cfq-iosched.c revision b0b78f81a5a3bfe9442fcc3a9c13e298a742556a
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/rbtree.h> 13#include <linux/ioprio.h> 14#include <linux/blktrace_api.h> 15 16/* 17 * tunables 18 */ 19/* max queue in one round of service */ 20static const int cfq_quantum = 4; 21static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; 22/* maximum backwards seek, in KiB */ 23static const int cfq_back_max = 16 * 1024; 24/* penalty of a backwards seek */ 25static const int cfq_back_penalty = 2; 26static const int cfq_slice_sync = HZ / 10; 27static int cfq_slice_async = HZ / 25; 28static const int cfq_slice_async_rq = 2; 29static int cfq_slice_idle = HZ / 125; 30 31/* 32 * offset from end of service tree 33 */ 34#define CFQ_IDLE_DELAY (HZ / 5) 35 36/* 37 * below this threshold, we consider thinktime immediate 38 */ 39#define CFQ_MIN_TT (2) 40 41#define CFQ_SLICE_SCALE (5) 42#define CFQ_HW_QUEUE_MIN (5) 43 44#define RQ_CIC(rq) \ 45 ((struct cfq_io_context *) (rq)->elevator_private) 46#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 47 48static struct kmem_cache *cfq_pool; 49static struct kmem_cache *cfq_ioc_pool; 50 51static DEFINE_PER_CPU(unsigned long, ioc_count); 52static struct completion *ioc_gone; 53static DEFINE_SPINLOCK(ioc_gone_lock); 54 55#define CFQ_PRIO_LISTS IOPRIO_BE_NR 56#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 57#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 58 59#define ASYNC (0) 60#define SYNC (1) 61 62#define sample_valid(samples) ((samples) > 80) 63 64/* 65 * Most of our rbtree usage is for sorting with min extraction, so 66 * if we cache the leftmost node we don't have to walk down the tree 67 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 68 * move this into the elevator for the rq sorting as well. 69 */ 70struct cfq_rb_root { 71 struct rb_root rb; 72 struct rb_node *left; 73}; 74#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } 75 76/* 77 * Per block device queue structure 78 */ 79struct cfq_data { 80 struct request_queue *queue; 81 82 /* 83 * rr list of queues with requests and the count of them 84 */ 85 struct cfq_rb_root service_tree; 86 unsigned int busy_queues; 87 /* 88 * Used to track any pending rt requests so we can pre-empt current 89 * non-RT cfqq in service when this value is non-zero. 90 */ 91 unsigned int busy_rt_queues; 92 93 int rq_in_driver; 94 int sync_flight; 95 96 /* 97 * queue-depth detection 98 */ 99 int rq_queued; 100 int hw_tag; 101 int hw_tag_samples; 102 int rq_in_driver_peak; 103 104 /* 105 * idle window management 106 */ 107 struct timer_list idle_slice_timer; 108 struct work_struct unplug_work; 109 110 struct cfq_queue *active_queue; 111 struct cfq_io_context *active_cic; 112 113 /* 114 * async queue for each priority case 115 */ 116 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 117 struct cfq_queue *async_idle_cfqq; 118 119 sector_t last_position; 120 unsigned long last_end_request; 121 122 /* 123 * tunables, see top of file 124 */ 125 unsigned int cfq_quantum; 126 unsigned int cfq_fifo_expire[2]; 127 unsigned int cfq_back_penalty; 128 unsigned int cfq_back_max; 129 unsigned int cfq_slice[2]; 130 unsigned int cfq_slice_async_rq; 131 unsigned int cfq_slice_idle; 132 133 struct list_head cic_list; 134}; 135 136/* 137 * Per process-grouping structure 138 */ 139struct cfq_queue { 140 /* reference count */ 141 atomic_t ref; 142 /* various state flags, see below */ 143 unsigned int flags; 144 /* parent cfq_data */ 145 struct cfq_data *cfqd; 146 /* service_tree member */ 147 struct rb_node rb_node; 148 /* service_tree key */ 149 unsigned long rb_key; 150 /* sorted list of pending requests */ 151 struct rb_root sort_list; 152 /* if fifo isn't expired, next request to serve */ 153 struct request *next_rq; 154 /* requests queued in sort_list */ 155 int queued[2]; 156 /* currently allocated requests */ 157 int allocated[2]; 158 /* fifo list of requests in sort_list */ 159 struct list_head fifo; 160 161 unsigned long slice_end; 162 long slice_resid; 163 unsigned int slice_dispatch; 164 165 /* pending metadata requests */ 166 int meta_pending; 167 /* number of requests that are on the dispatch list or inside driver */ 168 int dispatched; 169 170 /* io prio of this group */ 171 unsigned short ioprio, org_ioprio; 172 unsigned short ioprio_class, org_ioprio_class; 173 174 pid_t pid; 175}; 176 177enum cfqq_state_flags { 178 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 179 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 180 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ 181 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ 182 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 183 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 184 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 185 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 186 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 187 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 188}; 189 190#define CFQ_CFQQ_FNS(name) \ 191static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 192{ \ 193 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 194} \ 195static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 196{ \ 197 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 198} \ 199static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 200{ \ 201 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 202} 203 204CFQ_CFQQ_FNS(on_rr); 205CFQ_CFQQ_FNS(wait_request); 206CFQ_CFQQ_FNS(must_dispatch); 207CFQ_CFQQ_FNS(must_alloc); 208CFQ_CFQQ_FNS(must_alloc_slice); 209CFQ_CFQQ_FNS(fifo_expire); 210CFQ_CFQQ_FNS(idle_window); 211CFQ_CFQQ_FNS(prio_changed); 212CFQ_CFQQ_FNS(slice_new); 213CFQ_CFQQ_FNS(sync); 214#undef CFQ_CFQQ_FNS 215 216#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 217 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 218#define cfq_log(cfqd, fmt, args...) \ 219 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 220 221static void cfq_dispatch_insert(struct request_queue *, struct request *); 222static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, 223 struct io_context *, gfp_t); 224static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 225 struct io_context *); 226 227static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 228 int is_sync) 229{ 230 return cic->cfqq[!!is_sync]; 231} 232 233static inline void cic_set_cfqq(struct cfq_io_context *cic, 234 struct cfq_queue *cfqq, int is_sync) 235{ 236 cic->cfqq[!!is_sync] = cfqq; 237} 238 239/* 240 * We regard a request as SYNC, if it's either a read or has the SYNC bit 241 * set (in which case it could also be direct WRITE). 242 */ 243static inline int cfq_bio_sync(struct bio *bio) 244{ 245 if (bio_data_dir(bio) == READ || bio_sync(bio)) 246 return 1; 247 248 return 0; 249} 250 251/* 252 * scheduler run of queue, if there are requests pending and no one in the 253 * driver that will restart queueing 254 */ 255static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 256{ 257 if (cfqd->busy_queues) { 258 cfq_log(cfqd, "schedule dispatch"); 259 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 260 } 261} 262 263static int cfq_queue_empty(struct request_queue *q) 264{ 265 struct cfq_data *cfqd = q->elevator->elevator_data; 266 267 return !cfqd->busy_queues; 268} 269 270/* 271 * Scale schedule slice based on io priority. Use the sync time slice only 272 * if a queue is marked sync and has sync io queued. A sync queue with async 273 * io only, should not get full sync slice length. 274 */ 275static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync, 276 unsigned short prio) 277{ 278 const int base_slice = cfqd->cfq_slice[sync]; 279 280 WARN_ON(prio >= IOPRIO_BE_NR); 281 282 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 283} 284 285static inline int 286cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 287{ 288 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 289} 290 291static inline void 292cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 293{ 294 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 295 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 296} 297 298/* 299 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 300 * isn't valid until the first request from the dispatch is activated 301 * and the slice time set. 302 */ 303static inline int cfq_slice_used(struct cfq_queue *cfqq) 304{ 305 if (cfq_cfqq_slice_new(cfqq)) 306 return 0; 307 if (time_before(jiffies, cfqq->slice_end)) 308 return 0; 309 310 return 1; 311} 312 313/* 314 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 315 * We choose the request that is closest to the head right now. Distance 316 * behind the head is penalized and only allowed to a certain extent. 