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1/*
2 * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
3 *
4 * Uses a block device as cache for other block devices; optimized for SSDs.
5 * All allocation is done in buckets, which should match the erase block size
6 * of the device.
7 *
8 * Buckets containing cached data are kept on a heap sorted by priority;
9 * bucket priority is increased on cache hit, and periodically all the buckets
10 * on the heap have their priority scaled down. This currently is just used as
11 * an LRU but in the future should allow for more intelligent heuristics.
12 *
13 * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
14 * counter. Garbage collection is used to remove stale pointers.
15 *
16 * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
17 * as keys are inserted we only sort the pages that have not yet been written.
18 * When garbage collection is run, we resort the entire node.
19 *
20 * All configuration is done via sysfs; see Documentation/bcache.txt.
21 */
22
23#include "bcache.h"
24#include "btree.h"
25#include "debug.h"
26#include "extents.h"
27#include "writeback.h"
28
29static void sort_key_next(struct btree_iter *iter,
30 struct btree_iter_set *i)
31{
32 i->k = bkey_next(i->k);
33
34 if (i->k == i->end)
35 *i = iter->data[--iter->used];
36}
37
38static bool bch_key_sort_cmp(struct btree_iter_set l,
39 struct btree_iter_set r)
40{
41 int64_t c = bkey_cmp(l.k, r.k);
42
43 return c ? c > 0 : l.k < r.k;
44}
45
46static bool __ptr_invalid(struct cache_set *c, const struct bkey *k)
47{
48 unsigned i;
49
50 for (i = 0; i < KEY_PTRS(k); i++)
51 if (ptr_available(c, k, i)) {
52 struct cache *ca = PTR_CACHE(c, k, i);
53 size_t bucket = PTR_BUCKET_NR(c, k, i);
54 size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
55
56 if (KEY_SIZE(k) + r > c->sb.bucket_size ||
57 bucket < ca->sb.first_bucket ||
58 bucket >= ca->sb.nbuckets)
59 return true;
60 }
61
62 return false;
63}
64
65/* Common among btree and extent ptrs */
66
67static const char *bch_ptr_status(struct cache_set *c, const struct bkey *k)
68{
69 unsigned i;
70
71 for (i = 0; i < KEY_PTRS(k); i++)
72 if (ptr_available(c, k, i)) {
73 struct cache *ca = PTR_CACHE(c, k, i);
74 size_t bucket = PTR_BUCKET_NR(c, k, i);
75 size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
76
77 if (KEY_SIZE(k) + r > c->sb.bucket_size)
78 return "bad, length too big";
79 if (bucket < ca->sb.first_bucket)
80 return "bad, short offset";
81 if (bucket >= ca->sb.nbuckets)
82 return "bad, offset past end of device";
83 if (ptr_stale(c, k, i))
84 return "stale";
85 }
86
87 if (!bkey_cmp(k, &ZERO_KEY))
88 return "bad, null key";
89 if (!KEY_PTRS(k))
90 return "bad, no pointers";
91 if (!KEY_SIZE(k))
92 return "zeroed key";
93 return "";
94}
95
96void bch_extent_to_text(char *buf, size_t size, const struct bkey *k)
97{
98 unsigned i = 0;
99 char *out = buf, *end = buf + size;
100
101#define p(...) (out += scnprintf(out, end - out, __VA_ARGS__))
102
103 p("%llu:%llu len %llu -> [", KEY_INODE(k), KEY_START(k), KEY_SIZE(k));
104
105 for (i = 0; i < KEY_PTRS(k); i++) {
106 if (i)
107 p(", ");
108
109 if (PTR_DEV(k, i) == PTR_CHECK_DEV)
110 p("check dev");
111 else
112 p("%llu:%llu gen %llu", PTR_DEV(k, i),
113 PTR_OFFSET(k, i), PTR_GEN(k, i));
114 }
115
116 p("]");
117
118 if (KEY_DIRTY(k))
119 p(" dirty");
