cfq-iosched.c revision e6c5bc737ab71e4af6025ef7d150f5a26ae5f146
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/* 42 * Allow merged cfqqs to perform this amount of seeky I/O before 43 * deciding to break the queues up again. 44 */ 45#define CFQQ_COOP_TOUT (HZ) 46 47#define CFQ_SLICE_SCALE (5) 48#define CFQ_HW_QUEUE_MIN (5) 49 50#define RQ_CIC(rq) \ 51 ((struct cfq_io_context *) (rq)->elevator_private) 52#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) 53 54static struct kmem_cache *cfq_pool; 55static struct kmem_cache *cfq_ioc_pool; 56 57static DEFINE_PER_CPU(unsigned long, cfq_ioc_count); 58static struct completion *ioc_gone; 59static DEFINE_SPINLOCK(ioc_gone_lock); 60 61#define CFQ_PRIO_LISTS IOPRIO_BE_NR 62#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) 63#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) 64 65#define sample_valid(samples) ((samples) > 80) 66 67/* 68 * Most of our rbtree usage is for sorting with min extraction, so 69 * if we cache the leftmost node we don't have to walk down the tree 70 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should 71 * move this into the elevator for the rq sorting as well. 72 */ 73struct cfq_rb_root { 74 struct rb_root rb; 75 struct rb_node *left; 76}; 77#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } 78 79/* 80 * Per process-grouping structure 81 */ 82struct cfq_queue { 83 /* reference count */ 84 atomic_t ref; 85 /* various state flags, see below */ 86 unsigned int flags; 87 /* parent cfq_data */ 88 struct cfq_data *cfqd; 89 /* service_tree member */ 90 struct rb_node rb_node; 91 /* service_tree key */ 92 unsigned long rb_key; 93 /* prio tree member */ 94 struct rb_node p_node; 95 /* prio tree root we belong to, if any */ 96 struct rb_root *p_root; 97 /* sorted list of pending requests */ 98 struct rb_root sort_list; 99 /* if fifo isn't expired, next request to serve */ 100 struct request *next_rq; 101 /* requests queued in sort_list */ 102 int queued[2]; 103 /* currently allocated requests */ 104 int allocated[2]; 105 /* fifo list of requests in sort_list */ 106 struct list_head fifo; 107 108 unsigned long slice_end; 109 long slice_resid; 110 unsigned int slice_dispatch; 111 112 /* pending metadata requests */ 113 int meta_pending; 114 /* number of requests that are on the dispatch list or inside driver */ 115 int dispatched; 116 117 /* io prio of this group */ 118 unsigned short ioprio, org_ioprio; 119 unsigned short ioprio_class, org_ioprio_class; 120 121 unsigned int seek_samples; 122 u64 seek_total; 123 sector_t seek_mean; 124 sector_t last_request_pos; 125 unsigned long seeky_start; 126 127 pid_t pid; 128 129 struct cfq_queue *new_cfqq; 130}; 131 132/* 133 * Per block device queue structure 134 */ 135struct cfq_data { 136 struct request_queue *queue; 137 138 /* 139 * rr list of queues with requests and the count of them 140 */ 141 struct cfq_rb_root service_tree; 142 143 /* 144 * Each priority tree is sorted by next_request position. These 145 * trees are used when determining if two or more queues are 146 * interleaving requests (see cfq_close_cooperator). 147 */ 148 struct rb_root prio_trees[CFQ_PRIO_LISTS]; 149 150 unsigned int busy_queues; 151 152 int rq_in_driver[2]; 153 int sync_flight; 154 155 /* 156 * queue-depth detection 157 */ 158 int rq_queued; 159 int hw_tag; 160 int hw_tag_samples; 161 int rq_in_driver_peak; 162 163 /* 164 * idle window management 165 */ 166 struct timer_list idle_slice_timer; 167 struct work_struct unplug_work; 168 169 struct cfq_queue *active_queue; 170 struct cfq_io_context *active_cic; 171 172 /* 173 * async queue for each priority case 174 */ 175 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; 176 struct cfq_queue *async_idle_cfqq; 177 178 sector_t last_position; 179 180 /* 181 * tunables, see top of file 182 */ 183 unsigned int cfq_quantum; 184 unsigned int cfq_fifo_expire[2]; 185 unsigned int cfq_back_penalty; 186 unsigned int cfq_back_max; 187 unsigned int cfq_slice[2]; 188 unsigned int cfq_slice_async_rq; 189 unsigned int cfq_slice_idle; 190 unsigned int cfq_latency; 191 192 struct list_head cic_list; 193 194 /* 195 * Fallback dummy cfqq for extreme OOM conditions 196 */ 197 struct cfq_queue oom_cfqq; 198 199 unsigned long last_end_sync_rq; 200}; 201 202enum cfqq_state_flags { 203 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ 204 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ 205 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ 206 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ 207 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ 208 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ 209 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ 210 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ 211 CFQ_CFQQ_FLAG_sync, /* synchronous queue */ 212 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */ 213}; 214 215#define CFQ_CFQQ_FNS(name) \ 216static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ 217{ \ 218 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ 219} \ 220static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ 221{ \ 222 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ 223} \ 224static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ 225{ \ 226 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ 227} 228 229CFQ_CFQQ_FNS(on_rr); 230CFQ_CFQQ_FNS(wait_request); 231CFQ_CFQQ_FNS(must_dispatch); 232CFQ_CFQQ_FNS(must_alloc_slice); 233CFQ_CFQQ_FNS(fifo_expire); 234CFQ_CFQQ_FNS(idle_window); 235CFQ_CFQQ_FNS(prio_changed); 236CFQ_CFQQ_FNS(slice_new); 237CFQ_CFQQ_FNS(sync); 238CFQ_CFQQ_FNS(coop); 239#undef CFQ_CFQQ_FNS 240 241#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ 242 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) 243#define cfq_log(cfqd, fmt, args...) \ 244 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) 245 246static void cfq_dispatch_insert(struct request_queue *, struct request *); 247static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool, 248 struct io_context *, gfp_t); 249static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, 250 struct io_context *); 251 252static inline int rq_in_driver(struct cfq_data *cfqd) 253{ 254 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1]; 255} 256 257static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, 258 bool is_sync) 259{ 260 return cic->cfqq[is_sync]; 261} 262 263static inline void cic_set_cfqq(struct cfq_io_context *cic, 264 struct cfq_queue *cfqq, bool is_sync) 265{ 266 cic->cfqq[is_sync] = cfqq; 267} 268 269/* 270 * We regard a request as SYNC, if it's either a read or has the SYNC bit 271 * set (in which case it could also be direct WRITE). 272 */ 273static inline bool cfq_bio_sync(struct bio *bio) 274{ 275 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO); 276} 277 278/* 279 * scheduler run of queue, if there are requests pending and no one in the 280 * driver that will restart queueing 281 */ 282static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) 283{ 284 if (cfqd->busy_queues) { 285 cfq_log(cfqd, "schedule dispatch"); 286 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); 287 } 288} 289 290static int cfq_queue_empty(struct request_queue *q) 291{ 292 struct cfq_data *cfqd = q->elevator->elevator_data; 293 294 return !cfqd->busy_queues; 295} 296 297/* 298 * Scale schedule slice based on io priority. Use the sync time slice only 299 * if a queue is marked sync and has sync io queued. A sync queue with async 300 * io only, should not get full sync slice length. 301 */ 302static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync, 303 unsigned short prio) 304{ 305 const int base_slice = cfqd->cfq_slice[sync]; 306 307 WARN_ON(prio >= IOPRIO_BE_NR); 308 309 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); 310} 311 312static inline int 313cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 314{ 315 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); 316} 317 318static inline void 319cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 320{ 321 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 322 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); 323} 324 325/* 326 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end 327 * isn't valid until the first request from the dispatch is activated 328 * and the slice time set. 329 */ 330static inline bool cfq_slice_used(struct cfq_queue *cfqq) 331{ 332 if (cfq_cfqq_slice_new(cfqq)) 333 return 0; 334 if (time_before(jiffies, cfqq->slice_end)) 335 return 0; 336 337 return 1; 338} 339 340/* 341 * Lifted from AS - choose which of rq1 and rq2 that is best served now. 342 * We choose the request that is closest to the head right now. Distance 343 * behind the head is penalized and only allowed to a certain extent. 344 */ 345static struct request * 346cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2) 347{ 348 sector_t last, s1, s2, d1 = 0, d2 = 0; 349 unsigned long back_max; 350#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ 351#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ 352 unsigned wrap = 0; /* bit mask: requests behind the disk head? */ 353 354 if (rq1 == NULL || rq1 == rq2) 355 return rq2; 356 if (rq2 == NULL) 357 return rq1; 358 359 if (rq_is_sync(rq1) && !rq_is_sync(rq2)) 360 return rq1; 361 else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) 362 return rq2; 363 if (rq_is_meta(rq1) && !rq_is_meta(rq2)) 364 return rq1; 365 else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) 366 return rq2; 367 368 s1 = blk_rq_pos(rq1); 369 s2 = blk_rq_pos(rq2); 370 371 last = cfqd->last_position; 372 373 /* 374 * by definition, 1KiB is 2 sectors 375 */ 376 back_max = cfqd->cfq_back_max * 2; 377 378 /* 379 * Strict one way elevator _except_ in the case where we allow 380 * short backward seeks which are biased as twice the cost of a 381 * similar forward seek. 382 */ 383 if (s1 >= last) 384 d1 = s1 - last; 385 else if (s1 + back_max >= last) 386 d1 = (last - s1) * cfqd->cfq_back_penalty; 387 else 388 wrap |= CFQ_RQ1_WRAP; 389 390 if (s2 >= last) 391 d2 = s2 - last; 392 else if (s2 + back_max >= last) 393 d2 = (last - s2) * cfqd->cfq_back_penalty; 394 else 395 wrap |= CFQ_RQ2_WRAP; 396 397 /* Found required data */ 398 399 /* 400 * By doing switch() on the bit mask "wrap" we avoid having to 401 * check two variables for all permutations: --> faster! 