block/blk-throttle.c

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