1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Interface for controlling IO bandwidth on a request queue
4  *
5  * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
6  */
7 
8 #include <linux/module.h>
9 #include <linux/slab.h>
10 #include <linux/blkdev.h>
11 #include <linux/bio.h>
12 #include <linux/blktrace_api.h>
13 #include "blk.h"
14 #include "blk-cgroup-rwstat.h"
15 #include "blk-stat.h"
16 #include "blk-throttle.h"
17 
18 /* Max dispatch from a group in 1 round */
19 #define THROTL_GRP_QUANTUM 8
20 
21 /* Total max dispatch from all groups in one round */
22 #define THROTL_QUANTUM 32
23 
24 /* Throttling is performed over a slice and after that slice is renewed */
25 #define DFL_THROTL_SLICE_HD (HZ / 10)
26 #define DFL_THROTL_SLICE_SSD (HZ / 50)
27 #define MAX_THROTL_SLICE (HZ)
28 #define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
29 #define MIN_THROTL_BPS (320 * 1024)
30 #define MIN_THROTL_IOPS (10)
31 #define DFL_LATENCY_TARGET (-1L)
32 #define DFL_IDLE_THRESHOLD (0)
33 #define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
34 #define LATENCY_FILTERED_SSD (0)
35 /*
36  * For HD, very small latency comes from sequential IO. Such IO is helpless to
37  * help determine if its IO is impacted by others, hence we ignore the IO
38  */
39 #define LATENCY_FILTERED_HD (1000L) /* 1ms */
40 
41 /* A workqueue to queue throttle related work */
42 static struct workqueue_struct *kthrotld_workqueue;
43 
44 #define rb_entry_tg(node)	rb_entry((node), struct throtl_grp, rb_node)
45 
46 /* We measure latency for request size from <= 4k to >= 1M */
47 #define LATENCY_BUCKET_SIZE 9
48 
49 struct latency_bucket {
50 	unsigned long total_latency; /* ns / 1024 */
51 	int samples;
52 };
53 
54 struct avg_latency_bucket {
55 	unsigned long latency; /* ns / 1024 */
56 	bool valid;
57 };
58 
59 struct throtl_data
60 {
61 	/* service tree for active throtl groups */
62 	struct throtl_service_queue service_queue;
63 
64 	struct request_queue *queue;
65 
66 	/* Total Number of queued bios on READ and WRITE lists */
67 	unsigned int nr_queued[2];
68 
69 	unsigned int throtl_slice;
70 
71 	/* Work for dispatching throttled bios */
72 	struct work_struct dispatch_work;
73 	unsigned int limit_index;
74 	bool limit_valid[LIMIT_CNT];
75 
76 	unsigned long low_upgrade_time;
77 	unsigned long low_downgrade_time;
78 
79 	unsigned int scale;
80 
81 	struct latency_bucket tmp_buckets[2][LATENCY_BUCKET_SIZE];
82 	struct avg_latency_bucket avg_buckets[2][LATENCY_BUCKET_SIZE];
83 	struct latency_bucket __percpu *latency_buckets[2];
84 	unsigned long last_calculate_time;
85 	unsigned long filtered_latency;
86 
87 	bool track_bio_latency;
88 };
89 
90 static void throtl_pending_timer_fn(struct timer_list *t);
91 
tg_to_blkg(struct throtl_grp * tg)92 static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
93 {
94 	return pd_to_blkg(&tg->pd);
95 }
96 
97 /**
98  * sq_to_tg - return the throl_grp the specified service queue belongs to
99  * @sq: the throtl_service_queue of interest
100  *
101  * Return the throtl_grp @sq belongs to.  If @sq is the top-level one
102  * embedded in throtl_data, %NULL is returned.
103  */
sq_to_tg(struct throtl_service_queue * sq)104 static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
105 {
106 	if (sq && sq->parent_sq)
107 		return container_of(sq, struct throtl_grp, service_queue);
108 	else
109 		return NULL;
110 }
111 
112 /**
113  * sq_to_td - return throtl_data the specified service queue belongs to
114  * @sq: the throtl_service_queue of interest
115  *
116  * A service_queue can be embedded in either a throtl_grp or throtl_data.
117  * Determine the associated throtl_data accordingly and return it.
118  */
sq_to_td(struct throtl_service_queue * sq)119 static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
120 {
121 	struct throtl_grp *tg = sq_to_tg(sq);
122 
123 	if (tg)
124 		return tg->td;
125 	else
126 		return container_of(sq, struct throtl_data, service_queue);
127 }
128 
129 /*
130  * cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
131  * make the IO dispatch more smooth.
132  * Scale up: linearly scale up according to elapsed time since upgrade. For
133  *           every throtl_slice, the limit scales up 1/2 .low limit till the
134  *           limit hits .max limit
135  * Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
136  */
throtl_adjusted_limit(uint64_t low,struct throtl_data * td)137 static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
138 {
139 	/* arbitrary value to avoid too big scale */
140 	if (td->scale < 4096 && time_after_eq(jiffies,
141 	    td->low_upgrade_time + td->scale * td->throtl_slice))
142 		td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
143 
144 	return low + (low >> 1) * td->scale;
145 }
146 
tg_bps_limit(struct throtl_grp * tg,int rw)147 static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
148 {
149 	struct blkcg_gq *blkg = tg_to_blkg(tg);
150 	struct throtl_data *td;
151 	uint64_t ret;
152 
153 	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
154 		return U64_MAX;
155 
156 	td = tg->td;
157 	ret = tg->bps[rw][td->limit_index];
158 	if (ret == 0 && td->limit_index == LIMIT_LOW) {
159 		/* intermediate node or iops isn't 0 */
160 		if (!list_empty(&blkg->blkcg->css.children) ||
161 		    tg->iops[rw][td->limit_index])
162 			return U64_MAX;
163 		else
164 			return MIN_THROTL_BPS;
165 	}
166 
167 	if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
168 	    tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
169 		uint64_t adjusted;
170 
171 		adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
172 		ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
173 	}
174 	return ret;
175 }
176 
tg_iops_limit(struct throtl_grp * tg,int rw)177 static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
178 {
179 	struct blkcg_gq *blkg = tg_to_blkg(tg);
180 	struct throtl_data *td;
181 	unsigned int ret;
182 
183 	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
184 		return UINT_MAX;
185 
186 	td = tg->td;
187 	ret = tg->iops[rw][td->limit_index];
188 	if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
189 		/* intermediate node or bps isn't 0 */
190 		if (!list_empty(&blkg->blkcg->css.children) ||
191 		    tg->bps[rw][td->limit_index])
192 			return UINT_MAX;
193 		else
194 			return MIN_THROTL_IOPS;
195 	}
196 
197 	if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
198 	    tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
199 		uint64_t adjusted;
200 
201 		adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
202 		if (adjusted > UINT_MAX)
203 			adjusted = UINT_MAX;
204 		ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
205 	}
206 	return ret;
207 }
208 
209 #define request_bucket_index(sectors) \
210 	clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
211 
212 /**
213  * throtl_log - log debug message via blktrace
214  * @sq: the service_queue being reported
215  * @fmt: printf format string
216  * @args: printf args
217  *
218  * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
219  * throtl_grp; otherwise, just "throtl".
220  */
221 #define throtl_log(sq, fmt, args...)	do {				\
222 	struct throtl_grp *__tg = sq_to_tg((sq));			\
223 	struct throtl_data *__td = sq_to_td((sq));			\
224 									\
225 	(void)__td;							\
226 	if (likely(!blk_trace_note_message_enabled(__td->queue)))	\
227 		break;							\
228 	if ((__tg)) {							\
229 		blk_add_cgroup_trace_msg(__td->queue,			\
230 			&tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\
231 	} else {							\
232 		blk_add_trace_msg(__td->queue, "throtl " fmt, ##args);	\
233 	}								\
234 } while (0)
235 
throtl_bio_data_size(struct bio * bio)236 static inline unsigned int throtl_bio_data_size(struct bio *bio)
237 {
238 	/* assume it's one sector */
239 	if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
240 		return 512;
241 	return bio->bi_iter.bi_size;
242 }
243 
throtl_qnode_init(struct throtl_qnode * qn,struct throtl_grp * tg)244 static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
245 {
246 	INIT_LIST_HEAD(&qn->node);
247 	bio_list_init(&qn->bios);
248 	qn->tg = tg;
249 }
250 
251 /**
252  * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it
253  * @bio: bio being added
254  * @qn: qnode to add bio to
255  * @queued: the service_queue->queued[] list @qn belongs to
256  *
257  * Add @bio to @qn and put @qn on @queued if it's not already on.
258  * @qn->tg's reference count is bumped when @qn is activated.  See the
259  * comment on top of throtl_qnode definition for details.
260  */
throtl_qnode_add_bio(struct bio * bio,struct throtl_qnode * qn,struct list_head * queued)261 static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn,
262 				 struct list_head *queued)
263 {
264 	bio_list_add(&qn->bios, bio);
265 	if (list_empty(&qn->node)) {
266 		list_add_tail(&qn->node, queued);
267 		blkg_get(tg_to_blkg(qn->tg));
268 	}
269 }
270 
271 /**
272  * throtl_peek_queued - peek the first bio on a qnode list
273  * @queued: the qnode list to peek
274  */
throtl_peek_queued(struct list_head * queued)275 static struct bio *throtl_peek_queued(struct list_head *queued)
276 {
277 	struct throtl_qnode *qn;
278 	struct bio *bio;
279 
280 	if (list_empty(queued))
281 		return NULL;
282 
283 	qn = list_first_entry(queued, struct throtl_qnode, node);
284 	bio = bio_list_peek(&qn->bios);
285 	WARN_ON_ONCE(!bio);
286 	return bio;
287 }
288 
289 /**
290  * throtl_pop_queued - pop the first bio form a qnode list
291  * @queued: the qnode list to pop a bio from
292  * @tg_to_put: optional out argument for throtl_grp to put
293  *
294  * Pop the first bio from the qnode list @queued.  After popping, the first
295  * qnode is removed from @queued if empty or moved to the end of @queued so
296  * that the popping order is round-robin.
297  *
298  * When the first qnode is removed, its associated throtl_grp should be put
299  * too.  If @tg_to_put is NULL, this function automatically puts it;
300  * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is
301  * responsible for putting it.
