Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2015 Red Hat. All rights reserved. |
| 3 | * |
| 4 | * This file is released under the GPL. |
| 5 | */ |
| 6 | |
| 7 | #include "dm-cache-policy.h" |
| 8 | #include "dm-cache-policy-internal.h" |
| 9 | #include "dm.h" |
| 10 | |
| 11 | #include <linux/hash.h> |
| 12 | #include <linux/jiffies.h> |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/mutex.h> |
| 15 | #include <linux/vmalloc.h> |
| 16 | #include <linux/math64.h> |
| 17 | |
| 18 | #define DM_MSG_PREFIX "cache-policy-smq" |
| 19 | |
| 20 | /*----------------------------------------------------------------*/ |
| 21 | |
| 22 | /* |
| 23 | * Safe division functions that return zero on divide by zero. |
| 24 | */ |
| 25 | static unsigned safe_div(unsigned n, unsigned d) |
| 26 | { |
| 27 | return d ? n / d : 0u; |
| 28 | } |
| 29 | |
| 30 | static unsigned safe_mod(unsigned n, unsigned d) |
| 31 | { |
| 32 | return d ? n % d : 0u; |
| 33 | } |
| 34 | |
| 35 | /*----------------------------------------------------------------*/ |
| 36 | |
| 37 | struct entry { |
| 38 | unsigned hash_next:28; |
| 39 | unsigned prev:28; |
| 40 | unsigned next:28; |
| 41 | unsigned level:7; |
| 42 | bool dirty:1; |
| 43 | bool allocated:1; |
| 44 | bool sentinel:1; |
| 45 | |
| 46 | dm_oblock_t oblock; |
| 47 | }; |
| 48 | |
| 49 | /*----------------------------------------------------------------*/ |
| 50 | |
| 51 | #define INDEXER_NULL ((1u << 28u) - 1u) |
| 52 | |
| 53 | /* |
| 54 | * An entry_space manages a set of entries that we use for the queues. |
| 55 | * The clean and dirty queues share entries, so this object is separate |
| 56 | * from the queue itself. |
| 57 | */ |
| 58 | struct entry_space { |
| 59 | struct entry *begin; |
| 60 | struct entry *end; |
| 61 | }; |
| 62 | |
| 63 | static int space_init(struct entry_space *es, unsigned nr_entries) |
| 64 | { |
| 65 | if (!nr_entries) { |
| 66 | es->begin = es->end = NULL; |
| 67 | return 0; |
| 68 | } |
| 69 | |
| 70 | es->begin = vzalloc(sizeof(struct entry) * nr_entries); |
| 71 | if (!es->begin) |
| 72 | return -ENOMEM; |
| 73 | |
| 74 | es->end = es->begin + nr_entries; |
| 75 | return 0; |
| 76 | } |
| 77 | |
| 78 | static void space_exit(struct entry_space *es) |
| 79 | { |
| 80 | vfree(es->begin); |
| 81 | } |
| 82 | |
| 83 | static struct entry *__get_entry(struct entry_space *es, unsigned block) |
| 84 | { |
| 85 | struct entry *e; |
| 86 | |
| 87 | e = es->begin + block; |
| 88 | BUG_ON(e >= es->end); |
| 89 | |
| 90 | return e; |
| 91 | } |
| 92 | |
| 93 | static unsigned to_index(struct entry_space *es, struct entry *e) |
| 94 | { |
| 95 | BUG_ON(e < es->begin || e >= es->end); |
| 96 | return e - es->begin; |
| 97 | } |
| 98 | |
| 99 | static struct entry *to_entry(struct entry_space *es, unsigned block) |
| 100 | { |
| 101 | if (block == INDEXER_NULL) |
| 102 | return NULL; |
| 103 | |
| 104 | return __get_entry(es, block); |
| 105 | } |
| 106 | |
| 107 | /*----------------------------------------------------------------*/ |
| 108 | |
| 109 | struct ilist { |
| 110 | unsigned nr_elts; /* excluding sentinel entries */ |
| 111 | unsigned head, tail; |
| 112 | }; |
| 113 | |
| 114 | static void l_init(struct ilist *l) |
| 115 | { |
| 116 | l->nr_elts = 0; |
| 117 | l->head = l->tail = INDEXER_NULL; |
| 118 | } |
| 119 | |
| 120 | static struct entry *l_head(struct entry_space *es, struct ilist *l) |
| 121 | { |
| 122 | return to_entry(es, l->head); |
| 123 | } |
| 124 | |
| 125 | static struct entry *l_tail(struct entry_space *es, struct ilist *l) |
| 126 | { |
| 127 | return to_entry(es, l->tail); |
| 128 | } |
| 129 | |
| 130 | static struct entry *l_next(struct entry_space *es, struct entry *e) |
| 131 | { |
| 132 | return to_entry(es, e->next); |
| 133 | } |
| 134 | |
| 135 | static struct entry *l_prev(struct entry_space *es, struct entry *e) |
| 136 | { |
| 137 | return to_entry(es, e->prev); |
| 138 | } |
| 139 | |
| 140 | static bool l_empty(struct ilist *l) |
| 141 | { |
| 142 | return l->head == INDEXER_NULL; |
| 143 | } |
| 144 | |
| 145 | static void l_add_head(struct entry_space *es, struct ilist *l, struct entry *e) |
| 146 | { |
| 147 | struct entry *head = l_head(es, l); |
| 148 | |
| 149 | e->next = l->head; |
| 150 | e->prev = INDEXER_NULL; |
| 151 | |
| 152 | if (head) |
| 153 | head->prev = l->head = to_index(es, e); |
| 154 | else |
| 155 | l->head = l->tail = to_index(es, e); |
| 156 | |
| 157 | if (!e->sentinel) |
| 158 | l->nr_elts++; |
| 159 | } |
| 160 | |
| 161 | static void l_add_tail(struct entry_space *es, struct ilist *l, struct entry *e) |
| 162 | { |
| 163 | struct entry *tail = l_tail(es, l); |
| 164 | |
| 165 | e->next = INDEXER_NULL; |
| 166 | e->prev = l->tail; |
| 167 | |
| 168 | if (tail) |
| 169 | tail->next = l->tail = to_index(es, e); |
| 170 | else |
| 171 | l->head = l->tail = to_index(es, e); |
| 172 | |
| 173 | if (!e->sentinel) |
| 174 | l->nr_elts++; |
| 175 | } |
| 176 | |
| 177 | static void l_add_before(struct entry_space *es, struct ilist *l, |
| 178 | struct entry *old, struct entry *e) |
| 179 | { |
| 180 | struct entry *prev = l_prev(es, old); |
| 181 | |
| 182 | if (!prev) |
| 183 | l_add_head(es, l, e); |
| 184 | |
| 185 | else { |
| 186 | e->prev = old->prev; |
| 187 | e->next = to_index(es, old); |
| 188 | prev->next = old->prev = to_index(es, e); |
| 189 | |
| 190 | if (!e->sentinel) |
| 191 | l->nr_elts++; |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | static void l_del(struct entry_space *es, struct ilist *l, struct entry *e) |
| 196 | { |
| 197 | struct entry *prev = l_prev(es, e); |
| 198 | struct entry *next = l_next(es, e); |
| 199 | |
| 200 | if (prev) |
| 201 | prev->next = e->next; |
| 202 | else |
| 203 | l->head = e->next; |
| 204 | |
| 205 | if (next) |
| 206 | next->prev = e->prev; |
| 207 | else |
| 208 | l->tail = e->prev; |
| 209 | |
| 210 | if (!e->sentinel) |
| 211 | l->nr_elts--; |
| 212 | } |
| 213 | |
| 214 | static struct entry *l_pop_tail(struct entry_space *es, struct ilist *l) |
| 215 | { |
| 216 | struct entry *e; |
| 217 | |
| 218 | for (e = l_tail(es, l); e; e = l_prev(es, e)) |
| 219 | if (!e->sentinel) { |
| 220 | l_del(es, l, e); |
| 221 | return e; |
| 222 | } |
| 223 | |
| 224 | return NULL; |
| 225 | } |
| 226 | |
| 227 | /*----------------------------------------------------------------*/ |
| 228 | |
| 229 | /* |
| 230 | * The stochastic-multi-queue is a set of lru lists stacked into levels. |
| 231 | * Entries are moved up levels when they are used, which loosely orders the |
| 232 | * most accessed entries in the top levels and least in the bottom. This |
| 233 | * structure is *much* better than a single lru list. |
| 234 | */ |
| 235 | #define MAX_LEVELS 64u |
| 236 | |
| 237 | struct queue { |
| 238 | struct entry_space *es; |
| 239 | |
| 240 | unsigned nr_elts; |
| 241 | unsigned nr_levels; |
| 242 | struct ilist qs[MAX_LEVELS]; |
| 243 | |
| 244 | /* |
| 245 | * We maintain a count of the number of entries we would like in each |
| 246 | * level. |
| 247 | */ |
| 248 | unsigned last_target_nr_elts; |
| 249 | unsigned nr_top_levels; |
| 250 | unsigned nr_in_top_levels; |
| 251 | unsigned target_count[MAX_LEVELS]; |
| 252 | }; |
