cfq-iosched.c revision 9a0785b0da561e1e9c6617df85e93ae107a42f18
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 = 8; 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_CLOSE_THR (sector_t)(8 * 1024) 51#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32) 52#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8) 53 54#define RQ_CIC(rq) \ 55 ((struct cfq_io_context *) (rq)->elevator_private) 56#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 57 58static struct kmem_cache *cfq_pool; 59static struct kmem_cache *cfq_ioc_pool; 60 61static DEFINE_PER_CPU(unsigned long, cfq_ioc_count); 62static struct completion *ioc_gone; 63static DEFINE_SPINLOCK(ioc_gone_lock); 64 65#define CFQ_PRIO_LISTS IOPRIO_BE_NR 66#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 67#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 68 69#define sample_valid(samples) ((samples) > 80) 70#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node) 71 72/* 73 * Most of our rbtree usage is for sorting with min extraction, so 74 * if we cache the leftmost node we don't have to walk down the tree 75 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 76 * move this into the elevator for the rq sorting as well. 77 */ 78struct cfq_rb_root { 79 struct rb_root rb; 80 struct rb_node *left; 81 unsigned count; 82 unsigned total_weight; 83 u64 min_vdisktime; 84 struct rb_node *active; 85}; 86#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \ 87 .count = 0, .min_vdisktime = 0, } 88 89/* 90 * Per process-grouping structure 91 */ 92struct cfq_queue { 93 /* reference count */ 94 atomic_t ref; 95 /* various state flags, see below */ 96 unsigned int flags; 97 /* parent cfq_data */ 98 struct cfq_data *cfqd; 99 /* service_tree member */ 100 struct rb_node rb_node; 101 /* service_tree key */ 102 unsigned long rb_key; 103 /* prio tree member */ 104 struct rb_node p_node; 105 /* prio tree root we belong to, if any */ 106 struct rb_root *p_root; 107 /* sorted list of pending requests */ 108 struct rb_root sort_list; 109 /* if fifo isn't expired, next request to serve */ 110 struct request *next_rq; 111 /* requests queued in sort_list */ 112 int queued[2]; 113 /* currently allocated requests */ 114 int allocated[2]; 115 /* fifo list of requests in sort_list */ 116 struct list_head fifo; 117 118 /* time when queue got scheduled in to dispatch first request. */ 119 unsigned long dispatch_start; 120 unsigned int allocated_slice; 121 unsigned int slice_dispatch; 122 /* time when first request from queue completed and slice started. */ 123 unsigned long slice_start; 124 unsigned long slice_end; 125 long slice_resid; 126 127 /* pending metadata requests */ 128 int meta_pending; 129 /* number of requests that are on the dispatch list or inside driver */ 130 int dispatched; 131 132 /* io prio of this group */ 133 unsigned short ioprio, org_ioprio; 134 unsigned short ioprio_class, org_ioprio_class; 135 136 pid_t pid; 137 138 u32 seek_history; 139 sector_t last_request_pos; 140 141 struct cfq_rb_root *service_tree; 142 struct cfq_queue *new_cfqq; 143 struct cfq_group *cfqg; 144 struct cfq_group *orig_cfqg; 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; 226 int rq_in_flight[2]; 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 struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 420 bool is_sync) 421{ 422 return cic->cfqq[is_sync]; 423} 424 425static inline void cic_set_cfqq(struct cfq_io_context *cic, 426 struct cfq_queue *cfqq, bool is_sync) 427{ 428 cic->cfqq[is_sync] = cfqq; 429} 430 431/* 432 * We regard a request as SYNC, if it's either a read or has the SYNC bit 433 * set (in which case it could also be direct WRITE). 434 */ 435static inline bool cfq_bio_sync(struct bio *bio) 436{ 437 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO); 438} 439 440/* 441 * scheduler run of queue, if there are requests pending and no one in the 442 * driver that will restart queueing 443 */ 444static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 445{ 446 if (cfqd->busy_queues) { 447 cfq_log(cfqd, "schedule dispatch"); 448 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 449 } 450} 451 452static int cfq_queue_empty(struct request_queue *q) 453{ 454 struct cfq_data *cfqd = q->elevator->elevator_data; 455 456 return !cfqd->rq_queued; 457} 458 459/* 460 * Scale schedule slice based on io priority. Use the sync time slice only 461 * if a queue is marked sync and has sync io queued. A sync queue with async 462 * io only, should not get full sync slice length. 463 */ 464static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync, 465 unsigned short prio) 466{ 467 const int base_slice = cfqd->cfq_slice[sync]; 468 469 WARN_ON(prio >= IOPRIO_BE_NR); 470 471 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 472} 473 474static inline int 475cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 476{ 477 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 478} 479 480static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg) 481{ 482 u64 d = delta << CFQ_SERVICE_SHIFT; 483 484 d = d * BLKIO_WEIGHT_DEFAULT; 485 do_div(d, cfqg->weight); 486 return d; 487} 488 489static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime) 490{ 491 s64 delta = (s64)(vdisktime - min_vdisktime); 492 if (delta > 0) 493 min_vdisktime = vdisktime; 494 495 return min_vdisktime; 496} 497 498static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime) 499{ 500 s64 delta = (s64)(vdisktime - min_vdisktime); 501 if (delta < 0) 502 min_vdisktime = vdisktime; 503 504 return min_vdisktime; 505} 506 507static void update_min_vdisktime(struct cfq_rb_root *st) 508{ 509 u64 vdisktime = st->min_vdisktime; 510 struct cfq_group *cfqg; 511 512 if (st->active) { 513 cfqg = rb_entry_cfqg(st->active); 514 vdisktime = cfqg->vdisktime; 515 } 516 517 if (st->left) { 518 cfqg = rb_entry_cfqg(st->left); 519 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime); 520 } 521 522 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime); 523} 524 525/* 526 * get averaged number of queues of RT/BE priority. 527 * average is updated, with a formula that gives more weight to higher numbers, 528 * to quickly follows sudden increases and decrease slowly 529 */ 530 531static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd, 532 struct cfq_group *cfqg, bool rt) 533{ 534 unsigned min_q, max_q; 535 unsigned mult = cfq_hist_divisor - 1; 536 unsigned round = cfq_hist_divisor / 2; 537 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg); 538 539 min_q = min(cfqg->busy_queues_avg[rt], busy); 540 max_q = max(cfqg->busy_queues_avg[rt], busy); 541 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) / 542 cfq_hist_divisor; 543 return cfqg->busy_queues_avg[rt]; 544} 545 546static inline unsigned 547cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg) 548{ 549 struct cfq_rb_root *st = &cfqd->grp_service_tree; 550 551 return cfq_target_latency * cfqg->weight / st->total_weight; 552} 553 554static inline void 555cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 556{ 557 unsigned slice = cfq_prio_to_slice(cfqd, cfqq); 558 if (cfqd->cfq_latency) { 559 /* 560 * interested queues (we consider only the ones with the same 561 * priority class in the cfq group) 562 */ 563 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg, 564 cfq_class_rt(cfqq)); 565 unsigned sync_slice = cfqd->cfq_slice[1]; 566 unsigned expect_latency = sync_slice * iq; 567 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg); 568 569 if (expect_latency > group_slice) { 570 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle; 571 /* scale low_slice according to IO priority 572 * and sync vs async */ 573 unsigned low_slice = 574 min(slice, base_low_slice * slice / sync_slice); 575 /* the adapted slice value is scaled to fit all iqs 576 * into the target latency */ 577 slice = max(slice * group_slice / expect_latency, 578 low_slice); 579 } 580 } 581 cfqq->slice_start = jiffies; 582 cfqq->slice_end = jiffies + slice; 583 cfqq->allocated_slice = slice; 584 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 585} 586 587/* 588 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 589 * isn't valid until the first request from the dispatch is activated 590 * and the slice time set. 591 */ 592static inline bool cfq_slice_used(struct cfq_queue *cfqq) 593{ 594 if (cfq_cfqq_slice_new(cfqq)) 595 return 0; 596 if (time_before(jiffies, cfqq->slice_end)) 597 return 0; 598 599 return 1; 600} 601 602/* 603 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 604 * We choose the request that is closest to the head right now. Distance 605 * behind the head is penalized and only allowed to a certain extent. 606 */ 607static struct request * 608cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last) 609{ 610 sector_t s1, s2, d1 = 0, d2 = 0; 611 unsigned long back_max; 612#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 613#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 614 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 615 616 if (rq1 == NULL || rq1 == rq2) 617 return rq2; 618 if (rq2 == NULL) 619 return rq1; 620 621 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 622 return rq1; 623 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 624 return rq2; 625 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 626 return rq1; 627 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 628 return rq2; 629 630 s1 = blk_rq_pos(rq1); 631 s2 = blk_rq_pos(rq2); 632 633 /* 634 * by definition, 1KiB is 2 sectors 635 */ 636 back_max = cfqd->cfq_back_max * 2; 637 638 /* 639 * Strict one way elevator _except_ in the case where we allow 640 * short backward seeks which are biased as twice the cost of a 641 * similar forward seek. 642 */ 643 if (s1 >= last) 644 d1 = s1 - last; 645 else if (s1 + back_max >= last) 646 d1 = (last - s1) * cfqd->cfq_back_penalty; 647 else 648 wrap |= CFQ_RQ1_WRAP; 649 650 if (s2 >= last) 651 d2 = s2 - last; 652 else if (s2 + back_max >= last) 653 d2 = (last - s2) * cfqd->cfq_back_penalty; 654 else 655 wrap |= CFQ_RQ2_WRAP; 656 657 /* Found required data */ 658 659 /* 660 * By doing switch() on the bit mask "wrap" we avoid having to 661 * check two variables for all permutations: --> faster! 662 */ 663 switch (wrap) { 664 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 665 if (d1 < d2) 666 return rq1; 667 else if (d2 < d1) 668 return rq2; 669 else { 670 if (s1 >= s2) 671 return rq1; 672 else 673 return rq2; 674 } 675 676 case CFQ_RQ2_WRAP: 677 return rq1; 678 case CFQ_RQ1_WRAP: 679 return rq2; 680 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 681 default: 682 /* 683 * Since both rqs are wrapped, 684 * start with the one that's further behind head 685 * (--> only *one* back seek required), 686 * since back seek takes more time than forward. 