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blkio: Dynamic cfq group creation based on cgroup tasks belongs to
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1/*
2 * CFQ, or complete fairness queueing, disk scheduler.
3 *
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6 *
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8 */
9#include <linux/module.h>
10#include <linux/blkdev.h>
11#include <linux/elevator.h>
12#include <linux/jiffies.h>
13#include <linux/rbtree.h>
14#include <linux/ioprio.h>
15#include <linux/blktrace_api.h>
16#include "blk-cgroup.h"
17
18/*
19 * tunables
20 */
21/* max queue in one round of service */
22static const int cfq_quantum = 4;
23static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
24/* maximum backwards seek, in KiB */
25static const int cfq_back_max = 16 * 1024;
26/* penalty of a backwards seek */
27static const int cfq_back_penalty = 2;
28static const int cfq_slice_sync = HZ / 10;
29static int cfq_slice_async = HZ / 25;
30static const int cfq_slice_async_rq = 2;
31static int cfq_slice_idle = HZ / 125;
32static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
33static const int cfq_hist_divisor = 4;
34
35/*
36 * offset from end of service tree
37 */
38#define CFQ_IDLE_DELAY (HZ / 5)
39
40/*
41 * below this threshold, we consider thinktime immediate
42 */
43#define CFQ_MIN_TT (2)
44
45/*
46 * Allow merged cfqqs to perform this amount of seeky I/O before
47 * deciding to break the queues up again.
48 */
49#define CFQQ_COOP_TOUT (HZ)
50
51#define CFQ_SLICE_SCALE (5)
52#define CFQ_HW_QUEUE_MIN (5)
53#define CFQ_SERVICE_SHIFT 12
54
55#define RQ_CIC(rq) \
56 ((struct cfq_io_context *) (rq)->elevator_private)
57#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
58
59static struct kmem_cache *cfq_pool;
60static struct kmem_cache *cfq_ioc_pool;
61
62static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
63static struct completion *ioc_gone;
64static DEFINE_SPINLOCK(ioc_gone_lock);
65
66#define CFQ_PRIO_LISTS IOPRIO_BE_NR
67#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
69
70#define sample_valid(samples) ((samples) > 80)
71#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
72
73/*
74 * Most of our rbtree usage is for sorting with min extraction, so
75 * if we cache the leftmost node we don't have to walk down the tree
76 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77 * move this into the elevator for the rq sorting as well.
78 */
79struct cfq_rb_root {
80 struct rb_root rb;
81 struct rb_node *left;
82 unsigned count;
83 u64 min_vdisktime;
84 struct rb_node *active;
85 unsigned total_weight;
86};
87#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
88
89/*
90 * Per process-grouping structure
91 */
92struct cfq_queue {
93 /* reference count */
94 atomic_t ref;
95 /* various state flags, see below */
96 unsigned int flags;
97 /* parent cfq_data */
98 struct cfq_data *cfqd;
99 /* service_tree member */
100 struct rb_node rb_node;
101 /* service_tree key */
102 unsigned long rb_key;
103 /* prio tree member */
104 struct rb_node p_node;
105 /* prio tree root we belong to, if any */
106 struct rb_root *p_root;
107 /* sorted list of pending requests */
108 struct rb_root sort_list;
109 /* if fifo isn't expired, next request to serve */
110 struct request *next_rq;
111 /* requests queued in sort_list */
112 int queued[2];
113 /* currently allocated requests */
114 int allocated[2];
115 /* fifo list of requests in sort_list */
116 struct list_head fifo;
117
118 /* time when queue got scheduled in to dispatch first request. */
119 unsigned long dispatch_start;
120 /* time when first request from queue completed and slice started. */
121 unsigned long slice_start;
122 unsigned long slice_end;
123 long slice_resid;
124 unsigned int slice_dispatch;
125
126 /* pending metadata requests */
127 int meta_pending;
128 /* number of requests that are on the dispatch list or inside driver */
129 int dispatched;
130
131 /* io prio of this group */
132 unsigned short ioprio, org_ioprio;
133 unsigned short ioprio_class, org_ioprio_class;
134
135 unsigned int seek_samples;
136 u64 seek_total;
137 sector_t seek_mean;
138 sector_t last_request_pos;
139 unsigned long seeky_start;
140
141 pid_t pid;
142
143 struct cfq_rb_root *service_tree;
144 struct cfq_queue *new_cfqq;
145 struct cfq_group *cfqg;
146};
147
148/*
149 * First index in the service_trees.
150 * IDLE is handled separately, so it has negative index
151 */
152enum wl_prio_t {
153 BE_WORKLOAD = 0,
154 RT_WORKLOAD = 1,
155 IDLE_WORKLOAD = 2,
156};
157
158/*
159 * Second index in the service_trees.
160 */
161enum wl_type_t {
162 ASYNC_WORKLOAD = 0,
163 SYNC_NOIDLE_WORKLOAD = 1,
164 SYNC_WORKLOAD = 2
165};
166
167/* This is per cgroup per device grouping structure */
168struct cfq_group {
169 /* group service_tree member */
170 struct rb_node rb_node;
171
172 /* group service_tree key */
173 u64 vdisktime;
174 unsigned int weight;
175 bool on_st;
176
177 /* number of cfqq currently on this group */
178 int nr_cfqq;
179
180 /* Per group busy queus average. Useful for workload slice calc. */
181 unsigned int busy_queues_avg[2];
182 /*
183 * rr lists of queues with requests, onle rr for each priority class.
184 * Counts are embedded in the cfq_rb_root
185 */
186 struct cfq_rb_root service_trees[2][3];
187 struct cfq_rb_root service_tree_idle;
188
189 unsigned long saved_workload_slice;
190 enum wl_type_t saved_workload;
191 enum wl_prio_t saved_serving_prio;
192 struct blkio_group blkg;
193#ifdef CONFIG_CFQ_GROUP_IOSCHED
194 struct hlist_node cfqd_node;
195#endif
196};
197
198/*
199 * Per block device queue structure
200 */
201struct cfq_data {
202 struct request_queue *queue;
203 /* Root service tree for cfq_groups */
204 struct cfq_rb_root grp_service_tree;
205 struct cfq_group root_group;
206 /* Number of active cfq groups on group service tree */
207 int nr_groups;
208
209 /*
210 * The priority currently being served
211 */
212 enum wl_prio_t serving_prio;
213 enum wl_type_t serving_type;
214 unsigned long workload_expires;
215 struct cfq_group *serving_group;
216 bool noidle_tree_requires_idle;
217
218 /*
219 * Each priority tree is sorted by next_request position. These
220 * trees are used when determining if two or more queues are
221 * interleaving requests (see cfq_close_cooperator).
222 */
223 struct rb_root prio_trees[CFQ_PRIO_LISTS];
224
225 unsigned int busy_queues;
226
227 int rq_in_driver[2];
228 int sync_flight;
229
230 /*
231 * queue-depth detection
232 */
233 int rq_queued;
234 int hw_tag;
235 /*
236 * hw_tag can be
237 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
238 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
239 * 0 => no NCQ
240 */
241 int hw_tag_est_depth;
242 unsigned int hw_tag_samples;
243
244 /*
245 * idle window management
246 */
247 struct timer_list idle_slice_timer;
248 struct work_struct unplug_work;
249
250 struct cfq_queue *active_queue;
251 struct cfq_io_context *active_cic;
252
253 /*
254 * async queue for each priority case
255 */
256 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
257 struct cfq_queue *async_idle_cfqq;
258
259 sector_t last_position;
260
261 /*
262 * tunables, see top of file
263 */
264 unsigned int cfq_quantum;
265 unsigned int cfq_fifo_expire[2];
266 unsigned int cfq_back_penalty;
267 unsigned int cfq_back_max;
268 unsigned int cfq_slice[2];
269 unsigned int cfq_slice_async_rq;
270 unsigned int cfq_slice_idle;
271 unsigned int cfq_latency;
272
273 struct list_head cic_list;
274
275 /*
276 * Fallback dummy cfqq for extreme OOM conditions
277 */
278 struct cfq_queue oom_cfqq;
279
280 unsigned long last_end_sync_rq;
281
282 /* List of cfq groups being managed on this device*/
283 struct hlist_head cfqg_list;
284};
285
286static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
287
288static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
289 enum wl_prio_t prio,
290 enum wl_type_t type,
291 struct cfq_data *cfqd)
292{
293 if (!cfqg)
294 return NULL;
295
296 if (prio == IDLE_WORKLOAD)
297 return &cfqg->service_tree_idle;
298
299 return &cfqg->service_trees[prio][type];
300}
301
302enum cfqq_state_flags {
303 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
304 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
305 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
306 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
307 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
308 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
309 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
310 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
311 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
312 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
313 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
314};
315
316#define CFQ_CFQQ_FNS(name) \
317static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
318{ \
319 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
320} \
321static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
322{ \
323 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
324} \
325static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
326{ \
327 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
328}
329
330CFQ_CFQQ_FNS(on_rr);
331CFQ_CFQQ_FNS(wait_request);
332CFQ_CFQQ_FNS(must_dispatch);
333CFQ_CFQQ_FNS(must_alloc_slice);
334CFQ_CFQQ_FNS(fifo_expire);
335CFQ_CFQQ_FNS(idle_window);
336CFQ_CFQQ_FNS(prio_changed);
337CFQ_CFQQ_FNS(slice_new);
338CFQ_CFQQ_FNS(sync);
339CFQ_CFQQ_FNS(coop);
340CFQ_CFQQ_FNS(deep);
341#undef CFQ_CFQQ_FNS
342
343#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
344 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
345#define cfq_log(cfqd, fmt, args...) \
346 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
347
348/* Traverses through cfq group service trees */
349#define for_each_cfqg_st(cfqg, i, j, st) \
350 for (i = 0; i <= IDLE_WORKLOAD; i++) \
351 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
352 : &cfqg->service_tree_idle; \
353 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
354 (i == IDLE_WORKLOAD && j == 0); \
355 j++, st = i < IDLE_WORKLOAD ? \
356 &cfqg->service_trees[i][j]: NULL) \
357
358
359static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
360{
361 if (cfq_class_idle(cfqq))
362 return IDLE_WORKLOAD;
363 if (cfq_class_rt(cfqq))
364 return RT_WORKLOAD;
365 return BE_WORKLOAD;
366}
367
368
369static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
370{
371 if (!cfq_cfqq_sync(cfqq))
372 return ASYNC_WORKLOAD;
373 if (!cfq_cfqq_idle_window(cfqq))
374 return SYNC_NOIDLE_WORKLOAD;
375 return SYNC_WORKLOAD;
376}
377
378static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
379 struct cfq_data *cfqd,
380 struct cfq_group *cfqg)
381{
382 if (wl == IDLE_WORKLOAD)
383 return cfqg->service_tree_idle.count;
384
385 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
386 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
387 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
388}
389
390static void cfq_dispatch_insert(struct request_queue *, struct request *);
391static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
392 struct io_context *, gfp_t);
393static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
394 struct io_context *);
395
396static inline int rq_in_driver(struct cfq_data *cfqd)
397{
398 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
399}
400
401static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
402 bool is_sync)
403{
404 return cic->cfqq[is_sync];
405}
406
407static inline void cic_set_cfqq(struct cfq_io_context *cic,
408 struct cfq_queue *cfqq, bool is_sync)
409{
410 cic->cfqq[is_sync] = cfqq;
411}
412
413/*
414 * We regard a request as SYNC, if it's either a read or has the SYNC bit
415 * set (in which case it could also be direct WRITE).
416 */
417static inline bool cfq_bio_sync(struct bio *bio)
418{
419 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
420}
421
422/*
423 * scheduler run of queue, if there are requests pending and no one in the
424 * driver that will restart queueing
425 */
426static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
427{
428 if (cfqd->busy_queues) {
429 cfq_log(cfqd, "schedule dispatch");
430 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
431 }
432}
433
434static int cfq_queue_empty(struct request_queue *q)
435{
436 struct cfq_data *cfqd = q->elevator->elevator_data;
437
438 return !cfqd->rq_queued;
439}
440
441/*
442 * Scale schedule slice based on io priority. Use the sync time slice only
443 * if a queue is marked sync and has sync io queued. A sync queue with async
444 * io only, should not get full sync slice length.
445 */
446static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
447 unsigned short prio)
448{
449 const int base_slice = cfqd->cfq_slice[sync];
450
451 WARN_ON(prio >= IOPRIO_BE_NR);
452
453 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
454}
455
456static inline int
457cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
458{
459 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
460}
461
462static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
463{
464 u64 d = delta << CFQ_SERVICE_SHIFT;
465
466 d = d * BLKIO_WEIGHT_DEFAULT;
467 do_div(d, cfqg->weight);
468 return d;
469}
470
471static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
472{
473 s64 delta = (s64)(vdisktime - min_vdisktime);
474 if (delta > 0)
475 min_vdisktime = vdisktime;
476
477 return min_vdisktime;
478}
479
480static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
481{
482 s64 delta = (s64)(vdisktime - min_vdisktime);
483 if (delta < 0)
484 min_vdisktime = vdisktime;
485
486 return min_vdisktime;
487}
488
489static void update_min_vdisktime(struct cfq_rb_root *st)
490{
491 u64 vdisktime = st->min_vdisktime;
492 struct cfq_group *cfqg;
493
494 if (st->active) {
495 cfqg = rb_entry_cfqg(st->active);
496 vdisktime = cfqg->vdisktime;
497 }
498
499 if (st->left) {
500 cfqg = rb_entry_cfqg(st->left);
501 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
502 }
503
504 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
505}
506
507/*
508 * get averaged number of queues of RT/BE priority.
