cfq-iosched.c revision 41647e7a91338dba21773a16af7474ef95e0929e
1/* 2 * CFQ, or complete fairness queueing, disk scheduler. 3 * 4 * Based on ideas from a previously unfinished io 5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli. 6 * 7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> 8 */ 9#include <linux/module.h> 10#include <linux/blkdev.h> 11#include <linux/elevator.h> 12#include <linux/jiffies.h> 13#include <linux/rbtree.h> 14#include <linux/ioprio.h> 15#include <linux/blktrace_api.h> 16#include "blk-cgroup.h" 17 18/* 19 * tunables 20 */ 21/* max queue in one round of service */ 22static const int cfq_quantum = 4; 23static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; 24/* maximum backwards seek, in KiB */ 25static const int cfq_back_max = 16 * 1024; 26/* penalty of a backwards seek */ 27static const int cfq_back_penalty = 2; 28static const int cfq_slice_sync = HZ / 10; 29static int cfq_slice_async = HZ / 25; 30static const int cfq_slice_async_rq = 2; 31static int cfq_slice_idle = HZ / 125; 32static const int cfq_target_latency = HZ * 3/10; /* 300 ms */ 33static const int cfq_hist_divisor = 4; 34 35/* 36 * offset from end of service tree 37 */ 38#define CFQ_IDLE_DELAY (HZ / 5) 39 40/* 41 * below this threshold, we consider thinktime immediate 42 */ 43#define CFQ_MIN_TT (2) 44 45#define CFQ_SLICE_SCALE (5) 46#define CFQ_HW_QUEUE_MIN (5) 47#define CFQ_SERVICE_SHIFT 12 48 49#define CFQQ_SEEK_THR (sector_t)(8 * 100) 50#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32) 51#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8) 52 53#define RQ_CIC(rq) \ 54 ((struct cfq_io_context *) (rq)->elevator_private) 55#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 56 57static struct kmem_cache *cfq_pool; 58static struct kmem_cache *cfq_ioc_pool; 59 60static DEFINE_PER_CPU(unsigned long, cfq_ioc_count); 61static struct completion *ioc_gone; 62static DEFINE_SPINLOCK(ioc_gone_lock); 63 64#define CFQ_PRIO_LISTS IOPRIO_BE_NR 65#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 66#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 67 68#define sample_valid(samples) ((samples) > 80) 69#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node) 70 71/* 72 * Most of our rbtree usage is for sorting with min extraction, so 73 * if we cache the leftmost node we don't have to walk down the tree 74 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 75 * move this into the elevator for the rq sorting as well. 76 */ 77struct cfq_rb_root { 78 struct rb_root rb; 79 struct rb_node *left; 80 unsigned count; 81 u64 min_vdisktime; 82 struct rb_node *active; 83 unsigned total_weight; 84}; 85#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, } 86 87/* 88 * Per process-grouping structure 89 */ 90struct cfq_queue { 91 /* reference count */ 92 atomic_t ref; 93 /* various state flags, see below */ 94 unsigned int flags; 95 /* parent cfq_data */ 96 struct cfq_data *cfqd; 97 /* service_tree member */ 98 struct rb_node rb_node; 99 /* service_tree key */ 100 unsigned long rb_key; 101 /* prio tree member */ 102 struct rb_node p_node; 103 /* prio tree root we belong to, if any */ 104 struct rb_root *p_root; 105 /* sorted list of pending requests */ 106 struct rb_root sort_list; 107 /* if fifo isn't expired, next request to serve */ 108 struct request *next_rq; 109 /* requests queued in sort_list */ 110 int queued[2]; 111 /* currently allocated requests */ 112 int allocated[2]; 113 /* fifo list of requests in sort_list */ 114 struct list_head fifo; 115 116 /* time when queue got scheduled in to dispatch first request. */ 117 unsigned long dispatch_start; 118 unsigned int allocated_slice; 119 unsigned int slice_dispatch; 120 /* time when first request from queue completed and slice started. */ 121 unsigned long slice_start; 122 unsigned long slice_end; 123 long slice_resid; 124 125 /* pending metadata requests */ 126 int meta_pending; 127 /* number of requests that are on the dispatch list or inside driver */ 128 int dispatched; 129 130 /* io prio of this group */ 131 unsigned short ioprio, org_ioprio; 132 unsigned short ioprio_class, org_ioprio_class; 133 134 pid_t pid; 135 136 u32 seek_history; 137 sector_t last_request_pos; 138 139 struct cfq_rb_root *service_tree; 140 struct cfq_queue *new_cfqq; 141 struct cfq_group *cfqg; 142 struct cfq_group *orig_cfqg; 143 /* Sectors dispatched in current dispatch round */ 144 unsigned long nr_sectors; 145}; 146 147/* 148 * First index in the service_trees. 149 * IDLE is handled separately, so it has negative index 150 */ 151enum wl_prio_t { 152 BE_WORKLOAD = 0, 153 RT_WORKLOAD = 1, 154 IDLE_WORKLOAD = 2, 155}; 156 157/* 158 * Second index in the service_trees. 159 */ 160enum wl_type_t { 161 ASYNC_WORKLOAD = 0, 162 SYNC_NOIDLE_WORKLOAD = 1, 163 SYNC_WORKLOAD = 2 164}; 165 166/* This is per cgroup per device grouping structure */ 167struct cfq_group { 168 /* group service_tree member */ 169 struct rb_node rb_node; 170 171 /* group service_tree key */ 172 u64 vdisktime; 173 unsigned int weight; 174 bool on_st; 175 176 /* number of cfqq currently on this group */ 177 int nr_cfqq; 178 179 /* Per group busy queus average. Useful for workload slice calc. */ 180 unsigned int busy_queues_avg[2]; 181 /* 182 * rr lists of queues with requests, onle rr for each priority class. 183 * Counts are embedded in the cfq_rb_root 184 */ 185 struct cfq_rb_root service_trees[2][3]; 186 struct cfq_rb_root service_tree_idle; 187 188 unsigned long saved_workload_slice; 189 enum wl_type_t saved_workload; 190 enum wl_prio_t saved_serving_prio; 191 struct blkio_group blkg; 192#ifdef CONFIG_CFQ_GROUP_IOSCHED 193 struct hlist_node cfqd_node; 194 atomic_t ref; 195#endif 196}; 197 198/* 199 * Per block device queue structure 200 */ 201struct cfq_data { 202 struct request_queue *queue; 203 /* Root service tree for cfq_groups */ 204 struct cfq_rb_root grp_service_tree; 205 struct cfq_group root_group; 206 207 /* 208 * The priority currently being served 209 */ 210 enum wl_prio_t serving_prio; 211 enum wl_type_t serving_type; 212 unsigned long workload_expires; 213 struct cfq_group *serving_group; 214 bool noidle_tree_requires_idle; 215 216 /* 217 * Each priority tree is sorted by next_request position. These 218 * trees are used when determining if two or more queues are 219 * interleaving requests (see cfq_close_cooperator). 220 */ 221 struct rb_root prio_trees[CFQ_PRIO_LISTS]; 222 223 unsigned int busy_queues; 224 225 int rq_in_driver[2]; 226 int sync_flight; 227 228 /* 229 * queue-depth detection 230 */ 231 int rq_queued; 232 int hw_tag; 233 /* 234 * hw_tag can be 235 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection) 236 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth) 237 * 0 => no NCQ 238 */ 239 int hw_tag_est_depth; 240 unsigned int hw_tag_samples; 241 242 /* 243 * idle window management 244 */ 245 struct timer_list idle_slice_timer; 246 struct work_struct unplug_work; 247 248 struct cfq_queue *active_queue; 249 struct cfq_io_context *active_cic; 250 251 /* 252 * async queue for each priority case 253 */ 254 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 255 struct cfq_queue *async_idle_cfqq; 256 257 sector_t last_position; 258 259 /* 260 * tunables, see top of file 261 */ 262 unsigned int cfq_quantum; 263 unsigned int cfq_fifo_expire[2]; 264 unsigned int cfq_back_penalty; 265 unsigned int cfq_back_max; 266 unsigned int cfq_slice[2]; 267 unsigned int cfq_slice_async_rq; 268 unsigned int cfq_slice_idle; 269 unsigned int cfq_latency; 270 unsigned int cfq_group_isolation; 271 272 struct list_head cic_list; 273 274 /* 275 * Fallback dummy cfqq for extreme OOM conditions 276 */ 277 struct cfq_queue oom_cfqq; 278 279 unsigned long last_delayed_sync; 280 281 /* List of cfq groups being managed on this device*/ 282 struct hlist_head cfqg_list; 283 struct rcu_head rcu; 284}; 285 286static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd); 287 288static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg, 289 enum wl_prio_t prio, 290 enum wl_type_t type) 291{ 292 if (!cfqg) 293 return NULL; 294 295 if (prio == IDLE_WORKLOAD) 296 return &cfqg->service_tree_idle; 297 298 return &cfqg->service_trees[prio][type]; 299} 300 301enum cfqq_state_flags { 302 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 303 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 304 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ 305 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 306 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 307 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 308 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 309 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 310 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 311 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */ 312 CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */ 313 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */ 314 CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */ 315}; 316 317#define CFQ_CFQQ_FNS(name) \ 318static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 319{ \ 320 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 321} \ 322static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 323{ \ 324 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 325} \ 326static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 327{ \ 328 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 329} 330 331CFQ_CFQQ_FNS(on_rr); 332CFQ_CFQQ_FNS(wait_request); 333CFQ_CFQQ_FNS(must_dispatch); 334CFQ_CFQQ_FNS(must_alloc_slice); 335CFQ_CFQQ_FNS(fifo_expire); 336CFQ_CFQQ_FNS(idle_window); 337CFQ_CFQQ_FNS(prio_changed); 338CFQ_CFQQ_FNS(slice_new); 339CFQ_CFQQ_FNS(sync); 340CFQ_CFQQ_FNS(coop); 341CFQ_CFQQ_FNS(split_coop); 342CFQ_CFQQ_FNS(deep); 343CFQ_CFQQ_FNS(wait_busy); 344#undef CFQ_CFQQ_FNS 345 346#ifdef CONFIG_DEBUG_CFQ_IOSCHED 347#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 348 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \ 349 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \ 350 blkg_path(&(cfqq)->cfqg->blkg), ##args); 351 352#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \ 353 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \ 354 blkg_path(&(cfqg)->blkg), ##args); \ 355 356#else 357#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 358 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 359#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0); 360#endif 361#define cfq_log(cfqd, fmt, args...) \ 362 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 363 364/* Traverses through cfq group service trees */ 365#define for_each_cfqg_st(cfqg, i, j, st) \ 366 for (i = 0; i <= IDLE_WORKLOAD; i++) \ 367 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\ 368 : &cfqg->service_tree_idle; \ 369 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \ 370 (i == IDLE_WORKLOAD && j == 0); \ 371 j++, st = i < IDLE_WORKLOAD ? \ 372 &cfqg->service_trees[i][j]: NULL) \ 373 374 375static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq) 376{ 377 if (cfq_class_idle(cfqq)) 378 return IDLE_WORKLOAD; 379 if (cfq_class_rt(cfqq)) 380 return RT_WORKLOAD; 381 return BE_WORKLOAD; 382} 383 384 385static enum wl_type_t cfqq_type(struct cfq_queue *cfqq) 386{ 387 if (!cfq_cfqq_sync(cfqq)) 388 return ASYNC_WORKLOAD; 389 if (!cfq_cfqq_idle_window(cfqq)) 390 return SYNC_NOIDLE_WORKLOAD; 391 return SYNC_WORKLOAD; 392} 393 394static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl, 395 struct cfq_data *cfqd, 396 struct cfq_group *cfqg) 397{ 398 if (wl == IDLE_WORKLOAD) 399 return cfqg->service_tree_idle.count; 400 401 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count 402 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count 403 + cfqg->service_trees[wl][SYNC_WORKLOAD].count; 404} 405 406static inline int cfqg_busy_async_queues(struct cfq_data *cfqd, 407 struct cfq_group *cfqg) 408{ 409 return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count 410 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count; 411} 412 413static void cfq_dispatch_insert(struct request_queue *, struct request *); 414static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool, 415 struct io_context *, gfp_t); 416static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 417 struct io_context *); 418 419static inline int rq_in_driver(struct cfq_data *cfqd) 420{ 421 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1]; 422} 423 424static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 425 bool is_sync) 426{ 427 return cic->cfqq[is_sync]; 428} 429 430static inline void cic_set_cfqq(struct cfq_io_context *cic, 431 struct cfq_queue *cfqq, bool is_sync) 432{ 433 cic->cfqq[is_sync] = cfqq; 434} 435 436/* 437 * We regard a request as SYNC, if it's either a read or has the SYNC bit 438 * set (in which case it could also be direct WRITE). 439 */ 440static inline bool cfq_bio_sync(struct bio *bio) 441{ 442 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO); 443} 444 445/* 446 * scheduler run of queue, if there are requests pending and no one in the 447 * driver that will restart queueing 448 */ 449static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 450{ 451 if (cfqd->busy_queues) { 452 cfq_log(cfqd, "schedule dispatch"); 453 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 454 } 455} 456 457static int cfq_queue_empty(struct request_queue *q) 458{ 459 struct cfq_data *cfqd = q->elevator->elevator_data; 460 461 return !cfqd->rq_queued; 462} 463 464/* 465 * Scale schedule slice based on io priority. Use the sync time slice only 466 * if a queue is marked sync and has sync io queued. A sync queue with async 467 * io only, should not get full sync slice length. 