drivers/block/null_blk.c

   1 #include <linux/module.h>
   2
   3 #include <linux/moduleparam.h>
   4 #include <linux/sched.h>
   5 #include <linux/fs.h>
   6 #include <linux/blkdev.h>
   7 #include <linux/init.h>
   8 #include <linux/slab.h>
   9 #include <linux/blk-mq.h>
  10 #include <linux/hrtimer.h>
  11
  12 struct nullb_cmd {
  13         struct list_head list;
  14         struct llist_node ll_list;
  15         struct call_single_data csd;
  16         struct request *rq;
  17         struct bio *bio;
  18         unsigned int tag;
  19         struct nullb_queue *nq;
  20 };
  21
  22 struct nullb_queue {
  23         unsigned long *tag_map;
  24         wait_queue_head_t wait;
  25         unsigned int queue_depth;
  26
  27         struct nullb_cmd *cmds;
  28 };
  29
  30 struct nullb {
  31         struct list_head list;
  32         unsigned int index;
  33         struct request_queue *q;
  34         struct gendisk *disk;
  35         struct hrtimer timer;
  36         unsigned int queue_depth;
  37         spinlock_t lock;
  38
  39         struct nullb_queue *queues;
  40         unsigned int nr_queues;
  41 };
  42
  43 static LIST_HEAD(nullb_list);
  44 static struct mutex lock;
  45 static int null_major;
  46 static int nullb_indexes;
  47
  48 struct completion_queue {
  49         struct llist_head list;
  50         struct hrtimer timer;
  51 };
  52
  53 /*
  54  * These are per-cpu for now, they will need to be configured by the
  55  * complete_queues parameter and appropriately mapped.
  56  */
  57 static DEFINE_PER_CPU(struct completion_queue, completion_queues);
  58
  59 enum {
  60         NULL_IRQ_NONE           = 0,
  61         NULL_IRQ_SOFTIRQ        = 1,
  62         NULL_IRQ_TIMER          = 2,
  63 };
  64
  65 enum {
  66         NULL_Q_BIO              = 0,
  67         NULL_Q_RQ               = 1,
  68         NULL_Q_MQ               = 2,
  69 };
  70
  71 static int submit_queues;
  72 module_param(submit_queues, int, S_IRUGO);
  73 MODULE_PARM_DESC(submit_queues, "Number of submission queues");
  74
  75 static int home_node = NUMA_NO_NODE;
  76 module_param(home_node, int, S_IRUGO);
  77 MODULE_PARM_DESC(home_node, "Home node for the device");
  78
  79 static int queue_mode = NULL_Q_MQ;
  80 module_param(queue_mode, int, S_IRUGO);
  81 MODULE_PARM_DESC(use_mq, "Use blk-mq interface (0=bio,1=rq,2=multiqueue)");
  82
  83 static int gb = 250;
  84 module_param(gb, int, S_IRUGO);
  85 MODULE_PARM_DESC(gb, "Size in GB");
  86
  87 static int bs = 512;
  88 module_param(bs, int, S_IRUGO);
  89 MODULE_PARM_DESC(bs, "Block size (in bytes)");
  90
  91 static int nr_devices = 2;
  92 module_param(nr_devices, int, S_IRUGO);
  93 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
  94
  95 static int irqmode = NULL_IRQ_SOFTIRQ;
  96 module_param(irqmode, int, S_IRUGO);
  97 MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");
  98
  99 static int completion_nsec = 10000;
 100 module_param(completion_nsec, int, S_IRUGO);
 101 MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");
 102
 103 static int hw_queue_depth = 64;
 104 module_param(hw_queue_depth, int, S_IRUGO);
 105 MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");
 106
 107 static bool use_per_node_hctx = false;
 108 module_param(use_per_node_hctx, bool, S_IRUGO);
 109 MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");
 110
 111 static void put_tag(struct nullb_queue *nq, unsigned int tag)
 112 {
 113         clear_bit_unlock(tag, nq->tag_map);
 114
 115         if (waitqueue_active(&nq->wait))
 116                 wake_up(&nq->wait);
 117 }
 118
 119 static unsigned int get_tag(struct nullb_queue *nq)
 120 {
 121         unsigned int tag;
 122
 123         do {
 124                 tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
