drivers/md/dm-cache-target.c

   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
  22 DECLARE_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
  40 static 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
  45 static unsigned long *alloc_bitset(unsigned nr_entries)
  46 {
  47         size_t s = bitset_size_in_bytes(nr_entries);
  48         return vzalloc(s);
  49 }
  50
  51 static 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
  57 static void free_bitset(unsigned long *bits)
  58 {
  59         vfree(bits);
  60 }
  61
  62 /*----------------------------------------------------------------*/
  63
  64 /*
  65  * There are a couple of places where we let a bio run, but want to do some
  66  * work before calling its endio function.  We do this by temporarily
  67  * changing the endio fn.
  68  */
  69 struct dm_hook_info {
  70         bio_end_io_t *bi_end_io;
  71         void *bi_private;
  72 };
  73
  74 static void dm_hook_bio(struct dm_hook_info *h, struct bio *bio,
  75                         bio_end_io_t *bi_end_io, void *bi_private)
  76 {
  77         h->bi_end_io = bio->bi_end_io;
  78         h->bi_private = bio->bi_private;
  79
  80         bio->bi_end_io = bi_end_io;
  81         bio->bi_private = bi_private;
  82 }
  83
  84 static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio)
  85 {
  86         bio->bi_end_io = h->bi_end_io;
  87         bio->bi_private = h->bi_private;
  88 }
  89
  90 /*----------------------------------------------------------------*/
  91
  92 #define PRISON_CELLS 1024
  93 #define MIGRATION_POOL_SIZE 128
  94 #define COMMIT_PERIOD HZ
  95 #define MIGRATION_COUNT_WINDOW 10
  96
  97 /*
  98  * The block size of the device holding cache data must be
  99  * between 32KB and 1GB.
 100  */
 101 #define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
 102 #define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
 103
 104 /*
 105  * FIXME: the cache is read/write for the time being.
 106  */
 107 enum cache_metadata_mode {
 108         CM_WRITE,               /* metadata may be changed */
 109         CM_READ_ONLY,           /* metadata may not be changed */
 110 };
 111
 112 enum cache_io_mode {
 113         /*
 114          * Data is written to cached blocks only.  These blocks are marked
 115          * dirty.  If you lose the cache device you will lose data.
 116          * Potential performance increase for both reads and writes.
 117          */
 118         CM_IO_WRITEBACK,
 119
 120         /*
 121          * Data is written to both cache and origin.  Blocks are never
 122          * dirty.  Potential performance benfit for reads only.
 123          */
 124         CM_IO_WRITETHROUGH,
 125
 126         /*
 127          * A degraded mode useful for various cache coherency situations
 128          * (eg, rolling back snapshots).  Reads and writes always go to the
 129          * origin.  If a write goes to a cached oblock, then the cache
 130          * block is invalidated.
 131          */
 132         CM_IO_PASSTHROUGH
 133 };
 134
 135 struct cache_features {
 136         enum cache_metadata_mode mode;
 137         enum cache_io_mode io_mode;
 138 };
 139
 140 struct cache_stats {
 141         atomic_t read_hit;
 142         atomic_t read_miss;
 143         atomic_t write_hit;
 144         atomic_t write_miss;
 145         atomic_t demotion;
 146         atomic_t promotion;
 147         atomic_t copies_avoided;
 148         atomic_t cache_cell_clash;
 149         atomic_t commit_count;
 150         atomic_t discard_count;
 151 };
 152
 153 /*
 154  * Defines a range of cblocks, begin to (end - 1) are in the range.  end is
 155  * the one-past-the-end value.
 156  */
 157 struct cblock_range {
 158         dm_cblock_t begin;
 159         dm_cblock_t end;
 160 };
 161
 162 struct invalidation_request {
 163         struct list_head list;
 164         struct cblock_range *cblocks;
 165
 166         atomic_t complete;
 167         int err;
 168
 169         wait_queue_head_t result_wait;
 170 };
 171
 172 struct cache {
 173         struct dm_target *ti;
 174         struct dm_target_callbacks callbacks;
 175
 176         struct dm_cache_metadata *cmd;
 177
 178         /*
 179          * Metadata is written to this device.
 180          */
 181         struct dm_dev *metadata_dev;
 182
 183         /*
 184          * The slower of the two data devices.  Typically a spindle.
 185          */
 186         struct dm_dev *origin_dev;
 187
 188         /*
 189          * The faster of the two data devices.  Typically an SSD.
 190          */
 191         struct dm_dev *cache_dev;
 192
 193         /*
 194          * Size of the origin device in _complete_ blocks and native sectors.
 195          */
 196         dm_oblock_t origin_blocks;
 197         sector_t origin_sectors;
 198
 199         /*
 200          * Size of the cache device in blocks.
 201          */
 202         dm_cblock_t cache_size;
 203
 204         /*
 205          * Fields for converting from sectors to blocks.
 206          */
 207         uint32_t sectors_per_block;
 208         int sectors_per_block_shift;
 209
 210         spinlock_t lock;
 211         struct bio_list deferred_bios;
 212         struct bio_list deferred_flush_bios;
 213         struct bio_list deferred_writethrough_bios;
 214         struct list_head quiesced_migrations;
 215         struct list_head completed_migrations;
 216         struct list_head need_commit_migrations;
 217         sector_t migration_threshold;
 218         wait_queue_head_t migration_wait;
 219         atomic_t nr_migrations;
 220
 221         wait_queue_head_t quiescing_wait;
 222         atomic_t quiescing;
 223         atomic_t quiescing_ack;
 224
 225         /*
 226          * cache_size entries, dirty if set
 227          */
 228         dm_cblock_t nr_dirty;
 229         unsigned long *dirty_bitset;
 230
 231         /*
 232          * origin_blocks entries, discarded if set.
 233          */
 234         dm_dblock_t discard_nr_blocks;
 235         unsigned long *discard_bitset;
 236         uint32_t discard_block_size; /* a power of 2 times sectors per block */
 237
 238         /*
 239          * Rather than reconstructing the table line for the status we just
 240          * save it and regurgitate.
 241          */
 242         unsigned nr_ctr_args;
 243         const char **ctr_args;
 244
 245         struct dm_kcopyd_client *copier;
 246         struct workqueue_struct *wq;
 247         struct work_struct worker;
 248
 249         struct delayed_work waker;
 250         unsigned long last_commit_jiffies;
 251
 252         struct dm_bio_prison *prison;
 253         struct dm_deferred_set *all_io_ds;
 254
 255         mempool_t *migration_pool;
 256         struct dm_cache_migration *next_migration;
 257
 258         struct dm_cache_policy *policy;
 259         unsigned policy_nr_args;
 260
 261         bool need_tick_bio:1;
 262         bool sized:1;
 263         bool invalidate:1;
 264         bool commit_requested:1;
 265         bool loaded_mappings:1;
 266         bool loaded_discards:1;
 267
 268         /*
 269          * Cache features such as write-through.
 270          */
 271         struct cache_features features;
 272
 273         struct cache_stats stats;
 274
 275         /*
 276          * Invalidation fields.
 277          */
 278         spinlock_t invalidation_lock;
 279         struct list_head invalidation_requests;
 280 };
 281
 282 struct per_bio_data {
 283         bool tick:1;
 284         unsigned req_nr:2;
 285         struct dm_deferred_entry *all_io_entry;
 286
 287         /*
 288          * writethrough fields.  These MUST remain at the end of this
 289          * structure and the 'cache' member must be the first as it
 290          * is used to determine the offset of the writethrough fields.
 291          */
 292         struct cache *cache;
 293         dm_cblock_t cblock;
 294         struct dm_hook_info hook_info;
 295         struct dm_bio_details bio_details;
 296 };
 297
 298 struct dm_cache_migration {
 299         struct list_head list;
 300         struct cache *cache;
 301
 302         unsigned long start_jiffies;
 303         dm_oblock_t old_oblock;
 304         dm_oblock_t new_oblock;
 305         dm_cblock_t cblock;
 306
 307         bool err:1;
 308         bool writeback:1;
 309         bool demote:1;
 310         bool promote:1;
 311         bool requeue_holder:1;
 312         bool invalidate:1;
 313
 314         struct dm_bio_prison_cell *old_ocell;
 315         struct dm_bio_prison_cell *new_ocell;
 316 };
 317
 318 /*
 319  * Processing a bio in the worker thread may require these memory
 320  * allocations.  We prealloc to avoid deadlocks (the same worker thread
 321  * frees them back to the mempool).
 322  */
 323 struct prealloc {
 324         struct dm_cache_migration *mg;
 325         struct dm_bio_prison_cell *cell1;
 326         struct dm_bio_prison_cell *cell2;
 327 };
 328
 329 static void wake_worker(struct cache *cache)
 330 {
 331         queue_work(cache->wq, &cache->worker);
 332 }
 333
 334 /*----------------------------------------------------------------*/
 335
 336 static struct dm_bio_prison_cell *alloc_prison_cell(struct cache *cache)
 337 {
 338         /* FIXME: change to use a local slab. */
 339         return dm_bio_prison_alloc_cell(cache->prison, GFP_NOWAIT);
 340 }
 341
 342 static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell *cell)
 343 {
 344         dm_bio_prison_free_cell(cache->prison, cell);
 345 }
 346
 347 static int prealloc_data_structs(struct cache *cache, struct prealloc *p)
 348 {
 349         if (!p->mg) {
 350                 p->mg = mempool_alloc(cache->migration_pool, GFP_NOWAIT);
 351                 if (!p->mg)
 352                         return -ENOMEM;
 353         }
 354
 355         if (!p->cell1) {
 356                 p->cell1 = alloc_prison_cell(cache);
 357                 if (!p->cell1)
 358                         return -ENOMEM;
 359         }
 360
 361         if (!p->cell2) {
 362                 p->cell2 = alloc_prison_cell(cache);
 363                 if (!p->cell2)
 364                         return -ENOMEM;
 365         }
 366
 367         return 0;
 368 }
 369
 370 static void prealloc_free_structs(struct cache *cache, struct prealloc *p)
 371 {
 372         if (p->cell2)
 373                 free_prison_cell(cache, p->cell2);
 374
 375         if (p->cell1)
 376                 free_prison_cell(cache, p->cell1);
 377
 378         if (p->mg)
 379                 mempool_free(p->mg, cache->migration_pool);
 380 }
 381
 382 static struct dm_cache_migration *prealloc_get_migration(struct prealloc *p)
 383 {
 384         struct dm_cache_migration *mg = p->mg;
 385
 386         BUG_ON(!mg);
 387         p->mg = NULL;
 388
 389         return mg;
 390 }
 391
 392 /*
 393  * You must have a cell within the prealloc struct to return.  If not this
 394  * function will BUG() rather than returning NULL.
 395  */
 396 static struct dm_bio_prison_cell *prealloc_get_cell(struct prealloc *p)
 397 {
 398         struct dm_bio_prison_cell *r = NULL;
 399
 400         if (p->cell1) {
 401                 r = p->cell1;
 402                 p->cell1 = NULL;
 403
 404         } else if (p->cell2) {
 405                 r = p->cell2;
 406                 p->cell2 = NULL;
 407         } else
 408                 BUG();
 409
 410         return r;
 411 }
 412
 413 /*
 414  * You can't have more than two cells in a prealloc struct.  BUG() will be
 415  * called if you try and overfill.
 416  */
 417 static void prealloc_put_cell(struct prealloc *p, struct dm_bio_prison_cell *cell)
 418 {
 419         if (!p->cell2)
 420                 p->cell2 = cell;
 421
 422         else if (!p->cell1)
 423                 p->cell1 = cell;
 424
 425         else
 426                 BUG();
 427 }
 428
 429 /*----------------------------------------------------------------*/
 430
 431 static void build_key(dm_oblock_t oblock, struct dm_cell_key *key)
 432 {
 433         key->virtual = 0;
 434         key->dev = 0;
 435         key->block = from_oblock(oblock);
 436 }
 437
 438 /*
 439  * The caller hands in a preallocated cell, and a free function for it.
 440  * The cell will be freed if there's an error, or if it wasn't used because
 441  * a cell with that key already exists.
