inotify: remove debug code
[linux-2.6.22.y-op.git] / block / cfq-iosched.c
bloba131d414904b223f90ca9b475f77c3b4964f831c
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 static const int cfq_quantum = 4; /* max queue in one round of service */
19 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
20 static const int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
21 static const int cfq_back_penalty = 2; /* penalty of a backwards seek */
23 static const int cfq_slice_sync = HZ / 10;
24 static int cfq_slice_async = HZ / 25;
25 static const int cfq_slice_async_rq = 2;
26 static int cfq_slice_idle = HZ / 125;
29 * grace period before allowing idle class to get disk access
31 #define CFQ_IDLE_GRACE (HZ / 10)
34 * below this threshold, we consider thinktime immediate
36 #define CFQ_MIN_TT (2)
38 #define CFQ_SLICE_SCALE (5)
40 #define RQ_CIC(rq) ((struct cfq_io_context*)(rq)->elevator_private)
41 #define RQ_CFQQ(rq) ((rq)->elevator_private2)
43 static struct kmem_cache *cfq_pool;
44 static struct kmem_cache *cfq_ioc_pool;
46 static DEFINE_PER_CPU(unsigned long, ioc_count);
47 static struct completion *ioc_gone;
49 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
50 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
51 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
53 #define ASYNC (0)
54 #define SYNC (1)
56 #define sample_valid(samples) ((samples) > 80)
59 * Most of our rbtree usage is for sorting with min extraction, so
60 * if we cache the leftmost node we don't have to walk down the tree
61 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
62 * move this into the elevator for the rq sorting as well.
64 struct cfq_rb_root {
65 struct rb_root rb;
66 struct rb_node *left;
68 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
71 * Per block device queue structure
73 struct cfq_data {
74 request_queue_t *queue;
77 * rr list of queues with requests and the count of them
79 struct cfq_rb_root service_tree;
80 unsigned int busy_queues;
82 int rq_in_driver;
83 int sync_flight;
84 int hw_tag;
87 * idle window management
89 struct timer_list idle_slice_timer;
90 struct work_struct unplug_work;
92 struct cfq_queue *active_queue;
93 struct cfq_io_context *active_cic;
95 struct cfq_queue *async_cfqq[IOPRIO_BE_NR];
97 struct timer_list idle_class_timer;
99 sector_t last_position;
100 unsigned long last_end_request;
103 * tunables, see top of file
105 unsigned int cfq_quantum;
106 unsigned int cfq_fifo_expire[2];
107 unsigned int cfq_back_penalty;
108 unsigned int cfq_back_max;
109 unsigned int cfq_slice[2];
110 unsigned int cfq_slice_async_rq;
111 unsigned int cfq_slice_idle;
113 struct list_head cic_list;
115 sector_t new_seek_mean;
116 u64 new_seek_total;
120 * Per process-grouping structure
122 struct cfq_queue {
123 /* reference count */
124 atomic_t ref;
125 /* parent cfq_data */
126 struct cfq_data *cfqd;
127 /* service_tree member */
128 struct rb_node rb_node;
129 /* service_tree key */
130 unsigned long rb_key;
131 /* sorted list of pending requests */
132 struct rb_root sort_list;
133 /* if fifo isn't expired, next request to serve */
134 struct request *next_rq;
135 /* requests queued in sort_list */
136 int queued[2];
137 /* currently allocated requests */
138 int allocated[2];
139 /* pending metadata requests */
140 int meta_pending;
141 /* fifo list of requests in sort_list */
142 struct list_head fifo;
144 unsigned long slice_end;
145 long slice_resid;
147 /* number of requests that are on the dispatch list or inside driver */
148 int dispatched;
150 /* io prio of this group */
151 unsigned short ioprio, org_ioprio;
152 unsigned short ioprio_class, org_ioprio_class;
154 /* various state flags, see below */
155 unsigned int flags;
157 sector_t last_request_pos;
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(request_queue_t *, struct request *);
202 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
203 struct task_struct *, gfp_t);
204 static struct cfq_io_context *cfq_cic_rb_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(request_queue_t *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 rb_node *cfq_rb_first(struct cfq_rb_root *root)
390 if (!root->left)
391 root->left = rb_first(&root->rb);
393 return root->left;
396 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
398 if (root->left == n)
399 root->left = NULL;
401 rb_erase(n, &root->rb);
402 RB_CLEAR_NODE(n);
406 * would be nice to take fifo expire time into account as well
408 static struct request *
409 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
410 struct request *last)
412 struct rb_node *rbnext = rb_next(&last->rb_node);
413 struct rb_node *rbprev = rb_prev(&last->rb_node);
414 struct request *next = NULL, *prev = NULL;
416 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
418 if (rbprev)
419 prev = rb_entry_rq(rbprev);
421 if (rbnext)
422 next = rb_entry_rq(rbnext);
423 else {
424 rbnext = rb_first(&cfqq->sort_list);
425 if (rbnext && rbnext != &last->rb_node)
426 next = rb_entry_rq(rbnext);
429 return cfq_choose_req(cfqd, next, prev);
432 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
433 struct cfq_queue *cfqq)
436 * just an approximation, should be ok.
438 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
439 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
443 * The cfqd->service_tree holds all pending cfq_queue's that have
444 * requests waiting to be processed. It is sorted in the order that
445 * we will service the queues.
447 static void cfq_service_tree_add(struct cfq_data *cfqd,
448 struct cfq_queue *cfqq, int add_front)
450 struct rb_node **p = &cfqd->service_tree.rb.rb_node;
451 struct rb_node *parent = NULL;
452 unsigned long rb_key;
453 int left;
455 if (!add_front) {
456 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
457 rb_key += cfqq->slice_resid;
458 cfqq->slice_resid = 0;
459 } else
460 rb_key = 0;
462 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
464 * same position, nothing more to do
466 if (rb_key == cfqq->rb_key)
467 return;
469 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
472 left = 1;
473 while (*p) {
474 struct cfq_queue *__cfqq;
475 struct rb_node **n;
477 parent = *p;
478 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
481 * sort RT queues first, we always want to give
482 * preference to them. IDLE queues goes to the back.
483 * after that, sort on the next service time.
485 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
486 n = &(*p)->rb_left;
487 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
488 n = &(*p)->rb_right;
489 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
490 n = &(*p)->rb_left;
491 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
492 n = &(*p)->rb_right;
493 else if (rb_key < __cfqq->rb_key)
494 n = &(*p)->rb_left;
495 else
496 n = &(*p)->rb_right;
498 if (n == &(*p)->rb_right)
499 left = 0;
501 p = n;
504 if (left)
505 cfqd->service_tree.left = &cfqq->rb_node;
507 cfqq->rb_key = rb_key;
508 rb_link_node(&cfqq->rb_node, parent, p);
509 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
513 * Update cfqq's position in the service tree.
