1104 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * background writeback - scan btree for dirty data and write it to the backing4 * device5 *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 20static 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 */30static 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 for36 * flash-only devices37 */38 uint64_t cache_sectors = c->nbuckets * c->cache->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 the43 * 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 each45 * backing volume uses about 2% of the cache for dirty data.46 */47 uint32_t bdev_share =48 div64_u64(bdev_nr_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 61static 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 our68 * target) is calculated. The error is accumulated (numerically69 * integrated).70 *71 * Then, the proportional value and integral value are scaled72 * based on configured values. These are stored as inverses to73 * avoid fixed point math and to make configuration easy-- e.g.74 * the default value of 40 for writeback_rate_p_term_inverse75 * attempts to write at a rate that would retire all the dirty76 * blocks in 40 seconds.77 *78 * The writeback_rate_i_inverse value of 10000 means that 1/10000th79 * of the error is accumulated in the integral term per second.80 * This acts as a slow, long-term average that is not subject to81 * 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 /*92 * We need to consider the number of dirty buckets as well93 * when calculating the proportional_scaled, Otherwise we might94 * have an unreasonable small writeback rate at a highly fragmented situation95 * when very few dirty sectors consumed a lot dirty buckets, the96 * worst case is when dirty buckets reached cutoff_writeback_sync and97 * dirty data is still not even reached to writeback percent, so the rate98 * still will be at the minimum value, which will cause the write99 * stuck at a non-writeback mode.100 */101 struct cache_set *c = dc->disk.c;102 103 int64_t dirty_buckets = c->nbuckets - c->avail_nbuckets;104 105 if (dc->writeback_consider_fragment &&106 c->gc_stats.in_use > BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW && dirty > 0) {107 int64_t fragment =108 div_s64((dirty_buckets * c->cache->sb.bucket_size), dirty);109 int64_t fp_term;110 int64_t fps;111 112 if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID) {113 fp_term = (int64_t)dc->writeback_rate_fp_term_low *114 (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW);115 } else if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH) {116 fp_term = (int64_t)dc->writeback_rate_fp_term_mid *117 (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID);118 } else {119 fp_term = (int64_t)dc->writeback_rate_fp_term_high *120 (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH);121 }122 fps = div_s64(dirty, dirty_buckets) * fp_term;123 if (fragment > 3 && fps > proportional_scaled) {124 /* Only overrite the p when fragment > 3 */125 proportional_scaled = fps;126 }127 }128 129 if ((error < 0 && dc->writeback_rate_integral > 0) ||130 (error > 0 && time_before64(local_clock(),131 dc->writeback_rate.next + NSEC_PER_MSEC))) {132 /*133 * Only decrease the integral term if it's more than134 * zero. Only increase the integral term if the device135 * is keeping up. (Don't wind up the integral136 * ineffectively in either case).137 *138 * It's necessary to scale this by139 * writeback_rate_update_seconds to keep the integral140 * term dimensioned properly.141 */142 dc->writeback_rate_integral += error *143 dc->writeback_rate_update_seconds;144 }145 146 integral_scaled = div_s64(dc->writeback_rate_integral,147 dc->writeback_rate_i_term_inverse);148 149 new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),150 dc->writeback_rate_minimum, NSEC_PER_SEC);151 152 dc->writeback_rate_proportional = proportional_scaled;153 dc->writeback_rate_integral_scaled = integral_scaled;154 dc->writeback_rate_change = new_rate -155 atomic_long_read(&dc->writeback_rate.rate);156 atomic_long_set(&dc->writeback_rate.rate, new_rate);157 dc->writeback_rate_target = target;158}159 160static