lib/sbitmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2016 Facebook
   4  * Copyright (C) 2013-2014 Jens Axboe
   5  */
   6
   7 #include <linux/sched.h>
   8 #include <linux/random.h>
   9 #include <linux/sbitmap.h>
  10 #include <linux/seq_file.h>
  11
  12 static int init_alloc_hint(struct sbitmap *sb, gfp_t flags)
  13 {
  14         unsigned depth = sb->depth;
  15
  16         sb->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
  17         if (!sb->alloc_hint)
  18                 return -ENOMEM;
  19
  20         if (depth && !sb->round_robin) {
  21                 int i;
  22
  23                 for_each_possible_cpu(i)
  24                         *per_cpu_ptr(sb->alloc_hint, i) = get_random_u32_below(depth);
  25         }
  26         return 0;
  27 }
  28
  29 static inline unsigned update_alloc_hint_before_get(struct sbitmap *sb,
  30                                                     unsigned int depth)
  31 {
  32         unsigned hint;
  33
  34         hint = this_cpu_read(*sb->alloc_hint);
  35         if (unlikely(hint >= depth)) {
  36                 hint = depth ? get_random_u32_below(depth) : 0;
  37                 this_cpu_write(*sb->alloc_hint, hint);
  38         }
  39
  40         return hint;
  41 }
  42
  43 static inline void update_alloc_hint_after_get(struct sbitmap *sb,
  44                                                unsigned int depth,
  45                                                unsigned int hint,
  46                                                unsigned int nr)
  47 {
  48         if (nr == -1) {
  49                 /* If the map is full, a hint won't do us much good. */
  50                 this_cpu_write(*sb->alloc_hint, 0);
  51         } else if (nr == hint || unlikely(sb->round_robin)) {
  52                 /* Only update the hint if we used it. */
  53                 hint = nr + 1;
  54                 if (hint >= depth - 1)
  55                         hint = 0;
  56                 this_cpu_write(*sb->alloc_hint, hint);
  57         }
  58 }
  59
  60 /*
  61  * See if we have deferred clears that we can batch move
  62  */
  63 static inline bool sbitmap_deferred_clear(struct sbitmap_word *map,
  64                 unsigned int depth, unsigned int alloc_hint, bool wrap)
  65 {
  66         unsigned long mask, word_mask;
  67
  68         guard(raw_spinlock_irqsave)(&map->swap_lock);
  69
  70         if (!map->cleared) {
  71                 if (depth == 0)
  72                         return false;
  73
  74                 word_mask = (~0UL) >> (BITS_PER_LONG - depth);
  75                 /*
  76                  * The current behavior is to always retry after moving
  77                  * ->cleared to word, and we change it to retry in case
  78                  * of any free bits. To avoid an infinite loop, we need
  79                  * to take wrap & alloc_hint into account, otherwise a
  80                  * soft lockup may occur.
  81                  */
  82                 if (!wrap && alloc_hint)
  83                         word_mask &= ~((1UL << alloc_hint) - 1);
  84
  85                 return (READ_ONCE(map->word) & word_mask) != word_mask;
  86         }
  87
  88         /*
  89          * First get a stable cleared mask, setting the old mask to 0.