120 if (KEY_CSUM(k))
121 p(" cs%llu %llx", KEY_CSUM(k), k->ptr[1]);
122#undef p
123}
124
125static void bch_bkey_dump(struct btree_keys *keys, const struct bkey *k)
126{
127 struct btree *b = container_of(keys, struct btree, keys);
128 unsigned j;
129 char buf[80];
130
131 bch_extent_to_text(buf, sizeof(buf), k);
132 printk(" %s", buf);
133
134 for (j = 0; j < KEY_PTRS(k); j++) {
135 size_t n = PTR_BUCKET_NR(b->c, k, j);
136 printk(" bucket %zu", n);
137
138 if (n >= b->c->sb.first_bucket && n < b->c->sb.nbuckets)
139 printk(" prio %i",
140 PTR_BUCKET(b->c, k, j)->prio);
141 }
142
143 printk(" %s\n", bch_ptr_status(b->c, k));
144}
145
146/* Btree ptrs */
147
148bool __bch_btree_ptr_invalid(struct cache_set *c, const struct bkey *k)
149{
150 char buf[80];
151
152 if (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k))
153 goto bad;
154
155 if (__ptr_invalid(c, k))
156 goto bad;
157
158 return false;
159bad:
160 bch_extent_to_text(buf, sizeof(buf), k);
161 cache_bug(c, "spotted btree ptr %s: %s", buf, bch_ptr_status(c, k));
162 return true;
163}
164
165static bool bch_btree_ptr_invalid(struct btree_keys *bk, const struct bkey *k)
166{
167 struct btree *b = container_of(bk, struct btree, keys);
168 return __bch_btree_ptr_invalid(b->c, k);
169}
170
171static bool btree_ptr_bad_expensive(struct btree *b, const struct bkey *k)
172{
173 unsigned i;
174 char buf[80];
175 struct bucket *g;
176
177 if (mutex_trylock(&b->c->bucket_lock)) {
178 for (i = 0; i < KEY_PTRS(k); i++)
179 if (ptr_available(b->c, k, i)) {
180 g = PTR_BUCKET(b->c, k, i);
181
182 if (KEY_DIRTY(k) ||
183 g->prio != BTREE_PRIO ||
184 (b->c->gc_mark_valid &&
185 GC_MARK(g) != GC_MARK_METADATA))
186 goto err;
187 }
188
189 mutex_unlock(&b->c->bucket_lock);
190 }
191
192 return false;
193err:
194 mutex_unlock(&b->c->bucket_lock);
195 bch_extent_to_text(buf, sizeof(buf), k);
196 btree_bug(b,
197"inconsistent btree pointer %s: bucket %zi pin %i prio %i gen %i last_gc %i mark %llu",
198 buf, PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
199 g->prio, g->gen, g->last_gc, GC_MARK(g));
200 return true;
201}
202
203static bool bch_btree_ptr_bad(struct btree_keys *bk, const struct bkey *k)
204{
205 struct btree *b = container_of(bk, struct btree, keys);
206 unsigned i;
207
208 if (!bkey_cmp(k, &ZERO_KEY) ||
209 !KEY_PTRS(k) ||
210 bch_ptr_invalid(bk, k))
211 return true;
212
213 for (i = 0; i < KEY_PTRS(k); i++)
214 if (!ptr_available(b->c, k, i) ||
215 ptr_stale(b->c, k, i))
216 return true;
217
218 if (expensive_debug_checks(b->c) &&
219 btree_ptr_bad_expensive(b, k))
220 return true;
221
222 return false;
223}
224
225static bool bch_btree_ptr_insert_fixup(struct btree_keys *bk,
226 struct bkey *insert,
227 struct btree_iter *iter,
228 struct bkey *replace_key)
229{
230 struct btree *b = container_of(bk, struct btree, keys);
231
232 if (!KEY_OFFSET(insert))
233 btree_current_write(b)->prio_blocked++;
234
235 return false;
236}
237
238const struct btree_keys_ops bch_btree_keys_ops = {
239 .sort_cmp = bch_key_sort_cmp,
240 .insert_fixup = bch_btree_ptr_insert_fixup,
241 .key_invalid = bch_btree_ptr_invalid,
242 .key_bad = bch_btree_ptr_bad,
243 .key_to_text = bch_extent_to_text,
244 .key_dump = bch_bkey_dump,
245};
246
247/* Extents */
248
249/*
250 * Returns true if l > r - unless l == r, in which case returns true if l is
251 * older than r.
