block/blk-sysfs.c

   1 /*
   2  * Functions related to sysfs handling
   3  */
   4 #include <linux/kernel.h>
   5 #include <linux/slab.h>
   6 #include <linux/module.h>
   7 #include <linux/bio.h>
   8 #include <linux/blkdev.h>
   9 #include <linux/backing-dev.h>
  10 #include <linux/blktrace_api.h>
  11 #include <linux/blk-mq.h>
  12 #include <linux/blk-cgroup.h>
  13
  14 #include "blk.h"
  15 #include "blk-mq.h"
  16
  17 struct queue_sysfs_entry {
  18         struct attribute attr;
  19         ssize_t (*show)(struct request_queue *, char *);
  20         ssize_t (*store)(struct request_queue *, const char *, size_t);
  21 };
  22
  23 static ssize_t
  24 queue_var_show(unsigned long var, char *page)
  25 {
  26         return sprintf(page, "%lu\n", var);
  27 }
  28
  29 static ssize_t
  30 queue_var_store(unsigned long *var, const char *page, size_t count)
  31 {
  32         int err;
  33         unsigned long v;
  34
  35         err = kstrtoul(page, 10, &v);
  36         if (err || v > UINT_MAX)
  37                 return -EINVAL;
  38
  39         *var = v;
  40
  41         return count;
  42 }
  43
  44 static ssize_t queue_requests_show(struct request_queue *q, char *page)
  45 {
  46         return queue_var_show(q->nr_requests, (page));
  47 }
  48
  49 static ssize_t
  50 queue_requests_store(struct request_queue *q, const char *page, size_t count)
  51 {
  52         unsigned long nr;
  53         int ret, err;
  54
  55         if (!q->request_fn && !q->mq_ops)
  56                 return -EINVAL;
  57
  58         ret = queue_var_store(&nr, page, count);
  59         if (ret < 0)
  60                 return ret;
  61
  62         if (nr < BLKDEV_MIN_RQ)
  63                 nr = BLKDEV_MIN_RQ;
  64
  65         if (q->request_fn)
  66                 err = blk_update_nr_requests(q, nr);
  67         else
  68                 err = blk_mq_update_nr_requests(q, nr);
  69
  70         if (err)
  71                 return err;
  72
  73         return ret;
  74 }
  75
  76 static ssize_t queue_ra_show(struct request_queue *q, char *page)
  77 {
  78         unsigned long ra_kb = q->backing_dev_info.ra_pages <<
  79                                         (PAGE_SHIFT - 10);
  80
  81         return queue_var_show(ra_kb, (page));
  82 }
  83
  84 static ssize_t
  85 queue_ra_store(struct request_queue *q, const char *page, size_t count)
  86 {
  87         unsigned long ra_kb;
  88         ssize_t ret = queue_var_store(&ra_kb, page, count);
  89
  90         if (ret < 0)
  91                 return ret;
  92
  93         q->backing_dev_info.ra_pages = ra_kb >> (PAGE_SHIFT - 10);
  94
  95         return ret;
  96 }
  97
  98 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
  99 {
 100         int max_sectors_kb = queue_max_sectors(q) >> 1;
 101
 102         return queue_var_show(max_sectors_kb, (page));
 103 }
 104
 105 static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
 106 {
 107         return queue_var_show(queue_max_segments(q), (page));
 108 }
 109
 110 static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
 111 {
 112         return queue_var_show(q->limits.max_integrity_segments, (page));
 113 }
 114
 115 static ssize_t queue_max_segment_size_show(struct request_queue *q, char *page)
 116 {
 117         if (blk_queue_cluster(q))
 118                 return queue_var_show(queue_max_segment_size(q), (page));
 119
 120         return queue_var_show(PAGE_SIZE, (page));
 121 }
 122
 123 static ssize_t queue_logical_block_size_show(struct request_queue *q, char *page)
 124 {
 125         return queue_var_show(queue_logical_block_size(q), page);
 126 }
 127
 128 static ssize_t queue_physical_block_size_show(struct request_queue *q, char *page)
 129 {
 130         return queue_var_show(queue_physical_block_size(q), page);
 131 }
 132
 133 static ssize_t queue_io_min_show(struct request_queue *q, char *page)
 134 {
 135         return queue_var_show(queue_io_min(q), page);
 136 }
 137
 138 static ssize_t queue_io_opt_show(struct request_queue *q, char *page)
 139 {
 140         return queue_var_show(queue_io_opt(q), page);
 141 }
 142
 143 static ssize_t queue_discard_granularity_show(struct request_queue *q, char *page)
 144 {
 145         return queue_var_show(q->limits.discard_granularity, page);
 146 }
 147
 148 static ssize_t queue_discard_max_hw_show(struct request_queue *q, char *page)
 149 {
 150
