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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 <linux/blk-cgroup.h>
13#include "blk.h"
14
15/* Max dispatch from a group in 1 round */
16static int throtl_grp_quantum = 8;
17
18/* Total max dispatch from all groups in one round */
19static int throtl_quantum = 32;
20
21/* Throttling is performed over 100ms slice and after that slice is renewed */
22static unsigned long throtl_slice = HZ/10; /* 100 ms */
23
24static struct blkcg_policy blkcg_policy_throtl;
25
26/* A workqueue to queue throttle related work */
27static struct workqueue_struct *kthrotld_workqueue;
28
29/*
30 * To implement hierarchical throttling, throtl_grps form a tree and bios
31 * are dispatched upwards level by level until they reach the top and get
32 * issued. When dispatching bios from the children and local group at each
33 * level, if the bios are dispatched into a single bio_list, there's a risk
34 * of a local or child group which can queue many bios at once filling up
35 * the list starving others.
36 *
37 * To avoid such starvation, dispatched bios are queued separately
38 * according to where they came from. When they are again dispatched to
39 * the parent, they're popped in round-robin order so that no single source
40 * hogs the dispatch window.
41 *
42 * throtl_qnode is used to keep the queued bios separated by their sources.
43 * Bios are queued to throtl_qnode which in turn is queued to
44 * throtl_service_queue and then dispatched in round-robin order.
45 *
46 * It's also used to track the reference counts on blkg's. A qnode always
47 * belongs to a throtl_grp and gets queued on itself or the parent, so
48 * incrementing the reference of the associated throtl_grp when a qnode is
49 * queued and decrementing when dequeued is enough to keep the whole blkg
50 * tree pinned while bios are in flight.
51 */
52struct throtl_qnode {
53 struct list_head node; /* service_queue->queued[] */
54 struct bio_list bios; /* queued bios */
55 struct throtl_grp *tg; /* tg this qnode belongs to */
56};
57
58struct throtl_service_queue {
59 struct throtl_service_queue *parent_sq; /* the parent service_queue */
60
61 /*
62 * Bios queued directly to this service_queue or dispatched from
63 * children throtl_grp's.
64 */
65 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
66 unsigned int nr_queued[2]; /* number of queued bios */
67
68 /*
69 * RB tree of active children throtl_grp's, which are sorted by
70 * their ->disptime.
71 */
72 struct rb_root pending_tree; /* RB tree of active tgs */
73 struct rb_node *first_pending; /* first node in the tree */
74 unsigned int nr_pending; /* # queued in the tree */
75 unsigned long first_pending_disptime; /* disptime of the first tg */
76 struct timer_list pending_timer; /* fires on first_pending_disptime */
77};
78
79enum tg_state_flags {
80 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
81 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
82};
83
84#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
85
86struct throtl_grp {
87 /* must be the first member */
88 struct blkg_policy_data pd;
89
90 /* active throtl group service_queue member */
91 struct rb_node rb_node;
92
93 /* throtl_data this group belongs to */
94 struct throtl_data *td;
95
96 /* this group's service queue */
97 struct throtl_service_queue service_queue;
98
99 /*
100 * qnode_on_self is used when bios are directly queued to this
101 * throtl_grp so that local bios compete fairly with bios
102 * dispatched from children. qnode_on_parent is used when bios are
103 * dispatched from this throtl_grp into its parent and will compete
104 * with the sibling qnode_on_parents and the parent's
105 * qnode_on_self.
106 */
107 struct throtl_qnode qnode_on_self[2];
108 struct throtl_qnode qnode_on_parent[2];
109
110 /*
111 * Dispatch time in jiffies. This is the estimated time when group
112 * will unthrottle and is ready to dispatch more bio. It is used as
113 * key to sort active groups in service tree.
114 */
115 unsigned long disptime;
116
117 unsigned int flags;
118
119 /* are there any throtl rules between this group and td? */
120 bool has_rules[2];
121
122 /* bytes per second rate limits */
123 uint64_t bps[2];
124
125 /* IOPS limits */
126 unsigned int iops[2];
127
128 /* Number of bytes disptached in current slice */
129 uint64_t bytes_disp[2];
130 /* Number of bio's dispatched in current slice */
131 unsigned int io_disp[2];
132
133 /* When did we start a new slice */
134 unsigned long slice_start[2];
135 unsigned long slice_end[2];
136};
137
138struct throtl_data
139{
140 /* service tree for active throtl groups */
141 struct throtl_service_queue service_queue;
142
143 struct request_queue *queue;
144
145 /* Total Number of queued bios on READ and WRITE lists */
146 unsigned int nr_queued[2];
147
148 /*
149 * number of total undestroyed groups
150 */
151 unsigned int nr_undestroyed_grps;
152
153 /* Work for dispatching throttled bios */
154 struct work_struct dispatch_work;
155};
156
157static void throtl_pending_timer_fn(unsigned long arg);
158
159static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
160{
161 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
162}
163
164static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
165{
166 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
167}
168
169static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
170{
171 return pd_to_blkg(&tg->pd);
172}
173
174/**
175 * sq_to_tg - return the throl_grp the specified service queue belongs to
176 * @sq: the throtl_service_queue of interest
177 *
178 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
179 * embedded in throtl_data, %NULL is returned.
180 */
181static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
182{
183 if (sq && sq->parent_sq)
184 return container_of(sq, struct throtl_grp, service_queue);
185 else
186 return NULL;
187}
188
189/**
190 * sq_to_td - return throtl_data the specified service queue belongs to
191 * @sq: the throtl_service_queue of interest
192 *
193 * A service_queue can be embeded in either a throtl_grp or throtl_data.
194 * Determine the associated throtl_data accordingly and return it.
195 */
196static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
197{
198 struct throtl_grp *tg = sq_to_tg(sq);
199
200 if (tg)
201 return tg->td;
202 else
203 return container_of(sq, struct throtl_data, service_queue);
204}
205
206/**
207 * throtl_log - log debug message via blktrace
208 * @sq: the service_queue being reported
209 * @fmt: printf format string
210 * @args: printf args
211 *
212 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
213 * throtl_grp; otherwise, just "throtl".
214 *
215 * TODO: this should be made a function and name formatting should happen
216 * after testing whether blktrace is enabled.
217 */
218#define throtl_log(sq, fmt, args...) do { \
219 struct throtl_grp *__tg = sq_to_tg((sq)); \
220 struct throtl_data *__td = sq_to_td((sq)); \
221 \
222 (void)__td; \
223 if ((__tg)) { \
224 char __pbuf[128]; \
225 \
226 blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \
227 blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
228 } else { \
229 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
230 } \
231} while (0)
232
233static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
234{
235 INIT_LIST_HEAD(&qn->node);
236 bio_list_init(&qn->bios);
237 qn->tg = tg;
238}
239
240/**
241 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
242 * @bio: bio being added
243 * @qn: qnode to add bio to
244 * @queued: the service_queue->queued[] list @qn belongs to
245 *
246 * Add @bio to @qn and put @qn on @queued if it's not already on.
247 * @qn->tg's reference count is bumped when @qn is activated. See the
248 * comment on top of throtl_qnode definition for details.
249 */
250static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
251 struct list_head *queued)
252{
253 bio_list_add(&qn->bios, bio);
254 if (list_empty(&qn->node)) {
255 list_add_tail(&qn->node, queued);
256 blkg_get(tg_to_blkg(qn->tg));
257 }
258}
259
260/**
261 * throtl_peek_queued - peek the first bio on a qnode list
262 * @queued: the qnode list to peek
263 */
264static struct bio *throtl_peek_queued(struct list_head *queued)
265{
266 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
267 struct bio *bio;
268
269 if (list_empty(queued))
270 return NULL;
271
272 bio = bio_list_peek(&qn->bios);
273 WARN_ON_ONCE(!bio);
274 return bio;
275}
276
277/**
278 * throtl_pop_queued - pop the first bio form a qnode list
279 * @queued: the qnode list to pop a bio from
280 * @tg_to_put: optional out argument for throtl_grp to put
281 *
282 * Pop the first bio from the qnode list @queued. After popping, the first
283 * qnode is removed from @queued if empty or moved to the end of @queued so
284 * that the popping order is round-robin.
285 *
286 * When the first qnode is removed, its associated throtl_grp should be put
287 * too. If @tg_to_put is NULL, this function automatically puts it;
288 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
289 * responsible for putting it.
290 */
291static struct bio *throtl_pop_queued(struct list_head *queued,
292 struct throtl_grp **tg_to_put)
293{
294 struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node);
295 struct bio *bio;
296
297 if (list_empty(queued))
298 return NULL;
299
300 bio = bio_list_pop(&qn->bios);
301 WARN_ON_ONCE(!bio);
302
303 if (bio_list_empty(&qn->bios)) {
304 list_del_init(&qn->node);
305 if (tg_to_put)
306 *tg_to_put = qn->tg;
307 else
308 blkg_put(tg_to_blkg(qn->tg));
309 } else {
310 list_move_tail(&qn->node, queued);
311 }
312
313 return bio;
314}
315
316/* init a service_queue, assumes the caller zeroed it */
317static void throtl_service_queue_init(struct throtl_service_queue *sq)
318{
319 INIT_LIST_HEAD(&sq->queued[0]);
320 INIT_LIST_HEAD(&sq->queued[1]);
321 sq->pending_tree = RB_ROOT;
322 setup_timer(&sq->pending_timer, throtl_pending_timer_fn,
323 (unsigned long)sq);
324}
325
326static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
327{
328 struct throtl_grp *tg;
329 int rw;
330
331 tg = kzalloc_node(sizeof(*tg), gfp, node);
332 if (!tg)
333 return NULL;
334
335 throtl_service_queue_init(&tg->service_queue);
336
337 for (rw = READ; rw <= WRITE; rw++) {
338 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
339 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
340 }
341
342 RB_CLEAR_NODE(&tg->rb_node);
343 tg->bps[READ] = -1;
344 tg->bps[WRITE] = -1;
345 tg->iops[READ] = -1;
346 tg->iops[WRITE] = -1;
347
348 return &tg->pd;
349}
350
351static void throtl_pd_init(struct blkg_policy_data *pd)
352{
353 struct throtl_grp *tg = pd_to_tg(pd);
354 struct blkcg_gq *blkg = tg_to_blkg(tg);
355 struct throtl_data *td = blkg->q->td;
356 struct throtl_service_queue *sq = &tg->service_queue;
357
358 /*
359 * If on the default hierarchy, we switch to properly hierarchical
360 * behavior where limits on a given throtl_grp are applied to the
361 * whole subtree rather than just the group itself. e.g. If 16M
362 * read_bps limit is set on the root group, the whole system can't
363 * exceed 16M for the device.
364 *
365 * If not on the default hierarchy, the broken flat hierarchy
366 * behavior is retained where all throtl_grps are treated as if
367 * they're all separate root groups right below throtl_data.
368 * Limits of a group don't interact with limits of other groups
369 * regardless of the position of the group in the hierarchy.
370 */
371 sq->parent_sq = &td->service_queue;
372 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
373 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
374 tg->td = td;
375}
376
377/*
378 * Set has_rules[] if @tg or any of its parents have limits configured.
379 * This doesn't require walking up to the top of the hierarchy as the
380 * parent's has_rules[] is guaranteed to be correct.
381 */
382static void tg_update_has_rules(struct throtl_grp *tg)
383{
384 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
385 int rw;
386
387 for (rw = READ; rw <= WRITE; rw++)
388 tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
389 (tg->bps[rw] != -1 || tg->iops[rw] != -1);
390}
391
392static void throtl_pd_online(struct blkg_policy_data *pd)
393{
394 /*
395 * We don't want new groups to escape the limits of its ancestors.
396 * Update has_rules[] after a new group is brought online.
397 */
398 tg_update_has_rules(pd_to_tg(pd));
399}
400
401static void throtl_pd_free(struct blkg_policy_data *pd)
402{
403 struct throtl_grp *tg = pd_to_tg(pd);
404
405 del_timer_sync(&tg->service_queue.pending_timer);
406 kfree(tg);
407}
408
409static struct throtl_grp *
410throtl_rb_first(struct throtl_service_queue *parent_sq)
411{
412 /* Service tree is empty */
413 if (!parent_sq->nr_pending)
414 return NULL;
415
416 if (!parent_sq->first_pending)
417 parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
418
419 if (parent_sq->first_pending)
420 return rb_entry_tg(parent_sq->first_pending);
421
422 return NULL;
423}
424
425static void rb_erase_init(struct rb_node *n, struct rb_root *root)
426{
427 rb_erase(n, root);
428 RB_CLEAR_NODE(n);
429}
430
431static void throtl_rb_erase(struct rb_node *n,
432 struct throtl_service_queue *parent_sq)
433{
434 if (parent_sq->first_pending == n)
435 parent_sq->first_pending = NULL;
436 rb_erase_init(n, &parent_sq->pending_tree);
437 --parent_sq->nr_pending;
438}
439
440static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
441{
442 struct throtl_grp *tg;
443
444 tg = throtl_rb_first(parent_sq);
445 if (!tg)
446 return;
447
448 parent_sq->first_pending_disptime = tg->disptime;
449}
450
451static void tg_service_queue_add(struct throtl_grp *tg)
452{
453 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
454 struct rb_node **node = &parent_sq->pending_tree.rb_node;
455 struct rb_node *parent = NULL;
456 struct throtl_grp *__tg;
457 unsigned long key = tg->disptime;
458 int left = 1;
459
460 while (*node != NULL) {
461 parent = *node;
462 __tg = rb_entry_tg(parent);
463
464 if (time_before(key, __tg->disptime))
465 node = &parent->rb_left;
466 else {
467 node = &parent->rb_right;
468 left = 0;
469 }
470 }
471
472 if (left)
473 parent_sq->first_pending = &tg->rb_node;
474
475 rb_link_node(&tg->rb_node, parent, node);
476 rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
477}
478
479static void __throtl_enqueue_tg(struct throtl_grp *tg)
480{
481 tg_service_queue_add(tg);
482 tg->flags |= THROTL_TG_PENDING;
483 tg->service_queue.parent_sq->nr_pending++;
484}
485
486static void throtl_enqueue_tg(struct throtl_grp *tg)
487{
488 if (!(tg->flags & THROTL_TG_PENDING))
489 __throtl_enqueue_tg(tg);
490}
491
492static void __throtl_dequeue_tg(struct throtl_grp *tg)
493{
494 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
495 tg->flags &= ~THROTL_TG_PENDING;
496}
497
498static void throtl_dequeue_tg(struct throtl_grp *tg)
499{
500 if (tg->flags & THROTL_TG_PENDING)
501 __throtl_dequeue_tg(tg);
502}
503
504/* Call with queue lock held */
505static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
506 unsigned long expires)
507{
508 mod_timer(&sq->pending_timer, expires);
509 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
510 expires - jiffies, jiffies);
511}
512
513/**
514 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
515 * @sq: the service_queue to schedule dispatch for
516 * @force: force scheduling
517 *
518 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
519 * dispatch time of the first pending child. Returns %true if either timer
520 * is armed or there's no pending child left. %false if the current
521 * dispatch window is still open and the caller should continue
522 * dispatching.
523 *
524 * If @force is %true, the dispatch timer is always scheduled and this
525 * function is guaranteed to return %true. This is to be used when the
526 * caller can't dispatch itself and needs to invoke pending_timer
527 * unconditionally. Note that forced scheduling is likely to induce short
528 * delay before dispatch starts even if @sq->first_pending_disptime is not
529 * in the future and thus shouldn't be used in hot paths.
