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 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/closure.h>
183#include <linux/kobject.h>
184#include <linux/list.h>
185#include <linux/mutex.h>
186#include <linux/rbtree.h>
187#include <linux/rwsem.h>
188#include <linux/refcount.h>
189#include <linux/types.h>
190#include <linux/workqueue.h>
191#include <linux/kthread.h>
192
193#include "bcache_ondisk.h"
194#include "bset.h"
195#include "util.h"
196
197struct 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
210BITMASK(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))
216BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, GC_SECTORS_USED_SIZE);
217BITMASK(GC_MOVE, struct bucket, gc_mark, 15, 1);
218
219#include "journal.h"
220#include "stats.h"
221struct search;
222struct btree;
223struct keybuf;
224
225struct keybuf_key {
226 struct rb_node node;
227 BKEY_PADDED(key);
228 void *private;
229};
230
231struct 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
249struct 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, blk_mode_t mode,
279 unsigned int cmd, unsigned long arg);
280};
281
282struct 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
292enum 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
298struct cached_dev {
299 struct list_head list;
300 struct bcache_device disk;
301 struct block_device *bdev;
302 struct bdev_handle *bdev_handle;
303
304 struct cache_sb sb;
305 struct cache_sb_disk *sb_disk;
306 struct bio sb_bio;
307 struct bio_vec sb_bv[1];
308 struct closure sb_write;
309 struct semaphore sb_write_mutex;
310
311 /* Refcount on the cache set. Always nonzero when we're caching. */
312 refcount_t count;
313 struct work_struct detach;
314
315 /*
316 * Device might not be running if it's dirty and the cache set hasn't
317 * showed up yet.
318 */
319 atomic_t running;
320
321 /*
322 * Writes take a shared lock from start to finish; scanning for dirty
323 * data to refill the rb tree requires an exclusive lock.
324 */
325 struct rw_semaphore writeback_lock;
326
327 /*
328 * Nonzero, and writeback has a refcount (d->count), iff there is dirty
329 * data in the cache. Protected by writeback_lock; must have an
330 * shared lock to set and exclusive lock to clear.
331 */
332 atomic_t has_dirty;
333
334#define BCH_CACHE_READA_ALL 0
335#define BCH_CACHE_READA_META_ONLY 1
336 unsigned int cache_readahead_policy;
337 struct bch_ratelimit writeback_rate;
338 struct delayed_work writeback_rate_update;
339
340 /* Limit number of writeback bios in flight */
341 struct semaphore in_flight;
342 struct task_struct *writeback_thread;
343 struct workqueue_struct *writeback_write_wq;
344
345 struct keybuf writeback_keys;
346
347 struct task_struct *status_update_thread;
348 /*
349 * Order the write-half of writeback operations strongly in dispatch
350 * order. (Maintain LBA order; don't allow reads completing out of
351 * order to re-order the writes...)