 442  */
 443 typedef void (*cell_free_fn)(void *context, struct dm_bio_prison_cell *cell);
 444
 445 static int bio_detain(struct cache *cache, dm_oblock_t oblock,
 446                       struct bio *bio, struct dm_bio_prison_cell *cell_prealloc,
 447                       cell_free_fn free_fn, void *free_context,
 448                       struct dm_bio_prison_cell **cell_result)
 449 {
 450         int r;
 451         struct dm_cell_key key;
 452
 453         build_key(oblock, &key);
 454         r = dm_bio_detain(cache->prison, &key, bio, cell_prealloc, cell_result);
 455         if (r)
 456                 free_fn(free_context, cell_prealloc);
 457
 458         return r;
 459 }
 460
 461 static int get_cell(struct cache *cache,
 462                     dm_oblock_t oblock,
 463                     struct prealloc *structs,
 464                     struct dm_bio_prison_cell **cell_result)
 465 {
 466         int r;
 467         struct dm_cell_key key;
 468         struct dm_bio_prison_cell *cell_prealloc;
 469
 470         cell_prealloc = prealloc_get_cell(structs);
 471
 472         build_key(oblock, &key);
 473         r = dm_get_cell(cache->prison, &key, cell_prealloc, cell_result);
 474         if (r)
 475                 prealloc_put_cell(structs, cell_prealloc);
 476
 477         return r;
 478 }
 479
 480 /*----------------------------------------------------------------*/
 481
 482 static bool is_dirty(struct cache *cache, dm_cblock_t b)
 483 {
 484         return test_bit(from_cblock(b), cache->dirty_bitset);
 485 }
 486
 487 static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
 488 {
 489         if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
 490                 cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1);
 491                 policy_set_dirty(cache->policy, oblock);
 492         }
 493 }
 494
 495 static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
 496 {
 497         if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
 498                 policy_clear_dirty(cache->policy, oblock);
 499                 cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1);
 500                 if (!from_cblock(cache->nr_dirty))
 501                         dm_table_event(cache->ti->table);
 502         }
 503 }
 504
 505 /*----------------------------------------------------------------*/
 506
 507 static bool block_size_is_power_of_two(struct cache *cache)
 508 {
 509         return cache->sectors_per_block_shift >= 0;
 510 }
 511
 512 /* gcc on ARM generates spurious references to __udivdi3 and __umoddi3 */
 513 #if defined(CONFIG_ARM) && __GNUC__ == 4 && __GNUC_MINOR__ <= 6
 514 __always_inline
 515 #endif
 516 static dm_block_t block_div(dm_block_t b, uint32_t n)
 517 {
 518         do_div(b, n);
 519
 520         return b;
 521 }
 522
 523 static dm_dblock_t oblock_to_dblock(struct cache *cache, dm_oblock_t oblock)
 524 {
 525         uint32_t discard_blocks = cache->discard_block_size;
 526         dm_block_t b = from_oblock(oblock);
 527
 528         if (!block_size_is_power_of_two(cache))
 529                 discard_blocks = discard_blocks / cache->sectors_per_block;
 530         else
 531                 discard_blocks >>= cache->sectors_per_block_shift;
 532
 533         b = block_div(b, discard_blocks);
 534
 535         return to_dblock(b);
 536 }
 537
 538 static void set_discard(struct cache *cache, dm_dblock_t b)
 539 {
 540         unsigned long flags;
 541
 542         atomic_inc(&cache->stats.discard_count);
 543
 544         spin_lock_irqsave(&cache->lock, flags);
 545         set_bit(from_dblock(b), cache->discard_bitset);
 546         spin_unlock_irqrestore(&cache->lock, flags);
 547 }
 548
 549 static void clear_discard(struct cache *cache, dm_dblock_t b)
 550 {
 551         unsigned long flags;
 552
 553         spin_lock_irqsave(&cache->lock, flags);
 554         clear_bit(from_dblock(b), cache->discard_bitset);
 555         spin_unlock_irqrestore(&cache->lock, flags);
 556 }
 557
 558 static bool is_discarded(struct cache *cache, dm_dblock_t b)
 559 {
 560         int r;
 561         unsigned long flags;
 562
 563         spin_lock_irqsave(&cache->lock, flags);
 564         r = test_bit(from_dblock(b), cache->discard_bitset);
 565         spin_unlock_irqrestore(&cache->lock, flags);
 566
 567         return r;
 568 }
 569
 570 static bool is_discarded_oblock(struct cache *cache, dm_oblock_t b)
 571 {
 572         int r;
 573         unsigned long flags;
 574
 575         spin_lock_irqsave(&cache->lock, flags);
 576         r = test_bit(from_dblock(oblock_to_dblock(cache, b)),
 577                      cache->discard_bitset);
 578         spin_unlock_irqrestore(&cache->lock, flags);
 579
 580         return r;
 581 }
 582
 583 /*----------------------------------------------------------------*/
 584
 585 static void load_stats(struct cache *cache)
 586 {
 587         struct dm_cache_statistics stats;
 588
 589         dm_cache_metadata_get_stats(cache->cmd, &stats);
 590         atomic_set(&cache->stats.read_hit, stats.read_hits);
 591         atomic_set(&cache->stats.read_miss, stats.read_misses);
 592         atomic_set(&cache->stats.write_hit, stats.write_hits);
 593         atomic_set(&cache->stats.write_miss, stats.write_misses);
 594 }
 595
 596 static void save_stats(struct cache *cache)
 597 {
 598         struct dm_cache_statistics stats;
 599
 600         stats.read_hits = atomic_read(&cache->stats.read_hit);
 601         stats.read_misses = atomic_read(&cache->stats.read_miss);
 602         stats.write_hits = atomic_read(&cache->stats.write_hit);
 603         stats.write_misses = atomic_read(&cache->stats.write_miss);
 604
 605         dm_cache_metadata_set_stats(cache->cmd, &stats);
 606 }
 607
 608 /*----------------------------------------------------------------
 609  * Per bio data
 610  *--------------------------------------------------------------*/
 611
 612 /*
 613  * If using writeback, leave out struct per_bio_data's writethrough fields.
 614  */
 615 #define PB_DATA_SIZE_WB (offsetof(struct per_bio_data, cache))
 616 #define PB_DATA_SIZE_WT (sizeof(struct per_bio_data))
 617
 618 static bool writethrough_mode(struct cache_features *f)
 619 {
 620         return f->io_mode == CM_IO_WRITETHROUGH;
 621 }
 622
 623 static bool writeback_mode(struct cache_features *f)
 624 {
 625         return f->io_mode == CM_IO_WRITEBACK;
 626 }
 627
 628 static bool passthrough_mode(struct cache_features *f)
 629 {
 630         return f->io_mode == CM_IO_PASSTHROUGH;
 631 }
 632
 633 static size_t get_per_bio_data_size(struct cache *cache)
 634 {
 635         return writethrough_mode(&cache->features) ? PB_DATA_SIZE_WT : PB_DATA_SIZE_WB;
 636 }
 637
 638 static struct per_bio_data *get_per_bio_data(struct bio *bio, size_t data_size)
 639 {
 640         struct per_bio_data *pb = dm_per_bio_data(bio, data_size);
 641         BUG_ON(!pb);
 642         return pb;
 643 }
 644
 645 static struct per_bio_data *init_per_bio_data(struct bio *bio, size_t data_size)
 646 {
 647         struct per_bio_data *pb = get_per_bio_data(bio, data_size);
 648
 649         pb->tick = false;
 650         pb->req_nr = dm_bio_get_target_bio_nr(bio);
 651         pb->all_io_entry = NULL;
 652
 653         return pb;
 654 }
 655
 656 /*----------------------------------------------------------------
 657  * Remapping
 658  *--------------------------------------------------------------*/
 659 static void remap_to_origin(struct cache *cache, struct bio *bio)
 660 {
 661         bio->bi_bdev = cache->origin_dev->bdev;
 662 }
 663
 664 static void remap_to_cache(struct cache *cache, struct bio *bio,
 665                            dm_cblock_t cblock)
 666 {
 667         sector_t bi_sector = bio->bi_iter.bi_sector;
 668
 669         bio->bi_bdev = cache->cache_dev->bdev;
 670         if (!block_size_is_power_of_two(cache))
 671                 bio->bi_iter.bi_sector =
 672                         (from_cblock(cblock) * cache->sectors_per_block) +
 673                         sector_div(bi_sector, cache->sectors_per_block);
 674         else
 675                 bio->bi_iter.bi_sector =
 676                         (from_cblock(cblock) << cache->sectors_per_block_shift) |
 677                         (bi_sector & (cache->sectors_per_block - 1));
 678 }
 679
 680 static void check_if_tick_bio_needed(struct cache *cache, struct bio *bio)
 681 {
 682         unsigned long flags;
 683         size_t pb_data_size = get_per_bio_data_size(cache);
 684         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
 685
 686         spin_lock_irqsave(&cache->lock, flags);
 687         if (cache->need_tick_bio &&
 688             !(bio->bi_rw & (REQ_FUA | REQ_FLUSH | REQ_DISCARD))) {
 689                 pb->tick = true;
 690                 cache->need_tick_bio = false;
 691         }
 692         spin_unlock_irqrestore(&cache->lock, flags);
 693 }
 694
 695 static void remap_to_origin_clear_discard(struct cache *cache, struct bio *bio,
 696                                   dm_oblock_t oblock)
 697 {
 698         check_if_tick_bio_needed(cache, bio);
 699         remap_to_origin(cache, bio);
 700         if (bio_data_dir(bio) == WRITE)
 701                 clear_discard(cache, oblock_to_dblock(cache, oblock));
 702 }
 703
 704 static void remap_to_cache_dirty(struct cache *cache, struct bio *bio,
 705                                  dm_oblock_t oblock, dm_cblock_t cblock)
 706 {
 707         check_if_tick_bio_needed(cache, bio);
 708         remap_to_cache(cache, bio, cblock);
 709         if (bio_data_dir(bio) == WRITE) {
 710                 set_dirty(cache, oblock, cblock);
 711                 clear_discard(cache, oblock_to_dblock(cache, oblock));
 712         }
 713 }
 714
 715 static dm_oblock_t get_bio_block(struct cache *cache, struct bio *bio)
 716 {
 717         sector_t block_nr = bio->bi_iter.bi_sector;
 718
 719         if (!block_size_is_power_of_two(cache))
 720                 (void) sector_div(block_nr, cache->sectors_per_block);
 721         else
 722                 block_nr >>= cache->sectors_per_block_shift;
 723
 724         return to_oblock(block_nr);
 725 }
 726
 727 static int bio_triggers_commit(struct cache *cache, struct bio *bio)
 728 {
 729         return bio->bi_rw & (REQ_FLUSH | REQ_FUA);
 730 }
 731
 732 static void issue(struct cache *cache, struct bio *bio)
 733 {
 734         unsigned long flags;
 735
 736         if (!bio_triggers_commit(cache, bio)) {
 737                 generic_make_request(bio);
 738                 return;
 739         }
 740
 741         /*
 742          * Batch together any bios that trigger commits and then issue a
 743          * single commit for them in do_worker().
 744          */
 745         spin_lock_irqsave(&cache->lock, flags);
 746         cache->commit_requested = true;
 747         bio_list_add(&cache->deferred_flush_bios, bio);
 748         spin_unlock_irqrestore(&cache->lock, flags);
 749 }
 750
 751 static void defer_writethrough_bio(struct cache *cache, struct bio *bio)
 752 {
 753         unsigned long flags;
 754
 755         spin_lock_irqsave(&cache->lock, flags);
 756         bio_list_add(&cache->deferred_writethrough_bios, bio);
 757         spin_unlock_irqrestore(&cache->lock, flags);
 758
 759         wake_worker(cache);
 760 }
 761
 762 static void writethrough_endio(struct bio *bio, int err)
 763 {
 764         struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
 765
 766         dm_unhook_bio(&pb->hook_info, bio);
 767
 768         /*
 769          * Must bump bi_remaining to allow bio to complete with
 770          * restored bi_end_io.
 771          */
 772         atomic_inc(&bio->bi_remaining);
 773
 774         if (err) {
 775                 bio_endio(bio, err);
 776                 return;
 777         }
 778
 779         dm_bio_restore(&pb->bio_details, bio);
 780         remap_to_cache(pb->cache, bio, pb->cblock);
 781
 782         /*
 783          * We can't issue this bio directly, since we're in interrupt
 784          * context.  So it gets put on a bio list for processing by the
 785          * worker thread.
 786          */
 787         defer_writethrough_bio(pb->cache, bio);
 788 }
 789
 790 /*
 791  * When running in writethrough mode we need to send writes to clean blocks
 792  * to both the cache and origin devices.  In future we'd like to clone the
 793  * bio and send them in parallel, but for now we're doing them in
 794  * series as this is easier.
 795  */
 796 static void remap_to_origin_then_cache(struct cache *cache, struct bio *bio,
 797                                        dm_oblock_t oblock, dm_cblock_t cblock)
 798 {
 799         struct per_bio_data *pb = get_per_bio_data(bio, PB_DATA_SIZE_WT);
 800
 801         pb->cache = cache;
 802         pb->cblock = cblock;
 803         dm_hook_bio(&pb->hook_info, bio, writethrough_endio, NULL);
 804         dm_bio_record(&pb->bio_details, bio);
 805
 806         remap_to_origin_clear_discard(pb->cache, bio, oblock);
 807 }
 808
 809 /*----------------------------------------------------------------
 810  * Migration processing
 811  *
 812  * Migration covers moving data from the origin device to the cache, or
 813  * vice versa.
 814  *--------------------------------------------------------------*/
 815 static void free_migration(struct dm_cache_migration *mg)
 816 {
 817         mempool_free(mg, mg->cache->migration_pool);
 818 }
 819
 820 static void inc_nr_migrations(struct cache *cache)
 821 {
 822         atomic_inc(&cache->nr_migrations);
 823 }
 824
 825 static void dec_nr_migrations(struct cache *cache)
 826 {
 827         atomic_dec(&cache->nr_migrations);
 828
 829         /*
 830          * Wake the worker in case we're suspending the target.
