block/blk-mq-sched.c

   1 /*
   2  * blk-mq scheduling framework
   3  *
   4  * Copyright (C) 2016 Jens Axboe
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/blk-mq.h>
   9
  10 #include <trace/events/block.h>
  11
  12 #include "blk.h"
  13 #include "blk-mq.h"
  14 #include "blk-mq-sched.h"
  15 #include "blk-mq-tag.h"
  16 #include "blk-wbt.h"
  17
  18 void blk_mq_sched_free_hctx_data(struct request_queue *q,
  19                                  void (*exit)(struct blk_mq_hw_ctx *))
  20 {
  21         struct blk_mq_hw_ctx *hctx;
  22         int i;
  23
  24         queue_for_each_hw_ctx(q, hctx, i) {
  25                 if (exit && hctx->sched_data)
  26                         exit(hctx);
  27                 kfree(hctx->sched_data);
  28                 hctx->sched_data = NULL;
  29         }
  30 }
  31 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
  32
  33 int blk_mq_sched_init_hctx_data(struct request_queue *q, size_t size,
  34                                 int (*init)(struct blk_mq_hw_ctx *),
  35                                 void (*exit)(struct blk_mq_hw_ctx *))
  36 {
  37         struct blk_mq_hw_ctx *hctx;
  38         int ret;
  39         int i;
  40
  41         queue_for_each_hw_ctx(q, hctx, i) {
  42                 hctx->sched_data = kmalloc_node(size, GFP_KERNEL, hctx->numa_node);
  43                 if (!hctx->sched_data) {
  44                         ret = -ENOMEM;
  45                         goto error;
  46                 }
  47
  48                 if (init) {
  49                         ret = init(hctx);
  50                         if (ret) {
  51                                 /*
  52                                  * We don't want to give exit() a partially
  53                                  * initialized sched_data. init() must clean up
  54                                  * if it fails.
  55                                  */
  56                                 kfree(hctx->sched_data);
  57                                 hctx->sched_data = NULL;
  58                                 goto error;
  59                         }
  60                 }
  61         }
  62
  63         return 0;
  64 error:
  65         blk_mq_sched_free_hctx_data(q, exit);
  66         return ret;
  67 }
  68 EXPORT_SYMBOL_GPL(blk_mq_sched_init_hctx_data);
  69
  70 static void __blk_mq_sched_assign_ioc(struct request_queue *q,
  71                                       struct request *rq, struct io_context *ioc)
  72 {
  73         struct io_cq *icq;
  74
  75         spin_lock_irq(q->queue_lock);
  76         icq = ioc_lookup_icq(ioc, q);
  77         spin_unlock_irq(q->queue_lock);
  78
  79         if (!icq) {
  80                 icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
  81                 if (!icq)
  82                         return;
  83         }
  84
  85         rq->elv.icq = icq;
  86         if (!blk_mq_sched_get_rq_priv(q, rq)) {
  87                 rq->rq_flags |= RQF_ELVPRIV;
  88                 get_io_context(icq->ioc);
  89                 return;
  90         }
  91
  92         rq->elv.icq = NULL;
  93 }
  94
  95 static void blk_mq_sched_assign_ioc(struct request_queue *q,
  96                                     struct request *rq, struct bio *bio)
  97 {
  98         struct io_context *ioc;
  99
 100         ioc = rq_ioc(bio);
 101         if (ioc)
 102                 __blk_mq_sched_assign_ioc(q, rq, ioc);
 103 }
 104
 105 struct request *blk_mq_sched_get_request(struct request_queue *q,
 106                                          struct bio *bio,
 107                                          unsigned int op,
 108                                          struct blk_mq_alloc_data *data)
 109 {
 110         struct elevator_queue *e = q->elevator;
 111         struct blk_mq_hw_ctx *hctx;
 112         struct blk_mq_ctx *ctx;
 113         struct request *rq;
 114
 115         blk_queue_enter_live(q);
 116         ctx = blk_mq_get_ctx(q);
 117         hctx = blk_mq_map_queue(q, ctx->cpu);
 118
 119         blk_mq_set_alloc_data(data, q, data->flags, ctx, hctx);
 120
 121         if (e) {
 122                 data->flags |= BLK_MQ_REQ_INTERNAL;
 123
 124                 /*
 125                  * Flush requests are special and go directly to the
 126                  * dispatch list.
