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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
23/* A workqueue to queue throttle related work */
24static struct workqueue_struct *kthrotld_workqueue;
25static void throtl_schedule_delayed_work(struct throtl_data *td,
26 unsigned long delay);
27
28struct throtl_rb_root {
29 struct rb_root rb;
30 struct rb_node *left;
31 unsigned int count;
32 unsigned long min_disptime;
33};
34
35#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
36 .count = 0, .min_disptime = 0}
37
38#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
39
40struct throtl_grp {
41 /* List of throtl groups on the request queue*/
42 struct hlist_node tg_node;
43
44 /* active throtl group service_tree member */
45 struct rb_node rb_node;
46
47 /*
48 * Dispatch time in jiffies. This is the estimated time when group
49 * will unthrottle and is ready to dispatch more bio. It is used as
50 * key to sort active groups in service tree.
51 */
52 unsigned long disptime;
53
54 struct blkio_group blkg;
55 atomic_t ref;
56 unsigned int flags;
57
58 /* Two lists for READ and WRITE */
59 struct bio_list bio_lists[2];
60
61 /* Number of queued bios on READ and WRITE lists */
62 unsigned int nr_queued[2];
63
64 /* bytes per second rate limits */
65 uint64_t bps[2];
66
67 /* IOPS limits */
68 unsigned int iops[2];
69
70 /* Number of bytes disptached in current slice */
71 uint64_t bytes_disp[2];
72 /* Number of bio's dispatched in current slice */
73 unsigned int io_disp[2];
74
75 /* When did we start a new slice */
76 unsigned long slice_start[2];
77 unsigned long slice_end[2];
78
79 /* Some throttle limits got updated for the group */
80 int limits_changed;
81
82 struct rcu_head rcu_head;
83};
84
85struct throtl_data
86{
87 /* List of throtl groups */
88 struct hlist_head tg_list;
89
90 /* service tree for active throtl groups */
91 struct throtl_rb_root tg_service_tree;
92
93 struct throtl_grp *root_tg;
94 struct request_queue *queue;
95
96 /* Total Number of queued bios on READ and WRITE lists */
97 unsigned int nr_queued[2];
98
99 /*
100 * number of total undestroyed groups
101 */
102 unsigned int nr_undestroyed_grps;
103
104 /* Work for dispatching throttled bios */
105 struct delayed_work throtl_work;
106
107 int limits_changed;
108};
109
110enum tg_state_flags {
111 THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
112};
113
114#define THROTL_TG_FNS(name) \
115static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
116{ \
117 (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
118} \
119static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
120{ \
121 (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
122} \
123static inline int throtl_tg_##name(const struct throtl_grp *tg) \
124{ \
125 return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
126}
127
128THROTL_TG_FNS(on_rr);
129
130#define throtl_log_tg(td, tg, fmt, args...) \
131 blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
132 blkg_path(&(tg)->blkg), ##args); \
133
134#define throtl_log(td, fmt, args...) \
135 blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
136
137static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
138{
139 if (blkg)
140 return container_of(blkg, struct throtl_grp, blkg);
141
142 return NULL;
143}
144
145static inline unsigned int total_nr_queued(struct throtl_data *td)
146{
147 return td->nr_queued[0] + td->nr_queued[1];
148}
149
150static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
151{
152 atomic_inc(&tg->ref);
153 return tg;
154}
155
156static void throtl_free_tg(struct rcu_head *head)
157{
158 struct throtl_grp *tg;
159
160 tg = container_of(head, struct throtl_grp, rcu_head);
161 free_percpu(tg->blkg.stats_cpu);
162 kfree(tg);
163}
164
165static void throtl_put_tg(struct throtl_grp *tg)
166{
167 BUG_ON(atomic_read(&tg->ref) <= 0);
168 if (!atomic_dec_and_test(&tg->ref))
169 return;
170
171 /*
172 * A group is freed in rcu manner. But having an rcu lock does not
173 * mean that one can access all the fields of blkg and assume these
174 * are valid. For example, don't try to follow throtl_data and
175 * request queue links.
176 *
177 * Having a reference to blkg under an rcu allows acess to only
178 * values local to groups like group stats and group rate limits
179 */
180 call_rcu(&tg->rcu_head, throtl_free_tg);
181}
182
183static void throtl_init_group(struct throtl_grp *tg)
184{
185 INIT_HLIST_NODE(&tg->tg_node);
186 RB_CLEAR_NODE(&tg->rb_node);
187 bio_list_init(&tg->bio_lists[0]);
188 bio_list_init(&tg->bio_lists[1]);
189 tg->limits_changed = false;
190
191 /* Practically unlimited BW */
192 tg->bps[0] = tg->bps[1] = -1;
193 tg->iops[0] = tg->iops[1] = -1;
194
195 /*
196 * Take the initial reference that will be released on destroy
197 * This can be thought of a joint reference by cgroup and
198 * request queue which will be dropped by either request queue
199 * exit or cgroup deletion path depending on who is exiting first.
200 */
201 atomic_set(&tg->ref, 1);
202}
203
204/* Should be called with rcu read lock held (needed for blkcg) */
205static void
206throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg)
207{
208 hlist_add_head(&tg->tg_node, &td->tg_list);
209 td->nr_undestroyed_grps++;
210}
211
212static void
213__throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg)
214{
215 struct backing_dev_info *bdi = &td->queue->backing_dev_info;
216 unsigned int major, minor;
217
218 if (!tg || tg->blkg.dev)
219 return;
220
221 /*
222 * Fill in device details for a group which might not have been
223 * filled at group creation time as queue was being instantiated
224 * and driver had not attached a device yet
225 */
226 if (bdi->dev && dev_name(bdi->dev)) {
227 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
228 tg->blkg.dev = MKDEV(major, minor);
229 }
230}
231
232/*
233 * Should be called with without queue lock held. Here queue lock will be
234 * taken rarely. It will be taken only once during life time of a group
235 * if need be
236 */
237static void
238throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg)
239{
240 if (!tg || tg->blkg.dev)
241 return;
242
243 spin_lock_irq(td->queue->queue_lock);
244 __throtl_tg_fill_dev_details(td, tg);
245 spin_unlock_irq(td->queue->queue_lock);
246}
247
248static void throtl_init_add_tg_lists(struct throtl_data *td,
249 struct throtl_grp *tg, struct blkio_cgroup *blkcg)
250{
251 __throtl_tg_fill_dev_details(td, tg);
252
253 /* Add group onto cgroup list */
254 blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
255 tg->blkg.dev, BLKIO_POLICY_THROTL);
256
257 tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
258 tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
259 tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev);
260 tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev);
261
262 throtl_add_group_to_td_list(td, tg);
263}
264
265/* Should be called without queue lock and outside of rcu period */
266static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td)
267{
268 struct throtl_grp *tg = NULL;
269 int ret;
270
271 tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
272 if (!tg)
273 return NULL;
274
275 ret = blkio_alloc_blkg_stats(&tg->blkg);
276
277 if (ret) {
278 kfree(tg);
279 return NULL;
280 }
281
282 throtl_init_group(tg);
283 return tg;
284}
285
286static struct
287throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
288{
289 struct throtl_grp *tg = NULL;
290 void *key = td;
291
292 /*
293 * This is the common case when there are no blkio cgroups.
294 * Avoid lookup in this case
295 */
296 if (blkcg == &blkio_root_cgroup)
297 tg = td->root_tg;
298 else
299 tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
300
301 __throtl_tg_fill_dev_details(td, tg);
302 return tg;
303}
304
305/*
306 * This function returns with queue lock unlocked in case of error, like
307 * request queue is no more
308 */
309static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
310{
311 struct throtl_grp *tg = NULL, *__tg = NULL;
312 struct blkio_cgroup *blkcg;
313 struct request_queue *q = td->queue;
314
315 rcu_read_lock();
316 blkcg = task_blkio_cgroup(current);
317 tg = throtl_find_tg(td, blkcg);
318 if (tg) {
319 rcu_read_unlock();
320 return tg;
321 }
322
323 /*
324 * Need to allocate a group. Allocation of group also needs allocation
325 * of per cpu stats which in-turn takes a mutex() and can block. Hence
326 * we need to drop rcu lock and queue_lock before we call alloc
327 *
328 * Take the request queue reference to make sure queue does not
329 * go away once we return from allocation.
330 */
331 blk_get_queue(q);
332 rcu_read_unlock();
333 spin_unlock_irq(q->queue_lock);
334
335 tg = throtl_alloc_tg(td);
336 /*
337 * We might have slept in group allocation. Make sure queue is not
338 * dead
339 */
340 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
341 blk_put_queue(q);
342 if (tg)
343 kfree(tg);
344
345 return ERR_PTR(-ENODEV);
346 }
347 blk_put_queue(q);
348
349 /* Group allocated and queue is still alive. take the lock */
350 spin_lock_irq(q->queue_lock);
351
352 /*
353 * Initialize the new group. After sleeping, read the blkcg again.