 831          */
 832         wake_up(&cache->migration_wait);
 833 }
 834
 835 static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
 836                          bool holder)
 837 {
 838         (holder ? dm_cell_release : dm_cell_release_no_holder)
 839                 (cache->prison, cell, &cache->deferred_bios);
 840         free_prison_cell(cache, cell);
 841 }
 842
 843 static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
 844                        bool holder)
 845 {
 846         unsigned long flags;
 847
 848         spin_lock_irqsave(&cache->lock, flags);
 849         __cell_defer(cache, cell, holder);
 850         spin_unlock_irqrestore(&cache->lock, flags);
 851
 852         wake_worker(cache);
 853 }
 854
 855 static void cleanup_migration(struct dm_cache_migration *mg)
 856 {
 857         struct cache *cache = mg->cache;
 858         free_migration(mg);
 859         dec_nr_migrations(cache);
 860 }
 861
 862 static void migration_failure(struct dm_cache_migration *mg)
 863 {
 864         struct cache *cache = mg->cache;
 865
 866         if (mg->writeback) {
 867                 DMWARN_LIMIT("writeback failed; couldn't copy block");
 868                 set_dirty(cache, mg->old_oblock, mg->cblock);
 869                 cell_defer(cache, mg->old_ocell, false);
 870
 871         } else if (mg->demote) {
 872                 DMWARN_LIMIT("demotion failed; couldn't copy block");
 873                 policy_force_mapping(cache->policy, mg->new_oblock, mg->old_oblock);
 874
 875                 cell_defer(cache, mg->old_ocell, mg->promote ? false : true);
 876                 if (mg->promote)
 877                         cell_defer(cache, mg->new_ocell, true);
 878         } else {
 879                 DMWARN_LIMIT("promotion failed; couldn't copy block");
 880                 policy_remove_mapping(cache->policy, mg->new_oblock);
 881                 cell_defer(cache, mg->new_ocell, true);
 882         }
 883
 884         cleanup_migration(mg);
 885 }
 886
 887 static void migration_success_pre_commit(struct dm_cache_migration *mg)
 888 {
 889         unsigned long flags;
 890         struct cache *cache = mg->cache;
 891
 892         if (mg->writeback) {
 893                 cell_defer(cache, mg->old_ocell, false);
 894                 clear_dirty(cache, mg->old_oblock, mg->cblock);
 895                 cleanup_migration(mg);
 896                 return;
 897
 898         } else if (mg->demote) {
 899                 if (dm_cache_remove_mapping(cache->cmd, mg->cblock)) {
 900                         DMWARN_LIMIT("demotion failed; couldn't update on disk metadata");
 901                         policy_force_mapping(cache->policy, mg->new_oblock,
 902                                              mg->old_oblock);
 903                         if (mg->promote)
 904                                 cell_defer(cache, mg->new_ocell, true);
 905                         cleanup_migration(mg);
 906                         return;
 907                 }
 908         } else {
 909                 if (dm_cache_insert_mapping(cache->cmd, mg->cblock, mg->new_oblock)) {
 910                         DMWARN_LIMIT("promotion failed; couldn't update on disk metadata");
 911                         policy_remove_mapping(cache->policy, mg->new_oblock);
 912                         cleanup_migration(mg);
 913                         return;
 914                 }
 915         }
 916
 917         spin_lock_irqsave(&cache->lock, flags);
 918         list_add_tail(&mg->list, &cache->need_commit_migrations);
 919         cache->commit_requested = true;
 920         spin_unlock_irqrestore(&cache->lock, flags);
 921 }
 922
 923 static void migration_success_post_commit(struct dm_cache_migration *mg)
 924 {
 925         unsigned long flags;
 926         struct cache *cache = mg->cache;
 927
 928         if (mg->writeback) {
 929                 DMWARN("writeback unexpectedly triggered commit");
 930                 return;
 931
 932         } else if (mg->demote) {
 933                 cell_defer(cache, mg->old_ocell, mg->promote ? false : true);
 934
 935                 if (mg->promote) {
 936                         mg->demote = false;
 937
 938                         spin_lock_irqsave(&cache->lock, flags);
 939                         list_add_tail(&mg->list, &cache->quiesced_migrations);
 940                         spin_unlock_irqrestore(&cache->lock, flags);
 941
 942                 } else {
 943                         if (mg->invalidate)
 944                                 policy_remove_mapping(cache->policy, mg->old_oblock);
 945                         cleanup_migration(mg);
 946                 }
 947
 948         } else {
 949                 if (mg->requeue_holder)
 950                         cell_defer(cache, mg->new_ocell, true);
 951                 else {
 952                         bio_endio(mg->new_ocell->holder, 0);
 953                         cell_defer(cache, mg->new_ocell, false);
 954                 }
 955                 clear_dirty(cache, mg->new_oblock, mg->cblock);
 956                 cleanup_migration(mg);
 957         }
 958 }
 959
 960 static void copy_complete(int read_err, unsigned long write_err, void *context)
 961 {
 962         unsigned long flags;
 963         struct dm_cache_migration *mg = (struct dm_cache_migration *) context;
 964         struct cache *cache = mg->cache;
 965
 966         if (read_err || write_err)
 967                 mg->err = true;
 968
 969         spin_lock_irqsave(&cache->lock, flags);
 970         list_add_tail(&mg->list, &cache->completed_migrations);
 971         spin_unlock_irqrestore(&cache->lock, flags);
 972
 973         wake_worker(cache);
 974 }
 975
 976 static void issue_copy_real(struct dm_cache_migration *mg)
 977 {
 978         int r;
 979         struct dm_io_region o_region, c_region;
 980         struct cache *cache = mg->cache;
 981
 982         o_region.bdev = cache->origin_dev->bdev;
 983         o_region.count = cache->sectors_per_block;
 984
 985         c_region.bdev = cache->cache_dev->bdev;
 986         c_region.sector = from_cblock(mg->cblock) * cache->sectors_per_block;
 987         c_region.count = cache->sectors_per_block;
 988
 989         if (mg->writeback || mg->demote) {
 990                 /* demote */
 991                 o_region.sector = from_oblock(mg->old_oblock) * cache->sectors_per_block;
 992                 r = dm_kcopyd_copy(cache->copier, &c_region, 1, &o_region, 0, copy_complete, mg);
 993         } else {
 994                 /* promote */
 995                 o_region.sector = from_oblock(mg->new_oblock) * cache->sectors_per_block;
 996                 r = dm_kcopyd_copy(cache->copier, &o_region, 1, &c_region, 0, copy_complete, mg);
 997         }
 998
 999         if (r < 0) {
1000                 DMERR_LIMIT("issuing migration failed");
1001                 migration_failure(mg);
1002         }
1003 }
1004
1005 static void overwrite_endio(struct bio *bio, int err)
1006 {
1007         struct dm_cache_migration *mg = bio->bi_private;
1008         struct cache *cache = mg->cache;
1009         size_t pb_data_size = get_per_bio_data_size(cache);
1010         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1011         unsigned long flags;
1012
1013         if (err)
1014                 mg->err = true;
1015
1016         spin_lock_irqsave(&cache->lock, flags);
1017         list_add_tail(&mg->list, &cache->completed_migrations);
1018         dm_unhook_bio(&pb->hook_info, bio);
1019         mg->requeue_holder = false;
1020         spin_unlock_irqrestore(&cache->lock, flags);
1021
1022         wake_worker(cache);
1023 }
1024
1025 static void issue_overwrite(struct dm_cache_migration *mg, struct bio *bio)
1026 {
1027         size_t pb_data_size = get_per_bio_data_size(mg->cache);
1028         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1029
1030         dm_hook_bio(&pb->hook_info, bio, overwrite_endio, mg);
1031         remap_to_cache_dirty(mg->cache, bio, mg->new_oblock, mg->cblock);
1032         generic_make_request(bio);
1033 }
1034
1035 static bool bio_writes_complete_block(struct cache *cache, struct bio *bio)
1036 {
1037         return (bio_data_dir(bio) == WRITE) &&
1038                 (bio->bi_iter.bi_size == (cache->sectors_per_block << SECTOR_SHIFT));
1039 }
1040
1041 static void avoid_copy(struct dm_cache_migration *mg)
1042 {
1043         atomic_inc(&mg->cache->stats.copies_avoided);
1044         migration_success_pre_commit(mg);
1045 }
1046
1047 static void issue_copy(struct dm_cache_migration *mg)
1048 {
1049         bool avoid;
1050         struct cache *cache = mg->cache;
1051
1052         if (mg->writeback || mg->demote)
1053                 avoid = !is_dirty(cache, mg->cblock) ||
1054                         is_discarded_oblock(cache, mg->old_oblock);
1055         else {
1056                 struct bio *bio = mg->new_ocell->holder;
1057
1058                 avoid = is_discarded_oblock(cache, mg->new_oblock);
1059
1060                 if (!avoid && bio_writes_complete_block(cache, bio)) {
1061                         issue_overwrite(mg, bio);
1062                         return;
1063                 }
1064         }
1065
1066         avoid ? avoid_copy(mg) : issue_copy_real(mg);
1067 }
1068
1069 static void complete_migration(struct dm_cache_migration *mg)
1070 {
1071         if (mg->err)
1072                 migration_failure(mg);
1073         else
1074                 migration_success_pre_commit(mg);
1075 }
1076
1077 static void process_migrations(struct cache *cache, struct list_head *head,
1078                                void (*fn)(struct dm_cache_migration *))
1079 {
1080         unsigned long flags;
1081         struct list_head list;
1082         struct dm_cache_migration *mg, *tmp;
1083
1084         INIT_LIST_HEAD(&list);
1085         spin_lock_irqsave(&cache->lock, flags);
1086         list_splice_init(head, &list);
1087         spin_unlock_irqrestore(&cache->lock, flags);
1088
1089         list_for_each_entry_safe(mg, tmp, &list, list)
1090                 fn(mg);
1091 }
1092
1093 static void __queue_quiesced_migration(struct dm_cache_migration *mg)
1094 {
1095         list_add_tail(&mg->list, &mg->cache->quiesced_migrations);
1096 }
1097
1098 static void queue_quiesced_migration(struct dm_cache_migration *mg)
1099 {
1100         unsigned long flags;
1101         struct cache *cache = mg->cache;
1102
1103         spin_lock_irqsave(&cache->lock, flags);
1104         __queue_quiesced_migration(mg);
1105         spin_unlock_irqrestore(&cache->lock, flags);
1106
1107         wake_worker(cache);
1108 }
1109
1110 static void queue_quiesced_migrations(struct cache *cache, struct list_head *work)
1111 {
1112         unsigned long flags;
1113         struct dm_cache_migration *mg, *tmp;
1114
1115         spin_lock_irqsave(&cache->lock, flags);
1116         list_for_each_entry_safe(mg, tmp, work, list)
1117                 __queue_quiesced_migration(mg);
1118         spin_unlock_irqrestore(&cache->lock, flags);
1119
1120         wake_worker(cache);
1121 }
1122
1123 static void check_for_quiesced_migrations(struct cache *cache,
1124                                           struct per_bio_data *pb)
1125 {
1126         struct list_head work;
1127
1128         if (!pb->all_io_entry)
1129                 return;
1130
1131         INIT_LIST_HEAD(&work);
1132         if (pb->all_io_entry)
1133                 dm_deferred_entry_dec(pb->all_io_entry, &work);
1134
1135         if (!list_empty(&work))
1136                 queue_quiesced_migrations(cache, &work);
1137 }
1138
1139 static void quiesce_migration(struct dm_cache_migration *mg)
1140 {
1141         if (!dm_deferred_set_add_work(mg->cache->all_io_ds, &mg->list))
1142                 queue_quiesced_migration(mg);
1143 }
1144
1145 static void promote(struct cache *cache, struct prealloc *structs,
1146                     dm_oblock_t oblock, dm_cblock_t cblock,
1147                     struct dm_bio_prison_cell *cell)
1148 {
1149         struct dm_cache_migration *mg = prealloc_get_migration(structs);
1150
1151         mg->err = false;
1152         mg->writeback = false;
1153         mg->demote = false;
1154         mg->promote = true;
1155         mg->requeue_holder = true;
1156         mg->invalidate = false;
1157         mg->cache = cache;
1158         mg->new_oblock = oblock;
1159         mg->cblock = cblock;
1160         mg->old_ocell = NULL;
1161         mg->new_ocell = cell;
1162         mg->start_jiffies = jiffies;
1163
1164         inc_nr_migrations(cache);
1165         quiesce_migration(mg);
1166 }
1167
1168 static void writeback(struct cache *cache, struct prealloc *structs,
1169                       dm_oblock_t oblock, dm_cblock_t cblock,
1170                       struct dm_bio_prison_cell *cell)
1171 {
1172         struct dm_cache_migration *mg = prealloc_get_migration(structs);
1173
1174         mg->err = false;
1175         mg->writeback = true;
1176         mg->demote = false;
1177         mg->promote = false;
1178         mg->requeue_holder = true;
1179         mg->invalidate = false;
1180         mg->cache = cache;
1181         mg->old_oblock = oblock;
1182         mg->cblock = cblock;
1183         mg->old_ocell = cell;
1184         mg->new_ocell = NULL;
1185         mg->start_jiffies = jiffies;
1186
1187         inc_nr_migrations(cache);
1188         quiesce_migration(mg);
1189 }
1190
1191 static void demote_then_promote(struct cache *cache, struct prealloc *structs,
1192                                 dm_oblock_t old_oblock, dm_oblock_t new_oblock,
1193                                 dm_cblock_t cblock,
1194                                 struct dm_bio_prison_cell *old_ocell,
1195                                 struct dm_bio_prison_cell *new_ocell)
1196 {
1197         struct dm_cache_migration *mg = prealloc_get_migration(structs);
1198
1199         mg->err = false;
1200         mg->writeback = false;
1201         mg->demote = true;
1202         mg->promote = true;
1203         mg->requeue_holder = true;
1204         mg->invalidate = false;
1205         mg->cache = cache;
1206         mg->old_oblock = old_oblock;
1207         mg->new_oblock = new_oblock;
1208         mg->cblock = cblock;
1209         mg->old_ocell = old_ocell;
1210         mg->new_ocell = new_ocell;
1211         mg->start_jiffies = jiffies;
1212
1213         inc_nr_migrations(cache);
1214         quiesce_migration(mg);
1215 }
1216
1217 /*
1218  * Invalidate a cache entry.  No writeback occurs; any changes in the cache
1219  * block are thrown away.
