drivers/md/dm-cache-policy-smq.c

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This source file includes following definitions.
safe_div
safe_mod
space_init
space_exit
__get_entry
to_index
to_entry
l_init
l_head
l_tail
l_next
l_prev
l_empty
l_add_head
l_add_tail
l_add_before
l_del
l_pop_head
l_pop_tail
q_init
q_size
q_push
q_push_front
q_push_before
q_del
q_peek
q_pop
__redist_pop_from
q_set_targets_subrange_
q_set_targets
q_redistribute
q_requeue
stats_init
stats_reset
stats_level_accessed
stats_miss
stats_assess
h_init
h_exit
h_head
h_next
__h_insert
h_insert
__h_lookup
__h_unlink
h_lookup
h_remove
init_allocator
init_entry
alloc_entry
alloc_particular_entry
free_entry
allocator_empty
get_index
get_entry
get_sentinel
writeback_sentinel
demote_sentinel
__update_writeback_sentinels
__update_demote_sentinels
update_sentinels
__sentinels_init
sentinels_init
del_queue
push_queue
push
push_queue_front
push_front
infer_cblock
requeue
default_promote_level
update_promote_levels
update_level_jump
end_hotspot_period
end_cache_period
percent_to_target
clean_target_met
free_target_met
mark_pending
clear_pending
queue_writeback
queue_demotion
queue_promotion
maybe_promote
should_promote
to_hblock
update_hotspot_queue
to_smq_policy
smq_destroy
__lookup
smq_lookup
smq_lookup_with_work
smq_get_background_work
__complete_background_work
smq_complete_background_work
__smq_set_clear_dirty
smq_set_dirty
smq_clear_dirty
random_level
smq_load_mapping
smq_invalidate_mapping
smq_get_hint
smq_residency
smq_tick
smq_allow_migrations
mq_set_config_value
mq_emit_config_values
init_policy_functions
too_many_hotspot_blocks
calc_hotspot_params
__smq_create
smq_create
mq_create
cleaner_create
smq_init
smq_exit
   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-background-tracker.h"
   8 #include "dm-cache-policy-internal.h"
   9 #include "dm-cache-policy.h"
  10 #include "dm.h"
  11 
  12 #include <linux/hash.h>
  13 #include <linux/jiffies.h>
  14 #include <linux/module.h>
  15 #include <linux/mutex.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/math64.h>
  18 
  19 #define DM_MSG_PREFIX "cache-policy-smq"
  20 
  21 /*----------------------------------------------------------------*/
  22 
  23 /*
  24  * Safe division functions that return zero on divide by zero.
  25  */
  26 static unsigned safe_div(unsigned n, unsigned d)
  27 {
  28         return d ? n / d : 0u;
  29 }
  30 
  31 static unsigned safe_mod(unsigned n, unsigned d)
  32 {
  33         return d ? n % d : 0u;
  34 }
  35 
  36 /*----------------------------------------------------------------*/
  37 
  38 struct entry {
  39         unsigned hash_next:28;
  40         unsigned prev:28;
  41         unsigned next:28;
  42         unsigned level:6;
  43         bool dirty:1;
  44         bool allocated:1;
  45         bool sentinel:1;
  46         bool pending_work:1;
  47 
  48         dm_oblock_t oblock;
  49 };
  50 
  51 /*----------------------------------------------------------------*/
  52 
  53 #define INDEXER_NULL ((1u << 28u) - 1u)
  54 
  55 /*
  56  * An entry_space manages a set of entries that we use for the queues.
  57  * The clean and dirty queues share entries, so this object is separate
  58  * from the queue itself.
  59  */
  60 struct entry_space {
  61         struct entry *begin;
  62         struct entry *end;
  63 };
  64 
  65 static int space_init(struct entry_space *es, unsigned nr_entries)
  66 {
  67         if (!nr_entries) {
  68                 es->begin = es->end = NULL;
  69                 return 0;
  70         }
  71 
  72         es->begin = vzalloc(array_size(nr_entries, sizeof(struct entry)));
  73         if (!es->begin)
  74                 return -ENOMEM;
  75 
  76         es->end = es->begin + nr_entries;
  77         return 0;
  78 }
  79 
  80 static void space_exit(struct entry_space *es)
  81 {
  82         vfree(es->begin);
  83 }
  84 
  85 static struct entry *__get_entry(struct entry_space *es, unsigned block)
  86 {
  87         struct entry *e;
  88 
  89         e = es->begin + block;
  90         BUG_ON(e >= es->end);
  91 
  92         return e;
  93 }
  94 
  95 static unsigned to_index(struct entry_space *es, struct entry *e)
  96 {
  97         BUG_ON(e < es->begin || e >= es->end);
  98         return e - es->begin;
  99 }
 100 
 101 static struct entry *to_entry(struct entry_space *es, unsigned block)
 102 {
 103         if (block == INDEXER_NULL)
 104                 return NULL;
 105 
 106         return __get_entry(es, block);
 107 }
 108 
 109 /*----------------------------------------------------------------*/
 110 
 111 struct ilist {
 112         unsigned nr_elts;       /* excluding sentinel entries */
 113         unsigned head, tail;
 114 };
 115 
 116 static void l_init(struct ilist *l)
 117 {
 118         l->nr_elts = 0;
 119         l->head = l->tail = INDEXER_NULL;
 120 }
 121 
 122 static struct entry *l_head(struct entry_space *es, struct ilist *l)
 123 {
 124         return to_entry(es, l->head);
 125 }
 126 
 127 static struct entry *l_tail(struct entry_space *es, struct ilist *l)
 128 {
 129         return to_entry(es, l->tail);
 130 }
 131 
 132 static struct entry *l_next(struct entry_space *es, struct entry *e)
 133 {
 134         return to_entry(es, e->next);
 135 }
 136 
 137 static struct entry *l_prev(struct entry_space *es, struct entry *e)
 138 {
 139         return to_entry(es, e->prev);
 140 }
 141 
 142 static bool l_empty(struct ilist *l)
 143 {
 144         return l->head == INDEXER_NULL;
 145 }
 146 
 147 static void l_add_head(struct entry_space *es, struct ilist *l, struct entry *e)
 148 {
 149         struct entry *head = l_head(es, l);
 150 
 151         e->next = l->head;
 152         e->prev = INDEXER_NULL;
 153 
 154         if (head)
 155                 head->prev = l->head = to_index(es, e);
 156         else
 157                 l->head = l->tail = to_index(es, e);
 158 
 159         if (!e->sentinel)
 160                 l->nr_elts++;
 161 }
 162 
 163 static void l_add_tail(struct entry_space *es, struct ilist *l, struct entry *e)
 164 {
 165         struct entry *tail = l_tail(es, l);
 166 
 167         e->next = INDEXER_NULL;
 168         e->prev = l->tail;
 169 
 170         if (tail)
 171                 tail->next = l->tail = to_index(es, e);
 172         else
 173                 l->head = l->tail = to_index(es, e);
 174 
 175         if (!e->sentinel)
 176                 l->nr_elts++;
 177 }
 178 
 179 static void l_add_before(struct entry_space *es, struct ilist *l,
 180                          struct entry *old, struct entry *e)
 181 {
 182         struct entry *prev = l_prev(es, old);
 183 
 184         if (!prev)
 185                 l_add_head(es, l, e);
 186 
 187         else {
 188                 e->prev = old->prev;
 189                 e->next = to_index(es, old);
 190                 prev->next = old->prev = to_index(es, e);
 191 
 192                 if (!e->sentinel)
 193                         l->nr_elts++;
 194         }
 195 }
 196 
 197 static void l_del(struct entry_space *es, struct ilist *l, struct entry *e)
 198 {
 199         struct entry *prev = l_prev(es, e);
 200         struct entry *next = l_next(es, e);
 201 
 202         if (prev)
 203                 prev->next = e->next;
 204         else
 205                 l->head = e->next;
 206 
 207         if (next)
 208                 next->prev = e->prev;
 209         else
 210                 l->tail = e->prev;
 211 
 212         if (!e->sentinel)
 213                 l->nr_elts--;
 214 }
 215 
 216 static struct entry *l_pop_head(struct entry_space *es, struct ilist *l)
 217 {
 218         struct entry *e;
 219 
 220         for (e = l_head(es, l); e; e = l_next(es, e))
 221                 if (!e->sentinel) {
 222                         l_del(es, l, e);
 223                         return e;
 224                 }
 225 
 226         return NULL;
 227 }
 228 
 229 static struct entry *l_pop_tail(struct entry_space *es, struct ilist *l)
 230 {
 231         struct entry *e;
 232 
 233         for (e = l_tail(es, l); e; e = l_prev(es, e))
 234                 if (!e->sentinel) {
 235                         l_del(es, l, e);
 236                         return e;
 237                 }
 238 
 239         return NULL;
 240 }
 241 
 242 /*----------------------------------------------------------------*/
 243 
 244 /*
 245  * The stochastic-multi-queue is a set of lru lists stacked into levels.
