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) = prandom_u32() % 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 ? prandom_u32() % 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         unsigned int i;
  89
  90         if (shift < 0)
  91                 shift = sbitmap_calculate_shift(depth);
  92
  93         bits_per_word = 1U << shift;
  94         if (bits_per_word > BITS_PER_LONG)
  95                 return -EINVAL;
  96
  97         sb->shift = shift;
  98         sb->depth = depth;
  99         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
 100         sb->round_robin = round_robin;
 101
 102         if (depth == 0) {
 103                 sb->map = NULL;
 104                 return 0;
 105         }
 106
 107         if (alloc_hint) {
 108                 if (init_alloc_hint(sb, flags))
 109                         return -ENOMEM;
 110         } else {
 111                 sb->alloc_hint = NULL;
 112         }
 113
 114         sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
 115         if (!sb->map) {
 116                 free_percpu(sb->alloc_hint);
 117                 return -ENOMEM;
 118         }
 119
 120         for (i = 0; i < sb->map_nr; i++) {
 121                 sb->map[i].depth = min(depth, bits_per_word);
 122                 depth -= sb->map[i].depth;
 123         }
 124         return 0;
 125 }
 126 EXPORT_SYMBOL_GPL(sbitmap_init_node);
 127
 128 void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
 129 {
 130         unsigned int bits_per_word = 1U << sb->shift;
 131         unsigned int i;
 132
 133         for (i = 0; i < sb->map_nr; i++)
 134                 sbitmap_deferred_clear(&sb->map[i]);
 135
 136         sb->depth = depth;
 137         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
 138
 139         for (i = 0; i < sb->map_nr; i++) {
 140                 sb->map[i].depth = min(depth, bits_per_word);
 141                 depth -= sb->map[i].depth;
 142         }
 143 }
 144 EXPORT_SYMBOL_GPL(sbitmap_resize);
 145
 146 static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 147                               unsigned int hint, bool wrap)
 148 {
 149         int nr;
 150
 151         /* don't wrap if starting from 0 */
 152         wrap = wrap && hint;
 153
 154         while (1) {
 155                 nr = find_next_zero_bit(word, depth, hint);
 156                 if (unlikely(nr >= depth)) {
 157                         /*
 158                          * We started with an offset, and we didn't reset the
 159                          * offset to 0 in a failure case, so start from 0 to
 160                          * exhaust the map.
 161                          */
 162                         if (hint && wrap) {
 163                                 hint = 0;
 164                                 continue;
 165                         }
 166                         return -1;
 167                 }
 168
 169                 if (!test_and_set_bit_lock(nr, word))
 170                         break;
 171
 172                 hint = nr + 1;
 173                 if (hint >= depth - 1)
 174                         hint = 0;
 175         }
 176
 177         return nr;
 178 }
 179
 180 static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
 181                                      unsigned int alloc_hint)
 182 {
 183         struct sbitmap_word *map = &sb->map[index];
 184         int nr;
 185
 186         do {
 187                 nr = __sbitmap_get_word(&map->word, map->depth, alloc_hint,
 188                                         !sb->round_robin);
 189                 if (nr != -1)
 190                         break;
 191                 if (!sbitmap_deferred_clear(map))
 192                         break;
 193         } while (1);
 194
 195         return nr;
 196 }
 197
 198 static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 199 {
 200         unsigned int i, index;
 201         int nr = -1;
 202
 203         index = SB_NR_TO_INDEX(sb, alloc_hint);
 204
 205         /*
 206          * Unless we're doing round robin tag allocation, just use the
 207          * alloc_hint to find the right word index. No point in looping
 208          * twice in find_next_zero_bit() for that case.