1220  */
1221 static void invalidate(struct cache *cache, struct prealloc *structs,
1222                        dm_oblock_t oblock, dm_cblock_t cblock,
1223                        struct dm_bio_prison_cell *cell)
1224 {
1225         struct dm_cache_migration *mg = prealloc_get_migration(structs);
1226
1227         mg->err = false;
1228         mg->writeback = false;
1229         mg->demote = true;
1230         mg->promote = false;
1231         mg->requeue_holder = true;
1232         mg->invalidate = true;
1233         mg->cache = cache;
1234         mg->old_oblock = oblock;
1235         mg->cblock = cblock;
1236         mg->old_ocell = cell;
1237         mg->new_ocell = NULL;
1238         mg->start_jiffies = jiffies;
1239
1240         inc_nr_migrations(cache);
1241         quiesce_migration(mg);
1242 }
1243
1244 /*----------------------------------------------------------------
1245  * bio processing
1246  *--------------------------------------------------------------*/
1247 static void defer_bio(struct cache *cache, struct bio *bio)
1248 {
1249         unsigned long flags;
1250
1251         spin_lock_irqsave(&cache->lock, flags);
1252         bio_list_add(&cache->deferred_bios, bio);
1253         spin_unlock_irqrestore(&cache->lock, flags);
1254
1255         wake_worker(cache);
1256 }
1257
1258 static void process_flush_bio(struct cache *cache, struct bio *bio)
1259 {
1260         size_t pb_data_size = get_per_bio_data_size(cache);
1261         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1262
1263         BUG_ON(bio->bi_iter.bi_size);
1264         if (!pb->req_nr)
1265                 remap_to_origin(cache, bio);
1266         else
1267                 remap_to_cache(cache, bio, 0);
1268
1269         issue(cache, bio);
1270 }
1271
1272 /*
1273  * People generally discard large parts of a device, eg, the whole device
1274  * when formatting.  Splitting these large discards up into cache block
1275  * sized ios and then quiescing (always neccessary for discard) takes too
1276  * long.
1277  *
1278  * We keep it simple, and allow any size of discard to come in, and just
1279  * mark off blocks on the discard bitset.  No passdown occurs!
1280  *
1281  * To implement passdown we need to change the bio_prison such that a cell
1282  * can have a key that spans many blocks.
1283  */
1284 static void process_discard_bio(struct cache *cache, struct bio *bio)
1285 {
1286         dm_block_t start_block = dm_sector_div_up(bio->bi_iter.bi_sector,
1287                                                   cache->discard_block_size);
1288         dm_block_t end_block = bio_end_sector(bio);
1289         dm_block_t b;
1290
1291         end_block = block_div(end_block, cache->discard_block_size);
1292
1293         for (b = start_block; b < end_block; b++)
1294                 set_discard(cache, to_dblock(b));
1295
1296         bio_endio(bio, 0);
1297 }
1298
1299 static bool spare_migration_bandwidth(struct cache *cache)
1300 {
1301         sector_t current_volume = (atomic_read(&cache->nr_migrations) + 1) *
1302                 cache->sectors_per_block;
1303         return current_volume < cache->migration_threshold;
1304 }
1305
1306 static void inc_hit_counter(struct cache *cache, struct bio *bio)
1307 {
1308         atomic_inc(bio_data_dir(bio) == READ ?
1309                    &cache->stats.read_hit : &cache->stats.write_hit);
1310 }
1311
1312 static void inc_miss_counter(struct cache *cache, struct bio *bio)
1313 {
1314         atomic_inc(bio_data_dir(bio) == READ ?
1315                    &cache->stats.read_miss : &cache->stats.write_miss);
1316 }
1317
1318 static void issue_cache_bio(struct cache *cache, struct bio *bio,
1319                             struct per_bio_data *pb,
1320                             dm_oblock_t oblock, dm_cblock_t cblock)
1321 {
1322         pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1323         remap_to_cache_dirty(cache, bio, oblock, cblock);
1324         issue(cache, bio);
1325 }
1326
1327 static void process_bio(struct cache *cache, struct prealloc *structs,
1328                         struct bio *bio)
1329 {
1330         int r;
1331         bool release_cell = true;
1332         dm_oblock_t block = get_bio_block(cache, bio);
1333         struct dm_bio_prison_cell *cell_prealloc, *old_ocell, *new_ocell;
1334         struct policy_result lookup_result;
1335         size_t pb_data_size = get_per_bio_data_size(cache);
1336         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
1337         bool discarded_block = is_discarded_oblock(cache, block);
1338         bool passthrough = passthrough_mode(&cache->features);
1339         bool can_migrate = !passthrough && (discarded_block || spare_migration_bandwidth(cache));
1340
1341         /*
1342          * Check to see if that block is currently migrating.
1343          */
1344         cell_prealloc = prealloc_get_cell(structs);
1345         r = bio_detain(cache, block, bio, cell_prealloc,
1346                        (cell_free_fn) prealloc_put_cell,
1347                        structs, &new_ocell);
1348         if (r > 0)
1349                 return;
1350
1351         r = policy_map(cache->policy, block, true, can_migrate, discarded_block,
1352                        bio, &lookup_result);
1353
1354         if (r == -EWOULDBLOCK)
1355                 /* migration has been denied */
1356                 lookup_result.op = POLICY_MISS;
1357
1358         switch (lookup_result.op) {
1359         case POLICY_HIT:
1360                 if (passthrough) {
1361                         inc_miss_counter(cache, bio);
1362
1363                         /*
1364                          * Passthrough always maps to the origin,
1365                          * invalidating any cache blocks that are written
1366                          * to.
1367                          */
1368
1369                         if (bio_data_dir(bio) == WRITE) {
1370                                 atomic_inc(&cache->stats.demotion);
1371                                 invalidate(cache, structs, block, lookup_result.cblock, new_ocell);
1372                                 release_cell = false;
1373
1374                         } else {
1375                                 /* FIXME: factor out issue_origin() */
1376                                 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1377                                 remap_to_origin_clear_discard(cache, bio, block);
1378                                 issue(cache, bio);
1379                         }
1380                 } else {
1381                         inc_hit_counter(cache, bio);
1382
1383                         if (bio_data_dir(bio) == WRITE &&
1384                             writethrough_mode(&cache->features) &&
1385                             !is_dirty(cache, lookup_result.cblock)) {
1386                                 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1387                                 remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
1388                                 issue(cache, bio);
1389                         } else
1390                                 issue_cache_bio(cache, bio, pb, block, lookup_result.cblock);
1391                 }
1392
1393                 break;
1394
1395         case POLICY_MISS:
1396                 inc_miss_counter(cache, bio);
1397                 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
1398                 remap_to_origin_clear_discard(cache, bio, block);
1399                 issue(cache, bio);
1400                 break;
1401
1402         case POLICY_NEW:
1403                 atomic_inc(&cache->stats.promotion);
1404                 promote(cache, structs, block, lookup_result.cblock, new_ocell);
1405                 release_cell = false;
1406                 break;
1407
1408         case POLICY_REPLACE:
1409                 cell_prealloc = prealloc_get_cell(structs);
1410                 r = bio_detain(cache, lookup_result.old_oblock, bio, cell_prealloc,
1411                                (cell_free_fn) prealloc_put_cell,
1412                                structs, &old_ocell);
1413                 if (r > 0) {
1414                         /*
1415                          * We have to be careful to avoid lock inversion of
1416                          * the cells.  So we back off, and wait for the
1417                          * old_ocell to become free.
1418                          */
1419                         policy_force_mapping(cache->policy, block,
1420                                              lookup_result.old_oblock);
1421                         atomic_inc(&cache->stats.cache_cell_clash);
1422                         break;
1423                 }
1424                 atomic_inc(&cache->stats.demotion);
1425                 atomic_inc(&cache->stats.promotion);
1426
1427                 demote_then_promote(cache, structs, lookup_result.old_oblock,
1428                                     block, lookup_result.cblock,
1429                                     old_ocell, new_ocell);
1430                 release_cell = false;
1431                 break;
1432
1433         default:
1434                 DMERR_LIMIT("%s: erroring bio, unknown policy op: %u", __func__,
1435                             (unsigned) lookup_result.op);
1436                 bio_io_error(bio);
1437         }
1438
1439         if (release_cell)
1440                 cell_defer(cache, new_ocell, false);
1441 }
1442
1443 static int need_commit_due_to_time(struct cache *cache)
1444 {
1445         return jiffies < cache->last_commit_jiffies ||
1446                jiffies > cache->last_commit_jiffies + COMMIT_PERIOD;
1447 }
1448
1449 static int commit_if_needed(struct cache *cache)
1450 {
1451         int r = 0;
1452
1453         if ((cache->commit_requested || need_commit_due_to_time(cache)) &&
1454             dm_cache_changed_this_transaction(cache->cmd)) {
1455                 atomic_inc(&cache->stats.commit_count);
1456                 cache->commit_requested = false;
1457                 r = dm_cache_commit(cache->cmd, false);
1458                 cache->last_commit_jiffies = jiffies;
1459         }
1460
1461         return r;
1462 }
1463
1464 static void process_deferred_bios(struct cache *cache)
1465 {
1466         unsigned long flags;
1467         struct bio_list bios;
1468         struct bio *bio;
1469         struct prealloc structs;
1470
1471         memset(&structs, 0, sizeof(structs));
1472         bio_list_init(&bios);
1473
1474         spin_lock_irqsave(&cache->lock, flags);
1475         bio_list_merge(&bios, &cache->deferred_bios);
1476         bio_list_init(&cache->deferred_bios);
1477         spin_unlock_irqrestore(&cache->lock, flags);
1478
1479         while (!bio_list_empty(&bios)) {
1480                 /*
1481                  * If we've got no free migration structs, and processing
1482                  * this bio might require one, we pause until there are some
1483                  * prepared mappings to process.
1484                  */
1485                 if (prealloc_data_structs(cache, &structs)) {
1486                         spin_lock_irqsave(&cache->lock, flags);
1487                         bio_list_merge(&cache->deferred_bios, &bios);
1488                         spin_unlock_irqrestore(&cache->lock, flags);
1489                         break;
1490                 }
1491
1492                 bio = bio_list_pop(&bios);
1493
1494                 if (bio->bi_rw & REQ_FLUSH)
1495                         process_flush_bio(cache, bio);
1496                 else if (bio->bi_rw & REQ_DISCARD)
1497                         process_discard_bio(cache, bio);
1498                 else
1499                         process_bio(cache, &structs, bio);
1500         }
1501
1502         prealloc_free_structs(cache, &structs);
1503 }
1504
1505 static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
1506 {
1507         unsigned long flags;
1508         struct bio_list bios;
1509         struct bio *bio;
1510
1511         bio_list_init(&bios);
1512
1513         spin_lock_irqsave(&cache->lock, flags);
1514         bio_list_merge(&bios, &cache->deferred_flush_bios);
1515         bio_list_init(&cache->deferred_flush_bios);
1516         spin_unlock_irqrestore(&cache->lock, flags);
1517
1518         while ((bio = bio_list_pop(&bios)))
1519                 submit_bios ? generic_make_request(bio) : bio_io_error(bio);
1520 }
1521
1522 static void process_deferred_writethrough_bios(struct cache *cache)
1523 {
1524         unsigned long flags;
1525         struct bio_list bios;
1526         struct bio *bio;
1527
1528         bio_list_init(&bios);
1529
1530         spin_lock_irqsave(&cache->lock, flags);
1531         bio_list_merge(&bios, &cache->deferred_writethrough_bios);
1532         bio_list_init(&cache->deferred_writethrough_bios);
1533         spin_unlock_irqrestore(&cache->lock, flags);
1534
1535         while ((bio = bio_list_pop(&bios)))
1536                 generic_make_request(bio);
1537 }
1538
1539 static void writeback_some_dirty_blocks(struct cache *cache)
1540 {
1541         int r = 0;
1542         dm_oblock_t oblock;
1543         dm_cblock_t cblock;
1544         struct prealloc structs;
1545         struct dm_bio_prison_cell *old_ocell;
1546
1547         memset(&structs, 0, sizeof(structs));
1548
1549         while (spare_migration_bandwidth(cache)) {
1550                 if (prealloc_data_structs(cache, &structs))
1551                         break;
1552
1553                 r = policy_writeback_work(cache->policy, &oblock, &cblock);
1554                 if (r)
1555                         break;
1556
1557                 r = get_cell(cache, oblock, &structs, &old_ocell);
1558                 if (r) {
1559                         policy_set_dirty(cache->policy, oblock);
1560                         break;
1561                 }
1562
1563                 writeback(cache, &structs, oblock, cblock, old_ocell);
1564         }
1565
1566         prealloc_free_structs(cache, &structs);
1567 }
1568
1569 /*----------------------------------------------------------------
1570  * Invalidations.
