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 */
  26static unsigned safe_div(unsigned n, unsigned d)
  27{
  28	return d ? n / d : 0u;
  29}
  30
  31static unsigned safe_mod(unsigned n, unsigned d)
  32{
  33	return d ? n % d : 0u;
  34}
  35
  36/*----------------------------------------------------------------*/
  37
  38struct 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 */
  60struct entry_space {
  61	struct entry *begin;
  62	struct entry *end;
  63};
  64
  65static 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
  80static void space_exit(struct entry_space *es)
  81{
  82	vfree(es->begin);
  83}
  84
  85static 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
  95static 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
 101static 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
 111struct ilist {
 112	unsigned nr_elts;	/* excluding sentinel entries */
 113	unsigned head, tail;
 114};
 115
 116static void l_init(struct ilist *l)
 117{
 118	l->nr_elts = 0;
 119	l->head = l->tail = INDEXER_NULL;
 120}
 121
 122static struct entry *l_head(struct entry_space *es, struct ilist *l)
 123{
 124	return to_entry(es, l->head);
 125}
 126
 127static struct entry *l_tail(struct entry_space *es, struct ilist *l)
 128{
 129	return to_entry(es, l->tail);
 130}
 131
 132static struct entry *l_next(struct entry_space *es, struct entry *e)
 133{
 134	return to_entry(es, e->next);
 135}
 136
 137static struct entry *l_prev(struct entry_space *es, struct entry *e)
 138{
 139	return to_entry(es, e->prev);
 140}
 141
 142static bool l_empty(struct ilist *l)
 143{
 144	return l->head == INDEXER_NULL;
 145}
 146
 147static 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
 163static 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
 179static 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
 197static 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
 216static 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
 229static 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
 252struct 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
 269static 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
 287static 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 */
 295static 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
 305static 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
 315static 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
 325static 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 */
 335static 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
 357static 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 */
 372static 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
 386static 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 */
 405static 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
 427static 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
 470static 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
 514struct stats {
 515	unsigned hit_threshold;
 516	unsigned hits;
 517	unsigned misses;
 518};
 519
 520enum performance {
 521	Q_POOR,
 522	Q_FAIR,
 523	Q_WELL
 524};
 525
 526static 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
 533static void stats_reset(struct stats *s)
 534{
 535	s->hits = s->misses = 0u;
 536}
 537
 538static 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
 546static 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 */
 557static 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
 573struct 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 */
 583static 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
 601static void h_exit(struct smq_hash_table *ht)
 602{
 603	vfree(ht->buckets);
 604}
 605
 606static struct entry *h_head(struct smq_hash_table *ht, unsigned bucket)
 607{
 608	return to_entry(ht->es, ht->buckets[bucket]);
 609}
 610
 611static struct entry *h_next(struct smq_hash_table *ht, struct entry *e)
 612{
 613	return to_entry(ht->es, e->hash_next);
 614}
 615
 616static 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
 622static 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
 628static 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
 644static 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 */
 656static 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
 674static 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
 690struct entry_alloc {
 691	struct entry_space *es;
 692	unsigned begin;
 693
 694	unsigned nr_allocated;
 695	struct ilist free;
 696};
 697
 698static 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
 712static 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
 728static 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 */
 745static 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
 758static 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
 768static bool allocator_empty(struct entry_alloc *ea)
 769{
 770	return l_empty(&ea->free);
 771}
 772
 773static unsigned get_index(struct entry_alloc *ea, struct entry *e)
 774{
 775	return to_index(ea->es, e) - ea->begin;
 776}
 777
 778static 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
 794struct 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
 862static 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
 867static 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
 872static 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
 877static 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
 890static 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
 903static 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
 918static 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
 934static 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
 950static void del_queue(struct smq_policy *mq, struct entry *e)
 951{
 952	q_del(e->dirty ? &mq->dirty : &mq->clean, e);
 953}
 954
 955static 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
 964static 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
 971static 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
 979static 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
 986static 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
 991static 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
1011static 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 const unsigned int table[] = {
1030		1, 1, 1, 2, 4, 6, 7, 8, 7, 6, 4, 4, 3, 3, 2, 2, 1
1031	};
1032
1033	unsigned hits = mq->cache_stats.hits;
1034	unsigned misses = mq->cache_stats.misses;
1035	unsigned index = safe_div(hits << 4u, hits + misses);
1036	return table[index];
1037}
1038
1039static void update_promote_levels(struct smq_policy *mq)
1040{
1041	/*
1042	 * If there are unused cache entries then we want to be really
1043	 * eager to promote.
1044	 */
1045	unsigned threshold_level = allocator_empty(&mq->cache_alloc) ?
