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  * We need to do this before try to allocate driver tag, then even if fail
  27  * to get tag when first time, the other shared-tag users could reserve
  28  * budget for it.
  29  */
  30 bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
  31 {
  32         if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
  33             !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  34                 atomic_inc(&hctx->tags->active_queues);
  35
  36         return true;
  37 }
  38
  39 /*
  40  * Wakeup all potentially sleeping on tags
  41  */
  42 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
  43 {
  44         sbitmap_queue_wake_all(&tags->bitmap_tags);
  45         if (include_reserve)
  46                 sbitmap_queue_wake_all(&tags->breserved_tags);
  47 }
  48
  49 /*
  50  * If a previously busy queue goes inactive, potential waiters could now
  51  * be allowed to queue. Wake them up and check.
  52  */
  53 void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
  54 {
  55         struct blk_mq_tags *tags = hctx->tags;
  56
  57         if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  58                 return;
  59
  60         atomic_dec(&tags->active_queues);
  61
  62         blk_mq_tag_wakeup_all(tags, false);
  63 }
  64
  65 /*
  66  * For shared tag users, we track the number of currently active users
  67  * and attempt to provide a fair share of the tag depth for each of them.
  68  */
  69 static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
  70                                   struct sbitmap_queue *bt)
  71 {
  72         unsigned int depth, users;
  73
  74         if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
  75                 return true;
  76         if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
  77                 return true;
  78
  79         /*
  80          * Don't try dividing an ant
  81          */
  82         if (bt->sb.depth == 1)
  83                 return true;
  84
  85         users = atomic_read(&hctx->tags->active_queues);
  86         if (!users)
  87                 return true;
  88
  89         /*
  90          * Allow at least some tags
  91          */
  92         depth = max((bt->sb.depth + users - 1) / users, 4U);
  93         return atomic_read(&hctx->nr_active) < depth;
  94 }
  95
  96 static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
  97                             struct sbitmap_queue *bt)
  98 {
  99         if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
 100             !hctx_may_queue(data->hctx, bt))
 101                 return -1;
 102         if (data->shallow_depth)
 103                 return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
 104         else
 105                 return __sbitmap_queue_get(bt);
 106 }
 107
 108 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 109 {
 110         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 111         struct sbitmap_queue *bt;
 112         struct sbq_wait_state *ws;
 113         DEFINE_WAIT(wait);
 114         unsigned int tag_offset;
 115         bool drop_ctx;
 116         int tag;
 117
 118         if (data->flags & BLK_MQ_REQ_RESERVED) {
 119                 if (unlikely(!tags->nr_reserved_tags)) {
 120                         WARN_ON_ONCE(1);
 121                         return BLK_MQ_TAG_FAIL;
 122                 }
 123                 bt = &tags->breserved_tags;
 124                 tag_offset = 0;
 125         } else {
 126                 bt = &tags->bitmap_tags;
 127                 tag_offset = tags->nr_reserved_tags;
 128         }
 129
 130         tag = __blk_mq_get_tag(data, bt);
 131         if (tag != -1)
 132                 goto found_tag;
 133
 134         if (data->flags & BLK_MQ_REQ_NOWAIT)
 135                 return BLK_MQ_TAG_FAIL;
 136
 137         ws = bt_wait_ptr(bt, data->hctx);
 138         drop_ctx = data->ctx == NULL;
 139         do {
 140                 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 141
 142                 tag = __blk_mq_get_tag(data, bt);
 143                 if (tag != -1)
 144                         break;
 145
 146                 /*
 147                  * We're out of tags on this hardware queue, kick any
 148                  * pending IO submits before going to sleep waiting for
 149                  * some to complete.
 150                  */
 151                 blk_mq_run_hw_queue(data->hctx, false);
 152
 153                 /*
 154                  * Retry tag allocation after running the hardware queue,
 155                  * as running the queue may also have found completions.
