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         return __sbitmap_queue_get(bt);
 100 }
 101
 102 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 103 {
 104         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 105         struct sbitmap_queue *bt;
 106         struct sbq_wait_state *ws;
 107         DEFINE_WAIT(wait);
 108         unsigned int tag_offset;
 109         bool drop_ctx;
 110         int tag;
 111
 112         if (data->flags & BLK_MQ_REQ_RESERVED) {
 113                 if (unlikely(!tags->nr_reserved_tags)) {
 114                         WARN_ON_ONCE(1);
 115                         return BLK_MQ_TAG_FAIL;
 116                 }
 117                 bt = &tags->breserved_tags;
 118                 tag_offset = 0;
 119         } else {
 120                 bt = &tags->bitmap_tags;
 121                 tag_offset = tags->nr_reserved_tags;
 122         }
 123
 124         tag = __blk_mq_get_tag(data, bt);
 125         if (tag != -1)
 126                 goto found_tag;
 127
 128         if (data->flags & BLK_MQ_REQ_NOWAIT)
 129                 return BLK_MQ_TAG_FAIL;
 130
 131         ws = bt_wait_ptr(bt, data->hctx);
 132         drop_ctx = data->ctx == NULL;
 133         do {
 134                 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 135
 136                 tag = __blk_mq_get_tag(data, bt);
 137                 if (tag != -1)
 138                         break;
 139
 140                 /*
 141                  * We're out of tags on this hardware queue, kick any
 142                  * pending IO submits before going to sleep waiting for
 143                  * some to complete.
 144                  */
 145                 blk_mq_run_hw_queue(data->hctx, false);
 146
 147                 /*
 148                  * Retry tag allocation after running the hardware queue,
 149                  * as running the queue may also have found completions.
 150                  */
 151                 tag = __blk_mq_get_tag(data, bt);
 152                 if (tag != -1)
 153                         break;
 154
 155                 if (data->ctx)
 156                         blk_mq_put_ctx(data->ctx);
 157
 158                 io_schedule();
 159
 160                 data->ctx = blk_mq_get_ctx(data->q);
 161                 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu);
 162                 tags = blk_mq_tags_from_data(data);
 163                 if (data->flags & BLK_MQ_REQ_RESERVED)
 164                         bt = &tags->breserved_tags;
 165                 else
 166                         bt = &tags->bitmap_tags;
 167
 168                 finish_wait(&ws->wait, &wait);
 169                 ws = bt_wait_ptr(bt, data->hctx);
 170         } while (1);
 171
 172         if (drop_ctx && data->ctx)
 173                 blk_mq_put_ctx(data->ctx);
 174
 175         finish_wait(&ws->wait, &wait);
 176
 177 found_tag:
 178         return tag + tag_offset;
 179 }
 180
 181 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
 182                     struct blk_mq_ctx *ctx, unsigned int tag)
 183 {
 184         if (!blk_mq_tag_is_reserved(tags, tag)) {
 185                 const int real_tag = tag - tags->nr_reserved_tags;
 186
 187                 BUG_ON(real_tag >= tags->nr_tags);
 188                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 189         } else {
 190                 BUG_ON(tag >= tags->nr_reserved_tags);
 191                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 192         }
 193 }
 194
 195 struct bt_iter_data {
 196         struct blk_mq_hw_ctx *hctx;
 197         busy_iter_fn *fn;
 198         void *data;
 199         bool reserved;
 200 };
 201
 202 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 203 {
 204         struct bt_iter_data *iter_data = data;
 205         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 206         struct blk_mq_tags *tags = hctx->tags;
 207         bool reserved = iter_data->reserved;
 208         struct request *rq;
 209
 210         if (!reserved)
 211                 bitnr += tags->nr_reserved_tags;
 212         rq = tags->rqs[bitnr];
 213
 214         if (rq->q == hctx->queue)
 215                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 216         return true;
 217 }
 218
 219 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 220                         busy_iter_fn *fn, void *data, bool reserved)
 221 {
 222         struct bt_iter_data iter_data = {
 223                 .hctx = hctx,
 224                 .fn = fn,
 225                 .data = data,
 226                 .reserved = reserved,
 227         };
 228
 229         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 230 }
 231
 232 struct bt_tags_iter_data {
 233         struct blk_mq_tags *tags;
 234         busy_tag_iter_fn *fn;
 235         void *data;
 236         bool reserved;
 237 };
 238
 239 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 240 {
 241         struct bt_tags_iter_data *iter_data = data;
 242         struct blk_mq_tags *tags = iter_data->tags;
 243         bool reserved = iter_data->reserved;
 244         struct request *rq;
 245
 246         if (!reserved)
 247                 bitnr += tags->nr_reserved_tags;
 248         rq = tags->rqs[bitnr];
 249
 250         iter_data->fn(rq, iter_data->data, reserved);
 251         return true;
 252 }
 253
 254 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 255                              busy_tag_iter_fn *fn, void *data, bool reserved)
 256 {
 257         struct bt_tags_iter_data iter_data = {
 258                 .tags = tags,
 259                 .fn = fn,
 260                 .data = data,
 261                 .reserved = reserved,
 262         };
 263
 264         if (tags->rqs)
 265                 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 266 }
 267
 268 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 269                 busy_tag_iter_fn *fn, void *priv)
 270 {
 271         if (tags->nr_reserved_tags)
 272                 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 273         bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 274 }
 275
 276 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 277                 busy_tag_iter_fn *fn, void *priv)
 278 {
 279         int i;
 280
 281         for (i = 0; i < tagset->nr_hw_queues; i++) {
 282                 if (tagset->tags && tagset->tags[i])
 283                         blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
 284         }
 285 }
 286 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 287
 288 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set)
 289 {