 246  * Entries are moved up levels when they are used, which loosely orders the
 247  * most accessed entries in the top levels and least in the bottom.  This
 248  * structure is *much* better than a single lru list.
 249  */
 250 #define MAX_LEVELS 64u
 251 
 252 struct queue {
 253         struct entry_space *es;
 254 
 255         unsigned nr_elts;
 256         unsigned nr_levels;
 257         struct ilist qs[MAX_LEVELS];
 258 
 259         /*
 260          * We maintain a count of the number of entries we would like in each
 261          * level.
 262          */
 263         unsigned last_target_nr_elts;
 264         unsigned nr_top_levels;
 265         unsigned nr_in_top_levels;
 266         unsigned target_count[MAX_LEVELS];
 267 };
 268 
 269 static void q_init(struct queue *q, struct entry_space *es, unsigned nr_levels)
 270 {
 271         unsigned i;
 272 
 273         q->es = es;
 274         q->nr_elts = 0;
 275         q->nr_levels = nr_levels;
 276 
 277         for (i = 0; i < q->nr_levels; i++) {
 278                 l_init(q->qs + i);
 279                 q->target_count[i] = 0u;
 280         }
 281 
 282         q->last_target_nr_elts = 0u;
 283         q->nr_top_levels = 0u;
 284         q->nr_in_top_levels = 0u;
 285 }
 286 
 287 static unsigned q_size(struct queue *q)
 288 {
 289         return q->nr_elts;
 290 }
 291 
 292 /*
 293  * Insert an entry to the back of the given level.
 294  */
 295 static void q_push(struct queue *q, struct entry *e)
 296 {
 297         BUG_ON(e->pending_work);
 298 
 299         if (!e->sentinel)
 300                 q->nr_elts++;
 301 
 302         l_add_tail(q->es, q->qs + e->level, e);
 303 }
 304 
 305 static void q_push_front(struct queue *q, struct entry *e)
 306 {
 307         BUG_ON(e->pending_work);
 308 
 309         if (!e->sentinel)
 310                 q->nr_elts++;
 311 
 312         l_add_head(q->es, q->qs + e->level, e);
 313 }
 314 
 315 static void q_push_before(struct queue *q, struct entry *old, struct entry *e)
 316 {
 317         BUG_ON(e->pending_work);
 318 
 319         if (!e->sentinel)
 320                 q->nr_elts++;
 321 
 322         l_add_before(q->es, q->qs + e->level, old, e);
 323 }
 324 
 325 static void q_del(struct queue *q, struct entry *e)
 326 {
 327         l_del(q->es, q->qs + e->level, e);
 328         if (!e->sentinel)
 329                 q->nr_elts--;
 330 }
 331 
 332 /*
 333  * Return the oldest entry of the lowest populated level.
 334  */
 335 static struct entry *q_peek(struct queue *q, unsigned max_level, bool can_cross_sentinel)
 336 {
 337         unsigned level;
 338         struct entry *e;
 339 
 340         max_level = min(max_level, q->nr_levels);
 341 
 342         for (level = 0; level < max_level; level++)
 343                 for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e)) {
 344                         if (e->sentinel) {
 345                                 if (can_cross_sentinel)
 346                                         continue;
 347                                 else
 348                                         break;
 349                         }
 350 
 351                         return e;
 352                 }
 353 
 354         return NULL;
 355 }
 356 
 357 static struct entry *q_pop(struct queue *q)
 358 {
 359         struct entry *e = q_peek(q, q->nr_levels, true);
 360 
 361         if (e)
 362                 q_del(q, e);
 363 
 364         return e;
 365 }
 366 
 367 /*
 368  * This function assumes there is a non-sentinel entry to pop.  It's only
 369  * used by redistribute, so we know this is true.  It also doesn't adjust
 370  * the q->nr_elts count.
 371  */
 372 static struct entry *__redist_pop_from(struct queue *q, unsigned level)
 373 {
 374         struct entry *e;
 375 
 376         for (; level < q->nr_levels; level++)
 377                 for (e = l_head(q->es, q->qs + level); e; e = l_next(q->es, e))
 378                         if (!e->sentinel) {
 379                                 l_del(q->es, q->qs + e->level, e);
 380                                 return e;
 381                         }
 382 
 383         return NULL;
 384 }
 385 
 386 static void q_set_targets_subrange_(struct queue *q, unsigned nr_elts, unsigned lbegin, unsigned lend)
 387 {
 388         unsigned level, nr_levels, entries_per_level, remainder;
 389 
 390         BUG_ON(lbegin > lend);
 391         BUG_ON(lend > q->nr_levels);
 392         nr_levels = lend - lbegin;
 393         entries_per_level = safe_div(nr_elts, nr_levels);
 394         remainder = safe_mod(nr_elts, nr_levels);
 395 
 396         for (level = lbegin; level < lend; level++)
 397                 q->target_count[level] =
 398                         (level < (lbegin + remainder)) ? entries_per_level + 1u : entries_per_level;
 399 }
 400 
 401 /*
 402  * Typically we have fewer elements in the top few levels which allows us
 403  * to adjust the promote threshold nicely.
 404  */
 405 static void q_set_targets(struct queue *q)
 406 {
 407         if (q->last_target_nr_elts == q->nr_elts)
 408                 return;
 409 
 410         q->last_target_nr_elts = q->nr_elts;
 411 
 412         if (q->nr_top_levels > q->nr_levels)
 413                 q_set_targets_subrange_(q, q->nr_elts, 0, q->nr_levels);
 414 
 415         else {
 416                 q_set_targets_subrange_(q, q->nr_in_top_levels,
 417                                         q->nr_levels - q->nr_top_levels, q->nr_levels);
 418 
 419                 if (q->nr_in_top_levels < q->nr_elts)
 420                         q_set_targets_subrange_(q, q->nr_elts - q->nr_in_top_levels,
 421                                                 0, q->nr_levels - q->nr_top_levels);
 422                 else
 423                         q_set_targets_subrange_(q, 0, 0, q->nr_levels - q->nr_top_levels);
 424         }
 425 }
 426 
 427 static void q_redistribute(struct queue *q)
 428 {
 429         unsigned target, level;
 430         struct ilist *l, *l_above;
 431         struct entry *e;
 432 
 433         q_set_targets(q);
 434 
 435         for (level = 0u; level < q->nr_levels - 1u; level++) {
 436                 l = q->qs + level;
 437                 target = q->target_count[level];
 438 
 439                 /*
 440                  * Pull down some entries from the level above.
 441                  */
 442                 while (l->nr_elts < target) {
 443                         e = __redist_pop_from(q, level + 1u);
 444                         if (!e) {
 445                                 /* bug in nr_elts */
 446                                 break;
 447                         }
 448 
 449                         e->level = level;
 450                         l_add_tail(q->es, l, e);
 451                 }
 452 
 453                 /*
 454                  * Push some entries up.
