[TIPC]: Allow stream receive to read from multiple TIPC messages
[linux-2.6.git] / block / cfq-iosched.c
blobf26da2bfcc15714e0bbc10734aff7a91dae446ac
1 /*
2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
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>
16 * tunables
18 /* max queue in one round of service */
19 static const int cfq_quantum = 4;
20 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
21 /* maximum backwards seek, in KiB */
22 static const int cfq_back_max = 16 * 1024;
23 /* penalty of a backwards seek */
24 static const int cfq_back_penalty = 2;
25 static const int cfq_slice_sync = HZ / 10;
26 static int cfq_slice_async = HZ / 25;
27 static const int cfq_slice_async_rq = 2;
28 static int cfq_slice_idle = HZ / 125;
31 * offset from end of service tree
33 #define CFQ_IDLE_DELAY (HZ / 5)
36 * below this threshold, we consider thinktime immediate
38 #define CFQ_MIN_TT (2)
40 #define CFQ_SLICE_SCALE (5)
42 #define RQ_CIC(rq) \
43 ((struct cfq_io_context *) (rq)->elevator_private)
44 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
46 static struct kmem_cache *cfq_pool;
47 static struct kmem_cache *cfq_ioc_pool;
49 static DEFINE_PER_CPU(unsigned long, ioc_count);
50 static struct completion *ioc_gone;
52 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
53 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
54 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
56 #define ASYNC (0)
57 #define SYNC (1)
59 #define sample_valid(samples) ((samples) > 80)
62 * Most of our rbtree usage is for sorting with min extraction, so
63 * if we cache the leftmost node we don't have to walk down the tree
64 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
65 * move this into the elevator for the rq sorting as well.
67 struct cfq_rb_root {
68 struct rb_root rb;
69 struct rb_node *left;
71 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
74 * Per block device queue structure
76 struct cfq_data {
77 struct request_queue *queue;
80 * rr list of queues with requests and the count of them
82 struct cfq_rb_root service_tree;
83 unsigned int busy_queues;
85 int rq_in_driver;
86 int sync_flight;
87 int hw_tag;
90 * idle window management
92 struct timer_list idle_slice_timer;
93 struct work_struct unplug_work;
95 struct cfq_queue *active_queue;
96 struct cfq_io_context *active_cic;
99 * async queue for each priority case
101 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
102 struct cfq_queue *async_idle_cfqq;
104 sector_t last_position;
105 unsigned long last_end_request;
108 * tunables, see top of file
110 unsigned int cfq_quantum;
111 unsigned int cfq_fifo_expire[2];
112 unsigned int cfq_back_penalty;
113 unsigned int cfq_back_max;
114 unsigned int cfq_slice[2];
115 unsigned int cfq_slice_async_rq;
116 unsigned int cfq_slice_idle;
118 struct list_head cic_list;
122 * Per process-grouping structure
124 struct cfq_queue {
125 /* reference count */
126 atomic_t ref;
127 /* parent cfq_data */
128 struct cfq_data *cfqd;
129 /* service_tree member */
130 struct rb_node rb_node;
131 /* service_tree key */
132 unsigned long rb_key;
133 /* sorted list of pending requests */
134 struct rb_root sort_list;
135 /* if fifo isn't expired, next request to serve */
136 struct request *next_rq;
137 /* requests queued in sort_list */
138 int queued[2];
139 /* currently allocated requests */
140 int allocated[2];
141 /* pending metadata requests */
142 int meta_pending;
143 /* fifo list of requests in sort_list */
144 struct list_head fifo;
146 unsigned long slice_end;
147 long slice_resid;
149 /* number of requests that are on the dispatch list or inside driver */
150 int dispatched;
152 /* io prio of this group */
153 unsigned short ioprio, org_ioprio;
154 unsigned short ioprio_class, org_ioprio_class;
156 /* various state flags, see below */
157 unsigned int flags;
160 enum cfqq_state_flags {
161 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
162 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
163 CFQ_CFQQ_FLAG_must_alloc, /* must be allowed rq alloc */
164 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
165 CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */
166 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
167 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
168 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
169 CFQ_CFQQ_FLAG_queue_new, /* queue never been serviced */
170 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
171 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
174 #define CFQ_CFQQ_FNS(name) \
175 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
177 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
179 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
181 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
183 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
185 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
188 CFQ_CFQQ_FNS(on_rr);
189 CFQ_CFQQ_FNS(wait_request);
190 CFQ_CFQQ_FNS(must_alloc);
191 CFQ_CFQQ_FNS(must_alloc_slice);
192 CFQ_CFQQ_FNS(must_dispatch);
193 CFQ_CFQQ_FNS(fifo_expire);
194 CFQ_CFQQ_FNS(idle_window);
195 CFQ_CFQQ_FNS(prio_changed);
196 CFQ_CFQQ_FNS(queue_new);
197 CFQ_CFQQ_FNS(slice_new);
198 CFQ_CFQQ_FNS(sync);
199 #undef CFQ_CFQQ_FNS
201 static void cfq_dispatch_insert(struct request_queue *, struct request *);
202 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
203 struct io_context *, gfp_t);
204 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
205 struct io_context *);
207 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
208 int is_sync)
210 return cic->cfqq[!!is_sync];
213 static inline void cic_set_cfqq(struct cfq_io_context *cic,
214 struct cfq_queue *cfqq, int is_sync)
216 cic->cfqq[!!is_sync] = cfqq;
220 * We regard a request as SYNC, if it's either a read or has the SYNC bit
221 * set (in which case it could also be direct WRITE).
223 static inline int cfq_bio_sync(struct bio *bio)
225 if (bio_data_dir(bio) == READ || bio_sync(bio))
226 return 1;
228 return 0;
232 * scheduler run of queue, if there are requests pending and no one in the
233 * driver that will restart queueing
235 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
237 if (cfqd->busy_queues)
238 kblockd_schedule_work(&cfqd->unplug_work);
241 static int cfq_queue_empty(struct request_queue *q)
243 struct cfq_data *cfqd = q->elevator->elevator_data;
245 return !cfqd->busy_queues;
249 * Scale schedule slice based on io priority. Use the sync time slice only
250 * if a queue is marked sync and has sync io queued. A sync queue with async
251 * io only, should not get full sync slice length.
253 static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
254 unsigned short prio)
256 const int base_slice = cfqd->cfq_slice[sync];
258 WARN_ON(prio >= IOPRIO_BE_NR);
260 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
263 static inline int
264 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
266 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
269 static inline void
270 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
272 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
276 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
277 * isn't valid until the first request from the dispatch is activated
278 * and the slice time set.
280 static inline int cfq_slice_used(struct cfq_queue *cfqq)
282 if (cfq_cfqq_slice_new(cfqq))
283 return 0;
284 if (time_before(jiffies, cfqq->slice_end))
285 return 0;
287 return 1;
291 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
292 * We choose the request that is closest to the head right now. Distance
293 * behind the head is penalized and only allowed to a certain extent.