bool idle_counter_exceeded(struct cache_set *c)161{162 int counter, dev_nr;163 164 /*165 * If c->idle_counter is overflow (idel for really long time),166 * reset as 0 and not set maximum rate this time for code167 * simplicity.168 */169 counter = atomic_inc_return(&c->idle_counter);170 if (counter <= 0) {171 atomic_set(&c->idle_counter, 0);172 return false;173 }174 175 dev_nr = atomic_read(&c->attached_dev_nr);176 if (dev_nr == 0)177 return false;178 179 /*180 * c->idle_counter is increased by writeback thread of all181 * attached backing devices, in order to represent a rough182 * time period, counter should be divided by dev_nr.183 * Otherwise the idle time cannot be larger with more backing184 * device attached.185 * The following calculation equals to checking186 * (counter / dev_nr) < (dev_nr * 6)187 */188 if (counter < (dev_nr * dev_nr * 6))189 return false;190 191 return true;192}193 194/*195 * Idle_counter is increased every time when update_writeback_rate() is196 * called. If all backing devices attached to the same cache set have197 * identical dc->writeback_rate_update_seconds values, it is about 6198 * rounds of update_writeback_rate() on each backing device before199 * c->at_max_writeback_rate is set to 1, and then max wrteback rate set200 * to each dc->writeback_rate.rate.201 * In order to avoid extra locking cost for counting exact dirty cached202 * devices number, c->attached_dev_nr is used to calculate the idle203 * throushold. It might be bigger if not all cached device are in write-204 * back mode, but it still works well with limited extra rounds of205 * update_writeback_rate().206 */207static bool set_at_max_writeback_rate(struct cache_set *c,208 struct cached_dev *dc)209{210 /* Don't sst max writeback rate if it is disabled */211 if (!c->idle_max_writeback_rate_enabled)212 return false;213 214 /* Don't set max writeback rate if gc is running */215 if (!c->gc_mark_valid)216 return false;217 218 if (!idle_counter_exceeded(c))219 return false;220 221 if (atomic_read(&c->at_max_writeback_rate) != 1)222 atomic_set(&c->at_max_writeback_rate, 1);223 224 atomic_long_set(&dc->writeback_rate.rate, INT_MAX);225 226 /* keep writeback_rate_target as existing value */227 dc->writeback_rate_proportional = 0;228 dc->writeback_rate_integral_scaled = 0;229 dc->writeback_rate_change = 0;230 231 /*232 * In case new I/O arrives during before233 * set_at_max_writeback_rate() returns.234 */235 if (!idle_counter_exceeded(c) ||236 !atomic_read(&c->at_max_writeback_rate))237 return false;238 239 return true;240}241 242static void update_writeback_rate(struct work_struct *work)243{244 struct cached_dev *dc = container_of(to_delayed_work(work),245 struct cached_dev,246 writeback_rate_update);247 struct cache_set *c = dc->disk.c;248 249 /*250 * should check BCACHE_DEV_RATE_DW_RUNNING before calling251 * cancel_delayed_work_sync().252 */253 set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);254 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */255 smp_mb__after_atomic();256 257 /*258 * CACHE_SET_IO_DISABLE might be set via sysfs interface,259 * check it here too.260 */261 if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||262 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {263 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);264 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */265 smp_mb__after_atomic();266 return;267 }268 269 /*270 * If the whole cache set is idle, set_at_max_writeback_rate()271 * will set writeback rate to a max number. Then it is272 * unncessary to update writeback rate for an idle cache set273 * in maximum writeback rate number(s).274 */275 if (atomic_read(&dc->has_dirty) && dc->writeback_percent &&276 !set_at_max_writeback_rate(c, dc)) {277 do {278 if (!down_read_trylock((&dc->writeback_lock))) {279 dc->rate_update_retry++;280 if (dc->rate_update_retry <=281 BCH_WBRATE_UPDATE_MAX_SKIPS)282 break;283 down_read(&dc->writeback_lock);284 dc->rate_update_retry = 0;285 }286 __update_writeback_rate(dc);287 update_gc_after_writeback(c);288 up_read(&dc->writeback_lock);289 } while (0);290 }291 292 293 /*294 * CACHE_SET_IO_DISABLE might