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Kent Overstreetcafe5632013-03-23 16:11:31 -07001#ifndef _BCACHE_H
2#define _BCACHE_H
3
4/*
5 * SOME HIGH LEVEL CODE DOCUMENTATION:
6 *
7 * Bcache mostly works with cache sets, cache devices, and backing devices.
8 *
9 * Support for multiple cache devices hasn't quite been finished off yet, but
10 * it's about 95% plumbed through. A cache set and its cache devices is sort of
11 * like a md raid array and its component devices. Most of the code doesn't care
12 * about individual cache devices, the main abstraction is the cache set.
13 *
14 * Multiple cache devices is intended to give us the ability to mirror dirty
15 * cached data and metadata, without mirroring clean cached data.
16 *
17 * Backing devices are different, in that they have a lifetime independent of a
18 * cache set. When you register a newly formatted backing device it'll come up
19 * in passthrough mode, and then you can attach and detach a backing device from
20 * a cache set at runtime - while it's mounted and in use. Detaching implicitly
21 * invalidates any cached data for that backing device.
22 *
23 * A cache set can have multiple (many) backing devices attached to it.
24 *
25 * There's also flash only volumes - this is the reason for the distinction
26 * between struct cached_dev and struct bcache_device. A flash only volume
27 * works much like a bcache device that has a backing device, except the
28 * "cached" data is always dirty. The end result is that we get thin
29 * provisioning with very little additional code.
30 *
31 * Flash only volumes work but they're not production ready because the moving
32 * garbage collector needs more work. More on that later.
33 *
34 * BUCKETS/ALLOCATION:
35 *
36 * Bcache is primarily designed for caching, which means that in normal
37 * operation all of our available space will be allocated. Thus, we need an
38 * efficient way of deleting things from the cache so we can write new things to
39 * it.
40 *
41 * To do this, we first divide the cache device up into buckets. A bucket is the
42 * unit of allocation; they're typically around 1 mb - anywhere from 128k to 2M+
43 * works efficiently.
44 *
45 * Each bucket has a 16 bit priority, and an 8 bit generation associated with
46 * it. The gens and priorities for all the buckets are stored contiguously and
47 * packed on disk (in a linked list of buckets - aside from the superblock, all
48 * of bcache's metadata is stored in buckets).
49 *
50 * The priority is used to implement an LRU. We reset a bucket's priority when
51 * we allocate it or on cache it, and every so often we decrement the priority
52 * of each bucket. It could be used to implement something more sophisticated,
53 * if anyone ever gets around to it.
54 *
55 * The generation is used for invalidating buckets. Each pointer also has an 8
56 * bit generation embedded in it; for a pointer to be considered valid, its gen
57 * must match the gen of the bucket it points into. Thus, to reuse a bucket all
58 * we have to do is increment its gen (and write its new gen to disk; we batch
59 * this up).
60 *
61 * Bcache is entirely COW - we never write twice to a bucket, even buckets that
62 * contain metadata (including btree nodes).
63 *
64 * THE BTREE:
65 *
66 * Bcache is in large part design around the btree.
67 *
68 * At a high level, the btree is just an index of key -> ptr tuples.
69 *
70 * Keys represent extents, and thus have a size field. Keys also have a variable
71 * number of pointers attached to them (potentially zero, which is handy for
72 * invalidating the cache).
73 *
74 * The key itself is an inode:offset pair. The inode number corresponds to a
75 * backing device or a flash only volume. The offset is the ending offset of the
76 * extent within the inode - not the starting offset; this makes lookups
77 * slightly more convenient.
78 *
79 * Pointers contain the cache device id, the offset on that device, and an 8 bit
80 * generation number. More on the gen later.
81 *
82 * Index lookups are not fully abstracted - cache lookups in particular are
83 * still somewhat mixed in with the btree code, but things are headed in that
84 * direction.
85 *
86 * Updates are fairly well abstracted, though. There are two different ways of
87 * updating the btree; insert and replace.
88 *
89 * BTREE_INSERT will just take a list of keys and insert them into the btree -
90 * overwriting (possibly only partially) any extents they overlap with. This is
91 * used to update the index after a write.
92 *
93 * BTREE_REPLACE is really cmpxchg(); it inserts a key into the btree iff it is
94 * overwriting a key that matches another given key. This is used for inserting
95 * data into the cache after a cache miss, and for background writeback, and for
96 * the moving garbage collector.
97 *
98 * There is no "delete" operation; deleting things from the index is
99 * accomplished by either by invalidating pointers (by incrementing a bucket's
100 * gen) or by inserting a key with 0 pointers - which will overwrite anything
101 * previously present at that location in the index.
102 *
103 * This means that there are always stale/invalid keys in the btree. They're
104 * filtered out by the code that iterates through a btree node, and removed when
105 * a btree node is rewritten.
106 *
107 * BTREE NODES:
108 *
109 * Our unit of allocation is a bucket, and we we can't arbitrarily allocate and
110 * free smaller than a bucket - so, that's how big our btree nodes are.