 125                 if (tag >= nq->queue_depth)
 126                         return -1U;
 127         } while (test_and_set_bit_lock(tag, nq->tag_map));
 128
 129         return tag;
 130 }
 131
 132 static void free_cmd(struct nullb_cmd *cmd)
 133 {
 134         put_tag(cmd->nq, cmd->tag);
 135 }
 136
 137 static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
 138 {
 139         struct nullb_cmd *cmd;
 140         unsigned int tag;
 141
 142         tag = get_tag(nq);
 143         if (tag != -1U) {
 144                 cmd = &nq->cmds[tag];
 145                 cmd->tag = tag;
 146                 cmd->nq = nq;
 147                 return cmd;
 148         }
 149
 150         return NULL;
 151 }
 152
 153 static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
 154 {
 155         struct nullb_cmd *cmd;
 156         DEFINE_WAIT(wait);
 157
 158         cmd = __alloc_cmd(nq);
 159         if (cmd || !can_wait)
 160                 return cmd;
 161
 162         do {
 163                 prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
 164                 cmd = __alloc_cmd(nq);
 165                 if (cmd)
 166                         break;
 167
 168                 io_schedule();
 169         } while (1);
 170
 171         finish_wait(&nq->wait, &wait);
 172         return cmd;
 173 }
 174
 175 static void end_cmd(struct nullb_cmd *cmd)
 176 {
 177         switch (queue_mode)  {
 178         case NULL_Q_MQ:
 179                 blk_mq_end_io(cmd->rq, 0);
 180                 return;
 181         case NULL_Q_RQ:
 182                 INIT_LIST_HEAD(&cmd->rq->queuelist);
 183                 blk_end_request_all(cmd->rq, 0);
 184                 break;
 185         case NULL_Q_BIO:
 186                 bio_endio(cmd->bio, 0);
 187                 break;
 188         }
 189
 190         free_cmd(cmd);
 191 }
 192
 193 static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
 194 {
 195         struct completion_queue *cq;
 196         struct llist_node *entry;
 197         struct nullb_cmd *cmd;
 198
 199         cq = &per_cpu(completion_queues, smp_processor_id());
 200
 201         while ((entry = llist_del_all(&cq->list)) != NULL) {
 202                 entry = llist_reverse_order(entry);
 203                 do {
 204                         cmd = container_of(entry, struct nullb_cmd, ll_list);
 205                         end_cmd(cmd);
 206                         entry = entry->next;
 207                 } while (entry);
 208         }
 209
 210         return HRTIMER_NORESTART;
 211 }
 212
 213 static void null_cmd_end_timer(struct nullb_cmd *cmd)
 214 {
 215         struct completion_queue *cq = &per_cpu(completion_queues, get_cpu());
 216
 217         cmd->ll_list.next = NULL;
 218         if (llist_add(&cmd->ll_list, &cq->list)) {
 219                 ktime_t kt = ktime_set(0, completion_nsec);
 220
 221                 hrtimer_start(&cq->timer, kt, HRTIMER_MODE_REL);
 222         }
 223
 224         put_cpu();
 225 }
 226
 227 static void null_softirq_done_fn(struct request *rq)
 228 {
 229         end_cmd(rq->special);
 230 }
 231
 232 static inline void null_handle_cmd(struct nullb_cmd *cmd)
 233 {
 234         /* Complete IO by inline, softirq or timer */
 235         switch (irqmode) {
 236         case NULL_IRQ_SOFTIRQ:
 237                 switch (queue_mode)  {
 238                 case NULL_Q_MQ:
 239                         blk_mq_complete_request(cmd->rq);
 240                         break;
 241                 case NULL_Q_RQ:
 242                         blk_complete_request(cmd->rq);
 243                         break;
 244                 case NULL_Q_BIO:
 245                         /*
 246                          * XXX: no proper submitting cpu information available.