317 */ 318static struct request * 319cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) 320{ 321 sector_t last, s1, s2, d1 = 0, d2 = 0; 322 unsigned long back_max; 323#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 324#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 325 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 326 327 if (rq1 == NULL || rq1 == rq2) 328 return rq2; 329 if (rq2 == NULL) 330 return rq1; 331 332 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 333 return rq1; 334 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 335 return rq2; 336 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 337 return rq1; 338 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 339 return rq2; 340 341 s1 = rq1->sector; 342 s2 = rq2->sector; 343 344 last = cfqd->last_position; 345 346 /* 347 * by definition, 1KiB is 2 sectors 348 */ 349 back_max = cfqd->cfq_back_max * 2; 350 351 /* 352 * Strict one way elevator _except_ in the case where we allow 353 * short backward seeks which are biased as twice the cost of a 354 * similar forward seek. 355 */ 356 if (s1 >= last) 357 d1 = s1 - last; 358 else if (s1 + back_max >= last) 359 d1 = (last - s1) * cfqd->cfq_back_penalty; 360 else 361 wrap |= CFQ_RQ1_WRAP; 362 363 if (s2 >= last) 364 d2 = s2 - last; 365 else if (s2 + back_max >= last) 366 d2 = (last - s2) * cfqd->cfq_back_penalty; 367 else 368 wrap |= CFQ_RQ2_WRAP; 369 370 /* Found required data */ 371 372 /* 373 * By doing switch() on the bit mask "wrap" we avoid having to 374 * check two variables for all permutations: --> faster! 375 */ 376 switch (wrap) { 377 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 378 if (d1 < d2) 379 return rq1; 380 else if (d2 < d1) 381 return rq2; 382 else { 383 if (s1 >= s2) 384 return rq1; 385 else 386 return rq2; 387 } 388 389 case CFQ_RQ2_WRAP: 390 return rq1; 391 case CFQ_RQ1_WRAP: 392 return rq2; 393 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 394 default: 395 /* 396 * Since both rqs are wrapped, 397 * start with the one that's further behind head 398 * (--> only *one* back seek required), 399 * since back seek takes more time than forward. 400 */ 401 if (s1 <= s2) 402 return rq1; 403 else 404 return rq2; 405 } 406} 407 408/* 409 * The below is leftmost cache rbtree addon 410 */ 411static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 412{ 413 if (!root->left) 414 root->left = rb_first(&root->rb); 415 416 if (root->left) 417 return rb_entry(root->left, struct cfq_queue, rb_node); 418 419 return NULL; 420} 421 422static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 423{ 424 if (root->left == n) 425 root->left = NULL; 426 427 rb_erase(n, &root->rb); 428 RB_CLEAR_NODE(n); 429} 430 431/* 432 * would be nice to take fifo expire time into account as well 433 */ 434static struct request * 435cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 436 struct request *last) 437{ 438 struct rb_node *rbnext = rb_next(&last->rb_node); 439 struct rb_node *rbprev = rb_prev(&last->rb_node); 440 struct request *next = NULL, *prev = NULL; 441 442 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 443 444 if (rbprev) 445 prev = rb_entry_rq(rbprev); 446 447 if (rbnext) 448 next = rb_entry_rq(rbnext); 449 else { 450 rbnext = rb_first(&cfqq->sort_list); 451 if (rbnext && rbnext != &last->rb_node) 452 next = rb_entry_rq(rbnext); 453 } 454 455 return cfq_choose_req(cfqd, next, prev); 456} 457 458static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 459 struct cfq_queue *cfqq) 460{ 461 /* 462 * just an approximation, should be ok. 463 */ 464 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - 465 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 466} 467 468/* 469 * The cfqd->service_tree holds all pending cfq_queue's that have 470 * requests waiting to be processed. It is sorted in the order that 471 * we will service the queues. 472 */ 473static void cfq_service_tree_add(struct cfq_data *cfqd, 474 struct cfq_queue *cfqq, int add_front) 475{ 476 struct rb_node **p, *parent; 477 struct cfq_queue *__cfqq; 478 unsigned long rb_key; 479 int left; 480 481 if (cfq_class_idle(cfqq)) { 482 rb_key = CFQ_IDLE_DELAY; 483 parent = rb_last(&cfqd->service_tree.rb); 484 if (parent && parent != &cfqq->rb_node) { 485 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 486 rb_key += __cfqq->rb_key; 487 } else 488 rb_key += jiffies; 489 } else if (!add_front) { 490 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 491 rb_key += cfqq->slice_resid; 492 cfqq->slice_resid = 0; 493 } else 494 rb_key = 0; 495 496 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 497 /* 498 * same position, nothing more to do 499 */ 500 if (rb_key == cfqq->rb_key) 501 return; 502 503 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 504 } 505 506 left = 1; 507 parent = NULL; 508 p = &cfqd->service_tree.rb.rb_node; 509 while (*p) { 510 struct rb_node **n; 511 512 parent = *p; 513 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 514 515 /* 516 * sort RT queues first, we always want to give 517 * preference to them. IDLE queues goes to the back. 518 * after that, sort on the next service time. 519 */ 520 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) 521 n = &(*p)->rb_left; 522 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) 523 n = &(*p)->rb_right; 524 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) 525 n = &(*p)->rb_left; 526 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) 527 n = &(*p)->rb_right; 528 else if (rb_key < __cfqq->rb_key) 529 n = &(*p)->rb_left; 530 else 531 n = &(*p)->rb_right; 532 533 if (n == &(*p)->rb_right) 534 left = 0; 535 536 p = n; 537 } 538 539 if (left) 540 cfqd->service_tree.left = &cfqq->rb_node; 541 542 cfqq->rb_key = rb_key; 543 rb_link_node(&cfqq->rb_node, parent, p); 544 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); 545} 546 547/* 548 * Update cfqq's position in the service tree. 549 */ 550static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 551{ 552 /* 553 * Resorting requires the cfqq to be on the RR list already. 554 */ 555 if (cfq_cfqq_on_rr(cfqq)) 556 cfq_service_tree_add(cfqd, cfqq, 0); 557} 558 559/* 560 * add to busy list of queues for service, trying to be fair in ordering 561 * the pending list according to last request service 562 */ 563static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 564{ 565 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 566 BUG_ON(cfq_cfqq_on_rr(cfqq)); 567 cfq_mark_cfqq_on_rr(cfqq); 568 cfqd->busy_queues++; 569 if (cfq_class_rt(cfqq)) 570 cfqd->busy_rt_queues++; 571 572 cfq_resort_rr_list(cfqd, cfqq); 573} 574 575/* 576 * Called when the cfqq no longer has requests pending, remove it from 577 * the service tree. 578 */ 579static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 580{ 581 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 582 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 583 cfq_clear_cfqq_on_rr(cfqq); 584 585 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 586 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 587 588 BUG_ON(!cfqd->busy_queues); 589 cfqd->busy_queues--; 590 if (cfq_class_rt(cfqq)) 591 cfqd->busy_rt_queues--; 592} 593 594/* 595 * rb tree support functions 596 */ 597static void cfq_del_rq_rb(struct request *rq) 598{ 599 struct cfq_queue *cfqq = RQ_CFQQ(rq); 600 struct cfq_data *cfqd = cfqq->cfqd; 601 const int sync = rq_is_sync(rq); 602 603 BUG_ON(!cfqq->queued[sync]); 604 cfqq->queued[sync]--; 605 606 elv_rb_del(&cfqq->sort_list, rq); 607 608 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 609 cfq_del_cfqq_rr(cfqd, cfqq); 610} 611 612static void cfq_add_rq_rb(struct request *rq) 613{ 614 struct cfq_queue *cfqq = RQ_CFQQ(rq); 615 struct cfq_data *cfqd = cfqq->cfqd; 616 struct request *__alias; 617 618 cfqq->queued[rq_is_sync(rq)]++; 619 620 /* 621 * looks a little odd, but the first insert might return an alias. 