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