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 <[email protected]>
   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                                 bcache_flash_devs_sectors_dirty(c);
  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 - dc->writeback_rate.rate;
 108         dc->writeback_rate.rate = new_rate;
 109         dc->writeback_rate_target = target;
 110 }
 111
 112 static void update_writeback_rate(struct work_struct *work)
 113 {
 114         struct cached_dev *dc = container_of(to_delayed_work(work),
 115                                              struct cached_dev,
 116                                              writeback_rate_update);
 117         struct cache_set *c = dc->disk.c;
 118
 119         /*
 120          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 121          * cancel_delayed_work_sync().
 122          */
 123         set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 124         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 125         smp_mb();
 126
 127         /*
 128          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 129          * check it here too.
 130          */
 131         if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
 132             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 133                 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 134                 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 135                 smp_mb();
 136                 return;
 137         }
 138
 139         down_read(&dc->writeback_lock);
 140
 141         if (atomic_read(&dc->has_dirty) &&
 142             dc->writeback_percent)
 143                 __update_writeback_rate(dc);
 144
 145         up_read(&dc->writeback_lock);
 146
 147         /*
 148          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 149          * check it here too.
 150          */
 151         if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
 152             !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 153                 schedule_delayed_work(&dc->writeback_rate_update,
 154                               dc->writeback_rate_update_seconds * HZ);
 155         }
 156
 157         /*
 158          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 159          * cancel_delayed_work_sync().
 160          */
 161         clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 162         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 163         smp_mb();
 164 }
 165
 166 static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
 167 {
 168         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
 169             !dc->writeback_percent)
 170                 return 0;
 171
 172         return bch_next_delay(&dc->writeback_rate, sectors);
 173 }
 174
 175 struct dirty_io {
 176         struct closure          cl;
 177         struct cached_dev       *dc;
 178         uint16_t                sequence;
 179         struct bio              bio;
 180 };
 181
 182 static void dirty_init(struct keybuf_key *w)
 183 {
 184         struct dirty_io *io = w->private;
 185         struct bio *bio = &io->bio;
 186
 187         bio_init(bio, bio->bi_inline_vecs,
 188                  DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS));
 189         if (!io->dc->writeback_percent)
 190                 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 191
 192         bio->bi_iter.bi_size    = KEY_SIZE(&w->key) << 9;
 193         bio->bi_private         = w;
 194         bch_bio_map(bio, NULL);
 195 }
 196
 197 static void dirty_io_destructor(struct closure *cl)
 198 {
 199         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 200         kfree(io);
 201 }
 202
 203 static void write_dirty_finish(struct closure *cl)
 204 {
 205         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 206         struct keybuf_key *w = io->bio.bi_private;
 207         struct cached_dev *dc = io->dc;
 208
 209         bio_free_pages(&io->bio);
 210
 211         /* This is kind of a dumb way of signalling errors. */
 212         if (KEY_DIRTY(&w->key)) {
 213                 int ret;
 214                 unsigned i;
 215                 struct keylist keys;
 216
 217                 bch_keylist_init(&keys);
 218
 219                 bkey_copy(keys.top, &w->key);
 220                 SET_KEY_DIRTY(keys.top, false);
 221                 bch_keylist_push(&keys);
 222
 223                 for (i = 0; i < KEY_PTRS(&w->key); i++)
 224                         atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
 225
 226                 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
 227
 228                 if (ret)
 229                         trace_bcache_writeback_collision(&w->key);
 230
 231                 atomic_long_inc(ret
 232                                 ? &dc->disk.c->writeback_keys_failed
 233                                 : &dc->disk.c->writeback_keys_done);
 234         }
 235
 236         bch_keybuf_del(&dc->writeback_keys, w);
 237         up(&dc->in_flight);
 238
 239         closure_return_with_destructor(cl, dirty_io_destructor);
 240 }
 241
 242 static void dirty_endio(struct bio *bio)
 243 {
 244         struct keybuf_key *w = bio->bi_private;
 245         struct dirty_io *io = w->private;
 246
 247         if (bio->bi_status) {
 248                 SET_KEY_DIRTY(&w->key, false);
 249                 bch_count_backing_io_errors(io->dc, bio);
 250         }
 251
 252         closure_put(&io->cl);
 253 }
 254
 255 static void write_dirty(struct closure *cl)
 256 {
 257         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 258         struct keybuf_key *w = io->bio.bi_private;
 259         struct cached_dev *dc = io->dc;
 260
 261         uint16_t next_sequence;
 262
 263         if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
 264                 /* Not our turn to write; wait for a write to complete */
 265                 closure_wait(&dc->writeback_ordering_wait, cl);
 266
 267                 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
 268                         /*
 269                          * Edge case-- it happened in indeterminate order
 270                          * relative to when we were added to wait list..