 151         return sprintf(page, "%llu\n",
 152                 (unsigned long long)q->limits.max_hw_discard_sectors << 9);
 153 }
 154
 155 static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
 156 {
 157         return sprintf(page, "%llu\n",
 158                        (unsigned long long)q->limits.max_discard_sectors << 9);
 159 }
 160
 161 static ssize_t queue_discard_max_store(struct request_queue *q,
 162                                        const char *page, size_t count)
 163 {
 164         unsigned long max_discard;
 165         ssize_t ret = queue_var_store(&max_discard, page, count);
 166
 167         if (ret < 0)
 168                 return ret;
 169
 170         if (max_discard & (q->limits.discard_granularity - 1))
 171                 return -EINVAL;
 172
 173         max_discard >>= 9;
 174         if (max_discard > UINT_MAX)
 175                 return -EINVAL;
 176
 177         if (max_discard > q->limits.max_hw_discard_sectors)
 178                 max_discard = q->limits.max_hw_discard_sectors;
 179
 180         q->limits.max_discard_sectors = max_discard;
 181         return ret;
 182 }
 183
 184 static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
 185 {
 186         return queue_var_show(queue_discard_zeroes_data(q), page);
 187 }
 188
 189 static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
 190 {
 191         return sprintf(page, "%llu\n",
 192                 (unsigned long long)q->limits.max_write_same_sectors << 9);
 193 }
 194
 195
 196 static ssize_t
 197 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
 198 {
 199         unsigned long max_sectors_kb,
 200                 max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
 201                         page_kb = 1 << (PAGE_SHIFT - 10);
 202         ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
 203
 204         if (ret < 0)
 205                 return ret;
 206
 207         max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
 208                                          q->limits.max_dev_sectors >> 1);
 209
 210         if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
 211                 return -EINVAL;
 212
 213         spin_lock_irq(q->queue_lock);
 214         q->limits.max_sectors = max_sectors_kb << 1;
 215         spin_unlock_irq(q->queue_lock);
 216
 217         return ret;
 218 }
 219
 220 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
 221 {
 222         int max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1;
 223
 224         return queue_var_show(max_hw_sectors_kb, (page));
 225 }
 226
 227 #define QUEUE_SYSFS_BIT_FNS(name, flag, neg)                            \
 228 static ssize_t                                                          \
 229 queue_show_##name(struct request_queue *q, char *page)                  \
 230 {                                                                       \
 231         int bit;                                                        \
 232         bit = test_bit(QUEUE_FLAG_##flag, &q->queue_flags);             \
 233         return queue_var_show(neg ? !bit : bit, page);                  \
 234 }                                                                       \
 235 static ssize_t                                                          \
 236 queue_store_##name(struct request_queue *q, const char *page, size_t count) \
 237 {                                                                       \
 238         unsigned long val;                                              \
 239         ssize_t ret;                                                    \
 240         ret = queue_var_store(&val, page, count);                       \
 241         if (ret < 0)                                                    \
 242                  return ret;                                            \
 243         if (neg)                                                        \
 244                 val = !val;                                             \
 245                                                                         \
 246         spin_lock_irq(q->queue_lock);                                   \
 247         if (val)                                                        \
 248                 queue_flag_set(QUEUE_FLAG_##flag, q);                   \
 249         else                                                            \
 250                 queue_flag_clear(QUEUE_FLAG_##flag, q);                 \
