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Merge remote-tracking branch 'spi/topic/rspi' into spi-pdata
[deliverable/linux.git] / drivers / md / bcache / writeback.c
1 /*
2 * background writeback - scan btree for dirty data and write it to the backing
3 * device
4 *
5 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
6 * Copyright 2012 Google, Inc.
7 */
8
9 #include "bcache.h"
10 #include "btree.h"
11 #include "debug.h"
12 #include "writeback.h"
13
14 #include <trace/events/bcache.h>
15
16 static struct workqueue_struct *dirty_wq;
17
18 static void read_dirty(struct closure *);
19
20 struct dirty_io {
21 struct closure cl;
22 struct cached_dev *dc;
23 struct bio bio;
24 };
25
26 /* Rate limiting */
27
28 static void __update_writeback_rate(struct cached_dev *dc)
29 {
30 struct cache_set *c = dc->disk.c;
31 uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
32 uint64_t cache_dirty_target =
33 div_u64(cache_sectors * dc->writeback_percent, 100);
34
35 int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
36 c->cached_dev_sectors);
37
38 /* PD controller */
39
40 int change = 0;
41 int64_t error;
42 int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
43 int64_t derivative = dirty - dc->disk.sectors_dirty_last;
44
45 dc->disk.sectors_dirty_last = dirty;
46
47 derivative *= dc->writeback_rate_d_term;
48 derivative = clamp(derivative, -dirty, dirty);
49
50 derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
51 dc->writeback_rate_d_smooth, 0);
52
53 /* Avoid divide by zero */
54 if (!target)
55 goto out;
56
57 error = div64_s64((dirty + derivative - target) << 8, target);
58
59 change = div_s64((dc->writeback_rate.rate * error) >> 8,
60 dc->writeback_rate_p_term_inverse);
61
62 /* Don't increase writeback rate if the device isn't keeping up */
63 if (change > 0 &&
64 time_after64(local_clock(),
65 dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
66 change = 0;
67
68 dc->writeback_rate.rate =
69 clamp_t(int64_t, dc->writeback_rate.rate + change,
70 1, NSEC_PER_MSEC);
71 out:
72 dc->writeback_rate_derivative = derivative;
73 dc->writeback_rate_change = change;
74 dc->writeback_rate_target = target;
75
76 schedule_delayed_work(&dc->writeback_rate_update,
77 dc->writeback_rate_update_seconds * HZ);
78 }
79
80 static void update_writeback_rate(struct work_struct *work)
81 {
82 struct cached_dev *dc = container_of(to_delayed_work(work),
83 struct cached_dev,
84 writeback_rate_update);
85
86 down_read(&dc->writeback_lock);
87
88 if (atomic_read(&dc->has_dirty) &&
89 dc->writeback_percent)
90 __update_writeback_rate(dc);
91
92 up_read(&dc->writeback_lock);
93 }
94
95 static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
96 {
97 if (atomic_read(&dc->disk.detaching) ||
98 !dc->writeback_percent)
99 return 0;
100
101 return bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);
102 }
103
104 /* Background writeback */
105
106 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
107 {
108 return KEY_DIRTY(k);
109 }
110
111 static bool dirty_full_stripe_pred(struct keybuf *buf, struct bkey *k)
112 {
113 uint64_t stripe;
114 unsigned nr_sectors = KEY_SIZE(k);
115 struct cached_dev *dc = container_of(buf, struct cached_dev,
116 writeback_keys);
117 unsigned stripe_size = 1 << dc->disk.stripe_size_bits;
118
119 if (!KEY_DIRTY(k))
120 return false;
121
122 stripe = KEY_START(k) >> dc->disk.stripe_size_bits;
123 while (1) {
124 if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) !=