111 *
112 * (If buckets are really big we'll only use part of the bucket for a btree node
113 * - no less than 1/4th - but a bucket still contains no more than a single
114 * btree node. I'd actually like to change this, but for now we rely on the
115 * bucket's gen for deleting btree nodes when we rewrite/split a node.)
116 *
117 * Anyways, btree nodes are big - big enough to be inefficient with a textbook
118 * btree implementation.
119 *
120 * The way this is solved is that btree nodes are internally log structured; we
121 * can append new keys to an existing btree node without rewriting it. This
122 * means each set of keys we write is sorted, but the node is not.
123 *
124 * We maintain this log structure in memory - keeping 1Mb of keys sorted would
125 * be expensive, and we have to distinguish between the keys we have written and
126 * the keys we haven't. So to do a lookup in a btree node, we have to search
127 * each sorted set. But we do merge written sets together lazily, so the cost of
128 * these extra searches is quite low (normally most of the keys in a btree node
129 * will be in one big set, and then there'll be one or two sets that are much
130 * smaller).
131 *
132 * This log structure makes bcache's btree more of a hybrid between a
133 * conventional btree and a compacting data structure, with some of the
134 * advantages of both.
135 *
136 * GARBAGE COLLECTION:
137 *
138 * We can't just invalidate any bucket - it might contain dirty data or
139 * metadata. If it once contained dirty data, other writes might overwrite it
140 * later, leaving no valid pointers into that bucket in the index.
141 *
142 * Thus, the primary purpose of garbage collection is to find buckets to reuse.
143 * It also counts how much valid data it each bucket currently contains, so that
144 * allocation can reuse buckets sooner when they've been mostly overwritten.
145 *
146 * It also does some things that are really internal to the btree
147 * implementation. If a btree node contains pointers that are stale by more than
148 * some threshold, it rewrites the btree node to avoid the bucket's generation
149 * wrapping around. It also merges adjacent btree nodes if they're empty enough.
150 *
151 * THE JOURNAL:
152 *
153 * Bcache's journal is not necessary for consistency; we always strictly
154 * order metadata writes so that the btree and everything else is consistent on
155 * disk in the event of an unclean shutdown, and in fact bcache had writeback
156 * caching (with recovery from unclean shutdown) before journalling was
157 * implemented.
158 *
159 * Rather, the journal is purely a performance optimization; we can't complete a
160 * write until we've updated the index on disk, otherwise the cache would be
161 * inconsistent in the event of an unclean shutdown. This means that without the
162 * journal, on random write workloads we constantly have to update all the leaf
163 * nodes in the btree, and those writes will be mostly empty (appending at most
164 * a few keys each) - highly inefficient in terms of amount of metadata writes,
165 * and it puts more strain on the various btree resorting/compacting code.
166 *
167 * The journal is just a log of keys we've inserted; on startup we just reinsert
168 * all the keys in the open journal entries. That means that when we're updating
169 * a node in the btree, we can wait until a 4k block of keys fills up before
170 * writing them out.
171 *
172 * For simplicity, we only journal updates to leaf nodes; updates to parent
173 * nodes are rare enough (since our leaf nodes are huge) that it wasn't worth
174 * the complexity to deal with journalling them (in particular, journal replay)
175 * - updates to non leaf nodes just happen synchronously (see btree_split()).
176 */
177
178#define pr_fmt(fmt) "bcache: %s() " fmt "\n", __func__
179
Kent Overstreet81ab4192013-10-31 15:46:42 -0700180#include <linux/bcache.h>
Kent Overstreetcafe5632013-03-23 16:11:31 -0700181#include <linux/bio.h>
Kent Overstreetcafe5632013-03-23 16:11:31 -0700182#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/types.h>
188#include <linux/workqueue.h>
189
Kent Overstreet67539e82013-09-10 22:53:34 -0700190#include "bset.h"
Kent Overstreetcafe5632013-03-23 16:11:31 -0700191#include "util.h"
192#include "closure.h"
193
194struct bucket {
195 atomic_t pin;
196 uint16_t prio;
197 uint8_t gen;
198 uint8_t disk_gen;
199 uint8_t last_gc; /* Most out of date gen in the btree */
200 uint8_t gc_gen;
Nicholas Swenson981aa8c2013-11-07 17:53:19 -0800201 uint16_t gc_mark; /* Bitfield used by GC. See below for field */
Kent Overstreetcafe5632013-03-23 16:11:31 -0700202};
203
204/*
205 * I'd use bitfields for these, but I don't trust the compiler not to screw me
206 * as multiple threads touch struct bucket without locking
207 */
208
209BITMASK(GC_MARK, struct bucket, gc_mark, 0, 2);
210#define GC_MARK_RECLAIMABLE 0
211#define GC_MARK_DIRTY 1
212#define GC_MARK_METADATA 2
Nicholas Swenson981aa8c2013-11-07 17:53:19 -0800213BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, 13);
214BITMASK(GC_MOVE, struct bucket, gc_mark, 15, 1);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700215
Kent Overstreetcafe5632013-03-23 16:11:31 -0700216#include "journal.h"
217#include "stats.h"
218struct search;
219struct btree;
220struct keybuf;
221
222struct keybuf_key {
223 struct rb_node node;
224 BKEY_PADDED(key);
225 void *private;
226};
227
Kent Overstreetcafe5632013-03-23 16:11:31 -0700228struct keybuf {
Kent Overstreetcafe5632013-03-23 16:11:31 -0700229 struct bkey last_scanned;
230 spinlock_t lock;
231
232 /*
233 * Beginning and end of range in rb tree - so that we can skip taking
234 * lock and checking the rb tree when we need to check for overlapping
235 * keys.