468 */ 469static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync, 470 unsigned short prio) 471{ 472 const int base_slice = cfqd->cfq_slice[sync]; 473 474 WARN_ON(prio >= IOPRIO_BE_NR); 475 476 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 477} 478 479static inline int 480cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 481{ 482 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 483} 484 485static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg) 486{ 487 u64 d = delta << CFQ_SERVICE_SHIFT; 488 489 d = d * BLKIO_WEIGHT_DEFAULT; 490 do_div(d, cfqg->weight); 491 return d; 492} 493 494static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime) 495{ 496 s64 delta = (s64)(vdisktime - min_vdisktime); 497 if (delta > 0) 498 min_vdisktime = vdisktime; 499 500 return min_vdisktime; 501} 502 503static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime) 504{ 505 s64 delta = (s64)(vdisktime - min_vdisktime); 506 if (delta < 0) 507 min_vdisktime = vdisktime; 508 509 return min_vdisktime; 510} 511 512static void update_min_vdisktime(struct cfq_rb_root *st) 513{ 514 u64 vdisktime = st->min_vdisktime; 515 struct cfq_group *cfqg; 516 517 if (st->active) { 518 cfqg = rb_entry_cfqg(st->active); 519 vdisktime = cfqg->vdisktime; 520 } 521 522 if (st->left) { 523 cfqg = rb_entry_cfqg(st->left); 524 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime); 525 } 526 527 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime); 528} 529 530/* 531 * get averaged number of queues of RT/BE priority. 532 * average is updated, with a formula that gives more weight to higher numbers, 533 * to quickly follows sudden increases and decrease slowly 534 */ 535 536static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd, 537 struct cfq_group *cfqg, bool rt) 538{ 539 unsigned min_q, max_q; 540 unsigned mult = cfq_hist_divisor - 1; 541 unsigned round = cfq_hist_divisor / 2; 542 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg); 543 544 min_q = min(cfqg->busy_queues_avg[rt], busy); 545 max_q = max(cfqg->busy_queues_avg[rt], busy); 546 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) / 547 cfq_hist_divisor; 548 return cfqg->busy_queues_avg[rt]; 549} 550 551static inline unsigned 552cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg) 553{ 554 struct cfq_rb_root *st = &cfqd->grp_service_tree; 555 556 return cfq_target_latency * cfqg->weight / st->total_weight; 557} 558 559static inline void 560cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 561{ 562 unsigned slice = cfq_prio_to_slice(cfqd, cfqq); 563 if (cfqd->cfq_latency) { 564 /* 565 * interested queues (we consider only the ones with the same 566 * priority class in the cfq group) 567 */ 568 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg, 569 cfq_class_rt(cfqq)); 570 unsigned sync_slice = cfqd->cfq_slice[1]; 571 unsigned expect_latency = sync_slice * iq; 572 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg); 573 574 if (expect_latency > group_slice) { 575 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle; 576 /* scale low_slice according to IO priority 577 * and sync vs async */ 578 unsigned low_slice = 579 min(slice, base_low_slice * slice / sync_slice); 580 /* the adapted slice value is scaled to fit all iqs 581 * into the target latency */ 582 slice = max(slice * group_slice / expect_latency, 583 low_slice); 584 } 585 } 586 cfqq->slice_start = jiffies; 587 cfqq->slice_end = jiffies + slice; 588 cfqq->allocated_slice = slice; 589 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 590} 591 592/* 593 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 594 * isn't valid until the first request from the dispatch is activated 595 * and the slice time set. 596 */ 597static inline bool cfq_slice_used(struct cfq_queue *cfqq) 598{ 599 if (cfq_cfqq_slice_new(cfqq)) 600 return 0; 601 if (time_before(jiffies, cfqq->slice_end)) 602 return 0; 603 604 return 1; 605} 606 607/* 608 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 609 * We choose the request that is closest to the head right now. Distance 610 * behind the head is penalized and only allowed to a certain extent. 611 */ 612static struct request * 613cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last) 614{ 615 sector_t s1, s2, d1 = 0, d2 = 0; 616 unsigned long back_max; 617#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 618#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 619 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 620 621 if (rq1 == NULL || rq1 == rq2) 622 return rq2; 623 if (rq2 == NULL) 624 return rq1; 625 626 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 627 return rq1; 628 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 629 return rq2; 630 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 631 return rq1; 632 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 633 return rq2; 634 635 s1 = blk_rq_pos(rq1); 636 s2 = blk_rq_pos(rq2); 637 638 /* 639 * by definition, 1KiB is 2 sectors 640 */ 641 back_max = cfqd->cfq_back_max * 2; 642 643 /* 644 * Strict one way elevator _except_ in the case where we allow 645 * short backward seeks which are biased as twice the cost of a 646 * similar forward seek. 647 */ 648 if (s1 >= last) 649 d1 = s1 - last; 650 else if (s1 + back_max >= last) 651 d1 = (last - s1) * cfqd->cfq_back_penalty; 652 else 653 wrap |= CFQ_RQ1_WRAP; 654 655 if (s2 >= last) 656 d2 = s2 - last; 657 else if (s2 + back_max >= last) 658 d2 = (last - s2) * cfqd->cfq_back_penalty; 659 else 660 wrap |= CFQ_RQ2_WRAP; 661 662 /* Found required data */ 663 664 /* 665 * By doing switch() on the bit mask "wrap" we avoid having to 666 * check two variables for all permutations: --> faster! 667 */ 668 switch (wrap) { 669 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 670 if (d1 < d2) 671 return rq1; 672 else if (d2 < d1) 673 return rq2; 674 else { 675 if (s1 >= s2) 676 return rq1; 677 else 678 return rq2; 679 } 680 681 case CFQ_RQ2_WRAP: 682 return rq1; 683 case CFQ_RQ1_WRAP: 684 return rq2; 685 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 686 default: 687 /* 688 * Since both rqs are wrapped, 689 * start with the one that's further behind head 690 * (--> only *one* back seek required), 691 * since back seek takes more time than forward. 692 */ 693 if (s1 <= s2) 694 return rq1; 695 else 696 return rq2; 697 } 698} 699 700/* 701 * The below is leftmost cache rbtree addon 702 */ 703static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 704{ 705 /* Service tree is empty */ 706 if (!root->count) 707 return NULL; 708 709 if (!root->left) 710 root->left = rb_first(&root->rb); 711 712 if (root->left) 713 return rb_entry(root->left, struct cfq_queue, rb_node); 714 715 return NULL; 716} 717 718static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root) 719{ 720 if (!root->left) 721 root->left = rb_first(&root->rb); 722 723 if (root->left) 724 return rb_entry_cfqg(root->left); 725 726 return NULL; 727} 728 729static void rb_erase_init(struct rb_node *n, struct rb_root *root) 730{ 731 rb_erase(n, root); 732 RB_CLEAR_NODE(n); 733} 734 735static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 736{ 737 if (root->left == n) 738 root->left = NULL; 739 rb_erase_init(n, &root->rb); 740 --root->count; 741} 742 743/* 744 * would be nice to take fifo expire time into account as well 745 */ 746static struct request * 747cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 748 struct request *last) 749{ 750 struct rb_node *rbnext = rb_next(&last->rb_node); 751 struct rb_node *rbprev = rb_prev(&last->rb_node); 752 struct request *next = NULL, *prev = NULL; 753 754 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 755 756 if (rbprev) 757 prev = rb_entry_rq(rbprev); 758 759 if (rbnext) 760 next = rb_entry_rq(rbnext); 761 else { 762 rbnext = rb_first(&cfqq->sort_list); 763 if (rbnext && rbnext != &last->rb_node) 764 next = rb_entry_rq(rbnext); 765 } 766 767 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last)); 768} 769 770static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 771 struct cfq_queue *cfqq) 772{ 773 /* 774 * just an approximation, should be ok. 775 */ 776 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) - 777 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 778} 779 780static inline s64 781cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg) 782{ 783 return cfqg->vdisktime - st->min_vdisktime; 784} 785 786static void 787__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) 788{ 789 struct rb_node **node = &st->rb.rb_node; 790 struct rb_node *parent = NULL; 791 struct cfq_group *__cfqg; 792 s64 key = cfqg_key(st, cfqg); 793 int left = 1; 794 795 while (*node != NULL) { 796 parent = *node; 797 __cfqg = rb_entry_cfqg(parent); 798 799 if (key < cfqg_key(st, __cfqg)) 800 node = &parent->rb_left; 801 else { 802 node = &parent->rb_right; 803 left = 0; 804 } 805 } 806 807 if (left) 808 st->left = &cfqg->rb_node; 809 810 rb_link_node(&cfqg->rb_node, parent, node); 811 rb_insert_color(&cfqg->rb_node, &st->rb); 812} 813 814static void 815cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg) 816{ 817 struct cfq_rb_root *st = &cfqd->grp_service_tree; 818 struct cfq_group *__cfqg; 819 struct rb_node *n; 820 821 cfqg->nr_cfqq++; 822 if (cfqg->on_st) 823 return; 824 825 /* 826 * Currently put the group at the end. Later implement something 827 * so that groups get lesser vtime based on their weights, so that 828 * if group does not loose all if it was not continously backlogged. 829 */ 830 n = rb_last(&st->rb); 831 if (n) { 832 __cfqg = rb_entry_cfqg(n); 833 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; 834 } else 835 cfqg->vdisktime = st->min_vdisktime; 836 837 __cfq_group_service_tree_add(st, cfqg); 838 cfqg->on_st = true; 839 st->total_weight += cfqg->weight; 840} 841 842static void 843cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg) 844{ 845 struct cfq_rb_root *st = &cfqd->grp_service_tree; 846 847 if (st->active == &cfqg->rb_node) 848 st->active = NULL; 849 850 BUG_ON(cfqg->nr_cfqq < 1); 851 cfqg->nr_cfqq--; 852 853 /* If there are other cfq queues under this group, don't delete it */ 854 if (cfqg->nr_cfqq) 855 return; 856 857 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group"); 858 cfqg->on_st = false; 859 st->total_weight -= cfqg->weight; 860 if (!RB_EMPTY_NODE(&cfqg->rb_node)) 861 cfq_rb_erase(&cfqg->rb_node, st); 862 cfqg->saved_workload_slice = 0; 863 blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1); 864} 865 866static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq) 867{ 868 unsigned int slice_used; 869 870 /* 871 * Queue got expired before even a single request completed or 872 * got expired immediately after first request completion. 873 */ 874 if (!cfqq->slice_start || cfqq->slice_start == jiffies) { 875 /* 876 * Also charge the seek time incurred to the group, otherwise 877 * if there are mutiple queues in the group, each can dispatch 878 * a single request on seeky media and cause lots of seek time 879 * and group will never know it. 880 */ 881 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start), 882 1); 883 } else { 884 slice_used = jiffies - cfqq->slice_start; 885 if (slice_used > cfqq->allocated_slice) 886 slice_used = cfqq->allocated_slice; 887 } 888 889 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used, 890 cfqq->nr_sectors); 891 return slice_used; 892} 893 894static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg, 895 struct cfq_queue *cfqq) 896{ 897 struct cfq_rb_root *st = &cfqd->grp_service_tree; 898 unsigned int used_sl, charge_sl; 899 int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg) 900 - cfqg->service_tree_idle.count; 901 902 BUG_ON(nr_sync < 0); 903 used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq); 904 905 if (!cfq_cfqq_sync(cfqq) && !nr_sync) 906 charge_sl = cfqq->allocated_slice; 907 908 /* Can't update vdisktime while group is on service tree */ 909 cfq_rb_erase(&cfqg->rb_node, st); 910 cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg); 911 __cfq_group_service_tree_add(st, cfqg); 912 913 /* This group is being expired. Save the context */ 914 if (time_after(cfqd->workload_expires, jiffies)) { 915 cfqg->saved_workload_slice = cfqd->workload_expires 916 - jiffies; 917 cfqg->saved_workload = cfqd->serving_type; 918 cfqg->saved_serving_prio = cfqd->serving_prio; 919 } else 920 cfqg->saved_workload_slice = 0; 921 922 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime, 923 st->min_vdisktime); 924 blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl, 925 cfqq->nr_sectors); 926} 927 928#ifdef CONFIG_CFQ_GROUP_IOSCHED 929static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg) 930{ 931 if (blkg) 932 return container_of(blkg, struct cfq_group, blkg); 933 return NULL; 934} 935 936void 937cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight) 938{ 939 cfqg_of_blkg(blkg)->weight = weight; 940} 941 942static struct cfq_group * 943cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create) 944{ 945 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup); 946 struct cfq_group *cfqg = NULL; 947 void *key = cfqd; 948 int i, j; 949 struct cfq_rb_root *st; 950 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; 951 unsigned int major, minor; 952 953 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key)); 954 if (cfqg || !create) 955 goto done; 956 957 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node); 958 if (!cfqg) 959 goto done; 960 961 cfqg->weight = blkcg->weight; 962 for_each_cfqg_st(cfqg, i, j, st) 963 *st = CFQ_RB_ROOT; 964 RB_CLEAR_NODE(&cfqg->rb_node); 965 966 /* 967 * Take the initial reference that will be released on destroy 968 * This can be thought of a joint reference by cgroup and 969 * elevator which will be dropped by either elevator exit 970 * or cgroup deletion path depending on who is exiting first. 