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blk-cgroup: cgroup changes for IOPS limit support
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / block / blk-throttle.c
CommitLineData
e43473b7
VG		 1/*
2 * Interface for controlling IO bandwidth on a request queue
3 *
4 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
5 */
6
7#include <linux/module.h>
8#include <linux/slab.h>
9#include <linux/blkdev.h>
10#include <linux/bio.h>
11#include <linux/blktrace_api.h>
12#include "blk-cgroup.h"
13
14/* Max dispatch from a group in 1 round */
15static int throtl_grp_quantum = 8;
16
17/* Total max dispatch from all groups in one round */
18static int throtl_quantum = 32;
19
20/* Throttling is performed over 100ms slice and after that slice is renewed */
21static unsigned long throtl_slice = HZ/10; /* 100 ms */
22
23struct throtl_rb_root {
24 struct rb_root rb;
25 struct rb_node *left;
26 unsigned int count;
27 unsigned long min_disptime;
28};
29
30#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
31 .count = 0, .min_disptime = 0}
32
33#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
34
35struct throtl_grp {
36 /* List of throtl groups on the request queue*/
37 struct hlist_node tg_node;
38
39 /* active throtl group service_tree member */
40 struct rb_node rb_node;
41
42 /*
43 * Dispatch time in jiffies. This is the estimated time when group
44 * will unthrottle and is ready to dispatch more bio. It is used as
45 * key to sort active groups in service tree.
46 */
47 unsigned long disptime;
48
49 struct blkio_group blkg;
50 atomic_t ref;
51 unsigned int flags;
52
53 /* Two lists for READ and WRITE */
54 struct bio_list bio_lists[2];
55
56 /* Number of queued bios on READ and WRITE lists */
57 unsigned int nr_queued[2];
58
59 /* bytes per second rate limits */
60 uint64_t bps[2];
61
62 /* Number of bytes disptached in current slice */
63 uint64_t bytes_disp[2];
64
65 /* When did we start a new slice */
66 unsigned long slice_start[2];
67 unsigned long slice_end[2];
68};
69
70struct throtl_data
71{
72 /* List of throtl groups */
73 struct hlist_head tg_list;
74
75 /* service tree for active throtl groups */
76 struct throtl_rb_root tg_service_tree;
77
78 struct throtl_grp root_tg;
79 struct request_queue *queue;
80
81 /* Total Number of queued bios on READ and WRITE lists */
82 unsigned int nr_queued[2];
83
84 /*
85 * number of total undestroyed groups (excluding root group)
86 */
87 unsigned int nr_undestroyed_grps;
88
89 /* Work for dispatching throttled bios */
90 struct delayed_work throtl_work;
91};
92
93enum tg_state_flags {
94 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
95};
96
97#define THROTL_TG_FNS(name) \
98static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
99{ \
100 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
101} \
102static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
103{ \
104 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
105} \
106static inline int throtl_tg_##name(const struct throtl_grp *tg) \
107{ \
108 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
109}
110
111THROTL_TG_FNS(on_rr);
112
113#define throtl_log_tg(td, tg, fmt, args...) \
114 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
115 blkg_path(&(tg)->blkg), ##args); \
116
117#define throtl_log(td, fmt, args...) \
118 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
119
120static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
121{
122 if (blkg)
123 return container_of(blkg, struct throtl_grp, blkg);
124
125 return NULL;
126}
127
128static inline int total_nr_queued(struct throtl_data *td)
129{
130 return (td->nr_queued[0] + td->nr_queued[1]);
131}
132
133static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
134{
135 atomic_inc(&tg->ref);
136 return tg;
137}
138
139static void throtl_put_tg(struct throtl_grp *tg)
140{
141 BUG_ON(atomic_read(&tg->ref) <= 0);
142 if (!atomic_dec_and_test(&tg->ref))
143 return;
144 kfree(tg);
145}
146
147static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
148 struct cgroup *cgroup)
149{
150 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
151 struct throtl_grp *tg = NULL;
152 void *key = td;
153 struct backing_dev_info *bdi = &td->queue->backing_dev_info;
154 unsigned int major, minor;
155
156 /*
157 * TODO: Speed up blkiocg_lookup_group() by maintaining a radix
158 * tree of blkg (instead of traversing through hash list all
159 * the time.
