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 /*
  13  * See if we have deferred clears that we can batch move
  14  */
  15 static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
  16 {
  17         unsigned long mask, val;
  18         bool ret = false;
  19         unsigned long flags;
  20
  21         spin_lock_irqsave(&sb->map[index].swap_lock, flags);
  22
  23         if (!sb->map[index].cleared)
  24                 goto out_unlock;
  25
  26         /*
  27          * First get a stable cleared mask, setting the old mask to 0.
  28          */
  29         mask = xchg(&sb->map[index].cleared, 0);
  30
  31         /*
  32          * Now clear the masked bits in our free word
  33          */
  34         do {
  35                 val = sb->map[index].word;
  36         } while (cmpxchg(&sb->map[index].word, val, val & ~mask) != val);
  37
  38         ret = true;
  39 out_unlock:
  40         spin_unlock_irqrestore(&sb->map[index].swap_lock, flags);
  41         return ret;
  42 }
  43
  44 int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
  45                       gfp_t flags, int node)
  46 {
  47         unsigned int bits_per_word;
  48         unsigned int i;
  49
  50         if (shift < 0) {
  51                 shift = ilog2(BITS_PER_LONG);
  52                 /*
  53                  * If the bitmap is small, shrink the number of bits per word so
  54                  * we spread over a few cachelines, at least. If less than 4
  55                  * bits, just forget about it, it's not going to work optimally
  56                  * anyway.
  57                  */
  58                 if (depth >= 4) {
  59                         while ((4U << shift) > depth)
  60                                 shift--;
  61                 }
  62         }
  63         bits_per_word = 1U << shift;
  64         if (bits_per_word > BITS_PER_LONG)
  65                 return -EINVAL;
  66
  67         sb->shift = shift;
  68         sb->depth = depth;
  69         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
  70
  71         if (depth == 0) {
  72                 sb->map = NULL;
  73                 return 0;
  74         }
  75
  76         sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
  77         if (!sb->map)
  78                 return -ENOMEM;
  79
  80         for (i = 0; i < sb->map_nr; i++) {
  81                 sb->map[i].depth = min(depth, bits_per_word);
  82                 depth -= sb->map[i].depth;
  83                 spin_lock_init(&sb->map[i].swap_lock);
  84         }
  85         return 0;
  86 }
  87 EXPORT_SYMBOL_GPL(sbitmap_init_node);
  88
  89 void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
  90 {
  91         unsigned int bits_per_word = 1U << sb->shift;
  92         unsigned int i;
  93
  94         for (i = 0; i < sb->map_nr; i++)
  95                 sbitmap_deferred_clear(sb, i);
  96
  97         sb->depth = depth;
  98         sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
  99
 100         for (i = 0; i < sb->map_nr; i++) {
 101                 sb->map[i].depth = min(depth, bits_per_word);
 102                 depth -= sb->map[i].depth;
 103         }
 104 }
 105 EXPORT_SYMBOL_GPL(sbitmap_resize);
 106
 107 static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
 108                               unsigned int hint, bool wrap)
 109 {
 110         unsigned int orig_hint = hint;
 111         int nr;
 112
 113         while (1) {
 114                 nr = find_next_zero_bit(word, depth, hint);
 115                 if (unlikely(nr >= depth)) {
 116                         /*
 117                          * We started with an offset, and we didn't reset the
 118                          * offset to 0 in a failure case, so start from 0 to
 119                          * exhaust the map.
 120                          */
 121                         if (orig_hint && hint && wrap) {
 122                                 hint = orig_hint = 0;
 123                                 continue;
 124                         }
 125                         return -1;
 126                 }
 127
 128                 if (!test_and_set_bit_lock(nr, word))
 129                         break;
 130
 131                 hint = nr + 1;
 132                 if (hint >= depth - 1)
 133                         hint = 0;
 134         }
 135
 136         return nr;
 137 }
 138
 139 static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index,
 140                                      unsigned int alloc_hint, bool round_robin)
 141 {
 142         int nr;
 143
 144         do {
 145                 nr = __sbitmap_get_word(&sb->map[index].word,
 146                                         sb->map[index].depth, alloc_hint,
 147                                         !round_robin);
 148                 if (nr != -1)
 149                         break;
 150                 if (!sbitmap_deferred_clear(sb, index))
 151                         break;
 152         } while (1);
 153
 154         return nr;
 155 }
 156
 157 int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
 158 {
 159         unsigned int i, index;
 160         int nr = -1;
 161
 162         index = SB_NR_TO_INDEX(sb, alloc_hint);
 163
 164         /*
 165          * Unless we're doing round robin tag allocation, just use the
 166          * alloc_hint to find the right word index. No point in looping
 167          * twice in find_next_zero_bit() for that case.