295 static struct request *
296 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
298 sector_t last, s1, s2, d1 = 0, d2 = 0;
299 unsigned long back_max;
300 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
301 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
302 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
304 if (rq1 == NULL || rq1 == rq2)
305 return rq2;
306 if (rq2 == NULL)
307 return rq1;
309 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
310 return rq1;
311 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
312 return rq2;
313 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
314 return rq1;
315 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
316 return rq2;
318 s1 = rq1->sector;
319 s2 = rq2->sector;
321 last = cfqd->last_position;
324 * by definition, 1KiB is 2 sectors
326 back_max = cfqd->cfq_back_max * 2;
329 * Strict one way elevator _except_ in the case where we allow
330 * short backward seeks which are biased as twice the cost of a
331 * similar forward seek.
333 if (s1 >= last)
334 d1 = s1 - last;
335 else if (s1 + back_max >= last)
336 d1 = (last - s1) * cfqd->cfq_back_penalty;
337 else
338 wrap |= CFQ_RQ1_WRAP;
340 if (s2 >= last)
341 d2 = s2 - last;
342 else if (s2 + back_max >= last)
343 d2 = (last - s2) * cfqd->cfq_back_penalty;
344 else
345 wrap |= CFQ_RQ2_WRAP;
347 /* Found required data */
350 * By doing switch() on the bit mask "wrap" we avoid having to
351 * check two variables for all permutations: --> faster!
353 switch (wrap) {
354 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
355 if (d1 < d2)
356 return rq1;
357 else if (d2 < d1)
358 return rq2;
359 else {
360 if (s1 >= s2)
361 return rq1;
362 else
363 return rq2;
366 case CFQ_RQ2_WRAP:
367 return rq1;
368 case CFQ_RQ1_WRAP:
369 return rq2;
370 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
371 default:
373 * Since both rqs are wrapped,
374 * start with the one that's further behind head
375 * (--> only *one* back seek required),
376 * since back seek takes more time than forward.
378 if (s1 <= s2)
379 return rq1;
380 else
381 return rq2;
386 * The below is leftmost cache rbtree addon
388 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
390 if (!root->left)
391 root->left = rb_first(&root->rb);
393 if (root->left)
394 return rb_entry(root->left, struct cfq_queue, rb_node);
396 return NULL;
399 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
401 if (root->left == n)
402 root->left = NULL;
404 rb_erase(n, &root->rb);
405 RB_CLEAR_NODE(n);
409 * would be nice to take fifo expire time into account as well
411 static struct request *
412 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
413 struct request *last)
415 struct rb_node *rbnext = rb_next(&last->rb_node);
416 struct rb_node *rbprev = rb_prev(&last->rb_node);
417 struct request *next = NULL, *prev = NULL;
419 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
421 if (rbprev)
422 prev = rb_entry_rq(rbprev);
424 if (rbnext)
425 next = rb_entry_rq(rbnext);
426 else {
427 rbnext = rb_first(&cfqq->sort_list);
428 if (rbnext && rbnext != &last->rb_node)
429 next = rb_entry_rq(rbnext);
432 return cfq_choose_req(cfqd, next, prev);
435 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
436 struct cfq_queue *cfqq)
439 * just an approximation, should be ok.
441 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
442 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
446 * The cfqd->service_tree holds all pending cfq_queue's that have
447 * requests waiting to be processed. It is sorted in the order that
448 * we will service the queues.
450 static void cfq_service_tree_add(struct cfq_data *cfqd,
451 struct cfq_queue *cfqq, int add_front)
453 struct rb_node **p, *parent;
454 struct cfq_queue *__cfqq;
455 unsigned long rb_key;
456 int left;
458 if (cfq_class_idle(cfqq)) {
459 rb_key = CFQ_IDLE_DELAY;
460 parent = rb_last(&cfqd->service_tree.rb);
461 if (parent && parent != &cfqq->rb_node) {
462 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
463 rb_key += __cfqq->rb_key;
464 } else
465 rb_key += jiffies;
466 } else if (!add_front) {
467 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
468 rb_key += cfqq->slice_resid;
469 cfqq->slice_resid = 0;
470 } else
471 rb_key = 0;
473 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
475 * same position, nothing more to do
477 if (rb_key == cfqq->rb_key)
478 return;
480 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
483 left = 1;
484 parent = NULL;
485 p = &cfqd->service_tree.rb.rb_node;
486 while (*p) {
487 struct rb_node **n;
489 parent = *p;
490 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
493 * sort RT queues first, we always want to give
494 * preference to them. IDLE queues goes to the back.
495 * after that, sort on the next service time.
497 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
498 n = &(*p)->rb_left;
499 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
500 n = &(*p)->rb_right;
501 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
502 n = &(*p)->rb_left;
503 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
504 n = &(*p)->rb_right;
505 else if (rb_key < __cfqq->rb_key)
506 n = &(*p)->rb_left;
507 else
508 n = &(*p)->rb_right;
510 if (n == &(*p)->rb_right)
511 left = 0;
513 p = n;
516 if (left)
517 cfqd->service_tree.left = &cfqq->rb_node;
519 cfqq->rb_key = rb_key;
520 rb_link_node(&cfqq->rb_node, parent, p);
521 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
525 * Update cfqq's position in the service tree.
527 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
530 * Resorting requires the cfqq to be on the RR list already.
532 if (cfq_cfqq_on_rr(cfqq))
533 cfq_service_tree_add(cfqd, cfqq, 0);
537 * add to busy list of queues for service, trying to be fair in ordering
538 * the pending list according to last request service
540 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
542 BUG_ON(cfq_cfqq_on_rr(cfqq));
543 cfq_mark_cfqq_on_rr(cfqq);
544 cfqd->busy_queues++;
546 cfq_resort_rr_list(cfqd, cfqq);
550 * Called when the cfqq no longer has requests pending, remove it from
551 * the service tree.
553 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
555 BUG_ON(!cfq_cfqq_on_rr(cfqq));
556 cfq_clear_cfqq_on_rr(cfqq);
558 if (!RB_EMPTY_NODE(&cfqq->rb_node))
559 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
561 BUG_ON(!cfqd->busy_queues);
562 cfqd->busy_queues--;
566 * rb tree support functions
568 static void cfq_del_rq_rb(struct request *rq)
570 struct cfq_queue *cfqq = RQ_CFQQ(rq);
571 struct cfq_data *cfqd = cfqq->cfqd;
572 const int sync = rq_is_sync(rq);
574 BUG_ON(!cfqq->queued[sync]);
575 cfqq->queued[sync]--;
577 elv_rb_del(&cfqq->sort_list, rq);
579 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
580 cfq_del_cfqq_rr(cfqd, cfqq);
583 static void cfq_add_rq_rb(struct request *rq)
585 struct cfq_queue *cfqq = RQ_CFQQ(rq);
586 struct cfq_data *cfqd = cfqq->cfqd;
587 struct request *__alias;
589 cfqq->queued[rq_is_sync(rq)]++;
592 * looks a little odd, but the first insert might return an alias.
