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 static void update_gc_after_writeback(struct cache_set *c) 21 { 22 if (c->gc_after_writeback != (BCH_ENABLE_AUTO_GC) || 23 c->gc_stats.in_use < BCH_AUTO_GC_DIRTY_THRESHOLD) 24 return; 25 26 c->gc_after_writeback |= BCH_DO_AUTO_GC; 27 } 28 29 /* Rate limiting */ 30 static uint64_t __calc_target_rate(struct cached_dev *dc) 31 { 32 struct cache_set *c = dc->disk.c; 33 34 /* 35 * This is the size of the cache, minus the amount used for 36 * flash-only devices 37 */ 38 uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size - 39 atomic_long_read(&c->flash_dev_dirty_sectors); 40 41 /* 42 * Unfortunately there is no control of global dirty data. If the 43 * user states that they want 10% dirty data in the cache, and has, 44 * e.g., 5 backing volumes of equal size, we try and ensure each 45 * backing volume uses about 2% of the cache for dirty data. 46 */ 47 uint32_t bdev_share = 48 div64_u64(bdev_sectors(dc->bdev) << WRITEBACK_SHARE_SHIFT, 49 c->cached_dev_sectors); 50 51 uint64_t cache_dirty_target = 52 div_u64(cache_sectors * dc->writeback_percent, 100); 53 54 /* Ensure each backing dev gets at least one dirty share */ 55 if (bdev_share < 1) 56 bdev_share = 1; 57 58 return (cache_dirty_target * bdev_share) >> WRITEBACK_SHARE_SHIFT; 59 } 60 61 static void __update_writeback_rate(struct cached_dev *dc) 62 { 63 /* 64 * PI controller: 65 * Figures out the amount that should be written per second. 66 * 67 * First, the error (number of sectors that are dirty beyond our 68 * target) is calculated. The error is accumulated (numerically 69 * integrated). 70 * 71 * Then, the proportional value and integral value are scaled 72 * based on configured values. These are stored as inverses to 73 * avoid fixed point math and to make configuration easy-- e.g. 74 * the default value of 40 for writeback_rate_p_term_inverse 75 * attempts to write at a rate that would retire all the dirty 76 * blocks in 40 seconds. 77 * 78 * The writeback_rate_i_inverse value of 10000 means that 1/10000th 79 * of the error is accumulated in the integral term per second. 80 * This acts as a slow, long-term average that is not subject to 81 * variations in usage like the p term. 82 */ 83 int64_t target = __calc_target_rate(dc); 84 int64_t dirty = bcache_dev_sectors_dirty(&dc->disk); 85 int64_t error = dirty - target; 86 int64_t proportional_scaled = 87 div_s64(error, dc->writeback_rate_p_term_inverse); 88 int64_t integral_scaled; 89 uint32_t new_rate; 90 91 if ((error < 0 && dc->writeback_rate_integral > 0) || 92 (error > 0 && time_before64(local_clock(), 93 dc->writeback_rate.next + NSEC_PER_MSEC))) { 94 /* 95 * Only decrease the integral term if it's more than 96 * zero. Only increase the integral term if the device 97 * is keeping up. (Don't wind up the integral 98 * ineffectively in either case). 99 * 100 * It's necessary to scale this by 101 * writeback_rate_update_seconds to keep the integral 102 * term dimensioned properly. 