402 */ 403 switch (wrap) { 404 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ 405 if (d1 < d2) 406 return rq1; 407 else if (d2 < d1) 408 return rq2; 409 else { 410 if (s1 >= s2) 411 return rq1; 412 else 413 return rq2; 414 } 415 416 case CFQ_RQ2_WRAP: 417 return rq1; 418 case CFQ_RQ1_WRAP: 419 return rq2; 420 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ 421 default: 422 /* 423 * Since both rqs are wrapped, 424 * start with the one that's further behind head 425 * (--> only *one* back seek required), 426 * since back seek takes more time than forward. 427 */ 428 if (s1 <= s2) 429 return rq1; 430 else 431 return rq2; 432 } 433} 434 435/* 436 * The below is leftmost cache rbtree addon 437 */ 438static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) 439{ 440 if (!root->left) 441 root->left = rb_first(&root->rb); 442 443 if (root->left) 444 return rb_entry(root->left, struct cfq_queue, rb_node); 445 446 return NULL; 447} 448 449static void rb_erase_init(struct rb_node *n, struct rb_root *root) 450{ 451 rb_erase(n, root); 452 RB_CLEAR_NODE(n); 453} 454 455static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) 456{ 457 if (root->left == n) 458 root->left = NULL; 459 rb_erase_init(n, &root->rb); 460} 461 462/* 463 * would be nice to take fifo expire time into account as well 464 */ 465static struct request * 466cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 467 struct request *last) 468{ 469 struct rb_node *rbnext = rb_next(&last->rb_node); 470 struct rb_node *rbprev = rb_prev(&last->rb_node); 471 struct request *next = NULL, *prev = NULL; 472 473 BUG_ON(RB_EMPTY_NODE(&last->rb_node)); 474 475 if (rbprev) 476 prev = rb_entry_rq(rbprev); 477 478 if (rbnext) 479 next = rb_entry_rq(rbnext); 480 else { 481 rbnext = rb_first(&cfqq->sort_list); 482 if (rbnext && rbnext != &last->rb_node) 483 next = rb_entry_rq(rbnext); 484 } 485 486 return cfq_choose_req(cfqd, next, prev); 487} 488 489static unsigned long cfq_slice_offset(struct cfq_data *cfqd, 490 struct cfq_queue *cfqq) 491{ 492 /* 493 * just an approximation, should be ok. 494 */ 495 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - 496 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); 497} 498 499/* 500 * The cfqd->service_tree holds all pending cfq_queue's that have 501 * requests waiting to be processed. It is sorted in the order that 502 * we will service the queues. 503 */ 504static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 505 bool add_front) 506{ 507 struct rb_node **p, *parent; 508 struct cfq_queue *__cfqq; 509 unsigned long rb_key; 510 int left; 511 512 if (cfq_class_idle(cfqq)) { 513 rb_key = CFQ_IDLE_DELAY; 514 parent = rb_last(&cfqd->service_tree.rb); 515 if (parent && parent != &cfqq->rb_node) { 516 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 517 rb_key += __cfqq->rb_key; 518 } else 519 rb_key += jiffies; 520 } else if (!add_front) { 521 /* 522 * Get our rb key offset. Subtract any residual slice 523 * value carried from last service. A negative resid 524 * count indicates slice overrun, and this should position 525 * the next service time further away in the tree. 526 */ 527 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; 528 rb_key -= cfqq->slice_resid; 529 cfqq->slice_resid = 0; 530 } else { 531 rb_key = -HZ; 532 __cfqq = cfq_rb_first(&cfqd->service_tree); 533 rb_key += __cfqq ? __cfqq->rb_key : jiffies; 534 } 535 536 if (!RB_EMPTY_NODE(&cfqq->rb_node)) { 537 /* 538 * same position, nothing more to do 539 */ 540 if (rb_key == cfqq->rb_key) 541 return; 542 543 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 544 } 545 546 left = 1; 547 parent = NULL; 548 p = &cfqd->service_tree.rb.rb_node; 549 while (*p) { 550 struct rb_node **n; 551 552 parent = *p; 553 __cfqq = rb_entry(parent, struct cfq_queue, rb_node); 554 555 /* 556 * sort RT queues first, we always want to give 557 * preference to them. IDLE queues goes to the back. 558 * after that, sort on the next service time. 559 */ 560 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) 561 n = &(*p)->rb_left; 562 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) 563 n = &(*p)->rb_right; 564 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) 565 n = &(*p)->rb_left; 566 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) 567 n = &(*p)->rb_right; 568 else if (time_before(rb_key, __cfqq->rb_key)) 569 n = &(*p)->rb_left; 570 else 571 n = &(*p)->rb_right; 572 573 if (n == &(*p)->rb_right) 574 left = 0; 575 576 p = n; 577 } 578 579 if (left) 580 cfqd->service_tree.left = &cfqq->rb_node; 581 582 cfqq->rb_key = rb_key; 583 rb_link_node(&cfqq->rb_node, parent, p); 584 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb); 585} 586 587static struct cfq_queue * 588cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, 589 sector_t sector, struct rb_node **ret_parent, 590 struct rb_node ***rb_link) 591{ 592 struct rb_node **p, *parent; 593 struct cfq_queue *cfqq = NULL; 594 595 parent = NULL; 596 p = &root->rb_node; 597 while (*p) { 598 struct rb_node **n; 599 600 parent = *p; 601 cfqq = rb_entry(parent, struct cfq_queue, p_node); 602 603 /* 604 * Sort strictly based on sector. Smallest to the left, 605 * largest to the right. 606 */ 607 if (sector > blk_rq_pos(cfqq->next_rq)) 608 n = &(*p)->rb_right; 609 else if (sector < blk_rq_pos(cfqq->next_rq)) 610 n = &(*p)->rb_left; 611 else 612 break; 613 p = n; 614 cfqq = NULL; 615 } 616 617 *ret_parent = parent; 618 if (rb_link) 619 *rb_link = p; 620 return cfqq; 621} 622 623static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) 624{ 625 struct rb_node **p, *parent; 626 struct cfq_queue *__cfqq; 627 628 if (cfqq->p_root) { 629 rb_erase(&cfqq->p_node, cfqq->p_root); 630 cfqq->p_root = NULL; 631 } 632 633 if (cfq_class_idle(cfqq)) 634 return; 635 if (!cfqq->next_rq) 636 return; 637 638 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; 639 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, 640 blk_rq_pos(cfqq->next_rq), &parent, &p); 641 if (!__cfqq) { 642 rb_link_node(&cfqq->p_node, parent, p); 643 rb_insert_color(&cfqq->p_node, cfqq->p_root); 644 } else 645 cfqq->p_root = NULL; 646} 647 648/* 649 * Update cfqq's position in the service tree. 650 */ 651static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) 652{ 653 /* 654 * Resorting requires the cfqq to be on the RR list already. 655 */ 656 if (cfq_cfqq_on_rr(cfqq)) { 657 cfq_service_tree_add(cfqd, cfqq, 0); 658 cfq_prio_tree_add(cfqd, cfqq); 659 } 660} 661 662/* 663 * add to busy list of queues for service, trying to be fair in ordering 664 * the pending list according to last request service 665 */ 666static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 667{ 668 cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); 669 BUG_ON(cfq_cfqq_on_rr(cfqq)); 670 cfq_mark_cfqq_on_rr(cfqq); 671 cfqd->busy_queues++; 672 673 cfq_resort_rr_list(cfqd, cfqq); 674} 675 676/* 677 * Called when the cfqq no longer has requests pending, remove it from 678 * the service tree. 679 */ 680static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) 681{ 682 cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); 683 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 684 cfq_clear_cfqq_on_rr(cfqq); 685 686 if (!RB_EMPTY_NODE(&cfqq->rb_node)) 687 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); 688 if (cfqq->p_root) { 689 rb_erase(&cfqq->p_node, cfqq->p_root); 690 cfqq->p_root = NULL; 691 } 692 693 BUG_ON(!cfqd->busy_queues); 694 cfqd->busy_queues--; 695} 696 697/* 698 * rb tree support functions 699 */ 700static void cfq_del_rq_rb(struct request *rq) 701{ 702 struct cfq_queue *cfqq = RQ_CFQQ(rq); 703 struct cfq_data *cfqd = cfqq->cfqd; 704 const int sync = rq_is_sync(rq); 705 706 BUG_ON(!cfqq->queued[sync]); 707 cfqq->queued[sync]--; 708 709 elv_rb_del(&cfqq->sort_list, rq); 710 711 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) 712 cfq_del_cfqq_rr(cfqd, cfqq); 713} 714 715static void cfq_add_rq_rb(struct request *rq) 716{ 717 struct cfq_queue *cfqq = RQ_CFQQ(rq); 718 struct cfq_data *cfqd = cfqq->cfqd; 719 struct request *__alias, *prev; 720 721 cfqq->queued[rq_is_sync(rq)]++; 722 723 /* 724 * looks a little odd, but the first insert might return an alias. 