593 * if that happens, put the alias on the dispatch list
595 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
596 cfq_dispatch_insert(cfqd->queue, __alias);
598 if (!cfq_cfqq_on_rr(cfqq))
599 cfq_add_cfqq_rr(cfqd, cfqq);
602 * check if this request is a better next-serve candidate
604 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
605 BUG_ON(!cfqq->next_rq);
608 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
610 elv_rb_del(&cfqq->sort_list, rq);
611 cfqq->queued[rq_is_sync(rq)]--;
612 cfq_add_rq_rb(rq);
615 static struct request *
616 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
618 struct task_struct *tsk = current;
619 struct cfq_io_context *cic;
620 struct cfq_queue *cfqq;
622 cic = cfq_cic_lookup(cfqd, tsk->io_context);
623 if (!cic)
624 return NULL;
626 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
627 if (cfqq) {
628 sector_t sector = bio->bi_sector + bio_sectors(bio);
630 return elv_rb_find(&cfqq->sort_list, sector);
633 return NULL;
636 static void cfq_activate_request(struct request_queue *q, struct request *rq)
638 struct cfq_data *cfqd = q->elevator->elevator_data;
640 cfqd->rq_in_driver++;
643 * If the depth is larger 1, it really could be queueing. But lets
644 * make the mark a little higher - idling could still be good for
645 * low queueing, and a low queueing number could also just indicate
646 * a SCSI mid layer like behaviour where limit+1 is often seen.
648 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
649 cfqd->hw_tag = 1;
651 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
654 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
656 struct cfq_data *cfqd = q->elevator->elevator_data;
658 WARN_ON(!cfqd->rq_in_driver);
659 cfqd->rq_in_driver--;
662 static void cfq_remove_request(struct request *rq)
664 struct cfq_queue *cfqq = RQ_CFQQ(rq);
666 if (cfqq->next_rq == rq)
667 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
669 list_del_init(&rq->queuelist);
670 cfq_del_rq_rb(rq);
672 if (rq_is_meta(rq)) {
673 WARN_ON(!cfqq->meta_pending);
674 cfqq->meta_pending--;
678 static int cfq_merge(struct request_queue *q, struct request **req,
679 struct bio *bio)
681 struct cfq_data *cfqd = q->elevator->elevator_data;
682 struct request *__rq;
684 __rq = cfq_find_rq_fmerge(cfqd, bio);
685 if (__rq && elv_rq_merge_ok(__rq, bio)) {
686 *req = __rq;
687 return ELEVATOR_FRONT_MERGE;
690 return ELEVATOR_NO_MERGE;
693 static void cfq_merged_request(struct request_queue *q, struct request *req,
694 int type)
696 if (type == ELEVATOR_FRONT_MERGE) {
697 struct cfq_queue *cfqq = RQ_CFQQ(req);
699 cfq_reposition_rq_rb(cfqq, req);
703 static void
704 cfq_merged_requests(struct request_queue *q, struct request *rq,
705 struct request *next)
708 * reposition in fifo if next is older than rq
710 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
711 time_before(next->start_time, rq->start_time))
712 list_move(&rq->queuelist, &next->queuelist);
714 cfq_remove_request(next);
717 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
718 struct bio *bio)
720 struct cfq_data *cfqd = q->elevator->elevator_data;
721 struct cfq_io_context *cic;
722 struct cfq_queue *cfqq;
725 * Disallow merge of a sync bio into an async request.
727 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
728 return 0;
731 * Lookup the cfqq that this bio will be queued with. Allow
732 * merge only if rq is queued there.
734 cic = cfq_cic_lookup(cfqd, current->io_context);
735 if (!cic)
736 return 0;
738 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
739 if (cfqq == RQ_CFQQ(rq))
740 return 1;
742 return 0;
745 static void __cfq_set_active_queue(struct cfq_data *cfqd,
746 struct cfq_queue *cfqq)
748 if (cfqq) {
749 cfqq->slice_end = 0;
750 cfq_clear_cfqq_must_alloc_slice(cfqq);
751 cfq_clear_cfqq_fifo_expire(cfqq);
752 cfq_mark_cfqq_slice_new(cfqq);
753 cfq_clear_cfqq_queue_new(cfqq);
756 cfqd->active_queue = cfqq;
760 * current cfqq expired its slice (or was too idle), select new one
762 static void
763 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
764 int timed_out)
766 if (cfq_cfqq_wait_request(cfqq))
767 del_timer(&cfqd->idle_slice_timer);
769 cfq_clear_cfqq_must_dispatch(cfqq);
770 cfq_clear_cfqq_wait_request(cfqq);
773 * store what was left of this slice, if the queue idled/timed out
775 if (timed_out && !cfq_cfqq_slice_new(cfqq))
776 cfqq->slice_resid = cfqq->slice_end - jiffies;
778 cfq_resort_rr_list(cfqd, cfqq);
780 if (cfqq == cfqd->active_queue)
781 cfqd->active_queue = NULL;
783 if (cfqd->active_cic) {
784 put_io_context(cfqd->active_cic->ioc);
785 cfqd->active_cic = NULL;
789 static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
791 struct cfq_queue *cfqq = cfqd->active_queue;
793 if (cfqq)
794 __cfq_slice_expired(cfqd, cfqq, timed_out);
798 * Get next queue for service. Unless we have a queue preemption,
799 * we'll simply select the first cfqq in the service tree.
801 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
803 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
804 return NULL;
806 return cfq_rb_first(&cfqd->service_tree);
810 * Get and set a new active queue for service.
812 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
814 struct cfq_queue *cfqq;
816 cfqq = cfq_get_next_queue(cfqd);
817 __cfq_set_active_queue(cfqd, cfqq);
818 return cfqq;
821 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
822 struct request *rq)
824 if (rq->sector >= cfqd->last_position)
825 return rq->sector - cfqd->last_position;
826 else
827 return cfqd->last_position - rq->sector;
830 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
832 struct cfq_io_context *cic = cfqd->active_cic;
834 if (!sample_valid(cic->seek_samples))
835 return 0;
837 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
840 static int cfq_close_cooperator(struct cfq_data *cfq_data,
841 struct cfq_queue *cfqq)
844 * We should notice if some of the queues are cooperating, eg
845 * working closely on the same area of the disk. In that case,
846 * we can group them together and don't waste time idling.
848 return 0;
851 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
853 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
855 struct cfq_queue *cfqq = cfqd->active_queue;
856 struct cfq_io_context *cic;
857 unsigned long sl;
859 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
860 WARN_ON(cfq_cfqq_slice_new(cfqq));
863 * idle is disabled, either manually or by past process history
865 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
866 return;
869 * task has exited, don't wait
871 cic = cfqd->active_cic;
872 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
873 return;
876 * See if this prio level has a good candidate
878 if (cfq_close_cooperator(cfqd, cfqq) &&
879 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
880 return;
882 cfq_mark_cfqq_must_dispatch(cfqq);
883 cfq_mark_cfqq_wait_request(cfqq);
886 * we don't want to idle for seeks, but we do want to allow
887 * fair distribution of slice time for a process doing back-to-back
888 * seeks. so allow a little bit of time for him to submit a new rq
890 sl = cfqd->cfq_slice_idle;
891 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
892 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
894 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
898 * Move request from internal lists to the request queue dispatch list.