509 * average is updated, with a formula that gives more weight to higher numbers,
510 * to quickly follows sudden increases and decrease slowly
511 */
512
513static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
514 struct cfq_group *cfqg, bool rt)
515{
516 unsigned min_q, max_q;
517 unsigned mult = cfq_hist_divisor - 1;
518 unsigned round = cfq_hist_divisor / 2;
519 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
520
521 min_q = min(cfqg->busy_queues_avg[rt], busy);
522 max_q = max(cfqg->busy_queues_avg[rt], busy);
523 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
524 cfq_hist_divisor;
525 return cfqg->busy_queues_avg[rt];
526}
527
528static inline unsigned
529cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
530{
531 struct cfq_rb_root *st = &cfqd->grp_service_tree;
532
533 return cfq_target_latency * cfqg->weight / st->total_weight;
534}
535
536static inline void
537cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
538{
539 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
540 if (cfqd->cfq_latency) {
541 /*
542 * interested queues (we consider only the ones with the same
543 * priority class in the cfq group)
544 */
545 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
546 cfq_class_rt(cfqq));
547 unsigned sync_slice = cfqd->cfq_slice[1];
548 unsigned expect_latency = sync_slice * iq;
549 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
550
551 if (expect_latency > group_slice) {
552 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
553 /* scale low_slice according to IO priority
554 * and sync vs async */
555 unsigned low_slice =
556 min(slice, base_low_slice * slice / sync_slice);
557 /* the adapted slice value is scaled to fit all iqs
558 * into the target latency */
559 slice = max(slice * group_slice / expect_latency,
560 low_slice);
561 }
562 }
563 cfqq->slice_start = jiffies;
564 cfqq->slice_end = jiffies + slice;
565 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
566}
567
568/*
569 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
570 * isn't valid until the first request from the dispatch is activated
571 * and the slice time set.
572 */
573static inline bool cfq_slice_used(struct cfq_queue *cfqq)
574{
575 if (cfq_cfqq_slice_new(cfqq))
576 return 0;
577 if (time_before(jiffies, cfqq->slice_end))
578 return 0;
579
580 return 1;
581}
582
583/*
584 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
585 * We choose the request that is closest to the head right now. Distance
586 * behind the head is penalized and only allowed to a certain extent.
587 */
588static struct request *
589cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
590{
591 sector_t s1, s2, d1 = 0, d2 = 0;
592 unsigned long back_max;
593#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
594#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
595 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
596
597 if (rq1 == NULL || rq1 == rq2)
598 return rq2;
599 if (rq2 == NULL)
600 return rq1;
601
602 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
603 return rq1;
604 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
605 return rq2;
606 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
607 return rq1;
608 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
609 return rq2;
610
611 s1 = blk_rq_pos(rq1);
612 s2 = blk_rq_pos(rq2);
613
614 /*
615 * by definition, 1KiB is 2 sectors
616 */
617 back_max = cfqd->cfq_back_max * 2;
618
619 /*
620 * Strict one way elevator _except_ in the case where we allow
621 * short backward seeks which are biased as twice the cost of a
622 * similar forward seek.
623 */
624 if (s1 >= last)
625 d1 = s1 - last;
626 else if (s1 + back_max >= last)
627 d1 = (last - s1) * cfqd->cfq_back_penalty;
628 else
629 wrap |= CFQ_RQ1_WRAP;
630
631 if (s2 >= last)
632 d2 = s2 - last;
633 else if (s2 + back_max >= last)
634 d2 = (last - s2) * cfqd->cfq_back_penalty;
635 else
636 wrap |= CFQ_RQ2_WRAP;
637
638 /* Found required data */
639
640 /*
641 * By doing switch() on the bit mask "wrap" we avoid having to
642 * check two variables for all permutations: --> faster!
643 */
644 switch (wrap) {
645 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
646 if (d1 < d2)
647 return rq1;
648 else if (d2 < d1)
649 return rq2;
650 else {
651 if (s1 >= s2)
652 return rq1;
653 else
654 return rq2;
655 }
656
657 case CFQ_RQ2_WRAP:
658 return rq1;
659 case CFQ_RQ1_WRAP:
660 return rq2;
661 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
662 default:
663 /*
664 * Since both rqs are wrapped,
665 * start with the one that's further behind head
666 * (--> only *one* back seek required),
667 * since back seek takes more time than forward.
668 */
669 if (s1 <= s2)
670 return rq1;
671 else
672 return rq2;
673 }
674}
675
676/*
677 * The below is leftmost cache rbtree addon
678 */
679static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
680{
681 /* Service tree is empty */
682 if (!root->count)
683 return NULL;
684
685 if (!root->left)
686 root->left = rb_first(&root->rb);
687
688 if (root->left)
689 return rb_entry(root->left, struct cfq_queue, rb_node);
690
691 return NULL;
692}
693
694static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
695{
696 if (!root->left)
697 root->left = rb_first(&root->rb);
698
699 if (root->left)
700 return rb_entry_cfqg(root->left);
701
702 return NULL;
703}
704
705static void rb_erase_init(struct rb_node *n, struct rb_root *root)
706{
707 rb_erase(n, root);
708 RB_CLEAR_NODE(n);
709}
710
711static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
712{
713 if (root->left == n)
714 root->left = NULL;
715 rb_erase_init(n, &root->rb);
716 --root->count;
717}
718
719/*
720 * would be nice to take fifo expire time into account as well
721 */
722static struct request *
723cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
724 struct request *last)
725{
726 struct rb_node *rbnext = rb_next(&last->rb_node);
727 struct rb_node *rbprev = rb_prev(&last->rb_node);
728 struct request *next = NULL, *prev = NULL;
729
730 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
731
732 if (rbprev)
733 prev = rb_entry_rq(rbprev);
734
735 if (rbnext)
736 next = rb_entry_rq(rbnext);
737 else {
738 rbnext = rb_first(&cfqq->sort_list);
739 if (rbnext && rbnext != &last->rb_node)
740 next = rb_entry_rq(rbnext);
741 }
742
743 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
744}
745
746static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
747 struct cfq_queue *cfqq)
748{
749 /*
750 * just an approximation, should be ok.
751 */
752 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
753 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
754}
755
756static inline s64
757cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
758{
759 return cfqg->vdisktime - st->min_vdisktime;
760}
761
762static void
763__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
764{
765 struct rb_node **node = &st->rb.rb_node;
766 struct rb_node *parent = NULL;
767 struct cfq_group *__cfqg;
768 s64 key = cfqg_key(st, cfqg);
769 int left = 1;
770
771 while (*node != NULL) {
772 parent = *node;
773 __cfqg = rb_entry_cfqg(parent);
774
775 if (key < cfqg_key(st, __cfqg))
776 node = &parent->rb_left;
777 else {
778 node = &parent->rb_right;
779 left = 0;
780 }
781 }
782
783 if (left)
784 st->left = &cfqg->rb_node;
785
786 rb_link_node(&cfqg->rb_node, parent, node);
787 rb_insert_color(&cfqg->rb_node, &st->rb);
788}
789
790static void
791cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
792{
793 struct cfq_rb_root *st = &cfqd->grp_service_tree;
794 struct cfq_group *__cfqg;
795 struct rb_node *n;
796
797 cfqg->nr_cfqq++;
798 if (cfqg->on_st)
799 return;
800
801 /*
802 * Currently put the group at the end. Later implement something
803 * so that groups get lesser vtime based on their weights, so that
804 * if group does not loose all if it was not continously backlogged.
805 */
806 n = rb_last(&st->rb);
807 if (n) {
808 __cfqg = rb_entry_cfqg(n);
809 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
810 } else
811 cfqg->vdisktime = st->min_vdisktime;
812
813 __cfq_group_service_tree_add(st, cfqg);
814 cfqg->on_st = true;
815 cfqd->nr_groups++;
816 st->total_weight += cfqg->weight;
817}
818
819static void
820cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
821{
822 struct cfq_rb_root *st = &cfqd->grp_service_tree;
823
824 if (st->active == &cfqg->rb_node)
825 st->active = NULL;
826
827 BUG_ON(cfqg->nr_cfqq < 1);
828 cfqg->nr_cfqq--;
829
830 /* If there are other cfq queues under this group, don't delete it */
831 if (cfqg->nr_cfqq)
832 return;
833
834 cfqg->on_st = false;
835 cfqd->nr_groups--;
836 st->total_weight -= cfqg->weight;
837 if (!RB_EMPTY_NODE(&cfqg->rb_node))
838 cfq_rb_erase(&cfqg->rb_node, st);
839 cfqg->saved_workload_slice = 0;
840}
841
842static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
843{
844 unsigned int slice_used, allocated_slice;
845
846 /*
847 * Queue got expired before even a single request completed or
848 * got expired immediately after first request completion.
849 */
850 if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
851 /*
852 * Also charge the seek time incurred to the group, otherwise
853 * if there are mutiple queues in the group, each can dispatch
854 * a single request on seeky media and cause lots of seek time
855 * and group will never know it.
856 */
857 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
858 1);
859 } else {
860 slice_used = jiffies - cfqq->slice_start;
861 allocated_slice = cfqq->slice_end - cfqq->slice_start;
862 if (slice_used > allocated_slice)
863 slice_used = allocated_slice;
864 }
865
866 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
867 return slice_used;
868}
869
870static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
871 struct cfq_queue *cfqq)
872{
873 struct cfq_rb_root *st = &cfqd->grp_service_tree;
874 unsigned int used_sl;
875
876 used_sl = cfq_cfqq_slice_usage(cfqq);
877
878 /* Can't update vdisktime while group is on service tree */
879 cfq_rb_erase(&cfqg->rb_node, st);
880 cfqg->vdisktime += cfq_scale_slice(used_sl, cfqg);
881 __cfq_group_service_tree_add(st, cfqg);
882
883 /* This group is being expired. Save the context */
884 if (time_after(cfqd->workload_expires, jiffies)) {
885 cfqg->saved_workload_slice = cfqd->workload_expires
886 - jiffies;
887 cfqg->saved_workload = cfqd->serving_type;
888 cfqg->saved_serving_prio = cfqd->serving_prio;
889 } else
890 cfqg->saved_workload_slice = 0;
891}
892
893#ifdef CONFIG_CFQ_GROUP_IOSCHED
894static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
895{
896 if (blkg)
897 return container_of(blkg, struct cfq_group, blkg);
898 return NULL;
899}
900
901static struct cfq_group *
902cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
903{
904 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
905 struct cfq_group *cfqg = NULL;
906 void *key = cfqd;
907 int i, j;
908 struct cfq_rb_root *st;
909
910 /* Do we need to take this reference */
911 if (!css_tryget(&blkcg->css))
912 return NULL;;
913
914 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
915 if (cfqg || !create)
916 goto done;
917
918 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
919 if (!cfqg)
920 goto done;
921
922 cfqg->weight = blkcg->weight;
923 for_each_cfqg_st(cfqg, i, j, st)
924 *st = CFQ_RB_ROOT;
925 RB_CLEAR_NODE(&cfqg->rb_node);
926
927 /* Add group onto cgroup list */
928 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd);
929
930 /* Add group on cfqd list */
931 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
932
933done:
934 css_put(&blkcg->css);
935 return cfqg;
936}
937
938/*
939 * Search for the cfq group current task belongs to. If create = 1, then also
940 * create the cfq group if it does not exist. request_queue lock must be held.
941 */
942static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
943{
944 struct cgroup *cgroup;
945 struct cfq_group *cfqg = NULL;
946
947 rcu_read_lock();
948 cgroup = task_cgroup(current, blkio_subsys_id);
949 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
950 if (!cfqg && create)
951 cfqg = &cfqd->root_group;
952 rcu_read_unlock();
953 return cfqg;
954}
955
956static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
957{
958 /* Currently, all async queues are mapped to root group */
959 if (!cfq_cfqq_sync(cfqq))
960 cfqg = &cfqq->cfqd->root_group;
961
962 cfqq->cfqg = cfqg;
963}
964#else /* GROUP_IOSCHED */
965static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
966{
967 return &cfqd->root_group;
968}
969static inline void
970cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
971 cfqq->cfqg = cfqg;
972}
973
974#endif /* GROUP_IOSCHED */
975
976/*
977 * The cfqd->service_trees holds all pending cfq_queue's that have
978 * requests waiting to be processed. It is sorted in the order that
979 * we will service the queues.