 251         spin_unlock_irq(q->queue_lock);                                 \
 252         return ret;                                                     \
 253 }
 254
 255 QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
 256 QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
 257 QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
 258 #undef QUEUE_SYSFS_BIT_FNS
 259
 260 static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
 261 {
 262         return queue_var_show((blk_queue_nomerges(q) << 1) |
 263                                blk_queue_noxmerges(q), page);
 264 }
 265
 266 static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
 267                                     size_t count)
 268 {
 269         unsigned long nm;
 270         ssize_t ret = queue_var_store(&nm, page, count);
 271
 272         if (ret < 0)
 273                 return ret;
 274
 275         spin_lock_irq(q->queue_lock);
 276         queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
 277         queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
 278         if (nm == 2)
 279                 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
 280         else if (nm)
 281                 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
 282         spin_unlock_irq(q->queue_lock);
 283
 284         return ret;
 285 }
 286
 287 static ssize_t queue_rq_affinity_show(struct request_queue *q, char *page)
 288 {
 289         bool set = test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags);
 290         bool force = test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags);
 291
 292         return queue_var_show(set << force, page);
 293 }
 294
 295 static ssize_t
 296 queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
 297 {
 298         ssize_t ret = -EINVAL;
 299 #ifdef CONFIG_SMP
 300         unsigned long val;
 301
 302         ret = queue_var_store(&val, page, count);
 303         if (ret < 0)
 304                 return ret;
 305
 306         spin_lock_irq(q->queue_lock);
 307         if (val == 2) {
 308                 queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
 309                 queue_flag_set(QUEUE_FLAG_SAME_FORCE, q);
 310         } else if (val == 1) {
 311                 queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
 312                 queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
 313         } else if (val == 0) {
 314                 queue_flag_clear(QUEUE_FLAG_SAME_COMP, q);
 315                 queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
 316         }
 317         spin_unlock_irq(q->queue_lock);
 318 #endif
 319         return ret;
 320 }
 321
 322 static ssize_t queue_poll_show(struct request_queue *q, char *page)
 323 {
 324         return queue_var_show(test_bit(QUEUE_FLAG_POLL, &q->queue_flags), page);
 325 }
 326
 327 static ssize_t queue_poll_store(struct request_queue *q, const char *page,
 328                                 size_t count)
 329 {
 330         unsigned long poll_on;
 331         ssize_t ret;
 332
 333         if (!q->mq_ops || !q->mq_ops->poll)
 334                 return -EINVAL;
 335
 336         ret = queue_var_store(&poll_on, page, count);
 337         if (ret < 0)
 338                 return ret;
 339
 340         spin_lock_irq(q->queue_lock);
 341         if (poll_on)
 342                 queue_flag_set(QUEUE_FLAG_POLL, q);
 343         else
 344                 queue_flag_clear(QUEUE_FLAG_POLL, q);
 345         spin_unlock_irq(q->queue_lock);
 346
 347         return ret;
 348 }
 349
 350 static ssize_t queue_wc_show(struct request_queue *q, char *page)
 351 {
 352         if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
 353                 return sprintf(page, "write back\n");
 354
 355         return sprintf(page, "write through\n");
 356 }
 357
 358 static ssize_t queue_wc_store(struct request_queue *q, const char *page,
 359                               size_t count)
 360 {
 361         int set = -1;
 362
 363         if (!strncmp(page, "write back", 10))
 364                 set = 1;
 365         else if (!strncmp(page, "write through", 13) ||
 366                  !strncmp(page, "none", 4))
 367                 set = 0;
 368
 369         if (set == -1)
 370                 return -EINVAL;
 371
 372         spin_lock_irq(q->queue_lock);
 373         if (set)