  90          */
  91         mask = xchg(&map->cleared, 0);
  92
  93         /*
  94          * Now clear the masked bits in our free word
  95          */
  96         atomic_long_andnot(mask, (atomic_long_t *)&map->word);
  97         BUILD_BUG_ON(sizeof(atomic_long_t) != sizeof(map->word));
  98         return true;
  99 }
 100
 101 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 102                       gfp_t flags, int node, bool round_robin,
 103                       bool alloc_hint)
 104 {
 105         unsigned int bits_per_word;
 106         int i;
 107
 108         if (shift < 0)
 109                 shift = sbitmap_calculate_shift(depth);
 110
 111         bits_per_word = 1U << shift;
 112         if (bits_per_word > BITS_PER_LONG)
 113                 return -EINVAL;
 114
 115         sb->shift = shift;
 116         sb->depth = depth;
 117         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
 118         sb->round_robin = round_robin;
 119
 120         if (depth == 0) {
 121                 sb->map = NULL;
 122                 return 0;
 123         }
 124
 125         if (alloc_hint) {
 126                 if (init_alloc_hint(sb, flags))
 127                         return -ENOMEM;
 128         } else {
 129                 sb->alloc_hint = NULL;
 130         }
 131
 132         sb->map = kvzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
 133         if (!sb->map) {
 134                 free_percpu(sb->alloc_hint);
 135                 return -ENOMEM;
 136         }
 137
 138         for (i = 0; i < sb->map_nr; i++)
 139                 raw_spin_lock_init(&sb->map[i].swap_lock);
 140
 141         return 0;
 142 }
 143 EXPORT_SYMBOL_GPL(sbitmap_init_node);
 144
 145 void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
 146 {
 147         unsigned int bits_per_word = 1U << sb->shift;
 148         unsigned int i;
 149
 150         for (i = 0; i < sb->map_nr; i++)
 151                 sbitmap_deferred_clear(&sb->map[i], 0, 0, 0);
 152
 153         sb->depth = depth;
 154         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
 155 }
 156 EXPORT_SYMBOL_GPL(sbitmap_resize);
 157
 158 static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 159                               unsigned int hint, bool wrap)
 160 {
 161         int nr;
 162
 163         /* don't wrap if starting from 0 */
 164         wrap = wrap && hint;
 165
 166         while (1) {
 167                 nr = find_next_zero_bit(word, depth, hint);
 168                 if (unlikely(nr >= depth)) {
 169                         /*
 170                          * We started with an offset, and we didn't reset the
 171                          * offset to 0 in a failure case, so start from 0 to
 172                          * exhaust the map.
 173                          */
 174                         if (hint && wrap) {
 175                                 hint = 0;
 176                                 continue;
 177                         }
 178                         return -1;
 179                 }
 180
 181                 if (!test_and_set_bit_lock(nr, word))
 182                         break;
 183
 184                 hint = nr + 1;
 185                 if (hint >= depth - 1)
 186                         hint = 0;
 187         }
 188
 189         return nr;
 190 }
 191
 192 static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
 193                                     unsigned int depth,
 194                                     unsigned int alloc_hint,
 195                                     bool wrap)
 196 {
 197         int nr;
 198
 199         do {
 200                 nr = __sbitmap_get_word(&map->word, depth,
 201                                         alloc_hint, wrap);
 202                 if (nr != -1)
 203                         break;
 204                 if (!sbitmap_deferred_clear(map, depth, alloc_hint, wrap))
 205                         break;
 206         } while (1);
 207
 208         return nr;
 209 }
 210
 211 static int sbitmap_find_bit(struct sbitmap *sb,
 212                             unsigned int depth,
 213                             unsigned int index,
 214                             unsigned int alloc_hint,
 215                             bool wrap)
 216 {
 217         unsigned int i;
 218         int nr = -1;
 219
 220         for (i = 0; i < sb->map_nr; i++) {
 221                 nr = sbitmap_find_bit_in_word(&sb->map[index],
 222                                               min_t(unsigned int,
 223                                                     __map_depth(sb, index),
 224                                                     depth),
 225                                               alloc_hint, wrap);
 226
 227                 if (nr != -1) {
 228                         nr += index << sb->shift;
 229                         break;
 230                 }
 231
 232                 /* Jump to next index. */
 233                 alloc_hint = 0;
 234                 if (++index >= sb->map_nr)
 235                         index = 0;
 236         }
 237
 238         return nr;
 239 }
 240
 241 static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 242 {
 243         unsigned int index;
 244
 245         index = SB_NR_TO_INDEX(sb, alloc_hint);
 246
 247         /*
 248          * Unless we're doing round robin tag allocation, just use the
 249          * alloc_hint to find the right word index. No point in looping
 250          * twice in find_next_zero_bit() for that case.
