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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#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
86/* Per-cpu group stats */
87struct tg_stats_cpu {
88 /* total bytes transferred */
89 struct blkg_rwstat service_bytes;
90 /* total IOs serviced, post merge */
91 struct blkg_rwstat serviced;
92};
93
94struct throtl_grp {
95 /* must be the first member */
96 struct blkg_policy_data pd;
97
98 /* active throtl group service_queue member */
99 struct rb_node rb_node;
100
101 /* throtl_data this group belongs to */
102 struct throtl_data *td;
103
104 /* this group's service queue */
105 struct throtl_service_queue service_queue;
106
107 /*
108 * qnode_on_self is used when bios are directly queued to this
109 * throtl_grp so that local bios compete fairly with bios
110 * dispatched from children. qnode_on_parent is used when bios are
111 * dispatched from this throtl_grp into its parent and will compete
112 * with the sibling qnode_on_parents and the parent's
113 * qnode_on_self.
114 */
115 struct throtl_qnode qnode_on_self[2];
116 struct throtl_qnode qnode_on_parent[2];
117
118 /*
119 * Dispatch time in jiffies. This is the estimated time when group
120 * will unthrottle and is ready to dispatch more bio. It is used as
121 * key to sort active groups in service tree.
122 */
123 unsigned long disptime;
124
125 unsigned int flags;
126
127 /* are there any throtl rules between this group and td? */
128 bool has_rules[2];
129
130 /* bytes per second rate limits */
131 uint64_t bps[2];
132
133 /* IOPS limits */
134 unsigned int iops[2];
135
136 /* Number of bytes disptached in current slice */
137 uint64_t bytes_disp[2];
138 /* Number of bio's dispatched in current slice */
139 unsigned int io_disp[2];
140
141 /* When did we start a new slice */
142 unsigned long slice_start[2];
143 unsigned long slice_end[2];
144
145 /* Per cpu stats pointer */
146 struct tg_stats_cpu __percpu *stats_cpu;
147
148 /* List of tgs waiting for per cpu stats memory to be allocated */
149 struct list_head stats_alloc_node;
150};
151
152struct throtl_data
153{
154 /* service tree for active throtl groups */
155 struct throtl_service_queue service_queue;
156
157 struct request_queue *queue;
158
159 /* Total Number of queued bios on READ and WRITE lists */
160 unsigned int nr_queued[2];
161
162 /*
163 * number of total undestroyed groups
164 */
165 unsigned int nr_undestroyed_grps;
166
167 /* Work for dispatching throttled bios */
168 struct work_struct dispatch_work;
169};
170
171/* list and work item to allocate percpu group stats */
172static DEFINE_SPINLOCK(tg_stats_alloc_lock);
173static LIST_HEAD(tg_stats_alloc_list);
174
175static void tg_stats_alloc_fn(struct work_struct *);
176static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
177
178static void throtl_pending_timer_fn(unsigned long arg);
179
180static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
181{
182 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
183}
184
185static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
186{
187 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
188}
189
190static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
191{
192 return pd_to_blkg(&tg->pd);
193}
194
195static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
196{
197 return blkg_to_tg(td->queue->root_blkg);
198}
199
200/**
201 * sq_to_tg - return the throl_grp the specified service queue belongs to
202 * @sq: the throtl_service_queue of interest
203 *
204 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
205 * embedded in throtl_data, %NULL is returned.
206 */
207static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
208{
209 if (sq && sq->parent_sq)
210 return container_of(sq, struct throtl_grp, service_queue);
211 else
212 return NULL;
213}
214
215/**
216 * sq_to_td - return throtl_data the specified service queue belongs to
217 * @sq: the throtl_service_queue of interest
218 *
219 * A service_queue can be embeded in either a throtl_grp or throtl_data.
220 * Determine the associated throtl_data accordingly and return it.
221 */
222static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
223{
224 struct throtl_grp *tg = sq_to_tg(sq);
225
226 if (tg)
227 return tg->td;
228 else
229 return container_of(sq, struct throtl_data, service_queue);
230}
231
232/**
233 * throtl_log - log debug message via blktrace
234 * @sq: the service_queue being reported
235 * @fmt: printf format string
236 * @args: printf args
237 *
238 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
239 * throtl_grp; otherwise, just "throtl".
240 *
241 * TODO: this should be made a function and name formatting should happen
242 * after testing whether blktrace is enabled.
243 */
244#define throtl_log(sq, fmt, args...) do { \
245 struct throtl_grp *__tg = sq_to_tg((sq)); \
246 struct throtl_data *__td = sq_to_td((sq)); \
247 \
248 (void)__td; \
249 if ((__tg)) { \
250 char __pbuf[128]; \
251 \
252 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
253 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
254 } else { \
255 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
256 } \
257} while (0)
258
259static void tg_stats_init(struct tg_stats_cpu *tg_stats)
260{
261 blkg_rwstat_init(&tg_stats->service_bytes);
262 blkg_rwstat_init(&tg_stats->serviced);
263}
264
265/*
266 * Worker for allocating per cpu stat for tgs. This is scheduled on the
267 * system_wq once there are some groups on the alloc_list waiting for
268 * allocation.
269 */
270static void tg_stats_alloc_fn(struct work_struct *work)
271{
272 static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
273 struct delayed_work *dwork = to_delayed_work(work);
274 bool empty = false;
275
276alloc_stats:
277 if (!stats_cpu) {
278 int cpu;
279
280 stats_cpu = alloc_percpu(struct tg_stats_cpu);
281 if (!stats_cpu) {
282 /* allocation failed, try again after some time */
283 schedule_delayed_work(dwork, msecs_to_jiffies(10));
284 return;
285 }
286 for_each_possible_cpu(cpu)
287 tg_stats_init(per_cpu_ptr(stats_cpu, cpu));
288 }
289
290 spin_lock_irq(&tg_stats_alloc_lock);
291
292 if (!list_empty(&tg_stats_alloc_list)) {
293 struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
294 struct throtl_grp,
295 stats_alloc_node);
296 swap(tg->stats_cpu, stats_cpu);
297 list_del_init(&tg->stats_alloc_node);
298 }
299
300 empty = list_empty(&tg_stats_alloc_list);
301 spin_unlock_irq(&tg_stats_alloc_lock);
302 if (!empty)
303 goto alloc_stats;
304}
305
306static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
307{
308 INIT_LIST_HEAD(&qn->node);
309 bio_list_init(&qn->bios);
310 qn->tg = tg;
311}
312
313/**
314 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
315 * @bio: bio being added
316 * @qn: qnode to add bio to
317 * @queued: the service_queue->queued[] list @qn belongs to
318 *
319 * Add @bio to @qn and put @qn on @queued if it's not already on.
320 * @qn->tg's reference count is bumped when @qn is activated. See the
321 * comment on top of throtl_qnode definition for details.
322 */
323static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
324 struct list_head *queued)
325{
326 bio_list_add(&qn->bios, bio);
327 if (list_empty(&qn->node)) {
328 list_add_tail(&qn->node, queued);
329 blkg_get(tg_to_blkg(qn->tg));
330 }
331}
332
333/**
334 * throtl_peek_queued - peek the first bio on a qnode list
335 * @queued: the qnode list to peek
336 */
337static struct bio *throtl_peek_queued(struct list_head *queued)
338{
339 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
340 struct bio *bio;
341
342 if (list_empty(queued))
343 return NULL;
344
345 bio = bio_list_peek(&qn->bios);
346 WARN_ON_ONCE(!bio);
347 return bio;
348}
349
350/**
351 * throtl_pop_queued - pop the first bio form a qnode list
352 * @queued: the qnode list to pop a bio from
353 * @tg_to_put: optional out argument for throtl_grp to put
354 *
355 * Pop the first bio from the qnode list @queued. After popping, the first
356 * qnode is removed from @queued if empty or moved to the end of @queued so
357 * that the popping order is round-robin.
358 *
359 * When the first qnode is removed, its associated throtl_grp should be put
360 * too. If @tg_to_put is NULL, this function automatically puts it;
361 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
362 * responsible for putting it.
363 */
364static struct bio *throtl_pop_queued(struct list_head *queued,
365 struct throtl_grp **tg_to_put)
366{
367 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
368 struct bio *bio;
369
370 if (list_empty(queued))
371 return NULL;
372
373 bio = bio_list_pop(&qn->bios);
374 WARN_ON_ONCE(!bio);
375
376 if (bio_list_empty(&qn->bios)) {
377 list_del_init(&qn->node);
378 if (tg_to_put)
379 *tg_to_put = qn->tg;
380 else
381 blkg_put(tg_to_blkg(qn->tg));
382 } else {
383 list_move_tail(&qn->node, queued);
384 }
385
386 return bio;
387}
388
389/* init a service_queue, assumes the caller zeroed it */
390static void throtl_service_queue_init(struct throtl_service_queue *sq,
391 struct throtl_service_queue *parent_sq)
392{
393 INIT_LIST_HEAD(&sq->queued[0]);
394 INIT_LIST_HEAD(&sq->queued[1]);
395 sq->pending_tree = RB_ROOT;
396 sq->parent_sq = parent_sq;
397 setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
398 (unsigned long)sq);
399}
400
401static void throtl_service_queue_exit(struct throtl_service_queue *sq)
402{
403 del_timer_sync(&sq->pending_timer);
404}
405
406static void throtl_pd_init(struct blkcg_gq *blkg)
407{
408 struct throtl_grp *tg = blkg_to_tg(blkg);
409 struct throtl_data *td = blkg->q->td;
410 struct throtl_service_queue *parent_sq;
411 unsigned long flags;
412 int rw;
413
414 /*
415 * If sane_hierarchy is enabled, we switch to properly hierarchical
416 * behavior where limits on a given throtl_grp are applied to the
417 * whole subtree rather than just the group itself. e.g. If 16M
418 * read_bps limit is set on the root group, the whole system can't
419 * exceed 16M for the device.
420 *
421 * If sane_hierarchy is not enabled, the broken flat hierarchy
422 * behavior is retained where all throtl_grps are treated as if
423 * they're all separate root groups right below throtl_data.
424 * Limits of a group don't interact with limits of other groups
425 * regardless of the position of the group in the hierarchy.
426 */
427 parent_sq = &td->service_queue;
428
429 if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent)
430 parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
431
432 throtl_service_queue_init(&tg->service_queue, parent_sq);
433
434 for (rw = READ; rw <= WRITE; rw++) {
435 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
436 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
437 }
438
439 RB_CLEAR_NODE(&tg->rb_node);
440 tg->td = td;
441
442 tg->bps[READ] = -1;
443 tg->bps[WRITE] = -1;
444 tg->iops[READ] = -1;
445 tg->iops[WRITE] = -1;
446
447 /*
448 * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
449 * but percpu allocator can't be called from IO path. Queue tg on
450 * tg_stats_alloc_list and allocate from work item.
451 */
452 spin_lock_irqsave(&tg_stats_alloc_lock, flags);
453 list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
454 schedule_delayed_work(&tg_stats_alloc_work, 0);
455 spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
456}
457
458/*
459 * Set has_rules[] if @tg or any of its parents have limits configured.
460 * This doesn't require walking up to the top of the hierarchy as the
461 * parent's has_rules[] is guaranteed to be correct.
462 */
463static void tg_update_has_rules(struct throtl_grp *tg)
464{
465 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
466 int rw;
467
468 for (rw = READ; rw <= WRITE; rw++)
469 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
470 (tg->bps[rw] != -1 || tg->iops[rw] != -1);
471}
472
473static void throtl_pd_online(struct blkcg_gq *blkg)
474{
475 /*
476 * We don't want new groups to escape the limits of its ancestors.
477 * Update has_rules[] after a new group is brought online.
