1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _BCACHE_H 3 #define _BCACHE_H 4 5 /* 6 * SOME HIGH LEVEL CODE DOCUMENTATION: 7 * 8 * Bcache mostly works with cache sets, cache devices, and backing devices. 9 * 10 * Support for multiple cache devices hasn't quite been finished off yet, but 11 * it's about 95% plumbed through. A cache set and its cache devices is sort of 12 * like a md raid array and its component devices. Most of the code doesn't care 13 * about individual cache devices, the main abstraction is the cache set. 14 * 15 * Multiple cache devices is intended to give us the ability to mirror dirty 16 * cached data and metadata, without mirroring clean cached data. 17 * 18 * Backing devices are different, in that they have a lifetime independent of a 19 * cache set. When you register a newly formatted backing device it'll come up 20 * in passthrough mode, and then you can attach and detach a backing device from 21 * a cache set at runtime - while it's mounted and in use. Detaching implicitly 22 * invalidates any cached data for that backing device. 23 * 24 * A cache set can have multiple (many) backing devices attached to it. 25 * 26 * There's also flash only volumes - this is the reason for the distinction 27 * between struct cached_dev and struct bcache_device. A flash only volume 28 * works much like a bcache device that has a backing device, except the 29 * "cached" data is always dirty. The end result is that we get thin 30 * provisioning with very little additional code. 31 * 32 * Flash only volumes work but they're not production ready because the moving 33 * garbage collector needs more work. More on that later. 34 * 35 * BUCKETS/ALLOCATION: 36 * 37 * Bcache is primarily designed for caching, which means that in normal 38 * operation all of our available space will be allocated. Thus, we need an 39 * efficient way of deleting things from the cache so we can write new things to 40 * it. 41 * 42 * To do this, we first divide the cache device up into buckets. A bucket is the 43 * unit of allocation; they're typically around 1 mb - anywhere from 128k to 2M+ 44 * works efficiently. 45 * 46 * Each bucket has a 16 bit priority, and an 8 bit generation associated with 47 * it. The gens and priorities for all the buckets are stored contiguously and 48 * packed on disk (in a linked list of buckets - aside from the superblock, all 49 * of bcache's metadata is stored in buckets). 50 * 51 * The priority is used to implement an LRU. We reset a bucket's priority when 52 * we allocate it or on cache it, and every so often we decrement the priority 53 * of each bucket. It could be used to implement something more sophisticated, 54 * if anyone ever gets around to it. 55 * 56 * The generation is used for invalidating buckets. Each pointer also has an 8 57 * bit generation embedded in it; for a pointer to be considered valid, its gen 58 * must match the gen of the bucket it points into. Thus, to reuse a bucket all 59 * we have to do is increment its gen (and write its new gen to disk; we batch 60 * this up). 61 * 62 * Bcache is entirely COW - we never write twice to a bucket, even buckets that 63 * contain metadata (including btree nodes). 64 * 65 * THE BTREE: 66 * 67 * Bcache is in large part design around the btree. 68 * 69 * At a high level, the btree is just an index of key -> ptr tuples. 70 * 71 * Keys represent extents, and thus have a size field. Keys also have a variable 72 * number of pointers attached to them (potentially zero, which is handy for 73 * invalidating the cache). 74 * 75 * The key itself is an inode:offset pair. The inode number corresponds to a 76 * backing device or a flash only volume. The offset is the ending offset of the 77 * extent within the inode - not the starting offset; this makes lookups 78 * slightly more convenient. 79 * 80 * Pointers contain the cache device id, the offset on that device, and an 8 bit 81 * generation number. More on the gen later. 82 * 83 * Index lookups are not fully abstracted - cache lookups in particular are 84 * still somewhat mixed in with the btree code, but things are headed in that 85 * direction. 86 * 87 * Updates are fairly well abstracted, though. There are two different ways of 88 * updating the btree; insert and replace. 89 * 90 * BTREE_INSERT will just take a list of keys and insert them into the btree - 91 * overwriting (possibly only partially) any extents they overlap with. This is 92 * used to update the index after a write. 