 374                 queue_flag_set(QUEUE_FLAG_WC, q);
 375         else
 376                 queue_flag_clear(QUEUE_FLAG_WC, q);
 377         spin_unlock_irq(q->queue_lock);
 378
 379         return count;
 380 }
 381
 382 static struct queue_sysfs_entry queue_requests_entry = {
 383         .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
 384         .show = queue_requests_show,
 385         .store = queue_requests_store,
 386 };
 387
 388 static struct queue_sysfs_entry queue_ra_entry = {
 389         .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
 390         .show = queue_ra_show,
 391         .store = queue_ra_store,
 392 };
 393
 394 static struct queue_sysfs_entry queue_max_sectors_entry = {
 395         .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
 396         .show = queue_max_sectors_show,
 397         .store = queue_max_sectors_store,
 398 };
 399
 400 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
 401         .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
 402         .show = queue_max_hw_sectors_show,
 403 };
 404
 405 static struct queue_sysfs_entry queue_max_segments_entry = {
 406         .attr = {.name = "max_segments", .mode = S_IRUGO },
 407         .show = queue_max_segments_show,
 408 };
 409
 410 static struct queue_sysfs_entry queue_max_integrity_segments_entry = {
 411         .attr = {.name = "max_integrity_segments", .mode = S_IRUGO },
 412         .show = queue_max_integrity_segments_show,
 413 };
 414
 415 static struct queue_sysfs_entry queue_max_segment_size_entry = {
 416         .attr = {.name = "max_segment_size", .mode = S_IRUGO },
 417         .show = queue_max_segment_size_show,
 418 };
 419
 420 static struct queue_sysfs_entry queue_iosched_entry = {
 421         .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
 422         .show = elv_iosched_show,
 423         .store = elv_iosched_store,
 424 };
 425
 426 static struct queue_sysfs_entry queue_hw_sector_size_entry = {
 427         .attr = {.name = "hw_sector_size", .mode = S_IRUGO },
 428         .show = queue_logical_block_size_show,
 429 };
 430
 431 static struct queue_sysfs_entry queue_logical_block_size_entry = {
 432         .attr = {.name = "logical_block_size", .mode = S_IRUGO },
 433         .show = queue_logical_block_size_show,
 434 };
 435
 436 static struct queue_sysfs_entry queue_physical_block_size_entry = {
 437         .attr = {.name = "physical_block_size", .mode = S_IRUGO },
 438         .show = queue_physical_block_size_show,
 439 };
 440
 441 static struct queue_sysfs_entry queue_io_min_entry = {
 442         .attr = {.name = "minimum_io_size", .mode = S_IRUGO },
 443         .show = queue_io_min_show,
 444 };
 445
 446 static struct queue_sysfs_entry queue_io_opt_entry = {
 447         .attr = {.name = "optimal_io_size", .mode = S_IRUGO },
 448         .show = queue_io_opt_show,
 449 };
 450
 451 static struct queue_sysfs_entry queue_discard_granularity_entry = {
 452         .attr = {.name = "discard_granularity", .mode = S_IRUGO },
 453         .show = queue_discard_granularity_show,
 454 };
 455
 456 static struct queue_sysfs_entry queue_discard_max_hw_entry = {
 457         .attr = {.name = "discard_max_hw_bytes", .mode = S_IRUGO },
 458         .show = queue_discard_max_hw_show,
 459 };
 460
 461 static struct queue_sysfs_entry queue_discard_max_entry = {
 462         .attr = {.name = "discard_max_bytes", .mode = S_IRUGO | S_IWUSR },
 463         .show = queue_discard_max_show,
 464         .store = queue_discard_max_store,
 465 };
 466
 467 static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
 468         .attr = {.name = "discard_zeroes_data", .mode = S_IRUGO },
 469         .show = queue_discard_zeroes_data_show,
 470 };
 471
 472 static struct queue_sysfs_entry queue_write_same_max_entry = {
 473         .attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
 474         .show = queue_write_same_max_show,
 475 };
 476
 477 static struct queue_sysfs_entry queue_nonrot_entry = {
 478         .attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
 479         .show = queue_show_nonrot,
 480         .store = queue_store_nonrot,
 481 };
 482
 483 static struct queue_sysfs_entry queue_nomerges_entry = {
 484         .attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
 485         .show = queue_nomerges_show,
 486         .store = queue_nomerges_store,
 487 };
 488
 489 static struct queue_sysfs_entry queue_rq_affinity_entry = {