103 */ 104 dc->writeback_rate_integral += error * 105 dc->writeback_rate_update_seconds; 106 } 107 108 integral_scaled = div_s64(dc->writeback_rate_integral, 109 dc->writeback_rate_i_term_inverse); 110 111 new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled), 112 dc->writeback_rate_minimum, NSEC_PER_SEC); 113 114 dc->writeback_rate_proportional = proportional_scaled; 115 dc->writeback_rate_integral_scaled = integral_scaled; 116 dc->writeback_rate_change = new_rate - 117 atomic_long_read(&dc->writeback_rate.rate); 118 atomic_long_set(&dc->writeback_rate.rate, new_rate); 119 dc->writeback_rate_target = target; 120 } 121 122 static bool set_at_max_writeback_rate(struct cache_set *c, 123 struct cached_dev *dc) 124 { 125 /* Don't sst max writeback rate if it is disabled */ 126 if (!c->idle_max_writeback_rate_enabled) 127 return false; 128 129 /* Don't set max writeback rate if gc is running */ 130 if (!c->gc_mark_valid) 131 return false; 132 /* 133 * Idle_counter is increased everytime when update_writeback_rate() is 134 * called. If all backing devices attached to the same cache set have 135 * identical dc->writeback_rate_update_seconds values, it is about 6 136 * rounds of update_writeback_rate() on each backing device before 137 * c->at_max_writeback_rate is set to 1, and then max wrteback rate set 138 * to each dc->writeback_rate.rate. 139 * In order to avoid extra locking cost for counting exact dirty cached 140 * devices number, c->attached_dev_nr is used to calculate the idle 141 * throushold. It might be bigger if not all cached device are in write- 142 * back mode, but it still works well with limited extra rounds of 143 * update_writeback_rate(). 144 */ 145 if (atomic_inc_return(&c->idle_counter) < 146 atomic_read(&c->attached_dev_nr) * 6) 147 return false; 148 149 if (atomic_read(&c->at_max_writeback_rate) != 1) 150 atomic_set(&c->at_max_writeback_rate, 1); 151 152 atomic_long_set(&dc->writeback_rate.rate, INT_MAX); 153 154 /* keep writeback_rate_target as existing value */ 155 dc->writeback_rate_proportional = 0; 156 dc->writeback_rate_integral_scaled = 0; 157 dc->writeback_rate_change = 0; 158 159 /* 160 * Check c->idle_counter and c->at_max_writeback_rate agagain in case 161 * new I/O arrives during before set_at_max_writeback_rate() returns. 162 * Then the writeback rate is set to 1, and its new value should be 163 * decided via __update_writeback_rate(). 164 */ 165 if ((atomic_read(&c->idle_counter) < 166 atomic_read(&c->attached_dev_nr) * 6) || 167 !atomic_read(&c->at_max_writeback_rate)) 168 return false; 169 170 return true; 171 } 172 173 static void update_writeback_rate(struct work_struct *work) 174 { 175 struct cached_dev *dc = container_of(to_delayed_work(work), 176 struct cached_dev, 177 writeback_rate_update); 178 struct cache_set *c = dc->disk.c; 179 180 /* 181 * should check BCACHE_DEV_RATE_DW_RUNNING before calling 182 * cancel_delayed_work_sync(). 183 */ 184 set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 185 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 186 smp_mb(); 187 188 /* 189 * CACHE_SET_IO_DISABLE might be set via sysfs interface, 190 * check it here too. 191 */ 192 if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) || 193 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 194 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 195 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 196 smp_mb(); 197 return; 198 } 199 200 if (atomic_read(&dc->has_dirty) && dc->writeback_percent) { 201 /* 202 * If the whole cache set is idle, set_at_max_writeback_rate() 203 * will set writeback rate to a max number. Then it is 204 * unncessary to update writeback rate for an idle cache set 205 * in maximum writeback rate number(s). 