980 */
981static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
982 bool add_front)
983{
984 struct rb_node **p, *parent;
985 struct cfq_queue *__cfqq;
986 unsigned long rb_key;
987 struct cfq_rb_root *service_tree;
988 int left;
989 int new_cfqq = 1;
990
991 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
992 cfqq_type(cfqq), cfqd);
993 if (cfq_class_idle(cfqq)) {
994 rb_key = CFQ_IDLE_DELAY;
995 parent = rb_last(&service_tree->rb);
996 if (parent && parent != &cfqq->rb_node) {
997 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
998 rb_key += __cfqq->rb_key;
999 } else
1000 rb_key += jiffies;
1001 } else if (!add_front) {
1002 /*
1003 * Get our rb key offset. Subtract any residual slice
1004 * value carried from last service. A negative resid
1005 * count indicates slice overrun, and this should position
1006 * the next service time further away in the tree.
1007 */
1008 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1009 rb_key -= cfqq->slice_resid;
1010 cfqq->slice_resid = 0;
1011 } else {
1012 rb_key = -HZ;
1013 __cfqq = cfq_rb_first(service_tree);
1014 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1015 }
1016
1017 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1018 new_cfqq = 0;
1019 /*
1020 * same position, nothing more to do
1021 */
1022 if (rb_key == cfqq->rb_key &&
1023 cfqq->service_tree == service_tree)
1024 return;
1025
1026 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1027 cfqq->service_tree = NULL;
1028 }
1029
1030 left = 1;
1031 parent = NULL;
1032 cfqq->service_tree = service_tree;
1033 p = &service_tree->rb.rb_node;
1034 while (*p) {
1035 struct rb_node **n;
1036
1037 parent = *p;
1038 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1039
1040 /*
1041 * sort by key, that represents service time.
1042 */
1043 if (time_before(rb_key, __cfqq->rb_key))
1044 n = &(*p)->rb_left;
1045 else {
1046 n = &(*p)->rb_right;
1047 left = 0;
1048 }
1049
1050 p = n;
1051 }
1052
1053 if (left)
1054 service_tree->left = &cfqq->rb_node;
1055
1056 cfqq->rb_key = rb_key;
1057 rb_link_node(&cfqq->rb_node, parent, p);
1058 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1059 service_tree->count++;
1060 if (add_front || !new_cfqq)
1061 return;
1062 cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1063}
1064
1065static struct cfq_queue *
1066cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1067 sector_t sector, struct rb_node **ret_parent,
1068 struct rb_node ***rb_link)
1069{
1070 struct rb_node **p, *parent;
1071 struct cfq_queue *cfqq = NULL;
1072
1073 parent = NULL;
1074 p = &root->rb_node;
1075 while (*p) {
1076 struct rb_node **n;
1077
1078 parent = *p;
1079 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1080
1081 /*
1082 * Sort strictly based on sector. Smallest to the left,
1083 * largest to the right.
1084 */
1085 if (sector > blk_rq_pos(cfqq->next_rq))
1086 n = &(*p)->rb_right;
1087 else if (sector < blk_rq_pos(cfqq->next_rq))
1088 n = &(*p)->rb_left;
1089 else
1090 break;
1091 p = n;
1092 cfqq = NULL;
1093 }
1094
1095 *ret_parent = parent;
1096 if (rb_link)
1097 *rb_link = p;
1098 return cfqq;
1099}
1100
1101static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1102{
1103 struct rb_node **p, *parent;
1104 struct cfq_queue *__cfqq;
1105
1106 if (cfqq->p_root) {
1107 rb_erase(&cfqq->p_node, cfqq->p_root);
1108 cfqq->p_root = NULL;
1109 }
1110
1111 if (cfq_class_idle(cfqq))
1112 return;
1113 if (!cfqq->next_rq)
1114 return;
1115
1116 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1117 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1118 blk_rq_pos(cfqq->next_rq), &parent, &p);
1119 if (!__cfqq) {
1120 rb_link_node(&cfqq->p_node, parent, p);
1121 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1122 } else
1123 cfqq->p_root = NULL;
1124}
1125
1126/*
1127 * Update cfqq's position in the service tree.
1128 */
1129static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1130{
1131 /*
1132 * Resorting requires the cfqq to be on the RR list already.
1133 */
1134 if (cfq_cfqq_on_rr(cfqq)) {
1135 cfq_service_tree_add(cfqd, cfqq, 0);
1136 cfq_prio_tree_add(cfqd, cfqq);
1137 }
1138}
1139
1140/*
1141 * add to busy list of queues for service, trying to be fair in ordering
1142 * the pending list according to last request service
1143 */
1144static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1145{
1146 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1147 BUG_ON(cfq_cfqq_on_rr(cfqq));
1148 cfq_mark_cfqq_on_rr(cfqq);
1149 cfqd->busy_queues++;
1150
1151 cfq_resort_rr_list(cfqd, cfqq);
1152}
1153
1154/*
1155 * Called when the cfqq no longer has requests pending, remove it from
1156 * the service tree.
1157 */
1158static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1159{
1160 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1161 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1162 cfq_clear_cfqq_on_rr(cfqq);
1163
1164 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1165 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1166 cfqq->service_tree = NULL;
1167 }
1168 if (cfqq->p_root) {
1169 rb_erase(&cfqq->p_node, cfqq->p_root);
1170 cfqq->p_root = NULL;
1171 }
1172
1173 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1174 BUG_ON(!cfqd->busy_queues);
1175 cfqd->busy_queues--;
1176}
1177
1178/*
1179 * rb tree support functions
1180 */
1181static void cfq_del_rq_rb(struct request *rq)
1182{
1183 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1184 const int sync = rq_is_sync(rq);
1185
1186 BUG_ON(!cfqq->queued[sync]);
1187 cfqq->queued[sync]--;
1188
1189 elv_rb_del(&cfqq->sort_list, rq);
1190
1191 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1192 /*
1193 * Queue will be deleted from service tree when we actually
1194 * expire it later. Right now just remove it from prio tree
1195 * as it is empty.
1196 */
1197 if (cfqq->p_root) {
1198 rb_erase(&cfqq->p_node, cfqq->p_root);
1199 cfqq->p_root = NULL;
1200 }
1201 }
1202}
1203
1204static void cfq_add_rq_rb(struct request *rq)
1205{
1206 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1207 struct cfq_data *cfqd = cfqq->cfqd;
1208 struct request *__alias, *prev;
1209
1210 cfqq->queued[rq_is_sync(rq)]++;
1211
1212 /*
1213 * looks a little odd, but the first insert might return an alias.
1214 * if that happens, put the alias on the dispatch list
1215 */
1216 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1217 cfq_dispatch_insert(cfqd->queue, __alias);
1218
1219 if (!cfq_cfqq_on_rr(cfqq))
1220 cfq_add_cfqq_rr(cfqd, cfqq);
1221
1222 /*
1223 * check if this request is a better next-serve candidate
1224 */
1225 prev = cfqq->next_rq;
1226 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1227
1228 /*
1229 * adjust priority tree position, if ->next_rq changes
1230 */
1231 if (prev != cfqq->next_rq)
1232 cfq_prio_tree_add(cfqd, cfqq);
1233
1234 BUG_ON(!cfqq->next_rq);
1235}
1236
1237static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1238{
1239 elv_rb_del(&cfqq->sort_list, rq);
1240 cfqq->queued[rq_is_sync(rq)]--;
1241 cfq_add_rq_rb(rq);
1242}
1243
1244static struct request *
1245cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1246{
1247 struct task_struct *tsk = current;
1248 struct cfq_io_context *cic;
1249 struct cfq_queue *cfqq;
1250
1251 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1252 if (!cic)
1253 return NULL;
1254
1255 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1256 if (cfqq) {
1257 sector_t sector = bio->bi_sector + bio_sectors(bio);
1258
1259 return elv_rb_find(&cfqq->sort_list, sector);
1260 }
1261
1262 return NULL;
1263}
1264
1265static void cfq_activate_request(struct request_queue *q, struct request *rq)
1266{
1267 struct cfq_data *cfqd = q->elevator->elevator_data;
1268
1269 cfqd->rq_in_driver[rq_is_sync(rq)]++;
1270 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1271 rq_in_driver(cfqd));
1272
1273 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1274}
1275
1276static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1277{
1278 struct cfq_data *cfqd = q->elevator->elevator_data;
1279 const int sync = rq_is_sync(rq);
1280
1281 WARN_ON(!cfqd->rq_in_driver[sync]);
1282 cfqd->rq_in_driver[sync]--;
1283 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1284 rq_in_driver(cfqd));
1285}
1286
1287static void cfq_remove_request(struct request *rq)
1288{
1289 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1290
1291 if (cfqq->next_rq == rq)
1292 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1293
1294 list_del_init(&rq->queuelist);
1295 cfq_del_rq_rb(rq);
1296
1297 cfqq->cfqd->rq_queued--;
1298 if (rq_is_meta(rq)) {
1299 WARN_ON(!cfqq->meta_pending);
1300 cfqq->meta_pending--;
1301 }
1302}
1303
1304static int cfq_merge(struct request_queue *q, struct request **req,
1305 struct bio *bio)
1306{
1307 struct cfq_data *cfqd = q->elevator->elevator_data;
1308 struct request *__rq;
1309
1310 __rq = cfq_find_rq_fmerge(cfqd, bio);
1311 if (__rq && elv_rq_merge_ok(__rq, bio)) {
1312 *req = __rq;
1313 return ELEVATOR_FRONT_MERGE;
1314 }
1315
1316 return ELEVATOR_NO_MERGE;
1317}
1318
1319static void cfq_merged_request(struct request_queue *q, struct request *req,
1320 int type)
1321{
1322 if (type == ELEVATOR_FRONT_MERGE) {
1323 struct cfq_queue *cfqq = RQ_CFQQ(req);
1324
1325 cfq_reposition_rq_rb(cfqq, req);
1326 }
1327}
1328
1329static void
1330cfq_merged_requests(struct request_queue *q, struct request *rq,
1331 struct request *next)
1332{
1333 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1334 /*
1335 * reposition in fifo if next is older than rq
1336 */
1337 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1338 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1339 list_move(&rq->queuelist, &next->queuelist);
1340 rq_set_fifo_time(rq, rq_fifo_time(next));
1341 }
1342
1343 if (cfqq->next_rq == next)
1344 cfqq->next_rq = rq;
1345 cfq_remove_request(next);
1346}
1347
1348static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1349 struct bio *bio)
1350{
1351 struct cfq_data *cfqd = q->elevator->elevator_data;
1352 struct cfq_io_context *cic;
1353 struct cfq_queue *cfqq;
1354
1355 /*
1356 * Disallow merge of a sync bio into an async request.
1357 */
1358 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1359 return false;
1360
1361 /*
1362 * Lookup the cfqq that this bio will be queued with. Allow
1363 * merge only if rq is queued there.
1364 */
1365 cic = cfq_cic_lookup(cfqd, current->io_context);
1366 if (!cic)
1367 return false;
1368
1369 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1370 return cfqq == RQ_CFQQ(rq);
1371}
1372
1373static void __cfq_set_active_queue(struct cfq_data *cfqd,
1374 struct cfq_queue *cfqq)
1375{
1376 if (cfqq) {
1377 cfq_log_cfqq(cfqd, cfqq, "set_active");
1378 cfqq->slice_start = 0;
1379 cfqq->dispatch_start = jiffies;
1380 cfqq->slice_end = 0;
1381 cfqq->slice_dispatch = 0;
1382
1383 cfq_clear_cfqq_wait_request(cfqq);
1384 cfq_clear_cfqq_must_dispatch(cfqq);
1385 cfq_clear_cfqq_must_alloc_slice(cfqq);
1386 cfq_clear_cfqq_fifo_expire(cfqq);
1387 cfq_mark_cfqq_slice_new(cfqq);
1388
1389 del_timer(&cfqd->idle_slice_timer);
1390 }
1391
1392 cfqd->active_queue = cfqq;
1393}
1394
1395/*
1396 * current cfqq expired its slice (or was too idle), select new one
1397 */
1398static void
1399__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1400 bool timed_out)
1401{
1402 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1403
1404 if (cfq_cfqq_wait_request(cfqq))
1405 del_timer(&cfqd->idle_slice_timer);
1406
1407 cfq_clear_cfqq_wait_request(cfqq);
1408
1409 /*
1410 * store what was left of this slice, if the queue idled/timed out
1411 */
1412 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1413 cfqq->slice_resid = cfqq->slice_end - jiffies;
1414 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1415 }
1416
1417 cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1418
1419 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1420 cfq_del_cfqq_rr(cfqd, cfqq);
1421
1422 cfq_resort_rr_list(cfqd, cfqq);
1423
1424 if (cfqq == cfqd->active_queue)
1425 cfqd->active_queue = NULL;
1426
1427 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1428 cfqd->grp_service_tree.active = NULL;
1429
1430 if (cfqd->active_cic) {
1431 put_io_context(cfqd->active_cic->ioc);
1432 cfqd->active_cic = NULL;
1433 }
1434}
1435
1436static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1437{
1438 struct cfq_queue *cfqq = cfqd->active_queue;
1439
1440 if (cfqq)
1441 __cfq_slice_expired(cfqd, cfqq, timed_out);
1442}
1443
1444/*
1445 * Get next queue for service. Unless we have a queue preemption,
1446 * we'll simply select the first cfqq in the service tree.