352 */
353 struct closure_waitlist writeback_ordering_wait;
354 atomic_t writeback_sequence_next;
355
356 /* For tracking sequential IO */
357#define RECENT_IO_BITS 7
358#define RECENT_IO (1 << RECENT_IO_BITS)
359 struct io io[RECENT_IO];
360 struct hlist_head io_hash[RECENT_IO + 1];
361 struct list_head io_lru;
362 spinlock_t io_lock;
363
364 struct cache_accounting accounting;
365
366 /* The rest of this all shows up in sysfs */
367 unsigned int sequential_cutoff;
368
369 unsigned int io_disable:1;
370 unsigned int verify:1;
371 unsigned int bypass_torture_test:1;
372
373 unsigned int partial_stripes_expensive:1;
374 unsigned int writeback_metadata:1;
375 unsigned int writeback_running:1;
376 unsigned int writeback_consider_fragment:1;
377 unsigned char writeback_percent;
378 unsigned int writeback_delay;
379
380 uint64_t writeback_rate_target;
381 int64_t writeback_rate_proportional;
382 int64_t writeback_rate_integral;
383 int64_t writeback_rate_integral_scaled;
384 int32_t writeback_rate_change;
385
386 unsigned int writeback_rate_update_seconds;
387 unsigned int writeback_rate_i_term_inverse;
388 unsigned int writeback_rate_p_term_inverse;
389 unsigned int writeback_rate_fp_term_low;
390 unsigned int writeback_rate_fp_term_mid;
391 unsigned int writeback_rate_fp_term_high;
392 unsigned int writeback_rate_minimum;
393
394 enum stop_on_failure stop_when_cache_set_failed;
395#define DEFAULT_CACHED_DEV_ERROR_LIMIT 64
396 atomic_t io_errors;
397 unsigned int error_limit;
398 unsigned int offline_seconds;
399
400 /*
401 * Retry to update writeback_rate if contention happens for
402 * down_read(dc->writeback_lock) in update_writeback_rate()
403 */
404#define BCH_WBRATE_UPDATE_MAX_SKIPS 15
405 unsigned int rate_update_retry;
406};
407
408enum alloc_reserve {
409 RESERVE_BTREE,
410 RESERVE_PRIO,
411 RESERVE_MOVINGGC,
412 RESERVE_NONE,
413 RESERVE_NR,
414};
415
416struct cache {
417 struct cache_set *set;
418 struct cache_sb sb;
419 struct cache_sb_disk *sb_disk;
420 struct bio sb_bio;
421 struct bio_vec sb_bv[1];
422
423 struct kobject kobj;
424 struct block_device *bdev;
425 struct bdev_handle *bdev_handle;
426
427 struct task_struct *alloc_thread;
428
429 struct closure prio;
430 struct prio_set *disk_buckets;
431
432 /*
433 * When allocating new buckets, prio_write() gets first dibs - since we
434 * may not be allocate at all without writing priorities and gens.
435 * prio_last_buckets[] contains the last buckets we wrote priorities to
436 * (so gc can mark them as metadata), prio_buckets[] contains the
437 * buckets allocated for the next prio write.
438 */
439 uint64_t *prio_buckets;
440 uint64_t *prio_last_buckets;
441
442 /*
443 * free: Buckets that are ready to be used
444 *
445 * free_inc: Incoming buckets - these are buckets that currently have
446 * cached data in them, and we can't reuse them until after we write
447 * their new gen to disk. After prio_write() finishes writing the new
448 * gens/prios, they'll be moved to the free list (and possibly discarded
449 * in the process)
450 */
451 DECLARE_FIFO(long, free)[RESERVE_NR];
452 DECLARE_FIFO(long, free_inc);
453
454 size_t fifo_last_bucket;
455
456 /* Allocation stuff: */
457 struct bucket *buckets;
458
459 DECLARE_HEAP(struct bucket *, heap);
460
461 /*
462 * If nonzero, we know we aren't going to find any buckets to invalidate
463 * until a gc finishes - otherwise we could pointlessly burn a ton of
464 * cpu
465 */
466 unsigned int invalidate_needs_gc;
467
468 bool discard; /* Get rid of? */
469
470 struct journal_device journal;
471
472 /* The rest of this all shows up in sysfs */
473#define IO_ERROR_SHIFT 20
474 atomic_t io_errors;
475 atomic_t io_count;
476
477 atomic_long_t meta_sectors_written;
478 atomic_long_t btree_sectors_written;
479 atomic_long_t sectors_written;
480};
481
482struct gc_stat {
483 size_t nodes;
484 size_t nodes_pre;
485 size_t key_bytes;
486
487 size_t nkeys;
488 uint64_t data; /* sectors */
489 unsigned int in_use; /* percent */
490};
491
492/*
493 * Flag bits, for how the cache set is shutting down, and what phase it's at:
494 *
495 * CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching
496 * all the backing devices first (their cached data gets invalidated, and they
497 * won't automatically reattach).