 209          */
 210         if (sb->round_robin)
 211                 alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 212         else
 213                 alloc_hint = 0;
 214
 215         for (i = 0; i < sb->map_nr; i++) {
 216                 nr = sbitmap_find_bit_in_index(sb, index, alloc_hint);
 217                 if (nr != -1) {
 218                         nr += index << sb->shift;
 219                         break;
 220                 }
 221
 222                 /* Jump to next index. */
 223                 alloc_hint = 0;
 224                 if (++index >= sb->map_nr)
 225                         index = 0;
 226         }
 227
 228         return nr;
 229 }
 230
 231 int sbitmap_get(struct sbitmap *sb)
 232 {
 233         int nr;
 234         unsigned int hint, depth;
 235
 236         if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
 237                 return -1;
 238
 239         depth = READ_ONCE(sb->depth);
 240         hint = update_alloc_hint_before_get(sb, depth);
 241         nr = __sbitmap_get(sb, hint);
 242         update_alloc_hint_after_get(sb, depth, hint, nr);
 243
 244         return nr;
 245 }
 246 EXPORT_SYMBOL_GPL(sbitmap_get);
 247
 248 static int __sbitmap_get_shallow(struct sbitmap *sb,
 249                                  unsigned int alloc_hint,
 250                                  unsigned long shallow_depth)
 251 {
 252         unsigned int i, index;
 253         int nr = -1;
 254
 255         index = SB_NR_TO_INDEX(sb, alloc_hint);
 256
 257         for (i = 0; i < sb->map_nr; i++) {
 258 again:
 259                 nr = __sbitmap_get_word(&sb->map[index].word,
 260                                         min(sb->map[index].depth, shallow_depth),
 261                                         SB_NR_TO_BIT(sb, alloc_hint), true);
 262                 if (nr != -1) {
 263                         nr += index << sb->shift;
 264                         break;
 265                 }
 266
 267                 if (sbitmap_deferred_clear(&sb->map[index]))
 268                         goto again;
 269
 270                 /* Jump to next index. */
 271                 index++;
 272                 alloc_hint = index << sb->shift;
 273
 274                 if (index >= sb->map_nr) {
 275                         index = 0;
 276                         alloc_hint = 0;
 277                 }
 278         }
 279
 280         return nr;
 281 }
 282
 283 int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth)
 284 {
 285         int nr;
 286         unsigned int hint, depth;
 287
 288         if (WARN_ON_ONCE(unlikely(!sb->alloc_hint)))
 289                 return -1;
 290
 291         depth = READ_ONCE(sb->depth);
 292         hint = update_alloc_hint_before_get(sb, depth);
 293         nr = __sbitmap_get_shallow(sb, hint, shallow_depth);
 294         update_alloc_hint_after_get(sb, depth, hint, nr);
 295
 296         return nr;
 297 }
 298 EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
 299
 300 bool sbitmap_any_bit_set(const struct sbitmap *sb)
 301 {
 302         unsigned int i;
 303
 304         for (i = 0; i < sb->map_nr; i++) {
 305                 if (sb->map[i].word & ~sb->map[i].cleared)
 306                         return true;
 307         }
 308         return false;
 309 }
 310 EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
 311
 312 static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
 313 {
 314         unsigned int i, weight = 0;
 315
 316         for (i = 0; i < sb->map_nr; i++) {
 317                 const struct sbitmap_word *word = &sb->map[i];
 318
 319                 if (set)
 320                         weight += bitmap_weight(&word->word, word->depth);
 321                 else
 322                         weight += bitmap_weight(&word->cleared, word->depth);
 323         }
 324         return weight;
 325 }
 326
 327 static unsigned int sbitmap_cleared(const struct sbitmap *sb)
 328 {
 329         return __sbitmap_weight(sb, false);
 330 }
 331
 332 unsigned int sbitmap_weight(const struct sbitmap *sb)
 333 {
 334         return __sbitmap_weight(sb, true) - sbitmap_cleared(sb);
 335 }
 336 EXPORT_SYMBOL_GPL(sbitmap_weight);
 337
 338 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 339 {
 340         seq_printf(m, "depth=%u\n", sb->depth);
 341         seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
 342         seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
 343         seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 344         seq_printf(m, "map_nr=%u\n", sb->map_nr);
 345 }
 346 EXPORT_SYMBOL_GPL(sbitmap_show);
 347
 348 static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
 349 {
 350         if ((offset & 0xf) == 0) {
 351                 if (offset != 0)
 352                         seq_putc(m, '\n');
 353                 seq_printf(m, "%08x:", offset);
 354         }
 355         if ((offset & 0x1) == 0)
 356                 seq_putc(m, ' ');
 357         seq_printf(m, "%02x", byte);
 358 }
 359
 360 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
 361 {
 362         u8 byte = 0;
 363         unsigned int byte_bits = 0;
 364         unsigned int offset = 0;
 365         int i;
 366
 367         for (i = 0; i < sb->map_nr; i++) {
 368                 unsigned long word = READ_ONCE(sb->map[i].word);
 369                 unsigned long cleared = READ_ONCE(sb->map[i].cleared);
 370                 unsigned int word_bits = READ_ONCE(sb->map[i].depth);
 371
 372                 word &= ~cleared;
 373
 374                 while (word_bits > 0) {
 375                         unsigned int bits = min(8 - byte_bits, word_bits);
 376
 377                         byte |= (word & (BIT(bits) - 1)) << byte_bits;
 378                         byte_bits += bits;
 379                         if (byte_bits == 8) {
 380                                 emit_byte(m, offset, byte);
 381                                 byte = 0;
 382                                 byte_bits = 0;
 383                                 offset++;
 384                         }
 385                         word >>= bits;
 386                         word_bits -= bits;
 387                 }
 388         }
 389         if (byte_bits) {
 390                 emit_byte(m, offset, byte);
 391                 offset++;
 392         }
 393         if (offset)
 394                 seq_putc(m, '\n');
 395 }
 396 EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
 397
 398 static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq,
 399                                         unsigned int depth)
 400 {
 401         unsigned int wake_batch;
 402         unsigned int shallow_depth;
 403
 404         /*
 405          * For each batch, we wake up one queue. We need to make sure that our
 406          * batch size is small enough that the full depth of the bitmap,
 407          * potentially limited by a shallow depth, is enough to wake up all of
 408          * the queues.