206 */ 207 if (!set_at_max_writeback_rate(c, dc)) { 208 down_read(&dc->writeback_lock); 209 __update_writeback_rate(dc); 210 update_gc_after_writeback(c); 211 up_read(&dc->writeback_lock); 212 } 213 } 214 215 216 /* 217 * CACHE_SET_IO_DISABLE might be set via sysfs interface, 218 * check it here too. 219 */ 220 if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) && 221 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 222 schedule_delayed_work(&dc->writeback_rate_update, 223 dc->writeback_rate_update_seconds * HZ); 224 } 225 226 /* 227 * should check BCACHE_DEV_RATE_DW_RUNNING before calling 228 * cancel_delayed_work_sync(). 229 */ 230 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 231 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 232 smp_mb(); 233 } 234 235 static unsigned int writeback_delay(struct cached_dev *dc, 236 unsigned int sectors) 237 { 238 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || 239 !dc->writeback_percent) 240 return 0; 241 242 return bch_next_delay(&dc->writeback_rate, sectors); 243 } 244 245 struct dirty_io { 246 struct closure cl; 247 struct cached_dev *dc; 248 uint16_t sequence; 249 struct bio bio; 250 }; 251 252 static void dirty_init(struct keybuf_key *w) 253 { 254 struct dirty_io *io = w->private; 255 struct bio *bio = &io->bio; 256 257 bio_init(bio, bio->bi_inline_vecs, 258 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)); 259 if (!io->dc->writeback_percent) 260 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)); 261 262 bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9; 263 bio->bi_private = w; 264 bch_bio_map(bio, NULL); 265 } 266 267 static void dirty_io_destructor(struct closure *cl) 268 { 269 struct dirty_io *io = container_of(cl, struct dirty_io, cl); 270 271 kfree(io); 272 } 273 274 static void write_dirty_finish(struct closure *cl) 275 { 276 struct dirty_io *io = container_of(cl, struct dirty_io, cl); 277 struct keybuf_key *w = io->bio.bi_private; 278 struct cached_dev *dc = io->dc; 279 280 bio_free_pages(&io->bio); 281 282 /* This is kind of a dumb way of signalling errors. */ 283 if (KEY_DIRTY(&w->key)) { 284 int ret; 285 unsigned int i; 286 struct keylist keys; 287 288 bch_keylist_init(&keys); 289 290 bkey_copy(keys.top, &w->key); 291 SET_KEY_DIRTY(keys.top, false); 292 bch_keylist_push(&keys); 293 294 for (i = 0; i < KEY_PTRS(&w->key); i++) 295 atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin); 296 297 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key); 298 299 if (ret) 300 trace_bcache_writeback_collision(&w->key); 301 302 atomic_long_inc(ret 303 ? &dc->disk.c->writeback_keys_failed 304 : &dc->disk.c->writeback_keys_done); 305 } 306 307 bch_keybuf_del(&dc->writeback_keys, w); 308 up(&dc->in_flight); 309 310 closure_return_with_destructor(cl, dirty_io_destructor); 311 } 312 313 static void dirty_endio(struct bio *bio) 314 { 315 struct keybuf_key *w = bio->bi_private; 316 struct dirty_io *io = w->private; 317 318 if (bio->bi_status) { 319 SET_KEY_DIRTY(&w->key, false); 320 bch_count_backing_io_errors(io->dc, bio); 321 } 322 323 closure_put(&io->cl); 324 } 325 326 static void write_dirty(struct closure *cl) 327 { 328 struct dirty_io *io = container_of(cl, struct dirty_io, cl); 329 struct keybuf_key *w = io->bio.bi_private; 330 struct cached_dev *dc = io->dc; 331 332 uint16_t next_sequence; 333 334 if (atomic_read(&dc->writeback_sequence_next) != io->sequence) { 335 /* Not our turn to write; wait for a write to complete */ 336 closure_wait(&dc->writeback_ordering_wait, cl); 337 338 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) { 339 /* 340 * Edge case-- it happened in indeterminate order 341 * relative to when we were added to wait list.. 