 251          */
 252         if (sb->round_robin)
 253                 alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 254         else
 255                 alloc_hint = 0;
 256
 257         return sbitmap_find_bit(sb, UINT_MAX, index, alloc_hint,
 258                                 !sb->round_robin);
 259 }
 260
 261 int sbitmap_get(struct sbitmap *sb)
 262 {
 263         int nr;
 264         unsigned int hint, depth;
 265
 266         if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
 267                 return -1;
 268
 269         depth = READ_ONCE(sb->depth);
 270         hint = update_alloc_hint_before_get(sb, depth);
 271         nr = __sbitmap_get(sb, hint);
 272         update_alloc_hint_after_get(sb, depth, hint, nr);
 273
 274         return nr;
 275 }
 276 EXPORT_SYMBOL_GPL(sbitmap_get);
 277
 278 static int __sbitmap_get_shallow(struct sbitmap *sb,
 279                                  unsigned int alloc_hint,
 280                                  unsigned long shallow_depth)
 281 {
 282         unsigned int index;
 283
 284         index = SB_NR_TO_INDEX(sb, alloc_hint);
 285         alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 286
 287         return sbitmap_find_bit(sb, shallow_depth, index, alloc_hint, true);
 288 }
 289
 290 int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth)
 291 {
 292         int nr;
 293         unsigned int hint, depth;
 294
 295         if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
 296                 return -1;
 297
 298         depth = READ_ONCE(sb->depth);
 299         hint = update_alloc_hint_before_get(sb, depth);
 300         nr = __sbitmap_get_shallow(sb, hint, shallow_depth);
 301         update_alloc_hint_after_get(sb, depth, hint, nr);
 302
 303         return nr;
 304 }
 305 EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
 306
 307 bool sbitmap_any_bit_set(const struct sbitmap *sb)
 308 {
 309         unsigned int i;
 310
 311         for (i = 0; i < sb->map_nr; i++) {
 312                 if (sb->map[i].word & ~sb->map[i].cleared)
 313                         return true;
 314         }
 315         return false;
 316 }
 317 EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
 318
 319 static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
 320 {
 321         unsigned int i, weight = 0;
 322
 323         for (i = 0; i < sb->map_nr; i++) {
 324                 const struct sbitmap_word *word = &sb->map[i];
 325                 unsigned int word_depth = __map_depth(sb, i);
 326
 327                 if (set)
 328                         weight += bitmap_weight(&word->word, word_depth);
 329                 else
 330                         weight += bitmap_weight(&word->cleared, word_depth);
 331         }
 332         return weight;
 333 }
 334
 335 static unsigned int sbitmap_cleared(const struct sbitmap *sb)
 336 {
 337         return __sbitmap_weight(sb, false);
 338 }
 339
 340 unsigned int sbitmap_weight(const struct sbitmap *sb)
 341 {
 342         return __sbitmap_weight(sb, true) - sbitmap_cleared(sb);
 343 }
 344 EXPORT_SYMBOL_GPL(sbitmap_weight);
 345
 346 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 347 {
 348         seq_printf(m, "depth=%u\n", sb->depth);
 349         seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
 350         seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
 351         seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 352         seq_printf(m, "map_nr=%u\n", sb->map_nr);
 353 }
 354 EXPORT_SYMBOL_GPL(sbitmap_show);
 355
 356 static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
 357 {
 358         if ((offset & 0xf) == 0) {
 359                 if (offset != 0)
 360                         seq_putc(m, '\n');
 361                 seq_printf(m, "%08x:", offset);
 362         }
 363         if ((offset & 0x1) == 0)
 364                 seq_putc(m, ' ');
 365         seq_printf(m, "%02x", byte);
 366 }
 367
 368 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
 369 {
 370         u8 byte = 0;
 371         unsigned int byte_bits = 0;
 372         unsigned int offset = 0;
 373         int i;
 374
 375         for (i = 0; i < sb->map_nr; i++) {
 376                 unsigned long word = READ_ONCE(sb->map[i].word);
 377                 unsigned long cleared = READ_ONCE(sb->map[i].cleared);
 378                 unsigned int word_bits = __map_depth(sb, i);
 379
 380                 word &= ~cleared;
 381
 382                 while (word_bits > 0) {
 383                         unsigned int bits = min(8 - byte_bits, word_bits);
 384
 385                         byte |= (word & (BIT(bits) - 1)) << byte_bits;
 386                         byte_bits += bits;
 387                         if (byte_bits == 8) {
 388                                 emit_byte(m, offset, byte);
 389                                 byte = 0;
 390                                 byte_bits = 0;
 391                                 offset++;
 392                         }
 393                         word >>= bits;
 394                         word_bits -= bits;
 395                 }
 396         }
 397         if (byte_bits) {
 398                 emit_byte(m, offset, byte);
 399                 offset++;
 400         }
 401         if (offset)
 402                 seq_putc(m, '\n');
 403 }
 404 EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
 405
 406 static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq,
 407                                         unsigned int depth)
 408 {
 409         unsigned int wake_batch;
 410         unsigned int shallow_depth;
 411
 412         /*
 413          * Each full word of the bitmap has bits_per_word bits, and there might
 414          * be a partial word. There are depth / bits_per_word full words and
 415          * depth % bits_per_word bits left over. In bitwise arithmetic:
 416          *
 417          * bits_per_word = 1 << shift
 418          * depth / bits_per_word = depth >> shift
 419          * depth % bits_per_word = depth & ((1 << shift) - 1)
 420          *
 421          * Each word can be limited to sbq->min_shallow_depth bits.