478 */
479 tg_update_has_rules(blkg_to_tg(blkg));
480}
481
482static void throtl_pd_exit(struct blkcg_gq *blkg)
483{
484 struct throtl_grp *tg = blkg_to_tg(blkg);
485 unsigned long flags;
486
487 spin_lock_irqsave(&tg_stats_alloc_lock, flags);
488 list_del_init(&tg->stats_alloc_node);
489 spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
490
491 free_percpu(tg->stats_cpu);
492
493 throtl_service_queue_exit(&tg->service_queue);
494}
495
496static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
497{
498 struct throtl_grp *tg = blkg_to_tg(blkg);
499 int cpu;
500
501 if (tg->stats_cpu == NULL)
502 return;
503
504 for_each_possible_cpu(cpu) {
505 struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
506
507 blkg_rwstat_reset(&sc->service_bytes);
508 blkg_rwstat_reset(&sc->serviced);
509 }
510}
511
512static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
513 struct blkcg *blkcg)
514{
515 /*
516 * This is the common case when there are no blkcgs. Avoid lookup
517 * in this case
518 */
519 if (blkcg == &blkcg_root)
520 return td_root_tg(td);
521
522 return blkg_to_tg(blkg_lookup(blkcg, td->queue));
523}
524
525static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
526 struct blkcg *blkcg)
527{
528 struct request_queue *q = td->queue;
529 struct throtl_grp *tg = NULL;
530
531 /*
532 * This is the common case when there are no blkcgs. Avoid lookup
533 * in this case
534 */
535 if (blkcg == &blkcg_root) {
536 tg = td_root_tg(td);
537 } else {
538 struct blkcg_gq *blkg;
539
540 blkg = blkg_lookup_create(blkcg, q);
541
542 /* if %NULL and @q is alive, fall back to root_tg */
543 if (!IS_ERR(blkg))
544 tg = blkg_to_tg(blkg);
545 else if (!blk_queue_dying(q))
546 tg = td_root_tg(td);
547 }
548
549 return tg;
550}
551
552static struct throtl_grp *
553throtl_rb_first(struct throtl_service_queue *parent_sq)
554{
555 /* Service tree is empty */
556 if (!parent_sq->nr_pending)
557 return NULL;
558
559 if (!parent_sq->first_pending)
560 parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
561
562 if (parent_sq->first_pending)
563 return rb_entry_tg(parent_sq->first_pending);
564
565 return NULL;
566}
567
568static void rb_erase_init(struct rb_node *n, struct rb_root *root)
569{
570 rb_erase(n, root);
571 RB_CLEAR_NODE(n);
572}
573
574static void throtl_rb_erase(struct rb_node *n,
575 struct throtl_service_queue *parent_sq)
576{
577 if (parent_sq->first_pending == n)
578 parent_sq->first_pending = NULL;
579 rb_erase_init(n, &parent_sq->pending_tree);
580 --parent_sq->nr_pending;
581}
582
583static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
584{
585 struct throtl_grp *tg;
586
587 tg = throtl_rb_first(parent_sq);
588 if (!tg)
589 return;
590
591 parent_sq->first_pending_disptime = tg->disptime;
592}
593
594static void tg_service_queue_add(struct throtl_grp *tg)
595{
596 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
597 struct rb_node **node = &parent_sq->pending_tree.rb_node;
598 struct rb_node *parent = NULL;
599 struct throtl_grp *__tg;
600 unsigned long key = tg->disptime;
601 int left = 1;
602
603 while (*node != NULL) {
604 parent = *node;
605 __tg = rb_entry_tg(parent);
606
607 if (time_before(key, __tg->disptime))
608 node = &parent->rb_left;
609 else {
610 node = &parent->rb_right;
611 left = 0;
612 }
613 }
614
615 if (left)
616 parent_sq->first_pending = &tg->rb_node;
617
618 rb_link_node(&tg->rb_node, parent, node);
619 rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
620}
621
622static void __throtl_enqueue_tg(struct throtl_grp *tg)
623{
624 tg_service_queue_add(tg);
625 tg->flags |= THROTL_TG_PENDING;
626 tg->service_queue.parent_sq->nr_pending++;
627}
628
629static void throtl_enqueue_tg(struct throtl_grp *tg)
630{
631 if (!(tg->flags & THROTL_TG_PENDING))
632 __throtl_enqueue_tg(tg);
633}
634
635static void __throtl_dequeue_tg(struct throtl_grp *tg)
636{
637 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
638 tg->flags &= ~THROTL_TG_PENDING;
639}
640
641static void throtl_dequeue_tg(struct throtl_grp *tg)
642{
643 if (tg->flags & THROTL_TG_PENDING)
644 __throtl_dequeue_tg(tg);
645}
646
647/* Call with queue lock held */
648static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
649 unsigned long expires)
650{
651 mod_timer(&sq->pending_timer, expires);
652 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
653 expires - jiffies, jiffies);
654}
655
656/**
657 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
658 * @sq: the service_queue to schedule dispatch for
659 * @force: force scheduling
660 *
661 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
662 * dispatch time of the first pending child. Returns %true if either timer
663 * is armed or there's no pending child left. %false if the current
664 * dispatch window is still open and the caller should continue
665 * dispatching.
666 *
667 * If @force is %true, the dispatch timer is always scheduled and this
668 * function is guaranteed to return %true. This is to be used when the
669 * caller can't dispatch itself and needs to invoke pending_timer
670 * unconditionally. Note that forced scheduling is likely to induce short
671 * delay before dispatch starts even if @sq->first_pending_disptime is not
672 * in the future and thus shouldn't be used in hot paths.
673 */
674static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
675 bool force)
676{
677 /* any pending children left? */
678 if (!sq->nr_pending)
679 return true;
680
681 update_min_dispatch_time(sq);
682
683 /* is the next dispatch time in the future? */
684 if (force || time_after(sq->first_pending_disptime, jiffies)) {
685 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
686 return true;
687 }
688
689 /* tell the caller to continue dispatching */
690 return false;
691}
692
693static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
694 bool rw, unsigned long start)
695{
696 tg->bytes_disp[rw] = 0;
697 tg->io_disp[rw] = 0;
698
699 /*
700 * Previous slice has expired. We must have trimmed it after last
701 * bio dispatch. That means since start of last slice, we never used
702 * that bandwidth. Do try to make use of that bandwidth while giving
703 * credit.
704 */
705 if (time_after_eq(start, tg->slice_start[rw]))
706 tg->slice_start[rw] = start;
707
708 tg->slice_end[rw] = jiffies + throtl_slice;
709 throtl_log(&tg->service_queue,
710 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
711 rw == READ ? 'R' : 'W', tg->slice_start[rw],
712 tg->slice_end[rw], jiffies);
713}
714
715static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
716{
717 tg->bytes_disp[rw] = 0;
718 tg->io_disp[rw] = 0;
719 tg->slice_start[rw] = jiffies;
720 tg->slice_end[rw] = jiffies + throtl_slice;
721 throtl_log(&tg->service_queue,
722 "[%c] new slice start=%lu end=%lu jiffies=%lu",
723 rw == READ ? 'R' : 'W', tg->slice_start[rw],
724 tg->slice_end[rw], jiffies);
725}
726
727static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
728 unsigned long jiffy_end)
729{
730 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
731}
732
733static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
734 unsigned long jiffy_end)
735{
736 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
737 throtl_log(&tg->service_queue,
738 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
739 rw == READ ? 'R' : 'W', tg->slice_start[rw],
740 tg->slice_end[rw], jiffies);
741}
742
743/* Determine if previously allocated or extended slice is complete or not */
744static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
745{
746 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
747 return 0;
748
749 return 1;
750}
751
752/* Trim the used slices and adjust slice start accordingly */
753static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
754{
755 unsigned long nr_slices, time_elapsed, io_trim;
756 u64 bytes_trim, tmp;
757
758 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
759
760 /*
761 * If bps are unlimited (-1), then time slice don't get
762 * renewed. Don't try to trim the slice if slice is used. A new
763 * slice will start when appropriate.
764 */
765 if (throtl_slice_used(tg, rw))
766 return;
767
768 /*
769 * A bio has been dispatched. Also adjust slice_end. It might happen
770 * that initially cgroup limit was very low resulting in high
771 * slice_end, but later limit was bumped up and bio was dispached
772 * sooner, then we need to reduce slice_end. A high bogus slice_end
773 * is bad because it does not allow new slice to start.
774 */
775
776 throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
777
778 time_elapsed = jiffies - tg->slice_start[rw];
779
780 nr_slices = time_elapsed / throtl_slice;
781
782 if (!nr_slices)
783 return;
784 tmp = tg->bps[rw] * throtl_slice * nr_slices;
785 do_div(tmp, HZ);
786 bytes_trim = tmp;
787
788 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
789
790 if (!bytes_trim && !io_trim)
791 return;
792
793 if (tg->bytes_disp[rw] >= bytes_trim)
794 tg->bytes_disp[rw] -= bytes_trim;
795 else
796 tg->bytes_disp[rw] = 0;
797
798 if (tg->io_disp[rw] >= io_trim)
799 tg->io_disp[rw] -= io_trim;
800 else
801 tg->io_disp[rw] = 0;
802
803 tg->slice_start[rw] += nr_slices * throtl_slice;
804
805 throtl_log(&tg->service_queue,
806 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
807 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
808 tg->slice_start[rw], tg->slice_end[rw], jiffies);
809}
810
811static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
812 unsigned long *wait)
813{
814 bool rw = bio_data_dir(bio);
815 unsigned int io_allowed;
816 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
817 u64 tmp;
818
819 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
820
821 /* Slice has just started. Consider one slice interval */
822 if (!jiffy_elapsed)
823 jiffy_elapsed_rnd = throtl_slice;
824
825 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
826
827 /*
828 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
829 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
830 * will allow dispatch after 1 second and after that slice should
831 * have been trimmed.
832 */
833
834 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
835 do_div(tmp, HZ);
836
837 if (tmp > UINT_MAX)
838 io_allowed = UINT_MAX;
839 else
840 io_allowed = tmp;
841
842 if (tg->io_disp[rw] + 1 <= io_allowed) {
843 if (wait)
844 *wait = 0;
845 return 1;
846 }
847
848 /* Calc approx time to dispatch */
849 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
850
851 if (jiffy_wait > jiffy_elapsed)
852 jiffy_wait = jiffy_wait - jiffy_elapsed;
853 else
854 jiffy_wait = 1;
855
856 if (wait)
857 *wait = jiffy_wait;
858 return 0;
859}
860
861static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
862 unsigned long *wait)
863{
864 bool rw = bio_data_dir(bio);
865 u64 bytes_allowed, extra_bytes, tmp;
866 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
867
868 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
869
870 /* Slice has just started. Consider one slice interval */
871 if (!jiffy_elapsed)
872 jiffy_elapsed_rnd = throtl_slice;
873
874 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
875
876 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
877 do_div(tmp, HZ);
878 bytes_allowed = tmp;
879
880 if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
881 if (wait)
882 *wait = 0;
883 return 1;
884 }
885
886 /* Calc approx time to dispatch */
887 extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
888 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
889
890 if (!jiffy_wait)
891 jiffy_wait = 1;
892
893 /*
894 * This wait time is without taking into consideration the rounding
895 * up we did. Add that time also.
896 */
897 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
898 if (wait)
899 *wait = jiffy_wait;
900 return 0;
901}
902
903/*
904 * Returns whether one can dispatch a bio or not. Also returns approx number
905 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
906 */
907static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
908 unsigned long *wait)
909{
910 bool rw = bio_data_dir(bio);
911 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
912
913 /*
914 * Currently whole state machine of group depends on first bio
915 * queued in the group bio list. So one should not be calling
916 * this function with a different bio if there are other bios
917 * queued.
918 */
919 BUG_ON(tg->service_queue.nr_queued[rw] &&
920 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
921
922 /* If tg->bps = -1, then BW is unlimited */
923 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
924 if (wait)
925 *wait = 0;
926 return 1;
927 }
928
929 /*
930 * If previous slice expired, start a new one otherwise renew/extend
931 * existing slice to make sure it is at least throtl_slice interval
932 * long since now.
933 */
934 if (throtl_slice_used(tg, rw))
935 throtl_start_new_slice(tg, rw);
936 else {
937 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
938 throtl_extend_slice(tg, rw, jiffies + throtl_slice);
939 }
940
941 if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
942 tg_with_in_iops_limit(tg, bio, &iops_wait)) {
943 if (wait)
944 *wait = 0;
945 return 1;
946 }
947
948 max_wait = max(bps_wait, iops_wait);
949
950 if (wait)
951 *wait = max_wait;
952
953 if (time_before(tg->slice_end[rw], jiffies + max_wait))
954 throtl_extend_slice(tg, rw, jiffies + max_wait);
955
956 return 0;
957}
958
959static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
960 int rw)
961{
962 struct throtl_grp *tg = blkg_to_tg(blkg);
963 struct tg_stats_cpu *stats_cpu;
964 unsigned long flags;
965
966 /* If per cpu stats are not allocated yet, don't do any accounting. */
967 if (tg->stats_cpu == NULL)
968 return;
969
970 /*
971 * Disabling interrupts to provide mutual exclusion between two
972 * writes on same cpu. It probably is not needed for 64bit. Not
973 * optimizing that case yet.