93 * 94 * BTREE_REPLACE is really cmpxchg(); it inserts a key into the btree iff it is 95 * overwriting a key that matches another given key. This is used for inserting 96 * data into the cache after a cache miss, and for background writeback, and for 97 * the moving garbage collector. 98 * 99 * There is no "delete" operation; deleting things from the index is 100 * accomplished by either by invalidating pointers (by incrementing a bucket's 101 * gen) or by inserting a key with 0 pointers - which will overwrite anything 102 * previously present at that location in the index. 103 * 104 * This means that there are always stale/invalid keys in the btree. They're 105 * filtered out by the code that iterates through a btree node, and removed when 106 * a btree node is rewritten. 107 * 108 * BTREE NODES: 109 * 110 * Our unit of allocation is a bucket, and we we can't arbitrarily allocate and 111 * free smaller than a bucket - so, that's how big our btree nodes are. 112 * 113 * (If buckets are really big we'll only use part of the bucket for a btree node 114 * - no less than 1/4th - but a bucket still contains no more than a single 115 * btree node. I'd actually like to change this, but for now we rely on the 116 * bucket's gen for deleting btree nodes when we rewrite/split a node.) 117 * 118 * Anyways, btree nodes are big - big enough to be inefficient with a textbook 119 * btree implementation. 120 * 121 * The way this is solved is that btree nodes are internally log structured; we 122 * can append new keys to an existing btree node without rewriting it. This 123 * means each set of keys we write is sorted, but the node is not. 124 * 125 * We maintain this log structure in memory - keeping 1Mb of keys sorted would 126 * be expensive, and we have to distinguish between the keys we have written and 127 * the keys we haven't. So to do a lookup in a btree node, we have to search 128 * each sorted set. But we do merge written sets together lazily, so the cost of 129 * these extra searches is quite low (normally most of the keys in a btree node 130 * will be in one big set, and then there'll be one or two sets that are much 131 * smaller). 132 * 133 * This log structure makes bcache's btree more of a hybrid between a 134 * conventional btree and a compacting data structure, with some of the 135 * advantages of both. 136 * 137 * GARBAGE COLLECTION: 138 * 139 * We can't just invalidate any bucket - it might contain dirty data or 140 * metadata. If it once contained dirty data, other writes might overwrite it 141 * later, leaving no valid pointers into that bucket in the index. 142 * 143 * Thus, the primary purpose of garbage collection is to find buckets to reuse. 144 * It also counts how much valid data it each bucket currently contains, so that 145 * allocation can reuse buckets sooner when they've been mostly overwritten. 146 * 147 * It also does some things that are really internal to the btree 148 * implementation. If a btree node contains pointers that are stale by more than 149 * some threshold, it rewrites the btree node to avoid the bucket's generation 150 * wrapping around. It also merges adjacent btree nodes if they're empty enough. 151 * 152 * THE JOURNAL: 153 * 154 * Bcache's journal is not necessary for consistency; we always strictly 155 * order metadata writes so that the btree and everything else is consistent on 156 * disk in the event of an unclean shutdown, and in fact bcache had writeback 157 * caching (with recovery from unclean shutdown) before journalling was 158 * implemented. 159 * 160 * Rather, the journal is purely a performance optimization; we can't complete a 161 * write until we've updated the index on disk, otherwise the cache would be 162 * inconsistent in the event of an unclean shutdown. This means that without the 163 * journal, on random write workloads we constantly have to update all the leaf 164 * nodes in the btree, and those writes will be mostly empty (appending at most 165 * a few keys each) - highly inefficient in terms of amount of metadata writes, 166 * and it puts more strain on the various btree resorting/compacting code. 167 * 168 * The journal is just a log of keys we've inserted; on startup we just reinsert 169 * all the keys in the open journal entries. That means that when we're updating 170 * a node in the btree, we can wait until a 4k block of keys fills up before 171 * writing them out. 172 * 173 * For simplicity, we only journal updates to leaf nodes; updates to parent 174 * nodes are rare enough (since our leaf nodes are huge) that it wasn't worth 175 * the complexity to deal with journalling them (in particular, journal replay) 176 * - updates to non leaf nodes just happen synchronously (see btree_split()). 