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