302  */
throtl_pop_queued(struct list_head * queued,struct throtl_grp ** tg_to_put)303 static struct bio *throtl_pop_queued(struct list_head *queued,
304 				     struct throtl_grp **tg_to_put)
305 {
306 	struct throtl_qnode *qn;
307 	struct bio *bio;
308 
309 	if (list_empty(queued))
310 		return NULL;
311 
312 	qn = list_first_entry(queued, struct throtl_qnode, node);
313 	bio = bio_list_pop(&qn->bios);
314 	WARN_ON_ONCE(!bio);
315 
316 	if (bio_list_empty(&qn->bios)) {
317 		list_del_init(&qn->node);
318 		if (tg_to_put)
319 			*tg_to_put = qn->tg;
320 		else
321 			blkg_put(tg_to_blkg(qn->tg));
322 	} else {
323 		list_move_tail(&qn->node, queued);
324 	}
325 
326 	return bio;
327 }
328 
329 /* init a service_queue, assumes the caller zeroed it */
throtl_service_queue_init(struct throtl_service_queue * sq)330 static void throtl_service_queue_init(struct throtl_service_queue *sq)
331 {
332 	INIT_LIST_HEAD(&sq->queued[READ]);
333 	INIT_LIST_HEAD(&sq->queued[WRITE]);
334 	sq->pending_tree = RB_ROOT_CACHED;
335 	timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
336 }
337 
throtl_pd_alloc(struct gendisk * disk,struct blkcg * blkcg,gfp_t gfp)338 static struct blkg_policy_data *throtl_pd_alloc(struct gendisk *disk,
339 		struct blkcg *blkcg, gfp_t gfp)
340 {
341 	struct throtl_grp *tg;
342 	int rw;
343 
344 	tg = kzalloc_node(sizeof(*tg), gfp, disk->node_id);
345 	if (!tg)
346 		return NULL;
347 
348 	if (blkg_rwstat_init(&tg->stat_bytes, gfp))
349 		goto err_free_tg;
350 
351 	if (blkg_rwstat_init(&tg->stat_ios, gfp))
352 		goto err_exit_stat_bytes;
353 
354 	throtl_service_queue_init(&tg->service_queue);
355 
356 	for (rw = READ; rw <= WRITE; rw++) {
357 		throtl_qnode_init(&tg->qnode_on_self[rw], tg);
358 		throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
359 	}
360 
361 	RB_CLEAR_NODE(&tg->rb_node);
362 	tg->bps[READ][LIMIT_MAX] = U64_MAX;
363 	tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
364 	tg->iops[READ][LIMIT_MAX] = UINT_MAX;
365 	tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
366 	tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
367 	tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
368 	tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
369 	tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
370 	/* LIMIT_LOW will have default value 0 */
371 
372 	tg->latency_target = DFL_LATENCY_TARGET;
373 	tg->latency_target_conf = DFL_LATENCY_TARGET;
374 	tg->idletime_threshold = DFL_IDLE_THRESHOLD;
375 	tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
376 
377 	return &tg->pd;
378 
379 err_exit_stat_bytes:
380 	blkg_rwstat_exit(&tg->stat_bytes);
381 err_free_tg:
382 	kfree(tg);
383 	return NULL;
384 }
385 
throtl_pd_init(struct blkg_policy_data * pd)386 static void throtl_pd_init(struct blkg_policy_data *pd)
387 {
388 	struct throtl_grp *tg = pd_to_tg(pd);
389 	struct blkcg_gq *blkg = tg_to_blkg(tg);
390 	struct throtl_data *td = blkg->q->td;
391 	struct throtl_service_queue *sq = &tg->service_queue;
392 
393 	/*
394 	 * If on the default hierarchy, we switch to properly hierarchical
395 	 * behavior where limits on a given throtl_grp are applied to the
396 	 * whole subtree rather than just the group itself.  e.g. If 16M
397 	 * read_bps limit is set on a parent group, summary bps of
398 	 * parent group and its subtree groups can't exceed 16M for the
399 	 * device.
400 	 *
401 	 * If not on the default hierarchy, the broken flat hierarchy
402 	 * behavior is retained where all throtl_grps are treated as if
403 	 * they're all separate root groups right below throtl_data.
404 	 * Limits of a group don't interact with limits of other groups
405 	 * regardless of the position of the group in the hierarchy.
406 	 */
407 	sq->parent_sq = &td->service_queue;
408 	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
409 		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
410 	tg->td = td;
411 }
412 
413 /*
414  * Set has_rules[] if @tg or any of its parents have limits configured.
415  * This doesn't require walking up to the top of the hierarchy as the
416  * parent's has_rules[] is guaranteed to be correct.
417  */
tg_update_has_rules(struct throtl_grp * tg)418 static void tg_update_has_rules(struct throtl_grp *tg)
419 {
420 	struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
421 	struct throtl_data *td = tg->td;
422 	int rw;
423 
424 	for (rw = READ; rw <= WRITE; rw++) {
425 		tg->has_rules_iops[rw] =
426 			(parent_tg && parent_tg->has_rules_iops[rw]) ||
427 			(td->limit_valid[td->limit_index] &&
428 			  tg_iops_limit(tg, rw) != UINT_MAX);
429 		tg->has_rules_bps[rw] =
430 			(parent_tg && parent_tg->has_rules_bps[rw]) ||
431 			(td->limit_valid[td->limit_index] &&
432 			 (tg_bps_limit(tg, rw) != U64_MAX));
433 	}
434 }
435 
throtl_pd_online(struct blkg_policy_data * pd)436 static void throtl_pd_online(struct blkg_policy_data *pd)
437 {
438 	struct throtl_grp *tg = pd_to_tg(pd);
439 	/*
440 	 * We don't want new groups to escape the limits of its ancestors.
441 	 * Update has_rules[] after a new group is brought online.
442 	 */
443 	tg_update_has_rules(tg);
444 }
445 
446 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
blk_throtl_update_limit_valid(struct throtl_data * td)447 static void blk_throtl_update_limit_valid(struct throtl_data *td)
448 {
449 	struct cgroup_subsys_state *pos_css;
450 	struct blkcg_gq *blkg;
451 	bool low_valid = false;
452 
453 	rcu_read_lock();
454 	blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
455 		struct throtl_grp *tg = blkg_to_tg(blkg);
456 
457 		if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
458 		    tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) {
459 			low_valid = true;
460 			break;
461 		}
462 	}
463 	rcu_read_unlock();
464 
465 	td->limit_valid[LIMIT_LOW] = low_valid;
466 }
467 #else
blk_throtl_update_limit_valid(struct throtl_data * td)468 static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
469 {
470 }
471 #endif
472 
473 static void throtl_upgrade_state(struct throtl_data *td);
throtl_pd_offline(struct blkg_policy_data * pd)474 static void throtl_pd_offline(struct blkg_policy_data *pd)
475 {
476 	struct throtl_grp *tg = pd_to_tg(pd);
477 
478 	tg->bps[READ][LIMIT_LOW] = 0;
479 	tg->bps[WRITE][LIMIT_LOW] = 0;
480 	tg->iops[READ][LIMIT_LOW] = 0;
481 	tg->iops[WRITE][LIMIT_LOW] = 0;
482 
483 	blk_throtl_update_limit_valid(tg->td);
484 
485 	if (!tg->td->limit_valid[tg->td->limit_index])
486 		throtl_upgrade_state(tg->td);
487 }
488 
throtl_pd_free(struct blkg_policy_data * pd)489 static void throtl_pd_free(struct blkg_policy_data *pd)
490 {
491 	struct throtl_grp *tg = pd_to_tg(pd);
492 
493 	del_timer_sync(&tg->service_queue.pending_timer);
494 	blkg_rwstat_exit(&tg->stat_bytes);
495 	blkg_rwstat_exit(&tg->stat_ios);
496 	kfree(tg);
497 }
498 
499 static struct throtl_grp *
throtl_rb_first(struct throtl_service_queue * parent_sq)500 throtl_rb_first(struct throtl_service_queue *parent_sq)
501 {
502 	struct rb_node *n;
503 
504 	n = rb_first_cached(&parent_sq->pending_tree);
505 	WARN_ON_ONCE(!n);
506 	if (!n)
507 		return NULL;
508 	return rb_entry_tg(n);
509 }
510 
throtl_rb_erase(struct rb_node * n,struct throtl_service_queue * parent_sq)511 static void throtl_rb_erase(struct rb_node *n,
512 			    struct throtl_service_queue *parent_sq)
513 {
514 	rb_erase_cached(n, &parent_sq->pending_tree);
515 	RB_CLEAR_NODE(n);
516 }
517 
update_min_dispatch_time(struct throtl_service_queue * parent_sq)518 static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
519 {
520 	struct throtl_grp *tg;
521 
522 	tg = throtl_rb_first(parent_sq);
523 	if (!tg)
524 		return;
525 
526 	parent_sq->first_pending_disptime = tg->disptime;
527 }
528 
tg_service_queue_add(struct throtl_grp * tg)529 static void tg_service_queue_add(struct throtl_grp *tg)
530 {
531 	struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
532 	struct rb_node **node = &parent_sq->pending_tree.rb_root.rb_node;
533 	struct rb_node *parent = NULL;
534 	struct throtl_grp *__tg;
535 	unsigned long key = tg->disptime;
536 	bool leftmost = true;
537 
538 	while (*node != NULL) {
539 		parent = *node;
540 		__tg = rb_entry_tg(parent);
541 
542 		if (time_before(key, __tg->disptime))
543 			node = &parent->rb_left;
544 		else {
545 			node = &parent->rb_right;
546 			leftmost = false;
547 		}
548 	}
549 
550 	rb_link_node(&tg->rb_node, parent, node);
551 	rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
552 			       leftmost);
553 }
554 
throtl_enqueue_tg(struct throtl_grp * tg)555 static void throtl_enqueue_tg(struct throtl_grp *tg)
556 {
557 	if (!(tg->flags & THROTL_TG_PENDING)) {
558 		tg_service_queue_add(tg);
559 		tg->flags |= THROTL_TG_PENDING;
560 		tg->service_queue.parent_sq->nr_pending++;
561 	}
562 }
563 
throtl_dequeue_tg(struct throtl_grp * tg)564 static void throtl_dequeue_tg(struct throtl_grp *tg)
565 {
566 	if (tg->flags & THROTL_TG_PENDING) {
567 		struct throtl_service_queue *parent_sq =
568 			tg->service_queue.parent_sq;
569 
570 		throtl_rb_erase(&tg->rb_node, parent_sq);
571 		--parent_sq->nr_pending;
572 		tg->flags &= ~THROTL_TG_PENDING;
573 	}
574 }
575 
576 /* Call with queue lock held */
throtl_schedule_pending_timer(struct throtl_service_queue * sq,unsigned long expires)577 static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
578 					  unsigned long expires)
579 {
580 	unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
581 
582 	/*
583 	 * Since we are adjusting the throttle limit dynamically, the sleep
584 	 * time calculated according to previous limit might be invalid. It's
585 	 * possible the cgroup sleep time is very long and no other cgroups
586 	 * have IO running so notify the limit changes. Make sure the cgroup
587 	 * doesn't sleep too long to avoid the missed notification.
588 	 */
589 	if (time_after(expires, max_expire))
590 		expires = max_expire;
591 	mod_timer(&sq->pending_timer, expires);
592 	throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
593 		   expires - jiffies, jiffies);
594 }
595 
596 /**
597  * throtl_schedule_next_dispatch - schedule the next dispatch cycle
598  * @sq: the service_queue to schedule dispatch for
599  * @force: force scheduling
600  *
601  * Arm @sq->pending_timer so that the next dispatch cycle starts on the
602  * dispatch time of the first pending child.  Returns %true if either timer
603  * is armed or there's no pending child left.  %false if the current
604  * dispatch window is still open and the caller should continue
605  * dispatching.
606  *
607  * If @force is %true, the dispatch timer is always scheduled and this
608  * function is guaranteed to return %true.  This is to be used when the
609  * caller can't dispatch itself and needs to invoke pending_timer
610  * unconditionally.  Note that forced scheduling is likely to induce short
611  * delay before dispatch starts even if @sq->first_pending_disptime is not
612  * in the future and thus shouldn't be used in hot paths.
613  */
throtl_schedule_next_dispatch(struct throtl_service_queue * sq,bool force)614 static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq,
615 					  bool force)
616 {
617 	/* any pending children left? */
618 	if (!sq->nr_pending)
619 		return true;
620 
621 	update_min_dispatch_time(sq);
622 
623 	/* is the next dispatch time in the future? */
624 	if (force || time_after(sq->first_pending_disptime, jiffies)) {
625 		throtl_schedule_pending_timer(sq, sq->first_pending_disptime);
626 		return true;
627 	}
628 
629 	/* tell the caller to continue dispatching */
630 	return false;
631 }
632 
throtl_start_new_slice_with_credit(struct throtl_grp * tg,bool rw,unsigned long start)633 static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
634 		bool rw, unsigned long start)
635 {
636 	tg->bytes_disp[rw] = 0;
637 	tg->io_disp[rw] = 0;
638 	tg->carryover_bytes[rw] = 0;
639 	tg->carryover_ios[rw] = 0;
640 
641 	/*
642 	 * Previous slice has expired. We must have trimmed it after last
643 	 * bio dispatch. That means since start of last slice, we never used
644 	 * that bandwidth. Do try to make use of that bandwidth while giving
645 	 * credit.