236 */
237 struct bkey start;
238 struct bkey end;
239
240 struct rb_root keys;
241
Kent Overstreet48a915a2013-10-31 15:43:22 -0700242#define KEYBUF_NR 500
Kent Overstreetcafe5632013-03-23 16:11:31 -0700243 DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR);
244};
245
246struct bio_split_pool {
247 struct bio_set *bio_split;
248 mempool_t *bio_split_hook;
249};
250
251struct bio_split_hook {
252 struct closure cl;
253 struct bio_split_pool *p;
254 struct bio *bio;
255 bio_end_io_t *bi_end_io;
256 void *bi_private;
257};
258
259struct bcache_device {
260 struct closure cl;
261
262 struct kobject kobj;
263
264 struct cache_set *c;
265 unsigned id;
266#define BCACHEDEVNAME_SIZE 12
267 char name[BCACHEDEVNAME_SIZE];
268
269 struct gendisk *disk;
270
Kent Overstreetc4d951d2013-08-21 17:49:09 -0700271 unsigned long flags;
272#define BCACHE_DEV_CLOSING 0
273#define BCACHE_DEV_DETACHING 1
274#define BCACHE_DEV_UNLINK_DONE 2
Kent Overstreetcafe5632013-03-23 16:11:31 -0700275
Kent Overstreet48a915a2013-10-31 15:43:22 -0700276 unsigned nr_stripes;
Kent Overstreet2d679fc2013-08-17 02:13:15 -0700277 unsigned stripe_size;
Kent Overstreet279afba2013-06-05 06:21:07 -0700278 atomic_t *stripe_sectors_dirty;
Kent Overstreet48a915a2013-10-31 15:43:22 -0700279 unsigned long *full_dirty_stripes;
Kent Overstreet279afba2013-06-05 06:21:07 -0700280
Kent Overstreetcafe5632013-03-23 16:11:31 -0700281 unsigned long sectors_dirty_last;
282 long sectors_dirty_derivative;
283
Kent Overstreetcafe5632013-03-23 16:11:31 -0700284 struct bio_set *bio_split;
285
286 unsigned data_csum:1;
287
288 int (*cache_miss)(struct btree *, struct search *,
289 struct bio *, unsigned);
290 int (*ioctl) (struct bcache_device *, fmode_t, unsigned, unsigned long);
291
292 struct bio_split_pool bio_split_hook;
293};
294
295struct io {
296 /* Used to track sequential IO so it can be skipped */
297 struct hlist_node hash;
298 struct list_head lru;
299
300 unsigned long jiffies;
301 unsigned sequential;
302 sector_t last;
303};
304
305struct cached_dev {
306 struct list_head list;
307 struct bcache_device disk;
308 struct block_device *bdev;
309
310 struct cache_sb sb;
311 struct bio sb_bio;
312 struct bio_vec sb_bv[1];
Kent Overstreetcb7a5832013-12-16 15:27:25 -0800313 struct closure sb_write;
314 struct semaphore sb_write_mutex;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700315
316 /* Refcount on the cache set. Always nonzero when we're caching. */
317 atomic_t count;
318 struct work_struct detach;
319
320 /*
321 * Device might not be running if it's dirty and the cache set hasn't
322 * showed up yet.
323 */
324 atomic_t running;
325
326 /*
327 * Writes take a shared lock from start to finish; scanning for dirty
328 * data to refill the rb tree requires an exclusive lock.
329 */
330 struct rw_semaphore writeback_lock;
331
332 /*
333 * Nonzero, and writeback has a refcount (d->count), iff there is dirty
334 * data in the cache. Protected by writeback_lock; must have an
335 * shared lock to set and exclusive lock to clear.
336 */
337 atomic_t has_dirty;
338
Kent Overstreetc2a4f312013-09-23 23:17:31 -0700339 struct bch_ratelimit writeback_rate;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700340 struct delayed_work writeback_rate_update;
341
342 /*
343 * Internal to the writeback code, so read_dirty() can keep track of
344 * where it's at.
