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