687 */ 688 if (s1 <= s2) 689 return rq1; 690 else 691 return rq2; 692 } 693} 694 695/* 696 * The below is leftmost cache rbtree addon 697 */ 698static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 699{ 700 /* Service tree is empty */ 701 if (!root->count) 702 return NULL; 703 704 if (!root->left) 705 root->left = rb_first(&root->rb); 706 707 if (root->left) 708 return rb_entry(root->left, struct cfq_queue, rb_node); 709 710 return NULL; 711} 712 713static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root) 714{ 715 if (!root->left) 716 root->left = rb_first(&root->rb); 717 718 if (root->left) 719 return rb_entry_cfqg(root->left); 720 721 return NULL; 722} 723 724static void rb_erase_init(struct rb_node *n, struct rb_root *root) 725{ 726 rb_erase(n, root); 727 RB_CLEAR_NODE(n); 728} 729 730static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 731{ 732 if (root->left == n) 733 root->left = NULL; 734 rb_erase_init(n, &root->rb); 735 --root->count; 736} 737 738/* 739 * would be nice to take fifo expire time into account as well 740 */ 741static struct request * 742cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 743 struct request *last) 744{ 745 struct rb_node *rbnext = rb_next(&last->rb_node); 746 struct rb_node *rbprev = rb_prev(&last->rb_node); 747 struct request *next = NULL, *prev = NULL; 748 749 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 750 751 if (rbprev) 752 prev = rb_entry_rq(rbprev); 753 754 if (rbnext) 755 next = rb_entry_rq(rbnext); 756 else { 757 rbnext = rb_first(&cfqq->sort_list); 758 if (rbnext && rbnext != &last->rb_node) 759 next = rb_entry_rq(rbnext); 760 } 761 762 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last)); 763} 764 765static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 766 struct cfq_queue *cfqq) 767{ 768 /* 769 * just an approximation, should be ok. 770 */ 771 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) - 772 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 773} 774 775static inline s64 776cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg) 777{ 778 return cfqg->vdisktime - st->min_vdisktime; 779} 780 781static void 782__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) 783{ 784 struct rb_node **node = &st->rb.rb_node; 785 struct rb_node *parent = NULL; 786 struct cfq_group *__cfqg; 787 s64 key = cfqg_key(st, cfqg); 788 int left = 1; 789 790 while (*node != NULL) { 791 parent = *node; 792 __cfqg = rb_entry_cfqg(parent); 793 794 if (key < cfqg_key(st, __cfqg)) 795 node = &parent->rb_left; 796 else { 797 node = &parent->rb_right; 798 left = 0; 799 } 800 } 801 802 if (left) 803 st->left = &cfqg->rb_node; 804 805 rb_link_node(&cfqg->rb_node, parent, node); 806 rb_insert_color(&cfqg->rb_node, &st->rb); 807} 808 809static void 810cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg) 811{ 812 struct cfq_rb_root *st = &cfqd->grp_service_tree; 813 struct cfq_group *__cfqg; 814 struct rb_node *n; 815 816 cfqg->nr_cfqq++; 817 if (cfqg->on_st) 818 return; 819 820 /* 821 * Currently put the group at the end. Later implement something 822 * so that groups get lesser vtime based on their weights, so that 823 * if group does not loose all if it was not continously backlogged. 824 */ 825 n = rb_last(&st->rb); 826 if (n) { 827 __cfqg = rb_entry_cfqg(n); 828 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; 829 } else 830 cfqg->vdisktime = st->min_vdisktime; 831 832 __cfq_group_service_tree_add(st, cfqg); 833 cfqg->on_st = true; 834 st->total_weight += cfqg->weight; 835} 836 837static void 838cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg) 839{ 840 struct cfq_rb_root *st = &cfqd->grp_service_tree; 841 842 if (st->active == &cfqg->rb_node) 843 st->active = NULL; 844 845 BUG_ON(cfqg->nr_cfqq < 1); 846 cfqg->nr_cfqq--; 847 848 /* If there are other cfq queues under this group, don't delete it */ 849 if (cfqg->nr_cfqq) 850 return; 851 852 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group"); 853 cfqg->on_st = false; 854 st->total_weight -= cfqg->weight; 855 if (!RB_EMPTY_NODE(&cfqg->rb_node)) 856 cfq_rb_erase(&cfqg->rb_node, st); 857 cfqg->saved_workload_slice = 0; 858 blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1); 859} 860 861static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq) 862{ 863 unsigned int slice_used; 864 865 /* 866 * Queue got expired before even a single request completed or 867 * got expired immediately after first request completion. 868 */ 869 if (!cfqq->slice_start || cfqq->slice_start == jiffies) { 870 /* 871 * Also charge the seek time incurred to the group, otherwise 872 * if there are mutiple queues in the group, each can dispatch 873 * a single request on seeky media and cause lots of seek time 874 * and group will never know it. 875 */ 876 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start), 877 1); 878 } else { 879 slice_used = jiffies - cfqq->slice_start; 880 if (slice_used > cfqq->allocated_slice) 881 slice_used = cfqq->allocated_slice; 882 } 883 884 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used); 885 return slice_used; 886} 887 888static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg, 889 struct cfq_queue *cfqq) 890{ 891 struct cfq_rb_root *st = &cfqd->grp_service_tree; 892 unsigned int used_sl, charge_sl; 893 int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg) 894 - cfqg->service_tree_idle.count; 895 896 BUG_ON(nr_sync < 0); 897 used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq); 898 899 if (!cfq_cfqq_sync(cfqq) && !nr_sync) 900 charge_sl = cfqq->allocated_slice; 901 902 /* Can't update vdisktime while group is on service tree */ 903 cfq_rb_erase(&cfqg->rb_node, st); 904 cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg); 905 __cfq_group_service_tree_add(st, cfqg); 906 907 /* This group is being expired. Save the context */ 908 if (time_after(cfqd->workload_expires, jiffies)) { 909 cfqg->saved_workload_slice = cfqd->workload_expires 910 - jiffies; 911 cfqg->saved_workload = cfqd->serving_type; 912 cfqg->saved_serving_prio = cfqd->serving_prio; 913 } else 914 cfqg->saved_workload_slice = 0; 915 916 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime, 917 st->min_vdisktime); 918 blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl); 919} 920 921#ifdef CONFIG_CFQ_GROUP_IOSCHED 922static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg) 923{ 924 if (blkg) 925 return container_of(blkg, struct cfq_group, blkg); 926 return NULL; 927} 928 929void 930cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight) 931{ 932 cfqg_of_blkg(blkg)->weight = weight; 933} 934 935static struct cfq_group * 936cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create) 937{ 938 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup); 939 struct cfq_group *cfqg = NULL; 940 void *key = cfqd; 941 int i, j; 942 struct cfq_rb_root *st; 943 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; 944 unsigned int major, minor; 945 946 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key)); 947 if (cfqg || !create) 948 goto done; 949 950 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node); 951 if (!cfqg) 952 goto done; 953 954 cfqg->weight = blkcg->weight; 955 for_each_cfqg_st(cfqg, i, j, st) 956 *st = CFQ_RB_ROOT; 957 RB_CLEAR_NODE(&cfqg->rb_node); 958 959 /* 960 * Take the initial reference that will be released on destroy 961 * This can be thought of a joint reference by cgroup and 962 * elevator which will be dropped by either elevator exit 963 * or cgroup deletion path depending on who is exiting first. 964 */ 965 atomic_set(&cfqg->ref, 1); 966 967 /* Add group onto cgroup list */ 968 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); 969 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd, 970 MKDEV(major, minor)); 971 972 /* Add group on cfqd list */ 973 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list); 974 975done: 976 return cfqg; 977} 978 979/* 980 * Search for the cfq group current task belongs to. If create = 1, then also 981 * create the cfq group if it does not exist. request_queue lock must be held. 982 */ 983static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) 984{ 985 struct cgroup *cgroup; 986 struct cfq_group *cfqg = NULL; 987 988 rcu_read_lock(); 989 cgroup = task_cgroup(current, blkio_subsys_id); 990 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create); 991 if (!cfqg && create) 992 cfqg = &cfqd->root_group; 993 rcu_read_unlock(); 994 return cfqg; 995} 996 997static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) 998{ 999 /* Currently, all async queues are mapped to root group */ 1000 if (!cfq_cfqq_sync(cfqq)) 1001 cfqg = &cfqq->cfqd->root_group; 1002 1003 cfqq->cfqg = cfqg; 1004 /* cfqq reference on cfqg */ 1005 atomic_inc(&cfqq->cfqg->ref); 1006} 1007 1008static void cfq_put_cfqg(struct cfq_group *cfqg) 1009{ 1010 struct cfq_rb_root *st; 1011 int i, j; 1012 1013 BUG_ON(atomic_read(&cfqg->ref) <= 0); 1014 if (!atomic_dec_and_test(&cfqg->ref)) 1015 return; 1016 for_each_cfqg_st(cfqg, i, j, st) 1017 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL); 1018 kfree(cfqg); 1019} 1020 1021static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) 1022{ 1023 /* Something wrong if we are trying to remove same group twice */ 1024 BUG_ON(hlist_unhashed(&cfqg->cfqd_node)); 1025 1026 hlist_del_init(&cfqg->cfqd_node); 1027 1028 /* 1029 * Put the reference taken at the time of creation so that when all 1030 * queues are gone, group can be destroyed. 1031 */ 1032 cfq_put_cfqg(cfqg); 1033} 1034 1035static void cfq_release_cfq_groups(struct cfq_data *cfqd) 1036{ 1037 struct hlist_node *pos, *n; 1038 struct cfq_group *cfqg; 1039 1040 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) { 1041 /* 1042 * If cgroup removal path got to blk_group first and removed 1043 * it from cgroup list, then it will take care of destroying 1044 * cfqg also. 1045 */ 1046 if (!blkiocg_del_blkio_group(&cfqg->blkg)) 1047 cfq_destroy_cfqg(cfqd, cfqg); 1048 } 1049} 1050 1051/* 1052 * Blk cgroup controller notification saying that blkio_group object is being 1053 * delinked as associated cgroup object is going away. That also means that 1054 * no new IO will come in this group. So get rid of this group as soon as 1055 * any pending IO in the group is finished. 1056 * 1057 * This function is called under rcu_read_lock(). key is the rcu protected 1058 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu 1059 * read lock. 1060 * 1061 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means 1062 * it should not be NULL as even if elevator was exiting, cgroup deltion 1063 * path got to it first. 1064 */ 1065void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg) 1066{ 1067 unsigned long flags; 1068 struct cfq_data *cfqd = key; 1069 1070 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1071 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg)); 1072 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1073} 1074 1075#else /* GROUP_IOSCHED */ 1076static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) 1077{ 1078 return &cfqd->root_group; 1079} 1080static inline void 1081cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { 1082 cfqq->cfqg = cfqg; 1083} 1084 1085static void cfq_release_cfq_groups(struct cfq_data *cfqd) {} 1086static inline void cfq_put_cfqg(struct cfq_group *cfqg) {} 1087 1088#endif /* GROUP_IOSCHED */ 1089 1090/* 1091 * The cfqd->service_trees holds all pending cfq_queue's that have 1092 * requests waiting to be processed. It is sorted in the order that 1093 * we will service the queues. 1094 */ 1095static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1096 bool add_front) 1097{ 1098 struct rb_node **p, *parent; 1099 struct cfq_queue *__cfqq; 1100 unsigned long rb_key; 1101 struct cfq_rb_root *service_tree; 1102 int left; 1103 int new_cfqq = 1; 1104 int group_changed = 0; 1105 1106#ifdef CONFIG_CFQ_GROUP_IOSCHED 1107 if (!cfqd->cfq_group_isolation 1108 && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD 1109 && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) { 1110 /* Move this cfq to root group */ 1111 cfq_log_cfqq(cfqd, cfqq, "moving to root group"); 1112 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 1113 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1114 cfqq->orig_cfqg = cfqq->cfqg; 1115 cfqq->cfqg = &cfqd->root_group; 1116 atomic_inc(&cfqd->root_group.ref); 1117 group_changed = 1; 1118 } else if (!cfqd->cfq_group_isolation 1119 && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) { 1120 /* cfqq is sequential now needs to go to its original group */ 1121 BUG_ON(cfqq->cfqg != &cfqd->root_group); 1122 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 1123 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1124 cfq_put_cfqg(cfqq->cfqg); 1125 cfqq->cfqg = cfqq->orig_cfqg; 1126 cfqq->orig_cfqg = NULL; 1127 group_changed = 1; 1128 cfq_log_cfqq(cfqd, cfqq, "moved to origin group"); 1129 } 1130#endif 1131 1132 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), 1133 cfqq_type(cfqq)); 1134 if (cfq_class_idle(cfqq)) { 1135 rb_key = CFQ_IDLE_DELAY; 1136 parent = rb_last(&service_tree->rb); 1137 if (parent && parent != &cfqq->rb_node) { 1138 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 1139 rb_key += __cfqq->rb_key; 1140 } else 1141 rb_key += jiffies; 1142 } else if (!add_front) { 1143 /* 1144 * Get our rb key offset. Subtract any residual slice 1145 * value carried from last service. A negative resid 1146 * count indicates slice overrun, and this should position 1147 * the next service time further away in the tree. 1148 */ 1149 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 1150 rb_key -= cfqq->slice_resid; 1151 cfqq->slice_resid = 0; 1152 } else { 1153 rb_key = -HZ; 1154 __cfqq = cfq_rb_first(service_tree); 1155 rb_key += __cfqq ? __cfqq->rb_key : jiffies; 1156 } 1157 1158 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 1159 new_cfqq = 0; 1160 /* 1161 * same position, nothing more to do 1162 */ 1163 if (rb_key == cfqq->rb_key && 1164 cfqq->service_tree == service_tree) 1165 return; 1166 1167 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); 1168 cfqq->service_tree = NULL; 1169 } 1170 1171 left = 1; 1172 parent = NULL; 1173 cfqq->service_tree = service_tree; 1174 p = &service_tree->rb.rb_node; 1175 while (*p) { 1176 struct rb_node **n; 1177 1178 parent = *p; 1179 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 1180 1181 /* 1182 * sort by key, that represents service time. 1183 */ 1184 if (time_before(rb_key, __cfqq->rb_key)) 1185 n = &(*p)->rb_left; 1186 else { 1187 n = &(*p)->rb_right; 1188 left = 0; 1189 } 1190 1191 p = n; 1192 } 1193 1194 if (left) 1195 service_tree->left = &cfqq->rb_node; 1196 1197 cfqq->rb_key = rb_key; 1198 rb_link_node(&cfqq->rb_node, parent, p); 1199 rb_insert_color(&cfqq->rb_node, &service_tree->rb); 1200 service_tree->count++; 1201 if ((add_front || !new_cfqq) && !group_changed) 1202 return; 1203 cfq_group_service_tree_add(cfqd, cfqq->cfqg); 1204} 1205 1206static struct cfq_queue * 1207cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, 1208 sector_t sector, struct rb_node **ret_parent, 1209 struct rb_node ***rb_link) 1210{ 1211 struct rb_node **p, *parent; 1212 struct cfq_queue *cfqq = NULL; 1213 1214 parent = NULL; 1215 p = &root->rb_node; 1216 while (*p) { 1217 struct rb_node **n; 1218 1219 parent = *p; 1220 cfqq = rb_entry(parent, struct cfq_queue, p_node); 1221 1222 /* 1223 * Sort strictly based on sector. Smallest to the left, 1224 * largest to the right. 