354 */
355 rcu_read_lock();
356 blkcg = task_blkio_cgroup(current);
357
358 /*
359 * If some other thread already allocated the group while we were
360 * not holding queue lock, free up the group
361 */
362 __tg = throtl_find_tg(td, blkcg);
363
364 if (__tg) {
365 kfree(tg);
366 rcu_read_unlock();
367 return __tg;
368 }
369
370 /* Group allocation failed. Account the IO to root group */
371 if (!tg) {
372 tg = td->root_tg;
373 return tg;
374 }
375
376 throtl_init_add_tg_lists(td, tg, blkcg);
377 rcu_read_unlock();
378 return tg;
379}
380
381static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
382{
383 /* Service tree is empty */
384 if (!root->count)
385 return NULL;
386
387 if (!root->left)
388 root->left = rb_first(&root->rb);
389
390 if (root->left)
391 return rb_entry_tg(root->left);
392
393 return NULL;
394}
395
396static void rb_erase_init(struct rb_node *n, struct rb_root *root)
397{
398 rb_erase(n, root);
399 RB_CLEAR_NODE(n);
400}
401
402static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
403{
404 if (root->left == n)
405 root->left = NULL;
406 rb_erase_init(n, &root->rb);
407 --root->count;
408}
409
410static void update_min_dispatch_time(struct throtl_rb_root *st)
411{
412 struct throtl_grp *tg;
413
414 tg = throtl_rb_first(st);
415 if (!tg)
416 return;
417
418 st->min_disptime = tg->disptime;
419}
420
421static void
422tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
423{
424 struct rb_node **node = &st->rb.rb_node;
425 struct rb_node *parent = NULL;
426 struct throtl_grp *__tg;
427 unsigned long key = tg->disptime;
428 int left = 1;
429
430 while (*node != NULL) {
431 parent = *node;
432 __tg = rb_entry_tg(parent);
433
434 if (time_before(key, __tg->disptime))
435 node = &parent->rb_left;
436 else {
437 node = &parent->rb_right;
438 left = 0;
439 }
440 }
441
442 if (left)
443 st->left = &tg->rb_node;
444
445 rb_link_node(&tg->rb_node, parent, node);
446 rb_insert_color(&tg->rb_node, &st->rb);
447}
448
449static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
450{
451 struct throtl_rb_root *st = &td->tg_service_tree;
452
453 tg_service_tree_add(st, tg);
454 throtl_mark_tg_on_rr(tg);
455 st->count++;
456}
457
458static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
459{
460 if (!throtl_tg_on_rr(tg))
461 __throtl_enqueue_tg(td, tg);
462}
463
464static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
465{
466 throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
467 throtl_clear_tg_on_rr(tg);
468}
469
470static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
471{
472 if (throtl_tg_on_rr(tg))
473 __throtl_dequeue_tg(td, tg);
474}
475
476static void throtl_schedule_next_dispatch(struct throtl_data *td)
477{
478 struct throtl_rb_root *st = &td->tg_service_tree;
479
480 /*
481 * If there are more bios pending, schedule more work.
482 */
483 if (!total_nr_queued(td))
484 return;
485
486 BUG_ON(!st->count);
487
488 update_min_dispatch_time(st);
489
490 if (time_before_eq(st->min_disptime, jiffies))
491 throtl_schedule_delayed_work(td, 0);
492 else
493 throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
494}
495
496static inline void
497throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
498{
499 tg->bytes_disp[rw] = 0;
500 tg->io_disp[rw] = 0;
501 tg->slice_start[rw] = jiffies;
502 tg->slice_end[rw] = jiffies + throtl_slice;
503 throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
504 rw == READ ? 'R' : 'W', tg->slice_start[rw],
505 tg->slice_end[rw], jiffies);
506}
507
508static inline void throtl_set_slice_end(struct throtl_data *td,
509 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
510{
511 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
512}
513
514static inline void throtl_extend_slice(struct throtl_data *td,
515 struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
516{
517 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
518 throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
519 rw == READ ? 'R' : 'W', tg->slice_start[rw],
520 tg->slice_end[rw], jiffies);
521}
522
523/* Determine if previously allocated or extended slice is complete or not */
524static bool
525throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
526{
527 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
528 return 0;
529
530 return 1;
531}
532
533/* Trim the used slices and adjust slice start accordingly */
534static inline void
535throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
536{
537 unsigned long nr_slices, time_elapsed, io_trim;
538 u64 bytes_trim, tmp;
539
540 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
541
542 /*
543 * If bps are unlimited (-1), then time slice don't get
544 * renewed. Don't try to trim the slice if slice is used. A new
545 * slice will start when appropriate.
546 */
547 if (throtl_slice_used(td, tg, rw))
548 return;
549
550 /*
551 * A bio has been dispatched. Also adjust slice_end. It might happen
552 * that initially cgroup limit was very low resulting in high
553 * slice_end, but later limit was bumped up and bio was dispached
554 * sooner, then we need to reduce slice_end. A high bogus slice_end
555 * is bad because it does not allow new slice to start.
556 */
557
558 throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
559
560 time_elapsed = jiffies - tg->slice_start[rw];
561
562 nr_slices = time_elapsed / throtl_slice;
563
564 if (!nr_slices)
565 return;
566 tmp = tg->bps[rw] * throtl_slice * nr_slices;
567 do_div(tmp, HZ);
568 bytes_trim = tmp;
569
570 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
571
572 if (!bytes_trim && !io_trim)
573 return;
574
575 if (tg->bytes_disp[rw] >= bytes_trim)
576 tg->bytes_disp[rw] -= bytes_trim;
577 else
578 tg->bytes_disp[rw] = 0;
579
580 if (tg->io_disp[rw] >= io_trim)
581 tg->io_disp[rw] -= io_trim;
582 else
583 tg->io_disp[rw] = 0;
584
585 tg->slice_start[rw] += nr_slices * throtl_slice;
586
587 throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
588 " start=%lu end=%lu jiffies=%lu",
589 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
590 tg->slice_start[rw], tg->slice_end[rw], jiffies);
591}
592
593static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
594 struct bio *bio, unsigned long *wait)
595{
596 bool rw = bio_data_dir(bio);
597 unsigned int io_allowed;
598 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
599 u64 tmp;
600
601 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
602
603 /* Slice has just started. Consider one slice interval */
604 if (!jiffy_elapsed)
605 jiffy_elapsed_rnd = throtl_slice;
606
607 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
608
609 /*
610 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
611 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
612 * will allow dispatch after 1 second and after that slice should
613 * have been trimmed.
614 */
615
616 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
617 do_div(tmp, HZ);
618
619 if (tmp > UINT_MAX)
620 io_allowed = UINT_MAX;
621 else
622 io_allowed = tmp;
623
624 if (tg->io_disp[rw] + 1 <= io_allowed) {
625 if (wait)
626 *wait = 0;
627 return 1;
628 }
629
630 /* Calc approx time to dispatch */
631 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
632
633 if (jiffy_wait > jiffy_elapsed)
634 jiffy_wait = jiffy_wait - jiffy_elapsed;
635 else
636 jiffy_wait = 1;
637
638 if (wait)
639 *wait = jiffy_wait;
640 return 0;
641}
642
643static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
644 struct bio *bio, unsigned long *wait)
645{
646 bool rw = bio_data_dir(bio);
647 u64 bytes_allowed, extra_bytes, tmp;
648 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
649
650 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
651
652 /* Slice has just started. Consider one slice interval */
653 if (!jiffy_elapsed)
654 jiffy_elapsed_rnd = throtl_slice;
655
656 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
657
658 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
659 do_div(tmp, HZ);
660 bytes_allowed = tmp;
661
662 if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
663 if (wait)
664 *wait = 0;
665 return 1;
666 }
667
668 /* Calc approx time to dispatch */
669 extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
670 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
671
672 if (!jiffy_wait)
673 jiffy_wait = 1;
674
675 /*
676 * This wait time is without taking into consideration the rounding
677 * up we did. Add that time also.
678 */
679 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
680 if (wait)
681 *wait = jiffy_wait;
682 return 0;
683}
684
685static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
686 if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
687 return 1;
688 return 0;
689}
690
691/*
692 * Returns whether one can dispatch a bio or not. Also returns approx number
693 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
694 */
695static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
696 struct bio *bio, unsigned long *wait)
697{
698 bool rw = bio_data_dir(bio);
699 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
700
701 /*
702 * Currently whole state machine of group depends on first bio
703 * queued in the group bio list. So one should not be calling
704 * this function with a different bio if there are other bios
705 * queued.
706 */
707 BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
708
709 /* If tg->bps = -1, then BW is unlimited */
710 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
711 if (wait)
712 *wait = 0;
713 return 1;
714 }
715
716 /*
717 * If previous slice expired, start a new one otherwise renew/extend
718 * existing slice to make sure it is at least throtl_slice interval
719 * long since now.