 422          */
 423         shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
 424         depth = ((depth >> sbq->sb.shift) * shallow_depth +
 425                  min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
 426         wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
 427                              SBQ_WAKE_BATCH);
 428
 429         return wake_batch;
 430 }
 431
 432 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 433                             int shift, bool round_robin, gfp_t flags, int node)
 434 {
 435         int ret;
 436         int i;
 437
 438         ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node,
 439                                 round_robin, true);
 440         if (ret)
 441                 return ret;
 442
 443         sbq->min_shallow_depth = UINT_MAX;
 444         sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 445         atomic_set(&sbq->wake_index, 0);
 446         atomic_set(&sbq->ws_active, 0);
 447         atomic_set(&sbq->completion_cnt, 0);
 448         atomic_set(&sbq->wakeup_cnt, 0);
 449
 450         sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 451         if (!sbq->ws) {
 452                 sbitmap_free(&sbq->sb);
 453                 return -ENOMEM;
 454         }
 455
 456         for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 457                 init_waitqueue_head(&sbq->ws[i].wait);
 458
 459         return 0;
 460 }
 461 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
 462
 463 static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
 464                                             unsigned int depth)
 465 {
 466         unsigned int wake_batch;
 467
 468         wake_batch = sbq_calc_wake_batch(sbq, depth);
 469         if (sbq->wake_batch != wake_batch)
 470                 WRITE_ONCE(sbq->wake_batch, wake_batch);
 471 }
 472
 473 void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
 474                                             unsigned int users)
 475 {
 476         unsigned int wake_batch;
 477         unsigned int depth = (sbq->sb.depth + users - 1) / users;
 478
 479         wake_batch = clamp_val(depth / SBQ_WAIT_QUEUES,
 480                         1, SBQ_WAKE_BATCH);
 481
 482         WRITE_ONCE(sbq->wake_batch, wake_batch);
 483 }
 484 EXPORT_SYMBOL_GPL(sbitmap_queue_recalculate_wake_batch);
 485
 486 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 487 {
 488         sbitmap_queue_update_wake_batch(sbq, depth);
 489         sbitmap_resize(&sbq->sb, depth);
 490 }
 491 EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
 492
 493 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 494 {
 495         return sbitmap_get(&sbq->sb);
 496 }
 497 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
 498
 499 unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
 500                                         unsigned int *offset)
 501 {
 502         struct sbitmap *sb = &sbq->sb;
 503         unsigned int hint, depth;
 504         unsigned long index, nr;
 505         int i;
 506
 507         if (unlikely(sb->round_robin))
 508                 return 0;
 509
 510         depth = READ_ONCE(sb->depth);
 511         hint = update_alloc_hint_before_get(sb, depth);
 512
 513         index = SB_NR_TO_INDEX(sb, hint);
 514
 515         for (i = 0; i < sb->map_nr; i++) {
 516                 struct sbitmap_word *map = &sb->map[index];
 517                 unsigned long get_mask;
 518                 unsigned int map_depth = __map_depth(sb, index);
 519                 unsigned long val;
 520
 521                 sbitmap_deferred_clear(map, 0, 0, 0);
 522                 val = READ_ONCE(map->word);
 523                 if (val == (1UL << (map_depth - 1)) - 1)
 524                         goto next;
 525
 526                 nr = find_first_zero_bit(&val, map_depth);
 527                 if (nr + nr_tags <= map_depth) {
 528                         atomic_long_t *ptr = (atomic_long_t *) &map->word;
 529
 530                         get_mask = ((1UL << nr_tags) - 1) << nr;
 531                         while (!atomic_long_try_cmpxchg(ptr, &val,
 532                                                           get_mask | val))
 533                                 ;
 534                         get_mask = (get_mask & ~val) >> nr;
 535                         if (get_mask) {
 536                                 *offset = nr + (index << sb->shift);
 537                                 update_alloc_hint_after_get(sb, depth, hint,
 538                                                         *offset + nr_tags - 1);
 539                                 return get_mask;