1225 */ 1226 if (sector > blk_rq_pos(cfqq->next_rq)) 1227 n = &(*p)->rb_right; 1228 else if (sector < blk_rq_pos(cfqq->next_rq)) 1229 n = &(*p)->rb_left; 1230 else 1231 break; 1232 p = n; 1233 cfqq = NULL; 1234 } 1235 1236 *ret_parent = parent; 1237 if (rb_link) 1238 *rb_link = p; 1239 return cfqq; 1240} 1241 1242static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1243{ 1244 struct rb_node **p, *parent; 1245 struct cfq_queue *__cfqq; 1246 1247 if (cfqq->p_root) { 1248 rb_erase(&cfqq->p_node, cfqq->p_root); 1249 cfqq->p_root = NULL; 1250 } 1251 1252 if (cfq_class_idle(cfqq)) 1253 return; 1254 if (!cfqq->next_rq) 1255 return; 1256 1257 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; 1258 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, 1259 blk_rq_pos(cfqq->next_rq), &parent, &p); 1260 if (!__cfqq) { 1261 rb_link_node(&cfqq->p_node, parent, p); 1262 rb_insert_color(&cfqq->p_node, cfqq->p_root); 1263 } else 1264 cfqq->p_root = NULL; 1265} 1266 1267/* 1268 * Update cfqq's position in the service tree. 1269 */ 1270static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1271{ 1272 /* 1273 * Resorting requires the cfqq to be on the RR list already. 1274 */ 1275 if (cfq_cfqq_on_rr(cfqq)) { 1276 cfq_service_tree_add(cfqd, cfqq, 0); 1277 cfq_prio_tree_add(cfqd, cfqq); 1278 } 1279} 1280 1281/* 1282 * add to busy list of queues for service, trying to be fair in ordering 1283 * the pending list according to last request service 1284 */ 1285static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1286{ 1287 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 1288 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1289 cfq_mark_cfqq_on_rr(cfqq); 1290 cfqd->busy_queues++; 1291 1292 cfq_resort_rr_list(cfqd, cfqq); 1293} 1294 1295/* 1296 * Called when the cfqq no longer has requests pending, remove it from 1297 * the service tree. 1298 */ 1299static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1300{ 1301 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 1302 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 1303 cfq_clear_cfqq_on_rr(cfqq); 1304 1305 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 1306 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); 1307 cfqq->service_tree = NULL; 1308 } 1309 if (cfqq->p_root) { 1310 rb_erase(&cfqq->p_node, cfqq->p_root); 1311 cfqq->p_root = NULL; 1312 } 1313 1314 cfq_group_service_tree_del(cfqd, cfqq->cfqg); 1315 BUG_ON(!cfqd->busy_queues); 1316 cfqd->busy_queues--; 1317} 1318 1319/* 1320 * rb tree support functions 1321 */ 1322static void cfq_del_rq_rb(struct request *rq) 1323{ 1324 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1325 const int sync = rq_is_sync(rq); 1326 1327 BUG_ON(!cfqq->queued[sync]); 1328 cfqq->queued[sync]--; 1329 1330 elv_rb_del(&cfqq->sort_list, rq); 1331 1332 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) { 1333 /* 1334 * Queue will be deleted from service tree when we actually 1335 * expire it later. Right now just remove it from prio tree 1336 * as it is empty. 1337 */ 1338 if (cfqq->p_root) { 1339 rb_erase(&cfqq->p_node, cfqq->p_root); 1340 cfqq->p_root = NULL; 1341 } 1342 } 1343} 1344 1345static void cfq_add_rq_rb(struct request *rq) 1346{ 1347 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1348 struct cfq_data *cfqd = cfqq->cfqd; 1349 struct request *__alias, *prev; 1350 1351 cfqq->queued[rq_is_sync(rq)]++; 1352 1353 /* 1354 * looks a little odd, but the first insert might return an alias. 1355 * if that happens, put the alias on the dispatch list 1356 */ 1357 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 1358 cfq_dispatch_insert(cfqd->queue, __alias); 1359 1360 if (!cfq_cfqq_on_rr(cfqq)) 1361 cfq_add_cfqq_rr(cfqd, cfqq); 1362 1363 /* 1364 * check if this request is a better next-serve candidate 1365 */ 1366 prev = cfqq->next_rq; 1367 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position); 1368 1369 /* 1370 * adjust priority tree position, if ->next_rq changes 1371 */ 1372 if (prev != cfqq->next_rq) 1373 cfq_prio_tree_add(cfqd, cfqq); 1374 1375 BUG_ON(!cfqq->next_rq); 1376} 1377 1378static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 1379{ 1380 elv_rb_del(&cfqq->sort_list, rq); 1381 cfqq->queued[rq_is_sync(rq)]--; 1382 cfq_add_rq_rb(rq); 1383} 1384 1385static struct request * 1386cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 1387{ 1388 struct task_struct *tsk = current; 1389 struct cfq_io_context *cic; 1390 struct cfq_queue *cfqq; 1391 1392 cic = cfq_cic_lookup(cfqd, tsk->io_context); 1393 if (!cic) 1394 return NULL; 1395 1396 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 1397 if (cfqq) { 1398 sector_t sector = bio->bi_sector + bio_sectors(bio); 1399 1400 return elv_rb_find(&cfqq->sort_list, sector); 1401 } 1402 1403 return NULL; 1404} 1405 1406static void cfq_activate_request(struct request_queue *q, struct request *rq) 1407{ 1408 struct cfq_data *cfqd = q->elevator->elevator_data; 1409 1410 cfqd->rq_in_driver++; 1411 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 1412 cfqd->rq_in_driver); 1413 1414 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); 1415} 1416 1417static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 1418{ 1419 struct cfq_data *cfqd = q->elevator->elevator_data; 1420 1421 WARN_ON(!cfqd->rq_in_driver); 1422 cfqd->rq_in_driver--; 1423 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 1424 cfqd->rq_in_driver); 1425} 1426 1427static void cfq_remove_request(struct request *rq) 1428{ 1429 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1430 1431 if (cfqq->next_rq == rq) 1432 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 1433 1434 list_del_init(&rq->queuelist); 1435 cfq_del_rq_rb(rq); 1436 1437 cfqq->cfqd->rq_queued--; 1438 if (rq_is_meta(rq)) { 1439 WARN_ON(!cfqq->meta_pending); 1440 cfqq->meta_pending--; 1441 } 1442} 1443 1444static int cfq_merge(struct request_queue *q, struct request **req, 1445 struct bio *bio) 1446{ 1447 struct cfq_data *cfqd = q->elevator->elevator_data; 1448 struct request *__rq; 1449 1450 __rq = cfq_find_rq_fmerge(cfqd, bio); 1451 if (__rq && elv_rq_merge_ok(__rq, bio)) { 1452 *req = __rq; 1453 return ELEVATOR_FRONT_MERGE; 1454 } 1455 1456 return ELEVATOR_NO_MERGE; 1457} 1458 1459static void cfq_merged_request(struct request_queue *q, struct request *req, 1460 int type) 1461{ 1462 if (type == ELEVATOR_FRONT_MERGE) { 1463 struct cfq_queue *cfqq = RQ_CFQQ(req); 1464 1465 cfq_reposition_rq_rb(cfqq, req); 1466 } 1467} 1468 1469static void 1470cfq_merged_requests(struct request_queue *q, struct request *rq, 1471 struct request *next) 1472{ 1473 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1474 /* 1475 * reposition in fifo if next is older than rq 1476 */ 1477 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 1478 time_before(rq_fifo_time(next), rq_fifo_time(rq))) { 1479 list_move(&rq->queuelist, &next->queuelist); 1480 rq_set_fifo_time(rq, rq_fifo_time(next)); 1481 } 1482 1483 if (cfqq->next_rq == next) 1484 cfqq->next_rq = rq; 1485 cfq_remove_request(next); 1486} 1487 1488static int cfq_allow_merge(struct request_queue *q, struct request *rq, 1489 struct bio *bio) 1490{ 1491 struct cfq_data *cfqd = q->elevator->elevator_data; 1492 struct cfq_io_context *cic; 1493 struct cfq_queue *cfqq; 1494 1495 /* 1496 * Disallow merge of a sync bio into an async request. 1497 */ 1498 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 1499 return false; 1500 1501 /* 1502 * Lookup the cfqq that this bio will be queued with. Allow 1503 * merge only if rq is queued there. 1504 */ 1505 cic = cfq_cic_lookup(cfqd, current->io_context); 1506 if (!cic) 1507 return false; 1508 1509 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 1510 return cfqq == RQ_CFQQ(rq); 1511} 1512 1513static void __cfq_set_active_queue(struct cfq_data *cfqd, 1514 struct cfq_queue *cfqq) 1515{ 1516 if (cfqq) { 1517 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d", 1518 cfqd->serving_prio, cfqd->serving_type); 1519 cfqq->slice_start = 0; 1520 cfqq->dispatch_start = jiffies; 1521 cfqq->allocated_slice = 0; 1522 cfqq->slice_end = 0; 1523 cfqq->slice_dispatch = 0; 1524 1525 cfq_clear_cfqq_wait_request(cfqq); 1526 cfq_clear_cfqq_must_dispatch(cfqq); 1527 cfq_clear_cfqq_must_alloc_slice(cfqq); 1528 cfq_clear_cfqq_fifo_expire(cfqq); 1529 cfq_mark_cfqq_slice_new(cfqq); 1530 1531 del_timer(&cfqd->idle_slice_timer); 1532 } 1533 1534 cfqd->active_queue = cfqq; 1535} 1536 1537/* 1538 * current cfqq expired its slice (or was too idle), select new one 1539 */ 1540static void 1541__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1542 bool timed_out) 1543{ 1544 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 1545 1546 if (cfq_cfqq_wait_request(cfqq)) 1547 del_timer(&cfqd->idle_slice_timer); 1548 1549 cfq_clear_cfqq_wait_request(cfqq); 1550 cfq_clear_cfqq_wait_busy(cfqq); 1551 1552 /* 1553 * If this cfqq is shared between multiple processes, check to 1554 * make sure that those processes are still issuing I/Os within 1555 * the mean seek distance. If not, it may be time to break the 1556 * queues apart again. 1557 */ 1558 if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq)) 1559 cfq_mark_cfqq_split_coop(cfqq); 1560 1561 /* 1562 * store what was left of this slice, if the queue idled/timed out 1563 */ 1564 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 1565 cfqq->slice_resid = cfqq->slice_end - jiffies; 1566 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 1567 } 1568 1569 cfq_group_served(cfqd, cfqq->cfqg, cfqq); 1570 1571 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 1572 cfq_del_cfqq_rr(cfqd, cfqq); 1573 1574 cfq_resort_rr_list(cfqd, cfqq); 1575 1576 if (cfqq == cfqd->active_queue) 1577 cfqd->active_queue = NULL; 1578 1579 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active) 1580 cfqd->grp_service_tree.active = NULL; 1581 1582 if (cfqd->active_cic) { 1583 put_io_context(cfqd->active_cic->ioc); 1584 cfqd->active_cic = NULL; 1585 } 1586} 1587 1588static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out) 1589{ 1590 struct cfq_queue *cfqq = cfqd->active_queue; 1591 1592 if (cfqq) 1593 __cfq_slice_expired(cfqd, cfqq, timed_out); 1594} 1595 1596/* 1597 * Get next queue for service. Unless we have a queue preemption, 1598 * we'll simply select the first cfqq in the service tree. 1599 */ 1600static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 1601{ 1602 struct cfq_rb_root *service_tree = 1603 service_tree_for(cfqd->serving_group, cfqd->serving_prio, 1604 cfqd->serving_type); 1605 1606 if (!cfqd->rq_queued) 1607 return NULL; 1608 1609 /* There is nothing to dispatch */ 1610 if (!service_tree) 1611 return NULL; 1612 if (RB_EMPTY_ROOT(&service_tree->rb)) 1613 return NULL; 1614 return cfq_rb_first(service_tree); 1615} 1616 1617static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd) 1618{ 1619 struct cfq_group *cfqg; 1620 struct cfq_queue *cfqq; 1621 int i, j; 1622 struct cfq_rb_root *st; 1623 1624 if (!cfqd->rq_queued) 1625 return NULL; 1626 1627 cfqg = cfq_get_next_cfqg(cfqd); 1628 if (!cfqg) 1629 return NULL; 1630 1631 for_each_cfqg_st(cfqg, i, j, st) 1632 if ((cfqq = cfq_rb_first(st)) != NULL) 1633 return cfqq; 1634 return NULL; 1635} 1636 1637/* 1638 * Get and set a new active queue for service. 