530 */
531static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
532 bool force)
533{
534 /* any pending children left? */
535 if (!sq->nr_pending)
536 return true;
537
538 update_min_dispatch_time(sq);
539
540 /* is the next dispatch time in the future? */
541 if (force || time_after(sq->first_pending_disptime, jiffies)) {
542 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
543 return true;
544 }
545
546 /* tell the caller to continue dispatching */
547 return false;
548}
549
550static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
551 bool rw, unsigned long start)
552{
553 tg->bytes_disp[rw] = 0;
554 tg->io_disp[rw] = 0;
555
556 /*
557 * Previous slice has expired. We must have trimmed it after last
558 * bio dispatch. That means since start of last slice, we never used
559 * that bandwidth. Do try to make use of that bandwidth while giving
560 * credit.
561 */
562 if (time_after_eq(start, tg->slice_start[rw]))
563 tg->slice_start[rw] = start;
564
565 tg->slice_end[rw] = jiffies + throtl_slice;
566 throtl_log(&tg->service_queue,
567 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
568 rw == READ ? 'R' : 'W', tg->slice_start[rw],
569 tg->slice_end[rw], jiffies);
570}
571
572static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
573{
574 tg->bytes_disp[rw] = 0;
575 tg->io_disp[rw] = 0;
576 tg->slice_start[rw] = jiffies;
577 tg->slice_end[rw] = jiffies + throtl_slice;
578 throtl_log(&tg->service_queue,
579 "[%c] new slice start=%lu end=%lu jiffies=%lu",
580 rw == READ ? 'R' : 'W', tg->slice_start[rw],
581 tg->slice_end[rw], jiffies);
582}
583
584static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
585 unsigned long jiffy_end)
586{
587 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
588}
589
590static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
591 unsigned long jiffy_end)
592{
593 tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
594 throtl_log(&tg->service_queue,
595 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
596 rw == READ ? 'R' : 'W', tg->slice_start[rw],
597 tg->slice_end[rw], jiffies);
598}
599
600/* Determine if previously allocated or extended slice is complete or not */
601static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
602{
603 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
604 return false;
605
606 return 1;
607}
608
609/* Trim the used slices and adjust slice start accordingly */
610static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
611{
612 unsigned long nr_slices, time_elapsed, io_trim;
613 u64 bytes_trim, tmp;
614
615 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
616
617 /*
618 * If bps are unlimited (-1), then time slice don't get
619 * renewed. Don't try to trim the slice if slice is used. A new
620 * slice will start when appropriate.
621 */
622 if (throtl_slice_used(tg, rw))
623 return;
624
625 /*
626 * A bio has been dispatched. Also adjust slice_end. It might happen
627 * that initially cgroup limit was very low resulting in high
628 * slice_end, but later limit was bumped up and bio was dispached
629 * sooner, then we need to reduce slice_end. A high bogus slice_end
630 * is bad because it does not allow new slice to start.
631 */
632
633 throtl_set_slice_end(tg, rw, jiffies + throtl_slice);
634
635 time_elapsed = jiffies - tg->slice_start[rw];
636
637 nr_slices = time_elapsed / throtl_slice;
638
639 if (!nr_slices)
640 return;
641 tmp = tg->bps[rw] * throtl_slice * nr_slices;
642 do_div(tmp, HZ);
643 bytes_trim = tmp;
644
645 io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
646
647 if (!bytes_trim && !io_trim)
648 return;
649
650 if (tg->bytes_disp[rw] >= bytes_trim)
651 tg->bytes_disp[rw] -= bytes_trim;
652 else
653 tg->bytes_disp[rw] = 0;
654
655 if (tg->io_disp[rw] >= io_trim)
656 tg->io_disp[rw] -= io_trim;
657 else
658 tg->io_disp[rw] = 0;
659
660 tg->slice_start[rw] += nr_slices * throtl_slice;
661
662 throtl_log(&tg->service_queue,
663 "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
664 rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
665 tg->slice_start[rw], tg->slice_end[rw], jiffies);
666}
667
668static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
669 unsigned long *wait)
670{
671 bool rw = bio_data_dir(bio);
672 unsigned int io_allowed;
673 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
674 u64 tmp;
675
676 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
677
678 /* Slice has just started. Consider one slice interval */
679 if (!jiffy_elapsed)
680 jiffy_elapsed_rnd = throtl_slice;
681
682 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
683
684 /*
685 * jiffy_elapsed_rnd should not be a big value as minimum iops can be
686 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
687 * will allow dispatch after 1 second and after that slice should
688 * have been trimmed.
689 */
690
691 tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
692 do_div(tmp, HZ);
693
694 if (tmp > UINT_MAX)
695 io_allowed = UINT_MAX;
696 else
697 io_allowed = tmp;
698
699 if (tg->io_disp[rw] + 1 <= io_allowed) {
700 if (wait)
701 *wait = 0;
702 return true;
703 }
704
705 /* Calc approx time to dispatch */
706 jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
707
708 if (jiffy_wait > jiffy_elapsed)
709 jiffy_wait = jiffy_wait - jiffy_elapsed;
710 else
711 jiffy_wait = 1;
712
713 if (wait)
714 *wait = jiffy_wait;
715 return 0;
716}
717
718static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
719 unsigned long *wait)
720{
721 bool rw = bio_data_dir(bio);
722 u64 bytes_allowed, extra_bytes, tmp;
723 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
724
725 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
726
727 /* Slice has just started. Consider one slice interval */
728 if (!jiffy_elapsed)
729 jiffy_elapsed_rnd = throtl_slice;
730
731 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
732
733 tmp = tg->bps[rw] * jiffy_elapsed_rnd;
734 do_div(tmp, HZ);
735 bytes_allowed = tmp;
736
737 if (tg->bytes_disp[rw] + bio->bi_iter.bi_size <= bytes_allowed) {
738 if (wait)
739 *wait = 0;
740 return true;
741 }
742
743 /* Calc approx time to dispatch */
744 extra_bytes = tg->bytes_disp[rw] + bio->bi_iter.bi_size - bytes_allowed;
745 jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
746
747 if (!jiffy_wait)
748 jiffy_wait = 1;
749
750 /*
751 * This wait time is without taking into consideration the rounding
752 * up we did. Add that time also.
753 */
754 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
755 if (wait)
756 *wait = jiffy_wait;
757 return 0;
758}
759
760/*
761 * Returns whether one can dispatch a bio or not. Also returns approx number
762 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
763 */
764static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
765 unsigned long *wait)
766{
767 bool rw = bio_data_dir(bio);
768 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
769
770 /*
771 * Currently whole state machine of group depends on first bio
772 * queued in the group bio list. So one should not be calling
773 * this function with a different bio if there are other bios
774 * queued.
775 */
776 BUG_ON(tg->service_queue.nr_queued[rw] &&
777 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
778
779 /* If tg->bps = -1, then BW is unlimited */
780 if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
781 if (wait)
782 *wait = 0;
783 return true;
784 }
785
786 /*
787 * If previous slice expired, start a new one otherwise renew/extend
788 * existing slice to make sure it is at least throtl_slice interval
789 * long since now.
790 */
791 if (throtl_slice_used(tg, rw))
792 throtl_start_new_slice(tg, rw);
793 else {
794 if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
795 throtl_extend_slice(tg, rw, jiffies + throtl_slice);
796 }
797
798 if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
799 tg_with_in_iops_limit(tg, bio, &iops_wait)) {
800 if (wait)
801 *wait = 0;
802 return 1;
803 }
804
805 max_wait = max(bps_wait, iops_wait);
806
807 if (wait)
808 *wait = max_wait;
809
810 if (time_before(tg->slice_end[rw], jiffies + max_wait))
811 throtl_extend_slice(tg, rw, jiffies + max_wait);
812
813 return 0;
814}
815
816static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
817{
818 bool rw = bio_data_dir(bio);
819
820 /* Charge the bio to the group */
821 tg->bytes_disp[rw] += bio->bi_iter.bi_size;
822 tg->io_disp[rw]++;
823
824 /*
825 * REQ_THROTTLED is used to prevent the same bio to be throttled
826 * more than once as a throttled bio will go through blk-throtl the
827 * second time when it eventually gets issued. Set it when a bio
828 * is being charged to a tg.
829 */
830 if (!(bio->bi_rw & REQ_THROTTLED))
831 bio->bi_rw |= REQ_THROTTLED;
832}
833
834/**
835 * throtl_add_bio_tg - add a bio to the specified throtl_grp
836 * @bio: bio to add
837 * @qn: qnode to use
838 * @tg: the target throtl_grp
839 *
840 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
841 * tg->qnode_on_self[] is used.
842 */
843static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
844 struct throtl_grp *tg)
845{
846 struct throtl_service_queue *sq = &tg->service_queue;
847 bool rw = bio_data_dir(bio);
848
849 if (!qn)
850 qn = &tg->qnode_on_self[rw];
851
852 /*
853 * If @tg doesn't currently have any bios queued in the same
854 * direction, queueing @bio can change when @tg should be
855 * dispatched. Mark that @tg was empty. This is automatically
856 * cleaered on the next tg_update_disptime().
857 */
858 if (!sq->nr_queued[rw])
859 tg->flags |= THROTL_TG_WAS_EMPTY;
860
861 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
862
863 sq->nr_queued[rw]++;
864 throtl_enqueue_tg(tg);
865}
866
867static void tg_update_disptime(struct throtl_grp *tg)
868{
869 struct throtl_service_queue *sq = &tg->service_queue;
870 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
871 struct bio *bio;
872
873 if ((bio = throtl_peek_queued(&sq->queued[READ])))
874 tg_may_dispatch(tg, bio, &read_wait);
875
876 if ((bio = throtl_peek_queued(&sq->queued[WRITE])))
877 tg_may_dispatch(tg, bio, &write_wait);
878
879 min_wait = min(read_wait, write_wait);
880 disptime = jiffies + min_wait;
881
882 /* Update dispatch time */
883 throtl_dequeue_tg(tg);
884 tg->disptime = disptime;
885 throtl_enqueue_tg(tg);
886
887 /* see throtl_add_bio_tg() */
888 tg->flags &= ~THROTL_TG_WAS_EMPTY;
889}
890
891static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
892 struct throtl_grp *parent_tg, bool rw)
893{
894 if (throtl_slice_used(parent_tg, rw)) {
895 throtl_start_new_slice_with_credit(parent_tg, rw,
896 child_tg->slice_start[rw]);
897 }
898
899}
900
901static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
902{
903 struct throtl_service_queue *sq = &tg->service_queue;
904 struct throtl_service_queue *parent_sq = sq->parent_sq;
905 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
906 struct throtl_grp *tg_to_put = NULL;
907 struct bio *bio;
908
909 /*
910 * @bio is being transferred from @tg to @parent_sq. Popping a bio
911 * from @tg may put its reference and @parent_sq might end up
912 * getting released prematurely. Remember the tg to put and put it
913 * after @bio is transferred to @parent_sq.
914 */
915 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
916 sq->nr_queued[rw]--;
917
918 throtl_charge_bio(tg, bio);
919
920 /*
921 * If our parent is another tg, we just need to transfer @bio to
922 * the parent using throtl_add_bio_tg(). If our parent is
923 * @td->service_queue, @bio is ready to be issued. Put it on its
924 * bio_lists[] and decrease total number queued. The caller is
925 * responsible for issuing these bios.
926 */
927 if (parent_tg) {
928 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
929 start_parent_slice_with_credit(tg, parent_tg, rw);
930 } else {
931 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
932 &parent_sq->queued[rw]);
933 BUG_ON(tg->td->nr_queued[rw] <= 0);
934 tg->td->nr_queued[rw]--;
935 }
936
937 throtl_trim_slice(tg, rw);
938
939 if (tg_to_put)
940 blkg_put(tg_to_blkg(tg_to_put));
941}
942
943static int throtl_dispatch_tg(struct throtl_grp *tg)
944{
945 struct throtl_service_queue *sq = &tg->service_queue;
946 unsigned int nr_reads = 0, nr_writes = 0;
947 unsigned int max_nr_reads = throtl_grp_quantum*3/4;
948 unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
949 struct bio *bio;
950
951 /* Try to dispatch 75% READS and 25% WRITES */
952
953 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
954 tg_may_dispatch(tg, bio, NULL)) {
955
956 tg_dispatch_one_bio(tg, bio_data_dir(bio));
957 nr_reads++;
958
959 if (nr_reads >= max_nr_reads)
960 break;
961 }
962
963 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
964 tg_may_dispatch(tg, bio, NULL)) {
965
966 tg_dispatch_one_bio(tg, bio_data_dir(bio));
967 nr_writes++;
968
969 if (nr_writes >= max_nr_writes)
970 break;
971 }
972
973 return nr_reads + nr_writes;
974}
975
976static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
977{
978 unsigned int nr_disp = 0;
979
980 while (1) {
981 struct throtl_grp *tg = throtl_rb_first(parent_sq);
982 struct throtl_service_queue *sq = &tg->service_queue;
983
984 if (!tg)
985 break;
986
987 if (time_before(jiffies, tg->disptime))
988 break;
989
990 throtl_dequeue_tg(tg);
991
992 nr_disp += throtl_dispatch_tg(tg);
993
994 if (sq->nr_queued[0] || sq->nr_queued[1])
995 tg_update_disptime(tg);
996
997 if (nr_disp >= throtl_quantum)
998 break;
999 }
1000
1001 return nr_disp;
1002}
1003
1004/**
1005 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1006 * @arg: the throtl_service_queue being serviced
1007 *
1008 * This timer is armed when a child throtl_grp with active bio's become
1009 * pending and queued on the service_queue's pending_tree and expires when
1010 * the first child throtl_grp should be dispatched. This function
1011 * dispatches bio's from the children throtl_grps to the parent
1012 * service_queue.
1013 *
1014 * If the parent's parent is another throtl_grp, dispatching is propagated
1015 * by either arming its pending_timer or repeating dispatch directly. If
1016 * the top-level service_tree is reached, throtl_data->dispatch_work is
1017 * kicked so that the ready bio's are issued.
1018 */
1019static void throtl_pending_timer_fn(unsigned long arg)
1020{
1021 struct throtl_service_queue *sq = (void *)arg;
1022 struct throtl_grp *tg = sq_to_tg(sq);
1023 struct throtl_data *td = sq_to_td(sq);
1024 struct request_queue *q = td->queue;
1025 struct throtl_service_queue *parent_sq;
1026 bool dispatched;
1027 int ret;
1028
1029 spin_lock_irq(q->queue_lock);
1030again:
1031 parent_sq = sq->parent_sq;
1032 dispatched = false;
1033
1034 while (true) {
1035 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1036 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1037 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1038
1039 ret = throtl_select_dispatch(sq);
1040 if (ret) {
1041 throtl_log(sq, "bios disp=%u", ret);
1042 dispatched = true;
1043 }
1044
1045 if (throtl_schedule_next_dispatch(sq, false))
1046 break;
1047
1048 /* this dispatch windows is still open, relax and repeat */
1049 spin_unlock_irq(q->queue_lock);
1050 cpu_relax();
1051 spin_lock_irq(q->queue_lock);
1052 }
1053
1054 if (!dispatched)
1055 goto out_unlock;
1056
1057 if (parent_sq) {
1058 /* @parent_sq is another throl_grp, propagate dispatch */
1059 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1060 tg_update_disptime(tg);
1061 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1062 /* window is already open, repeat dispatching */
1063 sq = parent_sq;
1064 tg = sq_to_tg(sq);
1065 goto again;
1066 }
1067 }
1068 } else {
1069 /* reached the top-level, queue issueing */
1070 queue_work(kthrotld_workqueue, &td->dispatch_work);
1071 }
1072out_unlock:
1073 spin_unlock_irq(q->queue_lock);
1074}
1075
1076/**
1077 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1078 * @work: work item being executed
1079 *
1080 * This function is queued for execution when bio's reach the bio_lists[]
1081 * of throtl_data->service_queue. Those bio's are ready and issued by this
1082 * function.