 156                  */
 157                 tag = __blk_mq_get_tag(data, bt);
 158                 if (tag != -1)
 159                         break;
 160
 161                 if (data->ctx)
 162                         blk_mq_put_ctx(data->ctx);
 163
 164                 io_schedule();
 165
 166                 data->ctx = blk_mq_get_ctx(data->q);
 167                 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
 168                 tags = blk_mq_tags_from_data(data);
 169                 if (data->flags & BLK_MQ_REQ_RESERVED)
 170                         bt = &tags->breserved_tags;
 171                 else
 172                         bt = &tags->bitmap_tags;
 173
 174                 finish_wait(&ws->wait, &wait);
 175                 ws = bt_wait_ptr(bt, data->hctx);
 176         } while (1);
 177
 178         if (drop_ctx && data->ctx)
 179                 blk_mq_put_ctx(data->ctx);
 180
 181         finish_wait(&ws->wait, &wait);
 182
 183 found_tag:
 184         return tag + tag_offset;
 185 }
 186
 187 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
 188                     struct blk_mq_ctx *ctx, unsigned int tag)
 189 {
 190         if (!blk_mq_tag_is_reserved(tags, tag)) {
 191                 const int real_tag = tag - tags->nr_reserved_tags;
 192
 193                 BUG_ON(real_tag >= tags->nr_tags);
 194                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 195         } else {
 196                 BUG_ON(tag >= tags->nr_reserved_tags);
 197                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 198         }
 199 }
 200
 201 struct bt_iter_data {
 202         struct blk_mq_hw_ctx *hctx;
 203         busy_iter_fn *fn;
 204         void *data;
 205         bool reserved;
 206 };
 207
 208 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 209 {
 210         struct bt_iter_data *iter_data = data;
 211         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 212         struct blk_mq_tags *tags = hctx->tags;
 213         bool reserved = iter_data->reserved;
 214         struct request *rq;
 215
 216         if (!reserved)
 217                 bitnr += tags->nr_reserved_tags;
 218         rq = tags->rqs[bitnr];
 219
 220         /*
 221          * We can hit rq == NULL here, because the tagging functions
 222          * test and set the bit before assining ->rqs[].
 223          */
 224         if (rq && rq->q == hctx->queue)
 225                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 226         return true;
 227 }
 228
 229 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 230                         busy_iter_fn *fn, void *data, bool reserved)
 231 {
 232         struct bt_iter_data iter_data = {
 233                 .hctx = hctx,
 234                 .fn = fn,
 235                 .data = data,
 236                 .reserved = reserved,
 237         };
 238
 239         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 240 }
 241
 242 struct bt_tags_iter_data {
 243         struct blk_mq_tags *tags;
 244         busy_tag_iter_fn *fn;
 245         void *data;
 246         bool reserved;
 247 };
 248
 249 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 250 {
 251         struct bt_tags_iter_data *iter_data = data;
 252         struct blk_mq_tags *tags = iter_data->tags;
 253         bool reserved = iter_data->reserved;
 254         struct request *rq;
 255
 256         if (!reserved)
 257                 bitnr += tags->nr_reserved_tags;
 258
 259         /*
 260          * We can hit rq == NULL here, because the tagging functions
 261          * test and set the bit before assining ->rqs[].
 262          */
 263         rq = tags->rqs[bitnr];
 264         if (rq)
 265                 iter_data->fn(rq, iter_data->data, reserved);
 266
 267         return true;
 268 }
 269
 270 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 271                              busy_tag_iter_fn *fn, void *data, bool reserved)
 272 {
 273         struct bt_tags_iter_data iter_data = {
 274                 .tags = tags,
 275                 .fn = fn,
 276                 .data = data,
 277                 .reserved = reserved,
 278         };
 279
 280         if (tags->rqs)
 281                 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 282 }
 283
 284 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 285                 busy_tag_iter_fn *fn, void *priv)
 286 {
 287         if (tags->nr_reserved_tags)
 288                 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 289         bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 290 }
 291
 292 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 293                 busy_tag_iter_fn *fn, void *priv)
 294 {
 295         int i;
 296
 297         for (i = 0; i < tagset->nr_hw_queues; i++) {
 298                 if (tagset->tags && tagset->tags[i])
 299                         blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
 300         }
 301 }
 302 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 303
 304 int blk_mq_tagset_iter(struct blk_mq_tag_set *set, void *data,
 305                          int (fn)(void *, struct request *))
 306 {
 307         int i, j, ret = 0;
 308
 309         if (WARN_ON_ONCE(!fn))
 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                 if (!tags)
 316                         continue;
 317
 318                 for (j = 0; j < tags->nr_tags; j++) {
 319                         if (!tags->static_rqs[j])
 320                                 continue;
 321
 322                         ret = fn(data, tags->static_rqs[j]);
 323                         if (ret)
 324                                 goto out;
 325                 }
 326         }
 327
 328 out:
 329         return ret;
 330 }
 331 EXPORT_SYMBOL_GPL(blk_mq_tagset_iter);
 332