177 */ 178 179 #define pr_fmt(fmt) "bcache: %s() " fmt, __func__ 180 181 #include <linux/bio.h> 182 #include <linux/kobject.h> 183 #include <linux/list.h> 184 #include <linux/mutex.h> 185 #include <linux/rbtree.h> 186 #include <linux/rwsem.h> 187 #include <linux/refcount.h> 188 #include <linux/types.h> 189 #include <linux/workqueue.h> 190 #include <linux/kthread.h> 191 192 #include "bcache_ondisk.h" 193 #include "bset.h" 194 #include "util.h" 195 #include "closure.h" 196 197 struct bucket { 198 atomic_t pin; 199 uint16_t prio; 200 uint8_t gen; 201 uint8_t last_gc; /* Most out of date gen in the btree */ 202 uint16_t gc_mark; /* Bitfield used by GC. See below for field */ 203 }; 204 205 /* 206 * I'd use bitfields for these, but I don't trust the compiler not to screw me 207 * as multiple threads touch struct bucket without locking 208 */ 209 210 BITMASK(GC_MARK, struct bucket, gc_mark, 0, 2); 211 #define GC_MARK_RECLAIMABLE 1 212 #define GC_MARK_DIRTY 2 213 #define GC_MARK_METADATA 3 214 #define GC_SECTORS_USED_SIZE 13 215 #define MAX_GC_SECTORS_USED (~(~0ULL << GC_SECTORS_USED_SIZE)) 216 BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, GC_SECTORS_USED_SIZE); 217 BITMASK(GC_MOVE, struct bucket, gc_mark, 15, 1); 218 219 #include "journal.h" 220 #include "stats.h" 221 struct search; 222 struct btree; 223 struct keybuf; 224 225 struct keybuf_key { 226 struct rb_node node; 227 BKEY_PADDED(key); 228 void *private; 229 }; 230 231 struct keybuf { 232 struct bkey last_scanned; 233 spinlock_t lock; 234 235 /* 236 * Beginning and end of range in rb tree - so that we can skip taking 237 * lock and checking the rb tree when we need to check for overlapping 238 * keys. 239 */ 240 struct bkey start; 241 struct bkey end; 242 243 struct rb_root keys; 244 245 #define KEYBUF_NR 500 246 DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR); 247 }; 248 249 struct bcache_device { 250 struct closure cl; 251 252 struct kobject kobj; 253 254 struct cache_set *c; 255 unsigned int id; 256 #define BCACHEDEVNAME_SIZE 12 257 char name[BCACHEDEVNAME_SIZE]; 258 259 struct gendisk *disk; 260 261 unsigned long flags; 262 #define BCACHE_DEV_CLOSING 0 263 #define BCACHE_DEV_DETACHING 1 264 #define BCACHE_DEV_UNLINK_DONE 2 265 #define BCACHE_DEV_WB_RUNNING 3 266 #define BCACHE_DEV_RATE_DW_RUNNING 4 267 int nr_stripes; 268 unsigned int stripe_size; 269 atomic_t *stripe_sectors_dirty; 270 unsigned long *full_dirty_stripes; 271 272 struct bio_set bio_split; 273 274 unsigned int data_csum:1; 275 276 int (*cache_miss)(struct btree *b, struct search *s, 277 struct bio *bio, unsigned int sectors); 278 int (*ioctl)(struct bcache_device *d, fmode_t mode, 279 unsigned int cmd, unsigned long arg); 280 }; 281 282 struct io { 283 /* Used to track sequential IO so it can be skipped */ 284 struct hlist_node hash; 285 struct list_head lru; 286 287 unsigned long jiffies; 288 unsigned int sequential; 289 sector_t last; 290 }; 291 292 enum stop_on_failure { 293 BCH_CACHED_DEV_STOP_AUTO = 0, 294 BCH_CACHED_DEV_STOP_ALWAYS, 295 BCH_CACHED_DEV_STOP_MODE_MAX, 296 }; 297 298 struct cached_dev { 299 struct list_head list; 300 struct bcache_device disk; 301 struct block_device *bdev; 302 303 struct cache_sb sb; 304 struct cache_sb_disk *sb_disk; 305 struct bio sb_bio; 306 struct bio_vec sb_bv[1]; 307 struct closure sb_write; 308 struct semaphore sb_write_mutex; 309 310 /* Refcount on the cache set. Always nonzero when we're caching. */ 311 refcount_t count; 312 struct work_struct detach; 313 314 /* 315 * Device might not be running if it's dirty and the cache set hasn't 316 * showed up yet. 317 */ 318 atomic_t running; 319 320 /* 321 * Writes take a shared lock from start to finish; scanning for dirty 322 * data to refill the rb tree requires an exclusive lock. 323 */ 324 struct rw_semaphore writeback_lock; 325 326 /* 327 * Nonzero, and writeback has a refcount (d->count), iff there is dirty 328 * data in the cache. Protected by writeback_lock; must have an 329 * shared lock to set and exclusive lock to clear. 