160 */
161 tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
162
163 /* Fill in device details for root group */
164 if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
165 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
166 tg->blkg.dev = MKDEV(major, minor);
167 goto done;
168 }
169
170 if (tg)
171 goto done;
172
173 tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
174 if (!tg)
175 goto done;
176
177 INIT_HLIST_NODE(&tg->tg_node);
178 RB_CLEAR_NODE(&tg->rb_node);
179 bio_list_init(&tg->bio_lists[0]);
180 bio_list_init(&tg->bio_lists[1]);
181
182 /*
183 * Take the initial reference that will be released on destroy
184 * This can be thought of a joint reference by cgroup and
185 * request queue which will be dropped by either request queue
186 * exit or cgroup deletion path depending on who is exiting first.
187 */
188 atomic_set(&tg->ref, 1);
189
190 /* Add group onto cgroup list */
191 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
192 blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
193 MKDEV(major, minor), BLKIO_POLICY_THROTL);
194
195 tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
196 tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
197
198 hlist_add_head(&tg->tg_node, &td->tg_list);
199 td->nr_undestroyed_grps++;
200done:
201 return tg;
202}
203
204static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
205{
206 struct cgroup *cgroup;
207 struct throtl_grp *tg = NULL;
208
209 rcu_read_lock();
210 cgroup = task_cgroup(current, blkio_subsys_id);
211 tg = throtl_find_alloc_tg(td, cgroup);
212 if (!tg)
213 tg = &td->root_tg;
214 rcu_read_unlock();
215 return tg;
216}
217
218static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
219{
220 /* Service tree is empty */
221 if (!root->count)
222 return NULL;
223
224 if (!root->left)
225 root->left = rb_first(&root->rb);
226
227 if (root->left)
228 return rb_entry_tg(root->left);
229
230 return NULL;
231}
232
233static void rb_erase_init(struct rb_node *n, struct rb_root *root)
234{
235 rb_erase(n, root);
236 RB_CLEAR_NODE(n);
237}
238
239static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
240{
241 if (root->left == n)
242 root->left = NULL;
243 rb_erase_init(n, &root->rb);
244 --root->count;
245}
246
247static void update_min_dispatch_time(struct throtl_rb_root *st)
248{
249 struct throtl_grp *tg;
250
251 tg = throtl_rb_first(st);
252 if (!tg)
253 return;
254
255 st->min_disptime = tg->disptime;
256}
257
258static void
259tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
260{
261 struct rb_node **node = &st->rb.rb_node;
262 struct rb_node *parent = NULL;
263 struct throtl_grp *__tg;
264 unsigned long key = tg->disptime;
265 int left = 1;
266
267 while (*node != NULL) {
268 parent = *node;
269 __tg = rb_entry_tg(parent);
270
271 if (time_before(key, __tg->disptime))
272 node = &parent->rb_left;
273 else {
274 node = &parent->rb_right;
275 left = 0;
276 }
277 }
278
279 if (left)
280 st->left = &tg->rb_node;
281
282 rb_link_node(&tg->rb_node, parent, node);
283 rb_insert_color(&tg->rb_node, &st->rb);
284}
285
286static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
287{
288 struct throtl_rb_root *st = &td->tg_service_tree;
289
290 tg_service_tree_add(st, tg);
291 throtl_mark_tg_on_rr(tg);
292 st->count++;
293}
294
295static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
296{
297 if (!throtl_tg_on_rr(tg))
298 __throtl_enqueue_tg(td, tg);
299}
300
301static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
302{
303 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
304 throtl_clear_tg_on_rr(tg);
305}
306
307static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
308{
309 if (throtl_tg_on_rr(tg))
310 __throtl_dequeue_tg(td, tg);
311}
312
313static void throtl_schedule_next_dispatch(struct throtl_data *td)
314{
315 struct throtl_rb_root *st = &td->tg_service_tree;
316
317 /*
318 * If there are more bios pending, schedule more work.