 409          *
 410          * Each full word of the bitmap has bits_per_word bits, and there might
 411          * be a partial word. There are depth / bits_per_word full words and
 412          * depth % bits_per_word bits left over. In bitwise arithmetic:
 413          *
 414          * bits_per_word = 1 << shift
 415          * depth / bits_per_word = depth >> shift
 416          * depth % bits_per_word = depth & ((1 << shift) - 1)
 417          *
 418          * Each word can be limited to sbq->min_shallow_depth bits.
 419          */
 420         shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
 421         depth = ((depth >> sbq->sb.shift) * shallow_depth +
 422                  min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
 423         wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
 424                              SBQ_WAKE_BATCH);
 425
 426         return wake_batch;
 427 }
 428
 429 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 430                             int shift, bool round_robin, gfp_t flags, int node)
 431 {
 432         int ret;
 433         int i;
 434
 435         ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node,
 436                                 round_robin, true);
 437         if (ret)
 438                 return ret;
 439
 440         sbq->min_shallow_depth = UINT_MAX;
 441         sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 442         atomic_set(&sbq->wake_index, 0);
 443         atomic_set(&sbq->ws_active, 0);
 444
 445         sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 446         if (!sbq->ws) {
 447                 sbitmap_free(&sbq->sb);
 448                 return -ENOMEM;
 449         }
 450
 451         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 452                 init_waitqueue_head(&sbq->ws[i].wait);
 453                 atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
 454         }
 455
 456         return 0;
 457 }
 458 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
 459
 460 static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
 461                                             unsigned int depth)
 462 {
 463         unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth);
 464         int i;
 465
 466         if (sbq->wake_batch != wake_batch) {
 467                 WRITE_ONCE(sbq->wake_batch, wake_batch);
 468                 /*
 469                  * Pairs with the memory barrier in sbitmap_queue_wake_up()
 470                  * to ensure that the batch size is updated before the wait
 471                  * counts.
 472                  */
 473                 smp_mb();
 474                 for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 475                         atomic_set(&sbq->ws[i].wait_cnt, 1);
 476         }
 477 }
 478
 479 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 480 {
 481         sbitmap_queue_update_wake_batch(sbq, depth);
 482         sbitmap_resize(&sbq->sb, depth);
 483 }
 484 EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
 485
 486 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 487 {
 488         return sbitmap_get(&sbq->sb);
 489 }
 490 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
 491
 492 unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
 493                                         unsigned int *offset)
 494 {
 495         struct sbitmap *sb = &sbq->sb;
 496         unsigned int hint, depth;
 497         unsigned long index, nr;
 498         int i;
 499
 500         if (unlikely(sb->round_robin))
 501                 return 0;
 502
 503         depth = READ_ONCE(sb->depth);
 504         hint = update_alloc_hint_before_get(sb, depth);
 505
 506         index = SB_NR_TO_INDEX(sb, hint);
 507
 508         for (i = 0; i < sb->map_nr; i++) {
 509                 struct sbitmap_word *map = &sb->map[index];
 510                 unsigned long get_mask;
 511
 512                 sbitmap_deferred_clear(map);
 513                 if (map->word == (1UL << (map->depth - 1)) - 1)
 514                         continue;
 515
 516                 nr = find_first_zero_bit(&map->word, map->depth);
 517                 if (nr + nr_tags <= map->depth) {
 518                         atomic_long_t *ptr = (atomic_long_t *) &map->word;
 519                         int map_tags = min_t(int, nr_tags, map->depth);
 520                         unsigned long val, ret;
 521
 522                         get_mask = ((1UL << map_tags) - 1) << nr;
 523                         do {
 524                                 val = READ_ONCE(map->word);
 525                                 ret = atomic_long_cmpxchg(ptr, val, get_mask | val);
 526                         } while (ret != val);
 527                         get_mask = (get_mask & ~ret) >> nr;
 528                         if (get_mask) {
 529                                 *offset = nr + (index << sb->shift);
 530                                 update_alloc_hint_after_get(sb, depth, hint,
 531                                                         *offset + map_tags - 1);
 532                                 return get_mask;
 533                         }