be set via sysfs interface,295 * check it here too.296 */297 if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&298 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {299 schedule_delayed_work(&dc->writeback_rate_update,300 dc->writeback_rate_update_seconds * HZ);301 }302 303 /*304 * should check BCACHE_DEV_RATE_DW_RUNNING before calling305 * cancel_delayed_work_sync().306 */307 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);308 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */309 smp_mb__after_atomic();310}311 312static unsigned int writeback_delay(struct cached_dev *dc,313 unsigned int sectors)314{315 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||316 !dc->writeback_percent)317 return 0;318 319 return bch_next_delay(&dc->writeback_rate, sectors);320}321 322struct dirty_io {323 struct closure cl;324 struct cached_dev *dc;325 uint16_t sequence;326 struct bio bio;327};328 329static void dirty_init(struct keybuf_key *w)330{331 struct dirty_io *io = w->private;332 struct bio *bio = &io->bio;333 334 bio_init(bio, NULL, bio->bi_inline_vecs,335 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), 0);336 if (!io->dc->writeback_percent)337 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));338 339 bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9;340 bio->bi_private = w;341 bch_bio_map(bio, NULL);342}343 344static CLOSURE_CALLBACK(dirty_io_destructor)345{346 closure_type(io, struct dirty_io, cl);347 348 kfree(io);349}350 351static CLOSURE_CALLBACK(write_dirty_finish)352{353 closure_type(io, struct dirty_io, cl);354 struct keybuf_key *w = io->bio.bi_private;355 struct cached_dev *dc = io->dc;356 357 bio_free_pages(&io->bio);358 359 /* This is kind of a dumb way of signalling errors. */360 if (KEY_DIRTY(&w->key)) {361 int ret;362 unsigned int i;363 struct keylist keys;364 365 bch_keylist_init(&keys);366 367 bkey_copy(keys.top, &w->key);368 SET_KEY_DIRTY(keys.top, false);369 bch_keylist_push(&keys);370 371 for (i = 0; i < KEY_PTRS(&w->key); i++)372 atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);373 374 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);375 376 if (ret)377 trace_bcache_writeback_collision(&w->key);378 379 atomic_long_inc(ret380 ? &dc->disk.c->writeback_keys_failed381 : &dc->disk.c->writeback_keys_done);382 }383 384 bch_keybuf_del(&dc->writeback_keys, w);385 up(&dc->in_flight);386 387 closure_return_with_destructor(cl, dirty_io_destructor);388}389 390static void dirty_endio(struct bio *bio)391{392 struct keybuf_key *w = bio->bi_private;393 struct dirty_io *io = w->private;394 395 if (bio->bi_status) {396 SET_KEY_DIRTY(&w->key, false);397 bch_count_backing_io_errors(io->dc, bio);398 }399 400 closure_put(&io->cl);401}402 403static CLOSURE_CALLBACK(write_dirty)404{405 closure_type(io, struct dirty_io, cl);406 struct keybuf_key *w = io->bio.bi_private;407 struct cached_dev *dc = io->dc;408 409 uint16_t next_sequence;410 411 if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {412 /* Not our turn to write; wait for a write to complete */413 closure_wait(&dc->writeback_ordering_wait, cl);414 415 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {416 /*417 * Edge case-- it happened in indeterminate order418 * relative to when we were added to wait list..419 */420 closure_wake_up(&dc->writeback_ordering_wait);421 }422 423 continue_at(cl, write_dirty, io->dc->writeback_write_wq);424 return;425 }426 427 next_sequence = io->sequence + 1;428 429 /*430 * IO errors are signalled using the dirty bit on the key.431 * If we failed to read, we should not attempt to write to the432 * backing device. Instead, immediately go to write_dirty_finish433 * to clean up.434 */435 if (KEY_DIRTY(&w->key)) {436 dirty_init(w);437 io->bio.bi_opf = REQ_OP_WRITE;438 io->bio.bi_iter.bi_sector = KEY_START(&w->key);439 bio_set_dev(&io->bio, io->dc->bdev);440 io->bio.bi_end_io = dirty_endio;441 442 /* I/O request sent to backing device */443 closure_bio_submit(io->dc->disk.c, &io->bio, cl);444 }445 446 atomic_set(&dc->writeback_sequence_next, next_sequence);447 closure_wake_up(&dc->writeback_ordering_wait);448 449 continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);450}451 