900 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
902 struct cfq_data *cfqd = q->elevator->elevator_data;
903 struct cfq_queue *cfqq = RQ_CFQQ(rq);
905 cfq_remove_request(rq);
906 cfqq->dispatched++;
907 elv_dispatch_sort(q, rq);
909 if (cfq_cfqq_sync(cfqq))
910 cfqd->sync_flight++;
914 * return expired entry, or NULL to just start from scratch in rbtree
916 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
918 struct cfq_data *cfqd = cfqq->cfqd;
919 struct request *rq;
920 int fifo;
922 if (cfq_cfqq_fifo_expire(cfqq))
923 return NULL;
925 cfq_mark_cfqq_fifo_expire(cfqq);
927 if (list_empty(&cfqq->fifo))
928 return NULL;
930 fifo = cfq_cfqq_sync(cfqq);
931 rq = rq_entry_fifo(cfqq->fifo.next);
933 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
934 return NULL;
936 return rq;
939 static inline int
940 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
942 const int base_rq = cfqd->cfq_slice_async_rq;
944 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
946 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
950 * Select a queue for service. If we have a current active queue,
951 * check whether to continue servicing it, or retrieve and set a new one.
953 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
955 struct cfq_queue *cfqq;
957 cfqq = cfqd->active_queue;
958 if (!cfqq)
959 goto new_queue;
962 * The active queue has run out of time, expire it and select new.
964 if (cfq_slice_used(cfqq))
965 goto expire;
968 * The active queue has requests and isn't expired, allow it to
969 * dispatch.
971 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
972 goto keep_queue;
975 * No requests pending. If the active queue still has requests in
976 * flight or is idling for a new request, allow either of these
977 * conditions to happen (or time out) before selecting a new queue.
979 if (timer_pending(&cfqd->idle_slice_timer) ||
980 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
981 cfqq = NULL;
982 goto keep_queue;
985 expire:
986 cfq_slice_expired(cfqd, 0);
987 new_queue:
988 cfqq = cfq_set_active_queue(cfqd);
989 keep_queue:
990 return cfqq;
994 * Dispatch some requests from cfqq, moving them to the request queue
995 * dispatch list.
997 static int
998 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
999 int max_dispatch)
1001 int dispatched = 0;
1003 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1005 do {
1006 struct request *rq;
1009 * follow expired path, else get first next available
1011 rq = cfq_check_fifo(cfqq);
1012 if (rq == NULL)
1013 rq = cfqq->next_rq;
1016 * finally, insert request into driver dispatch list
1018 cfq_dispatch_insert(cfqd->queue, rq);
1020 dispatched++;
1022 if (!cfqd->active_cic) {
1023 atomic_inc(&RQ_CIC(rq)->ioc->refcount);
1024 cfqd->active_cic = RQ_CIC(rq);
1027 if (RB_EMPTY_ROOT(&cfqq->sort_list))
1028 break;
1030 } while (dispatched < max_dispatch);
1033 * expire an async queue immediately if it has used up its slice. idle
1034 * queue always expire after 1 dispatch round.
1036 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1037 dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1038 cfq_class_idle(cfqq))) {
1039 cfqq->slice_end = jiffies + 1;
1040 cfq_slice_expired(cfqd, 0);
1043 return dispatched;
1046 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1048 int dispatched = 0;
1050 while (cfqq->next_rq) {
1051 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1052 dispatched++;
1055 BUG_ON(!list_empty(&cfqq->fifo));
1056 return dispatched;
1060 * Drain our current requests. Used for barriers and when switching
1061 * io schedulers on-the-fly.
1063 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1065 struct cfq_queue *cfqq;
1066 int dispatched = 0;
1068 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
1069 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1071 cfq_slice_expired(cfqd, 0);
1073 BUG_ON(cfqd->busy_queues);
1075 return dispatched;
1078 static int cfq_dispatch_requests(struct request_queue *q, int force)
1080 struct cfq_data *cfqd = q->elevator->elevator_data;
1081 struct cfq_queue *cfqq;
1082 int dispatched;
1084 if (!cfqd->busy_queues)
1085 return 0;
1087 if (unlikely(force))
1088 return cfq_forced_dispatch(cfqd);
1090 dispatched = 0;
1091 while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1092 int max_dispatch;
1094 max_dispatch = cfqd->cfq_quantum;
1095 if (cfq_class_idle(cfqq))
1096 max_dispatch = 1;
1098 if (cfqq->dispatched >= max_dispatch) {
1099 if (cfqd->busy_queues > 1)
1100 break;
1101 if (cfqq->dispatched >= 4 * max_dispatch)
1102 break;
1105 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1106 break;
1108 cfq_clear_cfqq_must_dispatch(cfqq);
1109 cfq_clear_cfqq_wait_request(cfqq);
1110 del_timer(&cfqd->idle_slice_timer);
1112 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1115 return dispatched;
1119 * task holds one reference to the queue, dropped when task exits. each rq
1120 * in-flight on this queue also holds a reference, dropped when rq is freed.
1122 * queue lock must be held here.
1124 static void cfq_put_queue(struct cfq_queue *cfqq)
1126 struct cfq_data *cfqd = cfqq->cfqd;
1128 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1130 if (!atomic_dec_and_test(&cfqq->ref))
1131 return;
1133 BUG_ON(rb_first(&cfqq->sort_list));
1134 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1135 BUG_ON(cfq_cfqq_on_rr(cfqq));
1137 if (unlikely(cfqd->active_queue == cfqq)) {
1138 __cfq_slice_expired(cfqd, cfqq, 0);
1139 cfq_schedule_dispatch(cfqd);
1142 kmem_cache_free(cfq_pool, cfqq);
1146 * Call func for each cic attached to this ioc.
1148 static void
1149 call_for_each_cic(struct io_context *ioc,
1150 void (*func)(struct io_context *, struct cfq_io_context *))
1152 struct cfq_io_context *cic;
1153 struct hlist_node *n;
1155 rcu_read_lock();
1156 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1157 func(ioc, cic);
1158 rcu_read_unlock();
1161 static void cfq_cic_free_rcu(struct rcu_head *head)
1163 struct cfq_io_context *cic;
1165 cic = container_of(head, struct cfq_io_context, rcu_head);
1167 kmem_cache_free(cfq_ioc_pool, cic);
1168 elv_ioc_count_dec(ioc_count);
1170 if (ioc_gone && !elv_ioc_count_read(ioc_count))
1171 complete(ioc_gone);
1174 static void cfq_cic_free(struct cfq_io_context *cic)
1176 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1179 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1181 unsigned long flags;
1183 BUG_ON(!cic->dead_key);
1185 spin_lock_irqsave(&ioc->lock, flags);
1186 radix_tree_delete(&ioc->radix_root, cic->dead_key);
1187 hlist_del_rcu(&cic->cic_list);
1188 spin_unlock_irqrestore(&ioc->lock, flags);
1190 cfq_cic_free(cic);
1193 static void cfq_free_io_context(struct io_context *ioc)
1196 * ioc->refcount is zero here, or we are called from elv_unregister(),
1197 * so no more cic's are allowed to be linked into this ioc. So it
1198 * should be ok to iterate over the known list, we will see all cic's
1199 * since no new ones are added.
