linux/block/blk-throttle.c
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   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 "blk-cgroup.h"
  13#include "blk.h"
  14
  15/* Max dispatch from a group in 1 round */
  16static int throtl_grp_quantum = 8;
  17
  18/* Total max dispatch from all groups in one round */
  19static int throtl_quantum = 32;
  20
  21/* Throttling is performed over 100ms slice and after that slice is renewed */
  22static unsigned long throtl_slice = HZ/10;      /* 100 ms */
  23
  24static struct blkcg_policy blkcg_policy_throtl;
  25
  26/* A workqueue to queue throttle related work */
  27static struct workqueue_struct *kthrotld_workqueue;
  28static void throtl_schedule_delayed_work(struct throtl_data *td,
  29                                unsigned long delay);
  30
  31struct throtl_rb_root {
  32        struct rb_root rb;
  33        struct rb_node *left;
  34        unsigned int count;
  35        unsigned long min_disptime;
  36};
  37
  38#define THROTL_RB_ROOT  (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
  39                        .count = 0, .min_disptime = 0}
  40
  41#define rb_entry_tg(node)       rb_entry((node), struct throtl_grp, rb_node)
  42
  43/* Per-cpu group stats */
  44struct tg_stats_cpu {
  45        /* total bytes transferred */
  46        struct blkg_rwstat              service_bytes;
  47        /* total IOs serviced, post merge */
  48        struct blkg_rwstat              serviced;
  49};
  50
  51struct throtl_grp {
  52        /* must be the first member */
  53        struct blkg_policy_data pd;
  54
  55        /* active throtl group service_tree member */
  56        struct rb_node rb_node;
  57
  58        /*
  59         * Dispatch time in jiffies. This is the estimated time when group
  60         * will unthrottle and is ready to dispatch more bio. It is used as
  61         * key to sort active groups in service tree.
  62         */
  63        unsigned long disptime;
  64
  65        unsigned int flags;
  66
  67        /* Two lists for READ and WRITE */
  68        struct bio_list bio_lists[2];
  69
  70        /* Number of queued bios on READ and WRITE lists */
  71        unsigned int nr_queued[2];
  72
  73        /* bytes per second rate limits */
  74        uint64_t bps[2];
  75
  76        /* IOPS limits */
  77        unsigned int iops[2];
  78
  79        /* Number of bytes disptached in current slice */
  80        uint64_t bytes_disp[2];
  81        /* Number of bio's dispatched in current slice */
  82        unsigned int io_disp[2];
  83
  84        /* When did we start a new slice */
  85        unsigned long slice_start[2];
  86        unsigned long slice_end[2];
  87
  88        /* Some throttle limits got updated for the group */
  89        int limits_changed;
  90
  91        /* Per cpu stats pointer */
  92        struct tg_stats_cpu __percpu *stats_cpu;
  93
  94        /* List of tgs waiting for per cpu stats memory to be allocated */
  95        struct list_head stats_alloc_node;
  96};
  97
  98struct throtl_data
  99{
 100        /* service tree for active throtl groups */
 101        struct throtl_rb_root tg_service_tree;
 102
 103        struct request_queue *queue;
 104
 105        /* Total Number of queued bios on READ and WRITE lists */
 106        unsigned int nr_queued[2];
 107
 108        /*
 109         * number of total undestroyed groups
 110         */
 111        unsigned int nr_undestroyed_grps;
 112
 113        /* Work for dispatching throttled bios */
 114        struct delayed_work throtl_work;
 115
 116        int limits_changed;
 117};
 118
 119/* list and work item to allocate percpu group stats */
 120static DEFINE_SPINLOCK(tg_stats_alloc_lock);
 121static LIST_HEAD(tg_stats_alloc_list);
 122
 123static void tg_stats_alloc_fn(struct work_struct *);
 124static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
 125
 126static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
 127{
 128        return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
 129}
 130
 131static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
 132{
 133        return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
 134}
 135
 136static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
 137{
 138        return pd_to_blkg(&tg->pd);
 139}
 140
 141static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
 142{
 143        return blkg_to_tg(td->queue->root_blkg);
 144}
 145
 146enum tg_state_flags {
 147        THROTL_TG_FLAG_on_rr = 0,       /* on round-robin busy list */
 148};
 149
 150#define THROTL_TG_FNS(name)                                             \
 151static inline void throtl_mark_tg_##name(struct throtl_grp *tg)         \
 152{                                                                       \
 153        (tg)->flags |= (1 << THROTL_TG_FLAG_##name);                    \
 154}                                                                       \
 155static inline void throtl_clear_tg_##name(struct throtl_grp *tg)        \
 156{                                                                       \
 157        (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name);                   \
 158}                                                                       \
 159static inline int throtl_tg_##name(const struct throtl_grp *tg)         \
 160{                                                                       \
 161        return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0;       \
 162}
 163
 164THROTL_TG_FNS(on_rr);
 165
 166#define throtl_log_tg(td, tg, fmt, args...)     do {                    \
 167        char __pbuf[128];                                               \
 168                                                                        \
 169        blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf));              \
 170        blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \
 171} while (0)
 172
 173#define throtl_log(td, fmt, args...)    \
 174        blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
 175
 176static inline unsigned int total_nr_queued(struct throtl_data *td)
 177{
 178        return td->nr_queued[0] + td->nr_queued[1];
 179}
 180
 181/*
 182 * Worker for allocating per cpu stat for tgs. This is scheduled on the
 183 * system_wq once there are some groups on the alloc_list waiting for
 184 * allocation.
