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