 247                          */
 248                         end_cmd(cmd);
 249                         break;
 250                 }
 251                 break;
 252         case NULL_IRQ_NONE:
 253                 end_cmd(cmd);
 254                 break;
 255         case NULL_IRQ_TIMER:
 256                 null_cmd_end_timer(cmd);
 257                 break;
 258         }
 259 }
 260
 261 static struct nullb_queue *nullb_to_queue(struct nullb *nullb)
 262 {
 263         int index = 0;
 264
 265         if (nullb->nr_queues != 1)
 266                 index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);
 267
 268         return &nullb->queues[index];
 269 }
 270
 271 static void null_queue_bio(struct request_queue *q, struct bio *bio)
 272 {
 273         struct nullb *nullb = q->queuedata;
 274         struct nullb_queue *nq = nullb_to_queue(nullb);
 275         struct nullb_cmd *cmd;
 276
 277         cmd = alloc_cmd(nq, 1);
 278         cmd->bio = bio;
 279
 280         null_handle_cmd(cmd);
 281 }
 282
 283 static int null_rq_prep_fn(struct request_queue *q, struct request *req)
 284 {
 285         struct nullb *nullb = q->queuedata;
 286         struct nullb_queue *nq = nullb_to_queue(nullb);
 287         struct nullb_cmd *cmd;
 288
 289         cmd = alloc_cmd(nq, 0);
 290         if (cmd) {
 291                 cmd->rq = req;
 292                 req->special = cmd;
 293                 return BLKPREP_OK;
 294         }
 295
 296         return BLKPREP_DEFER;
 297 }
 298
 299 static void null_request_fn(struct request_queue *q)
 300 {
 301         struct request *rq;
 302
 303         while ((rq = blk_fetch_request(q)) != NULL) {
 304                 struct nullb_cmd *cmd = rq->special;
 305
 306                 spin_unlock_irq(q->queue_lock);
 307                 null_handle_cmd(cmd);
 308                 spin_lock_irq(q->queue_lock);
 309         }
 310 }
 311
 312 static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)
 313 {
 314         struct nullb_cmd *cmd = rq->special;
 315
 316         cmd->rq = rq;
 317         cmd->nq = hctx->driver_data;
 318
 319         null_handle_cmd(cmd);
 320         return BLK_MQ_RQ_QUEUE_OK;
 321 }
 322
 323 static struct blk_mq_hw_ctx *null_alloc_hctx(struct blk_mq_reg *reg, unsigned int hctx_index)
 324 {
 325         int b_size = DIV_ROUND_UP(reg->nr_hw_queues, nr_online_nodes);
 326         int tip = (reg->nr_hw_queues % nr_online_nodes);
 327         int node = 0, i, n;
 328
 329         /*
 330          * Split submit queues evenly wrt to the number of nodes. If uneven,
 331          * fill the first buckets with one extra, until the rest is filled with
 332          * no extra.
 333          */
 334         for (i = 0, n = 1; i < hctx_index; i++, n++) {
 335                 if (n % b_size == 0) {
 336                         n = 0;
 337                         node++;
 338
 339                         tip--;
 340                         if (!tip)
 341                                 b_size = reg->nr_hw_queues / nr_online_nodes;
 342                 }
 343         }
 344
 345         /*
 346          * A node might not be online, therefore map the relative node id to the
 347          * real node id.
 348          */
 349         for_each_online_node(n) {
 350                 if (!node)
 351                         break;
 352                 node--;
 353         }
 354
 355         return kzalloc_node(sizeof(struct blk_mq_hw_ctx), GFP_KERNEL, n);
 356 }
 357
 358 static void null_free_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_index)
 359 {
 360         kfree(hctx);
 361 }
 362
 363 static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
 364 {
 365         BUG_ON(!nullb);
 366         BUG_ON(!nq);
 367
 368         init_waitqueue_head(&nq->wait);
 369         nq->queue_depth = nullb->queue_depth;
 370 }
 371
 372 static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
 373                           unsigned int index)
 374 {
 375         struct nullb *nullb = data;
 376         struct nullb_queue *nq = &nullb->queues[index];
 377
 378         hctx->driver_data = nq;
 379         null_init_queue(nullb, nq);
 380         nullb->nr_queues++;
 381
 382         return 0;
 383 }
 384
 385 static struct blk_mq_ops null_mq_ops = {
 386         .queue_rq       = null_queue_rq,
 387         .map_queue      = blk_mq_map_queue,
 388         .init_hctx      = null_init_hctx,