1639 */ 1640static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, 1641 struct cfq_queue *cfqq) 1642{ 1643 if (!cfqq) 1644 cfqq = cfq_get_next_queue(cfqd); 1645 1646 __cfq_set_active_queue(cfqd, cfqq); 1647 return cfqq; 1648} 1649 1650static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 1651 struct request *rq) 1652{ 1653 if (blk_rq_pos(rq) >= cfqd->last_position) 1654 return blk_rq_pos(rq) - cfqd->last_position; 1655 else 1656 return cfqd->last_position - blk_rq_pos(rq); 1657} 1658 1659static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1660 struct request *rq) 1661{ 1662 return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR; 1663} 1664 1665static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 1666 struct cfq_queue *cur_cfqq) 1667{ 1668 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; 1669 struct rb_node *parent, *node; 1670 struct cfq_queue *__cfqq; 1671 sector_t sector = cfqd->last_position; 1672 1673 if (RB_EMPTY_ROOT(root)) 1674 return NULL; 1675 1676 /* 1677 * First, if we find a request starting at the end of the last 1678 * request, choose it. 1679 */ 1680 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); 1681 if (__cfqq) 1682 return __cfqq; 1683 1684 /* 1685 * If the exact sector wasn't found, the parent of the NULL leaf 1686 * will contain the closest sector. 1687 */ 1688 __cfqq = rb_entry(parent, struct cfq_queue, p_node); 1689 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) 1690 return __cfqq; 1691 1692 if (blk_rq_pos(__cfqq->next_rq) < sector) 1693 node = rb_next(&__cfqq->p_node); 1694 else 1695 node = rb_prev(&__cfqq->p_node); 1696 if (!node) 1697 return NULL; 1698 1699 __cfqq = rb_entry(node, struct cfq_queue, p_node); 1700 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) 1701 return __cfqq; 1702 1703 return NULL; 1704} 1705 1706/* 1707 * cfqd - obvious 1708 * cur_cfqq - passed in so that we don't decide that the current queue is 1709 * closely cooperating with itself. 1710 * 1711 * So, basically we're assuming that that cur_cfqq has dispatched at least 1712 * one request, and that cfqd->last_position reflects a position on the disk 1713 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid 1714 * assumption. 1715 */ 1716static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, 1717 struct cfq_queue *cur_cfqq) 1718{ 1719 struct cfq_queue *cfqq; 1720 1721 if (cfq_class_idle(cur_cfqq)) 1722 return NULL; 1723 if (!cfq_cfqq_sync(cur_cfqq)) 1724 return NULL; 1725 if (CFQQ_SEEKY(cur_cfqq)) 1726 return NULL; 1727 1728 /* 1729 * Don't search priority tree if it's the only queue in the group. 1730 */ 1731 if (cur_cfqq->cfqg->nr_cfqq == 1) 1732 return NULL; 1733 1734 /* 1735 * We should notice if some of the queues are cooperating, eg 1736 * working closely on the same area of the disk. In that case, 1737 * we can group them together and don't waste time idling. 1738 */ 1739 cfqq = cfqq_close(cfqd, cur_cfqq); 1740 if (!cfqq) 1741 return NULL; 1742 1743 /* If new queue belongs to different cfq_group, don't choose it */ 1744 if (cur_cfqq->cfqg != cfqq->cfqg) 1745 return NULL; 1746 1747 /* 1748 * It only makes sense to merge sync queues. 1749 */ 1750 if (!cfq_cfqq_sync(cfqq)) 1751 return NULL; 1752 if (CFQQ_SEEKY(cfqq)) 1753 return NULL; 1754 1755 /* 1756 * Do not merge queues of different priority classes 1757 */ 1758 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq)) 1759 return NULL; 1760 1761 return cfqq; 1762} 1763 1764/* 1765 * Determine whether we should enforce idle window for this queue. 1766 */ 1767 1768static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1769{ 1770 enum wl_prio_t prio = cfqq_prio(cfqq); 1771 struct cfq_rb_root *service_tree = cfqq->service_tree; 1772 1773 BUG_ON(!service_tree); 1774 BUG_ON(!service_tree->count); 1775 1776 /* We never do for idle class queues. */ 1777 if (prio == IDLE_WORKLOAD) 1778 return false; 1779 1780 /* We do for queues that were marked with idle window flag. */ 1781 if (cfq_cfqq_idle_window(cfqq) && 1782 !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)) 1783 return true; 1784 1785 /* 1786 * Otherwise, we do only if they are the last ones 1787 * in their service tree. 1788 */ 1789 if (service_tree->count == 1 && cfq_cfqq_sync(cfqq)) 1790 return 1; 1791 cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", 1792 service_tree->count); 1793 return 0; 1794} 1795 1796static void cfq_arm_slice_timer(struct cfq_data *cfqd) 1797{ 1798 struct cfq_queue *cfqq = cfqd->active_queue; 1799 struct cfq_io_context *cic; 1800 unsigned long sl; 1801 1802 /* 1803 * SSD device without seek penalty, disable idling. But only do so 1804 * for devices that support queuing, otherwise we still have a problem 1805 * with sync vs async workloads. 1806 */ 1807 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 1808 return; 1809 1810 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 1811 WARN_ON(cfq_cfqq_slice_new(cfqq)); 1812 1813 /* 1814 * idle is disabled, either manually or by past process history 1815 */ 1816 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq)) 1817 return; 1818 1819 /* 1820 * still active requests from this queue, don't idle 1821 */ 1822 if (cfqq->dispatched) 1823 return; 1824 1825 /* 1826 * task has exited, don't wait 1827 */ 1828 cic = cfqd->active_cic; 1829 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 1830 return; 1831 1832 /* 1833 * If our average think time is larger than the remaining time 1834 * slice, then don't idle. This avoids overrunning the allotted 1835 * time slice. 1836 */ 1837 if (sample_valid(cic->ttime_samples) && 1838 (cfqq->slice_end - jiffies < cic->ttime_mean)) { 1839 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d", 1840 cic->ttime_mean); 1841 return; 1842 } 1843 1844 cfq_mark_cfqq_wait_request(cfqq); 1845 1846 sl = cfqd->cfq_slice_idle; 1847 1848 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 1849 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl); 1850} 1851 1852/* 1853 * Move request from internal lists to the request queue dispatch list. 1854 */ 1855static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 1856{ 1857 struct cfq_data *cfqd = q->elevator->elevator_data; 1858 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1859 1860 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 1861 1862 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq); 1863 cfq_remove_request(rq); 1864 cfqq->dispatched++; 1865 elv_dispatch_sort(q, rq); 1866 1867 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++; 1868} 1869 1870/* 1871 * return expired entry, or NULL to just start from scratch in rbtree 1872 */ 1873static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 1874{ 1875 struct request *rq = NULL; 1876 1877 if (cfq_cfqq_fifo_expire(cfqq)) 1878 return NULL; 1879 1880 cfq_mark_cfqq_fifo_expire(cfqq); 1881 1882 if (list_empty(&cfqq->fifo)) 1883 return NULL; 1884 1885 rq = rq_entry_fifo(cfqq->fifo.next); 1886 if (time_before(jiffies, rq_fifo_time(rq))) 1887 rq = NULL; 1888 1889 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); 1890 return rq; 1891} 1892 1893static inline int 1894cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1895{ 1896 const int base_rq = cfqd->cfq_slice_async_rq; 1897 1898 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 1899 1900 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 1901} 1902 1903/* 1904 * Must be called with the queue_lock held. 1905 */ 1906static int cfqq_process_refs(struct cfq_queue *cfqq) 1907{ 1908 int process_refs, io_refs; 1909 1910 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE]; 1911 process_refs = atomic_read(&cfqq->ref) - io_refs; 1912 BUG_ON(process_refs < 0); 1913 return process_refs; 1914} 1915 1916static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) 1917{ 1918 int process_refs, new_process_refs; 1919 struct cfq_queue *__cfqq; 1920 1921 /* Avoid a circular list and skip interim queue merges */ 1922 while ((__cfqq = new_cfqq->new_cfqq)) { 1923 if (__cfqq == cfqq) 1924 return; 1925 new_cfqq = __cfqq; 1926 } 1927 1928 process_refs = cfqq_process_refs(cfqq); 1929 /* 1930 * If the process for the cfqq has gone away, there is no 1931 * sense in merging the queues. 1932 */ 1933 if (process_refs == 0) 1934 return; 1935 1936 /* 1937 * Merge in the direction of the lesser amount of work. 1938 */ 1939 new_process_refs = cfqq_process_refs(new_cfqq); 1940 if (new_process_refs >= process_refs) { 1941 cfqq->new_cfqq = new_cfqq; 1942 atomic_add(process_refs, &new_cfqq->ref); 1943 } else { 1944 new_cfqq->new_cfqq = cfqq; 1945 atomic_add(new_process_refs, &cfqq->ref); 1946 } 1947} 1948 1949static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, 1950 struct cfq_group *cfqg, enum wl_prio_t prio) 1951{ 1952 struct cfq_queue *queue; 1953 int i; 1954 bool key_valid = false; 1955 unsigned long lowest_key = 0; 1956 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; 1957 1958 for (i = 0; i <= SYNC_WORKLOAD; ++i) { 1959 /* select the one with lowest rb_key */ 1960 queue = cfq_rb_first(service_tree_for(cfqg, prio, i)); 1961 if (queue && 1962 (!key_valid || time_before(queue->rb_key, lowest_key))) { 1963 lowest_key = queue->rb_key; 1964 cur_best = i; 1965 key_valid = true; 1966 } 1967 } 1968 1969 return cur_best; 1970} 1971 1972static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg) 1973{ 1974 unsigned slice; 1975 unsigned count; 1976 struct cfq_rb_root *st; 1977 unsigned group_slice; 1978 1979 if (!cfqg) { 1980 cfqd->serving_prio = IDLE_WORKLOAD; 1981 cfqd->workload_expires = jiffies + 1; 1982 return; 1983 } 1984 1985 /* Choose next priority. RT > BE > IDLE */ 1986 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg)) 1987 cfqd->serving_prio = RT_WORKLOAD; 1988 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg)) 1989 cfqd->serving_prio = BE_WORKLOAD; 1990 else { 1991 cfqd->serving_prio = IDLE_WORKLOAD; 1992 cfqd->workload_expires = jiffies + 1; 1993 return; 1994 } 1995 1996 /* 1997 * For RT and BE, we have to choose also the type 1998 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload 1999 * expiration time 2000 */ 2001 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); 2002 count = st->count; 2003 2004 /* 2005 * check workload expiration, and that we still have other queues ready 2006 */ 2007 if (count && !time_after(jiffies, cfqd->workload_expires)) 2008 return; 2009 2010 /* otherwise select new workload type */ 2011 cfqd->serving_type = 2012 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio); 2013 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); 2014 count = st->count; 2015 2016 /* 2017 * the workload slice is computed as a fraction of target latency 2018 * proportional to the number of queues in that workload, over 2019 * all the queues in the same priority class 2020 */ 2021 group_slice = cfq_group_slice(cfqd, cfqg); 2022 2023 slice = group_slice * count / 2024 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio], 2025 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg)); 2026 2027 if (cfqd->serving_type == ASYNC_WORKLOAD) { 2028 unsigned int tmp; 2029 2030 /* 2031 * Async queues are currently system wide. Just taking 2032 * proportion of queues with-in same group will lead to higher 2033 * async ratio system wide as generally root group is going 2034 * to have higher weight. A more accurate thing would be to 2035 * calculate system wide asnc/sync ratio. 