1046		default_promote_level(mq) : (NR_HOTSPOT_LEVELS / 2u);
1047
1048	threshold_level = max(threshold_level, NR_HOTSPOT_LEVELS);
1049
1050	/*
1051	 * If the hotspot queue is performing badly then we have little
1052	 * confidence that we know which blocks to promote.  So we cut down
1053	 * the amount of promotions.
1054	 */
1055	switch (stats_assess(&mq->hotspot_stats)) {
1056	case Q_POOR:
1057		threshold_level /= 4u;
1058		break;
1059
1060	case Q_FAIR:
1061		threshold_level /= 2u;
1062		break;
1063
1064	case Q_WELL:
1065		break;
1066	}
1067
1068	mq->read_promote_level = NR_HOTSPOT_LEVELS - threshold_level;
1069	mq->write_promote_level = (NR_HOTSPOT_LEVELS - threshold_level);
1070}
1071
1072/*
1073 * If the hotspot queue is performing badly, then we try and move entries
1074 * around more quickly.
1075 */
1076static void update_level_jump(struct smq_policy *mq)
1077{
1078	switch (stats_assess(&mq->hotspot_stats)) {
1079	case Q_POOR:
1080		mq->hotspot_level_jump = 4u;
1081		break;
1082
1083	case Q_FAIR:
1084		mq->hotspot_level_jump = 2u;
1085		break;
1086
1087	case Q_WELL:
1088		mq->hotspot_level_jump = 1u;
1089		break;
1090	}
1091}
1092
1093static void end_hotspot_period(struct smq_policy *mq)
1094{
1095	clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1096	update_promote_levels(mq);
1097
1098	if (time_after(jiffies, mq->next_hotspot_period)) {
1099		update_level_jump(mq);
1100		q_redistribute(&mq->hotspot);
1101		stats_reset(&mq->hotspot_stats);
1102		mq->next_hotspot_period = jiffies + HOTSPOT_UPDATE_PERIOD;
1103	}
1104}
1105
1106static void end_cache_period(struct smq_policy *mq)
1107{
1108	if (time_after(jiffies, mq->next_cache_period)) {
1109		clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1110
1111		q_redistribute(&mq->dirty);
1112		q_redistribute(&mq->clean);
1113		stats_reset(&mq->cache_stats);
1114
1115		mq->next_cache_period = jiffies + CACHE_UPDATE_PERIOD;
1116	}
1117}
1118
1119/*----------------------------------------------------------------*/
1120
1121/*
1122 * Targets are given as a percentage.
1123 */
1124#define CLEAN_TARGET 25u
1125#define FREE_TARGET 25u
1126
1127static unsigned percent_to_target(struct smq_policy *mq, unsigned p)
1128{
1129	return from_cblock(mq->cache_size) * p / 100u;
1130}
1131
1132static bool clean_target_met(struct smq_policy *mq, bool idle)
1133{
1134	/*
1135	 * Cache entries may not be populated.  So we cannot rely on the
1136	 * size of the clean queue.
1137	 */
1138	if (idle) {
1139		/*
1140		 * We'd like to clean everything.
1141		 */
1142		return q_size(&mq->dirty) == 0u;
1143	}
1144
1145	/*
1146	 * If we're busy we don't worry about cleaning at all.
