drivers/md/bcache/writeback.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * background writeback - scan btree for dirty data and write it to the backing
   4  * device
   5  *
   6  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   7  * Copyright 2012 Google, Inc.
   8  */
   9
  10 #include "bcache.h"
  11 #include "btree.h"
  12 #include "debug.h"
  13 #include "writeback.h"
  14
  15 #include <linux/delay.h>
  16 #include <linux/kthread.h>
  17 #include <linux/sched/clock.h>
  18 #include <trace/events/bcache.h>
  19
  20 /* Rate limiting */
  21 static uint64_t __calc_target_rate(struct cached_dev *dc)
  22 {
  23         struct cache_set *c = dc->disk.c;
  24
  25         /*
  26          * This is the size of the cache, minus the amount used for
  27          * flash-only devices
  28          */
  29         uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size -
  30                                 atomic_long_read(&c->flash_dev_dirty_sectors);
  31
  32         /*
  33          * Unfortunately there is no control of global dirty data.  If the
  34          * user states that they want 10% dirty data in the cache, and has,
  35          * e.g., 5 backing volumes of equal size, we try and ensure each
  36          * backing volume uses about 2% of the cache for dirty data.
  37          */
  38         uint32_t bdev_share =
  39                 div64_u64(bdev_sectors(dc->bdev) << WRITEBACK_SHARE_SHIFT,
  40                                 c->cached_dev_sectors);
  41
  42         uint64_t cache_dirty_target =
  43                 div_u64(cache_sectors * dc->writeback_percent, 100);
  44
  45         /* Ensure each backing dev gets at least one dirty share */
  46         if (bdev_share < 1)
  47                 bdev_share = 1;
  48
  49         return (cache_dirty_target * bdev_share) >> WRITEBACK_SHARE_SHIFT;
  50 }
  51
  52 static void __update_writeback_rate(struct cached_dev *dc)
  53 {
  54         /*
  55          * PI controller:
  56          * Figures out the amount that should be written per second.
  57          *
  58          * First, the error (number of sectors that are dirty beyond our
  59          * target) is calculated.  The error is accumulated (numerically
  60          * integrated).
  61          *
  62          * Then, the proportional value and integral value are scaled
  63          * based on configured values.  These are stored as inverses to
  64          * avoid fixed point math and to make configuration easy-- e.g.
  65          * the default value of 40 for writeback_rate_p_term_inverse
  66          * attempts to write at a rate that would retire all the dirty
  67          * blocks in 40 seconds.
  68          *
  69          * The writeback_rate_i_inverse value of 10000 means that 1/10000th
  70          * of the error is accumulated in the integral term per second.
  71          * This acts as a slow, long-term average that is not subject to
  72          * variations in usage like the p term.
  73          */
  74         int64_t target = __calc_target_rate(dc);
  75         int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
  76         int64_t error = dirty - target;
  77         int64_t proportional_scaled =
  78                 div_s64(error, dc->writeback_rate_p_term_inverse);
  79         int64_t integral_scaled;
  80         uint32_t new_rate;
  81
  82         if ((error < 0 && dc->writeback_rate_integral > 0) ||
  83             (error > 0 && time_before64(local_clock(),
  84                          dc->writeback_rate.next + NSEC_PER_MSEC))) {
  85                 /*
  86                  * Only decrease the integral term if it's more than
  87                  * zero.  Only increase the integral term if the device
  88                  * is keeping up.  (Don't wind up the integral
  89                  * ineffectively in either case).
  90                  *
  91                  * It's necessary to scale this by
  92                  * writeback_rate_update_seconds to keep the integral
  93                  * term dimensioned properly.
