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