1147	 */
1148	return true;
1149}
1150
1151static bool free_target_met(struct smq_policy *mq)
1152{
1153	unsigned nr_free;
1154
1155	nr_free = from_cblock(mq->cache_size) - mq->cache_alloc.nr_allocated;
1156	return (nr_free + btracker_nr_demotions_queued(mq->bg_work)) >=
1157		percent_to_target(mq, FREE_TARGET);
1158}
1159
1160/*----------------------------------------------------------------*/
1161
1162static void mark_pending(struct smq_policy *mq, struct entry *e)
1163{
1164	BUG_ON(e->sentinel);
1165	BUG_ON(!e->allocated);
1166	BUG_ON(e->pending_work);
1167	e->pending_work = true;
1168}
1169
1170static void clear_pending(struct smq_policy *mq, struct entry *e)
1171{
1172	BUG_ON(!e->pending_work);
1173	e->pending_work = false;
1174}
1175
1176static void queue_writeback(struct smq_policy *mq, bool idle)
1177{
1178	int r;
1179	struct policy_work work;
1180	struct entry *e;
1181
1182	e = q_peek(&mq->dirty, mq->dirty.nr_levels, idle);
1183	if (e) {
1184		mark_pending(mq, e);
1185		q_del(&mq->dirty, e);
1186
1187		work.op = POLICY_WRITEBACK;
1188		work.oblock = e->oblock;
1189		work.cblock = infer_cblock(mq, e);
1190
1191		r = btracker_queue(mq->bg_work, &work, NULL);
1192		if (r) {
1193			clear_pending(mq, e);
1194			q_push_front(&mq->dirty, e);
1195		}
1196	}
1197}
1198
1199static void queue_demotion(struct smq_policy *mq)
1200{
1201	int r;
1202	struct policy_work work;
1203	struct entry *e;
1204
1205	if (WARN_ON_ONCE(!mq->migrations_allowed))
1206		return;
1207
1208	e = q_peek(&mq->clean, mq->clean.nr_levels / 2, true);
1209	if (!e) {
1210		if (!clean_target_met(mq, true))
1211			queue_writeback(mq, false);
1212		return;
1213	}
1214
1215	mark_pending(mq, e);
1216	q_del(&mq->clean, e);
1217
1218	work.op = POLICY_DEMOTE;
1219	work.oblock = e->oblock;
1220	work.cblock = infer_cblock(mq, e);
1221	r = btracker_queue(mq->bg_work, &work, NULL);
1222	if (r) {
1223		clear_pending(mq, e);
1224		q_push_front(&mq->clean, e);
1225	}
1226}
1227
1228static void queue_promotion(struct smq_policy *mq, dm_oblock_t oblock,
1229			    struct policy_work **workp)
1230{
1231	int r;
1232	struct entry *e;
1233	struct policy_work work;
1234
1235	if (!mq->migrations_allowed)
1236		return;
1237
1238	if (allocator_empty(&mq->cache_alloc)) {
1239		/*
1240		 * We always claim to be 'idle' to ensure some demotions happen
1241		 * with continuous loads.
1242		 */
1243		if (!free_target_met(mq))
1244			queue_demotion(mq);
1245		return;
1246	}
1247
1248	if (btracker_promotion_already_present(mq->bg_work, oblock))
1249		return;
1250
1251	/*
1252	 * We allocate the entry now to reserve the cblock.  If the
1253	 * background work is aborted we must remember to free it.
1254	 */
1255	e = alloc_entry(&mq->cache_alloc);
1256	BUG_ON(!e);
1257	e->pending_work = true;
1258	work.op = POLICY_PROMOTE;
1259	work.oblock = oblock;
1260	work.cblock = infer_cblock(mq, e);
1261	r = btracker_queue(mq->bg_work, &work, workp);
1262	if (r)
1263		free_entry(&mq->cache_alloc, e);
1264}
1265
1266/*----------------------------------------------------------------*/
1267
1268enum promote_result {
1269	PROMOTE_NOT,
1270	PROMOTE_TEMPORARY,
1271	PROMOTE_PERMANENT
1272};
1273
1274/*
1275 * Converts a boolean into a promote result.
1276 */
1277static enum promote_result maybe_promote(bool promote)
1278{
1279	return promote ? PROMOTE_PERMANENT : PROMOTE_NOT;
1280}
1281
1282static enum promote_result should_promote(struct smq_policy *mq, struct entry *hs_e,
1283					  int data_dir, bool fast_promote)
1284{
1285	if (data_dir == WRITE) {
1286		if (!allocator_empty(&mq->cache_alloc) && fast_promote)
1287			return PROMOTE_TEMPORARY;
1288
1289		return maybe_promote(hs_e->level >= mq->write_promote_level);
1290	} else
1291		return maybe_promote(hs_e->level >= mq->read_promote_level);
1292}
1293
1294static dm_oblock_t to_hblock(struct smq_policy *mq, dm_oblock_t b)
1295{
1296	sector_t r = from_oblock(b);
1297	(void) sector_div(r, mq->cache_blocks_per_hotspot_block);
1298	return to_oblock(r);
1299}
1300
1301static struct entry *update_hotspot_queue(struct smq_policy *mq, dm_oblock_t b)
1302{
1303	unsigned hi;
1304	dm_oblock_t hb = to_hblock(mq, b);
1305	struct entry *e = h_lookup(&mq->hotspot_table, hb);
1306
1307	if (e) {
1308		stats_level_accessed(&mq->hotspot_stats, e->level);
1309
1310		hi = get_index(&mq->hotspot_alloc, e);
1311		q_requeue(&mq->hotspot, e,
1312			  test_and_set_bit(hi, mq->hotspot_hit_bits) ?