452static void read_dirty_endio(struct bio *bio)453{454 struct keybuf_key *w = bio->bi_private;455 struct dirty_io *io = w->private;456 457 /* is_read = 1 */458 bch_count_io_errors(io->dc->disk.c->cache,459 bio->bi_status, 1,460 "reading dirty data from cache");461 462 dirty_endio(bio);463}464 465static CLOSURE_CALLBACK(read_dirty_submit)466{467 closure_type(io, struct dirty_io, cl);468 469 closure_bio_submit(io->dc->disk.c, &io->bio, cl);470 471 continue_at(cl, write_dirty, io->dc->writeback_write_wq);472}473 474static void read_dirty(struct cached_dev *dc)475{476 unsigned int delay = 0;477 struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;478 size_t size;479 int nk, i;480 struct dirty_io *io;481 struct closure cl;482 uint16_t sequence = 0;483 484 BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));485 atomic_set(&dc->writeback_sequence_next, sequence);486 closure_init_stack(&cl);487 488 /*489 * XXX: if we error, background writeback just spins. Should use some490 * mempools.491 */492 493 next = bch_keybuf_next(&dc->writeback_keys);494 495 while (!kthread_should_stop() &&496 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&497 next) {498 size = 0;499 nk = 0;500 501 do {502 BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));503 504 /*505 * Don't combine too many operations, even if they506 * are all small.507 */508 if (nk >= MAX_WRITEBACKS_IN_PASS)509 break;510 511 /*512 * If the current operation is very large, don't513 * further combine operations.514 */515 if (size >= MAX_WRITESIZE_IN_PASS)516 break;517 518 /*519 * Operations are only eligible to be combined520 * if they are contiguous.521 *522 * TODO: add a heuristic willing to fire a523 * certain amount of non-contiguous IO per pass,524 * so that we can benefit from backing device525 * command queueing.526 */527 if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,528 &START_KEY(&next->key)))529 break;530 531 size += KEY_SIZE(&next->key);532 keys[nk++] = next;533 } while ((next = bch_keybuf_next(&dc->writeback_keys)));534 535 /* Now we have gathered a set of 1..5 keys to write back. */536 for (i = 0; i < nk; i++) {537 w = keys[i];538 539 io = kzalloc(struct_size(io, bio.bi_inline_vecs,540 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)),541 GFP_KERNEL);542 if (!io)543 goto err;544 545 w->private = io;546 io->dc = dc;547 io->sequence = sequence++;548 549 dirty_init(w);550 io->bio.bi_opf = REQ_OP_READ;551 io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);552 bio_set_dev(&io->bio, dc->disk.c->cache->bdev);553 io->bio.bi_end_io = read_dirty_endio;554 555 if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))556 goto err_free;557 558 trace_bcache_writeback(&w->key);559 560 down(&dc->in_flight);561 562 /*563 * We've acquired a semaphore for the maximum564 * simultaneous number of writebacks; from here565 * everything happens asynchronously.566 */567 closure_call(&io->cl, read_dirty_submit, NULL, &cl);568 }569 570 delay = writeback_delay(dc, size);571 572 while (!kthread_should_stop() &&573 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&574 delay) {575 schedule_timeout_interruptible(delay);576 delay = writeback_delay(dc, 0);577 }578 }579 580 if (0) {581err_free:582 kfree(w->private);583err:584 bch_keybuf_del(&dc->writeback_keys, w);585 }586 587 /*588 * Wait for outstanding writeback IOs to finish (and keybuf slots to be589 * freed) before refilling again590 */591 closure_sync(&cl);592}593 594/* Scan for dirty data */595 596void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,597 uint64_t offset, int nr_sectors)598{599 struct bcache_device *d = c->devices[inode];600 unsigned int stripe_offset, sectors_dirty;601 int stripe;602 603 if (!d)604 return;605 606 stripe = offset_to_stripe(d, offset);607 if (stripe < 0)608 return;609 610 if (UUID_FLASH_ONLY(&c->uuids[inode]))611 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);612 613 stripe_offset = offset & (d->stripe_size - 1);614 615 while (nr_sectors) {616 int s = min_t(unsigned int, abs(nr_sectors),617 d->stripe_size - stripe_offset);618 619 if (nr_sectors < 0)620 s = -s;621 622 if (stripe >= d->nr_stripes)623 return;624 625 sectors_dirty = atomic_add_return(s,626 d->stripe_sectors_dirty + stripe);627 if (sectors_dirty == d->stripe_size) {628 if (!test_bit(stripe, d->full_dirty_stripes))629 set_bit(stripe, d->full_dirty_stripes);630 } else {631 if (test_bit(stripe, d->full_dirty_stripes))632 clear_bit(stripe, d->full_dirty_stripes);633 }634 635 nr_sectors -= s;636 stripe_offset = 0;637 stripe++;638 }639}640 641static bool dirty_pred(struct keybuf *buf, struct bkey *k)642{643 struct cached_dev *dc = container_of(buf,644 struct cached_dev,645 writeback_keys);646 647 BUG_ON(KEY_INODE(k) != dc->disk.id);648 649 return KEY_DIRTY(k);650}651 652static void refill_full_stripes(struct cached_dev *dc)653{654 struct keybuf *buf = &dc->writeback_keys;655 unsigned int start_stripe, next_stripe;656 int stripe;657 bool wrapped = false;658 659 stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));660 if (stripe < 0)661 stripe = 0;662 663 start_stripe = stripe;664 665 while (1) {666 stripe = find_next_bit(dc->disk.full_dirty_stripes,667 dc->disk.nr_stripes, stripe);668 669 if (stripe == dc->disk.nr_stripes)670 goto next;671 672 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,673 dc->disk.nr_stripes, stripe);674 675 buf->last_scanned = KEY(dc->disk.id,676 stripe * dc->disk.stripe_size, 0);677 678 bch_refill_keybuf(dc->disk.c, buf,679 &KEY(dc->disk.id,680 next_stripe * dc->disk.stripe_size, 0),681 dirty_pred);682 683 if (array_freelist_empty(&buf->freelist))684 return;685 686 stripe = next_stripe;687next:688 if (wrapped && stripe > start_stripe)689 return;690 691 if (stripe == dc->disk.nr_stripes) {692 stripe = 0;693 wrapped = true;694 }695 }696}697 698/*699 * Returns true if we scanned the entire disk700 */701static bool refill_dirty(struct cached_dev *dc)702{703 struct keybuf *buf = &dc->writeback_keys;704 struct bkey start = KEY(dc->disk.id, 0, 0);705 struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);706 struct bkey start_pos;707 708 /*709 * make sure keybuf pos is inside the range for this disk - at bringup710 * we might not be attached yet so this disk's inode nr isn't711 * initialized then712 */713 if (bkey_cmp(&buf->last_scanned, &start) < 0 ||714 bkey_cmp(&buf->last_scanned, &end) > 0)715 buf->last_scanned = start;716 717 if (dc->partial_stripes_expensive) {718 refill_full_stripes(dc);719 if (array_freelist_empty(&buf->freelist))720 return false;721 }722 723 start_pos = buf->last_scanned;724 bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);725 726 if (bkey_cmp(&buf->last_scanned, &end) < 0)727 return false;728 729 /*730 * If we get to the end start scanning again from the beginning, and731 * only scan up to where we initially started scanning from:732 */733 buf->last_scanned = start;734 bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);735 736 return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;737}738 739static int bch_writeback_thread(void *arg)740{741 struct cached_dev *dc = arg;742 struct cache_set *c = dc->disk.c;743 bool searched_full_index;744 745 bch_ratelimit_reset(&dc->writeback_rate);746 747 while (!kthread_should_stop() &&748 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {749 down_write(&dc->writeback_lock);750 set_current_state(TASK_INTERRUPTIBLE);751 /*752 * If the bache device is detaching, skip here and continue753 * to perform writeback. Otherwise, if no dirty data on cache,754 * or there is dirty data on cache but writeback is disabled,755 * the writeback thread should sleep here and wait for others756 * to wake up it.757 */758 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&759 (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {760 up_write(&dc->writeback_lock);761 762 if (kthread_should_stop() ||763 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {764 set_current_state(TASK_RUNNING);765 break;766 }767 768 schedule();769 continue;770 }771 set_current_state(TASK_RUNNING);772 773 searched_full_index = refill_dirty(dc);774 775 if (searched_full_index &&776 RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {777 atomic_set(&dc->has_dirty, 0);778 SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);779 