1571  * Dropping something from the cache *without* writing back.
1572  *--------------------------------------------------------------*/
1573
1574 static void process_invalidation_request(struct cache *cache, struct invalidation_request *req)
1575 {
1576         int r = 0;
1577         uint64_t begin = from_cblock(req->cblocks->begin);
1578         uint64_t end = from_cblock(req->cblocks->end);
1579
1580         while (begin != end) {
1581                 r = policy_remove_cblock(cache->policy, to_cblock(begin));
1582                 if (!r) {
1583                         r = dm_cache_remove_mapping(cache->cmd, to_cblock(begin));
1584                         if (r)
1585                                 break;
1586
1587                 } else if (r == -ENODATA) {
1588                         /* harmless, already unmapped */
1589                         r = 0;
1590
1591                 } else {
1592                         DMERR("policy_remove_cblock failed");
1593                         break;
1594                 }
1595
1596                 begin++;
1597         }
1598
1599         cache->commit_requested = true;
1600
1601         req->err = r;
1602         atomic_set(&req->complete, 1);
1603
1604         wake_up(&req->result_wait);
1605 }
1606
1607 static void process_invalidation_requests(struct cache *cache)
1608 {
1609         struct list_head list;
1610         struct invalidation_request *req, *tmp;
1611
1612         INIT_LIST_HEAD(&list);
1613         spin_lock(&cache->invalidation_lock);
1614         list_splice_init(&cache->invalidation_requests, &list);
1615         spin_unlock(&cache->invalidation_lock);
1616
1617         list_for_each_entry_safe (req, tmp, &list, list)
1618                 process_invalidation_request(cache, req);
1619 }
1620
1621 /*----------------------------------------------------------------
1622  * Main worker loop
1623  *--------------------------------------------------------------*/
1624 static bool is_quiescing(struct cache *cache)
1625 {
1626         return atomic_read(&cache->quiescing);
1627 }
1628
1629 static void ack_quiescing(struct cache *cache)
1630 {
1631         if (is_quiescing(cache)) {
1632                 atomic_inc(&cache->quiescing_ack);
1633                 wake_up(&cache->quiescing_wait);
1634         }
1635 }
1636
1637 static void wait_for_quiescing_ack(struct cache *cache)
1638 {
1639         wait_event(cache->quiescing_wait, atomic_read(&cache->quiescing_ack));
1640 }
1641
1642 static void start_quiescing(struct cache *cache)
1643 {
1644         atomic_inc(&cache->quiescing);
1645         wait_for_quiescing_ack(cache);
1646 }
1647
1648 static void stop_quiescing(struct cache *cache)
1649 {
1650         atomic_set(&cache->quiescing, 0);
1651         atomic_set(&cache->quiescing_ack, 0);
1652 }
1653
1654 static void wait_for_migrations(struct cache *cache)
1655 {
1656         wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations));
1657 }
1658
1659 static void stop_worker(struct cache *cache)
1660 {
1661         cancel_delayed_work(&cache->waker);
1662         flush_workqueue(cache->wq);
1663 }
1664
1665 static void requeue_deferred_io(struct cache *cache)
1666 {
1667         struct bio *bio;
1668         struct bio_list bios;
1669
1670         bio_list_init(&bios);
1671         bio_list_merge(&bios, &cache->deferred_bios);
1672         bio_list_init(&cache->deferred_bios);
1673
1674         while ((bio = bio_list_pop(&bios)))
1675                 bio_endio(bio, DM_ENDIO_REQUEUE);
1676 }
1677
1678 static int more_work(struct cache *cache)
1679 {
1680         if (is_quiescing(cache))
1681                 return !list_empty(&cache->quiesced_migrations) ||
1682                         !list_empty(&cache->completed_migrations) ||
1683                         !list_empty(&cache->need_commit_migrations);
1684         else
1685                 return !bio_list_empty(&cache->deferred_bios) ||
1686                         !bio_list_empty(&cache->deferred_flush_bios) ||
1687                         !bio_list_empty(&cache->deferred_writethrough_bios) ||
1688                         !list_empty(&cache->quiesced_migrations) ||
1689                         !list_empty(&cache->completed_migrations) ||
1690                         !list_empty(&cache->need_commit_migrations) ||
1691                         cache->invalidate;
1692 }
1693
1694 static void do_worker(struct work_struct *ws)
1695 {
1696         struct cache *cache = container_of(ws, struct cache, worker);
1697
1698         do {
1699                 if (!is_quiescing(cache)) {
1700                         writeback_some_dirty_blocks(cache);
1701                         process_deferred_writethrough_bios(cache);
1702                         process_deferred_bios(cache);
1703                         process_invalidation_requests(cache);
1704                 }
1705
1706                 process_migrations(cache, &cache->quiesced_migrations, issue_copy);
1707                 process_migrations(cache, &cache->completed_migrations, complete_migration);
1708
1709                 if (commit_if_needed(cache)) {
1710                         process_deferred_flush_bios(cache, false);
1711
1712                         /*
1713                          * FIXME: rollback metadata or just go into a
1714                          * failure mode and error everything
1715                          */
1716                 } else {
1717                         process_deferred_flush_bios(cache, true);
1718                         process_migrations(cache, &cache->need_commit_migrations,
1719                                            migration_success_post_commit);
1720                 }
1721
1722                 ack_quiescing(cache);
1723
1724         } while (more_work(cache));
1725 }
1726
1727 /*
1728  * We want to commit periodically so that not too much
1729  * unwritten metadata builds up.
1730  */
1731 static void do_waker(struct work_struct *ws)
1732 {
1733         struct cache *cache = container_of(to_delayed_work(ws), struct cache, waker);
1734         policy_tick(cache->policy);
1735         wake_worker(cache);
1736         queue_delayed_work(cache->wq, &cache->waker, COMMIT_PERIOD);
1737 }
1738
1739 /*----------------------------------------------------------------*/
1740
1741 static int is_congested(struct dm_dev *dev, int bdi_bits)
1742 {
1743         struct request_queue *q = bdev_get_queue(dev->bdev);
1744         return bdi_congested(&q->backing_dev_info, bdi_bits);
1745 }
1746
1747 static int cache_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
1748 {
1749         struct cache *cache = container_of(cb, struct cache, callbacks);
1750
1751         return is_congested(cache->origin_dev, bdi_bits) ||
1752                 is_congested(cache->cache_dev, bdi_bits);
1753 }
1754
1755 /*----------------------------------------------------------------
1756  * Target methods
1757  *--------------------------------------------------------------*/
1758
1759 /*
1760  * This function gets called on the error paths of the constructor, so we
1761  * have to cope with a partially initialised struct.
1762  */
1763 static void destroy(struct cache *cache)
1764 {
1765         unsigned i;
1766
1767         if (cache->next_migration)
1768                 mempool_free(cache->next_migration, cache->migration_pool);
1769
1770         if (cache->migration_pool)
1771                 mempool_destroy(cache->migration_pool);
1772
1773         if (cache->all_io_ds)
1774                 dm_deferred_set_destroy(cache->all_io_ds);
1775
1776         if (cache->prison)
1777                 dm_bio_prison_destroy(cache->prison);
1778
1779         if (cache->wq)
1780                 destroy_workqueue(cache->wq);
1781
1782         if (cache->dirty_bitset)
1783                 free_bitset(cache->dirty_bitset);
1784
1785         if (cache->discard_bitset)
1786                 free_bitset(cache->discard_bitset);
1787
1788         if (cache->copier)
1789                 dm_kcopyd_client_destroy(cache->copier);
1790
1791         if (cache->cmd)
1792                 dm_cache_metadata_close(cache->cmd);
1793
1794         if (cache->metadata_dev)
1795                 dm_put_device(cache->ti, cache->metadata_dev);
1796
1797         if (cache->origin_dev)
1798                 dm_put_device(cache->ti, cache->origin_dev);
1799
1800         if (cache->cache_dev)
1801                 dm_put_device(cache->ti, cache->cache_dev);
1802
1803         if (cache->policy)
1804                 dm_cache_policy_destroy(cache->policy);
1805
1806         for (i = 0; i < cache->nr_ctr_args ; i++)
1807                 kfree(cache->ctr_args[i]);
1808         kfree(cache->ctr_args);
1809
1810         kfree(cache);
1811 }
1812
1813 static void cache_dtr(struct dm_target *ti)
1814 {
1815         struct cache *cache = ti->private;
1816
1817         destroy(cache);
1818 }
1819
1820 static sector_t get_dev_size(struct dm_dev *dev)
1821 {
1822         return i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
1823 }
1824
1825 /*----------------------------------------------------------------*/
1826
1827 /*
1828  * Construct a cache device mapping.
1829  *
1830  * cache <metadata dev> <cache dev> <origin dev> <block size>
1831  *       <#feature args> [<feature arg>]*
1832  *       <policy> <#policy args> [<policy arg>]*
1833  *
1834  * metadata dev    : fast device holding the persistent metadata
1835  * cache dev       : fast device holding cached data blocks
1836  * origin dev      : slow device holding original data blocks
1837  * block size      : cache unit size in sectors
1838  *
1839  * #feature args   : number of feature arguments passed
1840  * feature args    : writethrough.  (The default is writeback.)
1841  *
1842  * policy          : the replacement policy to use
1843  * #policy args    : an even number of policy arguments corresponding
1844  *                   to key/value pairs passed to the policy
1845  * policy args     : key/value pairs passed to the policy
1846  *                   E.g. 'sequential_threshold 1024'
1847  *                   See cache-policies.txt for details.
1848  *
1849  * Optional feature arguments are:
1850  *   writethrough  : write through caching that prohibits cache block
1851  *                   content from being different from origin block content.
1852  *                   Without this argument, the default behaviour is to write
1853  *                   back cache block contents later for performance reasons,
1854  *                   so they may differ from the corresponding origin blocks.