 455                  */
 456                 l_above = q->qs + level + 1u;
 457                 while (l->nr_elts > target) {
 458                         e = l_pop_tail(q->es, l);
 459 
 460                         if (!e)
 461                                 /* bug in nr_elts */
 462                                 break;
 463 
 464                         e->level = level + 1u;
 465                         l_add_tail(q->es, l_above, e);
 466                 }
 467         }
 468 }
 469 
 470 static void q_requeue(struct queue *q, struct entry *e, unsigned extra_levels,
 471                       struct entry *s1, struct entry *s2)
 472 {
 473         struct entry *de;
 474         unsigned sentinels_passed = 0;
 475         unsigned new_level = min(q->nr_levels - 1u, e->level + extra_levels);
 476 
 477         /* try and find an entry to swap with */
 478         if (extra_levels && (e->level < q->nr_levels - 1u)) {
 479                 for (de = l_head(q->es, q->qs + new_level); de && de->sentinel; de = l_next(q->es, de))
 480                         sentinels_passed++;
 481 
 482                 if (de) {
 483                         q_del(q, de);
 484                         de->level = e->level;
 485                         if (s1) {
 486                                 switch (sentinels_passed) {
 487                                 case 0:
 488                                         q_push_before(q, s1, de);
 489                                         break;
 490 
 491                                 case 1:
 492                                         q_push_before(q, s2, de);
 493                                         break;
 494 
 495                                 default:
 496                                         q_push(q, de);
 497                                 }
 498                         } else
 499                                 q_push(q, de);
 500                 }
 501         }
 502 
 503         q_del(q, e);
 504         e->level = new_level;
 505         q_push(q, e);
 506 }
 507 
 508 /*----------------------------------------------------------------*/
 509 
 510 #define FP_SHIFT 8
 511 #define SIXTEENTH (1u << (FP_SHIFT - 4u))
 512 #define EIGHTH (1u << (FP_SHIFT - 3u))
 513 
 514 struct stats {
 515         unsigned hit_threshold;
 516         unsigned hits;
 517         unsigned misses;
 518 };
 519 
 520 enum performance {
 521         Q_POOR,
 522         Q_FAIR,
 523         Q_WELL
 524 };
 525 
 526 static void stats_init(struct stats *s, unsigned nr_levels)
 527 {
 528         s->hit_threshold = (nr_levels * 3u) / 4u;
 529         s->hits = 0u;
 530         s->misses = 0u;
 531 }
 532 
 533 static void stats_reset(struct stats *s)
 534 {
 535         s->hits = s->misses = 0u;
 536 }
 537 
 538 static void stats_level_accessed(struct stats *s, unsigned level)
 539 {
 540         if (level >= s->hit_threshold)
 541                 s->hits++;
 542         else
 543                 s->misses++;
 544 }
 545 
 546 static void stats_miss(struct stats *s)
 547 {
 548         s->misses++;
 549 }
 550 
 551 /*
 552  * There are times when we don't have any confidence in the hotspot queue.
 553  * Such as when a fresh cache is created and the blocks have been spread
 554  * out across the levels, or if an io load changes.  We detect this by
 555  * seeing how often a lookup is in the top levels of the hotspot queue.
 556  */
 557 static enum performance stats_assess(struct stats *s)
 558 {
 559         unsigned confidence = safe_div(s->hits << FP_SHIFT, s->hits + s->misses);
 560 
 561         if (confidence < SIXTEENTH)
 562                 return Q_POOR;
 563 
 564         else if (confidence < EIGHTH)
 565                 return Q_FAIR;
 566 
 567         else
 568                 return Q_WELL;
 569 }
 570 
 571 /*----------------------------------------------------------------*/
 572 
 573 struct smq_hash_table {
 574         struct entry_space *es;
 575         unsigned long long hash_bits;
 576         unsigned *buckets;
 577 };
 578 
 579 /*
 580  * All cache entries are stored in a chained hash table.  To save space we
 581  * use indexing again, and only store indexes to the next entry.
 582  */
 583 static int h_init(struct smq_hash_table *ht, struct entry_space *es, unsigned nr_entries)
 584 {
 585         unsigned i, nr_buckets;
 586 
 587         ht->es = es;
 588         nr_buckets = roundup_pow_of_two(max(nr_entries / 4u, 16u));
 589         ht->hash_bits = __ffs(nr_buckets);
 590 
 591         ht->buckets = vmalloc(array_size(nr_buckets, sizeof(*ht->buckets)));
 592         if (!ht->buckets)
 593                 return -ENOMEM;
 594 
 595         for (i = 0; i < nr_buckets; i++)
 596                 ht->buckets[i] = INDEXER_NULL;
 597 
 598         return 0;
 599 }
 600 
 601 static void h_exit(struct smq_hash_table *ht)
 602 {
 603         vfree(ht->buckets);
 604 }
 605 
 606 static struct entry *h_head(struct smq_hash_table *ht, unsigned bucket)
 607 {
 608         return to_entry(ht->es, ht->buckets[bucket]);
 609 }
 610 
 611 static struct entry *h_next(struct smq_hash_table *ht, struct entry *e)
 612 {
 613         return to_entry(ht->es, e->hash_next);
 614 }
 615 
 616 static void __h_insert(struct smq_hash_table *ht, unsigned bucket, struct entry *e)
 617 {
 618         e->hash_next = ht->buckets[bucket];
 619         ht->buckets[bucket] = to_index(ht->es, e);
 620 }
 621 
 622 static void h_insert(struct smq_hash_table *ht, struct entry *e)
 623 {
 624         unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
 625         __h_insert(ht, h, e);
 626 }
 627 
 628 static struct entry *__h_lookup(struct smq_hash_table *ht, unsigned h, dm_oblock_t oblock,
 629                                 struct entry **prev)
 630 {
 631         struct entry *e;
 632 
 633         *prev = NULL;
 634         for (e = h_head(ht, h); e; e = h_next(ht, e)) {
 635                 if (e->oblock == oblock)
 636                         return e;
 637 
 638                 *prev = e;
 639         }
 640 
 641         return NULL;
 642 }
 643 
 644 static void __h_unlink(struct smq_hash_table *ht, unsigned h,
 645                        struct entry *e, struct entry *prev)
 646 {
 647         if (prev)
 648                 prev->hash_next = e->hash_next;
 649         else
 650                 ht->buckets[h] = e->hash_next;
 651 }
 652 
 653 /*
 654  * Also moves each entry to the front of the bucket.
 655  */
 656 static struct entry *h_lookup(struct smq_hash_table *ht, dm_oblock_t oblock)
 657 {
 658         struct entry *e, *prev;
 659         unsigned h = hash_64(from_oblock(oblock), ht->hash_bits);
 660 
 661         e = __h_lookup(ht, h, oblock, &prev);
 662         if (e && prev) {
 663                 /*
 664                  * Move to the front because this entry is likely
 665                  * to be hit again.
 666                  */
 667                 __h_unlink(ht, h, e, prev);
 668                 __h_insert(ht, h, e);
 669         }
 670 
 671         return e;
 672 }
 673 
 674 static void h_remove(struct smq_hash_table *ht, struct entry *e)
 675 {
 676         unsigned h = hash_64(from_oblock(e->oblock), ht->hash_bits);
 677         struct entry *prev;
 678 
 679         /*
 680          * The down side of using a singly linked list is we have to
 681          * iterate the bucket to remove an item.
 682          */
 683         e = __h_lookup(ht, h, e->oblock, &prev);
 684         if (e)
 685                 __h_unlink(ht, h, e, prev);
 686 }
 687 
 688 /*----------------------------------------------------------------*/
 689 
 690 struct entry_alloc {
 691         struct entry_space *es;
 692         unsigned begin;
 693 
 694         unsigned nr_allocated;
 695         struct ilist free;
 696 };
 697 
 698 static void init_allocator(struct entry_alloc *ea, struct entry_space *es,
 699                            unsigned begin, unsigned end)
 700 {
 701         unsigned i;
 702 
 703         ea->es = es;
 704         ea->nr_allocated = 0u;
 705         ea->begin = begin;
 706 
 707         l_init(&ea->free);
 708         for (i = begin; i != end; i++)
 709                 l_add_tail(ea->es, &ea->free, __get_entry(ea->es, i));
 710 }
 711 
 712 static void init_entry(struct entry *e)
 713 {
 714         /*
 715          * We can't memset because that would clear the hotspot and
 716          * sentinel bits which remain constant.
 717          */
 718         e->hash_next = INDEXER_NULL;
 719         e->next = INDEXER_NULL;
 720         e->prev = INDEXER_NULL;
 721         e->level = 0u;
 722         e->dirty = true;        /* FIXME: audit */
 723         e->allocated = true;
 724         e->sentinel = false;
 725         e->pending_work = false;
 726 }
 727 
 728 static struct entry *alloc_entry(struct entry_alloc *ea)
 729 {
 730         struct entry *e;
 731 
 732         if (l_empty(&ea->free))
 733                 return NULL;
 734 
 735         e = l_pop_head(ea->es, &ea->free);
 736         init_entry(e);
 737         ea->nr_allocated++;
 738 
 739         return e;
 740 }
 741 
 742 /*
 743  * This assumes the cblock hasn't already been allocated.