720 */
721 if (throtl_slice_used(td, tg, rw))
722 throtl_start_new_slice(td, tg, rw);
723 else {
724 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
725 throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
726 }
727
728 if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
729 && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
730 if (wait)
731 *wait = 0;
732 return 1;
733 }
734
735 max_wait = max(bps_wait, iops_wait);
736
737 if (wait)
738 *wait = max_wait;
739
740 if (time_before(tg->slice_end[rw], jiffies + max_wait))
741 throtl_extend_slice(td, tg, rw, jiffies + max_wait);
742
743 return 0;
744}
745
746static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
747{
748 bool rw = bio_data_dir(bio);
749 bool sync = rw_is_sync(bio->bi_rw);
750
751 /* Charge the bio to the group */
752 tg->bytes_disp[rw] += bio->bi_size;
753 tg->io_disp[rw]++;
754
755 blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
756}
757
758static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
759 struct bio *bio)
760{
761 bool rw = bio_data_dir(bio);
762
763 bio_list_add(&tg->bio_lists[rw], bio);
764 /* Take a bio reference on tg */
765 throtl_ref_get_tg(tg);
766 tg->nr_queued[rw]++;
767 td->nr_queued[rw]++;
768 throtl_enqueue_tg(td, tg);
769}
770
771static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
772{
773 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
774 struct bio *bio;
775
776 if ((bio = bio_list_peek(&tg->bio_lists[READ])))
777 tg_may_dispatch(td, tg, bio, &read_wait);
778
779 if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
780 tg_may_dispatch(td, tg, bio, &write_wait);
781
782 min_wait = min(read_wait, write_wait);
783 disptime = jiffies + min_wait;
784
785 /* Update dispatch time */
786 throtl_dequeue_tg(td, tg);
787 tg->disptime = disptime;
788 throtl_enqueue_tg(td, tg);
789}
790
791static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
792 bool rw, struct bio_list *bl)
793{
794 struct bio *bio;
795
796 bio = bio_list_pop(&tg->bio_lists[rw]);
797 tg->nr_queued[rw]--;
798 /* Drop bio reference on tg */
799 throtl_put_tg(tg);
800
801 BUG_ON(td->nr_queued[rw] <= 0);
802 td->nr_queued[rw]--;
803
804 throtl_charge_bio(tg, bio);
805 bio_list_add(bl, bio);
806 bio->bi_rw |= REQ_THROTTLED;
807
808 throtl_trim_slice(td, tg, rw);
809}
810
811static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
812 struct bio_list *bl)
813{
814 unsigned int nr_reads = 0, nr_writes = 0;
815 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
816 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
817 struct bio *bio;
818
819 /* Try to dispatch 75% READS and 25% WRITES */
820
821 while ((bio = bio_list_peek(&tg->bio_lists[READ]))
822 && tg_may_dispatch(td, tg, bio, NULL)) {
823
824 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
825 nr_reads++;
826
827 if (nr_reads >= max_nr_reads)
828 break;
829 }
830
831 while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
832 && tg_may_dispatch(td, tg, bio, NULL)) {
833
834 tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
835 nr_writes++;
836
837 if (nr_writes >= max_nr_writes)
838 break;
839 }
840
841 return nr_reads + nr_writes;
842}
843
844static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
845{
846 unsigned int nr_disp = 0;
847 struct throtl_grp *tg;
848 struct throtl_rb_root *st = &td->tg_service_tree;
849
850 while (1) {
851 tg = throtl_rb_first(st);
852
853 if (!tg)
854 break;
855
856 if (time_before(jiffies, tg->disptime))
857 break;
858
859 throtl_dequeue_tg(td, tg);
860
861 nr_disp += throtl_dispatch_tg(td, tg, bl);
862
863 if (tg->nr_queued[0] || tg->nr_queued[1]) {
864 tg_update_disptime(td, tg);
865 throtl_enqueue_tg(td, tg);
866 }
867
868 if (nr_disp >= throtl_quantum)
869 break;
870 }
871
872 return nr_disp;
873}
874
875static void throtl_process_limit_change(struct throtl_data *td)
876{
877 struct throtl_grp *tg;
878 struct hlist_node *pos, *n;
879
880 if (!td->limits_changed)
881 return;
882
883 xchg(&td->limits_changed, false);
884
885 throtl_log(td, "limits changed");
886
887 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
888 if (!tg->limits_changed)
889 continue;
890
891 if (!xchg(&tg->limits_changed, false))
892 continue;
893
894 throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
895 " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
896 tg->iops[READ], tg->iops[WRITE]);
897
898 /*
899 * Restart the slices for both READ and WRITES. It
900 * might happen that a group's limit are dropped
901 * suddenly and we don't want to account recently
902 * dispatched IO with new low rate
903 */
904 throtl_start_new_slice(td, tg, 0);
905 throtl_start_new_slice(td, tg, 1);
906
907 if (throtl_tg_on_rr(tg))
908 tg_update_disptime(td, tg);
909 }
910}
911
912/* Dispatch throttled bios. Should be called without queue lock held. */
913static int throtl_dispatch(struct request_queue *q)
914{
915 struct throtl_data *td = q->td;
916 unsigned int nr_disp = 0;
917 struct bio_list bio_list_on_stack;
918 struct bio *bio;
919 struct blk_plug plug;
920
921 spin_lock_irq(q->queue_lock);
922
923 throtl_process_limit_change(td);
924
925 if (!total_nr_queued(td))
926 goto out;
927
928 bio_list_init(&bio_list_on_stack);
929
930 throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
931 total_nr_queued(td), td->nr_queued[READ],
932 td->nr_queued[WRITE]);
933
934 nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
935
936 if (nr_disp)
937 throtl_log(td, "bios disp=%u", nr_disp);
938
939 throtl_schedule_next_dispatch(td);
940out:
941 spin_unlock_irq(q->queue_lock);
942
943 /*
944 * If we dispatched some requests, unplug the queue to make sure
945 * immediate dispatch
946 */
947 if (nr_disp) {
948 blk_start_plug(&plug);
949 while((bio = bio_list_pop(&bio_list_on_stack)))
950 generic_make_request(bio);
951 blk_finish_plug(&plug);
952 }
953 return nr_disp;
954}
955
956void blk_throtl_work(struct work_struct *work)
957{
958 struct throtl_data *td = container_of(work, struct throtl_data,
959 throtl_work.work);
960 struct request_queue *q = td->queue;
961
962 throtl_dispatch(q);
963}
964
965/* Call with queue lock held */
966static void
967throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
968{
969
970 struct delayed_work *dwork = &td->throtl_work;
971
972 /* schedule work if limits changed even if no bio is queued */
973 if (total_nr_queued(td) || td->limits_changed) {
974 /*
975 * We might have a work scheduled to be executed in future.
976 * Cancel that and schedule a new one.
977 */
978 __cancel_delayed_work(dwork);
979 queue_delayed_work(kthrotld_workqueue, dwork, delay);
980 throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
981 delay, jiffies);
982 }
983}
984
985static void
986throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
987{
988 /* Something wrong if we are trying to remove same group twice */
989 BUG_ON(hlist_unhashed(&tg->tg_node));
990
991 hlist_del_init(&tg->tg_node);
992
993 /*
994 * Put the reference taken at the time of creation so that when all
995 * queues are gone, group can be destroyed.
996 */
997 throtl_put_tg(tg);
998 td->nr_undestroyed_grps--;
999}
1000
1001static void throtl_release_tgs(struct throtl_data *td)
1002{
1003 struct hlist_node *pos, *n;
1004 struct throtl_grp *tg;
1005
1006 hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
1007 /*
1008 * If cgroup removal path got to blk_group first and removed
1009 * it from cgroup list, then it will take care of destroying
1010 * cfqg also.
1011 */
1012 if (!blkiocg_del_blkio_group(&tg->blkg))
1013 throtl_destroy_tg(td, tg);
1014 }
1015}
1016
1017static void throtl_td_free(struct throtl_data *td)
1018{
1019 kfree(td);
1020}
1021
1022/*
1023 * Blk cgroup controller notification saying that blkio_group object is being
1024 * delinked as associated cgroup object is going away. That also means that
1025 * no new IO will come in this group. So get rid of this group as soon as
1026 * any pending IO in the group is finished.
1027 *
1028 * This function is called under rcu_read_lock(). key is the rcu protected
1029 * pointer. That means "key" is a valid throtl_data pointer as long as we are
1030 * rcu read lock.
1031 *
1032 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1033 * it should not be NULL as even if queue was going away, cgroup deltion
1034 * path got to it first.
1035 */
1036void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
1037{
1038 unsigned long flags;
1039 struct throtl_data *td = key;
1040
1041 spin_lock_irqsave(td->queue->queue_lock, flags);
1042 throtl_destroy_tg(td, tg_of_blkg(blkg));
1043 spin_unlock_irqrestore(td->queue->queue_lock, flags);
1044}
1045
1046static void throtl_update_blkio_group_common(struct throtl_data *td,
1047 struct throtl_grp *tg)
1048{
1049 xchg(&tg->limits_changed, true);
1050 xchg(&td->limits_changed, true);
1051 /* Schedule a work now to process the limit change */
1052 throtl_schedule_delayed_work(td, 0);
1053}
1054
1055/*
1056 * For all update functions, key should be a valid pointer because these
1057 * update functions are called under blkcg_lock, that means, blkg is
1058 * valid and in turn key is valid. queue exit path can not race because
1059 * of blkcg_lock
1060 *
1061 * Can not take queue lock in update functions as queue lock under blkcg_lock
1062 * is not allowed. Under other paths we take blkcg_lock under queue_lock.
1063 */
1064static void throtl_update_blkio_group_read_bps(void *key,
1065 struct blkio_group *blkg, u64 read_bps)
1066{
1067 struct throtl_data *td = key;
1068 struct throtl_grp *tg = tg_of_blkg(blkg);
1069
1070 tg->bps[READ] = read_bps;
1071 throtl_update_blkio_group_common(td, tg);
1072}
1073
1074static void throtl_update_blkio_group_write_bps(void *key,
1075 struct blkio_group *blkg, u64 write_bps)
1076{
1077 struct throtl_data *td = key;
1078 struct throtl_grp *tg = tg_of_blkg(blkg);
1079
1080 tg->bps[WRITE] = write_bps;
1081 throtl_update_blkio_group_common(td, tg);
1082}
1083
1084static void throtl_update_blkio_group_read_iops(void *key,
1085 struct blkio_group *blkg, unsigned int read_iops)
1086{
1087 struct throtl_data *td = key;
1088 struct throtl_grp *tg = tg_of_blkg(blkg);
1089
1090 tg->iops[READ] = read_iops;
1091 throtl_update_blkio_group_common(td, tg);
1092}
1093
1094static void throtl_update_blkio_group_write_iops(void *key,
1095 struct blkio_group *blkg, unsigned int write_iops)
1096{
1097 struct throtl_data *td = key;
1098 struct throtl_grp *tg = tg_of_blkg(blkg);
1099
1100 tg->iops[WRITE] = write_iops;
1101 throtl_update_blkio_group_common(td, tg);
1102}
1103
1104static void throtl_shutdown_wq(struct request_queue *q)
1105{
1106 struct throtl_data *td = q->td;
1107
1108 cancel_delayed_work_sync(&td->throtl_work);
1109}
1110
1111static struct blkio_policy_type blkio_policy_throtl = {
1112 .ops = {
1113 .blkio_unlink_group_fn = throtl_unlink_blkio_group,
1114 .blkio_update_group_read_bps_fn =
1115 throtl_update_blkio_group_read_bps,
1116 .blkio_update_group_write_bps_fn =
1117 throtl_update_blkio_group_write_bps,
1118 .blkio_update_group_read_iops_fn =
1119 throtl_update_blkio_group_read_iops,
1120 .blkio_update_group_write_iops_fn =
1121 throtl_update_blkio_group_write_iops,
1122 },
1123 .plid = BLKIO_POLICY_THROTL,
1124};
1125
1126int blk_throtl_bio(struct request_queue *q, struct bio **biop)
1127{
1128 struct throtl_data *td = q->td;
1129 struct throtl_grp *tg;
1130 struct bio *bio = *biop;
1131 bool rw = bio_data_dir(bio), update_disptime = true;
1132 struct blkio_cgroup *blkcg;
1133
1134 if (bio->bi_rw & REQ_THROTTLED) {
1135 bio->bi_rw &= ~REQ_THROTTLED;
1136 return 0;
1137 }
1138
1139 /*
1140 * A throtl_grp pointer retrieved under rcu can be used to access
1141 * basic fields like stats and io rates. If a group has no rules,
1142 * just update the dispatch stats in lockless manner and return.
1143 */
1144
1145 rcu_read_lock();
1146 blkcg = task_blkio_cgroup(current);
1147 tg = throtl_find_tg(td, blkcg);
1148 if (tg) {
1149 throtl_tg_fill_dev_details(td, tg);
1150
1151 if (tg_no_rule_group(tg, rw)) {
1152 blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size,
1153 rw, rw_is_sync(bio->bi_rw));
1154 rcu_read_unlock();
1155 return 0;
1156 }
1157 }
1158 rcu_read_unlock();
1159
1160 /*
1161 * Either group has not been allocated yet or it is not an unlimited
1162 * IO group
1163 */
1164
1165 spin_lock_irq(q->queue_lock);
1166 tg = throtl_get_tg(td);
1167
1168 if (IS_ERR(tg)) {
1169 if (PTR_ERR(tg) == -ENODEV) {
1170 /*
1171 * Queue is gone. No queue lock held here.