  94                  */
  95                 dc->writeback_rate_integral += error *
  96                         dc->writeback_rate_update_seconds;
  97         }
  98
  99         integral_scaled = div_s64(dc->writeback_rate_integral,
 100                         dc->writeback_rate_i_term_inverse);
 101
 102         new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
 103                         dc->writeback_rate_minimum, NSEC_PER_SEC);
 104
 105         dc->writeback_rate_proportional = proportional_scaled;
 106         dc->writeback_rate_integral_scaled = integral_scaled;
 107         dc->writeback_rate_change = new_rate -
 108                         atomic_long_read(&dc->writeback_rate.rate);
 109         atomic_long_set(&dc->writeback_rate.rate, new_rate);
 110         dc->writeback_rate_target = target;
 111 }
 112
 113 static bool set_at_max_writeback_rate(struct cache_set *c,
 114                                        struct cached_dev *dc)
 115 {
 116         /*
 117          * Idle_counter is increased everytime when update_writeback_rate() is
 118          * called. If all backing devices attached to the same cache set have
 119          * identical dc->writeback_rate_update_seconds values, it is about 6
 120          * rounds of update_writeback_rate() on each backing device before
 121          * c->at_max_writeback_rate is set to 1, and then max wrteback rate set
 122          * to each dc->writeback_rate.rate.
 123          * In order to avoid extra locking cost for counting exact dirty cached
 124          * devices number, c->attached_dev_nr is used to calculate the idle
 125          * throushold. It might be bigger if not all cached device are in write-
 126          * back mode, but it still works well with limited extra rounds of
 127          * update_writeback_rate().
 128          */
 129         if (atomic_inc_return(&c->idle_counter) <
 130             atomic_read(&c->attached_dev_nr) * 6)
 131                 return false;
 132
 133         if (atomic_read(&c->at_max_writeback_rate) != 1)
 134                 atomic_set(&c->at_max_writeback_rate, 1);
 135
 136         atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
 137
 138         /* keep writeback_rate_target as existing value */
 139         dc->writeback_rate_proportional = 0;
 140         dc->writeback_rate_integral_scaled = 0;
 141         dc->writeback_rate_change = 0;
 142
 143         /*
 144          * Check c->idle_counter and c->at_max_writeback_rate agagain in case
 145          * new I/O arrives during before set_at_max_writeback_rate() returns.
 146          * Then the writeback rate is set to 1, and its new value should be
 147          * decided via __update_writeback_rate().
 148          */
 149         if ((atomic_read(&c->idle_counter) <
 150              atomic_read(&c->attached_dev_nr) * 6) ||
 151             !atomic_read(&c->at_max_writeback_rate))
 152                 return false;
 153
 154         return true;
 155 }
 156
 157 static void update_writeback_rate(struct work_struct *work)
 158 {
 159         struct cached_dev *dc = container_of(to_delayed_work(work),
 160                                              struct cached_dev,
 161                                              writeback_rate_update);
 162         struct cache_set *c = dc->disk.c;
 163
 164         /*
 165          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 166          * cancel_delayed_work_sync().
 167          */
 168         set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 169         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 170         smp_mb();
 171
 172         /*
 173          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 174          * check it here too.
 175          */
 176         if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
 177             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 178                 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 179                 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 180                 smp_mb();
 181                 return;
 182         }
 183
 184         if (atomic_read(&dc->has_dirty) && dc->writeback_percent) {
 185                 /*
 186                  * If the whole cache set is idle, set_at_max_writeback_rate()
 187                  * will set writeback rate to a max number. Then it is
 188                  * unncessary to update writeback rate for an idle cache set
 189                  * in maximum writeback rate number(s).
 190                  */
 191                 if (!set_at_max_writeback_rate(c, dc)) {
 192                         down_read(&dc->writeback_lock);
 193                         __update_writeback_rate(dc);
 194                         up_read(&dc->writeback_lock);
 195                 }
 196         }
 197
 198
 199         /*
 200          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 201          * check it here too.
 202          */
 203         if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
 204             !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 205                 schedule_delayed_work(&dc->writeback_rate_update,
 206                               dc->writeback_rate_update_seconds * HZ);
 207         }
 208
 209         /*
 210          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 211          * cancel_delayed_work_sync().