 185 */
 186static void tg_stats_alloc_fn(struct work_struct *work)
 187{
 188        static struct tg_stats_cpu *stats_cpu;  /* this fn is non-reentrant */
 189        struct delayed_work *dwork = to_delayed_work(work);
 190        bool empty = false;
 191
 192alloc_stats:
 193        if (!stats_cpu) {
 194                stats_cpu = alloc_percpu(struct tg_stats_cpu);
 195                if (!stats_cpu) {
 196                        /* allocation failed, try again after some time */
 197                        schedule_delayed_work(dwork, msecs_to_jiffies(10));
 198                        return;
 199                }
 200        }
 201
 202        spin_lock_irq(&tg_stats_alloc_lock);
 203
 204        if (!list_empty(&tg_stats_alloc_list)) {
 205                struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
 206                                                         struct throtl_grp,
 207                                                         stats_alloc_node);
 208                swap(tg->stats_cpu, stats_cpu);
 209                list_del_init(&tg->stats_alloc_node);
 210        }
 211
 212        empty = list_empty(&tg_stats_alloc_list);
 213        spin_unlock_irq(&tg_stats_alloc_lock);
 214        if (!empty)
 215                goto alloc_stats;
 216}
 217
 218static void throtl_pd_init(struct blkcg_gq *blkg)
 219{
 220        struct throtl_grp *tg = blkg_to_tg(blkg);
 221        unsigned long flags;
 222
 223        RB_CLEAR_NODE(&tg->rb_node);
 224        bio_list_init(&tg->bio_lists[0]);
 225        bio_list_init(&tg->bio_lists[1]);
 226        tg->limits_changed = false;
 227
 228        tg->bps[READ] = -1;
 229        tg->bps[WRITE] = -1;
 230        tg->iops[READ] = -1;
 231        tg->iops[WRITE] = -1;
 232
 233        /*
 234         * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
 235         * but percpu allocator can't be called from IO path.  Queue tg on
 236         * tg_stats_alloc_list and allocate from work item.
 237         */
 238        spin_lock_irqsave(&tg_stats_alloc_lock, flags);
 239        list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
 240        schedule_delayed_work(&tg_stats_alloc_work, 0);
 241        spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
 242}
 243
 244static void throtl_pd_exit(struct blkcg_gq *blkg)
 245{
 246        struct throtl_grp *tg = blkg_to_tg(blkg);
 247        unsigned long flags;
 248
 249        spin_lock_irqsave(&tg_stats_alloc_lock, flags);
 250        list_del_init(&tg->stats_alloc_node);
 251        spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
 252
 253        free_percpu(tg->stats_cpu);
 254}
 255
 256static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
 257{
 258        struct throtl_grp *tg = blkg_to_tg(blkg);
 259        int cpu;
 260
 261        if (tg->stats_cpu == NULL)
 262                return;
 263
 264        for_each_possible_cpu(cpu) {
 265                struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
 266
 267                blkg_rwstat_reset(&sc->service_bytes);
 268                blkg_rwstat_reset(&sc->serviced);
 269        }
 270}
 271
 272static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
 273                                           struct blkcg *blkcg)
 274{
 275        /*
 276         * This is the common case when there are no blkcgs.  Avoid lookup
 277         * in this case
 278         */
 279        if (blkcg == &blkcg_root)
 280                return td_root_tg(td);
 281
 282        return blkg_to_tg(blkg_lookup(blkcg, td->queue));
 283}
 284
 285static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
 286                                                  struct blkcg *blkcg)
 287{
 288        struct request_queue *q = td->queue;
 289        struct throtl_grp *tg = NULL;
 290
 291        /*
 292         * This is the common case when there are no blkcgs.  Avoid lookup
 293         * in this case
 294         */
 295        if (blkcg == &blkcg_root) {
 296                tg = td_root_tg(td);
 297        } else {
 298                struct blkcg_gq *blkg;
 299
 300                blkg = blkg_lookup_create(blkcg, q);
 301
 302                /* if %NULL and @q is alive, fall back to root_tg */
 303                if (!IS_ERR(blkg))
 304                        tg = blkg_to_tg(blkg);
 305                else if (!blk_queue_dead(q))
 306                        tg = td_root_tg(td);
 307        }
 308
 309        return tg;
 310}
 311
 312static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
 313{
 314        /* Service tree is empty */
 315        if (!root->count)
 316                return NULL;
 317
 318        if (!root->left)
 319                root->left = rb_first(&root->rb);
 320
 321        if (root->left)
 322                return rb_entry_tg(root->left);
 323
 324        return NULL;
 325}
 326
 327static void rb_erase_init(struct rb_node *n, struct rb_root *root)
 328{
 329        rb_erase(n, root);
 330        RB_CLEAR_NODE(n);
 331}
 332
 333static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
 334{
 335        if (root->left == n)