646 	 */
647 	if (time_after(start, tg->slice_start[rw]))
648 		tg->slice_start[rw] = start;
649 
650 	tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
651 	throtl_log(&tg->service_queue,
652 		   "[%c] new slice with credit start=%lu end=%lu jiffies=%lu",
653 		   rw == READ ? 'R' : 'W', tg->slice_start[rw],
654 		   tg->slice_end[rw], jiffies);
655 }
656 
throtl_start_new_slice(struct throtl_grp * tg,bool rw,bool clear_carryover)657 static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
658 					  bool clear_carryover)
659 {
660 	tg->bytes_disp[rw] = 0;
661 	tg->io_disp[rw] = 0;
662 	tg->slice_start[rw] = jiffies;
663 	tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
664 	if (clear_carryover) {
665 		tg->carryover_bytes[rw] = 0;
666 		tg->carryover_ios[rw] = 0;
667 	}
668 
669 	throtl_log(&tg->service_queue,
670 		   "[%c] new slice start=%lu end=%lu jiffies=%lu",
671 		   rw == READ ? 'R' : 'W', tg->slice_start[rw],
672 		   tg->slice_end[rw], jiffies);
673 }
674 
throtl_set_slice_end(struct throtl_grp * tg,bool rw,unsigned long jiffy_end)675 static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
676 					unsigned long jiffy_end)
677 {
678 	tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
679 }
680 
throtl_extend_slice(struct throtl_grp * tg,bool rw,unsigned long jiffy_end)681 static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
682 				       unsigned long jiffy_end)
683 {
684 	throtl_set_slice_end(tg, rw, jiffy_end);
685 	throtl_log(&tg->service_queue,
686 		   "[%c] extend slice start=%lu end=%lu jiffies=%lu",
687 		   rw == READ ? 'R' : 'W', tg->slice_start[rw],
688 		   tg->slice_end[rw], jiffies);
689 }
690 
691 /* Determine if previously allocated or extended slice is complete or not */
throtl_slice_used(struct throtl_grp * tg,bool rw)692 static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
693 {
694 	if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
695 		return false;
696 
697 	return true;
698 }
699 
calculate_io_allowed(u32 iops_limit,unsigned long jiffy_elapsed)700 static unsigned int calculate_io_allowed(u32 iops_limit,
701 					 unsigned long jiffy_elapsed)
702 {
703 	unsigned int io_allowed;
704 	u64 tmp;
705 
706 	/*
707 	 * jiffy_elapsed should not be a big value as minimum iops can be
708 	 * 1 then at max jiffy elapsed should be equivalent of 1 second as we
709 	 * will allow dispatch after 1 second and after that slice should
710 	 * have been trimmed.
711 	 */
712 
713 	tmp = (u64)iops_limit * jiffy_elapsed;
714 	do_div(tmp, HZ);
715 
716 	if (tmp > UINT_MAX)
717 		io_allowed = UINT_MAX;
718 	else
719 		io_allowed = tmp;
720 
721 	return io_allowed;
722 }
723 
calculate_bytes_allowed(u64 bps_limit,unsigned long jiffy_elapsed)724 static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
725 {
726 	/*
727 	 * Can result be wider than 64 bits?
728 	 * We check against 62, not 64, due to ilog2 truncation.
729 	 */
730 	if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62)
731 		return U64_MAX;
732 	return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
733 }
734 
735 /* Trim the used slices and adjust slice start accordingly */
throtl_trim_slice(struct throtl_grp * tg,bool rw)736 static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
737 {
738 	unsigned long time_elapsed;
739 	long long bytes_trim;
740 	int io_trim;
741 
742 	BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
743 
744 	/*
745 	 * If bps are unlimited (-1), then time slice don't get
746 	 * renewed. Don't try to trim the slice if slice is used. A new
747 	 * slice will start when appropriate.
748 	 */
749 	if (throtl_slice_used(tg, rw))
750 		return;
751 
752 	/*
753 	 * A bio has been dispatched. Also adjust slice_end. It might happen
754 	 * that initially cgroup limit was very low resulting in high
755 	 * slice_end, but later limit was bumped up and bio was dispatched
756 	 * sooner, then we need to reduce slice_end. A high bogus slice_end
757 	 * is bad because it does not allow new slice to start.
758 	 */
759 
760 	throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
761 
762 	time_elapsed = rounddown(jiffies - tg->slice_start[rw],
763 				 tg->td->throtl_slice);
764 	if (!time_elapsed)
765 		return;
766 
767 	bytes_trim = calculate_bytes_allowed(tg_bps_limit(tg, rw),
768 					     time_elapsed) +
769 		     tg->carryover_bytes[rw];
770 	io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed) +
771 		  tg->carryover_ios[rw];
772 	if (bytes_trim <= 0 && io_trim <= 0)
773 		return;
774 
775 	tg->carryover_bytes[rw] = 0;
776 	if ((long long)tg->bytes_disp[rw] >= bytes_trim)
777 		tg->bytes_disp[rw] -= bytes_trim;
778 	else
779 		tg->bytes_disp[rw] = 0;
780 
781 	tg->carryover_ios[rw] = 0;
782 	if ((int)tg->io_disp[rw] >= io_trim)
783 		tg->io_disp[rw] -= io_trim;
784 	else
785 		tg->io_disp[rw] = 0;
786 
787 	tg->slice_start[rw] += time_elapsed;
788 
789 	throtl_log(&tg->service_queue,
790 		   "[%c] trim slice nr=%lu bytes=%lld io=%d start=%lu end=%lu jiffies=%lu",
791 		   rw == READ ? 'R' : 'W', time_elapsed / tg->td->throtl_slice,
792 		   bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw],
793 		   jiffies);
794 }
795 
__tg_update_carryover(struct throtl_grp * tg,bool rw)796 static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
797 {
798 	unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
799 	u64 bps_limit = tg_bps_limit(tg, rw);
800 	u32 iops_limit = tg_iops_limit(tg, rw);
801 
802 	/*
803 	 * If config is updated while bios are still throttled, calculate and
804 	 * accumulate how many bytes/ios are waited across changes. And
805 	 * carryover_bytes/ios will be used to calculate new wait time under new
806 	 * configuration.
807 	 */
808 	if (bps_limit != U64_MAX)
809 		tg->carryover_bytes[rw] +=
810 			calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
811 			tg->bytes_disp[rw];
812 	if (iops_limit != UINT_MAX)
813 		tg->carryover_ios[rw] +=
814 			calculate_io_allowed(iops_limit, jiffy_elapsed) -
815 			tg->io_disp[rw];
816 }
817 
tg_update_carryover(struct throtl_grp * tg)818 static void tg_update_carryover(struct throtl_grp *tg)
819 {
820 	if (tg->service_queue.nr_queued[READ])
821 		__tg_update_carryover(tg, READ);
822 	if (tg->service_queue.nr_queued[WRITE])
823 		__tg_update_carryover(tg, WRITE);
824 
825 	/* see comments in struct throtl_grp for meaning of these fields. */
826 	throtl_log(&tg->service_queue, "%s: %lld %lld %d %d\n", __func__,
827 		   tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
828 		   tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
829 }
830 
tg_within_iops_limit(struct throtl_grp * tg,struct bio * bio,u32 iops_limit)831 static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
832 				 u32 iops_limit)
833 {
834 	bool rw = bio_data_dir(bio);
835 	int io_allowed;
836 	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
837 
838 	if (iops_limit == UINT_MAX) {
839 		return 0;
840 	}
841 
842 	jiffy_elapsed = jiffies - tg->slice_start[rw];
843 
844 	/* Round up to the next throttle slice, wait time must be nonzero */
845 	jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
846 	io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
847 		     tg->carryover_ios[rw];
848 	if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed)
849 		return 0;
850 
851 	/* Calc approx time to dispatch */
852 	jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
853 	return jiffy_wait;
854 }
855 
tg_within_bps_limit(struct throtl_grp * tg,struct bio * bio,u64 bps_limit)856 static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
857 				u64 bps_limit)
858 {
859 	bool rw = bio_data_dir(bio);
860 	long long bytes_allowed;
861 	u64 extra_bytes;
862 	unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
863 	unsigned int bio_size = throtl_bio_data_size(bio);
864 
865 	/* no need to throttle if this bio's bytes have been accounted */
866 	if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
867 		return 0;
868 	}
869 
870 	jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
871 
872 	/* Slice has just started. Consider one slice interval */
873 	if (!jiffy_elapsed)
874 		jiffy_elapsed_rnd = tg->td->throtl_slice;
875 
876 	jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
877 	bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
878 			tg->carryover_bytes[rw];
879 	if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
880 		return 0;
881 
882 	/* Calc approx time to dispatch */
883 	extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
884 	jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
885 
886 	if (!jiffy_wait)
887 		jiffy_wait = 1;
888 
889 	/*
890 	 * This wait time is without taking into consideration the rounding
891 	 * up we did. Add that time also.
892 	 */
893 	jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
894 	return jiffy_wait;
895 }
896 
897 /*
898  * Returns whether one can dispatch a bio or not. Also returns approx number
899  * of jiffies to wait before this bio is with-in IO rate and can be dispatched
900  */
tg_may_dispatch(struct throtl_grp * tg,struct bio * bio,unsigned long * wait)901 static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
902 			    unsigned long *wait)
903 {
904 	bool rw = bio_data_dir(bio);
905 	unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
906 	u64 bps_limit = tg_bps_limit(tg, rw);
907 	u32 iops_limit = tg_iops_limit(tg, rw);
908 
909 	/*
910  	 * Currently whole state machine of group depends on first bio
911 	 * queued in the group bio list. So one should not be calling
912 	 * this function with a different bio if there are other bios
913 	 * queued.
914 	 */
915 	BUG_ON(tg->service_queue.nr_queued[rw] &&
916 	       bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
917 
918 	/* If tg->bps = -1, then BW is unlimited */
919 	if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
920 	    tg->flags & THROTL_TG_CANCELING) {
921 		if (wait)
922 			*wait = 0;
923 		return true;
924 	}
925 
926 	/*
927 	 * If previous slice expired, start a new one otherwise renew/extend
928 	 * existing slice to make sure it is at least throtl_slice interval
929 	 * long since now. New slice is started only for empty throttle group.
930 	 * If there is queued bio, that means there should be an active
931 	 * slice and it should be extended instead.
932 	 */
933 	if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
934 		throtl_start_new_slice(tg, rw, true);
935 	else {
936 		if (time_before(tg->slice_end[rw],
937 		    jiffies + tg->td->throtl_slice))
938 			throtl_extend_slice(tg, rw,
939 				jiffies + tg->td->throtl_slice);
940 	}
941 
942 	bps_wait = tg_within_bps_limit(tg, bio, bps_limit);
943 	iops_wait = tg_within_iops_limit(tg, bio, iops_limit);
944 	if (bps_wait + iops_wait == 0) {
945 		if (wait)
946 			*wait = 0;
947 		return true;
948 	}
949 
950 	max_wait = max(bps_wait, iops_wait);
951 
952 	if (wait)
953 		*wait = max_wait;
954 
955 	if (time_before(tg->slice_end[rw], jiffies + max_wait))
956 		throtl_extend_slice(tg, rw, jiffies + max_wait);
957 
958 	return false;
959 }
960 
throtl_charge_bio(struct throtl_grp * tg,struct bio * bio)961 static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
962 {
963 	bool rw = bio_data_dir(bio);
964 	unsigned int bio_size = throtl_bio_data_size(bio);
965 
966 	/* Charge the bio to the group */
967 	if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
968 		tg->bytes_disp[rw] += bio_size;
969 		tg->last_bytes_disp[rw] += bio_size;
970 	}
971 
972 	tg->io_disp[rw]++;
973 	tg->last_io_disp[rw]++;
974 }
975 
976 /**
977  * throtl_add_bio_tg - add a bio to the specified throtl_grp
978  * @bio: bio to add
979  * @qn: qnode to use
980  * @tg: the target throtl_grp
981  *
982  * Add @bio to @tg's service_queue using @qn.  If @qn is not specified,
983  * tg->qnode_on_self[] is used.
