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                 /*
 138                  * We're out of tags on this hardware queue, kick any
 139                  * pending IO submits before going to sleep waiting for
 140                  * some to complete.
 141                  */
 142                 blk_mq_run_hw_queue(data->hctx, false);
 143
 144                 /*
 145                  * Retry tag allocation after running the hardware queue,
 146                  * as running the queue may also have found completions.
 147                  */
 148                 tag = __blk_mq_get_tag(data, bt);
 149                 if (tag != -1)
 150                         break;
 151
 152                 prepare_to_wait_exclusive(&ws->wait, &wait,
 153                                                 TASK_UNINTERRUPTIBLE);
 154
 155                 tag = __blk_mq_get_tag(data, bt);
 156                 if (tag != -1)
 157                         break;
 158
 159                 if (data->ctx)
 160                         blk_mq_put_ctx(data->ctx);
 161
 162                 io_schedule();
 163
 164                 data->ctx = blk_mq_get_ctx(data->q);
 165                 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
 166                 tags = blk_mq_tags_from_data(data);
 167                 if (data->flags & BLK_MQ_REQ_RESERVED)
 168                         bt = &tags->breserved_tags;
 169                 else
 170                         bt = &tags->bitmap_tags;
 171
 172                 finish_wait(&ws->wait, &wait);
 173                 ws = bt_wait_ptr(bt, data->hctx);
 174         } while (1);
 175
 176         if (drop_ctx && data->ctx)
 177                 blk_mq_put_ctx(data->ctx);
 178
 179         finish_wait(&ws->wait, &wait);
 180
 181 found_tag:
 182         return tag + tag_offset;
 183 }
 184
 185 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
 186                     struct blk_mq_ctx *ctx, unsigned int tag)
 187 {
 188         if (!blk_mq_tag_is_reserved(tags, tag)) {
 189                 const int real_tag = tag - tags->nr_reserved_tags;
 190
 191                 BUG_ON(real_tag >= tags->nr_tags);
 192                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 193         } else {
 194                 BUG_ON(tag >= tags->nr_reserved_tags);
 195                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 196         }
 197 }
 198
 199 struct bt_iter_data {
 200         struct blk_mq_hw_ctx *hctx;
 201         busy_iter_fn *fn;
 202         void *data;
 203         bool reserved;
 204 };
 205
 206 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 207 {
 208         struct bt_iter_data *iter_data = data;
 209         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 210         struct blk_mq_tags *tags = hctx->tags;
 211         bool reserved = iter_data->reserved;
 212         struct request *rq;
 213
 214         if (!reserved)
 215                 bitnr += tags->nr_reserved_tags;
 216         rq = tags->rqs[bitnr];
 217
 218         /*
 219          * We can hit rq == NULL here, because the tagging functions
 220          * test and set the bit before assining ->rqs[].
 221          */
 222         if (rq && rq->q == hctx->queue)
 223                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 224         return true;
 225 }
 226
 227 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 228                         busy_iter_fn *fn, void *data, bool reserved)
 229 {
 230         struct bt_iter_data iter_data = {
 231                 .hctx = hctx,
 232                 .fn = fn,
 233                 .data = data,
 234                 .reserved = reserved,
 235         };
 236
 237         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 238 }
 239
 240 struct bt_tags_iter_data {
 241         struct blk_mq_tags *tags;
 242         busy_tag_iter_fn *fn;
 243         void *data;
 244         bool reserved;
 245 };
 246
 247 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 248 {
 249         struct bt_tags_iter_data *iter_data = data;
 250         struct blk_mq_tags *tags = iter_data->tags;
 251         bool reserved = iter_data->reserved;
 252         struct request *rq;
 253
 254         if (!reserved)
 255                 bitnr += tags->nr_reserved_tags;
 256
 257         /*
 258          * We can hit rq == NULL here, because the tagging functions
 259          * test and set the bit before assining ->rqs[].
