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/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, blk_mode_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
meta_bucket_pages(struct cache_sb * sb)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
meta_bucket_bytes(struct cache_sb * sb)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
sector_to_bucket(struct cache_set * c,sector_t s)794 static inline size_t sector_to_bucket(struct cache_set *c, sector_t s)
795 {
796 return s >> c->bucket_bits;
797 }
798
bucket_to_sector(struct cache_set * c,size_t b)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
bucket_remainder(struct cache_set * c,sector_t s)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
PTR_BUCKET_NR(struct cache_set * c,const struct bkey * k,unsigned int ptr)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
PTR_BUCKET(struct cache_set * c,const struct bkey * k,unsigned int ptr)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
gen_after(uint8_t a,uint8_t b)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
ptr_stale(struct cache_set * c,const struct bkey * k,unsigned int i)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
ptr_available(struct cache_set * c,const struct bkey * k,unsigned int i)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
cached_dev_put(struct cached_dev * dc)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
cached_dev_get(struct cached_dev * dc)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
bucket_gc_gen(struct bucket * b)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
wake_up_allocators(struct cache_set * c)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
closure_bio_submit(struct cache_set * c,struct bio * bio,struct closure * cl)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 */
wait_for_kthread_stop(void)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 const struct kobj_type bch_cached_dev_ktype;
1008 extern const struct kobj_type bch_flash_dev_ktype;
1009 extern const struct kobj_type bch_cache_set_ktype;
1010 extern const struct kobj_type bch_cache_set_internal_ktype;
1011 extern const 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