974 */
975 local_irq_save(flags);
976
977 stats_cpu = this_cpu_ptr(tg->stats_cpu);
978
979 blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
980 blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
981
982 local_irq_restore(flags);
983}
984
985static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
986{
987 bool rw = bio_data_dir(bio);
988
989 /* Charge the bio to the group */
990 tg->bytes_disp[rw] += bio->bi_iter.bi_size;
991 tg->io_disp[rw]++;
992
993 /*
994 * REQ_THROTTLED is used to prevent the same bio to be throttled
995 * more than once as a throttled bio will go through blk-throtl the
996 * second time when it eventually gets issued. Set it when a bio
997 * is being charged to a tg.
998 *
999 * Dispatch stats aren't recursive and each @bio should only be
1000 * accounted by the @tg it was originally associated with. Let's
1001 * update the stats when setting REQ_THROTTLED for the first time
1002 * which is guaranteed to be for the @bio's original tg.
1003 */
1004 if (!(bio->bi_rw & REQ_THROTTLED)) {
1005 bio->bi_rw |= REQ_THROTTLED;
1006 throtl_update_dispatch_stats(tg_to_blkg(tg),
1007 bio->bi_iter.bi_size, bio->bi_rw);
1008 }
1009}
1010
1011/**
1012 * throtl_add_bio_tg - add a bio to the specified throtl_grp
1013 * @bio: bio to add
1014 * @qn: qnode to use
1015 * @tg: the target throtl_grp
1016 *
1017 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
1018 * tg->qnode_on_self[] is used.
1019 */
1020static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
1021 struct throtl_grp *tg)
1022{
1023 struct throtl_service_queue *sq = &tg->service_queue;
1024 bool rw = bio_data_dir(bio);
1025
1026 if (!qn)
1027 qn = &tg->qnode_on_self[rw];
1028
1029 /*
1030 * If @tg doesn't currently have any bios queued in the same
1031 * direction, queueing @bio can change when @tg should be
1032 * dispatched. Mark that @tg was empty. This is automatically
1033 * cleaered on the next tg_update_disptime().
1034 */
1035 if (!sq->nr_queued[rw])
1036 tg->flags |= THROTL_TG_WAS_EMPTY;
1037
1038 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
1039
1040 sq->nr_queued[rw]++;
1041 throtl_enqueue_tg(tg);
1042}
1043
1044static void tg_update_disptime(struct throtl_grp *tg)
1045{
1046 struct throtl_service_queue *sq = &tg->service_queue;
1047 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1048 struct bio *bio;
1049
1050 if ((bio = throtl_peek_queued(&sq->queued[READ])))
1051 tg_may_dispatch(tg, bio, &read_wait);
1052
1053 if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
1054 tg_may_dispatch(tg, bio, &write_wait);
1055
1056 min_wait = min(read_wait, write_wait);
1057 disptime = jiffies + min_wait;
1058
1059 /* Update dispatch time */
1060 throtl_dequeue_tg(tg);
1061 tg->disptime = disptime;
1062 throtl_enqueue_tg(tg);
1063
1064 /* see throtl_add_bio_tg() */
1065 tg->flags &= ~THROTL_TG_WAS_EMPTY;
1066}
1067
1068static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1069 struct throtl_grp *parent_tg, bool rw)
1070{
1071 if (throtl_slice_used(parent_tg, rw)) {
1072 throtl_start_new_slice_with_credit(parent_tg, rw,
1073 child_tg->slice_start[rw]);
1074 }
1075
1076}
1077
1078static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1079{
1080 struct throtl_service_queue *sq = &tg->service_queue;
1081 struct throtl_service_queue *parent_sq = sq->parent_sq;
1082 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1083 struct throtl_grp *tg_to_put = NULL;
1084 struct bio *bio;
1085
1086 /*
1087 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1088 * from @tg may put its reference and @parent_sq might end up
1089 * getting released prematurely. Remember the tg to put and put it
1090 * after @bio is transferred to @parent_sq.
1091 */
1092 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1093 sq->nr_queued[rw]--;
1094
1095 throtl_charge_bio(tg, bio);
1096
1097 /*
1098 * If our parent is another tg, we just need to transfer @bio to
1099 * the parent using throtl_add_bio_tg(). If our parent is
1100 * @td->service_queue, @bio is ready to be issued. Put it on its
1101 * bio_lists[] and decrease total number queued. The caller is
1102 * responsible for issuing these bios.
1103 */
1104 if (parent_tg) {
1105 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1106 start_parent_slice_with_credit(tg, parent_tg, rw);
1107 } else {
1108 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1109 &parent_sq->queued[rw]);
1110 BUG_ON(tg->td->nr_queued[rw] <= 0);
1111 tg->td->nr_queued[rw]--;
1112 }
1113
1114 throtl_trim_slice(tg, rw);
1115
1116 if (tg_to_put)
1117 blkg_put(tg_to_blkg(tg_to_put));
1118}
1119
1120static int throtl_dispatch_tg(struct throtl_grp *tg)
1121{
1122 struct throtl_service_queue *sq = &tg->service_queue;
1123 unsigned int nr_reads = 0, nr_writes = 0;
1124 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
1125 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
1126 struct bio *bio;
1127
1128 /* Try to dispatch 75% READS and 25% WRITES */
1129
1130 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1131 tg_may_dispatch(tg, bio, NULL)) {
1132
1133 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1134 nr_reads++;
1135
1136 if (nr_reads >= max_nr_reads)
1137 break;
1138 }
1139
1140 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1141 tg_may_dispatch(tg, bio, NULL)) {
1142
1143 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1144 nr_writes++;
1145
1146 if (nr_writes >= max_nr_writes)
1147 break;
1148 }
1149
1150 return nr_reads + nr_writes;
1151}
1152
1153static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1154{
1155 unsigned int nr_disp = 0;
1156
1157 while (1) {
1158 struct throtl_grp *tg = throtl_rb_first(parent_sq);
1159 struct throtl_service_queue *sq = &tg->service_queue;
1160
1161 if (!tg)
1162 break;
1163
1164 if (time_before(jiffies, tg->disptime))
1165 break;
1166
1167 throtl_dequeue_tg(tg);
1168
1169 nr_disp += throtl_dispatch_tg(tg);
1170
1171 if (sq->nr_queued[0] || sq->nr_queued[1])
1172 tg_update_disptime(tg);
1173
1174 if (nr_disp >= throtl_quantum)
1175 break;
1176 }
1177
1178 return nr_disp;
1179}
1180
1181/**
1182 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1183 * @arg: the throtl_service_queue being serviced
1184 *
1185 * This timer is armed when a child throtl_grp with active bio's become
1186 * pending and queued on the service_queue's pending_tree and expires when
1187 * the first child throtl_grp should be dispatched. This function
1188 * dispatches bio's from the children throtl_grps to the parent
1189 * service_queue.
1190 *
1191 * If the parent's parent is another throtl_grp, dispatching is propagated
1192 * by either arming its pending_timer or repeating dispatch directly. If
1193 * the top-level service_tree is reached, throtl_data->dispatch_work is
1194 * kicked so that the ready bio's are issued.
1195 */
1196static void throtl_pending_timer_fn(unsigned long arg)
1197{
1198 struct throtl_service_queue *sq = (void *)arg;
1199 struct throtl_grp *tg = sq_to_tg(sq);
1200 struct throtl_data *td = sq_to_td(sq);
1201 struct request_queue *q = td->queue;
1202 struct throtl_service_queue *parent_sq;
1203 bool dispatched;
1204 int ret;
1205
1206 spin_lock_irq(q->queue_lock);
1207again:
1208 parent_sq = sq->parent_sq;
1209 dispatched = false;
1210
1211 while (true) {
1212 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1213 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1214 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1215
1216 ret = throtl_select_dispatch(sq);
1217 if (ret) {
1218 throtl_log(sq, "bios disp=%u", ret);
1219 dispatched = true;
1220 }
1221
1222 if (throtl_schedule_next_dispatch(sq, false))
1223 break;
1224
1225 /* this dispatch windows is still open, relax and repeat */
1226 spin_unlock_irq(q->queue_lock);
1227 cpu_relax();
1228 spin_lock_irq(q->queue_lock);
1229 }
1230
1231 if (!dispatched)
1232 goto out_unlock;
1233
1234 if (parent_sq) {
1235 /* @parent_sq is another throl_grp, propagate dispatch */
1236 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1237 tg_update_disptime(tg);
1238 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1239 /* window is already open, repeat dispatching */
1240 sq = parent_sq;
1241 tg = sq_to_tg(sq);
1242 goto again;
1243 }
1244 }
1245 } else {
1246 /* reached the top-level, queue issueing */
1247 queue_work(kthrotld_workqueue, &td->dispatch_work);
1248 }
1249out_unlock:
1250 spin_unlock_irq(q->queue_lock);
1251}
1252
1253/**
1254 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1255 * @work: work item being executed
1256 *
1257 * This function is queued for execution when bio's reach the bio_lists[]
1258 * of throtl_data->service_queue. Those bio's are ready and issued by this
1259 * function.
1260 */
1261void blk_throtl_dispatch_work_fn(struct work_struct *work)
1262{
1263 struct throtl_data *td = container_of(work, struct throtl_data,
1264 dispatch_work);
1265 struct throtl_service_queue *td_sq = &td->service_queue;
1266 struct request_queue *q = td->queue;
1267 struct bio_list bio_list_on_stack;
1268 struct bio *bio;
1269 struct blk_plug plug;
1270 int rw;
1271
1272 bio_list_init(&bio_list_on_stack);
1273
1274 spin_lock_irq(q->queue_lock);
1275 for (rw = READ; rw <= WRITE; rw++)
1276 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1277 bio_list_add(&bio_list_on_stack, bio);
1278 spin_unlock_irq(q->queue_lock);
1279
1280 if (!bio_list_empty(&bio_list_on_stack)) {
1281 blk_start_plug(&plug);
1282 while((bio = bio_list_pop(&bio_list_on_stack)))
1283 generic_make_request(bio);
1284 blk_finish_plug(&plug);
1285 }
1286}
1287
1288static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
1289 struct blkg_policy_data *pd, int off)
1290{
1291 struct throtl_grp *tg = pd_to_tg(pd);
1292 struct blkg_rwstat rwstat = { }, tmp;
1293 int i, cpu;
1294
1295 for_each_possible_cpu(cpu) {
1296 struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
1297
1298 tmp = blkg_rwstat_read((void *)sc + off);
1299 for (i = 0; i < BLKG_RWSTAT_NR; i++)
1300 rwstat.cnt[i] += tmp.cnt[i];
1301 }
1302
1303 return __blkg_prfill_rwstat(sf, pd, &rwstat);
1304}
1305
1306static int tg_print_cpu_rwstat(struct seq_file *sf, void *v)
1307{
1308 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_cpu_rwstat,
1309 &blkcg_policy_throtl, seq_cft(sf)->private, true);
1310 return 0;
1311}
1312
1313static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1314 int off)
1315{
1316 struct throtl_grp *tg = pd_to_tg(pd);
1317 u64 v = *(u64 *)((void *)tg + off);
1318
1319 if (v == -1)
1320 return 0;
1321 return __blkg_prfill_u64(sf, pd, v);
1322}
1323
1324static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1325 int off)
1326{
1327 struct throtl_grp *tg = pd_to_tg(pd);
1328 unsigned int v = *(unsigned int *)((void *)tg + off);
1329
1330 if (v == -1)
1331 return 0;
1332 return __blkg_prfill_u64(sf, pd, v);
1333}
1334
1335static int tg_print_conf_u64(struct seq_file *sf, void *v)
1336{
1337 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1338 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1339 return 0;
1340}
1341
1342static int tg_print_conf_uint(struct seq_file *sf, void *v)
1343{
1344 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1345 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1346 return 0;
1347}
1348
1349static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft,
1350 const char *buf, bool is_u64)
1351{
1352 struct blkcg *blkcg = css_to_blkcg(css);
1353 struct blkg_conf_ctx ctx;
1354 struct throtl_grp *tg;
1355 struct throtl_service_queue *sq;
1356 struct blkcg_gq *blkg;
1357 struct cgroup_subsys_state *pos_css;
1358 int ret;
1359
1360 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1361 if (ret)
1362 return ret;
1363
1364 tg = blkg_to_tg(ctx.blkg);
1365 sq = &tg->service_queue;
1366
1367 if (!ctx.v)
1368 ctx.v = -1;
1369
1370 if (is_u64)
1371 *(u64 *)((void *)tg + cft->private) = ctx.v;
1372 else
1373 *(unsigned int *)((void *)tg + cft->private) = ctx.v;
1374
1375 throtl_log(&tg->service_queue,
1376 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1377 tg->bps[READ], tg->bps[WRITE],
1378 tg->iops[READ], tg->iops[WRITE]);
1379
1380 /*
1381 * Update has_rules[] flags for the updated tg's subtree. A tg is
1382 * considered to have rules if either the tg itself or any of its
1383 * ancestors has rules. This identifies groups without any
1384 * restrictions in the whole hierarchy and allows them to bypass
1385 * blk-throttle.