2036 */ 2037 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg); 2038 tmp = tmp/cfqd->busy_queues; 2039 slice = min_t(unsigned, slice, tmp); 2040 2041 /* async workload slice is scaled down according to 2042 * the sync/async slice ratio. */ 2043 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1]; 2044 } else 2045 /* sync workload slice is at least 2 * cfq_slice_idle */ 2046 slice = max(slice, 2 * cfqd->cfq_slice_idle); 2047 2048 slice = max_t(unsigned, slice, CFQ_MIN_TT); 2049 cfq_log(cfqd, "workload slice:%d", slice); 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 inline bool cfq_slice_used_soon(struct cfq_data *cfqd, 2208 struct cfq_queue *cfqq) 2209{ 2210 /* the queue hasn't finished any request, can't estimate */ 2211 if (cfq_cfqq_slice_new(cfqq)) 2212 return 1; 2213 if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched, 2214 cfqq->slice_end)) 2215 return 1; 2216 2217 return 0; 2218} 2219 2220static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2221{ 2222 unsigned int max_dispatch; 2223 2224 /* 2225 * Drain async requests before we start sync IO 2226 */ 2227 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC]) 2228 return false; 2229 2230 /* 2231 * If this is an async queue and we have sync IO in flight, let it wait 2232 */ 2233 if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq)) 2234 return false; 2235 2236 max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1); 2237 if (cfq_class_idle(cfqq)) 2238 max_dispatch = 1; 2239 2240 /* 2241 * Does this cfqq already have too much IO in flight? 2242 */ 2243 if (cfqq->dispatched >= max_dispatch) { 2244 /* 2245 * idle queue must always only have a single IO in flight 2246 */ 2247 if (cfq_class_idle(cfqq)) 2248 return false; 2249 2250 /* 2251 * We have other queues, don't allow more IO from this one 2252 */ 2253 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq)) 2254 return false; 2255 2256 /* 2257 * Sole queue user, no limit 2258 */ 2259 if (cfqd->busy_queues == 1) 2260 max_dispatch = -1; 2261 else 2262 /* 2263 * Normally we start throttling cfqq when cfq_quantum/2 2264 * requests have been dispatched. But we can drive 2265 * deeper queue depths at the beginning of slice 2266 * subjected to upper limit of cfq_quantum. 2267 * */ 2268 max_dispatch = cfqd->cfq_quantum; 2269 } 2270 2271 /* 2272 * Async queues must wait a bit before being allowed dispatch. 2273 * We also ramp up the dispatch depth gradually for async IO, 2274 * based on the last sync IO we serviced 2275 */ 2276 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { 2277 unsigned long last_sync = jiffies - cfqd->last_delayed_sync; 2278 unsigned int depth; 2279 2280 depth = last_sync / cfqd->cfq_slice[1]; 2281 if (!depth && !cfqq->dispatched) 2282 depth = 1; 2283 if (depth < max_dispatch) 2284 max_dispatch = depth; 2285 } 2286 2287 /* 2288 * If we're below the current max, allow a dispatch 2289 */ 2290 return cfqq->dispatched < max_dispatch; 2291} 2292 2293/* 2294 * Dispatch a request from cfqq, moving them to the request queue 2295 * dispatch list. 2296 */ 2297static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2298{ 2299 struct request *rq; 2300 2301 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 2302 2303 if (!cfq_may_dispatch(cfqd, cfqq)) 2304 return false; 2305 2306 /* 2307 * follow expired path, else get first next available 2308 */ 2309 rq = cfq_check_fifo(cfqq); 2310 if (!rq) 2311 rq = cfqq->next_rq; 2312 2313 /* 2314 * insert request into driver dispatch list 2315 */ 2316 cfq_dispatch_insert(cfqd->queue, rq); 2317 2318 if (!cfqd->active_cic) { 2319 struct cfq_io_context *cic = RQ_CIC(rq); 2320 2321 atomic_long_inc(&cic->ioc->refcount); 2322 cfqd->active_cic = cic; 2323 } 2324 2325 return true; 2326} 2327 2328/* 2329 * Find the cfqq that we need to service and move a request from that to the 2330 * dispatch list 2331 */ 2332static int cfq_dispatch_requests(struct request_queue *q, int force) 2333{ 2334 struct cfq_data *cfqd = q->elevator->elevator_data; 2335 struct cfq_queue *cfqq; 2336 2337 if (!cfqd->busy_queues) 2338 return 0; 2339 2340 if (unlikely(force)) 2341 return cfq_forced_dispatch(cfqd); 2342 2343 cfqq = cfq_select_queue(cfqd); 2344 if (!cfqq) 2345 return 0; 2346 2347 /* 2348 * Dispatch a request from this cfqq, if it is allowed 2349 */ 2350 if (!cfq_dispatch_request(cfqd, cfqq)) 2351 return 0; 2352 2353 cfqq->slice_dispatch++; 2354 cfq_clear_cfqq_must_dispatch(cfqq); 2355 2356 /* 2357 * expire an async queue immediately if it has used up its slice. idle 2358 * queue always expire after 1 dispatch round. 2359 */ 2360 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 2361 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || 2362 cfq_class_idle(cfqq))) { 2363 cfqq->slice_end = jiffies + 1; 2364 cfq_slice_expired(cfqd, 0); 2365 } 2366 2367 cfq_log_cfqq(cfqd, cfqq, "dispatched a request"); 2368 return 1; 2369} 2370 2371/* 2372 * task holds one reference to the queue, dropped when task exits. each rq 2373 * in-flight on this queue also holds a reference, dropped when rq is freed. 2374 * 2375 * Each cfq queue took a reference on the parent group. Drop it now. 2376 * queue lock must be held here. 2377 */ 2378static void cfq_put_queue(struct cfq_queue *cfqq) 2379{ 2380 struct cfq_data *cfqd = cfqq->cfqd; 2381 struct cfq_group *cfqg, *orig_cfqg; 2382 2383 BUG_ON(atomic_read(&cfqq->ref) <= 0); 2384 2385 if (!atomic_dec_and_test(&cfqq->ref)) 2386 return; 2387 2388 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 2389 BUG_ON(rb_first(&cfqq->sort_list)); 2390 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 2391 cfqg = cfqq->cfqg; 2392 orig_cfqg = cfqq->orig_cfqg; 2393 2394 if (unlikely(cfqd->active_queue == cfqq)) { 2395 __cfq_slice_expired(cfqd, cfqq, 0); 2396 cfq_schedule_dispatch(cfqd); 2397 } 2398 2399 BUG_ON(cfq_cfqq_on_rr(cfqq)); 2400 kmem_cache_free(cfq_pool, cfqq); 2401 cfq_put_cfqg(cfqg); 2402 if (orig_cfqg) 2403 cfq_put_cfqg(orig_cfqg); 2404} 2405 2406/* 2407 * Must always be called with the rcu_read_lock() held 2408 */ 2409static void 2410__call_for_each_cic(struct io_context *ioc, 2411 void (*func)(struct io_context *, struct cfq_io_context *)) 2412{ 2413 struct cfq_io_context *cic; 2414 struct hlist_node *n; 2415 2416 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 2417 func(ioc, cic); 2418} 2419 2420/* 2421 * Call func for each cic attached to this ioc. 2422 */ 2423static void 2424call_for_each_cic(struct io_context *ioc, 2425 void (*func)(struct io_context *, struct cfq_io_context *)) 2426{ 2427 rcu_read_lock(); 2428 __call_for_each_cic(ioc, func); 2429 rcu_read_unlock(); 2430} 2431 2432static void cfq_cic_free_rcu(struct rcu_head *head) 2433{ 2434 struct cfq_io_context *cic; 2435 2436 cic = container_of(head, struct cfq_io_context, rcu_head); 2437 2438 kmem_cache_free(cfq_ioc_pool, cic); 2439 elv_ioc_count_dec(cfq_ioc_count); 2440 2441 if (ioc_gone) { 2442 /* 2443 * CFQ scheduler is exiting, grab exit lock and check 2444 * the pending io context count. If it hits zero, 2445 * complete ioc_gone and set it back to NULL 2446 */ 2447 spin_lock(&ioc_gone_lock); 2448 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) { 2449 complete(ioc_gone); 2450 ioc_gone = NULL; 2451 } 2452 spin_unlock(&ioc_gone_lock); 2453 } 2454} 2455 2456static void cfq_cic_free(struct cfq_io_context *cic) 2457{ 2458 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 2459} 2460 2461static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 2462{ 2463 unsigned long flags; 2464 2465 BUG_ON(!cic->dead_key); 2466 2467 spin_lock_irqsave(&ioc->lock, flags); 2468 radix_tree_delete(&ioc->radix_root, cic->dead_key); 2469 hlist_del_rcu(&cic->cic_list); 2470 spin_unlock_irqrestore(&ioc->lock, flags); 2471 2472 cfq_cic_free(cic); 2473} 2474 2475/* 2476 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 2477 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 2478 * and ->trim() which is called with the task lock held 2479 */ 2480static void cfq_free_io_context(struct io_context *ioc) 2481{ 2482 /* 2483 * ioc->refcount is zero here, or we are called from elv_unregister(), 2484 * so no more cic's are allowed to be linked into this ioc. So it 2485 * should be ok to iterate over the known list, we will see all cic's 2486 * since no new ones are added. 2487 */ 2488 __call_for_each_cic(ioc, cic_free_func); 2489} 2490 2491static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2492{ 2493 struct cfq_queue *__cfqq, *next; 2494 2495 if (unlikely(cfqq == cfqd->active_queue)) { 2496 __cfq_slice_expired(cfqd, cfqq, 0); 2497 cfq_schedule_dispatch(cfqd); 2498 } 2499 2500 /* 2501 * If this queue was scheduled to merge with another queue, be 2502 * sure to drop the reference taken on that queue (and others in 2503 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs. 2504 */ 2505 __cfqq = cfqq->new_cfqq; 2506 while (__cfqq) { 2507 if (__cfqq == cfqq) { 2508 WARN(1, "cfqq->new_cfqq loop detected\n"); 2509 break; 2510 } 2511 next = __cfqq->new_cfqq; 2512 cfq_put_queue(__cfqq); 2513 __cfqq = next; 2514 } 2515 2516 cfq_put_queue(cfqq); 2517} 2518 2519static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 2520 struct cfq_io_context *cic) 2521{ 2522 struct io_context *ioc = cic->ioc; 2523 2524 list_del_init(&cic->queue_list); 2525 2526 /* 2527 * Make sure key == NULL is seen for dead queues 2528 */ 2529 smp_wmb(); 2530 cic->dead_key = (unsigned long) cic->key; 2531 cic->key = NULL; 2532 2533 if (ioc->ioc_data == cic) 2534 rcu_assign_pointer(ioc->ioc_data, NULL); 2535 2536 if (cic->cfqq[BLK_RW_ASYNC]) { 2537 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); 2538 cic->cfqq[BLK_RW_ASYNC] = NULL; 2539 } 2540 2541 if (cic->cfqq[BLK_RW_SYNC]) { 2542 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); 2543 cic->cfqq[BLK_RW_SYNC] = NULL; 2544 } 2545} 2546 2547static void cfq_exit_single_io_context(struct io_context *ioc, 2548 struct cfq_io_context *cic) 2549{ 2550 struct cfq_data *cfqd = cic->key; 2551 2552 if (cfqd) { 2553 struct request_queue *q = cfqd->queue; 2554 unsigned long flags; 2555 2556 spin_lock_irqsave(q->queue_lock, flags); 2557 2558 /* 2559 * Ensure we get a fresh copy of the ->key to prevent 2560 * race between exiting task and queue 2561 */ 2562 smp_read_barrier_depends(); 2563 if (cic->key) 2564 __cfq_exit_single_io_context(cfqd, cic); 2565 2566 spin_unlock_irqrestore(q->queue_lock, flags); 2567 } 2568} 2569 2570/* 2571 * The process that ioc belongs to has exited, we need to clean up 2572 * and put the internal structures we have that belongs to that process. 2573 */ 2574static void cfq_exit_io_context(struct io_context *ioc) 2575{ 2576 call_for_each_cic(ioc, cfq_exit_single_io_context); 2577} 2578 2579static struct cfq_io_context * 2580cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 2581{ 2582 struct cfq_io_context *cic; 2583 2584 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 2585 cfqd->queue->node); 2586 if (cic) { 2587 cic->last_end_request = jiffies; 2588 INIT_LIST_HEAD(&cic->queue_list); 2589 INIT_HLIST_NODE(&cic->cic_list); 2590 cic->dtor = cfq_free_io_context; 2591 cic->exit = cfq_exit_io_context; 2592 elv_ioc_count_inc(cfq_ioc_count); 2593 } 2594 2595 return cic; 2596} 2597 2598static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 2599{ 2600 struct task_struct *tsk = current; 2601 int ioprio_class; 2602 2603 if (!cfq_cfqq_prio_changed(cfqq)) 2604 return; 2605 2606 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 2607 switch (ioprio_class) { 2608 default: 2609 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 2610 case IOPRIO_CLASS_NONE: 2611 /* 2612 * no prio set, inherit CPU scheduling settings 2613 */ 2614 cfqq->ioprio = task_nice_ioprio(tsk); 2615 cfqq->ioprio_class = task_nice_ioclass(tsk); 2616 break; 2617 case IOPRIO_CLASS_RT: 2618 cfqq->ioprio = task_ioprio(ioc); 2619 cfqq->ioprio_class = IOPRIO_CLASS_RT; 2620 break; 2621 case IOPRIO_CLASS_BE: 2622 cfqq->ioprio = task_ioprio(ioc); 2623 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2624 break; 2625 case IOPRIO_CLASS_IDLE: 2626 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 2627 cfqq->ioprio = 7; 2628 cfq_clear_cfqq_idle_window(cfqq); 2629 break; 2630 } 2631 2632 /* 2633 * keep track of original prio settings in case we have to temporarily 2634 * elevate the priority of this queue 2635 */ 2636 cfqq->org_ioprio = cfqq->ioprio; 2637 cfqq->org_ioprio_class = cfqq->ioprio_class; 2638 cfq_clear_cfqq_prio_changed(cfqq); 2639} 2640 