 212          */
 213         clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 214         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 215         smp_mb();
 216 }
 217
 218 static unsigned int writeback_delay(struct cached_dev *dc,
 219                                     unsigned int sectors)
 220 {
 221         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
 222             !dc->writeback_percent)
 223                 return 0;
 224
 225         return bch_next_delay(&dc->writeback_rate, sectors);
 226 }
 227
 228 struct dirty_io {
 229         struct closure          cl;
 230         struct cached_dev       *dc;
 231         uint16_t                sequence;
 232         struct bio              bio;
 233 };
 234
 235 static void dirty_init(struct keybuf_key *w)
 236 {
 237         struct dirty_io *io = w->private;
 238         struct bio *bio = &io->bio;
 239
 240         bio_init(bio, bio->bi_inline_vecs,
 241                  DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS));
 242         if (!io->dc->writeback_percent)
 243                 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 244
 245         bio->bi_iter.bi_size    = KEY_SIZE(&w->key) << 9;
 246         bio->bi_private         = w;
 247         bch_bio_map(bio, NULL);
 248 }
 249
 250 static void dirty_io_destructor(struct closure *cl)
 251 {
 252         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 253
 254         kfree(io);
 255 }
 256
 257 static void write_dirty_finish(struct closure *cl)
 258 {
 259         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 260         struct keybuf_key *w = io->bio.bi_private;
 261         struct cached_dev *dc = io->dc;
 262
 263         bio_free_pages(&io->bio);
 264
 265         /* This is kind of a dumb way of signalling errors. */
 266         if (KEY_DIRTY(&w->key)) {
 267                 int ret;
 268                 unsigned int i;
 269                 struct keylist keys;
 270
 271                 bch_keylist_init(&keys);
 272
 273                 bkey_copy(keys.top, &w->key);
 274                 SET_KEY_DIRTY(keys.top, false);
 275                 bch_keylist_push(&keys);
 276
 277                 for (i = 0; i < KEY_PTRS(&w->key); i++)
 278                         atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
 279
 280                 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
 281
 282                 if (ret)
 283                         trace_bcache_writeback_collision(&w->key);
 284
 285                 atomic_long_inc(ret
 286                                 ? &dc->disk.c->writeback_keys_failed
 287                                 : &dc->disk.c->writeback_keys_done);
 288         }
 289
 290         bch_keybuf_del(&dc->writeback_keys, w);
 291         up(&dc->in_flight);
 292
 293         closure_return_with_destructor(cl, dirty_io_destructor);
 294 }
 295
 296 static void dirty_endio(struct bio *bio)
 297 {
 298         struct keybuf_key *w = bio->bi_private;
 299         struct dirty_io *io = w->private;
 300
 301         if (bio->bi_status) {
 302                 SET_KEY_DIRTY(&w->key, false);
 303                 bch_count_backing_io_errors(io->dc, bio);
 304         }
 305
 306         closure_put(&io->cl);
 307 }
 308
 309 static void write_dirty(struct closure *cl)
 310 {
 311         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 312         struct keybuf_key *w = io->bio.bi_private;
 313         struct cached_dev *dc = io->dc;
 314
 315         uint16_t next_sequence;
 316
 317         if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
 318                 /* Not our turn to write; wait for a write to complete */
 319                 closure_wait(&dc->writeback_ordering_wait, cl);
 320
 321                 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
 322                         /*
 323                          * Edge case-- it happened in indeterminate order
 324                          * relative to when we were added to wait list..
 325                          */
 326                         closure_wake_up(&dc->writeback_ordering_wait);
 327                 }
 328
 329                 continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 330                 return;
 331         }
 332
 333         next_sequence = io->sequence + 1;
 334
 335         /*
 336          * IO errors are signalled using the dirty bit on the key.
 337          * If we failed to read, we should not attempt to write to the
 338          * backing device.  Instead, immediately go to write_dirty_finish
 339          * to clean up.
