block/blk-throttle.c

   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);
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         if (unlikely(blk_queue_bypass(q)))
2139                 goto out_unlock;
2140
2141         blk_throtl_update_idletime(tg);
2142
2143         sq = &tg->service_queue;
2144
2145 again:
2146         while (true) {
2147                 if (tg->last_low_overflow_time[rw] == 0)
2148                         tg->last_low_overflow_time[rw] = jiffies;
2149                 throtl_downgrade_check(tg);
2150                 throtl_upgrade_check(tg);
2151                 /* throtl is FIFO - if bios are already queued, should queue */
2152                 if (sq->nr_queued[rw])
2153                         break;
2154
2155                 /* if above limits, break to queue */
2156                 if (!tg_may_dispatch(tg, bio, NULL)) {
2157                         tg->last_low_overflow_time[rw] = jiffies;
2158                         if (throtl_can_upgrade(td, tg)) {
2159                                 throtl_upgrade_state(td);
2160                                 goto again;
2161                         }
2162                         break;
2163                 }
2164
2165                 /* within limits, let's charge and dispatch directly */
2166                 throtl_charge_bio(tg, bio);
2167
2168                 /*
2169                  * We need to trim slice even when bios are not being queued
2170                  * otherwise it might happen that a bio is not queued for
2171                  * a long time and slice keeps on extending and trim is not
2172                  * called for a long time. Now if limits are reduced suddenly
2173                  * we take into account all the IO dispatched so far at new
2174                  * low rate and * newly queued IO gets a really long dispatch
2175                  * time.
2176                  *
2177                  * So keep on trimming slice even if bio is not queued.
2178                  */
2179                 throtl_trim_slice(tg, rw);
2180
2181                 /*
2182                  * @bio passed through this layer without being throttled.
2183                  * Climb up the ladder.  If we''re already at the top, it
2184                  * can be executed directly.
2185                  */
2186                 qn = &tg->qnode_on_parent[rw];
2187                 sq = sq->parent_sq;
2188                 tg = sq_to_tg(sq);
2189                 if (!tg)
2190                         goto out_unlock;
2191         }
2192
2193         /* out-of-limit, queue to @tg */
2194         throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
2195                    rw == READ ? 'R' : 'W',
2196                    tg->bytes_disp[rw], bio->bi_iter.bi_size,
2197                    tg_bps_limit(tg, rw),
2198                    tg->io_disp[rw], tg_iops_limit(tg, rw),
2199                    sq->nr_queued[READ], sq->nr_queued[WRITE]);
2200
2201         tg->last_low_overflow_time[rw] = jiffies;
2202
2203         td->nr_queued[rw]++;
2204         throtl_add_bio_tg(bio, qn, tg);
2205         throttled = true;
2206
2207         /*
2208          * Update @tg's dispatch time and force schedule dispatch if @tg
2209          * was empty before @bio.  The forced scheduling isn't likely to
2210          * cause undue delay as @bio is likely to be dispatched directly if
2211          * its @tg's disptime is not in the future.
2212          */
2213         if (tg->flags & THROTL_TG_WAS_EMPTY) {
2214                 tg_update_disptime(tg);
2215                 throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true);
2216         }
2217
2218 out_unlock:
2219         spin_unlock_irq(q->queue_lock);
2220 out:
2221         bio_set_flag(bio, BIO_THROTTLED);
2222
2223 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2224         if (throttled || !td->track_bio_latency)
2225                 bio->bi_issue.value |= BIO_ISSUE_THROTL_SKIP_LATENCY;
2226 #endif
2227         return throttled;
2228 }
2229
2230 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2231 static void throtl_track_latency(struct throtl_data *td, sector_t size,
2232         int op, unsigned long time)
2233 {
2234         struct latency_bucket *latency;
2235         int index;
2236
2237         if (!td || td->limit_index != LIMIT_LOW ||
2238             !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