498 *
499 * CACHE_SET_STOPPING always gets set first when we're closing down a cache set;
500 * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e.
501 * flushing dirty data).
502 *
503 * CACHE_SET_RUNNING means all cache devices have been registered and journal
504 * replay is complete.
505 *
506 * CACHE_SET_IO_DISABLE is set when bcache is stopping the whold cache set, all
507 * external and internal I/O should be denied when this flag is set.
508 *
509 */
510#define CACHE_SET_UNREGISTERING 0
511#define CACHE_SET_STOPPING 1
512#define CACHE_SET_RUNNING 2
513#define CACHE_SET_IO_DISABLE 3
514
515struct cache_set {
516 struct closure cl;
517
518 struct list_head list;
519 struct kobject kobj;
520 struct kobject internal;
521 struct dentry *debug;
522 struct cache_accounting accounting;
523
524 unsigned long flags;
525 atomic_t idle_counter;
526 atomic_t at_max_writeback_rate;
527
528 struct cache *cache;
529
530 struct bcache_device **devices;
531 unsigned int devices_max_used;
532 atomic_t attached_dev_nr;
533 struct list_head cached_devs;
534 uint64_t cached_dev_sectors;
535 atomic_long_t flash_dev_dirty_sectors;
536 struct closure caching;
537
538 struct closure sb_write;
539 struct semaphore sb_write_mutex;
540
541 mempool_t search;
542 mempool_t bio_meta;
543 struct bio_set bio_split;
544
545 /* For the btree cache */
546 struct shrinker *shrink;
547
548 /* For the btree cache and anything allocation related */
549 struct mutex bucket_lock;
550
551 /* log2(bucket_size), in sectors */
552 unsigned short bucket_bits;
553
554 /* log2(block_size), in sectors */
555 unsigned short block_bits;
556
557 /*
558 * Default number of pages for a new btree node - may be less than a
559 * full bucket
560 */
561 unsigned int btree_pages;
562
563 /*
564 * Lists of struct btrees; lru is the list for structs that have memory
565 * allocated for actual btree node, freed is for structs that do not.
566 *
567 * We never free a struct btree, except on shutdown - we just put it on
568 * the btree_cache_freed list and reuse it later. This simplifies the
569 * code, and it doesn't cost us much memory as the memory usage is
570 * dominated by buffers that hold the actual btree node data and those
571 * can be freed - and the number of struct btrees allocated is
572 * effectively bounded.
573 *
574 * btree_cache_freeable effectively is a small cache - we use it because
575 * high order page allocations can be rather expensive, and it's quite
576 * common to delete and allocate btree nodes in quick succession. It
577 * should never grow past ~2-3 nodes in practice.
578 */
579 struct list_head btree_cache;
580 struct list_head btree_cache_freeable;
581 struct list_head btree_cache_freed;
582
583 /* Number of elements in btree_cache + btree_cache_freeable lists */
584 unsigned int btree_cache_used;
585
586 /*
587 * If we need to allocate memory for a new btree node and that
588 * allocation fails, we can cannibalize another node in the btree cache
589 * to satisfy the allocation - lock to guarantee only one thread does
590 * this at a time:
591 */
592 wait_queue_head_t btree_cache_wait;
593 struct task_struct *btree_cache_alloc_lock;
594 spinlock_t btree_cannibalize_lock;
595
596 /*
597 * When we free a btree node, we increment the gen of the bucket the
598 * node is in - but we can't rewrite the prios and gens until we
599 * finished whatever it is we were doing, otherwise after a crash the
600 * btree node would be freed but for say a split, we might not have the
601 * pointers to the new nodes inserted into the btree yet.
602 *
603 * This is a refcount that blocks prio_write() until the new keys are
604 * written.
605 */
606 atomic_t prio_blocked;
607 wait_queue_head_t bucket_wait;
608
609 /*
610 * For any bio we don't skip we subtract the number of sectors from
611 * rescale; when it hits 0 we rescale all the bucket priorities.
