2 * background writeback - scan btree for dirty data and write it to the backing
5 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
6 * Copyright 2012 Google, Inc.
12 #include "writeback.h"
14 #include <linux/delay.h>
15 #include <linux/freezer.h>
16 #include <linux/kthread.h>
17 #include <trace/events/bcache.h>
21 static void __update_writeback_rate(struct cached_dev *dc)
23 struct cache_set *c = dc->disk.c;
24 uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
25 uint64_t cache_dirty_target =
26 div_u64(cache_sectors * dc->writeback_percent, 100);
28 int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
29 c->cached_dev_sectors);
35 int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
36 int64_t derivative = dirty - dc->disk.sectors_dirty_last;
38 dc->disk.sectors_dirty_last = dirty;
40 derivative *= dc->writeback_rate_d_term;
41 derivative = clamp(derivative, -dirty, dirty);
43 derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
44 dc->writeback_rate_d_smooth, 0);
46 /* Avoid divide by zero */
50 error = div64_s64((dirty + derivative - target) << 8, target);
52 change = div_s64((dc->writeback_rate.rate * error) >> 8,
53 dc->writeback_rate_p_term_inverse);
55 /* Don't increase writeback rate if the device isn't keeping up */
57 time_after64(local_clock(),
58 dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
61 dc->writeback_rate.rate =
62 clamp_t(int64_t, dc->writeback_rate.rate + change,
65 dc->writeback_rate_derivative = derivative;
66 dc->writeback_rate_change = change;
67 dc->writeback_rate_target = target;
70 static void update_writeback_rate(struct work_struct *work)
72 struct cached_dev *dc = container_of(to_delayed_work(work),
74 writeback_rate_update);
76 down_read(&dc->writeback_lock);
78 if (atomic_read(&dc->has_dirty) &&
79 dc->writeback_percent)
80 __update_writeback_rate(dc);
82 up_read(&dc->writeback_lock);
84 schedule_delayed_work(&dc->writeback_rate_update,
85 dc->writeback_rate_update_seconds * HZ);
88 static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
92 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
93 !dc->writeback_percent)
96 ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);
98 return min_t(uint64_t, ret, HZ);
103 struct cached_dev *dc;
107 static void dirty_init(struct keybuf_key *w)
109 struct dirty_io *io = w->private;
110 struct bio *bio = &io->bio;
113 if (!io->dc->writeback_percent)
114 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
116 bio->bi_size = KEY_SIZE(&w->key) << 9;
117 bio->bi_max_vecs = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
119 bio->bi_io_vec = bio->bi_inline_vecs;
120 bch_bio_map(bio, NULL);
123 static void dirty_io_destructor(struct closure *cl)
125 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
129 static void write_dirty_finish(struct closure *cl)
131 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
132 struct keybuf_key *w = io->bio.bi_private;
133 struct cached_dev *dc = io->dc;
137 bio_for_each_segment_all(bv, &io->bio, i)
138 __free_page(bv->bv_page);
140 /* This is kind of a dumb way of signalling errors. */
141 if (KEY_DIRTY(&w->key)) {
146 bch_keylist_init(&keys);
148 bkey_copy(keys.top, &w->key);
149 SET_KEY_DIRTY(keys.top, false);
150 bch_keylist_push(&keys);
152 for (i = 0; i < KEY_PTRS(&w->key); i++)
153 atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
155 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
158 trace_bcache_writeback_collision(&w->key);
161 ? &dc->disk.c->writeback_keys_failed
162 : &dc->disk.c->writeback_keys_done);
165 bch_keybuf_del(&dc->writeback_keys, w);
168 closure_return_with_destructor(cl, dirty_io_destructor);
171 static void dirty_endio(struct bio *bio, int error)
173 struct keybuf_key *w = bio->bi_private;
174 struct dirty_io *io = w->private;
177 SET_KEY_DIRTY(&w->key, false);
179 closure_put(&io->cl);
182 static void write_dirty(struct closure *cl)
184 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
185 struct keybuf_key *w = io->bio.bi_private;
188 io->bio.bi_rw = WRITE;
189 io->bio.bi_sector = KEY_START(&w->key);
190 io->bio.bi_bdev = io->dc->bdev;
191 io->bio.bi_end_io = dirty_endio;
193 closure_bio_submit(&io->bio, cl, &io->dc->disk);
195 continue_at(cl, write_dirty_finish, system_wq);
198 static void read_dirty_endio(struct bio *bio, int error)
200 struct keybuf_key *w = bio->bi_private;
201 struct dirty_io *io = w->private;
203 bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
204 error, "reading dirty data from cache");
206 dirty_endio(bio, error);
209 static void read_dirty_submit(struct closure *cl)
211 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
213 closure_bio_submit(&io->bio, cl, &io->dc->disk);
215 continue_at(cl, write_dirty, system_wq);
218 static void read_dirty(struct cached_dev *dc)
221 struct keybuf_key *w;
225 closure_init_stack(&cl);
228 * XXX: if we error, background writeback just spins. Should use some
232 while (!kthread_should_stop()) {
235 w = bch_keybuf_next(&dc->writeback_keys);
239 BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
241 if (KEY_START(&w->key) != dc->last_read ||
242 jiffies_to_msecs(delay) > 50)
243 while (!kthread_should_stop() && delay)
244 delay = schedule_timeout_interruptible(delay);