342 */ 343 closure_wake_up(&dc->writeback_ordering_wait); 344 } 345 346 continue_at(cl, write_dirty, io->dc->writeback_write_wq); 347 return; 348 } 349 350 next_sequence = io->sequence + 1; 351 352 /* 353 * IO errors are signalled using the dirty bit on the key. 354 * If we failed to read, we should not attempt to write to the 355 * backing device. Instead, immediately go to write_dirty_finish 356 * to clean up. 357 */ 358 if (KEY_DIRTY(&w->key)) { 359 dirty_init(w); 360 bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0); 361 io->bio.bi_iter.bi_sector = KEY_START(&w->key); 362 bio_set_dev(&io->bio, io->dc->bdev); 363 io->bio.bi_end_io = dirty_endio; 364 365 /* I/O request sent to backing device */ 366 closure_bio_submit(io->dc->disk.c, &io->bio, cl); 367 } 368 369 atomic_set(&dc->writeback_sequence_next, next_sequence); 370 closure_wake_up(&dc->writeback_ordering_wait); 371 372 continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq); 373 } 374 375 static void read_dirty_endio(struct bio *bio) 376 { 377 struct keybuf_key *w = bio->bi_private; 378 struct dirty_io *io = w->private; 379 380 /* is_read = 1 */ 381 bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0), 382 bio->bi_status, 1, 383 "reading dirty data from cache"); 384 385 dirty_endio(bio); 386 } 387 388 static void read_dirty_submit(struct closure *cl) 389 { 390 struct dirty_io *io = container_of(cl, struct dirty_io, cl); 391 392 closure_bio_submit(io->dc->disk.c, &io->bio, cl); 393 394 continue_at(cl, write_dirty, io->dc->writeback_write_wq); 395 } 396 397 static void read_dirty(struct cached_dev *dc) 398 { 399 unsigned int delay = 0; 400 struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w; 401 size_t size; 402 int nk, i; 403 struct dirty_io *io; 404 struct closure cl; 405 uint16_t sequence = 0; 406 407 BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list)); 408 atomic_set(&dc->writeback_sequence_next, sequence); 409 closure_init_stack(&cl); 410 411 /* 412 * XXX: if we error, background writeback just spins. Should use some 413 * mempools. 414 */ 415 416 next = bch_keybuf_next(&dc->writeback_keys); 417 418 while (!kthread_should_stop() && 419 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) && 420 next) { 421 size = 0; 422 nk = 0; 423 424 do { 425 BUG_ON(ptr_stale(dc->disk.c, &next->key, 0)); 426 427 /* 428 * Don't combine too many operations, even if they 429 * are all small. 430 */ 431 if (nk >= MAX_WRITEBACKS_IN_PASS) 432 break; 433 434 /* 435 * If the current operation is very large, don't 436 * further combine operations. 437 */ 438 if (size >= MAX_WRITESIZE_IN_PASS) 439 break; 440 441 /* 442 * Operations are only eligible to be combined 443 * if they are contiguous. 444 * 445 * TODO: add a heuristic willing to fire a 446 * certain amount of non-contiguous IO per pass, 447 * so that we can benefit from backing device 448 * command queueing. 449 */ 450 if ((nk != 0) && bkey_cmp(&keys[nk-1]->key, 451 &START_KEY(&next->key))) 452 break; 453 454 size += KEY_SIZE(&next->key); 455 keys[nk++] = next; 456 } while ((next = bch_keybuf_next(&dc->writeback_keys))); 457 458 /* Now we have gathered a set of 1..5 keys to write back. */ 459 for (i = 0; i < nk; i++) { 460 w = keys[i]; 461 462 io = kzalloc(sizeof(struct dirty_io) + 463 sizeof(struct bio_vec) * 464 DIV_ROUND_UP(KEY_SIZE(&w->key), 465 PAGE_SECTORS), 466 GFP_KERNEL); 467 if (!io) 468 goto err; 469 470 w->private = io; 471 io->dc = dc; 472 io->sequence = sequence++; 473 474 dirty_init(w); 