache_block_size,
1896                                             sector_t origin_size)
1897{
1898        sector_t discard_block_size;
1899
1900        discard_block_size = roundup_pow_of_two(cache_block_size);
1901
1902        if (origin_size)
1903                while (too_many_discard_blocks(discard_block_size, origin_size))
1904                        discard_block_size *= 2;
1905
1906        return discard_block_size;
1907}
1908
1909#define DEFAULT_MIGRATION_THRESHOLD 2048
1910
1911static int cache_create(struct cache_args *ca, struct cache **result)
1912{
1913        int r = 0;
1914        char **error = &ca->ti->error;
1915        struct cache *cache;
1916        struct dm_target *ti = ca->ti;
1917        dm_block_t origin_blocks;
1918        struct dm_cache_metadata *cmd;
1919        bool may_format = ca->features.mode == CM_WRITE;
1920
1921        cache = kzalloc(sizeof(*cache), GFP_KERNEL);
1922        if (!cache)
1923                return -ENOMEM;
1924
1925        cache->ti = ca->ti;
1926        ti->private = cache;
1927        ti->num_flush_bios = 2;
1928        ti->flush_supported = true;
1929
1930        ti->num_discard_bios = 1;
1931        ti->discards_supported = true;
1932        ti->discard_zeroes_data_unsupported = true;
1933
1934        cache->features = ca->features;
1935        ti->per_bio_data_size = get_per_bio_data_size(cache);
1936
1937        cache->callbacks.congested_fn = cache_is_congested;
1938        dm_table_add_target_callbacks(ti->table, &cache->callbacks);
1939
1940        cache->metadata_dev = ca->metadata_dev;
1941        cache->origin_dev = ca->origin_dev;
1942        cache->cache_dev = ca->cache_dev;
1943
1944        ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL;
1945
1946        /* FIXME: factor out this whole section */
1947        origin_blocks = cache->origin_sectors = ca->origin_sectors;
1948        origin_blocks = block_div(origin_blocks, ca->block_size);
1949        cache->origin_blocks = to_oblock(origin_blocks);
1950
1951        cache->sectors_per_block = ca->block_size;
1952        if (dm_set_target_max_io_len(ti, cache->sectors_per_block)) {
1953                r = -EINVAL;
1954                goto bad;
1955        }
1956
1957        if (ca->block_size & (ca->block_size - 1)) {
1958                dm_block_t cache_size = ca->cache_sectors;
1959
1960                cache->sectors_per_block_shift = -1;
1961                cache_size = block_div(cache_size, ca->block_size);
1962                cache->cache_size = to_cblock(cache_size);
1963        } else {
1964                cache->sectors_per_block_shift = __ffs(ca->block_size);
1965                cache->cache_size = to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift);
1966        }
1967
1968        r = create_cache_policy(cache, ca, error);
1969        if (r)
1970                goto bad;
1971
1972        cache->policy_nr_args = ca->policy_argc;
1973        cache->migration_threshold = DEFAULT_MIGRATION_THRESHOLD;
1974
1975        r = set_config_values(cache, ca->policy_argc, ca->policy_argv);
1976        if (r) {
1977                *error = "Error setting cache policy's config values";
1978                goto bad;
1979        }
1980
1981        cmd = dm_cache_metadata_open(cache->metadata_dev->bdev,
1982                                     ca->block_size, may_format,
1983                                     dm_cache_policy_get_hint_size(cache->policy));
1984        if (IS_ERR(cmd)) {
1985                *error = "Error creating metadata object";
1986                r = PTR_ERR(cmd);
1987                goto bad;
1988        }
1989        cache->cmd = cmd;
1990
1991        spin_lock_init(&cache->lock);
1992        bio_list_init(&cache->deferred_bios);
1993        bio_list_init(&cache->deferred_flush_bios);
1994        bio_list_init(&cache->deferred_writethrough_bios);
1995        INIT_LIST_HEAD(&cache->quiesced_migrations);
1996        INIT_LIST_HEAD(&cache->completed_migrations);
1997        INIT_LIST_HEAD(&cache->need_commit_migrations);
1998        atomic_set(&cache->nr_migrations, 0);
1999        init_waitqueue_head(&cache->migration_wait);
2000
2001        r = -ENOMEM;
2002        cache->nr_dirty = 0;
2003        cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));
2004        if (!cache->dirty_bitset) {
2005                *error = "could not allocate dirty bitset";
2006                goto bad;
2007        }
2008        clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size));
2009
2010        cache->discard_block_size =
2011                calculate_discard_block_size(cache->sectors_per_block,
2012                                             cache->origin_sectors);
2013        cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks);
2014        cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks));