1201 call_for_each_cic(ioc, cic_free_func);
1204 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1206 if (unlikely(cfqq == cfqd->active_queue)) {
1207 __cfq_slice_expired(cfqd, cfqq, 0);
1208 cfq_schedule_dispatch(cfqd);
1211 cfq_put_queue(cfqq);
1214 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1215 struct cfq_io_context *cic)
1217 list_del_init(&cic->queue_list);
1220 * Make sure key == NULL is seen for dead queues
1222 smp_wmb();
1223 cic->dead_key = (unsigned long) cic->key;
1224 cic->key = NULL;
1226 if (cic->cfqq[ASYNC]) {
1227 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1228 cic->cfqq[ASYNC] = NULL;
1231 if (cic->cfqq[SYNC]) {
1232 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1233 cic->cfqq[SYNC] = NULL;
1237 static void cfq_exit_single_io_context(struct io_context *ioc,
1238 struct cfq_io_context *cic)
1240 struct cfq_data *cfqd = cic->key;
1242 if (cfqd) {
1243 struct request_queue *q = cfqd->queue;
1244 unsigned long flags;
1246 spin_lock_irqsave(q->queue_lock, flags);
1247 __cfq_exit_single_io_context(cfqd, cic);
1248 spin_unlock_irqrestore(q->queue_lock, flags);
1253 * The process that ioc belongs to has exited, we need to clean up
1254 * and put the internal structures we have that belongs to that process.
1256 static void cfq_exit_io_context(struct io_context *ioc)
1258 rcu_assign_pointer(ioc->ioc_data, NULL);
1259 call_for_each_cic(ioc, cfq_exit_single_io_context);
1262 static struct cfq_io_context *
1263 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1265 struct cfq_io_context *cic;
1267 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1268 cfqd->queue->node);
1269 if (cic) {
1270 cic->last_end_request = jiffies;
1271 INIT_LIST_HEAD(&cic->queue_list);
1272 INIT_HLIST_NODE(&cic->cic_list);
1273 cic->dtor = cfq_free_io_context;
1274 cic->exit = cfq_exit_io_context;
1275 elv_ioc_count_inc(ioc_count);
1278 return cic;
1281 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1283 struct task_struct *tsk = current;
1284 int ioprio_class;
1286 if (!cfq_cfqq_prio_changed(cfqq))
1287 return;
1289 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1290 switch (ioprio_class) {
1291 default:
1292 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1293 case IOPRIO_CLASS_NONE:
1295 * no prio set, place us in the middle of the BE classes
1297 cfqq->ioprio = task_nice_ioprio(tsk);
1298 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1299 break;
1300 case IOPRIO_CLASS_RT:
1301 cfqq->ioprio = task_ioprio(ioc);
1302 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1303 break;
1304 case IOPRIO_CLASS_BE:
1305 cfqq->ioprio = task_ioprio(ioc);
1306 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1307 break;
1308 case IOPRIO_CLASS_IDLE:
1309 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1310 cfqq->ioprio = 7;
1311 cfq_clear_cfqq_idle_window(cfqq);
1312 break;
1316 * keep track of original prio settings in case we have to temporarily
1317 * elevate the priority of this queue
1319 cfqq->org_ioprio = cfqq->ioprio;
1320 cfqq->org_ioprio_class = cfqq->ioprio_class;
1321 cfq_clear_cfqq_prio_changed(cfqq);
1324 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1326 struct cfq_data *cfqd = cic->key;
1327 struct cfq_queue *cfqq;
1328 unsigned long flags;
1330 if (unlikely(!cfqd))
1331 return;
1333 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1335 cfqq = cic->cfqq[ASYNC];
1336 if (cfqq) {
1337 struct cfq_queue *new_cfqq;
1338 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
1339 if (new_cfqq) {
1340 cic->cfqq[ASYNC] = new_cfqq;
1341 cfq_put_queue(cfqq);
1345 cfqq = cic->cfqq[SYNC];
1346 if (cfqq)
1347 cfq_mark_cfqq_prio_changed(cfqq);
1349 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1352 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1354 call_for_each_cic(ioc, changed_ioprio);
1355 ioc->ioprio_changed = 0;
1358 static struct cfq_queue *
1359 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1360 struct io_context *ioc, gfp_t gfp_mask)
1362 struct cfq_queue *cfqq, *new_cfqq = NULL;
1363 struct cfq_io_context *cic;
1365 retry:
1366 cic = cfq_cic_lookup(cfqd, ioc);
1367 /* cic always exists here */
1368 cfqq = cic_to_cfqq(cic, is_sync);
1370 if (!cfqq) {
1371 if (new_cfqq) {
1372 cfqq = new_cfqq;
1373 new_cfqq = NULL;
1374 } else if (gfp_mask & __GFP_WAIT) {
1376 * Inform the allocator of the fact that we will
1377 * just repeat this allocation if it fails, to allow
1378 * the allocator to do whatever it needs to attempt to
1379 * free memory.
1381 spin_unlock_irq(cfqd->queue->queue_lock);
1382 new_cfqq = kmem_cache_alloc_node(cfq_pool,
1383 gfp_mask | __GFP_NOFAIL | __GFP_ZERO,
1384 cfqd->queue->node);
1385 spin_lock_irq(cfqd->queue->queue_lock);
1386 goto retry;
1387 } else {
1388 cfqq = kmem_cache_alloc_node(cfq_pool,
1389 gfp_mask | __GFP_ZERO,
1390 cfqd->queue->node);
1391 if (!cfqq)
1392 goto out;
1395 RB_CLEAR_NODE(&cfqq->rb_node);
1396 INIT_LIST_HEAD(&cfqq->fifo);
1398 atomic_set(&cfqq->ref, 0);
1399 cfqq->cfqd = cfqd;
1401 cfq_mark_cfqq_prio_changed(cfqq);
1402 cfq_mark_cfqq_queue_new(cfqq);
1404 cfq_init_prio_data(cfqq, ioc);
1406 if (is_sync) {
1407 if (!cfq_class_idle(cfqq))
1408 cfq_mark_cfqq_idle_window(cfqq);
1409 cfq_mark_cfqq_sync(cfqq);
1413 if (new_cfqq)
1414 kmem_cache_free(cfq_pool, new_cfqq);
1416 out:
1417 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1418 return cfqq;
1421 static struct cfq_queue **
1422 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1424 switch (ioprio_class) {
1425 case IOPRIO_CLASS_RT:
1426 return &cfqd->async_cfqq[0][ioprio];
1427 case IOPRIO_CLASS_BE:
1428 return &cfqd->async_cfqq[1][ioprio];
1429 case IOPRIO_CLASS_IDLE:
1430 return &cfqd->async_idle_cfqq;
1431 default:
1432 BUG();
1436 static struct cfq_queue *
1437 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
1438 gfp_t gfp_mask)
1440 const int ioprio = task_ioprio(ioc);
1441 const int ioprio_class = task_ioprio_class(ioc);
1442 struct cfq_queue **async_cfqq = NULL;
1443 struct cfq_queue *cfqq = NULL;
1445 if (!is_sync) {
1446 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1447 cfqq = *async_cfqq;
1450 if (!cfqq) {
1451 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
1452 if (!cfqq)
1453 return NULL;
1457 * pin the queue now that it's allocated, scheduler exit will prune it
1459 if (!is_sync && !(*async_cfqq)) {
1460 atomic_inc(&cfqq->ref);
1461 *async_cfqq = cfqq;
1464 atomic_inc(&cfqq->ref);
1465 return cfqq;
1469 * We drop cfq io contexts lazily, so we may find a dead one.
