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 __blk_mq_get_tag(struct blk_mq_alloc_data *data,
  94                             struct sbitmap_queue *bt)
  95 {
  96         if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
  97             !hctx_may_queue(data->hctx, bt))
  98                 return -1;
  99         if (data->shallow_depth)
 100                 return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
 101         else
 102                 return __sbitmap_queue_get(bt);
 103 }
 104
 105 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 106 {
 107         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 108         struct sbitmap_queue *bt;
 109         struct sbq_wait_state *ws;
 110         DEFINE_WAIT(wait);
 111         unsigned int tag_offset;
 112         bool drop_ctx;
 113         int tag;
 114
 115         if (data->flags & BLK_MQ_REQ_RESERVED) {
 116                 if (unlikely(!tags->nr_reserved_tags)) {
 117                         WARN_ON_ONCE(1);
 118                         return BLK_MQ_TAG_FAIL;
 119                 }
 120                 bt = &tags->breserved_tags;
 121                 tag_offset = 0;
 122         } else {
 123                 bt = &tags->bitmap_tags;
 124                 tag_offset = tags->nr_reserved_tags;
 125         }
 126
 127         tag = __blk_mq_get_tag(data, bt);
 128         if (tag != -1)
 129                 goto found_tag;
 130
 131         if (data->flags & BLK_MQ_REQ_NOWAIT)
 132                 return BLK_MQ_TAG_FAIL;
 133
 134         ws = bt_wait_ptr(bt, data->hctx);
 135         drop_ctx = data->ctx == NULL;
 136         do {
 137                 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 138
 139                 tag = __blk_mq_get_tag(data, bt);
 140                 if (tag != -1)
 141                         break;
 142
 143                 /*
 144                  * We're out of tags on this hardware queue, kick any
 145                  * pending IO submits before going to sleep waiting for
 146                  * some to complete.
 147                  */
 148                 blk_mq_run_hw_queue(data->hctx, false);
 149
 150                 /*
 151                  * Retry tag allocation after running the hardware queue,
 152                  * as running the queue may also have found completions.
 153                  */
 154                 tag = __blk_mq_get_tag(data, bt);
 155                 if (tag != -1)
 156                         break;
 157
 158                 if (data->ctx)
 159                         blk_mq_put_ctx(data->ctx);
 160
 161                 io_schedule();
 162
 163                 data->ctx = blk_mq_get_ctx(data->q);
 164                 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
 165                 tags = blk_mq_tags_from_data(data);
 166                 if (data->flags & BLK_MQ_REQ_RESERVED)
 167                         bt = &tags->breserved_tags;
 168                 else
 169                         bt = &tags->bitmap_tags;
 170
 171                 finish_wait(&ws->wait, &wait);
 172                 ws = bt_wait_ptr(bt, data->hctx);
 173         } while (1);
 174
 175         if (drop_ctx && data->ctx)
 176                 blk_mq_put_ctx(data->ctx);
 177
 178         finish_wait(&ws->wait, &wait);
 179
 180 found_tag:
 181         return tag + tag_offset;
 182 }
 183
 184 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
 185                     struct blk_mq_ctx *ctx, unsigned int tag)
 186 {
 187         if (!blk_mq_tag_is_reserved(tags, tag)) {
 188                 const int real_tag = tag - tags->nr_reserved_tags;
 189
 190                 BUG_ON(real_tag >= tags->nr_tags);
 191                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 192         } else {
 193                 BUG_ON(tag >= tags->nr_reserved_tags);
 194                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 195         }
 196 }
 197
 198 struct bt_iter_data {
 199         struct blk_mq_hw_ctx *hctx;
 200         busy_iter_fn *fn;
 201         void *data;
 202         bool reserved;
 203 };
 204
 205 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 206 {
 207         struct bt_iter_data *iter_data = data;
 208         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 209         struct blk_mq_tags *tags = hctx->tags;
 210         bool reserved = iter_data->reserved;
 211         struct request *rq;
 212
 213         if (!reserved)
 214                 bitnr += tags->nr_reserved_tags;
 215         rq = tags->rqs[bitnr];
 216
 217         /*
 218          * We can hit rq == NULL here, because the tagging functions
 219          * test and set the bit before assining ->rqs[].