 336                root->left = NULL;
 337        rb_erase_init(n, &root->rb);
 338        --root->count;
 339}
 340
 341static void update_min_dispatch_time(struct throtl_rb_root *st)
 342{
 343        struct throtl_grp *tg;
 344
 345        tg = throtl_rb_first(st);
 346        if (!tg)
 347                return;
 348
 349        st->min_disptime = tg->disptime;
 350}
 351
 352static void
 353tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
 354{
 355        struct rb_node **node = &st->rb.rb_node;
 356        struct rb_node *parent = NULL;
 357        struct throtl_grp *__tg;
 358        unsigned long key = tg->disptime;
 359        int left = 1;
 360
 361        while (*node != NULL) {
 362                parent = *node;
 363                __tg = rb_entry_tg(parent);
 364
 365                if (time_before(key, __tg->disptime))
 366                        node = &parent->rb_left;
 367                else {
 368                        node = &parent->rb_right;
 369                        left = 0;
 370                }
 371        }
 372
 373        if (left)
 374                st->left = &tg->rb_node;
 375
 376        rb_link_node(&tg->rb_node, parent, node);
 377        rb_insert_color(&tg->rb_node, &st->rb);
 378}
 379
 380static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
 381{
 382        struct throtl_rb_root *st = &td->tg_service_tree;
 383
 384        tg_service_tree_add(st, tg);
 385        throtl_mark_tg_on_rr(tg);
 386        st->count++;
 387}
 388
 389static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
 390{
 391        if (!throtl_tg_on_rr(tg))
 392                __throtl_enqueue_tg(td, tg);
 393}
 394
 395static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
 396{
 397        throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
 398        throtl_clear_tg_on_rr(tg);
 399}
 400
 401static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
 402{
 403        if (throtl_tg_on_rr(tg))
 404                __throtl_dequeue_tg(td, tg);
 405}
 406
 407static void throtl_schedule_next_dispatch(struct throtl_data *td)
 408{
 409        struct throtl_rb_root *st = &td->tg_service_tree;
 410
 411        /*
 412         * If there are more bios pending, schedule more work.
 413         */
 414        if (!total_nr_queued(td))
 415                return;
 416
 417        BUG_ON(!st->count);
 418
 419        update_min_dispatch_time(st);
 420
 421        if (time_before_eq(st->min_disptime, jiffies))
 422                throtl_schedule_delayed_work(td, 0);
 423        else
 424                throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
 425}
 426
 427static inline void
 428throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 429{
 430        tg->bytes_disp[rw] = 0;
 431        tg->io_disp[rw] = 0;
 432        tg->slice_start[rw] = jiffies;
 433        tg->slice_end[rw] = jiffies + throtl_slice;
 434        throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
 435                        rw == READ ? 'R' : 'W', tg->slice_start[rw],
 436                        tg->slice_end[rw], jiffies);
 437}
 438
 439static inline void throtl_set_slice_end(struct throtl_data *td,
 440                struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
 441{
 442        tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
 443}
 444
 445static inline void throtl_extend_slice(struct throtl_data *td,
 446                struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
 447{
 448        tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
 449        throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
 450                        rw == READ ? 'R' : 'W', tg->slice_start[rw],
 451                        tg->slice_end[rw], jiffies);
 452}
 453
 454/* Determine if previously allocated or extended slice is complete or not */
 455static bool
 456throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 457{
 458        if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
 459                return 0;
 460
 461        return 1;
 462}
 463
 464/* Trim the used slices and adjust slice start accordingly */
 465static inline void
 466throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
 467{
 468        unsigned long nr_slices, time_elapsed, io_trim;
 469        u64 bytes_trim, tmp;
 470
 471        BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
 472
 473        /*
 474         * If bps are unlimited (-1), then time slice don't get
 475         * renewed. Don't try to trim the slice if slice is used. A new
 476         * slice will start when appropriate.
 477         */
 478        if (throtl_slice_used(td, tg, rw))
 479                return;
 480
 481        /*
 482         * A bio has been dispatched. Also adjust slice_end. It might happen
 483         * that initially cgroup limit was very low resulting in high
 484         * slice_end, but later limit was bumped up and bio was dispached
 485         * sooner, then we need to reduce slice_end. A high bogus slice_end
 486         * is bad because it does not allow new slice to start.