515 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
518 * Resorting requires the cfqq to be on the RR list already.
520 if (cfq_cfqq_on_rr(cfqq))
521 cfq_service_tree_add(cfqd, cfqq, 0);
525 * add to busy list of queues for service, trying to be fair in ordering
526 * the pending list according to last request service
528 static inline void
529 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
531 BUG_ON(cfq_cfqq_on_rr(cfqq));
532 cfq_mark_cfqq_on_rr(cfqq);
533 cfqd->busy_queues++;
535 cfq_resort_rr_list(cfqd, cfqq);
539 * Called when the cfqq no longer has requests pending, remove it from
540 * the service tree.
542 static inline void
543 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
545 BUG_ON(!cfq_cfqq_on_rr(cfqq));
546 cfq_clear_cfqq_on_rr(cfqq);
548 if (!RB_EMPTY_NODE(&cfqq->rb_node))
549 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
551 BUG_ON(!cfqd->busy_queues);
552 cfqd->busy_queues--;
556 * rb tree support functions
558 static inline void cfq_del_rq_rb(struct request *rq)
560 struct cfq_queue *cfqq = RQ_CFQQ(rq);
561 struct cfq_data *cfqd = cfqq->cfqd;
562 const int sync = rq_is_sync(rq);
564 BUG_ON(!cfqq->queued[sync]);
565 cfqq->queued[sync]--;
567 elv_rb_del(&cfqq->sort_list, rq);
569 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
570 cfq_del_cfqq_rr(cfqd, cfqq);
573 static void cfq_add_rq_rb(struct request *rq)
575 struct cfq_queue *cfqq = RQ_CFQQ(rq);
576 struct cfq_data *cfqd = cfqq->cfqd;
577 struct request *__alias;
579 cfqq->queued[rq_is_sync(rq)]++;
582 * looks a little odd, but the first insert might return an alias.
583 * if that happens, put the alias on the dispatch list
585 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
586 cfq_dispatch_insert(cfqd->queue, __alias);
588 if (!cfq_cfqq_on_rr(cfqq))
589 cfq_add_cfqq_rr(cfqd, cfqq);
592 * check if this request is a better next-serve candidate
594 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
595 BUG_ON(!cfqq->next_rq);
598 static inline void
599 cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
601 elv_rb_del(&cfqq->sort_list, rq);
602 cfqq->queued[rq_is_sync(rq)]--;
603 cfq_add_rq_rb(rq);
606 static struct request *
607 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
609 struct task_struct *tsk = current;
610 struct cfq_io_context *cic;
611 struct cfq_queue *cfqq;
613 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
614 if (!cic)
615 return NULL;
617 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
618 if (cfqq) {
619 sector_t sector = bio->bi_sector + bio_sectors(bio);
621 return elv_rb_find(&cfqq->sort_list, sector);
624 return NULL;
627 static void cfq_activate_request(request_queue_t *q, struct request *rq)
629 struct cfq_data *cfqd = q->elevator->elevator_data;
631 cfqd->rq_in_driver++;
634 * If the depth is larger 1, it really could be queueing. But lets
635 * make the mark a little higher - idling could still be good for
636 * low queueing, and a low queueing number could also just indicate
637 * a SCSI mid layer like behaviour where limit+1 is often seen.
639 if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
640 cfqd->hw_tag = 1;
642 cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
645 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
647 struct cfq_data *cfqd = q->elevator->elevator_data;
649 WARN_ON(!cfqd->rq_in_driver);
650 cfqd->rq_in_driver--;
653 static void cfq_remove_request(struct request *rq)
655 struct cfq_queue *cfqq = RQ_CFQQ(rq);
657 if (cfqq->next_rq == rq)
658 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
660 list_del_init(&rq->queuelist);
661 cfq_del_rq_rb(rq);
663 if (rq_is_meta(rq)) {
664 WARN_ON(!cfqq->meta_pending);
665 cfqq->meta_pending--;
669 static int cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
671 struct cfq_data *cfqd = q->elevator->elevator_data;
672 struct request *__rq;
674 __rq = cfq_find_rq_fmerge(cfqd, bio);
675 if (__rq && elv_rq_merge_ok(__rq, bio)) {
676 *req = __rq;
677 return ELEVATOR_FRONT_MERGE;
680 return ELEVATOR_NO_MERGE;
683 static void cfq_merged_request(request_queue_t *q, struct request *req,
684 int type)
686 if (type == ELEVATOR_FRONT_MERGE) {
687 struct cfq_queue *cfqq = RQ_CFQQ(req);
689 cfq_reposition_rq_rb(cfqq, req);
693 static void
694 cfq_merged_requests(request_queue_t *q, struct request *rq,
695 struct request *next)
698 * reposition in fifo if next is older than rq
700 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
701 time_before(next->start_time, rq->start_time))
702 list_move(&rq->queuelist, &next->queuelist);
704 cfq_remove_request(next);
707 static int cfq_allow_merge(request_queue_t *q, struct request *rq,
708 struct bio *bio)
710 struct cfq_data *cfqd = q->elevator->elevator_data;
711 struct cfq_io_context *cic;
712 struct cfq_queue *cfqq;
715 * Disallow merge of a sync bio into an async request.
717 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
718 return 0;
721 * Lookup the cfqq that this bio will be queued with. Allow
722 * merge only if rq is queued there.
724 cic = cfq_cic_rb_lookup(cfqd, current->io_context);
725 if (!cic)
726 return 0;
728 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
729 if (cfqq == RQ_CFQQ(rq))
730 return 1;
732 return 0;
735 static inline void
736 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
738 if (cfqq) {
740 * stop potential idle class queues waiting service
742 del_timer(&cfqd->idle_class_timer);
744 cfqq->slice_end = 0;
745 cfq_clear_cfqq_must_alloc_slice(cfqq);
746 cfq_clear_cfqq_fifo_expire(cfqq);
747 cfq_mark_cfqq_slice_new(cfqq);
748 cfq_clear_cfqq_queue_new(cfqq);
751 cfqd->active_queue = cfqq;
755 * current cfqq expired its slice (or was too idle), select new one
757 static void
758 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
759 int timed_out)
761 if (cfq_cfqq_wait_request(cfqq))
762 del_timer(&cfqd->idle_slice_timer);
764 cfq_clear_cfqq_must_dispatch(cfqq);
765 cfq_clear_cfqq_wait_request(cfqq);
768 * store what was left of this slice, if the queue idled/timed out
770 if (timed_out && !cfq_cfqq_slice_new(cfqq))
771 cfqq->slice_resid = cfqq->slice_end - jiffies;
773 cfq_resort_rr_list(cfqd, cfqq);
775 if (cfqq == cfqd->active_queue)
776 cfqd->active_queue = NULL;
778 if (cfqd->active_cic) {
779 put_io_context(cfqd->active_cic->ioc);
780 cfqd->active_cic = NULL;
784 static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
786 struct cfq_queue *cfqq = cfqd->active_queue;
788 if (cfqq)
789 __cfq_slice_expired(cfqd, cfqq, timed_out);
793 * Get next queue for service. Unless we have a queue preemption,
794 * we'll simply select the first cfqq in the service tree.