246 dc->last_read = KEY_OFFSET(&w->key);
248 io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
249 * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
258 io->bio.bi_sector = PTR_OFFSET(&w->key, 0);
259 io->bio.bi_bdev = PTR_CACHE(dc->disk.c,
261 io->bio.bi_rw = READ;
262 io->bio.bi_end_io = read_dirty_endio;
264 if (bio_alloc_pages(&io->bio, GFP_KERNEL))
267 trace_bcache_writeback(&w->key);
269 down(&dc->in_flight);
270 closure_call(&io->cl, read_dirty_submit, NULL, &cl);
272 delay = writeback_delay(dc, KEY_SIZE(&w->key));
279 bch_keybuf_del(&dc->writeback_keys, w);
283 * Wait for outstanding writeback IOs to finish (and keybuf slots to be
284 * freed) before refilling again
289 /* Scan for dirty data */
291 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
292 uint64_t offset, int nr_sectors)
294 struct bcache_device *d = c->devices[inode];
295 unsigned stripe_offset, stripe, sectors_dirty;
300 stripe = offset_to_stripe(d, offset);
301 stripe_offset = offset & (d->stripe_size - 1);
304 int s = min_t(unsigned, abs(nr_sectors),
305 d->stripe_size - stripe_offset);
310 if (stripe >= d->nr_stripes)
313 sectors_dirty = atomic_add_return(s,
314 d->stripe_sectors_dirty + stripe);
315 if (sectors_dirty == d->stripe_size)
316 set_bit(stripe, d->full_dirty_stripes);
318 clear_bit(stripe, d->full_dirty_stripes);
326 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
331 static void refill_full_stripes(struct cached_dev *dc)
333 struct keybuf *buf = &dc->writeback_keys;
334 unsigned start_stripe, stripe, next_stripe;
335 bool wrapped = false;
337 stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
339 if (stripe >= dc->disk.nr_stripes)
342 start_stripe = stripe;
345 stripe = find_next_bit(dc->disk.full_dirty_stripes,
346 dc->disk.nr_stripes, stripe);
348 if (stripe == dc->disk.nr_stripes)
351 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
352 dc->disk.nr_stripes, stripe);
354 buf->last_scanned = KEY(dc->disk.id,
355 stripe * dc->disk.stripe_size, 0);
357 bch_refill_keybuf(dc->disk.c, buf,
359 next_stripe * dc->disk.stripe_size, 0),
362 if (array_freelist_empty(&buf->freelist))
365 stripe = next_stripe;
367 if (wrapped && stripe > start_stripe)
370 if (stripe == dc->disk.nr_stripes) {
377 static bool refill_dirty(struct cached_dev *dc)
379 struct keybuf *buf = &dc->writeback_keys;
380 struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
381 bool searched_from_start = false;
383 if (dc->partial_stripes_expensive) {
384 refill_full_stripes(dc);
385 if (array_freelist_empty(&buf->freelist))
389 if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
390 buf->last_scanned = KEY(dc->disk.id, 0, 0);
391 searched_from_start = true;
394 bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
396 return bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start;
399 static int bch_writeback_thread(void *arg)
401 struct cached_dev *dc = arg;
402 bool searched_full_index;
404 while (!kthread_should_stop()) {
405 down_write(&dc->writeback_lock);
406 if (!atomic_read(&dc->has_dirty) ||
407 (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
408 !dc->writeback_running)) {
409 up_write(&dc->writeback_lock);
410 set_current_state(TASK_INTERRUPTIBLE);
412 if (kthread_should_stop())
420 searched_full_index = refill_dirty(dc);
422 if (searched_full_index &&
423 RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
424 atomic_set(&dc->has_dirty, 0);
426 SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
427 bch_write_bdev_super(dc, NULL);
430 up_write(&dc->writeback_lock);
432 bch_ratelimit_reset(&dc->writeback_rate);
435 if (searched_full_index) {
436 unsigned delay = dc->writeback_delay * HZ;
439 !kthread_should_stop() &&
440 !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
441 delay = schedule_timeout_interruptible(delay);
450 struct sectors_dirty_init {
455 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
458 struct sectors_dirty_init *op = container_of(_op,
459 struct sectors_dirty_init, op);
460 if (KEY_INODE(k) > op->inode)
464 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
465 KEY_START(k), KEY_SIZE(k));
470 void bch_sectors_dirty_init(struct cached_dev *dc)
472 struct sectors_dirty_init op;
474 bch_btree_op_init(&op.op, -1);
475 op.inode = dc->disk.id;
477 bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0),
478 sectors_dirty_init_fn, 0);
481 int bch_cached_dev_writeback_init(struct cached_dev *dc)
483 sema_init(&dc->in_flight, 64);
484 init_rwsem(&dc->writeback_lock);
485 bch_keybuf_init(&dc->writeback_keys);
487 dc->writeback_metadata = true;
488 dc->writeback_running = true;
489 dc->writeback_percent = 10;
490 dc->writeback_delay = 30;
491 dc->writeback_rate.rate = 1024;
493 dc->writeback_rate_update_seconds = 30;
494 dc->writeback_rate_d_term = 16;
495 dc->writeback_rate_p_term_inverse = 64;
496 dc->writeback_rate_d_smooth = 8;
498 dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
500 if (IS_ERR(dc->writeback_thread))
501 return PTR_ERR(dc->writeback_thread);
503 set_task_state(dc->writeback_thread, TASK_INTERRUPTIBLE);
505 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
506 schedule_delayed_work(&dc->writeback_rate_update,
507 dc->writeback_rate_update_seconds * HZ);