 534                 }
 535                 /* Jump to next index. */
 536                 if (++index >= sb->map_nr)
 537                         index = 0;
 538         }
 539
 540         return 0;
 541 }
 542
 543 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 544                                 unsigned int shallow_depth)
 545 {
 546         WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 547
 548         return sbitmap_get_shallow(&sbq->sb, shallow_depth);
 549 }
 550 EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
 551
 552 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 553                                      unsigned int min_shallow_depth)
 554 {
 555         sbq->min_shallow_depth = min_shallow_depth;
 556         sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
 557 }
 558 EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
 559
 560 static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
 561 {
 562         int i, wake_index;
 563
 564         if (!atomic_read(&sbq->ws_active))
 565                 return NULL;
 566
 567         wake_index = atomic_read(&sbq->wake_index);
 568         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 569                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 570
 571                 if (waitqueue_active(&ws->wait)) {
 572                         if (wake_index != atomic_read(&sbq->wake_index))
 573                                 atomic_set(&sbq->wake_index, wake_index);
 574                         return ws;
 575                 }
 576
 577                 wake_index = sbq_index_inc(wake_index);
 578         }
 579
 580         return NULL;
 581 }
 582
 583 static bool __sbq_wake_up(struct sbitmap_queue *sbq)
 584 {
 585         struct sbq_wait_state *ws;
 586         unsigned int wake_batch;
 587         int wait_cnt;
 588
 589         ws = sbq_wake_ptr(sbq);
 590         if (!ws)
 591                 return false;
 592
 593         wait_cnt = atomic_dec_return(&ws->wait_cnt);
 594         if (wait_cnt <= 0) {
 595                 int ret;
 596
 597                 wake_batch = READ_ONCE(sbq->wake_batch);
 598
 599                 /*
 600                  * Pairs with the memory barrier in sbitmap_queue_resize() to
 601                  * ensure that we see the batch size update before the wait
 602                  * count is reset.
 603                  */
 604                 smp_mb__before_atomic();
 605
 606                 /*
 607                  * For concurrent callers of this, the one that failed the
 608                  * atomic_cmpxhcg() race should call this function again
 609                  * to wakeup a new batch on a different 'ws'.
 610                  */
 611                 ret = atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wake_batch);
 612                 if (ret == wait_cnt) {
 613                         sbq_index_atomic_inc(&sbq->wake_index);
 614                         wake_up_nr(&ws->wait, wake_batch);
 615                         return false;
 616                 }
 617
 618                 return true;
 619         }
 620
 621         return false;
 622 }
 623
 624 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
 625 {
 626         while (__sbq_wake_up(sbq))
 627                 ;
 628 }
 629 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 630
 631 static inline void sbitmap_update_cpu_hint(struct sbitmap *sb, int cpu, int tag)
 632 {
 633         if (likely(!sb->round_robin && tag < sb->depth))
 634                 data_race(*per_cpu_ptr(sb->alloc_hint, cpu) = tag);
 635 }
 636
 637 void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset,
 638                                 int *tags, int nr_tags)
 639 {
 640         struct sbitmap *sb = &sbq->sb;
 641         unsigned long *addr = NULL;
 642         unsigned long mask = 0;
 643         int i;
 644
 645         smp_mb__before_atomic();
 646         for (i = 0; i < nr_tags; i++) {
 647                 const int tag = tags[i] - offset;
 648                 unsigned long *this_addr;
 649
 650                 /* since we're clearing a batch, skip the deferred map */
 651                 this_addr = &sb->map[SB_NR_TO_INDEX(sb, tag)].word;
 652                 if (!addr) {
 653                         addr = this_addr;
 654                 } else if (addr != this_addr) {
 655                         atomic_long_andnot(mask, (atomic_long_t *) addr);
 656                         mask = 0;
 657                         addr = this_addr;
 658                 }
 659                 mask |= (1UL << SB_NR_TO_BIT(sb, tag));
 660         }
 661
 662         if (mask)
 663                 atomic_long_andnot(mask, (atomic_long_t *) addr);
 664
 665         smp_mb__after_atomic();
 666         sbitmap_queue_wake_up(sbq);
 667         sbitmap_update_cpu_hint(&sbq->sb, raw_smp_processor_id(),
 668                                         tags[nr_tags - 1] - offset);
 669 }
 670
 671 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 672                          unsigned int cpu)
 673 {
 674         /*
 675          * Once the clear bit is set, the bit may be allocated out.