1447 */
1448static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1449{
1450 struct cfq_rb_root *service_tree =
1451 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1452 cfqd->serving_type, cfqd);
1453
1454 if (!cfqd->rq_queued)
1455 return NULL;
1456
1457 /* There is nothing to dispatch */
1458 if (!service_tree)
1459 return NULL;
1460 if (RB_EMPTY_ROOT(&service_tree->rb))
1461 return NULL;
1462 return cfq_rb_first(service_tree);
1463}
1464
1465static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1466{
1467 struct cfq_group *cfqg;
1468 struct cfq_queue *cfqq;
1469 int i, j;
1470 struct cfq_rb_root *st;
1471
1472 if (!cfqd->rq_queued)
1473 return NULL;
1474
1475 cfqg = cfq_get_next_cfqg(cfqd);
1476 if (!cfqg)
1477 return NULL;
1478
1479 for_each_cfqg_st(cfqg, i, j, st)
1480 if ((cfqq = cfq_rb_first(st)) != NULL)
1481 return cfqq;
1482 return NULL;
1483}
1484
1485/*
1486 * Get and set a new active queue for service.
1487 */
1488static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1489 struct cfq_queue *cfqq)
1490{
1491 if (!cfqq)
1492 cfqq = cfq_get_next_queue(cfqd);
1493
1494 __cfq_set_active_queue(cfqd, cfqq);
1495 return cfqq;
1496}
1497
1498static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1499 struct request *rq)
1500{
1501 if (blk_rq_pos(rq) >= cfqd->last_position)
1502 return blk_rq_pos(rq) - cfqd->last_position;
1503 else
1504 return cfqd->last_position - blk_rq_pos(rq);
1505}
1506
1507#define CFQQ_SEEK_THR 8 * 1024
1508#define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1509
1510static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1511 struct request *rq)
1512{
1513 sector_t sdist = cfqq->seek_mean;
1514
1515 if (!sample_valid(cfqq->seek_samples))
1516 sdist = CFQQ_SEEK_THR;
1517
1518 return cfq_dist_from_last(cfqd, rq) <= sdist;
1519}
1520
1521static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1522 struct cfq_queue *cur_cfqq)
1523{
1524 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1525 struct rb_node *parent, *node;
1526 struct cfq_queue *__cfqq;
1527 sector_t sector = cfqd->last_position;
1528
1529 if (RB_EMPTY_ROOT(root))
1530 return NULL;
1531
1532 /*
1533 * First, if we find a request starting at the end of the last
1534 * request, choose it.
1535 */
1536 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1537 if (__cfqq)
1538 return __cfqq;
1539
1540 /*
1541 * If the exact sector wasn't found, the parent of the NULL leaf
1542 * will contain the closest sector.
1543 */
1544 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1545 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1546 return __cfqq;
1547
1548 if (blk_rq_pos(__cfqq->next_rq) < sector)
1549 node = rb_next(&__cfqq->p_node);
1550 else
1551 node = rb_prev(&__cfqq->p_node);
1552 if (!node)
1553 return NULL;
1554
1555 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1556 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1557 return __cfqq;
1558
1559 return NULL;
1560}
1561
1562/*
1563 * cfqd - obvious
1564 * cur_cfqq - passed in so that we don't decide that the current queue is
1565 * closely cooperating with itself.
1566 *
1567 * So, basically we're assuming that that cur_cfqq has dispatched at least
1568 * one request, and that cfqd->last_position reflects a position on the disk
1569 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1570 * assumption.
1571 */
1572static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1573 struct cfq_queue *cur_cfqq)
1574{
1575 struct cfq_queue *cfqq;
1576
1577 if (!cfq_cfqq_sync(cur_cfqq))
1578 return NULL;
1579 if (CFQQ_SEEKY(cur_cfqq))
1580 return NULL;
1581
1582 /*
1583 * We should notice if some of the queues are cooperating, eg
1584 * working closely on the same area of the disk. In that case,
1585 * we can group them together and don't waste time idling.
1586 */
1587 cfqq = cfqq_close(cfqd, cur_cfqq);
1588 if (!cfqq)
1589 return NULL;
1590
1591 /*
1592 * It only makes sense to merge sync queues.
1593 */
1594 if (!cfq_cfqq_sync(cfqq))
1595 return NULL;
1596 if (CFQQ_SEEKY(cfqq))
1597 return NULL;
1598
1599 /*
1600 * Do not merge queues of different priority classes
1601 */
1602 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1603 return NULL;
1604
1605 return cfqq;
1606}
1607
1608/*
1609 * Determine whether we should enforce idle window for this queue.
1610 */
1611
1612static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1613{
1614 enum wl_prio_t prio = cfqq_prio(cfqq);
1615 struct cfq_rb_root *service_tree = cfqq->service_tree;
1616
1617 BUG_ON(!service_tree);
1618 BUG_ON(!service_tree->count);
1619
1620 /* We never do for idle class queues. */
1621 if (prio == IDLE_WORKLOAD)
1622 return false;
1623
1624 /* We do for queues that were marked with idle window flag. */
1625 if (cfq_cfqq_idle_window(cfqq))
1626 return true;
1627
1628 /*
1629 * Otherwise, we do only if they are the last ones
1630 * in their service tree.
1631 */
1632 return service_tree->count == 1;
1633}
1634
1635static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1636{
1637 struct cfq_queue *cfqq = cfqd->active_queue;
1638 struct cfq_io_context *cic;
1639 unsigned long sl;
1640
1641 /*
1642 * SSD device without seek penalty, disable idling. But only do so
1643 * for devices that support queuing, otherwise we still have a problem
1644 * with sync vs async workloads.
1645 */
1646 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1647 return;
1648
1649 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1650 WARN_ON(cfq_cfqq_slice_new(cfqq));
1651
1652 /*
1653 * idle is disabled, either manually or by past process history
1654 */
1655 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1656 return;
1657
1658 /*
1659 * still active requests from this queue, don't idle
1660 */
1661 if (cfqq->dispatched)
1662 return;
1663
1664 /*
1665 * task has exited, don't wait
1666 */
1667 cic = cfqd->active_cic;
1668 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1669 return;
1670
1671 /*
1672 * If our average think time is larger than the remaining time
1673 * slice, then don't idle. This avoids overrunning the allotted
1674 * time slice.
1675 */
1676 if (sample_valid(cic->ttime_samples) &&
1677 (cfqq->slice_end - jiffies < cic->ttime_mean))
1678 return;
1679
1680 cfq_mark_cfqq_wait_request(cfqq);
1681
1682 sl = cfqd->cfq_slice_idle;
1683
1684 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1685 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1686}
1687
1688/*
1689 * Move request from internal lists to the request queue dispatch list.
1690 */
1691static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1692{
1693 struct cfq_data *cfqd = q->elevator->elevator_data;
1694 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1695
1696 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1697
1698 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1699 cfq_remove_request(rq);
1700 cfqq->dispatched++;
1701 elv_dispatch_sort(q, rq);
1702
1703 if (cfq_cfqq_sync(cfqq))
1704 cfqd->sync_flight++;
1705}
1706
1707/*
1708 * return expired entry, or NULL to just start from scratch in rbtree
1709 */
1710static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1711{
1712 struct request *rq = NULL;
1713
1714 if (cfq_cfqq_fifo_expire(cfqq))
1715 return NULL;
1716
1717 cfq_mark_cfqq_fifo_expire(cfqq);
1718
1719 if (list_empty(&cfqq->fifo))
1720 return NULL;
1721
1722 rq = rq_entry_fifo(cfqq->fifo.next);
1723 if (time_before(jiffies, rq_fifo_time(rq)))
1724 rq = NULL;
1725
1726 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1727 return rq;
1728}
1729
1730static inline int
1731cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1732{
1733 const int base_rq = cfqd->cfq_slice_async_rq;
1734
1735 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1736
1737 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1738}
1739
1740/*
1741 * Must be called with the queue_lock held.
1742 */
1743static int cfqq_process_refs(struct cfq_queue *cfqq)
1744{
1745 int process_refs, io_refs;
1746
1747 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1748 process_refs = atomic_read(&cfqq->ref) - io_refs;
1749 BUG_ON(process_refs < 0);
1750 return process_refs;
1751}
1752
1753static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1754{
1755 int process_refs, new_process_refs;
1756 struct cfq_queue *__cfqq;
1757
1758 /* Avoid a circular list and skip interim queue merges */
1759 while ((__cfqq = new_cfqq->new_cfqq)) {
1760 if (__cfqq == cfqq)
1761 return;
1762 new_cfqq = __cfqq;
1763 }
1764
1765 process_refs = cfqq_process_refs(cfqq);
1766 /*
1767 * If the process for the cfqq has gone away, there is no
1768 * sense in merging the queues.
1769 */
1770 if (process_refs == 0)
1771 return;
1772
1773 /*
1774 * Merge in the direction of the lesser amount of work.
1775 */
1776 new_process_refs = cfqq_process_refs(new_cfqq);
1777 if (new_process_refs >= process_refs) {
1778 cfqq->new_cfqq = new_cfqq;
1779 atomic_add(process_refs, &new_cfqq->ref);
1780 } else {
1781 new_cfqq->new_cfqq = cfqq;
1782 atomic_add(new_process_refs, &cfqq->ref);
1783 }
1784}
1785
1786static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1787 struct cfq_group *cfqg, enum wl_prio_t prio,
1788 bool prio_changed)
1789{
1790 struct cfq_queue *queue;
1791 int i;
1792 bool key_valid = false;
1793 unsigned long lowest_key = 0;
1794 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1795
1796 if (prio_changed) {
1797 /*
1798 * When priorities switched, we prefer starting
1799 * from SYNC_NOIDLE (first choice), or just SYNC
1800 * over ASYNC
1801 */
1802 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1803 return cur_best;
1804 cur_best = SYNC_WORKLOAD;
1805 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1806 return cur_best;
1807
1808 return ASYNC_WORKLOAD;
1809 }
1810
1811 for (i = 0; i < 3; ++i) {
1812 /* otherwise, select the one with lowest rb_key */
1813 queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
1814 if (queue &&
1815 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1816 lowest_key = queue->rb_key;
1817 cur_best = i;
1818 key_valid = true;
1819 }
1820 }
1821
1822 return cur_best;
1823}
1824
1825static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1826{
1827 enum wl_prio_t previous_prio = cfqd->serving_prio;
1828 bool prio_changed;
1829 unsigned slice;
1830 unsigned count;
1831 struct cfq_rb_root *st;
1832 unsigned group_slice;
1833
1834 if (!cfqg) {
1835 cfqd->serving_prio = IDLE_WORKLOAD;
1836 cfqd->workload_expires = jiffies + 1;
1837 return;
1838 }
1839
1840 /* Choose next priority. RT > BE > IDLE */
1841 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
1842 cfqd->serving_prio = RT_WORKLOAD;
1843 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
1844 cfqd->serving_prio = BE_WORKLOAD;
1845 else {
1846 cfqd->serving_prio = IDLE_WORKLOAD;
1847 cfqd->workload_expires = jiffies + 1;
1848 return;
1849 }
1850
1851 /*
1852 * For RT and BE, we have to choose also the type
1853 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1854 * expiration time
1855 */
1856 prio_changed = (cfqd->serving_prio != previous_prio);
1857 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1858 cfqd);
1859 count = st->count;
1860
1861 /*
1862 * If priority didn't change, check workload expiration,
1863 * and that we still have other queues ready
1864 */
1865 if (!prio_changed && count &&
1866 !time_after(jiffies, cfqd->workload_expires))
1867 return;
1868
1869 /* otherwise select new workload type */
1870 cfqd->serving_type =
1871 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
1872 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1873 cfqd);
1874 count = st->count;
1875
1876 /*
1877 * the workload slice is computed as a fraction of target latency
1878 * proportional to the number of queues in that workload, over
1879 * all the queues in the same priority class
1880 */
1881 group_slice = cfq_group_slice(cfqd, cfqg);
1882
1883 slice = group_slice * count /
1884 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
1885 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
1886
1887 if (cfqd->serving_type == ASYNC_WORKLOAD)
1888 /* async workload slice is scaled down according to
1889 * the sync/async slice ratio. */
1890 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
1891 else
1892 /* sync workload slice is at least 2 * cfq_slice_idle */
1893 slice = max(slice, 2 * cfqd->cfq_slice_idle);
1894
1895 slice = max_t(unsigned, slice, CFQ_MIN_TT);
1896 cfqd->workload_expires = jiffies + slice;
1897 cfqd->noidle_tree_requires_idle = false;
1898}
1899
1900static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
1901{
1902 struct cfq_rb_root *st = &cfqd->grp_service_tree;
1903 struct cfq_group *cfqg;
1904
1905 if (RB_EMPTY_ROOT(&st->rb))
1906 return NULL;
1907 cfqg = cfq_rb_first_group(st);
1908 st->active = &cfqg->rb_node;
1909 update_min_vdisktime(st);
1910 return cfqg;
1911}
1912
1913static void cfq_choose_cfqg(struct cfq_data *cfqd)
1914{
1915 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
1916
1917 cfqd->serving_group = cfqg;
1918
1919 /* Restore the workload type data */
1920 if (cfqg->saved_workload_slice) {
1921 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
1922 cfqd->serving_type = cfqg->saved_workload;
1923 cfqd->serving_prio = cfqg->saved_serving_prio;
1924 }
1925 choose_service_tree(cfqd, cfqg);
1926}
1927
1928/*
1929 * Select a queue for service. If we have a current active queue,
1930 * check whether to continue servicing it, or retrieve and set a new one.