1083 */
1084static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1085{
1086 struct throtl_data *td = container_of(work, struct throtl_data,
1087 dispatch_work);
1088 struct throtl_service_queue *td_sq = &td->service_queue;
1089 struct request_queue *q = td->queue;
1090 struct bio_list bio_list_on_stack;
1091 struct bio *bio;
1092 struct blk_plug plug;
1093 int rw;
1094
1095 bio_list_init(&bio_list_on_stack);
1096
1097 spin_lock_irq(q->queue_lock);
1098 for (rw = READ; rw <= WRITE; rw++)
1099 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1100 bio_list_add(&bio_list_on_stack, bio);
1101 spin_unlock_irq(q->queue_lock);
1102
1103 if (!bio_list_empty(&bio_list_on_stack)) {
1104 blk_start_plug(&plug);
1105 while((bio = bio_list_pop(&bio_list_on_stack)))
1106 generic_make_request(bio);
1107 blk_finish_plug(&plug);
1108 }
1109}
1110
1111static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1112 int off)
1113{
1114 struct throtl_grp *tg = pd_to_tg(pd);
1115 u64 v = *(u64 *)((void *)tg + off);
1116
1117 if (v == -1)
1118 return 0;
1119 return __blkg_prfill_u64(sf, pd, v);
1120}
1121
1122static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1123 int off)
1124{
1125 struct throtl_grp *tg = pd_to_tg(pd);
1126 unsigned int v = *(unsigned int *)((void *)tg + off);
1127
1128 if (v == -1)
1129 return 0;
1130 return __blkg_prfill_u64(sf, pd, v);
1131}
1132
1133static int tg_print_conf_u64(struct seq_file *sf, void *v)
1134{
1135 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1136 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1137 return 0;
1138}
1139
1140static int tg_print_conf_uint(struct seq_file *sf, void *v)
1141{
1142 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1143 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1144 return 0;
1145}
1146
1147static void tg_conf_updated(struct throtl_grp *tg)
1148{
1149 struct throtl_service_queue *sq = &tg->service_queue;
1150 struct cgroup_subsys_state *pos_css;
1151 struct blkcg_gq *blkg;
1152
1153 throtl_log(&tg->service_queue,
1154 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1155 tg->bps[READ], tg->bps[WRITE],
1156 tg->iops[READ], tg->iops[WRITE]);
1157
1158 /*
1159 * Update has_rules[] flags for the updated tg's subtree. A tg is
1160 * considered to have rules if either the tg itself or any of its
1161 * ancestors has rules. This identifies groups without any
1162 * restrictions in the whole hierarchy and allows them to bypass
1163 * blk-throttle.
1164 */
1165 blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg))
1166 tg_update_has_rules(blkg_to_tg(blkg));
1167
1168 /*
1169 * We're already holding queue_lock and know @tg is valid. Let's
1170 * apply the new config directly.
1171 *
1172 * Restart the slices for both READ and WRITES. It might happen
1173 * that a group's limit are dropped suddenly and we don't want to
1174 * account recently dispatched IO with new low rate.
1175 */
1176 throtl_start_new_slice(tg, 0);
1177 throtl_start_new_slice(tg, 1);
1178
1179 if (tg->flags & THROTL_TG_PENDING) {
1180 tg_update_disptime(tg);
1181 throtl_schedule_next_dispatch(sq->parent_sq, true);
1182 }
1183}
1184
1185static ssize_t tg_set_conf(struct kernfs_open_file *of,
1186 char *buf, size_t nbytes, loff_t off, bool is_u64)
1187{
1188 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1189 struct blkg_conf_ctx ctx;
1190 struct throtl_grp *tg;
1191 int ret;
1192 u64 v;
1193
1194 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1195 if (ret)
1196 return ret;
1197
1198 ret = -EINVAL;
1199 if (sscanf(ctx.body, "%llu", &v) != 1)
1200 goto out_finish;
1201 if (!v)
1202 v = -1;
1203
1204 tg = blkg_to_tg(ctx.blkg);
1205
1206 if (is_u64)
1207 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1208 else
1209 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1210
1211 tg_conf_updated(tg);
1212 ret = 0;
1213out_finish:
1214 blkg_conf_finish(&ctx);
1215 return ret ?: nbytes;
1216}
1217
1218static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1219 char *buf, size_t nbytes, loff_t off)
1220{
1221 return tg_set_conf(of, buf, nbytes, off, true);
1222}
1223
1224static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1225 char *buf, size_t nbytes, loff_t off)
1226{
1227 return tg_set_conf(of, buf, nbytes, off, false);
1228}
1229
1230static struct cftype throtl_legacy_files[] = {
1231 {
1232 .name = "throttle.read_bps_device",
1233 .private = offsetof(struct throtl_grp, bps[READ]),
1234 .seq_show = tg_print_conf_u64,
1235 .write = tg_set_conf_u64,
1236 },
1237 {
1238 .name = "throttle.write_bps_device",
1239 .private = offsetof(struct throtl_grp, bps[WRITE]),
1240 .seq_show = tg_print_conf_u64,
1241 .write = tg_set_conf_u64,
1242 },
1243 {
1244 .name = "throttle.read_iops_device",
1245 .private = offsetof(struct throtl_grp, iops[READ]),
1246 .seq_show = tg_print_conf_uint,
1247 .write = tg_set_conf_uint,
1248 },
1249 {
1250 .name = "throttle.write_iops_device",
1251 .private = offsetof(struct throtl_grp, iops[WRITE]),
1252 .seq_show = tg_print_conf_uint,
1253 .write = tg_set_conf_uint,
1254 },
1255 {
1256 .name = "throttle.io_service_bytes",
1257 .private = (unsigned long)&blkcg_policy_throtl,
1258 .seq_show = blkg_print_stat_bytes,
1259 },
1260 {
1261 .name = "throttle.io_serviced",
1262 .private = (unsigned long)&blkcg_policy_throtl,
1263 .seq_show = blkg_print_stat_ios,
1264 },
1265 { } /* terminate */
1266};
1267
1268static u64 tg_prfill_max(struct seq_file *sf, struct blkg_policy_data *pd,
1269 int off)
1270{
1271 struct throtl_grp *tg = pd_to_tg(pd);
1272 const char *dname = blkg_dev_name(pd->blkg);
1273 char bufs[4][21] = { "max", "max", "max", "max" };
1274
1275 if (!dname)
1276 return 0;
1277 if (tg->bps[READ] == -1 && tg->bps[WRITE] == -1 &&
1278 tg->iops[READ] == -1 && tg->iops[WRITE] == -1)
1279 return 0;
1280
1281 if (tg->bps[READ] != -1)
1282 snprintf(bufs[0], sizeof(bufs[0]), "%llu", tg->bps[READ]);
1283 if (tg->bps[WRITE] != -1)
1284 snprintf(bufs[1], sizeof(bufs[1]), "%llu", tg->bps[WRITE]);
1285 if (tg->iops[READ] != -1)
1286 snprintf(bufs[2], sizeof(bufs[2]), "%u", tg->iops[READ]);
1287 if (tg->iops[WRITE] != -1)
1288 snprintf(bufs[3], sizeof(bufs[3]), "%u", tg->iops[WRITE]);
1289
1290 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s\n",
1291 dname, bufs[0], bufs[1], bufs[2], bufs[3]);
1292 return 0;
1293}
1294
1295static int tg_print_max(struct seq_file *sf, void *v)
1296{
1297 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_max,
1298 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1299 return 0;
1300}
1301
1302static ssize_t tg_set_max(struct kernfs_open_file *of,
1303 char *buf, size_t nbytes, loff_t off)
1304{
1305 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1306 struct blkg_conf_ctx ctx;
1307 struct throtl_grp *tg;
1308 u64 v[4];
1309 int ret;
1310
1311 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1312 if (ret)
1313 return ret;
1314
1315 tg = blkg_to_tg(ctx.blkg);
1316
1317 v[0] = tg->bps[READ];
1318 v[1] = tg->bps[WRITE];
1319 v[2] = tg->iops[READ];
1320 v[3] = tg->iops[WRITE];
1321
1322 while (true) {
1323 char tok[27]; /* wiops=18446744073709551616 */
1324 char *p;
1325 u64 val = -1;
1326 int len;
1327
1328 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1329 break;
1330 if (tok[0] == '\0')
1331 break;
1332 ctx.body += len;
1333
1334 ret = -EINVAL;
1335 p = tok;
1336 strsep(&p, "=");
1337 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1338 goto out_finish;
1339
1340 ret = -ERANGE;
1341 if (!val)
1342 goto out_finish;
1343
1344 ret = -EINVAL;
1345 if (!strcmp(tok, "rbps"))
1346 v[0] = val;
1347 else if (!strcmp(tok, "wbps"))
1348 v[1] = val;
1349 else if (!strcmp(tok, "riops"))
1350 v[2] = min_t(u64, val, UINT_MAX);
1351 else if (!strcmp(tok, "wiops"))
1352 v[3] = min_t(u64, val, UINT_MAX);
1353 else
1354 goto out_finish;
1355 }
1356
1357 tg->bps[READ] = v[0];
1358 tg->bps[WRITE] = v[1];
1359 tg->iops[READ] = v[2];
1360 tg->iops[WRITE] = v[3];
1361
1362 tg_conf_updated(tg);
1363 ret = 0;
1364out_finish:
1365 blkg_conf_finish(&ctx);
1366 return ret ?: nbytes;
1367}
1368
1369static struct cftype throtl_files[] = {
1370 {
1371 .name = "max",
1372 .flags = CFTYPE_NOT_ON_ROOT,
1373 .seq_show = tg_print_max,
1374 .write = tg_set_max,
1375 },
1376 { } /* terminate */
1377};
1378
1379static void throtl_shutdown_wq(struct request_queue *q)
1380{
1381 struct throtl_data *td = q->td;
1382
1383 cancel_work_sync(&td->dispatch_work);
1384}
1385
1386static struct blkcg_policy blkcg_policy_throtl = {
1387 .dfl_cftypes = throtl_files,
1388 .legacy_cftypes = throtl_legacy_files,
1389
1390 .pd_alloc_fn = throtl_pd_alloc,
1391 .pd_init_fn = throtl_pd_init,
1392 .pd_online_fn = throtl_pd_online,
1393 .pd_free_fn = throtl_pd_free,
1394};
1395
1396bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
1397 struct bio *bio)
1398{
1399 struct throtl_qnode *qn = NULL;
1400 struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
1401 struct throtl_service_queue *sq;
1402 bool rw = bio_data_dir(bio);
1403 bool throttled = false;
1404
1405 WARN_ON_ONCE(!rcu_read_lock_held());
1406
1407 /* see throtl_charge_bio() */
1408 if ((bio->bi_rw & REQ_THROTTLED) || !tg->has_rules[rw])
1409 goto out;
1410
1411 spin_lock_irq(q->queue_lock);
1412
1413 if (unlikely(blk_queue_bypass(q)))
1414 goto out_unlock;
1415
1416 sq = &tg->service_queue;
1417
1418 while (true) {
1419 /* throtl is FIFO - if bios are already queued, should queue */
1420 if (sq->nr_queued[rw])
1421 break;
1422
1423 /* if above limits, break to queue */
1424 if (!tg_may_dispatch(tg, bio, NULL))
1425 break;
1426
1427 /* within limits, let's charge and dispatch directly */
1428 throtl_charge_bio(tg, bio);
1429
1430 /*
1431 * We need to trim slice even when bios are not being queued
1432 * otherwise it might happen that a bio is not queued for
1433 * a long time and slice keeps on extending and trim is not
1434 * called for a long time. Now if limits are reduced suddenly
1435 * we take into account all the IO dispatched so far at new
1436 * low rate and * newly queued IO gets a really long dispatch
1437 * time.
1438 *
1439 * So keep on trimming slice even if bio is not queued.
1440 */
1441 throtl_trim_slice(tg, rw);
1442
1443 /*
1444 * @bio passed through this layer without being throttled.
1445 * Climb up the ladder. If we''re already at the top, it
1446 * can be executed directly.
1447 */
1448 qn = &tg->qnode_on_parent[rw];
1449 sq = sq->parent_sq;
1450 tg = sq_to_tg(sq);
1451 if (!tg)
1452 goto out_unlock;
1453 }
1454
1455 /* out-of-limit, queue to @tg */
1456 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
1457 rw == READ ? 'R' : 'W',
1458 tg->bytes_disp[rw], bio->bi_iter.bi_size, tg->bps[rw],
1459 tg->io_disp[rw], tg->iops[rw],
1460 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1461
1462 bio_associate_current(bio);
1463 tg->td->nr_queued[rw]++;
1464 throtl_add_bio_tg(bio, qn, tg);
1465 throttled = true;
1466
1467 /*
1468 * Update @tg's dispatch time and force schedule dispatch if @tg
1469 * was empty before @bio. The forced scheduling isn't likely to
1470 * cause undue delay as @bio is likely to be dispatched directly if
1471 * its @tg's disptime is not in the future.
1472 */
1473 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1474 tg_update_disptime(tg);
1475 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
1476 }
1477
1478out_unlock:
1479 spin_unlock_irq(q->queue_lock);
1480out:
1481 /*
1482 * As multiple blk-throtls may stack in the same issue path, we
1483 * don't want bios to leave with the flag set. Clear the flag if
1484 * being issued.
1485 */
1486 if (!throttled)
1487 bio->bi_rw &= ~REQ_THROTTLED;
1488 return throttled;
1489}
1490
1491/*
1492 * Dispatch all bios from all children tg's queued on @parent_sq. On
1493 * return, @parent_sq is guaranteed to not have any active children tg's
1494 * and all bios from previously active tg's are on @parent_sq->bio_lists[].
1495 */
1496static void tg_drain_bios(struct throtl_service_queue *parent_sq)
1497{
1498 struct throtl_grp *tg;
1499
1500 while ((tg = throtl_rb_first(parent_sq))) {
1501 struct throtl_service_queue *sq = &tg->service_queue;
1502 struct bio *bio;
1503
1504 throtl_dequeue_tg(tg);
1505
1506 while ((bio = throtl_peek_queued(&sq->queued[READ])))
1507 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1508 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
1509 tg_dispatch_one_bio(tg, bio_data_dir(bio));
1510 }
1511}
1512
1513/**
1514 * blk_throtl_drain - drain throttled bios
1515 * @q: request_queue to drain throttled bios for
1516 *
1517 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1518 */
1519void blk_throtl_drain(struct request_queue *q)
1520 __releases(q->queue_lock) __acquires(q->queue_lock)
1521{
1522 struct throtl_data *td = q->td;
1523 struct blkcg_gq *blkg;
1524 struct cgroup_subsys_state *pos_css;
1525 struct bio *bio;
1526 int rw;
1527
1528 queue_lockdep_assert_held(q);
1529 rcu_read_lock();
1530
1531 /*
1532 * Drain each tg while doing post-order walk on the blkg tree, so
1533 * that all bios are propagated to td->service_queue. It'd be
1534 * better to walk service_queue tree directly but blkg walk is
1535 * easier.