1855  */
1856 struct cache_args {
1857         struct dm_target *ti;
1858
1859         struct dm_dev *metadata_dev;
1860
1861         struct dm_dev *cache_dev;
1862         sector_t cache_sectors;
1863
1864         struct dm_dev *origin_dev;
1865         sector_t origin_sectors;
1866
1867         uint32_t block_size;
1868
1869         const char *policy_name;
1870         int policy_argc;
1871         const char **policy_argv;
1872
1873         struct cache_features features;
1874 };
1875
1876 static void destroy_cache_args(struct cache_args *ca)
1877 {
1878         if (ca->metadata_dev)
1879                 dm_put_device(ca->ti, ca->metadata_dev);
1880
1881         if (ca->cache_dev)
1882                 dm_put_device(ca->ti, ca->cache_dev);
1883
1884         if (ca->origin_dev)
1885                 dm_put_device(ca->ti, ca->origin_dev);
1886
1887         kfree(ca);
1888 }
1889
1890 static bool at_least_one_arg(struct dm_arg_set *as, char **error)
1891 {
1892         if (!as->argc) {
1893                 *error = "Insufficient args";
1894                 return false;
1895         }
1896
1897         return true;
1898 }
1899
1900 static int parse_metadata_dev(struct cache_args *ca, struct dm_arg_set *as,
1901                               char **error)
1902 {
1903         int r;
1904         sector_t metadata_dev_size;
1905         char b[BDEVNAME_SIZE];
1906
1907         if (!at_least_one_arg(as, error))
1908                 return -EINVAL;
1909
1910         r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1911                           &ca->metadata_dev);
1912         if (r) {
1913                 *error = "Error opening metadata device";
1914                 return r;
1915         }
1916
1917         metadata_dev_size = get_dev_size(ca->metadata_dev);
1918         if (metadata_dev_size > DM_CACHE_METADATA_MAX_SECTORS_WARNING)
1919                 DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
1920                        bdevname(ca->metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);
1921
1922         return 0;
1923 }
1924
1925 static int parse_cache_dev(struct cache_args *ca, struct dm_arg_set *as,
1926                            char **error)
1927 {
1928         int r;
1929
1930         if (!at_least_one_arg(as, error))
1931                 return -EINVAL;
1932
1933         r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1934                           &ca->cache_dev);
1935         if (r) {
1936                 *error = "Error opening cache device";
1937                 return r;
1938         }
1939         ca->cache_sectors = get_dev_size(ca->cache_dev);
1940
1941         return 0;
1942 }
1943
1944 static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
1945                             char **error)
1946 {
1947         int r;
1948
1949         if (!at_least_one_arg(as, error))
1950                 return -EINVAL;
1951
1952         r = dm_get_device(ca->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
1953                           &ca->origin_dev);
1954         if (r) {
1955                 *error = "Error opening origin device";
1956                 return r;
1957         }
1958
1959         ca->origin_sectors = get_dev_size(ca->origin_dev);
1960         if (ca->ti->len > ca->origin_sectors) {
1961                 *error = "Device size larger than cached device";
1962                 return -EINVAL;
1963         }
1964
1965         return 0;
1966 }
1967
1968 static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
1969                             char **error)
1970 {
1971         unsigned long block_size;
1972
1973         if (!at_least_one_arg(as, error))
1974                 return -EINVAL;
1975
1976         if (kstrtoul(dm_shift_arg(as), 10, &block_size) || !block_size ||
1977             block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
1978             block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
1979             block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
1980                 *error = "Invalid data block size";
1981                 return -EINVAL;
1982         }
1983
1984         if (block_size > ca->cache_sectors) {
1985                 *error = "Data block size is larger than the cache device";
1986                 return -EINVAL;
1987         }
1988
1989         ca->block_size = block_size;
1990
1991         return 0;
1992 }
1993
1994 static void init_features(struct cache_features *cf)
1995 {
1996         cf->mode = CM_WRITE;
1997         cf->io_mode = CM_IO_WRITEBACK;
1998 }
1999
2000 static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
2001                           char **error)
2002 {
2003         static struct dm_arg _args[] = {
2004                 {0, 1, "Invalid number of cache feature arguments"},
2005         };
2006
2007         int r;
2008         unsigned argc;
2009         const char *arg;
2010         struct cache_features *cf = &ca->features;
2011
2012         init_features(cf);
2013
2014         r = dm_read_arg_group(_args, as, &argc, error);
2015         if (r)
2016                 return -EINVAL;
2017
2018         while (argc--) {
2019                 arg = dm_shift_arg(as);
2020
2021                 if (!strcasecmp(arg, "writeback"))
2022                         cf->io_mode = CM_IO_WRITEBACK;
2023
2024                 else if (!strcasecmp(arg, "writethrough"))
2025                         cf->io_mode = CM_IO_WRITETHROUGH;
2026
2027                 else if (!strcasecmp(arg, "passthrough"))
2028                         cf->io_mode = CM_IO_PASSTHROUGH;
2029
2030                 else {
2031                         *error = "Unrecognised cache feature requested";
2032                         return -EINVAL;
2033                 }
2034         }
2035
2036         return 0;
2037 }
2038
2039 static int parse_policy(struct cache_args *ca, struct dm_arg_set *as,
2040                         char **error)
2041 {
2042         static struct dm_arg _args[] = {
2043                 {0, 1024, "Invalid number of policy arguments"},
2044         };
2045
2046         int r;
2047
2048         if (!at_least_one_arg(as, error))
2049                 return -EINVAL;
2050
2051         ca->policy_name = dm_shift_arg(as);
2052
2053         r = dm_read_arg_group(_args, as, &ca->policy_argc, error);
2054         if (r)
2055                 return -EINVAL;
2056
2057         ca->policy_argv = (const char **)as->argv;
2058         dm_consume_args(as, ca->policy_argc);
2059
2060         return 0;
2061 }
2062
2063 static int parse_cache_args(struct cache_args *ca, int argc, char **argv,
2064                             char **error)
2065 {
2066         int r;
2067         struct dm_arg_set as;
2068
2069         as.argc = argc;
2070         as.argv = argv;
2071
2072         r = parse_metadata_dev(ca, &as, error);
2073         if (r)
2074                 return r;
2075
2076         r = parse_cache_dev(ca, &as, error);
2077         if (r)
2078                 return r;
2079
2080         r = parse_origin_dev(ca, &as, error);
2081         if (r)
2082                 return r;
2083
2084         r = parse_block_size(ca, &as, error);
2085         if (r)
2086                 return r;
2087
2088         r = parse_features(ca, &as, error);
2089         if (r)
2090                 return r;
2091
2092         r = parse_policy(ca, &as, error);
2093         if (r)
2094                 return r;
2095
2096         return 0;
2097 }
2098
2099 /*----------------------------------------------------------------*/
2100
2101 static struct kmem_cache *migration_cache;
2102
2103 #define NOT_CORE_OPTION 1
2104
2105 static int process_config_option(struct cache *cache, const char *key, const char *value)
2106 {
2107         unsigned long tmp;
2108
2109         if (!strcasecmp(key, "migration_threshold")) {
2110                 if (kstrtoul(value, 10, &tmp))
2111                         return -EINVAL;
2112
2113                 cache->migration_threshold = tmp;
2114                 return 0;
2115         }
2116
2117         return NOT_CORE_OPTION;
2118 }
2119
2120 static int set_config_value(struct cache *cache, const char *key, const char *value)
2121 {
2122         int r = process_config_option(cache, key, value);
2123
2124         if (r == NOT_CORE_OPTION)
2125                 r = policy_set_config_value(cache->policy, key, value);
2126
2127         if (r)
2128                 DMWARN("bad config value for %s: %s", key, value);
2129
2130         return r;
2131 }
2132
2133 static int set_config_values(struct cache *cache, int argc, const char **argv)
2134 {
2135         int r = 0;
2136
2137         if (argc & 1) {
2138                 DMWARN("Odd number of policy arguments given but they should be <key> <value> pairs.");
2139                 return -EINVAL;
2140         }
2141
2142         while (argc) {
2143                 r = set_config_value(cache, argv[0], argv[1]);
2144                 if (r)
2145                         break;
2146
2147                 argc -= 2;
2148                 argv += 2;
2149         }
2150
2151         return r;
2152 }
2153
2154 static int create_cache_policy(struct cache *cache, struct cache_args *ca,
2155                                char **error)
2156 {
2157         struct dm_cache_policy *p = dm_cache_policy_create(ca->policy_name,
2158                                                            cache->cache_size,
2159                                                            cache->origin_sectors,
2160                                                            cache->sectors_per_block);
2161         if (IS_ERR(p)) {
2162                 *error = "Error creating cache's policy";
2163                 return PTR_ERR(p);
2164         }
2165         cache->policy = p;
2166
2167         return 0;
2168 }
2169
2170 /*
2171  * We want the discard block size to be a power of two, at least the size
2172  * of the cache block size, and have no more than 2^14 discard blocks
2173  * across the origin.
2174  */
2175 #define MAX_DISCARD_BLOCKS (1 << 14)
2176
2177 static bool too_many_discard_blocks(sector_t discard_block_size,
2178                                     sector_t origin_size)
2179 {
2180         (void) sector_div(origin_size, discard_block_size);
2181
2182         return origin_size > MAX_DISCARD_BLOCKS;
2183 }
2184
2185 static sector_t calculate_discard_block_size(sector_t cache_block_size,
2186                                              sector_t origin_size)
2187 {
2188         sector_t discard_block_size;
2189
2190         discard_block_size = roundup_pow_of_two(cache_block_size);
2191
2192         if (origin_size)
2193                 while (too_many_discard_blocks(discard_block_size, origin_size))
2194                         discard_block_size *= 2;
2195
2196         return discard_block_size;
2197 }
2198
2199 #define DEFAULT_MIGRATION_THRESHOLD 2048
2200
2201 static int cache_create(struct cache_args *ca, struct cache **result)
2202 {
2203         int r = 0;
2204         char **error = &ca->ti->error;
2205         struct cache *cache;
2206         struct dm_target *ti = ca->ti;
2207         dm_block_t origin_blocks;
2208         struct dm_cache_metadata *cmd;
2209         bool may_format = ca->features.mode == CM_WRITE;
2210
2211         cache = kzalloc(sizeof(*cache), GFP_KERNEL);
2212         if (!cache)
2213                 return -ENOMEM;
2214
2215         cache->ti = ca->ti;
2216         ti->private = cache;
2217         ti->num_flush_bios = 2;
2218         ti->flush_supported = true;
2219
2220         ti->num_discard_bios = 1;
2221         ti->discards_supported = true;
2222         ti->discard_zeroes_data_unsupported = true;
2223
2224         cache->features = ca->features;
2225         ti->per_bio_data_size = get_per_bio_data_size(cache);
2226
2227         cache->callbacks.congested_fn = cache_is_congested;
2228         dm_table_add_target_callbacks(ti->table, &cache->callbacks);
2229
2230         cache->metadata_dev = ca->metadata_dev;
2231         cache->origin_dev = ca->origin_dev;
2232         cache->cache_dev = ca->cache_dev;
2233
2234         ca->metadata_dev = ca->origin_dev = ca->cache_dev = NULL;
2235
2236         /* FIXME: factor out this whole section */
2237         origin_blocks = cache->origin_sectors = ca->origin_sectors;
2238         origin_blocks = block_div(origin_blocks, ca->block_size);
2239         cache->origin_blocks = to_oblock(origin_blocks);
2240
2241         cache->sectors_per_block = ca->block_size;
2242         if (dm_set_target_max_io_len(ti, cache->sectors_per_block)) {
2243                 r = -EINVAL;
2244                 goto bad;
2245         }
2246
2247         if (ca->block_size & (ca->block_size - 1)) {
2248                 dm_block_t cache_size = ca->cache_sectors;
2249
2250                 cache->sectors_per_block_shift = -1;
2251                 cache_size = block_div(cache_size, ca->block_size);
2252                 cache->cache_size = to_cblock(cache_size);
2253         } else {
2254                 cache->sectors_per_block_shift = __ffs(ca->block_size);
2255                 cache->cache_size = to_cblock(ca->cache_sectors >> cache->sectors_per_block_shift);
2256         }
2257
2258         r = create_cache_policy(cache, ca, error);
2259         if (r)
2260                 goto bad;
2261
2262         cache->policy_nr_args = ca->policy_argc;
2263         cache->migration_threshold = DEFAULT_MIGRATION_THRESHOLD;
2264
2265         r = set_config_values(cache, ca->policy_argc, ca->policy_argv);
2266         if (r) {
2267                 *error = "Error setting cache policy's config values";
2268                 goto bad;
2269         }
2270
2271         cmd = dm_cache_metadata_open(cache->metadata_dev->bdev,
2272                                      ca->block_size, may_format,
2273                                      dm_cache_policy_get_hint_size(cache->policy));
2274         if (IS_ERR(cmd)) {
2275                 *error = "Error creating metadata object";
2276                 r = PTR_ERR(cmd);
2277                 goto bad;
2278         }
2279         cache->cmd = cmd;
2280
2281         if (passthrough_mode(&cache->features)) {
2282                 bool all_clean;
2283
2284                 r = dm_cache_metadata_all_clean(cache->cmd, &all_clean);
2285                 if (r) {
2286                         *error = "dm_cache_metadata_all_clean() failed";
2287                         goto bad;
2288                 }
2289
2290                 if (!all_clean) {
2291                         *error = "Cannot enter passthrough mode unless all blocks are clean";
2292                         r = -EINVAL;
2293                         goto bad;
2294                 }
2295         }
2296
2297         spin_lock_init(&cache->lock);
2298         bio_list_init(&cache->deferred_bios);
2299         bio_list_init(&cache->deferred_flush_bios);
2300         bio_list_init(&cache->deferred_writethrough_bios);
2301         INIT_LIST_HEAD(&cache->quiesced_migrations);
2302         INIT_LIST_HEAD(&cache->completed_migrations);
2303         INIT_LIST_HEAD(&cache->need_commit_migrations);
2304         atomic_set(&cache->nr_migrations, 0);
2305         init_waitqueue_head(&cache->migration_wait);
2306
2307         init_waitqueue_head(&cache->quiescing_wait);
2308         atomic_set(&cache->quiescing, 0);
2309         atomic_set(&cache->quiescing_ack, 0);
2310
2311         r = -ENOMEM;
2312         cache->nr_dirty = 0;
2313         cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));
2314         if (!cache->dirty_bitset) {
2315                 *error = "could not allocate dirty bitset";
2316                 goto bad;
2317         }
2318         clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size));
2319
2320         cache->discard_block_size =
2321                 calculate_discard_block_size(cache->sectors_per_block,
2322                                              cache->origin_sectors);
2323         cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks);
2324         cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks));
2325         if (!cache->discard_bitset) {
2326                 *error = "could not allocate discard bitset";
2327                 goto bad;
2328         }
2329         clear_bitset(cache->discard_bitset, from_dblock(cache->discard_nr_blocks));
2330
2331         cache->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle);
2332         if (IS_ERR(cache->copier)) {
2333                 *error = "could not create kcopyd client";
2334                 r = PTR_ERR(cache->copier);
2335                 goto bad;
2336         }
2337
2338         cache->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
2339         if (!cache->wq) {
2340                 *error = "could not create workqueue for metadata object";
2341                 goto bad;
2342         }
2343         INIT_WORK(&cache->worker, do_worker);
2344         INIT_DELAYED_WORK(&cache->waker, do_waker);
2345         cache->last_commit_jiffies = jiffies;
2346
2347         cache->prison = dm_bio_prison_create(PRISON_CELLS);
2348         if (!cache->prison) {
2349                 *error = "could not create bio prison";
2350                 goto bad;
2351         }
2352
2353         cache->all_io_ds = dm_deferred_set_create();
2354         if (!cache->all_io_ds) {
2355                 *error = "could not create all_io deferred set";
2356                 goto bad;
2357         }
2358
2359         cache->migration_pool = mempool_create_slab_pool(MIGRATION_POOL_SIZE,
2360                                                          migration_cache);
2361         if (!cache->migration_pool) {
2362                 *error = "Error creating cache's migration mempool";
2363                 goto bad;
2364         }
2365
2366         cache->next_migration = NULL;
2367
2368         cache->need_tick_bio = true;
2369         cache->sized = false;
2370         cache->invalidate = false;
2371         cache->commit_requested = false;
2372         cache->loaded_mappings = false;
2373         cache->loaded_discards = false;
2374
2375         load_stats(cache);
2376
2377         atomic_set(&cache->stats.demotion, 0);
2378         atomic_set(&cache->stats.promotion, 0);
2379         atomic_set(&cache->stats.copies_avoided, 0);
2380         atomic_set(&cache->stats.cache_cell_clash, 0);
2381         atomic_set(&cache->stats.commit_count, 0);
2382         atomic_set(&cache->stats.discard_count, 0);
2383
2384         spin_lock_init(&cache->invalidation_lock);
2385         INIT_LIST_HEAD(&cache->invalidation_requests);
2386
2387         *result = cache;
2388         return 0;
2389
2390 bad:
2391         destroy(cache);
2392         return r;
2393 }
2394
2395 static int copy_ctr_args(struct cache *cache, int argc, const char **argv)
2396 {
2397         unsigned i;
2398         const char **copy;
2399
2400         copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL);
2401         if (!copy)
2402                 return -ENOMEM;
2403         for (i = 0; i < argc; i++) {
2404                 copy[i] = kstrdup(argv[i], GFP_KERNEL);
2405                 if (!copy[i]) {
2406                         while (i--)
2407                                 kfree(copy[i]);
2408                         kfree(copy);
2409                         return -ENOMEM;
2410                 }
2411         }
2412
2413         cache->nr_ctr_args = argc;
2414         cache->ctr_args = copy;
2415
2416         return 0;
2417 }
2418
2419 static int cache_ctr(struct dm_target *ti, unsigned argc, char **argv)
2420 {
2421         int r = -EINVAL;
2422         struct cache_args *ca;
2423         struct cache *cache = NULL;
2424
2425         ca = kzalloc(sizeof(*ca), GFP_KERNEL);
2426         if (!ca) {
2427                 ti->error = "Error allocating memory for cache";
2428                 return -ENOMEM;
2429         }
2430         ca->ti = ti;
2431
2432         r = parse_cache_args(ca, argc, argv, &ti->error);
2433         if (r)
2434                 goto out;
2435
2436         r = cache_create(ca, &cache);
2437         if (r)
2438                 goto out;
2439
2440         r = copy_ctr_args(cache, argc - 3, (const char **)argv + 3);
2441         if (r) {
2442                 destroy(cache);
2443                 goto out;
2444         }
2445
2446         ti->private = cache;
2447
2448 out:
2449         destroy_cache_args(ca);
2450         return r;
2451 }
2452
2453 static int cache_map(struct dm_target *ti, struct bio *bio)
2454 {
2455         struct cache *cache = ti->private;
2456
2457         int r;
2458         dm_oblock_t block = get_bio_block(cache, bio);
2459         size_t pb_data_size = get_per_bio_data_size(cache);
2460         bool can_migrate = false;
2461         bool discarded_block;
2462         struct dm_bio_prison_cell *cell;
2463         struct policy_result lookup_result;
2464         struct per_bio_data *pb;
2465
2466         if (from_oblock(block) > from_oblock(cache->origin_blocks)) {
2467                 /*
2468                  * This can only occur if the io goes to a partial block at
2469                  * the end of the origin device.  We don't cache these.