 271                          */
 272                         closure_wake_up(&dc->writeback_ordering_wait);
 273                 }
 274
 275                 continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 276                 return;
 277         }
 278
 279         next_sequence = io->sequence + 1;
 280
 281         /*
 282          * IO errors are signalled using the dirty bit on the key.
 283          * If we failed to read, we should not attempt to write to the
 284          * backing device.  Instead, immediately go to write_dirty_finish
 285          * to clean up.
 286          */
 287         if (KEY_DIRTY(&w->key)) {
 288                 dirty_init(w);
 289                 bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
 290                 io->bio.bi_iter.bi_sector = KEY_START(&w->key);
 291                 bio_set_dev(&io->bio, io->dc->bdev);
 292                 io->bio.bi_end_io       = dirty_endio;
 293
 294                 /* I/O request sent to backing device */
 295                 closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 296         }
 297
 298         atomic_set(&dc->writeback_sequence_next, next_sequence);
 299         closure_wake_up(&dc->writeback_ordering_wait);
 300
 301         continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
 302 }
 303
 304 static void read_dirty_endio(struct bio *bio)
 305 {
 306         struct keybuf_key *w = bio->bi_private;
 307         struct dirty_io *io = w->private;
 308
 309         /* is_read = 1 */
 310         bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
 311                             bio->bi_status, 1,
 312                             "reading dirty data from cache");
 313
 314         dirty_endio(bio);
 315 }
 316
 317 static void read_dirty_submit(struct closure *cl)
 318 {
 319         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 320
 321         closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 322
 323         continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 324 }
 325
 326 static void read_dirty(struct cached_dev *dc)
 327 {
 328         unsigned delay = 0;
 329         struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
 330         size_t size;
 331         int nk, i;
 332         struct dirty_io *io;
 333         struct closure cl;
 334         uint16_t sequence = 0;
 335
 336         BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
 337         atomic_set(&dc->writeback_sequence_next, sequence);
 338         closure_init_stack(&cl);
 339
 340         /*
 341          * XXX: if we error, background writeback just spins. Should use some
 342          * mempools.
 343          */
 344
 345         next = bch_keybuf_next(&dc->writeback_keys);
 346
 347         while (!kthread_should_stop() &&
 348                !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 349                next) {
 350                 size = 0;
 351                 nk = 0;
 352
 353                 do {
 354                         BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
 355
 356                         /*
 357                          * Don't combine too many operations, even if they
 358                          * are all small.
 359                          */
 360                         if (nk >= MAX_WRITEBACKS_IN_PASS)
 361                                 break;
 362
 363                         /*
 364                          * If the current operation is very large, don't
 365                          * further combine operations.
 366                          */
 367                         if (size >= MAX_WRITESIZE_IN_PASS)
 368                                 break;
 369
 370                         /*
 371                          * Operations are only eligible to be combined
 372                          * if they are contiguous.
 373                          *
 374                          * TODO: add a heuristic willing to fire a
 375                          * certain amount of non-contiguous IO per pass,
 376                          * so that we can benefit from backing device
 377                          * command queueing.