1536 */
1537 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
1538 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
1539
1540 /* finally, transfer bios from top-level tg's into the td */
1541 tg_drain_bios(&td->service_queue);
1542
1543 rcu_read_unlock();
1544 spin_unlock_irq(q->queue_lock);
1545
1546 /* all bios now should be in td->service_queue, issue them */
1547 for (rw = READ; rw <= WRITE; rw++)
1548 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
1549 NULL)))
1550 generic_make_request(bio);
1551
1552 spin_lock_irq(q->queue_lock);
1553}
1554
1555int blk_throtl_init(struct request_queue *q)
1556{
1557 struct throtl_data *td;
1558 int ret;
1559
1560 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1561 if (!td)
1562 return -ENOMEM;
1563
1564 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
1565 throtl_service_queue_init(&td->service_queue);
1566
1567 q->td = td;
1568 td->queue = q;
1569
1570 /* activate policy */
1571 ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1572 if (ret)
1573 kfree(td);
1574 return ret;
1575}
1576
1577void blk_throtl_exit(struct request_queue *q)
1578{
1579 BUG_ON(!q->td);
1580 throtl_shutdown_wq(q);
1581 blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1582 kfree(q->td);
1583}
1584
1585static int __init throtl_init(void)
1586{
1587 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1588 if (!kthrotld_workqueue)
1589 panic("Failed to create kthrotld\n");
1590
1591 return blkcg_policy_register(&blkcg_policy_throtl);
1592}
1593
1594module_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#define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
29#define MIN_THROTL_BPS (320 * 1024)
30#define MIN_THROTL_IOPS (10)
31#define DFL_LATENCY_TARGET (-1L)
32#define DFL_IDLE_THRESHOLD (0)
33#define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
34#define LATENCY_FILTERED_SSD (0)
35/*
36 * For HD, very small latency comes from sequential IO. Such IO is helpless to
37 * help determine if its IO is impacted by others, hence we ignore the IO
38 */
39#define LATENCY_FILTERED_HD (1000L) /* 1ms */
40
41/* A workqueue to queue throttle related work */
42static struct workqueue_struct *kthrotld_workqueue;
43
44#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
45
46/* We measure latency for request size from <= 4k to >= 1M */
47#define LATENCY_BUCKET_SIZE 9
48
49struct latency_bucket {
50 unsigned long total_latency; /* ns / 1024 */
51 int samples;
52};
53
54struct avg_latency_bucket {
55 unsigned long latency; /* ns / 1024 */
56 bool valid;
57};
58
59struct throtl_data
60{
61 /* service tree for active throtl groups */
62 struct throtl_service_queue service_queue;
63
64 struct request_queue *queue;
65
66 /* Total Number of queued bios on READ and WRITE lists */
67 unsigned int nr_queued[2];
68
69 unsigned int throtl_slice;
70
71 /* Work for dispatching throttled bios */
72 struct work_struct dispatch_work;
73 unsigned int limit_index;
74 bool limit_valid[LIMIT_CNT];
75
76 unsigned long low_upgrade_time;
77 unsigned long low_downgrade_time;
78
79 unsigned int scale;
80
81 struct latency_bucket tmp_buckets[2][LATENCY_BUCKET_SIZE];
82 struct avg_latency_bucket avg_buckets[2][LATENCY_BUCKET_SIZE];
83 struct latency_bucket __percpu *latency_buckets[2];
84 unsigned long last_calculate_time;
85 unsigned long filtered_latency;
86
87 bool track_bio_latency;
88};
89
90static void throtl_pending_timer_fn(struct timer_list *t);
91
92static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
93{
94 return pd_to_blkg(&tg->pd);
95}
96
97/**
98 * sq_to_tg - return the throl_grp the specified service queue belongs to
99 * @sq: the throtl_service_queue of interest
100 *
101 * Return the throtl_grp @sq belongs to. If @sq is the top-level one
102 * embedded in throtl_data, %NULL is returned.
103 */
104static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
105{
106 if (sq && sq->parent_sq)
107 return container_of(sq, struct throtl_grp, service_queue);
108 else
109 return NULL;
110}
111
112/**
113 * sq_to_td - return throtl_data the specified service queue belongs to
114 * @sq: the throtl_service_queue of interest
115 *
116 * A service_queue can be embedded in either a throtl_grp or throtl_data.
117 * Determine the associated throtl_data accordingly and return it.
118 */
119static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
120{
121 struct throtl_grp *tg = sq_to_tg(sq);
122
123 if (tg)
124 return tg->td;
125 else
126 return container_of(sq, struct throtl_data, service_queue);
127}
128
129/*
130 * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
131 * make the IO dispatch more smooth.
132 * Scale up: linearly scale up according to elapsed time since upgrade. For
133 * every throtl_slice, the limit scales up 1/2 .low limit till the
134 * limit hits .max limit
135 * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
136 */
137static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
138{
139 /* arbitrary value to avoid too big scale */
140 if (td->scale < 4096 && time_after_eq(jiffies,
141 td->low_upgrade_time + td->scale * td->throtl_slice))
142 td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
143
144 return low + (low >> 1) * td->scale;
145}
146
147static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
148{
149 struct blkcg_gq *blkg = tg_to_blkg(tg);
150 struct throtl_data *td;
151 uint64_t ret;
152
153 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
154 return U64_MAX;
155
156 td = tg->td;
157 ret = tg->bps[rw][td->limit_index];
158 if (ret == 0 && td->limit_index == LIMIT_LOW) {
159 /* intermediate node or iops isn't 0 */
160 if (!list_empty(&blkg->blkcg->css.children) ||
161 tg->iops[rw][td->limit_index])
162 return U64_MAX;
163 else
164 return MIN_THROTL_BPS;
165 }
166
167 if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
168 tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
169 uint64_t adjusted;
170
171 adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
172 ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
173 }
174 return ret;
175}
176
177static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
178{
179 struct blkcg_gq *blkg = tg_to_blkg(tg);
180 struct throtl_data *td;
181 unsigned int ret;
182
183 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
184 return UINT_MAX;
185
186 td = tg->td;
187 ret = tg->iops[rw][td->limit_index];
188 if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
189 /* intermediate node or bps isn't 0 */
190 if (!list_empty(&blkg->blkcg->css.children) ||
191 tg->bps[rw][td->limit_index])
192 return UINT_MAX;
193 else
194 return MIN_THROTL_IOPS;
195 }
196
197 if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
198 tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
199 uint64_t adjusted;
200
201 adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
202 if (adjusted > UINT_MAX)
203 adjusted = UINT_MAX;
204 ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
205 }
206 return ret;
207}
208
209#define request_bucket_index(sectors) \
210 clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
211
212/**
213 * throtl_log - log debug message via blktrace
214 * @sq: the service_queue being reported
215 * @fmt: printf format string
216 * @args: printf args
217 *
218 * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
219 * throtl_grp; otherwise, just "throtl".
220 */
221#define throtl_log(sq, fmt, args...) do { \
222 struct throtl_grp *__tg = sq_to_tg((sq)); \
223 struct throtl_data *__td = sq_to_td((sq)); \
224 \
225 (void)__td; \
226 if (likely(!blk_trace_note_message_enabled(__td->queue))) \
227 break; \
228 if ((__tg)) { \
229 blk_add_cgroup_trace_msg(__td->queue, \
230 &tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\
231 } else { \
232 blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
233 } \
234} while (0)
235
236static inline unsigned int throtl_bio_data_size(struct bio *bio)
237{
238 /* assume it's one sector */
239 if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
240 return 512;
241 return bio->bi_iter.bi_size;
242}
243
244static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
245{
246 INIT_LIST_HEAD(&qn->node);
247 bio_list_init(&qn->bios);
248 qn->tg = tg;
249}
250
251/**
252 * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
253 * @bio: bio being added
254 * @qn: qnode to add bio to
255 * @queued: the service_queue->queued[] list @qn belongs to
256 *
257 * Add @bio to @qn and put @qn on @queued if it's not already on.
258 * @qn->tg's reference count is bumped when @qn is activated. See the
259 * comment on top of throtl_qnode definition for details.
260 */
261static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
262 struct list_head *queued)
263{
264 bio_list_add(&qn->bios, bio);
265 if (list_empty(&qn->node)) {
266 list_add_tail(&qn->node, queued);
267 blkg_get(tg_to_blkg(qn->tg));
268 }
269}
270
271/**
272 * throtl_peek_queued - peek the first bio on a qnode list
273 * @queued: the qnode list to peek
274 */
275static struct bio *throtl_peek_queued(struct list_head *queued)
276{
277 struct throtl_qnode *qn;
278 struct bio *bio;
279
280 if (list_empty(queued))
281 return NULL;
282
283 qn = list_first_entry(queued, struct throtl_qnode, node);
284 bio = bio_list_peek(&qn->bios);
285 WARN_ON_ONCE(!bio);
286 return bio;
287}
288
289/**
290 * throtl_pop_queued - pop the first bio form a qnode list
291 * @queued: the qnode list to pop a bio from
292 * @tg_to_put: optional out argument for throtl_grp to put
293 *
294 * Pop the first bio from the qnode list @queued. After popping, the first
295 * qnode is removed from @queued if empty or moved to the end of @queued so
296 * that the popping order is round-robin.
297 *
298 * When the first qnode is removed, its associated throtl_grp should be put
299 * too. If @tg_to_put is NULL, this function automatically puts it;
300 * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
301 * responsible for putting it.
302 */
303static struct bio *throtl_pop_queued(struct list_head *queued,
304 struct throtl_grp **tg_to_put)
305{
306 struct throtl_qnode *qn;
307 struct bio *bio;
308
309 if (list_empty(queued))
310 return NULL;
311
312 qn = list_first_entry(queued, struct throtl_qnode, node);
313 bio = bio_list_pop(&qn->bios);
314 WARN_ON_ONCE(!bio);
315
316 if (bio_list_empty(&qn->bios)) {
317 list_del_init(&qn->node);
318 if (tg_to_put)
319 *tg_to_put = qn->tg;
320 else
321 blkg_put(tg_to_blkg(qn->tg));
322 } else {
323 list_move_tail(&qn->node, queued);
324 }
325
326 return bio;
327}
328
329/* init a service_queue, assumes the caller zeroed it */
330static void throtl_service_queue_init(struct throtl_service_queue *sq)
331{
332 INIT_LIST_HEAD(&sq->queued[READ]);
333 INIT_LIST_HEAD(&sq->queued[WRITE]);
334 sq->pending_tree = RB_ROOT_CACHED;
335 timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
336}
337
338static struct blkg_policy_data *throtl_pd_alloc(struct gendisk *disk,
339 struct blkcg *blkcg, gfp_t gfp)
340{
341 struct throtl_grp *tg;
342 int rw;
343
344 tg = kzalloc_node(sizeof(*tg), gfp, disk->node_id);
345 if (!tg)
346 return NULL;
347
348 if (blkg_rwstat_init(&tg->stat_bytes, gfp))
349 goto err_free_tg;
350
351 if (blkg_rwstat_init(&tg->stat_ios, gfp))
352 goto err_exit_stat_bytes;
353
354 throtl_service_queue_init(&tg->service_queue);
355
356 for (rw = READ; rw <= WRITE; rw++) {
357 throtl_qnode_init(&tg->qnode_on_self[rw], tg);
358 throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
359 }
360
361 RB_CLEAR_NODE(&tg->rb_node);
362 tg->bps[READ][LIMIT_MAX] = U64_MAX;
363 tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
364 tg->iops[READ][LIMIT_MAX] = UINT_MAX;
365 tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
366 tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
367 tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
368 tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
369 tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
370 /* LIMIT_LOW will have default value 0 */
371
372 tg->latency_target = DFL_LATENCY_TARGET;
373 tg->latency_target_conf = DFL_LATENCY_TARGET;
374 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
375 tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
376
377 return &tg->pd;
378
379err_exit_stat_bytes:
380 blkg_rwstat_exit(&tg->stat_bytes);
381err_free_tg:
382 kfree(tg);
383 return NULL;
384}
385
386static void throtl_pd_init(struct blkg_policy_data *pd)
387{
388 struct throtl_grp *tg = pd_to_tg(pd);
389 struct blkcg_gq *blkg = tg_to_blkg(tg);
390 struct throtl_data *td = blkg->q->td;
391 struct throtl_service_queue *sq = &tg->service_queue;
392
393 /*
394 * If on the default hierarchy, we switch to properly hierarchical
395 * behavior where limits on a given throtl_grp are applied to the
396 * whole subtree rather than just the group itself. e.g. If 16M
397 * read_bps limit is set on a parent group, summary bps of
398 * parent group and its subtree groups can't exceed 16M for the
399 * device.
400 *
401 * If not on the default hierarchy, the broken flat hierarchy
402 * behavior is retained where all throtl_grps are treated as if
403 * they're all separate root groups right below throtl_data.
404 * Limits of a group don't interact with limits of other groups
405 * regardless of the position of the group in the hierarchy.
406 */
407 sq->parent_sq = &td->service_queue;
408 if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
409 sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
410 tg->td = td;
411}
412
413/*
414 * Set has_rules[] if @tg or any of its parents have limits configured.
415 * This doesn't require walking up to the top of the hierarchy as the
416 * parent's has_rules[] is guaranteed to be correct.
417 */
418static void tg_update_has_rules(struct throtl_grp *tg)
419{
420 struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
421 struct throtl_data *td = tg->td;
422 int rw;
423
424 for (rw = READ; rw <= WRITE; rw++) {
425 tg->has_rules_iops[rw] =
426 (parent_tg && parent_tg->has_rules_iops[rw]) ||
427 (td->limit_valid[td->limit_index] &&
428 tg_iops_limit(tg, rw) != UINT_MAX);
429 tg->has_rules_bps[rw] =
430 (parent_tg && parent_tg->has_rules_bps[rw]) ||
431 (td->limit_valid[td->limit_index] &&
432 (tg_bps_limit(tg, rw) != U64_MAX));
433 }
434}
435
436static void throtl_pd_online(struct blkg_policy_data *pd)
437{
438 struct throtl_grp *tg = pd_to_tg(pd);
439 /*
440 * We don't want new groups to escape the limits of its ancestors.
441 * Update has_rules[] after a new group is brought online.
442 */
443 tg_update_has_rules(tg);
444}
445
446#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
447static void blk_throtl_update_limit_valid(struct throtl_data *td)
448{
449 struct cgroup_subsys_state *pos_css;
450 struct blkcg_gq *blkg;
451 bool low_valid = false;
452
453 rcu_read_lock();
454 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
455 struct throtl_grp *tg = blkg_to_tg(blkg);
456
457 if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
458 tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) {
459 low_valid = true;
460 break;
461 }
462 }
463 rcu_read_unlock();
464
465 td->limit_valid[LIMIT_LOW] = low_valid;
466}
467#else
468static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
469{
470}
471#endif
472
473static void throtl_upgrade_state(struct throtl_data *td);
474static void throtl_pd_offline(struct blkg_policy_data *pd)
475{
476 struct throtl_grp *tg = pd_to_tg(pd);
477
478 tg->bps[READ][LIMIT_LOW] = 0;
479 tg->bps[WRITE][LIMIT_LOW] = 0;
480 tg->iops[READ][LIMIT_LOW] = 0;
481 tg->iops[WRITE][LIMIT_LOW] = 0;
482
483 blk_throtl_update_limit_valid(tg->td);
484
485 if (!tg->td->limit_valid[tg->td->limit_index])
486 throtl_upgrade_state(tg->td);
487}
488
489static void throtl_pd_free(struct blkg_policy_data *pd)
490{
491 struct throtl_grp *tg = pd_to_tg(pd);
492
493 del_timer_sync(&tg->service_queue.pending_timer);
494 blkg_rwstat_exit(&tg->stat_bytes);
495 blkg_rwstat_exit(&tg->stat_ios);
496 kfree(tg);
497}
498
499static struct throtl_grp *
500throtl_rb_first(struct throtl_service_queue *parent_sq)
501{
502 struct rb_node *n;
503
504 n = rb_first_cached(&parent_sq->pending_tree);
505 WARN_ON_ONCE(!n);
506 if (!n)
507 return NULL;
508 return rb_entry_tg(n);
509}
510
511static void throtl_rb_erase(struct rb_node *n,
512 struct throtl_service_queue *parent_sq)
513{
514 rb_erase_cached(n, &parent_sq->pending_tree);
515 RB_CLEAR_NODE(n);
516}
517
518static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
519{
520 struct throtl_grp *tg;
521
522 tg = throtl_rb_first(parent_sq);
523 if (!tg)
524 return;
525
526 parent_sq->first_pending_disptime = tg->disptime;
527}
528
529static void tg_service_queue_add(struct throtl_grp *tg)
530{
531 struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
532 struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
533 struct rb_node *parent = NULL;
534 struct throtl_grp *__tg;
535 unsigned long key = tg->disptime;
536 bool leftmost = true;
537
538 while (*node != NULL) {
539 parent = *node;
540 __tg = rb_entry_tg(parent);
541
542 if (time_before(key, __tg->disptime))
543 node = &parent->rb_left;
544 else {
545 node = &parent->rb_right;
546 leftmost = false;
547 }
548 }
549
550 rb_link_node(&tg->rb_node, parent, node);
551 rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
552 leftmost);
553}
554
555static void throtl_enqueue_tg(struct throtl_grp *tg)
556{
557 if (!(tg->flags & THROTL_TG_PENDING)) {
558 tg_service_queue_add(tg);
559 tg->flags |= THROTL_TG_PENDING;
560 tg->service_queue.parent_sq->nr_pending++;
561 }
562}
563
564static void throtl_dequeue_tg(struct throtl_grp *tg)
565{
566 if (tg->flags & THROTL_TG_PENDING) {
567 struct throtl_service_queue *parent_sq =
568 tg->service_queue.parent_sq;
569
570 throtl_rb_erase(&tg->rb_node, parent_sq);
571 --parent_sq->nr_pending;
572 tg->flags &= ~THROTL_TG_PENDING;
573 }
574}
575
576/* Call with queue lock held */
577static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
578 unsigned long expires)
579{
580 unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
581
582 /*
583 * Since we are adjusting the throttle limit dynamically, the sleep
584 * time calculated according to previous limit might be invalid. It's
585 * possible the cgroup sleep time is very long and no other cgroups
586 * have IO running so notify the limit changes. Make sure the cgroup
587 * doesn't sleep too long to avoid the missed notification.
