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