345 */
346 sector_t last_read;
347
Kent Overstreetc2a4f312013-09-23 23:17:31 -0700348 /* Limit number of writeback bios in flight */
349 struct semaphore in_flight;
Kent Overstreet5e6926d2013-07-24 17:50:06 -0700350 struct task_struct *writeback_thread;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700351
352 struct keybuf writeback_keys;
353
354 /* For tracking sequential IO */
355#define RECENT_IO_BITS 7
356#define RECENT_IO (1 << RECENT_IO_BITS)
357 struct io io[RECENT_IO];
358 struct hlist_head io_hash[RECENT_IO + 1];
359 struct list_head io_lru;
360 spinlock_t io_lock;
361
362 struct cache_accounting accounting;
363
364 /* The rest of this all shows up in sysfs */
365 unsigned sequential_cutoff;
366 unsigned readahead;
367
Kent Overstreetcafe5632013-03-23 16:11:31 -0700368 unsigned verify:1;
Kent Overstreet5ceaaad2013-09-10 14:27:42 -0700369 unsigned bypass_torture_test:1;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700370
Kent Overstreet72c27062013-06-05 06:24:39 -0700371 unsigned partial_stripes_expensive:1;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700372 unsigned writeback_metadata:1;
373 unsigned writeback_running:1;
374 unsigned char writeback_percent;
375 unsigned writeback_delay;
376
Kent Overstreetcafe5632013-03-23 16:11:31 -0700377 uint64_t writeback_rate_target;
Kent Overstreet16749c22013-11-11 13:58:34 -0800378 int64_t writeback_rate_proportional;
379 int64_t writeback_rate_derivative;
380 int64_t writeback_rate_change;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700381
382 unsigned writeback_rate_update_seconds;
383 unsigned writeback_rate_d_term;
384 unsigned writeback_rate_p_term_inverse;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700385};
386
Kent Overstreet78365412013-12-17 01:29:34 -0800387enum alloc_reserve {
388 RESERVE_BTREE,
389 RESERVE_PRIO,
390 RESERVE_MOVINGGC,
391 RESERVE_NONE,
392 RESERVE_NR,
Kent Overstreetcafe5632013-03-23 16:11:31 -0700393};
394
395struct cache {
396 struct cache_set *set;
397 struct cache_sb sb;
398 struct bio sb_bio;
399 struct bio_vec sb_bv[1];
400
401 struct kobject kobj;
402 struct block_device *bdev;
403
Kent Overstreet119ba0f2013-04-24 19:01:12 -0700404 struct task_struct *alloc_thread;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700405
406 struct closure prio;
407 struct prio_set *disk_buckets;
408
409 /*
410 * When allocating new buckets, prio_write() gets first dibs - since we
411 * may not be allocate at all without writing priorities and gens.
412 * prio_buckets[] contains the last buckets we wrote priorities to (so
413 * gc can mark them as metadata), prio_next[] contains the buckets
414 * allocated for the next prio write.
415 */
416 uint64_t *prio_buckets;
417 uint64_t *prio_last_buckets;
418
419 /*
420 * free: Buckets that are ready to be used
421 *
422 * free_inc: Incoming buckets - these are buckets that currently have
423 * cached data in them, and we can't reuse them until after we write
424 * their new gen to disk. After prio_write() finishes writing the new
425 * gens/prios, they'll be moved to the free list (and possibly discarded
426 * in the process)
427 *
428 * unused: GC found nothing pointing into these buckets (possibly
429 * because all the data they contained was overwritten), so we only
430 * need to discard them before they can be moved to the free list.
431 */
Kent Overstreet78365412013-12-17 01:29:34 -0800432 DECLARE_FIFO(long, free)[RESERVE_NR];
Kent Overstreetcafe5632013-03-23 16:11:31 -0700433 DECLARE_FIFO(long, free_inc);
434 DECLARE_FIFO(long, unused);
435
436 size_t fifo_last_bucket;
437
438 /* Allocation stuff: */
439 struct bucket *buckets;
440
441 DECLARE_HEAP(struct bucket *, heap);
442
443 /*
444 * max(gen - disk_gen) for all buckets. When it gets too big we have to
445 * call prio_write() to keep gens from wrapping.
446 */
447 uint8_t need_save_prio;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700448
449 /*
450 * If nonzero, we know we aren't going to find any buckets to invalidate
451 * until a gc finishes - otherwise we could pointlessly burn a ton of
452 * cpu
453 */
454 unsigned invalidate_needs_gc:1;
455
456 bool discard; /* Get rid of? */
457
Kent Overstreetcafe5632013-03-23 16:11:31 -0700458 struct journal_device journal;
459
460 /* The rest of this all shows up in sysfs */
461#define IO_ERROR_SHIFT 20
462 atomic_t io_errors;
463 atomic_t io_count;
464
465 atomic_long_t meta_sectors_written;
466 atomic_long_t btree_sectors_written;
467 atomic_long_t sectors_written;
468
469 struct bio_split_pool bio_split_hook;
470};
471
472struct gc_stat {
473 size_t nodes;
474 size_t key_bytes;
475
476 size_t nkeys;
477 uint64_t data; /* sectors */
Kent Overstreetcafe5632013-03-23 16:11:31 -0700478 unsigned in_use; /* percent */
479};
480
481/*
482 * Flag bits, for how the cache set is shutting down, and what phase it's at:
483 *
484 * CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching
485 * all the backing devices first (their cached data gets invalidated, and they
486 * won't automatically reattach).