2015        if (!cache->discard_bitset) {
2016                *error = "could not allocate discard bitset";
2017                goto bad;
2018        }
2019        clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks));
2020
2021        cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle);
2022        if (IS_ERR(cache->copier)) {
2023                *error = "could not create kcopyd client";
2024                r = PTR_ERR(cache->copier);
2025                goto bad;
2026        }
2027
2028        cache->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
2029        if (!cache->wq) {
2030                *error = "could not create workqueue for metadata object";
2031                goto bad;
2032        }
2033        INIT_WORK(&cache->worker, do_worker);
2034        INIT_DELAYED_WORK(&cache->waker, do_waker);
2035        cache->last_commit_jiffies = jiffies;
2036
2037        cache->prison = dm_bio_prison_create(PRISON_CELLS);
2038        if (!cache->prison) {
2039                *error = "could not create bio prison";
2040                goto bad;
2041        }
2042
2043        cache->all_io_ds = dm_deferred_set_create();
2044        if (!cache->all_io_ds) {
2045                *error = "could not create all_io deferred set";
2046                goto bad;
2047        }
2048
2049        cache->migration_pool = mempool_create_slab_pool(MIGRATION_POOL_SIZE,
2050                                                         migration_cache);
2051        if (!cache->migration_pool) {
2052                *error = "Error creating cache's migration mempool";
2053                goto bad;
2054        }
2055
2056        cache->next_migration = NULL;
2057
2058        cache->need_tick_bio = true;
2059        cache->sized = false;
2060        cache->quiescing = false;
2061        cache->commit_requested = false;
2062        cache->loaded_mappings = false;
2063        cache->loaded_discards = false;
2064
2065        load_stats(cache);
2066
2067        atomic_set(&cache->stats.demotion, 0);
2068        atomic_set(&cache->stats.promotion, 0);
2069        atomic_set(&cache->stats.copies_avoided, 0);
2070        atomic_set(&cache->stats.cache_cell_clash, 0);
2071        atomic_set(&cache->stats.commit_count, 0);
2072        atomic_set(&cache->stats.discard_count, 0);
2073
2074        *result = cache;
2075        return 0;
2076
2077bad:
2078        destroy(cache);
2079        return r;
2080}
2081
2082static int copy_ctr_args(struct cache *cache, int argc, const char **argv)
2083{
2084        unsigned i;
2085        const char **copy;
2086
2087        copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL);
2088        if (!copy)
2089                return -ENOMEM;
2090        for (i = 0; i < argc; i++) {
2091                copy[i] = kstrdup(argv[i], GFP_KERNEL);
2092                if (!copy[i]) {
2093                        while (i--)
2094                                kfree(copy[i]);
2095                        kfree(copy);
2096                        return -ENOMEM;
2097                }
2098        }
2099
2100        cache->nr_ctr_args = argc;
2101        cache->ctr_args = copy;
2102
2103        return 0;
2104}
2105
2106static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
2107{
2108        int r = -EINVAL;
2109        struct cache_args *ca;
2110        struct cache *cache = NULL;
2111
2112        ca = kzalloc(sizeof(*ca), GFP_KERNEL);
2113        if (!ca) {
2114                ti->error = "Error allocating memory for cache";
2115                return -ENOMEM;
2116        }
2117        ca->ti = ti;
2118
2119        r = parse_cache_args(ca, argc, argv, &ti->error);
2120        if (r)
2121                goto out;
2122
2123        r = cache_create(ca, &cache);
2124        if (r)
2125                goto out;
2126
2127        r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3);
2128        if (r) {
2129                destroy(cache);
2130                goto out;
2131        }
2132
2133        ti->private = cache;
2134
2135out:
2136        destroy_cache_args(ca);
2137        return r;
2138}
2139
2140static int cache_map(struct dm_target *ti, struct bio *bio)
2141{
2142        struct cache *cache = ti->private;
2143
2144        int r;
2145        dm_oblock_t block = get_bio_block(cache, bio);
2146        size_t pb_data_size = get_per_bio_data_size(cache);
2147        bool can_migrate = false;
2148        bool discarded_block;
2149        struct dm_bio_prison_cell *cell;
2150        struct policy_result lookup_result;
2151        struct per_bio_data *pb;
2152
2153        if (from_oblock(block) > from_oblock(cache->origin_blocks)) {
2154                /*
2155                 * This can only occur if the io goes to a partial block at
2156                 * the end of the origin device.  We don't cache these.