 490         .attr = {.name = "rq_affinity", .mode = S_IRUGO | S_IWUSR },
 491         .show = queue_rq_affinity_show,
 492         .store = queue_rq_affinity_store,
 493 };
 494
 495 static struct queue_sysfs_entry queue_iostats_entry = {
 496         .attr = {.name = "iostats", .mode = S_IRUGO | S_IWUSR },
 497         .show = queue_show_iostats,
 498         .store = queue_store_iostats,
 499 };
 500
 501 static struct queue_sysfs_entry queue_random_entry = {
 502         .attr = {.name = "add_random", .mode = S_IRUGO | S_IWUSR },
 503         .show = queue_show_random,
 504         .store = queue_store_random,
 505 };
 506
 507 static struct queue_sysfs_entry queue_poll_entry = {
 508         .attr = {.name = "io_poll", .mode = S_IRUGO | S_IWUSR },
 509         .show = queue_poll_show,
 510         .store = queue_poll_store,
 511 };
 512
 513 static struct queue_sysfs_entry queue_wc_entry = {
 514         .attr = {.name = "write_cache", .mode = S_IRUGO | S_IWUSR },
 515         .show = queue_wc_show,
 516         .store = queue_wc_store,
 517 };
 518
 519 static struct attribute *default_attrs[] = {
 520         &queue_requests_entry.attr,
 521         &queue_ra_entry.attr,
 522         &queue_max_hw_sectors_entry.attr,
 523         &queue_max_sectors_entry.attr,
 524         &queue_max_segments_entry.attr,
 525         &queue_max_integrity_segments_entry.attr,
 526         &queue_max_segment_size_entry.attr,
 527         &queue_iosched_entry.attr,
 528         &queue_hw_sector_size_entry.attr,
 529         &queue_logical_block_size_entry.attr,
 530         &queue_physical_block_size_entry.attr,
 531         &queue_io_min_entry.attr,
 532         &queue_io_opt_entry.attr,
 533         &queue_discard_granularity_entry.attr,
 534         &queue_discard_max_entry.attr,
 535         &queue_discard_max_hw_entry.attr,
 536         &queue_discard_zeroes_data_entry.attr,
 537         &queue_write_same_max_entry.attr,
 538         &queue_nonrot_entry.attr,
 539         &queue_nomerges_entry.attr,
 540         &queue_rq_affinity_entry.attr,
 541         &queue_iostats_entry.attr,
 542         &queue_random_entry.attr,
 543         &queue_poll_entry.attr,
 544         &queue_wc_entry.attr,
 545         NULL,
 546 };
 547
 548 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
 549
 550 static ssize_t
 551 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 552 {
 553         struct queue_sysfs_entry *entry = to_queue(attr);
 554         struct request_queue *q =
 555                 container_of(kobj, struct request_queue, kobj);
 556         ssize_t res;
 557
 558         if (!entry->show)
 559                 return -EIO;
 560         mutex_lock(&q->sysfs_lock);
 561         if (blk_queue_dying(q)) {
 562                 mutex_unlock(&q->sysfs_lock);
 563                 return -ENOENT;
 564         }
 565         res = entry->show(q, page);
 566         mutex_unlock(&q->sysfs_lock);
 567         return res;
 568 }
 569
 570 static ssize_t
 571 queue_attr_store(struct kobject *kobj, struct attribute *attr,
 572                     const char *page, size_t length)
 573 {
 574         struct queue_sysfs_entry *entry = to_queue(attr);
 575         struct request_queue *q;
 576         ssize_t res;
 577
 578         if (!entry->store)
 579                 return -EIO;
 580
 581         q = container_of(kobj, struct request_queue, kobj);
 582         mutex_lock(&q->sysfs_lock);
 583         if (blk_queue_dying(q)) {
 584                 mutex_unlock(&q->sysfs_lock);
 585                 return -ENOENT;
 586         }
 587         res = entry->store(q, page, length);
 588         mutex_unlock(&q->sysfs_lock);
 589         return res;
 590 }
 591
 592 static void blk_free_queue_rcu(struct rcu_head *rcu_head)
 593 {
 594         struct request_queue *q = container_of(rcu_head, struct request_queue,
 595                                                rcu_head);
 596         kmem_cache_free(blk_requestq_cachep, q);
 597 }
 598
 599 /**
 600  * blk_release_queue: - release a &struct request_queue when it is no longer needed
 601  * @kobj:    the kobj belonging to the request queue to be released
 602  *
 603  * Description:
 604  *     blk_release_queue is the pair to blk_init_queue() or
 605  *     blk_queue_make_request().  It should be called when a request queue is
 606  *     being released; typically when a block device is being de-registered.