622 * if that happens, put the alias on the dispatch list 623 */ 624 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 625 cfq_dispatch_insert(cfqd->queue, __alias); 626 627 if (!cfq_cfqq_on_rr(cfqq)) 628 cfq_add_cfqq_rr(cfqd, cfqq); 629 630 /* 631 * check if this request is a better next-serve candidate 632 */ 633 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); 634 BUG_ON(!cfqq->next_rq); 635} 636 637static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 638{ 639 elv_rb_del(&cfqq->sort_list, rq); 640 cfqq->queued[rq_is_sync(rq)]--; 641 cfq_add_rq_rb(rq); 642} 643 644static struct request * 645cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 646{ 647 struct task_struct *tsk = current; 648 struct cfq_io_context *cic; 649 struct cfq_queue *cfqq; 650 651 cic = cfq_cic_lookup(cfqd, tsk->io_context); 652 if (!cic) 653 return NULL; 654 655 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 656 if (cfqq) { 657 sector_t sector = bio->bi_sector + bio_sectors(bio); 658 659 return elv_rb_find(&cfqq->sort_list, sector); 660 } 661 662 return NULL; 663} 664 665static void cfq_activate_request(struct request_queue *q, struct request *rq) 666{ 667 struct cfq_data *cfqd = q->elevator->elevator_data; 668 669 cfqd->rq_in_driver++; 670 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 671 cfqd->rq_in_driver); 672 673 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors; 674} 675 676static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 677{ 678 struct cfq_data *cfqd = q->elevator->elevator_data; 679 680 WARN_ON(!cfqd->rq_in_driver); 681 cfqd->rq_in_driver--; 682 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 683 cfqd->rq_in_driver); 684} 685 686static void cfq_remove_request(struct request *rq) 687{ 688 struct cfq_queue *cfqq = RQ_CFQQ(rq); 689 690 if (cfqq->next_rq == rq) 691 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 692 693 list_del_init(&rq->queuelist); 694 cfq_del_rq_rb(rq); 695 696 cfqq->cfqd->rq_queued--; 697 if (rq_is_meta(rq)) { 698 WARN_ON(!cfqq->meta_pending); 699 cfqq->meta_pending--; 700 } 701} 702 703static int cfq_merge(struct request_queue *q, struct request **req, 704 struct bio *bio) 705{ 706 struct cfq_data *cfqd = q->elevator->elevator_data; 707 struct request *__rq; 708 709 __rq = cfq_find_rq_fmerge(cfqd, bio); 710 if (__rq && elv_rq_merge_ok(__rq, bio)) { 711 *req = __rq; 712 return ELEVATOR_FRONT_MERGE; 713 } 714 715 return ELEVATOR_NO_MERGE; 716} 717 718static void cfq_merged_request(struct request_queue *q, struct request *req, 719 int type) 720{ 721 if (type == ELEVATOR_FRONT_MERGE) { 722 struct cfq_queue *cfqq = RQ_CFQQ(req); 723 724 cfq_reposition_rq_rb(cfqq, req); 725 } 726} 727 728static void 729cfq_merged_requests(struct request_queue *q, struct request *rq, 730 struct request *next) 731{ 732 /* 733 * reposition in fifo if next is older than rq 734 */ 735 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 736 time_before(next->start_time, rq->start_time)) 737 list_move(&rq->queuelist, &next->queuelist); 738 739 cfq_remove_request(next); 740} 741 742static int cfq_allow_merge(struct request_queue *q, struct request *rq, 743 struct bio *bio) 744{ 745 struct cfq_data *cfqd = q->elevator->elevator_data; 746 struct cfq_io_context *cic; 747 struct cfq_queue *cfqq; 748 749 /* 750 * Disallow merge of a sync bio into an async request. 751 */ 752 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 753 return 0; 754 755 /* 756 * Lookup the cfqq that this bio will be queued with. Allow 757 * merge only if rq is queued there. 758 */ 759 cic = cfq_cic_lookup(cfqd, current->io_context); 760 if (!cic) 761 return 0; 762 763 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 764 if (cfqq == RQ_CFQQ(rq)) 765 return 1; 766 767 return 0; 768} 769 770static void __cfq_set_active_queue(struct cfq_data *cfqd, 771 struct cfq_queue *cfqq) 772{ 773 if (cfqq) { 774 cfq_log_cfqq(cfqd, cfqq, "set_active"); 775 cfqq->slice_end = 0; 776 cfqq->slice_dispatch = 0; 777 778 cfq_clear_cfqq_wait_request(cfqq); 779 cfq_clear_cfqq_must_dispatch(cfqq); 780 cfq_clear_cfqq_must_alloc_slice(cfqq); 781 cfq_clear_cfqq_fifo_expire(cfqq); 782 cfq_mark_cfqq_slice_new(cfqq); 783 784 del_timer(&cfqd->idle_slice_timer); 785 } 786 787 cfqd->active_queue = cfqq; 788} 789 790/* 791 * current cfqq expired its slice (or was too idle), select new one 792 */ 793static void 794__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 795 int timed_out) 796{ 797 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 798 799 if (cfq_cfqq_wait_request(cfqq)) 800 del_timer(&cfqd->idle_slice_timer); 801 802 cfq_clear_cfqq_wait_request(cfqq); 803 804 /* 805 * store what was left of this slice, if the queue idled/timed out 806 */ 807 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 808 cfqq->slice_resid = cfqq->slice_end - jiffies; 809 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 810 } 811 812 cfq_resort_rr_list(cfqd, cfqq); 813 814 if (cfqq == cfqd->active_queue) 815 cfqd->active_queue = NULL; 816 817 if (cfqd->active_cic) { 818 put_io_context(cfqd->active_cic->ioc); 819 cfqd->active_cic = NULL; 820 } 821} 822 823static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) 824{ 825 struct cfq_queue *cfqq = cfqd->active_queue; 826 827 if (cfqq) 828 __cfq_slice_expired(cfqd, cfqq, timed_out); 829} 830 831/* 832 * Get next queue for service. Unless we have a queue preemption, 833 * we'll simply select the first cfqq in the service tree. 834 */ 835static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 836{ 837 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) 838 return NULL; 839 840 return cfq_rb_first(&cfqd->service_tree); 841} 842 843/* 844 * Get and set a new active queue for service. 845 */ 846static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) 847{ 848 struct cfq_queue *cfqq; 849 850 cfqq = cfq_get_next_queue(cfqd); 851 __cfq_set_active_queue(cfqd, cfqq); 852 return cfqq; 853} 854 855static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 856 struct request *rq) 857{ 858 if (rq->sector >= cfqd->last_position) 859 return rq->sector - cfqd->last_position; 860 else 861 return cfqd->last_position - rq->sector; 862} 863 864static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) 865{ 866 struct cfq_io_context *cic = cfqd->active_cic; 867 868 if (!sample_valid(cic->seek_samples)) 869 return 0; 870 871 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean; 872} 873 874static int cfq_close_cooperator(struct cfq_data *cfq_data, 875 struct cfq_queue *cfqq) 876{ 877 /* 878 * We should notice if some of the queues are cooperating, eg 879 * working closely on the same area of the disk. In that case, 880 * we can group them together and don't waste time idling. 881 */ 882 return 0; 883} 884 885#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024)) 886 887static void cfq_arm_slice_timer(struct cfq_data *cfqd) 888{ 889 struct cfq_queue *cfqq = cfqd->active_queue; 890 struct cfq_io_context *cic; 891 unsigned long sl; 892 893 /* 894 * SSD device without seek penalty, disable idling. But only do so 895 * for devices that support queuing, otherwise we still have a problem 896 * with sync vs async workloads. 