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