984  */
throtl_add_bio_tg(struct bio * bio,struct throtl_qnode * qn,struct throtl_grp * tg)985 static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn,
986 			      struct throtl_grp *tg)
987 {
988 	struct throtl_service_queue *sq = &tg->service_queue;
989 	bool rw = bio_data_dir(bio);
990 
991 	if (!qn)
992 		qn = &tg->qnode_on_self[rw];
993 
994 	/*
995 	 * If @tg doesn't currently have any bios queued in the same
996 	 * direction, queueing @bio can change when @tg should be
997 	 * dispatched.  Mark that @tg was empty.  This is automatically
998 	 * cleared on the next tg_update_disptime().
999 	 */
1000 	if (!sq->nr_queued[rw])
1001 		tg->flags |= THROTL_TG_WAS_EMPTY;
1002 
1003 	throtl_qnode_add_bio(bio, qn, &sq->queued[rw]);
1004 
1005 	sq->nr_queued[rw]++;
1006 	throtl_enqueue_tg(tg);
1007 }
1008 
tg_update_disptime(struct throtl_grp * tg)1009 static void tg_update_disptime(struct throtl_grp *tg)
1010 {
1011 	struct throtl_service_queue *sq = &tg->service_queue;
1012 	unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
1013 	struct bio *bio;
1014 
1015 	bio = throtl_peek_queued(&sq->queued[READ]);
1016 	if (bio)
1017 		tg_may_dispatch(tg, bio, &read_wait);
1018 
1019 	bio = throtl_peek_queued(&sq->queued[WRITE]);
1020 	if (bio)
1021 		tg_may_dispatch(tg, bio, &write_wait);
1022 
1023 	min_wait = min(read_wait, write_wait);
1024 	disptime = jiffies + min_wait;
1025 
1026 	/* Update dispatch time */
1027 	throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
1028 	tg->disptime = disptime;
1029 	tg_service_queue_add(tg);
1030 
1031 	/* see throtl_add_bio_tg() */
1032 	tg->flags &= ~THROTL_TG_WAS_EMPTY;
1033 }
1034 
start_parent_slice_with_credit(struct throtl_grp * child_tg,struct throtl_grp * parent_tg,bool rw)1035 static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
1036 					struct throtl_grp *parent_tg, bool rw)
1037 {
1038 	if (throtl_slice_used(parent_tg, rw)) {
1039 		throtl_start_new_slice_with_credit(parent_tg, rw,
1040 				child_tg->slice_start[rw]);
1041 	}
1042 
1043 }
1044 
tg_dispatch_one_bio(struct throtl_grp * tg,bool rw)1045 static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
1046 {
1047 	struct throtl_service_queue *sq = &tg->service_queue;
1048 	struct throtl_service_queue *parent_sq = sq->parent_sq;
1049 	struct throtl_grp *parent_tg = sq_to_tg(parent_sq);
1050 	struct throtl_grp *tg_to_put = NULL;
1051 	struct bio *bio;
1052 
1053 	/*
1054 	 * @bio is being transferred from @tg to @parent_sq.  Popping a bio
1055 	 * from @tg may put its reference and @parent_sq might end up
1056 	 * getting released prematurely.  Remember the tg to put and put it
1057 	 * after @bio is transferred to @parent_sq.
1058 	 */
1059 	bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put);
1060 	sq->nr_queued[rw]--;
1061 
1062 	throtl_charge_bio(tg, bio);
1063 
1064 	/*
1065 	 * If our parent is another tg, we just need to transfer @bio to
1066 	 * the parent using throtl_add_bio_tg().  If our parent is
1067 	 * @td->service_queue, @bio is ready to be issued.  Put it on its
1068 	 * bio_lists[] and decrease total number queued.  The caller is
1069 	 * responsible for issuing these bios.
1070 	 */
1071 	if (parent_tg) {
1072 		throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
1073 		start_parent_slice_with_credit(tg, parent_tg, rw);
1074 	} else {
1075 		bio_set_flag(bio, BIO_BPS_THROTTLED);
1076 		throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
1077 				     &parent_sq->queued[rw]);
1078 		BUG_ON(tg->td->nr_queued[rw] <= 0);
1079 		tg->td->nr_queued[rw]--;
1080 	}
1081 
1082 	throtl_trim_slice(tg, rw);
1083 
1084 	if (tg_to_put)
1085 		blkg_put(tg_to_blkg(tg_to_put));
1086 }
1087 
throtl_dispatch_tg(struct throtl_grp * tg)1088 static int throtl_dispatch_tg(struct throtl_grp *tg)
1089 {
1090 	struct throtl_service_queue *sq = &tg->service_queue;
1091 	unsigned int nr_reads = 0, nr_writes = 0;
1092 	unsigned int max_nr_reads = THROTL_GRP_QUANTUM * 3 / 4;
1093 	unsigned int max_nr_writes = THROTL_GRP_QUANTUM - max_nr_reads;
1094 	struct bio *bio;
1095 
1096 	/* Try to dispatch 75% READS and 25% WRITES */
1097 
1098 	while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
1099 	       tg_may_dispatch(tg, bio, NULL)) {
1100 
1101 		tg_dispatch_one_bio(tg, bio_data_dir(bio));
1102 		nr_reads++;
1103 
1104 		if (nr_reads >= max_nr_reads)
1105 			break;
1106 	}
1107 
1108 	while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
1109 	       tg_may_dispatch(tg, bio, NULL)) {
1110 
1111 		tg_dispatch_one_bio(tg, bio_data_dir(bio));
1112 		nr_writes++;
1113 
1114 		if (nr_writes >= max_nr_writes)
1115 			break;
1116 	}
1117 
1118 	return nr_reads + nr_writes;
1119 }
1120 
throtl_select_dispatch(struct throtl_service_queue * parent_sq)1121 static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
1122 {
1123 	unsigned int nr_disp = 0;
1124 
1125 	while (1) {
1126 		struct throtl_grp *tg;
1127 		struct throtl_service_queue *sq;
1128 
1129 		if (!parent_sq->nr_pending)
1130 			break;
1131 
1132 		tg = throtl_rb_first(parent_sq);
1133 		if (!tg)
1134 			break;
1135 
1136 		if (time_before(jiffies, tg->disptime))
1137 			break;
1138 
1139 		nr_disp += throtl_dispatch_tg(tg);
1140 
1141 		sq = &tg->service_queue;
1142 		if (sq->nr_queued[READ] || sq->nr_queued[WRITE])
1143 			tg_update_disptime(tg);
1144 		else
1145 			throtl_dequeue_tg(tg);
1146 
1147 		if (nr_disp >= THROTL_QUANTUM)
1148 			break;
1149 	}
1150 
1151 	return nr_disp;
1152 }
1153 
1154 static bool throtl_can_upgrade(struct throtl_data *td,
1155 	struct throtl_grp *this_tg);
1156 /**
1157  * throtl_pending_timer_fn - timer function for service_queue->pending_timer
1158  * @t: the pending_timer member of the throtl_service_queue being serviced
1159  *
1160  * This timer is armed when a child throtl_grp with active bio's become
1161  * pending and queued on the service_queue's pending_tree and expires when
1162  * the first child throtl_grp should be dispatched.  This function
1163  * dispatches bio's from the children throtl_grps to the parent
1164  * service_queue.
1165  *
1166  * If the parent's parent is another throtl_grp, dispatching is propagated
1167  * by either arming its pending_timer or repeating dispatch directly.  If
1168  * the top-level service_tree is reached, throtl_data->dispatch_work is
1169  * kicked so that the ready bio's are issued.
1170  */
throtl_pending_timer_fn(struct timer_list * t)1171 static void throtl_pending_timer_fn(struct timer_list *t)
1172 {
1173 	struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
1174 	struct throtl_grp *tg = sq_to_tg(sq);
1175 	struct throtl_data *td = sq_to_td(sq);
1176 	struct throtl_service_queue *parent_sq;
1177 	struct request_queue *q;
1178 	bool dispatched;
1179 	int ret;
1180 
1181 	/* throtl_data may be gone, so figure out request queue by blkg */
1182 	if (tg)
1183 		q = tg->pd.blkg->q;
1184 	else
1185 		q = td->queue;
1186 
1187 	spin_lock_irq(&q->queue_lock);
1188 
1189 	if (!q->root_blkg)
1190 		goto out_unlock;
1191 
1192 	if (throtl_can_upgrade(td, NULL))
1193 		throtl_upgrade_state(td);
1194 
1195 again:
1196 	parent_sq = sq->parent_sq;
1197 	dispatched = false;
1198 
1199 	while (true) {
1200 		throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
1201 			   sq->nr_queued[READ] + sq->nr_queued[WRITE],
1202 			   sq->nr_queued[READ], sq->nr_queued[WRITE]);
1203 
1204 		ret = throtl_select_dispatch(sq);
1205 		if (ret) {
1206 			throtl_log(sq, "bios disp=%u", ret);
1207 			dispatched = true;
1208 		}
1209 
1210 		if (throtl_schedule_next_dispatch(sq, false))
1211 			break;
1212 
1213 		/* this dispatch windows is still open, relax and repeat */
1214 		spin_unlock_irq(&q->queue_lock);
1215 		cpu_relax();
1216 		spin_lock_irq(&q->queue_lock);
1217 	}
1218 
1219 	if (!dispatched)
1220 		goto out_unlock;
1221 
1222 	if (parent_sq) {
1223 		/* @parent_sq is another throl_grp, propagate dispatch */
1224 		if (tg->flags & THROTL_TG_WAS_EMPTY) {
1225 			tg_update_disptime(tg);
1226 			if (!throtl_schedule_next_dispatch(parent_sq, false)) {
1227 				/* window is already open, repeat dispatching */
1228 				sq = parent_sq;
1229 				tg = sq_to_tg(sq);
1230 				goto again;
1231 			}
1232 		}
1233 	} else {
1234 		/* reached the top-level, queue issuing */
1235 		queue_work(kthrotld_workqueue, &td->dispatch_work);
1236 	}
1237 out_unlock:
1238 	spin_unlock_irq(&q->queue_lock);
1239 }
1240 
1241 /**
1242  * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work
1243  * @work: work item being executed
1244  *
1245  * This function is queued for execution when bios reach the bio_lists[]
1246  * of throtl_data->service_queue.  Those bios are ready and issued by this
1247  * function.