475 bio_set_op_attrs(&io->bio, REQ_OP_READ, 0); 476 io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0); 477 bio_set_dev(&io->bio, 478 PTR_CACHE(dc->disk.c, &w->key, 0)->bdev); 479 io->bio.bi_end_io = read_dirty_endio; 480 481 if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL)) 482 goto err_free; 483 484 trace_bcache_writeback(&w->key); 485 486 down(&dc->in_flight); 487 488 /* 489 * We've acquired a semaphore for the maximum 490 * simultaneous number of writebacks; from here 491 * everything happens asynchronously. 492 */ 493 closure_call(&io->cl, read_dirty_submit, NULL, &cl); 494 } 495 496 delay = writeback_delay(dc, size); 497 498 while (!kthread_should_stop() && 499 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) && 500 delay) { 501 schedule_timeout_interruptible(delay); 502 delay = writeback_delay(dc, 0); 503 } 504 } 505 506 if (0) { 507 err_free: 508 kfree(w->private); 509 err: 510 bch_keybuf_del(&dc->writeback_keys, w); 511 } 512 513 /* 514 * Wait for outstanding writeback IOs to finish (and keybuf slots to be 515 * freed) before refilling again 516 */ 517 closure_sync(&cl); 518 } 519 520 /* Scan for dirty data */ 521 522 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode, 523 uint64_t offset, int nr_sectors) 524 { 525 struct bcache_device *d = c->devices[inode]; 526 unsigned int stripe_offset, stripe, sectors_dirty; 527 528 if (!d) 529 return; 530 531 if (UUID_FLASH_ONLY(&c->uuids[inode])) 532 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors); 533 534 stripe = offset_to_stripe(d, offset); 535 stripe_offset = offset & (d->stripe_size - 1); 536 537 while (nr_sectors) { 538 int s = min_t(unsigned int, abs(nr_sectors), 539 d->stripe_size - stripe_offset); 540 541 if (nr_sectors < 0) 542 s = -s; 543 544 if (stripe >= d->nr_stripes) 545 return; 546 547 sectors_dirty = atomic_add_return(s, 548 d->stripe_sectors_dirty + stripe); 549 if (sectors_dirty == d->stripe_size) 550 set_bit(stripe, d->full_dirty_stripes); 551 else 552 clear_bit(stripe, d->full_dirty_stripes); 553 554 nr_sectors -= s; 555 stripe_offset = 0; 556 stripe++; 557 } 558 } 559 560 static bool dirty_pred(struct keybuf *buf, struct bkey *k) 561 { 562 struct cached_dev *dc = container_of(buf, 563 struct cached_dev, 564 writeback_keys); 565 566 BUG_ON(KEY_INODE(k) != dc->disk.id); 567 568 return KEY_DIRTY(k); 569 } 570 571 static void refill_full_stripes(struct cached_dev *dc) 572 { 573 struct keybuf *buf = &dc->writeback_keys; 574 unsigned int start_stripe, stripe, next_stripe; 575 bool wrapped = false; 576 577 stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned)); 578 579 if (stripe >= dc->disk.nr_stripes) 580 stripe = 0; 581 582 start_stripe = stripe; 583 584 while (1) { 585 stripe = find_next_bit(dc->disk.full_dirty_stripes, 586 dc->disk.nr_stripes, stripe); 587 588 if (stripe == dc->disk.nr_stripes) 589 goto next; 590 591 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes, 592 dc->disk.nr_stripes, stripe); 593 594 buf->last_scanned = KEY(dc->disk.id, 595 stripe * dc->disk.stripe_size, 0); 596 597 bch_refill_keybuf(dc->disk.c, buf, 598 &KEY(dc->disk.id, 599 next_stripe * dc->disk.stripe_size, 0), 600 dirty_pred); 601 602 if (array_freelist_empty(&buf->freelist)) 603 return; 604 605 stripe = next_stripe; 606 next: 607 if (wrapped && stripe > start_stripe) 608 return; 609 610 if (stripe == dc->disk.nr_stripes) { 611 stripe = 0; 612 wrapped = true; 613 } 614 } 615 } 616 617 /* 618 * Returns true if we scanned the