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