1248  */
blk_throtl_dispatch_work_fn(struct work_struct * work)1249 static void blk_throtl_dispatch_work_fn(struct work_struct *work)
1250 {
1251 	struct throtl_data *td = container_of(work, struct throtl_data,
1252 					      dispatch_work);
1253 	struct throtl_service_queue *td_sq = &td->service_queue;
1254 	struct request_queue *q = td->queue;
1255 	struct bio_list bio_list_on_stack;
1256 	struct bio *bio;
1257 	struct blk_plug plug;
1258 	int rw;
1259 
1260 	bio_list_init(&bio_list_on_stack);
1261 
1262 	spin_lock_irq(&q->queue_lock);
1263 	for (rw = READ; rw <= WRITE; rw++)
1264 		while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL)))
1265 			bio_list_add(&bio_list_on_stack, bio);
1266 	spin_unlock_irq(&q->queue_lock);
1267 
1268 	if (!bio_list_empty(&bio_list_on_stack)) {
1269 		blk_start_plug(&plug);
1270 		while ((bio = bio_list_pop(&bio_list_on_stack)))
1271 			submit_bio_noacct_nocheck(bio);
1272 		blk_finish_plug(&plug);
1273 	}
1274 }
1275 
tg_prfill_conf_u64(struct seq_file * sf,struct blkg_policy_data * pd,int off)1276 static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
1277 			      int off)
1278 {
1279 	struct throtl_grp *tg = pd_to_tg(pd);
1280 	u64 v = *(u64 *)((void *)tg + off);
1281 
1282 	if (v == U64_MAX)
1283 		return 0;
1284 	return __blkg_prfill_u64(sf, pd, v);
1285 }
1286 
tg_prfill_conf_uint(struct seq_file * sf,struct blkg_policy_data * pd,int off)1287 static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
1288 			       int off)
1289 {
1290 	struct throtl_grp *tg = pd_to_tg(pd);
1291 	unsigned int v = *(unsigned int *)((void *)tg + off);
1292 
1293 	if (v == UINT_MAX)
1294 		return 0;
1295 	return __blkg_prfill_u64(sf, pd, v);
1296 }
1297 
tg_print_conf_u64(struct seq_file * sf,void * v)1298 static int tg_print_conf_u64(struct seq_file *sf, void *v)
1299 {
1300 	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
1301 			  &blkcg_policy_throtl, seq_cft(sf)->private, false);
1302 	return 0;
1303 }
1304 
tg_print_conf_uint(struct seq_file * sf,void * v)1305 static int tg_print_conf_uint(struct seq_file *sf, void *v)
1306 {
1307 	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
1308 			  &blkcg_policy_throtl, seq_cft(sf)->private, false);
1309 	return 0;
1310 }
1311 
tg_conf_updated(struct throtl_grp * tg,bool global)1312 static void tg_conf_updated(struct throtl_grp *tg, bool global)
1313 {
1314 	struct throtl_service_queue *sq = &tg->service_queue;
1315 	struct cgroup_subsys_state *pos_css;
1316 	struct blkcg_gq *blkg;
1317 
1318 	throtl_log(&tg->service_queue,
1319 		   "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
1320 		   tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
1321 		   tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
1322 
1323 	rcu_read_lock();
1324 	/*
1325 	 * Update has_rules[] flags for the updated tg's subtree.  A tg is
1326 	 * considered to have rules if either the tg itself or any of its
1327 	 * ancestors has rules.  This identifies groups without any
1328 	 * restrictions in the whole hierarchy and allows them to bypass
1329 	 * blk-throttle.
1330 	 */
1331 	blkg_for_each_descendant_pre(blkg, pos_css,
1332 			global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
1333 		struct throtl_grp *this_tg = blkg_to_tg(blkg);
1334 		struct throtl_grp *parent_tg;
1335 
1336 		tg_update_has_rules(this_tg);
1337 		/* ignore root/second level */
1338 		if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
1339 		    !blkg->parent->parent)
1340 			continue;
1341 		parent_tg = blkg_to_tg(blkg->parent);
1342 		/*
1343 		 * make sure all children has lower idle time threshold and
1344 		 * higher latency target
1345 		 */
1346 		this_tg->idletime_threshold = min(this_tg->idletime_threshold,
1347 				parent_tg->idletime_threshold);
1348 		this_tg->latency_target = max(this_tg->latency_target,
1349 				parent_tg->latency_target);
1350 	}
1351 	rcu_read_unlock();
1352 
1353 	/*
1354 	 * We're already holding queue_lock and know @tg is valid.  Let's
1355 	 * apply the new config directly.
1356 	 *
1357 	 * Restart the slices for both READ and WRITES. It might happen
1358 	 * that a group's limit are dropped suddenly and we don't want to
1359 	 * account recently dispatched IO with new low rate.
1360 	 */
1361 	throtl_start_new_slice(tg, READ, false);
1362 	throtl_start_new_slice(tg, WRITE, false);
1363 
1364 	if (tg->flags & THROTL_TG_PENDING) {
1365 		tg_update_disptime(tg);
1366 		throtl_schedule_next_dispatch(sq->parent_sq, true);
1367 	}
1368 }
1369 
tg_set_conf(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off,bool is_u64)1370 static ssize_t tg_set_conf(struct kernfs_open_file *of,
1371 			   char *buf, size_t nbytes, loff_t off, bool is_u64)
1372 {
1373 	struct blkcg *blkcg = css_to_blkcg(of_css(of));
1374 	struct blkg_conf_ctx ctx;
1375 	struct throtl_grp *tg;
1376 	int ret;
1377 	u64 v;
1378 
1379 	blkg_conf_init(&ctx, buf);
1380 
1381 	ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1382 	if (ret)
1383 		goto out_finish;
1384 
1385 	ret = -EINVAL;
1386 	if (sscanf(ctx.body, "%llu", &v) != 1)
1387 		goto out_finish;
1388 	if (!v)
1389 		v = U64_MAX;
1390 
1391 	tg = blkg_to_tg(ctx.blkg);
1392 	tg_update_carryover(tg);
1393 
1394 	if (is_u64)
1395 		*(u64 *)((void *)tg + of_cft(of)->private) = v;
1396 	else
1397 		*(unsigned int *)((void *)tg + of_cft(of)->private) = v;
1398 
1399 	tg_conf_updated(tg, false);
1400 	ret = 0;
1401 out_finish:
1402 	blkg_conf_exit(&ctx);
1403 	return ret ?: nbytes;
1404 }
1405 
tg_set_conf_u64(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)1406 static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
1407 			       char *buf, size_t nbytes, loff_t off)
1408 {
1409 	return tg_set_conf(of, buf, nbytes, off, true);
1410 }
1411 
tg_set_conf_uint(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)1412 static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
1413 				char *buf, size_t nbytes, loff_t off)
1414 {
1415 	return tg_set_conf(of, buf, nbytes, off, false);
1416 }
1417 
tg_print_rwstat(struct seq_file * sf,void * v)1418 static int tg_print_rwstat(struct seq_file *sf, void *v)
1419 {
1420 	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1421 			  blkg_prfill_rwstat, &blkcg_policy_throtl,
1422 			  seq_cft(sf)->private, true);
1423 	return 0;
1424 }
1425 
tg_prfill_rwstat_recursive(struct seq_file * sf,struct blkg_policy_data * pd,int off)1426 static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
1427 				      struct blkg_policy_data *pd, int off)
1428 {
1429 	struct blkg_rwstat_sample sum;
1430 
1431 	blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
1432 				  &sum);
1433 	return __blkg_prfill_rwstat(sf, pd, &sum);
1434 }
1435 
tg_print_rwstat_recursive(struct seq_file * sf,void * v)1436 static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
1437 {
1438 	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1439 			  tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
1440 			  seq_cft(sf)->private, true);
1441 	return 0;
1442 }
1443 
1444 static struct cftype throtl_legacy_files[] = {
1445 	{
1446 		.name = "throttle.read_bps_device",
1447 		.private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
1448 		.seq_show = tg_print_conf_u64,
1449 		.write = tg_set_conf_u64,
1450 	},
1451 	{
1452 		.name = "throttle.write_bps_device",
1453 		.private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
1454 		.seq_show = tg_print_conf_u64,
1455 		.write = tg_set_conf_u64,
1456 	},
1457 	{
1458 		.name = "throttle.read_iops_device",
1459 		.private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
1460 		.seq_show = tg_print_conf_uint,
1461 		.write = tg_set_conf_uint,
1462 	},
1463 	{
1464 		.name = "throttle.write_iops_device",
1465 		.private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
1466 		.seq_show = tg_print_conf_uint,
1467 		.write = tg_set_conf_uint,
1468 	},
1469 	{
1470 		.name = "throttle.io_service_bytes",
1471 		.private = offsetof(struct throtl_grp, stat_bytes),
1472 		.seq_show = tg_print_rwstat,
1473 	},
1474 	{
1475 		.name = "throttle.io_service_bytes_recursive",
1476 		.private = offsetof(struct throtl_grp, stat_bytes),
1477 		.seq_show = tg_print_rwstat_recursive,
1478 	},
1479 	{
1480 		.name = "throttle.io_serviced",
1481 		.private = offsetof(struct throtl_grp, stat_ios),
1482 		.seq_show = tg_print_rwstat,
1483 	},
1484 	{
1485 		.name = "throttle.io_serviced_recursive",
1486 		.private = offsetof(struct throtl_grp, stat_ios),
1487 		.seq_show = tg_print_rwstat_recursive,
1488 	},
1489 	{ }	/* terminate */
1490 };
1491 
tg_prfill_limit(struct seq_file * sf,struct blkg_policy_data * pd,int off)1492 static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
1493 			 int off)
1494 {
1495 	struct throtl_grp *tg = pd_to_tg(pd);
1496 	const char *dname = blkg_dev_name(pd->blkg);
1497 	char bufs[4][21] = { "max", "max", "max", "max" };
1498 	u64 bps_dft;
1499 	unsigned int iops_dft;
1500 	char idle_time[26] = "";
1501 	char latency_time[26] = "";
1502 
1503 	if (!dname)
1504 		return 0;
1505 
1506 	if (off == LIMIT_LOW) {
1507 		bps_dft = 0;
1508 		iops_dft = 0;
1509 	} else {
1510 		bps_dft = U64_MAX;
1511 		iops_dft = UINT_MAX;
1512 	}
1513 
1514 	if (tg->bps_conf[READ][off] == bps_dft &&
1515 	    tg->bps_conf[WRITE][off] == bps_dft &&
1516 	    tg->iops_conf[READ][off] == iops_dft &&
1517 	    tg->iops_conf[WRITE][off] == iops_dft &&
1518 	    (off != LIMIT_LOW ||
1519 	     (tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
1520 	      tg->latency_target_conf == DFL_LATENCY_TARGET)))
1521 		return 0;
1522 
1523 	if (tg->bps_conf[READ][off] != U64_MAX)
1524 		snprintf(bufs[0], sizeof(bufs[0]), "%llu",
1525 			tg->bps_conf[READ][off]);
1526 	if (tg->bps_conf[WRITE][off] != U64_MAX)
1527 		snprintf(bufs[1], sizeof(bufs[1]), "%llu",
1528 			tg->bps_conf[WRITE][off]);
1529 	if (tg->iops_conf[READ][off] != UINT_MAX)
1530 		snprintf(bufs[2], sizeof(bufs[2]), "%u",
1531 			tg->iops_conf[READ][off]);
1532 	if (tg->iops_conf[WRITE][off] != UINT_MAX)
1533 		snprintf(bufs[3], sizeof(bufs[3]), "%u",
1534 			tg->iops_conf[WRITE][off]);
1535 	if (off == LIMIT_LOW) {
1536 		if (tg->idletime_threshold_conf == ULONG_MAX)
1537 			strcpy(idle_time, " idle=max");
1538 		else
1539 			snprintf(idle_time, sizeof(idle_time), " idle=%lu",
1540 				tg->idletime_threshold_conf);
1541 