725 * if that happens, put the alias on the dispatch list 726 */ 727 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) 728 cfq_dispatch_insert(cfqd->queue, __alias); 729 730 if (!cfq_cfqq_on_rr(cfqq)) 731 cfq_add_cfqq_rr(cfqd, cfqq); 732 733 /* 734 * check if this request is a better next-serve candidate 735 */ 736 prev = cfqq->next_rq; 737 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); 738 739 /* 740 * adjust priority tree position, if ->next_rq changes 741 */ 742 if (prev != cfqq->next_rq) 743 cfq_prio_tree_add(cfqd, cfqq); 744 745 BUG_ON(!cfqq->next_rq); 746} 747 748static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) 749{ 750 elv_rb_del(&cfqq->sort_list, rq); 751 cfqq->queued[rq_is_sync(rq)]--; 752 cfq_add_rq_rb(rq); 753} 754 755static struct request * 756cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) 757{ 758 struct task_struct *tsk = current; 759 struct cfq_io_context *cic; 760 struct cfq_queue *cfqq; 761 762 cic = cfq_cic_lookup(cfqd, tsk->io_context); 763 if (!cic) 764 return NULL; 765 766 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 767 if (cfqq) { 768 sector_t sector = bio->bi_sector + bio_sectors(bio); 769 770 return elv_rb_find(&cfqq->sort_list, sector); 771 } 772 773 return NULL; 774} 775 776static void cfq_activate_request(struct request_queue *q, struct request *rq) 777{ 778 struct cfq_data *cfqd = q->elevator->elevator_data; 779 780 cfqd->rq_in_driver[rq_is_sync(rq)]++; 781 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", 782 rq_in_driver(cfqd)); 783 784 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); 785} 786 787static void cfq_deactivate_request(struct request_queue *q, struct request *rq) 788{ 789 struct cfq_data *cfqd = q->elevator->elevator_data; 790 const int sync = rq_is_sync(rq); 791 792 WARN_ON(!cfqd->rq_in_driver[sync]); 793 cfqd->rq_in_driver[sync]--; 794 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", 795 rq_in_driver(cfqd)); 796} 797 798static void cfq_remove_request(struct request *rq) 799{ 800 struct cfq_queue *cfqq = RQ_CFQQ(rq); 801 802 if (cfqq->next_rq == rq) 803 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); 804 805 list_del_init(&rq->queuelist); 806 cfq_del_rq_rb(rq); 807 808 cfqq->cfqd->rq_queued--; 809 if (rq_is_meta(rq)) { 810 WARN_ON(!cfqq->meta_pending); 811 cfqq->meta_pending--; 812 } 813} 814 815static int cfq_merge(struct request_queue *q, struct request **req, 816 struct bio *bio) 817{ 818 struct cfq_data *cfqd = q->elevator->elevator_data; 819 struct request *__rq; 820 821 __rq = cfq_find_rq_fmerge(cfqd, bio); 822 if (__rq && elv_rq_merge_ok(__rq, bio)) { 823 *req = __rq; 824 return ELEVATOR_FRONT_MERGE; 825 } 826 827 return ELEVATOR_NO_MERGE; 828} 829 830static void cfq_merged_request(struct request_queue *q, struct request *req, 831 int type) 832{ 833 if (type == ELEVATOR_FRONT_MERGE) { 834 struct cfq_queue *cfqq = RQ_CFQQ(req); 835 836 cfq_reposition_rq_rb(cfqq, req); 837 } 838} 839 840static void 841cfq_merged_requests(struct request_queue *q, struct request *rq, 842 struct request *next) 843{ 844 /* 845 * reposition in fifo if next is older than rq 846 */ 847 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && 848 time_before(rq_fifo_time(next), rq_fifo_time(rq))) { 849 list_move(&rq->queuelist, &next->queuelist); 850 rq_set_fifo_time(rq, rq_fifo_time(next)); 851 } 852 853 cfq_remove_request(next); 854} 855 856static int cfq_allow_merge(struct request_queue *q, struct request *rq, 857 struct bio *bio) 858{ 859 struct cfq_data *cfqd = q->elevator->elevator_data; 860 struct cfq_io_context *cic; 861 struct cfq_queue *cfqq; 862 863 /* 864 * Disallow merge of a sync bio into an async request. 865 */ 866 if (cfq_bio_sync(bio) && !rq_is_sync(rq)) 867 return false; 868 869 /* 870 * Lookup the cfqq that this bio will be queued with. Allow 871 * merge only if rq is queued there. 872 */ 873 cic = cfq_cic_lookup(cfqd, current->io_context); 874 if (!cic) 875 return false; 876 877 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); 878 return cfqq == RQ_CFQQ(rq); 879} 880 881static void __cfq_set_active_queue(struct cfq_data *cfqd, 882 struct cfq_queue *cfqq) 883{ 884 if (cfqq) { 885 cfq_log_cfqq(cfqd, cfqq, "set_active"); 886 cfqq->slice_end = 0; 887 cfqq->slice_dispatch = 0; 888 889 cfq_clear_cfqq_wait_request(cfqq); 890 cfq_clear_cfqq_must_dispatch(cfqq); 891 cfq_clear_cfqq_must_alloc_slice(cfqq); 892 cfq_clear_cfqq_fifo_expire(cfqq); 893 cfq_mark_cfqq_slice_new(cfqq); 894 895 del_timer(&cfqd->idle_slice_timer); 896 } 897 898 cfqd->active_queue = cfqq; 899} 900 901/* 902 * current cfqq expired its slice (or was too idle), select new one 903 */ 904static void 905__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 906 bool timed_out) 907{ 908 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); 909 910 if (cfq_cfqq_wait_request(cfqq)) 911 del_timer(&cfqd->idle_slice_timer); 912 913 cfq_clear_cfqq_wait_request(cfqq); 914 915 /* 916 * store what was left of this slice, if the queue idled/timed out 917 */ 918 if (timed_out && !cfq_cfqq_slice_new(cfqq)) { 919 cfqq->slice_resid = cfqq->slice_end - jiffies; 920 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); 921 } 922 923 cfq_resort_rr_list(cfqd, cfqq); 924 925 if (cfqq == cfqd->active_queue) 926 cfqd->active_queue = NULL; 927 928 if (cfqd->active_cic) { 929 put_io_context(cfqd->active_cic->ioc); 930 cfqd->active_cic = NULL; 931 } 932} 933 934static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out) 935{ 936 struct cfq_queue *cfqq = cfqd->active_queue; 937 938 if (cfqq) 939 __cfq_slice_expired(cfqd, cfqq, timed_out); 940} 941 942/* 943 * Get next queue for service. Unless we have a queue preemption, 944 * we'll simply select the first cfqq in the service tree. 945 */ 946static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 947{ 948 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) 949 return NULL; 950 951 return cfq_rb_first(&cfqd->service_tree); 952} 953 954/* 955 * Get and set a new active queue for service. 956 */ 957static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, 958 struct cfq_queue *cfqq) 959{ 960 if (!cfqq) 961 cfqq = cfq_get_next_queue(cfqd); 962 963 __cfq_set_active_queue(cfqd, cfqq); 964 return cfqq; 965} 966 967static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, 968 struct request *rq) 969{ 970 if (blk_rq_pos(rq) >= cfqd->last_position) 971 return blk_rq_pos(rq) - cfqd->last_position; 972 else 973 return cfqd->last_position - blk_rq_pos(rq); 974} 975 976#define CFQQ_SEEK_THR 8 * 1024 977#define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR) 978 979static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, 980 struct request *rq) 981{ 982 sector_t sdist = cfqq->seek_mean; 983 984 if (!sample_valid(cfqq->seek_samples)) 985 sdist = CFQQ_SEEK_THR; 986 987 return cfq_dist_from_last(cfqd, rq) <= sdist; 988} 989 990static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, 991 struct cfq_queue *cur_cfqq) 992{ 993 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; 994 struct rb_node *parent, *node; 995 struct cfq_queue *__cfqq; 996 sector_t sector = cfqd->last_position; 997 998 if (RB_EMPTY_ROOT(root)) 999 return NULL; 1000 1001 /* 1002 * First, if we find a request starting at the end of the last 1003 * request, choose it. 1004 */ 1005 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); 1006 if (__cfqq) 1007 return __cfqq; 1008 1009 /* 1010 * If the exact sector wasn't found, the parent of the NULL leaf 1011 * will contain the closest sector. 1012 */ 1013 __cfqq = rb_entry(parent, struct cfq_queue, p_node); 1014 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) 1015 return __cfqq; 1016 1017 if (blk_rq_pos(__cfqq->next_rq) < sector) 1018 node = rb_next(&__cfqq->p_node); 1019 else 1020 node = rb_prev(&__cfqq->p_node); 1021 if (!node) 1022 return NULL; 1023 1024 __cfqq = rb_entry(node, struct cfq_queue, p_node); 1025 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq)) 1026 return __cfqq; 1027 1028 return NULL; 1029} 1030 1031/* 1032 * cfqd - obvious 1033 * cur_cfqq - passed in so that we don't decide that the current queue is 1034 * closely cooperating with itself. 1035 * 1036 * So, basically we're assuming that that cur_cfqq has dispatched at least 1037 * one request, and that cfqd->last_position reflects a position on the disk 1038 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid 1039 * assumption. 1040 */ 1041static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, 1042 struct cfq_queue *cur_cfqq) 1043{ 1044 struct cfq_queue *cfqq; 1045 1046 if (!cfq_cfqq_sync(cur_cfqq)) 1047 return NULL; 1048 if (CFQQ_SEEKY(cur_cfqq)) 1049 return NULL; 1050 1051 /* 1052 * We should notice if some of the queues are cooperating, eg 1053 * working closely on the same area of the disk. In that case, 1054 * we can group them together and don't waste time idling. 1055 */ 1056 cfqq = cfqq_close(cfqd, cur_cfqq); 1057 if (!cfqq) 1058 return NULL; 1059 1060 /* 1061 * It only makes sense to merge sync queues. 1062 */ 1063 if (!cfq_cfqq_sync(cfqq)) 1064 return NULL; 1065 if (CFQQ_SEEKY(cfqq)) 1066 return NULL; 1067 1068 return cfqq; 1069} 1070 1071static void cfq_arm_slice_timer(struct cfq_data *cfqd) 1072{ 1073 struct cfq_queue *cfqq = cfqd->active_queue; 1074 struct cfq_io_context *cic; 1075 unsigned long sl; 1076 1077 /* 1078 * SSD device without seek penalty, disable idling. But only do so 1079 * for devices that support queuing, otherwise we still have a problem 1080 * with sync vs async workloads. 1081 */ 1082 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) 1083 return; 1084 1085 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); 1086 WARN_ON(cfq_cfqq_slice_new(cfqq)); 1087 1088 /* 1089 * idle is disabled, either manually or by past process history 1090 */ 1091 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq)) 1092 return; 1093 1094 /* 1095 * still requests with the driver, don't idle 1096 */ 1097 if (rq_in_driver(cfqd)) 1098 return; 1099 1100 /* 1101 * task has exited, don't wait 1102 */ 1103 cic = cfqd->active_cic; 1104 if (!cic || !atomic_read(&cic->ioc->nr_tasks)) 1105 return; 1106 1107 /* 1108 * If our average think time is larger than the remaining time 1109 * slice, then don't idle. This avoids overrunning the allotted 1110 * time slice. 