252 *
253 * Necessary for btree_sort_fixup() - if there are multiple keys that compare
254 * equal in different sets, we have to process them newest to oldest.
255 */
256static bool bch_extent_sort_cmp(struct btree_iter_set l,
257 struct btree_iter_set r)
258{
259 int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
260
261 return c ? c > 0 : l.k < r.k;
262}
263
264static struct bkey *bch_extent_sort_fixup(struct btree_iter *iter,
265 struct bkey *tmp)
266{
267 while (iter->used > 1) {
268 struct btree_iter_set *top = iter->data, *i = top + 1;
269
270 if (iter->used > 2 &&
271 bch_extent_sort_cmp(i[0], i[1]))
272 i++;
273
274 if (bkey_cmp(top->k, &START_KEY(i->k)) <= 0)
275 break;
276
277 if (!KEY_SIZE(i->k)) {
278 sort_key_next(iter, i);
279 heap_sift(iter, i - top, bch_extent_sort_cmp);
280 continue;
281 }
282
283 if (top->k > i->k) {
284 if (bkey_cmp(top->k, i->k) >= 0)
285 sort_key_next(iter, i);
286 else
287 bch_cut_front(top->k, i->k);
288
289 heap_sift(iter, i - top, bch_extent_sort_cmp);
290 } else {
291 /* can't happen because of comparison func */
292 BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));
293
294 if (bkey_cmp(i->k, top->k) < 0) {
295 bkey_copy(tmp, top->k);
296
297 bch_cut_back(&START_KEY(i->k), tmp);
298 bch_cut_front(i->k, top->k);
299 heap_sift(iter, 0, bch_extent_sort_cmp);
300
301 return tmp;
302 } else {
303 bch_cut_back(&START_KEY(i->k), top->k);
304 }
305 }
306 }
307
308 return NULL;
309}
310
311static void bch_subtract_dirty(struct bkey *k,
312 struct cache_set *c,
313 uint64_t offset,
314 int sectors)
315{
316 if (KEY_DIRTY(k))
317 bcache_dev_sectors_dirty_add(c, KEY_INODE(k),
318 offset, -sectors);
319}
320
321static bool bch_extent_insert_fixup(struct btree_keys *b,
322 struct bkey *insert,
323 struct btree_iter *iter,
324 struct bkey *replace_key)
325{
326 struct cache_set *c = container_of(b, struct btree, keys)->c;
327
328 uint64_t old_offset;
329 unsigned old_size, sectors_found = 0;
330
331 BUG_ON(!KEY_OFFSET(insert));
332 BUG_ON(!KEY_SIZE(insert));
333
334 while (1) {
335 struct bkey *k = bch_btree_iter_next(iter);
336 if (!k)
337 break;
338
339 if (bkey_cmp(&START_KEY(k), insert) >= 0) {
340 if (KEY_SIZE(k))
341 break;
342 else
343 continue;
344 }
345
346 if (bkey_cmp(k, &START_KEY(insert)) <= 0)
347 continue;
348
349 old_offset = KEY_START(k);
350 old_size = KEY_SIZE(k);
351
352 /*
353 * We might overlap with 0 size extents; we can't skip these
354 * because if they're in the set we're inserting to we have to
355 * adjust them so they don't overlap with the key we're
356 * inserting. But we don't want to check them for replace
357 * operations.