897 */ 898 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 899 return; 900 901 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 902 WARN_ON(cfq_cfqq_slice_new(cfqq)); 903 904 /* 905 * idle is disabled, either manually or by past process history 906 */ 907 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) 908 return; 909 910 /* 911 * still requests with the driver, don't idle 912 */ 913 if (cfqd->rq_in_driver) 914 return; 915 916 /* 917 * task has exited, don't wait 918 */ 919 cic = cfqd->active_cic; 920 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 921 return; 922 923 /* 924 * See if this prio level has a good candidate 925 */ 926 if (cfq_close_cooperator(cfqd, cfqq) && 927 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2)) 928 return; 929 930 cfq_mark_cfqq_wait_request(cfqq); 931 932 /* 933 * we don't want to idle for seeks, but we do want to allow 934 * fair distribution of slice time for a process doing back-to-back 935 * seeks. so allow a little bit of time for him to submit a new rq 936 */ 937 sl = cfqd->cfq_slice_idle; 938 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) 939 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); 940 941 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 942 cfq_log(cfqd, "arm_idle: %lu", sl); 943} 944 945/* 946 * Move request from internal lists to the request queue dispatch list. 947 */ 948static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 949{ 950 struct cfq_data *cfqd = q->elevator->elevator_data; 951 struct cfq_queue *cfqq = RQ_CFQQ(rq); 952 953 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 954 955 cfq_remove_request(rq); 956 cfqq->dispatched++; 957 elv_dispatch_sort(q, rq); 958 959 if (cfq_cfqq_sync(cfqq)) 960 cfqd->sync_flight++; 961} 962 963/* 964 * return expired entry, or NULL to just start from scratch in rbtree 965 */ 966static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 967{ 968 struct cfq_data *cfqd = cfqq->cfqd; 969 struct request *rq; 970 int fifo; 971 972 if (cfq_cfqq_fifo_expire(cfqq)) 973 return NULL; 974 975 cfq_mark_cfqq_fifo_expire(cfqq); 976 977 if (list_empty(&cfqq->fifo)) 978 return NULL; 979 980 fifo = cfq_cfqq_sync(cfqq); 981 rq = rq_entry_fifo(cfqq->fifo.next); 982 983 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) 984 rq = NULL; 985 986 cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq); 987 return rq; 988} 989 990static inline int 991cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 992{ 993 const int base_rq = cfqd->cfq_slice_async_rq; 994 995 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 996 997 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 998} 999 1000/* 1001 * Select a queue for service. If we have a current active queue, 1002 * check whether to continue servicing it, or retrieve and set a new one. 1003 */ 1004static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 1005{ 1006 struct cfq_queue *cfqq; 1007 1008 cfqq = cfqd->active_queue; 1009 if (!cfqq) 1010 goto new_queue; 1011 1012 /* 1013 * The active queue has run out of time, expire it and select new. 1014 */ 1015 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) 1016 goto expire; 1017 1018 /* 1019 * If we have a RT cfqq waiting, then we pre-empt the current non-rt 1020 * cfqq. 1021 */ 1022 if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) { 1023 /* 1024 * We simulate this as cfqq timed out so that it gets to bank 1025 * the remaining of its time slice. 1026 */ 1027 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1028 cfq_slice_expired(cfqd, 1); 1029 goto new_queue; 1030 } 1031 1032 /* 1033 * The active queue has requests and isn't expired, allow it to 1034 * dispatch. 1035 */ 1036 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 1037 goto keep_queue; 1038 1039 /* 1040 * No requests pending. If the active queue still has requests in 1041 * flight or is idling for a new request, allow either of these 1042 * conditions to happen (or time out) before selecting a new queue. 1043 */ 1044 if (timer_pending(&cfqd->idle_slice_timer) || 1045 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { 1046 cfqq = NULL; 1047 goto keep_queue; 1048 } 1049 1050expire: 1051 cfq_slice_expired(cfqd, 0); 1052new_queue: 1053 cfqq = cfq_set_active_queue(cfqd); 1054keep_queue: 1055 return cfqq; 1056} 1057 1058static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 1059{ 1060 int dispatched = 0; 1061 1062 while (cfqq->next_rq) { 1063 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 1064 dispatched++; 1065 } 1066 1067 BUG_ON(!list_empty(&cfqq->fifo)); 1068 return dispatched; 1069} 1070 1071/* 1072 * Drain our current requests. Used for barriers and when switching 1073 * io schedulers on-the-fly. 1074 */ 1075static int cfq_forced_dispatch(struct cfq_data *cfqd) 1076{ 1077 struct cfq_queue *cfqq; 1078 int dispatched = 0; 1079 1080 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) 1081 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 1082 1083 cfq_slice_expired(cfqd, 0); 1084 1085 BUG_ON(cfqd->busy_queues); 1086 1087 cfq_log(cfqd, "forced_dispatch=%d\n", dispatched); 1088 return dispatched; 1089} 1090 1091/* 1092 * Dispatch a request from cfqq, moving them to the request queue 1093 * dispatch list. 1094 */ 1095static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1096{ 1097 struct request *rq; 1098 1099 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 1100 1101 /* 1102 * follow expired path, else get first next available 1103 */ 1104 rq = cfq_check_fifo(cfqq); 1105 if (!rq) 1106 rq = cfqq->next_rq; 1107 1108 /* 1109 * insert request into driver dispatch list 1110 */ 1111 cfq_dispatch_insert(cfqd->queue, rq); 1112 1113 if (!cfqd->active_cic) { 1114 struct cfq_io_context *cic = RQ_CIC(rq); 1115 1116 atomic_inc(&cic->ioc->refcount); 1117 cfqd->active_cic = cic; 1118 } 1119} 1120 1121/* 1122 * Find the cfqq that we need to service and move a request from that to the 1123 * dispatch list 1124 */ 1125static int cfq_dispatch_requests(struct request_queue *q, int force) 1126{ 1127 struct cfq_data *cfqd = q->elevator->elevator_data; 1128 struct cfq_queue *cfqq; 1129 unsigned int max_dispatch; 1130 1131 if (!cfqd->busy_queues) 1132 return 0; 1133 1134 if (unlikely(force)) 1135 return cfq_forced_dispatch(cfqd); 1136 1137 cfqq = cfq_select_queue(cfqd); 1138 if (!cfqq) 1139 return 0; 1140 1141 /* 1142 * If this is an async queue and we have sync IO in flight, let it wait 1143 */ 1144 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 1145 return 0; 1146 1147 max_dispatch = cfqd->cfq_quantum; 1148 if (cfq_class_idle(cfqq)) 1149 max_dispatch = 1; 1150 1151 /* 1152 * Does this cfqq already have too much IO in flight? 1153 */ 1154 if (cfqq->dispatched >= max_dispatch) { 1155 /* 1156 * idle queue must always only have a single IO in flight 1157 */ 1158 if (cfq_class_idle(cfqq)) 1159 return 0; 1160 1161 /* 1162 * We have other queues, don't allow more IO from this one 1163 */ 1164 if (cfqd->busy_queues > 1) 1165 return 0; 1166 1167 /* 1168 * we are the only queue, allow up to 4 times of 'quantum' 1169 */ 1170 if (cfqq->dispatched >= 4 * max_dispatch) 1171 return 0; 1172 } 1173 1174 /* 1175 * Dispatch a request from this cfqq 1176 */ 1177 cfq_dispatch_request(cfqd, cfqq); 1178 cfqq->slice_dispatch++; 1179 cfq_clear_cfqq_must_dispatch(cfqq); 1180 1181 /* 1182 * expire an async queue immediately if it has used up its slice. idle 1183 * queue always expire after 1 dispatch round. 1184 */ 1185 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 1186 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1187 cfq_class_idle(cfqq))) { 1188 cfqq->slice_end = jiffies + 1; 1189 cfq_slice_expired(cfqd, 0); 1190 } 1191 1192 cfq_log(cfqd, "dispatched a request"); 1193 return 1; 1194} 1195 1196/* 1197 * task holds one reference to the queue, dropped when task exits. each rq 1198 * in-flight on this queue also holds a reference, dropped when rq is freed. 1199 * 1200 * queue lock must be held here. 1201 */ 1202static void cfq_put_queue(struct cfq_queue *cfqq) 1203{ 1204 struct cfq_data *cfqd = cfqq->cfqd; 1205 1206 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1207 1208 if (!atomic_dec_and_test(&cfqq->ref)) 1209 return; 1210 1211 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 1212 BUG_ON(rb_first(&cfqq->sort_list)); 1213 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1214 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1215 1216 if (unlikely(cfqd->active_queue == cfqq)) { 1217 __cfq_slice_expired(cfqd, cfqq, 0); 1218 cfq_schedule_dispatch(cfqd); 1219 } 1220 1221 kmem_cache_free(cfq_pool, cfqq); 1222} 1223 1224/* 1225 * Must always be called with the rcu_read_lock() held 1226 */ 1227static void 1228__call_for_each_cic(struct io_context *ioc, 1229 void (*func)(struct io_context *, struct cfq_io_context *)) 1230{ 1231 struct cfq_io_context *cic; 1232 struct hlist_node *n; 1233 1234 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 1235 func(ioc, cic); 1236} 1237 1238/* 1239 * Call func for each cic attached to this ioc. 1240 */ 1241static void 1242call_for_each_cic(struct io_context *ioc, 1243 void (*func)(struct io_context *, struct cfq_io_context *)) 1244{ 1245 rcu_read_lock(); 1246 __call_for_each_cic(ioc, func); 1247 rcu_read_unlock(); 1248} 1249 1250static void cfq_cic_free_rcu(struct rcu_head *head) 1251{ 1252 struct cfq_io_context *cic; 1253 1254 cic = container_of(head, struct cfq_io_context, rcu_head); 1255 1256 kmem_cache_free(cfq_ioc_pool, cic); 1257 elv_ioc_count_dec(ioc_count); 