125 stripe_size)
126 return false;
127
128 if (nr_sectors <= stripe_size)
129 return true;
130
131 nr_sectors -= stripe_size;
132 stripe++;
133 }
134 }
135
136 static void dirty_init(struct keybuf_key *w)
137 {
138 struct dirty_io *io = w->private;
139 struct bio *bio = &io->bio;
140
141 bio_init(bio);
142 if (!io->dc->writeback_percent)
143 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
144
145 bio->bi_size = KEY_SIZE(&w->key) << 9;
146 bio->bi_max_vecs = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
147 bio->bi_private = w;
148 bio->bi_io_vec = bio->bi_inline_vecs;
149 bch_bio_map(bio, NULL);
150 }
151
152 static void refill_dirty(struct closure *cl)
153 {
154 struct cached_dev *dc = container_of(cl, struct cached_dev,
155 writeback.cl);
156 struct keybuf *buf = &dc->writeback_keys;
157 bool searched_from_start = false;
158 struct bkey end = MAX_KEY;
159 SET_KEY_INODE(&end, dc->disk.id);
160
161 if (!atomic_read(&dc->disk.detaching) &&
162 !dc->writeback_running)
163 closure_return(cl);
164
165 down_write(&dc->writeback_lock);
166
167 if (!atomic_read(&dc->has_dirty)) {
168 SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
169 bch_write_bdev_super(dc, NULL);
170
171 up_write(&dc->writeback_lock);
172 closure_return(cl);
173 }
174
175 if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
176 buf->last_scanned = KEY(dc->disk.id, 0, 0);
177 searched_from_start = true;
178 }
179
180 if (dc->partial_stripes_expensive) {
181 uint64_t i;
182
183 for (i = 0; i < dc->disk.nr_stripes; i++)
184 if (atomic_read(dc->disk.stripe_sectors_dirty + i) ==
185 1 << dc->disk.stripe_size_bits)
186 goto full_stripes;
187
188 goto normal_refill;
189 full_stripes:
190 bch_refill_keybuf(dc->disk.c, buf, &end,
191 dirty_full_stripe_pred);
192 } else {
193 normal_refill:
194 bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
195 }
196
197 if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) {
198 /* Searched the entire btree - delay awhile */
199
200 if (RB_EMPTY_ROOT(&buf->keys)) {
201 atomic_set(&dc->has_dirty, 0);
202 cached_dev_put(dc);
203 }
204
205 if (!atomic_read(&dc->disk.detaching))
206 closure_delay(&dc->writeback, dc->writeback_delay * HZ);
207 }
208
209 up_write(&dc->writeback_lock);
210
211 ratelimit_reset(&dc->writeback_rate);
212
213 /* Punt to workqueue only so we don't recurse and blow the stack */
214 continue_at(cl, read_dirty, dirty_wq);
215 }
216
217 void bch_writeback_queue(struct cached_dev *dc)
218 {
219 if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) {
220 if (!atomic_read(&dc->disk.detaching))
221 closure_delay(&dc->writeback, dc->writeback_delay * HZ);
222
223 continue_at(&dc->writeback.cl, refill_dirty, dirty_wq);
224 }
225 }
226
227 void bch_writeback_add(struct cached_dev *dc)
228 {
229 if (!atomic_read(&dc->has_dirty) &&
230 !atomic_xchg(&dc->has_dirty, 1)) {
231 atomic_inc(&dc->count);
232
233 if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
234 SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
235 /* XXX: should do this synchronously */
236 bch_write_bdev_super(dc, NULL);
237 }
238
239 bch_writeback_queue(dc);
240
241 if (dc->writeback_percent)
242 schedule_delayed_work(&dc->writeback_rate_update,
243 dc->writeback_rate_update_seconds * HZ);
244 }
245 }
246
247 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
248 uint64_t offset, int nr_sectors)
249 {
250 struct bcache_device *d = c->devices[inode];
251 unsigned stripe_size, stripe_offset;