bch_write_bdev_super(dc, NULL);780 /*781 * If bcache device is detaching via sysfs interface,782 * writeback thread should stop after there is no dirty783 * data on cache. BCACHE_DEV_DETACHING flag is set in784 * bch_cached_dev_detach().785 */786 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {787 struct closure cl;788 789 closure_init_stack(&cl);790 memset(&dc->sb.set_uuid, 0, 16);791 SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);792 793 bch_write_bdev_super(dc, &cl);794 closure_sync(&cl);795 796 up_write(&dc->writeback_lock);797 break;798 }799 800 /*801 * When dirty data rate is high (e.g. 50%+), there might802 * be heavy buckets fragmentation after writeback803 * finished, which hurts following write performance.804 * If users really care about write performance they805 * may set BCH_ENABLE_AUTO_GC via sysfs, then when806 * BCH_DO_AUTO_GC is set, garbage collection thread807 * will be wake up here. After moving gc, the shrunk808 * btree and discarded free buckets SSD space may be809 * helpful for following write requests.810 */811 if (c->gc_after_writeback ==812 (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) {813 c->gc_after_writeback &= ~BCH_DO_AUTO_GC;814 force_wake_up_gc(c);815 }816 }817 818 up_write(&dc->writeback_lock);819 820 read_dirty(dc);821 822 if (searched_full_index) {823 unsigned int delay = dc->writeback_delay * HZ;824 825 while (delay &&826 !kthread_should_stop() &&827 !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&828 !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))829 delay = schedule_timeout_interruptible(delay);830 831 bch_ratelimit_reset(&dc->writeback_rate);832 }833 }834 835 if (dc->writeback_write_wq)836 destroy_workqueue(dc->writeback_write_wq);837 838 cached_dev_put(dc);839 wait_for_kthread_stop();840 841 return 0;842}843 844/* Init */845#define INIT_KEYS_EACH_TIME 500000846 847struct sectors_dirty_init {848 struct btree_op op;849 unsigned int inode;850 size_t count;851};852 853static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,854 struct bkey *k)855{856 struct sectors_dirty_init *op = container_of(_op,857 struct sectors_dirty_init, op);858 if (KEY_INODE(k) > op->inode)859 return MAP_DONE;860 861 if (KEY_DIRTY(k))862 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),863 KEY_START(k), KEY_SIZE(k));864 865 op->count++;866 if (!(op->count % INIT_KEYS_EACH_TIME))867 cond_resched();868 869 return MAP_CONTINUE;870}871 872static int bch_root_node_dirty_init(struct cache_set *c,873 struct bcache_device *d,874 struct bkey *k)875{876 struct sectors_dirty_init op;877 int ret;878 879 bch_btree_op_init(&op.op, -1);880 op.inode = d->id;881 op.count = 0;882 883 ret = bcache_btree(map_keys_recurse,884 k,885 c->root,886 &op.op,887 &KEY(op.inode, 0, 0),888 sectors_dirty_init_fn,889 0);890 if (ret < 0)891 pr_warn("sectors dirty init failed, ret=%d!\n", ret);892 893 /*894 * The op may be added to cache_set's btree_cache_wait895 * in mca_cannibalize(), must ensure it is removed from896 * the list and release btree_cache_alloc_lock before897 * free op memory.898 * Otherwise, the btree_cache_wait will be damaged.899 */900 bch_cannibalize_unlock(c);901 finish_wait(&c->btree_cache_wait, &(&op.op)->wait);902 903 return ret;904}905 906static int bch_dirty_init_thread(void *arg)907{908 struct dirty_init_thrd_info *info = arg;909 struct bch_dirty_init_state *state = info->state;910 struct cache_set *c = state->c;911 struct btree_iter iter;912 struct bkey *k, *p;913 int cur_idx, prev_idx, skip_nr;914 915 k = p = NULL;916 prev_idx = 0;917 918 min_heap_init(&iter.heap, NULL, MAX_BSETS);919 bch_btree_iter_init(&c->root->keys, &iter, NULL);920 k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);921 BUG_ON(!k);922 923 p = k;924 925 while (k) {926 spin_lock(&state->idx_lock);927 cur_idx = state->key_idx;928 state->key_idx++;929 spin_unlock(&state->idx_lock);930 931 skip_nr = cur_idx - prev_idx;932 933 while (skip_nr) {934 k = bch_btree_iter_next_filter(&iter,935 &c->root->keys,936 bch_ptr_bad);937 if (k)938 p = k;939 else {940 atomic_set(&state->enough, 1);941 /* Update state->enough earlier */942 smp_mb__after_atomic();943 