entire disk 619 */ 620 static bool refill_dirty(struct cached_dev *dc) 621 { 622 struct keybuf *buf = &dc->writeback_keys; 623 struct bkey start = KEY(dc->disk.id, 0, 0); 624 struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0); 625 struct bkey start_pos; 626 627 /* 628 * make sure keybuf pos is inside the range for this disk - at bringup 629 * we might not be attached yet so this disk's inode nr isn't 630 * initialized then 631 */ 632 if (bkey_cmp(&buf->last_scanned, &start) < 0 || 633 bkey_cmp(&buf->last_scanned, &end) > 0) 634 buf->last_scanned = start; 635 636 if (dc->partial_stripes_expensive) { 637 refill_full_stripes(dc); 638 if (array_freelist_empty(&buf->freelist)) 639 return false; 640 } 641 642 start_pos = buf->last_scanned; 643 bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred); 644 645 if (bkey_cmp(&buf->last_scanned, &end) < 0) 646 return false; 647 648 /* 649 * If we get to the end start scanning again from the beginning, and 650 * only scan up to where we initially started scanning from: 651 */ 652 buf->last_scanned = start; 653 bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred); 654 655 return bkey_cmp(&buf->last_scanned, &start_pos) >= 0; 656 } 657 658 static int bch_writeback_thread(void *arg) 659 { 660 struct cached_dev *dc = arg; 661 struct cache_set *c = dc->disk.c; 662 bool searched_full_index; 663 664 bch_ratelimit_reset(&dc->writeback_rate); 665 666 while (!kthread_should_stop() && 667 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 668 down_write(&dc->writeback_lock); 669 set_current_state(TASK_INTERRUPTIBLE); 670 /* 671 * If the bache device is detaching, skip here and continue 672 * to perform writeback. Otherwise, if no dirty data on cache, 673 * or there is dirty data on cache but writeback is disabled, 674 * the writeback thread should sleep here and wait for others 675 * to wake up it. 676 */ 677 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && 678 (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) { 679 up_write(&dc->writeback_lock); 680 681 if (kthread_should_stop() || 682 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 683 set_current_state(TASK_RUNNING); 684 break; 685 } 686 687 schedule(); 688 continue; 689 } 690 set_current_state(TASK_RUNNING); 691 692 searched_full_index = refill_dirty(dc); 693 694 if (searched_full_index && 695 RB_EMPTY_ROOT(&dc->writeback_keys.keys)) { 696 atomic_set(&dc->has_dirty, 0); 697 SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN); 698 bch_write_bdev_super(dc, NULL); 699 /* 700 * If bcache device is detaching via sysfs interface, 701 * writeback thread should stop after there is no dirty 702 * data on cache. BCACHE_DEV_DETACHING flag is set in 703 * bch_cached_dev_detach(). 704 */ 705 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) { 706 up_write(&dc->writeback_lock); 707 break; 708 } 709 710 /* 711 * When dirty data rate is high (e.g. 50%+), there might 712 * be heavy buckets fragmentation after writeback 713 * finished, which hurts following write performance. 714 * If users really care about write performance they 715 * may set BCH_ENABLE_AUTO_GC via sysfs, then when 716 * BCH_DO_AUTO_GC is set, garbage collection thread 717 * will be wake up here. After moving gc, the shrunk 718 * btree and discarded free buckets SSD space may be 719 * helpful for following write requests. 