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 bool sbitmap_any_bit_clear(const struct sbitmap *sb)
 240 {
 241         unsigned int i;
 242
 243         for (i = 0; i < sb->map_nr; i++) {
 244                 const struct sbitmap_word *word = &sb->map[i];
 245                 unsigned long mask = word->word & ~word->cleared;
 246                 unsigned long ret;
 247
 248                 ret = find_first_zero_bit(&mask, word->depth);
 249                 if (ret < word->depth)
 250                         return true;
 251         }
 252         return false;
 253 }
 254 EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);
 255
 256 static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set)
 257 {
 258         unsigned int i, weight = 0;
 259
 260         for (i = 0; i < sb->map_nr; i++) {
 261                 const struct sbitmap_word *word = &sb->map[i];
 262
 263                 if (set)
 264                         weight += bitmap_weight(&word->word, word->depth);
 265                 else
 266                         weight += bitmap_weight(&word->cleared, word->depth);
 267         }
 268         return weight;
 269 }
 270
 271 static unsigned int sbitmap_weight(const struct sbitmap *sb)
 272 {
 273         return __sbitmap_weight(sb, true);
 274 }
 275
 276 static unsigned int sbitmap_cleared(const struct sbitmap *sb)
 277 {
 278         return __sbitmap_weight(sb, false);
 279 }
 280
 281 void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
 282 {
 283         seq_printf(m, "depth=%u\n", sb->depth);
 284         seq_printf(m, "busy=%u\n", sbitmap_weight(sb) - sbitmap_cleared(sb));
 285         seq_printf(m, "cleared=%u\n", sbitmap_cleared(sb));
 286         seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
 287         seq_printf(m, "map_nr=%u\n", sb->map_nr);
 288 }
 289 EXPORT_SYMBOL_GPL(sbitmap_show);
 290
 291 static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
 292 {
 293         if ((offset & 0xf) == 0) {
 294                 if (offset != 0)
 295                         seq_putc(m, '\n');
 296                 seq_printf(m, "%08x:", offset);
 297         }
 298         if ((offset & 0x1) == 0)
 299                 seq_putc(m, ' ');
 300         seq_printf(m, "%02x", byte);
 301 }
 302
 303 void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
 304 {
 305         u8 byte = 0;
 306         unsigned int byte_bits = 0;
 307         unsigned int offset = 0;
 308         int i;
 309
 310         for (i = 0; i < sb->map_nr; i++) {
 311                 unsigned long word = READ_ONCE(sb->map[i].word);
 312                 unsigned int word_bits = READ_ONCE(sb->map[i].depth);
 313
 314                 while (word_bits > 0) {
 315                         unsigned int bits = min(8 - byte_bits, word_bits);
 316
 317                         byte |= (word & (BIT(bits) - 1)) << byte_bits;
 318                         byte_bits += bits;
 319                         if (byte_bits == 8) {
 320                                 emit_byte(m, offset, byte);
 321                                 byte = 0;
 322                                 byte_bits = 0;
 323                                 offset++;
 324                         }
 325                         word >>= bits;
 326                         word_bits -= bits;
 327                 }
 328         }
 329         if (byte_bits) {
 330                 emit_byte(m, offset, byte);
 331                 offset++;
 332         }
 333         if (offset)
 334                 seq_putc(m, '\n');
 335 }
 336 EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
 337
 338 static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq,
 339                                         unsigned int depth)
 340 {
 341         unsigned int wake_batch;
 342         unsigned int shallow_depth;
 343
 344         /*
 345          * For each batch, we wake up one queue. We need to make sure that our
 346          * batch size is small enough that the full depth of the bitmap,
 347          * potentially limited by a shallow depth, is enough to wake up all of
 348          * the queues.