1542 		if (tg->latency_target_conf == ULONG_MAX)
1543 			strcpy(latency_time, " latency=max");
1544 		else
1545 			snprintf(latency_time, sizeof(latency_time),
1546 				" latency=%lu", tg->latency_target_conf);
1547 	}
1548 
1549 	seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
1550 		   dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
1551 		   latency_time);
1552 	return 0;
1553 }
1554 
tg_print_limit(struct seq_file * sf,void * v)1555 static int tg_print_limit(struct seq_file *sf, void *v)
1556 {
1557 	blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
1558 			  &blkcg_policy_throtl, seq_cft(sf)->private, false);
1559 	return 0;
1560 }
1561 
tg_set_limit(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)1562 static ssize_t tg_set_limit(struct kernfs_open_file *of,
1563 			  char *buf, size_t nbytes, loff_t off)
1564 {
1565 	struct blkcg *blkcg = css_to_blkcg(of_css(of));
1566 	struct blkg_conf_ctx ctx;
1567 	struct throtl_grp *tg;
1568 	u64 v[4];
1569 	unsigned long idle_time;
1570 	unsigned long latency_time;
1571 	int ret;
1572 	int index = of_cft(of)->private;
1573 
1574 	blkg_conf_init(&ctx, buf);
1575 
1576 	ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
1577 	if (ret)
1578 		goto out_finish;
1579 
1580 	tg = blkg_to_tg(ctx.blkg);
1581 	tg_update_carryover(tg);
1582 
1583 	v[0] = tg->bps_conf[READ][index];
1584 	v[1] = tg->bps_conf[WRITE][index];
1585 	v[2] = tg->iops_conf[READ][index];
1586 	v[3] = tg->iops_conf[WRITE][index];
1587 
1588 	idle_time = tg->idletime_threshold_conf;
1589 	latency_time = tg->latency_target_conf;
1590 	while (true) {
1591 		char tok[27];	/* wiops=18446744073709551616 */
1592 		char *p;
1593 		u64 val = U64_MAX;
1594 		int len;
1595 
1596 		if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
1597 			break;
1598 		if (tok[0] == '\0')
1599 			break;
1600 		ctx.body += len;
1601 
1602 		ret = -EINVAL;
1603 		p = tok;
1604 		strsep(&p, "=");
1605 		if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
1606 			goto out_finish;
1607 
1608 		ret = -ERANGE;
1609 		if (!val)
1610 			goto out_finish;
1611 
1612 		ret = -EINVAL;
1613 		if (!strcmp(tok, "rbps") && val > 1)
1614 			v[0] = val;
1615 		else if (!strcmp(tok, "wbps") && val > 1)
1616 			v[1] = val;
1617 		else if (!strcmp(tok, "riops") && val > 1)
1618 			v[2] = min_t(u64, val, UINT_MAX);
1619 		else if (!strcmp(tok, "wiops") && val > 1)
1620 			v[3] = min_t(u64, val, UINT_MAX);
1621 		else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
1622 			idle_time = val;
1623 		else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
1624 			latency_time = val;
1625 		else
1626 			goto out_finish;
1627 	}
1628 
1629 	tg->bps_conf[READ][index] = v[0];
1630 	tg->bps_conf[WRITE][index] = v[1];
1631 	tg->iops_conf[READ][index] = v[2];
1632 	tg->iops_conf[WRITE][index] = v[3];
1633 
1634 	if (index == LIMIT_MAX) {
1635 		tg->bps[READ][index] = v[0];
1636 		tg->bps[WRITE][index] = v[1];
1637 		tg->iops[READ][index] = v[2];
1638 		tg->iops[WRITE][index] = v[3];
1639 	}
1640 	tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
1641 		tg->bps_conf[READ][LIMIT_MAX]);
1642 	tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
1643 		tg->bps_conf[WRITE][LIMIT_MAX]);
1644 	tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
1645 		tg->iops_conf[READ][LIMIT_MAX]);
1646 	tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
1647 		tg->iops_conf[WRITE][LIMIT_MAX]);
1648 	tg->idletime_threshold_conf = idle_time;
1649 	tg->latency_target_conf = latency_time;
1650 
1651 	/* force user to configure all settings for low limit  */
1652 	if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
1653 	      tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
1654 	    tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
1655 	    tg->latency_target_conf == DFL_LATENCY_TARGET) {
1656 		tg->bps[READ][LIMIT_LOW] = 0;
1657 		tg->bps[WRITE][LIMIT_LOW] = 0;
1658 		tg->iops[READ][LIMIT_LOW] = 0;
1659 		tg->iops[WRITE][LIMIT_LOW] = 0;
1660 		tg->idletime_threshold = DFL_IDLE_THRESHOLD;
1661 		tg->latency_target = DFL_LATENCY_TARGET;
1662 	} else if (index == LIMIT_LOW) {
1663 		tg->idletime_threshold = tg->idletime_threshold_conf;
1664 		tg->latency_target = tg->latency_target_conf;
1665 	}
1666 
1667 	blk_throtl_update_limit_valid(tg->td);
1668 	if (tg->td->limit_valid[LIMIT_LOW]) {
1669 		if (index == LIMIT_LOW)
1670 			tg->td->limit_index = LIMIT_LOW;
1671 	} else
1672 		tg->td->limit_index = LIMIT_MAX;
1673 	tg_conf_updated(tg, index == LIMIT_LOW &&
1674 		tg->td->limit_valid[LIMIT_LOW]);
1675 	ret = 0;
1676 out_finish:
1677 	blkg_conf_exit(&ctx);
1678 	return ret ?: nbytes;
1679 }
1680 
1681 static struct cftype throtl_files[] = {
1682 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
1683 	{
1684 		.name = "low",
1685 		.flags = CFTYPE_NOT_ON_ROOT,
1686 		.seq_show = tg_print_limit,
1687 		.write = tg_set_limit,
1688 		.private = LIMIT_LOW,
1689 	},
1690 #endif
1691 	{
1692 		.name = "max",
1693 		.flags = CFTYPE_NOT_ON_ROOT,
1694 		.seq_show = tg_print_limit,
1695 		.write = tg_set_limit,
1696 		.private = LIMIT_MAX,
1697 	},
1698 	{ }	/* terminate */
1699 };
1700 
throtl_shutdown_wq(struct request_queue * q)1701 static void throtl_shutdown_wq(struct request_queue *q)
1702 {
1703 	struct throtl_data *td = q->td;
1704 
1705 	cancel_work_sync(&td->dispatch_work);
1706 }
1707 
1708 struct blkcg_policy blkcg_policy_throtl = {
1709 	.dfl_cftypes		= throtl_files,
1710 	.legacy_cftypes		= throtl_legacy_files,
1711 
1712 	.pd_alloc_fn		= throtl_pd_alloc,
1713 	.pd_init_fn		= throtl_pd_init,
1714 	.pd_online_fn		= throtl_pd_online,
1715 	.pd_offline_fn		= throtl_pd_offline,
1716 	.pd_free_fn		= throtl_pd_free,
1717 };
1718 
blk_throtl_cancel_bios(struct gendisk * disk)1719 void blk_throtl_cancel_bios(struct gendisk *disk)
1720 {
1721 	struct request_queue *q = disk->queue;
1722 	struct cgroup_subsys_state *pos_css;
1723 	struct blkcg_gq *blkg;
1724 
1725 	spin_lock_irq(&q->queue_lock);
1726 	/*
1727 	 * queue_lock is held, rcu lock is not needed here technically.
1728 	 * However, rcu lock is still held to emphasize that following
1729 	 * path need RCU protection and to prevent warning from lockdep.
1730 	 */
1731 	rcu_read_lock();
1732 	blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
1733 		struct throtl_grp *tg = blkg_to_tg(blkg);
1734 		struct throtl_service_queue *sq = &tg->service_queue;
1735 
1736 		/*
1737 		 * Set the flag to make sure throtl_pending_timer_fn() won't
1738 		 * stop until all throttled bios are dispatched.
1739 		 */
1740 		tg->flags |= THROTL_TG_CANCELING;
1741 
1742 		/*
1743 		 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup
1744 		 * will be inserted to service queue without THROTL_TG_PENDING
1745 		 * set in tg_update_disptime below. Then IO dispatched from
1746 		 * child in tg_dispatch_one_bio will trigger double insertion
1747 		 * and corrupt the tree.
1748 		 */
1749 		if (!(tg->flags & THROTL_TG_PENDING))
1750 			continue;
1751 
1752 		/*
1753 		 * Update disptime after setting the above flag to make sure
1754 		 * throtl_select_dispatch() won't exit without dispatching.
1755 		 */
1756 		tg_update_disptime(tg);
1757 
1758 		throtl_schedule_pending_timer(sq, jiffies + 1);
1759 	}
1760 	rcu_read_unlock();
1761 	spin_unlock_irq(&q->queue_lock);
1762 }
1763 
1764 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
__tg_last_low_overflow_time(struct throtl_grp * tg)1765 static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
1766 {
1767 	unsigned long rtime = jiffies, wtime = jiffies;
1768 
1769 	if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
1770 		rtime = tg->last_low_overflow_time[READ];
1771 	if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
1772 		wtime = tg->last_low_overflow_time[WRITE];
1773 	return min(rtime, wtime);
1774 }
1775 
tg_last_low_overflow_time(struct throtl_grp * tg)1776 static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
1777 {
1778 	struct throtl_service_queue *parent_sq;
1779 	struct throtl_grp *parent = tg;
1780 	unsigned long ret = __tg_last_low_overflow_time(tg);
1781 
1782 	while (true) {
1783 		parent_sq = parent->service_queue.parent_sq;
1784 		parent = sq_to_tg(parent_sq);
1785 		if (!parent)
1786 			break;
1787 
1788 		/*
1789 		 * The parent doesn't have low limit, it always reaches low
1790 		 * limit. Its overflow time is useless for children
1791 		 */
1792 		if (!parent->bps[READ][LIMIT_LOW] &&
1793 		    !parent->iops[READ][LIMIT_LOW] &&
1794 		    !parent->bps[WRITE][LIMIT_LOW] &&
1795 		    !parent->iops[WRITE][LIMIT_LOW])
1796 			continue;
1797 		if (time_after(__tg_last_low_overflow_time(parent), ret))
1798 			ret = __tg_last_low_overflow_time(parent);
1799 	}
1800 	return ret;
1801 }
1802 
throtl_tg_is_idle(struct throtl_grp * tg)1803 static bool throtl_tg_is_idle(struct throtl_grp *tg)
1804 {
1805 	/*
1806 	 * cgroup is idle if:
1807 	 * - single idle is too long, longer than a fixed value (in case user
1808 	 *   configure a too big threshold) or 4 times of idletime threshold
1809 	 * - average think time is more than threshold
1810 	 * - IO latency is largely below threshold
1811 	 */
1812 	unsigned long time;
1813 	bool ret;
1814 
1815 	time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
1816 	ret = tg->latency_target == DFL_LATENCY_TARGET ||
1817 	      tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
1818 	      (ktime_get_ns() >> 10) - tg->last_finish_time > time ||
1819 	      tg->avg_idletime > tg->idletime_threshold ||
1820 	      (tg->latency_target && tg->bio_cnt &&
1821 		tg->bad_bio_cnt * 5 < tg->bio_cnt);
1822 	throtl_log(&tg->service_queue,
1823 		"avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
1824 		tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
1825 		tg->bio_cnt, ret, tg->td->scale);
1826 	return ret;
1827 }
1828 
throtl_low_limit_reached(struct throtl_grp * tg,int rw)1829 static bool throtl_low_limit_reached(struct throtl_grp *tg, int rw)
1830 {
1831 	struct throtl_service_queue *sq = &tg->service_queue;
1832 	bool limit = tg->bps[rw][LIMIT_LOW] || tg->iops[rw][LIMIT_LOW];
1833 
1834 	/*
1835 	 * if low limit is zero, low limit is always reached.
1836 	 * if low limit is non-zero, we can check if there is any request
1837 	 * is queued to determine if low limit is reached as we throttle
1838 	 * request according to limit.