| 253 | |
| 254 | static void q_init(struct queue *q, struct entry_space *es, unsigned nr_levels) |
| 255 | { |
| 256 | unsigned i; |
| 257 | |
| 258 | q->es = es; |
| 259 | q->nr_elts = 0; |
| 260 | q->nr_levels = nr_levels; |
| 261 | |
| 262 | for (i = 0; i < q->nr_levels; i++) { |
| 263 | l_init(q->qs + i); |
| 264 | q->target_count[i] = 0u; |
| 265 | } |
| 266 | |
| 267 | q->last_target_nr_elts = 0u; |
| 268 | q->nr_top_levels = 0u; |
| 269 | q->nr_in_top_levels = 0u; |
| 270 | } |
| 271 | |
| 272 | static unsigned q_size(struct queue *q) |
| 273 | { |
| 274 | return q->nr_elts; |
| 275 | } |
| 276 | |
| 277 | /* |
| 278 | * Insert an entry to the back of the given level. |
| 279 | */ |
| 280 | static void q_push(struct queue *q, struct entry *e) |
| 281 | { |
| 282 | if (!e->sentinel) |
| 283 | q->nr_elts++; |
| 284 | |
| 285 | l_add_tail(q->es, q->qs + e->level, e); |
| 286 | } |
| 287 | |
| 288 | static void q_push_before(struct queue *q, struct entry *old, struct entry *e) |
| 289 | { |
| 290 | if (!e->sentinel) |
| 291 | q->nr_elts++; |
| 292 | |
| 293 | l_add_before(q->es, q->qs + e->level, old, e); |
| 294 | } |
| 295 | |
| 296 | static void q_del(struct queue *q, struct entry *e) |
| 297 | { |
| 298 | l_del(q->es, q->qs + e->level, e); |
| 299 | if (!e->sentinel) |
| 300 | q->nr_elts--; |
| 301 | } |
| 302 | |
| 303 | /* |
| 304 | * Return the oldest entry of the lowest populated level. |
| 305 | */ |
| 306 | static struct entry *q_peek(struct queue *q, unsigned max_level, bool can_cross_sentinel) |
| 307 | { |
| 308 | unsigned level; |
| 309 | struct entry *e; |
| 310 | |
| 311 | max_level = min(max_level, q->nr_levels); |
| 312 | |
| 313 | for (level = 0; level < max_level; level++) |
| 314 | for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) { |
| 315 | if (e->sentinel) { |
| 316 | if (can_cross_sentinel) |
| 317 | continue; |
| 318 | else |
| 319 | break; |
| 320 | } |
| 321 | |
| 322 | return e; |
| 323 | } |
| 324 | |
| 325 | return NULL; |
| 326 | } |
| 327 | |
| 328 | static struct entry *q_pop(struct queue *q) |
| 329 | { |
| 330 | struct entry *e = q_peek(q, q->nr_levels, true); |
| 331 | |
| 332 | if (e) |
| 333 | q_del(q, e); |
| 334 | |
| 335 | return e; |
| 336 | } |
| 337 | |
| 338 | /* |
| 339 | * Pops an entry from a level that is not past a sentinel. |
| 340 | */ |
| 341 | static struct entry *q_pop_old(struct queue *q, unsigned max_level) |
| 342 | { |
| 343 | struct entry *e = q_peek(q, max_level, false); |
| 344 | |
| 345 | if (e) |
| 346 | q_del(q, e); |
| 347 | |
| 348 | return e; |
| 349 | } |
| 350 | |
| 351 | /* |
| 352 | * This function assumes there is a non-sentinel entry to pop. It's only |
| 353 | * used by redistribute, so we know this is true. It also doesn't adjust |
| 354 | * the q->nr_elts count. |
| 355 | */ |
| 356 | static struct entry *__redist_pop_from(struct queue *q, unsigned level) |
| 357 | { |
| 358 | struct entry *e; |
| 359 | |
| 360 | for (; level < q->nr_levels; level++) |
| 361 | for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) |
| 362 | if (!e->sentinel) { |
| 363 | l_del(q->es, q->qs + e->level, e); |
| 364 | return e; |
| 365 | } |
| 366 | |
| 367 | return NULL; |
| 368 | } |
| 369 | |
| 370 | static void q_set_targets_subrange_(struct queue *q, unsigned nr_elts, unsigned lbegin, unsigned lend) |
| 371 | { |
| 372 | unsigned level, nr_levels, entries_per_level, remainder; |
| 373 | |
| 374 | BUG_ON(lbegin > lend); |
| 375 | BUG_ON(lend > q->nr_levels); |
| 376 | nr_levels = lend - lbegin; |
| 377 | entries_per_level = safe_div(nr_elts, nr_levels); |
| 378 | remainder = safe_mod(nr_elts, nr_levels); |
| 379 | |
| 380 | for (level = lbegin; level < lend; level++) |
| 381 | q->target_count[level] = |
| 382 | (level < (lbegin + remainder)) ? entries_per_level + 1u : entries_per_level; |
| 383 | } |
| 384 | |
| 385 | /* |
| 386 | * Typically we have fewer elements in the top few levels which allows us |
| 387 | * to adjust the promote threshold nicely. |
| 388 | */ |
| 389 | static void q_set_targets(struct queue *q) |
| 390 | { |
| 391 | if (q->last_target_nr_elts == q->nr_elts) |
| 392 | return; |
| 393 | |
| 394 | q->last_target_nr_elts = q->nr_elts; |
| 395 | |
| 396 | if (q->nr_top_levels > q->nr_levels) |
| 397 | q_set_targets_subrange_(q, q->nr_elts, 0, q->nr_levels); |
| 398 | |
| 399 | else { |
| 400 | q_set_targets_subrange_(q, q->nr_in_top_levels, |
| 401 | q->nr_levels - q->nr_top_levels, q->nr_levels); |
| 402 | |
| 403 | if (q->nr_in_top_levels < q->nr_elts) |
| 404 | q_set_targets_subrange_(q, q->nr_elts - q->nr_in_top_levels, |
| 405 | 0, q->nr_levels - q->nr_top_levels); |
| 406 | else |
| 407 | q_set_targets_subrange_(q, 0, 0, q->nr_levels - q->nr_top_levels); |
| 408 | } |
| 409 | } |
| 410 | |
| 411 | static void q_redistribute(struct queue *q) |
| 412 | { |
| 413 | unsigned target, level; |
| 414 | struct ilist *l, *l_above; |
| 415 | struct entry *e; |
| 416 | |
| 417 | q_set_targets(q); |
| 418 | |
| 419 | for (level = 0u; level < q->nr_levels - 1u; level++) { |
| 420 | l = q->qs + level; |
| 421 | target = q->target_count[level]; |
| 422 | |
| 423 | /* |
| 424 | * Pull down some entries from the level above. |
| 425 | */ |
| 426 | while (l->nr_elts < target) { |
| 427 | e = __redist_pop_from(q, level + 1u); |
| 428 | if (!e) { |
| 429 | /* bug in nr_elts */ |
| 430 | break; |
| 431 | } |
| 432 | |
| 433 | e->level = level; |
| 434 | l_add_tail(q->es, l, e); |
| 435 | } |
| 436 | |
| 437 | /* |
| 438 | * Push some entries up. |
| 439 | */ |
| 440 | l_above = q->qs + level + 1u; |
| 441 | while (l->nr_elts > target) { |
| 442 | e = l_pop_tail(q->es, l); |
| 443 | |
| 444 | if (!e) |
| 445 | /* bug in nr_elts */ |
| 446 | break; |
| 447 | |
| 448 | e->level = level + 1u; |
| 449 | l_add_head(q->es, l_above, e); |
| 450 | } |
| 451 | } |
| 452 | } |
| 453 | |
| 454 | static void q_requeue_before(struct queue *q, struct entry *dest, struct entry *e, unsigned extra_levels) |
| 455 | { |
| 456 | struct entry *de; |
| 457 | unsigned new_level; |
| 458 | |
| 459 | q_del(q, e); |
| 460 | |
| 461 | if (extra_levels && (e->level < q->nr_levels - 1u)) { |
| 462 | new_level = min(q->nr_levels - 1u, e->level + extra_levels); |
| 463 | for (de = l_head(q->es, q->qs + new_level); de; de = l_next(q->es, de)) { |
| 464 | if (de->sentinel) |
| 465 | continue; |
| 466 | |
| 467 | q_del(q, de); |
| 468 | de->level = e->level; |
| 469 | |
| 470 | if (dest) |
| 471 | q_push_before(q, dest, de); |
| 472 | else |
| 473 | q_push(q, de); |
| 474 | break; |
| 475 | } |
| 476 | |
| 477 | e->level = new_level; |
| 478 | } |
| 479 | |
| 480 | q_push(q, e); |
| 481 | } |
| 482 | |
| 483 | static void q_requeue(struct queue *q, struct entry *e, unsigned extra_levels) |
| 484 | { |
| 485 | q_requeue_before(q, NULL, e, extra_levels); |
| 486 | } |
| 487 | |
| 488 | /*----------------------------------------------------------------*/ |
| 489 | |
| 490 | #define FP_SHIFT 8 |
| 491 | #define SIXTEENTH (1u << (FP_SHIFT - 4u)) |
| 492 | #define EIGHTH (1u << (FP_SHIFT - 3u)) |
| 493 | |
| 494 | struct stats { |
| 495 | unsigned hit_threshold; |
| 496 | unsigned hits; |
| 497 | unsigned misses; |
| 498 | }; |
| 499 | |
| 500 | enum performance { |