971 */ 972 atomic_set(&cfqg->ref, 1); 973 974 /* Add group onto cgroup list */ 975 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); 976 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd, 977 MKDEV(major, minor)); 978 979 /* Add group on cfqd list */ 980 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list); 981 982done: 983 return cfqg; 984} 985 986/* 987 * Search for the cfq group current task belongs to. If create = 1, then also 988 * create the cfq group if it does not exist. request_queue lock must be held. 989 */ 990static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) 991{ 992 struct cgroup *cgroup; 993 struct cfq_group *cfqg = NULL; 994 995 rcu_read_lock(); 996 cgroup = task_cgroup(current, blkio_subsys_id); 997 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create); 998 if (!cfqg && create) 999 cfqg = &cfqd->root_group; 1000 rcu_read_unlock(); 1001 return cfqg; 1002} 1003 1004static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) 1005{ 1006 /* Currently, all async queues are mapped to root group */ 1007 if (!cfq_cfqq_sync(cfqq)) 1008 cfqg = &cfqq->cfqd->root_group; 1009 1010 cfqq->cfqg = cfqg; 1011 /* cfqq reference on cfqg */ 1012 atomic_inc(&cfqq->cfqg->ref); 1013} 1014 1015static void cfq_put_cfqg(struct cfq_group *cfqg) 1016{ 1017 struct cfq_rb_root *st; 1018 int i, j; 1019 1020 BUG_ON(atomic_read(&cfqg->ref) <= 0); 1021 if (!atomic_dec_and_test(&cfqg->ref)) 1022 return; 1023 for_each_cfqg_st(cfqg, i, j, st) 1024 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL); 1025 kfree(cfqg); 1026} 1027 1028static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) 1029{ 1030 /* Something wrong if we are trying to remove same group twice */ 1031 BUG_ON(hlist_unhashed(&cfqg->cfqd_node)); 1032 1033 hlist_del_init(&cfqg->cfqd_node); 1034 1035 /* 1036 * Put the reference taken at the time of creation so that when all 1037 * queues are gone, group can be destroyed. 1038 */ 1039 cfq_put_cfqg(cfqg); 1040} 1041 1042static void cfq_release_cfq_groups(struct cfq_data *cfqd) 1043{ 1044 struct hlist_node *pos, *n; 1045 struct cfq_group *cfqg; 1046 1047 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) { 1048 /* 1049 * If cgroup removal path got to blk_group first and removed 1050 * it from cgroup list, then it will take care of destroying 1051 * cfqg also. 1052 */ 1053 if (!blkiocg_del_blkio_group(&cfqg->blkg)) 1054 cfq_destroy_cfqg(cfqd, cfqg); 1055 } 1056} 1057 1058/* 1059 * Blk cgroup controller notification saying that blkio_group object is being 1060 * delinked as associated cgroup object is going away. That also means that 1061 * no new IO will come in this group. So get rid of this group as soon as 1062 * any pending IO in the group is finished. 1063 * 1064 * This function is called under rcu_read_lock(). key is the rcu protected 1065 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu 1066 * read lock. 1067 * 1068 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means 1069 * it should not be NULL as even if elevator was exiting, cgroup deltion 1070 * path got to it first. 1071 */ 1072void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg) 1073{ 1074 unsigned long flags; 1075 struct cfq_data *cfqd = key; 1076 1077 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1078 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg)); 1079 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1080} 1081 1082#else /* GROUP_IOSCHED */ 1083static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) 1084{ 1085 return &cfqd->root_group; 1086} 1087static inline void 1088cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { 1089 cfqq->cfqg = cfqg; 1090} 1091 1092static void cfq_release_cfq_groups(struct cfq_data *cfqd) {} 1093static inline void cfq_put_cfqg(struct cfq_group *cfqg) {} 1094 1095#endif /* GROUP_IOSCHED */ 1096 1097/* 1098 * The cfqd->service_trees holds all pending cfq_queue's that have 1099 * requests waiting to be processed. It is sorted in the order that 1100 * we will service the queues. 1101 */ 1102static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1103 bool add_front) 1104{ 1105 struct rb_node **p, *parent; 1106 struct cfq_queue *__cfqq; 1107 unsigned long rb_key; 1108 struct cfq_rb_root *service_tree; 1109 int left; 1110 int new_cfqq = 1; 1111 int group_changed = 0; 1112 1113#ifdef CONFIG_CFQ_GROUP_IOSCHED 1114 if (!cfqd->cfq_group_isolation 1115 && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD 1116 && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) { 1117 /* Move this cfq to root group */ 1118 cfq_log_cfqq(cfqd, cfqq, "moving to root group"); 1119 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 1120 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1121 cfqq->orig_cfqg = cfqq->cfqg; 1122 cfqq->cfqg = &cfqd->root_group; 1123 atomic_inc(&cfqd->root_group.ref); 1124 group_changed = 1; 1125 } else if (!cfqd->cfq_group_isolation 1126 && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) { 1127 /* cfqq is sequential now needs to go to its original group */ 1128 BUG_ON(cfqq->cfqg != &cfqd->root_group); 1129 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 1130 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1131 cfq_put_cfqg(cfqq->cfqg); 1132 cfqq->cfqg = cfqq->orig_cfqg; 1133 cfqq->orig_cfqg = NULL; 1134 group_changed = 1; 1135 cfq_log_cfqq(cfqd, cfqq, "moved to origin group"); 1136 } 1137#endif 1138 1139 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), 1140 cfqq_type(cfqq)); 1141 if (cfq_class_idle(cfqq)) { 1142 rb_key = CFQ_IDLE_DELAY; 1143 parent = rb_last(&service_tree->rb); 1144 if (parent && parent != &cfqq->rb_node) { 1145 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 1146 rb_key += __cfqq->rb_key; 1147 } else 1148 rb_key += jiffies; 1149 } else if (!add_front) { 1150 /* 1151 * Get our rb key offset. Subtract any residual slice 1152 * value carried from last service. A negative resid 1153 * count indicates slice overrun, and this should position 1154 * the next service time further away in the tree. 1155 */ 1156 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 1157 rb_key -= cfqq->slice_resid; 1158 cfqq->slice_resid = 0; 1159 } else { 1160 rb_key = -HZ; 1161 __cfqq = cfq_rb_first(service_tree); 1162 rb_key += __cfqq ? __cfqq->rb_key : jiffies; 1163 } 1164 1165 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 1166 new_cfqq = 0; 1167 /* 1168 * same position, nothing more to do 1169 */ 1170 if (rb_key == cfqq->rb_key && 1171 cfqq->service_tree == service_tree) 1172 return; 1173 1174 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); 1175 cfqq->service_tree = NULL; 1176 } 1177 1178 left = 1; 1179 parent = NULL; 1180 cfqq->service_tree = service_tree; 1181 p = &service_tree->rb.rb_node; 1182 while (*p) { 1183 struct rb_node **n; 1184 1185 parent = *p; 1186 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 1187 1188 /* 1189 * sort by key, that represents service time. 1190 */ 1191 if (time_before(rb_key, __cfqq->rb_key)) 1192 n = &(*p)->rb_left; 1193 else { 1194 n = &(*p)->rb_right; 1195 left = 0; 1196 } 1197 1198 p = n; 1199 } 1200 1201 if (left) 1202 service_tree->left = &cfqq->rb_node; 1203 1204 cfqq->rb_key = rb_key; 1205 rb_link_node(&cfqq->rb_node, parent, p); 1206 rb_insert_color(&cfqq->rb_node, &service_tree->rb); 1207 service_tree->count++; 1208 if ((add_front || !new_cfqq) && !group_changed) 1209 return; 1210 cfq_group_service_tree_add(cfqd, cfqq->cfqg); 1211} 1212 1213static struct cfq_queue * 1214cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, 1215 sector_t sector, struct rb_node **ret_parent, 1216 struct rb_node ***rb_link) 1217{ 1218 struct rb_node **p, *parent; 1219 struct cfq_queue *cfqq = NULL; 1220 1221 parent = NULL; 1222 p = &root->rb_node; 1223 while (*p) { 1224 struct rb_node **n; 1225 1226 parent = *p; 1227 cfqq = rb_entry(parent, struct cfq_queue, p_node); 1228 1229 /* 1230 * Sort strictly based on sector. Smallest to the left, 1231 * largest to the right. 1232 */ 1233 if (sector > blk_rq_pos(cfqq->next_rq)) 1234 n = &(*p)->rb_right; 1235 else if (sector < blk_rq_pos(cfqq->next_rq)) 1236 n = &(*p)->rb_left; 1237 else 1238 break; 1239 p = n; 1240 cfqq = NULL; 1241 } 1242 1243 *ret_parent = parent; 1244 if (rb_link) 1245 *rb_link = p; 1246 return cfqq; 1247} 1248 1249static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1250{ 1251 struct rb_node **p, *parent; 1252 struct cfq_queue *__cfqq; 1253 1254 if (cfqq->p_root) { 1255 rb_erase(&cfqq->p_node, cfqq->p_root); 1256 cfqq->p_root = NULL; 1257 } 1258 1259 if (cfq_class_idle(cfqq)) 1260 return; 1261 if (!cfqq->next_rq) 1262 return; 1263 1264 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; 1265 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, 1266 blk_rq_pos(cfqq->next_rq), &parent, &p); 1267 if (!__cfqq) { 1268 rb_link_node(&cfqq->p_node, parent, p); 1269 rb_insert_color(&cfqq->p_node, cfqq->p_root); 1270 } else 1271 cfqq->p_root = NULL; 1272} 1273 1274/* 1275 * Update cfqq's position in the service tree. 1276 */ 1277static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1278{ 1279 /* 1280 * Resorting requires the cfqq to be on the RR list already. 1281 */ 1282 if (cfq_cfqq_on_rr(cfqq)) { 1283 cfq_service_tree_add(cfqd, cfqq, 0); 1284 cfq_prio_tree_add(cfqd, cfqq); 1285 } 1286} 1287 1288/* 1289 * add to busy list of queues for service, trying to be fair in ordering 1290 * the pending list according to last request service 1291 */ 1292static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1293{ 1294 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 1295 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1296 cfq_mark_cfqq_on_rr(cfqq); 1297 cfqd->busy_queues++; 1298 1299 cfq_resort_rr_list(cfqd, cfqq); 1300} 1301 1302/* 1303 * Called when the cfqq no longer has requests pending, remove it from 1304 * the service tree. 1305 */ 1306static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1307{ 1308 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 1309 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 1310 cfq_clear_cfqq_on_rr(cfqq); 1311 1312 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 1313 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); 1314 cfqq->service_tree = NULL; 1315 } 1316 if (cfqq->p_root) { 1317 rb_erase(&cfqq->p_node, cfqq->p_root); 1318 cfqq->p_root = NULL; 1319 } 1320 1321 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1322 BUG_ON(!cfqd->busy_queues); 1323 cfqd->busy_queues--; 1324} 1325 1326/* 1327 * rb tree support functions 1328 */ 1329static void cfq_del_rq_rb(struct request *rq) 1330{ 1331 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1332 const int sync = rq_is_sync(rq); 1333 1334 BUG_ON(!cfqq->queued[sync]); 1335 cfqq->queued[sync]--; 1336 1337 elv_rb_del(&cfqq->sort_list, rq); 1338 1339 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) { 1340 /* 1341 * Queue will be deleted from service tree when we actually 1342 * expire it later. Right now just remove it from prio tree 1343 * as it is empty. 1344 */ 1345 if (cfqq->p_root) { 1346 rb_erase(&cfqq->p_node, cfqq->p_root); 1347 cfqq->p_root = NULL; 1348 } 1349 } 1350} 1351 1352static void cfq_add_rq_rb(struct request *rq) 1353{ 1354 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1355 struct cfq_data *cfqd = cfqq->cfqd; 1356 struct request *__alias, *prev; 1357 1358 cfqq->queued[rq_is_sync(rq)]++; 1359 1360 /* 1361 * looks a little odd, but the first insert might return an alias. 1362 * if that happens, put the alias on the dispatch list 1363 */ 1364 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 1365 cfq_dispatch_insert(cfqd->queue, __alias); 1366 1367 if (!cfq_cfqq_on_rr(cfqq)) 1368 cfq_add_cfqq_rr(cfqd, cfqq); 1369 1370 /* 1371 * check if this request is a better next-serve candidate 1372 */ 1373 prev = cfqq->next_rq; 1374 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position); 1375 1376 /* 1377 * adjust priority tree position, if ->next_rq changes 1378 */ 1379 if (prev != cfqq->next_rq) 1380 cfq_prio_tree_add(cfqd, cfqq); 1381 1382 BUG_ON(!cfqq->next_rq); 1383} 1384 1385static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 1386{ 1387 elv_rb_del(&cfqq->sort_list, rq); 1388 cfqq->queued[rq_is_sync(rq)]--; 1389 cfq_add_rq_rb(rq); 1390} 1391 1392static struct request * 1393cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 1394{ 1395 struct task_struct *tsk = current; 1396 struct cfq_io_context *cic; 1397 struct cfq_queue *cfqq; 1398 1399 cic = cfq_cic_lookup(cfqd, tsk->io_context); 1400 if (!cic) 1401 return NULL; 1402 1403 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 1404 if (cfqq) { 1405 sector_t sector = bio->bi_sector + bio_sectors(bio); 1406 1407 return elv_rb_find(&cfqq->sort_list, sector); 1408 } 1409 1410 return NULL; 1411} 1412 1413static void cfq_activate_request(struct request_queue *q, struct request *rq) 1414{ 1415 struct cfq_data *cfqd = q->elevator->elevator_data; 1416 1417 cfqd->rq_in_driver[rq_is_sync(rq)]++; 1418 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 1419 rq_in_driver(cfqd)); 1420 1421 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); 1422} 1423 1424static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 1425{ 1426 struct cfq_data *cfqd = q->elevator->elevator_data; 1427 const int sync = rq_is_sync(rq); 1428 1429 WARN_ON(!cfqd->rq_in_driver[sync]); 1430 cfqd->rq_in_driver[sync]--; 1431 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 1432 rq_in_driver(cfqd)); 1433} 1434 1435static void cfq_remove_request(struct request *rq) 1436{ 1437 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1438 1439 if (cfqq->next_rq == rq) 1440 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 1441 1442 list_del_init(&rq->queuelist); 1443 cfq_del_rq_rb(rq); 1444 1445 cfqq->cfqd->rq_queued--; 1446 if (rq_is_meta(rq)) { 1447 WARN_ON(!cfqq->meta_pending); 1448 cfqq->meta_pending--; 1449 } 1450} 1451 1452static int cfq_merge(struct request_queue *q, struct request **req, 1453 struct bio *bio) 1454{ 1455 struct cfq_data *cfqd = q->elevator->elevator_data; 1456 struct request *__rq; 1457 1458 __rq = cfq_find_rq_fmerge(cfqd, bio); 1459 if (__rq && elv_rq_merge_ok(__rq, bio)) { 1460 *req = __rq; 1461 return ELEVATOR_FRONT_MERGE; 1462 } 1463 1464 return ELEVATOR_NO_MERGE; 1465} 1466 1467static void cfq_merged_request(struct request_queue *q, struct request *req, 1468 int type) 1469{ 1470 if (type == ELEVATOR_FRONT_MERGE) { 1471 struct cfq_queue *cfqq = RQ_CFQQ(req); 1472 1473 cfq_reposition_rq_rb(cfqq, req); 1474 } 1475} 1476 1477static void 1478cfq_merged_requests(struct request_queue *q, struct request *rq, 1479 struct request *next) 1480{ 1481 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1482 /* 1483 * reposition in fifo if next is older than rq 1484 */ 1485 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 1486 time_before(rq_fifo_time(next), rq_fifo_time(rq))) { 1487 list_move(&rq->queuelist, &next->queuelist); 1488 rq_set_fifo_time(rq, rq_fifo_time(next)); 1489 } 1490 1491 if (cfqq->next_rq == next) 1492 cfqq->next_rq = rq; 1493 cfq_remove_request(next); 1494} 1495 1496static int cfq_allow_merge(struct request_queue *q, struct request *rq, 1497 struct bio *bio) 1498{ 1499 struct cfq_data *cfqd = q->elevator->elevator_data; 1500 struct cfq_io_context *cic; 1501 struct cfq_queue *cfqq; 1502 1503 /* 1504 * Disallow merge of a sync bio into an async request. 