588 */
589 if (time_after(expires, max_expire))
590 expires = max_expire;
591 mod_timer(&sq->pending_timer, expires);
592 throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
593 expires - jiffies, jiffies);
594}
595
596/**
597 * throtl_schedule_next_dispatch - schedule the next dispatch cycle
598 * @sq: the service_queue to schedule dispatch for
599 * @force: force scheduling
600 *
601 * Arm @sq->pending_timer so that the next dispatch cycle starts on the
602 * dispatch time of the first pending child. Returns %true if either timer
603 * is armed or there's no pending child left. %false if the current
604 * dispatch window is still open and the caller should continue
605 * dispatching.
606 *
607 * If @force is %true, the dispatch timer is always scheduled and this
608 * function is guaranteed to return %true. This is to be used when the
609 * caller can't dispatch itself and needs to invoke pending_timer
610 * unconditionally. Note that forced scheduling is likely to induce short
611 * delay before dispatch starts even if @sq->first_pending_disptime is not
612 * in the future and thus shouldn't be used in hot paths.
613 */
614static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
615 bool force)
616{
617 /* any pending children left? */
618 if (!sq->nr_pending)
619 return true;
620
621 update_min_dispatch_time(sq);
622
623 /* is the next dispatch time in the future? */
624 if (force || time_after(sq->first_pending_disptime, jiffies)) {
625 throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
626 return true;
627 }
628
629 /* tell the caller to continue dispatching */
630 return false;
631}
632
633static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
634 bool rw, unsigned long start)
635{
636 tg->bytes_disp[rw] = 0;
637 tg->io_disp[rw] = 0;
638 tg->carryover_bytes[rw] = 0;
639 tg->carryover_ios[rw] = 0;
640
641 /*
642 * Previous slice has expired. We must have trimmed it after last
643 * bio dispatch. That means since start of last slice, we never used
644 * that bandwidth. Do try to make use of that bandwidth while giving
645 * credit.
646 */
647 if (time_after(start, tg->slice_start[rw]))
648 tg->slice_start[rw] = start;
649
650 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
651 throtl_log(&tg->service_queue,
652 "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
653 rw == READ ? 'R' : 'W', tg->slice_start[rw],
654 tg->slice_end[rw], jiffies);
655}
656
657static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
658 bool clear_carryover)
659{
660 tg->bytes_disp[rw] = 0;
661 tg->io_disp[rw] = 0;
662 tg->slice_start[rw] = jiffies;
663 tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
664 if (clear_carryover) {
665 tg->carryover_bytes[rw] = 0;
666 tg->carryover_ios[rw] = 0;
667 }
668
669 throtl_log(&tg->service_queue,
670 "[%c] new slice start=%lu end=%lu jiffies=%lu",
671 rw == READ ? 'R' : 'W', tg->slice_start[rw],
672 tg->slice_end[rw], jiffies);
673}
674
675static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
676 unsigned long jiffy_end)
677{
678 tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
679}
680
681static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
682 unsigned long jiffy_end)
683{
684 throtl_set_slice_end(tg, rw, jiffy_end);
685 throtl_log(&tg->service_queue,
686 "[%c] extend slice start=%lu end=%lu jiffies=%lu",
687 rw == READ ? 'R' : 'W', tg->slice_start[rw],
688 tg->slice_end[rw], jiffies);
689}
690
691/* Determine if previously allocated or extended slice is complete or not */
692static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
693{
694 if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
695 return false;
696
697 return true;
698}
699
700static unsigned int calculate_io_allowed(u32 iops_limit,
701 unsigned long jiffy_elapsed)
702{
703 unsigned int io_allowed;
704 u64 tmp;
705
706 /*
707 * jiffy_elapsed should not be a big value as minimum iops can be
708 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
709 * will allow dispatch after 1 second and after that slice should
710 * have been trimmed.
711 */
712
713 tmp = (u64)iops_limit * jiffy_elapsed;
714 do_div(tmp, HZ);
715
716 if (tmp > UINT_MAX)
717 io_allowed = UINT_MAX;
718 else
719 io_allowed = tmp;
720
721 return io_allowed;
722}
723
724static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
725{
726 /*
727 * Can result be wider than 64 bits?
728 * We check against 62, not 64, due to ilog2 truncation.
729 */
730 if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62)
731 return U64_MAX;
732 return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
733}
734
735/* Trim the used slices and adjust slice start accordingly */
736static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
737{
738 unsigned long time_elapsed;
739 long long bytes_trim;
740 int io_trim;
741
742 BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
743
744 /*
745 * If bps are unlimited (-1), then time slice don't get
746 * renewed. Don't try to trim the slice if slice is used. A new
747 * slice will start when appropriate.
748 */
749 if (throtl_slice_used(tg, rw))
750 return;
751
752 /*
753 * A bio has been dispatched. Also adjust slice_end. It might happen
754 * that initially cgroup limit was very low resulting in high
755 * slice_end, but later limit was bumped up and bio was dispatched
756 * sooner, then we need to reduce slice_end. A high bogus slice_end
757 * is bad because it does not allow new slice to start.
758 */
759
760 throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
761
762 time_elapsed = rounddown(jiffies - tg->slice_start[rw],
763 tg->td->throtl_slice);
764 if (!time_elapsed)
765 return;
766
767 bytes_trim = calculate_bytes_allowed(tg_bps_limit(tg, rw),
768 time_elapsed) +
769 tg->carryover_bytes[rw];
770 io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed) +
771 tg->carryover_ios[rw];
772 if (bytes_trim <= 0 && io_trim <= 0)
773 return;
774
775 tg->carryover_bytes[rw] = 0;
776 if ((long long)tg->bytes_disp[rw] >= bytes_trim)
777 tg->bytes_disp[rw] -= bytes_trim;
778 else
779 tg->bytes_disp[rw] = 0;
780
781 tg->carryover_ios[rw] = 0;
782 if ((int)tg->io_disp[rw] >= io_trim)
783 tg->io_disp[rw] -= io_trim;
784 else
785 tg->io_disp[rw] = 0;
786
787 tg->slice_start[rw] += time_elapsed;
788
789 throtl_log(&tg->service_queue,
790 "[%c] trim slice nr=%lu bytes=%lld io=%d start=%lu end=%lu jiffies=%lu",
791 rw == READ ? 'R' : 'W', time_elapsed / tg->td->throtl_slice,
792 bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw],
793 jiffies);
794}
795
796static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
797{
798 unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
799 u64 bps_limit = tg_bps_limit(tg, rw);
800 u32 iops_limit = tg_iops_limit(tg, rw);
801
802 /*
803 * If config is updated while bios are still throttled, calculate and
804 * accumulate how many bytes/ios are waited across changes. And
805 * carryover_bytes/ios will be used to calculate new wait time under new
806 * configuration.
807 */
808 if (bps_limit != U64_MAX)
809 tg->carryover_bytes[rw] +=
810 calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
811 tg->bytes_disp[rw];
812 if (iops_limit != UINT_MAX)
813 tg->carryover_ios[rw] +=
814 calculate_io_allowed(iops_limit, jiffy_elapsed) -
815 tg->io_disp[rw];
816}
817
818static void tg_update_carryover(struct throtl_grp *tg)
819{
820 if (tg->service_queue.nr_queued[READ])
821 __tg_update_carryover(tg, READ);
822 if (tg->service_queue.nr_queued[WRITE])
823 __tg_update_carryover(tg, WRITE);
824
825 /* see comments in struct throtl_grp for meaning of these fields. */
826 throtl_log(&tg->service_queue, "%s: %lld %lld %d %d\n", __func__,
827 tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
828 tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
829}
830
831static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
832 u32 iops_limit)
833{
834 bool rw = bio_data_dir(bio);
835 int io_allowed;
836 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
837
838 if (iops_limit == UINT_MAX) {
839 return 0;
840 }
841
842 jiffy_elapsed = jiffies - tg->slice_start[rw];
843
844 /* Round up to the next throttle slice, wait time must be nonzero */
845 jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
846 io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
847 tg->carryover_ios[rw];
848 if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed)
849 return 0;
850
851 /* Calc approx time to dispatch */
852 jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
853 return jiffy_wait;
854}
855
856static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
857 u64 bps_limit)
858{
859 bool rw = bio_data_dir(bio);
860 long long bytes_allowed;
861 u64 extra_bytes;
862 unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
863 unsigned int bio_size = throtl_bio_data_size(bio);
864
865 /* no need to throttle if this bio's bytes have been accounted */
866 if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
867 return 0;
868 }
869
870 jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
871
872 /* Slice has just started. Consider one slice interval */
873 if (!jiffy_elapsed)
874 jiffy_elapsed_rnd = tg->td->throtl_slice;
875
876 jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
877 bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
878 tg->carryover_bytes[rw];
879 if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
880 return 0;
881
882 /* Calc approx time to dispatch */
883 extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
884 jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
885
886 if (!jiffy_wait)
887 jiffy_wait = 1;
888
889 /*
890 * This wait time is without taking into consideration the rounding
891 * up we did. Add that time also.
892 */
893 jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
894 return jiffy_wait;
895}
896
897/*
898 * Returns whether one can dispatch a bio or not. Also returns approx number
899 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
900 */
901static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
902 unsigned long *wait)
903{
904 bool rw = bio_data_dir(bio);
905 unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
906 u64 bps_limit = tg_bps_limit(tg, rw);
907 u32 iops_limit = tg_iops_limit(tg, rw);
908
909 /*
910 * Currently whole state machine of group depends on first bio
911 * queued in the group bio list. So one should not be calling
912 * this function with a different bio if there are other bios
913 * queued.
914 */
915 BUG_ON(tg->service_queue.nr_queued[rw] &&
916 bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
917
918 /* If tg->bps = -1, then BW is unlimited */
919 if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
920 tg->flags & THROTL_TG_CANCELING) {
921 if (wait)
922 *wait = 0;
923 return true;
924 }
925
926 /*
927 * If previous slice expired, start a new one otherwise renew/extend
928 * existing slice to make sure it is at least throtl_slice interval
929 * long since now. New slice is started only for empty throttle group.
930 * If there is queued bio, that means there should be an active
931 * slice and it should be extended instead.
932 */
933 if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
934 throtl_start_new_slice(tg, rw, true);
935 else {
936 if (time_before(tg->slice_end[rw],
937 jiffies + tg->td->throtl_slice))
938 throtl_extend_slice(tg, rw,
939 jiffies + tg->td->throtl_slice);
940 }
941
942 bps_wait = tg_within_bps_limit(tg, bio, bps_limit);
943 iops_wait = tg_within_iops_limit(tg, bio, iops_limit);
944 if (bps_wait + iops_wait == 0) {
945 if (wait)
946 *wait = 0;
947 return true;
948 }
949
950 max_wait = max(bps_wait, iops_wait);
951
952 if (wait)
953 *wait = max_wait;
954
955 if (time_before(tg->slice_end[rw], jiffies + max_wait))
956 throtl_extend_slice(tg, rw, jiffies + max_wait);
957
958 return false;
959}
960
961static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
962{
963 bool rw = bio_data_dir(bio);
964 unsigned int bio_size = throtl_bio_data_size(bio);
965
966 /* Charge the bio to the group */
967 if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
968 tg->bytes_disp[rw] += bio_size;
969 tg->last_bytes_disp[rw] += bio_size;
970 }
971
972 tg->io_disp[rw]++;
973 tg->last_io_disp[rw]++;
974}
975
976/**
977 * throtl_add_bio_tg - add a bio to the specified throtl_grp
978 * @bio: bio to add
979 * @qn: qnode to use
980 * @tg: the target throtl_grp
981 *
982 * Add @bio to @tg's service_queue using @qn. If @qn is not specified,
983 * tg->qnode_on_self[] is used.
984 */
985static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
986 struct throtl_grp *tg)
987{
988 struct throtl_service_queue *sq = &tg->service_queue;
989 bool rw = bio_data_dir(bio);
990
991 if (!qn)
992 qn = &tg->qnode_on_self[rw];
993
994 /*
995 * If @tg doesn't currently have any bios queued in the same
996 * direction, queueing @bio can change when @tg should be
997 * dispatched. Mark that @tg was empty. This is automatically
998 * cleared on the next tg_update_disptime().
999 */
1000 if (!sq->nr_queued[rw])
1001 tg->flags |= THROTL_TG_WAS_EMPTY;
1002
1003 throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
1004
1005 sq->nr_queued[rw]++;
1006 throtl_enqueue_tg(tg);
1007}
1008
1009static void tg_update_disptime(struct throtl_grp *tg)
1010{
1011 struct throtl_service_queue *sq = &tg->service_queue;
1012 unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1013 struct bio *bio;
1014
1015 bio = throtl_peek_queued(&sq->queued[READ]);
1016 if (bio)
1017 tg_may_dispatch(tg, bio, &read_wait);
1018
1019 bio = throtl_peek_queued(&sq->queued[WRITE]);
1020 if (bio)
1021 tg_may_dispatch(tg, bio, &write_wait);
1022
1023 min_wait = min(read_wait, write_wait);
1024 disptime = jiffies + min_wait;
1025
1026 /* Update dispatch time */
1027 throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
1028 tg->disptime = disptime;
1029 tg_service_queue_add(tg);
1030
1031 /* see throtl_add_bio_tg() */
1032 tg->flags &= ~THROTL_TG_WAS_EMPTY;
1033}
1034
1035static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1036 struct throtl_grp *parent_tg, bool rw)
1037{
1038 if (throtl_slice_used(parent_tg, rw)) {
1039 throtl_start_new_slice_with_credit(parent_tg, rw,
1040 child_tg->slice_start[rw]);
1041 }
1042
1043}
1044
1045static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1046{
1047 struct throtl_service_queue *sq = &tg->service_queue;
1048 struct throtl_service_queue *parent_sq = sq->parent_sq;
1049 struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1050 struct throtl_grp *tg_to_put = NULL;
1051 struct bio *bio;
1052
1053 /*
1054 * @bio is being transferred from @tg to @parent_sq. Popping a bio
1055 * from @tg may put its reference and @parent_sq might end up
1056 * getting released prematurely. Remember the tg to put and put it
1057 * after @bio is transferred to @parent_sq.
1058 */
1059 bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1060 sq->nr_queued[rw]--;
1061
1062 throtl_charge_bio(tg, bio);
1063
1064 /*
1065 * If our parent is another tg, we just need to transfer @bio to
1066 * the parent using throtl_add_bio_tg(). If our parent is
1067 * @td->service_queue, @bio is ready to be issued. Put it on its
1068 * bio_lists[] and decrease total number queued. The caller is
1069 * responsible for issuing these bios.