319 */
320 if (!total_nr_queued(td))
321 return;
322
323 BUG_ON(!st->count);
324
325 update_min_dispatch_time(st);
326
327 if (time_before_eq(st->min_disptime, jiffies))
328 throtl_schedule_delayed_work(td->queue, 0);
329 else
330 throtl_schedule_delayed_work(td->queue,
331 (st->min_disptime - jiffies));
332}
333
334static inline void
335throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
336{
337 tg->bytes_disp[rw] = 0;
338 tg->slice_start[rw] = jiffies;
339 tg->slice_end[rw] = jiffies + throtl_slice;
340 throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
341 rw == READ ? 'R' : 'W', tg->slice_start[rw],
342 tg->slice_end[rw], jiffies);
343}
344
345static inline void throtl_extend_slice(struct throtl_data *td,
346 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
347{
348 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
349 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
350 rw == READ ? 'R' : 'W', tg->slice_start[rw],
351 tg->slice_end[rw], jiffies);
352}
353
354/* Determine if previously allocated or extended slice is complete or not */
355static bool
356throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
357{
358 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
359 return 0;
360
361 return 1;
362}
363
364/* Trim the used slices and adjust slice start accordingly */
365static inline void
366throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
367{
368 unsigned long nr_slices, bytes_trim, time_elapsed;
369
370 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
371
372 /*
373 * If bps are unlimited (-1), then time slice don't get
374 * renewed. Don't try to trim the slice if slice is used. A new
375 * slice will start when appropriate.
376 */
377 if (throtl_slice_used(td, tg, rw))
378 return;
379
380 time_elapsed = jiffies - tg->slice_start[rw];
381
382 nr_slices = time_elapsed / throtl_slice;
383
384 if (!nr_slices)
385 return;
386
387 bytes_trim = (tg->bps[rw] * throtl_slice * nr_slices)/HZ;
388
389 if (!bytes_trim)
390 return;
391
392 if (tg->bytes_disp[rw] >= bytes_trim)
393 tg->bytes_disp[rw] -= bytes_trim;
394 else
395 tg->bytes_disp[rw] = 0;
396
397 tg->slice_start[rw] += nr_slices * throtl_slice;
398
399 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu"
400 " start=%lu end=%lu jiffies=%lu",
401 rw == READ ? 'R' : 'W', nr_slices, bytes_trim,
402 tg->slice_start[rw], tg->slice_end[rw], jiffies);
403}
404
405/*
406 * Returns whether one can dispatch a bio or not. Also returns approx number
407 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
408 */
409static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
410 struct bio *bio, unsigned long *wait)
411{
412 bool rw = bio_data_dir(bio);
413 u64 bytes_allowed, extra_bytes;
414 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
415
416 /*
417 * Currently whole state machine of group depends on first bio
418 * queued in the group bio list. So one should not be calling
419 * this function with a different bio if there are other bios
420 * queued.
421 */
422 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
423
424 /* If tg->bps = -1, then BW is unlimited */
425 if (tg->bps[rw] == -1) {
426 if (wait)
427 *wait = 0;
428 return 1;
429 }
430
431 /*
432 * If previous slice expired, start a new one otherwise renew/extend
433 * existing slice to make sure it is at least throtl_slice interval
434 * long since now.
435 */
436 if (throtl_slice_used(td, tg, rw))
437 throtl_start_new_slice(td, tg, rw);
438 else {
439 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
440 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
441 }
442
443 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
444
445 /* Slice has just started. Consider one slice interval */
446 if (!jiffy_elapsed)
447 jiffy_elapsed_rnd = throtl_slice;
448
449 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
450
451 bytes_allowed = (tg->bps[rw] * jiffies_to_msecs(jiffy_elapsed_rnd))
452 / MSEC_PER_SEC;
453
454 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
455 if (wait)
456 *wait = 0;
457 return 1;
458 }
459
460 /* Calc approx time to dispatch */
461 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
462 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
463
464 if (!jiffy_wait)
465 jiffy_wait = 1;
466
467 /*
468 * This wait time is without taking into consideration the rounding
469 * up we did. Add that time also.