1505 */ 1506 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 1507 return false; 1508 1509 /* 1510 * Lookup the cfqq that this bio will be queued with. Allow 1511 * merge only if rq is queued there. 1512 */ 1513 cic = cfq_cic_lookup(cfqd, current->io_context); 1514 if (!cic) 1515 return false; 1516 1517 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 1518 return cfqq == RQ_CFQQ(rq); 1519} 1520 1521static void __cfq_set_active_queue(struct cfq_data *cfqd, 1522 struct cfq_queue *cfqq) 1523{ 1524 if (cfqq) { 1525 cfq_log_cfqq(cfqd, cfqq, "set_active"); 1526 cfqq->slice_start = 0; 1527 cfqq->dispatch_start = jiffies; 1528 cfqq->allocated_slice = 0; 1529 cfqq->slice_end = 0; 1530 cfqq->slice_dispatch = 0; 1531 cfqq->nr_sectors = 0; 1532 1533 cfq_clear_cfqq_wait_request(cfqq); 1534 cfq_clear_cfqq_must_dispatch(cfqq); 1535 cfq_clear_cfqq_must_alloc_slice(cfqq); 1536 cfq_clear_cfqq_fifo_expire(cfqq); 1537 cfq_mark_cfqq_slice_new(cfqq); 1538 1539 del_timer(&cfqd->idle_slice_timer); 1540 } 1541 1542 cfqd->active_queue = cfqq; 1543} 1544 1545/* 1546 * current cfqq expired its slice (or was too idle), select new one 1547 */ 1548static void 1549__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1550 bool timed_out) 1551{ 1552 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 1553 1554 if (cfq_cfqq_wait_request(cfqq)) 1555 del_timer(&cfqd->idle_slice_timer); 1556 1557 cfq_clear_cfqq_wait_request(cfqq); 1558 cfq_clear_cfqq_wait_busy(cfqq); 1559 1560 /* 1561 * If this cfqq is shared between multiple processes, check to 1562 * make sure that those processes are still issuing I/Os within 1563 * the mean seek distance. If not, it may be time to break the 1564 * queues apart again. 1565 */ 1566 if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq)) 1567 cfq_mark_cfqq_split_coop(cfqq); 1568 1569 /* 1570 * store what was left of this slice, if the queue idled/timed out 1571 */ 1572 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 1573 cfqq->slice_resid = cfqq->slice_end - jiffies; 1574 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 1575 } 1576 1577 cfq_group_served(cfqd, cfqq->cfqg, cfqq); 1578 1579 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 1580 cfq_del_cfqq_rr(cfqd, cfqq); 1581 1582 cfq_resort_rr_list(cfqd, cfqq); 1583 1584 if (cfqq == cfqd->active_queue) 1585 cfqd->active_queue = NULL; 1586 1587 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active) 1588 cfqd->grp_service_tree.active = NULL; 1589 1590 if (cfqd->active_cic) { 1591 put_io_context(cfqd->active_cic->ioc); 1592 cfqd->active_cic = NULL; 1593 } 1594} 1595 1596static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out) 1597{ 1598 struct cfq_queue *cfqq = cfqd->active_queue; 1599 1600 if (cfqq) 1601 __cfq_slice_expired(cfqd, cfqq, timed_out); 1602} 1603 1604/* 1605 * Get next queue for service. Unless we have a queue preemption, 1606 * we'll simply select the first cfqq in the service tree. 1607 */ 1608static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 1609{ 1610 struct cfq_rb_root *service_tree = 1611 service_tree_for(cfqd->serving_group, cfqd->serving_prio, 1612 cfqd->serving_type); 1613 1614 if (!cfqd->rq_queued) 1615 return NULL; 1616 1617 /* There is nothing to dispatch */ 1618 if (!service_tree) 1619 return NULL; 1620 if (RB_EMPTY_ROOT(&service_tree->rb)) 1621 return NULL; 1622 return cfq_rb_first(service_tree); 1623} 1624 1625static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd) 1626{ 1627 struct cfq_group *cfqg; 1628 struct cfq_queue *cfqq; 1629 int i, j; 1630 struct cfq_rb_root *st; 1631 1632 if (!cfqd->rq_queued) 1633 return NULL; 1634 1635 cfqg = cfq_get_next_cfqg(cfqd); 1636 if (!cfqg) 1637 return NULL; 1638 1639 for_each_cfqg_st(cfqg, i, j, st) 1640 if ((cfqq = cfq_rb_first(st)) != NULL) 1641 return cfqq; 1642 return NULL; 1643} 1644 1645/* 1646 * Get and set a new active queue for service. 1647 */ 1648static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, 1649 struct cfq_queue *cfqq) 1650{ 1651 if (!cfqq) 1652 cfqq = cfq_get_next_queue(cfqd); 1653 1654 __cfq_set_active_queue(cfqd, cfqq); 1655 return cfqq; 1656} 1657 1658static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 1659 struct request *rq) 1660{ 1661 if (blk_rq_pos(rq) >= cfqd->last_position) 1662 return blk_rq_pos(rq) - cfqd->last_position; 1663 else 1664 return cfqd->last_position - blk_rq_pos(rq); 1665} 1666 1667static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1668 struct request *rq, bool for_preempt) 1669{ 1670 return cfq_dist_from_last(cfqd, rq) <= CFQQ_SEEK_THR; 1671} 1672 1673static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 1674 struct cfq_queue *cur_cfqq) 1675{ 1676 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; 1677 struct rb_node *parent, *node; 1678 struct cfq_queue *__cfqq; 1679 sector_t sector = cfqd->last_position; 1680 1681 if (RB_EMPTY_ROOT(root)) 1682 return NULL; 1683 1684 /* 1685 * First, if we find a request starting at the end of the last 1686 * request, choose it. 1687 */ 1688 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); 1689 if (__cfqq) 1690 return __cfqq; 1691 1692 /* 1693 * If the exact sector wasn't found, the parent of the NULL leaf 1694 * will contain the closest sector. 1695 */ 1696 __cfqq = rb_entry(parent, struct cfq_queue, p_node); 1697 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false)) 1698 return __cfqq; 1699 1700 if (blk_rq_pos(__cfqq->next_rq) < sector) 1701 node = rb_next(&__cfqq->p_node); 1702 else 1703 node = rb_prev(&__cfqq->p_node); 1704 if (!node) 1705 return NULL; 1706 1707 __cfqq = rb_entry(node, struct cfq_queue, p_node); 1708 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false)) 1709 return __cfqq; 1710 1711 return NULL; 1712} 1713 1714/* 1715 * cfqd - obvious 1716 * cur_cfqq - passed in so that we don't decide that the current queue is 1717 * closely cooperating with itself. 1718 * 1719 * So, basically we're assuming that that cur_cfqq has dispatched at least 1720 * one request, and that cfqd->last_position reflects a position on the disk 1721 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid 1722 * assumption. 1723 */ 1724static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, 1725 struct cfq_queue *cur_cfqq) 1726{ 1727 struct cfq_queue *cfqq; 1728 1729 if (!cfq_cfqq_sync(cur_cfqq)) 1730 return NULL; 1731 if (CFQQ_SEEKY(cur_cfqq)) 1732 return NULL; 1733 1734 /* 1735 * Don't search priority tree if it's the only queue in the group. 1736 */ 1737 if (cur_cfqq->cfqg->nr_cfqq == 1) 1738 return NULL; 1739 1740 /* 1741 * We should notice if some of the queues are cooperating, eg 1742 * working closely on the same area of the disk. In that case, 1743 * we can group them together and don't waste time idling. 1744 */ 1745 cfqq = cfqq_close(cfqd, cur_cfqq); 1746 if (!cfqq) 1747 return NULL; 1748 1749 /* If new queue belongs to different cfq_group, don't choose it */ 1750 if (cur_cfqq->cfqg != cfqq->cfqg) 1751 return NULL; 1752 1753 /* 1754 * It only makes sense to merge sync queues. 1755 */ 1756 if (!cfq_cfqq_sync(cfqq)) 1757 return NULL; 1758 if (CFQQ_SEEKY(cfqq)) 1759 return NULL; 1760 1761 /* 1762 * Do not merge queues of different priority classes 1763 */ 1764 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq)) 1765 return NULL; 1766 1767 return cfqq; 1768} 1769 1770/* 1771 * Determine whether we should enforce idle window for this queue. 1772 */ 1773 1774static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1775{ 1776 enum wl_prio_t prio = cfqq_prio(cfqq); 1777 struct cfq_rb_root *service_tree = cfqq->service_tree; 1778 1779 BUG_ON(!service_tree); 1780 BUG_ON(!service_tree->count); 1781 1782 /* We never do for idle class queues. */ 1783 if (prio == IDLE_WORKLOAD) 1784 return false; 1785 1786 /* We do for queues that were marked with idle window flag. */ 1787 if (cfq_cfqq_idle_window(cfqq) && 1788 !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)) 1789 return true; 1790 1791 /* 1792 * Otherwise, we do only if they are the last ones 1793 * in their service tree. 1794 */ 1795 return service_tree->count == 1 && cfq_cfqq_sync(cfqq); 1796} 1797 1798static void cfq_arm_slice_timer(struct cfq_data *cfqd) 1799{ 1800 struct cfq_queue *cfqq = cfqd->active_queue; 1801 struct cfq_io_context *cic; 1802 unsigned long sl; 1803 1804 /* 1805 * SSD device without seek penalty, disable idling. But only do so 1806 * for devices that support queuing, otherwise we still have a problem 1807 * with sync vs async workloads. 1808 */ 1809 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 1810 return; 1811 1812 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 1813 WARN_ON(cfq_cfqq_slice_new(cfqq)); 1814 1815 /* 1816 * idle is disabled, either manually or by past process history 1817 */ 1818 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq)) 1819 return; 1820 1821 /* 1822 * still active requests from this queue, don't idle 1823 */ 1824 if (cfqq->dispatched) 1825 return; 1826 1827 /* 1828 * task has exited, don't wait 1829 */ 1830 cic = cfqd->active_cic; 1831 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 1832 return; 1833 1834 /* 1835 * If our average think time is larger than the remaining time 1836 * slice, then don't idle. This avoids overrunning the allotted 1837 * time slice. 1838 */ 1839 if (sample_valid(cic->ttime_samples) && 1840 (cfqq->slice_end - jiffies < cic->ttime_mean)) 1841 return; 1842 1843 cfq_mark_cfqq_wait_request(cfqq); 1844 1845 sl = cfqd->cfq_slice_idle; 1846 1847 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 1848 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl); 1849} 1850 1851/* 1852 * Move request from internal lists to the request queue dispatch list. 1853 */ 1854static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 1855{ 1856 struct cfq_data *cfqd = q->elevator->elevator_data; 1857 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1858 1859 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 1860 1861 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq); 1862 cfq_remove_request(rq); 1863 cfqq->dispatched++; 1864 elv_dispatch_sort(q, rq); 1865 1866 if (cfq_cfqq_sync(cfqq)) 1867 cfqd->sync_flight++; 1868 cfqq->nr_sectors += blk_rq_sectors(rq); 1869} 1870 1871/* 1872 * return expired entry, or NULL to just start from scratch in rbtree 1873 */ 1874static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 1875{ 1876 struct request *rq = NULL; 1877 1878 if (cfq_cfqq_fifo_expire(cfqq)) 1879 return NULL; 1880 1881 cfq_mark_cfqq_fifo_expire(cfqq); 1882 1883 if (list_empty(&cfqq->fifo)) 1884 return NULL; 1885 1886 rq = rq_entry_fifo(cfqq->fifo.next); 1887 if (time_before(jiffies, rq_fifo_time(rq))) 1888 rq = NULL; 1889 1890 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); 1891 return rq; 1892} 1893 1894static inline int 1895cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1896{ 1897 const int base_rq = cfqd->cfq_slice_async_rq; 1898 1899 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 1900 1901 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 1902} 1903 1904/* 1905 * Must be called with the queue_lock held. 1906 */ 1907static int cfqq_process_refs(struct cfq_queue *cfqq) 1908{ 1909 int process_refs, io_refs; 1910 1911 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE]; 1912 process_refs = atomic_read(&cfqq->ref) - io_refs; 1913 BUG_ON(process_refs < 0); 1914 return process_refs; 1915} 1916 1917static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) 1918{ 1919 int process_refs, new_process_refs; 1920 struct cfq_queue *__cfqq; 1921 1922 /* Avoid a circular list and skip interim queue merges */ 1923 while ((__cfqq = new_cfqq->new_cfqq)) { 1924 if (__cfqq == cfqq) 1925 return; 1926 new_cfqq = __cfqq; 1927 } 1928 1929 process_refs = cfqq_process_refs(cfqq); 1930 /* 1931 * If the process for the cfqq has gone away, there is no 1932 * sense in merging the queues. 