1111 */ 1112 if (sample_valid(cic->ttime_samples) && 1113 (cfqq->slice_end - jiffies < cic->ttime_mean)) 1114 return; 1115 1116 cfq_mark_cfqq_wait_request(cfqq); 1117 1118 /* 1119 * we don't want to idle for seeks, but we do want to allow 1120 * fair distribution of slice time for a process doing back-to-back 1121 * seeks. so allow a little bit of time for him to submit a new rq 1122 */ 1123 sl = cfqd->cfq_slice_idle; 1124 if (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)) 1125 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); 1126 1127 mod_timer(&cfqd->idle_slice_timer, jiffies + sl); 1128 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl); 1129} 1130 1131/* 1132 * Move request from internal lists to the request queue dispatch list. 1133 */ 1134static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 1135{ 1136 struct cfq_data *cfqd = q->elevator->elevator_data; 1137 struct cfq_queue *cfqq = RQ_CFQQ(rq); 1138 1139 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); 1140 1141 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq); 1142 cfq_remove_request(rq); 1143 cfqq->dispatched++; 1144 elv_dispatch_sort(q, rq); 1145 1146 if (cfq_cfqq_sync(cfqq)) 1147 cfqd->sync_flight++; 1148} 1149 1150/* 1151 * return expired entry, or NULL to just start from scratch in rbtree 1152 */ 1153static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 1154{ 1155 struct request *rq = NULL; 1156 1157 if (cfq_cfqq_fifo_expire(cfqq)) 1158 return NULL; 1159 1160 cfq_mark_cfqq_fifo_expire(cfqq); 1161 1162 if (list_empty(&cfqq->fifo)) 1163 return NULL; 1164 1165 rq = rq_entry_fifo(cfqq->fifo.next); 1166 if (time_before(jiffies, rq_fifo_time(rq))) 1167 rq = NULL; 1168 1169 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); 1170 return rq; 1171} 1172 1173static inline int 1174cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1175{ 1176 const int base_rq = cfqd->cfq_slice_async_rq; 1177 1178 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); 1179 1180 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); 1181} 1182 1183/* 1184 * Must be called with the queue_lock held. 1185 */ 1186static int cfqq_process_refs(struct cfq_queue *cfqq) 1187{ 1188 int process_refs, io_refs; 1189 1190 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE]; 1191 process_refs = atomic_read(&cfqq->ref) - io_refs; 1192 BUG_ON(process_refs < 0); 1193 return process_refs; 1194} 1195 1196static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) 1197{ 1198 int process_refs, new_process_refs; 1199 struct cfq_queue *__cfqq; 1200 1201 /* Avoid a circular list and skip interim queue merges */ 1202 while ((__cfqq = new_cfqq->new_cfqq)) { 1203 if (__cfqq == cfqq) 1204 return; 1205 new_cfqq = __cfqq; 1206 } 1207 1208 process_refs = cfqq_process_refs(cfqq); 1209 /* 1210 * If the process for the cfqq has gone away, there is no 1211 * sense in merging the queues. 1212 */ 1213 if (process_refs == 0) 1214 return; 1215 1216 /* 1217 * Merge in the direction of the lesser amount of work. 1218 */ 1219 new_process_refs = cfqq_process_refs(new_cfqq); 1220 if (new_process_refs >= process_refs) { 1221 cfqq->new_cfqq = new_cfqq; 1222 atomic_add(process_refs, &new_cfqq->ref); 1223 } else { 1224 new_cfqq->new_cfqq = cfqq; 1225 atomic_add(new_process_refs, &cfqq->ref); 1226 } 1227} 1228 1229/* 1230 * Select a queue for service. If we have a current active queue, 1231 * check whether to continue servicing it, or retrieve and set a new one. 1232 */ 1233static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 1234{ 1235 struct cfq_queue *cfqq, *new_cfqq = NULL; 1236 1237 cfqq = cfqd->active_queue; 1238 if (!cfqq) 1239 goto new_queue; 1240 1241 /* 1242 * The active queue has run out of time, expire it and select new. 1243 */ 1244 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) 1245 goto expire; 1246 1247 /* 1248 * The active queue has requests and isn't expired, allow it to 1249 * dispatch. 1250 */ 1251 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 1252 goto keep_queue; 1253 1254 /* 1255 * If another queue has a request waiting within our mean seek 1256 * distance, let it run. The expire code will check for close 1257 * cooperators and put the close queue at the front of the service 1258 * tree. If possible, merge the expiring queue with the new cfqq. 1259 */ 1260 new_cfqq = cfq_close_cooperator(cfqd, cfqq); 1261 if (new_cfqq) { 1262 if (!cfqq->new_cfqq) 1263 cfq_setup_merge(cfqq, new_cfqq); 1264 goto expire; 1265 } 1266 1267 /* 1268 * No requests pending. If the active queue still has requests in 1269 * flight or is idling for a new request, allow either of these 1270 * conditions to happen (or time out) before selecting a new queue. 1271 */ 1272 if (timer_pending(&cfqd->idle_slice_timer) || 1273 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) { 1274 cfqq = NULL; 1275 goto keep_queue; 1276 } 1277 1278expire: 1279 cfq_slice_expired(cfqd, 0); 1280new_queue: 1281 cfqq = cfq_set_active_queue(cfqd, new_cfqq); 1282keep_queue: 1283 return cfqq; 1284} 1285 1286static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) 1287{ 1288 int dispatched = 0; 1289 1290 while (cfqq->next_rq) { 1291 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); 1292 dispatched++; 1293 } 1294 1295 BUG_ON(!list_empty(&cfqq->fifo)); 1296 return dispatched; 1297} 1298 1299/* 1300 * Drain our current requests. Used for barriers and when switching 1301 * io schedulers on-the-fly. 1302 */ 1303static int cfq_forced_dispatch(struct cfq_data *cfqd) 1304{ 1305 struct cfq_queue *cfqq; 1306 int dispatched = 0; 1307 1308 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL) 1309 dispatched += __cfq_forced_dispatch_cfqq(cfqq); 1310 1311 cfq_slice_expired(cfqd, 0); 1312 1313 BUG_ON(cfqd->busy_queues); 1314 1315 cfq_log(cfqd, "forced_dispatch=%d", dispatched); 1316 return dispatched; 1317} 1318 1319static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1320{ 1321 unsigned int max_dispatch; 1322 1323 /* 1324 * Drain async requests before we start sync IO 1325 */ 1326 if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC]) 1327 return false; 1328 1329 /* 1330 * If this is an async queue and we have sync IO in flight, let it wait 1331 */ 1332 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) 1333 return false; 1334 1335 max_dispatch = cfqd->cfq_quantum; 1336 if (cfq_class_idle(cfqq)) 1337 max_dispatch = 1; 1338 1339 /* 1340 * Does this cfqq already have too much IO in flight? 1341 */ 1342 if (cfqq->dispatched >= max_dispatch) { 1343 /* 1344 * idle queue must always only have a single IO in flight 1345 */ 1346 if (cfq_class_idle(cfqq)) 1347 return false; 1348 1349 /* 1350 * We have other queues, don't allow more IO from this one 1351 */ 1352 if (cfqd->busy_queues > 1) 1353 return false; 1354 1355 /* 1356 * Sole queue user, allow bigger slice 1357 */ 1358 max_dispatch *= 4; 1359 } 1360 1361 /* 1362 * Async queues must wait a bit before being allowed dispatch. 1363 * We also ramp up the dispatch depth gradually for async IO, 1364 * based on the last sync IO we serviced 1365 */ 1366 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { 1367 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq; 1368 unsigned int depth; 1369 1370 depth = last_sync / cfqd->cfq_slice[1]; 1371 if (!depth && !cfqq->dispatched) 1372 depth = 1; 1373 if (depth < max_dispatch) 1374 max_dispatch = depth; 1375 } 1376 1377 /* 1378 * If we're below the current max, allow a dispatch 1379 */ 1380 return cfqq->dispatched < max_dispatch; 1381} 1382 1383/* 1384 * Dispatch a request from cfqq, moving them to the request queue 1385 * dispatch list. 1386 */ 1387static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1388{ 1389 struct request *rq; 1390 1391 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); 1392 1393 if (!cfq_may_dispatch(cfqd, cfqq)) 1394 return false; 1395 1396 /* 1397 * follow expired path, else get first next available 1398 */ 1399 rq = cfq_check_fifo(cfqq); 1400 if (!rq) 1401 rq = cfqq->next_rq; 1402 1403 /* 1404 * insert request into driver dispatch list 1405 */ 1406 cfq_dispatch_insert(cfqd->queue, rq); 1407 1408 if (!cfqd->active_cic) { 1409 struct cfq_io_context *cic = RQ_CIC(rq); 1410 1411 atomic_long_inc(&cic->ioc->refcount); 1412 cfqd->active_cic = cic; 1413 } 1414 1415 return true; 1416} 1417 1418/* 1419 * Find the cfqq that we need to service and move a request from that to the 1420 * dispatch list 1421 */ 1422static int cfq_dispatch_requests(struct request_queue *q, int force) 1423{ 1424 struct cfq_data *cfqd = q->elevator->elevator_data; 1425 struct cfq_queue *cfqq; 1426 1427 if (!cfqd->busy_queues) 1428 return 0; 1429 1430 if (unlikely(force)) 1431 return cfq_forced_dispatch(cfqd); 1432 1433 cfqq = cfq_select_queue(cfqd); 1434 if (!cfqq) 1435 return 0; 1436 1437 /* 1438 * Dispatch a request from this cfqq, if it is allowed 1439 */ 1440 if (!cfq_dispatch_request(cfqd, cfqq)) 1441 return 0; 1442 1443 cfqq->slice_dispatch++; 1444 cfq_clear_cfqq_must_dispatch(cfqq); 1445 1446 /* 1447 * expire an async queue immediately if it has used up its slice. idle 1448 * queue always expire after 1 dispatch round. 1449 */ 1450 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && 1451 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || 1452 cfq_class_idle(cfqq))) { 1453 cfqq->slice_end = jiffies + 1; 1454 cfq_slice_expired(cfqd, 0); 1455 } 1456 1457 cfq_log_cfqq(cfqd, cfqq, "dispatched a request"); 1458 return 1; 1459} 1460 1461/* 1462 * task holds one reference to the queue, dropped when task exits. each rq 1463 * in-flight on this queue also holds a reference, dropped when rq is freed. 