2641static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 2642{ 2643 struct cfq_data *cfqd = cic->key; 2644 struct cfq_queue *cfqq; 2645 unsigned long flags; 2646 2647 if (unlikely(!cfqd)) 2648 return; 2649 2650 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2651 2652 cfqq = cic->cfqq[BLK_RW_ASYNC]; 2653 if (cfqq) { 2654 struct cfq_queue *new_cfqq; 2655 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, 2656 GFP_ATOMIC); 2657 if (new_cfqq) { 2658 cic->cfqq[BLK_RW_ASYNC] = new_cfqq; 2659 cfq_put_queue(cfqq); 2660 } 2661 } 2662 2663 cfqq = cic->cfqq[BLK_RW_SYNC]; 2664 if (cfqq) 2665 cfq_mark_cfqq_prio_changed(cfqq); 2666 2667 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2668} 2669 2670static void cfq_ioc_set_ioprio(struct io_context *ioc) 2671{ 2672 call_for_each_cic(ioc, changed_ioprio); 2673 ioc->ioprio_changed = 0; 2674} 2675 2676static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2677 pid_t pid, bool is_sync) 2678{ 2679 RB_CLEAR_NODE(&cfqq->rb_node); 2680 RB_CLEAR_NODE(&cfqq->p_node); 2681 INIT_LIST_HEAD(&cfqq->fifo); 2682 2683 atomic_set(&cfqq->ref, 0); 2684 cfqq->cfqd = cfqd; 2685 2686 cfq_mark_cfqq_prio_changed(cfqq); 2687 2688 if (is_sync) { 2689 if (!cfq_class_idle(cfqq)) 2690 cfq_mark_cfqq_idle_window(cfqq); 2691 cfq_mark_cfqq_sync(cfqq); 2692 } 2693 cfqq->pid = pid; 2694} 2695 2696#ifdef CONFIG_CFQ_GROUP_IOSCHED 2697static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic) 2698{ 2699 struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1); 2700 struct cfq_data *cfqd = cic->key; 2701 unsigned long flags; 2702 struct request_queue *q; 2703 2704 if (unlikely(!cfqd)) 2705 return; 2706 2707 q = cfqd->queue; 2708 2709 spin_lock_irqsave(q->queue_lock, flags); 2710 2711 if (sync_cfqq) { 2712 /* 2713 * Drop reference to sync queue. A new sync queue will be 2714 * assigned in new group upon arrival of a fresh request. 2715 */ 2716 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup"); 2717 cic_set_cfqq(cic, NULL, 1); 2718 cfq_put_queue(sync_cfqq); 2719 } 2720 2721 spin_unlock_irqrestore(q->queue_lock, flags); 2722} 2723 2724static void cfq_ioc_set_cgroup(struct io_context *ioc) 2725{ 2726 call_for_each_cic(ioc, changed_cgroup); 2727 ioc->cgroup_changed = 0; 2728} 2729#endif /* CONFIG_CFQ_GROUP_IOSCHED */ 2730 2731static struct cfq_queue * 2732cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, 2733 struct io_context *ioc, gfp_t gfp_mask) 2734{ 2735 struct cfq_queue *cfqq, *new_cfqq = NULL; 2736 struct cfq_io_context *cic; 2737 struct cfq_group *cfqg; 2738 2739retry: 2740 cfqg = cfq_get_cfqg(cfqd, 1); 2741 cic = cfq_cic_lookup(cfqd, ioc); 2742 /* cic always exists here */ 2743 cfqq = cic_to_cfqq(cic, is_sync); 2744 2745 /* 2746 * Always try a new alloc if we fell back to the OOM cfqq 2747 * originally, since it should just be a temporary situation. 2748 */ 2749 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 2750 cfqq = NULL; 2751 if (new_cfqq) { 2752 cfqq = new_cfqq; 2753 new_cfqq = NULL; 2754 } else if (gfp_mask & __GFP_WAIT) { 2755 spin_unlock_irq(cfqd->queue->queue_lock); 2756 new_cfqq = kmem_cache_alloc_node(cfq_pool, 2757 gfp_mask | __GFP_ZERO, 2758 cfqd->queue->node); 2759 spin_lock_irq(cfqd->queue->queue_lock); 2760 if (new_cfqq) 2761 goto retry; 2762 } else { 2763 cfqq = kmem_cache_alloc_node(cfq_pool, 2764 gfp_mask | __GFP_ZERO, 2765 cfqd->queue->node); 2766 } 2767 2768 if (cfqq) { 2769 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); 2770 cfq_init_prio_data(cfqq, ioc); 2771 cfq_link_cfqq_cfqg(cfqq, cfqg); 2772 cfq_log_cfqq(cfqd, cfqq, "alloced"); 2773 } else 2774 cfqq = &cfqd->oom_cfqq; 2775 } 2776 2777 if (new_cfqq) 2778 kmem_cache_free(cfq_pool, new_cfqq); 2779 2780 return cfqq; 2781} 2782 2783static struct cfq_queue ** 2784cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 2785{ 2786 switch (ioprio_class) { 2787 case IOPRIO_CLASS_RT: 2788 return &cfqd->async_cfqq[0][ioprio]; 2789 case IOPRIO_CLASS_BE: 2790 return &cfqd->async_cfqq[1][ioprio]; 2791 case IOPRIO_CLASS_IDLE: 2792 return &cfqd->async_idle_cfqq; 2793 default: 2794 BUG(); 2795 } 2796} 2797 2798static struct cfq_queue * 2799cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc, 2800 gfp_t gfp_mask) 2801{ 2802 const int ioprio = task_ioprio(ioc); 2803 const int ioprio_class = task_ioprio_class(ioc); 2804 struct cfq_queue **async_cfqq = NULL; 2805 struct cfq_queue *cfqq = NULL; 2806 2807 if (!is_sync) { 2808 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 2809 cfqq = *async_cfqq; 2810 } 2811 2812 if (!cfqq) 2813 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 2814 2815 /* 2816 * pin the queue now that it's allocated, scheduler exit will prune it 2817 */ 2818 if (!is_sync && !(*async_cfqq)) { 2819 atomic_inc(&cfqq->ref); 2820 *async_cfqq = cfqq; 2821 } 2822 2823 atomic_inc(&cfqq->ref); 2824 return cfqq; 2825} 2826 2827/* 2828 * We drop cfq io contexts lazily, so we may find a dead one. 2829 */ 2830static void 2831cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 2832 struct cfq_io_context *cic) 2833{ 2834 unsigned long flags; 2835 2836 WARN_ON(!list_empty(&cic->queue_list)); 2837 2838 spin_lock_irqsave(&ioc->lock, flags); 2839 2840 BUG_ON(ioc->ioc_data == cic); 2841 2842 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 2843 hlist_del_rcu(&cic->cic_list); 2844 spin_unlock_irqrestore(&ioc->lock, flags); 2845 2846 cfq_cic_free(cic); 2847} 2848 2849static struct cfq_io_context * 2850cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 2851{ 2852 struct cfq_io_context *cic; 2853 unsigned long flags; 2854 void *k; 2855 2856 if (unlikely(!ioc)) 2857 return NULL; 2858 2859 rcu_read_lock(); 2860 2861 /* 2862 * we maintain a last-hit cache, to avoid browsing over the tree 2863 */ 2864 cic = rcu_dereference(ioc->ioc_data); 2865 if (cic && cic->key == cfqd) { 2866 rcu_read_unlock(); 2867 return cic; 2868 } 2869 2870 do { 2871 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 2872 rcu_read_unlock(); 2873 if (!cic) 2874 break; 2875 /* ->key must be copied to avoid race with cfq_exit_queue() */ 2876 k = cic->key; 2877 if (unlikely(!k)) { 2878 cfq_drop_dead_cic(cfqd, ioc, cic); 2879 rcu_read_lock(); 2880 continue; 2881 } 2882 2883 spin_lock_irqsave(&ioc->lock, flags); 2884 rcu_assign_pointer(ioc->ioc_data, cic); 2885 spin_unlock_irqrestore(&ioc->lock, flags); 2886 break; 2887 } while (1); 2888 2889 return cic; 2890} 2891 2892/* 2893 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 2894 * the process specific cfq io context when entered from the block layer. 2895 * Also adds the cic to a per-cfqd list, used when this queue is removed. 2896 */ 2897static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 2898 struct cfq_io_context *cic, gfp_t gfp_mask) 2899{ 2900 unsigned long flags; 2901 int ret; 2902 2903 ret = radix_tree_preload(gfp_mask); 2904 if (!ret) { 2905 cic->ioc = ioc; 2906 cic->key = cfqd; 2907 2908 spin_lock_irqsave(&ioc->lock, flags); 2909 ret = radix_tree_insert(&ioc->radix_root, 2910 (unsigned long) cfqd, cic); 2911 if (!ret) 2912 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 2913 spin_unlock_irqrestore(&ioc->lock, flags); 2914 2915 radix_tree_preload_end(); 2916 2917 if (!ret) { 2918 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2919 list_add(&cic->queue_list, &cfqd->cic_list); 2920 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2921 } 2922 } 2923 2924 if (ret) 2925 printk(KERN_ERR "cfq: cic link failed!\n"); 2926 2927 return ret; 2928} 2929 2930/* 2931 * Setup general io context and cfq io context. There can be several cfq 2932 * io contexts per general io context, if this process is doing io to more 2933 * than one device managed by cfq. 2934 */ 2935static struct cfq_io_context * 2936cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 2937{ 2938 struct io_context *ioc = NULL; 2939 struct cfq_io_context *cic; 2940 2941 might_sleep_if(gfp_mask & __GFP_WAIT); 2942 2943 ioc = get_io_context(gfp_mask, cfqd->queue->node); 2944 if (!ioc) 2945 return NULL; 2946 2947 cic = cfq_cic_lookup(cfqd, ioc); 2948 if (cic) 2949 goto out; 2950 2951 cic = cfq_alloc_io_context(cfqd, gfp_mask); 2952 if (cic == NULL) 2953 goto err; 2954 2955 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 2956 goto err_free; 2957 2958out: 2959 smp_read_barrier_depends(); 2960 if (unlikely(ioc->ioprio_changed)) 2961 cfq_ioc_set_ioprio(ioc); 2962 2963#ifdef CONFIG_CFQ_GROUP_IOSCHED 2964 if (unlikely(ioc->cgroup_changed)) 2965 cfq_ioc_set_cgroup(ioc); 2966#endif 2967 return cic; 2968err_free: 2969 cfq_cic_free(cic); 2970err: 2971 put_io_context(ioc); 2972 return NULL; 2973} 2974 2975static void 2976cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 2977{ 2978 unsigned long elapsed = jiffies - cic->last_end_request; 2979 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 2980 2981 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 2982 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 2983 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 2984} 2985 2986static void 2987cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2988 struct request *rq) 2989{ 2990 sector_t sdist = 0; 2991 sector_t n_sec = blk_rq_sectors(rq); 2992 if (cfqq->last_request_pos) { 2993 if (cfqq->last_request_pos < blk_rq_pos(rq)) 2994 sdist = blk_rq_pos(rq) - cfqq->last_request_pos; 2995 else 2996 sdist = cfqq->last_request_pos - blk_rq_pos(rq); 2997 } 2998 2999 cfqq->seek_history <<= 1; 3000 if (blk_queue_nonrot(cfqd->queue)) 3001 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT); 3002 else 3003 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR); 3004} 3005 3006/* 3007 * Disable idle window if the process thinks too long or seeks so much that 3008 * it doesn't matter 3009 */ 3010static void 3011cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 3012 struct cfq_io_context *cic) 3013{ 3014 int old_idle, enable_idle; 3015 3016 /* 3017 * Don't idle for async or idle io prio class 3018 */ 3019 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 3020 return; 3021 3022 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 3023 3024 if (cfqq->queued[0] + cfqq->queued[1] >= 4) 3025 cfq_mark_cfqq_deep(cfqq); 3026 3027 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 3028 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq))) 3029 enable_idle = 0; 3030 else if (sample_valid(cic->ttime_samples)) { 3031 if (cic->ttime_mean > cfqd->cfq_slice_idle) 3032 enable_idle = 0; 3033 else 3034 enable_idle = 1; 3035 } 3036 3037 if (old_idle != enable_idle) { 3038 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 3039 if (enable_idle) 3040 cfq_mark_cfqq_idle_window(cfqq); 3041 else 3042 cfq_clear_cfqq_idle_window(cfqq); 3043 } 3044} 3045 3046/* 3047 * Check if new_cfqq should preempt the currently active queue. Return 0 for 3048 * no or if we aren't sure, a 1 will cause a preempt. 3049 */ 3050static bool 3051cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 3052 struct request *rq) 3053{ 3054 struct cfq_queue *cfqq; 3055 3056 cfqq = cfqd->active_queue; 3057 if (!cfqq) 3058 return false; 3059 3060 if (cfq_class_idle(new_cfqq)) 3061 return false; 3062 3063 if (cfq_class_idle(cfqq)) 3064 return true; 3065 3066 /* 3067 * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice. 3068 */ 3069 if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq)) 3070 return false; 3071 3072 /* 3073 * if the new request is sync, but the currently running queue is 3074 * not, let the sync request have priority. 3075 */ 3076 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 3077 return true; 3078 3079 if (new_cfqq->cfqg != cfqq->cfqg) 3080 return false; 3081 3082 if (cfq_slice_used(cfqq)) 3083 return true; 3084 3085 /* Allow preemption only if we are idling on sync-noidle tree */ 3086 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && 3087 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && 3088 new_cfqq->service_tree->count == 2 && 3089 RB_EMPTY_ROOT(&cfqq->sort_list)) 3090 return true; 3091 3092 /* 3093 * So both queues are sync. Let the new request get disk time if 3094 * it's a metadata request and the current queue is doing regular IO. 3095 */ 3096 if (rq_is_meta(rq) && !cfqq->meta_pending) 3097 return true; 3098 3099 /* 3100 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 3101 */ 3102 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 3103 return true; 3104 3105 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 3106 return false; 3107 3108 /* 3109 * if this request is as-good as one we would expect from the 3110 * current cfqq, let it preempt 3111 */ 3112 if (cfq_rq_close(cfqd, cfqq, rq)) 3113 return true; 3114 3115 return false; 3116} 3117 3118/* 3119 * cfqq preempts the active queue. if we allowed preempt with no slice left, 3120 * let it have half of its nominal slice. 