 378                          */
 379                         if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
 380                                                 &START_KEY(&next->key)))
 381                                 break;
 382
 383                         size += KEY_SIZE(&next->key);
 384                         keys[nk++] = next;
 385                 } while ((next = bch_keybuf_next(&dc->writeback_keys)));
 386
 387                 /* Now we have gathered a set of 1..5 keys to write back. */
 388                 for (i = 0; i < nk; i++) {
 389                         w = keys[i];
 390
 391                         io = kzalloc(sizeof(struct dirty_io) +
 392                                      sizeof(struct bio_vec) *
 393                                      DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
 394                                      GFP_KERNEL);
 395                         if (!io)
 396                                 goto err;
 397
 398                         w->private      = io;
 399                         io->dc          = dc;
 400                         io->sequence    = sequence++;
 401
 402                         dirty_init(w);
 403                         bio_set_op_attrs(&io->bio, REQ_OP_READ, 0);
 404                         io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
 405                         bio_set_dev(&io->bio,
 406                                     PTR_CACHE(dc->disk.c, &w->key, 0)->bdev);
 407                         io->bio.bi_end_io       = read_dirty_endio;
 408
 409                         if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
 410                                 goto err_free;
 411
 412                         trace_bcache_writeback(&w->key);
 413
 414                         down(&dc->in_flight);
 415
 416                         /* We've acquired a semaphore for the maximum
 417                          * simultaneous number of writebacks; from here
 418                          * everything happens asynchronously.
 419                          */
 420                         closure_call(&io->cl, read_dirty_submit, NULL, &cl);
 421                 }
 422
 423                 delay = writeback_delay(dc, size);
 424
 425                 /* If the control system would wait for at least half a
 426                  * second, and there's been no reqs hitting the backing disk
 427                  * for awhile: use an alternate mode where we have at most
 428                  * one contiguous set of writebacks in flight at a time.  If
 429                  * someone wants to do IO it will be quick, as it will only
 430                  * have to contend with one operation in flight, and we'll
 431                  * be round-tripping data to the backing disk as quickly as
 432                  * it can accept it.
 433                  */
 434                 if (delay >= HZ / 2) {
 435                         /* 3 means at least 1.5 seconds, up to 7.5 if we
 436                          * have slowed way down.
 437                          */
 438                         if (atomic_inc_return(&dc->backing_idle) >= 3) {
 439                                 /* Wait for current I/Os to finish */
 440                                 closure_sync(&cl);
 441                                 /* And immediately launch a new set. */
 442                                 delay = 0;
 443                         }
 444                 }
 445
 446                 while (!kthread_should_stop() &&
 447                        !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 448                        delay) {
 449                         schedule_timeout_interruptible(delay);
 450                         delay = writeback_delay(dc, 0);
 451                 }
 452         }
 453
 454         if (0) {
 455 err_free:
 456                 kfree(w->private);
 457 err:
 458                 bch_keybuf_del(&dc->writeback_keys, w);
 459         }
 460
 461         /*
 462          * Wait for outstanding writeback IOs to finish (and keybuf slots to be
 463          * freed) before refilling again
 464          */
 465         closure_sync(&cl);
 466 }
 467
 468 /* Scan for dirty data */
 469
 470 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
 471                                   uint64_t offset, int nr_sectors)
 472 {
 473         struct bcache_device *d = c->devices[inode];
 474         unsigned stripe_offset, stripe, sectors_dirty;
 475
 476         if (!d)
 477                 return;
 478
 479         stripe = offset_to_stripe(d, offset);
 480         stripe_offset = offset & (d->stripe_size - 1);
 481
 482         while (nr_sectors) {
 483                 int s = min_t(unsigned, abs(nr_sectors),
 484                               d->stripe_size - stripe_offset);
 485
 486                 if (nr_sectors < 0)
 487                         s = -s;
 488
 489                 if (stripe >= d->nr_stripes)