2470                  * Just remap to the origin and carry on.
2471                  */
2472                 remap_to_origin_clear_discard(cache, bio, block);
2473                 return DM_MAPIO_REMAPPED;
2474         }
2475
2476         pb = init_per_bio_data(bio, pb_data_size);
2477
2478         if (bio->bi_rw & (REQ_FLUSH | REQ_FUA | REQ_DISCARD)) {
2479                 defer_bio(cache, bio);
2480                 return DM_MAPIO_SUBMITTED;
2481         }
2482
2483         /*
2484          * Check to see if that block is currently migrating.
2485          */
2486         cell = alloc_prison_cell(cache);
2487         if (!cell) {
2488                 defer_bio(cache, bio);
2489                 return DM_MAPIO_SUBMITTED;
2490         }
2491
2492         r = bio_detain(cache, block, bio, cell,
2493                        (cell_free_fn) free_prison_cell,
2494                        cache, &cell);
2495         if (r) {
2496                 if (r < 0)
2497                         defer_bio(cache, bio);
2498
2499                 return DM_MAPIO_SUBMITTED;
2500         }
2501
2502         discarded_block = is_discarded_oblock(cache, block);
2503
2504         r = policy_map(cache->policy, block, false, can_migrate, discarded_block,
2505                        bio, &lookup_result);
2506         if (r == -EWOULDBLOCK) {
2507                 cell_defer(cache, cell, true);
2508                 return DM_MAPIO_SUBMITTED;
2509
2510         } else if (r) {
2511                 DMERR_LIMIT("Unexpected return from cache replacement policy: %d", r);
2512                 bio_io_error(bio);
2513                 return DM_MAPIO_SUBMITTED;
2514         }
2515
2516         r = DM_MAPIO_REMAPPED;
2517         switch (lookup_result.op) {
2518         case POLICY_HIT:
2519                 if (passthrough_mode(&cache->features)) {
2520                         if (bio_data_dir(bio) == WRITE) {
2521                                 /*
2522                                  * We need to invalidate this block, so
2523                                  * defer for the worker thread.
2524                                  */
2525                                 cell_defer(cache, cell, true);
2526                                 r = DM_MAPIO_SUBMITTED;
2527
2528                         } else {
2529                                 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2530                                 inc_miss_counter(cache, bio);
2531                                 remap_to_origin_clear_discard(cache, bio, block);
2532
2533                                 cell_defer(cache, cell, false);
2534                         }
2535
2536                 } else {
2537                         inc_hit_counter(cache, bio);
2538
2539                         if (bio_data_dir(bio) == WRITE && writethrough_mode(&cache->features) &&
2540                             !is_dirty(cache, lookup_result.cblock))
2541                                 remap_to_origin_then_cache(cache, bio, block, lookup_result.cblock);
2542                         else
2543                                 remap_to_cache_dirty(cache, bio, block, lookup_result.cblock);
2544
2545                         cell_defer(cache, cell, false);
2546                 }
2547                 break;
2548
2549         case POLICY_MISS:
2550                 inc_miss_counter(cache, bio);
2551                 pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
2552
2553                 if (pb->req_nr != 0) {
2554                         /*
2555                          * This is a duplicate writethrough io that is no
2556                          * longer needed because the block has been demoted.
2557                          */
2558                         bio_endio(bio, 0);
2559                         cell_defer(cache, cell, false);
2560                         return DM_MAPIO_SUBMITTED;
2561                 } else {
2562                         remap_to_origin_clear_discard(cache, bio, block);
2563                         cell_defer(cache, cell, false);
2564                 }
2565                 break;
2566
2567         default:
2568                 DMERR_LIMIT("%s: erroring bio: unknown policy op: %u", __func__,
2569                             (unsigned) lookup_result.op);
2570                 bio_io_error(bio);
2571                 r = DM_MAPIO_SUBMITTED;
2572         }
2573
2574         return r;
2575 }
2576
2577 static int cache_end_io(struct dm_target *ti, struct bio *bio, int error)
2578 {
2579         struct cache *cache = ti->private;
2580         unsigned long flags;
2581         size_t pb_data_size = get_per_bio_data_size(cache);
2582         struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);
2583
2584         if (pb->tick) {
2585                 policy_tick(cache->policy);
2586
2587                 spin_lock_irqsave(&cache->lock, flags);
2588                 cache->need_tick_bio = true;
2589                 spin_unlock_irqrestore(&cache->lock, flags);
2590         }
2591
2592         check_for_quiesced_migrations(cache, pb);
2593
2594         return 0;
2595 }
2596
2597 static int write_dirty_bitset(struct cache *cache)
2598 {
2599         unsigned i, r;
2600
2601         for (i = 0; i < from_cblock(cache->cache_size); i++) {
2602                 r = dm_cache_set_dirty(cache->cmd, to_cblock(i),
2603                                        is_dirty(cache, to_cblock(i)));
2604                 if (r)
2605                         return r;
2606         }
2607
2608         return 0;
2609 }
2610
2611 static int write_discard_bitset(struct cache *cache)
2612 {
2613         unsigned i, r;
2614
2615         r = dm_cache_discard_bitset_resize(cache->cmd, cache->discard_block_size,
2616                                            cache->discard_nr_blocks);
2617         if (r) {
2618                 DMERR("could not resize on-disk discard bitset");
2619                 return r;
2620         }
2621
2622         for (i = 0; i < from_dblock(cache->discard_nr_blocks); i++) {
2623                 r = dm_cache_set_discard(cache->cmd, to_dblock(i),
2624                                          is_discarded(cache, to_dblock(i)));
2625                 if (r)
2626                         return r;
2627         }
2628
2629         return 0;
2630 }
2631
2632 static int save_hint(void *context, dm_cblock_t cblock, dm_oblock_t oblock,
2633                      uint32_t hint)
2634 {
2635         struct cache *cache = context;
2636         return dm_cache_save_hint(cache->cmd, cblock, hint);
2637 }
2638
2639 static int write_hints(struct cache *cache)
2640 {
2641         int r;
2642
2643         r = dm_cache_begin_hints(cache->cmd, cache->policy);
2644         if (r) {
2645                 DMERR("dm_cache_begin_hints failed");
2646                 return r;
2647         }
2648
2649         r = policy_walk_mappings(cache->policy, save_hint, cache);
2650         if (r)
2651                 DMERR("policy_walk_mappings failed");
2652
2653         return r;
2654 }
2655
2656 /*
2657  * returns true on success
2658  */
2659 static bool sync_metadata(struct cache *cache)
2660 {
2661         int r1, r2, r3, r4;
2662
2663         r1 = write_dirty_bitset(cache);
2664         if (r1)
2665                 DMERR("could not write dirty bitset");
2666
2667         r2 = write_discard_bitset(cache);
2668         if (r2)
2669                 DMERR("could not write discard bitset");
2670
2671         save_stats(cache);
2672
2673         r3 = write_hints(cache);
2674         if (r3)
2675                 DMERR("could not write hints");
2676
2677         /*
2678          * If writing the above metadata failed, we still commit, but don't
2679          * set the clean shutdown flag.  This will effectively force every
2680          * dirty bit to be set on reload.
2681          */
2682         r4 = dm_cache_commit(cache->cmd, !r1 && !r2 && !r3);
2683         if (r4)
2684                 DMERR("could not write cache metadata.  Data loss may occur.");
2685
2686         return !r1 && !r2 && !r3 && !r4;
2687 }
2688
2689 static void cache_postsuspend(struct dm_target *ti)
2690 {
2691         struct cache *cache = ti->private;
2692
2693         start_quiescing(cache);
2694         wait_for_migrations(cache);
2695         stop_worker(cache);
2696         requeue_deferred_io(cache);
2697         stop_quiescing(cache);
2698
2699         (void) sync_metadata(cache);
2700 }
2701
2702 static int load_mapping(void *context, dm_oblock_t oblock, dm_cblock_t cblock,
2703                         bool dirty, uint32_t hint, bool hint_valid)
2704 {
2705         int r;
2706         struct cache *cache = context;
2707
2708         r = policy_load_mapping(cache->policy, oblock, cblock, hint, hint_valid);
2709         if (r)
2710                 return r;
2711
2712         if (dirty)
2713                 set_dirty(cache, oblock, cblock);
2714         else
2715                 clear_dirty(cache, oblock, cblock);
2716
2717         return 0;
2718 }
2719
2720 static int load_discard(void *context, sector_t discard_block_size,
2721                         dm_dblock_t dblock, bool discard)
2722 {
2723         struct cache *cache = context;
2724
2725         /* FIXME: handle mis-matched block size */
2726
2727         if (discard)
2728                 set_discard(cache, dblock);
2729         else
2730                 clear_discard(cache, dblock);
2731
2732         return 0;
2733 }
2734
2735 static dm_cblock_t get_cache_dev_size(struct cache *cache)
2736 {
2737         sector_t size = get_dev_size(cache->cache_dev);
2738         (void) sector_div(size, cache->sectors_per_block);
2739         return to_cblock(size);
2740 }
2741
2742 static bool can_resize(struct cache *cache, dm_cblock_t new_size)
2743 {
2744         if (from_cblock(new_size) > from_cblock(cache->cache_size))
2745                 return true;
2746
2747         /*
2748          * We can't drop a dirty block when shrinking the cache.
2749          */
2750         while (from_cblock(new_size) < from_cblock(cache->cache_size)) {
2751                 new_size = to_cblock(from_cblock(new_size) + 1);
2752                 if (is_dirty(cache, new_size)) {
2753                         DMERR("unable to shrink cache; cache block %llu is dirty",
2754                               (unsigned long long) from_cblock(new_size));
2755                         return false;
2756                 }
2757         }
2758
2759         return true;
2760 }
2761
2762 static int resize_cache_dev(struct cache *cache, dm_cblock_t new_size)
2763 {
2764         int r;
2765
2766         r = dm_cache_resize(cache->cmd, cache->cache_size);
2767         if (r) {
2768                 DMERR("could not resize cache metadata");
2769                 return r;
2770         }
2771
2772         cache->cache_size = new_size;
2773
2774         return 0;
2775 }
2776
2777 static int cache_preresume(struct dm_target *ti)
2778 {
2779         int r = 0;
2780         struct cache *cache = ti->private;
2781         dm_cblock_t csize = get_cache_dev_size(cache);
2782
2783         /*
2784          * Check to see if the cache has resized.