 744  */
 745 static struct entry *alloc_particular_entry(struct entry_alloc *ea, unsigned i)
 746 {
 747         struct entry *e = __get_entry(ea->es, ea->begin + i);
 748 
 749         BUG_ON(e->allocated);
 750 
 751         l_del(ea->es, &ea->free, e);
 752         init_entry(e);
 753         ea->nr_allocated++;
 754 
 755         return e;
 756 }
 757 
 758 static void free_entry(struct entry_alloc *ea, struct entry *e)
 759 {
 760         BUG_ON(!ea->nr_allocated);
 761         BUG_ON(!e->allocated);
 762 
 763         ea->nr_allocated--;
 764         e->allocated = false;
 765         l_add_tail(ea->es, &ea->free, e);
 766 }
 767 
 768 static bool allocator_empty(struct entry_alloc *ea)
 769 {
 770         return l_empty(&ea->free);
 771 }
 772 
 773 static unsigned get_index(struct entry_alloc *ea, struct entry *e)
 774 {
 775         return to_index(ea->es, e) - ea->begin;
 776 }
 777 
 778 static struct entry *get_entry(struct entry_alloc *ea, unsigned index)
 779 {
 780         return __get_entry(ea->es, ea->begin + index);
 781 }
 782 
 783 /*----------------------------------------------------------------*/
 784 
 785 #define NR_HOTSPOT_LEVELS 64u
 786 #define NR_CACHE_LEVELS 64u
 787 
 788 #define WRITEBACK_PERIOD (10ul * HZ)
 789 #define DEMOTE_PERIOD (60ul * HZ)
 790 
 791 #define HOTSPOT_UPDATE_PERIOD (HZ)
 792 #define CACHE_UPDATE_PERIOD (60ul * HZ)
 793 
 794 struct smq_policy {
 795         struct dm_cache_policy policy;
 796 
 797         /* protects everything */
 798         spinlock_t lock;
 799         dm_cblock_t cache_size;
 800         sector_t cache_block_size;
 801 
 802         sector_t hotspot_block_size;
 803         unsigned nr_hotspot_blocks;
 804         unsigned cache_blocks_per_hotspot_block;
 805         unsigned hotspot_level_jump;
 806 
 807         struct entry_space es;
 808         struct entry_alloc writeback_sentinel_alloc;
 809         struct entry_alloc demote_sentinel_alloc;
 810         struct entry_alloc hotspot_alloc;
 811         struct entry_alloc cache_alloc;
 812 
 813         unsigned long *hotspot_hit_bits;
 814         unsigned long *cache_hit_bits;
 815 
 816         /*
 817          * We maintain three queues of entries.  The cache proper,
 818          * consisting of a clean and dirty queue, containing the currently
 819          * active mappings.  The hotspot queue uses a larger block size to
 820          * track blocks that are being hit frequently and potential
 821          * candidates for promotion to the cache.
 822          */
 823         struct queue hotspot;
 824         struct queue clean;
 825         struct queue dirty;
 826 
 827         struct stats hotspot_stats;
 828         struct stats cache_stats;
 829 
 830         /*
 831          * Keeps track of time, incremented by the core.  We use this to
 832          * avoid attributing multiple hits within the same tick.
 833          */
 834         unsigned tick;
 835 
 836         /*
 837          * The hash tables allows us to quickly find an entry by origin
 838          * block.
 839          */
 840         struct smq_hash_table table;
 841         struct smq_hash_table hotspot_table;
 842 
 843         bool current_writeback_sentinels;
 844         unsigned long next_writeback_period;
 845 
 846         bool current_demote_sentinels;
 847         unsigned long next_demote_period;
 848 
 849         unsigned write_promote_level;
 850         unsigned read_promote_level;
 851 
 852         unsigned long next_hotspot_period;
 853         unsigned long next_cache_period;
 854 
 855         struct background_tracker *bg_work;
 856 
 857         bool migrations_allowed;
 858 };
 859 
 860 /*----------------------------------------------------------------*/
 861 
 862 static struct entry *get_sentinel(struct entry_alloc *ea, unsigned level, bool which)
 863 {
 864         return get_entry(ea, which ? level : NR_CACHE_LEVELS + level);
 865 }
 866 
 867 static struct entry *writeback_sentinel(struct smq_policy *mq, unsigned level)
 868 {
 869         return get_sentinel(&mq->writeback_sentinel_alloc, level, mq->current_writeback_sentinels);
 870 }
 871 
 872 static struct entry *demote_sentinel(struct smq_policy *mq, unsigned level)
 873 {
 874         return get_sentinel(&mq->demote_sentinel_alloc, level, mq->current_demote_sentinels);
 875 }
 876 
 877 static void __update_writeback_sentinels(struct smq_policy *mq)
 878 {
 879         unsigned level;
 880         struct queue *q = &mq->dirty;
 881         struct entry *sentinel;
 882 
 883         for (level = 0; level < q->nr_levels; level++) {
 884                 sentinel = writeback_sentinel(mq, level);
 885                 q_del(q, sentinel);
 886                 q_push(q, sentinel);
 887         }
 888 }
 889 
 890 static void __update_demote_sentinels(struct smq_policy *mq)
 891 {
 892         unsigned level;
 893         struct queue *q = &mq->clean;
 894         struct entry *sentinel;
 895 
 896         for (level = 0; level < q->nr_levels; level++) {
 897                 sentinel = demote_sentinel(mq, level);
 898                 q_del(q, sentinel);
 899                 q_push(q, sentinel);
 900         }
 901 }
 902 
 903 static void update_sentinels(struct smq_policy *mq)
 904 {
 905         if (time_after(jiffies, mq->next_writeback_period)) {
 906                 mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
 907                 mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
 908                 __update_writeback_sentinels(mq);
 909         }
 910 
 911         if (time_after(jiffies, mq->next_demote_period)) {
 912                 mq->next_demote_period = jiffies + DEMOTE_PERIOD;
 913                 mq->current_demote_sentinels = !mq->current_demote_sentinels;
 914                 __update_demote_sentinels(mq);
 915         }
 916 }
 917 
 918 static void __sentinels_init(struct smq_policy *mq)
 919 {
 920         unsigned level;
 921         struct entry *sentinel;
 922 
 923         for (level = 0; level < NR_CACHE_LEVELS; level++) {
 924                 sentinel = writeback_sentinel(mq, level);
 925                 sentinel->level = level;
 926                 q_push(&mq->dirty, sentinel);
 927 
 928                 sentinel = demote_sentinel(mq, level);
 929                 sentinel->level = level;
 930                 q_push(&mq->clean, sentinel);
 931         }
 932 }
 933 
 934 static void sentinels_init(struct smq_policy *mq)
 935 {
 936         mq->next_writeback_period = jiffies + WRITEBACK_PERIOD;
 937         mq->next_demote_period = jiffies + DEMOTE_PERIOD;
 938 
 939         mq->current_writeback_sentinels = false;
 940         mq->current_demote_sentinels = false;
 941         __sentinels_init(mq);
 942 
 943         mq->current_writeback_sentinels = !mq->current_writeback_sentinels;
 944         mq->current_demote_sentinels = !mq->current_demote_sentinels;
 945         __sentinels_init(mq);
 946 }
 947 
 948 /*----------------------------------------------------------------*/
 949 
 950 static void del_queue(struct smq_policy *mq, struct entry *e)
 951 {
 952         q_del(e->dirty ? &mq->dirty : &mq->clean, e);
 953 }
 954 
 955 static void push_queue(struct smq_policy *mq, struct entry *e)
 956 {
 957         if (e->dirty)
 958                 q_push(&mq->dirty, e);
 959         else
 960                 q_push(&mq->clean, e);
 961 }
 962 
 963 // !h, !q, a -> h, q, a
 964 static void push(struct smq_policy *mq, struct entry *e)
 965 {
 966         h_insert(&mq->table, e);
 967         if (!e->pending_work)
 968                 push_queue(mq, e);
 969 }
 970 
 971 static void push_queue_front(struct smq_policy *mq, struct entry *e)
 972 {
 973         if (e->dirty)
 974                 q_push_front(&mq->dirty, e);
 975         else
 976                 q_push_front(&mq->clean, e);
 977 }
 978 
 979 static void push_front(struct smq_policy *mq, struct entry *e)
 980 {
 981         h_insert(&mq->table, e);
 982         if (!e->pending_work)
 983                 push_queue_front(mq, e);
 984 }
 985 
 986 static dm_cblock_t infer_cblock(struct smq_policy *mq, struct entry *e)
 987 {
 988         return to_cblock(get_index(&mq->cache_alloc, e));
 989 }
 990 
 991 static void requeue(struct smq_policy *mq, struct entry *e)
 992 {
 993         /*
 994          * Pending work has temporarily been taken out of the queues.
 995          */
 996         if (e->pending_work)
 997                 return;
 998 
 999         if (!test_and_set_bit(from_cblock(infer_cblock(mq, e)), mq->cache_hit_bits)) {
1000                 if (!e->dirty) {
1001                         q_requeue(&mq->clean, e, 1u, NULL, NULL);
1002                         return;
1003                 }
1004 
1005                 q_requeue(&mq->dirty, e, 1u,
1006                           get_sentinel(&mq->writeback_sentinel_alloc, e->level, !mq->current_writeback_sentinels),
1007                           get_sentinel(&mq->writeback_sentinel_alloc, e->level, mq->current_writeback_sentinels));
1008         }
1009 }
1010 
1011 static unsigned default_promote_level(struct smq_policy *mq)
1012 {
1013         /*
1014          * The promote level depends on the current performance of the
1015          * cache.