goto out;944 }945 skip_nr--;946 }947 948 if (p) {949 if (bch_root_node_dirty_init(c, state->d, p) < 0)950 goto out;951 }952 953 p = NULL;954 prev_idx = cur_idx;955 }956 957out:958 /* In order to wake up state->wait in time */959 smp_mb__before_atomic();960 if (atomic_dec_and_test(&state->started))961 wake_up(&state->wait);962 963 return 0;964}965 966static int bch_btre_dirty_init_thread_nr(void)967{968 int n = num_online_cpus()/2;969 970 if (n == 0)971 n = 1;972 else if (n > BCH_DIRTY_INIT_THRD_MAX)973 n = BCH_DIRTY_INIT_THRD_MAX;974 975 return n;976}977 978void bch_sectors_dirty_init(struct bcache_device *d)979{980 int i;981 struct btree *b = NULL;982 struct bkey *k = NULL;983 struct btree_iter iter;984 struct sectors_dirty_init op;985 struct cache_set *c = d->c;986 struct bch_dirty_init_state state;987 988 min_heap_init(&iter.heap, NULL, MAX_BSETS);989 990retry_lock:991 b = c->root;992 rw_lock(0, b, b->level);993 if (b != c->root) {994 rw_unlock(0, b);995 goto retry_lock;996 }997 998 /* Just count root keys if no leaf node */999 if (c->root->level == 0) {1000 bch_btree_op_init(&op.op, -1);1001 op.inode = d->id;1002 op.count = 0;1003 1004 for_each_key_filter(&c->root->keys,1005 k, &iter, bch_ptr_invalid) {1006 if (KEY_INODE(k) != op.inode)1007 continue;1008 sectors_dirty_init_fn(&op.op, c->root, k);1009 }1010 1011 rw_unlock(0, b);1012 return;1013 }1014 1015 memset(&state, 0, sizeof(struct bch_dirty_init_state));1016 state.c = c;1017 state.d = d;1018 state.total_threads = bch_btre_dirty_init_thread_nr();1019 state.key_idx = 0;1020 spin_lock_init(&state.idx_lock);1021 atomic_set(&state.started, 0);1022 atomic_set(&state.enough, 0);1023 init_waitqueue_head(&state.wait);1024 1025 for (i = 0; i < state.total_threads; i++) {1026 /* Fetch latest state.enough earlier */1027 smp_mb__before_atomic();1028 if (atomic_read(&state.enough))1029 break;1030 1031 atomic_inc(&state.started);1032 state.infos[i].state = &state;1033 state.infos[i].thread =1034 kthread_run(bch_dirty_init_thread, &state.infos[i],1035 "bch_dirtcnt[%d]", i);1036 if (IS_ERR(state.infos[i].thread)) {1037 pr_err("fails to run thread bch_dirty_init[%d]\n", i);1038 atomic_dec(&state.started);1039 for (--i; i >= 0; i--)1040 kthread_stop(state.infos[i].thread);1041 goto out;1042 }1043 }1044 1045out:1046 /* Must wait for all threads to stop. */1047 wait_event(state.wait, atomic_read(&state.started) == 0);1048 rw_unlock(0, b);1049}1050 1051void bch_cached_dev_writeback_init(struct cached_dev *dc)1052{1053 sema_init(&dc->in_flight, 64);1054 init_rwsem(&dc->writeback_lock);1055 bch_keybuf_init(&dc->writeback_keys);1056 1057 dc->writeback_metadata = true;1058 dc->writeback_running = false;1059 dc->writeback_consider_fragment = true;1060 dc->writeback_percent = 10;1061 dc->writeback_delay = 30;1062 atomic_long_set(&dc->writeback_rate.rate, 1024);1063 dc->writeback_rate_minimum = 8;1064 1065 dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;1066 dc->writeback_rate_p_term_inverse = 40;1067 dc->writeback_rate_fp_term_low = 1;1068 dc->writeback_rate_fp_term_mid = 10;1069 dc->writeback_rate_fp_term_high = 1000;1070 dc->writeback_rate_i_term_inverse = 10000;1071 1072 /* For dc->writeback_lock contention in update_writeback_rate() */1073 dc->rate_update_retry = 0;1074 1075 WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));1076 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);1077}1078 1079int bch_cached_dev_writeback_start(struct cached_dev *dc)1080{1081 dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",1082 WQ_MEM_RECLAIM, 0);1083 if (!dc->writeback_write_wq)1084 return -ENOMEM;1085 1086 cached_dev_get(dc);1087 dc->writeback_thread = kthread_create(bch_writeback_thread, dc,1088 "bcache_writeback");1089 if (IS_ERR(dc->writeback_thread)) {1090 cached_dev_put(dc);1091 destroy_workqueue(dc->writeback_write_wq);1092 return PTR_ERR(dc->writeback_thread);1093 }1094 dc->writeback_running = true;1095 1096 WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));1097 schedule_delayed_work(&dc->writeback_rate_update,1098 dc->writeback_rate_update_seconds * HZ);1099 1100 bch_writeback_queue(dc);1101 1102 return 0;1103}1104