drivers/md/kcopyd.c

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