kernel/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
  82 static int null_param_store_val(const char *str, int *val, int min, int max)
  83 {
  84         int ret, new_val;
  85
  86         ret = kstrtoint(str, 10, &new_val);
  87         if (ret)
  88                 return -EINVAL;
  89
  90         if (new_val < min || new_val > max)
  91                 return -EINVAL;
  92
  93         *val = new_val;
  94         return 0;
  95 }
  96
  97 static int null_set_queue_mode(const char *str, const struct kernel_param *kp)
  98 {
  99         return null_param_store_val(str, &queue_mode, NULL_Q_BIO, NULL_Q_MQ);
 100 }
 101
 102 static struct kernel_param_ops null_queue_mode_param_ops = {
 103         .set    = null_set_queue_mode,
 104         .get    = param_get_int,
 105 };
 106
 107 device_param_cb(queue_mode, &null_queue_mode_param_ops, &queue_mode, S_IRUGO);
 108 MODULE_PARM_DESC(queue_mode, "Block interface to use (0=bio,1=rq,2=multiqueue)");
 109
 110 static int gb = 250;
 111 module_param(gb, int, S_IRUGO);
 112 MODULE_PARM_DESC(gb, "Size in GB");
 113
 114 static int bs = 512;
 115 module_param(bs, int, S_IRUGO);
 116 MODULE_PARM_DESC(bs, "Block size (in bytes)");
 117
 118 static int nr_devices = 2;
 119 module_param(nr_devices, int, S_IRUGO);
 120 MODULE_PARM_DESC(nr_devices, "Number of devices to register");
 121
 122 static int irqmode = NULL_IRQ_SOFTIRQ;
 123
 124 static int null_set_irqmode(const char *str, const struct kernel_param *kp)
 125 {
 126         return null_param_store_val(str, &irqmode, NULL_IRQ_NONE,
 127                                         NULL_IRQ_TIMER);
 128 }
 129
 130 static struct kernel_param_ops null_irqmode_param_ops = {
 131         .set    = null_set_irqmode,
 132         .get    = param_get_int,
 133 };
 134
 135 device_param_cb(irqmode, &null_irqmode_param_ops, &irqmode, S_IRUGO);
 136 MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");
 137
 138 static int completion_nsec = 10000;
 139 module_param(completion_nsec, int, S_IRUGO);
 140 MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");
 141
 142 static int hw_queue_depth = 64;
 143 module_param(hw_queue_depth, int, S_IRUGO);
 144 MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");
 145
 146 static bool use_per_node_hctx = false;
 147 module_param(use_per_node_hctx, bool, S_IRUGO);
 148 MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");
 149
 150 static void put_tag(struct nullb_queue *nq, unsigned int tag)
 151 {
 152         clear_bit_unlock(tag, nq->tag_map);
 153
 154         if (waitqueue_active(&nq->wait))
 155                 wake_up(&nq->wait);
 156 }
 157
 158 static unsigned int get_tag(struct nullb_queue *nq)
 159 {
 160         unsigned int tag;
 161
 162         do {
 163                 tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
 164                 if (tag >= nq->queue_depth)
 165                         return -1U;
 166         } while (test_and_set_bit_lock(tag, nq->tag_map));
 167
 168         return tag;
 169 }
 170
 171 static void free_cmd(struct nullb_cmd *cmd)
 172 {
 173         put_tag(cmd->nq, cmd->tag);
 174 }
 175
 176 static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
 177 {
 178         struct nullb_cmd *cmd;
 179         unsigned int tag;
 180
 181         tag = get_tag(nq);
 182         if (tag != -1U) {
 183                 cmd = &nq->cmds[tag];
 184                 cmd->tag = tag;
 185                 cmd->nq = nq;
 186                 return cmd;
 187         }
 188
 189         return NULL;
 190 }
 191
 192 static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
 193 {
 194         struct nullb_cmd *cmd;
 195         DEFINE_WAIT(wait);
 196
 197         cmd = __alloc_cmd(nq);
 198         if (cmd || !can_wait)
 199                 return cmd;
 200
 201         do {
 202                 prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
 203                 cmd = __alloc_cmd(nq);
 204                 if (cmd)
 205                         break;
 206
 207                 io_schedule();
 208         } while (1);
 209
 210         finish_wait(&nq->wait, &wait);
 211         return cmd;
 212 }
 213
 214 static void end_cmd(struct nullb_cmd *cmd)
 215 {
 216         switch (queue_mode)  {
 217         case NULL_Q_MQ:
 218                 blk_mq_end_request(cmd->rq, 0);
 219                 return;
 220         case NULL_Q_RQ:
 221                 INIT_LIST_HEAD(&cmd->rq->queuelist);
 222                 blk_end_request_all(cmd->rq, 0);
 223                 break;
 224         case NULL_Q_BIO:
 225                 bio_endio(cmd->bio, 0);
 226                 break;
 227         }
 228
 229         free_cmd(cmd);
 230 }
 231
 232 static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
 233 {
 234         struct completion_queue *cq;
 235         struct llist_node *entry;
 236         struct nullb_cmd *cmd;
 237
 238         cq = &per_cpu(completion_queues, smp_processor_id());
 239
 240         while ((entry = llist_del_all(&cq->list)) != NULL) {
 241                 entry = llist_reverse_order(entry);
 242                 do {
 243                         cmd = container_of(entry, struct nullb_cmd, ll_list);
 244                         entry = entry->next;
 245                         end_cmd(cmd);
 246                 } while (entry);
 247         }
 248
 249         return HRTIMER_NORESTART;
 250 }
 251
 252 static void null_cmd_end_timer(struct nullb_cmd *cmd)
 253 {
 254         struct completion_queue *cq = &per_cpu(completion_queues, get_cpu());
 255
 256         cmd->ll_list.next = NULL;
 257         if (llist_add(&cmd->ll_list, &cq->list)) {
 258                 ktime_t kt = ktime_set(0, completion_nsec);
 259
 260                 hrtimer_start(&cq->timer, kt, HRTIMER_MODE_REL);
 261         }
 262
 263         put_cpu();
 264 }
 265
 266 static void null_softirq_done_fn(struct request *rq)
 267 {
 268         if (queue_mode == NULL_Q_MQ)
 269                 end_cmd(blk_mq_rq_to_pdu(rq));
 270         else
 271                 end_cmd(rq->special);
 272 }
 273
 274 static inline void null_handle_cmd(struct nullb_cmd *cmd)
 275 {
 276         /* Complete IO by inline, softirq or timer */
 277         switch (irqmode) {
 278         case NULL_IRQ_SOFTIRQ:
 279                 switch (queue_mode)  {
 280                 case NULL_Q_MQ:
 281                         blk_mq_complete_request(cmd->rq);
 282                         break;
 283                 case NULL_Q_RQ:
 284                         blk_complete_request(cmd->rq);
 285                         break;
 286                 case NULL_Q_BIO:
 287                         /*
 288                          * XXX: no proper submitting cpu information available.
 289                          */
 290                         end_cmd(cmd);
 291                         break;
 292                 }
 293                 break;
 294         case NULL_IRQ_NONE:
 295                 end_cmd(cmd);
 296                 break;
 297         case NULL_IRQ_TIMER:
 298                 null_cmd_end_timer(cmd);
 299                 break;
 300         }
 301 }
 302
 303 static struct nullb_queue *nullb_to_queue(struct nullb *nullb)
 304 {
 305         int index = 0;
 306
 307         if (nullb->nr_queues != 1)
 308                 index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);
 309
 310         return &nullb->queues[index];
 311 }
 312
 313 static void null_queue_bio(struct request_queue *q, struct bio *bio)
 314 {
 315         struct nullb *nullb = q->queuedata;
 316         struct nullb_queue *nq = nullb_to_queue(nullb);
 317         struct nullb_cmd *cmd;
 318
 319         cmd = alloc_cmd(nq, 1);
 320         cmd->bio = bio;
 321
 322         null_handle_cmd(cmd);
 323 }
 324
 325 static int null_rq_prep_fn(struct request_queue *q, struct request *req)
 326 {
 327         struct nullb *nullb = q->queuedata;
 328         struct nullb_queue *nq = nullb_to_queue(nullb);
 329         struct nullb_cmd *cmd;
 330
 331         cmd = alloc_cmd(nq, 0);
 332         if (cmd) {
 333                 cmd->rq = req;
 334                 req->special = cmd;
 335                 return BLKPREP_OK;
 336         }
 337
 338         return BLKPREP_DEFER;
 339 }
 340
 341 static void null_request_fn(struct request_queue *q)
 342 {
 343         struct request *rq;
 344
 345         while ((rq = blk_fetch_request(q)) != NULL) {
 346                 struct nullb_cmd *cmd = rq->special;
 347
 348                 spin_unlock_irq(q->queue_lock);
 349                 null_handle_cmd(cmd);