1016          *
1017          * If the cache is performing badly, then we can't afford
1018          * to promote much without causing performance to drop below that
1019          * of the origin device.
1020          *
1021          * If the cache is performing well, then we don't need to promote
1022          * much.  If it isn't broken, don't fix it.
1023          *
1024          * If the cache is middling then we promote more.
1025          *
1026          * This scheme reminds me of a graph of entropy vs probability of a
1027          * binary variable.
1028          */
1029         static unsigned table[] = {1, 1, 1, 2, 4, 6, 7, 8, 7, 6, 4, 4, 3, 3, 2, 2, 1};
1030 
1031         unsigned hits = mq->cache_stats.hits;
1032         unsigned misses = mq->cache_stats.misses;
1033         unsigned index = safe_div(hits << 4u, hits + misses);
1034         return table[index];
1035 }
1036 
1037 static void update_promote_levels(struct smq_policy *mq)
1038 {
1039         /*
1040          * If there are unused cache entries then we want to be really
1041          * eager to promote.
1042          */
1043         unsigned threshold_level = allocator_empty(&mq->cache_alloc) ?
1044                 default_promote_level(mq) : (NR_HOTSPOT_LEVELS / 2u);
1045 
1046         threshold_level = max(threshold_level, NR_HOTSPOT_LEVELS);
1047 
1048         /*
1049          * If the hotspot queue is performing badly then we have little
1050          * confidence that we know which blocks to promote.  So we cut down
1051          * the amount of promotions.
1052          */
1053         switch (stats_assess(&mq->hotspot_stats)) {
1054         case Q_POOR:
1055                 threshold_level /= 4u;
1056                 break;
1057 
1058         case Q_FAIR:
1059                 threshold_level /= 2u;
1060                 break;
1061 
1062         case Q_WELL:
1063                 break;
1064         }
1065 
1066         mq->read_promote_level = NR_HOTSPOT_LEVELS - threshold_level;
1067         mq->write_promote_level = (NR_HOTSPOT_LEVELS - threshold_level);
1068 }
1069 
1070 /*
1071  * If the hotspot queue is performing badly, then we try and move entries
1072  * around more quickly.
1073  */
1074 static void update_level_jump(struct smq_policy *mq)
1075 {
1076         switch (stats_assess(&mq->hotspot_stats)) {
1077         case Q_POOR:
1078                 mq->hotspot_level_jump = 4u;
1079                 break;
1080 
1081         case Q_FAIR:
1082                 mq->hotspot_level_jump = 2u;
1083                 break;
1084 
1085         case Q_WELL:
1086                 mq->hotspot_level_jump = 1u;
1087                 break;
1088         }
1089 }
1090 
1091 static void end_hotspot_period(struct smq_policy *mq)
1092 {
1093         clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1094         update_promote_levels(mq);
1095 
1096         if (time_after(jiffies, mq->next_hotspot_period)) {
1097                 update_level_jump(mq);
1098                 q_redistribute(&mq->hotspot);
1099                 stats_reset(&mq->hotspot_stats);
1100                 mq->next_hotspot_period = jiffies + HOTSPOT_UPDATE_PERIOD;
1101         }
1102 }
1103 
1104 static void end_cache_period(struct smq_policy *mq)
1105 {
1106         if (time_after(jiffies, mq->next_cache_period)) {
1107                 clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1108 
1109                 q_redistribute(&mq->dirty);
1110                 q_redistribute(&mq->clean);
1111                 stats_reset(&mq->cache_stats);
1112 
1113                 mq->next_cache_period = jiffies + CACHE_UPDATE_PERIOD;
1114         }
1115 }
1116 
1117 /*----------------------------------------------------------------*/
1118 
1119 /*
1120  * Targets are given as a percentage.
1121  */
1122 #define CLEAN_TARGET 25u
1123 #define FREE_TARGET 25u
1124 
1125 static unsigned percent_to_target(struct smq_policy *mq, unsigned p)
1126 {
1127         return from_cblock(mq->cache_size) * p / 100u;
1128 }
1129 
1130 static bool clean_target_met(struct smq_policy *mq, bool idle)
1131 {
1132         /*
1133          * Cache entries may not be populated.  So we cannot rely on the
1134          * size of the clean queue.
1135          */
1136         if (idle) {
1137                 /*
1138                  * We'd like to clean everything.
1139                  */
1140                 return q_size(&mq->dirty) == 0u;
1141         }
1142 
1143         /*
1144          * If we're busy we don't worry about cleaning at all.
1145          */
1146         return true;
1147 }
1148 
1149 static bool free_target_met(struct smq_policy *mq)
1150 {
1151         unsigned nr_free;
1152 
1153         nr_free = from_cblock(mq->cache_size) - mq->cache_alloc.nr_allocated;
1154         return (nr_free + btracker_nr_demotions_queued(mq->bg_work)) >=
1155                 percent_to_target(mq, FREE_TARGET);
1156 }
1157 
1158 /*----------------------------------------------------------------*/
1159 
1160 static void mark_pending(struct smq_policy *mq, struct entry *e)
1161 {
1162         BUG_ON(e->sentinel);
1163         BUG_ON(!e->allocated);
1164         BUG_ON(e->pending_work);
1165         e->pending_work = true;
1166 }
1167 
1168 static void clear_pending(struct smq_policy *mq, struct entry *e)
1169 {
1170         BUG_ON(!e->pending_work);
1171         e->pending_work = false;
1172 }
1173 
1174 static void queue_writeback(struct smq_policy *mq, bool idle)
1175 {
1176         int r;
1177         struct policy_work work;
1178         struct entry *e;
1179 
1180         e = q_peek(&mq->dirty, mq->dirty.nr_levels, idle);
1181         if (e) {
1182                 mark_pending(mq, e);
1183                 q_del(&mq->dirty, e);
1184 
1185                 work.op = POLICY_WRITEBACK;
1186                 work.oblock = e->oblock;
1187                 work.cblock = infer_cblock(mq, e);
1188 
1189                 r = btracker_queue(mq->bg_work, &work, NULL);
1190                 if (r) {
1191                         clear_pending(mq, e);
1192                         q_push_front(&mq->dirty, e);
1193                 }
1194         }
1195 }
1196 
1197 static void queue_demotion(struct smq_policy *mq)
1198 {
1199         int r;
1200         struct policy_work work;
1201         struct entry *e;
1202 
1203         if (WARN_ON_ONCE(!mq->migrations_allowed))
1204                 return;
1205 
1206         e = q_peek(&mq->clean, mq->clean.nr_levels / 2, true);
1207         if (!e) {
1208                 if (!clean_target_met(mq, true))
1209                         queue_writeback(mq, false);
1210                 return;
1211         }
1212 
1213         mark_pending(mq, e);
1214         q_del(&mq->clean, e);
1215 
1216         work.op = POLICY_DEMOTE;
1217         work.oblock = e->oblock;
1218         work.cblock = infer_cblock(mq, e);
1219         r = btracker_queue(mq->bg_work, &work, NULL);
1220         if (r) {
1221                 clear_pending(mq, e);
1222                 q_push_front(&mq->clean, e);
1223         }
1224 }
1225 
1226 static void queue_promotion(struct smq_policy *mq, dm_oblock_t oblock,
1227                             struct policy_work **workp)
1228 {
1229         int r;
1230         struct entry *e;
1231         struct policy_work work;
1232 
1233         if (!mq->migrations_allowed)
1234                 return;
1235 
1236         if (allocator_empty(&mq->cache_alloc)) {
1237                 /*
1238                  * We always claim to be 'idle' to ensure some demotions happen
1239                  * with continuous loads.
1240                  */
1241                 if (!free_target_met(mq))
1242                         queue_demotion(mq);
1243                 return;
1244         }
1245 
1246         if (btracker_promotion_already_present(mq->bg_work, oblock))
1247                 return;
1248 
1249         /*
1250          * We allocate the entry now to reserve the cblock.  If the
1251          * background work is aborted we must remember to free it.