 127                  */
 128                 if (!op_is_flush(op) && e->type->ops.mq.get_request) {
 129                         rq = e->type->ops.mq.get_request(q, op, data);
 130                         if (rq)
 131                                 rq->rq_flags |= RQF_QUEUED;
 132                 } else
 133                         rq = __blk_mq_alloc_request(data, op);
 134         } else {
 135                 rq = __blk_mq_alloc_request(data, op);
 136                 if (rq)
 137                         data->hctx->tags->rqs[rq->tag] = rq;
 138         }
 139
 140         if (rq) {
 141                 if (!op_is_flush(op)) {
 142                         rq->elv.icq = NULL;
 143                         if (e && e->type->icq_cache)
 144                                 blk_mq_sched_assign_ioc(q, rq, bio);
 145                 }
 146                 data->hctx->queued++;
 147                 return rq;
 148         }
 149
 150         blk_queue_exit(q);
 151         return NULL;
 152 }
 153
 154 void blk_mq_sched_put_request(struct request *rq)
 155 {
 156         struct request_queue *q = rq->q;
 157         struct elevator_queue *e = q->elevator;
 158
 159         if (rq->rq_flags & RQF_ELVPRIV) {
 160                 blk_mq_sched_put_rq_priv(rq->q, rq);
 161                 if (rq->elv.icq) {
 162                         put_io_context(rq->elv.icq->ioc);
 163                         rq->elv.icq = NULL;
 164                 }
 165         }
 166
 167         if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
 168                 e->type->ops.mq.put_request(rq);
 169         else
 170                 blk_mq_finish_request(rq);
 171 }
 172
 173 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 174 {
 175         struct elevator_queue *e = hctx->queue->elevator;
 176         LIST_HEAD(rq_list);
 177
 178         if (unlikely(blk_mq_hctx_stopped(hctx)))
 179                 return;
 180
 181         hctx->run++;
 182
 183         /*
 184          * If we have previous entries on our dispatch list, grab them first for
 185          * more fair dispatch.
 186          */
 187         if (!list_empty_careful(&hctx->dispatch)) {
 188                 spin_lock(&hctx->lock);
 189                 if (!list_empty(&hctx->dispatch))
 190                         list_splice_init(&hctx->dispatch, &rq_list);
 191                 spin_unlock(&hctx->lock);
 192         }
 193
 194         /*
 195          * Only ask the scheduler for requests, if we didn't have residual
 196          * requests from the dispatch list. This is to avoid the case where
 197          * we only ever dispatch a fraction of the requests available because
 198          * of low device queue depth. Once we pull requests out of the IO
 199          * scheduler, we can no longer merge or sort them. So it's best to
 200          * leave them there for as long as we can. Mark the hw queue as
 201          * needing a restart in that case.
 202          */
 203         if (!list_empty(&rq_list)) {
 204                 blk_mq_sched_mark_restart(hctx);
 205                 blk_mq_dispatch_rq_list(hctx, &rq_list);
 206         } else if (!e || !e->type->ops.mq.dispatch_request) {
 207                 blk_mq_flush_busy_ctxs(hctx, &rq_list);
 208                 blk_mq_dispatch_rq_list(hctx, &rq_list);
 209         } else {
 210                 do {
 211                         struct request *rq;
 212
 213                         rq = e->type->ops.mq.dispatch_request(hctx);
 214                         if (!rq)
 215                                 break;
 216                         list_add(&rq->queuelist, &rq_list);
 217                 } while (blk_mq_dispatch_rq_list(hctx, &rq_list));
 218         }
 219 }
 220
 221 void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx,
 222                                    struct list_head *rq_list,
 223                                    struct request *(*get_rq)(struct blk_mq_hw_ctx *))
 224 {
 225         do {
 226                 struct request *rq;
 227