487 *
488 * CACHE_SET_STOPPING always gets set first when we're closing down a cache set;
489 * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e.
490 * flushing dirty data).
Kent Overstreetcafe5632013-03-23 16:11:31 -0700491 */
492#define CACHE_SET_UNREGISTERING 0
493#define CACHE_SET_STOPPING 1
Kent Overstreetcafe5632013-03-23 16:11:31 -0700494
495struct cache_set {
496 struct closure cl;
497
498 struct list_head list;
499 struct kobject kobj;
500 struct kobject internal;
501 struct dentry *debug;
502 struct cache_accounting accounting;
503
504 unsigned long flags;
505
506 struct cache_sb sb;
507
508 struct cache *cache[MAX_CACHES_PER_SET];
509 struct cache *cache_by_alloc[MAX_CACHES_PER_SET];
510 int caches_loaded;
511
512 struct bcache_device **devices;
513 struct list_head cached_devs;
514 uint64_t cached_dev_sectors;
515 struct closure caching;
516
Kent Overstreetcb7a5832013-12-16 15:27:25 -0800517 struct closure sb_write;
518 struct semaphore sb_write_mutex;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700519
520 mempool_t *search;
521 mempool_t *bio_meta;
522 struct bio_set *bio_split;
523
524 /* For the btree cache */
525 struct shrinker shrink;
526
Kent Overstreetcafe5632013-03-23 16:11:31 -0700527 /* For the btree cache and anything allocation related */
528 struct mutex bucket_lock;
529
530 /* log2(bucket_size), in sectors */
531 unsigned short bucket_bits;
532
533 /* log2(block_size), in sectors */
534 unsigned short block_bits;
535
536 /*
537 * Default number of pages for a new btree node - may be less than a
538 * full bucket
539 */
540 unsigned btree_pages;
541
542 /*
543 * Lists of struct btrees; lru is the list for structs that have memory
544 * allocated for actual btree node, freed is for structs that do not.
545 *
546 * We never free a struct btree, except on shutdown - we just put it on
547 * the btree_cache_freed list and reuse it later. This simplifies the
548 * code, and it doesn't cost us much memory as the memory usage is
549 * dominated by buffers that hold the actual btree node data and those
550 * can be freed - and the number of struct btrees allocated is
551 * effectively bounded.
552 *
553 * btree_cache_freeable effectively is a small cache - we use it because
554 * high order page allocations can be rather expensive, and it's quite
555 * common to delete and allocate btree nodes in quick succession. It
556 * should never grow past ~2-3 nodes in practice.
557 */
558 struct list_head btree_cache;
559 struct list_head btree_cache_freeable;
560 struct list_head btree_cache_freed;
561
562 /* Number of elements in btree_cache + btree_cache_freeable lists */
563 unsigned bucket_cache_used;
564
565 /*
566 * If we need to allocate memory for a new btree node and that
567 * allocation fails, we can cannibalize another node in the btree cache
568 * to satisfy the allocation. However, only one thread can be doing this
569 * at a time, for obvious reasons - try_harder and try_wait are
570 * basically a lock for this that we can wait on asynchronously. The
571 * btree_root() macro releases the lock when it returns.
572 */
Kent Overstreete8e1d462013-07-24 17:27:07 -0700573 struct task_struct *try_harder;
574 wait_queue_head_t try_wait;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700575 uint64_t try_harder_start;
576
577 /*
578 * When we free a btree node, we increment the gen of the bucket the
579 * node is in - but we can't rewrite the prios and gens until we
580 * finished whatever it is we were doing, otherwise after a crash the
581 * btree node would be freed but for say a split, we might not have the
582 * pointers to the new nodes inserted into the btree yet.
583 *
584 * This is a refcount that blocks prio_write() until the new keys are
585 * written.
586 */
587 atomic_t prio_blocked;
Kent Overstreet35fcd842013-07-24 17:29:09 -0700588 wait_queue_head_t bucket_wait;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700589
590 /*
591 * For any bio we don't skip we subtract the number of sectors from
592 * rescale; when it hits 0 we rescale all the bucket priorities.
593 */
594 atomic_t rescale;
595 /*
596 * When we invalidate buckets, we use both the priority and the amount
597 * of good data to determine which buckets to reuse first - to weight
598 * those together consistently we keep track of the smallest nonzero
599 * priority of any bucket.
600 */
601 uint16_t min_prio;
602
603 /*
604 * max(gen - gc_gen) for all buckets. When it gets too big we have to gc
605 * to keep gens from wrapping around.
606 */
607 uint8_t need_gc;
608 struct gc_stat gc_stats;
609 size_t nbuckets;
610
Kent Overstreet72a44512013-10-24 17:19:26 -0700611 struct task_struct *gc_thread;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700612 /* Where in the btree gc currently is */
613 struct bkey gc_done;
614
615 /*
616 * The allocation code needs gc_mark in struct bucket to be correct, but
617 * it's not while a gc is in progress. Protected by bucket_lock.