1933 */ 1934 if (process_refs == 0) 1935 return; 1936 1937 /* 1938 * Merge in the direction of the lesser amount of work. 1939 */ 1940 new_process_refs = cfqq_process_refs(new_cfqq); 1941 if (new_process_refs >= process_refs) { 1942 cfqq->new_cfqq = new_cfqq; 1943 atomic_add(process_refs, &new_cfqq->ref); 1944 } else { 1945 new_cfqq->new_cfqq = cfqq; 1946 atomic_add(new_process_refs, &cfqq->ref); 1947 } 1948} 1949 1950static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, 1951 struct cfq_group *cfqg, enum wl_prio_t prio) 1952{ 1953 struct cfq_queue *queue; 1954 int i; 1955 bool key_valid = false; 1956 unsigned long lowest_key = 0; 1957 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; 1958 1959 for (i = 0; i <= SYNC_WORKLOAD; ++i) { 1960 /* select the one with lowest rb_key */ 1961 queue = cfq_rb_first(service_tree_for(cfqg, prio, i)); 1962 if (queue && 1963 (!key_valid || time_before(queue->rb_key, lowest_key))) { 1964 lowest_key = queue->rb_key; 1965 cur_best = i; 1966 key_valid = true; 1967 } 1968 } 1969 1970 return cur_best; 1971} 1972 1973static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg) 1974{ 1975 unsigned slice; 1976 unsigned count; 1977 struct cfq_rb_root *st; 1978 unsigned group_slice; 1979 1980 if (!cfqg) { 1981 cfqd->serving_prio = IDLE_WORKLOAD; 1982 cfqd->workload_expires = jiffies + 1; 1983 return; 1984 } 1985 1986 /* Choose next priority. RT > BE > IDLE */ 1987 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg)) 1988 cfqd->serving_prio = RT_WORKLOAD; 1989 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg)) 1990 cfqd->serving_prio = BE_WORKLOAD; 1991 else { 1992 cfqd->serving_prio = IDLE_WORKLOAD; 1993 cfqd->workload_expires = jiffies + 1; 1994 return; 1995 } 1996 1997 /* 1998 * For RT and BE, we have to choose also the type 1999 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload 2000 * expiration time 2001 */ 2002 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); 2003 count = st->count; 2004 2005 /* 2006 * check workload expiration, and that we still have other queues ready 2007 */ 2008 if (count && !time_after(jiffies, cfqd->workload_expires)) 2009 return; 2010 2011 /* otherwise select new workload type */ 2012 cfqd->serving_type = 2013 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio); 2014 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); 2015 count = st->count; 2016 2017 /* 2018 * the workload slice is computed as a fraction of target latency 2019 * proportional to the number of queues in that workload, over 2020 * all the queues in the same priority class 2021 */ 2022 group_slice = cfq_group_slice(cfqd, cfqg); 2023 2024 slice = group_slice * count / 2025 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio], 2026 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg)); 2027 2028 if (cfqd->serving_type == ASYNC_WORKLOAD) { 2029 unsigned int tmp; 2030 2031 /* 2032 * Async queues are currently system wide. Just taking 2033 * proportion of queues with-in same group will lead to higher 2034 * async ratio system wide as generally root group is going 2035 * to have higher weight. A more accurate thing would be to 2036 * calculate system wide asnc/sync ratio. 2037 */ 2038 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg); 2039 tmp = tmp/cfqd->busy_queues; 2040 slice = min_t(unsigned, slice, tmp); 2041 2042 /* async workload slice is scaled down according to 2043 * the sync/async slice ratio. */ 2044 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1]; 2045 } else 2046 /* sync workload slice is at least 2 * cfq_slice_idle */ 2047 slice = max(slice, 2 * cfqd->cfq_slice_idle); 2048 2049 slice = max_t(unsigned, slice, CFQ_MIN_TT); 2050 cfqd->workload_expires = jiffies + slice; 2051 cfqd->noidle_tree_requires_idle = false; 2052} 2053 2054static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd) 2055{ 2056 struct cfq_rb_root *st = &cfqd->grp_service_tree; 2057 struct cfq_group *cfqg; 2058 2059 if (RB_EMPTY_ROOT(&st->rb)) 2060 return NULL; 2061 cfqg = cfq_rb_first_group(st); 2062 st->active = &cfqg->rb_node; 2063 update_min_vdisktime(st); 2064 return cfqg; 2065} 2066 2067static void cfq_choose_cfqg(struct cfq_data *cfqd) 2068{ 2069 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd); 2070 2071 cfqd->serving_group = cfqg; 2072 2073 /* Restore the workload type data */ 2074 if (cfqg->saved_workload_slice) { 2075 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice; 2076 cfqd->serving_type = cfqg->saved_workload; 2077 cfqd->serving_prio = cfqg->saved_serving_prio; 2078 } else 2079 cfqd->workload_expires = jiffies - 1; 2080 2081 choose_service_tree(cfqd, cfqg); 2082} 2083 2084/* 2085 * Select a queue for service. If we have a current active queue, 2086 * check whether to continue servicing it, or retrieve and set a new one. 2087 */ 2088static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 2089{ 2090 struct cfq_queue *cfqq, *new_cfqq = NULL; 2091 2092 cfqq = cfqd->active_queue; 2093 if (!cfqq) 2094 goto new_queue; 2095 2096 if (!cfqd->rq_queued) 2097 return NULL; 2098 2099 /* 2100 * We were waiting for group to get backlogged. Expire the queue 2101 */ 2102 if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list)) 2103 goto expire; 2104 2105 /* 2106 * The active queue has run out of time, expire it and select new. 2107 */ 2108 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) { 2109 /* 2110 * If slice had not expired at the completion of last request 2111 * we might not have turned on wait_busy flag. Don't expire 2112 * the queue yet. Allow the group to get backlogged. 2113 * 2114 * The very fact that we have used the slice, that means we 2115 * have been idling all along on this queue and it should be 2116 * ok to wait for this request to complete. 2117 */ 2118 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list) 2119 && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) { 2120 cfqq = NULL; 2121 goto keep_queue; 2122 } else 2123 goto expire; 2124 } 2125 2126 /* 2127 * The active queue has requests and isn't expired, allow it to 2128 * dispatch. 2129 */ 2130 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 2131 goto keep_queue; 2132 2133 /* 2134 * If another queue has a request waiting within our mean seek 2135 * distance, let it run. The expire code will check for close 2136 * cooperators and put the close queue at the front of the service 2137 * tree. If possible, merge the expiring queue with the new cfqq. 2138 */ 2139 new_cfqq = cfq_close_cooperator(cfqd, cfqq); 2140 if (new_cfqq) { 2141 if (!cfqq->new_cfqq) 2142 cfq_setup_merge(cfqq, new_cfqq); 2143 goto expire; 2144 } 2145 2146 /* 2147 * No requests pending. If the active queue still has requests in 2148 * flight or is idling for a new request, allow either of these 2149 * conditions to happen (or time out) before selecting a new queue. 2150 */ 2151 if (timer_pending(&cfqd->idle_slice_timer) || 2152 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) { 2153 cfqq = NULL; 2154 goto keep_queue; 2155 } 2156 2157expire: 2158 cfq_slice_expired(cfqd, 0); 2159new_queue: 2160 /* 2161 * Current queue expired. Check if we have to switch to a new 2162 * service tree 2163 */ 2164 if (!new_cfqq) 2165 cfq_choose_cfqg(cfqd); 2166 2167 cfqq = cfq_set_active_queue(cfqd, new_cfqq); 2168keep_queue: 2169 return cfqq; 2170} 2171 2172static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 2173{ 2174 int dispatched = 0; 2175 2176 while (cfqq->next_rq) { 2177 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 2178 dispatched++; 2179 } 2180 2181 BUG_ON(!list_empty(&cfqq->fifo)); 2182 2183 /* By default cfqq is not expired if it is empty. Do it explicitly */ 2184 __cfq_slice_expired(cfqq->cfqd, cfqq, 0); 2185 return dispatched; 2186} 2187 2188/* 2189 * Drain our current requests. Used for barriers and when switching 2190 * io schedulers on-the-fly. 2191 */ 2192static int cfq_forced_dispatch(struct cfq_data *cfqd) 2193{ 2194 struct cfq_queue *cfqq; 2195 int dispatched = 0; 2196 2197 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) 2198 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 2199 2200 cfq_slice_expired(cfqd, 0); 2201 BUG_ON(cfqd->busy_queues); 2202 2203 cfq_log(cfqd, "forced_dispatch=%d", dispatched); 2204 return dispatched; 2205} 2206 2207static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2208{ 2209 unsigned int max_dispatch; 2210 2211 /* 2212 * Drain async requests before we start sync IO 2213 */ 2214 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC]) 2215 return false; 2216 2217 /* 2218 * If this is an async queue and we have sync IO in flight, let it wait 2219 */ 2220 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 2221 return false; 2222 2223 max_dispatch = cfqd->cfq_quantum; 2224 if (cfq_class_idle(cfqq)) 2225 max_dispatch = 1; 2226 2227 /* 2228 * Does this cfqq already have too much IO in flight? 2229 */ 2230 if (cfqq->dispatched >= max_dispatch) { 2231 /* 2232 * idle queue must always only have a single IO in flight 2233 */ 2234 if (cfq_class_idle(cfqq)) 2235 return false; 2236 2237 /* 2238 * We have other queues, don't allow more IO from this one 2239 */ 2240 if (cfqd->busy_queues > 1) 2241 return false; 2242 2243 /* 2244 * Sole queue user, no limit 2245 */ 2246 max_dispatch = -1; 2247 } 2248 2249 /* 2250 * Async queues must wait a bit before being allowed dispatch. 2251 * We also ramp up the dispatch depth gradually for async IO, 2252 * based on the last sync IO we serviced 2253 */ 2254 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { 2255 unsigned long last_sync = jiffies - cfqd->last_delayed_sync; 2256 unsigned int depth; 2257 2258 depth = last_sync / cfqd->cfq_slice[1]; 2259 if (!depth && !cfqq->dispatched) 2260 depth = 1; 2261 if (depth < max_dispatch) 2262 max_dispatch = depth; 2263 } 2264 2265 /* 2266 * If we're below the current max, allow a dispatch 2267 */ 2268 return cfqq->dispatched < max_dispatch; 2269} 2270 2271/* 2272 * Dispatch a request from cfqq, moving them to the request queue 2273 * dispatch list. 2274 */ 2275static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2276{ 2277 struct request *rq; 2278 2279 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 2280 2281 if (!cfq_may_dispatch(cfqd, cfqq)) 2282 return false; 2283 2284 /* 2285 * follow expired path, else get first next available 2286 */ 2287 rq = cfq_check_fifo(cfqq); 2288 if (!rq) 2289 rq = cfqq->next_rq; 2290 2291 /* 2292 * insert request into driver dispatch list 2293 */ 2294 cfq_dispatch_insert(cfqd->queue, rq); 2295 2296 if (!cfqd->active_cic) { 2297 struct cfq_io_context *cic = RQ_CIC(rq); 2298 2299 atomic_long_inc(&cic->ioc->refcount); 2300 cfqd->active_cic = cic; 2301 } 2302 2303 return true; 2304} 2305 2306/* 2307 * Find the cfqq that we need to service and move a request from that to the 2308 * dispatch list 2309 */ 2310static int cfq_dispatch_requests(struct request_queue *q, int force) 2311{ 2312 struct cfq_data *cfqd = q->elevator->elevator_data; 2313 struct cfq_queue *cfqq; 2314 2315 if (!cfqd->busy_queues) 2316 return 0; 2317 2318 if (unlikely(force)) 2319 return cfq_forced_dispatch(cfqd); 2320 2321 cfqq = cfq_select_queue(cfqd); 2322 if (!cfqq) 2323 return 0; 2324 2325 /* 2326 * Dispatch a request from this cfqq, if it is allowed 2327 */ 2328 if (!cfq_dispatch_request(cfqd, cfqq)) 2329 return 0; 2330 2331 cfqq->slice_dispatch++; 2332 cfq_clear_cfqq_must_dispatch(cfqq); 2333 2334 /* 2335 * expire an async queue immediately if it has used up its slice. idle 2336 * queue always expire after 1 dispatch round. 2337 */ 2338 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 2339 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || 2340 cfq_class_idle(cfqq))) { 2341 cfqq->slice_end = jiffies + 1; 2342 cfq_slice_expired(cfqd, 0); 2343 } 2344 2345 cfq_log_cfqq(cfqd, cfqq, "dispatched a request"); 2346 return 1; 2347} 2348 2349/* 2350 * task holds one reference to the queue, dropped when task exits. each rq 2351 * in-flight on this queue also holds a reference, dropped when rq is freed. 2352 * 2353 * Each cfq queue took a reference on the parent group. Drop it now. 2354 * queue lock must be held here. 2355 */ 2356static void cfq_put_queue(struct cfq_queue *cfqq) 2357{ 2358 struct cfq_data *cfqd = cfqq->cfqd; 2359 struct cfq_group *cfqg, *orig_cfqg; 2360 2361 BUG_ON(atomic_read(&cfqq->ref) <= 0); 2362 2363 if (!atomic_dec_and_test(&cfqq->ref)) 2364 return; 2365 2366 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 2367 BUG_ON(rb_first(&cfqq->sort_list)); 2368 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 2369 cfqg = cfqq->cfqg; 2370 orig_cfqg = cfqq->orig_cfqg; 2371 2372 if (unlikely(cfqd->active_queue == cfqq)) { 2373 __cfq_slice_expired(cfqd, cfqq, 0); 2374 cfq_schedule_dispatch(cfqd); 2375 } 2376 2377 BUG_ON(cfq_cfqq_on_rr(cfqq)); 2378 kmem_cache_free(cfq_pool, cfqq); 2379 cfq_put_cfqg(cfqg); 2380 if (orig_cfqg) 2381 cfq_put_cfqg(orig_cfqg); 2382} 2383 2384/* 2385 * Must always be called with the rcu_read_lock() held 2386 */ 2387static void 2388__call_for_each_cic(struct io_context *ioc, 2389 void (*func)(struct io_context *, struct cfq_io_context *)) 2390{ 2391 struct cfq_io_context *cic; 2392 struct hlist_node *n; 2393 2394 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 2395 func(ioc, cic); 2396} 2397 2398/* 2399 * Call func for each cic attached to this ioc. 2400 */ 2401static void 2402call_for_each_cic(struct io_context *ioc, 2403 void (*func)(struct io_context *, struct cfq_io_context *)) 2404{ 2405 rcu_read_lock(); 2406 __call_for_each_cic(ioc, func); 2407 rcu_read_unlock(); 2408} 2409 2410static void cfq_cic_free_rcu(struct rcu_head *head) 2411{ 2412 struct cfq_io_context *cic; 2413 2414 cic = container_of(head, struct cfq_io_context, rcu_head); 2415 2416 kmem_cache_free(cfq_ioc_pool, cic); 2417 elv_ioc_count_dec(cfq_ioc_count); 2418 2419 if (ioc_gone) { 2420 /* 2421 * CFQ scheduler is exiting, grab exit lock and check 2422 * the pending io context count. If it hits zero, 2423 * complete ioc_gone and set it back to NULL 2424 */ 2425 spin_lock(&ioc_gone_lock); 2426 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) { 2427 complete(ioc_gone); 2428 ioc_gone = NULL; 2429 } 2430 spin_unlock(&ioc_gone_lock); 2431 } 2432} 2433 2434static void cfq_cic_free(struct cfq_io_context *cic) 2435{ 2436 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 2437} 2438 2439static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 2440{ 2441 unsigned long flags; 2442 2443 BUG_ON(!cic->dead_key); 2444 2445 spin_lock_irqsave(&ioc->lock, flags); 2446 radix_tree_delete(&ioc->radix_root, cic->dead_key); 2447 hlist_del_rcu(&cic->cic_list); 2448 spin_unlock_irqrestore(&ioc->lock, flags); 2449 2450 cfq_cic_free(cic); 2451} 2452 2453/* 2454 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 2455 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 2456 * and ->trim() which is called with the task lock held 2457 */ 2458static void cfq_free_io_context(struct io_context *ioc) 2459{ 2460 /* 2461 * ioc->refcount is zero here, or we are called from elv_unregister(), 2462 * so no more cic's are allowed to be linked into this ioc. So it 2463 * should be ok to iterate over the known list, we will see all cic's 2464 * since no new ones are added. 