| 501 | Q_POOR, |
| 502 | Q_FAIR, |
| 503 | Q_WELL |
| 504 | }; |
| 505 | |
| 506 | static void stats_init(struct stats *s, unsigned nr_levels) |
| 507 | { |
| 508 | s->hit_threshold = (nr_levels * 3u) / 4u; |
| 509 | s->hits = 0u; |
| 510 | s->misses = 0u; |
| 511 | } |
| 512 | |
| 513 | static void stats_reset(struct stats *s) |
| 514 | { |
| 515 | s->hits = s->misses = 0u; |
| 516 | } |
| 517 | |
| 518 | static void stats_level_accessed(struct stats *s, unsigned level) |
| 519 | { |
| 520 | if (level >= s->hit_threshold) |
| 521 | s->hits++; |
| 522 | else |
| 523 | s->misses++; |
| 524 | } |
| 525 | |
| 526 | static void stats_miss(struct stats *s) |
| 527 | { |
| 528 | s->misses++; |
| 529 | } |
| 530 | |
| 531 | /* |
| 532 | * There are times when we don't have any confidence in the hotspot queue. |
| 533 | * Such as when a fresh cache is created and the blocks have been spread |
| 534 | * out across the levels, or if an io load changes. We detect this by |
| 535 | * seeing how often a lookup is in the top levels of the hotspot queue. |
| 536 | */ |
| 537 | static enum performance stats_assess(struct stats *s) |
| 538 | { |
| 539 | unsigned confidence = safe_div(s->hits << FP_SHIFT, s->hits + s->misses); |
| 540 | |
| 541 | if (confidence < SIXTEENTH) |
| 542 | return Q_POOR; |
| 543 | |
| 544 | else if (confidence < EIGHTH) |
| 545 | return Q_FAIR; |
| 546 | |
| 547 | else |
| 548 | return Q_WELL; |
| 549 | } |
| 550 | |
| 551 | /*----------------------------------------------------------------*/ |
| 552 | |
| 553 | struct hash_table { |
| 554 | struct entry_space *es; |
| 555 | unsigned long long hash_bits; |
| 556 | unsigned *buckets; |
| 557 | }; |
| 558 | |
| 559 | /* |
| 560 | * All cache entries are stored in a chained hash table. To save space we |
| 561 | * use indexing again, and only store indexes to the next entry. |
| 562 | */ |
| 563 | static int h_init(struct hash_table *ht, struct entry_space *es, unsigned nr_entries) |
| 564 | { |
| 565 | unsigned i, nr_buckets; |
| 566 | |
| 567 | ht->es = es; |
| 568 | nr_buckets = roundup_pow_of_two(max(nr_entries / 4u, 16u)); |
| 569 | ht->hash_bits = ffs(nr_buckets) - 1; |
| 570 | |
| 571 | ht->buckets = vmalloc(sizeof(*ht->buckets) * nr_buckets); |
| 572 | if (!ht->buckets) |
| 573 | return -ENOMEM; |
| 574 | |
| 575 | for (i = 0; i < nr_buckets; i++) |
| 576 | ht->buckets[i] = INDEXER_NULL; |
| 577 | |
| 578 | return 0; |
| 579 | } |
| 580 | |
| 581 | static void h_exit(struct hash_table *ht) |
| 582 | { |
| 583 | vfree(ht->buckets); |
| 584 | } |
| 585 | |
| 586 | static struct entry *h_head(struct hash_table *ht, unsigned bucket) |
| 587 | { |
| 588 | return to_entry(ht->es, ht->buckets[bucket]); |
| 589 | } |
| 590 | |
| 591 | static struct entry *h_next(struct hash_table *ht, struct entry *e) |
| 592 | { |
| 593 | return to_entry(ht->es, e->hash_next); |
| 594 | } |
| 595 | |
| 596 | static void __h_insert(struct hash_table *ht, unsigned bucket, struct entry *e) |
| 597 | { |
| 598 | e->hash_next = ht->buckets[bucket]; |
| 599 | ht->buckets[bucket] = to_index(ht->es, e); |
| 600 | } |
| 601 | |
| 602 | static void h_insert(struct hash_table *ht, struct entry *e) |
| 603 | { |
| 604 | unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits); |
| 605 | __h_insert(ht, h, e); |
| 606 | } |
| 607 | |
| 608 | static struct entry *__h_lookup(struct hash_table *ht, unsigned h, dm_oblock_t oblock, |
| 609 | struct entry **prev) |
| 610 | { |
| 611 | struct entry *e; |
| 612 | |
| 613 | *prev = NULL; |
| 614 | for (e = h_head(ht, h); e; e = h_next(ht, e)) { |
| 615 | if (e->oblock == oblock) |
| 616 | return e; |
| 617 | |
| 618 | *prev = e; |
| 619 | } |
| 620 | |
| 621 | return NULL; |
| 622 | } |
| 623 | |
| 624 | static void __h_unlink(struct hash_table *ht, unsigned h, |
| 625 | struct entry *e, struct entry *prev) |
| 626 | { |
| 627 | if (prev) |
| 628 | prev->hash_next = e->hash_next; |
| 629 | else |
| 630 | ht->buckets[h] = e->hash_next; |
| 631 | } |
| 632 | |
| 633 | /* |
| 634 | * Also moves each entry to the front of the bucket. |
| 635 | */ |
| 636 | static struct entry *h_lookup(struct hash_table *ht, dm_oblock_t oblock) |
| 637 | { |
| 638 | struct entry *e, *prev; |
| 639 | unsigned h = hash_64(from_oblock(oblock), ht->hash_bits); |
| 640 | |
| 641 | e = __h_lookup(ht, h, oblock, &prev); |
| 642 | if (e && prev) { |
| 643 | /* |
| 644 | * Move to the front because this entry is likely |
| 645 | * to be hit again. |
| 646 | */ |
| 647 | __h_unlink(ht, h, e, prev); |
| 648 | __h_insert(ht, h, e); |
| 649 | } |
| 650 | |
| 651 | return e; |
| 652 | } |
| 653 | |
| 654 | static void h_remove(struct hash_table *ht, struct entry *e) |
| 655 | { |
| 656 | unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits); |
| 657 | struct entry *prev; |
| 658 | |
| 659 | /* |
| 660 | * The down side of using a singly linked list is we have to |
| 661 | * iterate the bucket to remove an item. |
| 662 | */ |
| 663 | e = __h_lookup(ht, h, e->oblock, &prev); |
| 664 | if (e) |
| 665 | __h_unlink(ht, h, e, prev); |
| 666 | } |
| 667 | |
| 668 | /*----------------------------------------------------------------*/ |
| 669 | |
| 670 | struct entry_alloc { |
| 671 | struct entry_space *es; |
| 672 | unsigned begin; |
| 673 | |
| 674 | unsigned nr_allocated; |
| 675 | struct ilist free; |
| 676 | }; |
| 677 | |
| 678 | static void init_allocator(struct entry_alloc *ea, struct entry_space *es, |
| 679 | unsigned begin, unsigned end) |
| 680 | { |
| 681 | unsigned i; |
| 682 | |
| 683 | ea->es = es; |
| 684 | ea->nr_allocated = 0u; |
| 685 | ea->begin = begin; |
| 686 | |
| 687 | l_init(&ea->free); |
| 688 | for (i = begin; i != end; i++) |
| 689 | l_add_tail(ea->es, &ea->free, __get_entry(ea->es, i)); |
| 690 | } |
| 691 | |
| 692 | static void init_entry(struct entry *e) |
| 693 | { |
| 694 | /* |
| 695 | * We can't memset because that would clear the hotspot and |
| 696 | * sentinel bits which remain constant. |
| 697 | */ |
| 698 | e->hash_next = INDEXER_NULL; |
| 699 | e->next = INDEXER_NULL; |
| 700 | e->prev = INDEXER_NULL; |
| 701 | e->level = 0u; |
| 702 | e->allocated = true; |
| 703 | } |
| 704 | |
| 705 | static struct entry *alloc_entry(struct entry_alloc *ea) |
| 706 | { |
| 707 | struct entry *e; |
| 708 | |
| 709 | if (l_empty(&ea->free)) |
| 710 | return NULL; |
| 711 | |
| 712 | e = l_pop_tail(ea->es, &ea->free); |
| 713 | init_entry(e); |
| 714 | ea->nr_allocated++; |
| 715 | |
| 716 | return e; |
| 717 | } |
| 718 | |
| 719 | /* |
| 720 | * This assumes the cblock hasn't already been allocated. |
| 721 | */ |
| 722 | static struct entry *alloc_particular_entry(struct entry_alloc *ea, unsigned i) |
| 723 | { |
| 724 | struct entry *e = __get_entry(ea->es, ea->begin + i); |
| 725 | |
| 726 | BUG_ON(e->allocated); |
| 727 | |
| 728 | l_del(ea->es, &ea->free, e); |
| 729 | init_entry(e); |
| 730 | ea->nr_allocated++; |
| 731 | |
| 732 | return e; |
| 733 | } |
| 734 | |
| 735 | static void free_entry(struct entry_alloc *ea, struct entry *e) |
| 736 | { |
| 737 | BUG_ON(!ea->nr_allocated); |
| 738 | BUG_ON(!e->allocated); |
| 739 | |
| 740 | ea->nr_allocated--; |
| 741 | e->allocated = false; |
| 742 | l_add_tail(ea->es, &ea->free, e); |