 490                         return;
 491
 492                 sectors_dirty = atomic_add_return(s,
 493                                         d->stripe_sectors_dirty + stripe);
 494                 if (sectors_dirty == d->stripe_size)
 495                         set_bit(stripe, d->full_dirty_stripes);
 496                 else
 497                         clear_bit(stripe, d->full_dirty_stripes);
 498
 499                 nr_sectors -= s;
 500                 stripe_offset = 0;
 501                 stripe++;
 502         }
 503 }
 504
 505 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
 506 {
 507         struct cached_dev *dc = container_of(buf, struct cached_dev, writeback_keys);
 508
 509         BUG_ON(KEY_INODE(k) != dc->disk.id);
 510
 511         return KEY_DIRTY(k);
 512 }
 513
 514 static void refill_full_stripes(struct cached_dev *dc)
 515 {
 516         struct keybuf *buf = &dc->writeback_keys;
 517         unsigned start_stripe, stripe, next_stripe;
 518         bool wrapped = false;
 519
 520         stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 521
 522         if (stripe >= dc->disk.nr_stripes)
 523                 stripe = 0;
 524
 525         start_stripe = stripe;
 526
 527         while (1) {
 528                 stripe = find_next_bit(dc->disk.full_dirty_stripes,
 529                                        dc->disk.nr_stripes, stripe);
 530
 531                 if (stripe == dc->disk.nr_stripes)
 532                         goto next;
 533
 534                 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
 535                                                  dc->disk.nr_stripes, stripe);
 536
 537                 buf->last_scanned = KEY(dc->disk.id,
 538                                         stripe * dc->disk.stripe_size, 0);
 539
 540                 bch_refill_keybuf(dc->disk.c, buf,
 541                                   &KEY(dc->disk.id,
 542                                        next_stripe * dc->disk.stripe_size, 0),
 543                                   dirty_pred);
 544
 545                 if (array_freelist_empty(&buf->freelist))
 546                         return;
 547
 548                 stripe = next_stripe;
 549 next:
 550                 if (wrapped && stripe > start_stripe)
 551                         return;
 552
 553                 if (stripe == dc->disk.nr_stripes) {
 554                         stripe = 0;
 555                         wrapped = true;
 556                 }
 557         }
 558 }
 559
 560 /*
 561  * Returns true if we scanned the entire disk
 562  */
 563 static bool refill_dirty(struct cached_dev *dc)
 564 {
 565         struct keybuf *buf = &dc->writeback_keys;
 566         struct bkey start = KEY(dc->disk.id, 0, 0);
 567         struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
 568         struct bkey start_pos;
 569
 570         /*
 571          * make sure keybuf pos is inside the range for this disk - at bringup
 572          * we might not be attached yet so this disk's inode nr isn't
 573          * initialized then
 574          */
 575         if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
 576             bkey_cmp(&buf->last_scanned, &end) > 0)
 577                 buf->last_scanned = start;
 578
 579         if (dc->partial_stripes_expensive) {
 580                 refill_full_stripes(dc);
 581                 if (array_freelist_empty(&buf->freelist))
 582                         return false;
 583         }
 584
 585         start_pos = buf->last_scanned;
 586         bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 587
 588         if (bkey_cmp(&buf->last_scanned, &end) < 0)
 589                 return false;
 590
 591         /*
 592          * If we get to the end start scanning again from the beginning, and
 593          * only scan up to where we initially started scanning from:
 594          */
 595         buf->last_scanned = start;
 596         bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
 597
 598         return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
 599 }
 600
 601 static int bch_writeback_thread(void *arg)
 602 {
 603         struct cached_dev *dc = arg;
 604         struct cache_set *c = dc->disk.c;
 605         bool searched_full_index;
 606
 607         bch_ratelimit_reset(&dc->writeback_rate);
 608
 609         while (!kthread_should_stop() &&
 610                !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 611                 down_write(&dc->writeback_lock);
 612                 set_current_state(TASK_INTERRUPTIBLE);
 613                 /*
 614                  * If the bache device is detaching, skip here and continue
 615                  * to perform writeback. Otherwise, if no dirty data on cache,
 616                  * or there is dirty data on cache but writeback is disabled,
 617                  * the writeback thread should sleep here and wait for others
 618                  * to wake up it.