1386 */
1387 blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg)
1388 tg_update_has_rules(blkg_to_tg(blkg));
1389
1390 /*
1391 * We're already holding queue_lock and know @tg is valid. Let's
1392 * apply the new config directly.
1393 *
1394 * Restart the slices for both READ and WRITES. It might happen
1395 * that a group's limit are dropped suddenly and we don't want to
1396 * account recently dispatched IO with new low rate.
1397 */
1398 throtl_start_new_slice(tg, 0);
1399 throtl_start_new_slice(tg, 1);
1400
1401 if (tg->flags & THROTL_TG_PENDING) {
1402 tg_update_disptime(tg);
1403 throtl_schedule_next_dispatch(sq->parent_sq, true);
1404 }
1405
1406 blkg_conf_finish(&ctx);
1407 return 0;
1408}
1409
1410static int tg_set_conf_u64(struct cgroup_subsys_state *css, struct cftype *cft,
1411 char *buf)
1412{
1413 return tg_set_conf(css, cft, buf, true);
1414}
1415
1416static int tg_set_conf_uint(struct cgroup_subsys_state *css, struct cftype *cft,
1417 char *buf)
1418{
1419 return tg_set_conf(css, cft, buf, false);
1420}
1421
1422static struct cftype throtl_files[] = {
1423 {
1424 .name = "throttle.read_bps_device",
1425 .private = offsetof(struct throtl_grp, bps[READ]),
1426 .seq_show = tg_print_conf_u64,
1427 .write_string = tg_set_conf_u64,
1428 },
1429 {
1430 .name = "throttle.write_bps_device",
1431 .private = offsetof(struct throtl_grp, bps[WRITE]),
1432 .seq_show = tg_print_conf_u64,
1433 .write_string = tg_set_conf_u64,
1434 },
1435 {
1436 .name = "throttle.read_iops_device",
1437 .private = offsetof(struct throtl_grp, iops[READ]),
1438 .seq_show = tg_print_conf_uint,
1439 .write_string = tg_set_conf_uint,
1440 },
1441 {
1442 .name = "throttle.write_iops_device",
1443 .private = offsetof(struct throtl_grp, iops[WRITE]),
1444 .seq_show = tg_print_conf_uint,
1445 .write_string = tg_set_conf_uint,
1446 },
1447 {
1448 .name = "throttle.io_service_bytes",
1449 .private = offsetof(struct tg_stats_cpu, service_bytes),
1450 .seq_show = tg_print_cpu_rwstat,
1451 },
1452 {
1453 .name = "throttle.io_serviced",
1454 .private = offsetof(struct tg_stats_cpu, serviced),
1455 .seq_show = tg_print_cpu_rwstat,
1456 },
1457 { } /* terminate */
1458};
1459
1460static void throtl_shutdown_wq(struct request_queue *q)
1461{
1462 struct throtl_data *td = q->td;
1463
1464 cancel_work_sync(&td->dispatch_work);
1465}
1466
1467static struct blkcg_policy blkcg_policy_throtl = {
1468 .pd_size = sizeof(struct throtl_grp),
1469 .cftypes = throtl_files,
1470
1471 .pd_init_fn = throtl_pd_init,
1472 .pd_online_fn = throtl_pd_online,
1473 .pd_exit_fn = throtl_pd_exit,
1474 .pd_reset_stats_fn = throtl_pd_reset_stats,
1475};
1476
1477bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
1478{
1479 struct throtl_data *td = q->td;
1480 struct throtl_qnode *qn = NULL;
1481 struct throtl_grp *tg;
1482 struct throtl_service_queue *sq;
1483 bool rw = bio_data_dir(bio);
1484 struct blkcg *blkcg;
1485 bool throttled = false;
1486
1487 /* see throtl_charge_bio() */
1488 if (bio->bi_rw & REQ_THROTTLED)
1489 goto out;
1490
1491 /*
1492 * A throtl_grp pointer retrieved under rcu can be used to access
1493 * basic fields like stats and io rates. If a group has no rules,
1494 * just update the dispatch stats in lockless manner and return.
1495 */
1496 rcu_read_lock();
1497 blkcg = bio_blkcg(bio);
1498 tg = throtl_lookup_tg(td, blkcg);
1499 if (tg) {
1500 if (!tg->has_rules[rw]) {
1501 throtl_update_dispatch_stats(tg_to_blkg(tg),
1502 bio->bi_iter.bi_size, bio->bi_rw);
1503 goto out_unlock_rcu;
1504 }
1505 }
1506
1507 /*
1508 * Either group has not been allocated yet or it is not an unlimited
1509 * IO group
1510 */
1511 spin_lock_irq(q->queue_lock);
1512 tg = throtl_lookup_create_tg(td, blkcg);
1513 if (unlikely(!tg))
1514 goto out_unlock;
1515
1516 sq = &tg->service_queue;
1517
1518 while (true) {
1519 /* throtl is FIFO - if bios are already queued, should queue */
1520 if (sq->nr_queued[rw])
1521 break;
1522
1523 /* if above limits, break to queue */
1524 if (!tg_may_dispatch(tg, bio, NULL))
1525 break;
1526
1527 /* within limits, let's charge and dispatch directly */
1528 throtl_charge_bio(tg, bio);
1529
1530 /*
1531 * We need to trim slice even when bios are not being queued
1532 * otherwise it might happen that a bio is not queued for
1533 * a long time and slice keeps on extending and trim is not
1534 * called for a long time. Now if limits are reduced suddenly
1535 * we take into account all the IO dispatched so far at new
1536 * low rate and * newly queued IO gets a really long dispatch
1537 * time.
1538 *
1539 * So keep on trimming slice even if bio is not queued.
1540 */
1541 throtl_trim_slice(tg, rw);
1542
1543 /*
1544 * @bio passed through this layer without being throttled.
1545 * Climb up the ladder. If we''re already at the top, it
1546 * can be executed directly.
1547 */
1548 qn = &tg->qnode_on_parent[rw];
1549 sq = sq->parent_sq;
1550 tg = sq_to_tg(sq);
1551 if (!tg)
1552 goto out_unlock;
1553 }
1554
1555 /* out-of-limit, queue to @tg */
1556 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1557 rw == READ ? 'R' : 'W',
1558 tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
1559 tg->io_disp[rw], tg->iops[rw],
1560 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1561
1562 bio_associate_current(bio);
1563 tg->td->nr_queued[rw]++;
1564 throtl_add_bio_tg(bio, qn, tg);
1565 throttled = true;
1566
1567 /*
1568 * Update @tg's dispatch time and force schedule dispatch if @tg
1569 * was empty before @bio. The forced scheduling isn't likely to
1570 * cause undue delay as @bio is likely to be dispatched directly if
1571 * its @tg's disptime is not in the future.
1572 */
1573 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1574 tg_update_disptime(tg);
1575 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
1576 }
1577
1578out_unlock:
1579 spin_unlock_irq(q->queue_lock);
1580out_unlock_rcu:
1581 rcu_read_unlock();
1582out:
1583 /*
1584 * As multiple blk-throtls may stack in the same issue path, we
1585 * don't want bios to leave with the flag set. Clear the flag if
1586 * being issued.
1587 */
1588 if (!throttled)
1589 bio->bi_rw &= ~REQ_THROTTLED;
1590 return throttled;
1591}
1592
1593/*
1594 * Dispatch all bios from all children tg's queued on @parent_sq. On
1595 * return, @parent_sq is guaranteed to not have any active children tg's
1596 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1597 */
1598static void tg_drain_bios(struct throtl_service_queue *parent_sq)
1599{
1600 struct throtl_grp *tg;
1601
1602 while ((tg = throtl_rb_first(parent_sq))) {
1603 struct throtl_service_queue *sq = &tg->service_queue;
1604 struct bio *bio;
1605
1606 throtl_dequeue_tg(tg);
1607
1608 while ((bio = throtl_peek_queued(&sq->queued[READ])))
1609 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1610 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
1611 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1612 }
1613}
1614
1615/**
1616 * blk_throtl_drain - drain throttled bios
1617 * @q: request_queue to drain throttled bios for
1618 *
1619 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1620 */
1621void blk_throtl_drain(struct request_queue *q)
1622 __releases(q->queue_lock) __acquires(q->queue_lock)
1623{
1624 struct throtl_data *td = q->td;
1625 struct blkcg_gq *blkg;
1626 struct cgroup_subsys_state *pos_css;
1627 struct bio *bio;
1628 int rw;
1629
1630 queue_lockdep_assert_held(q);
1631 rcu_read_lock();
1632
1633 /*
1634 * Drain each tg while doing post-order walk on the blkg tree, so
1635 * that all bios are propagated to td->service_queue. It'd be
1636 * better to walk service_queue tree directly but blkg walk is
1637 * easier.
1638 */
1639 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
1640 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
1641
1642 /* finally, transfer bios from top-level tg's into the td */
1643 tg_drain_bios(&td->service_queue);
1644
1645 rcu_read_unlock();
1646 spin_unlock_irq(q->queue_lock);
1647
1648 /* all bios now should be in td->service_queue, issue them */
1649 for (rw = READ; rw <= WRITE; rw++)
1650 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
1651 NULL)))
1652 generic_make_request(bio);
1653
1654 spin_lock_irq(q->queue_lock);
1655}
1656
1657int blk_throtl_init(struct request_queue *q)
1658{
1659 struct throtl_data *td;
1660 int ret;
1661
1662 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1663 if (!td)
1664 return -ENOMEM;
1665
1666 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
1667 throtl_service_queue_init(&td->service_queue, NULL);
1668
1669 q->td = td;
1670 td->queue = q;
1671
1672 /* activate policy */
1673 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1674 if (ret)
1675 kfree(td);
1676 return ret;
1677}
1678
1679void blk_throtl_exit(struct request_queue *q)
1680{
1681 BUG_ON(!q->td);
1682 throtl_shutdown_wq(q);
1683 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1684 kfree(q->td);
1685}
1686
1687static int __init throtl_init(void)
1688{
1689 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1690 if (!kthrotld_workqueue)
1691 panic("Failed to create kthrotld\n");
1692
1693 return blkcg_policy_register(&blkcg_policy_throtl);
1694}
1695
1696module_init(throtl_init);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Interface for controlling IO bandwidth on a request queue
4 *
5 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
6 */
7
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/blkdev.h>
11#include <linux/bio.h>
12#include <linux/blktrace_api.h>
13#include "blk.h"
14#include "blk-cgroup-rwstat.h"
15#include "blk-stat.h"
16#include "blk-throttle.h"
17
18/* Max dispatch from a group in 1 round */
19#define THROTL_GRP_QUANTUM 8
20
21/* Total max dispatch from all groups in one round */
22#define THROTL_QUANTUM 32
23
24/* Throttling is performed over a slice and after that slice is renewed */
25#define DFL_THROTL_SLICE_HD (HZ / 10)
26#define DFL_THROTL_SLICE_SSD (HZ / 50)
27#define MAX_THROTL_SLICE (HZ)
28
29/* A workqueue to queue throttle related work */
30static struct workqueue_struct *kthrotld_workqueue;
31
32#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
33
34struct throtl_data
35{
36 /* service tree for active throtl groups */
37 struct throtl_service_queue service_queue;
38
39 struct request_queue *queue;
40
41 /* Total Number of queued bios on READ and WRITE lists */
42 unsigned int nr_queued[2];
43
44 unsigned int throtl_slice;
45
46 /* Work for dispatching throttled bios */
47 struct work_struct dispatch_work;
48
49 bool track_bio_latency;
50};
51
52static void throtl_pending_timer_fn(struct timer_list *t);
53
54static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
55{
56 return pd_to_blkg(&tg->pd);
57}
58
59/**
60 * sq_to_tg - return the throl_grp the specified service queue belongs to
61 * @sq: the throtl_service_queue of interest
62 *
63 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
64 * embedded in throtl_data, %NULL is returned.
65 */
66static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
67{
68 if (sq && sq->parent_sq)
69 return container_of(sq, struct throtl_grp, service_queue);
70 else
71 return NULL;
72}
73
74/**
75 * sq_to_td - return throtl_data the specified service queue belongs to
76 * @sq: the throtl_service_queue of interest
77 *
78 * A service_queue can be embedded in either a throtl_grp or throtl_data.