1313			  0u : mq->hotspot_level_jump,
1314			  NULL, NULL);
1315
1316	} else {
1317		stats_miss(&mq->hotspot_stats);
1318
1319		e = alloc_entry(&mq->hotspot_alloc);
1320		if (!e) {
1321			e = q_pop(&mq->hotspot);
1322			if (e) {
1323				h_remove(&mq->hotspot_table, e);
1324				hi = get_index(&mq->hotspot_alloc, e);
1325				clear_bit(hi, mq->hotspot_hit_bits);
1326			}
1327
1328		}
1329
1330		if (e) {
1331			e->oblock = hb;
1332			q_push(&mq->hotspot, e);
1333			h_insert(&mq->hotspot_table, e);
1334		}
1335	}
1336
1337	return e;
1338}
1339
1340/*----------------------------------------------------------------*/
1341
1342/*
1343 * Public interface, via the policy struct.  See dm-cache-policy.h for a
1344 * description of these.
1345 */
1346
1347static struct smq_policy *to_smq_policy(struct dm_cache_policy *p)
1348{
1349	return container_of(p, struct smq_policy, policy);
1350}
1351
1352static void smq_destroy(struct dm_cache_policy *p)
1353{
1354	struct smq_policy *mq = to_smq_policy(p);
1355
1356	btracker_destroy(mq->bg_work);
1357	h_exit(&mq->hotspot_table);
1358	h_exit(&mq->table);
1359	free_bitset(mq->hotspot_hit_bits);
1360	free_bitset(mq->cache_hit_bits);
1361	space_exit(&mq->es);
1362	kfree(mq);
1363}
1364
1365/*----------------------------------------------------------------*/
1366
1367static int __lookup(struct smq_policy *mq, dm_oblock_t oblock, dm_cblock_t *cblock,
1368		    int data_dir, bool fast_copy,
1369		    struct policy_work **work, bool *background_work)
1370{
1371	struct entry *e, *hs_e;
1372	enum promote_result pr;
1373
1374	*background_work = false;
1375
1376	e = h_lookup(&mq->table, oblock);
1377	if (e) {
1378		stats_level_accessed(&mq->cache_stats, e->level);
1379
1380		requeue(mq, e);
1381		*cblock = infer_cblock(mq, e);
1382		return 0;
1383
1384	} else {
1385		stats_miss(&mq->cache_stats);
1386
1387		/*
1388		 * The hotspot queue only gets updated with misses.
1389		 */
1390		hs_e = update_hotspot_queue(mq, oblock);
1391
1392		pr = should_promote(mq, hs_e, data_dir, fast_copy);
1393		if (pr != PROMOTE_NOT) {
1394			queue_promotion(mq, oblock, work);
1395			*background_work = true;
1396		}
1397
1398		return -ENOENT;
1399	}
1400}
1401
1402static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock,
1403		      int data_dir, bool fast_copy,
1404		      bool *background_work)
1405{
1406	int r;
1407	unsigned long flags;
1408	struct smq_policy *mq = to_smq_policy(p);
1409
1410	spin_lock_irqsave(&mq->lock, flags);
1411	r = __lookup(mq, oblock, cblock,
1412		     data_dir, fast_copy,
1413		     NULL, background_work);
1414	spin_unlock_irqrestore(&mq->lock, flags);
1415
1416	return r;
1417}
1418
1419static int smq_lookup_with_work(struct dm_cache_policy *p,
1420				dm_oblock_t oblock, dm_cblock_t *cblock,
1421				int data_dir, bool fast_copy,
1422				struct policy_work **work)
1423{
1424	int r;
1425	bool background_queued;
1426	unsigned long flags;
1427	struct smq_policy *mq = to_smq_policy(p);
1428
1429	spin_lock_irqsave(&mq->lock, flags);
1430	r = __lookup(mq, oblock, cblock, data_dir, fast_copy, work, &background_queued);
1431	spin_unlock_irqrestore(&mq->lock, flags);
1432
1433	return r;
1434}
1435
1436static int smq_get_background_work(struct dm_cache_policy *p, bool idle,
1437				   struct policy_work **result)
1438{
1439	int r;
1440	unsigned long flags;
1441	struct smq_policy *mq = to_smq_policy(p);
1442
1443	spin_lock_irqsave(&mq->lock, flags);
1444	r = btracker_issue(mq->bg_work, result);
1445	if (r == -ENODATA) {
1446		if (!clean_target_met(mq, idle)) {
1447			queue_writeback(mq, idle);
1448			r = btracker_issue(mq->bg_work, result);
1449		}
1450	}
1451	spin_unlock_irqrestore(&mq->lock, flags);
1452
1453	return r;
1454}
1455
1456/*
1457 * We need to clear any pending work flags that have been set, and in the
1458 * case of promotion free the entry for the destination cblock.
