drivers/md/kcopyd.c

   1 /*
   2  * Copyright (C) 2002 Sistina Software (UK) Limited.
   3  * Copyright (C) 2006 Red Hat GmbH
   4  *
   5  * This file is released under the GPL.
   6  *
   7  * Kcopyd provides a simple interface for copying an area of one
   8  * block-device to one or more other block-devices, with an asynchronous
   9  * completion notification.
  10  */
  11
  12 #include <asm/types.h>
  13 #include <asm/atomic.h>
  14
  15 #include <linux/blkdev.h>
  16 #include <linux/fs.h>
  17 #include <linux/init.h>
  18 #include <linux/list.h>
  19 #include <linux/mempool.h>
  20 #include <linux/module.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/slab.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/mutex.h>
  26
  27 #include "kcopyd.h"
  28
  29 static struct workqueue_struct *_kcopyd_wq;
  30 static struct work_struct _kcopyd_work;
  31
  32 static void wake(void)
  33 {
  34         queue_work(_kcopyd_wq, &_kcopyd_work);
  35 }
  36
  37 /*-----------------------------------------------------------------
  38  * Each kcopyd client has its own little pool of preallocated
  39  * pages for kcopyd io.
  40  *---------------------------------------------------------------*/
  41 struct kcopyd_client {
  42         struct list_head list;
  43
  44         spinlock_t lock;
  45         struct page_list *pages;
  46         unsigned int nr_pages;
  47         unsigned int nr_free_pages;
  48
  49         struct dm_io_client *io_client;
  50
  51         wait_queue_head_t destroyq;
  52         atomic_t nr_jobs;
  53 };
  54
  55 static struct page_list *alloc_pl(void)
  56 {
  57         struct page_list *pl;
  58
  59         pl = kmalloc(sizeof(*pl), GFP_KERNEL);
  60         if (!pl)
  61                 return NULL;
  62
  63         pl->page = alloc_page(GFP_KERNEL);
  64         if (!pl->page) {
  65                 kfree(pl);
  66                 return NULL;
  67         }
  68
  69         return pl;
  70 }
  71
  72 static void free_pl(struct page_list *pl)
  73 {
  74         __free_page(pl->page);
  75         kfree(pl);
  76 }
  77
  78 static int kcopyd_get_pages(struct kcopyd_client *kc,
  79                             unsigned int nr, struct page_list **pages)
  80 {
  81         struct page_list *pl;
  82
  83         spin_lock(&kc->lock);
  84         if (kc->nr_free_pages < nr) {
  85                 spin_unlock(&kc->lock);
  86                 return -ENOMEM;
  87         }
  88
  89         kc->nr_free_pages -= nr;
  90         for (*pages = pl = kc->pages; --nr; pl = pl->next)
  91                 ;
  92
  93         kc->pages = pl->next;
  94         pl->next = NULL;
  95
  96         spin_unlock(&kc->lock);
  97
  98         return 0;
  99 }
 100
 101 static void kcopyd_put_pages(struct kcopyd_client *kc, struct page_list *pl)
 102 {
 103         struct page_list *cursor;
 104
 105         spin_lock(&kc->lock);
 106         for (cursor = pl; cursor->next; cursor = cursor->next)
 107                 kc->nr_free_pages++;
 108
 109         kc->nr_free_pages++;
 110         cursor->next = kc->pages;
 111         kc->pages = pl;
 112         spin_unlock(&kc->lock);
 113 }
 114
 115 /*
 116  * These three functions resize the page pool.
 117  */
 118 static void drop_pages(struct page_list *pl)
 119 {
 120         struct page_list *next;
 121
 122         while (pl) {
 123                 next = pl->next;
 124                 free_pl(pl);
 125                 pl = next;
 126         }
 127 }
 128
 129 static int client_alloc_pages(struct kcopyd_client *kc, unsigned int nr)
 130 {
 131         unsigned int i;
 132         struct page_list *pl = NULL, *next;
 133
 134         for (i = 0; i < nr; i++) {
 135                 next = alloc_pl();
 136                 if (!next) {
 137                         if (pl)
 138                                 drop_pages(pl);
 139                         return -ENOMEM;
 140                 }
 141                 next->next = pl;
 142                 pl = next;
 143         }
 144
 145         kcopyd_put_pages(kc, pl);
 146         kc->nr_pages += nr;
 147         return 0;
 148 }
 149
 150 static void client_free_pages(struct kcopyd_client *kc)
 151 {
 152         BUG_ON(kc->nr_free_pages != kc->nr_pages);
 153         drop_pages(kc->pages);
 154         kc->pages = NULL;
 155         kc->nr_free_pages = kc->nr_pages = 0;
 156 }
 157
 158 /*-----------------------------------------------------------------
 159  * kcopyd_jobs need to be allocated by the *clients* of kcopyd,
 160  * for this reason we use a mempool to prevent the client from
 161  * ever having to do io (which could cause a deadlock).