1931 */
1932static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1933{
1934 struct cfq_queue *cfqq, *new_cfqq = NULL;
1935
1936 cfqq = cfqd->active_queue;
1937 if (!cfqq)
1938 goto new_queue;
1939
1940 if (!cfqd->rq_queued)
1941 return NULL;
1942 /*
1943 * The active queue has run out of time, expire it and select new.
1944 */
1945 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1946 goto expire;
1947
1948 /*
1949 * The active queue has requests and isn't expired, allow it to
1950 * dispatch.
1951 */
1952 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1953 goto keep_queue;
1954
1955 /*
1956 * If another queue has a request waiting within our mean seek
1957 * distance, let it run. The expire code will check for close
1958 * cooperators and put the close queue at the front of the service
1959 * tree. If possible, merge the expiring queue with the new cfqq.
1960 */
1961 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
1962 if (new_cfqq) {
1963 if (!cfqq->new_cfqq)
1964 cfq_setup_merge(cfqq, new_cfqq);
1965 goto expire;
1966 }
1967
1968 /*
1969 * No requests pending. If the active queue still has requests in
1970 * flight or is idling for a new request, allow either of these
1971 * conditions to happen (or time out) before selecting a new queue.
1972 */
1973 if (timer_pending(&cfqd->idle_slice_timer) ||
1974 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
1975 cfqq = NULL;
1976 goto keep_queue;
1977 }
1978
1979expire:
1980 cfq_slice_expired(cfqd, 0);
1981new_queue:
1982 /*
1983 * Current queue expired. Check if we have to switch to a new
1984 * service tree
1985 */
1986 if (!new_cfqq)
1987 cfq_choose_cfqg(cfqd);
1988
1989 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1990keep_queue:
1991 return cfqq;
1992}
1993
1994static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1995{
1996 int dispatched = 0;
1997
1998 while (cfqq->next_rq) {
1999 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2000 dispatched++;
2001 }
2002
2003 BUG_ON(!list_empty(&cfqq->fifo));
2004
2005 /* By default cfqq is not expired if it is empty. Do it explicitly */
2006 __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2007 return dispatched;
2008}
2009
2010/*
2011 * Drain our current requests. Used for barriers and when switching
2012 * io schedulers on-the-fly.
2013 */
2014static int cfq_forced_dispatch(struct cfq_data *cfqd)
2015{
2016 struct cfq_queue *cfqq;
2017 int dispatched = 0;
2018
2019 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
2020 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2021
2022 cfq_slice_expired(cfqd, 0);
2023 BUG_ON(cfqd->busy_queues);
2024
2025 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2026 return dispatched;
2027}
2028
2029static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2030{
2031 unsigned int max_dispatch;
2032
2033 /*
2034 * Drain async requests before we start sync IO
2035 */
2036 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
2037 return false;
2038
2039 /*
2040 * If this is an async queue and we have sync IO in flight, let it wait
2041 */
2042 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
2043 return false;
2044
2045 max_dispatch = cfqd->cfq_quantum;
2046 if (cfq_class_idle(cfqq))
2047 max_dispatch = 1;
2048
2049 /*
2050 * Does this cfqq already have too much IO in flight?
2051 */
2052 if (cfqq->dispatched >= max_dispatch) {
2053 /*
2054 * idle queue must always only have a single IO in flight
2055 */
2056 if (cfq_class_idle(cfqq))
2057 return false;
2058
2059 /*
2060 * We have other queues, don't allow more IO from this one
2061 */
2062 if (cfqd->busy_queues > 1)
2063 return false;
2064
2065 /*
2066 * Sole queue user, no limit
2067 */
2068 max_dispatch = -1;
2069 }
2070
2071 /*
2072 * Async queues must wait a bit before being allowed dispatch.
2073 * We also ramp up the dispatch depth gradually for async IO,
2074 * based on the last sync IO we serviced
2075 */
2076 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2077 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
2078 unsigned int depth;
2079
2080 depth = last_sync / cfqd->cfq_slice[1];
2081 if (!depth && !cfqq->dispatched)
2082 depth = 1;
2083 if (depth < max_dispatch)
2084 max_dispatch = depth;
2085 }
2086
2087 /*
2088 * If we're below the current max, allow a dispatch
2089 */
2090 return cfqq->dispatched < max_dispatch;
2091}
2092
2093/*
2094 * Dispatch a request from cfqq, moving them to the request queue
2095 * dispatch list.
2096 */
2097static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2098{
2099 struct request *rq;
2100
2101 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2102
2103 if (!cfq_may_dispatch(cfqd, cfqq))
2104 return false;
2105
2106 /*
2107 * follow expired path, else get first next available
2108 */
2109 rq = cfq_check_fifo(cfqq);
2110 if (!rq)
2111 rq = cfqq->next_rq;
2112
2113 /*
2114 * insert request into driver dispatch list
2115 */
2116 cfq_dispatch_insert(cfqd->queue, rq);
2117
2118 if (!cfqd->active_cic) {
2119 struct cfq_io_context *cic = RQ_CIC(rq);
2120
2121 atomic_long_inc(&cic->ioc->refcount);
2122 cfqd->active_cic = cic;
2123 }
2124
2125 return true;
2126}
2127
2128/*
2129 * Find the cfqq that we need to service and move a request from that to the
2130 * dispatch list
2131 */
2132static int cfq_dispatch_requests(struct request_queue *q, int force)
2133{
2134 struct cfq_data *cfqd = q->elevator->elevator_data;
2135 struct cfq_queue *cfqq;
2136
2137 if (!cfqd->busy_queues)
2138 return 0;
2139
2140 if (unlikely(force))
2141 return cfq_forced_dispatch(cfqd);
2142
2143 cfqq = cfq_select_queue(cfqd);
2144 if (!cfqq)
2145 return 0;
2146
2147 /*
2148 * Dispatch a request from this cfqq, if it is allowed
2149 */
2150 if (!cfq_dispatch_request(cfqd, cfqq))
2151 return 0;
2152
2153 cfqq->slice_dispatch++;
2154 cfq_clear_cfqq_must_dispatch(cfqq);
2155
2156 /*
2157 * expire an async queue immediately if it has used up its slice. idle
2158 * queue always expire after 1 dispatch round.
2159 */
2160 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2161 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2162 cfq_class_idle(cfqq))) {
2163 cfqq->slice_end = jiffies + 1;
2164 cfq_slice_expired(cfqd, 0);
2165 }
2166
2167 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2168 return 1;
2169}
2170
2171/*
2172 * task holds one reference to the queue, dropped when task exits. each rq
2173 * in-flight on this queue also holds a reference, dropped when rq is freed.
2174 *
2175 * queue lock must be held here.
2176 */
2177static void cfq_put_queue(struct cfq_queue *cfqq)
2178{
2179 struct cfq_data *cfqd = cfqq->cfqd;
2180
2181 BUG_ON(atomic_read(&cfqq->ref) <= 0);
2182
2183 if (!atomic_dec_and_test(&cfqq->ref))
2184 return;
2185
2186 cfq_log_cfqq(cfqd, cfqq, "put_queue");
2187 BUG_ON(rb_first(&cfqq->sort_list));
2188 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2189
2190 if (unlikely(cfqd->active_queue == cfqq)) {
2191 __cfq_slice_expired(cfqd, cfqq, 0);
2192 cfq_schedule_dispatch(cfqd);
2193 }
2194
2195 BUG_ON(cfq_cfqq_on_rr(cfqq));
2196 kmem_cache_free(cfq_pool, cfqq);
2197}
2198
2199/*
2200 * Must always be called with the rcu_read_lock() held
2201 */
2202static void
2203__call_for_each_cic(struct io_context *ioc,
2204 void (*func)(struct io_context *, struct cfq_io_context *))
2205{
2206 struct cfq_io_context *cic;
2207 struct hlist_node *n;
2208
2209 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2210 func(ioc, cic);
2211}
2212
2213/*
2214 * Call func for each cic attached to this ioc.
2215 */
2216static void
2217call_for_each_cic(struct io_context *ioc,
2218 void (*func)(struct io_context *, struct cfq_io_context *))
2219{
2220 rcu_read_lock();
2221 __call_for_each_cic(ioc, func);
2222 rcu_read_unlock();
2223}
2224
2225static void cfq_cic_free_rcu(struct rcu_head *head)
2226{
2227 struct cfq_io_context *cic;
2228
2229 cic = container_of(head, struct cfq_io_context, rcu_head);
2230
2231 kmem_cache_free(cfq_ioc_pool, cic);
2232 elv_ioc_count_dec(cfq_ioc_count);
2233
2234 if (ioc_gone) {
2235 /*
2236 * CFQ scheduler is exiting, grab exit lock and check
2237 * the pending io context count. If it hits zero,
2238 * complete ioc_gone and set it back to NULL
2239 */
2240 spin_lock(&ioc_gone_lock);
2241 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2242 complete(ioc_gone);
2243 ioc_gone = NULL;
2244 }
2245 spin_unlock(&ioc_gone_lock);
2246 }
2247}
2248
2249static void cfq_cic_free(struct cfq_io_context *cic)
2250{
2251 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2252}
2253
2254static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2255{
2256 unsigned long flags;
2257
2258 BUG_ON(!cic->dead_key);
2259
2260 spin_lock_irqsave(&ioc->lock, flags);
2261 radix_tree_delete(&ioc->radix_root, cic->dead_key);
2262 hlist_del_rcu(&cic->cic_list);
2263 spin_unlock_irqrestore(&ioc->lock, flags);
2264
2265 cfq_cic_free(cic);
2266}
2267
2268/*
2269 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2270 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2271 * and ->trim() which is called with the task lock held
2272 */
2273static void cfq_free_io_context(struct io_context *ioc)
2274{
2275 /*
2276 * ioc->refcount is zero here, or we are called from elv_unregister(),
2277 * so no more cic's are allowed to be linked into this ioc. So it
2278 * should be ok to iterate over the known list, we will see all cic's
2279 * since no new ones are added.
2280 */
2281 __call_for_each_cic(ioc, cic_free_func);
2282}
2283
2284static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2285{
2286 struct cfq_queue *__cfqq, *next;
2287
2288 if (unlikely(cfqq == cfqd->active_queue)) {
2289 __cfq_slice_expired(cfqd, cfqq, 0);
2290 cfq_schedule_dispatch(cfqd);
2291 }
2292
2293 /*
2294 * If this queue was scheduled to merge with another queue, be
2295 * sure to drop the reference taken on that queue (and others in
2296 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2297 */
2298 __cfqq = cfqq->new_cfqq;
2299 while (__cfqq) {
2300 if (__cfqq == cfqq) {
2301 WARN(1, "cfqq->new_cfqq loop detected\n");
2302 break;
2303 }
2304 next = __cfqq->new_cfqq;
2305 cfq_put_queue(__cfqq);
2306 __cfqq = next;
2307 }
2308
2309 cfq_put_queue(cfqq);
2310}
2311
2312static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2313 struct cfq_io_context *cic)
2314{
2315 struct io_context *ioc = cic->ioc;
2316
2317 list_del_init(&cic->queue_list);
2318
2319 /*
2320 * Make sure key == NULL is seen for dead queues
2321 */
2322 smp_wmb();
2323 cic->dead_key = (unsigned long) cic->key;
2324 cic->key = NULL;
2325
2326 if (ioc->ioc_data == cic)
2327 rcu_assign_pointer(ioc->ioc_data, NULL);
2328
2329 if (cic->cfqq[BLK_RW_ASYNC]) {
2330 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2331 cic->cfqq[BLK_RW_ASYNC] = NULL;
2332 }
2333
2334 if (cic->cfqq[BLK_RW_SYNC]) {
2335 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2336 cic->cfqq[BLK_RW_SYNC] = NULL;
2337 }
2338}
2339
2340static void cfq_exit_single_io_context(struct io_context *ioc,
2341 struct cfq_io_context *cic)
2342{
2343 struct cfq_data *cfqd = cic->key;
2344
2345 if (cfqd) {
2346 struct request_queue *q = cfqd->queue;
2347 unsigned long flags;
2348
2349 spin_lock_irqsave(q->queue_lock, flags);
2350
2351 /*
2352 * Ensure we get a fresh copy of the ->key to prevent
2353 * race between exiting task and queue
2354 */
2355 smp_read_barrier_depends();
2356 if (cic->key)
2357 __cfq_exit_single_io_context(cfqd, cic);
2358
2359 spin_unlock_irqrestore(q->queue_lock, flags);
2360 }
2361}
2362
2363/*
2364 * The process that ioc belongs to has exited, we need to clean up
2365 * and put the internal structures we have that belongs to that process.