3121 */ 3122static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 3123{ 3124 cfq_log_cfqq(cfqd, cfqq, "preempt"); 3125 cfq_slice_expired(cfqd, 1); 3126 3127 /* 3128 * Put the new queue at the front of the of the current list, 3129 * so we know that it will be selected next. 3130 */ 3131 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 3132 3133 cfq_service_tree_add(cfqd, cfqq, 1); 3134 3135 cfqq->slice_end = 0; 3136 cfq_mark_cfqq_slice_new(cfqq); 3137} 3138 3139/* 3140 * Called when a new fs request (rq) is added (to cfqq). Check if there's 3141 * something we should do about it 3142 */ 3143static void 3144cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 3145 struct request *rq) 3146{ 3147 struct cfq_io_context *cic = RQ_CIC(rq); 3148 3149 cfqd->rq_queued++; 3150 if (rq_is_meta(rq)) 3151 cfqq->meta_pending++; 3152 3153 cfq_update_io_thinktime(cfqd, cic); 3154 cfq_update_io_seektime(cfqd, cfqq, rq); 3155 cfq_update_idle_window(cfqd, cfqq, cic); 3156 3157 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); 3158 3159 if (cfqq == cfqd->active_queue) { 3160 /* 3161 * Remember that we saw a request from this process, but 3162 * don't start queuing just yet. Otherwise we risk seeing lots 3163 * of tiny requests, because we disrupt the normal plugging 3164 * and merging. If the request is already larger than a single 3165 * page, let it rip immediately. For that case we assume that 3166 * merging is already done. Ditto for a busy system that 3167 * has other work pending, don't risk delaying until the 3168 * idle timer unplug to continue working. 3169 */ 3170 if (cfq_cfqq_wait_request(cfqq)) { 3171 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || 3172 cfqd->busy_queues > 1) { 3173 del_timer(&cfqd->idle_slice_timer); 3174 cfq_clear_cfqq_wait_request(cfqq); 3175 __blk_run_queue(cfqd->queue); 3176 } else 3177 cfq_mark_cfqq_must_dispatch(cfqq); 3178 } 3179 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 3180 /* 3181 * not the active queue - expire current slice if it is 3182 * idle and has expired it's mean thinktime or this new queue 3183 * has some old slice time left and is of higher priority or 3184 * this new queue is RT and the current one is BE 3185 */ 3186 cfq_preempt_queue(cfqd, cfqq); 3187 __blk_run_queue(cfqd->queue); 3188 } 3189} 3190 3191static void cfq_insert_request(struct request_queue *q, struct request *rq) 3192{ 3193 struct cfq_data *cfqd = q->elevator->elevator_data; 3194 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3195 3196 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 3197 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 3198 3199 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]); 3200 list_add_tail(&rq->queuelist, &cfqq->fifo); 3201 cfq_add_rq_rb(rq); 3202 3203 cfq_rq_enqueued(cfqd, cfqq, rq); 3204} 3205 3206/* 3207 * Update hw_tag based on peak queue depth over 50 samples under 3208 * sufficient load. 3209 */ 3210static void cfq_update_hw_tag(struct cfq_data *cfqd) 3211{ 3212 struct cfq_queue *cfqq = cfqd->active_queue; 3213 3214 if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth) 3215 cfqd->hw_tag_est_depth = cfqd->rq_in_driver; 3216 3217 if (cfqd->hw_tag == 1) 3218 return; 3219 3220 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 3221 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) 3222 return; 3223 3224 /* 3225 * If active queue hasn't enough requests and can idle, cfq might not 3226 * dispatch sufficient requests to hardware. Don't zero hw_tag in this 3227 * case 3228 */ 3229 if (cfqq && cfq_cfqq_idle_window(cfqq) && 3230 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] < 3231 CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN) 3232 return; 3233 3234 if (cfqd->hw_tag_samples++ < 50) 3235 return; 3236 3237 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN) 3238 cfqd->hw_tag = 1; 3239 else 3240 cfqd->hw_tag = 0; 3241} 3242 3243static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq) 3244{ 3245 struct cfq_io_context *cic = cfqd->active_cic; 3246 3247 /* If there are other queues in the group, don't wait */ 3248 if (cfqq->cfqg->nr_cfqq > 1) 3249 return false; 3250 3251 if (cfq_slice_used(cfqq)) 3252 return true; 3253 3254 /* if slice left is less than think time, wait busy */ 3255 if (cic && sample_valid(cic->ttime_samples) 3256 && (cfqq->slice_end - jiffies < cic->ttime_mean)) 3257 return true; 3258 3259 /* 3260 * If think times is less than a jiffy than ttime_mean=0 and above 3261 * will not be true. It might happen that slice has not expired yet 3262 * but will expire soon (4-5 ns) during select_queue(). To cover the 3263 * case where think time is less than a jiffy, mark the queue wait 3264 * busy if only 1 jiffy is left in the slice. 3265 */ 3266 if (cfqq->slice_end - jiffies == 1) 3267 return true; 3268 3269 return false; 3270} 3271 3272static void cfq_completed_request(struct request_queue *q, struct request *rq) 3273{ 3274 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3275 struct cfq_data *cfqd = cfqq->cfqd; 3276 const int sync = rq_is_sync(rq); 3277 unsigned long now; 3278 3279 now = jiffies; 3280 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq)); 3281 3282 cfq_update_hw_tag(cfqd); 3283 3284 WARN_ON(!cfqd->rq_in_driver); 3285 WARN_ON(!cfqq->dispatched); 3286 cfqd->rq_in_driver--; 3287 cfqq->dispatched--; 3288 3289 cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--; 3290 3291 if (sync) { 3292 RQ_CIC(rq)->last_end_request = now; 3293 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now)) 3294 cfqd->last_delayed_sync = now; 3295 } 3296 3297 /* 3298 * If this is the active queue, check if it needs to be expired, 3299 * or if we want to idle in case it has no pending requests. 3300 */ 3301 if (cfqd->active_queue == cfqq) { 3302 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); 3303 3304 if (cfq_cfqq_slice_new(cfqq)) { 3305 cfq_set_prio_slice(cfqd, cfqq); 3306 cfq_clear_cfqq_slice_new(cfqq); 3307 } 3308 3309 /* 3310 * Should we wait for next request to come in before we expire 3311 * the queue. 3312 */ 3313 if (cfq_should_wait_busy(cfqd, cfqq)) { 3314 cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; 3315 cfq_mark_cfqq_wait_busy(cfqq); 3316 cfq_log_cfqq(cfqd, cfqq, "will busy wait"); 3317 } 3318 3319 /* 3320 * Idling is not enabled on: 3321 * - expired queues 3322 * - idle-priority queues 3323 * - async queues 3324 * - queues with still some requests queued 3325 * - when there is a close cooperator 3326 */ 3327 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 3328 cfq_slice_expired(cfqd, 1); 3329 else if (sync && cfqq_empty && 3330 !cfq_close_cooperator(cfqd, cfqq)) { 3331 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq); 3332 /* 3333 * Idling is enabled for SYNC_WORKLOAD. 3334 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree 3335 * only if we processed at least one !rq_noidle request 3336 */ 3337 if (cfqd->serving_type == SYNC_WORKLOAD 3338 || cfqd->noidle_tree_requires_idle 3339 || cfqq->cfqg->nr_cfqq == 1) 3340 cfq_arm_slice_timer(cfqd); 3341 } 3342 } 3343 3344 if (!cfqd->rq_in_driver) 3345 cfq_schedule_dispatch(cfqd); 3346} 3347 3348/* 3349 * we temporarily boost lower priority queues if they are holding fs exclusive 3350 * resources. they are boosted to normal prio (CLASS_BE/4) 3351 */ 3352static void cfq_prio_boost(struct cfq_queue *cfqq) 3353{ 3354 if (has_fs_excl()) { 3355 /* 3356 * boost idle prio on transactions that would lock out other 3357 * users of the filesystem 3358 */ 3359 if (cfq_class_idle(cfqq)) 3360 cfqq->ioprio_class = IOPRIO_CLASS_BE; 3361 if (cfqq->ioprio > IOPRIO_NORM) 3362 cfqq->ioprio = IOPRIO_NORM; 3363 } else { 3364 /* 3365 * unboost the queue (if needed) 3366 */ 3367 cfqq->ioprio_class = cfqq->org_ioprio_class; 3368 cfqq->ioprio = cfqq->org_ioprio; 3369 } 3370} 3371 3372static inline int __cfq_may_queue(struct cfq_queue *cfqq) 3373{ 3374 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) { 3375 cfq_mark_cfqq_must_alloc_slice(cfqq); 3376 return ELV_MQUEUE_MUST; 3377 } 3378 3379 return ELV_MQUEUE_MAY; 3380} 3381 3382static int cfq_may_queue(struct request_queue *q, int rw) 3383{ 3384 struct cfq_data *cfqd = q->elevator->elevator_data; 3385 struct task_struct *tsk = current; 3386 struct cfq_io_context *cic; 3387 struct cfq_queue *cfqq; 3388 3389 /* 3390 * don't force setup of a queue from here, as a call to may_queue 3391 * does not necessarily imply that a request actually will be queued. 3392 * so just lookup a possibly existing queue, or return 'may queue' 3393 * if that fails 3394 */ 3395 cic = cfq_cic_lookup(cfqd, tsk->io_context); 3396 if (!cic) 3397 return ELV_MQUEUE_MAY; 3398 3399 cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); 3400 if (cfqq) { 3401 cfq_init_prio_data(cfqq, cic->ioc); 3402 cfq_prio_boost(cfqq); 3403 3404 return __cfq_may_queue(cfqq); 3405 } 3406 3407 return ELV_MQUEUE_MAY; 3408} 3409 3410/* 3411 * queue lock held here 3412 */ 3413static void cfq_put_request(struct request *rq) 3414{ 3415 struct cfq_queue *cfqq = RQ_CFQQ(rq); 3416 3417 if (cfqq) { 3418 const int rw = rq_data_dir(rq); 3419 3420 BUG_ON(!cfqq->allocated[rw]); 3421 cfqq->allocated[rw]--; 3422 3423 put_io_context(RQ_CIC(rq)->ioc); 3424 3425 rq->elevator_private = NULL; 3426 rq->elevator_private2 = NULL; 3427 3428 cfq_put_queue(cfqq); 3429 } 3430} 3431 3432static struct cfq_queue * 3433cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, 3434 struct cfq_queue *cfqq) 3435{ 3436 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq); 3437 cic_set_cfqq(cic, cfqq->new_cfqq, 1); 3438 cfq_mark_cfqq_coop(cfqq->new_cfqq); 3439 cfq_put_queue(cfqq); 3440 return cic_to_cfqq(cic, 1); 3441} 3442 3443/* 3444 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this 3445 * was the last process referring to said cfqq. 3446 */ 3447static struct cfq_queue * 3448split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq) 3449{ 3450 if (cfqq_process_refs(cfqq) == 1) { 3451 cfqq->pid = current->pid; 3452 cfq_clear_cfqq_coop(cfqq); 3453 cfq_clear_cfqq_split_coop(cfqq); 3454 return cfqq; 3455 } 3456 3457 cic_set_cfqq(cic, NULL, 1); 3458 cfq_put_queue(cfqq); 3459 return NULL; 3460} 3461/* 3462 * Allocate cfq data structures associated with this request. 3463 */ 3464static int 3465cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 3466{ 3467 struct cfq_data *cfqd = q->elevator->elevator_data; 3468 struct cfq_io_context *cic; 3469 const int rw = rq_data_dir(rq); 3470 const bool is_sync = rq_is_sync(rq); 3471 struct cfq_queue *cfqq; 3472 unsigned long flags; 3473 3474 might_sleep_if(gfp_mask & __GFP_WAIT); 3475 3476 cic = cfq_get_io_context(cfqd, gfp_mask); 3477 3478 spin_lock_irqsave(q->queue_lock, flags); 3479 3480 if (!cic) 3481 goto queue_fail; 3482 3483new_queue: 3484 cfqq = cic_to_cfqq(cic, is_sync); 3485 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 3486 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 3487 cic_set_cfqq(cic, cfqq, is_sync); 3488 } else { 3489 /* 3490 * If the queue was seeky for too long, break it apart. 3491 */ 3492 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) { 3493 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq"); 3494 cfqq = split_cfqq(cic, cfqq); 3495 if (!cfqq) 3496 goto new_queue; 3497 } 3498 3499 /* 3500 * Check to see if this queue is scheduled to merge with 3501 * another, closely cooperating queue. The merging of 3502 * queues happens here as it must be done in process context. 3503 * The reference on new_cfqq was taken in merge_cfqqs. 