330 */ 331 atomic_t has_dirty; 332 333 #define BCH_CACHE_READA_ALL 0 334 #define BCH_CACHE_READA_META_ONLY 1 335 unsigned int cache_readahead_policy; 336 struct bch_ratelimit writeback_rate; 337 struct delayed_work writeback_rate_update; 338 339 /* Limit number of writeback bios in flight */ 340 struct semaphore in_flight; 341 struct task_struct *writeback_thread; 342 struct workqueue_struct *writeback_write_wq; 343 344 struct keybuf writeback_keys; 345 346 struct task_struct *status_update_thread; 347 /* 348 * Order the write-half of writeback operations strongly in dispatch 349 * order. (Maintain LBA order; don't allow reads completing out of 350 * order to re-order the writes...) 351 */ 352 struct closure_waitlist writeback_ordering_wait; 353 atomic_t writeback_sequence_next; 354 355 /* For tracking sequential IO */ 356 #define RECENT_IO_BITS 7 357 #define RECENT_IO (1 << RECENT_IO_BITS) 358 struct io io[RECENT_IO]; 359 struct hlist_head io_hash[RECENT_IO + 1]; 360 struct list_head io_lru; 361 spinlock_t io_lock; 362 363 struct cache_accounting accounting; 364 365 /* The rest of this all shows up in sysfs */ 366 unsigned int sequential_cutoff; 367 368 unsigned int io_disable:1; 369 unsigned int verify:1; 370 unsigned int bypass_torture_test:1; 371 372 unsigned int partial_stripes_expensive:1; 373 unsigned int writeback_metadata:1; 374 unsigned int writeback_running:1; 375 unsigned int writeback_consider_fragment:1; 376 unsigned char writeback_percent; 377 unsigned int writeback_delay; 378 379 uint64_t writeback_rate_target; 380 int64_t writeback_rate_proportional; 381 int64_t writeback_rate_integral; 382 int64_t writeback_rate_integral_scaled; 383 int32_t writeback_rate_change; 384 385 unsigned int writeback_rate_update_seconds; 386 unsigned int writeback_rate_i_term_inverse; 387 unsigned int writeback_rate_p_term_inverse; 388 unsigned int writeback_rate_fp_term_low; 389 unsigned int writeback_rate_fp_term_mid; 390 unsigned int writeback_rate_fp_term_high; 391 unsigned int writeback_rate_minimum; 392 393 enum stop_on_failure stop_when_cache_set_failed; 394 #define DEFAULT_CACHED_DEV_ERROR_LIMIT 64 395 atomic_t io_errors; 396 unsigned int error_limit; 397 unsigned int offline_seconds; 398 399 /* 400 * Retry to update writeback_rate if contention happens for 401 * down_read(dc->writeback_lock) in update_writeback_rate() 402 */ 403 #define BCH_WBRATE_UPDATE_MAX_SKIPS 15 404 unsigned int rate_update_retry; 405 }; 406 407 enum alloc_reserve { 408 RESERVE_BTREE, 409 RESERVE_PRIO, 410 RESERVE_MOVINGGC, 411 RESERVE_NONE, 412 RESERVE_NR, 413 }; 414 415 struct cache { 416 struct cache_set *set; 417 struct cache_sb sb; 418 struct cache_sb_disk *sb_disk; 419 struct bio sb_bio; 420 struct bio_vec sb_bv[1]; 421 422 struct kobject kobj; 423 struct block_device *bdev; 424 425 struct task_struct *alloc_thread; 426 427 struct closure prio; 428 struct prio_set *disk_buckets; 429 430 /* 431 * When allocating new buckets, prio_write() gets first dibs - since we 432 * may not be allocate at all without writing priorities and gens. 433 * prio_last_buckets[] contains the last buckets we wrote priorities to 434 * (so gc can mark them as metadata), prio_buckets[] contains the 435 * buckets allocated for the next prio write. 436 */ 437 uint64_t *prio_buckets; 438 uint64_t *prio_last_buckets; 439 440 /* 441 * free: Buckets that are ready to be used 442 * 443 * free_inc: Incoming buckets - these are buckets that currently have 444 * cached data in them, and we can't reuse them until after we write 445 * their new gen to disk. After prio_write() finishes writing the new 446 * gens/prios, they'll be moved to the free list (and possibly discarded 447 * in the process) 448 */ 449 DECLARE_FIFO(long, free)[RESERVE_NR]; 450 DECLARE_FIFO(long, free_inc); 451 452 size_t fifo_last_bucket; 453 454 /* Allocation stuff: */ 455 struct bucket *buckets; 456 457 DECLARE_HEAP(struct bucket *, heap); 458 459 /* 460 * If nonzero, we know we aren't going to find any buckets to invalidate 461 * until a gc finishes - otherwise we could pointlessly burn a ton of 462 * cpu 463 */ 464 unsigned int invalidate_needs_gc; 465 466 bool discard; /* Get rid of? */ 467 468 struct journal_device journal; 469 470 /* The rest of this all shows up in sysfs */ 471 #define IO_ERROR_SHIFT 20 472 atomic_t io_errors; 473 atomic_t io_count; 474 475 atomic_long_t meta_sectors_written; 476 atomic_long_t btree_sectors_written; 477 atomic_long_t sectors_written; 478 }; 479 480 struct gc_stat { 481 size_t nodes; 482 size_t nodes_pre; 483 size_t key_bytes; 484 485 size_t nkeys; 486 uint64_t data; /* sectors */ 487 unsigned int in_use; /* percent */ 488 }; 489 490 /* 491 * Flag bits, for how the cache set is shutting down, and what phase it's at: 492 * 493 * CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching 494 * all the backing devices first (their cached data gets invalidated, and they 495 * won't automatically reattach). 