 340          */
 341         if (KEY_DIRTY(&w->key)) {
 342                 dirty_init(w);
 343                 bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
 344                 io->bio.bi_iter.bi_sector = KEY_START(&w->key);
 345                 bio_set_dev(&io->bio, io->dc->bdev);
 346                 io->bio.bi_end_io       = dirty_endio;
 347
 348                 /* I/O request sent to backing device */
 349                 closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 350         }
 351
 352         atomic_set(&dc->writeback_sequence_next, next_sequence);
 353         closure_wake_up(&dc->writeback_ordering_wait);
 354
 355         continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
 356 }
 357
 358 static void read_dirty_endio(struct bio *bio)
 359 {
 360         struct keybuf_key *w = bio->bi_private;
 361         struct dirty_io *io = w->private;
 362
 363         /* is_read = 1 */
 364         bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
 365                             bio->bi_status, 1,
 366                             "reading dirty data from cache");
 367
 368         dirty_endio(bio);
 369 }
 370
 371 static void read_dirty_submit(struct closure *cl)
 372 {
 373         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 374
 375         closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 376
 377         continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 378 }
 379
 380 static void read_dirty(struct cached_dev *dc)
 381 {
 382         unsigned int delay = 0;
 383         struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
 384         size_t size;
 385         int nk, i;
 386         struct dirty_io *io;
 387         struct closure cl;
 388         uint16_t sequence = 0;
 389
 390         BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
 391         atomic_set(&dc->writeback_sequence_next, sequence);
 392         closure_init_stack(&cl);
 393
 394         /*
 395          * XXX: if we error, background writeback just spins. Should use some
 396          * mempools.
 397          */
 398
 399         next = bch_keybuf_next(&dc->writeback_keys);
 400
 401         while (!kthread_should_stop() &&
 402                !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 403                next) {
 404                 size = 0;
 405                 nk = 0;
 406
 407                 do {
 408                         BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
 409
 410                         /*
 411                          * Don't combine too many operations, even if they
 412                          * are all small.
 413                          */
 414                         if (nk >= MAX_WRITEBACKS_IN_PASS)
 415                                 break;
 416
 417                         /*
 418                          * If the current operation is very large, don't
 419                          * further combine operations.
 420                          */
 421                         if (size >= MAX_WRITESIZE_IN_PASS)
 422                                 break;
 423
 424                         /*
 425                          * Operations are only eligible to be combined
 426                          * if they are contiguous.
 427                          *
 428                          * TODO: add a heuristic willing to fire a
 429                          * certain amount of non-contiguous IO per pass,
 430                          * so that we can benefit from backing device
 431                          * command queueing.
 432                          */
 433                         if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
 434                                                 &START_KEY(&next->key)))
 435                                 break;
 436
 437                         size += KEY_SIZE(&next->key);
 438                         keys[nk++] = next;
 439                 } while ((next = bch_keybuf_next(&dc->writeback_keys)));
 440
 441                 /* Now we have gathered a set of 1..5 keys to write back. */
 442                 for (i = 0; i < nk; i++) {
 443                         w = keys[i];
 444
 445                         io = kzalloc(sizeof(struct dirty_io) +
 446                                      sizeof(struct bio_vec) *
 447                                      DIV_ROUND_UP(KEY_SIZE(&w->key),
 448                                                   PAGE_SECTORS),
 449                                      GFP_KERNEL);
 450                         if (!io)
 451                                 goto err;
 452
 453                         w->private      = io;
 454                         io->dc          = dc;
 455                         io->sequence    = sequence++;
 456
 457                         dirty_init(w);
 458                         bio_set_op_attrs(&io->bio, REQ_OP_READ, 0);
 459                         io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
 460                         bio_set_dev(&io->bio,
 461                                     PTR_CACHE(dc->disk.c, &w->key, 0)->bdev);
 462                         io->bio.bi_end_io       = read_dirty_endio;
 463
 464                         if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
 465                                 goto err_free;
 466
 467                         trace_bcache_writeback(&w->key);
 468
 469                         down(&dc->in_flight);
 470
 471                         /*
 472                          * We've acquired a semaphore for the maximum
 473                          * simultaneous number of writebacks; from here
 474                          * everything happens asynchronously.