1464 * 1465 * queue lock must be held here. 1466 */ 1467static void cfq_put_queue(struct cfq_queue *cfqq) 1468{ 1469 struct cfq_data *cfqd = cfqq->cfqd; 1470 1471 BUG_ON(atomic_read(&cfqq->ref) <= 0); 1472 1473 if (!atomic_dec_and_test(&cfqq->ref)) 1474 return; 1475 1476 cfq_log_cfqq(cfqd, cfqq, "put_queue"); 1477 BUG_ON(rb_first(&cfqq->sort_list)); 1478 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); 1479 BUG_ON(cfq_cfqq_on_rr(cfqq)); 1480 1481 if (unlikely(cfqd->active_queue == cfqq)) { 1482 __cfq_slice_expired(cfqd, cfqq, 0); 1483 cfq_schedule_dispatch(cfqd); 1484 } 1485 1486 kmem_cache_free(cfq_pool, cfqq); 1487} 1488 1489/* 1490 * Must always be called with the rcu_read_lock() held 1491 */ 1492static void 1493__call_for_each_cic(struct io_context *ioc, 1494 void (*func)(struct io_context *, struct cfq_io_context *)) 1495{ 1496 struct cfq_io_context *cic; 1497 struct hlist_node *n; 1498 1499 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) 1500 func(ioc, cic); 1501} 1502 1503/* 1504 * Call func for each cic attached to this ioc. 1505 */ 1506static void 1507call_for_each_cic(struct io_context *ioc, 1508 void (*func)(struct io_context *, struct cfq_io_context *)) 1509{ 1510 rcu_read_lock(); 1511 __call_for_each_cic(ioc, func); 1512 rcu_read_unlock(); 1513} 1514 1515static void cfq_cic_free_rcu(struct rcu_head *head) 1516{ 1517 struct cfq_io_context *cic; 1518 1519 cic = container_of(head, struct cfq_io_context, rcu_head); 1520 1521 kmem_cache_free(cfq_ioc_pool, cic); 1522 elv_ioc_count_dec(cfq_ioc_count); 1523 1524 if (ioc_gone) { 1525 /* 1526 * CFQ scheduler is exiting, grab exit lock and check 1527 * the pending io context count. If it hits zero, 1528 * complete ioc_gone and set it back to NULL 1529 */ 1530 spin_lock(&ioc_gone_lock); 1531 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) { 1532 complete(ioc_gone); 1533 ioc_gone = NULL; 1534 } 1535 spin_unlock(&ioc_gone_lock); 1536 } 1537} 1538 1539static void cfq_cic_free(struct cfq_io_context *cic) 1540{ 1541 call_rcu(&cic->rcu_head, cfq_cic_free_rcu); 1542} 1543 1544static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) 1545{ 1546 unsigned long flags; 1547 1548 BUG_ON(!cic->dead_key); 1549 1550 spin_lock_irqsave(&ioc->lock, flags); 1551 radix_tree_delete(&ioc->radix_root, cic->dead_key); 1552 hlist_del_rcu(&cic->cic_list); 1553 spin_unlock_irqrestore(&ioc->lock, flags); 1554 1555 cfq_cic_free(cic); 1556} 1557 1558/* 1559 * Must be called with rcu_read_lock() held or preemption otherwise disabled. 1560 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), 1561 * and ->trim() which is called with the task lock held 1562 */ 1563static void cfq_free_io_context(struct io_context *ioc) 1564{ 1565 /* 1566 * ioc->refcount is zero here, or we are called from elv_unregister(), 1567 * so no more cic's are allowed to be linked into this ioc. So it 1568 * should be ok to iterate over the known list, we will see all cic's 1569 * since no new ones are added. 1570 */ 1571 __call_for_each_cic(ioc, cic_free_func); 1572} 1573 1574static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) 1575{ 1576 struct cfq_queue *__cfqq, *next; 1577 1578 if (unlikely(cfqq == cfqd->active_queue)) { 1579 __cfq_slice_expired(cfqd, cfqq, 0); 1580 cfq_schedule_dispatch(cfqd); 1581 } 1582 1583 /* 1584 * If this queue was scheduled to merge with another queue, be 1585 * sure to drop the reference taken on that queue (and others in 1586 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs. 1587 */ 1588 __cfqq = cfqq->new_cfqq; 1589 while (__cfqq) { 1590 if (__cfqq == cfqq) { 1591 WARN(1, "cfqq->new_cfqq loop detected\n"); 1592 break; 1593 } 1594 next = __cfqq->new_cfqq; 1595 cfq_put_queue(__cfqq); 1596 __cfqq = next; 1597 } 1598 1599 cfq_put_queue(cfqq); 1600} 1601 1602static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 1603 struct cfq_io_context *cic) 1604{ 1605 struct io_context *ioc = cic->ioc; 1606 1607 list_del_init(&cic->queue_list); 1608 1609 /* 1610 * Make sure key == NULL is seen for dead queues 1611 */ 1612 smp_wmb(); 1613 cic->dead_key = (unsigned long) cic->key; 1614 cic->key = NULL; 1615 1616 if (ioc->ioc_data == cic) 1617 rcu_assign_pointer(ioc->ioc_data, NULL); 1618 1619 if (cic->cfqq[BLK_RW_ASYNC]) { 1620 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); 1621 cic->cfqq[BLK_RW_ASYNC] = NULL; 1622 } 1623 1624 if (cic->cfqq[BLK_RW_SYNC]) { 1625 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); 1626 cic->cfqq[BLK_RW_SYNC] = NULL; 1627 } 1628} 1629 1630static void cfq_exit_single_io_context(struct io_context *ioc, 1631 struct cfq_io_context *cic) 1632{ 1633 struct cfq_data *cfqd = cic->key; 1634 1635 if (cfqd) { 1636 struct request_queue *q = cfqd->queue; 1637 unsigned long flags; 1638 1639 spin_lock_irqsave(q->queue_lock, flags); 1640 1641 /* 1642 * Ensure we get a fresh copy of the ->key to prevent 1643 * race between exiting task and queue 1644 */ 1645 smp_read_barrier_depends(); 1646 if (cic->key) 1647 __cfq_exit_single_io_context(cfqd, cic); 1648 1649 spin_unlock_irqrestore(q->queue_lock, flags); 1650 } 1651} 1652 1653/* 1654 * The process that ioc belongs to has exited, we need to clean up 1655 * and put the internal structures we have that belongs to that process. 1656 */ 1657static void cfq_exit_io_context(struct io_context *ioc) 1658{ 1659 call_for_each_cic(ioc, cfq_exit_single_io_context); 1660} 1661 1662static struct cfq_io_context * 1663cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1664{ 1665 struct cfq_io_context *cic; 1666 1667 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, 1668 cfqd->queue->node); 1669 if (cic) { 1670 cic->last_end_request = jiffies; 1671 INIT_LIST_HEAD(&cic->queue_list); 1672 INIT_HLIST_NODE(&cic->cic_list); 1673 cic->dtor = cfq_free_io_context; 1674 cic->exit = cfq_exit_io_context; 1675 elv_ioc_count_inc(cfq_ioc_count); 1676 } 1677 1678 return cic; 1679} 1680 1681static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) 1682{ 1683 struct task_struct *tsk = current; 1684 int ioprio_class; 1685 1686 if (!cfq_cfqq_prio_changed(cfqq)) 1687 return; 1688 1689 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); 1690 switch (ioprio_class) { 1691 default: 1692 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); 1693 case IOPRIO_CLASS_NONE: 1694 /* 1695 * no prio set, inherit CPU scheduling settings 1696 */ 1697 cfqq->ioprio = task_nice_ioprio(tsk); 1698 cfqq->ioprio_class = task_nice_ioclass(tsk); 1699 break; 1700 case IOPRIO_CLASS_RT: 1701 cfqq->ioprio = task_ioprio(ioc); 1702 cfqq->ioprio_class = IOPRIO_CLASS_RT; 1703 break; 1704 case IOPRIO_CLASS_BE: 1705 cfqq->ioprio = task_ioprio(ioc); 1706 cfqq->ioprio_class = IOPRIO_CLASS_BE; 1707 break; 1708 case IOPRIO_CLASS_IDLE: 1709 cfqq->ioprio_class = IOPRIO_CLASS_IDLE; 1710 cfqq->ioprio = 7; 1711 cfq_clear_cfqq_idle_window(cfqq); 1712 break; 1713 } 1714 1715 /* 1716 * keep track of original prio settings in case we have to temporarily 1717 * elevate the priority of this queue 1718 */ 1719 cfqq->org_ioprio = cfqq->ioprio; 1720 cfqq->org_ioprio_class = cfqq->ioprio_class; 1721 cfq_clear_cfqq_prio_changed(cfqq); 1722} 1723 1724static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) 1725{ 1726 struct cfq_data *cfqd = cic->key; 1727 struct cfq_queue *cfqq; 1728 unsigned long flags; 1729 1730 if (unlikely(!cfqd)) 1731 return; 1732 1733 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1734 1735 cfqq = cic->cfqq[BLK_RW_ASYNC]; 1736 if (cfqq) { 1737 struct cfq_queue *new_cfqq; 1738 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, 1739 GFP_ATOMIC); 1740 if (new_cfqq) { 1741 cic->cfqq[BLK_RW_ASYNC] = new_cfqq; 1742 cfq_put_queue(cfqq); 1743 } 1744 } 1745 1746 cfqq = cic->cfqq[BLK_RW_SYNC]; 1747 if (cfqq) 1748 cfq_mark_cfqq_prio_changed(cfqq); 1749 1750 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1751} 1752 1753static void cfq_ioc_set_ioprio(struct io_context *ioc) 1754{ 1755 call_for_each_cic(ioc, changed_ioprio); 1756 ioc->ioprio_changed = 0; 1757} 1758 1759static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 1760 pid_t pid, bool is_sync) 1761{ 1762 RB_CLEAR_NODE(&cfqq->rb_node); 1763 RB_CLEAR_NODE(&cfqq->p_node); 1764 INIT_LIST_HEAD(&cfqq->fifo); 1765 1766 atomic_set(&cfqq->ref, 0); 1767 cfqq->cfqd = cfqd; 1768 1769 cfq_mark_cfqq_prio_changed(cfqq); 1770 1771 if (is_sync) { 1772 if (!cfq_class_idle(cfqq)) 1773 cfq_mark_cfqq_idle_window(cfqq); 1774 cfq_mark_cfqq_sync(cfqq); 1775 } 1776 cfqq->pid = pid; 1777} 1778 1779static struct cfq_queue * 1780cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, 1781 struct io_context *ioc, gfp_t gfp_mask) 1782{ 1783 struct cfq_queue *cfqq, *new_cfqq = NULL; 1784 struct cfq_io_context *cic; 1785 1786retry: 1787 cic = cfq_cic_lookup(cfqd, ioc); 1788 /* cic always exists here */ 1789 cfqq = cic_to_cfqq(cic, is_sync); 1790 1791 /* 1792 * Always try a new alloc if we fell back to the OOM cfqq 1793 * originally, since it should just be a temporary situation. 1794 */ 1795 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 1796 cfqq = NULL; 1797 if (new_cfqq) { 1798 cfqq = new_cfqq; 1799 new_cfqq = NULL; 1800 } else if (gfp_mask & __GFP_WAIT) { 1801 spin_unlock_irq(cfqd->queue->queue_lock); 1802 new_cfqq = kmem_cache_alloc_node(cfq_pool, 1803 gfp_mask | __GFP_ZERO, 1804 cfqd->queue->node); 1805 spin_lock_irq(cfqd->queue->queue_lock); 1806 if (new_cfqq) 1807 goto retry; 1808 } else { 1809 cfqq = kmem_cache_alloc_node(cfq_pool, 1810 gfp_mask | __GFP_ZERO, 1811 cfqd->queue->node); 1812 } 1813 1814 if (cfqq) { 1815 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); 1816 cfq_init_prio_data(cfqq, ioc); 1817 cfq_log_cfqq(cfqd, cfqq, "alloced"); 1818 } else 1819 cfqq = &cfqd->oom_cfqq; 1820 } 1821 1822 if (new_cfqq) 1823 kmem_cache_free(cfq_pool, new_cfqq); 1824 1825 return cfqq; 1826} 1827 1828static struct cfq_queue ** 1829cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) 1830{ 1831 switch (ioprio_class) { 1832 case IOPRIO_CLASS_RT: 1833 return &cfqd->async_cfqq[0][ioprio]; 1834 case IOPRIO_CLASS_BE: 1835 return &cfqd->async_cfqq[1][ioprio]; 1836 case IOPRIO_CLASS_IDLE: 1837 return &cfqd->async_idle_cfqq; 1838 default: 1839 BUG(); 1840 } 1841} 1842 1843static struct cfq_queue * 1844cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc, 1845 gfp_t gfp_mask) 1846{ 1847 const int ioprio = task_ioprio(ioc); 1848 const int ioprio_class = task_ioprio_class(ioc); 1849 struct cfq_queue **async_cfqq = NULL; 1850 struct cfq_queue *cfqq = NULL; 1851 1852 if (!is_sync) { 1853 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); 1854 cfqq = *async_cfqq; 1855 } 1856 1857 if (!cfqq) 1858 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); 1859 1860 /* 1861 * pin the queue now that it's allocated, scheduler exit will prune it 1862 */ 1863 if (!is_sync && !