 389         .complete       = null_softirq_done_fn,
 390 };
 391
 392 static struct blk_mq_reg null_mq_reg = {
 393         .ops            = &null_mq_ops,
 394         .queue_depth    = 64,
 395         .cmd_size       = sizeof(struct nullb_cmd),
 396         .flags          = BLK_MQ_F_SHOULD_MERGE,
 397 };
 398
 399 static void null_del_dev(struct nullb *nullb)
 400 {
 401         list_del_init(&nullb->list);
 402
 403         del_gendisk(nullb->disk);
 404         blk_cleanup_queue(nullb->q);
 405         put_disk(nullb->disk);
 406         kfree(nullb);
 407 }
 408
 409 static int null_open(struct block_device *bdev, fmode_t mode)
 410 {
 411         return 0;
 412 }
 413
 414 static void null_release(struct gendisk *disk, fmode_t mode)
 415 {
 416 }
 417
 418 static const struct block_device_operations null_fops = {
 419         .owner =        THIS_MODULE,
 420         .open =         null_open,
 421         .release =      null_release,
 422 };
 423
 424 static int setup_commands(struct nullb_queue *nq)
 425 {
 426         struct nullb_cmd *cmd;
 427         int i, tag_size;
 428
 429         nq->cmds = kzalloc(nq->queue_depth * sizeof(*cmd), GFP_KERNEL);
 430         if (!nq->cmds)
 431                 return -ENOMEM;
 432
 433         tag_size = ALIGN(nq->queue_depth, BITS_PER_LONG) / BITS_PER_LONG;
 434         nq->tag_map = kzalloc(tag_size * sizeof(unsigned long), GFP_KERNEL);
 435         if (!nq->tag_map) {
 436                 kfree(nq->cmds);
 437                 return -ENOMEM;
 438         }
 439
 440         for (i = 0; i < nq->queue_depth; i++) {
 441                 cmd = &nq->cmds[i];
 442                 INIT_LIST_HEAD(&cmd->list);
 443                 cmd->ll_list.next = NULL;
 444                 cmd->tag = -1U;
 445         }
 446
 447         return 0;
 448 }
 449
 450 static void cleanup_queue(struct nullb_queue *nq)
 451 {
 452         kfree(nq->tag_map);
 453         kfree(nq->cmds);
 454 }
 455
 456 static void cleanup_queues(struct nullb *nullb)
 457 {
 458         int i;
 459
 460         for (i = 0; i < nullb->nr_queues; i++)
 461                 cleanup_queue(&nullb->queues[i]);
 462
 463         kfree(nullb->queues);
 464 }
 465
 466 static int setup_queues(struct nullb *nullb)
 467 {
 468         nullb->queues = kzalloc(submit_queues * sizeof(struct nullb_queue),
 469                                                                 GFP_KERNEL);
 470         if (!nullb->queues)
 471                 return -ENOMEM;
 472
 473         nullb->nr_queues = 0;
 474         nullb->queue_depth = hw_queue_depth;
 475
 476         return 0;
 477 }
 478
 479 static int init_driver_queues(struct nullb *nullb)
 480 {
 481         struct nullb_queue *nq;
 482         int i, ret = 0;
 483
 484         for (i = 0; i < submit_queues; i++) {
 485                 nq = &nullb->queues[i];
 486
 487                 null_init_queue(nullb, nq);
 488
 489                 ret = setup_commands(nq);
 490                 if (ret)
 491                         goto err_queue;
 492                 nullb->nr_queues++;
 493         }
 494
 495         return 0;
 496 err_queue:
 497         cleanup_queues(nullb);
 498         return ret;
 499 }
 500
 501 static int null_add_dev(void)
 502 {
 503         struct gendisk *disk;
 504         struct nullb *nullb;
 505         sector_t size;
 506
 507         nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, home_node);
 508         if (!nullb)
 509                 return -ENOMEM;
 510
 511         spin_lock_init(&nullb->lock);
 512
 513         if (queue_mode == NULL_Q_MQ && use_per_node_hctx)
 514                 submit_queues = nr_online_nodes;
 515
 516         if (setup_queues(nullb))
 517                 goto err;
 518
 519         if (queue_mode == NULL_Q_MQ) {
 520                 null_mq_reg.numa_node = home_node;
 521                 null_mq_reg.queue_depth = hw_queue_depth;
 522                 null_mq_reg.nr_hw_queues = submit_queues;
 523
 524                 if (use_per_node_hctx) {
 525                         null_mq_reg.ops->alloc_hctx = null_alloc_hctx;
 526                         null_mq_reg.ops->free_hctx = null_free_hctx;
 527                 } else {
 528                         null_mq_reg.ops->alloc_hctx = blk_mq_alloc_single_hw_queue;
 529                         null_mq_reg.ops->free_hctx = blk_mq_free_single_hw_queue;
 530                 }
 531
 532                 nullb->q = blk_mq_init_queue(&null_mq_reg, nullb);