496 * 497 * CACHE_SET_STOPPING always gets set first when we're closing down a cache set; 498 * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e. 499 * flushing dirty data). 500 * 501 * CACHE_SET_RUNNING means all cache devices have been registered and journal 502 * replay is complete. 503 * 504 * CACHE_SET_IO_DISABLE is set when bcache is stopping the whold cache set, all 505 * external and internal I/O should be denied when this flag is set. 506 * 507 */ 508 #define CACHE_SET_UNREGISTERING 0 509 #define CACHE_SET_STOPPING 1 510 #define CACHE_SET_RUNNING 2 511 #define CACHE_SET_IO_DISABLE 3 512 513 struct cache_set { 514 struct closure cl; 515 516 struct list_head list; 517 struct kobject kobj; 518 struct kobject internal; 519 struct dentry *debug; 520 struct cache_accounting accounting; 521 522 unsigned long flags; 523 atomic_t idle_counter; 524 atomic_t at_max_writeback_rate; 525 526 struct cache *cache; 527 528 struct bcache_device **devices; 529 unsigned int devices_max_used; 530 atomic_t attached_dev_nr; 531 struct list_head cached_devs; 532 uint64_t cached_dev_sectors; 533 atomic_long_t flash_dev_dirty_sectors; 534 struct closure caching; 535 536 struct closure sb_write; 537 struct semaphore sb_write_mutex; 538 539 mempool_t search; 540 mempool_t bio_meta; 541 struct bio_set bio_split; 542 543 /* For the btree cache */ 544 struct shrinker shrink; 545 546 /* For the btree cache and anything allocation related */ 547 struct mutex bucket_lock; 548 549 /* log2(bucket_size), in sectors */ 550 unsigned short bucket_bits; 551 552 /* log2(block_size), in sectors */ 553 unsigned short block_bits; 554 555 /* 556 * Default number of pages for a new btree node - may be less than a 557 * full bucket 558 */ 559 unsigned int btree_pages; 560 561 /* 562 * Lists of struct btrees; lru is the list for structs that have memory 563 * allocated for actual btree node, freed is for structs that do not. 564 * 565 * We never free a struct btree, except on shutdown - we just put it on 566 * the btree_cache_freed list and reuse it later. This simplifies the 567 * code, and it doesn't cost us much memory as the memory usage is 568 * dominated by buffers that hold the actual btree node data and those 569 * can be freed - and the number of struct btrees allocated is 570 * effectively bounded. 571 * 572 * btree_cache_freeable effectively is a small cache - we use it because 573 * high order page allocations can be rather expensive, and it's quite 574 * common to delete and allocate btree nodes in quick succession. It 575 * should never grow past ~2-3 nodes in practice. 576 */ 577 struct list_head btree_cache; 578 struct list_head btree_cache_freeable; 579 struct list_head btree_cache_freed; 580 581 /* Number of elements in btree_cache + btree_cache_freeable lists */ 582 unsigned int btree_cache_used; 583 584 /* 585 * If we need to allocate memory for a new btree node and that 586 * allocation fails, we can cannibalize another node in the btree cache 587 * to satisfy the allocation - lock to guarantee only one thread does 588 * this at a time: 589 */ 590 wait_queue_head_t btree_cache_wait; 591 struct task_struct *btree_cache_alloc_lock; 592 spinlock_t btree_cannibalize_lock; 593 594 /* 595 * When we free a btree node, we increment the gen of the bucket the 596 * node is in - but we can't rewrite the prios and gens until we 597 * finished whatever it is we were doing, otherwise after a crash the 598 * btree node would be freed but for say a split, we might not have the 599 * pointers to the new nodes inserted into the btree yet. 600 * 601 * This is a refcount that blocks prio_write() until the new keys are 602 * written. 603 */ 604 atomic_t prio_blocked; 605 wait_queue_head_t bucket_wait; 606 607 /* 608 * For any bio we don't skip we subtract the number of sectors from 609 * rescale; when it hits 0 we rescale all the bucket priorities. 