1471 static void
1472 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
1473 struct cfq_io_context *cic)
1475 unsigned long flags;
1477 WARN_ON(!list_empty(&cic->queue_list));
1479 spin_lock_irqsave(&ioc->lock, flags);
1481 if (ioc->ioc_data == cic)
1482 rcu_assign_pointer(ioc->ioc_data, NULL);
1484 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
1485 hlist_del_rcu(&cic->cic_list);
1486 spin_unlock_irqrestore(&ioc->lock, flags);
1488 cfq_cic_free(cic);
1491 static struct cfq_io_context *
1492 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1494 struct cfq_io_context *cic;
1495 void *k;
1497 if (unlikely(!ioc))
1498 return NULL;
1501 * we maintain a last-hit cache, to avoid browsing over the tree
1503 cic = rcu_dereference(ioc->ioc_data);
1504 if (cic && cic->key == cfqd)
1505 return cic;
1507 do {
1508 rcu_read_lock();
1509 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
1510 rcu_read_unlock();
1511 if (!cic)
1512 break;
1513 /* ->key must be copied to avoid race with cfq_exit_queue() */
1514 k = cic->key;
1515 if (unlikely(!k)) {
1516 cfq_drop_dead_cic(cfqd, ioc, cic);
1517 continue;
1520 rcu_assign_pointer(ioc->ioc_data, cic);
1521 break;
1522 } while (1);
1524 return cic;
1528 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
1529 * the process specific cfq io context when entered from the block layer.
1530 * Also adds the cic to a per-cfqd list, used when this queue is removed.
1532 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1533 struct cfq_io_context *cic, gfp_t gfp_mask)
1535 unsigned long flags;
1536 int ret;
1538 ret = radix_tree_preload(gfp_mask);
1539 if (!ret) {
1540 cic->ioc = ioc;
1541 cic->key = cfqd;
1543 spin_lock_irqsave(&ioc->lock, flags);
1544 ret = radix_tree_insert(&ioc->radix_root,
1545 (unsigned long) cfqd, cic);
1546 if (!ret)
1547 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
1548 spin_unlock_irqrestore(&ioc->lock, flags);
1550 radix_tree_preload_end();
1552 if (!ret) {
1553 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1554 list_add(&cic->queue_list, &cfqd->cic_list);
1555 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1559 if (ret)
1560 printk(KERN_ERR "cfq: cic link failed!\n");
1562 return ret;
1566 * Setup general io context and cfq io context. There can be several cfq
1567 * io contexts per general io context, if this process is doing io to more
1568 * than one device managed by cfq.
1570 static struct cfq_io_context *
1571 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1573 struct io_context *ioc = NULL;
1574 struct cfq_io_context *cic;
1576 might_sleep_if(gfp_mask & __GFP_WAIT);
1578 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1579 if (!ioc)
1580 return NULL;
1582 cic = cfq_cic_lookup(cfqd, ioc);
1583 if (cic)
1584 goto out;
1586 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1587 if (cic == NULL)
1588 goto err;
1590 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
1591 goto err_free;
1593 out:
1594 smp_read_barrier_depends();
1595 if (unlikely(ioc->ioprio_changed))
1596 cfq_ioc_set_ioprio(ioc);
1598 return cic;
1599 err_free:
1600 cfq_cic_free(cic);
1601 err:
1602 put_io_context(ioc);
1603 return NULL;
1606 static void
1607 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1609 unsigned long elapsed = jiffies - cic->last_end_request;
1610 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1612 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1613 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1614 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1617 static void
1618 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1619 struct request *rq)
1621 sector_t sdist;
1622 u64 total;
1624 if (cic->last_request_pos < rq->sector)
1625 sdist = rq->sector - cic->last_request_pos;
1626 else
1627 sdist = cic->last_request_pos - rq->sector;
1630 * Don't allow the seek distance to get too large from the
1631 * odd fragment, pagein, etc
1633 if (cic->seek_samples <= 60) /* second&third seek */
1634 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1635 else
1636 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1638 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1639 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1640 total = cic->seek_total + (cic->seek_samples/2);
1641 do_div(total, cic->seek_samples);
1642 cic->seek_mean = (sector_t)total;
1646 * Disable idle window if the process thinks too long or seeks so much that
1647 * it doesn't matter
1649 static void
1650 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1651 struct cfq_io_context *cic)
1653 int enable_idle;
1656 * Don't idle for async or idle io prio class
1658 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
1659 return;
1661 enable_idle = cfq_cfqq_idle_window(cfqq);
1663 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
1664 (cfqd->hw_tag && CIC_SEEKY(cic)))
1665 enable_idle = 0;
1666 else if (sample_valid(cic->ttime_samples)) {
1667 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1668 enable_idle = 0;
1669 else
1670 enable_idle = 1;
1673 if (enable_idle)
1674 cfq_mark_cfqq_idle_window(cfqq);
1675 else
1676 cfq_clear_cfqq_idle_window(cfqq);
1680 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1681 * no or if we aren't sure, a 1 will cause a preempt.
1683 static int
1684 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1685 struct request *rq)
1687 struct cfq_queue *cfqq;
1689 cfqq = cfqd->active_queue;
1690 if (!cfqq)
1691 return 0;
1693 if (cfq_slice_used(cfqq))
1694 return 1;
1696 if (cfq_class_idle(new_cfqq))
1697 return 0;
1699 if (cfq_class_idle(cfqq))
1700 return 1;
1703 * if the new request is sync, but the currently running queue is
1704 * not, let the sync request have priority.
1706 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1707 return 1;
1710 * So both queues are sync. Let the new request get disk time if
1711 * it's a metadata request and the current queue is doing regular IO.
1713 if (rq_is_meta(rq) && !cfqq->meta_pending)
1714 return 1;
1716 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1717 return 0;
1720 * if this request is as-good as one we would expect from the
1721 * current cfqq, let it preempt
1723 if (cfq_rq_close(cfqd, rq))
1724 return 1;
1726 return 0;
1730 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1731 * let it have half of its nominal slice.
1733 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1735 cfq_slice_expired(cfqd, 1);
1738 * Put the new queue at the front of the of the current list,
1739 * so we know that it will be selected next.
1741 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1743 cfq_service_tree_add(cfqd, cfqq, 1);
1745 cfqq->slice_end = 0;
1746 cfq_mark_cfqq_slice_new(cfqq);
1750 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1751 * something we should do about it
1753 static void
1754 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1755 struct request *rq)
1757 struct cfq_io_context *cic = RQ_CIC(rq);
1759 if (rq_is_meta(rq))
1760 cfqq->meta_pending++;
1762 cfq_update_io_thinktime(cfqd, cic);
1763 cfq_update_io_seektime(cfqd, cic, rq);
1764 cfq_update_idle_window(cfqd, cfqq, cic);
1766 cic->last_request_pos = rq->sector + rq->nr_sectors;
1768 if (cfqq == cfqd->active_queue) {
1770 * if we are waiting for a request for this queue, let it rip
1771 * immediately and flag that we must not expire this queue
1772 * just now
1774 if (cfq_cfqq_wait_request(cfqq)) {
1775 cfq_mark_cfqq_must_dispatch(cfqq);
1776 del_timer(&cfqd->idle_slice_timer);
1777 blk_start_queueing(cfqd->queue);
1779 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1781 * not the active queue - expire current slice if it is
1782 * idle and has expired it's mean thinktime or this new queue
1783 * has some old slice time left and is of higher priority
1785 cfq_preempt_queue(cfqd, cfqq);
1786 cfq_mark_cfqq_must_dispatch(cfqq);
1787 blk_start_queueing(cfqd->queue);
1791 static void cfq_insert_request(struct request_queue *q, struct request *rq)
1793 struct cfq_data *cfqd = q->elevator->elevator_data;
1794 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1796 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
1798 cfq_add_rq_rb(rq);
1800 list_add_tail(&rq->queuelist, &cfqq->fifo);
1802 cfq_rq_enqueued(cfqd, cfqq, rq);
1805 static void cfq_completed_request(struct request_queue *q, struct request *rq)
1807 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1808 struct cfq_data *cfqd = cfqq->cfqd;
1809 const int sync = rq_is_sync(rq);
1810 unsigned long now;
1812 now = jiffies;
1814 WARN_ON(!cfqd->rq_in_driver);
1815 WARN_ON(!cfqq->dispatched);
1816 cfqd->rq_in_driver--;
1817 cfqq->dispatched--;
1819 if (cfq_cfqq_sync(cfqq))
1820 cfqd->sync_flight--;
1822 if (!cfq_class_idle(cfqq))
1823 cfqd->last_end_request = now;
1825 if (sync)
1826 RQ_CIC(rq)->last_end_request = now;
1829 * If this is the active queue, check if it needs to be expired,
1830 * or if we want to idle in case it has no pending requests.