1258 1259 if (ioc_gone) { 1260 /* 1261 * CFQ scheduler is exiting, grab exit lock and check 1262 * the pending io context count. If it hits zero, 1263 * complete ioc_gone and set it back to NULL 1264 */ 1265 spin_lock(&ioc_gone_lock); 1266 if (ioc_gone && !elv_ioc_count_read(ioc_count)) { 1267 complete(ioc_gone); 1268 ioc_gone = NULL; 1269 } 1270 spin_unlock(&ioc_gone_lock); 1271 } 1272} 1273 1274static void cfq_cic_free(struct cfq_io_context *cic) 1275{ 1276 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 1277} 1278 1279static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 1280{ 1281 unsigned long flags; 1282 1283 BUG_ON(!cic->dead_key); 1284 1285 spin_lock_irqsave(&ioc->lock, flags); 1286 radix_tree_delete(&ioc->radix_root, cic->dead_key); 1287 hlist_del_rcu(&cic->cic_list); 1288 spin_unlock_irqrestore(&ioc->lock, flags); 1289 1290 cfq_cic_free(cic); 1291} 1292 1293/* 1294 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 1295 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 1296 * and ->trim() which is called with the task lock held 1297 */ 1298static void cfq_free_io_context(struct io_context *ioc) 1299{ 1300 /* 1301 * ioc->refcount is zero here, or we are called from elv_unregister(), 1302 * so no more cic's are allowed to be linked into this ioc. So it 1303 * should be ok to iterate over the known list, we will see all cic's 1304 * since no new ones are added. 1305 */ 1306 __call_for_each_cic(ioc, cic_free_func); 1307} 1308 1309static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1310{ 1311 if (unlikely(cfqq == cfqd->active_queue)) { 1312 __cfq_slice_expired(cfqd, cfqq, 0); 1313 cfq_schedule_dispatch(cfqd); 1314 } 1315 1316 cfq_put_queue(cfqq); 1317} 1318 1319static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 1320 struct cfq_io_context *cic) 1321{ 1322 struct io_context *ioc = cic->ioc; 1323 1324 list_del_init(&cic->queue_list); 1325 1326 /* 1327 * Make sure key == NULL is seen for dead queues 1328 */ 1329 smp_wmb(); 1330 cic->dead_key = (unsigned long) cic->key; 1331 cic->key = NULL; 1332 1333 if (ioc->ioc_data == cic) 1334 rcu_assign_pointer(ioc->ioc_data, NULL); 1335 1336 if (cic->cfqq[ASYNC]) { 1337 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]); 1338 cic->cfqq[ASYNC] = NULL; 1339 } 1340 1341 if (cic->cfqq[SYNC]) { 1342 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]); 1343 cic->cfqq[SYNC] = NULL; 1344 } 1345} 1346 1347static void cfq_exit_single_io_context(struct io_context *ioc, 1348 struct cfq_io_context *cic) 1349{ 1350 struct cfq_data *cfqd = cic->key; 1351 1352 if (cfqd) { 1353 struct request_queue *q = cfqd->queue; 1354 unsigned long flags; 1355 1356 spin_lock_irqsave(q->queue_lock, flags); 1357 1358 /* 1359 * Ensure we get a fresh copy of the ->key to prevent 1360 * race between exiting task and queue 1361 */ 1362 smp_read_barrier_depends(); 1363 if (cic->key) 1364 __cfq_exit_single_io_context(cfqd, cic); 1365 1366 spin_unlock_irqrestore(q->queue_lock, flags); 1367 } 1368} 1369 1370/* 1371 * The process that ioc belongs to has exited, we need to clean up 1372 * and put the internal structures we have that belongs to that process. 1373 */ 1374static void cfq_exit_io_context(struct io_context *ioc) 1375{ 1376 call_for_each_cic(ioc, cfq_exit_single_io_context); 1377} 1378 1379static struct cfq_io_context * 1380cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1381{ 1382 struct cfq_io_context *cic; 1383 1384 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 1385 cfqd->queue->node); 1386 if (cic) { 1387 cic->last_end_request = jiffies; 1388 INIT_LIST_HEAD(&cic->queue_list); 1389 INIT_HLIST_NODE(&cic->cic_list); 1390 cic->dtor = cfq_free_io_context; 1391 cic->exit = cfq_exit_io_context; 1392 elv_ioc_count_inc(ioc_count); 1393 } 1394 1395 return cic; 1396} 1397 1398static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 1399{ 1400 struct task_struct *tsk = current; 1401 int ioprio_class; 1402 1403 if (!cfq_cfqq_prio_changed(cfqq)) 1404 return; 1405 1406 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 1407 switch (ioprio_class) { 1408 default: 1409 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1410 case IOPRIO_CLASS_NONE: 1411 /* 1412 * no prio set, inherit CPU scheduling settings 1413 */ 1414 cfqq->ioprio = task_nice_ioprio(tsk); 1415 cfqq->ioprio_class = task_nice_ioclass(tsk); 1416 break; 1417 case IOPRIO_CLASS_RT: 1418 cfqq->ioprio = task_ioprio(ioc); 1419 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1420 break; 1421 case IOPRIO_CLASS_BE: 1422 cfqq->ioprio = task_ioprio(ioc); 1423 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1424 break; 1425 case IOPRIO_CLASS_IDLE: 1426 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1427 cfqq->ioprio = 7; 1428 cfq_clear_cfqq_idle_window(cfqq); 1429 break; 1430 } 1431 1432 /* 1433 * keep track of original prio settings in case we have to temporarily 1434 * elevate the priority of this queue 1435 */ 1436 cfqq->org_ioprio = cfqq->ioprio; 1437 cfqq->org_ioprio_class = cfqq->ioprio_class; 1438 cfq_clear_cfqq_prio_changed(cfqq); 1439} 1440 1441static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 1442{ 1443 struct cfq_data *cfqd = cic->key; 1444 struct cfq_queue *cfqq; 1445 unsigned long flags; 1446 1447 if (unlikely(!cfqd)) 1448 return; 1449 1450 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1451 1452 cfqq = cic->cfqq[ASYNC]; 1453 if (cfqq) { 1454 struct cfq_queue *new_cfqq; 1455 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC); 1456 if (new_cfqq) { 1457 cic->cfqq[ASYNC] = new_cfqq; 1458 cfq_put_queue(cfqq); 1459 } 1460 } 1461 1462 cfqq = cic->cfqq[SYNC]; 1463 if (cfqq) 1464 cfq_mark_cfqq_prio_changed(cfqq); 1465 1466 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1467} 1468 1469static void cfq_ioc_set_ioprio(struct io_context *ioc) 1470{ 1471 call_for_each_cic(ioc, changed_ioprio); 1472 ioc->ioprio_changed = 0; 1473} 1474 1475static struct cfq_queue * 1476cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, 1477 struct io_context *ioc, gfp_t gfp_mask) 1478{ 1479 struct cfq_queue *cfqq, *new_cfqq = NULL; 1480 struct cfq_io_context *cic; 1481 1482retry: 1483 cic = cfq_cic_lookup(cfqd, ioc); 1484 /* cic always exists here */ 1485 cfqq = cic_to_cfqq(cic, is_sync); 1486 1487 if (!cfqq) { 1488 if (new_cfqq) { 1489 cfqq = new_cfqq; 1490 new_cfqq = NULL; 1491 } else if (gfp_mask & __GFP_WAIT) { 1492 /* 1493 * Inform the allocator of the fact that we will 1494 * just repeat this allocation if it fails, to allow 1495 * the allocator to do whatever it needs to attempt to 1496 * free memory. 1497 */ 1498 spin_unlock_irq(cfqd->queue->queue_lock); 1499 new_cfqq = kmem_cache_alloc_node(cfq_pool, 1500 gfp_mask | __GFP_NOFAIL | __GFP_ZERO, 1501 cfqd->queue->node); 1502 spin_lock_irq(cfqd->queue->queue_lock); 1503 goto retry; 1504 } else { 1505 cfqq = kmem_cache_alloc_node(cfq_pool, 1506 gfp_mask | __GFP_ZERO, 1507 cfqd->queue->node); 1508 if (!cfqq) 1509 goto out; 1510 } 1511 1512 RB_CLEAR_NODE(&cfqq->rb_node); 1513 INIT_LIST_HEAD(&cfqq->fifo); 1514 1515 atomic_set(&cfqq->ref, 0); 1516 cfqq->cfqd = cfqd; 1517 1518 cfq_mark_cfqq_prio_changed(cfqq); 1519 1520 cfq_init_prio_data(cfqq, ioc); 1521 1522 if (is_sync) { 1523 if (!cfq_class_idle(cfqq)) 1524 cfq_mark_cfqq_idle_window(cfqq); 1525 cfq_mark_cfqq_sync(cfqq); 1526 } 1527 cfqq->pid = current->pid; 1528 cfq_log_cfqq(cfqd, cfqq, "alloced"); 1529 } 1530 1531 if (new_cfqq) 1532 kmem_cache_free(cfq_pool, new_cfqq); 1533 1534out: 1535 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq); 1536 return cfqq; 1537} 1538 1539static struct cfq_queue ** 1540cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 1541{ 1542 switch (ioprio_class) { 1543 case IOPRIO_CLASS_RT: 1544 return &cfqd->async_cfqq[0][ioprio]; 1545 case IOPRIO_CLASS_BE: 1546 return &cfqd->async_cfqq[1][ioprio]; 1547 case IOPRIO_CLASS_IDLE: 1548 return &cfqd->async_idle_cfqq; 1549 default: 1550 BUG(); 1551 } 1552} 1553 1554static struct cfq_queue * 1555cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, 1556 gfp_t gfp_mask) 1557{ 1558 const int ioprio = task_ioprio(ioc); 1559 const int ioprio_class = task_ioprio_class(ioc); 1560 struct cfq_queue **async_cfqq = NULL; 1561 struct cfq_queue *cfqq = NULL; 1562 1563 if (!is_sync) { 1564 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 1565 cfqq = *async_cfqq; 1566 } 1567 1568 if (!cfqq) { 1569 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 1570 if (!cfqq) 1571 return NULL; 1572 } 1573 1574 /* 1575 * pin the queue now that it's allocated, scheduler exit will prune it 1576 */ 1577 if (!is_sync && !