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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 */
21static 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
52static 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
112static 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
166static 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
175struct dirty_io {
176 struct closure cl;
177 struct cached_dev *dc;
178 uint16_t sequence;
179 struct bio bio;
180};
181
182static 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
197static 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
203static 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
242static 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
255static 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
304static 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
317static 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
326static 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) {
455err_free:
456 kfree(w->private);
457err:
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
470void 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
505static 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
514static 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;
549next:
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 */
563static 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
601static 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
677struct sectors_dirty_init {
678 struct btree_op op;
679 unsigned inode;
680};
681
682static 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
697void 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
708void 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
729int 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}