252 uint64_t stripe;
253
254 if (!d)
255 return;
256
257 stripe_size = 1 << d->stripe_size_bits;
258 stripe = offset >> d->stripe_size_bits;
259 stripe_offset = offset & (stripe_size - 1);
260
261 while (nr_sectors) {
262 int s = min_t(unsigned, abs(nr_sectors),
263 stripe_size - stripe_offset);
264
265 if (nr_sectors < 0)
266 s = -s;
267
268 atomic_add(s, d->stripe_sectors_dirty + stripe);
269 nr_sectors -= s;
270 stripe_offset = 0;
271 stripe++;
272 }
273 }
274
275 /* Background writeback - IO loop */
276
277 static void dirty_io_destructor(struct closure *cl)
278 {
279 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
280 kfree(io);
281 }
282
283 static void write_dirty_finish(struct closure *cl)
284 {
285 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
286 struct keybuf_key *w = io->bio.bi_private;
287 struct cached_dev *dc = io->dc;
288 struct bio_vec *bv;
289 int i;
290
291 bio_for_each_segment_all(bv, &io->bio, i)
292 __free_page(bv->bv_page);
293
294 /* This is kind of a dumb way of signalling errors. */
295 if (KEY_DIRTY(&w->key)) {
296 unsigned i;
297 struct btree_op op;
298 bch_btree_op_init_stack(&op);
299
300 op.type = BTREE_REPLACE;
301 bkey_copy(&op.replace, &w->key);
302
303 SET_KEY_DIRTY(&w->key, false);
304 bch_keylist_add(&op.keys, &w->key);
305
306 for (i = 0; i < KEY_PTRS(&w->key); i++)
307 atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
308
309 bch_btree_insert(&op, dc->disk.c);
310 closure_sync(&op.cl);
311
312 if (op.insert_collision)
313 trace_bcache_writeback_collision(&w->key);
314
315 atomic_long_inc(op.insert_collision
316 ? &dc->disk.c->writeback_keys_failed
317 : &dc->disk.c->writeback_keys_done);
318 }
319
320 bch_keybuf_del(&dc->writeback_keys, w);
321 atomic_dec_bug(&dc->in_flight);
322
323 closure_wake_up(&dc->writeback_wait);
324
325 closure_return_with_destructor(cl, dirty_io_destructor);
326 }
327
328 static void dirty_endio(struct bio *bio, int error)
329 {
330 struct keybuf_key *w = bio->bi_private;
331 struct dirty_io *io = w->private;
332
333 if (error)
334 SET_KEY_DIRTY(&w->key, false);
335
336 closure_put(&io->cl);
337 }
338
339 static void write_dirty(struct closure *cl)
340 {
341 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
342 struct keybuf_key *w = io->bio.bi_private;
343
344 dirty_init(w);
345 io->bio.bi_rw = WRITE;
346 io->bio.bi_sector = KEY_START(&w->key);
347 io->bio.bi_bdev = io->dc->bdev;
348 io->bio.bi_end_io = dirty_endio;
349
350 closure_bio_submit(&io->bio, cl, &io->dc->disk);
351
352 continue_at(cl, write_dirty_finish, dirty_wq);
353 }
354
355 static void read_dirty_endio(struct bio *bio, int error)
356 {
357 struct keybuf_key *w = bio->bi_private;
358 struct dirty_io *io = w->private;
359
360 bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
361 error, "reading dirty data from cache");
362
363 dirty_endio(bio, error);
364 }
365
366 static void read_dirty_submit(struct closure *cl)
367 {
368 struct dirty_io *io = container_of(cl, struct dirty_io, cl);
369
370 closure_bio_submit(&io->bio, cl, &io->dc->disk);
371
372 continue_at(cl, write_dirty, dirty_wq);
373 }
374
375 static void read_dirty(struct closure *cl)
376 {
377 struct cached_dev *dc = container_of(cl, struct cached_dev,
378 writeback.cl);
379 unsigned delay = writeback_delay(dc, 0);
380 struct keybuf_key *w;
381 struct dirty_io *io;
382
383 /*
384 * XXX: if we error, background writeback just spins. Should use some
385 * mempools.