 487         */
 488
 489        throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
 490
 491        time_elapsed = jiffies - tg->slice_start[rw];
 492
 493        nr_slices = time_elapsed / throtl_slice;
 494
 495        if (!nr_slices)
 496                return;
 497        tmp = tg->bps[rw] * throtl_slice * nr_slices;
 498        do_div(tmp, HZ);
 499        bytes_trim = tmp;
 500
 501        io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
 502
 503        if (!bytes_trim && !io_trim)
 504                return;
 505
 506        if (tg->bytes_disp[rw] >= bytes_trim)
 507                tg->bytes_disp[rw] -= bytes_trim;
 508        else
 509                tg->bytes_disp[rw] = 0;
 510
 511        if (tg->io_disp[rw] >= io_trim)
 512                tg->io_disp[rw] -= io_trim;
 513        else
 514                tg->io_disp[rw] = 0;
 515
 516        tg->slice_start[rw] += nr_slices * throtl_slice;
 517
 518        throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
 519                        " start=%lu end=%lu jiffies=%lu",
 520                        rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
 521                        tg->slice_start[rw], tg->slice_end[rw], jiffies);
 522}
 523
 524static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
 525                struct bio *bio, unsigned long *wait)
 526{
 527        bool rw = bio_data_dir(bio);
 528        unsigned int io_allowed;
 529        unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
 530        u64 tmp;
 531
 532        jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
 533
 534        /* Slice has just started. Consider one slice interval */
 535        if (!jiffy_elapsed)
 536                jiffy_elapsed_rnd = throtl_slice;
 537
 538        jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
 539
 540        /*
 541         * jiffy_elapsed_rnd should not be a big value as minimum iops can be
 542         * 1 then at max jiffy elapsed should be equivalent of 1 second as we
 543         * will allow dispatch after 1 second and after that slice should
 544         * have been trimmed.
 545         */
 546
 547        tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
 548        do_div(tmp, HZ);
 549
 550        if (tmp > UINT_MAX)
 551                io_allowed = UINT_MAX;
 552        else
 553                io_allowed = tmp;
 554
 555        if (tg->io_disp[rw] + 1 <= io_allowed) {
 556                if (wait)
 557                        *wait = 0;
 558                return 1;
 559        }
 560
 561        /* Calc approx time to dispatch */
 562        jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
 563
 564        if (jiffy_wait > jiffy_elapsed)
 565                jiffy_wait = jiffy_wait - jiffy_elapsed;
 566        else
 567                jiffy_wait = 1;
 568
 569        if (wait)
 570                *wait = jiffy_wait;
 571        return 0;
 572}
 573
 574static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
 575                struct bio *bio, unsigned long *wait)
 576{
 577        bool rw = bio_data_dir(bio);
 578        u64 bytes_allowed, extra_bytes, tmp;
 579        unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
 580
 581        jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
 582
 583        /* Slice has just started. Consider one slice interval */
 584        if (!jiffy_elapsed)
 585                jiffy_elapsed_rnd = throtl_slice;
 586
 587        jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
 588
 589        tmp = tg->bps[rw] * jiffy_elapsed_rnd;
 590        do_div(tmp, HZ);
 591        bytes_allowed = tmp;
 592
 593        if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
 594                if (wait)
 595                        *wait = 0;
 596                return 1;
 597        }
 598
 599        /* Calc approx time to dispatch */
 600        extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
 601        jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
 602
 603        if (!jiffy_wait)
 604                jiffy_wait = 1;
 605
 606        /*
 607         * This wait time is without taking into consideration the rounding
 608         * up we did. Add that time also.
 609         */
 610        jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
 611        if (wait)
 612                *wait = jiffy_wait;
 613        return 0;
 614}
 615
 616static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
 617        if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
 618                return 1;
 619        return 0;
 620}
 621
 622/*
 623 * Returns whether one can dispatch a bio or not. Also returns approx number
 624 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
 625 */
 626static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
 627                                struct bio *bio, unsigned long *wait)
 628{
 629        bool rw = bio_data_dir(bio);
 630        unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
 631
 632        /*
 633         * Currently whole state machine of group depends on first bio
 634         * queued in the group bio list. So one should not be calling
 635         * this function with a different bio if there are other bios
 636         * queued.
 637         */
 638        BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
 639
 640        /* If tg->bps = -1, then BW is unlimited */
 641        if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
 642                if (wait)
 643                        *wait = 0;
 644                return 1;
 645        }
 646
 647        /*
 648         * If previous slice expired, start a new one otherwise renew/extend
 649         * existing slice to make sure it is at least throtl_slice interval
 650         * long since now.