(*async_cfqq)) { 1578 atomic_inc(&cfqq->ref); 1579 *async_cfqq = cfqq; 1580 } 1581 1582 atomic_inc(&cfqq->ref); 1583 return cfqq; 1584} 1585 1586/* 1587 * We drop cfq io contexts lazily, so we may find a dead one. 1588 */ 1589static void 1590cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 1591 struct cfq_io_context *cic) 1592{ 1593 unsigned long flags; 1594 1595 WARN_ON(!list_empty(&cic->queue_list)); 1596 1597 spin_lock_irqsave(&ioc->lock, flags); 1598 1599 BUG_ON(ioc->ioc_data == cic); 1600 1601 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 1602 hlist_del_rcu(&cic->cic_list); 1603 spin_unlock_irqrestore(&ioc->lock, flags); 1604 1605 cfq_cic_free(cic); 1606} 1607 1608static struct cfq_io_context * 1609cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 1610{ 1611 struct cfq_io_context *cic; 1612 unsigned long flags; 1613 void *k; 1614 1615 if (unlikely(!ioc)) 1616 return NULL; 1617 1618 rcu_read_lock(); 1619 1620 /* 1621 * we maintain a last-hit cache, to avoid browsing over the tree 1622 */ 1623 cic = rcu_dereference(ioc->ioc_data); 1624 if (cic && cic->key == cfqd) { 1625 rcu_read_unlock(); 1626 return cic; 1627 } 1628 1629 do { 1630 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 1631 rcu_read_unlock(); 1632 if (!cic) 1633 break; 1634 /* ->key must be copied to avoid race with cfq_exit_queue() */ 1635 k = cic->key; 1636 if (unlikely(!k)) { 1637 cfq_drop_dead_cic(cfqd, ioc, cic); 1638 rcu_read_lock(); 1639 continue; 1640 } 1641 1642 spin_lock_irqsave(&ioc->lock, flags); 1643 rcu_assign_pointer(ioc->ioc_data, cic); 1644 spin_unlock_irqrestore(&ioc->lock, flags); 1645 break; 1646 } while (1); 1647 1648 return cic; 1649} 1650 1651/* 1652 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 1653 * the process specific cfq io context when entered from the block layer. 1654 * Also adds the cic to a per-cfqd list, used when this queue is removed. 1655 */ 1656static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 1657 struct cfq_io_context *cic, gfp_t gfp_mask) 1658{ 1659 unsigned long flags; 1660 int ret; 1661 1662 ret = radix_tree_preload(gfp_mask); 1663 if (!ret) { 1664 cic->ioc = ioc; 1665 cic->key = cfqd; 1666 1667 spin_lock_irqsave(&ioc->lock, flags); 1668 ret = radix_tree_insert(&ioc->radix_root, 1669 (unsigned long) cfqd, cic); 1670 if (!ret) 1671 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 1672 spin_unlock_irqrestore(&ioc->lock, flags); 1673 1674 radix_tree_preload_end(); 1675 1676 if (!ret) { 1677 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1678 list_add(&cic->queue_list, &cfqd->cic_list); 1679 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1680 } 1681 } 1682 1683 if (ret) 1684 printk(KERN_ERR "cfq: cic link failed!\n"); 1685 1686 return ret; 1687} 1688 1689/* 1690 * Setup general io context and cfq io context. There can be several cfq 1691 * io contexts per general io context, if this process is doing io to more 1692 * than one device managed by cfq. 1693 */ 1694static struct cfq_io_context * 1695cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1696{ 1697 struct io_context *ioc = NULL; 1698 struct cfq_io_context *cic; 1699 1700 might_sleep_if(gfp_mask & __GFP_WAIT); 1701 1702 ioc = get_io_context(gfp_mask, cfqd->queue->node); 1703 if (!ioc) 1704 return NULL; 1705 1706 cic = cfq_cic_lookup(cfqd, ioc); 1707 if (cic) 1708 goto out; 1709 1710 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1711 if (cic == NULL) 1712 goto err; 1713 1714 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 1715 goto err_free; 1716 1717out: 1718 smp_read_barrier_depends(); 1719 if (unlikely(ioc->ioprio_changed)) 1720 cfq_ioc_set_ioprio(ioc); 1721 1722 return cic; 1723err_free: 1724 cfq_cic_free(cic); 1725err: 1726 put_io_context(ioc); 1727 return NULL; 1728} 1729 1730static void 1731cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 1732{ 1733 unsigned long elapsed = jiffies - cic->last_end_request; 1734 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 1735 1736 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 1737 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 1738 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 1739} 1740 1741static void 1742cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic, 1743 struct request *rq) 1744{ 1745 sector_t sdist; 1746 u64 total; 1747 1748 if (cic->last_request_pos < rq->sector) 1749 sdist = rq->sector - cic->last_request_pos; 1750 else 1751 sdist = cic->last_request_pos - rq->sector; 1752 1753 /* 1754 * Don't allow the seek distance to get too large from the 1755 * odd fragment, pagein, etc 1756 */ 1757 if (cic->seek_samples <= 60) /* second&third seek */ 1758 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); 1759 else 1760 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); 1761 1762 cic->seek_samples = (7*cic->seek_samples + 256) / 8; 1763 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; 1764 total = cic->seek_total + (cic->seek_samples/2); 1765 do_div(total, cic->seek_samples); 1766 cic->seek_mean = (sector_t)total; 1767} 1768 1769/* 1770 * Disable idle window if the process thinks too long or seeks so much that 1771 * it doesn't matter 1772 */ 1773static void 1774cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1775 struct cfq_io_context *cic) 1776{ 1777 int old_idle, enable_idle; 1778 1779 /* 1780 * Don't idle for async or idle io prio class 1781 */ 1782 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 1783 return; 1784 1785 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 1786 1787 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 1788 (cfqd->hw_tag && CIC_SEEKY(cic))) 1789 enable_idle = 0; 1790 else if (sample_valid(cic->ttime_samples)) { 1791 if (cic->ttime_mean > cfqd->cfq_slice_idle) 1792 enable_idle = 0; 1793 else 1794 enable_idle = 1; 1795 } 1796 1797 if (old_idle != enable_idle) { 1798 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 1799 if (enable_idle) 1800 cfq_mark_cfqq_idle_window(cfqq); 1801 else 1802 cfq_clear_cfqq_idle_window(cfqq); 1803 } 1804} 1805 1806/* 1807 * Check if new_cfqq should preempt the currently active queue. Return 0 for 1808 * no or if we aren't sure, a 1 will cause a preempt. 1809 */ 1810static int 1811cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 1812 struct request *rq) 1813{ 1814 struct cfq_queue *cfqq; 1815 1816 cfqq = cfqd->active_queue; 1817 if (!cfqq) 1818 return 0; 1819 1820 if (cfq_slice_used(cfqq)) 1821 return 1; 1822 1823 if (cfq_class_idle(new_cfqq)) 1824 return 0; 1825 1826 if (cfq_class_idle(cfqq)) 1827 return 1; 1828 1829 /* 1830 * if the new request is sync, but the currently running queue is 1831 * not, let the sync request have priority. 1832 */ 1833 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 1834 return 1; 1835 1836 /* 1837 * So both queues are sync. Let the new request get disk time if 1838 * it's a metadata request and the current queue is doing regular IO. 1839 */ 1840 if (rq_is_meta(rq) && !cfqq->meta_pending) 1841 return 1; 1842 1843 /* 1844 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 1845 */ 1846 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 1847 return 1; 1848 1849 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 1850 return 0; 1851 1852 /* 1853 * if this request is as-good as one we would expect from the 1854 * current cfqq, let it preempt 1855 */ 1856 if (cfq_rq_close(cfqd, rq)) 1857 return 1; 1858 1859 return 0; 1860} 1861 1862/* 1863 * cfqq preempts the active queue. if we allowed preempt with no slice left, 1864 * let it have half of its nominal slice. 