470 */
471 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
472
473 if (wait)
474 *wait = jiffy_wait;
475
476 if (time_before(tg->slice_end[rw], jiffies + jiffy_wait))
477 throtl_extend_slice(td, tg, rw, jiffies + jiffy_wait);
478
479 return 0;
480}
481
482static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
483{
484 bool rw = bio_data_dir(bio);
485 bool sync = bio->bi_rw & REQ_SYNC;
486
487 /* Charge the bio to the group */
488 tg->bytes_disp[rw] += bio->bi_size;
489
490 /*
491 * TODO: This will take blkg->stats_lock. Figure out a way
492 * to avoid this cost.
493 */
494 blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
495
496}
497
498static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
499 struct bio *bio)
500{
501 bool rw = bio_data_dir(bio);
502
503 bio_list_add(&tg->bio_lists[rw], bio);
504 /* Take a bio reference on tg */
505 throtl_ref_get_tg(tg);
506 tg->nr_queued[rw]++;
507 td->nr_queued[rw]++;
508 throtl_enqueue_tg(td, tg);
509}
510
511static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
512{
513 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
514 struct bio *bio;
515
516 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
517 tg_may_dispatch(td, tg, bio, &read_wait);
518
519 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
520 tg_may_dispatch(td, tg, bio, &write_wait);
521
522 min_wait = min(read_wait, write_wait);
523 disptime = jiffies + min_wait;
524
525 /*
526 * If group is already on active tree, then update dispatch time
527 * only if it is lesser than existing dispatch time. Otherwise
528 * always update the dispatch time
529 */
530
531 if (throtl_tg_on_rr(tg) && time_before(disptime, tg->disptime))
532 return;
533
534 /* Update dispatch time */
535 throtl_dequeue_tg(td, tg);
536 tg->disptime = disptime;
537 throtl_enqueue_tg(td, tg);
538}
539
540static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
541 bool rw, struct bio_list *bl)
542{
543 struct bio *bio;
544
545 bio = bio_list_pop(&tg->bio_lists[rw]);
546 tg->nr_queued[rw]--;
547 /* Drop bio reference on tg */
548 throtl_put_tg(tg);
549
550 BUG_ON(td->nr_queued[rw] <= 0);
551 td->nr_queued[rw]--;
552
553 throtl_charge_bio(tg, bio);
554 bio_list_add(bl, bio);
555 bio->bi_rw |= REQ_THROTTLED;
556
557 throtl_trim_slice(td, tg, rw);
558}
559
560static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
561 struct bio_list *bl)
562{
563 unsigned int nr_reads = 0, nr_writes = 0;
564 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
565 unsigned int max_nr_writes = throtl_grp_quantum - nr_reads;
566 struct bio *bio;
567
568 /* Try to dispatch 75% READS and 25% WRITES */
569
570 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
571 && tg_may_dispatch(td, tg, bio, NULL)) {
572
573 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
574 nr_reads++;
575
576 if (nr_reads >= max_nr_reads)
577 break;
578 }
579
580 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
581 && tg_may_dispatch(td, tg, bio, NULL)) {
582
583 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
584 nr_writes++;
585
586 if (nr_writes >= max_nr_writes)
587 break;
588 }
589
590 return nr_reads + nr_writes;
591}
592
593static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
594{
595 unsigned int nr_disp = 0;
596 struct throtl_grp *tg;
597 struct throtl_rb_root *st = &td->tg_service_tree;
598
599 while (1) {
600 tg = throtl_rb_first(st);
601
602 if (!tg)
603 break;
604
605 if (time_before(jiffies, tg->disptime))
606 break;
607
608 throtl_dequeue_tg(td, tg);
609
610 nr_disp += throtl_dispatch_tg(td, tg, bl);
611
612 if (tg->nr_queued[0] || tg->nr_queued[1]) {
613 tg_update_disptime(td, tg);
614 throtl_enqueue_tg(td, tg);
615 }
616
617 if (nr_disp >= throtl_quantum)
618 break;
619 }
620
621 return nr_disp;
622}
623
624/* Dispatch throttled bios. Should be called without queue lock held. */
625static int throtl_dispatch(struct request_queue *q)
626{
627 struct throtl_data *td = q->td;
628 unsigned int nr_disp = 0;
629 struct bio_list bio_list_on_stack;
630 struct bio *bio;
631
632 spin_lock_irq(q->queue_lock);
633
634 if (!total_nr_queued(td))
635 goto out;
636
637 bio_list_init(&bio_list_on_stack);
638
639 throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u",
640 total_nr_queued(td), td->nr_queued[READ],
641 td->nr_queued[WRITE]);
642
643 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
644