 676          *
 677          * Orders READ/WRITE on the associated instance(such as request
 678          * of blk_mq) by this bit for avoiding race with re-allocation,
 679          * and its pair is the memory barrier implied in __sbitmap_get_word.
 680          *
 681          * One invariant is that the clear bit has to be zero when the bit
 682          * is in use.
 683          */
 684         smp_mb__before_atomic();
 685         sbitmap_deferred_clear_bit(&sbq->sb, nr);
 686
 687         /*
 688          * Pairs with the memory barrier in set_current_state() to ensure the
 689          * proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
 690          * and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
 691          * waiter. See the comment on waitqueue_active().
 692          */
 693         smp_mb__after_atomic();
 694         sbitmap_queue_wake_up(sbq);
 695         sbitmap_update_cpu_hint(&sbq->sb, cpu, nr);
 696 }
 697 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
 698
 699 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
 700 {
 701         int i, wake_index;
 702
 703         /*
 704          * Pairs with the memory barrier in set_current_state() like in
 705          * sbitmap_queue_wake_up().
 706          */
 707         smp_mb();
 708         wake_index = atomic_read(&sbq->wake_index);
 709         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 710                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 711
 712                 if (waitqueue_active(&ws->wait))
 713                         wake_up(&ws->wait);
 714
 715                 wake_index = sbq_index_inc(wake_index);
 716         }
 717 }
 718 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
 719
 720 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 721 {
 722         bool first;
 723         int i;
 724
 725         sbitmap_show(&sbq->sb, m);
 726
 727         seq_puts(m, "alloc_hint={");
 728         first = true;
 729         for_each_possible_cpu(i) {
 730                 if (!first)
 731                         seq_puts(m, ", ");
 732                 first = false;
 733                 seq_printf(m, "%u", *per_cpu_ptr(sbq->sb.alloc_hint, i));
 734         }
 735         seq_puts(m, "}\n");
 736
 737         seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
 738         seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
 739         seq_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
 740
 741         seq_puts(m, "ws={\n");
 742         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 743                 struct sbq_wait_state *ws = &sbq->ws[i];
 744
 745                 seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
 746                            atomic_read(&ws->wait_cnt),
 747                            waitqueue_active(&ws->wait) ? "active" : "inactive");
 748         }
 749         seq_puts(m, "}\n");
 750
 751         seq_printf(m, "round_robin=%d\n", sbq->sb.round_robin);
 752         seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
 753 }
 754 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
 755
 756 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
 757                             struct sbq_wait_state *ws,
 758                             struct sbq_wait *sbq_wait)
 759 {
 760         if (!sbq_wait->sbq) {
 761                 sbq_wait->sbq = sbq;
 762                 atomic_inc(&sbq->ws_active);
 763                 add_wait_queue(&ws->wait, &sbq_wait->wait);
 764         }
 765 }
 766 EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
 767
 768 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
 769 {
 770         list_del_init(&sbq_wait->wait.entry);
 771         if (sbq_wait->sbq) {
 772                 atomic_dec(&sbq_wait->sbq->ws_active);
 773                 sbq_wait->sbq = NULL;
 774         }
 775 }
 776 EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
 777
 778 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
 779                              struct sbq_wait_state *ws,
 780                              struct sbq_wait *sbq_wait, int state)
 781 {
 782         if (!sbq_wait->sbq) {
 783                 atomic_inc(&sbq->ws_active);
 784                 sbq_wait->sbq = sbq;
 785         }
 786         prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
 787 }
 788 EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
 789
 790 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 791                          struct sbq_wait *sbq_wait)
 792 {
 793         finish_wait(&ws->wait, &sbq_wait->wait);
 794         if (sbq_wait->sbq) {
 795                 atomic_dec(&sbq->ws_active);
 796                 sbq_wait->sbq = NULL;
 797         }
 798 }
 799 EXPORT_SYMBOL_GPL(sbitmap_finish_wait);