358 */
359
360 if (replace_key && KEY_SIZE(k)) {
361 /*
362 * k might have been split since we inserted/found the
363 * key we're replacing
364 */
365 unsigned i;
366 uint64_t offset = KEY_START(k) -
367 KEY_START(replace_key);
368
369 /* But it must be a subset of the replace key */
370 if (KEY_START(k) < KEY_START(replace_key) ||
371 KEY_OFFSET(k) > KEY_OFFSET(replace_key))
372 goto check_failed;
373
374 /* We didn't find a key that we were supposed to */
375 if (KEY_START(k) > KEY_START(insert) + sectors_found)
376 goto check_failed;
377
378 if (!bch_bkey_equal_header(k, replace_key))
379 goto check_failed;
380
381 /* skip past gen */
382 offset <<= 8;
383
384 BUG_ON(!KEY_PTRS(replace_key));
385
386 for (i = 0; i < KEY_PTRS(replace_key); i++)
387 if (k->ptr[i] != replace_key->ptr[i] + offset)
388 goto check_failed;
389
390 sectors_found = KEY_OFFSET(k) - KEY_START(insert);
391 }
392
393 if (bkey_cmp(insert, k) < 0 &&
394 bkey_cmp(&START_KEY(insert), &START_KEY(k)) > 0) {
395 /*
396 * We overlapped in the middle of an existing key: that
397 * means we have to split the old key. But we have to do
398 * slightly different things depending on whether the
399 * old key has been written out yet.
400 */
401
402 struct bkey *top;
403
404 bch_subtract_dirty(k, c, KEY_START(insert),
405 KEY_SIZE(insert));
406
407 if (bkey_written(b, k)) {
408 /*
409 * We insert a new key to cover the top of the
410 * old key, and the old key is modified in place
411 * to represent the bottom split.
412 *
413 * It's completely arbitrary whether the new key
414 * is the top or the bottom, but it has to match
415 * up with what btree_sort_fixup() does - it
416 * doesn't check for this kind of overlap, it
417 * depends on us inserting a new key for the top
418 * here.
419 */
420 top = bch_bset_search(b, bset_tree_last(b),
421 insert);
422 bch_bset_insert(b, top, k);
423 } else {
424 BKEY_PADDED(key) temp;
425 bkey_copy(&temp.key, k);
426 bch_bset_insert(b, k, &temp.key);
427 top = bkey_next(k);
428 }
429
430 bch_cut_front(insert, top);
431 bch_cut_back(&START_KEY(insert), k);
432 bch_bset_fix_invalidated_key(b, k);
433 goto out;
434 }
435
436 if (bkey_cmp(insert, k) < 0) {
437 bch_cut_front(insert, k);
438 } else {
439 if (bkey_cmp(&START_KEY(insert), &START_KEY(k)) > 0)
440 old_offset = KEY_START(insert);
441
442 if (bkey_written(b, k) &&
443 bkey_cmp(&START_KEY(insert), &START_KEY(k)) <= 0) {
444 /*
445 * Completely overwrote, so we don't have to
446 * invalidate the binary search tree
447 */
448 bch_cut_front(k, k);
449 } else {
450 __bch_cut_back(&START_KEY(insert), k);
451 bch_bset_fix_invalidated_key(b, k);
452 }
453 }
454
455 bch_subtract_dirty(k, c, old_offset, old_size - KEY_SIZE(k));
456 }
457
458check_failed:
459 if (replace_key) {
460 if (!sectors_found) {
461 return true;
462 } else if (sectors_found < KEY_SIZE(insert)) {
463 SET_KEY_OFFSET(insert, KEY_OFFSET(insert) -
464 (KEY_SIZE(insert) - sectors_found));
465 SET_KEY_SIZE(insert, sectors_found);
466 }
467 }
468out:
469 if (KEY_DIRTY(insert))
470 bcache_dev_sectors_dirty_add(c, KEY_INODE(insert),
471 KEY_START(insert),
472 KEY_SIZE(insert));
473
474 return false;
475}
476
477static bool bch_extent_invalid(struct btree_keys *bk, const struct bkey *k)
478{
479 struct btree *b = container_of(bk, struct btree, keys);
480 char buf[80];
481
482 if (!KEY_SIZE(k))
483 return true;
484
485 if (KEY_SIZE(k) > KEY_OFFSET(k))
486 goto bad;
487
488 if (__ptr_invalid(b->c, k))
489 goto bad;
