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TOMOYO Linux Cross Reference
Linux/block/blk-throttle.c

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

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