block/blk-mq-tag.c

   1 /*
   2  * Tag allocation using scalable bitmaps. Uses active queue tracking to support
   3  * fairer distribution of tags between multiple submitters when a shared tag map
   4  * is used.
   5  *
   6  * Copyright (C) 2013-2014 Jens Axboe
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10
  11 #include <linux/blk-mq.h>
  12 #include "blk.h"
  13 #include "blk-mq.h"
  14 #include "blk-mq-tag.h"
  15
  16 bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
  17 {
  18         if (!tags)
  19                 return true;
  20
  21         return sbitmap_any_bit_clear(&tags->bitmap_tags.sb);
  22 }
  23
  24 /*
  25  * If a previously inactive queue goes active, bump the active user count.
  26  */
  27 bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
  28 {
  29         if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
  30             !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  31                 atomic_inc(&hctx->tags->active_queues);
  32
  33         return true;
  34 }
  35
  36 /*
  37  * Wakeup all potentially sleeping on tags
  38  */
  39 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
  40 {
  41         sbitmap_queue_wake_all(&tags->bitmap_tags);
  42         if (include_reserve)
  43                 sbitmap_queue_wake_all(&tags->breserved_tags);
  44 }
  45
  46 /*
  47  * If a previously busy queue goes inactive, potential waiters could now
  48  * be allowed to queue. Wake them up and check.
  49  */
  50 void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
  51 {
  52         struct blk_mq_tags *tags = hctx->tags;
  53
  54         if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  55                 return;
  56
  57         atomic_dec(&tags->active_queues);
  58
  59         blk_mq_tag_wakeup_all(tags, false);
  60 }
  61
  62 /*
  63  * For shared tag users, we track the number of currently active users
  64  * and attempt to provide a fair share of the tag depth for each of them.
  65  */
  66 static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
  67                                   struct sbitmap_queue *bt)
  68 {
  69         unsigned int depth, users;
  70
  71         if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
  72                 return true;
  73         if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  74                 return true;
  75
  76         /*
  77          * Don't try dividing an ant
  78          */
  79         if (bt->sb.depth == 1)
  80                 return true;
  81
  82         users = atomic_read(&hctx->tags->active_queues);
  83         if (!users)
  84                 return true;
  85
  86         /*
  87          * Allow at least some tags
  88          */
  89         depth = max((bt->sb.depth + users - 1) / users, 4U);
  90         return atomic_read(&hctx->nr_active) < depth;
  91 }
  92
  93 static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt)
  94 {
  95         if (!hctx_may_queue(hctx, bt))
  96                 return -1;
  97         return __sbitmap_queue_get(bt);
  98 }
  99
 100 static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt,
 101                   struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags)
 102 {
 103         struct sbq_wait_state *ws;
 104         DEFINE_WAIT(wait);
 105         int tag;
 106
 107         tag = __bt_get(hctx, bt);
 108         if (tag != -1)
 109                 return tag;
 110
 111         if (data->flags & BLK_MQ_REQ_NOWAIT)
 112                 return -1;
 113
 114         ws = bt_wait_ptr(bt, hctx);
 115         do {
 116                 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 117
 118                 tag = __bt_get(hctx, bt);
 119                 if (tag != -1)
 120                         break;
 121
 122                 /*
 123                  * We're out of tags on this hardware queue, kick any
 124                  * pending IO submits before going to sleep waiting for
 125                  * some to complete. Note that hctx can be NULL here for
 126                  * reserved tag allocation.
 127                  */
 128                 if (hctx)
 129                         blk_mq_run_hw_queue(hctx, false);
 130
 131                 /*
 132                  * Retry tag allocation after running the hardware queue,
 133                  * as running the queue may also have found completions.