 619                  */
 620                 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
 621                     (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
 622                         up_write(&dc->writeback_lock);
 623
 624                         if (kthread_should_stop() ||
 625                             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 626                                 set_current_state(TASK_RUNNING);
 627                                 break;
 628                         }
 629
 630                         schedule();
 631                         continue;
 632                 }
 633                 set_current_state(TASK_RUNNING);
 634
 635                 searched_full_index = refill_dirty(dc);
 636
 637                 if (searched_full_index &&
 638                     RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
 639                         atomic_set(&dc->has_dirty, 0);
 640                         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 641                         bch_write_bdev_super(dc, NULL);
 642                         /*
 643                          * If bcache device is detaching via sysfs interface,
 644                          * writeback thread should stop after there is no dirty
 645                          * data on cache. BCACHE_DEV_DETACHING flag is set in
 646                          * bch_cached_dev_detach().
 647                          */
 648                         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 649                                 break;
 650                 }
 651
 652                 up_write(&dc->writeback_lock);
 653
 654                 read_dirty(dc);
 655
 656                 if (searched_full_index) {
 657                         unsigned delay = dc->writeback_delay * HZ;
 658
 659                         while (delay &&
 660                                !kthread_should_stop() &&
 661                                !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
 662                                !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 663                                 delay = schedule_timeout_interruptible(delay);
 664
 665                         bch_ratelimit_reset(&dc->writeback_rate);
 666                 }
 667         }
 668
 669         cached_dev_put(dc);
 670         wait_for_kthread_stop();
 671
 672         return 0;
 673 }
 674
 675 /* Init */
 676
 677 struct sectors_dirty_init {
 678         struct btree_op op;
 679         unsigned        inode;
 680 };
 681
 682 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
 683                                  struct bkey *k)
 684 {
 685         struct sectors_dirty_init *op = container_of(_op,
 686                                                 struct sectors_dirty_init, op);
 687         if (KEY_INODE(k) > op->inode)
 688                 return MAP_DONE;
 689
 690         if (KEY_DIRTY(k))
 691                 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
 692                                              KEY_START(k), KEY_SIZE(k));
 693
 694         return MAP_CONTINUE;
 695 }
 696
 697 void bch_sectors_dirty_init(struct bcache_device *d)
 698 {
 699         struct sectors_dirty_init op;
 700
 701         bch_btree_op_init(&op.op, -1);
 702         op.inode = d->id;
 703
 704         bch_btree_map_keys(&op.op, d->c, &KEY(op.inode, 0, 0),
 705                            sectors_dirty_init_fn, 0);
 706 }
 707
 708 void bch_cached_dev_writeback_init(struct cached_dev *dc)
 709 {
 710         sema_init(&dc->in_flight, 64);
 711         init_rwsem(&dc->writeback_lock);
 712         bch_keybuf_init(&dc->writeback_keys);
 713
 714         dc->writeback_metadata          = true;
 715         dc->writeback_running           = true;
 716         dc->writeback_percent           = 10;
 717         dc->writeback_delay             = 30;
 718         dc->writeback_rate.rate         = 1024;
 719         dc->writeback_rate_minimum      = 8;
 720
 721         dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
 722         dc->writeback_rate_p_term_inverse = 40;
 723         dc->writeback_rate_i_term_inverse = 10000;
 724
 725         WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
 726         INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
 727 }
 728
 729 int bch_cached_dev_writeback_start(struct cached_dev *dc)
 730 {
 731         dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
 732                                                 WQ_MEM_RECLAIM, 0);
 733         if (!dc->writeback_write_wq)
 734                 return -ENOMEM;
 735
 736         cached_dev_get(dc);
 737         dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
 738                                               "bcache_writeback");
 739         if (IS_ERR(dc->writeback_thread)) {
 740                 cached_dev_put(dc);
 741                 return PTR_ERR(dc->writeback_thread);
 742         }
 743
 744         WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
 745         schedule_delayed_work(&dc->writeback_rate_update,
 746                               dc->writeback_rate_update_seconds * HZ);
 747
 748         bch_writeback_queue(dc);
 749
 750         return 0;
 751 }