1839 	 */
1840 	return !limit || sq->nr_queued[rw];
1841 }
1842 
throtl_tg_can_upgrade(struct throtl_grp * tg)1843 static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
1844 {
1845 	/*
1846 	 * cgroup reaches low limit when low limit of READ and WRITE are
1847 	 * both reached, it's ok to upgrade to next limit if cgroup reaches
1848 	 * low limit
1849 	 */
1850 	if (throtl_low_limit_reached(tg, READ) &&
1851 	    throtl_low_limit_reached(tg, WRITE))
1852 		return true;
1853 
1854 	if (time_after_eq(jiffies,
1855 		tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
1856 	    throtl_tg_is_idle(tg))
1857 		return true;
1858 	return false;
1859 }
1860 
throtl_hierarchy_can_upgrade(struct throtl_grp * tg)1861 static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
1862 {
1863 	while (true) {
1864 		if (throtl_tg_can_upgrade(tg))
1865 			return true;
1866 		tg = sq_to_tg(tg->service_queue.parent_sq);
1867 		if (!tg || !tg_to_blkg(tg)->parent)
1868 			return false;
1869 	}
1870 	return false;
1871 }
1872 
throtl_can_upgrade(struct throtl_data * td,struct throtl_grp * this_tg)1873 static bool throtl_can_upgrade(struct throtl_data *td,
1874 	struct throtl_grp *this_tg)
1875 {
1876 	struct cgroup_subsys_state *pos_css;
1877 	struct blkcg_gq *blkg;
1878 
1879 	if (td->limit_index != LIMIT_LOW)
1880 		return false;
1881 
1882 	if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
1883 		return false;
1884 
1885 	rcu_read_lock();
1886 	blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1887 		struct throtl_grp *tg = blkg_to_tg(blkg);
1888 
1889 		if (tg == this_tg)
1890 			continue;
1891 		if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
1892 			continue;
1893 		if (!throtl_hierarchy_can_upgrade(tg)) {
1894 			rcu_read_unlock();
1895 			return false;
1896 		}
1897 	}
1898 	rcu_read_unlock();
1899 	return true;
1900 }
1901 
throtl_upgrade_check(struct throtl_grp * tg)1902 static void throtl_upgrade_check(struct throtl_grp *tg)
1903 {
1904 	unsigned long now = jiffies;
1905 
1906 	if (tg->td->limit_index != LIMIT_LOW)
1907 		return;
1908 
1909 	if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
1910 		return;
1911 
1912 	tg->last_check_time = now;
1913 
1914 	if (!time_after_eq(now,
1915 	     __tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
1916 		return;
1917 
1918 	if (throtl_can_upgrade(tg->td, NULL))
1919 		throtl_upgrade_state(tg->td);
1920 }
1921 
throtl_upgrade_state(struct throtl_data * td)1922 static void throtl_upgrade_state(struct throtl_data *td)
1923 {
1924 	struct cgroup_subsys_state *pos_css;
1925 	struct blkcg_gq *blkg;
1926 
1927 	throtl_log(&td->service_queue, "upgrade to max");
1928 	td->limit_index = LIMIT_MAX;
1929 	td->low_upgrade_time = jiffies;
1930 	td->scale = 0;
1931 	rcu_read_lock();
1932 	blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
1933 		struct throtl_grp *tg = blkg_to_tg(blkg);
1934 		struct throtl_service_queue *sq = &tg->service_queue;
1935 
1936 		tg->disptime = jiffies - 1;
1937 		throtl_select_dispatch(sq);
1938 		throtl_schedule_next_dispatch(sq, true);
1939 	}
1940 	rcu_read_unlock();
1941 	throtl_select_dispatch(&td->service_queue);
1942 	throtl_schedule_next_dispatch(&td->service_queue, true);
1943 	queue_work(kthrotld_workqueue, &td->dispatch_work);
1944 }
1945 
throtl_downgrade_state(struct throtl_data * td)1946 static void throtl_downgrade_state(struct throtl_data *td)
1947 {
1948 	td->scale /= 2;
1949 
1950 	throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
1951 	if (td->scale) {
1952 		td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
1953 		return;
1954 	}
1955 
1956 	td->limit_index = LIMIT_LOW;
1957 	td->low_downgrade_time = jiffies;
1958 }
1959 
throtl_tg_can_downgrade(struct throtl_grp * tg)1960 static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
1961 {
1962 	struct throtl_data *td = tg->td;
1963 	unsigned long now = jiffies;
1964 
1965 	/*
1966 	 * If cgroup is below low limit, consider downgrade and throttle other
1967 	 * cgroups
1968 	 */
1969 	if (time_after_eq(now, tg_last_low_overflow_time(tg) +
1970 					td->throtl_slice) &&
1971 	    (!throtl_tg_is_idle(tg) ||
1972 	     !list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
1973 		return true;
1974 	return false;
1975 }
1976 
throtl_hierarchy_can_downgrade(struct throtl_grp * tg)1977 static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
1978 {
1979 	struct throtl_data *td = tg->td;
1980 
1981 	if (time_before(jiffies, td->low_upgrade_time + td->throtl_slice))
1982 		return false;
1983 
1984 	while (true) {
1985 		if (!throtl_tg_can_downgrade(tg))
1986 			return false;
1987 		tg = sq_to_tg(tg->service_queue.parent_sq);
1988 		if (!tg || !tg_to_blkg(tg)->parent)
1989 			break;
1990 	}
1991 	return true;
1992 }
1993 
throtl_downgrade_check(struct throtl_grp * tg)1994 static void throtl_downgrade_check(struct throtl_grp *tg)
1995 {
1996 	uint64_t bps;
1997 	unsigned int iops;
1998 	unsigned long elapsed_time;
1999 	unsigned long now = jiffies;
2000 
2001 	if (tg->td->limit_index != LIMIT_MAX ||
2002 	    !tg->td->limit_valid[LIMIT_LOW])
2003 		return;
2004 	if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
2005 		return;
2006 	if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
2007 		return;
2008 
2009 	elapsed_time = now - tg->last_check_time;
2010 	tg->last_check_time = now;
2011 
2012 	if (time_before(now, tg_last_low_overflow_time(tg) +
2013 			tg->td->throtl_slice))
2014 		return;
2015 
2016 	if (tg->bps[READ][LIMIT_LOW]) {
2017 		bps = tg->last_bytes_disp[READ] * HZ;
2018 		do_div(bps, elapsed_time);
2019 		if (bps >= tg->bps[READ][LIMIT_LOW])
2020 			tg->last_low_overflow_time[READ] = now;
2021 	}
2022 
2023 	if (tg->bps[WRITE][LIMIT_LOW]) {
2024 		bps = tg->last_bytes_disp[WRITE] * HZ;
2025 		do_div(bps, elapsed_time);
2026 		if (bps >= tg->bps[WRITE][LIMIT_LOW])
2027 			tg->last_low_overflow_time[WRITE] = now;
2028 	}
2029 
2030 	if (tg->iops[READ][LIMIT_LOW]) {
2031 		iops = tg->last_io_disp[READ] * HZ / elapsed_time;
2032 		if (iops >= tg->iops[READ][LIMIT_LOW])
2033 			tg->last_low_overflow_time[READ] = now;
2034 	}
2035 
2036 	if (tg->iops[WRITE][LIMIT_LOW]) {
2037 		iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
2038 		if (iops >= tg->iops[WRITE][LIMIT_LOW])
2039 			tg->last_low_overflow_time[WRITE] = now;
2040 	}
2041 
2042 	/*
2043 	 * If cgroup is below low limit, consider downgrade and throttle other
2044 	 * cgroups
2045 	 */
2046 	if (throtl_hierarchy_can_downgrade(tg))
2047 		throtl_downgrade_state(tg->td);
2048 
2049 	tg->last_bytes_disp[READ] = 0;
2050 	tg->last_bytes_disp[WRITE] = 0;
2051 	tg->last_io_disp[READ] = 0;
2052 	tg->last_io_disp[WRITE] = 0;
2053 }
2054 
blk_throtl_update_idletime(struct throtl_grp * tg)2055 static void blk_throtl_update_idletime(struct throtl_grp *tg)
2056 {
2057 	unsigned long now;
2058 	unsigned long last_finish_time = tg->last_finish_time;
2059 
2060 	if (last_finish_time == 0)
2061 		return;
2062 
2063 	now = ktime_get_ns() >> 10;
2064 	if (now <= last_finish_time ||
2065 	    last_finish_time == tg->checked_last_finish_time)
2066 		return;
2067 
2068 	tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
2069 	tg->checked_last_finish_time = last_finish_time;
2070 }
2071 
throtl_update_latency_buckets(struct throtl_data * td)2072 static void throtl_update_latency_buckets(struct throtl_data *td)
2073 {
2074 	struct avg_latency_bucket avg_latency[2][LATENCY_BUCKET_SIZE];
2075 	int i, cpu, rw;
2076 	unsigned long last_latency[2] = { 0 };
2077 	unsigned long latency[2];
2078 
2079 	if (!blk_queue_nonrot(td->queue) || !td->limit_valid[LIMIT_LOW])
2080 		return;
2081 	if (time_before(jiffies, td->last_calculate_time + HZ))
2082 		return;
2083 	td->last_calculate_time = jiffies;
2084 
2085 	memset(avg_latency, 0, sizeof(avg_latency));
2086 	for (rw = READ; rw <= WRITE; rw++) {
2087 		for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2088 			struct latency_bucket *tmp = &td->tmp_buckets[rw][i];
2089 
2090 			for_each_possible_cpu(cpu) {
2091 				struct latency_bucket *bucket;
2092 
2093 				/* this isn't race free, but ok in practice */
2094 				bucket = per_cpu_ptr(td->latency_buckets[rw],
2095 					cpu);
2096 				tmp->total_latency += bucket[i].total_latency;
2097 				tmp->samples += bucket[i].samples;
2098 				bucket[i].total_latency = 0;
2099 				bucket[i].samples = 0;
2100 			}
2101 
2102 			if (tmp->samples >= 32) {
2103 				int samples = tmp->samples;
2104 
2105 				latency[rw] = tmp->total_latency;
2106 
2107 				tmp->total_latency = 0;
2108 				tmp->samples = 0;
2109 				latency[rw] /= samples;
2110 				if (latency[rw] == 0)
2111 					continue;
2112 				avg_latency[rw][i].latency = latency[rw];
2113 			}
2114 		}
2115 	}
2116 
2117 	for (rw = READ; rw <= WRITE; rw++) {
2118 		for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2119 			if (!avg_latency[rw][i].latency) {
2120 				if (td->avg_buckets[rw][i].latency < last_latency[rw])
2121 					td->avg_buckets[rw][i].latency =
2122 						last_latency[rw];
2123 				continue;
2124 			}
2125 
2126 			if (!td->avg_buckets[rw][i].valid)
2127 				latency[rw] = avg_latency[rw][i].latency;
2128 			else
2129 				latency[rw] = (td->avg_buckets[rw][i].latency * 7 +
2130 					avg_latency[rw][i].latency) >> 3;
2131 
2132 			td->avg_buckets[rw][i].latency = max(latency[rw],
2133 				last_latency[rw]);
2134 			td->avg_buckets[rw][i].valid = true;
2135 			last_latency[rw] = td->avg_buckets[rw][i].latency;
2136 		}
2137 	}
2138 
2139 	for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
2140 		throtl_log(&td->service_queue,
2141 			"Latency bucket %d: read latency=%ld, read valid=%d, "
2142 			"write latency=%ld, write valid=%d", i,
2143 			td->avg_buckets[READ][i].latency,
2144 			td->avg_buckets[READ][i].valid,
2145 			td->avg_buckets[WRITE][i].latency,
2146 			td->avg_buckets[WRITE][i].valid);
2147 }
2148 #else
throtl_update_latency_buckets(struct throtl_data * td)2149 static inline void throtl_update_latency_buckets(struct throtl_data *td)
2150 {
2151 }
2152 
blk_throtl_update_idletime(struct throtl_grp * tg)2153 static void blk_throtl_update_idletime(struct throtl_grp *tg)
2154 {
2155 }
2156 
throtl_downgrade_check(struct throtl_grp * tg)2157 static void throtl_downgrade_check(struct throtl_grp *tg)
2158 {
2159 }
2160 
throtl_upgrade_check(struct throtl_grp * tg)2161 static void throtl_upgrade_check(struct throtl_grp *tg)
2162 {
2163 }
2164 
throtl_can_upgrade(struct throtl_data * td,struct throtl_grp * this_tg)2165 static bool throtl_can_upgrade(struct throtl_data *td,
2166 	struct throtl_grp *this_tg)
2167 {
2168 	return false;
2169 }
2170 
throtl_upgrade_state(struct throtl_data * td)2171 static void throtl_upgrade_state(struct throtl_data *td)
2172 {
2173 }
2174 #endif
2175 
__blk_throtl_bio(struct bio * bio)2176 bool __blk_throtl_bio(struct bio *bio)
2177 {
2178 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
2179 	struct blkcg_gq *blkg = bio->bi_blkg;
2180 	struct throtl_qnode *qn = NULL;
2181 	struct throtl_grp *tg = blkg_to_tg(blkg);
2182 	struct throtl_service_queue *sq;
2183 	bool rw = bio_data_dir(bio);
2184 	bool throttled = false;
2185 	struct throtl_data *td = tg->td;
2186 
2187 	rcu_read_lock();
2188 
2189 	spin_lock_irq(&q->queue_lock);
2190 
2191 	throtl_update_latency_buckets(td);
2192 
2193 	blk_throtl_update_idletime(tg);
2194 
2195 	sq = &tg->service_queue;
2196 
2197 again:
2198 	while (true) {
2199 		if (tg->last_low_overflow_time[rw] == 0)
2200 			tg->last_low_overflow_time[rw] = jiffies;
2201 		throtl_downgrade_check(tg);
2202 		throtl_upgrade_check(tg);
2203 		/* throtl is FIFO - if bios are already queued, should queue */
2204 		if (sq->nr_queued[rw])
2205 			break;
2206 
2207 		/* if above limits, break to queue */
2208 		if (!tg_may_dispatch(tg, bio, NULL)) {
2209 			tg->last_low_overflow_time[rw] = jiffies;
2210 			if (throtl_can_upgrade(td, tg)) {
2211 				throtl_upgrade_state(td);
2212 				goto again;
2213 			}
2214 			break;
2215 		}
2216 
2217 		/* within limits, let's charge and dispatch directly */
2218 		throtl_charge_bio(tg, bio);
2219 
2220 		/*
2221 		 * We need to trim slice even when bios are not being queued
2222 		 * otherwise it might happen that a bio is not queued for
2223 		 * a long time and slice keeps on extending and trim is not
2224 		 * called for a long time. Now if limits are reduced suddenly
2225 		 * we take into account all the IO dispatched so far at new
2226 		 * low rate and * newly queued IO gets a really long dispatch
2227 		 * time.