 162  *---------------------------------------------------------------*/
 163 struct kcopyd_job {
 164         struct kcopyd_client *kc;
 165         struct list_head list;
 166         unsigned long flags;
 167
 168         /*
 169          * Error state of the job.
 170          */
 171         int read_err;
 172         unsigned int write_err;
 173
 174         /*
 175          * Either READ or WRITE
 176          */
 177         int rw;
 178         struct io_region source;
 179
 180         /*
 181          * The destinations for the transfer.
 182          */
 183         unsigned int num_dests;
 184         struct io_region dests[KCOPYD_MAX_REGIONS];
 185
 186         sector_t offset;
 187         unsigned int nr_pages;
 188         struct page_list *pages;
 189
 190         /*
 191          * Set this to ensure you are notified when the job has
 192          * completed.  'context' is for callback to use.
 193          */
 194         kcopyd_notify_fn fn;
 195         void *context;
 196
 197         /*
 198          * These fields are only used if the job has been split
 199          * into more manageable parts.
 200          */
 201         struct mutex lock;
 202         atomic_t sub_jobs;
 203         sector_t progress;
 204 };
 205
 206 /* FIXME: this should scale with the number of pages */
 207 #define MIN_JOBS 512
 208
 209 static struct kmem_cache *_job_cache;
 210 static mempool_t *_job_pool;
 211
 212 /*
 213  * We maintain three lists of jobs:
 214  *
 215  * i)   jobs waiting for pages
 216  * ii)  jobs that have pages, and are waiting for the io to be issued.
 217  * iii) jobs that have completed.
 218  *
 219  * All three of these are protected by job_lock.
 220  */
 221 static DEFINE_SPINLOCK(_job_lock);
 222
 223 static LIST_HEAD(_complete_jobs);
 224 static LIST_HEAD(_io_jobs);
 225 static LIST_HEAD(_pages_jobs);
 226
 227 static int jobs_init(void)
 228 {
 229         _job_cache = KMEM_CACHE(kcopyd_job, 0);
 230         if (!_job_cache)
 231                 return -ENOMEM;
 232
 233         _job_pool = mempool_create_slab_pool(MIN_JOBS, _job_cache);
 234         if (!_job_pool) {
 235                 kmem_cache_destroy(_job_cache);
 236                 return -ENOMEM;
 237         }
 238
 239         return 0;
 240 }
 241
 242 static void jobs_exit(void)
 243 {
 244         BUG_ON(!list_empty(&_complete_jobs));
 245         BUG_ON(!list_empty(&_io_jobs));
 246         BUG_ON(!list_empty(&_pages_jobs));
 247
 248         mempool_destroy(_job_pool);
 249         kmem_cache_destroy(_job_cache);
 250         _job_pool = NULL;
 251         _job_cache = NULL;
 252 }
 253
 254 /*
 255  * Functions to push and pop a job onto the head of a given job
 256  * list.
 257  */
 258 static struct kcopyd_job *pop(struct list_head *jobs)
 259 {
 260         struct kcopyd_job *job = NULL;
 261         unsigned long flags;
 262
 263         spin_lock_irqsave(&_job_lock, flags);
 264
 265         if (!list_empty(jobs)) {
 266                 job = list_entry(jobs->next, struct kcopyd_job, list);
 267                 list_del(&job->list);
 268         }
 269         spin_unlock_irqrestore(&_job_lock, flags);
 270
 271         return job;
 272 }
 273
 274 static void push(struct list_head *jobs, struct kcopyd_job *job)
 275 {
 276         unsigned long flags;
 277
 278         spin_lock_irqsave(&_job_lock, flags);
 279         list_add_tail(&job->list, jobs);
 280         spin_unlock_irqrestore(&_job_lock, flags);
 281 }
 282
 283 /*
 284  * These three functions process 1 item from the corresponding
 285  * job list.