2157                 * Just remap to the origin and carry on.
2158                 */
2159                remap_to_origin_clear_discard(cache, bio, block);
2160                return DM_MAPIO_REMAPPED;
2161        }
2162
2163        pb = init_per_bio_data(bio, pb_data_size);
2164
2165        if (bio->bi_rw & (REQ_FLUSH | REQ_FUA | REQ_DISCARD)) {
2166                defer_bio(cache, bio);
2167                return DM_MAPIO_SUBMITTED;
2168        }
2169
2170        /*
2171         * Check to see if that block is currently migrating.
2172         */
2173        cell = alloc_prison_cell(cache);
2174        if (!cell) {
2175                defer_bio(cache, bio);
2176                return DM_MAPIO_SUBMITTED;
2177        }
2178
2179        r = bio_detain(cache, block, bio, cell,
2180                       (cell_free_fn) free_prison_cell,
2181                       cache, &cell);
2182        if (r) {
2183                if (r < 0)
2184                        defer_bio(cache, bio);
2185
2186                return DM_MAPIO_SUBMITTED;
2187        }
2188
2189        discarded_block = is_discarded_oblock(cache, block);
2190
2191        r = policy_map(cache->policy, block, false, can_migrate, discarded_block,
2192                       bio, &lookup_result);
2193        if (r == -EWOULDBLOCK) {
2194                cell_defer(cache, cell, true);
2195                return DM_MAPIO_SUBMITTED;
2196
2197        } else if (r) {
2198                DMERR_LIMIT("Unexpected return from cache replacement policy: %d", r);
2199                bio_io_error(bio);
2200                return DM_MAPIO_SUBMITTED;
2201        }
2202
2203        switch (lookup_result.op) {
2204        case POLICY_HIT:
2205                inc_hit_counter(cache, bio);
2206                pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2207
2208                if (is_writethrough_io(cache, bio, lookup_result.cblock))
2209                        remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
2210                else
2211                        remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
2212
2213                cell_defer(cache, cell, false);
2214                break;
2215
2216        case POLICY_MISS:
2217                inc_miss_counter(cache, bio);
2218                pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2219
2220                if (pb->req_nr != 0) {
2221                        /*
2222                         * This is a duplicate writethrough io that is no
2223                         * longer needed because the block has been demoted.
2224                         */
2225                        bio_endio(bio, 0);
2226                        cell_defer(cache, cell, false);
2227                        return DM_MAPIO_SUBMITTED;
2228                } else {
2229                        remap_to_origin_clear_discard(cache, bio, block);
2230                        cell_defer(cache, cell, false);
2231                }
2232                break;
2233
2234        default:
2235                DMERR_LIMIT("%s: erroring bio: unknown policy op: %u", __func__,
2236                            (unsigned) lookup_result.op);
2237                bio_io_error(bio);
2238                return DM_MAPIO_SUBMITTED;
2239        }
2240
2241        return DM_MAPIO_REMAPPED;
2242}
2243
2244static int cache_end_io(struct dm_target *ti, struct bio *bio, int error)
2245{
2246        struct cache *cache = ti->private;
2247        unsigned long flags;
2248        size_t pb_data_size = get_per_bio_data_size(cache);
2249        struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
2250
2251        if (pb->tick) {
2252                policy_tick(cache->policy);
2253
2254                spin_lock_irqsave(&cache->lock, flags);
2255                cache->need_tick_bio = true;
2256                spin_unlock_irqrestore(&cache->lock, flags);
2257        }
2258
2259        check_for_quiesced_migrations(cache, pb);
2260
2261        return 0;
2262}
2263
2264static int write_dirty_bitset(struct cache *cache)
2265{
2266        unsigned i, r;
2267
2268        for (i = 0; i < from_cblock(cache->cache_size); i++) {
2269                r = dm_cache_set_dirty(cache->cmd, to_cblock(i),
2270                                       is_dirty(cache, to_cblock(i)));