 350                 spin_lock_irq(q->queue_lock);
 351         }
 352 }
 353
 354 static int null_queue_rq(struct blk_mq_hw_ctx *hctx,
 355                          const struct blk_mq_queue_data *bd)
 356 {
 357         struct nullb_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
 358
 359         cmd->rq = bd->rq;
 360         cmd->nq = hctx->driver_data;
 361
 362         blk_mq_start_request(bd->rq);
 363
 364         null_handle_cmd(cmd);
 365         return BLK_MQ_RQ_QUEUE_OK;
 366 }
 367
 368 static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
 369 {
 370         BUG_ON(!nullb);
 371         BUG_ON(!nq);
 372
 373         init_waitqueue_head(&nq->wait);
 374         nq->queue_depth = nullb->queue_depth;
 375 }
 376
 377 static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
 378                           unsigned int index)
 379 {
 380         struct nullb *nullb = data;
 381         struct nullb_queue *nq = &nullb->queues[index];
 382
 383         hctx->driver_data = nq;
 384         null_init_queue(nullb, nq);
 385         nullb->nr_queues++;
 386
 387         return 0;
 388 }
 389
 390 static struct blk_mq_ops null_mq_ops = {
 391         .queue_rq       = null_queue_rq,
 392         .map_queue      = blk_mq_map_queue,
 393         .init_hctx      = null_init_hctx,
 394         .complete       = null_softirq_done_fn,
 395 };
 396
 397 static void null_del_dev(struct nullb *nullb)
 398 {
 399         list_del_init(&nullb->list);
 400
 401         del_gendisk(nullb->disk);
 402         blk_cleanup_queue(nullb->q);
 403         if (queue_mode == NULL_Q_MQ)
 404                 blk_mq_free_tag_set(&nullb->tag_set);
 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                         return ret;
 492                 nullb->nr_queues++;
 493         }
 494         return 0;
 495 }
 496
 497 static int null_add_dev(void)
 498 {
 499         struct gendisk *disk;
 500         struct nullb *nullb;
 501         sector_t size;
 502         int rv;
 503
 504         nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, home_node);
 505         if (!nullb) {
 506                 rv = -ENOMEM;
 507                 goto out;
 508         }
 509
 510         spin_lock_init(&nullb->lock);
 511
 512         if (queue_mode == NULL_Q_MQ && use_per_node_hctx)
 513                 submit_queues = nr_online_nodes;
 514
 515         rv = setup_queues(nullb);
 516         if (rv)
 517                 goto out_free_nullb;
 518
 519         if (queue_mode == NULL_Q_MQ) {
 520                 nullb->tag_set.ops = &null_mq_ops;
 521                 nullb->tag_set.nr_hw_queues = submit_queues;
 522                 nullb->tag_set.queue_depth = hw_queue_depth;
 523                 nullb->tag_set.numa_node = home_node;
 524                 nullb->tag_set.cmd_size = sizeof(struct nullb_cmd);
 525                 nullb->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 526                 nullb->tag_set.driver_data = nullb;
 527
 528                 rv = blk_mq_alloc_tag_set(&nullb->tag_set);
 529                 if (rv)
 530                         goto out_cleanup_queues;
 531
 532                 nullb->q = blk_mq_init_queue(&nullb->tag_set);
 533                 if (IS_ERR(nullb->q)) {
 534                         rv = -ENOMEM;
 535                         goto out_cleanup_tags;
 536                 }
 537         } else if (queue_mode == NULL_Q_BIO) {
 538                 nullb->q = blk_alloc_queue_node(GFP_KERNEL, home_node);
 539                 if (!nullb->q) {
 540                         rv = -ENOMEM;
 541                         goto out_cleanup_queues;
 542                 }
 543                 blk_queue_make_request(nullb->q, null_queue_bio);
 544                 rv = init_driver_queues(nullb);
 545                 if (rv)
 546                         goto out_cleanup_blk_queue;
 547         } else {
 548                 nullb->q = blk_init_queue_node(null_request_fn, &nullb->lock, home_node);
 549                 if (!nullb->q) {
 550                         rv = -ENOMEM;
 551                         goto out_cleanup_queues;
 552                 }
 553                 blk_queue_prep_rq(nullb->q, null_rq_prep_fn);
 554                 blk_queue_softirq_done(nullb->q, null_softirq_done_fn);