(*async_cfqq)) { 1864 atomic_inc(&cfqq->ref); 1865 *async_cfqq = cfqq; 1866 } 1867 1868 atomic_inc(&cfqq->ref); 1869 return cfqq; 1870} 1871 1872/* 1873 * We drop cfq io contexts lazily, so we may find a dead one. 1874 */ 1875static void 1876cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, 1877 struct cfq_io_context *cic) 1878{ 1879 unsigned long flags; 1880 1881 WARN_ON(!list_empty(&cic->queue_list)); 1882 1883 spin_lock_irqsave(&ioc->lock, flags); 1884 1885 BUG_ON(ioc->ioc_data == cic); 1886 1887 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); 1888 hlist_del_rcu(&cic->cic_list); 1889 spin_unlock_irqrestore(&ioc->lock, flags); 1890 1891 cfq_cic_free(cic); 1892} 1893 1894static struct cfq_io_context * 1895cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) 1896{ 1897 struct cfq_io_context *cic; 1898 unsigned long flags; 1899 void *k; 1900 1901 if (unlikely(!ioc)) 1902 return NULL; 1903 1904 rcu_read_lock(); 1905 1906 /* 1907 * we maintain a last-hit cache, to avoid browsing over the tree 1908 */ 1909 cic = rcu_dereference(ioc->ioc_data); 1910 if (cic && cic->key == cfqd) { 1911 rcu_read_unlock(); 1912 return cic; 1913 } 1914 1915 do { 1916 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); 1917 rcu_read_unlock(); 1918 if (!cic) 1919 break; 1920 /* ->key must be copied to avoid race with cfq_exit_queue() */ 1921 k = cic->key; 1922 if (unlikely(!k)) { 1923 cfq_drop_dead_cic(cfqd, ioc, cic); 1924 rcu_read_lock(); 1925 continue; 1926 } 1927 1928 spin_lock_irqsave(&ioc->lock, flags); 1929 rcu_assign_pointer(ioc->ioc_data, cic); 1930 spin_unlock_irqrestore(&ioc->lock, flags); 1931 break; 1932 } while (1); 1933 1934 return cic; 1935} 1936 1937/* 1938 * Add cic into ioc, using cfqd as the search key. This enables us to lookup 1939 * the process specific cfq io context when entered from the block layer. 1940 * Also adds the cic to a per-cfqd list, used when this queue is removed. 1941 */ 1942static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, 1943 struct cfq_io_context *cic, gfp_t gfp_mask) 1944{ 1945 unsigned long flags; 1946 int ret; 1947 1948 ret = radix_tree_preload(gfp_mask); 1949 if (!ret) { 1950 cic->ioc = ioc; 1951 cic->key = cfqd; 1952 1953 spin_lock_irqsave(&ioc->lock, flags); 1954 ret = radix_tree_insert(&ioc->radix_root, 1955 (unsigned long) cfqd, cic); 1956 if (!ret) 1957 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); 1958 spin_unlock_irqrestore(&ioc->lock, flags); 1959 1960 radix_tree_preload_end(); 1961 1962 if (!ret) { 1963 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 1964 list_add(&cic->queue_list, &cfqd->cic_list); 1965 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 1966 } 1967 } 1968 1969 if (ret) 1970 printk(KERN_ERR "cfq: cic link failed!\n"); 1971 1972 return ret; 1973} 1974 1975/* 1976 * Setup general io context and cfq io context. There can be several cfq 1977 * io contexts per general io context, if this process is doing io to more 1978 * than one device managed by cfq. 1979 */ 1980static struct cfq_io_context * 1981cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) 1982{ 1983 struct io_context *ioc = NULL; 1984 struct cfq_io_context *cic; 1985 1986 might_sleep_if(gfp_mask & __GFP_WAIT); 1987 1988 ioc = get_io_context(gfp_mask, cfqd->queue->node); 1989 if (!ioc) 1990 return NULL; 1991 1992 cic = cfq_cic_lookup(cfqd, ioc); 1993 if (cic) 1994 goto out; 1995 1996 cic = cfq_alloc_io_context(cfqd, gfp_mask); 1997 if (cic == NULL) 1998 goto err; 1999 2000 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) 2001 goto err_free; 2002 2003out: 2004 smp_read_barrier_depends(); 2005 if (unlikely(ioc->ioprio_changed)) 2006 cfq_ioc_set_ioprio(ioc); 2007 2008 return cic; 2009err_free: 2010 cfq_cic_free(cic); 2011err: 2012 put_io_context(ioc); 2013 return NULL; 2014} 2015 2016static void 2017cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) 2018{ 2019 unsigned long elapsed = jiffies - cic->last_end_request; 2020 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); 2021 2022 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; 2023 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; 2024 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; 2025} 2026 2027static void 2028cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2029 struct request *rq) 2030{ 2031 sector_t sdist; 2032 u64 total; 2033 2034 if (!cfqq->last_request_pos) 2035 sdist = 0; 2036 else if (cfqq->last_request_pos < blk_rq_pos(rq)) 2037 sdist = blk_rq_pos(rq) - cfqq->last_request_pos; 2038 else 2039 sdist = cfqq->last_request_pos - blk_rq_pos(rq); 2040 2041 /* 2042 * Don't allow the seek distance to get too large from the 2043 * odd fragment, pagein, etc 2044 */ 2045 if (cfqq->seek_samples <= 60) /* second&third seek */ 2046 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024); 2047 else 2048 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64); 2049 2050 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8; 2051 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8; 2052 total = cfqq->seek_total + (cfqq->seek_samples/2); 2053 do_div(total, cfqq->seek_samples); 2054 cfqq->seek_mean = (sector_t)total; 2055 2056 /* 2057 * If this cfqq is shared between multiple processes, check to 2058 * make sure that those processes are still issuing I/Os within 2059 * the mean seek distance. If not, it may be time to break the 2060 * queues apart again. 2061 */ 2062 if (cfq_cfqq_coop(cfqq)) { 2063 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start) 2064 cfqq->seeky_start = jiffies; 2065 else if (!CFQQ_SEEKY(cfqq)) 2066 cfqq->seeky_start = 0; 2067 } 2068} 2069 2070/* 2071 * Disable idle window if the process thinks too long or seeks so much that 2072 * it doesn't matter 2073 */ 2074static void 2075cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2076 struct cfq_io_context *cic) 2077{ 2078 int old_idle, enable_idle; 2079 2080 /* 2081 * Don't idle for async or idle io prio class 2082 */ 2083 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) 2084 return; 2085 2086 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); 2087 2088 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || 2089 (!cfqd->cfq_latency && cfqd->hw_tag && CFQQ_SEEKY(cfqq))) 2090 enable_idle = 0; 2091 else if (sample_valid(cic->ttime_samples)) { 2092 unsigned int slice_idle = cfqd->cfq_slice_idle; 2093 if (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)) 2094 slice_idle = msecs_to_jiffies(CFQ_MIN_TT); 2095 if (cic->ttime_mean > slice_idle) 2096 enable_idle = 0; 2097 else 2098 enable_idle = 1; 2099 } 2100 2101 if (old_idle != enable_idle) { 2102 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); 2103 if (enable_idle) 2104 cfq_mark_cfqq_idle_window(cfqq); 2105 else 2106 cfq_clear_cfqq_idle_window(cfqq); 2107 } 2108} 2109 2110/* 2111 * Check if new_cfqq should preempt the currently active queue. Return 0 for 2112 * no or if we aren't sure, a 1 will cause a preempt. 2113 */ 2114static bool 2115cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 2116 struct request *rq) 2117{ 2118 struct cfq_queue *cfqq; 2119 2120 cfqq = cfqd->active_queue; 2121 if (!cfqq) 2122 return false; 2123 2124 if (cfq_slice_used(cfqq)) 2125 return true; 2126 2127 if (cfq_class_idle(new_cfqq)) 2128 return false; 2129 2130 if (cfq_class_idle(cfqq)) 2131 return true; 2132 2133 /* 2134 * if the new request is sync, but the currently running queue is 2135 * not, let the sync request have priority. 2136 */ 2137 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 2138 return true; 2139 2140 /* 2141 * So both queues are sync. Let the new request get disk time if 2142 * it's a metadata request and the current queue is doing regular IO. 2143 */ 2144 if (rq_is_meta(rq) && !cfqq->meta_pending) 2145 return false; 2146 2147 /* 2148 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. 2149 */ 2150 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) 2151 return true; 2152 2153 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) 2154 return false; 2155 2156 /* 2157 * if this request is as-good as one we would expect from the 2158 * current cfqq, let it preempt 2159 */ 2160 if (cfq_rq_close(cfqd, cfqq, rq)) 2161 return true; 2162 2163 return false; 2164} 2165 2166/* 2167 * cfqq preempts the active queue. if we allowed preempt with no slice left, 2168 * let it have half of its nominal slice. 2169 */ 2170static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 2171{ 2172 cfq_log_cfqq(cfqd, cfqq, "preempt"); 2173 cfq_slice_expired(cfqd, 1); 2174 2175 /* 2176 * Put the new queue at the front of the of the current list, 2177 * so we know that it will be selected next. 2178 */ 2179 BUG_ON(!cfq_cfqq_on_rr(cfqq)); 2180 2181 cfq_service_tree_add(cfqd, cfqq, 1); 2182 2183 cfqq->slice_end = 0; 2184 cfq_mark_cfqq_slice_new(cfqq); 2185} 2186 2187/* 2188 * Called when a new fs request (rq) is added (to cfqq). Check if there's 2189 * something we should do about it 2190 */ 2191static void 2192cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, 2193 struct request *rq) 2194{ 2195 struct cfq_io_context *cic = RQ_CIC(rq); 2196 2197 cfqd->rq_queued++; 2198 if (rq_is_meta(rq)) 2199 cfqq->meta_pending++; 2200 2201 cfq_update_io_thinktime(cfqd, cic); 2202 cfq_update_io_seektime(cfqd, cfqq, rq); 2203 cfq_update_idle_window(cfqd, cfqq, cic); 2204 2205 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); 2206 2207 if (cfqq == cfqd->active_queue) { 2208 /* 2209 * Remember that we saw a request from this process, but 2210 * don't start queuing just yet. Otherwise we risk seeing lots 2211 * of tiny requests, because we disrupt the normal plugging 2212 * and merging. If the request is already larger than a single 2213 * page, let it rip immediately. For that case we assume that 2214 * merging is already done. Ditto for a busy system that 2215 * has other work pending, don't risk delaying until the 2216 * idle timer unplug to continue working. 