2271                if (r)
2272                        return r;
2273        }
2274
2275        return 0;
2276}
2277
2278static int write_discard_bitset(struct cache *cache)
2279{
2280        unsigned i, r;
2281
2282        r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size,
2283                                           cache->discard_nr_blocks);
2284        if (r) {
2285                DMERR("could not resize on-disk discard bitset");
2286                return r;
2287        }
2288
2289        for (i = 0; i < from_dblock(cache->discard_nr_blocks); i++) {
2290                r = dm_cache_set_discard(cache->cmd, to_dblock(i),
2291                                         is_discarded(cache, to_dblock(i)));
2292                if (r)
2293                        return r;
2294        }
2295
2296        return 0;
2297}
2298
2299static int save_hint(void *context, dm_cblock_t cblock, dm_oblock_t oblock,
2300                     uint32_t hint)
2301{
2302        struct cache *cache = context;
2303        return dm_cache_save_hint(cache->cmd, cblock, hint);
2304}
2305
2306static int write_hints(struct cache *cache)
2307{
2308        int r;
2309
2310        r = dm_cache_begin_hints(cache->cmd, cache->policy);
2311        if (r) {
2312                DMERR("dm_cache_begin_hints failed");
2313                return r;
2314        }
2315
2316        r = policy_walk_mappings(cache->policy, save_hint, cache);
2317        if (r)
2318                DMERR("policy_walk_mappings failed");
2319
2320        return r;
2321}
2322
2323/*
2324 * returns true on success
2325 */
2326static bool sync_metadata(struct cache *cache)
2327{
2328        int r1, r2, r3, r4;
2329
2330        r1 = write_dirty_bitset(cache);
2331        if (r1)
2332                DMERR("could not write dirty bitset");
2333
2334        r2 = write_discard_bitset(cache);
2335        if (r2)
2336                DMERR("could not write discard bitset");
2337
2338        save_stats(cache);
2339
2340        r3 = write_hints(cache);
2341        if (r3)
2342                DMERR("could not write hints");
2343
2344        /*
2345         * If writing the above metadata failed, we still commit, but don't
2346         * set the clean shutdown flag.  This will effectively force every
2347         * dirty bit to be set on reload.
2348         */
2349        r4 = dm_cache_commit(cache->cmd, !r1 && !r2 && !r3);
2350        if (r4)
2351                DMERR("could not write cache metadata.  Data loss may occur.");
2352
2353        return !r1 && !r2 && !r3 && !r4;
2354}
2355
2356static void cache_postsuspend(struct dm_target *ti)
2357{
2358        struct cache *cache = ti->private;
2359
2360        start_quiescing(cache);
2361        wait_for_migrations(cache);
2362        stop_worker(cache);
2363        requeue_deferred_io(cache);
2364        stop_quiescing(cache);
2365
2366        (void) sync_metadata(cache);
2367}
2368
2369static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock,
2370                        bool dirty, uint32_t hint, bool hint_valid)
2371{
2372        int r;
2373        struct cache *cache = context;
2374
2375        r = policy_load_mapping(cache->policy, oblock, cblock, hint, hint_valid);
2376        if (r)
2377                return r;
2378
2379        if (dirty)
2380                set_dirty(cache, oblock, cblock);
2381        else
2382                clear_dirty(cache, oblock, cblock);
2383
2384        return 0;
2385}
2386
2387static int load_discard(void *context, sector_t discard_block_size,
2388                        dm_dblock_t dblock, bool discard)
2389{
2390        struct cache *cache = context;
2391
2392        /* FIXME: handle mis-matched block size */
2393
2394        if (discard)
2395                set_discard(cache, dblock);
2396        else
2397                clear_discard(cache, dblock);
2398
2399        return 0;
2400}
2401
2402static int cache_preresume(struct dm_target *ti)
2403{
2404        int r = 0;
2405        struct cache *cache = ti->private;
2406        sector_t actual_cache_size = get_dev_size(cache->cache_dev);
2407        (void) sector_div(actual_cache_size, cache->sectors_per_block);
2408
2409        /*
2410         * Check to see if the cache has resized.