 651         */
 652        if (throtl_slice_used(td, tg, rw))
 653                throtl_start_new_slice(td, tg, rw);
 654        else {
 655                if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
 656                        throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
 657        }
 658
 659        if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
 660            && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
 661                if (wait)
 662                        *wait = 0;
 663                return 1;
 664        }
 665
 666        max_wait = max(bps_wait, iops_wait);
 667
 668        if (wait)
 669                *wait = max_wait;
 670
 671        if (time_before(tg->slice_end[rw], jiffies + max_wait))
 672                throtl_extend_slice(td, tg, rw, jiffies + max_wait);
 673
 674        return 0;
 675}
 676
 677static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
 678                                         int rw)
 679{
 680        struct throtl_grp *tg = blkg_to_tg(blkg);
 681        struct tg_stats_cpu *stats_cpu;
 682        unsigned long flags;
 683
 684        /* If per cpu stats are not allocated yet, don't do any accounting. */
 685        if (tg->stats_cpu == NULL)
 686                return;
 687
 688        /*
 689         * Disabling interrupts to provide mutual exclusion between two
 690         * writes on same cpu. It probably is not needed for 64bit. Not
 691         * optimizing that case yet.
 692         */
 693        local_irq_save(flags);
 694
 695        stats_cpu = this_cpu_ptr(tg->stats_cpu);
 696
 697        blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
 698        blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
 699
 700        local_irq_restore(flags);
 701}
 702
 703static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
 704{
 705        bool rw = bio_data_dir(bio);
 706
 707        /* Charge the bio to the group */
 708        tg->bytes_disp[rw] += bio->bi_size;
 709        tg->io_disp[rw]++;
 710
 711        throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw);
 712}
 713
 714static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
 715                        struct bio *bio)
 716{
 717        bool rw = bio_data_dir(bio);
 718
 719        bio_list_add(&tg->bio_lists[rw], bio);
 720        /* Take a bio reference on tg */
 721        blkg_get(tg_to_blkg(tg));
 722        tg->nr_queued[rw]++;
 723        td->nr_queued[rw]++;
 724        throtl_enqueue_tg(td, tg);
 725}
 726
 727static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
 728{
 729        unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
 730        struct bio *bio;
 731
 732        if ((bio = bio_list_peek(&tg->bio_lists[READ])))
 733                tg_may_dispatch(td, tg, bio, &read_wait);
 734
 735        if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
 736                tg_may_dispatch(td, tg, bio, &write_wait);
 737
 738        min_wait = min(read_wait, write_wait);
 739        disptime = jiffies + min_wait;
 740
 741        /* Update dispatch time */
 742        throtl_dequeue_tg(td, tg);
 743        tg->disptime = disptime;
 744        throtl_enqueue_tg(td, tg);
 745}
 746
 747static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
 748                                bool rw, struct bio_list *bl)
 749{
 750        struct bio *bio;
 751
 752        bio = bio_list_pop(&tg->bio_lists[rw]);
 753        tg->nr_queued[rw]--;
 754        /* Drop bio reference on blkg */
 755        blkg_put(tg_to_blkg(tg));
 756
 757        BUG_ON(td->nr_queued[rw] <= 0);
 758        td->nr_queued[rw]--;
 759
 760        throtl_charge_bio(tg, bio);
 761        bio_list_add(bl, bio);
 762        bio->bi_rw |= REQ_THROTTLED;
 763
 764        throtl_trim_slice(td, tg, rw);
 765}
 766
 767static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
 768                                struct bio_list *bl)
 769{
 770        unsigned int nr_reads = 0, nr_writes = 0;
 771        unsigned int max_nr_reads = throtl_grp_quantum*3/4;
 772        unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
 773        struct bio *bio;
 774
 775        /* Try to dispatch 75% READS and 25% WRITES */
 776
 777        while ((bio = bio_list_peek(&tg->bio_lists[READ]))
 778                && tg_may_dispatch(td, tg, bio, NULL)) {
 779
 780                tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
 781                nr_reads++;
 782
 783                if (nr_reads >= max_nr_reads)
 784                        break;
 785        }
 786
 787        while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
 788                && tg_may_dispatch(td, tg, bio, NULL)) {
 789
 790                tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
 791                nr_writes++;
 792
 793                if (nr_writes >= max_nr_writes)
 794                        break;
 795        }
 796
 797        return nr_reads + nr_writes;
 798}
 799
 800static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
 801{
 802        unsigned int nr_disp = 0;
 803        struct throtl_grp *tg;
 804        struct throtl_rb_root *st = &td->tg_service_tree;
 805
 806        while (1) {
 807                tg = throtl_rb_first(st);
 808
 809                if (!tg)
 810                        break;
 811
 812                if (time_before(jiffies, tg->disptime))
 813                        break;
 814