 168          */
 169         if (round_robin)
 170                 alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 171         else
 172                 alloc_hint = 0;
 173
 174         for (i = 0; i < sb->map_nr; i++) {
 175                 nr = sbitmap_find_bit_in_index(sb, index, alloc_hint,
 176                                                 round_robin);
 177                 if (nr != -1) {
 178                         nr += index << sb->shift;
 179                         break;
 180                 }
 181
 182                 /* Jump to next index. */
 183                 alloc_hint = 0;
 184                 if (++index >= sb->map_nr)
 185                         index = 0;
 186         }
 187
 188         return nr;
 189 }
 190 EXPORT_SYMBOL_GPL(sbitmap_get);
 191
 192 int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
 193                         unsigned long shallow_depth)
 194 {
 195         unsigned int i, index;
 196         int nr = -1;
 197
 198         index = SB_NR_TO_INDEX(sb, alloc_hint);
 199
 200         for (i = 0; i < sb->map_nr; i++) {
 201 again:
 202                 nr = __sbitmap_get_word(&sb->map[index].word,
 203                                         min(sb->map[index].depth, shallow_depth),
 204                                         SB_NR_TO_BIT(sb, alloc_hint), true);
 205                 if (nr != -1) {
 206                         nr += index << sb->shift;
 207                         break;
 208                 }
 209
 210                 if (sbitmap_deferred_clear(sb, index))
 211                         goto again;
 212
 213                 /* Jump to next index. */
 214                 index++;
 215                 alloc_hint = index << sb->shift;
 216
 217                 if (index >= sb->map_nr) {
 218                         index = 0;
 219                         alloc_hint = 0;
 220                 }
 221         }
 222
 223         return nr;
 224 }
 225 EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
 226
 227 bool sbitmap_any_bit_set(const struct sbitmap *sb)
 228 {
 229         unsigned int i;
 230
 231         for (i = 0; i < sb->map_nr; i++) {
 232                 if (sb->map[i].word & ~sb->map[i].cleared)
 233                         return true;
 234         }
 235         return false;
 236 }
 237 EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
 238
 239 static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
 240 {
 241         unsigned int i, weight = 0;
 242
 243         for (i = 0; i < sb->map_nr; i++) {
 244                 const struct sbitmap_word *word = &sb->map[i];
 245
 246                 if (set)
 247                         weight += bitmap_weight(&word->word, word->depth);
 248                 else
 249                         weight += bitmap_weight(&word->cleared, word->depth);
 250         }
 251         return weight;
 252 }
 253
 254 static unsigned int sbitmap_weight(const struct sbitmap *sb)
 255 {
 256         return __sbitmap_weight(sb, true);
 257 }
 258
 259 static unsigned int sbitmap_cleared(const struct sbitmap *sb)
 260 {
 261         return __sbitmap_weight(sb, false);
 262 }
 263
 264 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 265 {
 266         seq_printf(m, "depth=%u\n", sb->depth);
 267         seq_printf(m, "busy=%u\n", sbitmap_weight(sb) - sbitmap_cleared(sb));
 268         seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
 269         seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 270         seq_printf(m, "map_nr=%u\n", sb->map_nr);
 271 }
 272 EXPORT_SYMBOL_GPL(sbitmap_show);
 273
 274 static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
 275 {
 276         if ((offset & 0xf) == 0) {
 277                 if (offset != 0)
 278                         seq_putc(m, '\n');
 279                 seq_printf(m, "%08x:", offset);
 280         }
 281         if ((offset & 0x1) == 0)
 282                 seq_putc(m, ' ');
 283         seq_printf(m, "%02x", byte);
 284 }
 285
 286 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
 287 {
 288         u8 byte = 0;
 289         unsigned int byte_bits = 0;
 290         unsigned int offset = 0;
 291         int i;
 292
 293         for (i = 0; i < sb->map_nr; i++) {
 294                 unsigned long word = READ_ONCE(sb->map[i].word);
 295                 unsigned long cleared = READ_ONCE(sb->map[i].cleared);
 296                 unsigned int word_bits = READ_ONCE(sb->map[i].depth);
 297
 298                 word &= ~cleared;