2465 */ 2466 __call_for_each_cic(ioc, cic_free_func); 2467} 2468 2469static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2470{ 2471 struct cfq_queue *__cfqq, *next; 2472 2473 if (unlikely(cfqq == cfqd->active_queue)) { 2474 __cfq_slice_expired(cfqd, cfqq, 0); 2475 cfq_schedule_dispatch(cfqd); 2476 } 2477 2478 /* 2479 * If this queue was scheduled to merge with another queue, be 2480 * sure to drop the reference taken on that queue (and others in 2481 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs. 2482 */ 2483 __cfqq = cfqq->new_cfqq; 2484 while (__cfqq) { 2485 if (__cfqq == cfqq) { 2486 WARN(1, "cfqq->new_cfqq loop detected\n"); 2487 break; 2488 } 2489 next = __cfqq->new_cfqq; 2490 cfq_put_queue(__cfqq); 2491 __cfqq = next; 2492 } 2493 2494 cfq_put_queue(cfqq); 2495} 2496 2497static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 2498 struct cfq_io_context *cic) 2499{ 2500 struct io_context *ioc = cic->ioc; 2501 2502 list_del_init(&cic->queue_list); 2503 2504 /* 2505 * Make sure key == NULL is seen for dead queues 2506 */ 2507 smp_wmb(); 2508 cic->dead_key = (unsigned long) cic->key; 2509 cic->key = NULL; 2510 2511 if (ioc->ioc_data == cic) 2512 rcu_assign_pointer(ioc->ioc_data, NULL); 2513 2514 if (cic->cfqq[BLK_RW_ASYNC]) { 2515 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); 2516 cic->cfqq[BLK_RW_ASYNC] = NULL; 2517 } 2518 2519 if (cic->cfqq[BLK_RW_SYNC]) { 2520 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); 2521 cic->cfqq[BLK_RW_SYNC] = NULL; 2522 } 2523} 2524 2525static void cfq_exit_single_io_context(struct io_context *ioc, 2526 struct cfq_io_context *cic) 2527{ 2528 struct cfq_data *cfqd = cic->key; 2529 2530 if (cfqd) { 2531 struct request_queue *q = cfqd->queue; 2532 unsigned long flags; 2533 2534 spin_lock_irqsave(q->queue_lock, flags); 2535 2536 /* 2537 * Ensure we get a fresh copy of the ->key to prevent 2538 * race between exiting task and queue 2539 */ 2540 smp_read_barrier_depends(); 2541 if (cic->key) 2542 __cfq_exit_single_io_context(cfqd, cic); 2543 2544 spin_unlock_irqrestore(q->queue_lock, flags); 2545 } 2546} 2547 2548/* 2549 * The process that ioc belongs to has exited, we need to clean up 2550 * and put the internal structures we have that belongs to that process. 2551 */ 2552static void cfq_exit_io_context(struct io_context *ioc) 2553{ 2554 call_for_each_cic(ioc, cfq_exit_single_io_context); 2555} 2556 2557static struct cfq_io_context * 2558cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 2559{ 2560 struct cfq_io_context *cic; 2561 2562 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 2563 cfqd->queue->node); 2564 if (cic) { 2565 cic->last_end_request = jiffies; 2566 INIT_LIST_HEAD(&cic->queue_list); 2567 INIT_HLIST_NODE(&cic->cic_list); 2568 cic->dtor = cfq_free_io_context; 2569 cic->exit = cfq_exit_io_context; 2570 elv_ioc_count_inc(cfq_ioc_count); 2571 } 2572 2573 return cic; 2574} 2575 2576static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 2577{ 2578 struct task_struct *tsk = current; 2579 int ioprio_class; 2580 2581 if (!cfq_cfqq_prio_changed(cfqq)) 2582 return; 2583 2584 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 2585 switch (ioprio_class) { 2586 default: 2587 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 2588 case IOPRIO_CLASS_NONE: 2589 /* 2590 * no prio set, inherit CPU scheduling settings 2591 */ 2592 cfqq->ioprio = task_nice_ioprio(tsk); 2593 cfqq->ioprio_class = task_nice_ioclass(tsk); 2594 break; 2595 case IOPRIO_CLASS_RT: 2596 cfqq->ioprio = task_ioprio(ioc); 2597 cfqq->ioprio_class = IOPRIO_CLASS_RT; 2598 break; 2599 case IOPRIO_CLASS_BE: 2600 cfqq->ioprio = task_ioprio(ioc); 2601 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2602 break; 2603 case IOPRIO_CLASS_IDLE: 2604 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 2605 cfqq->ioprio = 7; 2606 cfq_clear_cfqq_idle_window(cfqq); 2607 break; 2608 } 2609 2610 /* 2611 * keep track of original prio settings in case we have to temporarily 2612 * elevate the priority of this queue 2613 */ 2614 cfqq->org_ioprio = cfqq->ioprio; 2615 cfqq->org_ioprio_class = cfqq->ioprio_class; 2616 cfq_clear_cfqq_prio_changed(cfqq); 2617} 2618 2619static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 2620{ 2621 struct cfq_data *cfqd = cic->key; 2622 struct cfq_queue *cfqq; 2623 unsigned long flags; 2624 2625 if (unlikely(!cfqd)) 2626 return; 2627 2628 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2629 2630 cfqq = cic->cfqq[BLK_RW_ASYNC]; 2631 if (cfqq) { 2632 struct cfq_queue *new_cfqq; 2633 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, 2634 GFP_ATOMIC); 2635 if (new_cfqq) { 2636 cic->cfqq[BLK_RW_ASYNC] = new_cfqq; 2637 cfq_put_queue(cfqq); 2638 } 2639 } 2640 2641 cfqq = cic->cfqq[BLK_RW_SYNC]; 2642 if (cfqq) 2643 cfq_mark_cfqq_prio_changed(cfqq); 2644 2645 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2646} 2647 2648static void cfq_ioc_set_ioprio(struct io_context *ioc) 2649{ 2650 call_for_each_cic(ioc, changed_ioprio); 2651 ioc->ioprio_changed = 0; 2652} 2653 2654static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2655 pid_t pid, bool is_sync) 2656{ 2657 RB_CLEAR_NODE(&cfqq->rb_node); 2658 RB_CLEAR_NODE(&cfqq->p_node); 2659 INIT_LIST_HEAD(&cfqq->fifo); 2660 2661 atomic_set(&cfqq->ref, 0); 2662 cfqq->cfqd = cfqd; 2663 2664 cfq_mark_cfqq_prio_changed(cfqq); 2665 2666 if (is_sync) { 2667 if (!cfq_class_idle(cfqq)) 2668 cfq_mark_cfqq_idle_window(cfqq); 2669 cfq_mark_cfqq_sync(cfqq); 2670 } 2671 cfqq->pid = pid; 2672} 2673 2674#ifdef CONFIG_CFQ_GROUP_IOSCHED 2675static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic) 2676{ 2677 struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1); 2678 struct cfq_data *cfqd = cic->key; 2679 unsigned long flags; 2680 struct request_queue *q; 2681 2682 if (unlikely(!cfqd)) 2683 return; 2684 2685 q = cfqd->queue; 2686 2687 spin_lock_irqsave(q->queue_lock, flags); 2688 2689 if (sync_cfqq) { 2690 /* 2691 * Drop reference to sync queue. A new sync queue will be 2692 * assigned in new group upon arrival of a fresh request. 2693 */ 2694 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup"); 2695 cic_set_cfqq(cic, NULL, 1); 2696 cfq_put_queue(sync_cfqq); 2697 } 2698 2699 spin_unlock_irqrestore(q->queue_lock, flags); 2700} 2701 2702static void cfq_ioc_set_cgroup(struct io_context *ioc) 2703{ 2704 call_for_each_cic(ioc, changed_cgroup); 2705 ioc->cgroup_changed = 0; 2706} 2707#endif /* CONFIG_CFQ_GROUP_IOSCHED */ 2708 2709static struct cfq_queue * 2710cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, 2711 struct io_context *ioc, gfp_t gfp_mask) 2712{ 2713 struct cfq_queue *cfqq, *new_cfqq = NULL; 2714 struct cfq_io_context *cic; 2715 struct cfq_group *cfqg; 2716 2717retry: 2718 cfqg = cfq_get_cfqg(cfqd, 1); 2719 cic = cfq_cic_lookup(cfqd, ioc); 2720 /* cic always exists here */ 2721 cfqq = cic_to_cfqq(cic, is_sync); 2722 2723 /* 2724 * Always try a new alloc if we fell back to the OOM cfqq 2725 * originally, since it should just be a temporary situation. 2726 */ 2727 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 2728 cfqq = NULL; 2729 if (new_cfqq) { 2730 cfqq = new_cfqq; 2731 new_cfqq = NULL; 2732 } else if (gfp_mask & __GFP_WAIT) { 2733 spin_unlock_irq(cfqd->queue->queue_lock); 2734 new_cfqq = kmem_cache_alloc_node(cfq_pool, 2735 gfp_mask | __GFP_ZERO, 2736 cfqd->queue->node); 2737 spin_lock_irq(cfqd->queue->queue_lock); 2738 if (new_cfqq) 2739 goto retry; 2740 } else { 2741 cfqq = kmem_cache_alloc_node(cfq_pool, 2742 gfp_mask | __GFP_ZERO, 2743 cfqd->queue->node); 2744 } 2745 2746 if (cfqq) { 2747 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); 2748 cfq_init_prio_data(cfqq, ioc); 2749 cfq_link_cfqq_cfqg(cfqq, cfqg); 2750 cfq_log_cfqq(cfqd, cfqq, "alloced"); 2751 } else 2752 cfqq = &cfqd->oom_cfqq; 2753 } 2754 2755 if (new_cfqq) 2756 kmem_cache_free(cfq_pool, new_cfqq); 2757 2758 return cfqq; 2759} 2760 2761static struct cfq_queue ** 2762cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 2763{ 2764 switch (ioprio_class) { 2765 case IOPRIO_CLASS_RT: 2766 return &cfqd->async_cfqq[0][ioprio]; 2767 case IOPRIO_CLASS_BE: 2768 return &cfqd->async_cfqq[1][ioprio]; 2769 case IOPRIO_CLASS_IDLE: 2770 return &cfqd->async_idle_cfqq; 2771 default: 2772 BUG(); 2773 } 2774} 2775 2776static struct cfq_queue * 2777cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc, 2778 gfp_t gfp_mask) 2779{ 2780 const int ioprio = task_ioprio(ioc); 2781 const int ioprio_class = task_ioprio_class(ioc); 2782 struct cfq_queue **async_cfqq = NULL; 2783 struct cfq_queue *cfqq = NULL; 2784 2785 if (!is_sync) { 2786 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 2787 cfqq = *async_cfqq; 2788 } 2789 2790 if (!cfqq) 2791 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 2792 2793 /* 2794 * pin the queue now that it's allocated, scheduler exit will prune it 2795 */ 2796 if (!is_sync && !(*async_cfqq)) { 2797 atomic_inc(&cfqq->ref); 2798 *async_cfqq = cfqq; 2799 } 2800 2801 atomic_inc(&cfqq->ref); 2802 return cfqq; 2803} 2804 2805/* 2806 * We drop cfq io contexts lazily, so we may find a dead one. 2807 */ 2808static void 2809cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 2810 struct cfq_io_context *cic) 2811{ 2812 unsigned long flags; 2813 2814 WARN_ON(!list_empty(&cic->queue_list)); 2815 2816 spin_lock_irqsave(&ioc->lock, flags); 2817 2818 BUG_ON(ioc->ioc_data == cic); 2819 2820 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 2821 hlist_del_rcu(&cic->cic_list); 2822 spin_unlock_irqrestore(&ioc->lock, flags); 2823 2824 cfq_cic_free(cic); 2825} 2826 2827static struct cfq_io_context * 2828cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 2829{ 2830 struct cfq_io_context *cic; 2831 unsigned long flags; 2832 void *k; 2833 2834 if (unlikely(!ioc)) 2835 return NULL; 2836 2837 rcu_read_lock(); 2838 2839 /* 2840 * we maintain a last-hit cache, to avoid browsing over the tree 2841 */ 2842 cic = rcu_dereference(ioc->ioc_data); 2843 if (cic && cic->key == cfqd) { 2844 rcu_read_unlock(); 2845 return cic; 2846 } 2847 2848 do { 2849 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 2850 rcu_read_unlock(); 2851 if (!cic) 2852 break; 2853 /* ->key must be copied to avoid race with cfq_exit_queue() */ 2854 k = cic->key; 2855 if (unlikely(!k)) { 2856 cfq_drop_dead_cic(cfqd, ioc, cic); 2857 rcu_read_lock(); 2858 continue; 2859 } 2860 2861 spin_lock_irqsave(&ioc->lock, flags); 2862 rcu_assign_pointer(ioc->ioc_data, cic); 2863 spin_unlock_irqrestore(&ioc->lock, flags); 2864 break; 2865 } while (1); 2866 2867 return cic; 2868} 2869 2870/* 2871 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 2872 * the process specific cfq io context when entered from the block layer. 2873 * Also adds the cic to a per-cfqd list, used when this queue is removed. 2874 */ 2875static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 2876 struct cfq_io_context *cic, gfp_t gfp_mask) 2877{ 2878 unsigned long flags; 2879 int ret; 2880 2881 ret = radix_tree_preload(gfp_mask); 2882 if (!ret) { 2883 cic->ioc = ioc; 2884 cic->key = cfqd; 2885 2886 spin_lock_irqsave(&ioc->lock, flags); 2887 ret = radix_tree_insert(&ioc->radix_root, 2888 (unsigned long) cfqd, cic); 2889 if (!ret) 2890 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 2891 spin_unlock_irqrestore(&ioc->lock, flags); 2892 2893 radix_tree_preload_end(); 2894 2895 if (!ret) { 2896 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2897 list_add(&cic->queue_list, &cfqd->cic_list); 2898 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2899 } 2900 } 2901 2902 if (ret) 2903 printk(KERN_ERR "cfq: cic link failed!