79 * Determine the associated throtl_data accordingly and return it.
80 */
81static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
82{
83 struct throtl_grp *tg = sq_to_tg(sq);
84
85 if (tg)
86 return tg->td;
87 else
88 return container_of(sq, struct throtl_data, service_queue);
89}
90
91static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
92{
93 struct blkcg_gq *blkg = tg_to_blkg(tg);
94
95 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
96 return U64_MAX;
97
98 return tg->bps[rw];
99}
100
101static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
102{
103 struct blkcg_gq *blkg = tg_to_blkg(tg);
104
105 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
106 return UINT_MAX;
107
108 return tg->iops[rw];
109}
110
111/**
112 * throtl_log - log debug message via blktrace
113 * @sq: the service_queue being reported
114 * @fmt: printf format string
115 * @args: printf args
116 *
117 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
118 * throtl_grp; otherwise, just "throtl".
119 */
120#define throtl_log(sq, fmt, args...) do { \
121 struct throtl_grp *__tg = sq_to_tg((sq)); \
122 struct throtl_data *__td = sq_to_td((sq)); \
123 \
124 (void)__td; \
125 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
126 break; \
127 if ((__tg)) { \
128 blk_add_cgroup_trace_msg(__td->queue, \
129 &tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\
130 } else { \
131 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
132 } \
133} while (0)
134
135static inline unsigned int throtl_bio_data_size(struct bio *bio)
136{
137 /* assume it's one sector */
138 if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
139 return 512;
140 return bio->bi_iter.bi_size;
141}
142
143static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
144{
145 INIT_LIST_HEAD(&qn->node);
146 bio_list_init(&qn->bios);
147 qn->tg = tg;
148}
149
150/**
151 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
152 * @bio: bio being added
153 * @qn: qnode to add bio to
154 * @queued: the service_queue->queued[] list @qn belongs to
155 *
156 * Add @bio to @qn and put @qn on @queued if it's not already on.
157 * @qn->tg's reference count is bumped when @qn is activated. See the
158 * comment on top of throtl_qnode definition for details.
159 */
160static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
161 struct list_head *queued)
162{
163 bio_list_add(&qn->bios, bio);
164 if (list_empty(&qn->node)) {
165 list_add_tail(&qn->node, queued);
166 blkg_get(tg_to_blkg(qn->tg));
167 }
168}
169
170/**
171 * throtl_peek_queued - peek the first bio on a qnode list
172 * @queued: the qnode list to peek
173 */
174static struct bio *throtl_peek_queued(struct list_head *queued)
175{
176 struct throtl_qnode *qn;
177 struct bio *bio;
178
179 if (list_empty(queued))
180 return NULL;
181
182 qn = list_first_entry(queued, struct throtl_qnode, node);
183 bio = bio_list_peek(&qn->bios);
184 WARN_ON_ONCE(!bio);
185 return bio;
186}
187
188/**
189 * throtl_pop_queued - pop the first bio form a qnode list
190 * @queued: the qnode list to pop a bio from
191 * @tg_to_put: optional out argument for throtl_grp to put
192 *
193 * Pop the first bio from the qnode list @queued. After popping, the first
194 * qnode is removed from @queued if empty or moved to the end of @queued so
195 * that the popping order is round-robin.
196 *
197 * When the first qnode is removed, its associated throtl_grp should be put
198 * too. If @tg_to_put is NULL, this function automatically puts it;
199 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
200 * responsible for putting it.
201 */
202static struct bio *throtl_pop_queued(struct list_head *queued,
203 struct throtl_grp **tg_to_put)
204{
205 struct throtl_qnode *qn;
206 struct bio *bio;
207
208 if (list_empty(queued))
209 return NULL;
210
211 qn = list_first_entry(queued, struct throtl_qnode, node);
212 bio = bio_list_pop(&qn->bios);
213 WARN_ON_ONCE(!bio);
214
215 if (bio_list_empty(&qn->bios)) {
216 list_del_init(&qn->node);
217 if (tg_to_put)
218 *tg_to_put = qn->tg;
219 else
220 blkg_put(tg_to_blkg(qn->tg));
221 } else {
222 list_move_tail(&qn->node, queued);
223 }
224
225 return bio;
226}
227
228/* init a service_queue, assumes the caller zeroed it */
229static void throtl_service_queue_init(struct throtl_service_queue *sq)
230{
231 INIT_LIST_HEAD(&sq->queued[READ]);
232 INIT_LIST_HEAD(&sq->queued[WRITE]);
233 sq->pending_tree = RB_ROOT_CACHED;
234 timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
235}
236
237static struct blkg_policy_data *throtl_pd_alloc(struct gendisk *disk,
238 struct blkcg *blkcg, gfp_t gfp)
239{
240 struct throtl_grp *tg;
241 int rw;
242
243 tg = kzalloc_node(sizeof(*tg), gfp, disk->node_id);
244 if (!tg)
245 return NULL;
246
247 if (blkg_rwstat_init(&tg->stat_bytes, gfp))
248 goto err_free_tg;
249
250 if (blkg_rwstat_init(&tg->stat_ios, gfp))
251 goto err_exit_stat_bytes;
252
253 throtl_service_queue_init(&tg->service_queue);
254
255 for (rw = READ; rw <= WRITE; rw++) {
256 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
257 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
258 }
259
260 RB_CLEAR_NODE(&tg->rb_node);
261 tg->bps[READ] = U64_MAX;
262 tg->bps[WRITE] = U64_MAX;
263 tg->iops[READ] = UINT_MAX;
264 tg->iops[WRITE] = UINT_MAX;
265
266 return &tg->pd;
267
268err_exit_stat_bytes:
269 blkg_rwstat_exit(&tg->stat_bytes);
270err_free_tg:
271 kfree(tg);
272 return NULL;
273}
274
275static void throtl_pd_init(struct blkg_policy_data *pd)
276{
277 struct throtl_grp *tg = pd_to_tg(pd);
278 struct blkcg_gq *blkg = tg_to_blkg(tg);
279 struct throtl_data *td = blkg->q->td;
280 struct throtl_service_queue *sq = &tg->service_queue;
281
282 /*
283 * If on the default hierarchy, we switch to properly hierarchical
284 * behavior where limits on a given throtl_grp are applied to the
285 * whole subtree rather than just the group itself. e.g. If 16M
286 * read_bps limit is set on a parent group, summary bps of
287 * parent group and its subtree groups can't exceed 16M for the
288 * device.
289 *
290 * If not on the default hierarchy, the broken flat hierarchy
291 * behavior is retained where all throtl_grps are treated as if
292 * they're all separate root groups right below throtl_data.
293 * Limits of a group don't interact with limits of other groups
294 * regardless of the position of the group in the hierarchy.
295 */
296 sq->parent_sq = &td->service_queue;
297 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
298 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
299 tg->td = td;
300}
301
302/*
303 * Set has_rules[] if @tg or any of its parents have limits configured.
304 * This doesn't require walking up to the top of the hierarchy as the
305 * parent's has_rules[] is guaranteed to be correct.
306 */
307static void tg_update_has_rules(struct throtl_grp *tg)
308{
309 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
310 int rw;
311
312 for (rw = READ; rw <= WRITE; rw++) {
313 tg->has_rules_iops[rw] =
314 (parent_tg && parent_tg->has_rules_iops[rw]) ||
315 tg_iops_limit(tg, rw) != UINT_MAX;
316 tg->has_rules_bps[rw] =
317 (parent_tg && parent_tg->has_rules_bps[rw]) ||
318 tg_bps_limit(tg, rw) != U64_MAX;
319 }
320}
321
322static void throtl_pd_online(struct blkg_policy_data *pd)
323{
324 struct throtl_grp *tg = pd_to_tg(pd);
325 /*
326 * We don't want new groups to escape the limits of its ancestors.
327 * Update has_rules[] after a new group is brought online.
328 */
329 tg_update_has_rules(tg);
330}
331
332static void throtl_pd_free(struct blkg_policy_data *pd)
333{
334 struct throtl_grp *tg = pd_to_tg(pd);
335
336 del_timer_sync(&tg->service_queue.pending_timer);
337 blkg_rwstat_exit(&tg->stat_bytes);
338 blkg_rwstat_exit(&tg->stat_ios);
339 kfree(tg);
340}
341
342static struct throtl_grp *
343throtl_rb_first(struct throtl_service_queue *parent_sq)
344{
345 struct rb_node *n;
346
347 n = rb_first_cached(&parent_sq->pending_tree);
348 WARN_ON_ONCE(!n);
349 if (!n)
350 return NULL;
351 return rb_entry_tg(n);
352}
353
354static void throtl_rb_erase(struct rb_node *n,
355 struct throtl_service_queue *parent_sq)
356{
357 rb_erase_cached(n, &parent_sq->pending_tree);
358 RB_CLEAR_NODE(n);
359}
360
361static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
362{
363 struct throtl_grp *tg;
364
365 tg = throtl_rb_first(parent_sq);
366 if (!tg)
367 return;
368
369 parent_sq->first_pending_disptime = tg->disptime;
370}
371
372static void tg_service_queue_add(struct throtl_grp *tg)
373{
374 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
375 struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
376 struct rb_node *parent = NULL;
377 struct throtl_grp *__tg;
378 unsigned long key = tg->disptime;
379 bool leftmost = true;
380
381 while (*node != NULL) {
382 parent = *node;
383 __tg = rb_entry_tg(parent);
384
385 if (time_before(key, __tg->disptime))
386 node = &parent->rb_left;
387 else {
388 node = &parent->rb_right;
389 leftmost = false;
390 }
391 }
392
393 rb_link_node(&tg->rb_node, parent, node);
394 rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
395 leftmost);
396}
397
398static void throtl_enqueue_tg(struct throtl_grp *tg)
399{
400 if (!(tg->flags & THROTL_TG_PENDING)) {
401 tg_service_queue_add(tg);
402 tg->flags |= THROTL_TG_PENDING;
403 tg->service_queue.parent_sq->nr_pending++;
404 }
405}
406
407static void throtl_dequeue_tg(struct throtl_grp *tg)
408{
409 if (tg->flags & THROTL_TG_PENDING) {
410 struct throtl_service_queue *parent_sq =
411 tg->service_queue.parent_sq;
412
413 throtl_rb_erase(&tg->rb_node, parent_sq);
414 --parent_sq->nr_pending;
415 tg->flags &= ~THROTL_TG_PENDING;
416 }
417}
418
419/* Call with queue lock held */
420static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
421 unsigned long expires)
422{
423 unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
424
425 /*
426 * Since we are adjusting the throttle limit dynamically, the sleep
427 * time calculated according to previous limit might be invalid. It's
428 * possible the cgroup sleep time is very long and no other cgroups
429 * have IO running so notify the limit changes. Make sure the cgroup
430 * doesn't sleep too long to avoid the missed notification.
431 */
432 if (time_after(expires, max_expire))
433 expires = max_expire;
434 mod_timer(&sq->pending_timer, expires);
435 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
436 expires - jiffies, jiffies);
437}
438
439/**
440 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
441 * @sq: the service_queue to schedule dispatch for
442 * @force: force scheduling
443 *
444 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
445 * dispatch time of the first pending child. Returns %true if either timer
446 * is armed or there's no pending child left. %false if the current
447 * dispatch window is still open and the caller should continue
448 * dispatching.
449 *
450 * If @force is %true, the dispatch timer is always scheduled and this
451 * function is guaranteed to return %true. This is to be used when the
452 * caller can't dispatch itself and needs to invoke pending_timer
453 * unconditionally. Note that forced scheduling is likely to induce short
454 * delay before dispatch starts even if @sq->first_pending_disptime is not
455 * in the future and thus shouldn't be used in hot paths.
456 */
457static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
458 bool force)
459{
460 /* any pending children left? */
461 if (!sq->nr_pending)
462 return true;
463
464 update_min_dispatch_time(sq);
465
466 /* is the next dispatch time in the future? */
467 if (force || time_after(sq->first_pending_disptime, jiffies)) {
468 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
469 return true;
470 }
471
472 /* tell the caller to continue dispatching */
473 return false;
474}
475
476static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
477 bool rw, unsigned long start)
478{
479 tg->bytes_disp[rw] = 0;
480 tg->io_disp[rw] = 0;
481 tg->carryover_bytes[rw] = 0;
482 tg->carryover_ios[rw] = 0;
483
484 /*
485 * Previous slice has expired. We must have trimmed it after last
486 * bio dispatch. That means since start of last slice, we never used
487 * that bandwidth. Do try to make use of that bandwidth while giving
488 * credit.