 134                  */
 135                 tag = __bt_get(hctx, bt);
 136                 if (tag != -1)
 137                         break;
 138
 139                 blk_mq_put_ctx(data->ctx);
 140
 141                 io_schedule();
 142
 143                 data->ctx = blk_mq_get_ctx(data->q);
 144                 data->hctx = data->q->mq_ops->map_queue(data->q,
 145                                 data->ctx->cpu);
 146                 if (data->flags & BLK_MQ_REQ_RESERVED) {
 147                         bt = &data->hctx->tags->breserved_tags;
 148                 } else {
 149                         hctx = data->hctx;
 150                         bt = &hctx->tags->bitmap_tags;
 151                 }
 152                 finish_wait(&ws->wait, &wait);
 153                 ws = bt_wait_ptr(bt, hctx);
 154         } while (1);
 155
 156         finish_wait(&ws->wait, &wait);
 157         return tag;
 158 }
 159
 160 static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
 161 {
 162         int tag;
 163
 164         tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
 165                      data->hctx->tags);
 166         if (tag >= 0)
 167                 return tag + data->hctx->tags->nr_reserved_tags;
 168
 169         return BLK_MQ_TAG_FAIL;
 170 }
 171
 172 static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
 173 {
 174         int tag;
 175
 176         if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
 177                 WARN_ON_ONCE(1);
 178                 return BLK_MQ_TAG_FAIL;
 179         }
 180
 181         tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL,
 182                      data->hctx->tags);
 183         if (tag < 0)
 184                 return BLK_MQ_TAG_FAIL;
 185
 186         return tag;
 187 }
 188
 189 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 190 {
 191         if (data->flags & BLK_MQ_REQ_RESERVED)
 192                 return __blk_mq_get_reserved_tag(data);
 193         return __blk_mq_get_tag(data);
 194 }
 195
 196 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
 197                     unsigned int tag)
 198 {
 199         struct blk_mq_tags *tags = hctx->tags;
 200
 201         if (tag >= tags->nr_reserved_tags) {
 202                 const int real_tag = tag - tags->nr_reserved_tags;
 203
 204                 BUG_ON(real_tag >= tags->nr_tags);
 205                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 206         } else {
 207                 BUG_ON(tag >= tags->nr_reserved_tags);
 208                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 209         }
 210 }
 211
 212 struct bt_iter_data {
 213         struct blk_mq_hw_ctx *hctx;
 214         busy_iter_fn *fn;
 215         void *data;
 216         bool reserved;
 217 };
 218
 219 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 220 {
 221         struct bt_iter_data *iter_data = data;
 222         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 223         struct blk_mq_tags *tags = hctx->tags;
 224         bool reserved = iter_data->reserved;
 225         struct request *rq;
 226
 227         if (!reserved)
 228                 bitnr += tags->nr_reserved_tags;
 229         rq = tags->rqs[bitnr];
 230
 231         if (rq->q == hctx->queue)
 232                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 233         return true;
 234 }
 235
 236 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 237                         busy_iter_fn *fn, void *data, bool reserved)
 238 {
 239         struct bt_iter_data iter_data = {
 240                 .hctx = hctx,
 241                 .fn = fn,
 242                 .data = data,
 243                 .reserved = reserved,
 244         };
 245
 246         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 247 }
 248
 249 struct bt_tags_iter_data {
 250         struct blk_mq_tags *tags;
 251         busy_tag_iter_fn *fn;
 252         void *data;
 253         bool reserved;
 254 };
 255
 256 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 257 {
 258         struct bt_tags_iter_data *iter_data = data;
 259         struct blk_mq_tags *tags = iter_data->tags;
 260         bool reserved = iter_data->reserved;
 261         struct request *rq;
 262
 263         if (!reserved)
 264                 bitnr += tags->nr_reserved_tags;
 265         rq = tags->rqs[bitnr];
 266
 267         iter_data->fn(rq, iter_data->data, reserved);
 268         return true;
 269 }
 270
 271 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 272                              busy_tag_iter_fn *fn, void *data, bool reserved)
 273 {
 274         struct bt_tags_iter_data iter_data = {
 275                 .tags = tags,
 276                 .fn = fn,
 277                 .data = data,
 278                 .reserved = reserved,
 279         };
 280
 281         if (tags->rqs)
 282                 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 283 }
 284
 285 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 286                 busy_tag_iter_fn *fn, void *priv)
 287 {
 288         if (tags->nr_reserved_tags)
 289                 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 290         bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 291 }
 292
 293 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 294                 busy_tag_iter_fn *fn, void *priv)
 295 {
 296         int i;
 297
 298         for (i = 0; i < tagset->nr_hw_queues; i++) {
 299                 if (tagset->tags && tagset->tags[i])
 300                         blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
 301         }
 302 }
 303 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 304
 305 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set)
 306 {
 307         int i, j, ret = 0;
 308
 309         if (!set->ops->reinit_request)
 310                 goto out;
 311
 312         for (i = 0; i < set->nr_hw_queues; i++) {
 313                 struct blk_mq_tags *tags = set->tags[i];