1172 */
1173 return -ENODEV;
1174 }
1175 }
1176
1177 if (tg->nr_queued[rw]) {
1178 /*
1179 * There is already another bio queued in same dir. No
1180 * need to update dispatch time.
1181 */
1182 update_disptime = false;
1183 goto queue_bio;
1184
1185 }
1186
1187 /* Bio is with-in rate limit of group */
1188 if (tg_may_dispatch(td, tg, bio, NULL)) {
1189 throtl_charge_bio(tg, bio);
1190
1191 /*
1192 * We need to trim slice even when bios are not being queued
1193 * otherwise it might happen that a bio is not queued for
1194 * a long time and slice keeps on extending and trim is not
1195 * called for a long time. Now if limits are reduced suddenly
1196 * we take into account all the IO dispatched so far at new
1197 * low rate and * newly queued IO gets a really long dispatch
1198 * time.
1199 *
1200 * So keep on trimming slice even if bio is not queued.
1201 */
1202 throtl_trim_slice(td, tg, rw);
1203 goto out;
1204 }
1205
1206queue_bio:
1207 throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1208 " iodisp=%u iops=%u queued=%d/%d",
1209 rw == READ ? 'R' : 'W',
1210 tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1211 tg->io_disp[rw], tg->iops[rw],
1212 tg->nr_queued[READ], tg->nr_queued[WRITE]);
1213
1214 throtl_add_bio_tg(q->td, tg, bio);
1215 *biop = NULL;
1216
1217 if (update_disptime) {
1218 tg_update_disptime(td, tg);
1219 throtl_schedule_next_dispatch(td);
1220 }
1221
1222out:
1223 spin_unlock_irq(q->queue_lock);
1224 return 0;
1225}
1226
1227int blk_throtl_init(struct request_queue *q)
1228{
1229 struct throtl_data *td;
1230 struct throtl_grp *tg;
1231
1232 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1233 if (!td)
1234 return -ENOMEM;
1235
1236 INIT_HLIST_HEAD(&td->tg_list);
1237 td->tg_service_tree = THROTL_RB_ROOT;
1238 td->limits_changed = false;
1239 INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1240
1241 /* alloc and Init root group. */
1242 td->queue = q;
1243 tg = throtl_alloc_tg(td);
1244
1245 if (!tg) {
1246 kfree(td);
1247 return -ENOMEM;
1248 }
1249
1250 td->root_tg = tg;
1251
1252 rcu_read_lock();
1253 throtl_init_add_tg_lists(td, tg, &blkio_root_cgroup);
1254 rcu_read_unlock();
1255
1256 /* Attach throtl data to request queue */
1257 q->td = td;
1258 return 0;
1259}
1260
1261void blk_throtl_exit(struct request_queue *q)
1262{
1263 struct throtl_data *td = q->td;
1264 bool wait = false;
1265
1266 BUG_ON(!td);
1267
1268 throtl_shutdown_wq(q);
1269
1270 spin_lock_irq(q->queue_lock);
1271 throtl_release_tgs(td);
1272
1273 /* If there are other groups */
1274 if (td->nr_undestroyed_grps > 0)
1275 wait = true;
1276
1277 spin_unlock_irq(q->queue_lock);
1278
1279 /*
1280 * Wait for tg->blkg->key accessors to exit their grace periods.
1281 * Do this wait only if there are other undestroyed groups out
1282 * there (other than root group). This can happen if cgroup deletion
1283 * path claimed the responsibility of cleaning up a group before
1284 * queue cleanup code get to the group.
1285 *
1286 * Do not call synchronize_rcu() unconditionally as there are drivers
1287 * which create/delete request queue hundreds of times during scan/boot
1288 * and synchronize_rcu() can take significant time and slow down boot.
1289 */
1290 if (wait)
1291 synchronize_rcu();
1292
1293 /*
1294 * Just being safe to make sure after previous flush if some body did
1295 * update limits through cgroup and another work got queued, cancel
1296 * it.
1297 */
1298 throtl_shutdown_wq(q);
1299 throtl_td_free(td);
1300}
1301
1302static int __init throtl_init(void)
1303{
1304 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1305 if (!kthrotld_workqueue)
1306 panic("Failed to create kthrotld\n");
1307
1308 blkio_policy_register(&blkio_policy_throtl);
1309 return 0;
1310}
1311
1312module_init(throtl_init);
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 <linux/blk-cgroup.h>
13#include "blk.h"
14
15/* Max dispatch from a group in 1 round */
16static int throtl_grp_quantum = 8;
17
18/* Total max dispatch from all groups in one round */
19static int throtl_quantum = 32;
20
21/* Throttling is performed over 100ms slice and after that slice is renewed */
22static unsigned long throtl_slice = HZ/10; /* 100 ms */
23
24static struct blkcg_policy blkcg_policy_throtl;
25
26/* A workqueue to queue throttle related work */
27static struct workqueue_struct *kthrotld_workqueue;
28
29/*
30 * To implement hierarchical throttling, throtl_grps form a tree and bios
31 * are dispatched upwards level by level until they reach the top and get
32 * issued. When dispatching bios from the children and local group at each
33 * level, if the bios are dispatched into a single bio_list, there's a risk
34 * of a local or child group which can queue many bios at once filling up
35 * the list starving others.
36 *
37 * To avoid such starvation, dispatched bios are queued separately
38 * according to where they came from. When they are again dispatched to
39 * the parent, they're popped in round-robin order so that no single source
40 * hogs the dispatch window.
41 *
42 * throtl_qnode is used to keep the queued bios separated by their sources.
43 * Bios are queued to throtl_qnode which in turn is queued to
44 * throtl_service_queue and then dispatched in round-robin order.
45 *
46 * It's also used to track the reference counts on blkg's. A qnode always
47 * belongs to a throtl_grp and gets queued on itself or the parent, so
48 * incrementing the reference of the associated throtl_grp when a qnode is
49 * queued and decrementing when dequeued is enough to keep the whole blkg
50 * tree pinned while bios are in flight.
51 */
52struct throtl_qnode {
53 struct list_head node; /* service_queue->queued[] */
54 struct bio_list bios; /* queued bios */
55 struct throtl_grp *tg; /* tg this qnode belongs to */
56};
57
58struct throtl_service_queue {
59 struct throtl_service_queue *parent_sq; /* the parent service_queue */
60
61 /*
62 * Bios queued directly to this service_queue or dispatched from
63 * children throtl_grp's.
64 */
65 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
66 unsigned int nr_queued[2]; /* number of queued bios */
67
68 /*
69 * RB tree of active children throtl_grp's, which are sorted by
70 * their ->disptime.
71 */
72 struct rb_root pending_tree; /* RB tree of active tgs */
73 struct rb_node *first_pending; /* first node in the tree */
74 unsigned int nr_pending; /* # queued in the tree */
75 unsigned long first_pending_disptime; /* disptime of the first tg */
76 struct timer_list pending_timer; /* fires on first_pending_disptime */
77};
78
79enum tg_state_flags {
80 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
81 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
82};
83
84#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
85
86struct throtl_grp {
87 /* must be the first member */
88 struct blkg_policy_data pd;
89
90 /* active throtl group service_queue member */
91 struct rb_node rb_node;
92
93 /* throtl_data this group belongs to */
94 struct throtl_data *td;
95
96 /* this group's service queue */
97 struct throtl_service_queue service_queue;
98
99 /*
100 * qnode_on_self is used when bios are directly queued to this
101 * throtl_grp so that local bios compete fairly with bios
102 * dispatched from children. qnode_on_parent is used when bios are
103 * dispatched from this throtl_grp into its parent and will compete
104 * with the sibling qnode_on_parents and the parent's
105 * qnode_on_self.
106 */
107 struct throtl_qnode qnode_on_self[2];
108 struct throtl_qnode qnode_on_parent[2];
109
110 /*
111 * Dispatch time in jiffies. This is the estimated time when group
112 * will unthrottle and is ready to dispatch more bio. It is used as
113 * key to sort active groups in service tree.
114 */
115 unsigned long disptime;
116
117 unsigned int flags;
118
119 /* are there any throtl rules between this group and td? */
120 bool has_rules[2];
121
122 /* bytes per second rate limits */
123 uint64_t bps[2];
124
125 /* IOPS limits */
126 unsigned int iops[2];
127
128 /* Number of bytes disptached in current slice */
129 uint64_t bytes_disp[2];
130 /* Number of bio's dispatched in current slice */
131 unsigned int io_disp[2];
132
133 /* When did we start a new slice */
134 unsigned long slice_start[2];
135 unsigned long slice_end[2];
136};
137
138struct throtl_data
139{
140 /* service tree for active throtl groups */
141 struct throtl_service_queue service_queue;
142
143 struct request_queue *queue;
144
145 /* Total Number of queued bios on READ and WRITE lists */
146 unsigned int nr_queued[2];
147
148 /* Work for dispatching throttled bios */
149 struct work_struct dispatch_work;
150};
151
152static void throtl_pending_timer_fn(unsigned long arg);
153
154static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
155{
156 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
157}
158
159static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
160{
161 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
162}
163
164static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
165{
166 return pd_to_blkg(&tg->pd);
167}
168
169/**
170 * sq_to_tg - return the throl_grp the specified service queue belongs to
171 * @sq: the throtl_service_queue of interest
172 *
173 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
174 * embedded in throtl_data, %NULL is returned.
175 */
176static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
177{
178 if (sq && sq->parent_sq)
179 return container_of(sq, struct throtl_grp, service_queue);
180 else
181 return NULL;
182}
183
184/**
185 * sq_to_td - return throtl_data the specified service queue belongs to
186 * @sq: the throtl_service_queue of interest
187 *
188 * A service_queue can be embeded in either a throtl_grp or throtl_data.
189 * Determine the associated throtl_data accordingly and return it.
190 */
191static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
192{
193 struct throtl_grp *tg = sq_to_tg(sq);
194
195 if (tg)
196 return tg->td;
197 else
198 return container_of(sq, struct throtl_data, service_queue);
199}
200
201/**
202 * throtl_log - log debug message via blktrace
203 * @sq: the service_queue being reported
204 * @fmt: printf format string
205 * @args: printf args
206 *
207 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
208 * throtl_grp; otherwise, just "throtl".