610 */ 611 atomic_t rescale; 612 /* 613 * used for GC, identify if any front side I/Os is inflight 614 */ 615 atomic_t search_inflight; 616 /* 617 * When we invalidate buckets, we use both the priority and the amount 618 * of good data to determine which buckets to reuse first - to weight 619 * those together consistently we keep track of the smallest nonzero 620 * priority of any bucket. 621 */ 622 uint16_t min_prio; 623 624 /* 625 * max(gen - last_gc) for all buckets. When it gets too big we have to 626 * gc to keep gens from wrapping around. 627 */ 628 uint8_t need_gc; 629 struct gc_stat gc_stats; 630 size_t nbuckets; 631 size_t avail_nbuckets; 632 633 struct task_struct *gc_thread; 634 /* Where in the btree gc currently is */ 635 struct bkey gc_done; 636 637 /* 638 * For automatical garbage collection after writeback completed, this 639 * varialbe is used as bit fields, 640 * - 0000 0001b (BCH_ENABLE_AUTO_GC): enable gc after writeback 641 * - 0000 0010b (BCH_DO_AUTO_GC): do gc after writeback 642 * This is an optimization for following write request after writeback 643 * finished, but read hit rate dropped due to clean data on cache is 644 * discarded. Unless user explicitly sets it via sysfs, it won't be 645 * enabled. 646 */ 647 #define BCH_ENABLE_AUTO_GC 1 648 #define BCH_DO_AUTO_GC 2 649 uint8_t gc_after_writeback; 650 651 /* 652 * The allocation code needs gc_mark in struct bucket to be correct, but 653 * it's not while a gc is in progress. Protected by bucket_lock. 654 */ 655 int gc_mark_valid; 656 657 /* Counts how many sectors bio_insert has added to the cache */ 658 atomic_t sectors_to_gc; 659 wait_queue_head_t gc_wait; 660 661 struct keybuf moving_gc_keys; 662 /* Number of moving GC bios in flight */ 663 struct semaphore moving_in_flight; 664 665 struct workqueue_struct *moving_gc_wq; 666 667 struct btree *root; 668 669 #ifdef CONFIG_BCACHE_DEBUG 670 struct btree *verify_data; 671 struct bset *verify_ondisk; 672 struct mutex verify_lock; 673 #endif 674 675 uint8_t set_uuid[16]; 676 unsigned int nr_uuids; 677 struct uuid_entry *uuids; 678 BKEY_PADDED(uuid_bucket); 679 struct closure uuid_write; 680 struct semaphore uuid_write_mutex; 681 682 /* 683 * A btree node on disk could have too many bsets for an iterator to fit 684 * on the stack - have to dynamically allocate them. 685 * bch_cache_set_alloc() will make sure the pool can allocate iterators 686 * equipped with enough room that can host 687 * (sb.bucket_size / sb.block_size) 688 * btree_iter_sets, which is more than static MAX_BSETS. 689 */ 690 mempool_t fill_iter; 691 692 struct bset_sort_state sort; 693 694 /* List of buckets we're currently writing data to */ 695 struct list_head data_buckets; 696 spinlock_t data_bucket_lock; 697 698 struct journal journal; 699 700 #define CONGESTED_MAX 1024 701 unsigned int congested_last_us; 702 atomic_t congested; 703 704 /* The rest of this all shows up in sysfs */ 705 unsigned int congested_read_threshold_us; 706 unsigned int congested_write_threshold_us; 707 708 struct time_stats btree_gc_time; 709 struct time_stats btree_split_time; 710 struct time_stats btree_read_time; 711 712 atomic_long_t cache_read_races; 713 atomic_long_t writeback_keys_done; 714 atomic_long_t writeback_keys_failed; 715 716 atomic_long_t reclaim; 717 atomic_long_t reclaimed_journal_buckets; 718 atomic_long_t flush_write; 719 720 enum { 721 ON_ERROR_UNREGISTER, 722 ON_ERROR_PANIC, 723 } on_error; 724 #define DEFAULT_IO_ERROR_LIMIT 8 725 unsigned int error_limit; 726 unsigned int error_decay; 727 728 unsigned short journal_delay_ms; 729 bool expensive_debug_checks; 730 unsigned int verify:1; 731 unsigned int key_merging_disabled:1; 732 unsigned int gc_always_rewrite:1; 733 unsigned int shrinker_disabled:1; 734 unsigned int copy_gc_enabled:1; 735 unsigned int idle_max_writeback_rate_enabled:1; 736 737 #define BUCKET_HASH_BITS 12 738 struct hlist_head bucket_hash[1 << BUCKET_HASH_BITS]; 739 }; 740 741 struct bbio { 742 unsigned int submit_time_us; 743 union { 744 struct bkey key; 745 uint64_t _pad[3]; 746 /* 747 * We only need pad = 3 here because we only ever carry around a 748 * single pointer - i.e. the pointer we're doing io to/from. 749 */ 750 }; 751 struct bio bio; 752 }; 753 754 #define BTREE_PRIO USHRT_MAX 755 #define INITIAL_PRIO 32768U 756 757 #define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE) 758 #define btree_blocks(b) \ 759 ((unsigned int) (KEY_SIZE(&b->key) >> (b)->c->block_bits)) 760 761 #define btree_default_blocks(c) \ 762 ((unsigned int) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits)) 