 290         int i, j, ret = 0;
 291
 292         if (!set->ops->reinit_request)
 293                 goto out;
 294
 295         for (i = 0; i < set->nr_hw_queues; i++) {
 296                 struct blk_mq_tags *tags = set->tags[i];
 297
 298                 if (!tags)
 299                         continue;
 300
 301                 for (j = 0; j < tags->nr_tags; j++) {
 302                         if (!tags->static_rqs[j])
 303                                 continue;
 304
 305                         ret = set->ops->reinit_request(set->driver_data,
 306                                                 tags->static_rqs[j]);
 307                         if (ret)
 308                                 goto out;
 309                 }
 310         }
 311
 312 out:
 313         return ret;
 314 }
 315 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
 316
 317 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 318                 void *priv)
 319 {
 320         struct blk_mq_hw_ctx *hctx;
 321         int i;
 322
 323
 324         queue_for_each_hw_ctx(q, hctx, i) {
 325                 struct blk_mq_tags *tags = hctx->tags;
 326
 327                 /*
 328                  * If not software queues are currently mapped to this
 329                  * hardware queue, there's nothing to check
 330                  */
 331                 if (!blk_mq_hw_queue_mapped(hctx))
 332                         continue;
 333
 334                 if (tags->nr_reserved_tags)
 335                         bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
 336                 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 337         }
 338
 339 }
 340
 341 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 342                     bool round_robin, int node)
 343 {
 344         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 345                                        node);
 346 }
 347
 348 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 349                                                    int node, int alloc_policy)
 350 {
 351         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 352         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 353
 354         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 355                 goto free_tags;
 356         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 357                      node))
 358                 goto free_bitmap_tags;
 359
 360         return tags;
 361 free_bitmap_tags:
 362         sbitmap_queue_free(&tags->bitmap_tags);
 363 free_tags:
 364         kfree(tags);
 365         return NULL;
 366 }
 367
 368 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 369                                      unsigned int reserved_tags,
 370                                      int node, int alloc_policy)
 371 {
 372         struct blk_mq_tags *tags;
 373
 374         if (total_tags > BLK_MQ_TAG_MAX) {
 375                 pr_err("blk-mq: tag depth too large\n");
 376                 return NULL;
 377         }
 378
 379         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 380         if (!tags)
 381                 return NULL;
 382
 383         tags->nr_tags = total_tags;
 384         tags->nr_reserved_tags = reserved_tags;
 385
 386         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 387 }
 388
 389 void blk_mq_free_tags(struct blk_mq_tags *tags)
 390 {
 391         sbitmap_queue_free(&tags->bitmap_tags);
 392         sbitmap_queue_free(&tags->breserved_tags);
 393         kfree(tags);
 394 }
 395
 396 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 397                             struct blk_mq_tags **tagsptr, unsigned int tdepth,
 398                             bool can_grow)
 399 {
 400         struct blk_mq_tags *tags = *tagsptr;
 401
 402         if (tdepth <= tags->nr_reserved_tags)
 403                 return -EINVAL;
 404
 405         tdepth -= tags->nr_reserved_tags;
 406
 407         /*
 408          * If we are allowed to grow beyond the original size, allocate
 409          * a new set of tags before freeing the old one.
 410          */
 411         if (tdepth > tags->nr_tags) {
 412                 struct blk_mq_tag_set *set = hctx->queue->tag_set;
 413                 struct blk_mq_tags *new;
 414                 bool ret;
 415
 416                 if (!can_grow)
 417                         return -EINVAL;
 418
 419                 /*
 420                  * We need some sort of upper limit, set it high enough that
 421                  * no valid use cases should require more.
 422                  */
 423                 if (tdepth > 16 * BLKDEV_MAX_RQ)
 424                         return -EINVAL;
 425
 426                 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth, 0);
 427                 if (!new)
 428                         return -ENOMEM;
 429                 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
 430                 if (ret) {
 431                         blk_mq_free_rq_map(new);
 432                         return -ENOMEM;
 433                 }
 434
 435                 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 436                 blk_mq_free_rq_map(*tagsptr);
 437                 *tagsptr = new;
 438         } else {
 439                 /*
 440                  * Don't need (or can't) update reserved tags here, they
 441                  * remain static and should never need resizing.
 442                  */
 443                 sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
 444         }
 445
 446         return 0;
 447 }
 448
 449 /**
 450  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 451  * @rq: request for which to compute a unique tag
 452  *
 453  * The tag field in struct request is unique per hardware queue but not over
 454  * all hardware queues. Hence this function that returns a tag with the
 455  * hardware context index in the upper bits and the per hardware queue tag in
 456  * the lower bits.
 457  *
 458  * Note: When called for a request that is queued on a non-multiqueue request
 459  * queue, the hardware context index is set to zero.
 460  */
 461 u32 blk_mq_unique_tag(struct request *rq)
 462 {
 463         struct request_queue *q = rq->q;
 464         struct blk_mq_hw_ctx *hctx;
 465         int hwq = 0;
 466
 467         if (q->mq_ops) {
 468                 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
 469                 hwq = hctx->queue_num;
 470         }
 471
 472         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 473                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 474 }
 475 EXPORT_SYMBOL(blk_mq_unique_tag);