490
491 return false;
492bad:
493 bch_extent_to_text(buf, sizeof(buf), k);
494 cache_bug(b->c, "spotted extent %s: %s", buf, bch_ptr_status(b->c, k));
495 return true;
496}
497
498static bool bch_extent_bad_expensive(struct btree *b, const struct bkey *k,
499 unsigned ptr)
500{
501 struct bucket *g = PTR_BUCKET(b->c, k, ptr);
502 char buf[80];
503
504 if (mutex_trylock(&b->c->bucket_lock)) {
505 if (b->c->gc_mark_valid &&
506 (!GC_MARK(g) ||
507 GC_MARK(g) == GC_MARK_METADATA ||
508 (GC_MARK(g) != GC_MARK_DIRTY && KEY_DIRTY(k))))
509 goto err;
510
511 if (g->prio == BTREE_PRIO)
512 goto err;
513
514 mutex_unlock(&b->c->bucket_lock);
515 }
516
517 return false;
518err:
519 mutex_unlock(&b->c->bucket_lock);
520 bch_extent_to_text(buf, sizeof(buf), k);
521 btree_bug(b,
522"inconsistent extent pointer %s:\nbucket %zu pin %i prio %i gen %i last_gc %i mark %llu",
523 buf, PTR_BUCKET_NR(b->c, k, ptr), atomic_read(&g->pin),
524 g->prio, g->gen, g->last_gc, GC_MARK(g));
525 return true;
526}
527
528static bool bch_extent_bad(struct btree_keys *bk, const struct bkey *k)
529{
530 struct btree *b = container_of(bk, struct btree, keys);
531 struct bucket *g;
532 unsigned i, stale;
533
534 if (!KEY_PTRS(k) ||
535 bch_extent_invalid(bk, k))
536 return true;
537
538 for (i = 0; i < KEY_PTRS(k); i++)
539 if (!ptr_available(b->c, k, i))
540 return true;
541
542 if (!expensive_debug_checks(b->c) && KEY_DIRTY(k))
543 return false;
544
545 for (i = 0; i < KEY_PTRS(k); i++) {
546 g = PTR_BUCKET(b->c, k, i);
547 stale = ptr_stale(b->c, k, i);
548
549 btree_bug_on(stale > 96, b,
550 "key too stale: %i, need_gc %u",
551 stale, b->c->need_gc);
552
553 btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
554 b, "stale dirty pointer");
555
556 if (stale)
557 return true;
558
559 if (expensive_debug_checks(b->c) &&
560 bch_extent_bad_expensive(b, k, i))
561 return true;
562 }
563
564 return false;
565}
566
567static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
568{
569 return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
570 ~((uint64_t)1 << 63);
571}
572
573static bool bch_extent_merge(struct btree_keys *bk, struct bkey *l, struct bkey *r)
574{
575 struct btree *b = container_of(bk, struct btree, keys);
576 unsigned i;
577
578 if (key_merging_disabled(b->c))
579 return false;
580
581 for (i = 0; i < KEY_PTRS(l); i++)
582 if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
583 PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
584 return false;
585
586 /* Keys with no pointers aren't restricted to one bucket and could
587 * overflow KEY_SIZE
588 */
589 if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
590 SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
591 SET_KEY_SIZE(l, USHRT_MAX);
592
593 bch_cut_front(l, r);
594 return false;
595 }
596
597 if (KEY_CSUM(l)) {
598 if (KEY_CSUM(r))
599 l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
600 else
601 SET_KEY_CSUM(l, 0);
602 }
603
604 SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
605 SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));
606
607 return true;
608}
609
610const struct btree_keys_ops bch_extent_keys_ops = {
611 .sort_cmp = bch_extent_sort_cmp,
612 .sort_fixup = bch_extent_sort_fixup,
613 .insert_fixup = bch_extent_insert_fixup,
614 .key_invalid = bch_extent_invalid,
615 .key_bad = bch_extent_bad,
616 .key_merge = bch_extent_merge,
617 .key_to_text = bch_extent_to_text,
618 .key_dump = bch_bkey_dump,
619 .is_extents = true,
620};