1832 if (cfqd->active_queue == cfqq) {
1833 if (cfq_cfqq_slice_new(cfqq)) {
1834 cfq_set_prio_slice(cfqd, cfqq);
1835 cfq_clear_cfqq_slice_new(cfqq);
1837 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
1838 cfq_slice_expired(cfqd, 1);
1839 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
1840 cfq_arm_slice_timer(cfqd);
1843 if (!cfqd->rq_in_driver)
1844 cfq_schedule_dispatch(cfqd);
1848 * we temporarily boost lower priority queues if they are holding fs exclusive
1849 * resources. they are boosted to normal prio (CLASS_BE/4)
1851 static void cfq_prio_boost(struct cfq_queue *cfqq)
1853 if (has_fs_excl()) {
1855 * boost idle prio on transactions that would lock out other
1856 * users of the filesystem
1858 if (cfq_class_idle(cfqq))
1859 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1860 if (cfqq->ioprio > IOPRIO_NORM)
1861 cfqq->ioprio = IOPRIO_NORM;
1862 } else {
1864 * check if we need to unboost the queue
1866 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1867 cfqq->ioprio_class = cfqq->org_ioprio_class;
1868 if (cfqq->ioprio != cfqq->org_ioprio)
1869 cfqq->ioprio = cfqq->org_ioprio;
1873 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1875 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1876 !cfq_cfqq_must_alloc_slice(cfqq)) {
1877 cfq_mark_cfqq_must_alloc_slice(cfqq);
1878 return ELV_MQUEUE_MUST;
1881 return ELV_MQUEUE_MAY;
1884 static int cfq_may_queue(struct request_queue *q, int rw)
1886 struct cfq_data *cfqd = q->elevator->elevator_data;
1887 struct task_struct *tsk = current;
1888 struct cfq_io_context *cic;
1889 struct cfq_queue *cfqq;
1892 * don't force setup of a queue from here, as a call to may_queue
1893 * does not necessarily imply that a request actually will be queued.
1894 * so just lookup a possibly existing queue, or return 'may queue'
1895 * if that fails
1897 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1898 if (!cic)
1899 return ELV_MQUEUE_MAY;
1901 cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
1902 if (cfqq) {
1903 cfq_init_prio_data(cfqq, cic->ioc);
1904 cfq_prio_boost(cfqq);
1906 return __cfq_may_queue(cfqq);
1909 return ELV_MQUEUE_MAY;
1913 * queue lock held here
1915 static void cfq_put_request(struct request *rq)
1917 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1919 if (cfqq) {
1920 const int rw = rq_data_dir(rq);
1922 BUG_ON(!cfqq->allocated[rw]);
1923 cfqq->allocated[rw]--;
1925 put_io_context(RQ_CIC(rq)->ioc);
1927 rq->elevator_private = NULL;
1928 rq->elevator_private2 = NULL;
1930 cfq_put_queue(cfqq);
1935 * Allocate cfq data structures associated with this request.
1937 static int
1938 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
1940 struct cfq_data *cfqd = q->elevator->elevator_data;
1941 struct cfq_io_context *cic;
1942 const int rw = rq_data_dir(rq);
1943 const int is_sync = rq_is_sync(rq);
1944 struct cfq_queue *cfqq;
1945 unsigned long flags;
1947 might_sleep_if(gfp_mask & __GFP_WAIT);
1949 cic = cfq_get_io_context(cfqd, gfp_mask);
1951 spin_lock_irqsave(q->queue_lock, flags);
1953 if (!cic)
1954 goto queue_fail;
1956 cfqq = cic_to_cfqq(cic, is_sync);
1957 if (!cfqq) {
1958 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
1960 if (!cfqq)
1961 goto queue_fail;
1963 cic_set_cfqq(cic, cfqq, is_sync);
1966 cfqq->allocated[rw]++;
1967 cfq_clear_cfqq_must_alloc(cfqq);
1968 atomic_inc(&cfqq->ref);
1970 spin_unlock_irqrestore(q->queue_lock, flags);
1972 rq->elevator_private = cic;
1973 rq->elevator_private2 = cfqq;
1974 return 0;
1976 queue_fail:
1977 if (cic)
1978 put_io_context(cic->ioc);
1980 cfq_schedule_dispatch(cfqd);
1981 spin_unlock_irqrestore(q->queue_lock, flags);
1982 return 1;
1985 static void cfq_kick_queue(struct work_struct *work)
1987 struct cfq_data *cfqd =
1988 container_of(work, struct cfq_data, unplug_work);
1989 struct request_queue *q = cfqd->queue;
1990 unsigned long flags;
1992 spin_lock_irqsave(q->queue_lock, flags);
1993 blk_start_queueing(q);
1994 spin_unlock_irqrestore(q->queue_lock, flags);
1998 * Timer running if the active_queue is currently idling inside its time slice
2000 static void cfq_idle_slice_timer(unsigned long data)
2002 struct cfq_data *cfqd = (struct cfq_data *) data;
2003 struct cfq_queue *cfqq;
2004 unsigned long flags;
2005 int timed_out = 1;
2007 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2009 cfqq = cfqd->active_queue;
2010 if (cfqq) {
2011 timed_out = 0;
2014 * expired
2016 if (cfq_slice_used(cfqq))
2017 goto expire;
2020 * only expire and reinvoke request handler, if there are
2021 * other queues with pending requests
2023 if (!cfqd->busy_queues)
2024 goto out_cont;
2027 * not expired and it has a request pending, let it dispatch
2029 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
2030 cfq_mark_cfqq_must_dispatch(cfqq);
2031 goto out_kick;
2034 expire:
2035 cfq_slice_expired(cfqd, timed_out);
2036 out_kick:
2037 cfq_schedule_dispatch(cfqd);
2038 out_cont:
2039 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2042 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2044 del_timer_sync(&cfqd->idle_slice_timer);
2045 kblockd_flush_work(&cfqd->unplug_work);
2048 static void cfq_put_async_queues(struct cfq_data *cfqd)
2050 int i;
2052 for (i = 0; i < IOPRIO_BE_NR; i++) {
2053 if (cfqd->async_cfqq[0][i])
2054 cfq_put_queue(cfqd->async_cfqq[0][i]);
2055 if (cfqd->async_cfqq[1][i])
2056 cfq_put_queue(cfqd->async_cfqq[1][i]);
2059 if (cfqd->async_idle_cfqq)
2060 cfq_put_queue(cfqd->async_idle_cfqq);
2063 static void cfq_exit_queue(elevator_t *e)
2065 struct cfq_data *cfqd = e->elevator_data;
2066 struct request_queue *q = cfqd->queue;
2068 cfq_shutdown_timer_wq(cfqd);
2070 spin_lock_irq(q->queue_lock);
2072 if (cfqd->active_queue)
2073 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2075 while (!list_empty(&cfqd->cic_list)) {
2076 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2077 struct cfq_io_context,
2078 queue_list);
2080 __cfq_exit_single_io_context(cfqd, cic);
2083 cfq_put_async_queues(cfqd);