618 */
619 int gc_mark_valid;
620
621 /* Counts how many sectors bio_insert has added to the cache */
622 atomic_t sectors_to_gc;
623
Kent Overstreet72a44512013-10-24 17:19:26 -0700624 wait_queue_head_t moving_gc_wait;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700625 struct keybuf moving_gc_keys;
626 /* Number of moving GC bios in flight */
Kent Overstreet72a44512013-10-24 17:19:26 -0700627 struct semaphore moving_in_flight;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700628
629 struct btree *root;
630
631#ifdef CONFIG_BCACHE_DEBUG
632 struct btree *verify_data;
Kent Overstreet78b77bf2013-12-17 22:49:08 -0800633 struct bset *verify_ondisk;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700634 struct mutex verify_lock;
635#endif
636
637 unsigned nr_uuids;
638 struct uuid_entry *uuids;
639 BKEY_PADDED(uuid_bucket);
Kent Overstreetcb7a5832013-12-16 15:27:25 -0800640 struct closure uuid_write;
641 struct semaphore uuid_write_mutex;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700642
643 /*
644 * A btree node on disk could have too many bsets for an iterator to fit
Kent Overstreet57943512013-04-25 13:58:35 -0700645 * on the stack - have to dynamically allocate them
Kent Overstreetcafe5632013-03-23 16:11:31 -0700646 */
Kent Overstreet57943512013-04-25 13:58:35 -0700647 mempool_t *fill_iter;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700648
Kent Overstreet67539e82013-09-10 22:53:34 -0700649 struct bset_sort_state sort;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700650
651 /* List of buckets we're currently writing data to */
652 struct list_head data_buckets;
653 spinlock_t data_bucket_lock;
654
655 struct journal journal;
656
657#define CONGESTED_MAX 1024
658 unsigned congested_last_us;
659 atomic_t congested;
660
661 /* The rest of this all shows up in sysfs */
662 unsigned congested_read_threshold_us;
663 unsigned congested_write_threshold_us;
664
Kent Overstreetcafe5632013-03-23 16:11:31 -0700665 struct time_stats btree_gc_time;
666 struct time_stats btree_split_time;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700667 struct time_stats btree_read_time;
668 struct time_stats try_harder_time;
669
670 atomic_long_t cache_read_races;
671 atomic_long_t writeback_keys_done;
672 atomic_long_t writeback_keys_failed;
Kent Overstreet77c320e2013-07-11 19:42:51 -0700673
674 enum {
675 ON_ERROR_UNREGISTER,
676 ON_ERROR_PANIC,
677 } on_error;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700678 unsigned error_limit;
679 unsigned error_decay;
Kent Overstreet77c320e2013-07-11 19:42:51 -0700680
Kent Overstreetcafe5632013-03-23 16:11:31 -0700681 unsigned short journal_delay_ms;
Kent Overstreeta85e9682013-12-20 17:28:16 -0800682 bool expensive_debug_checks;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700683 unsigned verify:1;
684 unsigned key_merging_disabled:1;
685 unsigned gc_always_rewrite:1;
686 unsigned shrinker_disabled:1;
687 unsigned copy_gc_enabled:1;
688
689#define BUCKET_HASH_BITS 12
690 struct hlist_head bucket_hash[1 << BUCKET_HASH_BITS];
691};
692
Kent Overstreetcafe5632013-03-23 16:11:31 -0700693struct bbio {
694 unsigned submit_time_us;
695 union {
696 struct bkey key;
697 uint64_t _pad[3];
698 /*
699 * We only need pad = 3 here because we only ever carry around a
700 * single pointer - i.e. the pointer we're doing io to/from.