1252          */
1253         e = alloc_entry(&mq->cache_alloc);
1254         BUG_ON(!e);
1255         e->pending_work = true;
1256         work.op = POLICY_PROMOTE;
1257         work.oblock = oblock;
1258         work.cblock = infer_cblock(mq, e);
1259         r = btracker_queue(mq->bg_work, &work, workp);
1260         if (r)
1261                 free_entry(&mq->cache_alloc, e);
1262 }
1263 
1264 /*----------------------------------------------------------------*/
1265 
1266 enum promote_result {
1267         PROMOTE_NOT,
1268         PROMOTE_TEMPORARY,
1269         PROMOTE_PERMANENT
1270 };
1271 
1272 /*
1273  * Converts a boolean into a promote result.
1274  */
1275 static enum promote_result maybe_promote(bool promote)
1276 {
1277         return promote ? PROMOTE_PERMANENT : PROMOTE_NOT;
1278 }
1279 
1280 static enum promote_result should_promote(struct smq_policy *mq, struct entry *hs_e,
1281                                           int data_dir, bool fast_promote)
1282 {
1283         if (data_dir == WRITE) {
1284                 if (!allocator_empty(&mq->cache_alloc) && fast_promote)
1285                         return PROMOTE_TEMPORARY;
1286 
1287                 return maybe_promote(hs_e->level >= mq->write_promote_level);
1288         } else
1289                 return maybe_promote(hs_e->level >= mq->read_promote_level);
1290 }
1291 
1292 static dm_oblock_t to_hblock(struct smq_policy *mq, dm_oblock_t b)
1293 {
1294         sector_t r = from_oblock(b);
1295         (void) sector_div(r, mq->cache_blocks_per_hotspot_block);
1296         return to_oblock(r);
1297 }
1298 
1299 static struct entry *update_hotspot_queue(struct smq_policy *mq, dm_oblock_t b)
1300 {
1301         unsigned hi;
1302         dm_oblock_t hb = to_hblock(mq, b);
1303         struct entry *e = h_lookup(&mq->hotspot_table, hb);
1304 
1305         if (e) {
1306                 stats_level_accessed(&mq->hotspot_stats, e->level);
1307 
1308                 hi = get_index(&mq->hotspot_alloc, e);
1309                 q_requeue(&mq->hotspot, e,
1310                           test_and_set_bit(hi, mq->hotspot_hit_bits) ?
1311                           0u : mq->hotspot_level_jump,
1312                           NULL, NULL);
1313 
1314         } else {
1315                 stats_miss(&mq->hotspot_stats);
1316 
1317                 e = alloc_entry(&mq->hotspot_alloc);
1318                 if (!e) {
1319                         e = q_pop(&mq->hotspot);
1320                         if (e) {
1321                                 h_remove(&mq->hotspot_table, e);
1322                                 hi = get_index(&mq->hotspot_alloc, e);
1323                                 clear_bit(hi, mq->hotspot_hit_bits);
1324                         }
1325 
1326                 }
1327 
1328                 if (e) {
1329                         e->oblock = hb;
1330                         q_push(&mq->hotspot, e);
1331                         h_insert(&mq->hotspot_table, e);
1332                 }
1333         }
1334 
1335         return e;
1336 }
1337 
1338 /*----------------------------------------------------------------*/
1339 
1340 /*
1341  * Public interface, via the policy struct.  See dm-cache-policy.h for a
1342  * description of these.
1343  */
1344 
1345 static struct smq_policy *to_smq_policy(struct dm_cache_policy *p)
1346 {
1347         return container_of(p, struct smq_policy, policy);
1348 }
1349 
1350 static void smq_destroy(struct dm_cache_policy *p)
1351 {
1352         struct smq_policy *mq = to_smq_policy(p);
1353 
1354         btracker_destroy(mq->bg_work);
1355         h_exit(&mq->hotspot_table);
1356         h_exit(&mq->table);
1357         free_bitset(mq->hotspot_hit_bits);
1358         free_bitset(mq->cache_hit_bits);
1359         space_exit(&mq->es);
1360         kfree(mq);
1361 }
1362 
1363 /*----------------------------------------------------------------*/
1364 
1365 static int __lookup(struct smq_policy *mq, dm_oblock_t oblock, dm_cblock_t *cblock,
1366                     int data_dir, bool fast_copy,
1367                     struct policy_work **work, bool *background_work)
1368 {
1369         struct entry *e, *hs_e;
1370         enum promote_result pr;
1371 
1372         *background_work = false;
1373 
1374         e = h_lookup(&mq->table, oblock);
1375         if (e) {
1376                 stats_level_accessed(&mq->cache_stats, e->level);
1377 
1378                 requeue(mq, e);
1379                 *cblock = infer_cblock(mq, e);
1380                 return 0;
1381 
1382         } else {
1383                 stats_miss(&mq->cache_stats);
1384 
1385                 /*
1386                  * The hotspot queue only gets updated with misses.
1387                  */
1388                 hs_e = update_hotspot_queue(mq, oblock);
1389 
1390                 pr = should_promote(mq, hs_e, data_dir, fast_copy);
1391                 if (pr != PROMOTE_NOT) {
1392                         queue_promotion(mq, oblock, work);
1393                         *background_work = true;
1394                 }
1395 
1396                 return -ENOENT;
1397         }
1398 }
1399 
1400 static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock,
1401                       int data_dir, bool fast_copy,
1402                       bool *background_work)
1403 {
1404         int r;
1405         unsigned long flags;
1406         struct smq_policy *mq = to_smq_policy(p);
1407 
1408         spin_lock_irqsave(&mq->lock, flags);
1409         r = __lookup(mq, oblock, cblock,
1410                      data_dir, fast_copy,
1411                      NULL, background_work);
1412         spin_unlock_irqrestore(&mq->lock, flags);
1413 
1414         return r;
1415 }
1416 
1417 static int smq_lookup_with_work(struct dm_cache_policy *p,
1418                                 dm_oblock_t oblock, dm_cblock_t *cblock,
1419                                 int data_dir, bool fast_copy,
1420                                 struct policy_work **work)
1421 {
1422         int r;
1423         bool background_queued;
1424         unsigned long flags;
1425         struct smq_policy *mq = to_smq_policy(p);
1426 
1427         spin_lock_irqsave(&mq->lock, flags);
1428         r = __lookup(mq, oblock, cblock, data_dir, fast_copy, work, &background_queued);
1429         spin_unlock_irqrestore(&mq->lock, flags);
1430 
1431         return r;
1432 }
1433 
1434 static int smq_get_background_work(struct dm_cache_policy *p, bool idle,
1435                                    struct policy_work **result)
1436 {
1437         int r;
1438         unsigned long flags;
1439         struct smq_policy *mq = to_smq_policy(p);
1440 
1441         spin_lock_irqsave(&mq->lock, flags);
1442         r = btracker_issue(mq->bg_work, result);
1443         if (r == -ENODATA) {
1444                 if (!clean_target_met(mq, idle)) {
1445                         queue_writeback(mq, idle);
1446                         r = btracker_issue(mq->bg_work, result);
1447                 }
1448         }
1449         spin_unlock_irqrestore(&mq->lock, flags);
1450 
1451         return r;
1452 }
1453 
1454 /*
1455  * We need to clear any pending work flags that have been set, and in the
1456  * case of promotion free the entry for the destination cblock.