2085 spin_unlock_irq(q->queue_lock);
2087 cfq_shutdown_timer_wq(cfqd);
2089 kfree(cfqd);
2092 static void *cfq_init_queue(struct request_queue *q)
2094 struct cfq_data *cfqd;
2096 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2097 if (!cfqd)
2098 return NULL;
2100 cfqd->service_tree = CFQ_RB_ROOT;
2101 INIT_LIST_HEAD(&cfqd->cic_list);
2103 cfqd->queue = q;
2105 init_timer(&cfqd->idle_slice_timer);
2106 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2107 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2109 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2111 cfqd->last_end_request = jiffies;
2112 cfqd->cfq_quantum = cfq_quantum;
2113 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2114 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2115 cfqd->cfq_back_max = cfq_back_max;
2116 cfqd->cfq_back_penalty = cfq_back_penalty;
2117 cfqd->cfq_slice[0] = cfq_slice_async;
2118 cfqd->cfq_slice[1] = cfq_slice_sync;
2119 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2120 cfqd->cfq_slice_idle = cfq_slice_idle;
2122 return cfqd;
2125 static void cfq_slab_kill(void)
2127 if (cfq_pool)
2128 kmem_cache_destroy(cfq_pool);
2129 if (cfq_ioc_pool)
2130 kmem_cache_destroy(cfq_ioc_pool);
2133 static int __init cfq_slab_setup(void)
2135 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2136 if (!cfq_pool)
2137 goto fail;
2139 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2140 if (!cfq_ioc_pool)
2141 goto fail;
2143 return 0;
2144 fail:
2145 cfq_slab_kill();
2146 return -ENOMEM;
2150 * sysfs parts below -->
2152 static ssize_t
2153 cfq_var_show(unsigned int var, char *page)
2155 return sprintf(page, "%d\n", var);
2158 static ssize_t
2159 cfq_var_store(unsigned int *var, const char *page, size_t count)
2161 char *p = (char *) page;
2163 *var = simple_strtoul(p, &p, 10);
2164 return count;
2167 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2168 static ssize_t __FUNC(elevator_t *e, char *page) \
2170 struct cfq_data *cfqd = e->elevator_data; \
2171 unsigned int __data = __VAR; \
2172 if (__CONV) \
2173 __data = jiffies_to_msecs(__data); \
2174 return cfq_var_show(__data, (page)); \
2176 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2177 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2178 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2179 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2180 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2181 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2182 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2183 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2184 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2185 #undef SHOW_FUNCTION
2187 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2188 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2190 struct cfq_data *cfqd = e->elevator_data; \
2191 unsigned int __data; \
2192 int ret = cfq_var_store(&__data, (page), count); \
2193 if (__data < (MIN)) \
2194 __data = (MIN); \
2195 else if (__data > (MAX)) \
2196 __data = (MAX); \
2197 if (__CONV) \
2198 *(__PTR) = msecs_to_jiffies(__data); \
2199 else \
2200 *(__PTR) = __data; \
2201 return ret; \
2203 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2204 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
2205 UINT_MAX, 1);
2206 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
2207 UINT_MAX, 1);
2208 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2209 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
2210 UINT_MAX, 0);
2211 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2212 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2213 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2214 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
2215 UINT_MAX, 0);
2216 #undef STORE_FUNCTION
2218 #define CFQ_ATTR(name) \
2219 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2221 static struct elv_fs_entry cfq_attrs[] = {
2222 CFQ_ATTR(quantum),
2223 CFQ_ATTR(fifo_expire_sync),
2224 CFQ_ATTR(fifo_expire_async),
2225 CFQ_ATTR(back_seek_max),
2226 CFQ_ATTR(back_seek_penalty),
2227 CFQ_ATTR(slice_sync),
2228 CFQ_ATTR(slice_async),
2229 CFQ_ATTR(slice_async_rq),
2230 CFQ_ATTR(slice_idle),
2231 __ATTR_NULL
2234 static struct elevator_type iosched_cfq = {
2235 .ops = {
2236 .elevator_merge_fn = cfq_merge,
2237 .elevator_merged_fn = cfq_merged_request,
2238 .elevator_merge_req_fn = cfq_merged_requests,
2239 .elevator_allow_merge_fn = cfq_allow_merge,
2240 .elevator_dispatch_fn = cfq_dispatch_requests,
2241 .elevator_add_req_fn = cfq_insert_request,
2242 .elevator_activate_req_fn = cfq_activate_request,
2243 .elevator_deactivate_req_fn = cfq_deactivate_request,
2244 .elevator_queue_empty_fn = cfq_queue_empty,
2245 .elevator_completed_req_fn = cfq_completed_request,
2246 .elevator_former_req_fn = elv_rb_former_request,
2247 .elevator_latter_req_fn = elv_rb_latter_request,
2248 .elevator_set_req_fn = cfq_set_request,
2249 .elevator_put_req_fn = cfq_put_request,
2250 .elevator_may_queue_fn = cfq_may_queue,
2251 .elevator_init_fn = cfq_init_queue,
2252 .elevator_exit_fn = cfq_exit_queue,
2253 .trim = cfq_free_io_context,
2255 .elevator_attrs = cfq_attrs,
2256 .elevator_name = "cfq",
2257 .elevator_owner = THIS_MODULE,
2260 static int __init cfq_init(void)
2263 * could be 0 on HZ < 1000 setups
2265 if (!cfq_slice_async)
2266 cfq_slice_async = 1;
2267 if (!cfq_slice_idle)
2268 cfq_slice_idle = 1;
2270 if (cfq_slab_setup())
2271 return -ENOMEM;
2273 elv_register(&iosched_cfq);
2275 return 0;
2278 static void __exit cfq_exit(void)
2280 DECLARE_COMPLETION_ONSTACK(all_gone);
2281 elv_unregister(&iosched_cfq);
2282 ioc_gone = &all_gone;
2283 /* ioc_gone's update must be visible before reading ioc_count */
2284 smp_wmb();
2285 if (elv_ioc_count_read(ioc_count))
2286 wait_for_completion(ioc_gone);
2287 cfq_slab_kill();
2290 module_init(cfq_init);
2291 module_exit(cfq_exit);
2293 MODULE_AUTHOR("Jens Axboe");
2294 MODULE_LICENSE("GPL");
2295 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");