763 764 #define bucket_bytes(ca) ((ca)->sb.bucket_size << 9) 765 #define block_bytes(ca) ((ca)->sb.block_size << 9) 766 767 static inline unsigned int meta_bucket_pages(struct cache_sb *sb) 768 { 769 unsigned int n, max_pages; 770 771 max_pages = min_t(unsigned int, 772 __rounddown_pow_of_two(USHRT_MAX) / PAGE_SECTORS, 773 MAX_ORDER_NR_PAGES); 774 775 n = sb->bucket_size / PAGE_SECTORS; 776 if (n > max_pages) 777 n = max_pages; 778 779 return n; 780 } 781 782 static inline unsigned int meta_bucket_bytes(struct cache_sb *sb) 783 { 784 return meta_bucket_pages(sb) << PAGE_SHIFT; 785 } 786 787 #define prios_per_bucket(ca) \ 788 ((meta_bucket_bytes(&(ca)->sb) - sizeof(struct prio_set)) / \ 789 sizeof(struct bucket_disk)) 790 791 #define prio_buckets(ca) \ 792 DIV_ROUND_UP((size_t) (ca)->sb.nbuckets, prios_per_bucket(ca)) 793 794 static inline size_t sector_to_bucket(struct cache_set *c, sector_t s) 795 { 796 return s >> c->bucket_bits; 797 } 798 799 static inline sector_t bucket_to_sector(struct cache_set *c, size_t b) 800 { 801 return ((sector_t) b) << c->bucket_bits; 802 } 803 804 static inline sector_t bucket_remainder(struct cache_set *c, sector_t s) 805 { 806 return s & (c->cache->sb.bucket_size - 1); 807 } 808 809 static inline size_t PTR_BUCKET_NR(struct cache_set *c, 810 const struct bkey *k, 811 unsigned int ptr) 812 { 813 return sector_to_bucket(c, PTR_OFFSET(k, ptr)); 814 } 815 816 static inline struct bucket *PTR_BUCKET(struct cache_set *c, 817 const struct bkey *k, 818 unsigned int ptr) 819 { 820 return c->cache->buckets + PTR_BUCKET_NR(c, k, ptr); 821 } 822 823 static inline uint8_t gen_after(uint8_t a, uint8_t b) 824 { 825 uint8_t r = a - b; 826 827 return r > 128U ? 0 : r; 828 } 829 830 static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k, 831 unsigned int i) 832 { 833 return gen_after(PTR_BUCKET(c, k, i)->gen, PTR_GEN(k, i)); 834 } 835 836 static inline bool ptr_available(struct cache_set *c, const struct bkey *k, 837 unsigned int i) 838 { 839 return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && c->cache; 840 } 841 842 /* Btree key macros */ 843 844 /* 845 * This is used for various on disk data structures - cache_sb, prio_set, bset, 846 * jset: The checksum is _always_ the first 8 bytes of these structs 847 */ 848 #define csum_set(i) \ 849 bch_crc64(((void *) (i)) + sizeof(uint64_t), \ 850 ((void *) bset_bkey_last(i)) - \ 851 (((void *) (i)) + sizeof(uint64_t))) 852 853 /* Error handling macros */ 854 855 #define btree_bug(b, ...) \ 856 do { \ 857 if (bch_cache_set_error((b)->c, __VA_ARGS__)) \ 858 dump_stack(); \ 859 } while (0) 860 861 #define cache_bug(c, ...) \ 862 do { \ 863 if (bch_cache_set_error(c, __VA_ARGS__)) \ 864 dump_stack(); \ 865 } while (0) 866 867 #define btree_bug_on(cond, b, ...) \ 868 do { \ 869 if (cond) \ 870 btree_bug(b, __VA_ARGS__); \ 871 } while (0) 872 873 #define cache_bug_on(cond, c, ...) \ 874 do { \ 875 if (cond) \ 876 cache_bug(c, __VA_ARGS__); \ 877 } while (0) 878 879 #define cache_set_err_on(cond, c, ...) \ 880 do { \ 881 if (cond) \ 882 bch_cache_set_error(c, __VA_ARGS__); \ 883 } while (0) 884 885 /* Looping macros */ 886 887 #define for_each_bucket(b, ca) \ 888 for (b = (ca)->buckets + (ca)->sb.first_bucket; \ 889 b < (ca)->buckets + (ca)->sb.nbuckets; b++) 890 891 static inline void cached_dev_put(struct cached_dev *dc) 892 { 893 if (refcount_dec_and_test(&dc->count)) 894 schedule_work(&dc->detach); 895 } 896 897 static inline bool cached_dev_get(struct cached_dev *dc) 898 { 899 if (!refcount_inc_not_zero(&dc->count)) 900 return false; 901 902 /* Paired with the mb in cached_dev_attach */ 903 smp_mb__after_atomic(); 904 return true; 905 } 906 907 /* 908 * bucket_gc_gen() returns the difference between the bucket's current gen and 909 * the oldest gen of any pointer into that bucket in the btree (last_gc). 910 */ 911 912 static inline uint8_t bucket_gc_gen(struct bucket *b) 913 { 914 return b->gen - b->last_gc; 915 } 916 917 #define BUCKET_GC_GEN_MAX 96U 918 919 #define kobj_attribute_write(n, fn) \ 920 static struct kobj_attribute ksysfs_##n = __ATTR(n, 0200, NULL, fn) 921 922 #define kobj_attribute_rw(n, show, store) \ 923 static struct kobj_attribute ksysfs_##n = \ 924 __ATTR(n, 0600, show, store) 925 926 static inline void wake_up_allocators(struct cache_set *c) 927 { 928 struct cache *ca = c->cache; 929 930 wake_up_process(ca->alloc_thread); 931 } 932 933 static inline void closure_bio_submit(struct cache_set *c, 934 struct bio *bio, 935 struct closure *cl) 936 { 937 closure_get(cl); 938 if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags))) { 939 bio->bi_status = BLK_STS_IOERR; 940 bio_endio(bio); 941 return; 942 } 943 submit_bio_noacct(bio); 944 } 945 946 /* 947 * Prevent the kthread exits directly, and make sure when kthread_stop() 948 * is called to stop a kthread, it is still alive. If a kthread might be 949 * stopped by CACHE_SET_IO_DISABLE bit set, wait_for_kthread_stop() is 950 * necessary before the kthread returns. 