645 if (nr_disp)
646 throtl_log(td, "bios disp=%u", nr_disp);
647
648 throtl_schedule_next_dispatch(td);
649out:
650 spin_unlock_irq(q->queue_lock);
651
652 /*
653 * If we dispatched some requests, unplug the queue to make sure
654 * immediate dispatch
655 */
656 if (nr_disp) {
657 while((bio = bio_list_pop(&bio_list_on_stack)))
658 generic_make_request(bio);
659 blk_unplug(q);
660 }
661 return nr_disp;
662}
663
664void blk_throtl_work(struct work_struct *work)
665{
666 struct throtl_data *td = container_of(work, struct throtl_data,
667 throtl_work.work);
668 struct request_queue *q = td->queue;
669
670 throtl_dispatch(q);
671}
672
673/* Call with queue lock held */
674void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay)
675{
676
677 struct throtl_data *td = q->td;
678 struct delayed_work *dwork = &td->throtl_work;
679
680 if (total_nr_queued(td) > 0) {
681 /*
682 * We might have a work scheduled to be executed in future.
683 * Cancel that and schedule a new one.
684 */
685 __cancel_delayed_work(dwork);
686 kblockd_schedule_delayed_work(q, dwork, delay);
687 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
688 delay, jiffies);
689 }
690}
691EXPORT_SYMBOL(throtl_schedule_delayed_work);
692
693static void
694throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
695{
696 /* Something wrong if we are trying to remove same group twice */
697 BUG_ON(hlist_unhashed(&tg->tg_node));
698
699 hlist_del_init(&tg->tg_node);
700
701 /*
702 * Put the reference taken at the time of creation so that when all
703 * queues are gone, group can be destroyed.
704 */
705 throtl_put_tg(tg);
706 td->nr_undestroyed_grps--;
707}
708
709static void throtl_release_tgs(struct throtl_data *td)
710{
711 struct hlist_node *pos, *n;
712 struct throtl_grp *tg;
713
714 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
715 /*
716 * If cgroup removal path got to blk_group first and removed
717 * it from cgroup list, then it will take care of destroying
718 * cfqg also.
719 */
720 if (!blkiocg_del_blkio_group(&tg->blkg))
721 throtl_destroy_tg(td, tg);
722 }
723}
724
725static void throtl_td_free(struct throtl_data *td)
726{
727 kfree(td);
728}
729
730/*
731 * Blk cgroup controller notification saying that blkio_group object is being
732 * delinked as associated cgroup object is going away. That also means that
733 * no new IO will come in this group. So get rid of this group as soon as
734 * any pending IO in the group is finished.
735 *
736 * This function is called under rcu_read_lock(). key is the rcu protected
737 * pointer. That means "key" is a valid throtl_data pointer as long as we are
738 * rcu read lock.
739 *
740 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
741 * it should not be NULL as even if queue was going away, cgroup deltion
742 * path got to it first.
743 */
744void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
745{
746 unsigned long flags;
747 struct throtl_data *td = key;
748
749 spin_lock_irqsave(td->queue->queue_lock, flags);
750 throtl_destroy_tg(td, tg_of_blkg(blkg));
751 spin_unlock_irqrestore(td->queue->queue_lock, flags);
752}
753
754static void throtl_update_blkio_group_read_bps (struct blkio_group *blkg,
755 u64 read_bps)
756{
757 tg_of_blkg(blkg)->bps[READ] = read_bps;
758}
759
760static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg,
761 u64 write_bps)
762{
763 tg_of_blkg(blkg)->bps[WRITE] = write_bps;
764}
765
766void throtl_shutdown_timer_wq(struct request_queue *q)
767{
768 struct throtl_data *td = q->td;
769
770 cancel_delayed_work_sync(&td->throtl_work);
771}
772
773static struct blkio_policy_type blkio_policy_throtl = {
774 .ops = {
775 .blkio_unlink_group_fn = throtl_unlink_blkio_group,
776 .blkio_update_group_read_bps_fn =
777 throtl_update_blkio_group_read_bps,
778 .blkio_update_group_write_bps_fn =
779 throtl_update_blkio_group_write_bps,
780 },
781};
782
783int blk_throtl_bio(struct request_queue *q, struct bio **biop)
784{
785 struct throtl_data *td = q->td;
786 struct throtl_grp *tg;
787 struct bio *bio = *biop;
788 bool rw = bio_data_dir(bio), update_disptime = true;
789
790 if (bio->bi_rw & REQ_THROTTLED) {
791 bio->bi_rw &= ~REQ_THROTTLED;
792 return 0;
793 }
794
795 spin_lock_irq(q->queue_lock);
796 tg = throtl_get_tg(td);
797
798 if (tg->nr_queued[rw]) {
799 /*
800 * There is already another bio queued in same dir. No
801 * need to update dispatch time.