 228                 rq = get_rq(hctx);
 229                 if (!rq)
 230                         break;
 231
 232                 list_add_tail(&rq->queuelist, rq_list);
 233         } while (1);
 234 }
 235 EXPORT_SYMBOL_GPL(blk_mq_sched_move_to_dispatch);
 236
 237 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio)
 238 {
 239         struct request *rq;
 240         int ret;
 241
 242         ret = elv_merge(q, &rq, bio);
 243         if (ret == ELEVATOR_BACK_MERGE) {
 244                 if (!blk_mq_sched_allow_merge(q, rq, bio))
 245                         return false;
 246                 if (bio_attempt_back_merge(q, rq, bio)) {
 247                         if (!attempt_back_merge(q, rq))
 248                                 elv_merged_request(q, rq, ret);
 249                         return true;
 250                 }
 251         } else if (ret == ELEVATOR_FRONT_MERGE) {
 252                 if (!blk_mq_sched_allow_merge(q, rq, bio))
 253                         return false;
 254                 if (bio_attempt_front_merge(q, rq, bio)) {
 255                         if (!attempt_front_merge(q, rq))
 256                                 elv_merged_request(q, rq, ret);
 257                         return true;
 258                 }
 259         }
 260
 261         return false;
 262 }
 263 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
 264
 265 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 266 {
 267         struct elevator_queue *e = q->elevator;
 268
 269         if (e->type->ops.mq.bio_merge) {
 270                 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
 271                 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 272
 273                 blk_mq_put_ctx(ctx);
 274                 return e->type->ops.mq.bio_merge(hctx, bio);
 275         }
 276
 277         return false;
 278 }
 279
 280 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
 281 {
 282         return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
 283 }
 284 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
 285
 286 void blk_mq_sched_request_inserted(struct request *rq)
 287 {
 288         trace_block_rq_insert(rq->q, rq);
 289 }
 290 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
 291
 292 bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
 293 {
 294         if (rq->tag == -1) {
 295                 rq->rq_flags |= RQF_SORTED;
 296                 return false;
 297         }
 298
 299         /*
 300          * If we already have a real request tag, send directly to
 301          * the dispatch list.
 302          */
 303         spin_lock(&hctx->lock);
 304         list_add(&rq->queuelist, &hctx->dispatch);
 305         spin_unlock(&hctx->lock);
 306         return true;
 307 }
 308 EXPORT_SYMBOL_GPL(blk_mq_sched_bypass_insert);
 309
 310 static void blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
 311 {
 312         if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) {
 313                 clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
 314                 if (blk_mq_hctx_has_pending(hctx))
 315                         blk_mq_run_hw_queue(hctx, true);
 316         }
 317 }
 318
 319 void blk_mq_sched_restart_queues(struct blk_mq_hw_ctx *hctx)
 320 {
 321         unsigned int i;
 322
 323         if (!(hctx->flags & BLK_MQ_F_TAG_SHARED))
 324                 blk_mq_sched_restart_hctx(hctx);
 325         else {
 326                 struct request_queue *q = hctx->queue;
 327
 328                 if (!test_bit(QUEUE_FLAG_RESTART, &q->queue_flags))
 329                         return;
 330
 331                 clear_bit(QUEUE_FLAG_RESTART, &q->queue_flags);
 332
 333                 queue_for_each_hw_ctx(q, hctx, i)
 334                         blk_mq_sched_restart_hctx(hctx);
 335         }
 336 }
 337
 338 /*
 339  * Add flush/fua to the queue. If we fail getting a driver tag, then
 340  * punt to the requeue list. Requeue will re-invoke us from a context
 341  * that's safe to block from.