209 */
210#define throtl_log(sq, fmt, args...) do { \
211 struct throtl_grp *__tg = sq_to_tg((sq)); \
212 struct throtl_data *__td = sq_to_td((sq)); \
213 \
214 (void)__td; \
215 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
216 break; \
217 if ((__tg)) { \
218 char __pbuf[128]; \
219 \
220 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
221 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
222 } else { \
223 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
224 } \
225} while (0)
226
227static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
228{
229 INIT_LIST_HEAD(&qn->node);
230 bio_list_init(&qn->bios);
231 qn->tg = tg;
232}
233
234/**
235 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
236 * @bio: bio being added
237 * @qn: qnode to add bio to
238 * @queued: the service_queue->queued[] list @qn belongs to
239 *
240 * Add @bio to @qn and put @qn on @queued if it's not already on.
241 * @qn->tg's reference count is bumped when @qn is activated. See the
242 * comment on top of throtl_qnode definition for details.
243 */
244static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
245 struct list_head *queued)
246{
247 bio_list_add(&qn->bios, bio);
248 if (list_empty(&qn->node)) {
249 list_add_tail(&qn->node, queued);
250 blkg_get(tg_to_blkg(qn->tg));
251 }
252}
253
254/**
255 * throtl_peek_queued - peek the first bio on a qnode list
256 * @queued: the qnode list to peek
257 */
258static struct bio *throtl_peek_queued(struct list_head *queued)
259{
260 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
261 struct bio *bio;
262
263 if (list_empty(queued))
264 return NULL;
265
266 bio = bio_list_peek(&qn->bios);
267 WARN_ON_ONCE(!bio);
268 return bio;
269}
270
271/**
272 * throtl_pop_queued - pop the first bio form a qnode list
273 * @queued: the qnode list to pop a bio from
274 * @tg_to_put: optional out argument for throtl_grp to put
275 *
276 * Pop the first bio from the qnode list @queued. After popping, the first
277 * qnode is removed from @queued if empty or moved to the end of @queued so
278 * that the popping order is round-robin.
279 *
280 * When the first qnode is removed, its associated throtl_grp should be put
281 * too. If @tg_to_put is NULL, this function automatically puts it;
282 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
283 * responsible for putting it.
284 */
285static struct bio *throtl_pop_queued(struct list_head *queued,
286 struct throtl_grp **tg_to_put)
287{
288 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
289 struct bio *bio;
290
291 if (list_empty(queued))
292 return NULL;
293
294 bio = bio_list_pop(&qn->bios);
295 WARN_ON_ONCE(!bio);
296
297 if (bio_list_empty(&qn->bios)) {
298 list_del_init(&qn->node);
299 if (tg_to_put)
300 *tg_to_put = qn->tg;
301 else
302 blkg_put(tg_to_blkg(qn->tg));
303 } else {
304 list_move_tail(&qn->node, queued);
305 }
306
307 return bio;
308}
309
310/* init a service_queue, assumes the caller zeroed it */
311static void throtl_service_queue_init(struct throtl_service_queue *sq)
312{
313 INIT_LIST_HEAD(&sq->queued[0]);
314 INIT_LIST_HEAD(&sq->queued[1]);
315 sq->pending_tree = RB_ROOT;
316 setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
317 (unsigned long)sq);
318}
319
320static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
321{
322 struct throtl_grp *tg;
323 int rw;
324
325 tg = kzalloc_node(sizeof(*tg), gfp, node);
326 if (!tg)
327 return NULL;
328
329 throtl_service_queue_init(&tg->service_queue);
330
331 for (rw = READ; rw <= WRITE; rw++) {
332 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
333 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
334 }
335
336 RB_CLEAR_NODE(&tg->rb_node);
337 tg->bps[READ] = -1;
338 tg->bps[WRITE] = -1;
339 tg->iops[READ] = -1;
340 tg->iops[WRITE] = -1;
341
342 return &tg->pd;
343}
344
345static void throtl_pd_init(struct blkg_policy_data *pd)
346{
347 struct throtl_grp *tg = pd_to_tg(pd);
348 struct blkcg_gq *blkg = tg_to_blkg(tg);
349 struct throtl_data *td = blkg->q->td;
350 struct throtl_service_queue *sq = &tg->service_queue;
351
352 /*
353 * If on the default hierarchy, we switch to properly hierarchical
354 * behavior where limits on a given throtl_grp are applied to the
355 * whole subtree rather than just the group itself. e.g. If 16M
356 * read_bps limit is set on the root group, the whole system can't
357 * exceed 16M for the device.
358 *
359 * If not on the default hierarchy, the broken flat hierarchy
360 * behavior is retained where all throtl_grps are treated as if
361 * they're all separate root groups right below throtl_data.
362 * Limits of a group don't interact with limits of other groups
363 * regardless of the position of the group in the hierarchy.
364 */
365 sq->parent_sq = &td->service_queue;
366 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
367 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
368 tg->td = td;
369}
370
371/*
372 * Set has_rules[] if @tg or any of its parents have limits configured.
373 * This doesn't require walking up to the top of the hierarchy as the
374 * parent's has_rules[] is guaranteed to be correct.
375 */
376static void tg_update_has_rules(struct throtl_grp *tg)
377{
378 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
379 int rw;
380
381 for (rw = READ; rw <= WRITE; rw++)
382 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
383 (tg->bps[rw] != -1 || tg->iops[rw] != -1);
384}
385
386static void throtl_pd_online(struct blkg_policy_data *pd)
387{
388 /*
389 * We don't want new groups to escape the limits of its ancestors.
390 * Update has_rules[] after a new group is brought online.
391 */
392 tg_update_has_rules(pd_to_tg(pd));
393}
394
395static void throtl_pd_free(struct blkg_policy_data *pd)
396{
397 struct throtl_grp *tg = pd_to_tg(pd);
398
399 del_timer_sync(&tg->service_queue.pending_timer);
400 kfree(tg);
401}
402
403static struct throtl_grp *
404throtl_rb_first(struct throtl_service_queue *parent_sq)
405{
406 /* Service tree is empty */
407 if (!parent_sq->nr_pending)
408 return NULL;
409
410 if (!parent_sq->first_pending)
411 parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
412
413 if (parent_sq->first_pending)
414 return rb_entry_tg(parent_sq->first_pending);
415
416 return NULL;
417}
418
419static void rb_erase_init(struct rb_node *n, struct rb_root *root)
420{
421 rb_erase(n, root);
422 RB_CLEAR_NODE(n);
423}
424
425static void throtl_rb_erase(struct rb_node *n,
426 struct throtl_service_queue *parent_sq)
427{
428 if (parent_sq->first_pending == n)
429 parent_sq->first_pending = NULL;
430 rb_erase_init(n, &parent_sq->pending_tree);
431 --parent_sq->nr_pending;
432}
433
434static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
435{
436 struct throtl_grp *tg;
437
438 tg = throtl_rb_first(parent_sq);
439 if (!tg)
440 return;
441
442 parent_sq->first_pending_disptime = tg->disptime;
443}
444
445static void tg_service_queue_add(struct throtl_grp *tg)
446{
447 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
448 struct rb_node **node = &parent_sq->pending_tree.rb_node;
449 struct rb_node *parent = NULL;
450 struct throtl_grp *__tg;
451 unsigned long key = tg->disptime;
452 int left = 1;
453
454 while (*node != NULL) {
455 parent = *node;
456 __tg = rb_entry_tg(parent);
457
458 if (time_before(key, __tg->disptime))
459 node = &parent->rb_left;
460 else {
461 node = &parent->rb_right;
462 left = 0;
463 }
464 }
465
466 if (left)
467 parent_sq->first_pending = &tg->rb_node;
468
469 rb_link_node(&tg->rb_node, parent, node);
470 rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
471}
472
473static void __throtl_enqueue_tg(struct throtl_grp *tg)
474{
475 tg_service_queue_add(tg);
476 tg->flags |= THROTL_TG_PENDING;
477 tg->service_queue.parent_sq->nr_pending++;
478}
479
480static void throtl_enqueue_tg(struct throtl_grp *tg)
481{
482 if (!(tg->flags & THROTL_TG_PENDING))
483 __throtl_enqueue_tg(tg);
484}
485
486static void __throtl_dequeue_tg(struct throtl_grp *tg)
487{
488 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
489 tg->flags &= ~THROTL_TG_PENDING;
490}
491
492static void throtl_dequeue_tg(struct throtl_grp *tg)
493{
494 if (tg->flags & THROTL_TG_PENDING)
495 __throtl_dequeue_tg(tg);
496}
497
498/* Call with queue lock held */
499static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
500 unsigned long expires)
501{
502 mod_timer(&sq->pending_timer, expires);
503 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
504 expires - jiffies, jiffies);
505}
506
507/**
508 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
509 * @sq: the service_queue to schedule dispatch for
510 * @force: force scheduling
511 *
512 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
513 * dispatch time of the first pending child. Returns %true if either timer
514 * is armed or there's no pending child left. %false if the current
515 * dispatch window is still open and the caller should continue
516 * dispatching.
517 *
518 * If @force is %true, the dispatch timer is always scheduled and this
519 * function is guaranteed to return %true. This is to be used when the
520 * caller can't dispatch itself and needs to invoke pending_timer
521 * unconditionally. Note that forced scheduling is likely to induce short
522 * delay before dispatch starts even if @sq->first_pending_disptime is not
523 * in the future and thus shouldn't be used in hot paths.
524 */
525static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
526 bool force)
527{
528 /* any pending children left? */
529 if (!sq->nr_pending)
530 return true;
531
532 update_min_dispatch_time(sq);
533
534 /* is the next dispatch time in the future? */
535 if (force || time_after(sq->first_pending_disptime, jiffies)) {
536 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
537 return true;
538 }
539
540 /* tell the caller to continue dispatching */
541 return false;
542}
543
544static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
545 bool rw, unsigned long start)
546{
547 tg->bytes_disp[rw] = 0;
548 tg->io_disp[rw] = 0;
549
550 /*
551 * Previous slice has expired. We must have trimmed it after last
552 * bio dispatch. That means since start of last slice, we never used
553 * that bandwidth. Do try to make use of that bandwidth while giving
554 * credit.