 815                throtl_dequeue_tg(td, tg);
 816
 817                nr_disp += throtl_dispatch_tg(td, tg, bl);
 818
 819                if (tg->nr_queued[0] || tg->nr_queued[1]) {
 820                        tg_update_disptime(td, tg);
 821                        throtl_enqueue_tg(td, tg);
 822                }
 823
 824                if (nr_disp >= throtl_quantum)
 825                        break;
 826        }
 827
 828        return nr_disp;
 829}
 830
 831static void throtl_process_limit_change(struct throtl_data *td)
 832{
 833        struct request_queue *q = td->queue;
 834        struct blkcg_gq *blkg, *n;
 835
 836        if (!td->limits_changed)
 837                return;
 838
 839        xchg(&td->limits_changed, false);
 840
 841        throtl_log(td, "limits changed");
 842
 843        list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 844                struct throtl_grp *tg = blkg_to_tg(blkg);
 845
 846                if (!tg->limits_changed)
 847                        continue;
 848
 849                if (!xchg(&tg->limits_changed, false))
 850                        continue;
 851
 852                throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
 853                        " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
 854                        tg->iops[READ], tg->iops[WRITE]);
 855
 856                /*
 857                 * Restart the slices for both READ and WRITES. It
 858                 * might happen that a group's limit are dropped
 859                 * suddenly and we don't want to account recently
 860                 * dispatched IO with new low rate
 861                 */
 862                throtl_start_new_slice(td, tg, 0);
 863                throtl_start_new_slice(td, tg, 1);
 864
 865                if (throtl_tg_on_rr(tg))
 866                        tg_update_disptime(td, tg);
 867        }
 868}
 869
 870/* Dispatch throttled bios. Should be called without queue lock held. */
 871static int throtl_dispatch(struct request_queue *q)
 872{
 873        struct throtl_data *td = q->td;
 874        unsigned int nr_disp = 0;
 875        struct bio_list bio_list_on_stack;
 876        struct bio *bio;
 877        struct blk_plug plug;
 878
 879        spin_lock_irq(q->queue_lock);
 880
 881        throtl_process_limit_change(td);
 882
 883        if (!total_nr_queued(td))
 884                goto out;
 885
 886        bio_list_init(&bio_list_on_stack);
 887
 888        throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
 889                        total_nr_queued(td), td->nr_queued[READ],
 890                        td->nr_queued[WRITE]);
 891
 892        nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
 893
 894        if (nr_disp)
 895                throtl_log(td, "bios disp=%u", nr_disp);
 896
 897        throtl_schedule_next_dispatch(td);
 898out:
 899        spin_unlock_irq(q->queue_lock);
 900
 901        /*
 902         * If we dispatched some requests, unplug the queue to make sure
 903         * immediate dispatch
 904         */
 905        if (nr_disp) {
 906                blk_start_plug(&plug);
 907                while((bio = bio_list_pop(&bio_list_on_stack)))
 908                        generic_make_request(bio);
 909                blk_finish_plug(&plug);
 910        }
 911        return nr_disp;
 912}
 913
 914void blk_throtl_work(struct work_struct *work)
 915{
 916        struct throtl_data *td = container_of(work, struct throtl_data,
 917                                        throtl_work.work);
 918        struct request_queue *q = td->queue;
 919
 920        throtl_dispatch(q);
 921}
 922
 923/* Call with queue lock held */
 924static void
 925throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
 926{
 927
 928        struct delayed_work *dwork = &td->throtl_work;
 929
 930        /* schedule work if limits changed even if no bio is queued */
 931        if (total_nr_queued(td) || td->limits_changed) {
 932                mod_delayed_work(kthrotld_workqueue, dwork, delay);
 933                throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
 934                                delay, jiffies);
 935        }
 936}
 937
 938static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
 939                                struct blkg_policy_data *pd, int off)
 940{
 941        struct throtl_grp *tg = pd_to_tg(pd);
 942        struct blkg_rwstat rwstat = { }, tmp;
 943        int i, cpu;
 944
 945        for_each_possible_cpu(cpu) {
 946                struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
 947
 948                tmp = blkg_rwstat_read((void *)sc + off);
 949                for (i = 0; i < BLKG_RWSTAT_NR; i++)
 950                        rwstat.cnt[i] += tmp.cnt[i];
 951        }
 952
 953        return __blkg_prfill_rwstat(sf, pd, &rwstat);
 954}
 955
 956static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
 957                               struct seq_file *sf)
 958{
 959        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
 960
 961        blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl,
 962                          cft->private, true);
 963        return 0;
 964}
 965
 966static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
 967                              int off)
 968{
 969        struct throtl_grp *tg = pd_to_tg(pd);
 970        u64 v = *(u64 *)((void *)tg + off);
 971
 972        if (v == -1)