1459 */
1460static void __complete_background_work(struct smq_policy *mq,
1461				       struct policy_work *work,
1462				       bool success)
1463{
1464	struct entry *e = get_entry(&mq->cache_alloc,
1465				    from_cblock(work->cblock));
1466
1467	switch (work->op) {
1468	case POLICY_PROMOTE:
1469		// !h, !q, a
1470		clear_pending(mq, e);
1471		if (success) {
1472			e->oblock = work->oblock;
1473			e->level = NR_CACHE_LEVELS - 1;
1474			push(mq, e);
1475			// h, q, a
1476		} else {
1477			free_entry(&mq->cache_alloc, e);
1478			// !h, !q, !a
1479		}
1480		break;
1481
1482	case POLICY_DEMOTE:
1483		// h, !q, a
1484		if (success) {
1485			h_remove(&mq->table, e);
1486			free_entry(&mq->cache_alloc, e);
1487			// !h, !q, !a
1488		} else {
1489			clear_pending(mq, e);
1490			push_queue(mq, e);
1491			// h, q, a
1492		}
1493		break;
1494
1495	case POLICY_WRITEBACK:
1496		// h, !q, a
1497		clear_pending(mq, e);
1498		push_queue(mq, e);
1499		// h, q, a
1500		break;
1501	}
1502
1503	btracker_complete(mq->bg_work, work);
1504}
1505
1506static void smq_complete_background_work(struct dm_cache_policy *p,
1507					 struct policy_work *work,
1508					 bool success)
1509{
1510	unsigned long flags;
1511	struct smq_policy *mq = to_smq_policy(p);
1512
1513	spin_lock_irqsave(&mq->lock, flags);
1514	__complete_background_work(mq, work, success);
1515	spin_unlock_irqrestore(&mq->lock, flags);
1516}
1517
1518// in_hash(oblock) -> in_hash(oblock)
1519static void __smq_set_clear_dirty(struct smq_policy *mq, dm_cblock_t cblock, bool set)
1520{
1521	struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1522
1523	if (e->pending_work)
1524		e->dirty = set;
1525	else {
1526		del_queue(mq, e);
1527		e->dirty = set;
1528		push_queue(mq, e);
1529	}
1530}
1531
1532static void smq_set_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1533{
1534	unsigned long flags;
1535	struct smq_policy *mq = to_smq_policy(p);
1536
1537	spin_lock_irqsave(&mq->lock, flags);
1538	__smq_set_clear_dirty(mq, cblock, true);
1539	spin_unlock_irqrestore(&mq->lock, flags);
1540}
1541
1542static void smq_clear_dirty(struct dm_cache_policy *p, dm_cblock_t cblock)
1543{
1544	struct smq_policy *mq = to_smq_policy(p);
1545	unsigned long flags;
1546
1547	spin_lock_irqsave(&mq->lock, flags);
1548	__smq_set_clear_dirty(mq, cblock, false);
1549	spin_unlock_irqrestore(&mq->lock, flags);
1550}
1551
1552static unsigned random_level(dm_cblock_t cblock)
1553{
1554	return hash_32(from_cblock(cblock), 9) & (NR_CACHE_LEVELS - 1);
1555}
1556
1557static int smq_load_mapping(struct dm_cache_policy *p,
1558			    dm_oblock_t oblock, dm_cblock_t cblock,
1559			    bool dirty, uint32_t hint, bool hint_valid)
1560{
1561	struct smq_policy *mq = to_smq_policy(p);
1562	struct entry *e;
1563
1564	e = alloc_particular_entry(&mq->cache_alloc, from_cblock(cblock));
1565	e->oblock = oblock;
1566	e->dirty = dirty;
1567	e->level = hint_valid ? min(hint, NR_CACHE_LEVELS - 1) : random_level(cblock);
1568	e->pending_work = false;
1569
1570	/*
1571	 * When we load mappings we push ahead of both sentinels in order to
1572	 * allow demotions and cleaning to occur immediately.
1573	 */
1574	push_front(mq, e);
1575
1576	return 0;
1577}
1578
1579static int smq_invalidate_mapping(struct dm_cache_policy *p, dm_cblock_t cblock)
1580{
1581	struct smq_policy *mq = to_smq_policy(p);
1582	struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1583
1584	if (!e->allocated)
1585		return -ENODATA;
1586
1587	// FIXME: what if this block has pending background work?