 349          *
 350          * Each full word of the bitmap has bits_per_word bits, and there might
 351          * be a partial word. There are depth / bits_per_word full words and
 352          * depth % bits_per_word bits left over. In bitwise arithmetic:
 353          *
 354          * bits_per_word = 1 << shift
 355          * depth / bits_per_word = depth >> shift
 356          * depth % bits_per_word = depth & ((1 << shift) - 1)
 357          *
 358          * Each word can be limited to sbq->min_shallow_depth bits.
 359          */
 360         shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth);
 361         depth = ((depth >> sbq->sb.shift) * shallow_depth +
 362                  min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth));
 363         wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1,
 364                              SBQ_WAKE_BATCH);
 365
 366         return wake_batch;
 367 }
 368
 369 int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
 370                             int shift, bool round_robin, gfp_t flags, int node)
 371 {
 372         int ret;
 373         int i;
 374
 375         ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
 376         if (ret)
 377                 return ret;
 378
 379         sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
 380         if (!sbq->alloc_hint) {
 381                 sbitmap_free(&sbq->sb);
 382                 return -ENOMEM;
 383         }
 384
 385         if (depth && !round_robin) {
 386                 for_each_possible_cpu(i)
 387                         *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
 388         }
 389
 390         sbq->min_shallow_depth = UINT_MAX;
 391         sbq->wake_batch = sbq_calc_wake_batch(sbq, depth);
 392         atomic_set(&sbq->wake_index, 0);
 393         atomic_set(&sbq->ws_active, 0);
 394
 395         sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
 396         if (!sbq->ws) {
 397                 free_percpu(sbq->alloc_hint);
 398                 sbitmap_free(&sbq->sb);
 399                 return -ENOMEM;
 400         }
 401
 402         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 403                 init_waitqueue_head(&sbq->ws[i].wait);
 404                 atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
 405         }
 406
 407         sbq->round_robin = round_robin;
 408         return 0;
 409 }
 410 EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
 411
 412 static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
 413                                             unsigned int depth)
 414 {
 415         unsigned int wake_batch = sbq_calc_wake_batch(sbq, depth);
 416         int i;
 417
 418         if (sbq->wake_batch != wake_batch) {
 419                 WRITE_ONCE(sbq->wake_batch, wake_batch);
 420                 /*
 421                  * Pairs with the memory barrier in sbitmap_queue_wake_up()
 422                  * to ensure that the batch size is updated before the wait
 423                  * counts.
 424                  */
 425                 smp_mb();
 426                 for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 427                         atomic_set(&sbq->ws[i].wait_cnt, 1);
 428         }
 429 }
 430
 431 void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 432 {
 433         sbitmap_queue_update_wake_batch(sbq, depth);
 434         sbitmap_resize(&sbq->sb, depth);
 435 }
 436 EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
 437
 438 int __sbitmap_queue_get(struct sbitmap_queue *sbq)
 439 {
 440         unsigned int hint, depth;
 441         int nr;
 442
 443         hint = this_cpu_read(*sbq->alloc_hint);
 444         depth = READ_ONCE(sbq->sb.depth);
 445         if (unlikely(hint >= depth)) {
 446                 hint = depth ? prandom_u32() % depth : 0;
 447                 this_cpu_write(*sbq->alloc_hint, hint);
 448         }
 449         nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
 450
 451         if (nr == -1) {
 452                 /* If the map is full, a hint won't do us much good. */
 453                 this_cpu_write(*sbq->alloc_hint, 0);
 454         } else if (nr == hint || unlikely(sbq->round_robin)) {
 455                 /* Only update the hint if we used it. */
 456                 hint = nr + 1;
 457                 if (hint >= depth - 1)
 458                         hint = 0;
 459                 this_cpu_write(*sbq->alloc_hint, hint);
 460         }
 461
 462         return nr;
 463 }
 464 EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
 465
 466 int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
 467                                 unsigned int shallow_depth)
 468 {
 469         unsigned int hint, depth;
 470         int nr;
 471