 299
 300                 while (word_bits > 0) {
 301                         unsigned int bits = min(8 - byte_bits, word_bits);
 302
 303                         byte |= (word & (BIT(bits) - 1)) << byte_bits;
 304                         byte_bits += bits;
 305                         if (byte_bits == 8) {
 306                                 emit_byte(m, offset, byte);
 307                                 byte = 0;
 308                                 byte_bits = 0;
 309                                 offset++;
 310                         }
 311                         word >>= bits;
 312                         word_bits -= bits;
 313                 }
 314         }
 315         if (byte_bits) {
 316                 emit_byte(m, offset, byte);
 317                 offset++;
 318         }
 319         if (offset)
 320                 seq_putc(m, '\n');
 321 }
 322 EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
 323
 324 static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq,
 325                                         unsigned int depth)
 326 {
 327         unsigned int wake_batch;
 328         unsigned int shallow_depth;
 329
 330         /*
 331          * For each batch, we wake up one queue. We need to make sure that our
 332          * batch size is small enough that the full depth of the bitmap,
 333          * potentially limited by a shallow depth, is enough to wake up all of
 334          * the queues.
 335          *
 336          * Each full word of the bitmap has bits_per_word bits, and there might
 337          * be a partial word. There are depth / bits_per_word full words and
 338          * depth % bits_per_word bits left over. In bitwise arithmetic:
 339          *
 340          * bits_per_word = 1 << shift
 341          * depth / bits_per_word = depth >> shift
 342          * depth % bits_per_word = depth & ((1 << shift) - 1)
 343          *
 344          * Each word can be limited to sbq->min_shallow_depth bits.
 345          */
 346         shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
 347         depth = ((depth >> sbq->sb.shift) * shallow_depth +
 348                  min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
 349         wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
 350                              SBQ_WAKE_BATCH);
 351
 352         return wake_batch;
 353 }
 354
 355 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 356                             int shift, bool round_robin, gfp_t flags, int node)
 357 {
 358         int ret;
 359         int i;
 360
 361         ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
 362         if (ret)
 363                 return ret;
 364
 365         sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
 366         if (!sbq->alloc_hint) {
 367                 sbitmap_free(&sbq->sb);
 368                 return -ENOMEM;
 369         }
 370
 371         if (depth && !round_robin) {
 372                 for_each_possible_cpu(i)
 373                         *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
 374         }
 375
 376         sbq->min_shallow_depth = UINT_MAX;
 377         sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 378         atomic_set(&sbq->wake_index, 0);
 379         atomic_set(&sbq->ws_active, 0);
 380
 381         sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 382         if (!sbq->ws) {
 383                 free_percpu(sbq->alloc_hint);
 384                 sbitmap_free(&sbq->sb);
 385                 return -ENOMEM;
 386         }
 387
 388         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 389                 init_waitqueue_head(&sbq->ws[i].wait);
 390                 atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
 391         }
 392
 393         sbq->round_robin = round_robin;
 394         return 0;
 395 }
 396 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
 397
 398 static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
 399                                             unsigned int depth)
 400 {
 401         unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth);
 402         int i;
 403
 404         if (sbq->wake_batch != wake_batch) {
 405                 WRITE_ONCE(sbq->wake_batch, wake_batch);
 406                 /*
 407                  * Pairs with the memory barrier in sbitmap_queue_wake_up()
 408                  * to ensure that the batch size is updated before the wait
 409                  * counts.