| 743 | } |
| 744 | |
| 745 | static bool allocator_empty(struct entry_alloc *ea) |
| 746 | { |
| 747 | return l_empty(&ea->free); |
| 748 | } |
| 749 | |
| 750 | static unsigned get_index(struct entry_alloc *ea, struct entry *e) |
| 751 | { |
| 752 | return to_index(ea->es, e) - ea->begin; |
| 753 | } |
| 754 | |
| 755 | static struct entry *get_entry(struct entry_alloc *ea, unsigned index) |
| 756 | { |
| 757 | return __get_entry(ea->es, ea->begin + index); |
| 758 | } |
| 759 | |
| 760 | /*----------------------------------------------------------------*/ |
| 761 | |
| 762 | #define NR_HOTSPOT_LEVELS 64u |
| 763 | #define NR_CACHE_LEVELS 64u |
| 764 | |
| 765 | #define WRITEBACK_PERIOD (10 * HZ) |
| 766 | #define DEMOTE_PERIOD (60 * HZ) |
| 767 | |
| 768 | #define HOTSPOT_UPDATE_PERIOD (HZ) |
| 769 | #define CACHE_UPDATE_PERIOD (10u * HZ) |
| 770 | |
| 771 | struct smq_policy { |
| 772 | struct dm_cache_policy policy; |
| 773 | |
| 774 | /* protects everything */ |
| 775 | struct mutex lock; |
| 776 | dm_cblock_t cache_size; |
| 777 | sector_t cache_block_size; |
| 778 | |
| 779 | sector_t hotspot_block_size; |
| 780 | unsigned nr_hotspot_blocks; |
| 781 | unsigned cache_blocks_per_hotspot_block; |
| 782 | unsigned hotspot_level_jump; |
| 783 | |
| 784 | struct entry_space es; |
| 785 | struct entry_alloc writeback_sentinel_alloc; |
| 786 | struct entry_alloc demote_sentinel_alloc; |
| 787 | struct entry_alloc hotspot_alloc; |
| 788 | struct entry_alloc cache_alloc; |
| 789 | |
| 790 | unsigned long *hotspot_hit_bits; |
| 791 | unsigned long *cache_hit_bits; |
| 792 | |
| 793 | /* |
| 794 | * We maintain three queues of entries. The cache proper, |
| 795 | * consisting of a clean and dirty queue, containing the currently |
| 796 | * active mappings. The hotspot queue uses a larger block size to |
| 797 | * track blocks that are being hit frequently and potential |
| 798 | * candidates for promotion to the cache. |
| 799 | */ |
| 800 | struct queue hotspot; |
| 801 | struct queue clean; |
| 802 | struct queue dirty; |
| 803 | |
| 804 | struct stats hotspot_stats; |
| 805 | struct stats cache_stats; |
| 806 | |
| 807 | /* |
| 808 | * Keeps track of time, incremented by the core. We use this to |
| 809 | * avoid attributing multiple hits within the same tick. |
| 810 | * |
| 811 | * Access to tick_protected should be done with the spin lock held. |
| 812 | * It's copied to tick at the start of the map function (within the |
| 813 | * mutex). |
| 814 | */ |
| 815 | spinlock_t tick_lock; |
| 816 | unsigned tick_protected; |
| 817 | unsigned tick; |
| 818 | |
| 819 | /* |
| 820 | * The hash tables allows us to quickly find an entry by origin |
| 821 | * block. |
| 822 | */ |
| 823 | struct hash_table table; |
| 824 | struct hash_table hotspot_table; |
| 825 | |
| 826 | bool current_writeback_sentinels; |
| 827 | unsigned long next_writeback_period; |
| 828 | |
| 829 | bool current_demote_sentinels; |
| 830 | unsigned long next_demote_period; |
| 831 | |
| 832 | unsigned write_promote_level; |
| 833 | unsigned read_promote_level; |
| 834 | |
| 835 | unsigned long next_hotspot_period; |
| 836 | unsigned long next_cache_period; |
| 837 | }; |
| 838 | |
| 839 | /*----------------------------------------------------------------*/ |
| 840 | |
| 841 | static struct entry *get_sentinel(struct entry_alloc *ea, unsigned level, bool which) |
| 842 | { |
| 843 | return get_entry(ea, which ? level : NR_CACHE_LEVELS + level); |
| 844 | } |
| 845 | |
| 846 | static struct entry *writeback_sentinel(struct smq_policy *mq, unsigned level) |
| 847 | { |
| 848 | return get_sentinel(&mq->writeback_sentinel_alloc, level, mq->current_writeback_sentinels); |
| 849 | } |
| 850 | |
| 851 | static struct entry *demote_sentinel(struct smq_policy *mq, unsigned level) |
| 852 | { |
| 853 | return get_sentinel(&mq->demote_sentinel_alloc, level, mq->current_demote_sentinels); |
| 854 | } |
| 855 | |
| 856 | static void __update_writeback_sentinels(struct smq_policy *mq) |
| 857 | { |
| 858 | unsigned level; |
| 859 | struct queue *q = &mq->dirty; |
| 860 | struct entry *sentinel; |
| 861 | |
| 862 | for (level = 0; level < q->nr_levels; level++) { |
| 863 | sentinel = writeback_sentinel(mq, level); |
| 864 | q_del(q, sentinel); |
| 865 | q_push(q, sentinel); |
| 866 | } |
| 867 | } |
| 868 | |
| 869 | static void __update_demote_sentinels(struct smq_policy *mq) |
| 870 | { |
| 871 | unsigned level; |
| 872 | struct queue *q = &mq->clean; |
| 873 | struct entry *sentinel; |
| 874 | |
| 875 | for (level = 0; level < q->nr_levels; level++) { |
| 876 | sentinel = demote_sentinel(mq, level); |
| 877 | q_del(q, sentinel); |
| 878 | q_push(q, sentinel); |
| 879 | } |
| 880 | } |
| 881 | |
| 882 | static void update_sentinels(struct smq_policy *mq) |
| 883 | { |
| 884 | if (time_after(jiffies, mq->next_writeback_period)) { |
| 885 | __update_writeback_sentinels(mq); |
| 886 | mq->next_writeback_period = jiffies + WRITEBACK_PERIOD; |
| 887 | mq->current_writeback_sentinels = !mq->current_writeback_sentinels; |
| 888 | } |
| 889 | |
| 890 | if (time_after(jiffies, mq->next_demote_period)) { |
| 891 | __update_demote_sentinels(mq); |
| 892 | mq->next_demote_period = jiffies + DEMOTE_PERIOD; |
| 893 | mq->current_demote_sentinels = !mq->current_demote_sentinels; |
| 894 | } |
| 895 | } |
| 896 | |
| 897 | static void __sentinels_init(struct smq_policy *mq) |
| 898 | { |
| 899 | unsigned level; |
| 900 | struct entry *sentinel; |
| 901 | |
| 902 | for (level = 0; level < NR_CACHE_LEVELS; level++) { |
| 903 | sentinel = writeback_sentinel(mq, level); |
| 904 | sentinel->level = level; |
| 905 | q_push(&mq->dirty, sentinel); |
| 906 | |
| 907 | sentinel = demote_sentinel(mq, level); |
| 908 | sentinel->level = level; |
| 909 | q_push(&mq->clean, sentinel); |
| 910 | } |
| 911 | } |
| 912 | |
| 913 | static void sentinels_init(struct smq_policy *mq) |
| 914 | { |
| 915 | mq->next_writeback_period = jiffies + WRITEBACK_PERIOD; |
| 916 | mq->next_demote_period = jiffies + DEMOTE_PERIOD; |
| 917 | |
| 918 | mq->current_writeback_sentinels = false; |
| 919 | mq->current_demote_sentinels = false; |
| 920 | __sentinels_init(mq); |
| 921 | |
| 922 | mq->current_writeback_sentinels = !mq->current_writeback_sentinels; |
| 923 | mq->current_demote_sentinels = !mq->current_demote_sentinels; |
| 924 | __sentinels_init(mq); |
| 925 | } |
| 926 | |
| 927 | /*----------------------------------------------------------------*/ |
| 928 | |
| 929 | /* |
| 930 | * These methods tie together the dirty queue, clean queue and hash table. |
| 931 | */ |
| 932 | static void push_new(struct smq_policy *mq, struct entry *e) |
| 933 | { |
| 934 | struct queue *q = e->dirty ? &mq->dirty : &mq->clean; |
| 935 | h_insert(&mq->table, e); |
| 936 | q_push(q, e); |
| 937 | } |
| 938 | |
| 939 | static void push(struct smq_policy *mq, struct entry *e) |
| 940 | { |
| 941 | struct entry *sentinel; |
| 942 | |
| 943 | h_insert(&mq->table, e); |
| 944 | |
| 945 | /* |
| 946 | * Punch this into the queue just in front of the sentinel, to |
| 947 | * ensure it's cleaned straight away. |
| 948 | */ |
| 949 | if (e->dirty) { |
| 950 | sentinel = writeback_sentinel(mq, e->level); |