612 */
613 atomic_t rescale;
614 /*
615 * used for GC, identify if any front side I/Os is inflight
616 */
617 atomic_t search_inflight;
618 /*
619 * When we invalidate buckets, we use both the priority and the amount
620 * of good data to determine which buckets to reuse first - to weight
621 * those together consistently we keep track of the smallest nonzero
622 * priority of any bucket.
623 */
624 uint16_t min_prio;
625
626 /*
627 * max(gen - last_gc) for all buckets. When it gets too big we have to
628 * gc to keep gens from wrapping around.
629 */
630 uint8_t need_gc;
631 struct gc_stat gc_stats;
632 size_t nbuckets;
633 size_t avail_nbuckets;
634
635 struct task_struct *gc_thread;
636 /* Where in the btree gc currently is */
637 struct bkey gc_done;
638
639 /*
640 * For automatical garbage collection after writeback completed, this
641 * varialbe is used as bit fields,
642 * - 0000 0001b (BCH_ENABLE_AUTO_GC): enable gc after writeback
643 * - 0000 0010b (BCH_DO_AUTO_GC): do gc after writeback
644 * This is an optimization for following write request after writeback
645 * finished, but read hit rate dropped due to clean data on cache is
646 * discarded. Unless user explicitly sets it via sysfs, it won't be
647 * enabled.
648 */
649#define BCH_ENABLE_AUTO_GC 1
650#define BCH_DO_AUTO_GC 2
651 uint8_t gc_after_writeback;
652
653 /*
654 * The allocation code needs gc_mark in struct bucket to be correct, but
655 * it's not while a gc is in progress. Protected by bucket_lock.
656 */
657 int gc_mark_valid;
658
659 /* Counts how many sectors bio_insert has added to the cache */
660 atomic_t sectors_to_gc;
661 wait_queue_head_t gc_wait;
662
663 struct keybuf moving_gc_keys;
664 /* Number of moving GC bios in flight */
665 struct semaphore moving_in_flight;
666
667 struct workqueue_struct *moving_gc_wq;
668
669 struct btree *root;
670
671#ifdef CONFIG_BCACHE_DEBUG
672 struct btree *verify_data;
673 struct bset *verify_ondisk;
674 struct mutex verify_lock;
675#endif
676
677 uint8_t set_uuid[16];
678 unsigned int nr_uuids;
679 struct uuid_entry *uuids;
680 BKEY_PADDED(uuid_bucket);
681 struct closure uuid_write;
682 struct semaphore uuid_write_mutex;
683
684 /*
685 * A btree node on disk could have too many bsets for an iterator to fit
686 * on the stack - have to dynamically allocate them.
687 * bch_cache_set_alloc() will make sure the pool can allocate iterators
688 * equipped with enough room that can host
689 * (sb.bucket_size / sb.block_size)
690 * btree_iter_sets, which is more than static MAX_BSETS.