 475                          */
 476                         closure_call(&io->cl, read_dirty_submit, NULL, &cl);
 477                 }
 478
 479                 delay = writeback_delay(dc, size);
 480
 481                 while (!kthread_should_stop() &&
 482                        !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 483                        delay) {
 484                         schedule_timeout_interruptible(delay);
 485                         delay = writeback_delay(dc, 0);
 486                 }
 487         }
 488
 489         if (0) {
 490 err_free:
 491                 kfree(w->private);
 492 err:
 493                 bch_keybuf_del(&dc->writeback_keys, w);
 494         }
 495
 496         /*
 497          * Wait for outstanding writeback IOs to finish (and keybuf slots to be
 498          * freed) before refilling again
 499          */
 500         closure_sync(&cl);
 501 }
 502
 503 /* Scan for dirty data */
 504
 505 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
 506                                   uint64_t offset, int nr_sectors)
 507 {
 508         struct bcache_device *d = c->devices[inode];
 509         unsigned int stripe_offset, sectors_dirty;
 510         int stripe;
 511
 512         if (!d)
 513                 return;
 514
 515         stripe = offset_to_stripe(d, offset);
 516         if (stripe < 0)
 517                 return;
 518
 519         if (UUID_FLASH_ONLY(&c->uuids[inode]))
 520                 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
 521
 522         stripe_offset = offset & (d->stripe_size - 1);
 523
 524         while (nr_sectors) {
 525                 int s = min_t(unsigned int, abs(nr_sectors),
 526                               d->stripe_size - stripe_offset);
 527
 528                 if (nr_sectors < 0)
 529                         s = -s;
 530
 531                 if (stripe >= d->nr_stripes)
 532                         return;
 533
 534                 sectors_dirty = atomic_add_return(s,
 535                                         d->stripe_sectors_dirty + stripe);
 536                 if (sectors_dirty == d->stripe_size)
 537                         set_bit(stripe, d->full_dirty_stripes);
 538                 else
 539                         clear_bit(stripe, d->full_dirty_stripes);
 540
 541                 nr_sectors -= s;
 542                 stripe_offset = 0;
 543                 stripe++;
 544         }
 545 }
 546
 547 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
 548 {
 549         struct cached_dev *dc = container_of(buf,
 550                                              struct cached_dev,
 551                                              writeback_keys);
 552
 553         BUG_ON(KEY_INODE(k) != dc->disk.id);
 554
 555         return KEY_DIRTY(k);
 556 }
 557
 558 static void refill_full_stripes(struct cached_dev *dc)
 559 {
 560         struct keybuf *buf = &dc->writeback_keys;
 561         unsigned int start_stripe, next_stripe;
 562         int stripe;
 563         bool wrapped = false;
 564
 565         stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 566         if (stripe < 0)
 567                 stripe = 0;
 568
 569         start_stripe = stripe;
 570
 571         while (1) {
 572                 stripe = find_next_bit(dc->disk.full_dirty_stripes,
 573                                        dc->disk.nr_stripes, stripe);
 574
 575                 if (stripe == dc->disk.nr_stripes)
 576                         goto next;
 577
 578                 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
 579                                                  dc->disk.nr_stripes, stripe);
 580
 581                 buf->last_scanned = KEY(dc->disk.id,
 582                                         stripe * dc->disk.stripe_size, 0);
 583
 584                 bch_refill_keybuf(dc->disk.c, buf,
 585                                   &KEY(dc->disk.id,
 586                                        next_stripe * dc->disk.stripe_size, 0),
 587                                   dirty_pred);
 588
 589                 if (array_freelist_empty(&buf->freelist))
 590                         return;
 591
 592                 stripe = next_stripe;