2785          */
2786         if (!cache->sized) {
2787                 r = resize_cache_dev(cache, csize);
2788                 if (r)
2789                         return r;
2790
2791                 cache->sized = true;
2792
2793         } else if (csize != cache->cache_size) {
2794                 if (!can_resize(cache, csize))
2795                         return -EINVAL;
2796
2797                 r = resize_cache_dev(cache, csize);
2798                 if (r)
2799                         return r;
2800         }
2801
2802         if (!cache->loaded_mappings) {
2803                 r = dm_cache_load_mappings(cache->cmd, cache->policy,
2804                                            load_mapping, cache);
2805                 if (r) {
2806                         DMERR("could not load cache mappings");
2807                         return r;
2808                 }
2809
2810                 cache->loaded_mappings = true;
2811         }
2812
2813         if (!cache->loaded_discards) {
2814                 r = dm_cache_load_discards(cache->cmd, load_discard, cache);
2815                 if (r) {
2816                         DMERR("could not load origin discards");
2817                         return r;
2818                 }
2819
2820                 cache->loaded_discards = true;
2821         }
2822
2823         return r;
2824 }
2825
2826 static void cache_resume(struct dm_target *ti)
2827 {
2828         struct cache *cache = ti->private;
2829
2830         cache->need_tick_bio = true;
2831         do_waker(&cache->waker.work);
2832 }
2833
2834 /*
2835  * Status format:
2836  *
2837  * <#used metadata blocks>/<#total metadata blocks>
2838  * <#read hits> <#read misses> <#write hits> <#write misses>
2839  * <#demotions> <#promotions> <#blocks in cache> <#dirty>
2840  * <#features> <features>*
2841  * <#core args> <core args>
2842  * <#policy args> <policy args>*
2843  */
2844 static void cache_status(struct dm_target *ti, status_type_t type,
2845                          unsigned status_flags, char *result, unsigned maxlen)
2846 {
2847         int r = 0;
2848         unsigned i;
2849         ssize_t sz = 0;
2850         dm_block_t nr_free_blocks_metadata = 0;
2851         dm_block_t nr_blocks_metadata = 0;
2852         char buf[BDEVNAME_SIZE];
2853         struct cache *cache = ti->private;
2854         dm_cblock_t residency;
2855
2856         switch (type) {
2857         case STATUSTYPE_INFO:
2858                 /* Commit to ensure statistics aren't out-of-date */
2859                 if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti)) {
2860                         r = dm_cache_commit(cache->cmd, false);
2861                         if (r)
2862                                 DMERR("could not commit metadata for accurate status");
2863                 }
2864
2865                 r = dm_cache_get_free_metadata_block_count(cache->cmd,
2866                                                            &nr_free_blocks_metadata);
2867                 if (r) {
2868                         DMERR("could not get metadata free block count");
2869                         goto err;
2870                 }
2871
2872                 r = dm_cache_get_metadata_dev_size(cache->cmd, &nr_blocks_metadata);
2873                 if (r) {
2874                         DMERR("could not get metadata device size");
2875                         goto err;
2876                 }
2877
2878                 residency = policy_residency(cache->policy);
2879
2880                 DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
2881                        (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
2882                        (unsigned long long)nr_blocks_metadata,
2883                        (unsigned) atomic_read(&cache->stats.read_hit),
2884                        (unsigned) atomic_read(&cache->stats.read_miss),
2885                        (unsigned) atomic_read(&cache->stats.write_hit),
2886                        (unsigned) atomic_read(&cache->stats.write_miss),
2887                        (unsigned) atomic_read(&cache->stats.demotion),
2888                        (unsigned) atomic_read(&cache->stats.promotion),
2889                        (unsigned long long) from_cblock(residency),
2890                        cache->nr_dirty);
2891
2892                 if (writethrough_mode(&cache->features))
2893                         DMEMIT("1 writethrough ");
2894
2895                 else if (passthrough_mode(&cache->features))
2896                         DMEMIT("1 passthrough ");
2897
2898                 else if (writeback_mode(&cache->features))
2899                         DMEMIT("1 writeback ");
2900
2901                 else {
2902                         DMERR("internal error: unknown io mode: %d", (int) cache->features.io_mode);
2903                         goto err;
2904                 }
2905
2906                 DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
2907                 if (sz < maxlen) {
2908                         r = policy_emit_config_values(cache->policy, result + sz, maxlen - sz);
2909                         if (r)
2910                                 DMERR("policy_emit_config_values returned %d", r);
2911                 }
2912
2913                 break;
2914
2915         case STATUSTYPE_TABLE:
2916                 format_dev_t(buf, cache->metadata_dev->bdev->bd_dev);
2917                 DMEMIT("%s ", buf);
2918                 format_dev_t(buf, cache->cache_dev->bdev->bd_dev);
2919                 DMEMIT("%s ", buf);
2920                 format_dev_t(buf, cache->origin_dev->bdev->bd_dev);
2921                 DMEMIT("%s", buf);
2922
2923                 for (i = 0; i < cache->nr_ctr_args - 1; i++)
2924                         DMEMIT(" %s", cache->ctr_args[i]);
2925                 if (cache->nr_ctr_args)
2926                         DMEMIT(" %s", cache->ctr_args[cache->nr_ctr_args - 1]);
2927         }
2928
2929         return;
2930
2931 err:
2932         DMEMIT("Error");
2933 }
2934
2935 /*
2936  * A cache block range can take two forms:
2937  *
2938  * i) A single cblock, eg. '3456'
2939  * ii) A begin and end cblock with dots between, eg. 123-234
2940  */
2941 static int parse_cblock_range(struct cache *cache, const char *str,
2942                               struct cblock_range *result)
2943 {
2944         char dummy;
2945         uint64_t b, e;
2946         int r;
2947
2948         /*
2949          * Try and parse form (ii) first.
2950          */
2951         r = sscanf(str, "%llu-%llu%c", &b, &e, &dummy);
2952         if (r < 0)
2953                 return r;
2954
2955         if (r == 2) {
2956                 result->begin = to_cblock(b);
2957                 result->end = to_cblock(e);
2958                 return 0;
2959         }
2960
2961         /*
2962          * That didn't work, try form (i).
2963          */
2964         r = sscanf(str, "%llu%c", &b, &dummy);
2965         if (r < 0)
2966                 return r;
2967
2968         if (r == 1) {
2969                 result->begin = to_cblock(b);
2970                 result->end = to_cblock(from_cblock(result->begin) + 1u);
2971                 return 0;
2972         }
2973
2974         DMERR("invalid cblock range '%s'", str);
2975         return -EINVAL;
2976 }
2977
2978 static int validate_cblock_range(struct cache *cache, struct cblock_range *range)
2979 {
2980         uint64_t b = from_cblock(range->begin);
2981         uint64_t e = from_cblock(range->end);
2982         uint64_t n = from_cblock(cache->cache_size);
2983
2984         if (b >= n) {
2985                 DMERR("begin cblock out of range: %llu >= %llu", b, n);
2986                 return -EINVAL;
2987         }
2988
2989         if (e > n) {
2990                 DMERR("end cblock out of range: %llu > %llu", e, n);
2991                 return -EINVAL;
2992         }
2993
2994         if (b >= e) {
2995                 DMERR("invalid cblock range: %llu >= %llu", b, e);
2996                 return -EINVAL;
2997         }
2998
2999         return 0;
3000 }
3001
3002 static int request_invalidation(struct cache *cache, struct cblock_range *range)
3003 {
3004         struct invalidation_request req;
3005
3006         INIT_LIST_HEAD(&req.list);
3007         req.cblocks = range;
3008         atomic_set(&req.complete, 0);
3009         req.err = 0;
3010         init_waitqueue_head(&req.result_wait);
3011
3012         spin_lock(&cache->invalidation_lock);
3013         list_add(&req.list, &cache->invalidation_requests);
3014         spin_unlock(&cache->invalidation_lock);
3015         wake_worker(cache);
3016
3017         wait_event(req.result_wait, atomic_read(&req.complete));
3018         return req.err;
3019 }
3020
3021 static int process_invalidate_cblocks_message(struct cache *cache, unsigned count,
3022                                               const char **cblock_ranges)
3023 {
3024         int r = 0;
3025         unsigned i;
3026         struct cblock_range range;
3027
3028         if (!passthrough_mode(&cache->features)) {
3029                 DMERR("cache has to be in passthrough mode for invalidation");
3030                 return -EPERM;
3031         }
3032
3033         for (i = 0; i < count; i++) {
3034                 r = parse_cblock_range(cache, cblock_ranges[i], &range);
3035                 if (r)
3036                         break;
3037
3038                 r = validate_cblock_range(cache, &range);
3039                 if (r)
3040                         break;
3041
3042                 /*
3043                  * Pass begin and end origin blocks to the worker and wake it.
3044                  */
3045                 r = request_invalidation(cache, &range);
3046                 if (r)
3047                         break;
3048         }
3049
3050         return r;
3051 }
3052
3053 /*
3054  * Supports
3055  *      "<key> <value>"
3056  * and
3057  *     "invalidate_cblocks [(<begin>)|(<begin>-<end>)]*
3058  *
3059  * The key migration_threshold is supported by the cache target core.
3060  */
3061 static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
3062 {
3063         struct cache *cache = ti->private;
3064
3065         if (!argc)
3066                 return -EINVAL;
3067
3068         if (!strcasecmp(argv[0], "invalidate_cblocks"))
3069                 return process_invalidate_cblocks_message(cache, argc - 1, (const char **) argv + 1);
3070
3071         if (argc != 2)
3072                 return -EINVAL;
3073
3074         return set_config_value(cache, argv[0], argv[1]);
3075 }
3076
3077 static int cache_iterate_devices(struct dm_target *ti,
3078                                  iterate_devices_callout_fn fn, void *data)
3079 {
3080         int r = 0;
3081         struct cache *cache = ti->private;
3082
3083         r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data);
3084         if (!r)
3085                 r = fn(ti, cache->origin_dev, 0, ti->len, data);
3086
3087         return r;
3088 }
3089
3090 /*
3091  * We assume I/O is going to the origin (which is the volume
3092  * more likely to have restrictions e.g. by being striped).
3093  * (Looking up the exact location of the data would be expensive
3094  * and could always be out of date by the time the bio is submitted.)
3095  */
3096 static int cache_bvec_merge(struct dm_target *ti,
3097                             struct bvec_merge_data *bvm,
3098                             struct bio_vec *biovec, int max_size)
3099 {
3100         struct cache *cache = ti->private;
3101         struct request_queue *q = bdev_get_queue(cache->origin_dev->bdev);
3102
3103         if (!q->merge_bvec_fn)
3104                 return max_size;
3105
3106         bvm->bi_bdev = cache->origin_dev->bdev;
3107         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
3108 }
3109
3110 static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
3111 {
3112         /*
3113          * FIXME: these limits may be incompatible with the cache device
3114          */
3115         limits->max_discard_sectors = cache->discard_block_size * 1024;
3116         limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
3117 }
3118
3119 static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
3120 {
3121         struct cache *cache = ti->private;
3122         uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
3123
3124         /*
3125          * If the system-determined stacked limits are compatible with the
3126          * cache's blocksize (io_opt is a factor) do not override them.
3127          */
3128         if (io_opt_sectors < cache->sectors_per_block ||
3129             do_div(io_opt_sectors, cache->sectors_per_block)) {
3130                 blk_limits_io_min(limits, 0);
3131                 blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
3132         }
3133         set_discard_limits(cache, limits);
3134 }
3135
3136 /*----------------------------------------------------------------*/
3137
3138 static struct target_type cache_target = {
3139         .name = "cache",
3140         .version = {1, 2, 0},
3141         .module = THIS_MODULE,
3142         .ctr = cache_ctr,
3143         .dtr = cache_dtr,
3144         .map = cache_map,
3145         .end_io = cache_end_io,
3146         .postsuspend = cache_postsuspend,
3147         .preresume = cache_preresume,
3148         .resume = cache_resume,
3149         .status = cache_status,
3150         .message = cache_message,
3151         .iterate_devices = cache_iterate_devices,
3152         .merge = cache_bvec_merge,
3153         .io_hints = cache_io_hints,
3154 };
3155
3156 static int __init dm_cache_init(void)
3157 {
3158         int r;
3159
3160         r = dm_register_target(&cache_target);
3161         if (r) {
3162                 DMERR("cache target registration failed: %d", r);
3163                 return r;
3164         }
3165
3166         migration_cache = KMEM_CACHE(dm_cache_migration, 0);
3167         if (!migration_cache) {
3168                 dm_unregister_target(&cache_target);
3169                 return -ENOMEM;
3170         }
3171
3172         return 0;
3173 }
3174
3175 static void __exit dm_cache_exit(void)
3176 {
3177         dm_unregister_target(&cache_target);
3178         kmem_cache_destroy(migration_cache);
3179 }
3180
3181 module_init(dm_cache_init);
3182 module_exit(dm_cache_exit);
3183
3184 MODULE_DESCRIPTION(DM_NAME " cache target");
3185 MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
3186 MODULE_LICENSE("GPL");