2228 		 *
2229 		 * So keep on trimming slice even if bio is not queued.
2230 		 */
2231 		throtl_trim_slice(tg, rw);
2232 
2233 		/*
2234 		 * @bio passed through this layer without being throttled.
2235 		 * Climb up the ladder.  If we're already at the top, it
2236 		 * can be executed directly.
2237 		 */
2238 		qn = &tg->qnode_on_parent[rw];
2239 		sq = sq->parent_sq;
2240 		tg = sq_to_tg(sq);
2241 		if (!tg) {
2242 			bio_set_flag(bio, BIO_BPS_THROTTLED);
2243 			goto out_unlock;
2244 		}
2245 	}
2246 
2247 	/* out-of-limit, queue to @tg */
2248 	throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2249 		   rw == READ ? 'R' : 'W',
2250 		   tg->bytes_disp[rw], bio->bi_iter.bi_size,
2251 		   tg_bps_limit(tg, rw),
2252 		   tg->io_disp[rw], tg_iops_limit(tg, rw),
2253 		   sq->nr_queued[READ], sq->nr_queued[WRITE]);
2254 
2255 	tg->last_low_overflow_time[rw] = jiffies;
2256 
2257 	td->nr_queued[rw]++;
2258 	throtl_add_bio_tg(bio, qn, tg);
2259 	throttled = true;
2260 
2261 	/*
2262 	 * Update @tg's dispatch time and force schedule dispatch if @tg
2263 	 * was empty before @bio.  The forced scheduling isn't likely to
2264 	 * cause undue delay as @bio is likely to be dispatched directly if
2265 	 * its @tg's disptime is not in the future.
2266 	 */
2267 	if (tg->flags & THROTL_TG_WAS_EMPTY) {
2268 		tg_update_disptime(tg);
2269 		throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2270 	}
2271 
2272 out_unlock:
2273 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2274 	if (throttled || !td->track_bio_latency)
2275 		bio->bi_issue.value |= BIO_ISSUE_THROTL_SKIP_LATENCY;
2276 #endif
2277 	spin_unlock_irq(&q->queue_lock);
2278 
2279 	rcu_read_unlock();
2280 	return throttled;
2281 }
2282 
2283 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
throtl_track_latency(struct throtl_data * td,sector_t size,enum req_op op,unsigned long time)2284 static void throtl_track_latency(struct throtl_data *td, sector_t size,
2285 				 enum req_op op, unsigned long time)
2286 {
2287 	const bool rw = op_is_write(op);
2288 	struct latency_bucket *latency;
2289 	int index;
2290 
2291 	if (!td || td->limit_index != LIMIT_LOW ||
2292 	    !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
2293 	    !blk_queue_nonrot(td->queue))
2294 		return;
2295 
2296 	index = request_bucket_index(size);
2297 
2298 	latency = get_cpu_ptr(td->latency_buckets[rw]);
2299 	latency[index].total_latency += time;
2300 	latency[index].samples++;
2301 	put_cpu_ptr(td->latency_buckets[rw]);
2302 }
2303 
blk_throtl_stat_add(struct request * rq,u64 time_ns)2304 void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2305 {
2306 	struct request_queue *q = rq->q;
2307 	struct throtl_data *td = q->td;
2308 
2309 	throtl_track_latency(td, blk_rq_stats_sectors(rq), req_op(rq),
2310 			     time_ns >> 10);
2311 }
2312 
blk_throtl_bio_endio(struct bio * bio)2313 void blk_throtl_bio_endio(struct bio *bio)
2314 {
2315 	struct blkcg_gq *blkg;
2316 	struct throtl_grp *tg;
2317 	u64 finish_time_ns;
2318 	unsigned long finish_time;
2319 	unsigned long start_time;
2320 	unsigned long lat;
2321 	int rw = bio_data_dir(bio);
2322 
2323 	blkg = bio->bi_blkg;
2324 	if (!blkg)
2325 		return;
2326 	tg = blkg_to_tg(blkg);
2327 	if (!tg->td->limit_valid[LIMIT_LOW])
2328 		return;
2329 
2330 	finish_time_ns = ktime_get_ns();
2331 	tg->last_finish_time = finish_time_ns >> 10;
2332 
2333 	start_time = bio_issue_time(&bio->bi_issue) >> 10;
2334 	finish_time = __bio_issue_time(finish_time_ns) >> 10;
2335 	if (!start_time || finish_time <= start_time)
2336 		return;
2337 
2338 	lat = finish_time - start_time;
2339 	/* this is only for bio based driver */
2340 	if (!(bio->bi_issue.value & BIO_ISSUE_THROTL_SKIP_LATENCY))
2341 		throtl_track_latency(tg->td, bio_issue_size(&bio->bi_issue),
2342 				     bio_op(bio), lat);
2343 
2344 	if (tg->latency_target && lat >= tg->td->filtered_latency) {
2345 		int bucket;
2346 		unsigned int threshold;
2347 
2348 		bucket = request_bucket_index(bio_issue_size(&bio->bi_issue));
2349 		threshold = tg->td->avg_buckets[rw][bucket].latency +
2350 			tg->latency_target;
2351 		if (lat > threshold)
2352 			tg->bad_bio_cnt++;
2353 		/*
2354 		 * Not race free, could get wrong count, which means cgroups
2355 		 * will be throttled
2356 		 */
2357 		tg->bio_cnt++;
2358 	}
2359 
2360 	if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2361 		tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2362 		tg->bio_cnt /= 2;
2363 		tg->bad_bio_cnt /= 2;
2364 	}
2365 }
2366 #endif
2367 
blk_throtl_init(struct gendisk * disk)2368 int blk_throtl_init(struct gendisk *disk)
2369 {
2370 	struct request_queue *q = disk->queue;
2371 	struct throtl_data *td;
2372 	int ret;
2373 
2374 	td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2375 	if (!td)
2376 		return -ENOMEM;
2377 	td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
2378 		LATENCY_BUCKET_SIZE, __alignof__(u64));
2379 	if (!td->latency_buckets[READ]) {
2380 		kfree(td);
2381 		return -ENOMEM;
2382 	}
2383 	td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
2384 		LATENCY_BUCKET_SIZE, __alignof__(u64));
2385 	if (!td->latency_buckets[WRITE]) {
2386 		free_percpu(td->latency_buckets[READ]);
2387 		kfree(td);
2388 		return -ENOMEM;
2389 	}
2390 
2391 	INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2392 	throtl_service_queue_init(&td->service_queue);
2393 
2394 	q->td = td;
2395 	td->queue = q;
2396 
2397 	td->limit_valid[LIMIT_MAX] = true;
2398 	td->limit_index = LIMIT_MAX;
2399 	td->low_upgrade_time = jiffies;
2400 	td->low_downgrade_time = jiffies;
2401 
2402 	/* activate policy */
2403 	ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
2404 	if (ret) {
2405 		free_percpu(td->latency_buckets[READ]);
2406 		free_percpu(td->latency_buckets[WRITE]);
2407 		kfree(td);
2408 	}
2409 	return ret;
2410 }
2411 
blk_throtl_exit(struct gendisk * disk)2412 void blk_throtl_exit(struct gendisk *disk)
2413 {
2414 	struct request_queue *q = disk->queue;
2415 
2416 	BUG_ON(!q->td);
2417 	del_timer_sync(&q->td->service_queue.pending_timer);
2418 	throtl_shutdown_wq(q);
2419 	blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
2420 	free_percpu(q->td->latency_buckets[READ]);
2421 	free_percpu(q->td->latency_buckets[WRITE]);
2422 	kfree(q->td);
2423 }
2424 
blk_throtl_register(struct gendisk * disk)2425 void blk_throtl_register(struct gendisk *disk)
2426 {
2427 	struct request_queue *q = disk->queue;
2428 	struct throtl_data *td;
2429 	int i;
2430 
2431 	td = q->td;
2432 	BUG_ON(!td);
2433 
2434 	if (blk_queue_nonrot(q)) {
2435 		td->throtl_slice = DFL_THROTL_SLICE_SSD;
2436 		td->filtered_latency = LATENCY_FILTERED_SSD;
2437 	} else {
2438 		td->throtl_slice = DFL_THROTL_SLICE_HD;
2439 		td->filtered_latency = LATENCY_FILTERED_HD;
2440 		for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2441 			td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
2442 			td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
2443 		}
2444 	}
2445 #ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2446 	/* if no low limit, use previous default */
2447 	td->throtl_slice = DFL_THROTL_SLICE_HD;
2448 
2449 #else
2450 	td->track_bio_latency = !queue_is_mq(q);
2451 	if (!td->track_bio_latency)
2452 		blk_stat_enable_accounting(q);
2453 #endif
2454 }
2455 
2456 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
blk_throtl_sample_time_show(struct request_queue * q,char * page)2457 ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2458 {
2459 	if (!q->td)
2460 		return -EINVAL;
2461 	return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2462 }
2463 
blk_throtl_sample_time_store(struct request_queue * q,const char * page,size_t count)2464 ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2465 	const char *page, size_t count)
2466 {
2467 	unsigned long v;
2468 	unsigned long t;
2469 
2470 	if (!q->td)
2471 		return -EINVAL;
2472 	if (kstrtoul(page, 10, &v))
2473 		return -EINVAL;
2474 	t = msecs_to_jiffies(v);
2475 	if (t == 0 || t > MAX_THROTL_SLICE)
2476 		return -EINVAL;
2477 	q->td->throtl_slice = t;
2478 	return count;
2479 }
2480 #endif
2481 
throtl_init(void)2482 static int __init throtl_init(void)
2483 {
2484 	kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2485 	if (!kthrotld_workqueue)
2486 		panic("Failed to create kthrotld\n");
2487 
2488 	return blkcg_policy_register(&blkcg_policy_throtl);
2489 }
2490 
2491 module_init(throtl_init);
2492