 410                  */
 411                 smp_mb();
 412                 for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 413                         atomic_set(&sbq->ws[i].wait_cnt, 1);
 414         }
 415 }
 416
 417 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 418 {
 419         sbitmap_queue_update_wake_batch(sbq, depth);
 420         sbitmap_resize(&sbq->sb, depth);
 421 }
 422 EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
 423
 424 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 425 {
 426         unsigned int hint, depth;
 427         int nr;
 428
 429         hint = this_cpu_read(*sbq->alloc_hint);
 430         depth = READ_ONCE(sbq->sb.depth);
 431         if (unlikely(hint >= depth)) {
 432                 hint = depth ? prandom_u32() % depth : 0;
 433                 this_cpu_write(*sbq->alloc_hint, hint);
 434         }
 435         nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
 436
 437         if (nr == -1) {
 438                 /* If the map is full, a hint won't do us much good. */
 439                 this_cpu_write(*sbq->alloc_hint, 0);
 440         } else if (nr == hint || unlikely(sbq->round_robin)) {
 441                 /* Only update the hint if we used it. */
 442                 hint = nr + 1;
 443                 if (hint >= depth - 1)
 444                         hint = 0;
 445                 this_cpu_write(*sbq->alloc_hint, hint);
 446         }
 447
 448         return nr;
 449 }
 450 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
 451
 452 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 453                                 unsigned int shallow_depth)
 454 {
 455         unsigned int hint, depth;
 456         int nr;
 457
 458         WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 459
 460         hint = this_cpu_read(*sbq->alloc_hint);
 461         depth = READ_ONCE(sbq->sb.depth);
 462         if (unlikely(hint >= depth)) {
 463                 hint = depth ? prandom_u32() % depth : 0;
 464                 this_cpu_write(*sbq->alloc_hint, hint);
 465         }
 466         nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
 467
 468         if (nr == -1) {
 469                 /* If the map is full, a hint won't do us much good. */
 470                 this_cpu_write(*sbq->alloc_hint, 0);
 471         } else if (nr == hint || unlikely(sbq->round_robin)) {
 472                 /* Only update the hint if we used it. */
 473                 hint = nr + 1;
 474                 if (hint >= depth - 1)
 475                         hint = 0;
 476                 this_cpu_write(*sbq->alloc_hint, hint);
 477         }
 478
 479         return nr;
 480 }
 481 EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
 482
 483 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 484                                      unsigned int min_shallow_depth)
 485 {
 486         sbq->min_shallow_depth = min_shallow_depth;
 487         sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
 488 }
 489 EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
 490
 491 static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
 492 {
 493         int i, wake_index;
 494
 495         if (!atomic_read(&sbq->ws_active))
 496                 return NULL;
 497
 498         wake_index = atomic_read(&sbq->wake_index);
 499         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 500                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 501
 502                 if (waitqueue_active(&ws->wait)) {
 503                         if (wake_index != atomic_read(&sbq->wake_index))
 504                                 atomic_set(&sbq->wake_index, wake_index);
 505                         return ws;
 506                 }
 507
 508                 wake_index = sbq_index_inc(wake_index);
 509         }
 510
 511         return NULL;
 512 }
 513
 514 static bool __sbq_wake_up(struct sbitmap_queue *sbq)
 515 {
 516         struct sbq_wait_state *ws;
 517         unsigned int wake_batch;
 518         int wait_cnt;
 519
 520         ws = sbq_wake_ptr(sbq);
 521         if (!ws)
 522                 return false;
 523
 524         wait_cnt = atomic_dec_return(&ws->wait_cnt);
 525         if (wait_cnt <= 0) {
 526                 int ret;
 527
 528                 wake_batch = READ_ONCE(sbq->wake_batch);
 529
 530                 /*
 531                  * Pairs with the memory barrier in sbitmap_queue_resize() to
 532                  * ensure that we see the batch size update before the wait
 533                  * count is reset.
 534                  */
 535                 smp_mb__before_atomic();
 536
 537                 /*
 538                  * For concurrent callers of this, the one that failed the
 539                  * atomic_cmpxhcg() race should call this function again
 540                  * to wakeup a new batch on a different 'ws'.