1070 */
1071 if (parent_tg) {
1072 throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1073 start_parent_slice_with_credit(tg, parent_tg, rw);
1074 } else {
1075 bio_set_flag(bio, BIO_BPS_THROTTLED);
1076 throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1077 &parent_sq->queued[rw]);
1078 BUG_ON(tg->td->nr_queued[rw] <= 0);
1079 tg->td->nr_queued[rw]--;
1080 }
1081
1082 throtl_trim_slice(tg, rw);
1083
1084 if (tg_to_put)
1085 blkg_put(tg_to_blkg(tg_to_put));
1086}
1087
1088static int throtl_dispatch_tg(struct throtl_grp *tg)
1089{
1090 struct throtl_service_queue *sq = &tg->service_queue;
1091 unsigned int nr_reads = 0, nr_writes = 0;
1092 unsigned int max_nr_reads = THROTL_GRP_QUANTUM * 3 / 4;
1093 unsigned int max_nr_writes = THROTL_GRP_QUANTUM - max_nr_reads;
1094 struct bio *bio;
1095
1096 /* Try to dispatch 75% READS and 25% WRITES */
1097
1098 while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1099 tg_may_dispatch(tg, bio, NULL)) {
1100
1101 tg_dispatch_one_bio(tg, READ);
1102 nr_reads++;
1103
1104 if (nr_reads >= max_nr_reads)
1105 break;
1106 }
1107
1108 while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1109 tg_may_dispatch(tg, bio, NULL)) {
1110
1111 tg_dispatch_one_bio(tg, WRITE);
1112 nr_writes++;
1113
1114 if (nr_writes >= max_nr_writes)
1115 break;
1116 }
1117
1118 return nr_reads + nr_writes;
1119}
1120
1121static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1122{
1123 unsigned int nr_disp = 0;
1124
1125 while (1) {
1126 struct throtl_grp *tg;
1127 struct throtl_service_queue *sq;
1128
1129 if (!parent_sq->nr_pending)
1130 break;
1131
1132 tg = throtl_rb_first(parent_sq);
1133 if (!tg)
1134 break;
1135
1136 if (time_before(jiffies, tg->disptime))
1137 break;
1138
1139 nr_disp += throtl_dispatch_tg(tg);
1140
1141 sq = &tg->service_queue;
1142 if (sq->nr_queued[READ] || sq->nr_queued[WRITE])
1143 tg_update_disptime(tg);
1144 else
1145 throtl_dequeue_tg(tg);
1146
1147 if (nr_disp >= THROTL_QUANTUM)
1148 break;
1149 }
1150
1151 return nr_disp;
1152}
1153
1154static bool throtl_can_upgrade(struct throtl_data *td,
1155 struct throtl_grp *this_tg);
1156/**
1157 * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1158 * @t: the pending_timer member of the throtl_service_queue being serviced
1159 *
1160 * This timer is armed when a child throtl_grp with active bio's become
1161 * pending and queued on the service_queue's pending_tree and expires when
1162 * the first child throtl_grp should be dispatched. This function
1163 * dispatches bio's from the children throtl_grps to the parent
1164 * service_queue.
1165 *
1166 * If the parent's parent is another throtl_grp, dispatching is propagated
1167 * by either arming its pending_timer or repeating dispatch directly. If
1168 * the top-level service_tree is reached, throtl_data->dispatch_work is
1169 * kicked so that the ready bio's are issued.
1170 */
1171static void throtl_pending_timer_fn(struct timer_list *t)
1172{
1173 struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
1174 struct throtl_grp *tg = sq_to_tg(sq);
1175 struct throtl_data *td = sq_to_td(sq);
1176 struct throtl_service_queue *parent_sq;
1177 struct request_queue *q;
1178 bool dispatched;
1179 int ret;
1180
1181 /* throtl_data may be gone, so figure out request queue by blkg */
1182 if (tg)
1183 q = tg->pd.blkg->q;
1184 else
1185 q = td->queue;
1186
1187 spin_lock_irq(&q->queue_lock);
1188
1189 if (!q->root_blkg)
1190 goto out_unlock;
1191
1192 if (throtl_can_upgrade(td, NULL))
1193 throtl_upgrade_state(td);
1194
1195again:
1196 parent_sq = sq->parent_sq;
1197 dispatched = false;
1198
1199 while (true) {
1200 throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1201 sq->nr_queued[READ] + sq->nr_queued[WRITE],
1202 sq->nr_queued[READ], sq->nr_queued[WRITE]);
1203
1204 ret = throtl_select_dispatch(sq);
1205 if (ret) {
1206 throtl_log(sq, "bios disp=%u", ret);
1207 dispatched = true;
1208 }
1209
1210 if (throtl_schedule_next_dispatch(sq, false))
1211 break;
1212
1213 /* this dispatch windows is still open, relax and repeat */
1214 spin_unlock_irq(&q->queue_lock);
1215 cpu_relax();
1216 spin_lock_irq(&q->queue_lock);
1217 }
1218
1219 if (!dispatched)
1220 goto out_unlock;
1221
1222 if (parent_sq) {
1223 /* @parent_sq is another throl_grp, propagate dispatch */
1224 if (tg->flags & THROTL_TG_WAS_EMPTY) {
1225 tg_update_disptime(tg);
1226 if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1227 /* window is already open, repeat dispatching */
1228 sq = parent_sq;
1229 tg = sq_to_tg(sq);
1230 goto again;
1231 }
1232 }
1233 } else {
1234 /* reached the top-level, queue issuing */
1235 queue_work(kthrotld_workqueue, &td->dispatch_work);
1236 }
1237out_unlock:
1238 spin_unlock_irq(&q->queue_lock);
1239}
1240
1241/**
1242 * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1243 * @work: work item being executed
1244 *
1245 * This function is queued for execution when bios reach the bio_lists[]
1246 * of throtl_data->service_queue. Those bios are ready and issued by this
1247 * function.
1248 */
1249static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1250{
1251 struct throtl_data *td = container_of(work, struct throtl_data,
1252 dispatch_work);
1253 struct throtl_service_queue *td_sq = &td->service_queue;
1254 struct request_queue *q = td->queue;
1255 struct bio_list bio_list_on_stack;
1256 struct bio *bio;
1257 struct blk_plug plug;
1258 int rw;
1259
1260 bio_list_init(&bio_list_on_stack);
1261
1262 spin_lock_irq(&q->queue_lock);
1263 for (rw = READ; rw <= WRITE; rw++)
1264 while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1265 bio_list_add(&bio_list_on_stack, bio);
1266 spin_unlock_irq(&q->queue_lock);
1267
1268 if (!bio_list_empty(&bio_list_on_stack)) {
1269 blk_start_plug(&plug);
1270 while ((bio = bio_list_pop(&bio_list_on_stack)))
1271 submit_bio_noacct_nocheck(bio);
1272 blk_finish_plug(&plug);
1273 }
1274}
1275
1276static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1277 int off)
1278{
1279 struct throtl_grp *tg = pd_to_tg(pd);
1280 u64 v = *(u64 *)((void *)tg + off);
1281
1282 if (v == U64_MAX)
1283 return 0;
1284 return __blkg_prfill_u64(sf, pd, v);
1285}
1286
1287static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1288 int off)
1289{
1290 struct throtl_grp *tg = pd_to_tg(pd);
1291 unsigned int v = *(unsigned int *)((void *)tg + off);
1292
1293 if (v == UINT_MAX)
1294 return 0;
1295 return __blkg_prfill_u64(sf, pd, v);
1296}
1297
1298static int tg_print_conf_u64(struct seq_file *sf, void *v)
1299{
1300 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1301 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1302 return 0;
1303}
1304
1305static int tg_print_conf_uint(struct seq_file *sf, void *v)
1306{
1307 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1308 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1309 return 0;
1310}
1311
1312static void tg_conf_updated(struct throtl_grp *tg, bool global)
1313{
1314 struct throtl_service_queue *sq = &tg->service_queue;
1315 struct cgroup_subsys_state *pos_css;
1316 struct blkcg_gq *blkg;
1317
1318 throtl_log(&tg->service_queue,
1319 "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1320 tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1321 tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1322
1323 rcu_read_lock();
1324 /*
1325 * Update has_rules[] flags for the updated tg's subtree. A tg is
1326 * considered to have rules if either the tg itself or any of its
1327 * ancestors has rules. This identifies groups without any
1328 * restrictions in the whole hierarchy and allows them to bypass
1329 * blk-throttle.
1330 */
1331 blkg_for_each_descendant_pre(blkg, pos_css,
1332 global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1333 struct throtl_grp *this_tg = blkg_to_tg(blkg);
1334 struct throtl_grp *parent_tg;
1335
1336 tg_update_has_rules(this_tg);
1337 /* ignore root/second level */
1338 if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1339 !blkg->parent->parent)
1340 continue;
1341 parent_tg = blkg_to_tg(blkg->parent);
1342 /*
1343 * make sure all children has lower idle time threshold and
1344 * higher latency target
1345 */
1346 this_tg->idletime_threshold = min(this_tg->idletime_threshold,
1347 parent_tg->idletime_threshold);
1348 this_tg->latency_target = max(this_tg->latency_target,
1349 parent_tg->latency_target);
1350 }
1351 rcu_read_unlock();
1352
1353 /*
1354 * We're already holding queue_lock and know @tg is valid. Let's
1355 * apply the new config directly.
1356 *
1357 * Restart the slices for both READ and WRITES. It might happen
1358 * that a group's limit are dropped suddenly and we don't want to
1359 * account recently dispatched IO with new low rate.
1360 */
1361 throtl_start_new_slice(tg, READ, false);
1362 throtl_start_new_slice(tg, WRITE, false);
1363
1364 if (tg->flags & THROTL_TG_PENDING) {
1365 tg_update_disptime(tg);
1366 throtl_schedule_next_dispatch(sq->parent_sq, true);
1367 }
1368}
1369
1370static ssize_t tg_set_conf(struct kernfs_open_file *of,
1371 char *buf, size_t nbytes, loff_t off, bool is_u64)
1372{
1373 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1374 struct blkg_conf_ctx ctx;
1375 struct throtl_grp *tg;
1376 int ret;
1377 u64 v;
1378
1379 blkg_conf_init(&ctx, buf);
1380
1381 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1382 if (ret)
1383 goto out_finish;
1384
1385 ret = -EINVAL;
1386 if (sscanf(ctx.body, "%llu", &v) != 1)
1387 goto out_finish;
1388 if (!v)
1389 v = U64_MAX;
1390
1391 tg = blkg_to_tg(ctx.blkg);
1392 tg_update_carryover(tg);
1393
1394 if (is_u64)
1395 *(u64 *)((void *)tg + of_cft(of)->private) = v;
1396 else
1397 *(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1398
1399 tg_conf_updated(tg, false);
1400 ret = 0;
1401out_finish:
1402 blkg_conf_exit(&ctx);
1403 return ret ?: nbytes;
1404}
1405
1406static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1407 char *buf, size_t nbytes, loff_t off)
1408{
1409 return tg_set_conf(of, buf, nbytes, off, true);
1410}
1411
1412static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1413 char *buf, size_t nbytes, loff_t off)
1414{
1415 return tg_set_conf(of, buf, nbytes, off, false);
1416}
1417
1418static int tg_print_rwstat(struct seq_file *sf, void *v)
1419{
1420 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1421 blkg_prfill_rwstat, &blkcg_policy_throtl,
1422 seq_cft(sf)->private, true);
1423 return 0;
1424}
1425
1426static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
1427 struct blkg_policy_data *pd, int off)
1428{
1429 struct blkg_rwstat_sample sum;
1430
1431 blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
1432 &sum);
1433 return __blkg_prfill_rwstat(sf, pd, &sum);
1434}
1435
1436static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
1437{
1438 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1439 tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
1440 seq_cft(sf)->private, true);
1441 return 0;
1442}
1443
1444static struct cftype throtl_legacy_files[] = {
1445 {
1446 .name = "throttle.read_bps_device",
1447 .private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
1448 .seq_show = tg_print_conf_u64,
1449 .write = tg_set_conf_u64,
1450 },
1451 {
1452 .name = "throttle.write_bps_device",
1453 .private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
1454 .seq_show = tg_print_conf_u64,
1455 .write = tg_set_conf_u64,
1456 },
1457 {
1458 .name = "throttle.read_iops_device",
1459 .private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
1460 .seq_show = tg_print_conf_uint,
1461 .write = tg_set_conf_uint,
1462 },
1463 {
1464 .name = "throttle.write_iops_device",
1465 .private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
1466 .seq_show = tg_print_conf_uint,
1467 .write = tg_set_conf_uint,
1468 },
1469 {
1470 .name = "throttle.io_service_bytes",
1471 .private = offsetof(struct throtl_grp, stat_bytes),
1472 .seq_show = tg_print_rwstat,
1473 },
1474 {
1475 .name = "throttle.io_service_bytes_recursive",
1476 .private = offsetof(struct throtl_grp, stat_bytes),
1477 .seq_show = tg_print_rwstat_recursive,
1478 },
1479 {
1480 .name = "throttle.io_serviced",
1481 .private = offsetof(struct throtl_grp, stat_ios),
1482 .seq_show = tg_print_rwstat,
1483 },
1484 {
1485 .name = "throttle.io_serviced_recursive",
1486 .private = offsetof(struct throtl_grp, stat_ios),
1487 .seq_show = tg_print_rwstat_recursive,
1488 },
1489 { } /* terminate */
1490};
1491
1492static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1493 int off)
1494{
1495 struct throtl_grp *tg = pd_to_tg(pd);
1496 const char *dname = blkg_dev_name(pd->blkg);
1497 char bufs[4][21] = { "max", "max", "max", "max" };
1498 u64 bps_dft;
1499 unsigned int iops_dft;
1500 char idle_time[26] = "";
1501 char latency_time[26] = "";
1502
1503 if (!dname)
1504 return 0;
1505
1506 if (off == LIMIT_LOW) {
1507 bps_dft = 0;
1508 iops_dft = 0;
1509 } else {
1510 bps_dft = U64_MAX;
1511 iops_dft = UINT_MAX;
1512 }
1513
1514 if (tg->bps_conf[READ][off] == bps_dft &&
1515 tg->bps_conf[WRITE][off] == bps_dft &&
1516 tg->iops_conf[READ][off] == iops_dft &&
1517 tg->iops_conf[WRITE][off] == iops_dft &&
1518 (off != LIMIT_LOW ||
1519 (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
1520 tg->latency_target_conf == DFL_LATENCY_TARGET)))
1521 return 0;
1522
1523 if (tg->bps_conf[READ][off] != U64_MAX)
1524 snprintf(bufs[0], sizeof(bufs[0]), "%llu",
1525 tg->bps_conf[READ][off]);
1526 if (tg->bps_conf[WRITE][off] != U64_MAX)
1527 snprintf(bufs[1], sizeof(bufs[1]), "%llu",
1528 tg->bps_conf[WRITE][off]);
1529 if (tg->iops_conf[READ][off] != UINT_MAX)
1530 snprintf(bufs[2], sizeof(bufs[2]), "%u",
1531 tg->iops_conf[READ][off]);
1532 if (tg->iops_conf[WRITE][off] != UINT_MAX)
1533 snprintf(bufs[3], sizeof(bufs[3]), "%u",
1534 tg->iops_conf[WRITE][off]);
1535 if (off == LIMIT_LOW) {
1536 if (tg->idletime_threshold_conf == ULONG_MAX)
1537 strcpy(idle_time, " idle=max");
1538 else
1539 snprintf(idle_time, sizeof(idle_time), " idle=%lu",
1540 tg->idletime_threshold_conf);