\n"); 2904 2905 return ret; 2906} 2907 2908/* 2909 * Setup general io context and cfq io context. There can be several cfq 2910 * io contexts per general io context, if this process is doing io to more 2911 * than one device managed by cfq. 2912 */ 2913static struct cfq_io_context * 2914cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 2915{ 2916 struct io_context *ioc = NULL; 2917 struct cfq_io_context *cic; 2918 2919 might_sleep_if(gfp_mask & __GFP_WAIT); 2920 2921 ioc = get_io_context(gfp_mask, cfqd->queue->node); 2922 if (!ioc) 2923 return NULL; 2924 2925 cic = cfq_cic_lookup(cfqd, ioc); 2926 if (cic) 2927 goto out; 2928 2929 cic = cfq_alloc_io_context(cfqd, gfp_mask); 2930 if (cic == NULL) 2931 goto err; 2932 2933 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 2934 goto err_free; 2935 2936out: 2937 smp_read_barrier_depends(); 2938 if (unlikely(ioc->ioprio_changed)) 2939 cfq_ioc_set_ioprio(ioc); 2940 2941#ifdef CONFIG_CFQ_GROUP_IOSCHED 2942 if (unlikely(ioc->cgroup_changed)) 2943 cfq_ioc_set_cgroup(ioc); 2944#endif 2945 return cic; 2946err_free: 2947 cfq_cic_free(cic); 2948err: 2949 put_io_context(ioc); 2950 return NULL; 2951} 2952 2953static void 2954cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 2955{ 2956 unsigned long elapsed = jiffies - cic->last_end_request; 2957 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 2958 2959 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 2960 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 2961 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 2962} 2963 2964static void 2965cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2966 struct request *rq) 2967{ 2968 sector_t sdist = 0; 2969 sector_t n_sec = blk_rq_sectors(rq); 2970 if (cfqq->last_request_pos) { 2971 if (cfqq->last_request_pos < blk_rq_pos(rq)) 2972 sdist = blk_rq_pos(rq) - cfqq->last_request_pos; 2973 else 2974 sdist = cfqq->last_request_pos - blk_rq_pos(rq); 2975 } 2976 2977 cfqq->seek_history <<= 1; 2978 if (blk_queue_nonrot(cfqd->queue)) 2979 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT); 2980 else 2981 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR); 2982} 2983 2984/* 2985 * Disable idle window if the process thinks too long or seeks so much that 2986 * it doesn't matter 2987 */ 2988static void 2989cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2990 struct cfq_io_context *cic) 2991{ 2992 int old_idle, enable_idle; 2993 2994 /* 2995 * Don't idle for async or idle io prio class 2996 */ 2997 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 2998 return; 2999 3000 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 3001 3002 if (cfqq->queued[0] + cfqq->queued[1] >= 4) 3003 cfq_mark_cfqq_deep(cfqq); 3004 3005 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 3006 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq))) 3007 enable_idle = 0; 3008 else if (sample_valid(cic->ttime_samples)) { 3009 if (cic->ttime_mean > cfqd->cfq_slice_idle) 3010 enable_idle = 0; 3011 else 3012 enable_idle = 1; 3013 } 3014 3015 if (old_idle != enable_idle) { 3016 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 3017 if (enable_idle) 3018 cfq_mark_cfqq_idle_window(cfqq); 3019 else 3020 cfq_clear_cfqq_idle_window(cfqq); 3021 } 3022} 3023 3024/* 3025 * Check if new_cfqq should preempt the currently active queue. Return 0 for 3026 * no or if we aren't sure, a 1 will cause a preempt. 3027 */ 3028static bool 3029cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 3030 struct request *rq) 3031{ 3032 struct cfq_queue *cfqq; 3033 3034 cfqq = cfqd->active_queue; 3035 if (!cfqq) 3036 return false; 3037 3038 if (cfq_class_idle(new_cfqq)) 3039 return false; 3040 3041 if (cfq_class_idle(cfqq)) 3042 return true; 3043 3044 /* 3045 * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice. 3046 */ 3047 if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq)) 3048 return false; 3049 3050 /* 3051 * if the new request is sync, but the currently running queue is 3052 * not, let the sync request have priority. 3053 */ 3054 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 3055 return true; 3056 3057 if (new_cfqq->cfqg != cfqq->cfqg) 3058 return false; 3059 3060 if (cfq_slice_used(cfqq)) 3061 return true; 3062 3063 /* Allow preemption only if we are idling on sync-noidle tree */ 3064 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && 3065 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && 3066 new_cfqq->service_tree->count == 2 && 3067 RB_EMPTY_ROOT(&cfqq->sort_list)) 3068 return true; 3069 3070 /* 3071 * So both queues are sync. Let the new request get disk time if 3072 * it's a metadata request and the current queue is doing regular IO. 3073 */ 3074 if (rq_is_meta(rq) && !cfqq->meta_pending) 3075 return true; 3076 3077 /* 3078 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 3079 */ 3080 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 3081 return true; 3082 3083 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 3084 return false; 3085 3086 /* 3087 * if this request is as-good as one we would expect from the 3088 * current cfqq, let it preempt 3089 */ 3090 if (cfq_rq_close(cfqd, cfqq, rq, true)) 3091 return true; 3092 3093 return false; 3094} 3095 3096/* 3097 * cfqq preempts the active queue. if we allowed preempt with no slice left, 3098 * let it have half of its nominal slice. 3099 */ 3100static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 3101{ 3102 cfq_log_cfqq(cfqd, cfqq, "preempt"); 3103 cfq_slice_expired(cfqd, 1); 3104 3105 /* 3106 * Put the new queue at the front of the of the current list, 3107 * so we know that it will be selected next. 3108 */ 3109 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 3110 3111 cfq_service_tree_add(cfqd, cfqq, 1); 3112 3113 cfqq->slice_end = 0; 3114 cfq_mark_cfqq_slice_new(cfqq); 3115} 3116 3117/* 3118 * Called when a new fs request (rq) is added (to cfqq). Check if there's 3119 * something we should do about it 3120 */ 3121static void 3122cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 3123 struct request *rq) 3124{ 3125 struct cfq_io_context *cic = RQ_CIC(rq); 3126 3127 cfqd->rq_queued++; 3128 if (rq_is_meta(rq)) 3129 cfqq->meta_pending++; 3130 3131 cfq_update_io_thinktime(cfqd, cic); 3132 cfq_update_io_seektime(cfqd, cfqq, rq); 3133 cfq_update_idle_window(cfqd, cfqq, cic); 3134 3135 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); 3136 3137 if (cfqq == cfqd->active_queue) { 3138 /* 3139 * Remember that we saw a request from this process, but 3140 * don't start queuing just yet. Otherwise we risk seeing lots 3141 * of tiny requests, because we disrupt the normal plugging 3142 * and merging. If the request is already larger than a single 3143 * page, let it rip immediately. For that case we assume that 3144 * merging is already done. Ditto for a busy system that 3145 * has other work pending, don't risk delaying until the 3146 * idle timer unplug to continue working. 3147 */ 3148 if (cfq_cfqq_wait_request(cfqq)) { 3149 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || 3150 cfqd->busy_queues > 1) { 3151 del_timer(&cfqd->idle_slice_timer); 3152 cfq_clear_cfqq_wait_request(cfqq); 3153 __blk_run_queue(cfqd->queue); 3154 } else 3155 cfq_mark_cfqq_must_dispatch(cfqq); 3156 } 3157 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 3158 /* 3159 * not the active queue - expire current slice if it is 3160 * idle and has expired it's mean thinktime or this new queue 3161 * has some old slice time left and is of higher priority or 3162 * this new queue is RT and the current one is BE 3163 */ 3164 cfq_preempt_queue(cfqd, cfqq); 3165 __blk_run_queue(cfqd->queue); 3166 } 3167} 3168 3169static void cfq_insert_request(struct request_queue *q, struct request *rq) 3170{ 3171 struct cfq_data *cfqd = q->elevator->elevator_data; 3172 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3173 3174 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 3175 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 3176 3177 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]); 3178 list_add_tail(&rq->queuelist, &cfqq->fifo); 3179 cfq_add_rq_rb(rq); 3180 3181 cfq_rq_enqueued(cfqd, cfqq, rq); 3182} 3183 3184/* 3185 * Update hw_tag based on peak queue depth over 50 samples under 3186 * sufficient load. 3187 */ 3188static void cfq_update_hw_tag(struct cfq_data *cfqd) 3189{ 3190 struct cfq_queue *cfqq = cfqd->active_queue; 3191 3192 if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth) 3193 cfqd->hw_tag_est_depth = rq_in_driver(cfqd); 3194 3195 if (cfqd->hw_tag == 1) 3196 return; 3197 3198 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 3199 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN) 3200 return; 3201 3202 /* 3203 * If active queue hasn't enough requests and can idle, cfq might not 3204 * dispatch sufficient requests to hardware. Don't zero hw_tag in this 3205 * case 3206 */ 3207 if (cfqq && cfq_cfqq_idle_window(cfqq) && 3208 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] < 3209 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN) 3210 return; 3211 3212 if (cfqd->hw_tag_samples++ < 50) 3213 return; 3214 3215 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN) 3216 cfqd->hw_tag = 1; 3217 else 3218 cfqd->hw_tag = 0; 3219} 3220 3221static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq) 3222{ 3223 struct cfq_io_context *cic = cfqd->active_cic; 3224 3225 /* If there are other queues in the group, don't wait */ 3226 if (cfqq->cfqg->nr_cfqq > 1) 3227 return false; 3228 3229 if (cfq_slice_used(cfqq)) 3230 return true; 3231 3232 /* if slice left is less than think time, wait busy */ 3233 if (cic && sample_valid(cic->ttime_samples) 3234 && (cfqq->slice_end - jiffies < cic->ttime_mean)) 3235 return true; 3236 3237 /* 3238 * If think times is less than a jiffy than ttime_mean=0 and above 3239 * will not be true. It might happen that slice has not expired yet 3240 * but will expire soon (4-5 ns) during select_queue(). To cover the 3241 * case where think time is less than a jiffy, mark the queue wait 3242 * busy if only 1 jiffy is left in the slice. 3243 */ 3244 if (cfqq->slice_end - jiffies == 1) 3245 return true; 3246 3247 return false; 3248} 3249 3250static void cfq_completed_request(struct request_queue *q, struct request *rq) 3251{ 3252 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3253 struct cfq_data *cfqd = cfqq->cfqd; 3254 const int sync = rq_is_sync(rq); 3255 unsigned long now; 3256 3257 now = jiffies; 3258 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq)); 3259 3260 cfq_update_hw_tag(cfqd); 3261 3262 WARN_ON(!cfqd->rq_in_driver[sync]); 3263 WARN_ON(!cfqq->dispatched); 3264 cfqd->rq_in_driver[sync]--; 3265 cfqq->dispatched--; 3266 3267 if (cfq_cfqq_sync(cfqq)) 3268 cfqd->sync_flight--; 3269 3270 if (sync) { 3271 RQ_CIC(rq)->last_end_request = now; 3272 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now)) 3273 cfqd->last_delayed_sync = now; 3274 } 3275 3276 /* 3277 * If this is the active queue, check if it needs to be expired, 3278 * or if we want to idle in case it has no pending requests. 3279 */ 3280 if (cfqd->active_queue == cfqq) { 3281 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); 3282 3283 if (cfq_cfqq_slice_new(cfqq)) { 3284 cfq_set_prio_slice(cfqd, cfqq); 3285 cfq_clear_cfqq_slice_new(cfqq); 3286 } 3287 3288 /* 3289 * Should we wait for next request to come in before we expire 3290 * the queue. 3291 */ 3292 if (cfq_should_wait_busy(cfqd, cfqq)) { 3293 cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; 3294 cfq_mark_cfqq_wait_busy(cfqq); 3295 } 3296 3297 /* 3298 * Idling is not enabled on: 3299 * - expired queues 3300 * - idle-priority queues 3301 * - async queues 3302 * - queues with still some requests queued 3303 * - when there is a close cooperator 3304 */ 3305 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 3306 cfq_slice_expired(cfqd, 1); 3307 else if (sync && cfqq_empty && 3308 !cfq_close_cooperator(cfqd, cfqq)) { 3309 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq); 3310 /* 3311 * Idling is enabled for SYNC_WORKLOAD. 3312 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree 3313 * only if we processed at least one !rq_noidle request 3314 */ 3315 if (cfqd->serving_type == SYNC_WORKLOAD 3316 || cfqd->noidle_tree_requires_idle 3317 || cfqq->cfqg->nr_cfqq == 1) 3318 cfq_arm_slice_timer(cfqd); 3319 } 3320 } 3321 3322 if (!rq_in_driver(cfqd)) 3323 cfq_schedule_dispatch(cfqd); 3324} 3325 3326/* 3327 * we temporarily boost lower priority queues if they are holding fs exclusive 3328 * resources. they are boosted to normal prio (CLASS_BE/4) 3329 */ 3330static void cfq_prio_boost(struct cfq_queue *cfqq) 3331{ 3332 if (has_fs_excl()) { 3333 /* 3334 * boost idle prio on transactions that would lock out other 3335 * users of the filesystem 3336 */ 3337 if (cfq_class_idle(cfqq)) 3338 cfqq->ioprio_class = IOPRIO_CLASS_BE; 3339 if (cfqq->ioprio > IOPRIO_NORM) 3340 cfqq->ioprio = IOPRIO_NORM; 3341 } else { 3342 /* 3343 * unboost the queue (if needed) 3344 */ 3345 cfqq->ioprio_class = cfqq->org_ioprio_class; 3346 cfqq->ioprio = cfqq->org_ioprio; 3347 } 3348} 3349 3350static inline int __cfq_may_queue(struct cfq_queue *cfqq) 3351{ 3352 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) { 3353 cfq_mark_cfqq_must_alloc_slice(cfqq); 3354 return ELV_MQUEUE_MUST; 3355 } 3356 3357 return ELV_MQUEUE_MAY; 3358} 3359 3360static int cfq_may_queue(struct request_queue *q, int rw) 3361{ 3362 struct cfq_data *cfqd = q->elevator->elevator_data; 3363 struct task_struct *tsk = current; 3364 struct cfq_io_context *cic; 3365 struct cfq_queue *cfqq; 3366 3367 /* 3368 * don't force setup of a queue from here, as a call to may_queue 3369 * does not necessarily imply that a request actually will be queued. 3370 * so just lookup a possibly existing queue, or return 'may queue' 3371 * if that fails 3372 */ 3373 cic = cfq_cic_lookup(cfqd, tsk->io_context); 3374 if (!cic) 3375 return ELV_MQUEUE_MAY; 3376 3377 cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); 3378 if (cfqq) { 3379 cfq_init_prio_data(cfqq, cic->ioc); 3380 cfq_prio_boost(cfqq); 3381 3382 return __cfq_may_queue(cfqq); 3383 } 3384 3385 return ELV_MQUEUE_MAY; 3386} 3387 3388/* 3389 * queue lock held here 3390 */ 3391static void cfq_put_request(struct request *rq) 3392{ 3393 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3394 3395 if (cfqq) { 3396 const int rw = rq_data_dir(rq); 3397 3398 BUG_ON(!cfqq->allocated[rw]); 3399 cfqq->allocated[rw]--; 3400 3401 put_io_context(RQ_CIC(rq)->ioc); 3402 3403 rq->elevator_private = NULL; 3404 rq->elevator_private2 = NULL; 3405 3406 cfq_put_queue(cfqq); 3407 } 3408} 3409 3410static struct cfq_queue * 3411cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, 3412 struct cfq_queue *cfqq) 3413{ 3414 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq); 3415 cic_set_cfqq(cic, cfqq->new_cfqq, 1); 3416 cfq_mark_cfqq_coop(cfqq->new_cfqq); 3417 cfq_put_queue(cfqq); 3418 return cic_to_cfqq(cic, 1); 3419} 3420 3421/* 3422 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this 3423 * was the last process referring to said cfqq. 3424 */ 3425static struct cfq_queue * 3426split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq) 3427{ 3428 if (cfqq_process_refs(cfqq) == 1) { 3429 cfqq->pid = current->pid; 3430 cfq_clear_cfqq_coop(cfqq); 3431 cfq_clear_cfqq_split_coop(cfqq); 3432 return cfqq; 3433 } 3434 3435 cic_set_cfqq(cic, NULL, 1); 3436 cfq_put_queue(cfqq); 3437 return NULL; 3438} 3439/* 3440 * Allocate cfq data structures associated with this request. 