 541                  */
 542                 ret = atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wake_batch);
 543                 if (ret == wait_cnt) {
 544                         sbq_index_atomic_inc(&sbq->wake_index);
 545                         wake_up_nr(&ws->wait, wake_batch);
 546                         return false;
 547                 }
 548
 549                 return true;
 550         }
 551
 552         return false;
 553 }
 554
 555 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
 556 {
 557         while (__sbq_wake_up(sbq))
 558                 ;
 559 }
 560 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 561
 562 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 563                          unsigned int cpu)
 564 {
 565         /*
 566          * Once the clear bit is set, the bit may be allocated out.
 567          *
 568          * Orders READ/WRITE on the asssociated instance(such as request
 569          * of blk_mq) by this bit for avoiding race with re-allocation,
 570          * and its pair is the memory barrier implied in __sbitmap_get_word.
 571          *
 572          * One invariant is that the clear bit has to be zero when the bit
 573          * is in use.
 574          */
 575         smp_mb__before_atomic();
 576         sbitmap_deferred_clear_bit(&sbq->sb, nr);
 577
 578         /*
 579          * Pairs with the memory barrier in set_current_state() to ensure the
 580          * proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
 581          * and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
 582          * waiter. See the comment on waitqueue_active().
 583          */
 584         smp_mb__after_atomic();
 585         sbitmap_queue_wake_up(sbq);
 586
 587         if (likely(!sbq->round_robin && nr < sbq->sb.depth))
 588                 *per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
 589 }
 590 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
 591
 592 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
 593 {
 594         int i, wake_index;
 595
 596         /*
 597          * Pairs with the memory barrier in set_current_state() like in
 598          * sbitmap_queue_wake_up().
 599          */
 600         smp_mb();
 601         wake_index = atomic_read(&sbq->wake_index);
 602         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 603                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 604
 605                 if (waitqueue_active(&ws->wait))
 606                         wake_up(&ws->wait);
 607
 608                 wake_index = sbq_index_inc(wake_index);
 609         }
 610 }
 611 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
 612
 613 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 614 {
 615         bool first;
 616         int i;
 617
 618         sbitmap_show(&sbq->sb, m);
 619
 620         seq_puts(m, "alloc_hint={");
 621         first = true;
 622         for_each_possible_cpu(i) {
 623                 if (!first)
 624                         seq_puts(m, ", ");
 625                 first = false;
 626                 seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
 627         }
 628         seq_puts(m, "}\n");
 629
 630         seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
 631         seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
 632         seq_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
 633
 634         seq_puts(m, "ws={\n");
 635         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 636                 struct sbq_wait_state *ws = &sbq->ws[i];
 637
 638                 seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
 639                            atomic_read(&ws->wait_cnt),
 640                            waitqueue_active(&ws->wait) ? "active" : "inactive");
 641         }
 642         seq_puts(m, "}\n");
 643
 644         seq_printf(m, "round_robin=%d\n", sbq->round_robin);
 645         seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
 646 }
 647 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
 648
 649 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
 650                             struct sbq_wait_state *ws,
 651                             struct sbq_wait *sbq_wait)
 652 {
 653         if (!sbq_wait->sbq) {
 654                 sbq_wait->sbq = sbq;
 655                 atomic_inc(&sbq->ws_active);
 656                 add_wait_queue(&ws->wait, &sbq_wait->wait);
 657         }
 658 }
 659 EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
 660
 661 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
 662 {
 663         list_del_init(&sbq_wait->wait.entry);
 664         if (sbq_wait->sbq) {
 665                 atomic_dec(&sbq_wait->sbq->ws_active);
 666                 sbq_wait->sbq = NULL;
 667         }
 668 }
 669 EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
 670
 671 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
 672                              struct sbq_wait_state *ws,
 673                              struct sbq_wait *sbq_wait, int state)
 674 {
 675         if (!sbq_wait->sbq) {
 676                 atomic_inc(&sbq->ws_active);
 677                 sbq_wait->sbq = sbq;
 678         }
 679         prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
 680 }
 681 EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
 682
 683 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 684                          struct sbq_wait *sbq_wait)
 685 {
 686         finish_wait(&ws->wait, &sbq_wait->wait);
 687         if (sbq_wait->sbq) {
 688                 atomic_dec(&sbq->ws_active);
 689                 sbq_wait->sbq = NULL;
 690         }
 691 }
 692 EXPORT_SYMBOL_GPL(sbitmap_finish_wait);