701 */
702 };
703 struct bio bio;
704};
705
Kent Overstreetcafe5632013-03-23 16:11:31 -0700706#define BTREE_PRIO USHRT_MAX
Kent Overstreete0a985a2013-11-12 13:49:10 -0800707#define INITIAL_PRIO 32768U
Kent Overstreetcafe5632013-03-23 16:11:31 -0700708
709#define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE)
710#define btree_blocks(b) \
711 ((unsigned) (KEY_SIZE(&b->key) >> (b)->c->block_bits))
712
713#define btree_default_blocks(c) \
714 ((unsigned) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits))
715
716#define bucket_pages(c) ((c)->sb.bucket_size / PAGE_SECTORS)
717#define bucket_bytes(c) ((c)->sb.bucket_size << 9)
718#define block_bytes(c) ((c)->sb.block_size << 9)
719
Kent Overstreetcafe5632013-03-23 16:11:31 -0700720#define prios_per_bucket(c) \
721 ((bucket_bytes(c) - sizeof(struct prio_set)) / \
722 sizeof(struct bucket_disk))
723#define prio_buckets(c) \
724 DIV_ROUND_UP((size_t) (c)->sb.nbuckets, prios_per_bucket(c))
725
Kent Overstreetcafe5632013-03-23 16:11:31 -0700726static inline size_t sector_to_bucket(struct cache_set *c, sector_t s)
727{
728 return s >> c->bucket_bits;
729}
730
731static inline sector_t bucket_to_sector(struct cache_set *c, size_t b)
732{
733 return ((sector_t) b) << c->bucket_bits;
734}
735
736static inline sector_t bucket_remainder(struct cache_set *c, sector_t s)
737{
738 return s & (c->sb.bucket_size - 1);
739}
740
741static inline struct cache *PTR_CACHE(struct cache_set *c,
742 const struct bkey *k,
743 unsigned ptr)
744{
745 return c->cache[PTR_DEV(k, ptr)];
746}
747
748static inline size_t PTR_BUCKET_NR(struct cache_set *c,
749 const struct bkey *k,
750 unsigned ptr)
751{
752 return sector_to_bucket(c, PTR_OFFSET(k, ptr));
753}
754
755static inline struct bucket *PTR_BUCKET(struct cache_set *c,
756 const struct bkey *k,
757 unsigned ptr)
758{
759 return PTR_CACHE(c, k, ptr)->buckets + PTR_BUCKET_NR(c, k, ptr);
760}
761
Kent Overstreet9a02b7e2013-12-20 17:24:46 -0800762static inline uint8_t gen_after(uint8_t a, uint8_t b)
763{
764 uint8_t r = a - b;
765 return r > 128U ? 0 : r;
766}
767
768static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
769 unsigned i)
770{
771 return gen_after(PTR_BUCKET(c, k, i)->gen, PTR_GEN(k, i));
772}
773
774static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
775 unsigned i)
776{
777 return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && PTR_CACHE(c, k, i);
778}
779
Kent Overstreetcafe5632013-03-23 16:11:31 -0700780/* Btree key macros */
781
Kent Overstreetcafe5632013-03-23 16:11:31 -0700782/*
783 * This is used for various on disk data structures - cache_sb, prio_set, bset,
784 * jset: The checksum is _always_ the first 8 bytes of these structs
785 */
786#define csum_set(i) \
Kent Overstreet169ef1c2013-03-28 12:50:55 -0600787 bch_crc64(((void *) (i)) + sizeof(uint64_t), \
Kent Overstreetfafff812013-12-17 21:56:21 -0800788 ((void *) bset_bkey_last(i)) - \
789 (((void *) (i)) + sizeof(uint64_t)))
Kent Overstreetcafe5632013-03-23 16:11:31 -0700790
791/* Error handling macros */
792
793#define btree_bug(b, ...) \
794do { \
795 if (bch_cache_set_error((b)->c, __VA_ARGS__)) \
796 dump_stack(); \
797} while (0)
798
799#define cache_bug(c, ...) \
800do { \
801 if (bch_cache_set_error(c, __VA_ARGS__)) \
802 dump_stack(); \
803} while (0)
804
805#define btree_bug_on(cond, b, ...) \
806do { \
807 if (cond) \
808 btree_bug(b, __VA_ARGS__); \
809} while (0)
810
811#define cache_bug_on(cond, c, ...) \
812do { \
813 if (cond) \
814 cache_bug(c, __VA_ARGS__); \
815} while (0)
816
817#define cache_set_err_on(cond, c, ...) \
818do { \
819 if (cond) \
820 bch_cache_set_error(c, __VA_ARGS__); \
821} while (0)
822
823/* Looping macros */
824
825#define for_each_cache(ca, cs, iter) \
826 for (iter = 0; ca = cs->cache[iter], iter < (cs)->sb.nr_in_set; iter++)
827
828#define for_each_bucket(b, ca) \
829 for (b = (ca)->buckets + (ca)->sb.first_bucket; \
830 b < (ca)->buckets + (ca)->sb.nbuckets; b++)
831
Kent Overstreetcafe5632013-03-23 16:11:31 -0700832static inline void cached_dev_put(struct cached_dev *dc)
833{
834 if (atomic_dec_and_test(&dc->count))
835 schedule_work(&dc->detach);
836}
837
838static inline bool cached_dev_get(struct cached_dev *dc)
839{
840 if (!atomic_inc_not_zero(&dc->count))
841 return false;
842
843 /* Paired with the mb in cached_dev_attach */
844 smp_mb__after_atomic_inc();
845 return true;
846}
847
848/*
849 * bucket_gc_gen() returns the difference between the bucket's current gen and
850 * the oldest gen of any pointer into that bucket in the btree (last_gc).
851 *
852 * bucket_disk_gen() returns the difference between the current gen and the gen
853 * on disk; they're both used to make sure gens don't wrap around.