 593 next:
 594                 if (wrapped && stripe > start_stripe)
 595                         return;
 596
 597                 if (stripe == dc->disk.nr_stripes) {
 598                         stripe = 0;
 599                         wrapped = true;
 600                 }
 601         }
 602 }
 603
 604 /*
 605  * Returns true if we scanned the entire disk
 606  */
 607 static bool refill_dirty(struct cached_dev *dc)
 608 {
 609         struct keybuf *buf = &dc->writeback_keys;
 610         struct bkey start = KEY(dc->disk.id, 0, 0);
 611         struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
 612         struct bkey start_pos;
 613
 614         /*
 615          * make sure keybuf pos is inside the range for this disk - at bringup
 616          * we might not be attached yet so this disk's inode nr isn't
 617          * initialized then
 618          */
 619         if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
 620             bkey_cmp(&buf->last_scanned, &end) > 0)
 621                 buf->last_scanned = start;
 622
 623         if (dc->partial_stripes_expensive) {
 624                 refill_full_stripes(dc);
 625                 if (array_freelist_empty(&buf->freelist))
 626                         return false;
 627         }
 628
 629         start_pos = buf->last_scanned;
 630         bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 631
 632         if (bkey_cmp(&buf->last_scanned, &end) < 0)
 633                 return false;
 634
 635         /*
 636          * If we get to the end start scanning again from the beginning, and
 637          * only scan up to where we initially started scanning from:
 638          */
 639         buf->last_scanned = start;
 640         bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
 641
 642         return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
 643 }
 644
 645 static int bch_writeback_thread(void *arg)
 646 {
 647         struct cached_dev *dc = arg;
 648         struct cache_set *c = dc->disk.c;
 649         bool searched_full_index;
 650
 651         bch_ratelimit_reset(&dc->writeback_rate);
 652
 653         while (!kthread_should_stop() &&
 654                !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 655                 down_write(&dc->writeback_lock);
 656                 set_current_state(TASK_INTERRUPTIBLE);
 657                 /*
 658                  * If the bache device is detaching, skip here and continue
 659                  * to perform writeback. Otherwise, if no dirty data on cache,
 660                  * or there is dirty data on cache but writeback is disabled,
 661                  * the writeback thread should sleep here and wait for others
 662                  * to wake up it.
 663                  */
 664                 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
 665                     (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
 666                         up_write(&dc->writeback_lock);
 667
 668                         if (kthread_should_stop() ||
 669                             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 670                                 set_current_state(TASK_RUNNING);
 671                                 break;
 672                         }
 673
 674                         schedule();
 675                         continue;
 676                 }
 677                 set_current_state(TASK_RUNNING);
 678
 679                 searched_full_index = refill_dirty(dc);
 680
 681                 if (searched_full_index &&
 682                     RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
 683                         atomic_set(&dc->has_dirty, 0);
 684                         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 685                         bch_write_bdev_super(dc, NULL);
 686                         /*
 687                          * If bcache device is detaching via sysfs interface,
 688                          * writeback thread should stop after there is no dirty
 689                          * data on cache. BCACHE_DEV_DETACHING flag is set in
 690                          * bch_cached_dev_detach().
