drivers/block/null_blk.c

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