1865 */ 1866static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1867{ 1868 cfq_log_cfqq(cfqd, cfqq, "preempt"); 1869 cfq_slice_expired(cfqd, 1); 1870 1871 /* 1872 * Put the new queue at the front of the of the current list, 1873 * so we know that it will be selected next. 1874 */ 1875 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 1876 1877 cfq_service_tree_add(cfqd, cfqq, 1); 1878 1879 cfqq->slice_end = 0; 1880 cfq_mark_cfqq_slice_new(cfqq); 1881} 1882 1883/* 1884 * Called when a new fs request (rq) is added (to cfqq). Check if there's 1885 * something we should do about it 1886 */ 1887static void 1888cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1889 struct request *rq) 1890{ 1891 struct cfq_io_context *cic = RQ_CIC(rq); 1892 1893 cfqd->rq_queued++; 1894 if (rq_is_meta(rq)) 1895 cfqq->meta_pending++; 1896 1897 cfq_update_io_thinktime(cfqd, cic); 1898 cfq_update_io_seektime(cfqd, cic, rq); 1899 cfq_update_idle_window(cfqd, cfqq, cic); 1900 1901 cic->last_request_pos = rq->sector + rq->nr_sectors; 1902 1903 if (cfqq == cfqd->active_queue) { 1904 /* 1905 * Remember that we saw a request from this process, but 1906 * don't start queuing just yet. Otherwise we risk seeing lots 1907 * of tiny requests, because we disrupt the normal plugging 1908 * and merging. 1909 */ 1910 if (cfq_cfqq_wait_request(cfqq)) 1911 cfq_mark_cfqq_must_dispatch(cfqq); 1912 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 1913 /* 1914 * not the active queue - expire current slice if it is 1915 * idle and has expired it's mean thinktime or this new queue 1916 * has some old slice time left and is of higher priority or 1917 * this new queue is RT and the current one is BE 1918 */ 1919 cfq_preempt_queue(cfqd, cfqq); 1920 blk_start_queueing(cfqd->queue); 1921 } 1922} 1923 1924static void cfq_insert_request(struct request_queue *q, struct request *rq) 1925{ 1926 struct cfq_data *cfqd = q->elevator->elevator_data; 1927 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1928 1929 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 1930 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 1931 1932 cfq_add_rq_rb(rq); 1933 1934 list_add_tail(&rq->queuelist, &cfqq->fifo); 1935 1936 cfq_rq_enqueued(cfqd, cfqq, rq); 1937} 1938 1939/* 1940 * Update hw_tag based on peak queue depth over 50 samples under 1941 * sufficient load. 1942 */ 1943static void cfq_update_hw_tag(struct cfq_data *cfqd) 1944{ 1945 if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak) 1946 cfqd->rq_in_driver_peak = cfqd->rq_in_driver; 1947 1948 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 1949 cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) 1950 return; 1951 1952 if (cfqd->hw_tag_samples++ < 50) 1953 return; 1954 1955 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN) 1956 cfqd->hw_tag = 1; 1957 else 1958 cfqd->hw_tag = 0; 1959 1960 cfqd->hw_tag_samples = 0; 1961 cfqd->rq_in_driver_peak = 0; 1962} 1963 1964static void cfq_completed_request(struct request_queue *q, struct request *rq) 1965{ 1966 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1967 struct cfq_data *cfqd = cfqq->cfqd; 1968 const int sync = rq_is_sync(rq); 1969 unsigned long now; 1970 1971 now = jiffies; 1972 cfq_log_cfqq(cfqd, cfqq, "complete"); 1973 1974 cfq_update_hw_tag(cfqd); 1975 1976 WARN_ON(!cfqd->rq_in_driver); 1977 WARN_ON(!cfqq->dispatched); 1978 cfqd->rq_in_driver--; 1979 cfqq->dispatched--; 1980 1981 if (cfq_cfqq_sync(cfqq)) 1982 cfqd->sync_flight--; 1983 1984 if (!cfq_class_idle(cfqq)) 1985 cfqd->last_end_request = now; 1986 1987 if (sync) 1988 RQ_CIC(rq)->last_end_request = now; 1989 1990 /* 1991 * If this is the active queue, check if it needs to be expired, 1992 * or if we want to idle in case it has no pending requests. 1993 */ 1994 if (cfqd->active_queue == cfqq) { 1995 if (cfq_cfqq_slice_new(cfqq)) { 1996 cfq_set_prio_slice(cfqd, cfqq); 1997 cfq_clear_cfqq_slice_new(cfqq); 1998 } 1999 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 2000 cfq_slice_expired(cfqd, 1); 2001 else if (sync && !rq_noidle(rq) && 2002 RB_EMPTY_ROOT(&cfqq->sort_list)) { 2003 cfq_arm_slice_timer(cfqd); 2004 } 2005 } 2006 2007 if (!cfqd->rq_in_driver) 2008 cfq_schedule_dispatch(cfqd); 2009} 2010 2011/* 2012 * we temporarily boost lower priority queues if they are holding fs exclusive 2013 * resources. they are boosted to normal prio (CLASS_BE/4) 2014 */ 2015static void cfq_prio_boost(struct cfq_queue *cfqq) 2016{ 2017 if (has_fs_excl()) { 2018 /* 2019 * boost idle prio on transactions that would lock out other 2020 * users of the filesystem 2021 */ 2022 if (cfq_class_idle(cfqq)) 2023 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2024 if (cfqq->ioprio > IOPRIO_NORM) 2025 cfqq->ioprio = IOPRIO_NORM; 2026 } else { 2027 /* 2028 * check if we need to unboost the queue 2029 */ 2030 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 2031 cfqq->ioprio_class = cfqq->org_ioprio_class; 2032 if (cfqq->ioprio != cfqq->org_ioprio) 2033 cfqq->ioprio = cfqq->org_ioprio; 2034 } 2035} 2036 2037static inline int __cfq_may_queue(struct cfq_queue *cfqq) 2038{ 2039 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) && 2040 !cfq_cfqq_must_alloc_slice(cfqq)) { 2041 cfq_mark_cfqq_must_alloc_slice(cfqq); 2042 return ELV_MQUEUE_MUST; 2043 } 2044 2045 return ELV_MQUEUE_MAY; 2046} 2047 2048static int cfq_may_queue(struct request_queue *q, int rw) 2049{ 2050 struct cfq_data *cfqd = q->elevator->elevator_data; 2051 struct task_struct *tsk = current; 2052 struct cfq_io_context *cic; 2053 struct cfq_queue *cfqq; 2054 2055 /* 2056 * don't force setup of a queue from here, as a call to may_queue 2057 * does not necessarily imply that a request actually will be queued. 2058 * so just lookup a possibly existing queue, or return 'may queue' 2059 * if that fails 2060 */ 2061 cic = cfq_cic_lookup(cfqd, tsk->io_context); 2062 if (!cic) 2063 return ELV_MQUEUE_MAY; 2064 2065 cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); 2066 if (cfqq) { 2067 cfq_init_prio_data(cfqq, cic->ioc); 2068 cfq_prio_boost(cfqq); 2069 2070 return __cfq_may_queue(cfqq); 2071 } 2072 2073 return ELV_MQUEUE_MAY; 2074} 2075 2076/* 2077 * queue lock held here 2078 */ 2079static void cfq_put_request(struct request *rq) 2080{ 2081 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2082 2083 if (cfqq) { 2084 const int rw = rq_data_dir(rq); 2085 2086 BUG_ON(!cfqq->allocated[rw]); 2087 cfqq->allocated[rw]--; 2088 2089 put_io_context(RQ_CIC(rq)->ioc); 2090 2091 rq->elevator_private = NULL; 2092 rq->elevator_private2 = NULL; 2093 2094 cfq_put_queue(cfqq); 2095 } 2096} 2097 2098/* 2099 * Allocate cfq data structures associated with this request. 2100 */ 2101static int 2102cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 2103{ 2104 struct cfq_data *cfqd = q->elevator->elevator_data; 2105 struct cfq_io_context *cic; 2106 const int rw = rq_data_dir(rq); 2107 const int is_sync = rq_is_sync(rq); 2108 struct cfq_queue *cfqq; 2109 unsigned long flags; 2110 2111 might_sleep_if(gfp_mask & __GFP_WAIT); 2112 2113 cic = cfq_get_io_context(cfqd, gfp_mask); 2114 2115 spin_lock_irqsave(q->queue_lock, flags); 2116 2117 if (!cic) 2118 goto queue_fail; 2119 2120 cfqq = cic_to_cfqq(cic, is_sync); 2121 if (!cfqq) { 2122 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 2123 2124 if (!cfqq) 2125 goto queue_fail; 2126 2127 cic_set_cfqq(cic, cfqq, is_sync); 2128 } 2129 2130 cfqq->allocated[rw]++; 2131 cfq_clear_cfqq_must_alloc(cfqq); 2132 atomic_inc(&cfqq->ref); 2133 2134 spin_unlock_irqrestore(q->queue_lock, flags); 2135 2136 rq->elevator_private = cic; 2137 rq->elevator_private2 = cfqq; 2138 return 0; 2139 2140queue_fail: 2141 if (cic) 2142 put_io_context(cic->ioc); 2143 2144 cfq_schedule_dispatch(cfqd); 2145 spin_unlock_irqrestore(q->queue_lock, flags); 2146 cfq_log(cfqd, "set_request fail"); 2147 return 1; 2148} 2149 2150static void cfq_kick_queue(struct work_struct *work) 2151{ 2152 struct cfq_data *cfqd = 2153 container_of(work, struct cfq_data, unplug_work); 2154 struct request_queue *q = cfqd->queue; 2155 unsigned long flags; 2156 2157 spin_lock_irqsave(q->queue_lock, flags); 2158 blk_start_queueing(q); 2159 spin_unlock_irqrestore(q->queue_lock, flags); 2160} 2161 2162/* 2163 * Timer running if the active_queue is currently idling inside its time slice 2164 */ 2165static void cfq_idle_slice_timer(unsigned long data) 2166{ 2167 struct cfq_data *cfqd = (struct cfq_data *) data; 2168 struct cfq_queue *cfqq; 2169 unsigned long flags; 2170 int timed_out = 1; 2171 2172 cfq_log(cfqd, "idle timer fired"); 2173 2174 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2175 2176 cfqq = cfqd->active_queue; 2177 if (cfqq) { 2178 timed_out = 0; 2179 2180 /* 2181 * We saw a request before the queue expired, let it through 2182 */ 2183 if (cfq_cfqq_must_dispatch(cfqq)) 2184 goto out_kick; 2185 2186 /* 2187 * expired 