386 */
387
388 while (1) {
389 w = bch_keybuf_next(&dc->writeback_keys);
390 if (!w)
391 break;
392
393 BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
394
395 if (delay > 0 &&
396 (KEY_START(&w->key) != dc->last_read ||
397 jiffies_to_msecs(delay) > 50)) {
398 w->private = NULL;
399
400 closure_delay(&dc->writeback, delay);
401 continue_at(cl, read_dirty, dirty_wq);
402 }
403
404 dc->last_read = KEY_OFFSET(&w->key);
405
406 io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
407 * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
408 GFP_KERNEL);
409 if (!io)
410 goto err;
411
412 w->private = io;
413 io->dc = dc;
414
415 dirty_init(w);
416 io->bio.bi_sector = PTR_OFFSET(&w->key, 0);
417 io->bio.bi_bdev = PTR_CACHE(dc->disk.c,
418 &w->key, 0)->bdev;
419 io->bio.bi_rw = READ;
420 io->bio.bi_end_io = read_dirty_endio;
421
422 if (bio_alloc_pages(&io->bio, GFP_KERNEL))
423 goto err_free;
424
425 trace_bcache_writeback(&w->key);
426
427 closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl);
428
429 delay = writeback_delay(dc, KEY_SIZE(&w->key));
430
431 atomic_inc(&dc->in_flight);
432
433 if (!closure_wait_event(&dc->writeback_wait, cl,
434 atomic_read(&dc->in_flight) < 64))
435 continue_at(cl, read_dirty, dirty_wq);
436 }
437
438 if (0) {
439 err_free:
440 kfree(w->private);
441 err:
442 bch_keybuf_del(&dc->writeback_keys, w);
443 }
444
445 refill_dirty(cl);
446 }
447
448 /* Init */
449
450 static int bch_btree_sectors_dirty_init(struct btree *b, struct btree_op *op,
451 struct cached_dev *dc)
452 {
453 struct bkey *k;
454 struct btree_iter iter;
455
456 bch_btree_iter_init(b, &iter, &KEY(dc->disk.id, 0, 0));
457 while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad)))
458 if (!b->level) {
459 if (KEY_INODE(k) > dc->disk.id)
460 break;
461
462 if (KEY_DIRTY(k))
463 bcache_dev_sectors_dirty_add(b->c, dc->disk.id,
464 KEY_START(k),
465 KEY_SIZE(k));
466 } else {
467 btree(sectors_dirty_init, k, b, op, dc);
468 if (KEY_INODE(k) > dc->disk.id)
469 break;
470
471 cond_resched();
472 }
473
474 return 0;
475 }
476
477 void bch_sectors_dirty_init(struct cached_dev *dc)
478 {
479 struct btree_op op;
480
481 bch_btree_op_init_stack(&op);
482 btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
483 }
484
485 void bch_cached_dev_writeback_init(struct cached_dev *dc)
486 {
487 closure_init_unlocked(&dc->writeback);
488 init_rwsem(&dc->writeback_lock);
489
490 bch_keybuf_init(&dc->writeback_keys);
491
492 dc->writeback_metadata = true;
493 dc->writeback_running = true;
494 dc->writeback_percent = 10;
495 dc->writeback_delay = 30;
496 dc->writeback_rate.rate = 1024;
497
498 dc->writeback_rate_update_seconds = 30;
499 dc->writeback_rate_d_term = 16;
500 dc->writeback_rate_p_term_inverse = 64;
501 dc->writeback_rate_d_smooth = 8;
502
503 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
504 schedule_delayed_work(&dc->writeback_rate_update,
505 dc->writeback_rate_update_seconds * HZ);
506 }
507
508 void bch_writeback_exit(void)
509 {
510 if (dirty_wq)
511 destroy_workqueue(dirty_wq);
512 }
513
514 int __init bch_writeback_init(void)
515 {
516 dirty_wq = create_singlethread_workqueue("bcache_writeback");
517 if (!dirty_wq)
518 return -ENOMEM;
519
520 return 0;
521 }
Linux kernel - Deliverables
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