 973                return 0;
 974        return __blkg_prfill_u64(sf, pd, v);
 975}
 976
 977static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
 978                               int off)
 979{
 980        struct throtl_grp *tg = pd_to_tg(pd);
 981        unsigned int v = *(unsigned int *)((void *)tg + off);
 982
 983        if (v == -1)
 984                return 0;
 985        return __blkg_prfill_u64(sf, pd, v);
 986}
 987
 988static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
 989                             struct seq_file *sf)
 990{
 991        blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_u64,
 992                          &blkcg_policy_throtl, cft->private, false);
 993        return 0;
 994}
 995
 996static int tg_print_conf_uint(struct cgroup *cgrp, struct cftype *cft,
 997                              struct seq_file *sf)
 998{
 999        blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_uint,
1000                          &blkcg_policy_throtl, cft->private, false);
1001        return 0;
1002}
1003
1004static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf,
1005                       bool is_u64)
1006{
1007        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1008        struct blkg_conf_ctx ctx;
1009        struct throtl_grp *tg;
1010        struct throtl_data *td;
1011        int ret;
1012
1013        ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1014        if (ret)
1015                return ret;
1016
1017        tg = blkg_to_tg(ctx.blkg);
1018        td = ctx.blkg->q->td;
1019
1020        if (!ctx.v)
1021                ctx.v = -1;
1022
1023        if (is_u64)
1024                *(u64 *)((void *)tg + cft->private) = ctx.v;
1025        else
1026                *(unsigned int *)((void *)tg + cft->private) = ctx.v;
1027
1028        /* XXX: we don't need the following deferred processing */
1029        xchg(&tg->limits_changed, true);
1030        xchg(&td->limits_changed, true);
1031        throtl_schedule_delayed_work(td, 0);
1032
1033        blkg_conf_finish(&ctx);
1034        return 0;
1035}
1036
1037static int tg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft,
1038                           const char *buf)
1039{
1040        return tg_set_conf(cgrp, cft, buf, true);
1041}
1042
1043static int tg_set_conf_uint(struct cgroup *cgrp, struct cftype *cft,
1044                            const char *buf)
1045{
1046        return tg_set_conf(cgrp, cft, buf, false);
1047}
1048
1049static struct cftype throtl_files[] = {
1050        {
1051                .name = "throttle.read_bps_device",
1052                .private = offsetof(struct throtl_grp, bps[READ]),
1053                .read_seq_string = tg_print_conf_u64,
1054                .write_string = tg_set_conf_u64,
1055                .max_write_len = 256,
1056        },
1057        {
1058                .name = "throttle.write_bps_device",
1059                .private = offsetof(struct throtl_grp, bps[WRITE]),
1060                .read_seq_string = tg_print_conf_u64,
1061                .write_string = tg_set_conf_u64,
1062                .max_write_len = 256,
1063        },
1064        {
1065                .name = "throttle.read_iops_device",
1066                .private = offsetof(struct throtl_grp, iops[READ]),
1067                .read_seq_string = tg_print_conf_uint,
1068                .write_string = tg_set_conf_uint,
1069                .max_write_len = 256,
1070        },
1071        {
1072                .name = "throttle.write_iops_device",
1073                .private = offsetof(struct throtl_grp, iops[WRITE]),
1074                .read_seq_string = tg_print_conf_uint,
1075                .write_string = tg_set_conf_uint,
1076                .max_write_len = 256,
1077        },
1078        {
1079                .name = "throttle.io_service_bytes",
1080                .private = offsetof(struct tg_stats_cpu, service_bytes),
1081                .read_seq_string = tg_print_cpu_rwstat,
1082        },
1083        {
1084                .name = "throttle.io_serviced",
1085                .private = offsetof(struct tg_stats_cpu, serviced),
1086                .read_seq_string = tg_print_cpu_rwstat,
1087        },
1088        { }     /* terminate */
1089};
1090
1091static void throtl_shutdown_wq(struct request_queue *q)
1092{
1093        struct throtl_data *td = q->td;
1094
1095        cancel_delayed_work_sync(&td->throtl_work);
1096}
1097
1098static struct blkcg_policy blkcg_policy_throtl = {
1099        .pd_size                = sizeof(struct throtl_grp),
1100        .cftypes                = throtl_files,
1101
1102        .pd_init_fn             = throtl_pd_init,
1103        .pd_exit_fn             = throtl_pd_exit,
1104        .pd_reset_stats_fn      = throtl_pd_reset_stats,
1105};
1106
1107bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
1108{
1109        struct throtl_data *td = q->td;
1110        struct throtl_grp *tg;
1111        bool rw = bio_data_dir(bio), update_disptime = true;
1112        struct blkcg *blkcg;
1113        bool throttled = false;
1114
1115        if (bio->bi_rw & REQ_THROTTLED) {
1116                bio->bi_rw &= ~REQ_THROTTLED;
1117                goto out;
1118        }
1119
1120        /*
1121         * A throtl_grp pointer retrieved under rcu can be used to access
1122         * basic fields like stats and io rates. If a group has no rules,
1123         * just update the dispatch stats in lockless manner and return.