2188 */ 2189 if (cfq_slice_used(cfqq)) 2190 goto expire; 2191 2192 /* 2193 * only expire and reinvoke request handler, if there are 2194 * other queues with pending requests 2195 */ 2196 if (!cfqd->busy_queues) 2197 goto out_cont; 2198 2199 /* 2200 * not expired and it has a request pending, let it dispatch 2201 */ 2202 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 2203 goto out_kick; 2204 } 2205expire: 2206 cfq_slice_expired(cfqd, timed_out); 2207out_kick: 2208 cfq_schedule_dispatch(cfqd); 2209out_cont: 2210 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2211} 2212 2213static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2214{ 2215 del_timer_sync(&cfqd->idle_slice_timer); 2216 cancel_work_sync(&cfqd->unplug_work); 2217} 2218 2219static void cfq_put_async_queues(struct cfq_data *cfqd) 2220{ 2221 int i; 2222 2223 for (i = 0; i < IOPRIO_BE_NR; i++) { 2224 if (cfqd->async_cfqq[0][i]) 2225 cfq_put_queue(cfqd->async_cfqq[0][i]); 2226 if (cfqd->async_cfqq[1][i]) 2227 cfq_put_queue(cfqd->async_cfqq[1][i]); 2228 } 2229 2230 if (cfqd->async_idle_cfqq) 2231 cfq_put_queue(cfqd->async_idle_cfqq); 2232} 2233 2234static void cfq_exit_queue(struct elevator_queue *e) 2235{ 2236 struct cfq_data *cfqd = e->elevator_data; 2237 struct request_queue *q = cfqd->queue; 2238 2239 cfq_shutdown_timer_wq(cfqd); 2240 2241 spin_lock_irq(q->queue_lock); 2242 2243 if (cfqd->active_queue) 2244 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2245 2246 while (!list_empty(&cfqd->cic_list)) { 2247 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2248 struct cfq_io_context, 2249 queue_list); 2250 2251 __cfq_exit_single_io_context(cfqd, cic); 2252 } 2253 2254 cfq_put_async_queues(cfqd); 2255 2256 spin_unlock_irq(q->queue_lock); 2257 2258 cfq_shutdown_timer_wq(cfqd); 2259 2260 kfree(cfqd); 2261} 2262 2263static void *cfq_init_queue(struct request_queue *q) 2264{ 2265 struct cfq_data *cfqd; 2266 2267 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 2268 if (!cfqd) 2269 return NULL; 2270 2271 cfqd->service_tree = CFQ_RB_ROOT; 2272 INIT_LIST_HEAD(&cfqd->cic_list); 2273 2274 cfqd->queue = q; 2275 2276 init_timer(&cfqd->idle_slice_timer); 2277 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2278 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2279 2280 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 2281 2282 cfqd->last_end_request = jiffies; 2283 cfqd->cfq_quantum = cfq_quantum; 2284 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2285 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2286 cfqd->cfq_back_max = cfq_back_max; 2287 cfqd->cfq_back_penalty = cfq_back_penalty; 2288 cfqd->cfq_slice[0] = cfq_slice_async; 2289 cfqd->cfq_slice[1] = cfq_slice_sync; 2290 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2291 cfqd->cfq_slice_idle = cfq_slice_idle; 2292 cfqd->hw_tag = 1; 2293 2294 return cfqd; 2295} 2296 2297static void cfq_slab_kill(void) 2298{ 2299 /* 2300 * Caller already ensured that pending RCU callbacks are completed, 2301 * so we should have no busy allocations at this point. 2302 */ 2303 if (cfq_pool) 2304 kmem_cache_destroy(cfq_pool); 2305 if (cfq_ioc_pool) 2306 kmem_cache_destroy(cfq_ioc_pool); 2307} 2308 2309static int __init cfq_slab_setup(void) 2310{ 2311 cfq_pool = KMEM_CACHE(cfq_queue, 0); 2312 if (!cfq_pool) 2313 goto fail; 2314 2315 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 2316 if (!cfq_ioc_pool) 2317 goto fail; 2318 2319 return 0; 2320fail: 2321 cfq_slab_kill(); 2322 return -ENOMEM; 2323} 2324 2325/* 2326 * sysfs parts below --> 2327 */ 2328static ssize_t 2329cfq_var_show(unsigned int var, char *page) 2330{ 2331 return sprintf(page, "%d\n", var); 2332} 2333 2334static ssize_t 2335cfq_var_store(unsigned int *var, const char *page, size_t count) 2336{ 2337 char *p = (char *) page; 2338 2339 *var = simple_strtoul(p, &p, 10); 2340 return count; 2341} 2342 2343#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2344static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 2345{ \ 2346 struct cfq_data *cfqd = e->elevator_data; \ 2347 unsigned int __data = __VAR; \ 2348 if (__CONV) \ 2349 __data = jiffies_to_msecs(__data); \ 2350 return cfq_var_show(__data, (page)); \ 2351} 2352SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2353SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2354SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2355SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 2356SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 2357SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2358SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2359SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2360SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2361#undef SHOW_FUNCTION 2362 2363#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2364static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 2365{ \ 2366 struct cfq_data *cfqd = e->elevator_data; \ 2367 unsigned int __data; \ 2368 int ret = cfq_var_store(&__data, (page), count); \ 2369 if (__data < (MIN)) \ 2370 __data = (MIN); \ 2371 else if (__data > (MAX)) \ 2372 __data = (MAX); \ 2373 if (__CONV) \ 2374 *(__PTR) = msecs_to_jiffies(__data); \ 2375 else \ 2376 *(__PTR) = __data; \ 2377 return ret; \ 2378} 2379STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2380STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 2381 UINT_MAX, 1); 2382STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 2383 UINT_MAX, 1); 2384STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2385STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 2386 UINT_MAX, 0); 2387STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2388STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2389STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2390STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 2391 UINT_MAX, 0); 2392#undef STORE_FUNCTION 2393 2394#define CFQ_ATTR(name) \ 2395 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 2396 2397static struct elv_fs_entry cfq_attrs[] = { 2398 CFQ_ATTR(quantum), 2399 CFQ_ATTR(fifo_expire_sync), 2400 CFQ_ATTR(fifo_expire_async), 2401 CFQ_ATTR(back_seek_max), 2402 CFQ_ATTR(back_seek_penalty), 2403 CFQ_ATTR(slice_sync), 2404 CFQ_ATTR(slice_async), 2405 CFQ_ATTR(slice_async_rq), 2406 CFQ_ATTR(slice_idle), 2407 __ATTR_NULL 2408}; 2409 2410static struct elevator_type iosched_cfq = { 2411 .ops = { 2412 .elevator_merge_fn = cfq_merge, 2413 .elevator_merged_fn = cfq_merged_request, 2414 .elevator_merge_req_fn = cfq_merged_requests, 2415 .elevator_allow_merge_fn = cfq_allow_merge, 2416 .elevator_dispatch_fn = cfq_dispatch_requests, 2417 .elevator_add_req_fn = cfq_insert_request, 2418 .elevator_activate_req_fn = cfq_activate_request, 2419 .elevator_deactivate_req_fn = cfq_deactivate_request, 2420 .elevator_queue_empty_fn = cfq_queue_empty, 2421 .elevator_completed_req_fn = cfq_completed_request, 2422 .elevator_former_req_fn = elv_rb_former_request, 2423 .elevator_latter_req_fn = elv_rb_latter_request, 2424 .elevator_set_req_fn = cfq_set_request, 2425 .elevator_put_req_fn = cfq_put_request, 2426 .elevator_may_queue_fn = cfq_may_queue, 2427 .elevator_init_fn = cfq_init_queue, 2428 .elevator_exit_fn = cfq_exit_queue, 2429 .trim = cfq_free_io_context, 2430 }, 2431 .elevator_attrs = cfq_attrs, 2432 .elevator_name = "cfq", 2433 .elevator_owner = THIS_MODULE, 2434}; 2435 2436static int __init cfq_init(void) 2437{ 2438 /* 2439 * could be 0 on HZ < 1000 setups 2440 */ 2441 if (!cfq_slice_async) 2442 cfq_slice_async = 1; 2443 if (!cfq_slice_idle) 2444 cfq_slice_idle = 1; 2445 2446 if (cfq_slab_setup()) 2447 return -ENOMEM; 2448 2449 elv_register(&iosched_cfq); 2450 2451 return 0; 2452} 2453 2454static void __exit cfq_exit(void) 2455{ 2456 DECLARE_COMPLETION_ONSTACK(all_gone); 2457 elv_unregister(&iosched_cfq); 2458 ioc_gone = &all_gone; 2459 /* ioc_gone's update must be visible before reading ioc_count */ 2460 smp_wmb(); 2461 2462 /* 2463 * this also protects us from entering cfq_slab_kill() with 2464 * pending RCU callbacks 2465 */ 2466 if (elv_ioc_count_read(ioc_count)) 2467 wait_for_completion(&all_gone); 2468 cfq_slab_kill(); 2469} 2470 2471module_init(cfq_init); 2472module_exit(cfq_exit); 2473 2474MODULE_AUTHOR("Jens Axboe"); 2475MODULE_LICENSE("GPL"); 2476MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2477