3504 */ 3505 if (cfqq->new_cfqq) 3506 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq); 3507 } 3508 3509 cfqq->allocated[rw]++; 3510 atomic_inc(&cfqq->ref); 3511 3512 spin_unlock_irqrestore(q->queue_lock, flags); 3513 3514 rq->elevator_private = cic; 3515 rq->elevator_private2 = cfqq; 3516 return 0; 3517 3518queue_fail: 3519 if (cic) 3520 put_io_context(cic->ioc); 3521 3522 cfq_schedule_dispatch(cfqd); 3523 spin_unlock_irqrestore(q->queue_lock, flags); 3524 cfq_log(cfqd, "set_request fail"); 3525 return 1; 3526} 3527 3528static void cfq_kick_queue(struct work_struct *work) 3529{ 3530 struct cfq_data *cfqd = 3531 container_of(work, struct cfq_data, unplug_work); 3532 struct request_queue *q = cfqd->queue; 3533 3534 spin_lock_irq(q->queue_lock); 3535 __blk_run_queue(cfqd->queue); 3536 spin_unlock_irq(q->queue_lock); 3537} 3538 3539/* 3540 * Timer running if the active_queue is currently idling inside its time slice 3541 */ 3542static void cfq_idle_slice_timer(unsigned long data) 3543{ 3544 struct cfq_data *cfqd = (struct cfq_data *) data; 3545 struct cfq_queue *cfqq; 3546 unsigned long flags; 3547 int timed_out = 1; 3548 3549 cfq_log(cfqd, "idle timer fired"); 3550 3551 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 3552 3553 cfqq = cfqd->active_queue; 3554 if (cfqq) { 3555 timed_out = 0; 3556 3557 /* 3558 * We saw a request before the queue expired, let it through 3559 */ 3560 if (cfq_cfqq_must_dispatch(cfqq)) 3561 goto out_kick; 3562 3563 /* 3564 * expired 3565 */ 3566 if (cfq_slice_used(cfqq)) 3567 goto expire; 3568 3569 /* 3570 * only expire and reinvoke request handler, if there are 3571 * other queues with pending requests 3572 */ 3573 if (!cfqd->busy_queues) 3574 goto out_cont; 3575 3576 /* 3577 * not expired and it has a request pending, let it dispatch 3578 */ 3579 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 3580 goto out_kick; 3581 3582 /* 3583 * Queue depth flag is reset only when the idle didn't succeed 3584 */ 3585 cfq_clear_cfqq_deep(cfqq); 3586 } 3587expire: 3588 cfq_slice_expired(cfqd, timed_out); 3589out_kick: 3590 cfq_schedule_dispatch(cfqd); 3591out_cont: 3592 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 3593} 3594 3595static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 3596{ 3597 del_timer_sync(&cfqd->idle_slice_timer); 3598 cancel_work_sync(&cfqd->unplug_work); 3599} 3600 3601static void cfq_put_async_queues(struct cfq_data *cfqd) 3602{ 3603 int i; 3604 3605 for (i = 0; i < IOPRIO_BE_NR; i++) { 3606 if (cfqd->async_cfqq[0][i]) 3607 cfq_put_queue(cfqd->async_cfqq[0][i]); 3608 if (cfqd->async_cfqq[1][i]) 3609 cfq_put_queue(cfqd->async_cfqq[1][i]); 3610 } 3611 3612 if (cfqd->async_idle_cfqq) 3613 cfq_put_queue(cfqd->async_idle_cfqq); 3614} 3615 3616static void cfq_cfqd_free(struct rcu_head *head) 3617{ 3618 kfree(container_of(head, struct cfq_data, rcu)); 3619} 3620 3621static void cfq_exit_queue(struct elevator_queue *e) 3622{ 3623 struct cfq_data *cfqd = e->elevator_data; 3624 struct request_queue *q = cfqd->queue; 3625 3626 cfq_shutdown_timer_wq(cfqd); 3627 3628 spin_lock_irq(q->queue_lock); 3629 3630 if (cfqd->active_queue) 3631 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 3632 3633 while (!list_empty(&cfqd->cic_list)) { 3634 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 3635 struct cfq_io_context, 3636 queue_list); 3637 3638 __cfq_exit_single_io_context(cfqd, cic); 3639 } 3640 3641 cfq_put_async_queues(cfqd); 3642 cfq_release_cfq_groups(cfqd); 3643 blkiocg_del_blkio_group(&cfqd->root_group.blkg); 3644 3645 spin_unlock_irq(q->queue_lock); 3646 3647 cfq_shutdown_timer_wq(cfqd); 3648 3649 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */ 3650 call_rcu(&cfqd->rcu, cfq_cfqd_free); 3651} 3652 3653static void *cfq_init_queue(struct request_queue *q) 3654{ 3655 struct cfq_data *cfqd; 3656 int i, j; 3657 struct cfq_group *cfqg; 3658 struct cfq_rb_root *st; 3659 3660 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 3661 if (!cfqd) 3662 return NULL; 3663 3664 /* Init root service tree */ 3665 cfqd->grp_service_tree = CFQ_RB_ROOT; 3666 3667 /* Init root group */ 3668 cfqg = &cfqd->root_group; 3669 for_each_cfqg_st(cfqg, i, j, st) 3670 *st = CFQ_RB_ROOT; 3671 RB_CLEAR_NODE(&cfqg->rb_node); 3672 3673 /* Give preference to root group over other groups */ 3674 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT; 3675 3676#ifdef CONFIG_CFQ_GROUP_IOSCHED 3677 /* 3678 * Take a reference to root group which we never drop. This is just 3679 * to make sure that cfq_put_cfqg() does not try to kfree root group 3680 */ 3681 atomic_set(&cfqg->ref, 1); 3682 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd, 3683 0); 3684#endif 3685 /* 3686 * Not strictly needed (since RB_ROOT just clears the node and we 3687 * zeroed cfqd on alloc), but better be safe in case someone decides 3688 * to add magic to the rb code 3689 */ 3690 for (i = 0; i < CFQ_PRIO_LISTS; i++) 3691 cfqd->prio_trees[i] = RB_ROOT; 3692 3693 /* 3694 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. 3695 * Grab a permanent reference to it, so that the normal code flow 3696 * will not attempt to free it. 3697 */ 3698 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); 3699 atomic_inc(&cfqd->oom_cfqq.ref); 3700 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group); 3701 3702 INIT_LIST_HEAD(&cfqd->cic_list); 3703 3704 cfqd->queue = q; 3705 3706 init_timer(&cfqd->idle_slice_timer); 3707 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 3708 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 3709 3710 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 3711 3712 cfqd->cfq_quantum = cfq_quantum; 3713 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 3714 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 3715 cfqd->cfq_back_max = cfq_back_max; 3716 cfqd->cfq_back_penalty = cfq_back_penalty; 3717 cfqd->cfq_slice[0] = cfq_slice_async; 3718 cfqd->cfq_slice[1] = cfq_slice_sync; 3719 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 3720 cfqd->cfq_slice_idle = cfq_slice_idle; 3721 cfqd->cfq_latency = 1; 3722 cfqd->cfq_group_isolation = 0; 3723 cfqd->hw_tag = -1; 3724 /* 3725 * we optimistically start assuming sync ops weren't delayed in last 3726 * second, in order to have larger depth for async operations. 3727 */ 3728 cfqd->last_delayed_sync = jiffies - HZ; 3729 INIT_RCU_HEAD(&cfqd->rcu); 3730 return cfqd; 3731} 3732 3733static void cfq_slab_kill(void) 3734{ 3735 /* 3736 * Caller already ensured that pending RCU callbacks are completed, 3737 * so we should have no busy allocations at this point. 3738 */ 3739 if (cfq_pool) 3740 kmem_cache_destroy(cfq_pool); 3741 if (cfq_ioc_pool) 3742 kmem_cache_destroy(cfq_ioc_pool); 3743} 3744 3745static int __init cfq_slab_setup(void) 3746{ 3747 cfq_pool = KMEM_CACHE(cfq_queue, 0); 3748 if (!cfq_pool) 3749 goto fail; 3750 3751 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 3752 if (!cfq_ioc_pool) 3753 goto fail; 3754 3755 return 0; 3756fail: 3757 cfq_slab_kill(); 3758 return -ENOMEM; 3759} 3760 3761/* 3762 * sysfs parts below --> 3763 */ 3764static ssize_t 3765cfq_var_show(unsigned int var, char *page) 3766{ 3767 return sprintf(page, "%d\n", var); 3768} 3769 3770static ssize_t 3771cfq_var_store(unsigned int *var, const char *page, size_t count) 3772{ 3773 char *p = (char *) page; 3774 3775 *var = simple_strtoul(p, &p, 10); 3776 return count; 3777} 3778 3779#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 3780static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 3781{ \ 3782 struct cfq_data *cfqd = e->elevator_data; \ 3783 unsigned int __data = __VAR; \ 3784 if (__CONV) \ 3785 __data = jiffies_to_msecs(__data); \ 3786 return cfq_var_show(__data, (page)); \ 3787} 3788SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 3789SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 3790SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 3791SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 3792SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 3793SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 3794SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 3795SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 3796SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 3797SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); 3798SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0); 3799#undef SHOW_FUNCTION 3800 3801#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 3802static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 3803{ \ 3804 struct cfq_data *cfqd = e->elevator_data; \ 3805 unsigned int __data; \ 3806 int ret = cfq_var_store(&__data, (page), count); \ 3807 if (__data < (MIN)) \ 3808 __data = (MIN); \ 3809 else if (__data > (MAX)) \ 3810 __data = (MAX); \ 3811 if (__CONV) \ 3812 *(__PTR) = msecs_to_jiffies(__data); \ 3813 else \ 3814 *(__PTR) = __data; \ 3815 return ret; \ 3816} 3817STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 3818STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 3819 UINT_MAX, 1); 3820STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 3821 UINT_MAX, 1); 3822STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 3823STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 3824 UINT_MAX, 0); 3825STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 3826STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 3827STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 3828STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 3829 UINT_MAX, 0); 3830STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); 3831STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0); 3832#undef STORE_FUNCTION 3833 3834#define CFQ_ATTR(name) \ 3835 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 3836 3837static struct elv_fs_entry cfq_attrs[] = { 3838 CFQ_ATTR(quantum), 3839 CFQ_ATTR(fifo_expire_sync), 3840 CFQ_ATTR(fifo_expire_async), 3841 CFQ_ATTR(back_seek_max), 3842 CFQ_ATTR(back_seek_penalty), 3843 CFQ_ATTR(slice_sync), 3844 CFQ_ATTR(slice_async), 3845 CFQ_ATTR(slice_async_rq), 3846 CFQ_ATTR(slice_idle), 3847 CFQ_ATTR(low_latency), 3848 CFQ_ATTR(group_isolation), 3849 __ATTR_NULL 3850}; 3851 3852static struct elevator_type iosched_cfq = { 3853 .ops = { 3854 .elevator_merge_fn = cfq_merge, 3855 .elevator_merged_fn = cfq_merged_request, 3856 .elevator_merge_req_fn = cfq_merged_requests, 3857 .elevator_allow_merge_fn = cfq_allow_merge, 3858 .elevator_dispatch_fn = cfq_dispatch_requests, 3859 .elevator_add_req_fn = cfq_insert_request, 3860 .elevator_activate_req_fn = cfq_activate_request, 3861 .elevator_deactivate_req_fn = cfq_deactivate_request, 3862 .elevator_queue_empty_fn = cfq_queue_empty, 3863 .elevator_completed_req_fn = cfq_completed_request, 3864 .elevator_former_req_fn = elv_rb_former_request, 3865 .elevator_latter_req_fn = elv_rb_latter_request, 3866 .elevator_set_req_fn = cfq_set_request, 3867 .elevator_put_req_fn = cfq_put_request, 3868 .elevator_may_queue_fn = cfq_may_queue, 3869 .elevator_init_fn = cfq_init_queue, 3870 .elevator_exit_fn = cfq_exit_queue, 3871 .trim = cfq_free_io_context, 3872 }, 3873 .elevator_attrs = cfq_attrs, 3874 .elevator_name = "cfq", 3875 .elevator_owner = THIS_MODULE, 3876}; 3877 3878#ifdef CONFIG_CFQ_GROUP_IOSCHED 3879static struct blkio_policy_type blkio_policy_cfq = { 3880 .ops = { 3881 .blkio_unlink_group_fn = cfq_unlink_blkio_group, 3882 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight, 3883 }, 3884}; 3885#else 3886static struct blkio_policy_type blkio_policy_cfq; 3887#endif 3888 3889static int __init cfq_init(void) 3890{ 3891 /* 3892 * could be 0 on HZ < 1000 setups 3893 */ 3894 if (!cfq_slice_async) 3895 cfq_slice_async = 1; 3896 if (!cfq_slice_idle) 3897 cfq_slice_idle = 1; 3898 3899 if (cfq_slab_setup()) 3900 return -ENOMEM; 3901 3902 elv_register(&iosched_cfq); 3903 blkio_policy_register(&blkio_policy_cfq); 3904 3905 return 0; 3906} 3907 3908static void __exit cfq_exit(void) 3909{ 3910 DECLARE_COMPLETION_ONSTACK(all_gone); 3911 blkio_policy_unregister(&blkio_policy_cfq); 3912 elv_unregister(&iosched_cfq); 3913 ioc_gone = &all_gone; 3914 /* ioc_gone's update must be visible before reading ioc_count */ 3915 smp_wmb(); 3916 3917 /* 3918 * this also protects us from entering cfq_slab_kill() with 3919 * pending RCU callbacks 3920 */ 3921 if (elv_ioc_count_read(cfq_ioc_count)) 3922 wait_for_completion(&all_gone); 3923 cfq_slab_kill(); 3924} 3925 3926module_init(cfq_init); 3927module_exit(cfq_exit); 3928 3929MODULE_AUTHOR("Jens Axboe"); 3930MODULE_LICENSE("GPL"); 3931MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 3932