555 */
556 if (time_after_eq(start, tg->slice_start[rw]))
557 tg->slice_start[rw] = start;
558
559 tg->slice_end[rw] = jiffies + throtl_slice;
560 throtl_log(&tg->service_queue,
561 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
562 rw == READ ? 'R' : 'W', tg->slice_start[rw],
563 tg->slice_end[rw], jiffies);
564}
565
566static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
567{
568 tg->bytes_disp[rw] = 0;
569 tg->io_disp[rw] = 0;
570 tg->slice_start[rw] = jiffies;
571 tg->slice_end[rw] = jiffies + throtl_slice;
572 throtl_log(&tg->service_queue,
573 "[%c] new slice start=%lu end=%lu jiffies=%lu",
574 rw == READ ? 'R' : 'W', tg->slice_start[rw],
575 tg->slice_end[rw], jiffies);
576}
577
578static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
579 unsigned long jiffy_end)
580{
581 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
582}
583
584static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
585 unsigned long jiffy_end)
586{
587 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
588 throtl_log(&tg->service_queue,
589 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
590 rw == READ ? 'R' : 'W', tg->slice_start[rw],
591 tg->slice_end[rw], jiffies);
592}
593
594/* Determine if previously allocated or extended slice is complete or not */
595static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
596{
597 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
598 return false;
599
600 return 1;
601}
602
603/* Trim the used slices and adjust slice start accordingly */
604static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
605{
606 unsigned long nr_slices, time_elapsed, io_trim;
607 u64 bytes_trim, tmp;
608
609 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
610
611 /*
612 * If bps are unlimited (-1), then time slice don't get
613 * renewed. Don't try to trim the slice if slice is used. A new
614 * slice will start when appropriate.
615 */
616 if (throtl_slice_used(tg, rw))
617 return;
618
619 /*
620 * A bio has been dispatched. Also adjust slice_end. It might happen
621 * that initially cgroup limit was very low resulting in high
622 * slice_end, but later limit was bumped up and bio was dispached
623 * sooner, then we need to reduce slice_end. A high bogus slice_end
624 * is bad because it does not allow new slice to start.
625 */
626
627 throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
628
629 time_elapsed = jiffies - tg->slice_start[rw];
630
631 nr_slices = time_elapsed / throtl_slice;
632
633 if (!nr_slices)
634 return;
635 tmp = tg->bps[rw] * throtl_slice * nr_slices;
636 do_div(tmp, HZ);
637 bytes_trim = tmp;
638
639 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
640
641 if (!bytes_trim && !io_trim)
642 return;
643
644 if (tg->bytes_disp[rw] >= bytes_trim)
645 tg->bytes_disp[rw] -= bytes_trim;
646 else
647 tg->bytes_disp[rw] = 0;
648
649 if (tg->io_disp[rw] >= io_trim)
650 tg->io_disp[rw] -= io_trim;
651 else
652 tg->io_disp[rw] = 0;
653
654 tg->slice_start[rw] += nr_slices * throtl_slice;
655
656 throtl_log(&tg->service_queue,
657 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
658 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
659 tg->slice_start[rw], tg->slice_end[rw], jiffies);
660}
661
662static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
663 unsigned long *wait)
664{
665 bool rw = bio_data_dir(bio);
666 unsigned int io_allowed;
667 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
668 u64 tmp;
669
670 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
671
672 /* Slice has just started. Consider one slice interval */
673 if (!jiffy_elapsed)
674 jiffy_elapsed_rnd = throtl_slice;
675
676 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
677
678 /*
679 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
680 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
681 * will allow dispatch after 1 second and after that slice should
682 * have been trimmed.
683 */
684
685 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
686 do_div(tmp, HZ);
687
688 if (tmp > UINT_MAX)
689 io_allowed = UINT_MAX;
690 else
691 io_allowed = tmp;
692
693 if (tg->io_disp[rw] + 1 <= io_allowed) {
694 if (wait)
695 *wait = 0;
696 return true;
697 }
698
699 /* Calc approx time to dispatch */
700 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
701
702 if (jiffy_wait > jiffy_elapsed)
703 jiffy_wait = jiffy_wait - jiffy_elapsed;
704 else
705 jiffy_wait = 1;
706
707 if (wait)
708 *wait = jiffy_wait;
709 return 0;
710}
711
712static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
713 unsigned long *wait)
714{
715 bool rw = bio_data_dir(bio);
716 u64 bytes_allowed, extra_bytes, tmp;
717 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
718
719 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
720
721 /* Slice has just started. Consider one slice interval */
722 if (!jiffy_elapsed)
723 jiffy_elapsed_rnd = throtl_slice;
724
725 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
726
727 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
728 do_div(tmp, HZ);
729 bytes_allowed = tmp;
730
731 if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
732 if (wait)
733 *wait = 0;
734 return true;
735 }
736
737 /* Calc approx time to dispatch */
738 extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
739 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
740
741 if (!jiffy_wait)
742 jiffy_wait = 1;
743
744 /*
745 * This wait time is without taking into consideration the rounding
746 * up we did. Add that time also.
747 */
748 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
749 if (wait)
750 *wait = jiffy_wait;
751 return 0;
752}
753
754/*
755 * Returns whether one can dispatch a bio or not. Also returns approx number
756 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
757 */
758static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
759 unsigned long *wait)
760{
761 bool rw = bio_data_dir(bio);
762 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
763
764 /*
765 * Currently whole state machine of group depends on first bio
766 * queued in the group bio list. So one should not be calling
767 * this function with a different bio if there are other bios
768 * queued.
769 */
770 BUG_ON(tg->service_queue.nr_queued[rw] &&
771 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
772
773 /* If tg->bps = -1, then BW is unlimited */
774 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
775 if (wait)
776 *wait = 0;
777 return true;
778 }
779
780 /*
781 * If previous slice expired, start a new one otherwise renew/extend
782 * existing slice to make sure it is at least throtl_slice interval
783 * long since now. New slice is started only for empty throttle group.
784 * If there is queued bio, that means there should be an active
785 * slice and it should be extended instead.
786 */
787 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
788 throtl_start_new_slice(tg, rw);
789 else {
790 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
791 throtl_extend_slice(tg, rw, jiffies + throtl_slice);
792 }
793
794 if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
795 tg_with_in_iops_limit(tg, bio, &iops_wait)) {
796 if (wait)
797 *wait = 0;
798 return 1;
799 }
800
801 max_wait = max(bps_wait, iops_wait);
802
803 if (wait)
804 *wait = max_wait;
805
806 if (time_before(tg->slice_end[rw], jiffies + max_wait))
807 throtl_extend_slice(tg, rw, jiffies + max_wait);
808
809 return 0;
810}
811
812static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
813{
814 bool rw = bio_data_dir(bio);
815
816 /* Charge the bio to the group */
817 tg->bytes_disp[rw] += bio->bi_iter.bi_size;
818 tg->io_disp[rw]++;
819
820 /*
821 * BIO_THROTTLED is used to prevent the same bio to be throttled
822 * more than once as a throttled bio will go through blk-throtl the
823 * second time when it eventually gets issued. Set it when a bio
824 * is being charged to a tg.
825 */
826 if (!bio_flagged(bio, BIO_THROTTLED))
827 bio_set_flag(bio, BIO_THROTTLED);
828}
829
830/**
831 * throtl_add_bio_tg - add a bio to the specified throtl_grp
832 * @bio: bio to add
833 * @qn: qnode to use
834 * @tg: the target throtl_grp
835 *
836 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
837 * tg->qnode_on_self[] is used.
838 */
839static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
840 struct throtl_grp *tg)
841{
842 struct throtl_service_queue *sq = &tg->service_queue;
843 bool rw = bio_data_dir(bio);
844
845 if (!qn)
846 qn = &tg->qnode_on_self[rw];
847
848 /*
849 * If @tg doesn't currently have any bios queued in the same
850 * direction, queueing @bio can change when @tg should be
851 * dispatched. Mark that @tg was empty. This is automatically
852 * cleaered on the next tg_update_disptime().
853 */
854 if (!sq->nr_queued[rw])
855 tg->flags |= THROTL_TG_WAS_EMPTY;
856
857 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
858
859 sq->nr_queued[rw]++;
860 throtl_enqueue_tg(tg);
861}
862
863static void tg_update_disptime(struct throtl_grp *tg)
864{
865 struct throtl_service_queue *sq = &tg->service_queue;
866 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
867 struct bio *bio;
868
869 if ((bio = throtl_peek_queued(&sq->queued[READ])))
870 tg_may_dispatch(tg, bio, &read_wait);
871
872 if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
873 tg_may_dispatch(tg, bio, &write_wait);
874
875 min_wait = min(read_wait, write_wait);
876 disptime = jiffies + min_wait;
877
878 /* Update dispatch time */
879 throtl_dequeue_tg(tg);
880 tg->disptime = disptime;
881 throtl_enqueue_tg(tg);
882
883 /* see throtl_add_bio_tg() */
884 tg->flags &= ~THROTL_TG_WAS_EMPTY;
885}
886
887static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
888 struct throtl_grp *parent_tg, bool rw)
889{
890 if (throtl_slice_used(parent_tg, rw)) {
891 throtl_start_new_slice_with_credit(parent_tg, rw,
892 child_tg->slice_start[rw]);
893 }
894
895}
896
897static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
898{
899 struct throtl_service_queue *sq = &tg->service_queue;
900 struct throtl_service_queue *parent_sq = sq->parent_sq;
901 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
902 struct throtl_grp *tg_to_put = NULL;
903 struct bio *bio;
904
905 /*
906 * @bio is being transferred from @tg to @parent_sq. Popping a bio
907 * from @tg may put its reference and @parent_sq might end up
908 * getting released prematurely. Remember the tg to put and put it
909 * after @bio is transferred to @parent_sq.
910 */
911 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
912 sq->nr_queued[rw]--;
913
914 throtl_charge_bio(tg, bio);
915
916 /*
917 * If our parent is another tg, we just need to transfer @bio to
918 * the parent using throtl_add_bio_tg(). If our parent is
919 * @td->service_queue, @bio is ready to be issued. Put it on its
920 * bio_lists[] and decrease total number queued. The caller is
921 * responsible for issuing these bios.