489 */
490 if (time_after(start, tg->slice_start[rw]))
491 tg->slice_start[rw] = start;
492
493 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
494 throtl_log(&tg->service_queue,
495 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
496 rw == READ ? 'R' : 'W', tg->slice_start[rw],
497 tg->slice_end[rw], jiffies);
498}
499
500static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
501 bool clear_carryover)
502{
503 tg->bytes_disp[rw] = 0;
504 tg->io_disp[rw] = 0;
505 tg->slice_start[rw] = jiffies;
506 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
507 if (clear_carryover) {
508 tg->carryover_bytes[rw] = 0;
509 tg->carryover_ios[rw] = 0;
510 }
511
512 throtl_log(&tg->service_queue,
513 "[%c] new slice start=%lu end=%lu jiffies=%lu",
514 rw == READ ? 'R' : 'W', tg->slice_start[rw],
515 tg->slice_end[rw], jiffies);
516}
517
518static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
519 unsigned long jiffy_end)
520{
521 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
522}
523
524static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
525 unsigned long jiffy_end)
526{
527 throtl_set_slice_end(tg, rw, jiffy_end);
528 throtl_log(&tg->service_queue,
529 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
530 rw == READ ? 'R' : 'W', tg->slice_start[rw],
531 tg->slice_end[rw], jiffies);
532}
533
534/* Determine if previously allocated or extended slice is complete or not */
535static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
536{
537 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
538 return false;
539
540 return true;
541}
542
543static unsigned int calculate_io_allowed(u32 iops_limit,
544 unsigned long jiffy_elapsed)
545{
546 unsigned int io_allowed;
547 u64 tmp;
548
549 /*
550 * jiffy_elapsed should not be a big value as minimum iops can be
551 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
552 * will allow dispatch after 1 second and after that slice should
553 * have been trimmed.
554 */
555
556 tmp = (u64)iops_limit * jiffy_elapsed;
557 do_div(tmp, HZ);
558
559 if (tmp > UINT_MAX)
560 io_allowed = UINT_MAX;
561 else
562 io_allowed = tmp;
563
564 return io_allowed;
565}
566
567static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
568{
569 /*
570 * Can result be wider than 64 bits?
571 * We check against 62, not 64, due to ilog2 truncation.
572 */
573 if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62)
574 return U64_MAX;
575 return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
576}
577
578/* Trim the used slices and adjust slice start accordingly */
579static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
580{
581 unsigned long time_elapsed;
582 long long bytes_trim;
583 int io_trim;
584
585 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
586
587 /*
588 * If bps are unlimited (-1), then time slice don't get
589 * renewed. Don't try to trim the slice if slice is used. A new
590 * slice will start when appropriate.
591 */
592 if (throtl_slice_used(tg, rw))
593 return;
594
595 /*
596 * A bio has been dispatched. Also adjust slice_end. It might happen
597 * that initially cgroup limit was very low resulting in high
598 * slice_end, but later limit was bumped up and bio was dispatched
599 * sooner, then we need to reduce slice_end. A high bogus slice_end
600 * is bad because it does not allow new slice to start.
601 */
602
603 throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
604
605 time_elapsed = rounddown(jiffies - tg->slice_start[rw],
606 tg->td->throtl_slice);
607 if (!time_elapsed)
608 return;
609
610 bytes_trim = calculate_bytes_allowed(tg_bps_limit(tg, rw),
611 time_elapsed) +
612 tg->carryover_bytes[rw];
613 io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed) +
614 tg->carryover_ios[rw];
615 if (bytes_trim <= 0 && io_trim <= 0)
616 return;
617
618 tg->carryover_bytes[rw] = 0;
619 if ((long long)tg->bytes_disp[rw] >= bytes_trim)
620 tg->bytes_disp[rw] -= bytes_trim;
621 else
622 tg->bytes_disp[rw] = 0;
623
624 tg->carryover_ios[rw] = 0;
625 if ((int)tg->io_disp[rw] >= io_trim)
626 tg->io_disp[rw] -= io_trim;
627 else
628 tg->io_disp[rw] = 0;
629
630 tg->slice_start[rw] += time_elapsed;
631
632 throtl_log(&tg->service_queue,
633 "[%c] trim slice nr=%lu bytes=%lld io=%d start=%lu end=%lu jiffies=%lu",
634 rw == READ ? 'R' : 'W', time_elapsed / tg->td->throtl_slice,
635 bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw],
636 jiffies);
637}
638
639static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
640{
641 unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
642 u64 bps_limit = tg_bps_limit(tg, rw);
643 u32 iops_limit = tg_iops_limit(tg, rw);
644
645 /*
646 * If config is updated while bios are still throttled, calculate and
647 * accumulate how many bytes/ios are waited across changes. And
648 * carryover_bytes/ios will be used to calculate new wait time under new
649 * configuration.
650 */
651 if (bps_limit != U64_MAX)
652 tg->carryover_bytes[rw] +=
653 calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
654 tg->bytes_disp[rw];
655 if (iops_limit != UINT_MAX)
656 tg->carryover_ios[rw] +=
657 calculate_io_allowed(iops_limit, jiffy_elapsed) -
658 tg->io_disp[rw];
659}
660
661static void tg_update_carryover(struct throtl_grp *tg)
662{
663 if (tg->service_queue.nr_queued[READ])
664 __tg_update_carryover(tg, READ);
665 if (tg->service_queue.nr_queued[WRITE])
666 __tg_update_carryover(tg, WRITE);
667
668 /* see comments in struct throtl_grp for meaning of these fields. */
669 throtl_log(&tg->service_queue, "%s: %lld %lld %d %d\n", __func__,
670 tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
671 tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
672}
673
674static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
675 u32 iops_limit)
676{
677 bool rw = bio_data_dir(bio);
678 int io_allowed;
679 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
680
681 if (iops_limit == UINT_MAX) {
682 return 0;
683 }
684
685 jiffy_elapsed = jiffies - tg->slice_start[rw];
686
687 /* Round up to the next throttle slice, wait time must be nonzero */
688 jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
689 io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
690 tg->carryover_ios[rw];
691 if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed)
692 return 0;
693
694 /* Calc approx time to dispatch */
695 jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
696
697 /* make sure at least one io can be dispatched after waiting */
698 jiffy_wait = max(jiffy_wait, HZ / iops_limit + 1);
699 return jiffy_wait;
700}
701
702static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
703 u64 bps_limit)
704{
705 bool rw = bio_data_dir(bio);
706 long long bytes_allowed;
707 u64 extra_bytes;
708 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
709 unsigned int bio_size = throtl_bio_data_size(bio);
710
711 /* no need to throttle if this bio's bytes have been accounted */
712 if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
713 return 0;
714 }
715
716 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
717
718 /* Slice has just started. Consider one slice interval */
719 if (!jiffy_elapsed)
720 jiffy_elapsed_rnd = tg->td->throtl_slice;
721
722 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
723 bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
724 tg->carryover_bytes[rw];
725 if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
726 return 0;
727
728 /* Calc approx time to dispatch */
729 extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
730 jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
731
732 if (!jiffy_wait)
733 jiffy_wait = 1;
734
735 /*
736 * This wait time is without taking into consideration the rounding
737 * up we did. Add that time also.
738 */
739 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
740 return jiffy_wait;
741}
742
743/*
744 * Returns whether one can dispatch a bio or not. Also returns approx number
745 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
746 */
747static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
748 unsigned long *wait)
749{
750 bool rw = bio_data_dir(bio);
751 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
752 u64 bps_limit = tg_bps_limit(tg, rw);
753 u32 iops_limit = tg_iops_limit(tg, rw);
754
755 /*
756 * Currently whole state machine of group depends on first bio
757 * queued in the group bio list. So one should not be calling
758 * this function with a different bio if there are other bios
759 * queued.
760 */
761 BUG_ON(tg->service_queue.nr_queued[rw] &&
762 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
763
764 /* If tg->bps = -1, then BW is unlimited */
765 if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
766 tg->flags & THROTL_TG_CANCELING) {
767 if (wait)
768 *wait = 0;
769 return true;
770 }
771
772 /*
773 * If previous slice expired, start a new one otherwise renew/extend
774 * existing slice to make sure it is at least throtl_slice interval
775 * long since now. New slice is started only for empty throttle group.
776 * If there is queued bio, that means there should be an active
777 * slice and it should be extended instead.
778 */
779 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
780 throtl_start_new_slice(tg, rw, true);
781 else {
782 if (time_before(tg->slice_end[rw],
783 jiffies + tg->td->throtl_slice))
784 throtl_extend_slice(tg, rw,
785 jiffies + tg->td->throtl_slice);
786 }
787
788 bps_wait = tg_within_bps_limit(tg, bio, bps_limit);
789 iops_wait = tg_within_iops_limit(tg, bio, iops_limit);
790 if (bps_wait + iops_wait == 0) {
791 if (wait)
792 *wait = 0;
793 return true;
794 }
795
796 max_wait = max(bps_wait, iops_wait);
797
798 if (wait)
799 *wait = max_wait;
800
801 if (time_before(tg->slice_end[rw], jiffies + max_wait))
802 throtl_extend_slice(tg, rw, jiffies + max_wait);
803
804 return false;
805}
806
807static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
808{
809 bool rw = bio_data_dir(bio);
810 unsigned int bio_size = throtl_bio_data_size(bio);
811
812 /* Charge the bio to the group */
813 if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
814 tg->bytes_disp[rw] += bio_size;
815 tg->last_bytes_disp[rw] += bio_size;
816 }
817
818 tg->io_disp[rw]++;
819 tg->last_io_disp[rw]++;
820}
821
822/**
823 * throtl_add_bio_tg - add a bio to the specified throtl_grp
824 * @bio: bio to add
825 * @qn: qnode to use
826 * @tg: the target throtl_grp
827 *
828 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
829 * tg->qnode_on_self[] is used.
830 */
831static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
832 struct throtl_grp *tg)
833{
834 struct throtl_service_queue *sq = &tg->service_queue;
835 bool rw = bio_data_dir(bio);
836
837 if (!qn)
838 qn = &tg->qnode_on_self[rw];
839
840 /*
841 * If @tg doesn't currently have any bios queued in the same
842 * direction, queueing @bio can change when @tg should be
843 * dispatched. Mark that @tg was empty. This is automatically
844 * cleared on the next tg_update_disptime().
845 */
846 if (!sq->nr_queued[rw])
847 tg->flags |= THROTL_TG_WAS_EMPTY;
848
849 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
850
851 sq->nr_queued[rw]++;
852 throtl_enqueue_tg(tg);
853}
854
855static void tg_update_disptime(struct throtl_grp *tg)
856{
857 struct throtl_service_queue *sq = &tg->service_queue;
858 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
859 struct bio *bio;
860
861 bio = throtl_peek_queued(&sq->queued[READ]);
862 if (bio)
863 tg_may_dispatch(tg, bio, &read_wait);
864
865 bio = throtl_peek_queued(&sq->queued[WRITE]);
866 if (bio)
867 tg_may_dispatch(tg, bio, &write_wait);
868
869 min_wait = min(read_wait, write_wait);
870 disptime = jiffies + min_wait;
871
872 /* Update dispatch time */
873 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
874 tg->disptime = disptime;
875 tg_service_queue_add(tg);
876
877 /* see throtl_add_bio_tg() */
878 tg->flags &= ~THROTL_TG_WAS_EMPTY;
879}
880
881static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
882 struct throtl_grp *parent_tg, bool rw)
883{
884 if (throtl_slice_used(parent_tg, rw)) {
885 throtl_start_new_slice_with_credit(parent_tg, rw,
886 child_tg->slice_start[rw]);
887 }
888
889}
890
891static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
892{
893 struct throtl_service_queue *sq = &tg->service_queue;
894 struct throtl_service_queue *parent_sq = sq->parent_sq;
895 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
896 struct throtl_grp *tg_to_put = NULL;
897 struct bio *bio;
898
899 /*
900 * @bio is being transferred from @tg to @parent_sq. Popping a bio
901 * from @tg may put its reference and @parent_sq might end up
902 * getting released prematurely. Remember the tg to put and put it
903 * after @bio is transferred to @parent_sq.
904 */
905 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
906 sq->nr_queued[rw]--;
907
908 throtl_charge_bio(tg, bio);
909
910 /*
911 * If our parent is another tg, we just need to transfer @bio to
912 * the parent using throtl_add_bio_tg(). If our parent is
913 * @td->service_queue, @bio is ready to be issued. Put it on its
914 * bio_lists[] and decrease total number queued. The caller is
915 * responsible for issuing these bios.