| 951 | q_push_before(&mq->dirty, sentinel, e); |
| 952 | } else { |
| 953 | sentinel = demote_sentinel(mq, e->level); |
| 954 | q_push_before(&mq->clean, sentinel, e); |
| 955 | } |
| 956 | } |
| 957 | |
| 958 | /* |
| 959 | * Removes an entry from cache. Removes from the hash table. |
| 960 | */ |
| 961 | static void __del(struct smq_policy *mq, struct queue *q, struct entry *e) |
| 962 | { |
| 963 | q_del(q, e); |
| 964 | h_remove(&mq->table, e); |
| 965 | } |
| 966 | |
| 967 | static void del(struct smq_policy *mq, struct entry *e) |
| 968 | { |
| 969 | __del(mq, e->dirty ? &mq->dirty : &mq->clean, e); |
| 970 | } |
| 971 | |
| 972 | static struct entry *pop_old(struct smq_policy *mq, struct queue *q, unsigned max_level) |
| 973 | { |
| 974 | struct entry *e = q_pop_old(q, max_level); |
| 975 | if (e) |
| 976 | h_remove(&mq->table, e); |
| 977 | return e; |
| 978 | } |
| 979 | |
| 980 | static dm_cblock_t infer_cblock(struct smq_policy *mq, struct entry *e) |
| 981 | { |
| 982 | return to_cblock(get_index(&mq->cache_alloc, e)); |
| 983 | } |
| 984 | |
| 985 | static void requeue(struct smq_policy *mq, struct entry *e) |
| 986 | { |
| 987 | struct entry *sentinel; |
| 988 | |
| 989 | if (!test_and_set_bit(from_cblock(infer_cblock(mq, e)), mq->cache_hit_bits)) { |
| 990 | if (e->dirty) { |
| 991 | sentinel = writeback_sentinel(mq, e->level); |
| 992 | q_requeue_before(&mq->dirty, sentinel, e, 1u); |
| 993 | } else { |
| 994 | sentinel = demote_sentinel(mq, e->level); |
| 995 | q_requeue_before(&mq->clean, sentinel, e, 1u); |
| 996 | } |
| 997 | } |
| 998 | } |
| 999 | |
| 1000 | static unsigned default_promote_level(struct smq_policy *mq) |
| 1001 | { |
| 1002 | /* |
| 1003 | * The promote level depends on the current performance of the |
| 1004 | * cache. |
| 1005 | * |
| 1006 | * If the cache is performing badly, then we can't afford |
| 1007 | * to promote much without causing performance to drop below that |
| 1008 | * of the origin device. |
| 1009 | * |
| 1010 | * If the cache is performing well, then we don't need to promote |
| 1011 | * much. If it isn't broken, don't fix it. |
| 1012 | * |
| 1013 | * If the cache is middling then we promote more. |
| 1014 | * |
| 1015 | * This scheme reminds me of a graph of entropy vs probability of a |
| 1016 | * binary variable. |
| 1017 | */ |
| 1018 | static unsigned table[] = {1, 1, 1, 2, 4, 6, 7, 8, 7, 6, 4, 4, 3, 3, 2, 2, 1}; |
| 1019 | |
| 1020 | unsigned hits = mq->cache_stats.hits; |
| 1021 | unsigned misses = mq->cache_stats.misses; |
| 1022 | unsigned index = safe_div(hits << 4u, hits + misses); |
| 1023 | return table[index]; |
| 1024 | } |
| 1025 | |
| 1026 | static void update_promote_levels(struct smq_policy *mq) |
| 1027 | { |
| 1028 | /* |
| 1029 | * If there are unused cache entries then we want to be really |
| 1030 | * eager to promote. |
| 1031 | */ |
| 1032 | unsigned threshold_level = allocator_empty(&mq->cache_alloc) ? |
| 1033 | default_promote_level(mq) : (NR_HOTSPOT_LEVELS / 2u); |
| 1034 | |
| 1035 | /* |
| 1036 | * If the hotspot queue is performing badly then we have little |
| 1037 | * confidence that we know which blocks to promote. So we cut down |
| 1038 | * the amount of promotions. |
| 1039 | */ |
| 1040 | switch (stats_assess(&mq->hotspot_stats)) { |
| 1041 | case Q_POOR: |
| 1042 | threshold_level /= 4u; |
| 1043 | break; |
| 1044 | |
| 1045 | case Q_FAIR: |
| 1046 | threshold_level /= 2u; |
| 1047 | break; |
| 1048 | |
| 1049 | case Q_WELL: |
| 1050 | break; |
| 1051 | } |
| 1052 | |
| 1053 | mq->read_promote_level = NR_HOTSPOT_LEVELS - threshold_level; |
| 1054 | mq->write_promote_level = (NR_HOTSPOT_LEVELS - threshold_level) + 2u; |
| 1055 | } |
| 1056 | |
| 1057 | /* |
| 1058 | * If the hotspot queue is performing badly, then we try and move entries |
| 1059 | * around more quickly. |
| 1060 | */ |
| 1061 | static void update_level_jump(struct smq_policy *mq) |
| 1062 | { |
| 1063 | switch (stats_assess(&mq->hotspot_stats)) { |
| 1064 | case Q_POOR: |
| 1065 | mq->hotspot_level_jump = 4u; |
| 1066 | break; |
| 1067 | |
| 1068 | case Q_FAIR: |
| 1069 | mq->hotspot_level_jump = 2u; |
| 1070 | break; |
| 1071 | |
| 1072 | case Q_WELL: |
| 1073 | mq->hotspot_level_jump = 1u; |
| 1074 | break; |
| 1075 | } |
| 1076 | } |
| 1077 | |
| 1078 | static void end_hotspot_period(struct smq_policy *mq) |
| 1079 | { |
| 1080 | clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks); |
| 1081 | update_promote_levels(mq); |
| 1082 | |
| 1083 | if (time_after(jiffies, mq->next_hotspot_period)) { |
| 1084 | update_level_jump(mq); |
| 1085 | q_redistribute(&mq->hotspot); |
| 1086 | stats_reset(&mq->hotspot_stats); |
| 1087 | mq->next_hotspot_period = jiffies + HOTSPOT_UPDATE_PERIOD; |
| 1088 | } |
| 1089 | } |
| 1090 | |
| 1091 | static void end_cache_period(struct smq_policy *mq) |
| 1092 | { |
| 1093 | if (time_after(jiffies, mq->next_cache_period)) { |
| 1094 | clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size)); |
| 1095 | |
| 1096 | q_redistribute(&mq->dirty); |
| 1097 | q_redistribute(&mq->clean); |
| 1098 | stats_reset(&mq->cache_stats); |
| 1099 | |
| 1100 | mq->next_cache_period = jiffies + CACHE_UPDATE_PERIOD; |
| 1101 | } |
| 1102 | } |
| 1103 | |
| 1104 | static int demote_cblock(struct smq_policy *mq, |
| 1105 | struct policy_locker *locker, |
| 1106 | dm_oblock_t *oblock) |
| 1107 | { |
| 1108 | struct entry *demoted = q_peek(&mq->clean, mq->clean.nr_levels, false); |
| 1109 | if (!demoted) |
| 1110 | /* |
| 1111 | * We could get a block from mq->dirty, but that |
| 1112 | * would add extra latency to the triggering bio as it |
| 1113 | * waits for the writeback. Better to not promote this |
| 1114 | * time and hope there's a clean block next time this block |
| 1115 | * is hit. |
| 1116 | */ |
| 1117 | return -ENOSPC; |
| 1118 | |
| 1119 | if (locker->fn(locker, demoted->oblock)) |
| 1120 | /* |
| 1121 | * We couldn't lock this block. |
| 1122 | */ |
| 1123 | return -EBUSY; |
| 1124 | |
| 1125 | del(mq, demoted); |
| 1126 | *oblock = demoted->oblock; |
| 1127 | free_entry(&mq->cache_alloc, demoted); |
| 1128 | |
| 1129 | return 0; |
| 1130 | } |
| 1131 | |
| 1132 | enum promote_result { |
| 1133 | PROMOTE_NOT, |
| 1134 | PROMOTE_TEMPORARY, |
| 1135 | PROMOTE_PERMANENT |
| 1136 | }; |
| 1137 | |
| 1138 | /* |
| 1139 | * Converts a boolean into a promote result. |
| 1140 | */ |
| 1141 | static enum promote_result maybe_promote(bool promote) |
| 1142 | { |
| 1143 | return promote ? PROMOTE_PERMANENT : PROMOTE_NOT; |
| 1144 | } |
| 1145 | |
| 1146 | static enum promote_result should_promote(struct smq_policy *mq, struct entry *hs_e, struct bio *bio, |
| 1147 | bool fast_promote) |
| 1148 | { |
| 1149 | if (bio_data_dir(bio) == WRITE) { |
| 1150 | if (!allocator_empty(&mq->cache_alloc) && fast_promote) |
| 1151 | return PROMOTE_TEMPORARY; |
| 1152 | |
| 1153 | else |
| 1154 | return maybe_promote(hs_e->level >= mq->write_promote_level); |
| 1155 | } else |
| 1156 | return maybe_promote(hs_e->level >= mq->read_promote_level); |
| 1157 | } |
| 1158 | |
| 1159 | static void insert_in_cache(struct smq_policy *mq, dm_oblock_t oblock, |
| 1160 | struct policy_locker *locker, |