 314
 315                 for (j = 0; j < tags->nr_tags; j++) {
 316                         if (!tags->rqs[j])
 317                                 continue;
 318
 319                         ret = set->ops->reinit_request(set->driver_data,
 320                                                 tags->rqs[j]);
 321                         if (ret)
 322                                 goto out;
 323                 }
 324         }
 325
 326 out:
 327         return ret;
 328 }
 329 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
 330
 331 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 332                 void *priv)
 333 {
 334         struct blk_mq_hw_ctx *hctx;
 335         int i;
 336
 337
 338         queue_for_each_hw_ctx(q, hctx, i) {
 339                 struct blk_mq_tags *tags = hctx->tags;
 340
 341                 /*
 342                  * If not software queues are currently mapped to this
 343                  * hardware queue, there's nothing to check
 344                  */
 345                 if (!blk_mq_hw_queue_mapped(hctx))
 346                         continue;
 347
 348                 if (tags->nr_reserved_tags)
 349                         bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
 350                 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 351         }
 352
 353 }
 354
 355 static unsigned int bt_unused_tags(const struct sbitmap_queue *bt)
 356 {
 357         return bt->sb.depth - sbitmap_weight(&bt->sb);
 358 }
 359
 360 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 361                     bool round_robin, int node)
 362 {
 363         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 364                                        node);
 365 }
 366
 367 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 368                                                    int node, int alloc_policy)
 369 {
 370         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 371         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 372
 373         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 374                 goto free_tags;
 375         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 376                      node))
 377                 goto free_bitmap_tags;
 378
 379         return tags;
 380 free_bitmap_tags:
 381         sbitmap_queue_free(&tags->bitmap_tags);
 382 free_tags:
 383         kfree(tags);
 384         return NULL;
 385 }
 386
 387 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 388                                      unsigned int reserved_tags,
 389                                      int node, int alloc_policy)
 390 {
 391         struct blk_mq_tags *tags;
 392
 393         if (total_tags > BLK_MQ_TAG_MAX) {
 394                 pr_err("blk-mq: tag depth too large\n");
 395                 return NULL;
 396         }
 397
 398         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 399         if (!tags)
 400                 return NULL;
 401
 402         if (!zalloc_cpumask_var(&tags->cpumask, GFP_KERNEL)) {
 403                 kfree(tags);
 404                 return NULL;
 405         }
 406
 407         tags->nr_tags = total_tags;
 408         tags->nr_reserved_tags = reserved_tags;
 409
 410         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 411 }
 412
 413 void blk_mq_free_tags(struct blk_mq_tags *tags)
 414 {
 415         sbitmap_queue_free(&tags->bitmap_tags);
 416         sbitmap_queue_free(&tags->breserved_tags);
 417         free_cpumask_var(tags->cpumask);
 418         kfree(tags);
 419 }
 420
 421 int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
 422 {
 423         tdepth -= tags->nr_reserved_tags;
 424         if (tdepth > tags->nr_tags)
 425                 return -EINVAL;
 426
 427         /*
 428          * Don't need (or can't) update reserved tags here, they remain
 429          * static and should never need resizing.
 430          */
 431         sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
 432
 433         blk_mq_tag_wakeup_all(tags, false);
 434         return 0;
 435 }
 436
 437 /**
 438  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 439  * @rq: request for which to compute a unique tag
 440  *
 441  * The tag field in struct request is unique per hardware queue but not over
 442  * all hardware queues. Hence this function that returns a tag with the
 443  * hardware context index in the upper bits and the per hardware queue tag in
 444  * the lower bits.
 445  *
 446  * Note: When called for a request that is queued on a non-multiqueue request
 447  * queue, the hardware context index is set to zero.
 448  */
 449 u32 blk_mq_unique_tag(struct request *rq)
 450 {
 451         struct request_queue *q = rq->q;
 452         struct blk_mq_hw_ctx *hctx;
 453         int hwq = 0;
 454
 455         if (q->mq_ops) {
 456                 hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
 457                 hwq = hctx->queue_num;
 458         }
 459
 460         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 461                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 462 }
 463 EXPORT_SYMBOL(blk_mq_unique_tag);
 464
 465 ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
 466 {
 467         char *orig_page = page;
 468         unsigned int free, res;
 469
 470         if (!tags)
 471                 return 0;
 472
 473         page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
 474                         "bits_per_word=%u\n",
 475                         tags->nr_tags, tags->nr_reserved_tags,
 476                         1U << tags->bitmap_tags.sb.shift);
 477
 478         free = bt_unused_tags(&tags->bitmap_tags);
 479         res = bt_unused_tags(&tags->breserved_tags);
 480
 481         page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
 482         page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));
 483
 484         return page - orig_page;
 485 }