691 */
692 mempool_t fill_iter;
693
694 struct bset_sort_state sort;
695
696 /* List of buckets we're currently writing data to */
697 struct list_head data_buckets;
698 spinlock_t data_bucket_lock;
699
700 struct journal journal;
701
702#define CONGESTED_MAX 1024
703 unsigned int congested_last_us;
704 atomic_t congested;
705
706 /* The rest of this all shows up in sysfs */
707 unsigned int congested_read_threshold_us;
708 unsigned int congested_write_threshold_us;
709
710 struct time_stats btree_gc_time;
711 struct time_stats btree_split_time;
712 struct time_stats btree_read_time;
713
714 atomic_long_t cache_read_races;
715 atomic_long_t writeback_keys_done;
716 atomic_long_t writeback_keys_failed;
717
718 atomic_long_t reclaim;
719 atomic_long_t reclaimed_journal_buckets;
720 atomic_long_t flush_write;
721
722 enum {
723 ON_ERROR_UNREGISTER,
724 ON_ERROR_PANIC,
725 } on_error;
726#define DEFAULT_IO_ERROR_LIMIT 8
727 unsigned int error_limit;
728 unsigned int error_decay;
729
730 unsigned short journal_delay_ms;
731 bool expensive_debug_checks;
732 unsigned int verify:1;
733 unsigned int key_merging_disabled:1;
734 unsigned int gc_always_rewrite:1;
735 unsigned int shrinker_disabled:1;
736 unsigned int copy_gc_enabled:1;
737 unsigned int idle_max_writeback_rate_enabled:1;
738
739#define BUCKET_HASH_BITS 12
740 struct hlist_head bucket_hash[1 << BUCKET_HASH_BITS];
741};
742
743struct bbio {
744 unsigned int submit_time_us;
745 union {
746 struct bkey key;
747 uint64_t _pad[3];
748 /*
749 * We only need pad = 3 here because we only ever carry around a
750 * single pointer - i.e. the pointer we're doing io to/from.
751 */
752 };
753 struct bio bio;
754};
755
756#define BTREE_PRIO USHRT_MAX
757#define INITIAL_PRIO 32768U
758
759#define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE)
760#define btree_blocks(b) \
761 ((unsigned int) (KEY_SIZE(&b->key) >> (b)->c->block_bits))
762
763#define btree_default_blocks(c) \
764 ((unsigned int) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits))
765
766#define bucket_bytes(ca) ((ca)->sb.bucket_size << 9)
767#define block_bytes(ca) ((ca)->sb.block_size << 9)
768
769static inline unsigned int meta_bucket_pages(struct cache_sb *sb)
770{
771 unsigned int n, max_pages;
772
773 max_pages = min_t(unsigned int,
774 __rounddown_pow_of_two(USHRT_MAX) / PAGE_SECTORS,
775 MAX_ORDER_NR_PAGES);
776
777 n = sb->bucket_size / PAGE_SECTORS;
778 if (n > max_pages)
779 n = max_pages;
780
781 return n;
782}
783
784static inline unsigned int meta_bucket_bytes(struct cache_sb *sb)
785{
786 return meta_bucket_pages(sb) << PAGE_SHIFT;
787}
788
789#define prios_per_bucket(ca) \
790 ((meta_bucket_bytes(&(ca)->sb) - sizeof(struct prio_set)) / \
791 sizeof(struct bucket_disk))
792
793#define prio_buckets(ca) \
794 DIV_ROUND_UP((size_t) (ca)->sb.nbuckets, prios_per_bucket(ca))
795
796static inline size_t sector_to_bucket(struct cache_set *c, sector_t s)
797{
798 return s >> c->bucket_bits;
799}
800
801static inline sector_t bucket_to_sector(struct cache_set *c, size_t b)
802{
803 return ((sector_t) b) << c->bucket_bits;
804}
805
806static inline sector_t bucket_remainder(struct cache_set *c, sector_t s)
807{
808 return s & (c->cache->sb.bucket_size - 1);
809}
810
811static inline size_t PTR_BUCKET_NR(struct cache_set *c,
812 const struct bkey *k,
813 unsigned int ptr)
814{
815 return sector_to_bucket(c, s: PTR_OFFSET(k, i: ptr));
816}
817
818static inline struct bucket *PTR_BUCKET(struct cache_set *c,