922 */
923 if (parent_tg) {
924 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
925 start_parent_slice_with_credit(tg, parent_tg, rw);
926 } else {
927 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
928 &parent_sq->queued[rw]);
929 BUG_ON(tg->td->nr_queued[rw] <= 0);
930 tg->td->nr_queued[rw]--;
931 }
932
933 throtl_trim_slice(tg, rw);
934
935 if (tg_to_put)
936 blkg_put(tg_to_blkg(tg_to_put));
937}
938
939static int throtl_dispatch_tg(struct throtl_grp *tg)
940{
941 struct throtl_service_queue *sq = &tg->service_queue;
942 unsigned int nr_reads = 0, nr_writes = 0;
943 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
944 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
945 struct bio *bio;
946
947 /* Try to dispatch 75% READS and 25% WRITES */
948
949 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
950 tg_may_dispatch(tg, bio, NULL)) {
951
952 tg_dispatch_one_bio(tg, bio_data_dir(bio));
953 nr_reads++;
954
955 if (nr_reads >= max_nr_reads)
956 break;
957 }
958
959 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
960 tg_may_dispatch(tg, bio, NULL)) {
961
962 tg_dispatch_one_bio(tg, bio_data_dir(bio));
963 nr_writes++;
964
965 if (nr_writes >= max_nr_writes)
966 break;
967 }
968
969 return nr_reads + nr_writes;
970}
971
972static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
973{
974 unsigned int nr_disp = 0;
975
976 while (1) {
977 struct throtl_grp *tg = throtl_rb_first(parent_sq);
978 struct throtl_service_queue *sq = &tg->service_queue;
979
980 if (!tg)
981 break;
982
983 if (time_before(jiffies, tg->disptime))
984 break;
985
986 throtl_dequeue_tg(tg);
987
988 nr_disp += throtl_dispatch_tg(tg);
989
990 if (sq->nr_queued[0] || sq->nr_queued[1])
991 tg_update_disptime(tg);
992
993 if (nr_disp >= throtl_quantum)
994 break;
995 }
996
997 return nr_disp;
998}
999
1000/**
1001 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1002 * @arg: the throtl_service_queue being serviced
1003 *
1004 * This timer is armed when a child throtl_grp with active bio's become
1005 * pending and queued on the service_queue's pending_tree and expires when
1006 * the first child throtl_grp should be dispatched. This function
1007 * dispatches bio's from the children throtl_grps to the parent
1008 * service_queue.
1009 *
1010 * If the parent's parent is another throtl_grp, dispatching is propagated
1011 * by either arming its pending_timer or repeating dispatch directly. If
1012 * the top-level service_tree is reached, throtl_data->dispatch_work is
1013 * kicked so that the ready bio's are issued.
1014 */
1015static void throtl_pending_timer_fn(unsigned long arg)
1016{
1017 struct throtl_service_queue *sq = (void *)arg;
1018 struct throtl_grp *tg = sq_to_tg(sq);
1019 struct throtl_data *td = sq_to_td(sq);
1020 struct request_queue *q = td->queue;
1021 struct throtl_service_queue *parent_sq;
1022 bool dispatched;
1023 int ret;
1024
1025 spin_lock_irq(q->queue_lock);
1026again:
1027 parent_sq = sq->parent_sq;
1028 dispatched = false;
1029
1030 while (true) {
1031 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1032 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1033 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1034
1035 ret = throtl_select_dispatch(sq);
1036 if (ret) {
1037 throtl_log(sq, "bios disp=%u", ret);
1038 dispatched = true;
1039 }
1040
1041 if (throtl_schedule_next_dispatch(sq, false))
1042 break;
1043
1044 /* this dispatch windows is still open, relax and repeat */
1045 spin_unlock_irq(q->queue_lock);
1046 cpu_relax();
1047 spin_lock_irq(q->queue_lock);
1048 }
1049
1050 if (!dispatched)
1051 goto out_unlock;
1052
1053 if (parent_sq) {
1054 /* @parent_sq is another throl_grp, propagate dispatch */
1055 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1056 tg_update_disptime(tg);
1057 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1058 /* window is already open, repeat dispatching */
1059 sq = parent_sq;
1060 tg = sq_to_tg(sq);
1061 goto again;
1062 }
1063 }
1064 } else {
1065 /* reached the top-level, queue issueing */
1066 queue_work(kthrotld_workqueue, &td->dispatch_work);
1067 }
1068out_unlock:
1069 spin_unlock_irq(q->queue_lock);
1070}
1071
1072/**
1073 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1074 * @work: work item being executed
1075 *
1076 * This function is queued for execution when bio's reach the bio_lists[]
1077 * of throtl_data->service_queue. Those bio's are ready and issued by this
1078 * function.
1079 */
1080static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1081{
1082 struct throtl_data *td = container_of(work, struct throtl_data,
1083 dispatch_work);
1084 struct throtl_service_queue *td_sq = &td->service_queue;
1085 struct request_queue *q = td->queue;
1086 struct bio_list bio_list_on_stack;
1087 struct bio *bio;
1088 struct blk_plug plug;
1089 int rw;
1090
1091 bio_list_init(&bio_list_on_stack);
1092
1093 spin_lock_irq(q->queue_lock);
1094 for (rw = READ; rw <= WRITE; rw++)
1095 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1096 bio_list_add(&bio_list_on_stack, bio);
1097 spin_unlock_irq(q->queue_lock);
1098
1099 if (!bio_list_empty(&bio_list_on_stack)) {
1100 blk_start_plug(&plug);
1101 while((bio = bio_list_pop(&bio_list_on_stack)))
1102 generic_make_request(bio);
1103 blk_finish_plug(&plug);
1104 }
1105}
1106
1107static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1108 int off)
1109{
1110 struct throtl_grp *tg = pd_to_tg(pd);
1111 u64 v = *(u64 *)((void *)tg + off);
1112
1113 if (v == -1)
1114 return 0;
1115 return __blkg_prfill_u64(sf, pd, v);
1116}
1117
1118static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1119 int off)
1120{
1121 struct throtl_grp *tg = pd_to_tg(pd);
1122 unsigned int v = *(unsigned int *)((void *)tg + off);
1123
1124 if (v == -1)
1125 return 0;
1126 return __blkg_prfill_u64(sf, pd, v);
1127}
1128
1129static int tg_print_conf_u64(struct seq_file *sf, void *v)
1130{
1131 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1132 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1133 return 0;
1134}
1135
1136static int tg_print_conf_uint(struct seq_file *sf, void *v)
1137{
1138 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1139 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1140 return 0;
1141}
1142
1143static void tg_conf_updated(struct throtl_grp *tg)
1144{
1145 struct throtl_service_queue *sq = &tg->service_queue;
1146 struct cgroup_subsys_state *pos_css;
1147 struct blkcg_gq *blkg;
1148
1149 throtl_log(&tg->service_queue,
1150 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1151 tg->bps[READ], tg->bps[WRITE],
1152 tg->iops[READ], tg->iops[WRITE]);
1153
1154 /*
1155 * Update has_rules[] flags for the updated tg's subtree. A tg is
1156 * considered to have rules if either the tg itself or any of its
1157 * ancestors has rules. This identifies groups without any
1158 * restrictions in the whole hierarchy and allows them to bypass
1159 * blk-throttle.
1160 */
1161 blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg))
1162 tg_update_has_rules(blkg_to_tg(blkg));
1163
1164 /*
1165 * We're already holding queue_lock and know @tg is valid. Let's
1166 * apply the new config directly.
1167 *
1168 * Restart the slices for both READ and WRITES. It might happen
1169 * that a group's limit are dropped suddenly and we don't want to
1170 * account recently dispatched IO with new low rate.