2411         */
2412        if (from_cblock(cache->cache_size) != actual_cache_size || !cache->sized) {
2413                cache->cache_size = to_cblock(actual_cache_size);
2414
2415                r = dm_cache_resize(cache->cmd, cache->cache_size);
2416                if (r) {
2417                        DMERR("could not resize cache metadata");
2418                        return r;
2419                }
2420
2421                cache->sized = true;
2422        }
2423
2424        if (!cache->loaded_mappings) {
2425                r = dm_cache_load_mappings(cache->cmd, cache->policy,
2426                                           load_mapping, cache);
2427                if (r) {
2428                        DMERR("could not load cache mappings");
2429                        return r;
2430                }
2431
2432                cache->loaded_mappings = true;
2433        }
2434
2435        if (!cache->loaded_discards) {
2436                r = dm_cache_load_discards(cache->cmd, load_discard, cache);
2437                if (r) {
2438                        DMERR("could not load origin discards");
2439                        return r;
2440                }
2441
2442                cache->loaded_discards = true;
2443        }
2444
2445        return r;
2446}
2447
2448static void cache_resume(struct dm_target *ti)
2449{
2450        struct cache *cache = ti->private;
2451
2452        cache->need_tick_bio = true;
2453        do_waker(&cache->waker.work);
2454}
2455
2456/*
2457 * Status format:
2458 *
2459 * <#used metadata blocks>/<#total metadata blocks>
2460 * <#read hits> <#read misses> <#write hits> <#write misses>
2461 * <#demotions> <#promotions> <#blocks in cache> <#dirty>
2462 * <#features> <features>*
2463 * <#core args> <core args>
2464 * <#policy args> <policy args>*
2465 */
2466static void cache_status(struct dm_target *ti, status_type_t type,
2467                         unsigned status_flags, char *result, unsigned maxlen)
2468{
2469        int r = 0;
2470        unsigned i;
2471        ssize_t sz = 0;
2472        dm_block_t nr_free_blocks_metadata = 0;
2473        dm_block_t nr_blocks_metadata = 0;
2474        char buf[BDEVNAME_SIZE];
2475        struct cache *cache = ti->private;
2476        dm_cblock_t residency;
2477
2478        switch (type) {
2479        case STATUSTYPE_INFO:
2480                /* Commit to ensure statistics aren't out-of-date */
2481                if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti)) {
2482                        r = dm_cache_commit(cache->cmd, false);
2483                        if (r)
2484                                DMERR("could not commit metadata for accurate status");
2485                }
2486
2487                r = dm_cache_get_free_metadata_block_count(cache->cmd,
2488                                                           &nr_free_blocks_metadata);
2489                if (r) {
2490                        DMERR("could not get metadata free block count");
2491                        goto err;
2492                }
2493
2494                r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata);
2495                if (r) {
2496                        DMERR("could not get metadata device size");
2497                        goto err;
2498                }
2499
2500                residency = policy_residency(cache->policy);
2501
2502                DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
2503                       (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
2504                       (unsigned long long)nr_blocks_metadata,
2505                       (unsigned) atomic_read(&cache->stats.read_hit),
2506                       (unsigned) atomic_read(&cache->stats.read_miss),
2507                       (unsigned) atomic_read(&cache->stats.write_hit),
2508                       (unsigned) atomic_read(&cache->stats.write_miss),
2509                       (unsigned) atomic_read(&cache->stats.demotion),
2510                       (unsigned) atomic_read(&cache->stats.promotion),
2511                       (unsigned long long) from_cblock(residency),
2512                       cache->nr_dirty);
2513
2514                if (cache->features.write_through)
2515                        DMEMIT("1 writethrough ");
2516                else
2517                        DMEMIT("0 ");
2518
2519                DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
2520                if (sz < maxlen) {
2521                        r = policy_emit_config_values(cache->policy, result + sz, maxlen - sz);
2522                        if (r)
2523                                DMERR("policy_emit_config_values returned %d", r);
2524                }
2525
2526                break;
2527
2528        case STATUSTYPE_TABLE:
2529                format_dev_t(buf, cache->metadata_dev->bdev->bd_dev);
2530                DMEMIT("%s ", buf);
2531                format_dev_t(buf, cache->cache_dev->bdev->bd_dev);
2532                DMEMIT("%s ", buf);
2533                format_dev_t(buf, cache->origin_dev->bdev->bd_dev);
2534                DMEMIT("%s", buf);
2535
2536                for (i = 0; i < cache->nr_ctr_args - 1; i++)
2537                        DMEMIT(" %s", cache->ctr_args[i]);
2538                if (cache->nr_ctr_args)
2539                        DMEMIT(" %s", cache->ctr_args[cache->nr_ctr_args - 1]);
2540        }
2541
2542        return;
2543
2544err:
2545        DMEMIT("Error");
2546}
2547
2548/*
2549 * Supports <key> <value>.