| 1161 | struct policy_result *result, enum promote_result pr) |
| 1162 | { |
| 1163 | int r; |
| 1164 | struct entry *e; |
| 1165 | |
| 1166 | if (allocator_empty(&mq->cache_alloc)) { |
| 1167 | result->op = POLICY_REPLACE; |
| 1168 | r = demote_cblock(mq, locker, &result->old_oblock); |
| 1169 | if (r) { |
| 1170 | result->op = POLICY_MISS; |
| 1171 | return; |
| 1172 | } |
| 1173 | |
| 1174 | } else |
| 1175 | result->op = POLICY_NEW; |
| 1176 | |
| 1177 | e = alloc_entry(&mq->cache_alloc); |
| 1178 | BUG_ON(!e); |
| 1179 | e->oblock = oblock; |
| 1180 | |
| 1181 | if (pr == PROMOTE_TEMPORARY) |
| 1182 | push(mq, e); |
| 1183 | else |
| 1184 | push_new(mq, e); |
| 1185 | |
| 1186 | result->cblock = infer_cblock(mq, e); |
| 1187 | } |
| 1188 | |
| 1189 | static dm_oblock_t to_hblock(struct smq_policy *mq, dm_oblock_t b) |
| 1190 | { |
| 1191 | sector_t r = from_oblock(b); |
| 1192 | (void) sector_div(r, mq->cache_blocks_per_hotspot_block); |
| 1193 | return to_oblock(r); |
| 1194 | } |
| 1195 | |
| 1196 | static struct entry *update_hotspot_queue(struct smq_policy *mq, dm_oblock_t b, struct bio *bio) |
| 1197 | { |
| 1198 | unsigned hi; |
| 1199 | dm_oblock_t hb = to_hblock(mq, b); |
| 1200 | struct entry *e = h_lookup(&mq->hotspot_table, hb); |
| 1201 | |
| 1202 | if (e) { |
| 1203 | stats_level_accessed(&mq->hotspot_stats, e->level); |
| 1204 | |
| 1205 | hi = get_index(&mq->hotspot_alloc, e); |
| 1206 | q_requeue(&mq->hotspot, e, |
| 1207 | test_and_set_bit(hi, mq->hotspot_hit_bits) ? |
| 1208 | 0u : mq->hotspot_level_jump); |
| 1209 | |
| 1210 | } else { |
| 1211 | stats_miss(&mq->hotspot_stats); |
| 1212 | |
| 1213 | e = alloc_entry(&mq->hotspot_alloc); |
| 1214 | if (!e) { |
| 1215 | e = q_pop(&mq->hotspot); |
| 1216 | if (e) { |
| 1217 | h_remove(&mq->hotspot_table, e); |
| 1218 | hi = get_index(&mq->hotspot_alloc, e); |
| 1219 | clear_bit(hi, mq->hotspot_hit_bits); |
| 1220 | } |
| 1221 | |
| 1222 | } |
| 1223 | |
| 1224 | if (e) { |
| 1225 | e->oblock = hb; |
| 1226 | q_push(&mq->hotspot, e); |
| 1227 | h_insert(&mq->hotspot_table, e); |
| 1228 | } |
| 1229 | } |
| 1230 | |
| 1231 | return e; |
| 1232 | } |
| 1233 | |
| 1234 | /* |
| 1235 | * Looks the oblock up in the hash table, then decides whether to put in |
| 1236 | * pre_cache, or cache etc. |
| 1237 | */ |
| 1238 | static int map(struct smq_policy *mq, struct bio *bio, dm_oblock_t oblock, |
| 1239 | bool can_migrate, bool fast_promote, |
| 1240 | struct policy_locker *locker, struct policy_result *result) |
| 1241 | { |
| 1242 | struct entry *e, *hs_e; |
| 1243 | enum promote_result pr; |
| 1244 | |
| 1245 | hs_e = update_hotspot_queue(mq, oblock, bio); |
| 1246 | |
| 1247 | e = h_lookup(&mq->table, oblock); |
| 1248 | if (e) { |
| 1249 | stats_level_accessed(&mq->cache_stats, e->level); |
| 1250 | |
| 1251 | requeue(mq, e); |
| 1252 | result->op = POLICY_HIT; |
| 1253 | result->cblock = infer_cblock(mq, e); |
| 1254 | |
| 1255 | } else { |
| 1256 | stats_miss(&mq->cache_stats); |
| 1257 | |
| 1258 | pr = should_promote(mq, hs_e, bio, fast_promote); |
| 1259 | if (pr == PROMOTE_NOT) |
| 1260 | result->op = POLICY_MISS; |
| 1261 | |
| 1262 | else { |
| 1263 | if (!can_migrate) { |
| 1264 | result->op = POLICY_MISS; |
| 1265 | return -EWOULDBLOCK; |
| 1266 | } |
| 1267 | |
| 1268 | insert_in_cache(mq, oblock, locker, result, pr); |
| 1269 | } |
| 1270 | } |
| 1271 | |
| 1272 | return 0; |
| 1273 | } |
| 1274 | |
| 1275 | /*----------------------------------------------------------------*/ |
| 1276 | |
| 1277 | /* |
| 1278 | * Public interface, via the policy struct. See dm-cache-policy.h for a |
| 1279 | * description of these. |
| 1280 | */ |
| 1281 | |
| 1282 | static struct smq_policy *to_smq_policy(struct dm_cache_policy *p) |
| 1283 | { |
| 1284 | return container_of(p, struct smq_policy, policy); |
| 1285 | } |
| 1286 | |
| 1287 | static void smq_destroy(struct dm_cache_policy *p) |
| 1288 | { |
| 1289 | struct smq_policy *mq = to_smq_policy(p); |
| 1290 | |
| 1291 | h_exit(&mq->hotspot_table); |
| 1292 | h_exit(&mq->table); |
| 1293 | free_bitset(mq->hotspot_hit_bits); |
| 1294 | free_bitset(mq->cache_hit_bits); |
| 1295 | space_exit(&mq->es); |
| 1296 | kfree(mq); |
| 1297 | } |
| 1298 | |
| 1299 | static void copy_tick(struct smq_policy *mq) |
| 1300 | { |
| 1301 | unsigned long flags, tick; |
| 1302 | |
| 1303 | spin_lock_irqsave(&mq->tick_lock, flags); |
| 1304 | tick = mq->tick_protected; |
| 1305 | if (tick != mq->tick) { |
| 1306 | update_sentinels(mq); |
| 1307 | end_hotspot_period(mq); |
| 1308 | end_cache_period(mq); |
| 1309 | mq->tick = tick; |
| 1310 | } |
| 1311 | spin_unlock_irqrestore(&mq->tick_lock, flags); |
| 1312 | } |
| 1313 | |
| 1314 | static bool maybe_lock(struct smq_policy *mq, bool can_block) |
| 1315 | { |
| 1316 | if (can_block) { |
| 1317 | mutex_lock(&mq->lock); |
| 1318 | return true; |
| 1319 | } else |
| 1320 | return mutex_trylock(&mq->lock); |
| 1321 | } |
| 1322 | |
| 1323 | static int smq_map(struct dm_cache_policy *p, dm_oblock_t oblock, |
| 1324 | bool can_block, bool can_migrate, bool fast_promote, |
| 1325 | struct bio *bio, struct policy_locker *locker, |
| 1326 | struct policy_result *result) |
| 1327 | { |
| 1328 | int r; |
| 1329 | struct smq_policy *mq = to_smq_policy(p); |
| 1330 | |
| 1331 | result->op = POLICY_MISS; |
| 1332 | |
| 1333 | if (!maybe_lock(mq, can_block)) |
| 1334 | return -EWOULDBLOCK; |
| 1335 | |
| 1336 | copy_tick(mq); |
| 1337 | r = map(mq, bio, oblock, can_migrate, fast_promote, locker, result); |
| 1338 | mutex_unlock(&mq->lock); |
| 1339 | |
| 1340 | return r; |
| 1341 | } |
| 1342 | |
| 1343 | static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock) |
| 1344 | { |
| 1345 | int r; |
| 1346 | struct smq_policy *mq = to_smq_policy(p); |
| 1347 | struct entry *e; |
| 1348 | |
| 1349 | if (!mutex_trylock(&mq->lock)) |
| 1350 | return -EWOULDBLOCK; |
| 1351 | |
| 1352 | e = h_lookup(&mq->table, oblock); |
| 1353 | if (e) { |
| 1354 | *cblock = infer_cblock(mq, e); |
| 1355 | r = 0; |
| 1356 | } else |
| 1357 | r = -ENOENT; |
| 1358 | |
| 1359 | mutex_unlock(&mq->lock); |
| 1360 | |
| 1361 | return r; |
| 1362 | } |
| 1363 | |
| 1364 | static void __smq_set_clear_dirty(struct smq_policy *mq, dm_oblock_t oblock, bool set) |
| 1365 | { |
| 1366 | struct entry *e; |
| 1367 | |
| 1368 | e = h_lookup(&mq->table, oblock); |
| 1369 | BUG_ON(!e); |
| 1370 | |
| 1371 | del(mq, e); |
| 1372 | e->dirty = set; |
| 1373 | push(mq, e); |
| 1374 | } |
| 1375 | |
| 1376 | static void smq_set_dirty(struct dm_cache_policy *p, dm_oblock_t oblock) |
| 1377 | { |
| 1378 | struct smq_policy *mq = to_smq_policy(p); |
| 1379 | |
| 1380 | mutex_lock(&mq->lock); |
| 1381 | __smq_set_clear_dirty(mq, oblock, true); |
| 1382 | mutex_unlock(&mq->lock); |
| 1383 | } |
| 1384 | |
| 1385 | static void smq_clear_dirty(struct dm_cache_policy *p, dm_oblock_t oblock) |
| 1386 | { |
| 1387 | struct smq_policy *mq = to_smq_policy(p); |
| 1388 | |
| 1389 | mutex_lock(&mq->lock); |
| 1390 | __smq_set_clear_dirty(mq, oblock, false); |
| 1391 | mutex_unlock(&mq->lock); |
| 1392 | } |
| 1393 | |
| 1394 | static int smq_load_mapping(struct dm_cache_policy *p, |
| 1395 | dm_oblock_t oblock, dm_cblock_t cblock, |