 472         WARN_ON_ONCE(shallow_depth < sbq->min_shallow_depth);
 473
 474         hint = this_cpu_read(*sbq->alloc_hint);
 475         depth = READ_ONCE(sbq->sb.depth);
 476         if (unlikely(hint >= depth)) {
 477                 hint = depth ? prandom_u32() % depth : 0;
 478                 this_cpu_write(*sbq->alloc_hint, hint);
 479         }
 480         nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
 481
 482         if (nr == -1) {
 483                 /* If the map is full, a hint won't do us much good. */
 484                 this_cpu_write(*sbq->alloc_hint, 0);
 485         } else if (nr == hint || unlikely(sbq->round_robin)) {
 486                 /* Only update the hint if we used it. */
 487                 hint = nr + 1;
 488                 if (hint >= depth - 1)
 489                         hint = 0;
 490                 this_cpu_write(*sbq->alloc_hint, hint);
 491         }
 492
 493         return nr;
 494 }
 495 EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
 496
 497 void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 498                                      unsigned int min_shallow_depth)
 499 {
 500         sbq->min_shallow_depth = min_shallow_depth;
 501         sbitmap_queue_update_wake_batch(sbq, sbq->sb.depth);
 502 }
 503 EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
 504
 505 static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
 506 {
 507         int i, wake_index;
 508
 509         if (!atomic_read(&sbq->ws_active))
 510                 return NULL;
 511
 512         wake_index = atomic_read(&sbq->wake_index);
 513         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 514                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 515
 516                 if (waitqueue_active(&ws->wait)) {
 517                         if (wake_index != atomic_read(&sbq->wake_index))
 518                                 atomic_set(&sbq->wake_index, wake_index);
 519                         return ws;
 520                 }
 521
 522                 wake_index = sbq_index_inc(wake_index);
 523         }
 524
 525         return NULL;
 526 }
 527
 528 static bool __sbq_wake_up(struct sbitmap_queue *sbq)
 529 {
 530         struct sbq_wait_state *ws;
 531         unsigned int wake_batch;
 532         int wait_cnt;
 533
 534         ws = sbq_wake_ptr(sbq);
 535         if (!ws)
 536                 return false;
 537
 538         wait_cnt = atomic_dec_return(&ws->wait_cnt);
 539         if (wait_cnt <= 0) {
 540                 int ret;
 541
 542                 wake_batch = READ_ONCE(sbq->wake_batch);
 543
 544                 /*
 545                  * Pairs with the memory barrier in sbitmap_queue_resize() to
 546                  * ensure that we see the batch size update before the wait
 547                  * count is reset.
 548                  */
 549                 smp_mb__before_atomic();
 550
 551                 /*
 552                  * For concurrent callers of this, the one that failed the
 553                  * atomic_cmpxhcg() race should call this function again
 554                  * to wakeup a new batch on a different 'ws'.
 555                  */
 556                 ret = atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wake_batch);
 557                 if (ret == wait_cnt) {
 558                         sbq_index_atomic_inc(&sbq->wake_index);
 559                         wake_up_nr(&ws->wait, wake_batch);
 560                         return false;
 561                 }
 562
 563                 return true;
 564         }
 565
 566         return false;
 567 }
 568
 569 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq)
 570 {
 571         while (__sbq_wake_up(sbq))
 572                 ;
 573 }
 574 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 575
 576 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 577                          unsigned int cpu)
 578 {
 579         /*
 580          * Once the clear bit is set, the bit may be allocated out.
 581          *
 582          * Orders READ/WRITE on the asssociated instance(such as request
 583          * of blk_mq) by this bit for avoiding race with re-allocation,
 584          * and its pair is the memory barrier implied in __sbitmap_get_word.
 585          *
 586          * One invariant is that the clear bit has to be zero when the bit
 587          * is in use.
 588          */
 589         smp_mb__before_atomic();
 590         sbitmap_deferred_clear_bit(&sbq->sb, nr);
 591
 592         /*
 593          * Pairs with the memory barrier in set_current_state() to ensure the
 594          * proper ordering of clear_bit_unlock()/waitqueue_active() in the waker
 595          * and test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
 596          * waiter. See the comment on waitqueue_active().