2217 */ 2218 if (cfq_cfqq_wait_request(cfqq)) { 2219 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || 2220 cfqd->busy_queues > 1) { 2221 del_timer(&cfqd->idle_slice_timer); 2222 __blk_run_queue(cfqd->queue); 2223 } 2224 cfq_mark_cfqq_must_dispatch(cfqq); 2225 } 2226 } else if (cfq_should_preempt(cfqd, cfqq, rq)) { 2227 /* 2228 * not the active queue - expire current slice if it is 2229 * idle and has expired it's mean thinktime or this new queue 2230 * has some old slice time left and is of higher priority or 2231 * this new queue is RT and the current one is BE 2232 */ 2233 cfq_preempt_queue(cfqd, cfqq); 2234 __blk_run_queue(cfqd->queue); 2235 } 2236} 2237 2238static void cfq_insert_request(struct request_queue *q, struct request *rq) 2239{ 2240 struct cfq_data *cfqd = q->elevator->elevator_data; 2241 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2242 2243 cfq_log_cfqq(cfqd, cfqq, "insert_request"); 2244 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); 2245 2246 cfq_add_rq_rb(rq); 2247 2248 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]); 2249 list_add_tail(&rq->queuelist, &cfqq->fifo); 2250 2251 cfq_rq_enqueued(cfqd, cfqq, rq); 2252} 2253 2254/* 2255 * Update hw_tag based on peak queue depth over 50 samples under 2256 * sufficient load. 2257 */ 2258static void cfq_update_hw_tag(struct cfq_data *cfqd) 2259{ 2260 if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak) 2261 cfqd->rq_in_driver_peak = rq_in_driver(cfqd); 2262 2263 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && 2264 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN) 2265 return; 2266 2267 if (cfqd->hw_tag_samples++ < 50) 2268 return; 2269 2270 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN) 2271 cfqd->hw_tag = 1; 2272 else 2273 cfqd->hw_tag = 0; 2274 2275 cfqd->hw_tag_samples = 0; 2276 cfqd->rq_in_driver_peak = 0; 2277} 2278 2279static void cfq_completed_request(struct request_queue *q, struct request *rq) 2280{ 2281 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2282 struct cfq_data *cfqd = cfqq->cfqd; 2283 const int sync = rq_is_sync(rq); 2284 unsigned long now; 2285 2286 now = jiffies; 2287 cfq_log_cfqq(cfqd, cfqq, "complete"); 2288 2289 cfq_update_hw_tag(cfqd); 2290 2291 WARN_ON(!cfqd->rq_in_driver[sync]); 2292 WARN_ON(!cfqq->dispatched); 2293 cfqd->rq_in_driver[sync]--; 2294 cfqq->dispatched--; 2295 2296 if (cfq_cfqq_sync(cfqq)) 2297 cfqd->sync_flight--; 2298 2299 if (sync) { 2300 RQ_CIC(rq)->last_end_request = now; 2301 cfqd->last_end_sync_rq = now; 2302 } 2303 2304 /* 2305 * If this is the active queue, check if it needs to be expired, 2306 * or if we want to idle in case it has no pending requests. 2307 */ 2308 if (cfqd->active_queue == cfqq) { 2309 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); 2310 2311 if (cfq_cfqq_slice_new(cfqq)) { 2312 cfq_set_prio_slice(cfqd, cfqq); 2313 cfq_clear_cfqq_slice_new(cfqq); 2314 } 2315 /* 2316 * If there are no requests waiting in this queue, and 2317 * there are other queues ready to issue requests, AND 2318 * those other queues are issuing requests within our 2319 * mean seek distance, give them a chance to run instead 2320 * of idling. 2321 */ 2322 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) 2323 cfq_slice_expired(cfqd, 1); 2324 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq) && 2325 sync && !rq_noidle(rq)) 2326 cfq_arm_slice_timer(cfqd); 2327 } 2328 2329 if (!rq_in_driver(cfqd)) 2330 cfq_schedule_dispatch(cfqd); 2331} 2332 2333/* 2334 * we temporarily boost lower priority queues if they are holding fs exclusive 2335 * resources. they are boosted to normal prio (CLASS_BE/4) 2336 */ 2337static void cfq_prio_boost(struct cfq_queue *cfqq) 2338{ 2339 if (has_fs_excl()) { 2340 /* 2341 * boost idle prio on transactions that would lock out other 2342 * users of the filesystem 2343 */ 2344 if (cfq_class_idle(cfqq)) 2345 cfqq->ioprio_class = IOPRIO_CLASS_BE; 2346 if (cfqq->ioprio > IOPRIO_NORM) 2347 cfqq->ioprio = IOPRIO_NORM; 2348 } else { 2349 /* 2350 * check if we need to unboost the queue 2351 */ 2352 if (cfqq->ioprio_class != cfqq->org_ioprio_class) 2353 cfqq->ioprio_class = cfqq->org_ioprio_class; 2354 if (cfqq->ioprio != cfqq->org_ioprio) 2355 cfqq->ioprio = cfqq->org_ioprio; 2356 } 2357} 2358 2359static inline int __cfq_may_queue(struct cfq_queue *cfqq) 2360{ 2361 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) { 2362 cfq_mark_cfqq_must_alloc_slice(cfqq); 2363 return ELV_MQUEUE_MUST; 2364 } 2365 2366 return ELV_MQUEUE_MAY; 2367} 2368 2369static int cfq_may_queue(struct request_queue *q, int rw) 2370{ 2371 struct cfq_data *cfqd = q->elevator->elevator_data; 2372 struct task_struct *tsk = current; 2373 struct cfq_io_context *cic; 2374 struct cfq_queue *cfqq; 2375 2376 /* 2377 * don't force setup of a queue from here, as a call to may_queue 2378 * does not necessarily imply that a request actually will be queued. 2379 * so just lookup a possibly existing queue, or return 'may queue' 2380 * if that fails 2381 */ 2382 cic = cfq_cic_lookup(cfqd, tsk->io_context); 2383 if (!cic) 2384 return ELV_MQUEUE_MAY; 2385 2386 cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); 2387 if (cfqq) { 2388 cfq_init_prio_data(cfqq, cic->ioc); 2389 cfq_prio_boost(cfqq); 2390 2391 return __cfq_may_queue(cfqq); 2392 } 2393 2394 return ELV_MQUEUE_MAY; 2395} 2396 2397/* 2398 * queue lock held here 2399 */ 2400static void cfq_put_request(struct request *rq) 2401{ 2402 struct cfq_queue *cfqq = RQ_CFQQ(rq); 2403 2404 if (cfqq) { 2405 const int rw = rq_data_dir(rq); 2406 2407 BUG_ON(!cfqq->allocated[rw]); 2408 cfqq->allocated[rw]--; 2409 2410 put_io_context(RQ_CIC(rq)->ioc); 2411 2412 rq->elevator_private = NULL; 2413 rq->elevator_private2 = NULL; 2414 2415 cfq_put_queue(cfqq); 2416 } 2417} 2418 2419static struct cfq_queue * 2420cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, 2421 struct cfq_queue *cfqq) 2422{ 2423 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq); 2424 cic_set_cfqq(cic, cfqq->new_cfqq, 1); 2425 cfq_mark_cfqq_coop(cfqq->new_cfqq); 2426 cfq_put_queue(cfqq); 2427 return cic_to_cfqq(cic, 1); 2428} 2429 2430static int should_split_cfqq(struct cfq_queue *cfqq) 2431{ 2432 if (cfqq->seeky_start && 2433 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT)) 2434 return 1; 2435 return 0; 2436} 2437 2438/* 2439 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this 2440 * was the last process referring to said cfqq. 2441 */ 2442static struct cfq_queue * 2443split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq) 2444{ 2445 if (cfqq_process_refs(cfqq) == 1) { 2446 cfqq->seeky_start = 0; 2447 cfqq->pid = current->pid; 2448 cfq_clear_cfqq_coop(cfqq); 2449 return cfqq; 2450 } 2451 2452 cic_set_cfqq(cic, NULL, 1); 2453 cfq_put_queue(cfqq); 2454 return NULL; 2455} 2456/* 2457 * Allocate cfq data structures associated with this request. 2458 */ 2459static int 2460cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) 2461{ 2462 struct cfq_data *cfqd = q->elevator->elevator_data; 2463 struct cfq_io_context *cic; 2464 const int rw = rq_data_dir(rq); 2465 const bool is_sync = rq_is_sync(rq); 2466 struct cfq_queue *cfqq; 2467 unsigned long flags; 2468 2469 might_sleep_if(gfp_mask & __GFP_WAIT); 2470 2471 cic = cfq_get_io_context(cfqd, gfp_mask); 2472 2473 spin_lock_irqsave(q->queue_lock, flags); 2474 2475 if (!cic) 2476 goto queue_fail; 2477 2478new_queue: 2479 cfqq = cic_to_cfqq(cic, is_sync); 2480 if (!cfqq || cfqq == &cfqd->oom_cfqq) { 2481 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); 2482 cic_set_cfqq(cic, cfqq, is_sync); 2483 } else { 2484 /* 2485 * If the queue was seeky for too long, break it apart. 2486 */ 2487 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) { 2488 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq"); 2489 cfqq = split_cfqq(cic, cfqq); 2490 if (!cfqq) 2491 goto new_queue; 2492 } 2493 2494 /* 2495 * Check to see if this queue is scheduled to merge with 2496 * another, closely cooperating queue. The merging of 2497 * queues happens here as it must be done in process context. 2498 * The reference on new_cfqq was taken in merge_cfqqs. 