| 1396 | uint32_t hint, bool hint_valid) |
| 1397 | { |
| 1398 | struct smq_policy *mq = to_smq_policy(p); |
| 1399 | struct entry *e; |
| 1400 | |
| 1401 | e = alloc_particular_entry(&mq->cache_alloc, from_cblock(cblock)); |
| 1402 | e->oblock = oblock; |
| 1403 | e->dirty = false; /* this gets corrected in a minute */ |
| 1404 | e->level = hint_valid ? min(hint, NR_CACHE_LEVELS - 1) : 1; |
| 1405 | push(mq, e); |
| 1406 | |
| 1407 | return 0; |
| 1408 | } |
| 1409 | |
| 1410 | static int smq_save_hints(struct smq_policy *mq, struct queue *q, |
| 1411 | policy_walk_fn fn, void *context) |
| 1412 | { |
| 1413 | int r; |
| 1414 | unsigned level; |
| 1415 | struct entry *e; |
| 1416 | |
| 1417 | for (level = 0; level < q->nr_levels; level++) |
| 1418 | for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) { |
| 1419 | if (!e->sentinel) { |
| 1420 | r = fn(context, infer_cblock(mq, e), |
| 1421 | e->oblock, e->level); |
| 1422 | if (r) |
| 1423 | return r; |
| 1424 | } |
| 1425 | } |
| 1426 | |
| 1427 | return 0; |
| 1428 | } |
| 1429 | |
| 1430 | static int smq_walk_mappings(struct dm_cache_policy *p, policy_walk_fn fn, |
| 1431 | void *context) |
| 1432 | { |
| 1433 | struct smq_policy *mq = to_smq_policy(p); |
| 1434 | int r = 0; |
| 1435 | |
| 1436 | mutex_lock(&mq->lock); |
| 1437 | |
| 1438 | r = smq_save_hints(mq, &mq->clean, fn, context); |
| 1439 | if (!r) |
| 1440 | r = smq_save_hints(mq, &mq->dirty, fn, context); |
| 1441 | |
| 1442 | mutex_unlock(&mq->lock); |
| 1443 | |
| 1444 | return r; |
| 1445 | } |
| 1446 | |
| 1447 | static void __remove_mapping(struct smq_policy *mq, dm_oblock_t oblock) |
| 1448 | { |
| 1449 | struct entry *e; |
| 1450 | |
| 1451 | e = h_lookup(&mq->table, oblock); |
| 1452 | BUG_ON(!e); |
| 1453 | |
| 1454 | del(mq, e); |
| 1455 | free_entry(&mq->cache_alloc, e); |
| 1456 | } |
| 1457 | |
| 1458 | static void smq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock) |
| 1459 | { |
| 1460 | struct smq_policy *mq = to_smq_policy(p); |
| 1461 | |
| 1462 | mutex_lock(&mq->lock); |
| 1463 | __remove_mapping(mq, oblock); |
| 1464 | mutex_unlock(&mq->lock); |
| 1465 | } |
| 1466 | |
| 1467 | static int __remove_cblock(struct smq_policy *mq, dm_cblock_t cblock) |
| 1468 | { |
| 1469 | struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock)); |
| 1470 | |
| 1471 | if (!e || !e->allocated) |
| 1472 | return -ENODATA; |
| 1473 | |
| 1474 | del(mq, e); |
| 1475 | free_entry(&mq->cache_alloc, e); |
| 1476 | |
| 1477 | return 0; |
| 1478 | } |
| 1479 | |
| 1480 | static int smq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock) |
| 1481 | { |
| 1482 | int r; |
| 1483 | struct smq_policy *mq = to_smq_policy(p); |
| 1484 | |
| 1485 | mutex_lock(&mq->lock); |
| 1486 | r = __remove_cblock(mq, cblock); |
| 1487 | mutex_unlock(&mq->lock); |
| 1488 | |
| 1489 | return r; |
| 1490 | } |
| 1491 | |
| 1492 | |
| 1493 | #define CLEAN_TARGET_CRITICAL 5u /* percent */ |
| 1494 | |
| 1495 | static bool clean_target_met(struct smq_policy *mq, bool critical) |
| 1496 | { |
| 1497 | if (critical) { |
| 1498 | /* |
| 1499 | * Cache entries may not be populated. So we're cannot rely on the |
| 1500 | * size of the clean queue. |
| 1501 | */ |
| 1502 | unsigned nr_clean = from_cblock(mq->cache_size) - q_size(&mq->dirty); |
| 1503 | unsigned target = from_cblock(mq->cache_size) * CLEAN_TARGET_CRITICAL / 100u; |
| 1504 | |
| 1505 | return nr_clean >= target; |
| 1506 | } else |
| 1507 | return !q_size(&mq->dirty); |
| 1508 | } |
| 1509 | |
| 1510 | static int __smq_writeback_work(struct smq_policy *mq, dm_oblock_t *oblock, |
| 1511 | dm_cblock_t *cblock, bool critical_only) |
| 1512 | { |
| 1513 | struct entry *e = NULL; |
| 1514 | bool target_met = clean_target_met(mq, critical_only); |
| 1515 | |
| 1516 | if (critical_only) |
| 1517 | /* |
| 1518 | * Always try and keep the bottom level clean. |
| 1519 | */ |
| 1520 | e = pop_old(mq, &mq->dirty, target_met ? 1u : mq->dirty.nr_levels); |
| 1521 | |
| 1522 | else |
| 1523 | e = pop_old(mq, &mq->dirty, mq->dirty.nr_levels); |
| 1524 | |
| 1525 | if (!e) |
| 1526 | return -ENODATA; |
| 1527 | |
| 1528 | *oblock = e->oblock; |
| 1529 | *cblock = infer_cblock(mq, e); |
| 1530 | e->dirty = false; |
| 1531 | push_new(mq, e); |
| 1532 | |
| 1533 | return 0; |
| 1534 | } |
| 1535 | |
| 1536 | static int smq_writeback_work(struct dm_cache_policy *p, dm_oblock_t *oblock, |
| 1537 | dm_cblock_t *cblock, bool critical_only) |
| 1538 | { |
| 1539 | int r; |
| 1540 | struct smq_policy *mq = to_smq_policy(p); |
| 1541 | |
| 1542 | mutex_lock(&mq->lock); |
| 1543 | r = __smq_writeback_work(mq, oblock, cblock, critical_only); |
| 1544 | mutex_unlock(&mq->lock); |
| 1545 | |
| 1546 | return r; |
| 1547 | } |
| 1548 | |
| 1549 | static void __force_mapping(struct smq_policy *mq, |
| 1550 | dm_oblock_t current_oblock, dm_oblock_t new_oblock) |
| 1551 | { |
| 1552 | struct entry *e = h_lookup(&mq->table, current_oblock); |
| 1553 | |
| 1554 | if (e) { |
| 1555 | del(mq, e); |
| 1556 | e->oblock = new_oblock; |
| 1557 | e->dirty = true; |
| 1558 | push(mq, e); |
| 1559 | } |
| 1560 | } |
| 1561 | |
| 1562 | static void smq_force_mapping(struct dm_cache_policy *p, |
| 1563 | dm_oblock_t current_oblock, dm_oblock_t new_oblock) |
| 1564 | { |
| 1565 | struct smq_policy *mq = to_smq_policy(p); |
| 1566 | |
| 1567 | mutex_lock(&mq->lock); |
| 1568 | __force_mapping(mq, current_oblock, new_oblock); |
| 1569 | mutex_unlock(&mq->lock); |
| 1570 | } |
| 1571 | |
| 1572 | static dm_cblock_t smq_residency(struct dm_cache_policy *p) |
| 1573 | { |
| 1574 | dm_cblock_t r; |
| 1575 | struct smq_policy *mq = to_smq_policy(p); |
| 1576 | |
| 1577 | mutex_lock(&mq->lock); |
| 1578 | r = to_cblock(mq->cache_alloc.nr_allocated); |
| 1579 | mutex_unlock(&mq->lock); |
| 1580 | |
| 1581 | return r; |
| 1582 | } |
| 1583 | |
Joe Thornber | fba1010 | 2015-05-29 10:20:56 +0100 | [diff] [blame] | 1584 | static void smq_tick(struct dm_cache_policy *p, bool can_block) |
Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1585 | { |
| 1586 | struct smq_policy *mq = to_smq_policy(p); |
| 1587 | unsigned long flags; |
| 1588 | |
| 1589 | spin_lock_irqsave(&mq->tick_lock, flags); |
| 1590 | mq->tick_protected++; |
| 1591 | spin_unlock_irqrestore(&mq->tick_lock, flags); |
Joe Thornber | fba1010 | 2015-05-29 10:20:56 +0100 | [diff] [blame] | 1592 | |
| 1593 | if (can_block) { |
| 1594 | mutex_lock(&mq->lock); |
| 1595 | copy_tick(mq); |
| 1596 | mutex_unlock(&mq->lock); |
| 1597 | } |
Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1598 | } |
| 1599 | |
| 1600 | /* Init the policy plugin interface function pointers. */ |
| 1601 | static void init_policy_functions(struct smq_policy *mq) |
| 1602 | { |
| 1603 | mq->policy.destroy = smq_destroy; |
| 1604 | mq->policy.map = smq_map; |
| 1605 | mq->policy.lookup = smq_lookup; |
| 1606 | mq->policy.set_dirty = smq_set_dirty; |
| 1607 | mq->policy.clear_dirty = smq_clear_dirty; |
| 1608 | mq->policy.load_mapping = smq_load_mapping; |
| 1609 | mq->policy.walk_mappings = smq_walk_mappings; |
| 1610 | mq->policy.remove_mapping = smq_remove_mapping; |
| 1611 | mq->policy.remove_cblock = smq_remove_cblock; |
| 1612 | mq->policy.writeback_work = smq_writeback_work; |