 333 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 334                 void *priv)
 335 {
 336         struct blk_mq_hw_ctx *hctx;
 337         int i;
 338
 339
 340         queue_for_each_hw_ctx(q, hctx, i) {
 341                 struct blk_mq_tags *tags = hctx->tags;
 342
 343                 /*
 344                  * If not software queues are currently mapped to this
 345                  * hardware queue, there's nothing to check
 346                  */
 347                 if (!blk_mq_hw_queue_mapped(hctx))
 348                         continue;
 349
 350                 if (tags->nr_reserved_tags)
 351                         bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
 352                 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 353         }
 354
 355 }
 356
 357 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 358                     bool round_robin, int node)
 359 {
 360         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 361                                        node);
 362 }
 363
 364 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 365                                                    int node, int alloc_policy)
 366 {
 367         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 368         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 369
 370         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 371                 goto free_tags;
 372         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 373                      node))
 374                 goto free_bitmap_tags;
 375
 376         return tags;
 377 free_bitmap_tags:
 378         sbitmap_queue_free(&tags->bitmap_tags);
 379 free_tags:
 380         kfree(tags);
 381         return NULL;
 382 }
 383
 384 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 385                                      unsigned int reserved_tags,
 386                                      int node, int alloc_policy)
 387 {
 388         struct blk_mq_tags *tags;
 389
 390         if (total_tags > BLK_MQ_TAG_MAX) {
 391                 pr_err("blk-mq: tag depth too large\n");
 392                 return NULL;
 393         }
 394
 395         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 396         if (!tags)
 397                 return NULL;
 398
 399         tags->nr_tags = total_tags;
 400         tags->nr_reserved_tags = reserved_tags;
 401
 402         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 403 }
 404
 405 void blk_mq_free_tags(struct blk_mq_tags *tags)
 406 {
 407         sbitmap_queue_free(&tags->bitmap_tags);
 408         sbitmap_queue_free(&tags->breserved_tags);
 409         kfree(tags);
 410 }
 411
 412 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 413                             struct blk_mq_tags **tagsptr, unsigned int tdepth,
 414                             bool can_grow)
 415 {
 416         struct blk_mq_tags *tags = *tagsptr;
 417
 418         if (tdepth <= tags->nr_reserved_tags)
 419                 return -EINVAL;
 420
 421         /*
 422          * If we are allowed to grow beyond the original size, allocate
 423          * a new set of tags before freeing the old one.
 424          */
 425         if (tdepth > tags->nr_tags) {
 426                 struct blk_mq_tag_set *set = hctx->queue->tag_set;
 427                 struct blk_mq_tags *new;
 428                 bool ret;
 429
 430                 if (!can_grow)
 431                         return -EINVAL;
 432
 433                 /*
 434                  * We need some sort of upper limit, set it high enough that
 435                  * no valid use cases should require more.
 436                  */
 437                 if (tdepth > 16 * BLKDEV_MAX_RQ)
 438                         return -EINVAL;
 439
 440                 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
 441                                 tags->nr_reserved_tags);
 442                 if (!new)
 443                         return -ENOMEM;
 444                 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
 445                 if (ret) {
 446                         blk_mq_free_rq_map(new);
 447                         return -ENOMEM;
 448                 }
 449
 450                 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 451                 blk_mq_free_rq_map(*tagsptr);
 452                 *tagsptr = new;
 453         } else {
 454                 /*
 455                  * Don't need (or can't) update reserved tags here, they
 456                  * remain static and should never need resizing.
 457                  */
 458                 sbitmap_queue_resize(&tags->bitmap_tags,
 459                                 tdepth - tags->nr_reserved_tags);
 460         }
 461
 462         return 0;
 463 }
 464
 465 /**
 466  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 467  * @rq: request for which to compute a unique tag
 468  *
 469  * The tag field in struct request is unique per hardware queue but not over
 470  * all hardware queues. Hence this function that returns a tag with the
 471  * hardware context index in the upper bits and the per hardware queue tag in
 472  * the lower bits.
 473  *
 474  * Note: When called for a request that is queued on a non-multiqueue request
 475  * queue, the hardware context index is set to zero.
 476  */
 477 u32 blk_mq_unique_tag(struct request *rq)
 478 {
 479         struct request_queue *q = rq->q;
 480         struct blk_mq_hw_ctx *hctx;
 481         int hwq = 0;
 482
 483         if (q->mq_ops) {
 484                 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
 485                 hwq = hctx->queue_num;
 486         }
 487
 488         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 489                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 490 }
 491 EXPORT_SYMBOL(blk_mq_unique_tag);