 220          */
 221         if (rq && rq->q == hctx->queue)
 222                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 223         return true;
 224 }
 225
 226 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 227                         busy_iter_fn *fn, void *data, bool reserved)
 228 {
 229         struct bt_iter_data iter_data = {
 230                 .hctx = hctx,
 231                 .fn = fn,
 232                 .data = data,
 233                 .reserved = reserved,
 234         };
 235
 236         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 237 }
 238
 239 struct bt_tags_iter_data {
 240         struct blk_mq_tags *tags;
 241         busy_tag_iter_fn *fn;
 242         void *data;
 243         bool reserved;
 244 };
 245
 246 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 247 {
 248         struct bt_tags_iter_data *iter_data = data;
 249         struct blk_mq_tags *tags = iter_data->tags;
 250         bool reserved = iter_data->reserved;
 251         struct request *rq;
 252
 253         if (!reserved)
 254                 bitnr += tags->nr_reserved_tags;
 255
 256         /*
 257          * We can hit rq == NULL here, because the tagging functions
 258          * test and set the bit before assining ->rqs[].
 259          */
 260         rq = tags->rqs[bitnr];
 261         if (rq)
 262                 iter_data->fn(rq, iter_data->data, reserved);
 263
 264         return true;
 265 }
 266
 267 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 268                              busy_tag_iter_fn *fn, void *data, bool reserved)
 269 {
 270         struct bt_tags_iter_data iter_data = {
 271                 .tags = tags,
 272                 .fn = fn,
 273                 .data = data,
 274                 .reserved = reserved,
 275         };
 276
 277         if (tags->rqs)
 278                 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 279 }
 280
 281 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 282                 busy_tag_iter_fn *fn, void *priv)
 283 {
 284         if (tags->nr_reserved_tags)
 285                 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 286         bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 287 }
 288
 289 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 290                 busy_tag_iter_fn *fn, void *priv)
 291 {
 292         int i;
 293
 294         for (i = 0; i < tagset->nr_hw_queues; i++) {
 295                 if (tagset->tags && tagset->tags[i])
 296                         blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
 297         }
 298 }
 299 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 300
 301 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
 302                          int (reinit_request)(void *, struct request *))
 303 {
 304         int i, j, ret = 0;
 305
 306         if (WARN_ON_ONCE(!reinit_request))
 307                 goto out;
 308
 309         for (i = 0; i < set->nr_hw_queues; i++) {
 310                 struct blk_mq_tags *tags = set->tags[i];
 311
 312                 if (!tags)
 313                         continue;
 314
 315                 for (j = 0; j < tags->nr_tags; j++) {
 316                         if (!tags->static_rqs[j])
 317                                 continue;
 318
 319                         ret = reinit_request(set->driver_data,
 320                                              tags->static_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          * __blk_mq_update_nr_hw_queues will update the nr_hw_queues and
 339          * queue_hw_ctx after freeze the queue, so we use q_usage_counter
 340          * to avoid race with it.