951 */ 952 static inline void wait_for_kthread_stop(void) 953 { 954 while (!kthread_should_stop()) { 955 set_current_state(TASK_INTERRUPTIBLE); 956 schedule(); 957 } 958 } 959 960 /* Forward declarations */ 961 962 void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio); 963 void bch_count_io_errors(struct cache *ca, blk_status_t error, 964 int is_read, const char *m); 965 void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio, 966 blk_status_t error, const char *m); 967 void bch_bbio_endio(struct cache_set *c, struct bio *bio, 968 blk_status_t error, const char *m); 969 void bch_bbio_free(struct bio *bio, struct cache_set *c); 970 struct bio *bch_bbio_alloc(struct cache_set *c); 971 972 void __bch_submit_bbio(struct bio *bio, struct cache_set *c); 973 void bch_submit_bbio(struct bio *bio, struct cache_set *c, 974 struct bkey *k, unsigned int ptr); 975 976 uint8_t bch_inc_gen(struct cache *ca, struct bucket *b); 977 void bch_rescale_priorities(struct cache_set *c, int sectors); 978 979 bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b); 980 void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b); 981 982 void __bch_bucket_free(struct cache *ca, struct bucket *b); 983 void bch_bucket_free(struct cache_set *c, struct bkey *k); 984 985 long bch_bucket_alloc(struct cache *ca, unsigned int reserve, bool wait); 986 int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve, 987 struct bkey *k, bool wait); 988 int bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve, 989 struct bkey *k, bool wait); 990 bool bch_alloc_sectors(struct cache_set *c, struct bkey *k, 991 unsigned int sectors, unsigned int write_point, 992 unsigned int write_prio, bool wait); 993 bool bch_cached_dev_error(struct cached_dev *dc); 994 995 __printf(2, 3) 996 bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...); 997 998 int bch_prio_write(struct cache *ca, bool wait); 999 void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent); 1000 1001 extern struct workqueue_struct *bcache_wq; 1002 extern struct workqueue_struct *bch_journal_wq; 1003 extern struct workqueue_struct *bch_flush_wq; 1004 extern struct mutex bch_register_lock; 1005 extern struct list_head bch_cache_sets; 1006 1007 extern struct kobj_type bch_cached_dev_ktype; 1008 extern struct kobj_type bch_flash_dev_ktype; 1009 extern struct kobj_type bch_cache_set_ktype; 1010 extern struct kobj_type bch_cache_set_internal_ktype; 1011 extern struct kobj_type bch_cache_ktype; 1012 1013 void bch_cached_dev_release(struct kobject *kobj); 1014 void bch_flash_dev_release(struct kobject *kobj); 1015 void bch_cache_set_release(struct kobject *kobj); 1016 void bch_cache_release(struct kobject *kobj); 1017 1018 int bch_uuid_write(struct cache_set *c); 1019 void bcache_write_super(struct cache_set *c); 1020 1021 int bch_flash_dev_create(struct cache_set *c, uint64_t size); 1022 1023 int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c, 1024 uint8_t *set_uuid); 1025 void bch_cached_dev_detach(struct cached_dev *dc); 1026 int bch_cached_dev_run(struct cached_dev *dc); 1027 void bcache_device_stop(struct bcache_device *d); 1028 1029 void bch_cache_set_unregister(struct cache_set *c); 1030 void bch_cache_set_stop(struct cache_set *c); 1031 1032 struct cache_set *bch_cache_set_alloc(struct cache_sb *sb); 1033 void bch_btree_cache_free(struct cache_set *c); 1034 int bch_btree_cache_alloc(struct cache_set *c); 1035 void bch_moving_init_cache_set(struct cache_set *c); 1036 int bch_open_buckets_alloc(struct cache_set *c); 1037 void bch_open_buckets_free(struct cache_set *c); 1038 1039 int bch_cache_allocator_start(struct cache *ca); 1040 1041 void bch_debug_exit(void); 1042 void bch_debug_init(void); 1043 void bch_request_exit(void); 1044 int bch_request_init(void); 1045 void bch_btree_exit(void); 1046 int bch_btree_init(void); 1047 1048 #endif /* _BCACHE_H */ 1049