 540                         }
 541                 }
 542 next:
 543                 /* Jump to next index. */
 544                 if (++index >= sb->map_nr)
 545                         index = 0;
 546         }
 547
 548         return 0;
 549 }
 550
 551 int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 552                               unsigned int shallow_depth)
 553 {
 554         WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 555
 556         return sbitmap_get_shallow(&sbq->sb, shallow_depth);
 557 }
 558 EXPORT_SYMBOL_GPL(sbitmap_queue_get_shallow);
 559
 560 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 561                                      unsigned int min_shallow_depth)
 562 {
 563         sbq->min_shallow_depth = min_shallow_depth;
 564         sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
 565 }
 566 EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
 567
 568 static void __sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
 569 {
 570         int i, wake_index, woken;
 571
 572         if (!atomic_read(&sbq->ws_active))
 573                 return;
 574
 575         wake_index = atomic_read(&sbq->wake_index);
 576         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 577                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 578
 579                 /*
 580                  * Advance the index before checking the current queue.
 581                  * It improves fairness, by ensuring the queue doesn't
 582                  * need to be fully emptied before trying to wake up
 583                  * from the next one.
 584                  */
 585                 wake_index = sbq_index_inc(wake_index);
 586
 587                 if (waitqueue_active(&ws->wait)) {
 588                         woken = wake_up_nr(&ws->wait, nr);
 589                         if (woken == nr)
 590                                 break;
 591                         nr -= woken;
 592                 }
 593         }
 594
 595         if (wake_index != atomic_read(&sbq->wake_index))
 596                 atomic_set(&sbq->wake_index, wake_index);
 597 }
 598
 599 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
 600 {
 601         unsigned int wake_batch = READ_ONCE(sbq->wake_batch);
 602         unsigned int wakeups;
 603
 604         if (!atomic_read(&sbq->ws_active))
 605                 return;
 606
 607         atomic_add(nr, &sbq->completion_cnt);
 608         wakeups = atomic_read(&sbq->wakeup_cnt);
 609
 610         do {
 611                 if (atomic_read(&sbq->completion_cnt) - wakeups < wake_batch)
 612                         return;
 613         } while (!atomic_try_cmpxchg(&sbq->wakeup_cnt,
 614                                      &wakeups, wakeups + wake_batch));
 615
 616         __sbitmap_queue_wake_up(sbq, wake_batch);
 617 }
 618 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 619
 620 static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag)
 621 {
 622         if (likely(!sb->round_robin && tag < sb->depth))
 623                 data_race(*per_cpu_ptr(sb->alloc_hint, cpu) = tag);
 624 }
 625
 626 void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
 627                                 int *tags, int nr_tags)
 628 {
 629         struct sbitmap *sb = &sbq->sb;
 630         unsigned long *addr = NULL;
 631         unsigned long mask = 0;
 632         int i;
 633
 634         smp_mb__before_atomic();
 635         for (i = 0; i < nr_tags; i++) {
 636                 const int tag = tags[i] - offset;
 637                 unsigned long *this_addr;
 638
 639                 /* since we're clearing a batch, skip the deferred map */
 640                 this_addr = &sb->map[SB_NR_TO_INDEX(sb, tag)].word;
 641                 if (!addr) {
 642                         addr = this_addr;
 643                 } else if (addr != this_addr) {
 644                         atomic_long_andnot(mask, (atomic_long_t *) addr);
 645                         mask = 0;
 646                         addr = this_addr;
 647                 }
 648                 mask |= (1UL << SB_NR_TO_BIT(sb, tag));
 649         }
 650
 651         if (mask)
 652                 atomic_long_andnot(mask, (atomic_long_t *) addr);
 653
 654         smp_mb__after_atomic();
 655         sbitmap_queue_wake_up(sbq, nr_tags);
 656         sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(),
 657                                         tags[nr_tags - 1] - offset);
 658 }
 659
 660 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 661                          unsigned int cpu)
 662 {
 663         /*
 664          * Once the clear bit is set, the bit may be allocated out.
