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