1588	del_queue(mq, e);
1589	h_remove(&mq->table, e);
1590	free_entry(&mq->cache_alloc, e);
1591	return 0;
1592}
1593
1594static uint32_t smq_get_hint(struct dm_cache_policy *p, dm_cblock_t cblock)
1595{
1596	struct smq_policy *mq = to_smq_policy(p);
1597	struct entry *e = get_entry(&mq->cache_alloc, from_cblock(cblock));
1598
1599	if (!e->allocated)
1600		return 0;
1601
1602	return e->level;
1603}
1604
1605static dm_cblock_t smq_residency(struct dm_cache_policy *p)
1606{
1607	dm_cblock_t r;
1608	unsigned long flags;
1609	struct smq_policy *mq = to_smq_policy(p);
1610
1611	spin_lock_irqsave(&mq->lock, flags);
1612	r = to_cblock(mq->cache_alloc.nr_allocated);
1613	spin_unlock_irqrestore(&mq->lock, flags);
1614
1615	return r;
1616}
1617
1618static void smq_tick(struct dm_cache_policy *p, bool can_block)
1619{
1620	struct smq_policy *mq = to_smq_policy(p);
1621	unsigned long flags;
1622
1623	spin_lock_irqsave(&mq->lock, flags);
1624	mq->tick++;
1625	update_sentinels(mq);
1626	end_hotspot_period(mq);
1627	end_cache_period(mq);
1628	spin_unlock_irqrestore(&mq->lock, flags);
1629}
1630
1631static void smq_allow_migrations(struct dm_cache_policy *p, bool allow)
1632{
1633	struct smq_policy *mq = to_smq_policy(p);
1634	mq->migrations_allowed = allow;
1635}
1636
1637/*
1638 * smq has no config values, but the old mq policy did.  To avoid breaking
1639 * software we continue to accept these configurables for the mq policy,
1640 * but they have no effect.
1641 */
1642static int mq_set_config_value(struct dm_cache_policy *p,
1643			       const char *key, const char *value)
1644{
1645	unsigned long tmp;
1646
1647	if (kstrtoul(value, 10, &tmp))
1648		return -EINVAL;
1649
1650	if (!strcasecmp(key, "random_threshold") ||
1651	    !strcasecmp(key, "sequential_threshold") ||
1652	    !strcasecmp(key, "discard_promote_adjustment") ||
1653	    !strcasecmp(key, "read_promote_adjustment") ||
1654	    !strcasecmp(key, "write_promote_adjustment")) {
1655		DMWARN("tunable '%s' no longer has any effect, mq policy is now an alias for smq", key);
1656		return 0;
1657	}
1658
1659	return -EINVAL;
1660}
1661
1662static int mq_emit_config_values(struct dm_cache_policy *p, char *result,
1663				 unsigned maxlen, ssize_t *sz_ptr)
1664{
1665	ssize_t sz = *sz_ptr;
1666
1667	DMEMIT("10 random_threshold 0 "
1668	       "sequential_threshold 0 "
1669	       "discard_promote_adjustment 0 "
1670	       "read_promote_adjustment 0 "
1671	       "write_promote_adjustment 0 ");
1672
1673	*sz_ptr = sz;
1674	return 0;
1675}
1676
1677/* Init the policy plugin interface function pointers. */
1678static void init_policy_functions(struct smq_policy *mq, bool mimic_mq)
1679{
1680	mq->policy.destroy = smq_destroy;
1681	mq->policy.lookup = smq_lookup;
1682	mq->policy.lookup_with_work = smq_lookup_with_work;
1683	mq->policy.get_background_work = smq_get_background_work;
1684	mq->policy.complete_background_work = smq_complete_background_work;
1685	mq->policy.set_dirty = smq_set_dirty;
1686	mq->policy.clear_dirty = smq_clear_dirty;
1687	mq->policy.load_mapping = smq_load_mapping;
1688	mq->policy.invalidate_mapping = smq_invalidate_mapping;
1689	mq->policy.get_hint = smq_get_hint;
1690	mq->policy.residency = smq_residency;
1691	mq->policy.tick = smq_tick;
1692	mq->policy.allow_migrations = smq_allow_migrations;
1693
1694	if (mimic_mq) {
1695		mq->policy.set_config_value = mq_set_config_value;
1696		mq->policy.emit_config_values = mq_emit_config_values;
1697	}
1698}
1699
1700static bool too_many_hotspot_blocks(sector_t origin_size,
1701				    sector_t hotspot_block_size,
1702				    unsigned nr_hotspot_blocks)
1703{
1704	return (hotspot_block_size * nr_hotspot_blocks) > origin_size;
1705}
1706
1707static void calc_hotspot_params(sector_t origin_size,