1541
1542 if (tg->latency_target_conf == ULONG_MAX)
1543 strcpy(latency_time, " latency=max");
1544 else
1545 snprintf(latency_time, sizeof(latency_time),
1546 " latency=%lu", tg->latency_target_conf);
1547 }
1548
1549 seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
1550 dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
1551 latency_time);
1552 return 0;
1553}
1554
1555static int tg_print_limit(struct seq_file *sf, void *v)
1556{
1557 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1558 &blkcg_policy_throtl, seq_cft(sf)->private, false);
1559 return 0;
1560}
1561
1562static ssize_t tg_set_limit(struct kernfs_open_file *of,
1563 char *buf, size_t nbytes, loff_t off)
1564{
1565 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1566 struct blkg_conf_ctx ctx;
1567 struct throtl_grp *tg;
1568 u64 v[4];
1569 unsigned long idle_time;
1570 unsigned long latency_time;
1571 int ret;
1572 int index = of_cft(of)->private;
1573
1574 blkg_conf_init(&ctx, buf);
1575
1576 ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1577 if (ret)
1578 goto out_finish;
1579
1580 tg = blkg_to_tg(ctx.blkg);
1581 tg_update_carryover(tg);
1582
1583 v[0] = tg->bps_conf[READ][index];
1584 v[1] = tg->bps_conf[WRITE][index];
1585 v[2] = tg->iops_conf[READ][index];
1586 v[3] = tg->iops_conf[WRITE][index];
1587
1588 idle_time = tg->idletime_threshold_conf;
1589 latency_time = tg->latency_target_conf;
1590 while (true) {
1591 char tok[27]; /* wiops=18446744073709551616 */
1592 char *p;
1593 u64 val = U64_MAX;
1594 int len;
1595
1596 if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1597 break;
1598 if (tok[0] == '\0')
1599 break;
1600 ctx.body += len;
1601
1602 ret = -EINVAL;
1603 p = tok;
1604 strsep(&p, "=");
1605 if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1606 goto out_finish;
1607
1608 ret = -ERANGE;
1609 if (!val)
1610 goto out_finish;
1611
1612 ret = -EINVAL;
1613 if (!strcmp(tok, "rbps") && val > 1)
1614 v[0] = val;
1615 else if (!strcmp(tok, "wbps") && val > 1)
1616 v[1] = val;
1617 else if (!strcmp(tok, "riops") && val > 1)
1618 v[2] = min_t(u64, val, UINT_MAX);
1619 else if (!strcmp(tok, "wiops") && val > 1)
1620 v[3] = min_t(u64, val, UINT_MAX);
1621 else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
1622 idle_time = val;
1623 else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
1624 latency_time = val;
1625 else
1626 goto out_finish;
1627 }
1628
1629 tg->bps_conf[READ][index] = v[0];
1630 tg->bps_conf[WRITE][index] = v[1];
1631 tg->iops_conf[READ][index] = v[2];
1632 tg->iops_conf[WRITE][index] = v[3];
1633
1634 if (index == LIMIT_MAX) {
1635 tg->bps[READ][index] = v[0];
1636 tg->bps[WRITE][index] = v[1];
1637 tg->iops[READ][index] = v[2];
1638 tg->iops[WRITE][index] = v[3];
1639 }
1640 tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
1641 tg->bps_conf[READ][LIMIT_MAX]);
1642 tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
1643 tg->bps_conf[WRITE][LIMIT_MAX]);
1644 tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
1645 tg->iops_conf[READ][LIMIT_MAX]);
1646 tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
1647 tg->iops_conf[WRITE][LIMIT_MAX]);
1648 tg->idletime_threshold_conf = idle_time;
1649 tg->latency_target_conf = latency_time;
1650
1651 /* force user to configure all settings for low limit */
1652 if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
1653 tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
1654 tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
1655 tg->latency_target_conf == DFL_LATENCY_TARGET) {
1656 tg->bps[READ][LIMIT_LOW] = 0;
1657 tg->bps[WRITE][LIMIT_LOW] = 0;
1658 tg->iops[READ][LIMIT_LOW] = 0;
1659 tg->iops[WRITE][LIMIT_LOW] = 0;
1660 tg->idletime_threshold = DFL_IDLE_THRESHOLD;
1661 tg->latency_target = DFL_LATENCY_TARGET;
1662 } else if (index == LIMIT_LOW) {
1663 tg->idletime_threshold = tg->idletime_threshold_conf;
1664 tg->latency_target = tg->latency_target_conf;
1665 }
1666
1667 blk_throtl_update_limit_valid(tg->td);
1668 if (tg->td->limit_valid[LIMIT_LOW]) {
1669 if (index == LIMIT_LOW)
1670 tg->td->limit_index = LIMIT_LOW;
1671 } else
1672 tg->td->limit_index = LIMIT_MAX;
1673 tg_conf_updated(tg, index == LIMIT_LOW &&
1674 tg->td->limit_valid[LIMIT_LOW]);
1675 ret = 0;
1676out_finish:
1677 blkg_conf_exit(&ctx);
1678 return ret ?: nbytes;
1679}
1680
1681static struct cftype throtl_files[] = {
1682#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1683 {
1684 .name = "low",
1685 .flags = CFTYPE_NOT_ON_ROOT,
1686 .seq_show = tg_print_limit,
1687 .write = tg_set_limit,
1688 .private = LIMIT_LOW,
1689 },
1690#endif
1691 {
1692 .name = "max",
1693 .flags = CFTYPE_NOT_ON_ROOT,
1694 .seq_show = tg_print_limit,
1695 .write = tg_set_limit,
1696 .private = LIMIT_MAX,
1697 },
1698 { } /* terminate */
1699};
1700
1701static void throtl_shutdown_wq(struct request_queue *q)
1702{
1703 struct throtl_data *td = q->td;
1704
1705 cancel_work_sync(&td->dispatch_work);
1706}
1707
1708struct blkcg_policy blkcg_policy_throtl = {
1709 .dfl_cftypes = throtl_files,
1710 .legacy_cftypes = throtl_legacy_files,
1711
1712 .pd_alloc_fn = throtl_pd_alloc,
1713 .pd_init_fn = throtl_pd_init,
1714 .pd_online_fn = throtl_pd_online,
1715 .pd_offline_fn = throtl_pd_offline,
1716 .pd_free_fn = throtl_pd_free,
1717};
1718
1719void blk_throtl_cancel_bios(struct gendisk *disk)
1720{
1721 struct request_queue *q = disk->queue;
1722 struct cgroup_subsys_state *pos_css;
1723 struct blkcg_gq *blkg;
1724
1725 spin_lock_irq(&q->queue_lock);
1726 /*
1727 * queue_lock is held, rcu lock is not needed here technically.
1728 * However, rcu lock is still held to emphasize that following
1729 * path need RCU protection and to prevent warning from lockdep.
1730 */
1731 rcu_read_lock();
1732 blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
1733 struct throtl_grp *tg = blkg_to_tg(blkg);
1734 struct throtl_service_queue *sq = &tg->service_queue;
1735
1736 /*
1737 * Set the flag to make sure throtl_pending_timer_fn() won't
1738 * stop until all throttled bios are dispatched.
1739 */
1740 tg->flags |= THROTL_TG_CANCELING;
1741
1742 /*
1743 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup
1744 * will be inserted to service queue without THROTL_TG_PENDING
1745 * set in tg_update_disptime below. Then IO dispatched from
1746 * child in tg_dispatch_one_bio will trigger double insertion
1747 * and corrupt the tree.
1748 */
1749 if (!(tg->flags & THROTL_TG_PENDING))
1750 continue;
1751
1752 /*
1753 * Update disptime after setting the above flag to make sure
1754 * throtl_select_dispatch() won't exit without dispatching.
1755 */
1756 tg_update_disptime(tg);
1757
1758 throtl_schedule_pending_timer(sq, jiffies + 1);
1759 }
1760 rcu_read_unlock();
1761 spin_unlock_irq(&q->queue_lock);
1762}
1763
1764#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1765static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
1766{
1767 unsigned long rtime = jiffies, wtime = jiffies;
1768
1769 if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
1770 rtime = tg->last_low_overflow_time[READ];
1771 if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
1772 wtime = tg->last_low_overflow_time[WRITE];
1773 return min(rtime, wtime);
1774}
1775
1776static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
1777{
1778 struct throtl_service_queue *parent_sq;
1779 struct throtl_grp *parent = tg;
1780 unsigned long ret = __tg_last_low_overflow_time(tg);
1781
1782 while (true) {
1783 parent_sq = parent->service_queue.parent_sq;
1784 parent = sq_to_tg(parent_sq);
1785 if (!parent)
1786 break;
1787
1788 /*
1789 * The parent doesn't have low limit, it always reaches low
1790 * limit. Its overflow time is useless for children
1791 */
1792 if (!parent->bps[READ][LIMIT_LOW] &&
1793 !parent->iops[READ][LIMIT_LOW] &&
1794 !parent->bps[WRITE][LIMIT_LOW] &&
1795 !parent->iops[WRITE][LIMIT_LOW])
1796 continue;
1797 if (time_after(__tg_last_low_overflow_time(parent), ret))
1798 ret = __tg_last_low_overflow_time(parent);
1799 }
1800 return ret;
1801}
1802
1803static bool throtl_tg_is_idle(struct throtl_grp *tg)
1804{
1805 /*
1806 * cgroup is idle if:
1807 * - single idle is too long, longer than a fixed value (in case user
1808 * configure a too big threshold) or 4 times of idletime threshold
1809 * - average think time is more than threshold
1810 * - IO latency is largely below threshold
1811 */
1812 unsigned long time;
1813 bool ret;
1814
1815 time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
1816 ret = tg->latency_target == DFL_LATENCY_TARGET ||
1817 tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
1818 (blk_time_get_ns() >> 10) - tg->last_finish_time > time ||
1819 tg->avg_idletime > tg->idletime_threshold ||
1820 (tg->latency_target && tg->bio_cnt &&
1821 tg->bad_bio_cnt * 5 < tg->bio_cnt);
1822 throtl_log(&tg->service_queue,
1823 "avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
1824 tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
1825 tg->bio_cnt, ret, tg->td->scale);
1826 return ret;
1827}
1828
1829static bool throtl_low_limit_reached(struct throtl_grp *tg, int rw)
1830{
1831 struct throtl_service_queue *sq = &tg->service_queue;
1832 bool limit = tg->bps[rw][LIMIT_LOW] || tg->iops[rw][LIMIT_LOW];
1833
1834 /*
1835 * if low limit is zero, low limit is always reached.
1836 * if low limit is non-zero, we can check if there is any request
1837 * is queued to determine if low limit is reached as we throttle
1838 * request according to limit.
1839 */
1840 return !limit || sq->nr_queued[rw];
1841}
1842
1843static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
1844{
1845 /*
1846 * cgroup reaches low limit when low limit of READ and WRITE are
1847 * both reached, it's ok to upgrade to next limit if cgroup reaches
1848 * low limit
1849 */
1850 if (throtl_low_limit_reached(tg, READ) &&
1851 throtl_low_limit_reached(tg, WRITE))
1852 return true;
1853
1854 if (time_after_eq(jiffies,
1855 tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
1856 throtl_tg_is_idle(tg))
1857 return true;
1858 return false;
1859}
1860
1861static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
1862{
1863 while (true) {
1864 if (throtl_tg_can_upgrade(tg))
1865 return true;
1866 tg = sq_to_tg(tg->service_queue.parent_sq);
1867 if (!tg || !tg_to_blkg(tg)->parent)
1868 return false;
1869 }
1870 return false;
1871}
1872
1873static bool throtl_can_upgrade(struct throtl_data *td,
1874 struct throtl_grp *this_tg)
1875{
1876 struct cgroup_subsys_state *pos_css;
1877 struct blkcg_gq *blkg;
1878
1879 if (td->limit_index != LIMIT_LOW)
1880 return false;
1881
1882 if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
1883 return false;
1884
1885 rcu_read_lock();
1886 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1887 struct throtl_grp *tg = blkg_to_tg(blkg);
1888
1889 if (tg == this_tg)
1890 continue;
1891 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1892 continue;
1893 if (!throtl_hierarchy_can_upgrade(tg)) {
1894 rcu_read_unlock();
1895 return false;
1896 }
1897 }
1898 rcu_read_unlock();
1899 return true;
1900}
1901
1902static void throtl_upgrade_check(struct throtl_grp *tg)
1903{
1904 unsigned long now = jiffies;
1905
1906 if (tg->td->limit_index != LIMIT_LOW)
1907 return;
1908
1909 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1910 return;
1911
1912 tg->last_check_time = now;
1913
1914 if (!time_after_eq(now,
1915 __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
1916 return;
1917
1918 if (throtl_can_upgrade(tg->td, NULL))
1919 throtl_upgrade_state(tg->td);
1920}
1921
1922static void throtl_upgrade_state(struct throtl_data *td)
1923{
1924 struct cgroup_subsys_state *pos_css;
1925 struct blkcg_gq *blkg;
1926
1927 throtl_log(&td->service_queue, "upgrade to max");
1928 td->limit_index = LIMIT_MAX;
1929 td->low_upgrade_time = jiffies;
1930 td->scale = 0;
1931 rcu_read_lock();
1932 blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1933 struct throtl_grp *tg = blkg_to_tg(blkg);
1934 struct throtl_service_queue *sq = &tg->service_queue;
1935
1936 tg->disptime = jiffies - 1;
1937 throtl_select_dispatch(sq);
1938 throtl_schedule_next_dispatch(sq, true);
1939 }
1940 rcu_read_unlock();
1941 throtl_select_dispatch(&td->service_queue);
1942 throtl_schedule_next_dispatch(&td->service_queue, true);
1943 queue_work(kthrotld_workqueue, &td->dispatch_work);
1944}
1945
1946static void throtl_downgrade_state(struct throtl_data *td)
1947{
1948 td->scale /= 2;
1949
1950 throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
1951 if (td->scale) {
1952 td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
1953 return;
1954 }
1955
1956 td->limit_index = LIMIT_LOW;
1957 td->low_downgrade_time = jiffies;
1958}
1959
1960static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
1961{
1962 struct throtl_data *td = tg->td;
1963 unsigned long now = jiffies;
1964
1965 /*
1966 * If cgroup is below low limit, consider downgrade and throttle other
1967 * cgroups
1968 */
1969 if (time_after_eq(now, tg_last_low_overflow_time(tg) +
1970 td->throtl_slice) &&
1971 (!throtl_tg_is_idle(tg) ||
1972 !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
1973 return true;
1974 return false;
1975}
1976
1977static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
1978{
1979 struct throtl_data *td = tg->td;
1980
1981 if (time_before(jiffies, td->low_upgrade_time + td->throtl_slice))
1982 return false;
1983
1984 while (true) {
1985 if (!throtl_tg_can_downgrade(tg))
1986 return false;
1987 tg = sq_to_tg(tg->service_queue.parent_sq);
1988 if (!tg || !tg_to_blkg(tg)->parent)
1989 break;
1990 }
1991 return true;
1992}
1993
1994static void throtl_downgrade_check(struct throtl_grp *tg)
1995{
1996 uint64_t bps;
1997 unsigned int iops;
1998 unsigned long elapsed_time;
1999 unsigned long now = jiffies;
2000
2001 if (tg->td->limit_index != LIMIT_MAX ||
2002 !tg->td->limit_valid[LIMIT_LOW])
2003 return;
2004 if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
2005 return;
2006 if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