1457  */
1458 static void __complete_background_work(struct smq_policy *mq,
1459                                        struct policy_work *work,
1460                                        bool success)
1461 {
1462         struct entry *e = get_entry(&mq->cache_alloc,
1463                                     from_cblock(work->cblock));
1464 
1465         switch (work->op) {
1466         case POLICY_PROMOTE:
1467                 // !h, !q, a
1468                 clear_pending(mq, e);
1469                 if (success) {
1470                         e->oblock = work->oblock;
1471                         e->level = NR_CACHE_LEVELS - 1;
1472                         push(mq, e);
1473                         // h, q, a
1474                 } else {
1475                         free_entry(&mq->cache_alloc, e);
1476                         // !h, !q, !a
1477                 }
1478                 break;
1479 
1480         case POLICY_DEMOTE:
1481                 // h, !q, a
1482                 if (success) {
1483                         h_remove(&mq->table, e);
1484                         free_entry(&mq->cache_alloc, e);
1485                         // !h, !q, !a
1486                 } else {
1487                         clear_pending(mq, e);
1488                         push_queue(mq, e);
1489                         // h, q, a
1490                 }
1491                 break;
1492 
1493         case POLICY_WRITEBACK:
1494                 // h, !q, a
1495                 clear_pending(mq, e);
1496                 push_queue(mq, e);
1497                 // h, q, a
1498                 break;
1499         }
1500 
1501         btracker_complete(mq->bg_work, work);
1502 }
1503 
1504 static void smq_complete_background_work(struct dm_cache_policy *p,
1505                                          struct policy_work *work,
1506                                          bool success)
1507 {
1508         unsigned long flags;
1509         struct smq_policy *mq = to_smq_policy(p);
1510 
1511         spin_lock_irqsave(&mq->lock, flags);
1512         __complete_background_work(mq, work, success);
1513         spin_unlock_irqrestore(&mq->lock, flags);
1514 }
1515 
1516 // in_hash(oblock) -> in_hash(oblock)
1517 static void __smq_set_clear_dirty(struct smq_policy *mq, dm_cblock_t cblock, bool set)
1518 {
1519         struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1520 
1521         if (e->pending_work)
1522                 e->dirty = set;
1523         else {
1524                 del_queue(mq, e);
1525                 e->dirty = set;
1526                 push_queue(mq, e);
1527         }
1528 }
1529 
1530 static void smq_set_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1531 {
1532         unsigned long flags;
1533         struct smq_policy *mq = to_smq_policy(p);
1534 
1535         spin_lock_irqsave(&mq->lock, flags);
1536         __smq_set_clear_dirty(mq, cblock, true);
1537         spin_unlock_irqrestore(&mq->lock, flags);
1538 }
1539 
1540 static void smq_clear_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1541 {
1542         struct smq_policy *mq = to_smq_policy(p);
1543         unsigned long flags;
1544 
1545         spin_lock_irqsave(&mq->lock, flags);
1546         __smq_set_clear_dirty(mq, cblock, false);
1547         spin_unlock_irqrestore(&mq->lock, flags);
1548 }
1549 
1550 static unsigned random_level(dm_cblock_t cblock)
1551 {
1552         return hash_32(from_cblock(cblock), 9) & (NR_CACHE_LEVELS - 1);
1553 }
1554 
1555 static int smq_load_mapping(struct dm_cache_policy *p,
1556                             dm_oblock_t oblock, dm_cblock_t cblock,
1557                             bool dirty, uint32_t hint, bool hint_valid)
1558 {
1559         struct smq_policy *mq = to_smq_policy(p);
1560         struct entry *e;
1561 
1562         e = alloc_particular_entry(&mq->cache_alloc, from_cblock(cblock));
1563         e->oblock = oblock;
1564         e->dirty = dirty;
1565         e->level = hint_valid ? min(hint, NR_CACHE_LEVELS - 1) : random_level(cblock);
1566         e->pending_work = false;
1567 
1568         /*
1569          * When we load mappings we push ahead of both sentinels in order to
1570          * allow demotions and cleaning to occur immediately.
1571          */
1572         push_front(mq, e);
1573 
1574         return 0;
1575 }
1576 
1577 static int smq_invalidate_mapping(struct dm_cache_policy *p, dm_cblock_t cblock)
1578 {
1579         struct smq_policy *mq = to_smq_policy(p);
1580         struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1581 
1582         if (!e->allocated)
1583                 return -ENODATA;
1584 
1585         // FIXME: what if this block has pending background work?
1586         del_queue(mq, e);
1587         h_remove(&mq->table, e);
1588         free_entry(&mq->cache_alloc, e);
1589         return 0;
1590 }
1591 
1592 static uint32_t smq_get_hint(struct dm_cache_policy *p, dm_cblock_t cblock)
1593 {
1594         struct smq_policy *mq = to_smq_policy(p);
1595         struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1596 
1597         if (!e->allocated)
1598                 return 0;
1599 
1600         return e->level;
1601 }
1602 
1603 static dm_cblock_t smq_residency(struct dm_cache_policy *p)
1604 {
1605         dm_cblock_t r;
1606         unsigned long flags;
1607         struct smq_policy *mq = to_smq_policy(p);
1608 
1609         spin_lock_irqsave(&mq->lock, flags);
1610         r = to_cblock(mq->cache_alloc.nr_allocated);
1611         spin_unlock_irqrestore(&mq->lock, flags);
1612 
1613         return r;
1614 }
1615 
1616 static void smq_tick(struct dm_cache_policy *p, bool can_block)
1617 {
1618         struct smq_policy *mq = to_smq_policy(p);
1619         unsigned long flags;
1620 
1621         spin_lock_irqsave(&mq->lock, flags);
1622         mq->tick++;
1623         update_sentinels(mq);
1624         end_hotspot_period(mq);
1625         end_cache_period(mq);
1626         spin_unlock_irqrestore(&mq->lock, flags);
1627 }
1628 
1629 static void smq_allow_migrations(struct dm_cache_policy *p, bool allow)
1630 {
1631         struct smq_policy *mq = to_smq_policy(p);
1632         mq->migrations_allowed = allow;
1633 }
1634 
1635 /*
1636  * smq has no config values, but the old mq policy did.  To avoid breaking
1637  * software we continue to accept these configurables for the mq policy,
1638  * but they have no effect.
1639  */
1640 static int mq_set_config_value(struct dm_cache_policy *p,
1641                                const char *key, const char *value)
1642 {
1643         unsigned long tmp;
1644 
1645         if (kstrtoul(value, 10, &tmp))
1646                 return -EINVAL;
1647 
1648         if (!strcasecmp(key, "random_threshold") ||
1649             !strcasecmp(key, "sequential_threshold") ||
1650             !strcasecmp(key, "discard_promote_adjustment") ||
1651             !strcasecmp(key, "read_promote_adjustment") ||
1652             !strcasecmp(key, "write_promote_adjustment")) {
1653                 DMWARN("tunable '%s' no longer has any effect, mq policy is now an alias for smq", key);
1654                 return 0;
1655         }
1656 
1657         return -EINVAL;
1658 }
1659 
1660 static int mq_emit_config_values(struct dm_cache_policy *p, char *result,
1661                                  unsigned maxlen, ssize_t *sz_ptr)
1662 {
1663         ssize_t sz = *sz_ptr;
1664 
1665         DMEMIT("10 random_threshold 0 "
1666                "sequential_threshold 0 "
1667                "discard_promote_adjustment 0 "
1668                "read_promote_adjustment 0 "
1669                "write_promote_adjustment 0 ");
1670 
1671         *sz_ptr = sz;
1672         return 0;
1673 }
1674 
1675 /* Init the policy plugin interface function pointers. */
1676 static void init_policy_functions(struct smq_policy *mq, bool mimic_mq)
1677 {
1678         mq->policy.destroy = smq_destroy;
1679         mq->policy.lookup = smq_lookup;
1680         mq->policy.lookup_with_work = smq_lookup_with_work;
1681         mq->policy.get_background_work = smq_get_background_work;
1682         mq->policy.complete_background_work = smq_complete_background_work;
1683         mq->policy.set_dirty = smq_set_dirty;
1684         mq->policy.clear_dirty = smq_clear_dirty;
1685         mq->policy.load_mapping = smq_load_mapping;
1686         mq->policy.invalidate_mapping = smq_invalidate_mapping;
1687         mq->policy.get_hint = smq_get_hint;
1688         mq->policy.residency = smq_residency;
1689         mq->policy.tick = smq_tick;
1690         mq->policy.allow_migrations = smq_allow_migrations;
1691 
1692         if (mimic_mq) {
1693                 mq->policy.set_config_value = mq_set_config_value;
1694                 mq->policy.emit_config_values = mq_emit_config_values;
1695         }
1696 }
1697 
1698 static bool too_many_hotspot_blocks(sector_t origin_size,
1699                                     sector_t hotspot_block_size,
1700                                     unsigned nr_hotspot_blocks)
1701 {
1702         return (hotspot_block_size * nr_hotspot_blocks) > origin_size;
1703 }
1704 
1705 static void calc_hotspot_params(sector_t origin_size,
1706                                 sector_t cache_block_size,
1707                                 unsigned nr_cache_blocks,