2366 */
2367static void cfq_exit_io_context(struct io_context *ioc)
2368{
2369 call_for_each_cic(ioc, cfq_exit_single_io_context);
2370}
2371
2372static struct cfq_io_context *
2373cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2374{
2375 struct cfq_io_context *cic;
2376
2377 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2378 cfqd->queue->node);
2379 if (cic) {
2380 cic->last_end_request = jiffies;
2381 INIT_LIST_HEAD(&cic->queue_list);
2382 INIT_HLIST_NODE(&cic->cic_list);
2383 cic->dtor = cfq_free_io_context;
2384 cic->exit = cfq_exit_io_context;
2385 elv_ioc_count_inc(cfq_ioc_count);
2386 }
2387
2388 return cic;
2389}
2390
2391static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2392{
2393 struct task_struct *tsk = current;
2394 int ioprio_class;
2395
2396 if (!cfq_cfqq_prio_changed(cfqq))
2397 return;
2398
2399 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2400 switch (ioprio_class) {
2401 default:
2402 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2403 case IOPRIO_CLASS_NONE:
2404 /*
2405 * no prio set, inherit CPU scheduling settings
2406 */
2407 cfqq->ioprio = task_nice_ioprio(tsk);
2408 cfqq->ioprio_class = task_nice_ioclass(tsk);
2409 break;
2410 case IOPRIO_CLASS_RT:
2411 cfqq->ioprio = task_ioprio(ioc);
2412 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2413 break;
2414 case IOPRIO_CLASS_BE:
2415 cfqq->ioprio = task_ioprio(ioc);
2416 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2417 break;
2418 case IOPRIO_CLASS_IDLE:
2419 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2420 cfqq->ioprio = 7;
2421 cfq_clear_cfqq_idle_window(cfqq);
2422 break;
2423 }
2424
2425 /*
2426 * keep track of original prio settings in case we have to temporarily
2427 * elevate the priority of this queue
2428 */
2429 cfqq->org_ioprio = cfqq->ioprio;
2430 cfqq->org_ioprio_class = cfqq->ioprio_class;
2431 cfq_clear_cfqq_prio_changed(cfqq);
2432}
2433
2434static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2435{
2436 struct cfq_data *cfqd = cic->key;
2437 struct cfq_queue *cfqq;
2438 unsigned long flags;
2439
2440 if (unlikely(!cfqd))
2441 return;
2442
2443 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2444
2445 cfqq = cic->cfqq[BLK_RW_ASYNC];
2446 if (cfqq) {
2447 struct cfq_queue *new_cfqq;
2448 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2449 GFP_ATOMIC);
2450 if (new_cfqq) {
2451 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2452 cfq_put_queue(cfqq);
2453 }
2454 }
2455
2456 cfqq = cic->cfqq[BLK_RW_SYNC];
2457 if (cfqq)
2458 cfq_mark_cfqq_prio_changed(cfqq);
2459
2460 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2461}
2462
2463static void cfq_ioc_set_ioprio(struct io_context *ioc)
2464{
2465 call_for_each_cic(ioc, changed_ioprio);
2466 ioc->ioprio_changed = 0;
2467}
2468
2469static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2470 pid_t pid, bool is_sync)
2471{
2472 RB_CLEAR_NODE(&cfqq->rb_node);
2473 RB_CLEAR_NODE(&cfqq->p_node);
2474 INIT_LIST_HEAD(&cfqq->fifo);
2475
2476 atomic_set(&cfqq->ref, 0);
2477 cfqq->cfqd = cfqd;
2478
2479 cfq_mark_cfqq_prio_changed(cfqq);
2480
2481 if (is_sync) {
2482 if (!cfq_class_idle(cfqq))
2483 cfq_mark_cfqq_idle_window(cfqq);
2484 cfq_mark_cfqq_sync(cfqq);
2485 }
2486 cfqq->pid = pid;
2487}
2488
2489static struct cfq_queue *
2490cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2491 struct io_context *ioc, gfp_t gfp_mask)
2492{
2493 struct cfq_queue *cfqq, *new_cfqq = NULL;
2494 struct cfq_io_context *cic;
2495 struct cfq_group *cfqg;
2496
2497retry:
2498 cfqg = cfq_get_cfqg(cfqd, 1);
2499 cic = cfq_cic_lookup(cfqd, ioc);
2500 /* cic always exists here */
2501 cfqq = cic_to_cfqq(cic, is_sync);
2502
2503 /*
2504 * Always try a new alloc if we fell back to the OOM cfqq
2505 * originally, since it should just be a temporary situation.
2506 */
2507 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2508 cfqq = NULL;
2509 if (new_cfqq) {
2510 cfqq = new_cfqq;
2511 new_cfqq = NULL;
2512 } else if (gfp_mask & __GFP_WAIT) {
2513 spin_unlock_irq(cfqd->queue->queue_lock);
2514 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2515 gfp_mask | __GFP_ZERO,
2516 cfqd->queue->node);
2517 spin_lock_irq(cfqd->queue->queue_lock);
2518 if (new_cfqq)
2519 goto retry;
2520 } else {
2521 cfqq = kmem_cache_alloc_node(cfq_pool,
2522 gfp_mask | __GFP_ZERO,
2523 cfqd->queue->node);
2524 }
2525
2526 if (cfqq) {
2527 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2528 cfq_init_prio_data(cfqq, ioc);
2529 cfq_link_cfqq_cfqg(cfqq, cfqg);
2530 cfq_log_cfqq(cfqd, cfqq, "alloced");
2531 } else
2532 cfqq = &cfqd->oom_cfqq;
2533 }
2534
2535 if (new_cfqq)
2536 kmem_cache_free(cfq_pool, new_cfqq);
2537
2538 return cfqq;
2539}
2540
2541static struct cfq_queue **
2542cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2543{
2544 switch (ioprio_class) {
2545 case IOPRIO_CLASS_RT:
2546 return &cfqd->async_cfqq[0][ioprio];
2547 case IOPRIO_CLASS_BE:
2548 return &cfqd->async_cfqq[1][ioprio];
2549 case IOPRIO_CLASS_IDLE:
2550 return &cfqd->async_idle_cfqq;
2551 default:
2552 BUG();
2553 }
2554}
2555
2556static struct cfq_queue *
2557cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2558 gfp_t gfp_mask)
2559{
2560 const int ioprio = task_ioprio(ioc);
2561 const int ioprio_class = task_ioprio_class(ioc);
2562 struct cfq_queue **async_cfqq = NULL;
2563 struct cfq_queue *cfqq = NULL;
2564
2565 if (!is_sync) {
2566 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2567 cfqq = *async_cfqq;
2568 }
2569
2570 if (!cfqq)
2571 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2572
2573 /*
2574 * pin the queue now that it's allocated, scheduler exit will prune it
2575 */
2576 if (!is_sync && !(*async_cfqq)) {
2577 atomic_inc(&cfqq->ref);
2578 *async_cfqq = cfqq;
2579 }
2580
2581 atomic_inc(&cfqq->ref);
2582 return cfqq;
2583}
2584
2585/*
2586 * We drop cfq io contexts lazily, so we may find a dead one.
2587 */
2588static void
2589cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2590 struct cfq_io_context *cic)
2591{
2592 unsigned long flags;
2593
2594 WARN_ON(!list_empty(&cic->queue_list));
2595
2596 spin_lock_irqsave(&ioc->lock, flags);
2597
2598 BUG_ON(ioc->ioc_data == cic);
2599
2600 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2601 hlist_del_rcu(&cic->cic_list);
2602 spin_unlock_irqrestore(&ioc->lock, flags);
2603
2604 cfq_cic_free(cic);
2605}
2606
2607static struct cfq_io_context *
2608cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2609{
2610 struct cfq_io_context *cic;
2611 unsigned long flags;
2612 void *k;
2613
2614 if (unlikely(!ioc))
2615 return NULL;
2616
2617 rcu_read_lock();
2618
2619 /*
2620 * we maintain a last-hit cache, to avoid browsing over the tree
2621 */
2622 cic = rcu_dereference(ioc->ioc_data);
2623 if (cic && cic->key == cfqd) {
2624 rcu_read_unlock();
2625 return cic;
2626 }
2627
2628 do {
2629 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2630 rcu_read_unlock();
2631 if (!cic)
2632 break;
2633 /* ->key must be copied to avoid race with cfq_exit_queue() */
2634 k = cic->key;
2635 if (unlikely(!k)) {
2636 cfq_drop_dead_cic(cfqd, ioc, cic);
2637 rcu_read_lock();
2638 continue;
2639 }
2640
2641 spin_lock_irqsave(&ioc->lock, flags);
2642 rcu_assign_pointer(ioc->ioc_data, cic);
2643 spin_unlock_irqrestore(&ioc->lock, flags);
2644 break;
2645 } while (1);
2646
2647 return cic;
2648}
2649
2650/*
2651 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2652 * the process specific cfq io context when entered from the block layer.
2653 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2654 */
2655static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2656 struct cfq_io_context *cic, gfp_t gfp_mask)
2657{
2658 unsigned long flags;
2659 int ret;
2660
2661 ret = radix_tree_preload(gfp_mask);
2662 if (!ret) {
2663 cic->ioc = ioc;
2664 cic->key = cfqd;
2665
2666 spin_lock_irqsave(&ioc->lock, flags);
2667 ret = radix_tree_insert(&ioc->radix_root,
2668 (unsigned long) cfqd, cic);
2669 if (!ret)
2670 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2671 spin_unlock_irqrestore(&ioc->lock, flags);
2672
2673 radix_tree_preload_end();
2674
2675 if (!ret) {
2676 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2677 list_add(&cic->queue_list, &cfqd->cic_list);
2678 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2679 }
2680 }
2681
2682 if (ret)
2683 printk(KERN_ERR "cfq: cic link failed!\n");
2684
2685 return ret;
2686}
2687
2688/*
2689 * Setup general io context and cfq io context. There can be several cfq
2690 * io contexts per general io context, if this process is doing io to more
2691 * than one device managed by cfq.
2692 */
2693static struct cfq_io_context *
2694cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2695{
2696 struct io_context *ioc = NULL;
2697 struct cfq_io_context *cic;
2698
2699 might_sleep_if(gfp_mask & __GFP_WAIT);
2700
2701 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2702 if (!ioc)
2703 return NULL;
2704
2705 cic = cfq_cic_lookup(cfqd, ioc);
2706 if (cic)
2707 goto out;
2708
2709 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2710 if (cic == NULL)
2711 goto err;
2712
2713 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2714 goto err_free;
2715
2716out:
2717 smp_read_barrier_depends();
2718 if (unlikely(ioc->ioprio_changed))
2719 cfq_ioc_set_ioprio(ioc);
2720
2721 return cic;
2722err_free:
2723 cfq_cic_free(cic);
2724err:
2725 put_io_context(ioc);
2726 return NULL;
2727}
2728
2729static void
2730cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2731{
2732 unsigned long elapsed = jiffies - cic->last_end_request;
2733 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2734
2735 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2736 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2737 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2738}
2739
2740static void
2741cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2742 struct request *rq)
2743{
2744 sector_t sdist;
2745 u64 total;
2746
2747 if (!cfqq->last_request_pos)
2748 sdist = 0;
2749 else if (cfqq->last_request_pos < blk_rq_pos(rq))
2750 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2751 else
2752 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2753
2754 /*
2755 * Don't allow the seek distance to get too large from the
2756 * odd fragment, pagein, etc
2757 */
2758 if (cfqq->seek_samples <= 60) /* second&third seek */
2759 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2760 else
2761 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2762
2763 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2764 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2765 total = cfqq->seek_total + (cfqq->seek_samples/2);
2766 do_div(total, cfqq->seek_samples);
2767 cfqq->seek_mean = (sector_t)total;
2768
2769 /*
2770 * If this cfqq is shared between multiple processes, check to
2771 * make sure that those processes are still issuing I/Os within
2772 * the mean seek distance. If not, it may be time to break the
2773 * queues apart again.