 665          *
 666          * Orders READ/WRITE on the associated instance(such as request
 667          * of blk_mq) by this bit for avoiding race with re-allocation,
 668          * and its pair is the memory barrier implied in __sbitmap_get_word.
 669          *
 670          * One invariant is that the clear bit has to be zero when the bit
 671          * is in use.
 672          */
 673         smp_mb__before_atomic();
 674         sbitmap_deferred_clear_bit(&sbq->sb, nr);
 675
 676         /*
 677          * Pairs with the memory barrier in set_current_state() to ensure the
 678          * proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
 679          * and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
 680          * waiter. See the comment on waitqueue_active().
 681          */
 682         smp_mb__after_atomic();
 683         sbitmap_queue_wake_up(sbq, 1);
 684         sbitmap_update_cpu_hint(&sbq->sb, cpu, nr);
 685 }
 686 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
 687
 688 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
 689 {
 690         int i, wake_index;
 691
 692         /*
 693          * Pairs with the memory barrier in set_current_state() like in
 694          * sbitmap_queue_wake_up().
 695          */
 696         smp_mb();
 697         wake_index = atomic_read(&sbq->wake_index);
 698         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 699                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 700
 701                 if (waitqueue_active(&ws->wait))
 702                         wake_up(&ws->wait);
 703
 704                 wake_index = sbq_index_inc(wake_index);
 705         }
 706 }
 707 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
 708
 709 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 710 {
 711         bool first;
 712         int i;
 713
 714         sbitmap_show(&sbq->sb, m);
 715
 716         seq_puts(m, "alloc_hint={");
 717         first = true;
 718         for_each_possible_cpu(i) {
 719                 if (!first)
 720                         seq_puts(m, ", ");
 721                 first = false;
 722                 seq_printf(m, "%u", *per_cpu_ptr(sbq->sb.alloc_hint, i));
 723         }
 724         seq_puts(m, "}\n");
 725
 726         seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
 727         seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
 728         seq_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
 729
 730         seq_puts(m, "ws={\n");
 731         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 732                 struct sbq_wait_state *ws = &sbq->ws[i];
 733                 seq_printf(m, "\t{.wait=%s},\n",
 734                            waitqueue_active(&ws->wait) ? "active" : "inactive");
 735         }
 736         seq_puts(m, "}\n");
 737
 738         seq_printf(m, "round_robin=%d\n", sbq->sb.round_robin);
 739         seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
 740 }
 741 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
 742
 743 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
 744                             struct sbq_wait_state *ws,
 745                             struct sbq_wait *sbq_wait)
 746 {
 747         if (!sbq_wait->sbq) {
 748                 sbq_wait->sbq = sbq;
 749                 atomic_inc(&sbq->ws_active);
 750                 add_wait_queue(&ws->wait, &sbq_wait->wait);
 751         }
 752 }
 753 EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
 754
 755 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
 756 {
 757         list_del_init(&sbq_wait->wait.entry);
 758         if (sbq_wait->sbq) {
 759                 atomic_dec(&sbq_wait->sbq->ws_active);
 760                 sbq_wait->sbq = NULL;
 761         }
 762 }
 763 EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
 764
 765 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
 766                              struct sbq_wait_state *ws,
 767                              struct sbq_wait *sbq_wait, int state)
 768 {
 769         if (!sbq_wait->sbq) {
 770                 atomic_inc(&sbq->ws_active);
 771                 sbq_wait->sbq = sbq;
 772         }
 773         prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
 774 }
 775 EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
 776
 777 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 778                          struct sbq_wait *sbq_wait)
 779 {
 780         finish_wait(&ws->wait, &sbq_wait->wait);
 781         if (sbq_wait->sbq) {
 782                 atomic_dec(&sbq->ws_active);
 783                 sbq_wait->sbq = NULL;
 784         }
 785 }
 786 EXPORT_SYMBOL_GPL(sbitmap_finish_wait);