 342  */
 343 static void blk_mq_sched_insert_flush(struct blk_mq_hw_ctx *hctx,
 344                                       struct request *rq, bool can_block)
 345 {
 346         if (blk_mq_get_driver_tag(rq, &hctx, can_block)) {
 347                 blk_insert_flush(rq);
 348                 blk_mq_run_hw_queue(hctx, true);
 349         } else
 350                 blk_mq_add_to_requeue_list(rq, true, true);
 351 }
 352
 353 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
 354                                  bool run_queue, bool async, bool can_block)
 355 {
 356         struct request_queue *q = rq->q;
 357         struct elevator_queue *e = q->elevator;
 358         struct blk_mq_ctx *ctx = rq->mq_ctx;
 359         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 360
 361         if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {
 362                 blk_mq_sched_insert_flush(hctx, rq, can_block);
 363                 return;
 364         }
 365
 366         if (e && e->type->ops.mq.insert_requests) {
 367                 LIST_HEAD(list);
 368
 369                 list_add(&rq->queuelist, &list);
 370                 e->type->ops.mq.insert_requests(hctx, &list, at_head);
 371         } else {
 372                 spin_lock(&ctx->lock);
 373                 __blk_mq_insert_request(hctx, rq, at_head);
 374                 spin_unlock(&ctx->lock);
 375         }
 376
 377         if (run_queue)
 378                 blk_mq_run_hw_queue(hctx, async);
 379 }
 380
 381 void blk_mq_sched_insert_requests(struct request_queue *q,
 382                                   struct blk_mq_ctx *ctx,
 383                                   struct list_head *list, bool run_queue_async)
 384 {
 385         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 386         struct elevator_queue *e = hctx->queue->elevator;
 387
 388         if (e && e->type->ops.mq.insert_requests)
 389                 e->type->ops.mq.insert_requests(hctx, list, false);
 390         else
 391                 blk_mq_insert_requests(hctx, ctx, list);
 392
 393         blk_mq_run_hw_queue(hctx, run_queue_async);
 394 }
 395
 396 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
 397                                    struct blk_mq_hw_ctx *hctx,
 398                                    unsigned int hctx_idx)
 399 {
 400         if (hctx->sched_tags) {
 401                 blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
 402                 blk_mq_free_rq_map(hctx->sched_tags);
 403                 hctx->sched_tags = NULL;
 404         }
 405 }
 406
 407 int blk_mq_sched_setup(struct request_queue *q)
 408 {
 409         struct blk_mq_tag_set *set = q->tag_set;
 410         struct blk_mq_hw_ctx *hctx;
 411         int ret, i;
 412
 413         /*
 414          * Default to 256, since we don't split into sync/async like the
 415          * old code did. Additionally, this is a per-hw queue depth.
 416          */
 417         q->nr_requests = 2 * BLKDEV_MAX_RQ;
 418
 419         /*
 420          * We're switching to using an IO scheduler, so setup the hctx
 421          * scheduler tags and switch the request map from the regular
 422          * tags to scheduler tags. First allocate what we need, so we
 423          * can safely fail and fallback, if needed.
 424          */
 425         ret = 0;
 426         queue_for_each_hw_ctx(q, hctx, i) {
 427                 hctx->sched_tags = blk_mq_alloc_rq_map(set, i, q->nr_requests, 0);
 428                 if (!hctx->sched_tags) {
 429                         ret = -ENOMEM;
 430                         break;
 431                 }
 432                 ret = blk_mq_alloc_rqs(set, hctx->sched_tags, i, q->nr_requests);
 433                 if (ret)
 434                         break;
 435         }
 436
 437         /*
 438          * If we failed, free what we did allocate
 439          */
 440         if (ret) {
 441                 queue_for_each_hw_ctx(q, hctx, i) {
 442                         if (!hctx->sched_tags)
 443                                 continue;
 444                         blk_mq_sched_free_tags(set, hctx, i);
 445                 }
 446
 447                 return ret;
 448         }
 449
 450         return 0;
 451 }
 452
 453 void blk_mq_sched_teardown(struct request_queue *q)
 454 {
 455         struct blk_mq_tag_set *set = q->tag_set;
 456         struct blk_mq_hw_ctx *hctx;
 457         int i;
 458
 459         queue_for_each_hw_ctx(q, hctx, i)
 460                 blk_mq_sched_free_tags(set, hctx, i);
 461 }
 462
 463 int blk_mq_sched_init(struct request_queue *q)
 464 {
 465         int ret;
 466
 467 #if defined(CONFIG_DEFAULT_SQ_NONE)
 468         if (q->nr_hw_queues == 1)
 469                 return 0;
 470 #endif
 471 #if defined(CONFIG_DEFAULT_MQ_NONE)
 472         if (q->nr_hw_queues > 1)
 473                 return 0;
 474 #endif
 475
 476         mutex_lock(&q->sysfs_lock);
 477         ret = elevator_init(q, NULL);
 478         mutex_unlock(&q->sysfs_lock);
 479
 480         return ret;
 481 }