2550 *
2551 * The key migration_threshold is supported by the cache target core.
2552 */
2553static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
2554{
2555        struct cache *cache = ti->private;
2556
2557        if (argc != 2)
2558                return -EINVAL;
2559
2560        return set_config_value(cache, argv[0], argv[1]);
2561}
2562
2563static int cache_iterate_devices(struct dm_target *ti,
2564                                 iterate_devices_callout_fn fn, void *data)
2565{
2566        int r = 0;
2567        struct cache *cache = ti->private;
2568
2569        r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data);
2570        if (!r)
2571                r = fn(ti, cache->origin_dev, 0, ti->len, data);
2572
2573        return r;
2574}
2575
2576/*
2577 * We assume I/O is going to the origin (which is the volume
2578 * more likely to have restrictions e.g. by being striped).
2579 * (Looking up the exact location of the data would be expensive
2580 * and could always be out of date by the time the bio is submitted.)
2581 */
2582static int cache_bvec_merge(struct dm_target *ti,
2583                            struct bvec_merge_data *bvm,
2584                            struct bio_vec *biovec, int max_size)
2585{
2586        struct cache *cache = ti->private;
2587        struct request_queue *q = bdev_get_queue(cache->origin_dev->bdev);
2588
2589        if (!q->merge_bvec_fn)
2590                return max_size;
2591
2592        bvm->bi_bdev = cache->origin_dev->bdev;
2593        return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
2594}
2595
2596static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
2597{
2598        /*
2599         * FIXME: these limits may be incompatible with the cache device
2600         */
2601        limits->max_discard_sectors = cache->discard_block_size * 1024;
2602        limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
2603}
2604
2605static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
2606{
2607        struct cache *cache = ti->private;
2608
2609        blk_limits_io_min(limits, 0);
2610        blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
2611        set_discard_limits(cache, limits);
2612}
2613
2614/*----------------------------------------------------------------*/
2615
2616static struct target_type cache_target = {
2617        .name = "cache",
2618        .version = {1, 1, 1},
2619        .module = THIS_MODULE,
2620        .ctr = cache_ctr,
2621        .dtr = cache_dtr,
2622        .map = cache_map,
2623        .end_io = cache_end_io,
2624        .postsuspend = cache_postsuspend,
2625        .preresume = cache_preresume,
2626        .resume = cache_resume,
2627        .status = cache_status,
2628        .message = cache_message,
2629        .iterate_devices = cache_iterate_devices,
2630        .merge = cache_bvec_merge,
2631        .io_hints = cache_io_hints,
2632};
2633
2634static int __init dm_cache_init(void)
2635{
2636        int r;
2637
2638        r = dm_register_target(&cache_target);
2639        if (r) {
2640                DMERR("cache target registration failed: %d", r);
2641                return r;
2642        }
2643
2644        migration_cache = KMEM_CACHE(dm_cache_migration, 0);
2645        if (!migration_cache) {
2646                dm_unregister_target(&cache_target);
2647                return -ENOMEM;
2648        }
2649
2650        return 0;
2651}
2652
2653static void __exit dm_cache_exit(void)
2654{
2655        dm_unregister_target(&cache_target);
2656        kmem_cache_destroy(migration_cache);
2657}
2658
2659module_init(dm_cache_init);
2660module_exit(dm_cache_exit);
2661
2662MODULE_DESCRIPTION(DM_NAME " cache target");
2663MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
2664MODULE_LICENSE("GPL");
2665
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