2239             !blk_queue_nonrot(td->queue))
2240                 return;
2241
2242         index = request_bucket_index(size);
2243
2244         latency = get_cpu_ptr(td->latency_buckets[op]);
2245         latency[index].total_latency += time;
2246         latency[index].samples++;
2247         put_cpu_ptr(td->latency_buckets[op]);
2248 }
2249
2250 void blk_throtl_stat_add(struct request *rq, u64 time_ns)
2251 {
2252         struct request_queue *q = rq->q;
2253         struct throtl_data *td = q->td;
2254
2255         throtl_track_latency(td, rq->throtl_size, req_op(rq), time_ns >> 10);
2256 }
2257
2258 void blk_throtl_bio_endio(struct bio *bio)
2259 {
2260         struct blkcg_gq *blkg;
2261         struct throtl_grp *tg;
2262         u64 finish_time_ns;
2263         unsigned long finish_time;
2264         unsigned long start_time;
2265         unsigned long lat;
2266         int rw = bio_data_dir(bio);
2267
2268         blkg = bio->bi_blkg;
2269         if (!blkg)
2270                 return;
2271         tg = blkg_to_tg(blkg);
2272
2273         finish_time_ns = ktime_get_ns();
2274         tg->last_finish_time = finish_time_ns >> 10;
2275
2276         start_time = bio_issue_time(&bio->bi_issue) >> 10;
2277         finish_time = __bio_issue_time(finish_time_ns) >> 10;
2278         if (!start_time || finish_time <= start_time)
2279                 return;
2280
2281         lat = finish_time - start_time;
2282         /* this is only for bio based driver */
2283         if (!(bio->bi_issue.value & BIO_ISSUE_THROTL_SKIP_LATENCY))
2284                 throtl_track_latency(tg->td, bio_issue_size(&bio->bi_issue),
2285                                      bio_op(bio), lat);
2286
2287         if (tg->latency_target && lat >= tg->td->filtered_latency) {
2288                 int bucket;
2289                 unsigned int threshold;
2290
2291                 bucket = request_bucket_index(bio_issue_size(&bio->bi_issue));
2292                 threshold = tg->td->avg_buckets[rw][bucket].latency +
2293                         tg->latency_target;
2294                 if (lat > threshold)
2295                         tg->bad_bio_cnt++;
2296                 /*
2297                  * Not race free, could get wrong count, which means cgroups
2298                  * will be throttled
2299                  */
2300                 tg->bio_cnt++;
2301         }
2302
2303         if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
2304                 tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
2305                 tg->bio_cnt /= 2;
2306                 tg->bad_bio_cnt /= 2;
2307         }
2308 }
2309 #endif
2310
2311 /*
2312  * Dispatch all bios from all children tg's queued on @parent_sq.  On
2313  * return, @parent_sq is guaranteed to not have any active children tg's
2314  * and all bios from previously active tg's are on @parent_sq->bio_lists[].
2315  */
2316 static void tg_drain_bios(struct throtl_service_queue *parent_sq)
2317 {
2318         struct throtl_grp *tg;
2319
2320         while ((tg = throtl_rb_first(parent_sq))) {
2321                 struct throtl_service_queue *sq = &tg->service_queue;
2322                 struct bio *bio;
2323
2324                 throtl_dequeue_tg(tg);
2325
2326                 while ((bio = throtl_peek_queued(&sq->queued[READ])))
2327                         tg_dispatch_one_bio(tg, bio_data_dir(bio));
2328                 while ((bio = throtl_peek_queued(&sq->queued[WRITE])))
2329                         tg_dispatch_one_bio(tg, bio_data_dir(bio));
2330         }
2331 }
2332
2333 /**
2334  * blk_throtl_drain - drain throttled bios
2335  * @q: request_queue to drain throttled bios for
2336  *
2337  * Dispatch all currently throttled bios on @q through ->make_request_fn().
2338  */
2339 void blk_throtl_drain(struct request_queue *q)
2340         __releases(q->queue_lock) __acquires(q->queue_lock)
2341 {
2342         struct throtl_data *td = q->td;
2343         struct blkcg_gq *blkg;
2344         struct cgroup_subsys_state *pos_css;
2345         struct bio *bio;
2346         int rw;
2347
2348         queue_lockdep_assert_held(q);
2349         rcu_read_lock();
2350
2351         /*
2352          * Drain each tg while doing post-order walk on the blkg tree, so
2353          * that all bios are propagated to td->service_queue.  It'd be
2354          * better to walk service_queue tree directly but blkg walk is
2355          * easier.