 286  *
 287  * They return:
 288  * < 0: error
 289  *   0: success
 290  * > 0: can't process yet.
 291  */
 292 static int run_complete_job(struct kcopyd_job *job)
 293 {
 294         void *context = job->context;
 295         int read_err = job->read_err;
 296         unsigned int write_err = job->write_err;
 297         kcopyd_notify_fn fn = job->fn;
 298         struct kcopyd_client *kc = job->kc;
 299
 300         kcopyd_put_pages(kc, job->pages);
 301         mempool_free(job, _job_pool);
 302         fn(read_err, write_err, context);
 303
 304         if (atomic_dec_and_test(&kc->nr_jobs))
 305                 wake_up(&kc->destroyq);
 306
 307         return 0;
 308 }
 309
 310 static void complete_io(unsigned long error, void *context)
 311 {
 312         struct kcopyd_job *job = (struct kcopyd_job *) context;
 313
 314         if (error) {
 315                 if (job->rw == WRITE)
 316                         job->write_err |= error;
 317                 else
 318                         job->read_err = 1;
 319
 320                 if (!test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
 321                         push(&_complete_jobs, job);
 322                         wake();
 323                         return;
 324                 }
 325         }
 326
 327         if (job->rw == WRITE)
 328                 push(&_complete_jobs, job);
 329
 330         else {
 331                 job->rw = WRITE;
 332                 push(&_io_jobs, job);
 333         }
 334
 335         wake();
 336 }
 337
 338 /*
 339  * Request io on as many buffer heads as we can currently get for
 340  * a particular job.
 341  */
 342 static int run_io_job(struct kcopyd_job *job)
 343 {
 344         int r;
 345         struct dm_io_request io_req = {
 346                 .bi_rw = job->rw,
 347                 .mem.type = DM_IO_PAGE_LIST,
 348                 .mem.ptr.pl = job->pages,
 349                 .mem.offset = job->offset,
 350                 .notify.fn = complete_io,
 351                 .notify.context = job,
 352                 .client = job->kc->io_client,
 353         };
 354
 355         if (job->rw == READ)
 356                 r = dm_io(&io_req, 1, &job->source, NULL);
 357         else
 358                 r = dm_io(&io_req, job->num_dests, job->dests, NULL);
 359
 360         return r;
 361 }
 362
 363 static int run_pages_job(struct kcopyd_job *job)
 364 {
 365         int r;
 366
 367         job->nr_pages = dm_div_up(job->dests[0].count + job->offset,
 368                                   PAGE_SIZE >> 9);
 369         r = kcopyd_get_pages(job->kc, job->nr_pages, &job->pages);
 370         if (!r) {
 371                 /* this job is ready for io */
 372                 push(&_io_jobs, job);
 373                 return 0;
 374         }
 375
 376         if (r == -ENOMEM)
 377                 /* can't complete now */
 378                 return 1;
 379
 380         return r;
 381 }
 382
 383 /*
 384  * Run through a list for as long as possible.  Returns the count
 385  * of successful jobs.
 386  */
 387 static int process_jobs(struct list_head *jobs, int (*fn) (struct kcopyd_job *))
 388 {
 389         struct kcopyd_job *job;
 390         int r, count = 0;
 391
 392         while ((job = pop(jobs))) {
 393
 394                 r = fn(job);
 395
 396                 if (r < 0) {
 397                         /* error this rogue job */
 398                         if (job->rw == WRITE)
 399                                 job->write_err = (unsigned int) -1;
 400                         else
 401                                 job->read_err = 1;
 402                         push(&_complete_jobs, job);
 403                         break;
 404                 }
 405
 406                 if (r > 0) {
 407                         /*
 408                          * We couldn't service this job ATM, so
 409                          * push this job back onto the list.
 410                          */
 411                         push(jobs, job);
 412                         break;
 413                 }
 414
 415                 count++;
 416         }
 417
 418         return count;
 419 }
 420
 421 /*
 422  * kcopyd does this every time it's woken up.
 423  */
 424 static void do_work(struct work_struct *ignored)
 425 {
 426         /*
 427          * The order that these are called is *very* important.
 428          * complete jobs can free some pages for pages jobs.
 429          * Pages jobs when successful will jump onto the io jobs
 430          * list.  io jobs call wake when they complete and it all
 431          * starts again.