796 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
798 struct cfq_queue *cfqq;
799 struct rb_node *n;
801 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
802 return NULL;
804 n = cfq_rb_first(&cfqd->service_tree);
805 cfqq = rb_entry(n, struct cfq_queue, rb_node);
807 if (cfq_class_idle(cfqq)) {
808 unsigned long end;
811 * if we have idle queues and no rt or be queues had
812 * pending requests, either allow immediate service if
813 * the grace period has passed or arm the idle grace
814 * timer
816 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
817 if (time_before(jiffies, end)) {
818 mod_timer(&cfqd->idle_class_timer, end);
819 cfqq = NULL;
823 return cfqq;
827 * Get and set a new active queue for service.
829 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
831 struct cfq_queue *cfqq;
833 cfqq = cfq_get_next_queue(cfqd);
834 __cfq_set_active_queue(cfqd, cfqq);
835 return cfqq;
838 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
839 struct request *rq)
841 if (rq->sector >= cfqd->last_position)
842 return rq->sector - cfqd->last_position;
843 else
844 return cfqd->last_position - rq->sector;
847 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
849 struct cfq_io_context *cic = cfqd->active_cic;
851 if (!sample_valid(cic->seek_samples))
852 return 0;
854 return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
857 static int cfq_close_cooperator(struct cfq_data *cfq_data,
858 struct cfq_queue *cfqq)
861 * We should notice if some of the queues are cooperating, eg
862 * working closely on the same area of the disk. In that case,
863 * we can group them together and don't waste time idling.
865 return 0;
868 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
870 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
872 struct cfq_queue *cfqq = cfqd->active_queue;
873 struct cfq_io_context *cic;
874 unsigned long sl;
876 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
877 WARN_ON(cfq_cfqq_slice_new(cfqq));
880 * idle is disabled, either manually or by past process history
882 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
883 return;
886 * task has exited, don't wait
888 cic = cfqd->active_cic;
889 if (!cic || !cic->ioc->task)
890 return;
893 * See if this prio level has a good candidate
895 if (cfq_close_cooperator(cfqd, cfqq) &&
896 (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
897 return;
899 cfq_mark_cfqq_must_dispatch(cfqq);
900 cfq_mark_cfqq_wait_request(cfqq);
903 * we don't want to idle for seeks, but we do want to allow
904 * fair distribution of slice time for a process doing back-to-back
905 * seeks. so allow a little bit of time for him to submit a new rq
907 sl = cfqd->cfq_slice_idle;
908 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
909 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
911 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
915 * Move request from internal lists to the request queue dispatch list.
917 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
919 struct cfq_data *cfqd = q->elevator->elevator_data;
920 struct cfq_queue *cfqq = RQ_CFQQ(rq);
922 cfq_remove_request(rq);
923 cfqq->dispatched++;
924 elv_dispatch_sort(q, rq);
926 if (cfq_cfqq_sync(cfqq))
927 cfqd->sync_flight++;
931 * return expired entry, or NULL to just start from scratch in rbtree
933 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
935 struct cfq_data *cfqd = cfqq->cfqd;
936 struct request *rq;
937 int fifo;
939 if (cfq_cfqq_fifo_expire(cfqq))
940 return NULL;
942 cfq_mark_cfqq_fifo_expire(cfqq);
944 if (list_empty(&cfqq->fifo))
945 return NULL;
947 fifo = cfq_cfqq_sync(cfqq);
948 rq = rq_entry_fifo(cfqq->fifo.next);
950 if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
951 return NULL;
953 return rq;
956 static inline int
957 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
959 const int base_rq = cfqd->cfq_slice_async_rq;
961 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
963 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
967 * Select a queue for service. If we have a current active queue,
968 * check whether to continue servicing it, or retrieve and set a new one.
970 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
972 struct cfq_queue *cfqq;
974 cfqq = cfqd->active_queue;
975 if (!cfqq)
976 goto new_queue;
979 * The active queue has run out of time, expire it and select new.
981 if (cfq_slice_used(cfqq))
982 goto expire;
985 * The active queue has requests and isn't expired, allow it to
986 * dispatch.
988 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
989 goto keep_queue;
992 * No requests pending. If the active queue still has requests in
993 * flight or is idling for a new request, allow either of these
994 * conditions to happen (or time out) before selecting a new queue.
996 if (timer_pending(&cfqd->idle_slice_timer) ||
997 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
998 cfqq = NULL;
999 goto keep_queue;
1002 expire:
1003 cfq_slice_expired(cfqd, 0);
1004 new_queue:
1005 cfqq = cfq_set_active_queue(cfqd);
1006 keep_queue:
1007 return cfqq;
1011 * Dispatch some requests from cfqq, moving them to the request queue
1012 * dispatch list.
1014 static int
1015 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1016 int max_dispatch)
1018 int dispatched = 0;
1020 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1022 do {
1023 struct request *rq;
1026 * follow expired path, else get first next available
1028 if ((rq = cfq_check_fifo(cfqq)) == NULL)
1029 rq = cfqq->next_rq;
1032 * finally, insert request into driver dispatch list
1034 cfq_dispatch_insert(cfqd->queue, rq);
1036 dispatched++;
1038 if (!cfqd->active_cic) {
1039 atomic_inc(&RQ_CIC(rq)->ioc->refcount);
1040 cfqd->active_cic = RQ_CIC(rq);
1043 if (RB_EMPTY_ROOT(&cfqq->sort_list))
1044 break;
1046 } while (dispatched < max_dispatch);
1049 * expire an async queue immediately if it has used up its slice. idle
1050 * queue always expire after 1 dispatch round.
