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 = blk_mq_map_queue(data->q, data->ctx->cpu);
 145                 if (data->flags & BLK_MQ_REQ_RESERVED) {
 146                         bt = &data->hctx->tags->breserved_tags;
 147                 } else {
 148                         hctx = data->hctx;
 149                         bt = &hctx->tags->bitmap_tags;
 150                 }
 151                 finish_wait(&ws->wait, &wait);
 152                 ws = bt_wait_ptr(bt, hctx);
 153         } while (1);
 154
 155         finish_wait(&ws->wait, &wait);
 156         return tag;
 157 }
 158
 159 static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
 160 {
 161         int tag;
 162
 163         tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
 164                      data->hctx->tags);
 165         if (tag >= 0)
 166                 return tag + data->hctx->tags->nr_reserved_tags;
 167
 168         return BLK_MQ_TAG_FAIL;
 169 }
 170
 171 static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
 172 {
 173         int tag;
 174
 175         if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
 176                 WARN_ON_ONCE(1);
 177                 return BLK_MQ_TAG_FAIL;
 178         }
 179
 180         tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL,
 181                      data->hctx->tags);
 182         if (tag < 0)
 183                 return BLK_MQ_TAG_FAIL;
 184
 185         return tag;
 186 }
 187
 188 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 189 {
 190         if (data->flags & BLK_MQ_REQ_RESERVED)
 191                 return __blk_mq_get_reserved_tag(data);
 192         return __blk_mq_get_tag(data);
 193 }
 194
 195 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
 196                     unsigned int tag)
 197 {
 198         struct blk_mq_tags *tags = hctx->tags;
 199
 200         if (tag >= tags->nr_reserved_tags) {
 201                 const int real_tag = tag - tags->nr_reserved_tags;
 202
 203                 BUG_ON(real_tag >= tags->nr_tags);
 204                 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
 205         } else {
 206                 BUG_ON(tag >= tags->nr_reserved_tags);
 207                 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
 208         }
 209 }
 210
 211 struct bt_iter_data {
 212         struct blk_mq_hw_ctx *hctx;
 213         busy_iter_fn *fn;
 214         void *data;
 215         bool reserved;
 216 };
 217
 218 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 219 {
 220         struct bt_iter_data *iter_data = data;
 221         struct blk_mq_hw_ctx *hctx = iter_data->hctx;
 222         struct blk_mq_tags *tags = hctx->tags;
 223         bool reserved = iter_data->reserved;
 224         struct request *rq;
 225
 226         if (!reserved)
 227                 bitnr += tags->nr_reserved_tags;
 228         rq = tags->rqs[bitnr];
 229
 230         if (rq->q == hctx->queue)
 231                 iter_data->fn(hctx, rq, iter_data->data, reserved);
 232         return true;
 233 }
 234
 235 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
 236                         busy_iter_fn *fn, void *data, bool reserved)
 237 {
 238         struct bt_iter_data iter_data = {
 239                 .hctx = hctx,
 240                 .fn = fn,
 241                 .data = data,
 242                 .reserved = reserved,
 243         };
 244
 245         sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
 246 }
 247
 248 struct bt_tags_iter_data {
 249         struct blk_mq_tags *tags;
 250         busy_tag_iter_fn *fn;
 251         void *data;
 252         bool reserved;
 253 };
 254
 255 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 256 {
 257         struct bt_tags_iter_data *iter_data = data;
 258         struct blk_mq_tags *tags = iter_data->tags;
 259         bool reserved = iter_data->reserved;
 260         struct request *rq;
 261
 262         if (!reserved)
 263                 bitnr += tags->nr_reserved_tags;
 264         rq = tags->rqs[bitnr];
 265
 266         iter_data->fn(rq, iter_data->data, reserved);
 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_reinit_tagset(struct blk_mq_tag_set *set)
 305 {
 306         int i, j, ret = 0;
 307
 308         if (!set->ops->reinit_request)
 309                 goto out;
 310
 311         for (i = 0; i < set->nr_hw_queues; i++) {
 312                 struct blk_mq_tags *tags = set->tags[i];
 313
 314                 for (j = 0; j < tags->nr_tags; j++) {
 315                         if (!tags->rqs[j])
 316                                 continue;
 317
 318                         ret = set->ops->reinit_request(set->driver_data,
 319                                                 tags->rqs[j]);
 320                         if (ret)
 321                                 goto out;
 322                 }
 323         }
 324
 325 out:
 326         return ret;
 327 }
 328 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
 329
 330 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
 331                 void *priv)
 332 {
 333         struct blk_mq_hw_ctx *hctx;
 334         int i;