 691                          */
 692                         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
 693                                 up_write(&dc->writeback_lock);
 694                                 break;
 695                         }
 696                 }
 697
 698                 up_write(&dc->writeback_lock);
 699
 700                 read_dirty(dc);
 701
 702                 if (searched_full_index) {
 703                         unsigned int delay = dc->writeback_delay * HZ;
 704
 705                         while (delay &&
 706                                !kthread_should_stop() &&
 707                                !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
 708                                !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 709                                 delay = schedule_timeout_interruptible(delay);
 710
 711                         bch_ratelimit_reset(&dc->writeback_rate);
 712                 }
 713         }
 714
 715         if (dc->writeback_write_wq) {
 716                 flush_workqueue(dc->writeback_write_wq);
 717                 destroy_workqueue(dc->writeback_write_wq);
 718         }
 719         cached_dev_put(dc);
 720         wait_for_kthread_stop();
 721
 722         return 0;
 723 }
 724
 725 /* Init */
 726 #define INIT_KEYS_EACH_TIME     500000
 727 #define INIT_KEYS_SLEEP_MS      100
 728
 729 struct sectors_dirty_init {
 730         struct btree_op op;
 731         unsigned int    inode;
 732         size_t          count;
 733         struct bkey     start;
 734 };
 735
 736 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
 737                                  struct bkey *k)
 738 {
 739         struct sectors_dirty_init *op = container_of(_op,
 740                                                 struct sectors_dirty_init, op);
 741         if (KEY_INODE(k) > op->inode)
 742                 return MAP_DONE;
 743
 744         if (KEY_DIRTY(k))
 745                 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
 746                                              KEY_START(k), KEY_SIZE(k));
 747
 748         op->count++;
 749         if (atomic_read(&b->c->search_inflight) &&
 750             !(op->count % INIT_KEYS_EACH_TIME)) {
 751                 bkey_copy_key(&op->start, k);
 752                 return -EAGAIN;
 753         }
 754
 755         return MAP_CONTINUE;
 756 }
 757
 758 void bch_sectors_dirty_init(struct bcache_device *d)
 759 {
 760         struct sectors_dirty_init op;
 761         int ret;
 762
 763         bch_btree_op_init(&op.op, -1);
 764         op.inode = d->id;
 765         op.count = 0;
 766         op.start = KEY(op.inode, 0, 0);
 767
 768         do {
 769                 ret = bch_btree_map_keys(&op.op, d->c, &op.start,
 770                                          sectors_dirty_init_fn, 0);
 771                 if (ret == -EAGAIN)
 772                         schedule_timeout_interruptible(
 773                                 msecs_to_jiffies(INIT_KEYS_SLEEP_MS));
 774                 else if (ret < 0) {
 775                         pr_warn("sectors dirty init failed, ret=%d!", ret);
 776                         break;
 777                 }
 778         } while (ret == -EAGAIN);
 779 }
 780
 781 void bch_cached_dev_writeback_init(struct cached_dev *dc)
 782 {
 783         sema_init(&dc->in_flight, 64);
 784         init_rwsem(&dc->writeback_lock);
 785         bch_keybuf_init(&dc->writeback_keys);
 786
 787         dc->writeback_metadata          = true;
 788         dc->writeback_running           = false;
 789         dc->writeback_percent           = 10;
 790         dc->writeback_delay             = 30;
 791         atomic_long_set(&dc->writeback_rate.rate, 1024);
 792         dc->writeback_rate_minimum      = 8;
 793
 794         dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
 795         dc->writeback_rate_p_term_inverse = 40;
 796         dc->writeback_rate_i_term_inverse = 10000;
 797
 798         WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
 799         INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
 800 }
 801
 802 int bch_cached_dev_writeback_start(struct cached_dev *dc)
 803 {
 804         dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
 805                                                 WQ_MEM_RECLAIM, 0);
 806         if (!dc->writeback_write_wq)
 807                 return -ENOMEM;
 808
 809         cached_dev_get(dc);
 810         dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
 811                                               "bcache_writeback");
 812         if (IS_ERR(dc->writeback_thread)) {
 813                 cached_dev_put(dc);
 814                 destroy_workqueue(dc->writeback_write_wq);
 815                 return PTR_ERR(dc->writeback_thread);
 816         }
 817         dc->writeback_running = true;
 818
 819         WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
 820         schedule_delayed_work(&dc->writeback_rate_update,
 821                               dc->writeback_rate_update_seconds * HZ);
 822
 823         bch_writeback_queue(dc);
 824
 825         return 0;
 826 }