 432          */
 433         process_jobs(&_complete_jobs, run_complete_job);
 434         process_jobs(&_pages_jobs, run_pages_job);
 435         process_jobs(&_io_jobs, run_io_job);
 436 }
 437
 438 /*
 439  * If we are copying a small region we just dispatch a single job
 440  * to do the copy, otherwise the io has to be split up into many
 441  * jobs.
 442  */
 443 static void dispatch_job(struct kcopyd_job *job)
 444 {
 445         atomic_inc(&job->kc->nr_jobs);
 446         push(&_pages_jobs, job);
 447         wake();
 448 }
 449
 450 #define SUB_JOB_SIZE 128
 451 static void segment_complete(int read_err,
 452                              unsigned int write_err, void *context)
 453 {
 454         /* FIXME: tidy this function */
 455         sector_t progress = 0;
 456         sector_t count = 0;
 457         struct kcopyd_job *job = (struct kcopyd_job *) context;
 458
 459         mutex_lock(&job->lock);
 460
 461         /* update the error */
 462         if (read_err)
 463                 job->read_err = 1;
 464
 465         if (write_err)
 466                 job->write_err |= write_err;
 467
 468         /*
 469          * Only dispatch more work if there hasn't been an error.
 470          */
 471         if ((!job->read_err && !job->write_err) ||
 472             test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
 473                 /* get the next chunk of work */
 474                 progress = job->progress;
 475                 count = job->source.count - progress;
 476                 if (count) {
 477                         if (count > SUB_JOB_SIZE)
 478                                 count = SUB_JOB_SIZE;
 479
 480                         job->progress += count;
 481                 }
 482         }
 483         mutex_unlock(&job->lock);
 484
 485         if (count) {
 486                 int i;
 487                 struct kcopyd_job *sub_job = mempool_alloc(_job_pool, GFP_NOIO);
 488
 489                 *sub_job = *job;
 490                 sub_job->source.sector += progress;
 491                 sub_job->source.count = count;
 492
 493                 for (i = 0; i < job->num_dests; i++) {
 494                         sub_job->dests[i].sector += progress;
 495                         sub_job->dests[i].count = count;
 496                 }
 497
 498                 sub_job->fn = segment_complete;
 499                 sub_job->context = job;
 500                 dispatch_job(sub_job);
 501
 502         } else if (atomic_dec_and_test(&job->sub_jobs)) {
 503
 504                 /*
 505                  * To avoid a race we must keep the job around
 506                  * until after the notify function has completed.
 507                  * Otherwise the client may try and stop the job
 508                  * after we've completed.
 509                  */
 510                 job->fn(read_err, write_err, job->context);
 511                 mempool_free(job, _job_pool);
 512         }
 513 }
 514
 515 /*
 516  * Create some little jobs that will do the move between
 517  * them.
 518  */
 519 #define SPLIT_COUNT 8
 520 static void split_job(struct kcopyd_job *job)
 521 {
 522         int i;
 523
 524         atomic_set(&job->sub_jobs, SPLIT_COUNT);
 525         for (i = 0; i < SPLIT_COUNT; i++)
 526                 segment_complete(0, 0u, job);
 527 }
 528
 529 int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from,
 530                 unsigned int num_dests, struct io_region *dests,
 531                 unsigned int flags, kcopyd_notify_fn fn, void *context)
 532 {
 533         struct kcopyd_job *job;
 534
 535         /*
 536          * Allocate a new job.
 537          */
 538         job = mempool_alloc(_job_pool, GFP_NOIO);
 539
 540         /*
 541          * set up for the read.
 542          */
 543         job->kc = kc;
 544         job->flags = flags;
 545         job->read_err = 0;
 546         job->write_err = 0;
 547         job->rw = READ;
 548
 549         job->source = *from;
 550
 551         job->num_dests = num_dests;
 552         memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
 553
 554         job->offset = 0;
 555         job->nr_pages = 0;
 556         job->pages = NULL;
 557
 558         job->fn = fn;
 559         job->context = context;
 560
 561         if (job->source.count < SUB_JOB_SIZE)
 562                 dispatch_job(job);
 563
 564         else {
 565                 mutex_init(&job->lock);
 566                 job->progress = 0;
 567                 split_job(job);
 568         }
 569
 570         return 0;
 571 }
 572
 573 /*
 574  * Cancels a kcopyd job, eg. someone might be deactivating a
 575  * mirror.