819 const struct bkey *k,
820 unsigned int ptr)
821{
822 return c->cache->buckets + PTR_BUCKET_NR(c, k, ptr);
823}
824
825static inline uint8_t gen_after(uint8_t a, uint8_t b)
826{
827 uint8_t r = a - b;
828
829 return r > 128U ? 0 : r;
830}
831
832static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
833 unsigned int i)
834{
835 return gen_after(a: PTR_BUCKET(c, k, ptr: i)->gen, b: PTR_GEN(k, i));
836}
837
838static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
839 unsigned int i)
840{
841 return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && c->cache;
842}
843
844/* Btree key macros */
845
846/*
847 * This is used for various on disk data structures - cache_sb, prio_set, bset,
848 * jset: The checksum is _always_ the first 8 bytes of these structs
849 */
850#define csum_set(i) \
851 bch_crc64(((void *) (i)) + sizeof(uint64_t), \
852 ((void *) bset_bkey_last(i)) - \
853 (((void *) (i)) + sizeof(uint64_t)))
854
855/* Error handling macros */
856
857#define btree_bug(b, ...) \
858do { \
859 if (bch_cache_set_error((b)->c, __VA_ARGS__)) \
860 dump_stack(); \
861} while (0)
862
863#define cache_bug(c, ...) \
864do { \
865 if (bch_cache_set_error(c, __VA_ARGS__)) \
866 dump_stack(); \
867} while (0)
868
869#define btree_bug_on(cond, b, ...) \
870do { \
871 if (cond) \
872 btree_bug(b, __VA_ARGS__); \
873} while (0)
874
875#define cache_bug_on(cond, c, ...) \
876do { \
877 if (cond) \
878 cache_bug(c, __VA_ARGS__); \
879} while (0)
880
881#define cache_set_err_on(cond, c, ...) \
882do { \
883 if (cond) \
884 bch_cache_set_error(c, __VA_ARGS__); \
885} while (0)
886
887/* Looping macros */
888
889#define for_each_bucket(b, ca) \
890 for (b = (ca)->buckets + (ca)->sb.first_bucket; \
891 b < (ca)->buckets + (ca)->sb.nbuckets; b++)
892
893static inline void cached_dev_put(struct cached_dev *dc)
894{
895 if (refcount_dec_and_test(r: &dc->count))
896 schedule_work(work: &dc->detach);
897}
898
899static inline bool cached_dev_get(struct cached_dev *dc)
900{
901 if (!refcount_inc_not_zero(r: &dc->count))
902 return false;
903
904 /* Paired with the mb in cached_dev_attach */
905 smp_mb__after_atomic();
906 return true;
907}
908
909/*
910 * bucket_gc_gen() returns the difference between the bucket's current gen and
911 * the oldest gen of any pointer into that bucket in the btree (last_gc).
912 */
913
914static inline uint8_t bucket_gc_gen(struct bucket *b)
915{
916 return b->gen - b->last_gc;
917}
918
919#define BUCKET_GC_GEN_MAX 96U
920
921#define kobj_attribute_write(n, fn) \
922 static struct kobj_attribute ksysfs_##n = __ATTR(n, 0200, NULL, fn)
923
924#define kobj_attribute_rw(n, show, store) \
925 static struct kobj_attribute ksysfs_##n = \
926 __ATTR(n, 0600, show, store)
927
928static inline void wake_up_allocators(struct cache_set *c)
929{
930 struct cache *ca = c->cache;
931
932 wake_up_process(tsk: ca->alloc_thread);
933}
934
935static inline void closure_bio_submit(struct cache_set *c,
936 struct bio *bio,
937 struct closure *cl)
938{
939 closure_get(cl);
940 if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags))) {
941 bio->bi_status = BLK_STS_IOERR;
942 bio_endio(bio);
943 return;
944 }
945 submit_bio_noacct(bio);
946}
947
948/*
949 * Prevent the kthread exits directly, and make sure when kthread_stop()
950 * is called to stop a kthread, it is still alive. If a kthread might be
951 * stopped by CACHE_SET_IO_DISABLE bit set, wait_for_kthread_stop() is
952 * necessary before the kthread returns.