3441 */ 3442static int 3443cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 3444{ 3445 struct cfq_data *cfqd = q->elevator->elevator_data; 3446 struct cfq_io_context *cic; 3447 const int rw = rq_data_dir(rq); 3448 const bool is_sync = rq_is_sync(rq); 3449 struct cfq_queue *cfqq; 3450 unsigned long flags; 3451 3452 might_sleep_if(gfp_mask & __GFP_WAIT); 3453 3454 cic = cfq_get_io_context(cfqd, gfp_mask); 3455 3456 spin_lock_irqsave(q->queue_lock, flags); 3457 3458 if (!cic) 3459 goto queue_fail; 3460 3461new_queue: 3462 cfqq = cic_to_cfqq(cic, is_sync); 3463 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 3464 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 3465 cic_set_cfqq(cic, cfqq, is_sync); 3466 } else { 3467 /* 3468 * If the queue was seeky for too long, break it apart. 3469 */ 3470 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) { 3471 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq"); 3472 cfqq = split_cfqq(cic, cfqq); 3473 if (!cfqq) 3474 goto new_queue; 3475 } 3476 3477 /* 3478 * Check to see if this queue is scheduled to merge with 3479 * another, closely cooperating queue. The merging of 3480 * queues happens here as it must be done in process context. 3481 * The reference on new_cfqq was taken in merge_cfqqs. 3482 */ 3483 if (cfqq->new_cfqq) 3484 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq); 3485 } 3486 3487 cfqq->allocated[rw]++; 3488 atomic_inc(&cfqq->ref); 3489 3490 spin_unlock_irqrestore(q->queue_lock, flags); 3491 3492 rq->elevator_private = cic; 3493 rq->elevator_private2 = cfqq; 3494 return 0; 3495 3496queue_fail: 3497 if (cic) 3498 put_io_context(cic->ioc); 3499 3500 cfq_schedule_dispatch(cfqd); 3501 spin_unlock_irqrestore(q->queue_lock, flags); 3502 cfq_log(cfqd, "set_request fail"); 3503 return 1; 3504} 3505 3506static void cfq_kick_queue(struct work_struct *work) 3507{ 3508 struct cfq_data *cfqd = 3509 container_of(work, struct cfq_data, unplug_work); 3510 struct request_queue *q = cfqd->queue; 3511 3512 spin_lock_irq(q->queue_lock); 3513 __blk_run_queue(cfqd->queue); 3514 spin_unlock_irq(q->queue_lock); 3515} 3516 3517/* 3518 * Timer running if the active_queue is currently idling inside its time slice 3519 */ 3520static void cfq_idle_slice_timer(unsigned long data) 3521{ 3522 struct cfq_data *cfqd = (struct cfq_data *) data; 3523 struct cfq_queue *cfqq; 3524 unsigned long flags; 3525 int timed_out = 1; 3526 3527 cfq_log(cfqd, "idle timer fired"); 3528 3529 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 3530 3531 cfqq = cfqd->active_queue; 3532 if (cfqq) { 3533 timed_out = 0; 3534 3535 /* 3536 * We saw a request before the queue expired, let it through 3537 */ 3538 if (cfq_cfqq_must_dispatch(cfqq)) 3539 goto out_kick; 3540 3541 /* 3542 * expired 3543 */ 3544 if (cfq_slice_used(cfqq)) 3545 goto expire; 3546 3547 /* 3548 * only expire and reinvoke request handler, if there are 3549 * other queues with pending requests 3550 */ 3551 if (!cfqd->busy_queues) 3552 goto out_cont; 3553 3554 /* 3555 * not expired and it has a request pending, let it dispatch 3556 */ 3557 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 3558 goto out_kick; 3559 3560 /* 3561 * Queue depth flag is reset only when the idle didn't succeed 3562 */ 3563 cfq_clear_cfqq_deep(cfqq); 3564 } 3565expire: 3566 cfq_slice_expired(cfqd, timed_out); 3567out_kick: 3568 cfq_schedule_dispatch(cfqd); 3569out_cont: 3570 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 3571} 3572 3573static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 3574{ 3575 del_timer_sync(&cfqd->idle_slice_timer); 3576 cancel_work_sync(&cfqd->unplug_work); 3577} 3578 3579static void cfq_put_async_queues(struct cfq_data *cfqd) 3580{ 3581 int i; 3582 3583 for (i = 0; i < IOPRIO_BE_NR; i++) { 3584 if (cfqd->async_cfqq[0][i]) 3585 cfq_put_queue(cfqd->async_cfqq[0][i]); 3586 if (cfqd->async_cfqq[1][i]) 3587 cfq_put_queue(cfqd->async_cfqq[1][i]); 3588 } 3589 3590 if (cfqd->async_idle_cfqq) 3591 cfq_put_queue(cfqd->async_idle_cfqq); 3592} 3593 3594static void cfq_cfqd_free(struct rcu_head *head) 3595{ 3596 kfree(container_of(head, struct cfq_data, rcu)); 3597} 3598 3599static void cfq_exit_queue(struct elevator_queue *e) 3600{ 3601 struct cfq_data *cfqd = e->elevator_data; 3602 struct request_queue *q = cfqd->queue; 3603 3604 cfq_shutdown_timer_wq(cfqd); 3605 3606 spin_lock_irq(q->queue_lock); 3607 3608 if (cfqd->active_queue) 3609 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 3610 3611 while (!list_empty(&cfqd->cic_list)) { 3612 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 3613 struct cfq_io_context, 3614 queue_list); 3615 3616 __cfq_exit_single_io_context(cfqd, cic); 3617 } 3618 3619 cfq_put_async_queues(cfqd); 3620 cfq_release_cfq_groups(cfqd); 3621 blkiocg_del_blkio_group(&cfqd->root_group.blkg); 3622 3623 spin_unlock_irq(q->queue_lock); 3624 3625 cfq_shutdown_timer_wq(cfqd); 3626 3627 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */ 3628 call_rcu(&cfqd->rcu, cfq_cfqd_free); 3629} 3630 3631static void *cfq_init_queue(struct request_queue *q) 3632{ 3633 struct cfq_data *cfqd; 3634 int i, j; 3635 struct cfq_group *cfqg; 3636 struct cfq_rb_root *st; 3637 3638 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 3639 if (!cfqd) 3640 return NULL; 3641 3642 /* Init root service tree */ 3643 cfqd->grp_service_tree = CFQ_RB_ROOT; 3644 3645 /* Init root group */ 3646 cfqg = &cfqd->root_group; 3647 for_each_cfqg_st(cfqg, i, j, st) 3648 *st = CFQ_RB_ROOT; 3649 RB_CLEAR_NODE(&cfqg->rb_node); 3650 3651 /* Give preference to root group over other groups */ 3652 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT; 3653 3654#ifdef CONFIG_CFQ_GROUP_IOSCHED 3655 /* 3656 * Take a reference to root group which we never drop. This is just 3657 * to make sure that cfq_put_cfqg() does not try to kfree root group 3658 */ 3659 atomic_set(&cfqg->ref, 1); 3660 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd, 3661 0); 3662#endif 3663 /* 3664 * Not strictly needed (since RB_ROOT just clears the node and we 3665 * zeroed cfqd on alloc), but better be safe in case someone decides 3666 * to add magic to the rb code 3667 */ 3668 for (i = 0; i < CFQ_PRIO_LISTS; i++) 3669 cfqd->prio_trees[i] = RB_ROOT; 3670 3671 /* 3672 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. 3673 * Grab a permanent reference to it, so that the normal code flow 3674 * will not attempt to free it. 3675 */ 3676 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); 3677 atomic_inc(&cfqd->oom_cfqq.ref); 3678 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group); 3679 3680 INIT_LIST_HEAD(&cfqd->cic_list); 3681 3682 cfqd->queue = q; 3683 3684 init_timer(&cfqd->idle_slice_timer); 3685 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 3686 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 3687 3688 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 3689 3690 cfqd->cfq_quantum = cfq_quantum; 3691 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 3692 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 3693 cfqd->cfq_back_max = cfq_back_max; 3694 cfqd->cfq_back_penalty = cfq_back_penalty; 3695 cfqd->cfq_slice[0] = cfq_slice_async; 3696 cfqd->cfq_slice[1] = cfq_slice_sync; 3697 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 3698 cfqd->cfq_slice_idle = cfq_slice_idle; 3699 cfqd->cfq_latency = 1; 3700 cfqd->cfq_group_isolation = 0; 3701 cfqd->hw_tag = -1; 3702 /* 3703 * we optimistically start assuming sync ops weren't delayed in last 3704 * second, in order to have larger depth for async operations. 3705 */ 3706 cfqd->last_delayed_sync = jiffies - HZ; 3707 INIT_RCU_HEAD(&cfqd->rcu); 3708 return cfqd; 3709} 3710 3711static void cfq_slab_kill(void) 3712{ 3713 /* 3714 * Caller already ensured that pending RCU callbacks are completed, 3715 * so we should have no busy allocations at this point. 3716 */ 3717 if (cfq_pool) 3718 kmem_cache_destroy(cfq_pool); 3719 if (cfq_ioc_pool) 3720 kmem_cache_destroy(cfq_ioc_pool); 3721} 3722 3723static int __init cfq_slab_setup(void) 3724{ 3725 cfq_pool = KMEM_CACHE(cfq_queue, 0); 3726 if (!cfq_pool) 3727 goto fail; 3728 3729 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 3730 if (!cfq_ioc_pool) 3731 goto fail; 3732 3733 return 0; 3734fail: 3735 cfq_slab_kill(); 3736 return -ENOMEM; 3737} 3738 3739/* 3740 * sysfs parts below --> 3741 */ 3742static ssize_t 3743cfq_var_show(unsigned int var, char *page) 3744{ 3745 return sprintf(page, "%d\n", var); 3746} 3747 3748static ssize_t 3749cfq_var_store(unsigned int *var, const char *page, size_t count) 3750{ 3751 char *p = (char *) page; 3752 3753 *var = simple_strtoul(p, &p, 10); 3754 return count; 3755} 3756 3757#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 3758static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 3759{ \ 3760 struct cfq_data *cfqd = e->elevator_data; \ 3761 unsigned int __data = __VAR; \ 3762 if (__CONV) \ 3763 __data = jiffies_to_msecs(__data); \ 3764 return cfq_var_show(__data, (page)); \ 3765} 3766SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 3767SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 3768SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 3769SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 3770SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 3771SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 3772SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 3773SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 3774SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 3775SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); 3776SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0); 3777#undef SHOW_FUNCTION 3778 3779#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 3780static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 3781{ \ 3782 struct cfq_data *cfqd = e->elevator_data; \ 3783 unsigned int __data; \ 3784 int ret = cfq_var_store(&__data, (page), count); \ 3785 if (__data < (MIN)) \ 3786 __data = (MIN); \ 3787 else if (__data > (MAX)) \ 3788 __data = (MAX); \ 3789 if (__CONV) \ 3790 *(__PTR) = msecs_to_jiffies(__data); \ 3791 else \ 3792 *(__PTR) = __data; \ 3793 return ret; \ 3794} 3795STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 3796STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 3797 UINT_MAX, 1); 3798STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 3799 UINT_MAX, 1); 3800STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 3801STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 3802 UINT_MAX, 0); 3803STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 3804STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 3805STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 3806STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 3807 UINT_MAX, 0); 3808STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); 3809STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0); 3810#undef STORE_FUNCTION 3811 3812#define CFQ_ATTR(name) \ 3813 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 3814 3815static struct elv_fs_entry cfq_attrs[] = { 3816 CFQ_ATTR(quantum), 3817 CFQ_ATTR(fifo_expire_sync), 3818 CFQ_ATTR(fifo_expire_async), 3819 CFQ_ATTR(back_seek_max), 3820 CFQ_ATTR(back_seek_penalty), 3821 CFQ_ATTR(slice_sync), 3822 CFQ_ATTR(slice_async), 3823 CFQ_ATTR(slice_async_rq), 3824 CFQ_ATTR(slice_idle), 3825 CFQ_ATTR(low_latency), 3826 CFQ_ATTR(group_isolation), 3827 __ATTR_NULL 3828}; 3829 3830static struct elevator_type iosched_cfq = { 3831 .ops = { 3832 .elevator_merge_fn = cfq_merge, 3833 .elevator_merged_fn = cfq_merged_request, 3834 .elevator_merge_req_fn = cfq_merged_requests, 3835 .elevator_allow_merge_fn = cfq_allow_merge, 3836 .elevator_dispatch_fn = cfq_dispatch_requests, 3837 .elevator_add_req_fn = cfq_insert_request, 3838 .elevator_activate_req_fn = cfq_activate_request, 3839 .elevator_deactivate_req_fn = cfq_deactivate_request, 3840 .elevator_queue_empty_fn = cfq_queue_empty, 3841 .elevator_completed_req_fn = cfq_completed_request, 3842 .elevator_former_req_fn = elv_rb_former_request, 3843 .elevator_latter_req_fn = elv_rb_latter_request, 3844 .elevator_set_req_fn = cfq_set_request, 3845 .elevator_put_req_fn = cfq_put_request, 3846 .elevator_may_queue_fn = cfq_may_queue, 3847 .elevator_init_fn = cfq_init_queue, 3848 .elevator_exit_fn = cfq_exit_queue, 3849 .trim = cfq_free_io_context, 3850 }, 3851 .elevator_attrs = cfq_attrs, 3852 .elevator_name = "cfq", 3853 .elevator_owner = THIS_MODULE, 3854}; 3855 3856#ifdef CONFIG_CFQ_GROUP_IOSCHED 3857static struct blkio_policy_type blkio_policy_cfq = { 3858 .ops = { 3859 .blkio_unlink_group_fn = cfq_unlink_blkio_group, 3860 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight, 3861 }, 3862}; 3863#else 3864static struct blkio_policy_type blkio_policy_cfq; 3865#endif 3866 3867static int __init cfq_init(void) 3868{ 3869 /* 3870 * could be 0 on HZ < 1000 setups 3871 */ 3872 if (!cfq_slice_async) 3873 cfq_slice_async = 1; 3874 if (!cfq_slice_idle) 3875 cfq_slice_idle = 1; 3876 3877 if (cfq_slab_setup()) 3878 return -ENOMEM; 3879 3880 elv_register(&iosched_cfq); 3881 blkio_policy_register(&blkio_policy_cfq); 3882 3883 return 0; 3884} 3885 3886static void __exit cfq_exit(void) 3887{ 3888 DECLARE_COMPLETION_ONSTACK(all_gone); 3889 blkio_policy_unregister(&blkio_policy_cfq); 3890 elv_unregister(&iosched_cfq); 3891 ioc_gone = &all_gone; 3892 /* ioc_gone's update must be visible before reading ioc_count */ 3893 smp_wmb(); 3894 3895 /* 3896 * this also protects us from entering cfq_slab_kill() with 3897 * pending RCU callbacks 3898 */ 3899 if (elv_ioc_count_read(cfq_ioc_count)) 3900 wait_for_completion(&all_gone); 3901 cfq_slab_kill(); 3902} 3903 3904module_init(cfq_init); 3905module_exit(cfq_exit); 3906 3907MODULE_AUTHOR("Jens Axboe"); 3908MODULE_LICENSE("GPL"); 3909MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 3910