1052 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1053 dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1054 cfq_class_idle(cfqq))) {
1055 cfqq->slice_end = jiffies + 1;
1056 cfq_slice_expired(cfqd, 0);
1059 return dispatched;
1062 static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1064 int dispatched = 0;
1066 while (cfqq->next_rq) {
1067 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1068 dispatched++;
1071 BUG_ON(!list_empty(&cfqq->fifo));
1072 return dispatched;
1076 * Drain our current requests. Used for barriers and when switching
1077 * io schedulers on-the-fly.
1079 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1081 int dispatched = 0;
1082 struct rb_node *n;
1084 while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) {
1085 struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
1087 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1090 cfq_slice_expired(cfqd, 0);
1092 BUG_ON(cfqd->busy_queues);
1094 return dispatched;
1097 static int cfq_dispatch_requests(request_queue_t *q, int force)
1099 struct cfq_data *cfqd = q->elevator->elevator_data;
1100 struct cfq_queue *cfqq;
1101 int dispatched;
1103 if (!cfqd->busy_queues)
1104 return 0;
1106 if (unlikely(force))
1107 return cfq_forced_dispatch(cfqd);
1109 dispatched = 0;
1110 while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1111 int max_dispatch;
1113 max_dispatch = cfqd->cfq_quantum;
1114 if (cfq_class_idle(cfqq))
1115 max_dispatch = 1;
1117 if (cfqq->dispatched >= max_dispatch) {
1118 if (cfqd->busy_queues > 1)
1119 break;
1120 if (cfqq->dispatched >= 4 * max_dispatch)
1121 break;
1124 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1125 break;
1127 cfq_clear_cfqq_must_dispatch(cfqq);
1128 cfq_clear_cfqq_wait_request(cfqq);
1129 del_timer(&cfqd->idle_slice_timer);
1131 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1134 return dispatched;
1138 * task holds one reference to the queue, dropped when task exits. each rq
1139 * in-flight on this queue also holds a reference, dropped when rq is freed.
1141 * queue lock must be held here.
1143 static void cfq_put_queue(struct cfq_queue *cfqq)
1145 struct cfq_data *cfqd = cfqq->cfqd;
1147 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1149 if (!atomic_dec_and_test(&cfqq->ref))
1150 return;
1152 BUG_ON(rb_first(&cfqq->sort_list));
1153 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1154 BUG_ON(cfq_cfqq_on_rr(cfqq));
1156 if (unlikely(cfqd->active_queue == cfqq)) {
1157 __cfq_slice_expired(cfqd, cfqq, 0);
1158 cfq_schedule_dispatch(cfqd);
1161 kmem_cache_free(cfq_pool, cfqq);
1164 static void cfq_free_io_context(struct io_context *ioc)
1166 struct cfq_io_context *__cic;
1167 struct rb_node *n;
1168 int freed = 0;
1170 ioc->ioc_data = NULL;
1172 while ((n = rb_first(&ioc->cic_root)) != NULL) {
1173 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1174 rb_erase(&__cic->rb_node, &ioc->cic_root);
1175 kmem_cache_free(cfq_ioc_pool, __cic);
1176 freed++;
1179 elv_ioc_count_mod(ioc_count, -freed);
1181 if (ioc_gone && !elv_ioc_count_read(ioc_count))
1182 complete(ioc_gone);
1185 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1187 if (unlikely(cfqq == cfqd->active_queue)) {
1188 __cfq_slice_expired(cfqd, cfqq, 0);
1189 cfq_schedule_dispatch(cfqd);
1192 cfq_put_queue(cfqq);
1195 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1196 struct cfq_io_context *cic)
1198 list_del_init(&cic->queue_list);
1199 smp_wmb();
1200 cic->key = NULL;
1202 if (cic->cfqq[ASYNC]) {
1203 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1204 cic->cfqq[ASYNC] = NULL;
1207 if (cic->cfqq[SYNC]) {
1208 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1209 cic->cfqq[SYNC] = NULL;
1213 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1215 struct cfq_data *cfqd = cic->key;
1217 if (cfqd) {
1218 request_queue_t *q = cfqd->queue;
1220 spin_lock_irq(q->queue_lock);
1221 __cfq_exit_single_io_context(cfqd, cic);
1222 spin_unlock_irq(q->queue_lock);
1227 * The process that ioc belongs to has exited, we need to clean up
1228 * and put the internal structures we have that belongs to that process.
1230 static void cfq_exit_io_context(struct io_context *ioc)
1232 struct cfq_io_context *__cic;
1233 struct rb_node *n;
1235 ioc->ioc_data = NULL;
1238 * put the reference this task is holding to the various queues
1240 n = rb_first(&ioc->cic_root);
1241 while (n != NULL) {
1242 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1244 cfq_exit_single_io_context(__cic);
1245 n = rb_next(n);
1249 static struct cfq_io_context *
1250 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1252 struct cfq_io_context *cic;
1254 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
1255 if (cic) {
1256 memset(cic, 0, sizeof(*cic));
1257 cic->last_end_request = jiffies;
1258 INIT_LIST_HEAD(&cic->queue_list);
1259 cic->dtor = cfq_free_io_context;
1260 cic->exit = cfq_exit_io_context;
1261 elv_ioc_count_inc(ioc_count);
1264 return cic;
1267 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1269 struct task_struct *tsk = current;
1270 int ioprio_class;
1272 if (!cfq_cfqq_prio_changed(cfqq))
1273 return;
1275 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1276 switch (ioprio_class) {
1277 default:
1278 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1279 case IOPRIO_CLASS_NONE:
1281 * no prio set, place us in the middle of the BE classes
1283 cfqq->ioprio = task_nice_ioprio(tsk);
1284 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1285 break;
1286 case IOPRIO_CLASS_RT:
1287 cfqq->ioprio = task_ioprio(tsk);
1288 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1289 break;
1290 case IOPRIO_CLASS_BE:
1291 cfqq->ioprio = task_ioprio(tsk);
1292 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1293 break;
1294 case IOPRIO_CLASS_IDLE:
1295 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1296 cfqq->ioprio = 7;
1297 cfq_clear_cfqq_idle_window(cfqq);
1298 break;
1302 * keep track of original prio settings in case we have to temporarily
1303 * elevate the priority of this queue
1305 cfqq->org_ioprio = cfqq->ioprio;
1306 cfqq->org_ioprio_class = cfqq->ioprio_class;
1307 cfq_clear_cfqq_prio_changed(cfqq);
1310 static inline void changed_ioprio(struct cfq_io_context *cic)
1312 struct cfq_data *cfqd = cic->key;
1313 struct cfq_queue *cfqq;
1314 unsigned long flags;
1316 if (unlikely(!cfqd))
1317 return;
1319 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1321 cfqq = cic->cfqq[ASYNC];
1322 if (cfqq) {
1323 struct cfq_queue *new_cfqq;
1324 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
1325 GFP_ATOMIC);
1326 if (new_cfqq) {
1327 cic->cfqq[ASYNC] = new_cfqq;
1328 cfq_put_queue(cfqq);
1332 cfqq = cic->cfqq[SYNC];
1333 if (cfqq)
1334 cfq_mark_cfqq_prio_changed(cfqq);
1336 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1339 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1341 struct cfq_io_context *cic;
1342 struct rb_node *n;
1344 ioc->ioprio_changed = 0;
1346 n = rb_first(&ioc->cic_root);
1347 while (n != NULL) {
1348 cic = rb_entry(n, struct cfq_io_context, rb_node);
1350 changed_ioprio(cic);
1351 n = rb_next(n);
1355 static struct cfq_queue *
1356 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1357 struct task_struct *tsk, gfp_t gfp_mask)
1359 struct cfq_queue *cfqq, *new_cfqq = NULL;
1360 struct cfq_io_context *cic;
1362 retry:
1363 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
1364 /* cic always exists here */
1365 cfqq = cic_to_cfqq(cic, is_sync);
1367 if (!cfqq) {
1368 if (new_cfqq) {
1369 cfqq = new_cfqq;
1370 new_cfqq = NULL;
1371 } else if (gfp_mask & __GFP_WAIT) {
1373 * Inform the allocator of the fact that we will
1374 * just repeat this allocation if it fails, to allow
1375 * the allocator to do whatever it needs to attempt to
1376 * free memory.