| 1613 | mq->policy.force_mapping = smq_force_mapping; |
| 1614 | mq->policy.residency = smq_residency; |
| 1615 | mq->policy.tick = smq_tick; |
| 1616 | } |
| 1617 | |
| 1618 | static bool too_many_hotspot_blocks(sector_t origin_size, |
| 1619 | sector_t hotspot_block_size, |
| 1620 | unsigned nr_hotspot_blocks) |
| 1621 | { |
| 1622 | return (hotspot_block_size * nr_hotspot_blocks) > origin_size; |
| 1623 | } |
| 1624 | |
| 1625 | static void calc_hotspot_params(sector_t origin_size, |
| 1626 | sector_t cache_block_size, |
| 1627 | unsigned nr_cache_blocks, |
| 1628 | sector_t *hotspot_block_size, |
| 1629 | unsigned *nr_hotspot_blocks) |
| 1630 | { |
| 1631 | *hotspot_block_size = cache_block_size * 16u; |
| 1632 | *nr_hotspot_blocks = max(nr_cache_blocks / 4u, 1024u); |
| 1633 | |
| 1634 | while ((*hotspot_block_size > cache_block_size) && |
| 1635 | too_many_hotspot_blocks(origin_size, *hotspot_block_size, *nr_hotspot_blocks)) |
| 1636 | *hotspot_block_size /= 2u; |
| 1637 | } |
| 1638 | |
| 1639 | static struct dm_cache_policy *smq_create(dm_cblock_t cache_size, |
| 1640 | sector_t origin_size, |
| 1641 | sector_t cache_block_size) |
| 1642 | { |
| 1643 | unsigned i; |
| 1644 | unsigned nr_sentinels_per_queue = 2u * NR_CACHE_LEVELS; |
| 1645 | unsigned total_sentinels = 2u * nr_sentinels_per_queue; |
| 1646 | struct smq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL); |
| 1647 | |
| 1648 | if (!mq) |
| 1649 | return NULL; |
| 1650 | |
| 1651 | init_policy_functions(mq); |
| 1652 | mq->cache_size = cache_size; |
| 1653 | mq->cache_block_size = cache_block_size; |
| 1654 | |
| 1655 | calc_hotspot_params(origin_size, cache_block_size, from_cblock(cache_size), |
| 1656 | &mq->hotspot_block_size, &mq->nr_hotspot_blocks); |
| 1657 | |
| 1658 | mq->cache_blocks_per_hotspot_block = div64_u64(mq->hotspot_block_size, mq->cache_block_size); |
| 1659 | mq->hotspot_level_jump = 1u; |
| 1660 | if (space_init(&mq->es, total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size))) { |
| 1661 | DMERR("couldn't initialize entry space"); |
| 1662 | goto bad_pool_init; |
| 1663 | } |
| 1664 | |
| 1665 | init_allocator(&mq->writeback_sentinel_alloc, &mq->es, 0, nr_sentinels_per_queue); |
| 1666 | for (i = 0; i < nr_sentinels_per_queue; i++) |
| 1667 | get_entry(&mq->writeback_sentinel_alloc, i)->sentinel = true; |
| 1668 | |
| 1669 | init_allocator(&mq->demote_sentinel_alloc, &mq->es, nr_sentinels_per_queue, total_sentinels); |
| 1670 | for (i = 0; i < nr_sentinels_per_queue; i++) |
| 1671 | get_entry(&mq->demote_sentinel_alloc, i)->sentinel = true; |
| 1672 | |
| 1673 | init_allocator(&mq->hotspot_alloc, &mq->es, total_sentinels, |
| 1674 | total_sentinels + mq->nr_hotspot_blocks); |
| 1675 | |
| 1676 | init_allocator(&mq->cache_alloc, &mq->es, |
| 1677 | total_sentinels + mq->nr_hotspot_blocks, |
| 1678 | total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size)); |
| 1679 | |
| 1680 | mq->hotspot_hit_bits = alloc_bitset(mq->nr_hotspot_blocks); |
| 1681 | if (!mq->hotspot_hit_bits) { |
| 1682 | DMERR("couldn't allocate hotspot hit bitset"); |
| 1683 | goto bad_hotspot_hit_bits; |
| 1684 | } |
| 1685 | clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks); |
| 1686 | |
| 1687 | if (from_cblock(cache_size)) { |
| 1688 | mq->cache_hit_bits = alloc_bitset(from_cblock(cache_size)); |
| 1689 | if (!mq->cache_hit_bits && mq->cache_hit_bits) { |
| 1690 | DMERR("couldn't allocate cache hit bitset"); |
| 1691 | goto bad_cache_hit_bits; |
| 1692 | } |
| 1693 | clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size)); |
| 1694 | } else |
| 1695 | mq->cache_hit_bits = NULL; |
| 1696 | |
| 1697 | mq->tick_protected = 0; |
| 1698 | mq->tick = 0; |
| 1699 | mutex_init(&mq->lock); |
| 1700 | spin_lock_init(&mq->tick_lock); |
| 1701 | |
| 1702 | q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS); |
| 1703 | mq->hotspot.nr_top_levels = 8; |
| 1704 | mq->hotspot.nr_in_top_levels = min(mq->nr_hotspot_blocks / NR_HOTSPOT_LEVELS, |
| 1705 | from_cblock(mq->cache_size) / mq->cache_blocks_per_hotspot_block); |
| 1706 | |
| 1707 | q_init(&mq->clean, &mq->es, NR_CACHE_LEVELS); |
| 1708 | q_init(&mq->dirty, &mq->es, NR_CACHE_LEVELS); |
| 1709 | |
| 1710 | stats_init(&mq->hotspot_stats, NR_HOTSPOT_LEVELS); |
| 1711 | stats_init(&mq->cache_stats, NR_CACHE_LEVELS); |
| 1712 | |
| 1713 | if (h_init(&mq->table, &mq->es, from_cblock(cache_size))) |
| 1714 | goto bad_alloc_table; |
| 1715 | |
| 1716 | if (h_init(&mq->hotspot_table, &mq->es, mq->nr_hotspot_blocks)) |
| 1717 | goto bad_alloc_hotspot_table; |
| 1718 | |
| 1719 | sentinels_init(mq); |
| 1720 | mq->write_promote_level = mq->read_promote_level = NR_HOTSPOT_LEVELS; |
| 1721 | |
| 1722 | mq->next_hotspot_period = jiffies; |
| 1723 | mq->next_cache_period = jiffies; |
| 1724 | |
| 1725 | return &mq->policy; |
| 1726 | |
| 1727 | bad_alloc_hotspot_table: |
| 1728 | h_exit(&mq->table); |
| 1729 | bad_alloc_table: |
| 1730 | free_bitset(mq->cache_hit_bits); |
| 1731 | bad_cache_hit_bits: |
| 1732 | free_bitset(mq->hotspot_hit_bits); |
| 1733 | bad_hotspot_hit_bits: |
| 1734 | space_exit(&mq->es); |
| 1735 | bad_pool_init: |
| 1736 | kfree(mq); |
| 1737 | |
| 1738 | return NULL; |
| 1739 | } |
| 1740 | |
| 1741 | /*----------------------------------------------------------------*/ |
| 1742 | |
| 1743 | static struct dm_cache_policy_type smq_policy_type = { |
| 1744 | .name = "smq", |
| 1745 | .version = {1, 0, 0}, |
| 1746 | .hint_size = 4, |
| 1747 | .owner = THIS_MODULE, |
| 1748 | .create = smq_create |
| 1749 | }; |
| 1750 | |
Mike Snitzer | bccab6a | 2015-06-17 11:43:38 -0400 | [diff] [blame^] | 1751 | static struct dm_cache_policy_type default_policy_type = { |
| 1752 | .name = "default", |
| 1753 | .version = {1, 0, 0}, |
| 1754 | .hint_size = 4, |
| 1755 | .owner = THIS_MODULE, |
| 1756 | .create = smq_create, |
| 1757 | .real = &smq_policy_type |
| 1758 | }; |
| 1759 | |
Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1760 | static int __init smq_init(void) |
| 1761 | { |
| 1762 | int r; |
| 1763 | |
| 1764 | r = dm_cache_policy_register(&smq_policy_type); |
| 1765 | if (r) { |
| 1766 | DMERR("register failed %d", r); |
| 1767 | return -ENOMEM; |
| 1768 | } |
| 1769 | |
Mike Snitzer | bccab6a | 2015-06-17 11:43:38 -0400 | [diff] [blame^] | 1770 | r = dm_cache_policy_register(&default_policy_type); |
| 1771 | if (r) { |
| 1772 | DMERR("register failed (as default) %d", r); |
| 1773 | dm_cache_policy_unregister(&smq_policy_type); |
| 1774 | return -ENOMEM; |
| 1775 | } |
| 1776 | |
Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1777 | return 0; |
| 1778 | } |
| 1779 | |
| 1780 | static void __exit smq_exit(void) |
| 1781 | { |
| 1782 | dm_cache_policy_unregister(&smq_policy_type); |
Mike Snitzer | bccab6a | 2015-06-17 11:43:38 -0400 | [diff] [blame^] | 1783 | dm_cache_policy_unregister(&default_policy_type); |
Joe Thornber | 66a6363 | 2015-05-15 15:33:34 +0100 | [diff] [blame] | 1784 | } |
| 1785 | |
| 1786 | module_init(smq_init); |
| 1787 | module_exit(smq_exit); |
| 1788 | |
| 1789 | MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>"); |
| 1790 | MODULE_LICENSE("GPL"); |
| 1791 | MODULE_DESCRIPTION("smq cache policy"); |