1708                                 sector_t *hotspot_block_size,
1709                                 unsigned *nr_hotspot_blocks)
1710 {
1711         *hotspot_block_size = cache_block_size * 16u;
1712         *nr_hotspot_blocks = max(nr_cache_blocks / 4u, 1024u);
1713 
1714         while ((*hotspot_block_size > cache_block_size) &&
1715                too_many_hotspot_blocks(origin_size, *hotspot_block_size, *nr_hotspot_blocks))
1716                 *hotspot_block_size /= 2u;
1717 }
1718 
1719 static struct dm_cache_policy *__smq_create(dm_cblock_t cache_size,
1720                                             sector_t origin_size,
1721                                             sector_t cache_block_size,
1722                                             bool mimic_mq,
1723                                             bool migrations_allowed)
1724 {
1725         unsigned i;
1726         unsigned nr_sentinels_per_queue = 2u * NR_CACHE_LEVELS;
1727         unsigned total_sentinels = 2u * nr_sentinels_per_queue;
1728         struct smq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
1729 
1730         if (!mq)
1731                 return NULL;
1732 
1733         init_policy_functions(mq, mimic_mq);
1734         mq->cache_size = cache_size;
1735         mq->cache_block_size = cache_block_size;
1736 
1737         calc_hotspot_params(origin_size, cache_block_size, from_cblock(cache_size),
1738                             &mq->hotspot_block_size, &mq->nr_hotspot_blocks);
1739 
1740         mq->cache_blocks_per_hotspot_block = div64_u64(mq->hotspot_block_size, mq->cache_block_size);
1741         mq->hotspot_level_jump = 1u;
1742         if (space_init(&mq->es, total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size))) {
1743                 DMERR("couldn't initialize entry space");
1744                 goto bad_pool_init;
1745         }
1746 
1747         init_allocator(&mq->writeback_sentinel_alloc, &mq->es, 0, nr_sentinels_per_queue);
1748         for (i = 0; i < nr_sentinels_per_queue; i++)
1749                 get_entry(&mq->writeback_sentinel_alloc, i)->sentinel = true;
1750 
1751         init_allocator(&mq->demote_sentinel_alloc, &mq->es, nr_sentinels_per_queue, total_sentinels);
1752         for (i = 0; i < nr_sentinels_per_queue; i++)
1753                 get_entry(&mq->demote_sentinel_alloc, i)->sentinel = true;
1754 
1755         init_allocator(&mq->hotspot_alloc, &mq->es, total_sentinels,
1756                        total_sentinels + mq->nr_hotspot_blocks);
1757 
1758         init_allocator(&mq->cache_alloc, &mq->es,
1759                        total_sentinels + mq->nr_hotspot_blocks,
1760                        total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size));
1761 
1762         mq->hotspot_hit_bits = alloc_bitset(mq->nr_hotspot_blocks);
1763         if (!mq->hotspot_hit_bits) {
1764                 DMERR("couldn't allocate hotspot hit bitset");
1765                 goto bad_hotspot_hit_bits;
1766         }
1767         clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1768 
1769         if (from_cblock(cache_size)) {
1770                 mq->cache_hit_bits = alloc_bitset(from_cblock(cache_size));
1771                 if (!mq->cache_hit_bits) {
1772                         DMERR("couldn't allocate cache hit bitset");
1773                         goto bad_cache_hit_bits;
1774                 }
1775                 clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1776         } else
1777                 mq->cache_hit_bits = NULL;
1778 
1779         mq->tick = 0;
1780         spin_lock_init(&mq->lock);
1781 
1782         q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS);
1783         mq->hotspot.nr_top_levels = 8;
1784         mq->hotspot.nr_in_top_levels = min(mq->nr_hotspot_blocks / NR_HOTSPOT_LEVELS,
1785                                            from_cblock(mq->cache_size) / mq->cache_blocks_per_hotspot_block);
1786 
1787         q_init(&mq->clean, &mq->es, NR_CACHE_LEVELS);
1788         q_init(&mq->dirty, &mq->es, NR_CACHE_LEVELS);
1789 
1790         stats_init(&mq->hotspot_stats, NR_HOTSPOT_LEVELS);
1791         stats_init(&mq->cache_stats, NR_CACHE_LEVELS);
1792 
1793         if (h_init(&mq->table, &mq->es, from_cblock(cache_size)))
1794                 goto bad_alloc_table;
1795 
1796         if (h_init(&mq->hotspot_table, &mq->es, mq->nr_hotspot_blocks))
1797                 goto bad_alloc_hotspot_table;
1798 
1799         sentinels_init(mq);
1800         mq->write_promote_level = mq->read_promote_level = NR_HOTSPOT_LEVELS;
1801 
1802         mq->next_hotspot_period = jiffies;
1803         mq->next_cache_period = jiffies;
1804 
1805         mq->bg_work = btracker_create(4096); /* FIXME: hard coded value */
1806         if (!mq->bg_work)
1807                 goto bad_btracker;
1808 
1809         mq->migrations_allowed = migrations_allowed;
1810 
1811         return &mq->policy;
1812 
1813 bad_btracker:
1814         h_exit(&mq->hotspot_table);
1815 bad_alloc_hotspot_table:
1816         h_exit(&mq->table);
1817 bad_alloc_table:
1818         free_bitset(mq->cache_hit_bits);
1819 bad_cache_hit_bits:
1820         free_bitset(mq->hotspot_hit_bits);
1821 bad_hotspot_hit_bits:
1822         space_exit(&mq->es);
1823 bad_pool_init:
1824         kfree(mq);
1825 
1826         return NULL;
1827 }
1828 
1829 static struct dm_cache_policy *smq_create(dm_cblock_t cache_size,
1830                                           sector_t origin_size,
1831                                           sector_t cache_block_size)
1832 {
1833         return __smq_create(cache_size, origin_size, cache_block_size, false, true);
1834 }
1835 
1836 static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,
1837                                          sector_t origin_size,
1838                                          sector_t cache_block_size)
1839 {
1840         return __smq_create(cache_size, origin_size, cache_block_size, true, true);
1841 }
1842 
1843 static struct dm_cache_policy *cleaner_create(dm_cblock_t cache_size,
1844                                               sector_t origin_size,
1845                                               sector_t cache_block_size)
1846 {
1847         return __smq_create(cache_size, origin_size, cache_block_size, false, false);
1848 }
1849 
1850 /*----------------------------------------------------------------*/
1851 
1852 static struct dm_cache_policy_type smq_policy_type = {
1853         .name = "smq",
1854         .version = {2, 0, 0},
1855         .hint_size = 4,
1856         .owner = THIS_MODULE,
1857         .create = smq_create
1858 };
1859 
1860 static struct dm_cache_policy_type mq_policy_type = {
1861         .name = "mq",
1862         .version = {2, 0, 0},
1863         .hint_size = 4,
1864         .owner = THIS_MODULE,
1865         .create = mq_create,
1866 };
1867 
1868 static struct dm_cache_policy_type cleaner_policy_type = {
1869         .name = "cleaner",
1870         .version = {2, 0, 0},
1871         .hint_size = 4,
1872         .owner = THIS_MODULE,
1873         .create = cleaner_create,
1874 };
1875 
1876 static struct dm_cache_policy_type default_policy_type = {
1877         .name = "default",
1878         .version = {2, 0, 0},
1879         .hint_size = 4,
1880         .owner = THIS_MODULE,
1881         .create = smq_create,
1882         .real = &smq_policy_type
1883 };
1884 
1885 static int __init smq_init(void)
1886 {
1887         int r;
1888 
1889         r = dm_cache_policy_register(&smq_policy_type);
1890         if (r) {
1891                 DMERR("register failed %d", r);
1892                 return -ENOMEM;
1893         }
1894 
1895         r = dm_cache_policy_register(&mq_policy_type);
1896         if (r) {
1897                 DMERR("register failed (as mq) %d", r);
1898                 goto out_mq;
1899         }
1900 
1901         r = dm_cache_policy_register(&cleaner_policy_type);
1902         if (r) {
1903                 DMERR("register failed (as cleaner) %d", r);
1904                 goto out_cleaner;
1905         }
1906 
1907         r = dm_cache_policy_register(&default_policy_type);
1908         if (r) {
1909                 DMERR("register failed (as default) %d", r);
1910                 goto out_default;
1911         }
1912 
1913         return 0;
1914 
1915 out_default:
1916         dm_cache_policy_unregister(&cleaner_policy_type);
1917 out_cleaner:
1918         dm_cache_policy_unregister(&mq_policy_type);
1919 out_mq:
1920         dm_cache_policy_unregister(&smq_policy_type);
1921 
1922         return -ENOMEM;
1923 }
1924 
1925 static void __exit smq_exit(void)
1926 {
1927         dm_cache_policy_unregister(&cleaner_policy_type);
1928         dm_cache_policy_unregister(&smq_policy_type);
1929         dm_cache_policy_unregister(&mq_policy_type);
1930         dm_cache_policy_unregister(&default_policy_type);
1931 }
1932 
1933 module_init(smq_init);
1934 module_exit(smq_exit);
1935 
1936 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
1937 MODULE_LICENSE("GPL");
1938 MODULE_DESCRIPTION("smq cache policy");
1939 
1940 MODULE_ALIAS("dm-cache-default");
1941 MODULE_ALIAS("dm-cache-mq");
1942 MODULE_ALIAS("dm-cache-cleaner");
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/md/dm-cache-policy-smq.c

DEFINITIONS