 533         } else if (queue_mode == NULL_Q_BIO) {
 534                 nullb->q = blk_alloc_queue_node(GFP_KERNEL, home_node);
 535                 blk_queue_make_request(nullb->q, null_queue_bio);
 536                 init_driver_queues(nullb);
 537         } else {
 538                 nullb->q = blk_init_queue_node(null_request_fn, &nullb->lock, home_node);
 539                 blk_queue_prep_rq(nullb->q, null_rq_prep_fn);
 540                 if (nullb->q)
 541                         blk_queue_softirq_done(nullb->q, null_softirq_done_fn);
 542                 init_driver_queues(nullb);
 543         }
 544
 545         if (!nullb->q)
 546                 goto queue_fail;
 547
 548         nullb->q->queuedata = nullb;
 549         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, nullb->q);
 550
 551         disk = nullb->disk = alloc_disk_node(1, home_node);
 552         if (!disk) {
 553 queue_fail:
 554                 blk_cleanup_queue(nullb->q);
 555                 cleanup_queues(nullb);
 556 err:
 557                 kfree(nullb);
 558                 return -ENOMEM;
 559         }
 560
 561         mutex_lock(&lock);
 562         list_add_tail(&nullb->list, &nullb_list);
 563         nullb->index = nullb_indexes++;
 564         mutex_unlock(&lock);
 565
 566         blk_queue_logical_block_size(nullb->q, bs);
 567         blk_queue_physical_block_size(nullb->q, bs);
 568
 569         size = gb * 1024 * 1024 * 1024ULL;
 570         sector_div(size, bs);
 571         set_capacity(disk, size);
 572
 573         disk->flags |= GENHD_FL_EXT_DEVT;
 574         disk->major             = null_major;
 575         disk->first_minor       = nullb->index;
 576         disk->fops              = &null_fops;
 577         disk->private_data      = nullb;
 578         disk->queue             = nullb->q;
 579         sprintf(disk->disk_name, "nullb%d", nullb->index);
 580         add_disk(disk);
 581         return 0;
 582 }
 583
 584 static int __init null_init(void)
 585 {
 586         unsigned int i;
 587
 588         if (bs > PAGE_SIZE) {
 589                 pr_warn("null_blk: invalid block size\n");
 590                 pr_warn("null_blk: defaults block size to %lu\n", PAGE_SIZE);
 591                 bs = PAGE_SIZE;
 592         }
 593
 594         if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {
 595                 if (submit_queues < nr_online_nodes) {
 596                         pr_warn("null_blk: submit_queues param is set to %u.",
 597                                                         nr_online_nodes);
 598                         submit_queues = nr_online_nodes;
 599                 }
 600         } else if (submit_queues > nr_cpu_ids)
 601                 submit_queues = nr_cpu_ids;
 602         else if (!submit_queues)
 603                 submit_queues = 1;
 604
 605         mutex_init(&lock);
 606
 607         /* Initialize a separate list for each CPU for issuing softirqs */
 608         for_each_possible_cpu(i) {
 609                 struct completion_queue *cq = &per_cpu(completion_queues, i);
 610
 611                 init_llist_head(&cq->list);
 612
 613                 if (irqmode != NULL_IRQ_TIMER)
 614                         continue;
 615
 616                 hrtimer_init(&cq->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 617                 cq->timer.function = null_cmd_timer_expired;
 618         }
 619
 620         null_major = register_blkdev(0, "nullb");
 621         if (null_major < 0)
 622                 return null_major;
 623
 624         for (i = 0; i < nr_devices; i++) {
 625                 if (null_add_dev()) {
 626                         unregister_blkdev(null_major, "nullb");
 627                         return -EINVAL;
 628                 }
 629         }
 630
 631         pr_info("null: module loaded\n");
 632         return 0;
 633 }
 634
 635 static void __exit null_exit(void)
 636 {
 637         struct nullb *nullb;
 638
 639         unregister_blkdev(null_major, "nullb");
 640
 641         mutex_lock(&lock);
 642         while (!list_empty(&nullb_list)) {
 643                 nullb = list_entry(nullb_list.next, struct nullb, list);
 644                 null_del_dev(nullb);
 645         }
 646         mutex_unlock(&lock);
 647 }
 648
 649 module_init(null_init);
 650 module_exit(null_exit);
 651
 652 MODULE_AUTHOR("Jens Axboe <jaxboe@fusionio.com>");
 653 MODULE_LICENSE("GPL");