854 */
855
856static inline uint8_t bucket_gc_gen(struct bucket *b)
857{
858 return b->gen - b->last_gc;
859}
860
861static inline uint8_t bucket_disk_gen(struct bucket *b)
862{
863 return b->gen - b->disk_gen;
864}
865
866#define BUCKET_GC_GEN_MAX 96U
867#define BUCKET_DISK_GEN_MAX 64U
868
869#define kobj_attribute_write(n, fn) \
870 static struct kobj_attribute ksysfs_##n = __ATTR(n, S_IWUSR, NULL, fn)
871
872#define kobj_attribute_rw(n, show, store) \
873 static struct kobj_attribute ksysfs_##n = \
874 __ATTR(n, S_IWUSR|S_IRUSR, show, store)
875
Kent Overstreet119ba0f2013-04-24 19:01:12 -0700876static inline void wake_up_allocators(struct cache_set *c)
877{
878 struct cache *ca;
879 unsigned i;
880
881 for_each_cache(ca, c, i)
882 wake_up_process(ca->alloc_thread);
883}
884
Kent Overstreetcafe5632013-03-23 16:11:31 -0700885/* Forward declarations */
886
Kent Overstreetcafe5632013-03-23 16:11:31 -0700887void bch_count_io_errors(struct cache *, int, const char *);
888void bch_bbio_count_io_errors(struct cache_set *, struct bio *,
889 int, const char *);
890void bch_bbio_endio(struct cache_set *, struct bio *, int, const char *);
891void bch_bbio_free(struct bio *, struct cache_set *);
892struct bio *bch_bbio_alloc(struct cache_set *);
893
Kent Overstreetcafe5632013-03-23 16:11:31 -0700894void bch_generic_make_request(struct bio *, struct bio_split_pool *);
895void __bch_submit_bbio(struct bio *, struct cache_set *);
896void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned);
897
898uint8_t bch_inc_gen(struct cache *, struct bucket *);
899void bch_rescale_priorities(struct cache_set *, int);
900bool bch_bucket_add_unused(struct cache *, struct bucket *);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700901
Kent Overstreet35fcd842013-07-24 17:29:09 -0700902long bch_bucket_alloc(struct cache *, unsigned, bool);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700903void bch_bucket_free(struct cache_set *, struct bkey *);
904
905int __bch_bucket_alloc_set(struct cache_set *, unsigned,
Kent Overstreet35fcd842013-07-24 17:29:09 -0700906 struct bkey *, int, bool);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700907int bch_bucket_alloc_set(struct cache_set *, unsigned,
Kent Overstreet35fcd842013-07-24 17:29:09 -0700908 struct bkey *, int, bool);
Kent Overstreet2599b532013-07-24 18:11:11 -0700909bool bch_alloc_sectors(struct cache_set *, struct bkey *, unsigned,
910 unsigned, unsigned, bool);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700911
912__printf(2, 3)
913bool bch_cache_set_error(struct cache_set *, const char *, ...);
914
915void bch_prio_write(struct cache *);
916void bch_write_bdev_super(struct cached_dev *, struct closure *);
917
Kent Overstreet72a44512013-10-24 17:19:26 -0700918extern struct workqueue_struct *bcache_wq;
Kent Overstreetcafe5632013-03-23 16:11:31 -0700919extern const char * const bch_cache_modes[];
920extern struct mutex bch_register_lock;
921extern struct list_head bch_cache_sets;
922
923extern struct kobj_type bch_cached_dev_ktype;
924extern struct kobj_type bch_flash_dev_ktype;
925extern struct kobj_type bch_cache_set_ktype;
926extern struct kobj_type bch_cache_set_internal_ktype;
927extern struct kobj_type bch_cache_ktype;
928
929void bch_cached_dev_release(struct kobject *);
930void bch_flash_dev_release(struct kobject *);
931void bch_cache_set_release(struct kobject *);
932void bch_cache_release(struct kobject *);
933
934int bch_uuid_write(struct cache_set *);
935void bcache_write_super(struct cache_set *);
936
937int bch_flash_dev_create(struct cache_set *c, uint64_t size);
938
939int bch_cached_dev_attach(struct cached_dev *, struct cache_set *);
940void bch_cached_dev_detach(struct cached_dev *);
941void bch_cached_dev_run(struct cached_dev *);
942void bcache_device_stop(struct bcache_device *);
943
944void bch_cache_set_unregister(struct cache_set *);
945void bch_cache_set_stop(struct cache_set *);
946
947struct cache_set *bch_cache_set_alloc(struct cache_sb *);
948void bch_btree_cache_free(struct cache_set *);
949int bch_btree_cache_alloc(struct cache_set *);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700950void bch_moving_init_cache_set(struct cache_set *);
Kent Overstreet2599b532013-07-24 18:11:11 -0700951int bch_open_buckets_alloc(struct cache_set *);
952void bch_open_buckets_free(struct cache_set *);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700953
Kent Overstreet119ba0f2013-04-24 19:01:12 -0700954int bch_cache_allocator_start(struct cache *ca);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700955int bch_cache_allocator_init(struct cache *ca);
956
957void bch_debug_exit(void);
958int bch_debug_init(struct kobject *);
Kent Overstreetcafe5632013-03-23 16:11:31 -0700959void bch_request_exit(void);
960int bch_request_init(void);
961void bch_btree_exit(void);
962int bch_btree_init(void);
963
964#endif /* _BCACHE_H */