2774 */
2775 if (cfq_cfqq_coop(cfqq)) {
2776 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2777 cfqq->seeky_start = jiffies;
2778 else if (!CFQQ_SEEKY(cfqq))
2779 cfqq->seeky_start = 0;
2780 }
2781}
2782
2783/*
2784 * Disable idle window if the process thinks too long or seeks so much that
2785 * it doesn't matter
2786 */
2787static void
2788cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2789 struct cfq_io_context *cic)
2790{
2791 int old_idle, enable_idle;
2792
2793 /*
2794 * Don't idle for async or idle io prio class
2795 */
2796 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2797 return;
2798
2799 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2800
2801 if (cfqq->queued[0] + cfqq->queued[1] >= 4)
2802 cfq_mark_cfqq_deep(cfqq);
2803
2804 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2805 (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
2806 && CFQQ_SEEKY(cfqq)))
2807 enable_idle = 0;
2808 else if (sample_valid(cic->ttime_samples)) {
2809 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2810 enable_idle = 0;
2811 else
2812 enable_idle = 1;
2813 }
2814
2815 if (old_idle != enable_idle) {
2816 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2817 if (enable_idle)
2818 cfq_mark_cfqq_idle_window(cfqq);
2819 else
2820 cfq_clear_cfqq_idle_window(cfqq);
2821 }
2822}
2823
2824/*
2825 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2826 * no or if we aren't sure, a 1 will cause a preempt.
2827 */
2828static bool
2829cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2830 struct request *rq)
2831{
2832 struct cfq_queue *cfqq;
2833
2834 cfqq = cfqd->active_queue;
2835 if (!cfqq)
2836 return false;
2837
2838 if (cfq_slice_used(cfqq))
2839 return true;
2840
2841 if (cfq_class_idle(new_cfqq))
2842 return false;
2843
2844 if (cfq_class_idle(cfqq))
2845 return true;
2846
2847 /* Allow preemption only if we are idling on sync-noidle tree */
2848 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
2849 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
2850 new_cfqq->service_tree->count == 2 &&
2851 RB_EMPTY_ROOT(&cfqq->sort_list))
2852 return true;
2853
2854 /*
2855 * if the new request is sync, but the currently running queue is
2856 * not, let the sync request have priority.
2857 */
2858 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2859 return true;
2860
2861 /*
2862 * So both queues are sync. Let the new request get disk time if
2863 * it's a metadata request and the current queue is doing regular IO.
2864 */
2865 if (rq_is_meta(rq) && !cfqq->meta_pending)
2866 return true;
2867
2868 /*
2869 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2870 */
2871 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2872 return true;
2873
2874 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2875 return false;
2876
2877 /*
2878 * if this request is as-good as one we would expect from the
2879 * current cfqq, let it preempt
2880 */
2881 if (cfq_rq_close(cfqd, cfqq, rq))
2882 return true;
2883
2884 return false;
2885}
2886
2887/*
2888 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2889 * let it have half of its nominal slice.
2890 */
2891static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2892{
2893 cfq_log_cfqq(cfqd, cfqq, "preempt");
2894 cfq_slice_expired(cfqd, 1);
2895
2896 /*
2897 * Put the new queue at the front of the of the current list,
2898 * so we know that it will be selected next.
2899 */
2900 BUG_ON(!cfq_cfqq_on_rr(cfqq));
2901
2902 cfq_service_tree_add(cfqd, cfqq, 1);
2903
2904 cfqq->slice_end = 0;
2905 cfq_mark_cfqq_slice_new(cfqq);
2906}
2907
2908/*
2909 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2910 * something we should do about it
2911 */
2912static void
2913cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2914 struct request *rq)
2915{
2916 struct cfq_io_context *cic = RQ_CIC(rq);
2917
2918 cfqd->rq_queued++;
2919 if (rq_is_meta(rq))
2920 cfqq->meta_pending++;
2921
2922 cfq_update_io_thinktime(cfqd, cic);
2923 cfq_update_io_seektime(cfqd, cfqq, rq);
2924 cfq_update_idle_window(cfqd, cfqq, cic);
2925
2926 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2927
2928 if (cfqq == cfqd->active_queue) {
2929 /*
2930 * Remember that we saw a request from this process, but
2931 * don't start queuing just yet. Otherwise we risk seeing lots
2932 * of tiny requests, because we disrupt the normal plugging
2933 * and merging. If the request is already larger than a single
2934 * page, let it rip immediately. For that case we assume that
2935 * merging is already done. Ditto for a busy system that
2936 * has other work pending, don't risk delaying until the
2937 * idle timer unplug to continue working.
2938 */
2939 if (cfq_cfqq_wait_request(cfqq)) {
2940 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2941 cfqd->busy_queues > 1) {
2942 del_timer(&cfqd->idle_slice_timer);
2943 __blk_run_queue(cfqd->queue);
2944 } else
2945 cfq_mark_cfqq_must_dispatch(cfqq);
2946 }
2947 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2948 /*
2949 * not the active queue - expire current slice if it is
2950 * idle and has expired it's mean thinktime or this new queue
2951 * has some old slice time left and is of higher priority or
2952 * this new queue is RT and the current one is BE
2953 */
2954 cfq_preempt_queue(cfqd, cfqq);
2955 __blk_run_queue(cfqd->queue);
2956 }
2957}
2958
2959static void cfq_insert_request(struct request_queue *q, struct request *rq)
2960{
2961 struct cfq_data *cfqd = q->elevator->elevator_data;
2962 struct cfq_queue *cfqq = RQ_CFQQ(rq);
2963
2964 cfq_log_cfqq(cfqd, cfqq, "insert_request");
2965 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2966
2967 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
2968 list_add_tail(&rq->queuelist, &cfqq->fifo);
2969 cfq_add_rq_rb(rq);
2970
2971 cfq_rq_enqueued(cfqd, cfqq, rq);
2972}
2973
2974/*
2975 * Update hw_tag based on peak queue depth over 50 samples under
2976 * sufficient load.
2977 */
2978static void cfq_update_hw_tag(struct cfq_data *cfqd)
2979{
2980 struct cfq_queue *cfqq = cfqd->active_queue;
2981
2982 if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
2983 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
2984
2985 if (cfqd->hw_tag == 1)
2986 return;
2987
2988 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2989 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
2990 return;
2991
2992 /*
2993 * If active queue hasn't enough requests and can idle, cfq might not
2994 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2995 * case
2996 */
2997 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
2998 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
2999 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
3000 return;
3001
3002 if (cfqd->hw_tag_samples++ < 50)
3003 return;
3004
3005 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3006 cfqd->hw_tag = 1;
3007 else
3008 cfqd->hw_tag = 0;
3009}
3010
3011static void cfq_completed_request(struct request_queue *q, struct request *rq)
3012{
3013 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3014 struct cfq_data *cfqd = cfqq->cfqd;
3015 const int sync = rq_is_sync(rq);
3016 unsigned long now;
3017
3018 now = jiffies;
3019 cfq_log_cfqq(cfqd, cfqq, "complete");
3020
3021 cfq_update_hw_tag(cfqd);
3022
3023 WARN_ON(!cfqd->rq_in_driver[sync]);
3024 WARN_ON(!cfqq->dispatched);
3025 cfqd->rq_in_driver[sync]--;
3026 cfqq->dispatched--;
3027
3028 if (cfq_cfqq_sync(cfqq))
3029 cfqd->sync_flight--;
3030
3031 if (sync) {
3032 RQ_CIC(rq)->last_end_request = now;
3033 cfqd->last_end_sync_rq = now;
3034 }
3035
3036 /*
3037 * If this is the active queue, check if it needs to be expired,
3038 * or if we want to idle in case it has no pending requests.
3039 */
3040 if (cfqd->active_queue == cfqq) {
3041 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3042
3043 if (cfq_cfqq_slice_new(cfqq)) {
3044 cfq_set_prio_slice(cfqd, cfqq);
3045 cfq_clear_cfqq_slice_new(cfqq);
3046 }
3047 /*
3048 * Idling is not enabled on:
3049 * - expired queues
3050 * - idle-priority queues
3051 * - async queues
3052 * - queues with still some requests queued
3053 * - when there is a close cooperator
3054 */
3055 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3056 cfq_slice_expired(cfqd, 1);
3057 else if (sync && cfqq_empty &&
3058 !cfq_close_cooperator(cfqd, cfqq)) {
3059 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3060 /*
3061 * Idling is enabled for SYNC_WORKLOAD.
3062 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3063 * only if we processed at least one !rq_noidle request
3064 */
3065 if (cfqd->serving_type == SYNC_WORKLOAD
3066 || cfqd->noidle_tree_requires_idle)
3067 cfq_arm_slice_timer(cfqd);
3068 }
3069 }
3070
3071 if (!rq_in_driver(cfqd))
3072 cfq_schedule_dispatch(cfqd);
3073}
3074
3075/*
3076 * we temporarily boost lower priority queues if they are holding fs exclusive
3077 * resources. they are boosted to normal prio (CLASS_BE/4)
3078 */
3079static void cfq_prio_boost(struct cfq_queue *cfqq)
3080{
3081 if (has_fs_excl()) {
3082 /*
3083 * boost idle prio on transactions that would lock out other
3084 * users of the filesystem
3085 */
3086 if (cfq_class_idle(cfqq))
3087 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3088 if (cfqq->ioprio > IOPRIO_NORM)
3089 cfqq->ioprio = IOPRIO_NORM;
3090 } else {
3091 /*
3092 * unboost the queue (if needed)
3093 */
3094 cfqq->ioprio_class = cfqq->org_ioprio_class;
3095 cfqq->ioprio = cfqq->org_ioprio;
3096 }
3097}
3098
3099static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3100{
3101 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3102 cfq_mark_cfqq_must_alloc_slice(cfqq);
3103 return ELV_MQUEUE_MUST;
3104 }
3105
3106 return ELV_MQUEUE_MAY;
3107}
3108
3109static int cfq_may_queue(struct request_queue *q, int rw)
3110{
3111 struct cfq_data *cfqd = q->elevator->elevator_data;
3112 struct task_struct *tsk = current;
3113 struct cfq_io_context *cic;
3114 struct cfq_queue *cfqq;
3115
3116 /*
3117 * don't force setup of a queue from here, as a call to may_queue
3118 * does not necessarily imply that a request actually will be queued.
3119 * so just lookup a possibly existing queue, or return 'may queue'
3120 * if that fails
3121 */
3122 cic = cfq_cic_lookup(cfqd, tsk->io_context);
3123 if (!cic)
3124 return ELV_MQUEUE_MAY;
3125
3126 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3127 if (cfqq) {
3128 cfq_init_prio_data(cfqq, cic->ioc);
3129 cfq_prio_boost(cfqq);
3130
3131 return __cfq_may_queue(cfqq);
3132 }
3133
3134 return ELV_MQUEUE_MAY;
3135}
3136
3137/*
3138 * queue lock held here
3139 */
3140static void cfq_put_request(struct request *rq)
3141{
3142 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3143
3144 if (cfqq) {
3145 const int rw = rq_data_dir(rq);
3146
3147 BUG_ON(!cfqq->allocated[rw]);
3148 cfqq->allocated[rw]--;
3149
3150 put_io_context(RQ_CIC(rq)->ioc);
3151
3152 rq->elevator_private = NULL;
3153 rq->elevator_private2 = NULL;
3154
3155 cfq_put_queue(cfqq);
3156 }
3157}
3158
3159static struct cfq_queue *
3160cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3161 struct cfq_queue *cfqq)
3162{
3163 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3164 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3165 cfq_mark_cfqq_coop(cfqq->new_cfqq);
3166 cfq_put_queue(cfqq);
3167 return cic_to_cfqq(cic, 1);
3168}
3169
3170static int should_split_cfqq(struct cfq_queue *cfqq)
3171{
3172 if (cfqq->seeky_start &&
3173 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
3174 return 1;
3175 return 0;
3176}
3177
3178/*
3179 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3180 * was the last process referring to said cfqq.
3181 */
3182static struct cfq_queue *
3183split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3184{
3185 if (cfqq_process_refs(cfqq) == 1) {
3186 cfqq->seeky_start = 0;
3187 cfqq->pid = current->pid;
3188 cfq_clear_cfqq_coop(cfqq);
3189 return cfqq;
3190 }
3191
3192 cic_set_cfqq(cic, NULL, 1);
3193 cfq_put_queue(cfqq);
3194 return NULL;
3195}
3196/*
3197 * Allocate cfq data structures associated with this request.
3198 */
3199static int
3200cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3201{
3202 struct cfq_data *cfqd = q->elevator->elevator_data;
3203 struct cfq_io_context *cic;
3204 const int rw = rq_data_dir(rq);
3205 const bool is_sync = rq_is_sync(rq);
3206 struct cfq_queue *cfqq;
3207 unsigned long flags;
3208
3209 might_sleep_if(gfp_mask & __GFP_WAIT);
3210
3211 cic = cfq_get_io_context(cfqd, gfp_mask);
3212
3213 spin_lock_irqsave(q->queue_lock, flags);
3214
3215 if (!cic)
3216 goto queue_fail;
3217
3218new_queue:
3219 cfqq = cic_to_cfqq(cic, is_sync);
3220 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3221 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3222 cic_set_cfqq(cic, cfqq, is_sync);
3223 } else {
3224 /*
3225 * If the queue was seeky for too long, break it apart.