 341          */
 342         if (!percpu_ref_tryget(&q->q_usage_counter))
 343                 return;
 344
 345         queue_for_each_hw_ctx(q, hctx, i) {
 346                 struct blk_mq_tags *tags = hctx->tags;
 347
 348                 /*
 349                  * If not software queues are currently mapped to this
 350                  * hardware queue, there's nothing to check
 351                  */
 352                 if (!blk_mq_hw_queue_mapped(hctx))
 353                         continue;
 354
 355                 if (tags->nr_reserved_tags)
 356                         bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
 357                 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 358         }
 359         blk_queue_exit(q);
 360 }
 361
 362 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 363                     bool round_robin, int node)
 364 {
 365         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 366                                        node);
 367 }
 368
 369 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 370                                                    int node, int alloc_policy)
 371 {
 372         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 373         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 374
 375         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 376                 goto free_tags;
 377         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 378                      node))
 379                 goto free_bitmap_tags;
 380
 381         return tags;
 382 free_bitmap_tags:
 383         sbitmap_queue_free(&tags->bitmap_tags);
 384 free_tags:
 385         kfree(tags);
 386         return NULL;
 387 }
 388
 389 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 390                                      unsigned int reserved_tags,
 391                                      int node, int alloc_policy)
 392 {
 393         struct blk_mq_tags *tags;
 394
 395         if (total_tags > BLK_MQ_TAG_MAX) {
 396                 pr_err("blk-mq: tag depth too large\n");
 397                 return NULL;
 398         }
 399
 400         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 401         if (!tags)
 402                 return NULL;
 403
 404         tags->nr_tags = total_tags;
 405         tags->nr_reserved_tags = reserved_tags;
 406
 407         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 408 }
 409
 410 void blk_mq_free_tags(struct blk_mq_tags *tags)
 411 {
 412         sbitmap_queue_free(&tags->bitmap_tags);
 413         sbitmap_queue_free(&tags->breserved_tags);
 414         kfree(tags);
 415 }
 416
 417 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 418                             struct blk_mq_tags **tagsptr, unsigned int tdepth,
 419                             bool can_grow)
 420 {
 421         struct blk_mq_tags *tags = *tagsptr;
 422
 423         if (tdepth <= tags->nr_reserved_tags)
 424                 return -EINVAL;
 425
 426         /*
 427          * If we are allowed to grow beyond the original size, allocate
 428          * a new set of tags before freeing the old one.
 429          */
 430         if (tdepth > tags->nr_tags) {
 431                 struct blk_mq_tag_set *set = hctx->queue->tag_set;
 432                 struct blk_mq_tags *new;
 433                 bool ret;
 434
 435                 if (!can_grow)
 436                         return -EINVAL;
 437
 438                 /*
 439                  * We need some sort of upper limit, set it high enough that
 440                  * no valid use cases should require more.
 441                  */
 442                 if (tdepth > 16 * BLKDEV_MAX_RQ)
 443                         return -EINVAL;
 444
 445                 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
 446                                 tags->nr_reserved_tags);
 447                 if (!new)
 448                         return -ENOMEM;
 449                 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
 450                 if (ret) {
 451                         blk_mq_free_rq_map(new);
 452                         return -ENOMEM;
 453                 }
 454
 455                 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 456                 blk_mq_free_rq_map(*tagsptr);
 457                 *tagsptr = new;
 458         } else {
 459                 /*
 460                  * Don't need (or can't) update reserved tags here, they
 461                  * remain static and should never need resizing.
 462                  */
 463                 sbitmap_queue_resize(&tags->bitmap_tags,
 464                                 tdepth - tags->nr_reserved_tags);
 465         }
 466
 467         return 0;
 468 }
 469
 470 /**
 471  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 472  * @rq: request for which to compute a unique tag
 473  *
 474  * The tag field in struct request is unique per hardware queue but not over
 475  * all hardware queues. Hence this function that returns a tag with the
 476  * hardware context index in the upper bits and the per hardware queue tag in
 477  * the lower bits.
 478  *
 479  * Note: When called for a request that is queued on a non-multiqueue request
 480  * queue, the hardware context index is set to zero.
 481  */
 482 u32 blk_mq_unique_tag(struct request *rq)
 483 {
 484         struct request_queue *q = rq->q;
 485         struct blk_mq_hw_ctx *hctx;
 486         int hwq = 0;
 487
 488         if (q->mq_ops) {
 489                 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
 490                 hwq = hctx->queue_num;
 491         }
 492
 493         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 494                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 495 }
 496 EXPORT_SYMBOL(blk_mq_unique_tag);