 607  *     Currently, its primary task it to free all the &struct request
 608  *     structures that were allocated to the queue and the queue itself.
 609  *
 610  * Note:
 611  *     The low level driver must have finished any outstanding requests first
 612  *     via blk_cleanup_queue().
 613  **/
 614 static void blk_release_queue(struct kobject *kobj)
 615 {
 616         struct request_queue *q =
 617                 container_of(kobj, struct request_queue, kobj);
 618
 619         bdi_exit(&q->backing_dev_info);
 620         blkcg_exit_queue(q);
 621
 622         if (q->elevator) {
 623                 spin_lock_irq(q->queue_lock);
 624                 ioc_clear_queue(q);
 625                 spin_unlock_irq(q->queue_lock);
 626                 elevator_exit(q->elevator);
 627         }
 628
 629         blk_exit_rl(&q->root_rl);
 630
 631         if (q->queue_tags)
 632                 __blk_queue_free_tags(q);
 633
 634         if (!q->mq_ops)
 635                 blk_free_flush_queue(q->fq);
 636         else
 637                 blk_mq_release(q);
 638
 639         blk_trace_shutdown(q);
 640
 641         if (q->bio_split)
 642                 bioset_free(q->bio_split);
 643
 644         ida_simple_remove(&blk_queue_ida, q->id);
 645         call_rcu(&q->rcu_head, blk_free_queue_rcu);
 646 }
 647
 648 static const struct sysfs_ops queue_sysfs_ops = {
 649         .show   = queue_attr_show,
 650         .store  = queue_attr_store,
 651 };
 652
 653 struct kobj_type blk_queue_ktype = {
 654         .sysfs_ops      = &queue_sysfs_ops,
 655         .default_attrs  = default_attrs,
 656         .release        = blk_release_queue,
 657 };
 658
 659 int blk_register_queue(struct gendisk *disk)
 660 {
 661         int ret;
 662         struct device *dev = disk_to_dev(disk);
 663         struct request_queue *q = disk->queue;
 664
 665         if (WARN_ON(!q))
 666                 return -ENXIO;
 667
 668         /*
 669          * SCSI probing may synchronously create and destroy a lot of
 670          * request_queues for non-existent devices.  Shutting down a fully
 671          * functional queue takes measureable wallclock time as RCU grace
 672          * periods are involved.  To avoid excessive latency in these
 673          * cases, a request_queue starts out in a degraded mode which is
 674          * faster to shut down and is made fully functional here as
 675          * request_queues for non-existent devices never get registered.
 676          */
 677         if (!blk_queue_init_done(q)) {
 678                 queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
 679                 percpu_ref_switch_to_percpu(&q->q_usage_counter);
 680                 blk_queue_bypass_end(q);
 681         }
 682
 683         ret = blk_trace_init_sysfs(dev);
 684         if (ret)
 685                 return ret;
 686
 687         ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
 688         if (ret < 0) {
 689                 blk_trace_remove_sysfs(dev);
 690                 return ret;
 691         }
 692
 693         kobject_uevent(&q->kobj, KOBJ_ADD);
 694
 695         if (q->mq_ops)
 696                 blk_mq_register_disk(disk);
 697
 698         if (!q->request_fn)
 699                 return 0;
 700
 701         ret = elv_register_queue(q);
 702         if (ret) {
 703                 kobject_uevent(&q->kobj, KOBJ_REMOVE);
 704                 kobject_del(&q->kobj);
 705                 blk_trace_remove_sysfs(dev);
 706                 kobject_put(&dev->kobj);
 707                 return ret;
 708         }
 709
 710         return 0;
 711 }
 712
 713 void blk_unregister_queue(struct gendisk *disk)
 714 {
 715         struct request_queue *q = disk->queue;
 716
 717         if (WARN_ON(!q))
 718                 return;
 719
 720         if (q->mq_ops)
 721                 blk_mq_unregister_disk(disk);
 722
 723         if (q->request_fn)
 724                 elv_unregister_queue(q);
 725
 726         kobject_uevent(&q->kobj, KOBJ_REMOVE);
 727         kobject_del(&q->kobj);
 728         blk_trace_remove_sysfs(disk_to_dev(disk));
 729         kobject_put(&disk_to_dev(disk)->kobj);
 730 }