3226 */
3227 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
3228 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3229 cfqq = split_cfqq(cic, cfqq);
3230 if (!cfqq)
3231 goto new_queue;
3232 }
3233
3234 /*
3235 * Check to see if this queue is scheduled to merge with
3236 * another, closely cooperating queue. The merging of
3237 * queues happens here as it must be done in process context.
3238 * The reference on new_cfqq was taken in merge_cfqqs.
3239 */
3240 if (cfqq->new_cfqq)
3241 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3242 }
3243
3244 cfqq->allocated[rw]++;
3245 atomic_inc(&cfqq->ref);
3246
3247 spin_unlock_irqrestore(q->queue_lock, flags);
3248
3249 rq->elevator_private = cic;
3250 rq->elevator_private2 = cfqq;
3251 return 0;
3252
3253queue_fail:
3254 if (cic)
3255 put_io_context(cic->ioc);
3256
3257 cfq_schedule_dispatch(cfqd);
3258 spin_unlock_irqrestore(q->queue_lock, flags);
3259 cfq_log(cfqd, "set_request fail");
3260 return 1;
3261}
3262
3263static void cfq_kick_queue(struct work_struct *work)
3264{
3265 struct cfq_data *cfqd =
3266 container_of(work, struct cfq_data, unplug_work);
3267 struct request_queue *q = cfqd->queue;
3268
3269 spin_lock_irq(q->queue_lock);
3270 __blk_run_queue(cfqd->queue);
3271 spin_unlock_irq(q->queue_lock);
3272}
3273
3274/*
3275 * Timer running if the active_queue is currently idling inside its time slice
3276 */
3277static void cfq_idle_slice_timer(unsigned long data)
3278{
3279 struct cfq_data *cfqd = (struct cfq_data *) data;
3280 struct cfq_queue *cfqq;
3281 unsigned long flags;
3282 int timed_out = 1;
3283
3284 cfq_log(cfqd, "idle timer fired");
3285
3286 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3287
3288 cfqq = cfqd->active_queue;
3289 if (cfqq) {
3290 timed_out = 0;
3291
3292 /*
3293 * We saw a request before the queue expired, let it through
3294 */
3295 if (cfq_cfqq_must_dispatch(cfqq))
3296 goto out_kick;
3297
3298 /*
3299 * expired
3300 */
3301 if (cfq_slice_used(cfqq))
3302 goto expire;
3303
3304 /*
3305 * only expire and reinvoke request handler, if there are
3306 * other queues with pending requests
3307 */
3308 if (!cfqd->busy_queues)
3309 goto out_cont;
3310
3311 /*
3312 * not expired and it has a request pending, let it dispatch
3313 */
3314 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3315 goto out_kick;
3316
3317 /*
3318 * Queue depth flag is reset only when the idle didn't succeed
3319 */
3320 cfq_clear_cfqq_deep(cfqq);
3321 }
3322expire:
3323 cfq_slice_expired(cfqd, timed_out);
3324out_kick:
3325 cfq_schedule_dispatch(cfqd);
3326out_cont:
3327 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3328}
3329
3330static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3331{
3332 del_timer_sync(&cfqd->idle_slice_timer);
3333 cancel_work_sync(&cfqd->unplug_work);
3334}
3335
3336static void cfq_put_async_queues(struct cfq_data *cfqd)
3337{
3338 int i;
3339
3340 for (i = 0; i < IOPRIO_BE_NR; i++) {
3341 if (cfqd->async_cfqq[0][i])
3342 cfq_put_queue(cfqd->async_cfqq[0][i]);
3343 if (cfqd->async_cfqq[1][i])
3344 cfq_put_queue(cfqd->async_cfqq[1][i]);
3345 }
3346
3347 if (cfqd->async_idle_cfqq)
3348 cfq_put_queue(cfqd->async_idle_cfqq);
3349}
3350
3351static void cfq_exit_queue(struct elevator_queue *e)
3352{
3353 struct cfq_data *cfqd = e->elevator_data;
3354 struct request_queue *q = cfqd->queue;
3355
3356 cfq_shutdown_timer_wq(cfqd);
3357
3358 spin_lock_irq(q->queue_lock);
3359
3360 if (cfqd->active_queue)
3361 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3362
3363 while (!list_empty(&cfqd->cic_list)) {
3364 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3365 struct cfq_io_context,
3366 queue_list);
3367
3368 __cfq_exit_single_io_context(cfqd, cic);
3369 }
3370
3371 cfq_put_async_queues(cfqd);
3372
3373 spin_unlock_irq(q->queue_lock);
3374
3375 cfq_shutdown_timer_wq(cfqd);
3376
3377 kfree(cfqd);
3378}
3379
3380static void *cfq_init_queue(struct request_queue *q)
3381{
3382 struct cfq_data *cfqd;
3383 int i, j;
3384 struct cfq_group *cfqg;
3385 struct cfq_rb_root *st;
3386
3387 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3388 if (!cfqd)
3389 return NULL;
3390
3391 /* Init root service tree */
3392 cfqd->grp_service_tree = CFQ_RB_ROOT;
3393
3394 /* Init root group */
3395 cfqg = &cfqd->root_group;
3396 for_each_cfqg_st(cfqg, i, j, st)
3397 *st = CFQ_RB_ROOT;
3398 RB_CLEAR_NODE(&cfqg->rb_node);
3399
3400 /* Give preference to root group over other groups */
3401 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3402
3403#ifdef CONFIG_CFQ_GROUP_IOSCHED
3404 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd);
3405#endif
3406 /*
3407 * Not strictly needed (since RB_ROOT just clears the node and we
3408 * zeroed cfqd on alloc), but better be safe in case someone decides
3409 * to add magic to the rb code
3410 */
3411 for (i = 0; i < CFQ_PRIO_LISTS; i++)
3412 cfqd->prio_trees[i] = RB_ROOT;
3413
3414 /*
3415 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3416 * Grab a permanent reference to it, so that the normal code flow
3417 * will not attempt to free it.
3418 */
3419 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3420 atomic_inc(&cfqd->oom_cfqq.ref);
3421 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3422
3423 INIT_LIST_HEAD(&cfqd->cic_list);
3424
3425 cfqd->queue = q;
3426
3427 init_timer(&cfqd->idle_slice_timer);
3428 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3429 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3430
3431 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3432
3433 cfqd->cfq_quantum = cfq_quantum;
3434 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3435 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3436 cfqd->cfq_back_max = cfq_back_max;
3437 cfqd->cfq_back_penalty = cfq_back_penalty;
3438 cfqd->cfq_slice[0] = cfq_slice_async;
3439 cfqd->cfq_slice[1] = cfq_slice_sync;
3440 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3441 cfqd->cfq_slice_idle = cfq_slice_idle;
3442 cfqd->cfq_latency = 1;
3443 cfqd->hw_tag = -1;
3444 cfqd->last_end_sync_rq = jiffies;
3445 return cfqd;
3446}
3447
3448static void cfq_slab_kill(void)
3449{
3450 /*
3451 * Caller already ensured that pending RCU callbacks are completed,
3452 * so we should have no busy allocations at this point.
3453 */
3454 if (cfq_pool)
3455 kmem_cache_destroy(cfq_pool);
3456 if (cfq_ioc_pool)
3457 kmem_cache_destroy(cfq_ioc_pool);
3458}
3459
3460static int __init cfq_slab_setup(void)
3461{
3462 cfq_pool = KMEM_CACHE(cfq_queue, 0);
3463 if (!cfq_pool)
3464 goto fail;
3465
3466 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3467 if (!cfq_ioc_pool)
3468 goto fail;
3469
3470 return 0;
3471fail:
3472 cfq_slab_kill();
3473 return -ENOMEM;
3474}
3475
3476/*
3477 * sysfs parts below -->
3478 */
3479static ssize_t
3480cfq_var_show(unsigned int var, char *page)
3481{
3482 return sprintf(page, "%d\n", var);
3483}
3484
3485static ssize_t
3486cfq_var_store(unsigned int *var, const char *page, size_t count)
3487{
3488 char *p = (char *) page;
3489
3490 *var = simple_strtoul(p, &p, 10);
3491 return count;
3492}
3493
3494#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3495static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3496{ \
3497 struct cfq_data *cfqd = e->elevator_data; \
3498 unsigned int __data = __VAR; \
3499 if (__CONV) \
3500 __data = jiffies_to_msecs(__data); \
3501 return cfq_var_show(__data, (page)); \
3502}
3503SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3504SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3505SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3506SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3507SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3508SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3509SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3510SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3511SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3512SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3513#undef SHOW_FUNCTION
3514
3515#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3516static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3517{ \
3518 struct cfq_data *cfqd = e->elevator_data; \
3519 unsigned int __data; \
3520 int ret = cfq_var_store(&__data, (page), count); \
3521 if (__data < (MIN)) \
3522 __data = (MIN); \
3523 else if (__data > (MAX)) \
3524 __data = (MAX); \
3525 if (__CONV) \
3526 *(__PTR) = msecs_to_jiffies(__data); \
3527 else \
3528 *(__PTR) = __data; \
3529 return ret; \
3530}
3531STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3532STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3533 UINT_MAX, 1);
3534STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3535 UINT_MAX, 1);
3536STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3537STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3538 UINT_MAX, 0);
3539STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3540STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3541STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3542STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3543 UINT_MAX, 0);
3544STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3545#undef STORE_FUNCTION
3546
3547#define CFQ_ATTR(name) \
3548 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3549
3550static struct elv_fs_entry cfq_attrs[] = {
3551 CFQ_ATTR(quantum),
3552 CFQ_ATTR(fifo_expire_sync),
3553 CFQ_ATTR(fifo_expire_async),
3554 CFQ_ATTR(back_seek_max),
3555 CFQ_ATTR(back_seek_penalty),
3556 CFQ_ATTR(slice_sync),
3557 CFQ_ATTR(slice_async),
3558 CFQ_ATTR(slice_async_rq),
3559 CFQ_ATTR(slice_idle),
3560 CFQ_ATTR(low_latency),
3561 __ATTR_NULL
3562};
3563
3564static struct elevator_type iosched_cfq = {
3565 .ops = {
3566 .elevator_merge_fn = cfq_merge,
3567 .elevator_merged_fn = cfq_merged_request,
3568 .elevator_merge_req_fn = cfq_merged_requests,
3569 .elevator_allow_merge_fn = cfq_allow_merge,
3570 .elevator_dispatch_fn = cfq_dispatch_requests,
3571 .elevator_add_req_fn = cfq_insert_request,
3572 .elevator_activate_req_fn = cfq_activate_request,
3573 .elevator_deactivate_req_fn = cfq_deactivate_request,
3574 .elevator_queue_empty_fn = cfq_queue_empty,
3575 .elevator_completed_req_fn = cfq_completed_request,
3576 .elevator_former_req_fn = elv_rb_former_request,
3577 .elevator_latter_req_fn = elv_rb_latter_request,
3578 .elevator_set_req_fn = cfq_set_request,
3579 .elevator_put_req_fn = cfq_put_request,
3580 .elevator_may_queue_fn = cfq_may_queue,
3581 .elevator_init_fn = cfq_init_queue,
3582 .elevator_exit_fn = cfq_exit_queue,
3583 .trim = cfq_free_io_context,
3584 },
3585 .elevator_attrs = cfq_attrs,
3586 .elevator_name = "cfq",
3587 .elevator_owner = THIS_MODULE,
3588};
3589
3590static int __init cfq_init(void)
3591{
3592 /*
3593 * could be 0 on HZ < 1000 setups
3594 */
3595 if (!cfq_slice_async)
3596 cfq_slice_async = 1;
3597 if (!cfq_slice_idle)
3598 cfq_slice_idle = 1;
3599
3600 if (cfq_slab_setup())
3601 return -ENOMEM;
3602
3603 elv_register(&iosched_cfq);
3604
3605 return 0;
3606}
3607
3608static void __exit cfq_exit(void)
3609{
3610 DECLARE_COMPLETION_ONSTACK(all_gone);
3611 elv_unregister(&iosched_cfq);
3612 ioc_gone = &all_gone;
3613 /* ioc_gone's update must be visible before reading ioc_count */
3614 smp_wmb();
3615
3616 /*
3617 * this also protects us from entering cfq_slab_kill() with
3618 * pending RCU callbacks
3619 */
3620 if (elv_ioc_count_read(cfq_ioc_count))
3621 wait_for_completion(&all_gone);
3622 cfq_slab_kill();
3623}
3624
3625module_init(cfq_init);
3626module_exit(cfq_exit);
3627
3628MODULE_AUTHOR("Jens Axboe");
3629MODULE_LICENSE("GPL");
3630MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
Linux 6.x block layer and io_uring tree(s)