1708				sector_t cache_block_size,
1709				unsigned nr_cache_blocks,
1710				sector_t *hotspot_block_size,
1711				unsigned *nr_hotspot_blocks)
1712{
1713	*hotspot_block_size = cache_block_size * 16u;
1714	*nr_hotspot_blocks = max(nr_cache_blocks / 4u, 1024u);
1715
1716	while ((*hotspot_block_size > cache_block_size) &&
1717	       too_many_hotspot_blocks(origin_size, *hotspot_block_size, *nr_hotspot_blocks))
1718		*hotspot_block_size /= 2u;
1719}
1720
1721static struct dm_cache_policy *__smq_create(dm_cblock_t cache_size,
1722					    sector_t origin_size,
1723					    sector_t cache_block_size,
1724					    bool mimic_mq,
1725					    bool migrations_allowed)
1726{
1727	unsigned i;
1728	unsigned nr_sentinels_per_queue = 2u * NR_CACHE_LEVELS;
1729	unsigned total_sentinels = 2u * nr_sentinels_per_queue;
1730	struct smq_policy *mq = kzalloc(sizeof(*mq), GFP_KERNEL);
1731
1732	if (!mq)
1733		return NULL;
1734
1735	init_policy_functions(mq, mimic_mq);
1736	mq->cache_size = cache_size;
1737	mq->cache_block_size = cache_block_size;
1738
1739	calc_hotspot_params(origin_size, cache_block_size, from_cblock(cache_size),
1740			    &mq->hotspot_block_size, &mq->nr_hotspot_blocks);
1741
1742	mq->cache_blocks_per_hotspot_block = div64_u64(mq->hotspot_block_size, mq->cache_block_size);
1743	mq->hotspot_level_jump = 1u;
1744	if (space_init(&mq->es, total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size))) {
1745		DMERR("couldn't initialize entry space");
1746		goto bad_pool_init;
1747	}
1748
1749	init_allocator(&mq->writeback_sentinel_alloc, &mq->es, 0, nr_sentinels_per_queue);
1750	for (i = 0; i < nr_sentinels_per_queue; i++)
1751		get_entry(&mq->writeback_sentinel_alloc, i)->sentinel = true;
1752
1753	init_allocator(&mq->demote_sentinel_alloc, &mq->es, nr_sentinels_per_queue, total_sentinels);
1754	for (i = 0; i < nr_sentinels_per_queue; i++)
1755		get_entry(&mq->demote_sentinel_alloc, i)->sentinel = true;
1756
1757	init_allocator(&mq->hotspot_alloc, &mq->es, total_sentinels,
1758		       total_sentinels + mq->nr_hotspot_blocks);
1759
1760	init_allocator(&mq->cache_alloc, &mq->es,
1761		       total_sentinels + mq->nr_hotspot_blocks,
1762		       total_sentinels + mq->nr_hotspot_blocks + from_cblock(cache_size));
1763
1764	mq->hotspot_hit_bits = alloc_bitset(mq->nr_hotspot_blocks);
1765	if (!mq->hotspot_hit_bits) {
1766		DMERR("couldn't allocate hotspot hit bitset");
1767		goto bad_hotspot_hit_bits;
1768	}
1769	clear_bitset(mq->hotspot_hit_bits, mq->nr_hotspot_blocks);
1770
1771	if (from_cblock(cache_size)) {
1772		mq->cache_hit_bits = alloc_bitset(from_cblock(cache_size));
1773		if (!mq->cache_hit_bits) {
1774			DMERR("couldn't allocate cache hit bitset");
1775			goto bad_cache_hit_bits;
1776		}
1777		clear_bitset(mq->cache_hit_bits, from_cblock(mq->cache_size));
1778	} else
1779		mq->cache_hit_bits = NULL;
1780
1781	mq->tick = 0;
1782	spin_lock_init(&mq->lock);
1783
1784	q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS);
1785	mq->hotspot.nr_top_levels = 8;
1786	mq->hotspot.nr_in_top_levels = min(mq->nr_hotspot_blocks / NR_HOTSPOT_LEVELS,
1787					   from_cblock(mq->cache_size) / mq->cache_blocks_per_hotspot_block);
1788
1789	q_init(&mq->clean, &mq->es, NR_CACHE_LEVELS);
1790	q_init(&mq->dirty, &mq->es, NR_CACHE_LEVELS);
1791
1792	stats_init(&mq->hotspot_stats, NR_HOTSPOT_LEVELS);
1793	stats_init(&mq->cache_stats, NR_CACHE_LEVELS);
1794
1795	if (h_init(&mq->table, &mq->es, from_cblock(cache_size)))
1796		goto bad_alloc_table;
1797
1798	if (h_init(&mq->hotspot_table, &mq->es, mq->nr_hotspot_blocks))
1799		goto bad_alloc_hotspot_table;
1800
1801	sentinels_init(mq);
1802	mq->write_promote_level = mq->read_promote_level = NR_HOTSPOT_LEVELS;
1803