2356          */
2357         blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
2358                 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
2359
2360         /* finally, transfer bios from top-level tg's into the td */
2361         tg_drain_bios(&td->service_queue);
2362
2363         rcu_read_unlock();
2364         spin_unlock_irq(q->queue_lock);
2365
2366         /* all bios now should be in td->service_queue, issue them */
2367         for (rw = READ; rw <= WRITE; rw++)
2368                 while ((bio = throtl_pop_queued(&td->service_queue.queued[rw],
2369                                                 NULL)))
2370                         generic_make_request(bio);
2371
2372         spin_lock_irq(q->queue_lock);
2373 }
2374
2375 int blk_throtl_init(struct request_queue *q)
2376 {
2377         struct throtl_data *td;
2378         int ret;
2379
2380         td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
2381         if (!td)
2382                 return -ENOMEM;
2383         td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
2384                 LATENCY_BUCKET_SIZE, __alignof__(u64));
2385         if (!td->latency_buckets[READ]) {
2386                 kfree(td);
2387                 return -ENOMEM;
2388         }
2389         td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
2390                 LATENCY_BUCKET_SIZE, __alignof__(u64));
2391         if (!td->latency_buckets[WRITE]) {
2392                 free_percpu(td->latency_buckets[READ]);
2393                 kfree(td);
2394                 return -ENOMEM;
2395         }
2396
2397         INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
2398         throtl_service_queue_init(&td->service_queue);
2399
2400         q->td = td;
2401         td->queue = q;
2402
2403         td->limit_valid[LIMIT_MAX] = true;
2404         td->limit_index = LIMIT_MAX;
2405         td->low_upgrade_time = jiffies;
2406         td->low_downgrade_time = jiffies;
2407
2408         /* activate policy */
2409         ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
2410         if (ret) {
2411                 free_percpu(td->latency_buckets[READ]);
2412                 free_percpu(td->latency_buckets[WRITE]);
2413                 kfree(td);
2414         }
2415         return ret;
2416 }
2417
2418 void blk_throtl_exit(struct request_queue *q)
2419 {
2420         BUG_ON(!q->td);
2421         throtl_shutdown_wq(q);
2422         blkcg_deactivate_policy(q, &blkcg_policy_throtl);
2423         free_percpu(q->td->latency_buckets[READ]);
2424         free_percpu(q->td->latency_buckets[WRITE]);
2425         kfree(q->td);
2426 }
2427
2428 void blk_throtl_register_queue(struct request_queue *q)
2429 {
2430         struct throtl_data *td;
2431         int i;
2432
2433         td = q->td;
2434         BUG_ON(!td);
2435
2436         if (blk_queue_nonrot(q)) {
2437                 td->throtl_slice = DFL_THROTL_SLICE_SSD;
2438                 td->filtered_latency = LATENCY_FILTERED_SSD;
2439         } else {
2440                 td->throtl_slice = DFL_THROTL_SLICE_HD;
2441                 td->filtered_latency = LATENCY_FILTERED_HD;
2442                 for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
2443                         td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
2444                         td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
2445                 }
2446         }
2447 #ifndef CONFIG_BLK_DEV_THROTTLING_LOW
2448         /* if no low limit, use previous default */
2449         td->throtl_slice = DFL_THROTL_SLICE_HD;
2450 #endif
2451
2452         td->track_bio_latency = !queue_is_rq_based(q);
2453         if (!td->track_bio_latency)
2454                 blk_stat_enable_accounting(q);
2455 }
2456
2457 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
2458 ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
2459 {
2460         if (!q->td)
2461                 return -EINVAL;
2462         return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
2463 }
2464
2465 ssize_t blk_throtl_sample_time_store(struct request_queue *q,
2466         const char *page, size_t count)
2467 {
2468         unsigned long v;
2469         unsigned long t;
2470
2471         if (!q->td)
2472                 return -EINVAL;
2473         if (kstrtoul(page, 10, &v))
2474                 return -EINVAL;
2475         t = msecs_to_jiffies(v);
2476         if (t == 0 || t > MAX_THROTL_SLICE)
2477                 return -EINVAL;
2478         q->td->throtl_slice = t;
2479         return count;
2480 }
2481 #endif
2482
2483 static int __init throtl_init(void)
2484 {
2485         kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
2486         if (!kthrotld_workqueue)
2487                 panic("Failed to create kthrotld\n");
2488
2489         return blkcg_policy_register(&blkcg_policy_throtl);
2490 }
2491
2492 module_init(throtl_init);