2007 return;
2008
2009 elapsed_time = now - tg->last_check_time;
2010 tg->last_check_time = now;
2011
2012 if (time_before(now, tg_last_low_overflow_time(tg) +
2013 tg->td->throtl_slice))
2014 return;
2015
2016 if (tg->bps[READ][LIMIT_LOW]) {
2017 bps = tg->last_bytes_disp[READ] * HZ;
2018 do_div(bps, elapsed_time);
2019 if (bps >= tg->bps[READ][LIMIT_LOW])
2020 tg->last_low_overflow_time[READ] = now;
2021 }
2022
2023 if (tg->bps[WRITE][LIMIT_LOW]) {
2024 bps = tg->last_bytes_disp[WRITE] * HZ;
2025 do_div(bps, elapsed_time);
2026 if (bps >= tg->bps[WRITE][LIMIT_LOW])
2027 tg->last_low_overflow_time[WRITE] = now;
2028 }
2029
2030 if (tg->iops[READ][LIMIT_LOW]) {
2031 iops = tg->last_io_disp[READ] * HZ / elapsed_time;
2032 if (iops >= tg->iops[READ][LIMIT_LOW])
2033 tg->last_low_overflow_time[READ] = now;
2034 }
2035
2036 if (tg->iops[WRITE][LIMIT_LOW]) {
2037 iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
2038 if (iops >= tg->iops[WRITE][LIMIT_LOW])
2039 tg->last_low_overflow_time[WRITE] = now;
2040 }
2041
2042 /*
2043 * If cgroup is below low limit, consider downgrade and throttle other
2044 * cgroups
2045 */
2046 if (throtl_hierarchy_can_downgrade(tg))
2047 throtl_downgrade_state(tg->td);
2048
2049 tg->last_bytes_disp[READ] = 0;
2050 tg->last_bytes_disp[WRITE] = 0;
2051 tg->last_io_disp[READ] = 0;
2052 tg->last_io_disp[WRITE] = 0;
2053}
2054
2055static void blk_throtl_update_idletime(struct throtl_grp *tg)
2056{
2057 unsigned long now;
2058 unsigned long last_finish_time = tg->last_finish_time;
2059
2060 if (last_finish_time == 0)
2061 return;
2062
2063 now = blk_time_get_ns() >> 10;
2064 if (now <= last_finish_time ||
2065 last_finish_time == tg->checked_last_finish_time)
2066 return;
2067
2068 tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
2069 tg->checked_last_finish_time = last_finish_time;
2070}
2071
2072static void throtl_update_latency_buckets(struct throtl_data *td)
2073{
2074 struct avg_latency_bucket avg_latency[2][LATENCY_BUCKET_SIZE];
2075 int i, cpu, rw;
2076 unsigned long last_latency[2] = { 0 };
2077 unsigned long latency[2];
2078
2079 if (!blk_queue_nonrot(td->queue) || !td->limit_valid[LIMIT_LOW])
2080 return;
2081 if (time_before(jiffies, td->last_calculate_time + HZ))
2082 return;
2083 td->last_calculate_time = jiffies;
2084
2085 memset(avg_latency, 0, sizeof(avg_latency));
2086 for (rw = READ; rw <= WRITE; rw++) {
2087 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2088 struct latency_bucket *tmp = &td->tmp_buckets[rw][i];
2089
2090 for_each_possible_cpu(cpu) {
2091 struct latency_bucket *bucket;
2092
2093 /* this isn't race free, but ok in practice */
2094 bucket = per_cpu_ptr(td->latency_buckets[rw],
2095 cpu);
2096 tmp->total_latency += bucket[i].total_latency;
2097 tmp->samples += bucket[i].samples;
2098 bucket[i].total_latency = 0;
2099 bucket[i].samples = 0;
2100 }
2101
2102 if (tmp->samples >= 32) {
2103 int samples = tmp->samples;
2104
2105 latency[rw] = tmp->total_latency;
2106
2107 tmp->total_latency = 0;
2108 tmp->samples = 0;
2109 latency[rw] /= samples;
2110 if (latency[rw] == 0)
2111 continue;
2112 avg_latency[rw][i].latency = latency[rw];
2113 }
2114 }
2115 }
2116
2117 for (rw = READ; rw <= WRITE; rw++) {
2118 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2119 if (!avg_latency[rw][i].latency) {
2120 if (td->avg_buckets[rw][i].latency < last_latency[rw])
2121 td->avg_buckets[rw][i].latency =
2122 last_latency[rw];
2123 continue;
2124 }
2125
2126 if (!td->avg_buckets[rw][i].valid)
2127 latency[rw] = avg_latency[rw][i].latency;
2128 else
2129 latency[rw] = (td->avg_buckets[rw][i].latency * 7 +
2130 avg_latency[rw][i].latency) >> 3;
2131
2132 td->avg_buckets[rw][i].latency = max(latency[rw],
2133 last_latency[rw]);
2134 td->avg_buckets[rw][i].valid = true;
2135 last_latency[rw] = td->avg_buckets[rw][i].latency;
2136 }
2137 }
2138
2139 for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2140 throtl_log(&td->service_queue,
2141 "Latency bucket %d: read latency=%ld, read valid=%d, "
2142 "write latency=%ld, write valid=%d", i,
2143 td->avg_buckets[READ][i].latency,
2144 td->avg_buckets[READ][i].valid,
2145 td->avg_buckets[WRITE][i].latency,
2146 td->avg_buckets[WRITE][i].valid);
2147}
2148#else
2149static inline void throtl_update_latency_buckets(struct throtl_data *td)
2150{
2151}
2152
2153static void blk_throtl_update_idletime(struct throtl_grp *tg)
2154{
2155}
2156
2157static void throtl_downgrade_check(struct throtl_grp *tg)
2158{
2159}
2160
2161static void throtl_upgrade_check(struct throtl_grp *tg)
2162{
2163}
2164
2165static bool throtl_can_upgrade(struct throtl_data *td,
2166 struct throtl_grp *this_tg)
2167{
2168 return false;
2169}
2170
2171static void throtl_upgrade_state(struct throtl_data *td)
2172{
2173}
2174#endif
2175
2176bool __blk_throtl_bio(struct bio *bio)
2177{
2178 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
2179 struct blkcg_gq *blkg = bio->bi_blkg;
2180 struct throtl_qnode *qn = NULL;
2181 struct throtl_grp *tg = blkg_to_tg(blkg);
2182 struct throtl_service_queue *sq;
2183 bool rw = bio_data_dir(bio);
2184 bool throttled = false;
2185 struct throtl_data *td = tg->td;
2186
2187 rcu_read_lock();
2188
2189 spin_lock_irq(&q->queue_lock);
2190
2191 throtl_update_latency_buckets(td);
2192
2193 blk_throtl_update_idletime(tg);
2194
2195 sq = &tg->service_queue;
2196
2197again:
2198 while (true) {
2199 if (tg->last_low_overflow_time[rw] == 0)
2200 tg->last_low_overflow_time[rw] = jiffies;
2201 throtl_downgrade_check(tg);
2202 throtl_upgrade_check(tg);
2203 /* throtl is FIFO - if bios are already queued, should queue */
2204 if (sq->nr_queued[rw])
2205 break;
2206
2207 /* if above limits, break to queue */
2208 if (!tg_may_dispatch(tg, bio, NULL)) {
2209 tg->last_low_overflow_time[rw] = jiffies;
2210 if (throtl_can_upgrade(td, tg)) {
2211 throtl_upgrade_state(td);
2212 goto again;
2213 }
2214 break;
2215 }
2216
2217 /* within limits, let's charge and dispatch directly */
2218 throtl_charge_bio(tg, bio);
2219
2220 /*
2221 * We need to trim slice even when bios are not being queued
2222 * otherwise it might happen that a bio is not queued for
2223 * a long time and slice keeps on extending and trim is not
2224 * called for a long time. Now if limits are reduced suddenly
2225 * we take into account all the IO dispatched so far at new
2226 * low rate and * newly queued IO gets a really long dispatch
2227 * time.
2228 *
2229 * So keep on trimming slice even if bio is not queued.
2230 */
2231 throtl_trim_slice(tg, rw);
2232
2233 /*
2234 * @bio passed through this layer without being throttled.
2235 * Climb up the ladder. If we're already at the top, it
2236 * can be executed directly.
2237 */
2238 qn = &tg->qnode_on_parent[rw];
2239 sq = sq->parent_sq;
2240 tg = sq_to_tg(sq);
2241 if (!tg) {
2242 bio_set_flag(bio, BIO_BPS_THROTTLED);
2243 goto out_unlock;
2244 }
2245 }
2246
2247 /* out-of-limit, queue to @tg */
2248 throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2249 rw == READ ? 'R' : 'W',
2250 tg->bytes_disp[rw], bio->bi_iter.bi_size,
2251 tg_bps_limit(tg, rw),
2252 tg->io_disp[rw], tg_iops_limit(tg, rw),
2253 sq->nr_queued[READ], sq->nr_queued[WRITE]);
2254
2255 tg->last_low_overflow_time[rw] = jiffies;
2256
2257 td->nr_queued[rw]++;
2258 throtl_add_bio_tg(bio, qn, tg);
2259 throttled = true;
2260
2261 /*
2262 * Update @tg's dispatch time and force schedule dispatch if @tg
2263 * was empty before @bio. The forced scheduling isn't likely to
2264 * cause undue delay as @bio is likely to be dispatched directly if
2265 * its @tg's disptime is not in the future.
2266 */
2267 if (tg->flags & THROTL_TG_WAS_EMPTY) {
2268 tg_update_disptime(tg);
2269 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2270 }
2271
2272out_unlock:
2273#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2274 if (throttled || !td->track_bio_latency)
2275 bio->bi_issue.value |= BIO_ISSUE_THROTL_SKIP_LATENCY;
2276#endif
2277 spin_unlock_irq(&q->queue_lock);
2278
2279 rcu_read_unlock();
2280 return throttled;
2281}
2282
2283#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2284static void throtl_track_latency(struct throtl_data *td, sector_t size,
2285 enum req_op op, unsigned long time)
2286{
2287 const bool rw = op_is_write(op);
2288 struct latency_bucket *latency;
2289 int index;
2290
2291 if (!td || td->limit_index != LIMIT_LOW ||
2292 !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
2293 !blk_queue_nonrot(td->queue))
2294 return;
2295
2296 index = request_bucket_index(size);
2297
2298 latency = get_cpu_ptr(td->latency_buckets[rw]);
2299 latency[index].total_latency += time;
2300 latency[index].samples++;
2301 put_cpu_ptr(td->latency_buckets[rw]);
2302}
2303
2304void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2305{
2306 struct request_queue *q = rq->q;
2307 struct throtl_data *td = q->td;
2308
2309 throtl_track_latency(td, blk_rq_stats_sectors(rq), req_op(rq),
2310 time_ns >> 10);
2311}
2312
2313void blk_throtl_bio_endio(struct bio *bio)
2314{
2315 struct blkcg_gq *blkg;
2316 struct throtl_grp *tg;
2317 u64 finish_time_ns;
2318 unsigned long finish_time;
2319 unsigned long start_time;
2320 unsigned long lat;
2321 int rw = bio_data_dir(bio);
2322
2323 blkg = bio->bi_blkg;
2324 if (!blkg)
2325 return;
2326 tg = blkg_to_tg(blkg);
2327 if (!tg->td->limit_valid[LIMIT_LOW])
2328 return;
2329
2330 finish_time_ns = blk_time_get_ns();
2331 tg->last_finish_time = finish_time_ns >> 10;
2332
2333 start_time = bio_issue_time(&bio->bi_issue) >> 10;
2334 finish_time = __bio_issue_time(finish_time_ns) >> 10;
2335 if (!start_time || finish_time <= start_time)
2336 return;
2337
2338 lat = finish_time - start_time;
2339 /* this is only for bio based driver */
2340 if (!(bio->bi_issue.value & BIO_ISSUE_THROTL_SKIP_LATENCY))
2341 throtl_track_latency(tg->td, bio_issue_size(&bio->bi_issue),
2342 bio_op(bio), lat);
2343
2344 if (tg->latency_target && lat >= tg->td->filtered_latency) {
2345 int bucket;
2346 unsigned int threshold;
2347
2348 bucket = request_bucket_index(bio_issue_size(&bio->bi_issue));
2349 threshold = tg->td->avg_buckets[rw][bucket].latency +
2350 tg->latency_target;
2351 if (lat > threshold)
2352 tg->bad_bio_cnt++;
2353 /*
2354 * Not race free, could get wrong count, which means cgroups
2355 * will be throttled
2356 */
2357 tg->bio_cnt++;
2358 }
2359
2360 if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2361 tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2362 tg->bio_cnt /= 2;
2363 tg->bad_bio_cnt /= 2;
2364 }
2365}
2366#endif
2367
2368int blk_throtl_init(struct gendisk *disk)
2369{
2370 struct request_queue *q = disk->queue;
2371 struct throtl_data *td;
2372 int ret;
2373
2374 td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2375 if (!td)
2376 return -ENOMEM;
2377 td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
2378 LATENCY_BUCKET_SIZE, __alignof__(u64));
2379 if (!td->latency_buckets[READ]) {
2380 kfree(td);
2381 return -ENOMEM;
2382 }
2383 td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
2384 LATENCY_BUCKET_SIZE, __alignof__(u64));
2385 if (!td->latency_buckets[WRITE]) {
2386 free_percpu(td->latency_buckets[READ]);
2387 kfree(td);
2388 return -ENOMEM;
2389 }
2390
2391 INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2392 throtl_service_queue_init(&td->service_queue);
2393
2394 q->td = td;
2395 td->queue = q;
2396
2397 td->limit_valid[LIMIT_MAX] = true;
2398 td->limit_index = LIMIT_MAX;
2399 td->low_upgrade_time = jiffies;
2400 td->low_downgrade_time = jiffies;
2401
2402 /* activate policy */
2403 ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
2404 if (ret) {
2405 free_percpu(td->latency_buckets[READ]);
2406 free_percpu(td->latency_buckets[WRITE]);
2407 kfree(td);
2408 }
2409 return ret;
2410}
2411
2412void blk_throtl_exit(struct gendisk *disk)
2413{
2414 struct request_queue *q = disk->queue;
2415
2416 BUG_ON(!q->td);
2417 del_timer_sync(&q->td->service_queue.pending_timer);
2418 throtl_shutdown_wq(q);
2419 blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
2420 free_percpu(q->td->latency_buckets[READ]);
2421 free_percpu(q->td->latency_buckets[WRITE]);
2422 kfree(q->td);
2423}
2424
2425void blk_throtl_register(struct gendisk *disk)
2426{
2427 struct request_queue *q = disk->queue;
2428 struct throtl_data *td;
2429 int i;
2430
2431 td = q->td;
2432 BUG_ON(!td);
2433
2434 if (blk_queue_nonrot(q)) {
2435 td->throtl_slice = DFL_THROTL_SLICE_SSD;
2436 td->filtered_latency = LATENCY_FILTERED_SSD;
2437 } else {
2438 td->throtl_slice = DFL_THROTL_SLICE_HD;
2439 td->filtered_latency = LATENCY_FILTERED_HD;
2440 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2441 td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
2442 td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
2443 }
2444 }
2445#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2446 /* if no low limit, use previous default */
2447 td->throtl_slice = DFL_THROTL_SLICE_HD;
2448
2449#else
2450 td->track_bio_latency = !queue_is_mq(q);
2451 if (!td->track_bio_latency)
2452 blk_stat_enable_accounting(q);
2453#endif
2454}
2455
2456#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2457ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2458{
2459 if (!q->td)
2460 return -EINVAL;
2461 return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2462}
2463
2464ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2465 const char *page, size_t count)
2466{
2467 unsigned long v;
2468 unsigned long t;
2469
2470 if (!q->td)
2471 return -EINVAL;
2472 if (kstrtoul(page, 10, &v))
2473 return -EINVAL;
2474 t = msecs_to_jiffies(v);
2475 if (t == 0 || t > MAX_THROTL_SLICE)
2476 return -EINVAL;
2477 q->td->throtl_slice = t;
2478 return count;
2479}
2480#endif
2481
2482static int __init throtl_init(void)
2483{
2484 kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2485 if (!kthrotld_workqueue)
2486 panic("Failed to create kthrotld\n");
2487
2488 return blkcg_policy_register(&blkcg_policy_throtl);
2489}
2490
2491module_init(throtl_init);