1804	mq->next_hotspot_period = jiffies;
1805	mq->next_cache_period = jiffies;
1806
1807	mq->bg_work = btracker_create(4096); /* FIXME: hard coded value */
1808	if (!mq->bg_work)
1809		goto bad_btracker;
1810
1811	mq->migrations_allowed = migrations_allowed;
1812
1813	return &mq->policy;
1814
1815bad_btracker:
1816	h_exit(&mq->hotspot_table);
1817bad_alloc_hotspot_table:
1818	h_exit(&mq->table);
1819bad_alloc_table:
1820	free_bitset(mq->cache_hit_bits);
1821bad_cache_hit_bits:
1822	free_bitset(mq->hotspot_hit_bits);
1823bad_hotspot_hit_bits:
1824	space_exit(&mq->es);
1825bad_pool_init:
1826	kfree(mq);
1827
1828	return NULL;
1829}
1830
1831static struct dm_cache_policy *smq_create(dm_cblock_t cache_size,
1832					  sector_t origin_size,
1833					  sector_t cache_block_size)
1834{
1835	return __smq_create(cache_size, origin_size, cache_block_size, false, true);
1836}
1837
1838static struct dm_cache_policy *mq_create(dm_cblock_t cache_size,
1839					 sector_t origin_size,
1840					 sector_t cache_block_size)
1841{
1842	return __smq_create(cache_size, origin_size, cache_block_size, true, true);
1843}
1844
1845static struct dm_cache_policy *cleaner_create(dm_cblock_t cache_size,
1846					      sector_t origin_size,
1847					      sector_t cache_block_size)
1848{
1849	return __smq_create(cache_size, origin_size, cache_block_size, false, false);
1850}
1851
1852/*----------------------------------------------------------------*/
1853
1854static struct dm_cache_policy_type smq_policy_type = {
1855	.name = "smq",
1856	.version = {2, 0, 0},
1857	.hint_size = 4,
1858	.owner = THIS_MODULE,
1859	.create = smq_create
1860};
1861
1862static struct dm_cache_policy_type mq_policy_type = {
1863	.name = "mq",
1864	.version = {2, 0, 0},
1865	.hint_size = 4,
1866	.owner = THIS_MODULE,
1867	.create = mq_create,
1868};
1869
1870static struct dm_cache_policy_type cleaner_policy_type = {
1871	.name = "cleaner",
1872	.version = {2, 0, 0},
1873	.hint_size = 4,
1874	.owner = THIS_MODULE,
1875	.create = cleaner_create,
1876};
1877
1878static struct dm_cache_policy_type default_policy_type = {
1879	.name = "default",
1880	.version = {2, 0, 0},
1881	.hint_size = 4,
1882	.owner = THIS_MODULE,
1883	.create = smq_create,
1884	.real = &smq_policy_type
1885};
1886
1887static int __init smq_init(void)
1888{
1889	int r;
1890
1891	r = dm_cache_policy_register(&smq_policy_type);
1892	if (r) {
1893		DMERR("register failed %d", r);
1894		return -ENOMEM;
1895	}
1896
1897	r = dm_cache_policy_register(&mq_policy_type);
1898	if (r) {
1899		DMERR("register failed (as mq) %d", r);
1900		goto out_mq;
1901	}
1902
1903	r = dm_cache_policy_register(&cleaner_policy_type);
1904	if (r) {
1905		DMERR("register failed (as cleaner) %d", r);
1906		goto out_cleaner;
1907	}
1908
1909	r = dm_cache_policy_register(&default_policy_type);
1910	if (r) {
1911		DMERR("register failed (as default) %d", r);
1912		goto out_default;
1913	}
1914
1915	return 0;
1916
1917out_default:
1918	dm_cache_policy_unregister(&cleaner_policy_type);
1919out_cleaner:
1920	dm_cache_policy_unregister(&mq_policy_type);
1921out_mq:
1922	dm_cache_policy_unregister(&smq_policy_type);
1923
1924	return -ENOMEM;
1925}
1926
1927static void __exit smq_exit(void)
1928{
1929	dm_cache_policy_unregister(&cleaner_policy_type);
1930	dm_cache_policy_unregister(&smq_policy_type);
1931	dm_cache_policy_unregister(&mq_policy_type);
1932	dm_cache_policy_unregister(&default_policy_type);
1933}
1934
1935module_init(smq_init);
1936module_exit(smq_exit);
1937
1938MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
1939MODULE_LICENSE("GPL");
1940MODULE_DESCRIPTION("smq cache policy");
1941
1942MODULE_ALIAS("dm-cache-default");
1943MODULE_ALIAS("dm-cache-mq");
1944MODULE_ALIAS("dm-cache-cleaner");