2499 */ 2500 if (cfqq->new_cfqq) 2501 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq); 2502 } 2503 2504 cfqq->allocated[rw]++; 2505 atomic_inc(&cfqq->ref); 2506 2507 spin_unlock_irqrestore(q->queue_lock, flags); 2508 2509 rq->elevator_private = cic; 2510 rq->elevator_private2 = cfqq; 2511 return 0; 2512 2513queue_fail: 2514 if (cic) 2515 put_io_context(cic->ioc); 2516 2517 cfq_schedule_dispatch(cfqd); 2518 spin_unlock_irqrestore(q->queue_lock, flags); 2519 cfq_log(cfqd, "set_request fail"); 2520 return 1; 2521} 2522 2523static void cfq_kick_queue(struct work_struct *work) 2524{ 2525 struct cfq_data *cfqd = 2526 container_of(work, struct cfq_data, unplug_work); 2527 struct request_queue *q = cfqd->queue; 2528 2529 spin_lock_irq(q->queue_lock); 2530 __blk_run_queue(cfqd->queue); 2531 spin_unlock_irq(q->queue_lock); 2532} 2533 2534/* 2535 * Timer running if the active_queue is currently idling inside its time slice 2536 */ 2537static void cfq_idle_slice_timer(unsigned long data) 2538{ 2539 struct cfq_data *cfqd = (struct cfq_data *) data; 2540 struct cfq_queue *cfqq; 2541 unsigned long flags; 2542 int timed_out = 1; 2543 2544 cfq_log(cfqd, "idle timer fired"); 2545 2546 spin_lock_irqsave(cfqd->queue->queue_lock, flags); 2547 2548 cfqq = cfqd->active_queue; 2549 if (cfqq) { 2550 timed_out = 0; 2551 2552 /* 2553 * We saw a request before the queue expired, let it through 2554 */ 2555 if (cfq_cfqq_must_dispatch(cfqq)) 2556 goto out_kick; 2557 2558 /* 2559 * expired 2560 */ 2561 if (cfq_slice_used(cfqq)) 2562 goto expire; 2563 2564 /* 2565 * only expire and reinvoke request handler, if there are 2566 * other queues with pending requests 2567 */ 2568 if (!cfqd->busy_queues) 2569 goto out_cont; 2570 2571 /* 2572 * not expired and it has a request pending, let it dispatch 2573 */ 2574 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) 2575 goto out_kick; 2576 } 2577expire: 2578 cfq_slice_expired(cfqd, timed_out); 2579out_kick: 2580 cfq_schedule_dispatch(cfqd); 2581out_cont: 2582 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); 2583} 2584 2585static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) 2586{ 2587 del_timer_sync(&cfqd->idle_slice_timer); 2588 cancel_work_sync(&cfqd->unplug_work); 2589} 2590 2591static void cfq_put_async_queues(struct cfq_data *cfqd) 2592{ 2593 int i; 2594 2595 for (i = 0; i < IOPRIO_BE_NR; i++) { 2596 if (cfqd->async_cfqq[0][i]) 2597 cfq_put_queue(cfqd->async_cfqq[0][i]); 2598 if (cfqd->async_cfqq[1][i]) 2599 cfq_put_queue(cfqd->async_cfqq[1][i]); 2600 } 2601 2602 if (cfqd->async_idle_cfqq) 2603 cfq_put_queue(cfqd->async_idle_cfqq); 2604} 2605 2606static void cfq_exit_queue(struct elevator_queue *e) 2607{ 2608 struct cfq_data *cfqd = e->elevator_data; 2609 struct request_queue *q = cfqd->queue; 2610 2611 cfq_shutdown_timer_wq(cfqd); 2612 2613 spin_lock_irq(q->queue_lock); 2614 2615 if (cfqd->active_queue) 2616 __cfq_slice_expired(cfqd, cfqd->active_queue, 0); 2617 2618 while (!list_empty(&cfqd->cic_list)) { 2619 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, 2620 struct cfq_io_context, 2621 queue_list); 2622 2623 __cfq_exit_single_io_context(cfqd, cic); 2624 } 2625 2626 cfq_put_async_queues(cfqd); 2627 2628 spin_unlock_irq(q->queue_lock); 2629 2630 cfq_shutdown_timer_wq(cfqd); 2631 2632 kfree(cfqd); 2633} 2634 2635static void *cfq_init_queue(struct request_queue *q) 2636{ 2637 struct cfq_data *cfqd; 2638 int i; 2639 2640 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); 2641 if (!cfqd) 2642 return NULL; 2643 2644 cfqd->service_tree = CFQ_RB_ROOT; 2645 2646 /* 2647 * Not strictly needed (since RB_ROOT just clears the node and we 2648 * zeroed cfqd on alloc), but better be safe in case someone decides 2649 * to add magic to the rb code 2650 */ 2651 for (i = 0; i < CFQ_PRIO_LISTS; i++) 2652 cfqd->prio_trees[i] = RB_ROOT; 2653 2654 /* 2655 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. 2656 * Grab a permanent reference to it, so that the normal code flow 2657 * will not attempt to free it. 2658 */ 2659 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); 2660 atomic_inc(&cfqd->oom_cfqq.ref); 2661 2662 INIT_LIST_HEAD(&cfqd->cic_list); 2663 2664 cfqd->queue = q; 2665 2666 init_timer(&cfqd->idle_slice_timer); 2667 cfqd->idle_slice_timer.function = cfq_idle_slice_timer; 2668 cfqd->idle_slice_timer.data = (unsigned long) cfqd; 2669 2670 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); 2671 2672 cfqd->cfq_quantum = cfq_quantum; 2673 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; 2674 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; 2675 cfqd->cfq_back_max = cfq_back_max; 2676 cfqd->cfq_back_penalty = cfq_back_penalty; 2677 cfqd->cfq_slice[0] = cfq_slice_async; 2678 cfqd->cfq_slice[1] = cfq_slice_sync; 2679 cfqd->cfq_slice_async_rq = cfq_slice_async_rq; 2680 cfqd->cfq_slice_idle = cfq_slice_idle; 2681 cfqd->cfq_latency = 1; 2682 cfqd->hw_tag = 1; 2683 cfqd->last_end_sync_rq = jiffies; 2684 return cfqd; 2685} 2686 2687static void cfq_slab_kill(void) 2688{ 2689 /* 2690 * Caller already ensured that pending RCU callbacks are completed, 2691 * so we should have no busy allocations at this point. 2692 */ 2693 if (cfq_pool) 2694 kmem_cache_destroy(cfq_pool); 2695 if (cfq_ioc_pool) 2696 kmem_cache_destroy(cfq_ioc_pool); 2697} 2698 2699static int __init cfq_slab_setup(void) 2700{ 2701 cfq_pool = KMEM_CACHE(cfq_queue, 0); 2702 if (!cfq_pool) 2703 goto fail; 2704 2705 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); 2706 if (!cfq_ioc_pool) 2707 goto fail; 2708 2709 return 0; 2710fail: 2711 cfq_slab_kill(); 2712 return -ENOMEM; 2713} 2714 2715/* 2716 * sysfs parts below --> 2717 */ 2718static ssize_t 2719cfq_var_show(unsigned int var, char *page) 2720{ 2721 return sprintf(page, "%d\n", var); 2722} 2723 2724static ssize_t 2725cfq_var_store(unsigned int *var, const char *page, size_t count) 2726{ 2727 char *p = (char *) page; 2728 2729 *var = simple_strtoul(p, &p, 10); 2730 return count; 2731} 2732 2733#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ 2734static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 2735{ \ 2736 struct cfq_data *cfqd = e->elevator_data; \ 2737 unsigned int __data = __VAR; \ 2738 if (__CONV) \ 2739 __data = jiffies_to_msecs(__data); \ 2740 return cfq_var_show(__data, (page)); \ 2741} 2742SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); 2743SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); 2744SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); 2745SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); 2746SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); 2747SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); 2748SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); 2749SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); 2750SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); 2751SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); 2752#undef SHOW_FUNCTION 2753 2754#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 2755static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 2756{ \ 2757 struct cfq_data *cfqd = e->elevator_data; \ 2758 unsigned int __data; \ 2759 int ret = cfq_var_store(&__data, (page), count); \ 2760 if (__data < (MIN)) \ 2761 __data = (MIN); \ 2762 else if (__data > (MAX)) \ 2763 __data = (MAX); \ 2764 if (__CONV) \ 2765 *(__PTR) = msecs_to_jiffies(__data); \ 2766 else \ 2767 *(__PTR) = __data; \ 2768 return ret; \ 2769} 2770STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); 2771STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, 2772 UINT_MAX, 1); 2773STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, 2774 UINT_MAX, 1); 2775STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); 2776STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, 2777 UINT_MAX, 0); 2778STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); 2779STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); 2780STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); 2781STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, 2782 UINT_MAX, 0); 2783STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); 2784#undef STORE_FUNCTION 2785 2786#define CFQ_ATTR(name) \ 2787 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) 2788 2789static struct elv_fs_entry cfq_attrs[] = { 2790 CFQ_ATTR(quantum), 2791 CFQ_ATTR(fifo_expire_sync), 2792 CFQ_ATTR(fifo_expire_async), 2793 CFQ_ATTR(back_seek_max), 2794 CFQ_ATTR(back_seek_penalty), 2795 CFQ_ATTR(slice_sync), 2796 CFQ_ATTR(slice_async), 2797 CFQ_ATTR(slice_async_rq), 2798 CFQ_ATTR(slice_idle), 2799 CFQ_ATTR(low_latency), 2800 __ATTR_NULL 2801}; 2802 2803static struct elevator_type iosched_cfq = { 2804 .ops = { 2805 .elevator_merge_fn = cfq_merge, 2806 .elevator_merged_fn = cfq_merged_request, 2807 .elevator_merge_req_fn = cfq_merged_requests, 2808 .elevator_allow_merge_fn = cfq_allow_merge, 2809 .elevator_dispatch_fn = cfq_dispatch_requests, 2810 .elevator_add_req_fn = cfq_insert_request, 2811 .elevator_activate_req_fn = cfq_activate_request, 2812 .elevator_deactivate_req_fn = cfq_deactivate_request, 2813 .elevator_queue_empty_fn = cfq_queue_empty, 2814 .elevator_completed_req_fn = cfq_completed_request, 2815 .elevator_former_req_fn = elv_rb_former_request, 2816 .elevator_latter_req_fn = elv_rb_latter_request, 2817 .elevator_set_req_fn = cfq_set_request, 2818 .elevator_put_req_fn = cfq_put_request, 2819 .elevator_may_queue_fn = cfq_may_queue, 2820 .elevator_init_fn = cfq_init_queue, 2821 .elevator_exit_fn = cfq_exit_queue, 2822 .trim = cfq_free_io_context, 2823 }, 2824 .elevator_attrs = cfq_attrs, 2825 .elevator_name = "cfq", 2826 .elevator_owner = THIS_MODULE, 2827}; 2828 2829static int __init cfq_init(void) 2830{ 2831 /* 2832 * could be 0 on HZ < 1000 setups 2833 */ 2834 if (!cfq_slice_async) 2835 cfq_slice_async = 1; 2836 if (!cfq_slice_idle) 2837 cfq_slice_idle = 1; 2838 2839 if (cfq_slab_setup()) 2840 return -ENOMEM; 2841 2842 elv_register(&iosched_cfq); 2843 2844 return 0; 2845} 2846 2847static void __exit cfq_exit(void) 2848{ 2849 DECLARE_COMPLETION_ONSTACK(all_gone); 2850 elv_unregister(&iosched_cfq); 2851 ioc_gone = &all_gone; 2852 /* ioc_gone's update must be visible before reading ioc_count */ 2853 smp_wmb(); 2854 2855 /* 2856 * this also protects us from entering cfq_slab_kill() with 2857 * pending RCU callbacks 2858 */ 2859 if (elv_ioc_count_read(cfq_ioc_count)) 2860 wait_for_completion(&all_gone); 2861 cfq_slab_kill(); 2862} 2863 2864module_init(cfq_init); 2865module_exit(cfq_exit); 2866 2867MODULE_AUTHOR("Jens Axboe"); 2868MODULE_LICENSE("GPL"); 2869MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 2870