1378 spin_unlock_irq(cfqd->queue->queue_lock);
1379 new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
1380 spin_lock_irq(cfqd->queue->queue_lock);
1381 goto retry;
1382 } else {
1383 cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
1384 if (!cfqq)
1385 goto out;
1388 memset(cfqq, 0, sizeof(*cfqq));
1390 RB_CLEAR_NODE(&cfqq->rb_node);
1391 INIT_LIST_HEAD(&cfqq->fifo);
1393 atomic_set(&cfqq->ref, 0);
1394 cfqq->cfqd = cfqd;
1396 if (is_sync) {
1397 cfq_mark_cfqq_idle_window(cfqq);
1398 cfq_mark_cfqq_sync(cfqq);
1401 cfq_mark_cfqq_prio_changed(cfqq);
1402 cfq_mark_cfqq_queue_new(cfqq);
1404 cfq_init_prio_data(cfqq);
1407 if (new_cfqq)
1408 kmem_cache_free(cfq_pool, new_cfqq);
1410 out:
1411 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1412 return cfqq;
1415 static struct cfq_queue *
1416 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
1417 gfp_t gfp_mask)
1419 const int ioprio = task_ioprio(tsk);
1420 struct cfq_queue *cfqq = NULL;
1422 if (!is_sync)
1423 cfqq = cfqd->async_cfqq[ioprio];
1424 if (!cfqq)
1425 cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
1428 * pin the queue now that it's allocated, scheduler exit will prune it
1430 if (!is_sync && !cfqd->async_cfqq[ioprio]) {
1431 atomic_inc(&cfqq->ref);
1432 cfqd->async_cfqq[ioprio] = cfqq;
1435 atomic_inc(&cfqq->ref);
1436 return cfqq;
1440 * We drop cfq io contexts lazily, so we may find a dead one.
1442 static void
1443 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1445 WARN_ON(!list_empty(&cic->queue_list));
1447 if (ioc->ioc_data == cic)
1448 ioc->ioc_data = NULL;
1450 rb_erase(&cic->rb_node, &ioc->cic_root);
1451 kmem_cache_free(cfq_ioc_pool, cic);
1452 elv_ioc_count_dec(ioc_count);
1455 static struct cfq_io_context *
1456 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1458 struct rb_node *n;
1459 struct cfq_io_context *cic;
1460 void *k, *key = cfqd;
1462 if (unlikely(!ioc))
1463 return NULL;
1466 * we maintain a last-hit cache, to avoid browsing over the tree
1468 cic = ioc->ioc_data;
1469 if (cic && cic->key == cfqd)
1470 return cic;
1472 restart:
1473 n = ioc->cic_root.rb_node;
1474 while (n) {
1475 cic = rb_entry(n, struct cfq_io_context, rb_node);
1476 /* ->key must be copied to avoid race with cfq_exit_queue() */
1477 k = cic->key;
1478 if (unlikely(!k)) {
1479 cfq_drop_dead_cic(ioc, cic);
1480 goto restart;
1483 if (key < k)
1484 n = n->rb_left;
1485 else if (key > k)
1486 n = n->rb_right;
1487 else {
1488 ioc->ioc_data = cic;
1489 return cic;
1493 return NULL;
1496 static inline void
1497 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1498 struct cfq_io_context *cic)
1500 struct rb_node **p;
1501 struct rb_node *parent;
1502 struct cfq_io_context *__cic;
1503 unsigned long flags;
1504 void *k;
1506 cic->ioc = ioc;
1507 cic->key = cfqd;
1509 restart:
1510 parent = NULL;
1511 p = &ioc->cic_root.rb_node;
1512 while (*p) {
1513 parent = *p;
1514 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1515 /* ->key must be copied to avoid race with cfq_exit_queue() */
1516 k = __cic->key;
1517 if (unlikely(!k)) {
1518 cfq_drop_dead_cic(ioc, __cic);
1519 goto restart;
1522 if (cic->key < k)
1523 p = &(*p)->rb_left;
1524 else if (cic->key > k)
1525 p = &(*p)->rb_right;
1526 else
1527 BUG();
1530 rb_link_node(&cic->rb_node, parent, p);
1531 rb_insert_color(&cic->rb_node, &ioc->cic_root);
1533 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1534 list_add(&cic->queue_list, &cfqd->cic_list);
1535 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1539 * Setup general io context and cfq io context. There can be several cfq
1540 * io contexts per general io context, if this process is doing io to more
1541 * than one device managed by cfq.