 576  */
 577 #if 0
 578 int kcopyd_cancel(struct kcopyd_job *job, int block)
 579 {
 580         /* FIXME: finish */
 581         return -1;
 582 }
 583 #endif  /*  0  */
 584
 585 /*-----------------------------------------------------------------
 586  * Unit setup
 587  *---------------------------------------------------------------*/
 588 static DEFINE_MUTEX(_client_lock);
 589 static LIST_HEAD(_clients);
 590
 591 static void client_add(struct kcopyd_client *kc)
 592 {
 593         mutex_lock(&_client_lock);
 594         list_add(&kc->list, &_clients);
 595         mutex_unlock(&_client_lock);
 596 }
 597
 598 static void client_del(struct kcopyd_client *kc)
 599 {
 600         mutex_lock(&_client_lock);
 601         list_del(&kc->list);
 602         mutex_unlock(&_client_lock);
 603 }
 604
 605 static DEFINE_MUTEX(kcopyd_init_lock);
 606 static int kcopyd_clients = 0;
 607
 608 static int kcopyd_init(void)
 609 {
 610         int r;
 611
 612         mutex_lock(&kcopyd_init_lock);
 613
 614         if (kcopyd_clients) {
 615                 /* Already initialized. */
 616                 kcopyd_clients++;
 617                 mutex_unlock(&kcopyd_init_lock);
 618                 return 0;
 619         }
 620
 621         r = jobs_init();
 622         if (r) {
 623                 mutex_unlock(&kcopyd_init_lock);
 624                 return r;
 625         }
 626
 627         _kcopyd_wq = create_singlethread_workqueue("kcopyd");
 628         if (!_kcopyd_wq) {
 629                 jobs_exit();
 630                 mutex_unlock(&kcopyd_init_lock);
 631                 return -ENOMEM;
 632         }
 633
 634         kcopyd_clients++;
 635         INIT_WORK(&_kcopyd_work, do_work);
 636         mutex_unlock(&kcopyd_init_lock);
 637         return 0;
 638 }
 639
 640 static void kcopyd_exit(void)
 641 {
 642         mutex_lock(&kcopyd_init_lock);
 643         kcopyd_clients--;
 644         if (!kcopyd_clients) {
 645                 jobs_exit();
 646                 destroy_workqueue(_kcopyd_wq);
 647                 _kcopyd_wq = NULL;
 648         }
 649         mutex_unlock(&kcopyd_init_lock);
 650 }
 651
 652 int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result)
 653 {
 654         int r = 0;
 655         struct kcopyd_client *kc;
 656
 657         r = kcopyd_init();
 658         if (r)
 659                 return r;
 660
 661         kc = kmalloc(sizeof(*kc), GFP_KERNEL);
 662         if (!kc) {
 663                 kcopyd_exit();
 664                 return -ENOMEM;
 665         }
 666
 667         spin_lock_init(&kc->lock);
 668         kc->pages = NULL;
 669         kc->nr_pages = kc->nr_free_pages = 0;
 670         r = client_alloc_pages(kc, nr_pages);
 671         if (r) {
 672                 kfree(kc);
 673                 kcopyd_exit();
 674                 return r;
 675         }
 676
 677         kc->io_client = dm_io_client_create(nr_pages);
 678         if (IS_ERR(kc->io_client)) {
 679                 r = PTR_ERR(kc->io_client);
 680                 client_free_pages(kc);
 681                 kfree(kc);
 682                 kcopyd_exit();
 683                 return r;
 684         }
 685
 686         init_waitqueue_head(&kc->destroyq);
 687         atomic_set(&kc->nr_jobs, 0);
 688
 689         client_add(kc);
 690         *result = kc;
 691         return 0;
 692 }
 693
 694 void kcopyd_client_destroy(struct kcopyd_client *kc)
 695 {
 696         /* Wait for completion of all jobs submitted by this client. */
 697         wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs));
 698
 699         dm_io_client_destroy(kc->io_client);
 700         client_free_pages(kc);
 701         client_del(kc);
 702         kfree(kc);
 703         kcopyd_exit();
 704 }
 705
 706 EXPORT_SYMBOL(kcopyd_client_create);
 707 EXPORT_SYMBOL(kcopyd_client_destroy);
 708 EXPORT_SYMBOL(kcopyd_copy);