 335
 336
 337         queue_for_each_hw_ctx(q, hctx, i) {
 338                 struct blk_mq_tags *tags = hctx->tags;
 339
 340                 /*
 341                  * If not software queues are currently mapped to this
 342                  * hardware queue, there's nothing to check
 343                  */
 344                 if (!blk_mq_hw_queue_mapped(hctx))
 345                         continue;
 346
 347                 if (tags->nr_reserved_tags)
 348                         bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
 349                 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
 350         }
 351
 352 }
 353
 354 static unsigned int bt_unused_tags(const struct sbitmap_queue *bt)
 355 {
 356         return bt->sb.depth - sbitmap_weight(&bt->sb);
 357 }
 358
 359 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
 360                     bool round_robin, int node)
 361 {
 362         return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
 363                                        node);
 364 }
 365
 366 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
 367                                                    int node, int alloc_policy)
 368 {
 369         unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
 370         bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
 371
 372         if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
 373                 goto free_tags;
 374         if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 375                      node))
 376                 goto free_bitmap_tags;
 377
 378         return tags;
 379 free_bitmap_tags:
 380         sbitmap_queue_free(&tags->bitmap_tags);
 381 free_tags:
 382         kfree(tags);
 383         return NULL;
 384 }
 385
 386 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 387                                      unsigned int reserved_tags,
 388                                      int node, int alloc_policy)
 389 {
 390         struct blk_mq_tags *tags;
 391
 392         if (total_tags > BLK_MQ_TAG_MAX) {
 393                 pr_err("blk-mq: tag depth too large\n");
 394                 return NULL;
 395         }
 396
 397         tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
 398         if (!tags)
 399                 return NULL;
 400
 401         tags->nr_tags = total_tags;
 402         tags->nr_reserved_tags = reserved_tags;
 403
 404         return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 405 }
 406
 407 void blk_mq_free_tags(struct blk_mq_tags *tags)
 408 {
 409         sbitmap_queue_free(&tags->bitmap_tags);
 410         sbitmap_queue_free(&tags->breserved_tags);
 411         kfree(tags);
 412 }
 413
 414 int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth)
 415 {
 416         tdepth -= tags->nr_reserved_tags;
 417         if (tdepth > tags->nr_tags)
 418                 return -EINVAL;
 419
 420         /*
 421          * Don't need (or can't) update reserved tags here, they remain
 422          * static and should never need resizing.
 423          */
 424         sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
 425
 426         blk_mq_tag_wakeup_all(tags, false);
 427         return 0;
 428 }
 429
 430 /**
 431  * blk_mq_unique_tag() - return a tag that is unique queue-wide
 432  * @rq: request for which to compute a unique tag
 433  *
 434  * The tag field in struct request is unique per hardware queue but not over
 435  * all hardware queues. Hence this function that returns a tag with the
 436  * hardware context index in the upper bits and the per hardware queue tag in
 437  * the lower bits.
 438  *
 439  * Note: When called for a request that is queued on a non-multiqueue request
 440  * queue, the hardware context index is set to zero.
 441  */
 442 u32 blk_mq_unique_tag(struct request *rq)
 443 {
 444         struct request_queue *q = rq->q;
 445         struct blk_mq_hw_ctx *hctx;
 446         int hwq = 0;
 447
 448         if (q->mq_ops) {
 449                 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
 450                 hwq = hctx->queue_num;
 451         }
 452
 453         return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
 454                 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
 455 }
 456 EXPORT_SYMBOL(blk_mq_unique_tag);
 457
 458 ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page)
 459 {
 460         char *orig_page = page;
 461         unsigned int free, res;
 462
 463         if (!tags)
 464                 return 0;
 465
 466         page += sprintf(page, "nr_tags=%u, reserved_tags=%u, "
 467                         "bits_per_word=%u\n",
 468                         tags->nr_tags, tags->nr_reserved_tags,
 469                         1U << tags->bitmap_tags.sb.shift);
 470
 471         free = bt_unused_tags(&tags->bitmap_tags);
 472         res = bt_unused_tags(&tags->breserved_tags);
 473
 474         page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res);
 475         page += sprintf(page, "active_queues=%u\n", atomic_read(&tags->active_queues));
 476
 477         return page - orig_page;
 478 }