916 */
917 if (parent_tg) {
918 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
919 start_parent_slice_with_credit(tg, parent_tg, rw);
920 } else {
921 bio_set_flag(bio, BIO_BPS_THROTTLED);
922 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
923 &parent_sq->queued[rw]);
924 BUG_ON(tg->td->nr_queued[rw] <= 0);
925 tg->td->nr_queued[rw]--;
926 }
927
928 throtl_trim_slice(tg, rw);
929
930 if (tg_to_put)
931 blkg_put(tg_to_blkg(tg_to_put));
932}
933
934static int throtl_dispatch_tg(struct throtl_grp *tg)
935{
936 struct throtl_service_queue *sq = &tg->service_queue;
937 unsigned int nr_reads = 0, nr_writes = 0;
938 unsigned int max_nr_reads = THROTL_GRP_QUANTUM * 3 / 4;
939 unsigned int max_nr_writes = THROTL_GRP_QUANTUM - max_nr_reads;
940 struct bio *bio;
941
942 /* Try to dispatch 75% READS and 25% WRITES */
943
944 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
945 tg_may_dispatch(tg, bio, NULL)) {
946
947 tg_dispatch_one_bio(tg, READ);
948 nr_reads++;
949
950 if (nr_reads >= max_nr_reads)
951 break;
952 }
953
954 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
955 tg_may_dispatch(tg, bio, NULL)) {
956
957 tg_dispatch_one_bio(tg, WRITE);
958 nr_writes++;
959
960 if (nr_writes >= max_nr_writes)
961 break;
962 }
963
964 return nr_reads + nr_writes;
965}
966
967static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
968{
969 unsigned int nr_disp = 0;
970
971 while (1) {
972 struct throtl_grp *tg;
973 struct throtl_service_queue *sq;
974
975 if (!parent_sq->nr_pending)
976 break;
977
978 tg = throtl_rb_first(parent_sq);
979 if (!tg)
980 break;
981
982 if (time_before(jiffies, tg->disptime))
983 break;
984
985 nr_disp += throtl_dispatch_tg(tg);
986
987 sq = &tg->service_queue;
988 if (sq->nr_queued[READ] || sq->nr_queued[WRITE])
989 tg_update_disptime(tg);
990 else
991 throtl_dequeue_tg(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 * @t: the pending_timer member of 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(struct timer_list *t)
1016{
1017 struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
1018 struct throtl_grp *tg = sq_to_tg(sq);
1019 struct throtl_data *td = sq_to_td(sq);
1020 struct throtl_service_queue *parent_sq;
1021 struct request_queue *q;
1022 bool dispatched;
1023 int ret;
1024
1025 /* throtl_data may be gone, so figure out request queue by blkg */
1026 if (tg)
1027 q = tg->pd.blkg->q;
1028 else
1029 q = td->queue;
1030
1031 spin_lock_irq(&q->queue_lock);
1032
1033 if (!q->root_blkg)
1034 goto out_unlock;
1035
1036again:
1037 parent_sq = sq->parent_sq;
1038 dispatched = false;
1039
1040 while (true) {
1041 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1042 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1043 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1044
1045 ret = throtl_select_dispatch(sq);
1046 if (ret) {
1047 throtl_log(sq, "bios disp=%u", ret);
1048 dispatched = true;
1049 }
1050
1051 if (throtl_schedule_next_dispatch(sq, false))
1052 break;
1053
1054 /* this dispatch windows is still open, relax and repeat */
1055 spin_unlock_irq(&q->queue_lock);
1056 cpu_relax();
1057 spin_lock_irq(&q->queue_lock);
1058 }
1059
1060 if (!dispatched)
1061 goto out_unlock;
1062
1063 if (parent_sq) {
1064 /* @parent_sq is another throl_grp, propagate dispatch */
1065 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1066 tg_update_disptime(tg);
1067 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1068 /* window is already open, repeat dispatching */
1069 sq = parent_sq;
1070 tg = sq_to_tg(sq);
1071 goto again;
1072 }
1073 }
1074 } else {
1075 /* reached the top-level, queue issuing */
1076 queue_work(kthrotld_workqueue, &td->dispatch_work);
1077 }
1078out_unlock:
1079 spin_unlock_irq(&q->queue_lock);
1080}
1081
1082/**
1083 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1084 * @work: work item being executed
1085 *
1086 * This function is queued for execution when bios reach the bio_lists[]
1087 * of throtl_data->service_queue. Those bios are ready and issued by this
1088 * function.
1089 */
1090static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1091{
1092 struct throtl_data *td = container_of(work, struct throtl_data,
1093 dispatch_work);
1094 struct throtl_service_queue *td_sq = &td->service_queue;
1095 struct request_queue *q = td->queue;
1096 struct bio_list bio_list_on_stack;
1097 struct bio *bio;
1098 struct blk_plug plug;
1099 int rw;
1100
1101 bio_list_init(&bio_list_on_stack);
1102
1103 spin_lock_irq(&q->queue_lock);
1104 for (rw = READ; rw <= WRITE; rw++)
1105 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1106 bio_list_add(&bio_list_on_stack, bio);
1107 spin_unlock_irq(&q->queue_lock);
1108
1109 if (!bio_list_empty(&bio_list_on_stack)) {
1110 blk_start_plug(&plug);
1111 while ((bio = bio_list_pop(&bio_list_on_stack)))
1112 submit_bio_noacct_nocheck(bio);
1113 blk_finish_plug(&plug);
1114 }
1115}
1116
1117static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1118 int off)
1119{
1120 struct throtl_grp *tg = pd_to_tg(pd);
1121 u64 v = *(u64 *)((void *)tg + off);
1122
1123 if (v == U64_MAX)
1124 return 0;
1125 return __blkg_prfill_u64(sf, pd, v);
1126}
1127
1128static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1129 int off)
1130{
1131 struct throtl_grp *tg = pd_to_tg(pd);
1132 unsigned int v = *(unsigned int *)((void *)tg + off);
1133
1134 if (v == UINT_MAX)
1135 return 0;
1136 return __blkg_prfill_u64(sf, pd, v);
1137}
1138
1139static int tg_print_conf_u64(struct seq_file *sf, void *v)
1140{
1141 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1142 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1143 return 0;
1144}
1145
1146static int tg_print_conf_uint(struct seq_file *sf, void *v)
1147{
1148 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1149 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1150 return 0;
1151}
1152
1153static void tg_conf_updated(struct throtl_grp *tg, bool global)
1154{
1155 struct throtl_service_queue *sq = &tg->service_queue;
1156 struct cgroup_subsys_state *pos_css;
1157 struct blkcg_gq *blkg;
1158
1159 throtl_log(&tg->service_queue,
1160 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1161 tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1162 tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1163
1164 rcu_read_lock();
1165 /*
1166 * Update has_rules[] flags for the updated tg's subtree. A tg is
1167 * considered to have rules if either the tg itself or any of its
1168 * ancestors has rules. This identifies groups without any
1169 * restrictions in the whole hierarchy and allows them to bypass
1170 * blk-throttle.
1171 */
1172 blkg_for_each_descendant_pre(blkg, pos_css,
1173 global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1174 struct throtl_grp *this_tg = blkg_to_tg(blkg);
1175
1176 tg_update_has_rules(this_tg);
1177 /* ignore root/second level */
1178 if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1179 !blkg->parent->parent)
1180 continue;
1181 }
1182 rcu_read_unlock();
1183
1184 /*
1185 * We're already holding queue_lock and know @tg is valid. Let's
1186 * apply the new config directly.
1187 *
1188 * Restart the slices for both READ and WRITES. It might happen
1189 * that a group's limit are dropped suddenly and we don't want to
1190 * account recently dispatched IO with new low rate.
1191 */
1192 throtl_start_new_slice(tg, READ, false);
1193 throtl_start_new_slice(tg, WRITE, false);
1194
1195 if (tg->flags & THROTL_TG_PENDING) {
1196 tg_update_disptime(tg);
1197 throtl_schedule_next_dispatch(sq->parent_sq, true);
1198 }
1199}
1200
1201static int blk_throtl_init(struct gendisk *disk)
1202{
1203 struct request_queue *q = disk->queue;
1204 struct throtl_data *td;
1205 int ret;
1206
1207 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1208 if (!td)
1209 return -ENOMEM;
1210
1211 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
1212 throtl_service_queue_init(&td->service_queue);
1213
1214 /*
1215 * Freeze queue before activating policy, to synchronize with IO path,
1216 * which is protected by 'q_usage_counter'.
1217 */
1218 blk_mq_freeze_queue(disk->queue);
1219 blk_mq_quiesce_queue(disk->queue);
1220
1221 q->td = td;
1222 td->queue = q;
1223
1224 /* activate policy */
1225 ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
1226 if (ret) {
1227 q->td = NULL;
1228 kfree(td);
1229 goto out;
1230 }
1231
1232 if (blk_queue_nonrot(q))
1233 td->throtl_slice = DFL_THROTL_SLICE_SSD;
1234 else
1235 td->throtl_slice = DFL_THROTL_SLICE_HD;
1236 td->track_bio_latency = !queue_is_mq(q);
1237 if (!td->track_bio_latency)
1238 blk_stat_enable_accounting(q);
1239
1240out:
1241 blk_mq_unquiesce_queue(disk->queue);
1242 blk_mq_unfreeze_queue(disk->queue);
1243
1244 return ret;
1245}
1246
1247
1248static ssize_t tg_set_conf(struct kernfs_open_file *of,
1249 char *buf, size_t nbytes, loff_t off, bool is_u64)
1250{
1251 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1252 struct blkg_conf_ctx ctx;
1253 struct throtl_grp *tg;
1254 int ret;
1255 u64 v;
1256
1257 blkg_conf_init(&ctx, buf);
1258
1259 ret = blkg_conf_open_bdev(&ctx);
1260 if (ret)
1261 goto out_finish;
1262
1263 if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
1264 ret = blk_throtl_init(ctx.bdev->bd_disk);
1265 if (ret)
1266 goto out_finish;
1267 }
1268
1269 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1270 if (ret)
1271 goto out_finish;
1272
1273 ret = -EINVAL;
1274 if (sscanf(ctx.body, "%llu", &v) != 1)
1275 goto out_finish;
1276 if (!v)
1277 v = U64_MAX;
1278
1279 tg = blkg_to_tg(ctx.blkg);
1280 tg_update_carryover(tg);
1281
1282 if (is_u64)
1283 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1284 else
1285 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1286
1287 tg_conf_updated(tg, false);
1288 ret = 0;
1289out_finish:
1290 blkg_conf_exit(&ctx);
1291 return ret ?: nbytes;
1292}
1293
1294static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1295 char *buf, size_t nbytes, loff_t off)
1296{
1297 return tg_set_conf(of, buf, nbytes, off, true);
1298}
1299
1300static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1301 char *buf, size_t nbytes, loff_t off)
1302{
1303 return tg_set_conf(of, buf, nbytes, off, false);
1304}
1305
1306static int tg_print_rwstat(struct seq_file *sf, void *v)
1307{
1308 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1309 blkg_prfill_rwstat, &blkcg_policy_throtl,
1310 seq_cft(sf)->private, true);
1311 return 0;
1312}
1313
1314static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
1315 struct blkg_policy_data *pd, int off)
1316{
1317 struct blkg_rwstat_sample sum;
1318
1319 blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
1320 &sum);
1321 return __blkg_prfill_rwstat(sf, pd, &sum);
1322}
1323
1324static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
1325{
1326 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1327 tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
1328 seq_cft(sf)->private, true);
1329 return 0;
1330}
1331
1332static struct cftype throtl_legacy_files[] = {
1333 {
1334 .name = "throttle.read_bps_device",
1335 .private = offsetof(struct throtl_grp, bps[READ]),
1336 .seq_show = tg_print_conf_u64,