802 */
803 update_disptime = false;
804 goto queue_bio;
805 }
806
807 /* Bio is with-in rate limit of group */
808 if (tg_may_dispatch(td, tg, bio, NULL)) {
809 throtl_charge_bio(tg, bio);
810 goto out;
811 }
812
813queue_bio:
814 throtl_log_tg(td, tg, "[%c] bio. disp=%u sz=%u bps=%llu"
815 " queued=%d/%d", rw == READ ? 'R' : 'W',
816 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
817 tg->nr_queued[READ], tg->nr_queued[WRITE]);
818
819 throtl_add_bio_tg(q->td, tg, bio);
820 *biop = NULL;
821
822 if (update_disptime) {
823 tg_update_disptime(td, tg);
824 throtl_schedule_next_dispatch(td);
825 }
826
827out:
828 spin_unlock_irq(q->queue_lock);
829 return 0;
830}
831
832int blk_throtl_init(struct request_queue *q)
833{
834 struct throtl_data *td;
835 struct throtl_grp *tg;
836
837 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
838 if (!td)
839 return -ENOMEM;
840
841 INIT_HLIST_HEAD(&td->tg_list);
842 td->tg_service_tree = THROTL_RB_ROOT;
843
844 /* Init root group */
845 tg = &td->root_tg;
846 INIT_HLIST_NODE(&tg->tg_node);
847 RB_CLEAR_NODE(&tg->rb_node);
848 bio_list_init(&tg->bio_lists[0]);
849 bio_list_init(&tg->bio_lists[1]);
850
851 /* Practically unlimited BW */
852 tg->bps[0] = tg->bps[1] = -1;
853 atomic_set(&tg->ref, 1);
854
855 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
856
857 rcu_read_lock();
858 blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td,
859 0, BLKIO_POLICY_THROTL);
860 rcu_read_unlock();
861
862 /* Attach throtl data to request queue */
863 td->queue = q;
864 q->td = td;
865 return 0;
866}
867
868void blk_throtl_exit(struct request_queue *q)
869{
870 struct throtl_data *td = q->td;
871 bool wait = false;
872
873 BUG_ON(!td);
874
875 throtl_shutdown_timer_wq(q);
876
877 spin_lock_irq(q->queue_lock);
878 throtl_release_tgs(td);
879 blkiocg_del_blkio_group(&td->root_tg.blkg);
880
881 /* If there are other groups */
882 if (td->nr_undestroyed_grps >= 1)
883 wait = true;
884
885 spin_unlock_irq(q->queue_lock);
886
887 /*
888 * Wait for tg->blkg->key accessors to exit their grace periods.
889 * Do this wait only if there are other undestroyed groups out
890 * there (other than root group). This can happen if cgroup deletion
891 * path claimed the responsibility of cleaning up a group before
892 * queue cleanup code get to the group.
893 *
894 * Do not call synchronize_rcu() unconditionally as there are drivers
895 * which create/delete request queue hundreds of times during scan/boot
896 * and synchronize_rcu() can take significant time and slow down boot.
897 */
898 if (wait)
899 synchronize_rcu();
900 throtl_td_free(td);
901}
902
903static int __init throtl_init(void)
904{
905 blkio_policy_register(&blkio_policy_throtl);
906 return 0;
907}
908
909module_init(throtl_init);
kernel source for telekom puls (alcatel/mediatek)