1543 static struct cfq_io_context *
1544 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1546 struct io_context *ioc = NULL;
1547 struct cfq_io_context *cic;
1549 might_sleep_if(gfp_mask & __GFP_WAIT);
1551 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1552 if (!ioc)
1553 return NULL;
1555 cic = cfq_cic_rb_lookup(cfqd, ioc);
1556 if (cic)
1557 goto out;
1559 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1560 if (cic == NULL)
1561 goto err;
1563 cfq_cic_link(cfqd, ioc, cic);
1564 out:
1565 smp_read_barrier_depends();
1566 if (unlikely(ioc->ioprio_changed))
1567 cfq_ioc_set_ioprio(ioc);
1569 return cic;
1570 err:
1571 put_io_context(ioc);
1572 return NULL;
1575 static void
1576 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1578 unsigned long elapsed = jiffies - cic->last_end_request;
1579 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1581 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1582 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1583 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1586 static void
1587 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1588 struct request *rq)
1590 sector_t sdist;
1591 u64 total;
1593 if (cic->last_request_pos < rq->sector)
1594 sdist = rq->sector - cic->last_request_pos;
1595 else
1596 sdist = cic->last_request_pos - rq->sector;
1598 if (!cic->seek_samples) {
1599 cfqd->new_seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1600 cfqd->new_seek_mean = cfqd->new_seek_total / 256;
1604 * Don't allow the seek distance to get too large from the
1605 * odd fragment, pagein, etc
1607 if (cic->seek_samples <= 60) /* second&third seek */
1608 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1609 else
1610 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1612 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1613 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1614 total = cic->seek_total + (cic->seek_samples/2);
1615 do_div(total, cic->seek_samples);
1616 cic->seek_mean = (sector_t)total;
1620 * Disable idle window if the process thinks too long or seeks so much that
1621 * it doesn't matter
1623 static void
1624 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1625 struct cfq_io_context *cic)
1627 int enable_idle;
1629 if (!cfq_cfqq_sync(cfqq))
1630 return;
1632 enable_idle = cfq_cfqq_idle_window(cfqq);
1634 if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1635 (cfqd->hw_tag && CIC_SEEKY(cic)))
1636 enable_idle = 0;
1637 else if (sample_valid(cic->ttime_samples)) {
1638 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1639 enable_idle = 0;
1640 else
1641 enable_idle = 1;
1644 if (enable_idle)
1645 cfq_mark_cfqq_idle_window(cfqq);
1646 else
1647 cfq_clear_cfqq_idle_window(cfqq);
1651 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1652 * no or if we aren't sure, a 1 will cause a preempt.
1654 static int
1655 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1656 struct request *rq)
1658 struct cfq_queue *cfqq;
1660 cfqq = cfqd->active_queue;
1661 if (!cfqq)
1662 return 0;
1664 if (cfq_slice_used(cfqq))
1665 return 1;
1667 if (cfq_class_idle(new_cfqq))
1668 return 0;
1670 if (cfq_class_idle(cfqq))
1671 return 1;
1674 * if the new request is sync, but the currently running queue is
1675 * not, let the sync request have priority.
1677 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1678 return 1;
1681 * So both queues are sync. Let the new request get disk time if
1682 * it's a metadata request and the current queue is doing regular IO.
1684 if (rq_is_meta(rq) && !cfqq->meta_pending)
1685 return 1;
1687 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1688 return 0;
1691 * if this request is as-good as one we would expect from the
1692 * current cfqq, let it preempt
1694 if (cfq_rq_close(cfqd, rq))
1695 return 1;
1697 return 0;
1701 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1702 * let it have half of its nominal slice.
1704 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1706 cfq_slice_expired(cfqd, 1);
1709 * Put the new queue at the front of the of the current list,
1710 * so we know that it will be selected next.
1712 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1714 cfq_service_tree_add(cfqd, cfqq, 1);
1716 cfqq->slice_end = 0;
1717 cfq_mark_cfqq_slice_new(cfqq);
1721 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1722 * something we should do about it
1724 static void
1725 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1726 struct request *rq)
1728 struct cfq_io_context *cic = RQ_CIC(rq);
1730 if (rq_is_meta(rq))
1731 cfqq->meta_pending++;
1733 cfq_update_io_thinktime(cfqd, cic);
1734 cfq_update_io_seektime(cfqd, cic, rq);
1735 cfq_update_idle_window(cfqd, cfqq, cic);
1737 cic->last_request_pos = rq->sector + rq->nr_sectors;
1738 cfqq->last_request_pos = cic->last_request_pos;
1740 if (cfqq == cfqd->active_queue) {
1742 * if we are waiting for a request for this queue, let it rip
1743 * immediately and flag that we must not expire this queue
1744 * just now
1746 if (cfq_cfqq_wait_request(cfqq)) {
1747 cfq_mark_cfqq_must_dispatch(cfqq);
1748 del_timer(&cfqd->idle_slice_timer);
1749 blk_start_queueing(cfqd->queue);
1751 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1753 * not the active queue - expire current slice if it is
1754 * idle and has expired it's mean thinktime or this new queue
1755 * has some old slice time left and is of higher priority
1757 cfq_preempt_queue(cfqd, cfqq);
1758 cfq_mark_cfqq_must_dispatch(cfqq);
1759 blk_start_queueing(cfqd->queue);
1763 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1765 struct cfq_data *cfqd = q->elevator->elevator_data;
1766 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1768 cfq_init_prio_data(cfqq);
1770 cfq_add_rq_rb(rq);
1772 list_add_tail(&rq->queuelist, &cfqq->fifo);
1774 cfq_rq_enqueued(cfqd, cfqq, rq);
1777 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1779 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1780 struct cfq_data *cfqd = cfqq->cfqd;
1781 const int sync = rq_is_sync(rq);
1782 unsigned long now;
1784 now = jiffies;
1786 WARN_ON(!cfqd->rq_in_driver);
1787 WARN_ON(!cfqq->dispatched);
1788 cfqd->rq_in_driver--;
1789 cfqq->dispatched--;
1791 if (cfq_cfqq_sync(cfqq))
1792 cfqd->sync_flight--;
1794 if (!cfq_class_idle(cfqq))
1795 cfqd->last_end_request = now;
1797 if (sync)
1798 RQ_CIC(rq)->last_end_request = now;
1801 * If this is the active queue, check if it needs to be expired,
1802 * or if we want to idle in case it has no pending requests.