1337 .write = tg_set_conf_u64,
1338 },
1339 {
1340 .name = "throttle.write_bps_device",
1341 .private = offsetof(struct throtl_grp, bps[WRITE]),
1342 .seq_show = tg_print_conf_u64,
1343 .write = tg_set_conf_u64,
1344 },
1345 {
1346 .name = "throttle.read_iops_device",
1347 .private = offsetof(struct throtl_grp, iops[READ]),
1348 .seq_show = tg_print_conf_uint,
1349 .write = tg_set_conf_uint,
1350 },
1351 {
1352 .name = "throttle.write_iops_device",
1353 .private = offsetof(struct throtl_grp, iops[WRITE]),
1354 .seq_show = tg_print_conf_uint,
1355 .write = tg_set_conf_uint,
1356 },
1357 {
1358 .name = "throttle.io_service_bytes",
1359 .private = offsetof(struct throtl_grp, stat_bytes),
1360 .seq_show = tg_print_rwstat,
1361 },
1362 {
1363 .name = "throttle.io_service_bytes_recursive",
1364 .private = offsetof(struct throtl_grp, stat_bytes),
1365 .seq_show = tg_print_rwstat_recursive,
1366 },
1367 {
1368 .name = "throttle.io_serviced",
1369 .private = offsetof(struct throtl_grp, stat_ios),
1370 .seq_show = tg_print_rwstat,
1371 },
1372 {
1373 .name = "throttle.io_serviced_recursive",
1374 .private = offsetof(struct throtl_grp, stat_ios),
1375 .seq_show = tg_print_rwstat_recursive,
1376 },
1377 { } /* terminate */
1378};
1379
1380static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1381 int off)
1382{
1383 struct throtl_grp *tg = pd_to_tg(pd);
1384 const char *dname = blkg_dev_name(pd->blkg);
1385 u64 bps_dft;
1386 unsigned int iops_dft;
1387
1388 if (!dname)
1389 return 0;
1390
1391 bps_dft = U64_MAX;
1392 iops_dft = UINT_MAX;
1393
1394 if (tg->bps[READ] == bps_dft &&
1395 tg->bps[WRITE] == bps_dft &&
1396 tg->iops[READ] == iops_dft &&
1397 tg->iops[WRITE] == iops_dft)
1398 return 0;
1399
1400 seq_printf(sf, "%s", dname);
1401 if (tg->bps[READ] == U64_MAX)
1402 seq_printf(sf, " rbps=max");
1403 else
1404 seq_printf(sf, " rbps=%llu", tg->bps[READ]);
1405
1406 if (tg->bps[WRITE] == U64_MAX)
1407 seq_printf(sf, " wbps=max");
1408 else
1409 seq_printf(sf, " wbps=%llu", tg->bps[WRITE]);
1410
1411 if (tg->iops[READ] == UINT_MAX)
1412 seq_printf(sf, " riops=max");
1413 else
1414 seq_printf(sf, " riops=%u", tg->iops[READ]);
1415
1416 if (tg->iops[WRITE] == UINT_MAX)
1417 seq_printf(sf, " wiops=max");
1418 else
1419 seq_printf(sf, " wiops=%u", tg->iops[WRITE]);
1420
1421 seq_printf(sf, "\n");
1422 return 0;
1423}
1424
1425static int tg_print_limit(struct seq_file *sf, void *v)
1426{
1427 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1428 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1429 return 0;
1430}
1431
1432static ssize_t tg_set_limit(struct kernfs_open_file *of,
1433 char *buf, size_t nbytes, loff_t off)
1434{
1435 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1436 struct blkg_conf_ctx ctx;
1437 struct throtl_grp *tg;
1438 u64 v[4];
1439 int ret;
1440
1441 blkg_conf_init(&ctx, buf);
1442
1443 ret = blkg_conf_open_bdev(&ctx);
1444 if (ret)
1445 goto out_finish;
1446
1447 if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
1448 ret = blk_throtl_init(ctx.bdev->bd_disk);
1449 if (ret)
1450 goto out_finish;
1451 }
1452
1453 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1454 if (ret)
1455 goto out_finish;
1456
1457 tg = blkg_to_tg(ctx.blkg);
1458 tg_update_carryover(tg);
1459
1460 v[0] = tg->bps[READ];
1461 v[1] = tg->bps[WRITE];
1462 v[2] = tg->iops[READ];
1463 v[3] = tg->iops[WRITE];
1464
1465 while (true) {
1466 char tok[27]; /* wiops=18446744073709551616 */
1467 char *p;
1468 u64 val = U64_MAX;
1469 int len;
1470
1471 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1472 break;
1473 if (tok[0] == '\0')
1474 break;
1475 ctx.body += len;
1476
1477 ret = -EINVAL;
1478 p = tok;
1479 strsep(&p, "=");
1480 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1481 goto out_finish;
1482
1483 ret = -ERANGE;
1484 if (!val)
1485 goto out_finish;
1486
1487 ret = -EINVAL;
1488 if (!strcmp(tok, "rbps"))
1489 v[0] = val;
1490 else if (!strcmp(tok, "wbps"))
1491 v[1] = val;
1492 else if (!strcmp(tok, "riops"))
1493 v[2] = min_t(u64, val, UINT_MAX);
1494 else if (!strcmp(tok, "wiops"))
1495 v[3] = min_t(u64, val, UINT_MAX);
1496 else
1497 goto out_finish;
1498 }
1499
1500 tg->bps[READ] = v[0];
1501 tg->bps[WRITE] = v[1];
1502 tg->iops[READ] = v[2];
1503 tg->iops[WRITE] = v[3];
1504
1505 tg_conf_updated(tg, false);
1506 ret = 0;
1507out_finish:
1508 blkg_conf_exit(&ctx);
1509 return ret ?: nbytes;
1510}
1511
1512static struct cftype throtl_files[] = {
1513 {
1514 .name = "max",
1515 .flags = CFTYPE_NOT_ON_ROOT,
1516 .seq_show = tg_print_limit,
1517 .write = tg_set_limit,
1518 },
1519 { } /* terminate */
1520};
1521
1522static void throtl_shutdown_wq(struct request_queue *q)
1523{
1524 struct throtl_data *td = q->td;
1525
1526 cancel_work_sync(&td->dispatch_work);
1527}
1528
1529static void tg_flush_bios(struct throtl_grp *tg)
1530{
1531 struct throtl_service_queue *sq = &tg->service_queue;
1532
1533 if (tg->flags & THROTL_TG_CANCELING)
1534 return;
1535 /*
1536 * Set the flag to make sure throtl_pending_timer_fn() won't
1537 * stop until all throttled bios are dispatched.
1538 */
1539 tg->flags |= THROTL_TG_CANCELING;
1540
1541 /*
1542 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup
1543 * will be inserted to service queue without THROTL_TG_PENDING
1544 * set in tg_update_disptime below. Then IO dispatched from
1545 * child in tg_dispatch_one_bio will trigger double insertion
1546 * and corrupt the tree.
1547 */
1548 if (!(tg->flags & THROTL_TG_PENDING))
1549 return;
1550
1551 /*
1552 * Update disptime after setting the above flag to make sure
1553 * throtl_select_dispatch() won't exit without dispatching.
1554 */
1555 tg_update_disptime(tg);
1556
1557 throtl_schedule_pending_timer(sq, jiffies + 1);
1558}
1559
1560static void throtl_pd_offline(struct blkg_policy_data *pd)
1561{
1562 tg_flush_bios(pd_to_tg(pd));
1563}
1564
1565struct blkcg_policy blkcg_policy_throtl = {
1566 .dfl_cftypes = throtl_files,
1567 .legacy_cftypes = throtl_legacy_files,
1568
1569 .pd_alloc_fn = throtl_pd_alloc,
1570 .pd_init_fn = throtl_pd_init,
1571 .pd_online_fn = throtl_pd_online,
1572 .pd_offline_fn = throtl_pd_offline,
1573 .pd_free_fn = throtl_pd_free,
1574};
1575
1576void blk_throtl_cancel_bios(struct gendisk *disk)
1577{
1578 struct request_queue *q = disk->queue;
1579 struct cgroup_subsys_state *pos_css;
1580 struct blkcg_gq *blkg;
1581
1582 if (!blk_throtl_activated(q))
1583 return;
1584
1585 spin_lock_irq(&q->queue_lock);
1586 /*
1587 * queue_lock is held, rcu lock is not needed here technically.
1588 * However, rcu lock is still held to emphasize that following
1589 * path need RCU protection and to prevent warning from lockdep.
1590 */
1591 rcu_read_lock();
1592 blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
1593 /*
1594 * disk_release will call pd_offline_fn to cancel bios.
1595 * However, disk_release can't be called if someone get
1596 * the refcount of device and issued bios which are
1597 * inflight after del_gendisk.
1598 * Cancel bios here to ensure no bios are inflight after
1599 * del_gendisk.
1600 */
1601 tg_flush_bios(blkg_to_tg(blkg));
1602 }
1603 rcu_read_unlock();
1604 spin_unlock_irq(&q->queue_lock);
1605}
1606
1607static bool tg_within_limit(struct throtl_grp *tg, struct bio *bio, bool rw)
1608{
1609 /* throtl is FIFO - if bios are already queued, should queue */
1610 if (tg->service_queue.nr_queued[rw])
1611 return false;
1612
1613 return tg_may_dispatch(tg, bio, NULL);
1614}
1615
1616static void tg_dispatch_in_debt(struct throtl_grp *tg, struct bio *bio, bool rw)
1617{
1618 if (!bio_flagged(bio, BIO_BPS_THROTTLED))
1619 tg->carryover_bytes[rw] -= throtl_bio_data_size(bio);
1620 tg->carryover_ios[rw]--;
1621}
1622
1623bool __blk_throtl_bio(struct bio *bio)
1624{
1625 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1626 struct blkcg_gq *blkg = bio->bi_blkg;
1627 struct throtl_qnode *qn = NULL;
1628 struct throtl_grp *tg = blkg_to_tg(blkg);
1629 struct throtl_service_queue *sq;
1630 bool rw = bio_data_dir(bio);
1631 bool throttled = false;
1632 struct throtl_data *td = tg->td;
1633
1634 rcu_read_lock();
1635 spin_lock_irq(&q->queue_lock);
1636 sq = &tg->service_queue;
1637
1638 while (true) {
1639 if (tg_within_limit(tg, bio, rw)) {
1640 /* within limits, let's charge and dispatch directly */
1641 throtl_charge_bio(tg, bio);
1642
1643 /*
1644 * We need to trim slice even when bios are not being
1645 * queued otherwise it might happen that a bio is not
1646 * queued for a long time and slice keeps on extending
1647 * and trim is not called for a long time. Now if limits
1648 * are reduced suddenly we take into account all the IO
1649 * dispatched so far at new low rate and * newly queued
1650 * IO gets a really long dispatch time.
1651 *
1652 * So keep on trimming slice even if bio is not queued.
1653 */
1654 throtl_trim_slice(tg, rw);
1655 } else if (bio_issue_as_root_blkg(bio)) {
1656 /*
1657 * IOs which may cause priority inversions are
1658 * dispatched directly, even if they're over limit.
1659 * Debts are handled by carryover_bytes/ios while
1660 * calculating wait time.
1661 */
1662 tg_dispatch_in_debt(tg, bio, rw);
1663 } else {
1664 /* if above limits, break to queue */
1665 break;
1666 }
1667
1668 /*
1669 * @bio passed through this layer without being throttled.
1670 * Climb up the ladder. If we're already at the top, it
1671 * can be executed directly.
1672 */
1673 qn = &tg->qnode_on_parent[rw];
1674 sq = sq->parent_sq;
1675 tg = sq_to_tg(sq);
1676 if (!tg) {
1677 bio_set_flag(bio, BIO_BPS_THROTTLED);
1678 goto out_unlock;
1679 }
1680 }
1681
1682 /* out-of-limit, queue to @tg */
1683 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1684 rw == READ ? 'R' : 'W',
1685 tg->bytes_disp[rw], bio->bi_iter.bi_size,
1686 tg_bps_limit(tg, rw),
1687 tg->io_disp[rw], tg_iops_limit(tg, rw),
1688 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1689
1690 td->nr_queued[rw]++;
1691 throtl_add_bio_tg(bio, qn, tg);
1692 throttled = true;
1693
1694 /*
1695 * Update @tg's dispatch time and force schedule dispatch if @tg
1696 * was empty before @bio. The forced scheduling isn't likely to
1697 * cause undue delay as @bio is likely to be dispatched directly if
1698 * its @tg's disptime is not in the future.
1699 */
1700 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1701 tg_update_disptime(tg);
1702 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
1703 }
1704
1705out_unlock:
1706 spin_unlock_irq(&q->queue_lock);
1707
1708 rcu_read_unlock();
1709 return throttled;
1710}
1711
1712void blk_throtl_exit(struct gendisk *disk)
1713{
1714 struct request_queue *q = disk->queue;
1715
1716 if (!blk_throtl_activated(q))
1717 return;
1718
1719 del_timer_sync(&q->td->service_queue.pending_timer);
1720 throtl_shutdown_wq(q);
1721 blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
1722 kfree(q->td);
1723}
1724
1725static int __init throtl_init(void)
1726{
1727 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1728 if (!kthrotld_workqueue)
1729 panic("Failed to create kthrotld\n");
1730
1731 return blkcg_policy_register(&blkcg_policy_throtl);
1732}
1733
1734module_init(throtl_init);