720 */ 721 if (c->gc_after_writeback == 722 (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) { 723 c->gc_after_writeback &= ~BCH_DO_AUTO_GC; 724 force_wake_up_gc(c); 725 } 726 } 727 728 up_write(&dc->writeback_lock); 729 730 read_dirty(dc); 731 732 if (searched_full_index) { 733 unsigned int delay = dc->writeback_delay * HZ; 734 735 while (delay && 736 !kthread_should_stop() && 737 !test_bit(CACHE_SET_IO_DISABLE, &c->flags) && 738 !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) 739 delay = schedule_timeout_interruptible(delay); 740 741 bch_ratelimit_reset(&dc->writeback_rate); 742 } 743 } 744 745 if (dc->writeback_write_wq) { 746 flush_workqueue(dc->writeback_write_wq); 747 destroy_workqueue(dc->writeback_write_wq); 748 } 749 cached_dev_put(dc); 750 wait_for_kthread_stop(); 751 752 return 0; 753 } 754 755 /* Init */ 756 #define INIT_KEYS_EACH_TIME 500000 757 #define INIT_KEYS_SLEEP_MS 100 758 759 struct sectors_dirty_init { 760 struct btree_op op; 761 unsigned int inode; 762 size_t count; 763 struct bkey start; 764 }; 765 766 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b, 767 struct bkey *k) 768 { 769 struct sectors_dirty_init *op = container_of(_op, 770 struct sectors_dirty_init, op); 771 if (KEY_INODE(k) > op->inode) 772 return MAP_DONE; 773 774 if (KEY_DIRTY(k)) 775 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k), 776 KEY_START(k), KEY_SIZE(k)); 777 778 op->count++; 779 if (atomic_read(&b->c->search_inflight) && 780 !(op->count % INIT_KEYS_EACH_TIME)) { 781 bkey_copy_key(&op->start, k); 782 return -EAGAIN; 783 } 784 785 return MAP_CONTINUE; 786 } 787 788 void bch_sectors_dirty_init(struct bcache_device *d) 789 { 790 struct sectors_dirty_init op; 791 int ret; 792 793 bch_btree_op_init(&op.op, -1); 794 op.inode = d->id; 795 op.count = 0; 796 op.start = KEY(op.inode, 0, 0); 797 798 do { 799 ret = bch_btree_map_keys(&op.op, d->c, &op.start, 800 sectors_dirty_init_fn, 0); 801 if (ret == -EAGAIN) 802 schedule_timeout_interruptible( 803 msecs_to_jiffies(INIT_KEYS_SLEEP_MS)); 804 else if (ret < 0) { 805 pr_warn("sectors dirty init failed, ret=%d!", ret); 806 break; 807 } 808 } while (ret == -EAGAIN); 809 } 810 811 void bch_cached_dev_writeback_init(struct cached_dev *dc) 812 { 813 sema_init(&dc->in_flight, 64); 814 init_rwsem(&dc->writeback_lock); 815 bch_keybuf_init(&dc->writeback_keys); 816 817 dc->writeback_metadata = true; 818 dc->writeback_running = false; 819 dc->writeback_percent = 10; 820 dc->writeback_delay = 30; 821 atomic_long_set(&dc->writeback_rate.rate, 1024); 822 dc->writeback_rate_minimum = 8; 823 824 dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT; 825 dc->writeback_rate_p_term_inverse = 40; 826 dc->writeback_rate_i_term_inverse = 10000; 827 828 WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 829 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); 830 } 831 832 int bch_cached_dev_writeback_start(struct cached_dev *dc) 833 { 834 dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq", 835 WQ_MEM_RECLAIM, 0); 836 if (!dc->writeback_write_wq) 837 return -ENOMEM; 838 839 cached_dev_get(dc); 840 dc->writeback_thread = kthread_create(bch_writeback_thread, dc, 841 "bcache_writeback"); 842 if (IS_ERR(dc->writeback_thread)) { 843 cached_dev_put(dc); 844 destroy_workqueue(dc->writeback_write_wq); 845 return PTR_ERR(dc->writeback_thread); 846 } 847 dc->writeback_running = true; 848 849 WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 850 schedule_delayed_work(&dc->writeback_rate_update, 851 dc->writeback_rate_update_seconds * HZ); 852 853 bch_writeback_queue(dc); 854 855 return 0; 856 } 857