1171 */
1172 throtl_start_new_slice(tg, 0);
1173 throtl_start_new_slice(tg, 1);
1174
1175 if (tg->flags & THROTL_TG_PENDING) {
1176 tg_update_disptime(tg);
1177 throtl_schedule_next_dispatch(sq->parent_sq, true);
1178 }
1179}
1180
1181static ssize_t tg_set_conf(struct kernfs_open_file *of,
1182 char *buf, size_t nbytes, loff_t off, bool is_u64)
1183{
1184 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1185 struct blkg_conf_ctx ctx;
1186 struct throtl_grp *tg;
1187 int ret;
1188 u64 v;
1189
1190 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1191 if (ret)
1192 return ret;
1193
1194 ret = -EINVAL;
1195 if (sscanf(ctx.body, "%llu", &v) != 1)
1196 goto out_finish;
1197 if (!v)
1198 v = -1;
1199
1200 tg = blkg_to_tg(ctx.blkg);
1201
1202 if (is_u64)
1203 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1204 else
1205 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1206
1207 tg_conf_updated(tg);
1208 ret = 0;
1209out_finish:
1210 blkg_conf_finish(&ctx);
1211 return ret ?: nbytes;
1212}
1213
1214static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1215 char *buf, size_t nbytes, loff_t off)
1216{
1217 return tg_set_conf(of, buf, nbytes, off, true);
1218}
1219
1220static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1221 char *buf, size_t nbytes, loff_t off)
1222{
1223 return tg_set_conf(of, buf, nbytes, off, false);
1224}
1225
1226static struct cftype throtl_legacy_files[] = {
1227 {
1228 .name = "throttle.read_bps_device",
1229 .private = offsetof(struct throtl_grp, bps[READ]),
1230 .seq_show = tg_print_conf_u64,
1231 .write = tg_set_conf_u64,
1232 },
1233 {
1234 .name = "throttle.write_bps_device",
1235 .private = offsetof(struct throtl_grp, bps[WRITE]),
1236 .seq_show = tg_print_conf_u64,
1237 .write = tg_set_conf_u64,
1238 },
1239 {
1240 .name = "throttle.read_iops_device",
1241 .private = offsetof(struct throtl_grp, iops[READ]),
1242 .seq_show = tg_print_conf_uint,
1243 .write = tg_set_conf_uint,
1244 },
1245 {
1246 .name = "throttle.write_iops_device",
1247 .private = offsetof(struct throtl_grp, iops[WRITE]),
1248 .seq_show = tg_print_conf_uint,
1249 .write = tg_set_conf_uint,
1250 },
1251 {
1252 .name = "throttle.io_service_bytes",
1253 .private = (unsigned long)&blkcg_policy_throtl,
1254 .seq_show = blkg_print_stat_bytes,
1255 },
1256 {
1257 .name = "throttle.io_serviced",
1258 .private = (unsigned long)&blkcg_policy_throtl,
1259 .seq_show = blkg_print_stat_ios,
1260 },
1261 { } /* terminate */
1262};
1263
1264static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
1265 int off)
1266{
1267 struct throtl_grp *tg = pd_to_tg(pd);
1268 const char *dname = blkg_dev_name(pd->blkg);
1269 char bufs[4][21] = { "max", "max", "max", "max" };
1270
1271 if (!dname)
1272 return 0;
1273 if (tg->bps[READ] == -1 && tg->bps[WRITE] == -1 &&
1274 tg->iops[READ] == -1 && tg->iops[WRITE] == -1)
1275 return 0;
1276
1277 if (tg->bps[READ] != -1)
1278 snprintf(bufs[0], sizeof(bufs[0]), "%llu", tg->bps[READ]);
1279 if (tg->bps[WRITE] != -1)
1280 snprintf(bufs[1], sizeof(bufs[1]), "%llu", tg->bps[WRITE]);
1281 if (tg->iops[READ] != -1)
1282 snprintf(bufs[2], sizeof(bufs[2]), "%u", tg->iops[READ]);
1283 if (tg->iops[WRITE] != -1)
1284 snprintf(bufs[3], sizeof(bufs[3]), "%u", tg->iops[WRITE]);
1285
1286 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
1287 dname, bufs[0], bufs[1], bufs[2], bufs[3]);
1288 return 0;
1289}
1290
1291static int tg_print_max(struct seq_file *sf, void *v)
1292{
1293 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_max,
1294 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1295 return 0;
1296}
1297
1298static ssize_t tg_set_max(struct kernfs_open_file *of,
1299 char *buf, size_t nbytes, loff_t off)
1300{
1301 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1302 struct blkg_conf_ctx ctx;
1303 struct throtl_grp *tg;
1304 u64 v[4];
1305 int ret;
1306
1307 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1308 if (ret)
1309 return ret;
1310
1311 tg = blkg_to_tg(ctx.blkg);
1312
1313 v[0] = tg->bps[READ];
1314 v[1] = tg->bps[WRITE];
1315 v[2] = tg->iops[READ];
1316 v[3] = tg->iops[WRITE];
1317
1318 while (true) {
1319 char tok[27]; /* wiops=18446744073709551616 */
1320 char *p;
1321 u64 val = -1;
1322 int len;
1323
1324 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1325 break;
1326 if (tok[0] == '\0')
1327 break;
1328 ctx.body += len;
1329
1330 ret = -EINVAL;
1331 p = tok;
1332 strsep(&p, "=");
1333 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1334 goto out_finish;
1335
1336 ret = -ERANGE;
1337 if (!val)
1338 goto out_finish;
1339
1340 ret = -EINVAL;
1341 if (!strcmp(tok, "rbps"))
1342 v[0] = val;
1343 else if (!strcmp(tok, "wbps"))
1344 v[1] = val;
1345 else if (!strcmp(tok, "riops"))
1346 v[2] = min_t(u64, val, UINT_MAX);
1347 else if (!strcmp(tok, "wiops"))
1348 v[3] = min_t(u64, val, UINT_MAX);
1349 else
1350 goto out_finish;
1351 }
1352
1353 tg->bps[READ] = v[0];
1354 tg->bps[WRITE] = v[1];
1355 tg->iops[READ] = v[2];
1356 tg->iops[WRITE] = v[3];
1357
1358 tg_conf_updated(tg);
1359 ret = 0;
1360out_finish:
1361 blkg_conf_finish(&ctx);
1362 return ret ?: nbytes;
1363}
1364
1365static struct cftype throtl_files[] = {
1366 {
1367 .name = "max",
1368 .flags = CFTYPE_NOT_ON_ROOT,
1369 .seq_show = tg_print_max,
1370 .write = tg_set_max,
1371 },
1372 { } /* terminate */
1373};
1374
1375static void throtl_shutdown_wq(struct request_queue *q)
1376{
1377 struct throtl_data *td = q->td;
1378
1379 cancel_work_sync(&td->dispatch_work);
1380}
1381
1382static struct blkcg_policy blkcg_policy_throtl = {
1383 .dfl_cftypes = throtl_files,
1384 .legacy_cftypes = throtl_legacy_files,
1385
1386 .pd_alloc_fn = throtl_pd_alloc,
1387 .pd_init_fn = throtl_pd_init,
1388 .pd_online_fn = throtl_pd_online,
1389 .pd_free_fn = throtl_pd_free,
1390};
1391
1392bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
1393 struct bio *bio)
1394{
1395 struct throtl_qnode *qn = NULL;
1396 struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
1397 struct throtl_service_queue *sq;
1398 bool rw = bio_data_dir(bio);
1399 bool throttled = false;
1400
1401 WARN_ON_ONCE(!rcu_read_lock_held());
1402
1403 /* see throtl_charge_bio() */
1404 if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw])
1405 goto out;
1406
1407 spin_lock_irq(q->queue_lock);
1408
1409 if (unlikely(blk_queue_bypass(q)))
1410 goto out_unlock;
1411
1412 sq = &tg->service_queue;
1413
1414 while (true) {
1415 /* throtl is FIFO - if bios are already queued, should queue */
1416 if (sq->nr_queued[rw])
1417 break;
1418
1419 /* if above limits, break to queue */
1420 if (!tg_may_dispatch(tg, bio, NULL))
1421 break;
1422
1423 /* within limits, let's charge and dispatch directly */
1424 throtl_charge_bio(tg, bio);
1425
1426 /*
1427 * We need to trim slice even when bios are not being queued
1428 * otherwise it might happen that a bio is not queued for
1429 * a long time and slice keeps on extending and trim is not
1430 * called for a long time. Now if limits are reduced suddenly
1431 * we take into account all the IO dispatched so far at new
1432 * low rate and * newly queued IO gets a really long dispatch
1433 * time.
1434 *
1435 * So keep on trimming slice even if bio is not queued.
1436 */
1437 throtl_trim_slice(tg, rw);
1438
1439 /*
1440 * @bio passed through this layer without being throttled.
1441 * Climb up the ladder. If we''re already at the top, it
1442 * can be executed directly.
1443 */
1444 qn = &tg->qnode_on_parent[rw];
1445 sq = sq->parent_sq;
1446 tg = sq_to_tg(sq);
1447 if (!tg)
1448 goto out_unlock;
1449 }
1450
1451 /* out-of-limit, queue to @tg */
1452 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1453 rw == READ ? 'R' : 'W',
1454 tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
1455 tg->io_disp[rw], tg->iops[rw],
1456 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1457
1458 bio_associate_current(bio);
1459 tg->td->nr_queued[rw]++;
1460 throtl_add_bio_tg(bio, qn, tg);
1461 throttled = true;
1462
1463 /*
1464 * Update @tg's dispatch time and force schedule dispatch if @tg
1465 * was empty before @bio. The forced scheduling isn't likely to
1466 * cause undue delay as @bio is likely to be dispatched directly if
1467 * its @tg's disptime is not in the future.
1468 */
1469 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1470 tg_update_disptime(tg);
1471 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
1472 }
1473
1474out_unlock:
1475 spin_unlock_irq(q->queue_lock);
1476out:
1477 /*
1478 * As multiple blk-throtls may stack in the same issue path, we
1479 * don't want bios to leave with the flag set. Clear the flag if
1480 * being issued.
1481 */
1482 if (!throttled)
1483 bio_clear_flag(bio, BIO_THROTTLED);
1484 return throttled;
1485}
1486
1487/*
1488 * Dispatch all bios from all children tg's queued on @parent_sq. On
1489 * return, @parent_sq is guaranteed to not have any active children tg's
1490 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1491 */
1492static void tg_drain_bios(struct throtl_service_queue *parent_sq)
1493{
1494 struct throtl_grp *tg;
1495
1496 while ((tg = throtl_rb_first(parent_sq))) {
1497 struct throtl_service_queue *sq = &tg->service_queue;
1498 struct bio *bio;
1499
1500 throtl_dequeue_tg(tg);
1501
1502 while ((bio = throtl_peek_queued(&sq->queued[READ])))
1503 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1504 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
1505 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1506 }
1507}
1508
1509/**
1510 * blk_throtl_drain - drain throttled bios
1511 * @q: request_queue to drain throttled bios for
1512 *
1513 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1514 */
1515void blk_throtl_drain(struct request_queue *q)
1516 __releases(q->queue_lock) __acquires(q->queue_lock)
1517{
1518 struct throtl_data *td = q->td;
1519 struct blkcg_gq *blkg;
1520 struct cgroup_subsys_state *pos_css;
1521 struct bio *bio;
1522 int rw;
1523
1524 queue_lockdep_assert_held(q);
1525 rcu_read_lock();
1526
1527 /*
1528 * Drain each tg while doing post-order walk on the blkg tree, so
1529 * that all bios are propagated to td->service_queue. It'd be
1530 * better to walk service_queue tree directly but blkg walk is
1531 * easier.
1532 */
1533 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
1534 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
1535
1536 /* finally, transfer bios from top-level tg's into the td */
1537 tg_drain_bios(&td->service_queue);
1538
1539 rcu_read_unlock();
1540 spin_unlock_irq(q->queue_lock);
1541
1542 /* all bios now should be in td->service_queue, issue them */
1543 for (rw = READ; rw <= WRITE; rw++)
1544 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
1545 NULL)))
1546 generic_make_request(bio);
1547
1548 spin_lock_irq(q->queue_lock);
1549}
1550
1551int blk_throtl_init(struct request_queue *q)
1552{
1553 struct throtl_data *td;
1554 int ret;
1555
1556 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1557 if (!td)
1558 return -ENOMEM;
1559
1560 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
1561 throtl_service_queue_init(&td->service_queue);
1562
1563 q->td = td;
1564 td->queue = q;
1565
1566 /* activate policy */
1567 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1568 if (ret)
1569 kfree(td);
1570 return ret;
1571}
1572
1573void blk_throtl_exit(struct request_queue *q)
1574{
1575 BUG_ON(!q->td);
1576 throtl_shutdown_wq(q);
1577 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1578 kfree(q->td);
1579}
1580
1581static int __init throtl_init(void)
1582{
1583 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1584 if (!kthrotld_workqueue)
1585 panic("Failed to create kthrotld\n");
1586
1587 return blkcg_policy_register(&blkcg_policy_throtl);
1588}
1589
1590module_init(throtl_init);