1124         */
1125        rcu_read_lock();
1126        blkcg = bio_blkcg(bio);
1127        tg = throtl_lookup_tg(td, blkcg);
1128        if (tg) {
1129                if (tg_no_rule_group(tg, rw)) {
1130                        throtl_update_dispatch_stats(tg_to_blkg(tg),
1131                                                     bio->bi_size, bio->bi_rw);
1132                        goto out_unlock_rcu;
1133                }
1134        }
1135
1136        /*
1137         * Either group has not been allocated yet or it is not an unlimited
1138         * IO group
1139         */
1140        spin_lock_irq(q->queue_lock);
1141        tg = throtl_lookup_create_tg(td, blkcg);
1142        if (unlikely(!tg))
1143                goto out_unlock;
1144
1145        if (tg->nr_queued[rw]) {
1146                /*
1147                 * There is already another bio queued in same dir. No
1148                 * need to update dispatch time.
1149                 */
1150                update_disptime = false;
1151                goto queue_bio;
1152
1153        }
1154
1155        /* Bio is with-in rate limit of group */
1156        if (tg_may_dispatch(td, tg, bio, NULL)) {
1157                throtl_charge_bio(tg, bio);
1158
1159                /*
1160                 * We need to trim slice even when bios are not being queued
1161                 * otherwise it might happen that a bio is not queued for
1162                 * a long time and slice keeps on extending and trim is not
1163                 * called for a long time. Now if limits are reduced suddenly
1164                 * we take into account all the IO dispatched so far at new
1165                 * low rate and * newly queued IO gets a really long dispatch
1166                 * time.
1167                 *
1168                 * So keep on trimming slice even if bio is not queued.
1169                 */
1170                throtl_trim_slice(td, tg, rw);
1171                goto out_unlock;
1172        }
1173
1174queue_bio:
1175        throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1176                        " iodisp=%u iops=%u queued=%d/%d",
1177                        rw == READ ? 'R' : 'W',
1178                        tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1179                        tg->io_disp[rw], tg->iops[rw],
1180                        tg->nr_queued[READ], tg->nr_queued[WRITE]);
1181
1182        bio_associate_current(bio);
1183        throtl_add_bio_tg(q->td, tg, bio);
1184        throttled = true;
1185
1186        if (update_disptime) {
1187                tg_update_disptime(td, tg);
1188                throtl_schedule_next_dispatch(td);
1189        }
1190
1191out_unlock:
1192        spin_unlock_irq(q->queue_lock);
1193out_unlock_rcu:
1194        rcu_read_unlock();
1195out:
1196        return throttled;
1197}
1198
1199/**
1200 * blk_throtl_drain - drain throttled bios
1201 * @q: request_queue to drain throttled bios for
1202 *
1203 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1204 */
1205void blk_throtl_drain(struct request_queue *q)
1206        __releases(q->queue_lock) __acquires(q->queue_lock)
1207{
1208        struct throtl_data *td = q->td;
1209        struct throtl_rb_root *st = &td->tg_service_tree;
1210        struct throtl_grp *tg;
1211        struct bio_list bl;
1212        struct bio *bio;
1213
1214        queue_lockdep_assert_held(q);
1215
1216        bio_list_init(&bl);
1217
1218        while ((tg = throtl_rb_first(st))) {
1219                throtl_dequeue_tg(td, tg);
1220
1221                while ((bio = bio_list_peek(&tg->bio_lists[READ])))
1222                        tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1223                while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
1224                        tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1225        }
1226        spin_unlock_irq(q->queue_lock);
1227
1228        while ((bio = bio_list_pop(&bl)))
1229                generic_make_request(bio);
1230
1231        spin_lock_irq(q->queue_lock);
1232}
1233
1234int blk_throtl_init(struct request_queue *q)
1235{
1236        struct throtl_data *td;
1237        int ret;
1238
1239        td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1240        if (!td)
1241                return -ENOMEM;
1242
1243        td->tg_service_tree = THROTL_RB_ROOT;
1244        td->limits_changed = false;
1245        INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1246
1247        q->td = td;
1248        td->queue = q;
1249
1250        /* activate policy */
1251        ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1252        if (ret)
1253                kfree(td);
1254        return ret;
1255}
1256
1257void blk_throtl_exit(struct request_queue *q)
1258{
1259        BUG_ON(!q->td);
1260        throtl_shutdown_wq(q);
1261        blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1262        kfree(q->td);
1263}
1264
1265static int __init throtl_init(void)
1266{
1267        kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1268        if (!kthrotld_workqueue)
1269                panic("Failed to create kthrotld\n");
1270
1271        return blkcg_policy_register(&blkcg_policy_throtl);
1272}
1273
1274module_init(throtl_init);
1275
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