953 */
954static inline void wait_for_kthread_stop(void)
955{
956 while (!kthread_should_stop()) {
957 set_current_state(TASK_INTERRUPTIBLE);
958 schedule();
959 }
960}
961
962/* Forward declarations */
963
964void bch_count_backing_io_errors(struct cached_dev *dc, struct bio *bio);
965void bch_count_io_errors(struct cache *ca, blk_status_t error,
966 int is_read, const char *m);
967void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
968 blk_status_t error, const char *m);
969void bch_bbio_endio(struct cache_set *c, struct bio *bio,
970 blk_status_t error, const char *m);
971void bch_bbio_free(struct bio *bio, struct cache_set *c);
972struct bio *bch_bbio_alloc(struct cache_set *c);
973
974void __bch_submit_bbio(struct bio *bio, struct cache_set *c);
975void bch_submit_bbio(struct bio *bio, struct cache_set *c,
976 struct bkey *k, unsigned int ptr);
977
978uint8_t bch_inc_gen(struct cache *ca, struct bucket *b);
979void bch_rescale_priorities(struct cache_set *c, int sectors);
980
981bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b);
982void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b);
983
984void __bch_bucket_free(struct cache *ca, struct bucket *b);
985void bch_bucket_free(struct cache_set *c, struct bkey *k);
986
987long bch_bucket_alloc(struct cache *ca, unsigned int reserve, bool wait);
988int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
989 struct bkey *k, bool wait);
990int bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
991 struct bkey *k, bool wait);
992bool bch_alloc_sectors(struct cache_set *c, struct bkey *k,
993 unsigned int sectors, unsigned int write_point,
994 unsigned int write_prio, bool wait);
995bool bch_cached_dev_error(struct cached_dev *dc);
996
997__printf(2, 3)
998bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...);
999
1000int bch_prio_write(struct cache *ca, bool wait);
1001void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent);
1002
1003extern struct workqueue_struct *bcache_wq;
1004extern struct workqueue_struct *bch_journal_wq;
1005extern struct workqueue_struct *bch_flush_wq;
1006extern struct mutex bch_register_lock;
1007extern struct list_head bch_cache_sets;
1008
1009extern const struct kobj_type bch_cached_dev_ktype;
1010extern const struct kobj_type bch_flash_dev_ktype;
1011extern const struct kobj_type bch_cache_set_ktype;
1012extern const struct kobj_type bch_cache_set_internal_ktype;
1013extern const struct kobj_type bch_cache_ktype;
1014
1015void bch_cached_dev_release(struct kobject *kobj);
1016void bch_flash_dev_release(struct kobject *kobj);
1017void bch_cache_set_release(struct kobject *kobj);
1018void bch_cache_release(struct kobject *kobj);
1019
1020int bch_uuid_write(struct cache_set *c);
1021void bcache_write_super(struct cache_set *c);
1022
1023int bch_flash_dev_create(struct cache_set *c, uint64_t size);
1024
1025int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
1026 uint8_t *set_uuid);
1027void bch_cached_dev_detach(struct cached_dev *dc);
1028int bch_cached_dev_run(struct cached_dev *dc);
1029void bcache_device_stop(struct bcache_device *d);
1030
1031void bch_cache_set_unregister(struct cache_set *c);
1032void bch_cache_set_stop(struct cache_set *c);
1033
1034struct cache_set *bch_cache_set_alloc(struct cache_sb *sb);
1035void bch_btree_cache_free(struct cache_set *c);
1036int bch_btree_cache_alloc(struct cache_set *c);
1037void bch_moving_init_cache_set(struct cache_set *c);
1038int bch_open_buckets_alloc(struct cache_set *c);
1039void bch_open_buckets_free(struct cache_set *c);
1040
1041int bch_cache_allocator_start(struct cache *ca);
1042
1043void bch_debug_exit(void);
1044void bch_debug_init(void);
1045void bch_request_exit(void);
1046int bch_request_init(void);
1047void bch_btree_exit(void);
1048int bch_btree_init(void);
1049
1050#endif /* _BCACHE_H */
1051

source code of linux/drivers/md/bcache/bcache.h