 555                 rv = init_driver_queues(nullb);
 556                 if (rv)
 557                         goto out_cleanup_blk_queue;
 558         }
 559
 560         nullb->q->queuedata = nullb;
 561         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, nullb->q);
 562         queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, nullb->q);
 563
 564         disk = nullb->disk = alloc_disk_node(1, home_node);
 565         if (!disk) {
 566                 rv = -ENOMEM;
 567                 goto out_cleanup_blk_queue;
 568         }
 569
 570         mutex_lock(&lock);
 571         list_add_tail(&nullb->list, &nullb_list);
 572         nullb->index = nullb_indexes++;
 573         mutex_unlock(&lock);
 574
 575         blk_queue_logical_block_size(nullb->q, bs);
 576         blk_queue_physical_block_size(nullb->q, bs);
 577
 578         size = gb * 1024 * 1024 * 1024ULL;
 579         sector_div(size, bs);
 580         set_capacity(disk, size);
 581
 582         disk->flags |= GENHD_FL_EXT_DEVT | GENHD_FL_SUPPRESS_PARTITION_INFO;
 583         disk->major             = null_major;
 584         disk->first_minor       = nullb->index;
 585         disk->fops              = &null_fops;
 586         disk->private_data      = nullb;
 587         disk->queue             = nullb->q;
 588         sprintf(disk->disk_name, "nullb%d", nullb->index);
 589         add_disk(disk);
 590         return 0;
 591
 592 out_cleanup_blk_queue:
 593         blk_cleanup_queue(nullb->q);
 594 out_cleanup_tags:
 595         if (queue_mode == NULL_Q_MQ)
 596                 blk_mq_free_tag_set(&nullb->tag_set);
 597 out_cleanup_queues:
 598         cleanup_queues(nullb);
 599 out_free_nullb:
 600         kfree(nullb);
 601 out:
 602         return rv;
 603 }
 604
 605 static int __init null_init(void)
 606 {
 607         unsigned int i;
 608
 609         if (bs > PAGE_SIZE) {
 610                 pr_warn("null_blk: invalid block size\n");
 611                 pr_warn("null_blk: defaults block size to %lu\n", PAGE_SIZE);
 612                 bs = PAGE_SIZE;
 613         }
 614
 615         if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {
 616                 if (submit_queues < nr_online_nodes) {
 617                         pr_warn("null_blk: submit_queues param is set to %u.",
 618                                                         nr_online_nodes);
 619                         submit_queues = nr_online_nodes;
 620                 }
 621         } else if (submit_queues > nr_cpu_ids)
 622                 submit_queues = nr_cpu_ids;
 623         else if (!submit_queues)
 624                 submit_queues = 1;
 625
 626         mutex_init(&lock);
 627
 628         /* Initialize a separate list for each CPU for issuing softirqs */
 629         for_each_possible_cpu(i) {
 630                 struct completion_queue *cq = &per_cpu(completion_queues, i);
 631
 632                 init_llist_head(&cq->list);
 633
 634                 if (irqmode != NULL_IRQ_TIMER)
 635                         continue;
 636
 637                 hrtimer_init(&cq->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 638                 cq->timer.function = null_cmd_timer_expired;
 639         }
 640
 641         null_major = register_blkdev(0, "nullb");
 642         if (null_major < 0)
 643                 return null_major;
 644
 645         for (i = 0; i < nr_devices; i++) {
 646                 if (null_add_dev()) {
 647                         unregister_blkdev(null_major, "nullb");
 648                         return -EINVAL;
 649                 }
 650         }
 651
 652         pr_info("null: module loaded\n");
 653         return 0;
 654 }
 655
 656 static void __exit null_exit(void)
 657 {
 658         struct nullb *nullb;
 659
 660         unregister_blkdev(null_major, "nullb");
 661
 662         mutex_lock(&lock);
 663         while (!list_empty(&nullb_list)) {
 664                 nullb = list_entry(nullb_list.next, struct nullb, list);
 665                 null_del_dev(nullb);
 666         }
 667         mutex_unlock(&lock);
 668 }
 669
 670 module_init(null_init);
 671 module_exit(null_exit);
 672
 673 MODULE_AUTHOR("Jens Axboe <jaxboe@fusionio.com>");
 674 MODULE_LICENSE("GPL");