1804 if (cfqd->active_queue == cfqq) {
1805 if (cfq_cfqq_slice_new(cfqq)) {
1806 cfq_set_prio_slice(cfqd, cfqq);
1807 cfq_clear_cfqq_slice_new(cfqq);
1809 if (cfq_slice_used(cfqq))
1810 cfq_slice_expired(cfqd, 1);
1811 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
1812 cfq_arm_slice_timer(cfqd);
1815 if (!cfqd->rq_in_driver)
1816 cfq_schedule_dispatch(cfqd);
1820 * we temporarily boost lower priority queues if they are holding fs exclusive
1821 * resources. they are boosted to normal prio (CLASS_BE/4)
1823 static void cfq_prio_boost(struct cfq_queue *cfqq)
1825 if (has_fs_excl()) {
1827 * boost idle prio on transactions that would lock out other
1828 * users of the filesystem
1830 if (cfq_class_idle(cfqq))
1831 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1832 if (cfqq->ioprio > IOPRIO_NORM)
1833 cfqq->ioprio = IOPRIO_NORM;
1834 } else {
1836 * check if we need to unboost the queue
1838 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1839 cfqq->ioprio_class = cfqq->org_ioprio_class;
1840 if (cfqq->ioprio != cfqq->org_ioprio)
1841 cfqq->ioprio = cfqq->org_ioprio;
1845 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1847 if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1848 !cfq_cfqq_must_alloc_slice(cfqq)) {
1849 cfq_mark_cfqq_must_alloc_slice(cfqq);
1850 return ELV_MQUEUE_MUST;
1853 return ELV_MQUEUE_MAY;
1856 static int cfq_may_queue(request_queue_t *q, int rw)
1858 struct cfq_data *cfqd = q->elevator->elevator_data;
1859 struct task_struct *tsk = current;
1860 struct cfq_io_context *cic;
1861 struct cfq_queue *cfqq;
1864 * don't force setup of a queue from here, as a call to may_queue
1865 * does not necessarily imply that a request actually will be queued.
1866 * so just lookup a possibly existing queue, or return 'may queue'
1867 * if that fails
1869 cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
1870 if (!cic)
1871 return ELV_MQUEUE_MAY;
1873 cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
1874 if (cfqq) {
1875 cfq_init_prio_data(cfqq);
1876 cfq_prio_boost(cfqq);
1878 return __cfq_may_queue(cfqq);
1881 return ELV_MQUEUE_MAY;
1885 * queue lock held here
1887 static void cfq_put_request(struct request *rq)
1889 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1891 if (cfqq) {
1892 const int rw = rq_data_dir(rq);
1894 BUG_ON(!cfqq->allocated[rw]);
1895 cfqq->allocated[rw]--;
1897 put_io_context(RQ_CIC(rq)->ioc);
1899 rq->elevator_private = NULL;
1900 rq->elevator_private2 = NULL;
1902 cfq_put_queue(cfqq);
1907 * Allocate cfq data structures associated with this request.
1909 static int
1910 cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
1912 struct cfq_data *cfqd = q->elevator->elevator_data;
1913 struct task_struct *tsk = current;
1914 struct cfq_io_context *cic;
1915 const int rw = rq_data_dir(rq);
1916 const int is_sync = rq_is_sync(rq);
1917 struct cfq_queue *cfqq;
1918 unsigned long flags;
1920 might_sleep_if(gfp_mask & __GFP_WAIT);
1922 cic = cfq_get_io_context(cfqd, gfp_mask);
1924 spin_lock_irqsave(q->queue_lock, flags);
1926 if (!cic)
1927 goto queue_fail;
1929 cfqq = cic_to_cfqq(cic, is_sync);
1930 if (!cfqq) {
1931 cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
1933 if (!cfqq)
1934 goto queue_fail;
1936 cic_set_cfqq(cic, cfqq, is_sync);
1939 cfqq->allocated[rw]++;
1940 cfq_clear_cfqq_must_alloc(cfqq);
1941 atomic_inc(&cfqq->ref);
1943 spin_unlock_irqrestore(q->queue_lock, flags);
1945 rq->elevator_private = cic;
1946 rq->elevator_private2 = cfqq;
1947 return 0;
1949 queue_fail:
1950 if (cic)
1951 put_io_context(cic->ioc);
1953 cfq_schedule_dispatch(cfqd);
1954 spin_unlock_irqrestore(q->queue_lock, flags);
1955 return 1;
1958 static void cfq_kick_queue(struct work_struct *work)
1960 struct cfq_data *cfqd =
1961 container_of(work, struct cfq_data, unplug_work);
1962 request_queue_t *q = cfqd->queue;
1963 unsigned long flags;
1965 spin_lock_irqsave(q->queue_lock, flags);
1966 blk_start_queueing(q);
1967 spin_unlock_irqrestore(q->queue_lock, flags);
1971 * Timer running if the active_queue is currently idling inside its time slice
1973 static void cfq_idle_slice_timer(unsigned long data)
1975 struct cfq_data *cfqd = (struct cfq_data *) data;
1976 struct cfq_queue *cfqq;
1977 unsigned long flags;
1978 int timed_out = 1;
1980 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1982 if ((cfqq = cfqd->active_queue) != NULL) {
1983 timed_out = 0;
1986 * expired
1988 if (cfq_slice_used(cfqq))
1989 goto expire;
1992 * only expire and reinvoke request handler, if there are
1993 * other queues with pending requests
1995 if (!cfqd->busy_queues)
1996 goto out_cont;
1999 * not expired and it has a request pending, let it dispatch
2001 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
2002 cfq_mark_cfqq_must_dispatch(cfqq);
2003 goto out_kick;
2006 expire:
2007 cfq_slice_expired(cfqd, timed_out);
2008 out_kick:
2009 cfq_schedule_dispatch(cfqd);
2010 out_cont:
2011 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2015 * Timer running if an idle class queue is waiting for service
2017 static void cfq_idle_class_timer(unsigned long data)
2019 struct cfq_data *cfqd = (struct cfq_data *) data;
2020 unsigned long flags, end;
2022 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2025 * race with a non-idle queue, reset timer
2027 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2028 if (!time_after_eq(jiffies, end))
2029 mod_timer(&cfqd->idle_class_timer, end);
2030 else
2031 cfq_schedule_dispatch(cfqd);
2033 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2036 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2038 del_timer_sync(&cfqd->idle_slice_timer);
2039 del_timer_sync(&cfqd->idle_class_timer);
2040 blk_sync_queue(cfqd->queue);
2043 static void cfq_exit_queue(elevator_t *e)
2045 struct cfq_data *cfqd = e->elevator_data;
2046 request_queue_t *q = cfqd->queue;
2047 int i;
2049 cfq_shutdown_timer_wq(cfqd);
2051 spin_lock_irq(q->queue_lock);
2053 if (cfqd->active_queue)
2054 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2056 while (!list_empty(&cfqd->cic_list)) {
2057 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2058 struct cfq_io_context,
2059 queue_list);
2061 __cfq_exit_single_io_context(cfqd, cic);
2065 * Put the async queues
2067 for (i = 0; i < IOPRIO_BE_NR; i++)