 597          */
 598         smp_mb__after_atomic();
 599         sbitmap_queue_wake_up(sbq);
 600
 601         if (likely(!sbq->round_robin && nr < sbq->sb.depth))
 602                 *per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
 603 }
 604 EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
 605
 606 void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
 607 {
 608         int i, wake_index;
 609
 610         /*
 611          * Pairs with the memory barrier in set_current_state() like in
 612          * sbitmap_queue_wake_up().
 613          */
 614         smp_mb();
 615         wake_index = atomic_read(&sbq->wake_index);
 616         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 617                 struct sbq_wait_state *ws = &sbq->ws[wake_index];
 618
 619                 if (waitqueue_active(&ws->wait))
 620                         wake_up(&ws->wait);
 621
 622                 wake_index = sbq_index_inc(wake_index);
 623         }
 624 }
 625 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
 626
 627 void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
 628 {
 629         bool first;
 630         int i;
 631
 632         sbitmap_show(&sbq->sb, m);
 633
 634         seq_puts(m, "alloc_hint={");
 635         first = true;
 636         for_each_possible_cpu(i) {
 637                 if (!first)
 638                         seq_puts(m, ", ");
 639                 first = false;
 640                 seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
 641         }
 642         seq_puts(m, "}\n");
 643
 644         seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
 645         seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
 646         seq_printf(m, "ws_active=%d\n", atomic_read(&sbq->ws_active));
 647
 648         seq_puts(m, "ws={\n");
 649         for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
 650                 struct sbq_wait_state *ws = &sbq->ws[i];
 651
 652                 seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
 653                            atomic_read(&ws->wait_cnt),
 654                            waitqueue_active(&ws->wait) ? "active" : "inactive");
 655         }
 656         seq_puts(m, "}\n");
 657
 658         seq_printf(m, "round_robin=%d\n", sbq->round_robin);
 659         seq_printf(m, "min_shallow_depth=%u\n", sbq->min_shallow_depth);
 660 }
 661 EXPORT_SYMBOL_GPL(sbitmap_queue_show);
 662
 663 void sbitmap_add_wait_queue(struct sbitmap_queue *sbq,
 664                             struct sbq_wait_state *ws,
 665                             struct sbq_wait *sbq_wait)
 666 {
 667         if (!sbq_wait->sbq) {
 668                 sbq_wait->sbq = sbq;
 669                 atomic_inc(&sbq->ws_active);
 670         }
 671         add_wait_queue(&ws->wait, &sbq_wait->wait);
 672 }
 673 EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue);
 674
 675 void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait)
 676 {
 677         list_del_init(&sbq_wait->wait.entry);
 678         if (sbq_wait->sbq) {
 679                 atomic_dec(&sbq_wait->sbq->ws_active);
 680                 sbq_wait->sbq = NULL;
 681         }
 682 }
 683 EXPORT_SYMBOL_GPL(sbitmap_del_wait_queue);
 684
 685 void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq,
 686                              struct sbq_wait_state *ws,
 687                              struct sbq_wait *sbq_wait, int state)
 688 {
 689         if (!sbq_wait->sbq) {
 690                 atomic_inc(&sbq->ws_active);
 691                 sbq_wait->sbq = sbq;
 692         }
 693         prepare_to_wait_exclusive(&ws->wait, &sbq_wait->wait, state);
 694 }
 695 EXPORT_SYMBOL_GPL(sbitmap_prepare_to_wait);
 696
 697 void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws,
 698                          struct sbq_wait *sbq_wait)
 699 {
 700         finish_wait(&ws->wait, &sbq_wait->wait);
 701         if (sbq_wait->sbq) {
 702                 atomic_dec(&sbq->ws_active);
 703                 sbq_wait->sbq = NULL;
 704         }
 705 }
 706 EXPORT_SYMBOL_GPL(sbitmap_finish_wait);