 260          */
 261         rq = tags->rqs[bitnr];
 262         if (rq)
 263                 iter_data->fn(rq, iter_data->data, reserved);
 264
 265         return true;
 266 }
 267
 268 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 269                              busy_tag_iter_fn *fn, void *data, bool reserved)
 270 {
 271         struct bt_tags_iter_data iter_data = {
 272                 .tags = tags,
 273                 .fn = fn,
 274                 .data = data,
 275                 .reserved = reserved,
 276         };
 277
 278         if (tags->rqs)
 279                 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 280 }
 281
 282 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 283                 busy_tag_iter_fn *fn, void *priv)
 284 {
 285         if (tags->nr_reserved_tags)
 286                 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 287         bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 288 }
 289
 290 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 291                 busy_tag_iter_fn *fn, void *priv)
 292 {
 293         int i;
 294
 295         for (i = 0; i < tagset->nr_hw_queues; i++) {
 296                 if (tagset->tags && tagset->tags[i])
 297                         blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
 298         }
 299 }
 300 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 301
 302 int blk_mq_tagset_iter(struct blk_mq_tag_set *set, void *data,
 303                          int (fn)(void *, struct request *))
 304 {
 305         int i, j, ret = 0;
 306
 307         if (WARN_ON_ONCE(!fn))
 308                 goto out;
 309
 310         for (i = 0; i < set->nr_hw_queues; i++) {
 311                 struct blk_mq_tags *tags = set->tags[i];
 312
 313                 if (!tags)
 314                         continue;
 315
 316                 for (j = 0; j < tags->nr_tags; j++) {
 317                         if (!tags->static_rqs[j])
 318                                 continue;
 319
 320                         ret = fn(data, 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_tagset_iter);
 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 int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 356                     bool round_robin, int node)
 357 {
 358         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 359                                        node);
 360 }
 361
 362 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 363                                                    int node, int alloc_policy)
 364 {
 365         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 366         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 367
 368         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 369                 goto free_tags;
 370         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 371                      node))
 372                 goto free_bitmap_tags;
 373
 374         return tags;
 375 free_bitmap_tags:
 376         sbitmap_queue_free(&tags->bitmap_tags);
 377 free_tags:
 378         kfree(tags);
 379         return NULL;
 380 }
 381
 382 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 383                                      unsigned int reserved_tags,
 384                                      int node, int alloc_policy)
 385 {
 386         struct blk_mq_tags *tags;
 387
 388         if (total_tags > BLK_MQ_TAG_MAX) {
 389                 pr_err("blk-mq: tag depth too large\n");
 390                 return NULL;
 391         }
 392
 393         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 394         if (!tags)
 395                 return NULL;
 396
 397         tags->nr_tags = total_tags;
 398         tags->nr_reserved_tags = reserved_tags;
 399
 400         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 401 }
 402
 403 void blk_mq_free_tags(struct blk_mq_tags *tags)
 404 {
 405         sbitmap_queue_free(&tags->bitmap_tags);
 406         sbitmap_queue_free(&tags->breserved_tags);
 407         kfree(tags);
 408 }
 409
 410 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 411                             struct blk_mq_tags **tagsptr, unsigned int tdepth,
 412                             bool can_grow)
 413 {
 414         struct blk_mq_tags *tags = *tagsptr;
 415
 416         if (tdepth <= tags->nr_reserved_tags)
 417                 return -EINVAL;
 418
 419         tdepth -= tags->nr_reserved_tags;
 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, 0);
 441                 if (!new)
 442                         return -ENOMEM;
 443                 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
 444                 if (ret) {
 445                         blk_mq_free_rq_map(new);
 446                         return -ENOMEM;
 447                 }
 448
 449                 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 450                 blk_mq_free_rq_map(*tagsptr);
 451                 *tagsptr = new;
 452         } else {
 453                 /*
 454                  * Don't need (or can't) update reserved tags here, they
 455                  * remain static and should never need resizing.
 456                  */
 457                 sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
 458         }
 459
 460         return 0;
 461 }
 462
 463 /**
 464  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 465  * @rq: request for which to compute a unique tag
 466  *
 467  * The tag field in struct request is unique per hardware queue but not over
 468  * all hardware queues. Hence this function that returns a tag with the
 469  * hardware context index in the upper bits and the per hardware queue tag in
 470  * the lower bits.
 471  *
 472  * Note: When called for a request that is queued on a non-multiqueue request
 473  * queue, the hardware context index is set to zero.
 474  */
 475 u32 blk_mq_unique_tag(struct request *rq)
 476 {
 477         struct request_queue *q = rq->q;
 478         struct blk_mq_hw_ctx *hctx;
 479         int hwq = 0;
 480
 481         if (q->mq_ops) {
 482                 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
 483                 hwq = hctx->queue_num;
 484         }
 485
 486         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 487                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 488 }
 489 EXPORT_SYMBOL(blk_mq_unique_tag);