2068 if (cfqd->async_cfqq[i])
2069 cfq_put_queue(cfqd->async_cfqq[i]);
2071 spin_unlock_irq(q->queue_lock);
2073 cfq_shutdown_timer_wq(cfqd);
2075 kfree(cfqd);
2078 static void *cfq_init_queue(request_queue_t *q)
2080 struct cfq_data *cfqd;
2082 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
2083 if (!cfqd)
2084 return NULL;
2086 memset(cfqd, 0, sizeof(*cfqd));
2088 cfqd->service_tree = CFQ_RB_ROOT;
2089 INIT_LIST_HEAD(&cfqd->cic_list);
2091 cfqd->queue = q;
2093 init_timer(&cfqd->idle_slice_timer);
2094 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2095 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2097 init_timer(&cfqd->idle_class_timer);
2098 cfqd->idle_class_timer.function = cfq_idle_class_timer;
2099 cfqd->idle_class_timer.data = (unsigned long) cfqd;
2101 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2103 cfqd->cfq_quantum = cfq_quantum;
2104 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2105 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2106 cfqd->cfq_back_max = cfq_back_max;
2107 cfqd->cfq_back_penalty = cfq_back_penalty;
2108 cfqd->cfq_slice[0] = cfq_slice_async;
2109 cfqd->cfq_slice[1] = cfq_slice_sync;
2110 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2111 cfqd->cfq_slice_idle = cfq_slice_idle;
2113 return cfqd;
2116 static void cfq_slab_kill(void)
2118 if (cfq_pool)
2119 kmem_cache_destroy(cfq_pool);
2120 if (cfq_ioc_pool)
2121 kmem_cache_destroy(cfq_ioc_pool);
2124 static int __init cfq_slab_setup(void)
2126 cfq_pool = KMEM_CACHE(cfq_queue, 0);
2127 if (!cfq_pool)
2128 goto fail;
2130 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2131 if (!cfq_ioc_pool)
2132 goto fail;
2134 return 0;
2135 fail:
2136 cfq_slab_kill();
2137 return -ENOMEM;
2141 * sysfs parts below -->
2143 static ssize_t
2144 cfq_var_show(unsigned int var, char *page)
2146 return sprintf(page, "%d\n", var);
2149 static ssize_t
2150 cfq_var_store(unsigned int *var, const char *page, size_t count)
2152 char *p = (char *) page;
2154 *var = simple_strtoul(p, &p, 10);
2155 return count;
2158 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2159 static ssize_t __FUNC(elevator_t *e, char *page) \
2161 struct cfq_data *cfqd = e->elevator_data; \
2162 unsigned int __data = __VAR; \
2163 if (__CONV) \
2164 __data = jiffies_to_msecs(__data); \
2165 return cfq_var_show(__data, (page)); \
2167 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2168 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2169 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2170 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2171 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2172 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2173 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2174 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2175 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2176 #undef SHOW_FUNCTION
2178 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2179 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count) \
2181 struct cfq_data *cfqd = e->elevator_data; \
2182 unsigned int __data; \
2183 int ret = cfq_var_store(&__data, (page), count); \
2184 if (__data < (MIN)) \
2185 __data = (MIN); \
2186 else if (__data > (MAX)) \
2187 __data = (MAX); \
2188 if (__CONV) \
2189 *(__PTR) = msecs_to_jiffies(__data); \
2190 else \
2191 *(__PTR) = __data; \
2192 return ret; \
2194 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2195 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2196 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2197 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2198 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2199 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2200 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2201 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2202 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2203 #undef STORE_FUNCTION
2205 #define CFQ_ATTR(name) \
2206 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2208 static struct elv_fs_entry cfq_attrs[] = {
2209 CFQ_ATTR(quantum),
2210 CFQ_ATTR(fifo_expire_sync),
2211 CFQ_ATTR(fifo_expire_async),
2212 CFQ_ATTR(back_seek_max),
2213 CFQ_ATTR(back_seek_penalty),
2214 CFQ_ATTR(slice_sync),
2215 CFQ_ATTR(slice_async),
2216 CFQ_ATTR(slice_async_rq),
2217 CFQ_ATTR(slice_idle),
2218 __ATTR_NULL
2221 static struct elevator_type iosched_cfq = {
2222 .ops = {
2223 .elevator_merge_fn = cfq_merge,
2224 .elevator_merged_fn = cfq_merged_request,
2225 .elevator_merge_req_fn = cfq_merged_requests,
2226 .elevator_allow_merge_fn = cfq_allow_merge,
2227 .elevator_dispatch_fn = cfq_dispatch_requests,
2228 .elevator_add_req_fn = cfq_insert_request,
2229 .elevator_activate_req_fn = cfq_activate_request,
2230 .elevator_deactivate_req_fn = cfq_deactivate_request,
2231 .elevator_queue_empty_fn = cfq_queue_empty,
2232 .elevator_completed_req_fn = cfq_completed_request,
2233 .elevator_former_req_fn = elv_rb_former_request,
2234 .elevator_latter_req_fn = elv_rb_latter_request,
2235 .elevator_set_req_fn = cfq_set_request,
2236 .elevator_put_req_fn = cfq_put_request,
2237 .elevator_may_queue_fn = cfq_may_queue,
2238 .elevator_init_fn = cfq_init_queue,
2239 .elevator_exit_fn = cfq_exit_queue,
2240 .trim = cfq_free_io_context,
2242 .elevator_attrs = cfq_attrs,
2243 .elevator_name = "cfq",
2244 .elevator_owner = THIS_MODULE,
2247 static int __init cfq_init(void)
2249 int ret;
2252 * could be 0 on HZ < 1000 setups
2254 if (!cfq_slice_async)
2255 cfq_slice_async = 1;
2256 if (!cfq_slice_idle)
2257 cfq_slice_idle = 1;
2259 if (cfq_slab_setup())
2260 return -ENOMEM;
2262 ret = elv_register(&iosched_cfq);
2263 if (ret)
2264 cfq_slab_kill();
2266 return ret;
2269 static void __exit cfq_exit(void)
2271 DECLARE_COMPLETION_ONSTACK(all_gone);
2272 elv_unregister(&iosched_cfq);
2273 ioc_gone = &all_gone;
2274 /* ioc_gone's update must be visible before reading ioc_count */
2275 smp_wmb();
2276 if (elv_ioc_count_read(ioc_count))
2277 wait_for_completion(ioc_gone);
2278 synchronize_rcu();
2279 cfq_slab_kill();
2282 module_init(cfq_init);
2283 module_exit(cfq_exit);
2285 MODULE_AUTHOR("Jens Axboe");
2286 MODULE_LICENSE("GPL");
2287 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");