blkio: Provide some isolation between groups
[linux-2.6-block.git] / block / cfq-iosched.c
... / ...
CommitLineData
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 /* Sectors dispatched in current dispatch round */
147 unsigned long nr_sectors;
148};
149
150/*
151 * First index in the service_trees.
152 * IDLE is handled separately, so it has negative index
153 */
154enum wl_prio_t {
155 BE_WORKLOAD = 0,
156 RT_WORKLOAD = 1,
157 IDLE_WORKLOAD = 2,
158};
159
160/*
161 * Second index in the service_trees.
162 */
163enum wl_type_t {
164 ASYNC_WORKLOAD = 0,
165 SYNC_NOIDLE_WORKLOAD = 1,
166 SYNC_WORKLOAD = 2
167};
168
169/* This is per cgroup per device grouping structure */
170struct cfq_group {
171 /* group service_tree member */
172 struct rb_node rb_node;
173
174 /* group service_tree key */
175 u64 vdisktime;
176 unsigned int weight;
177 bool on_st;
178
179 /* number of cfqq currently on this group */
180 int nr_cfqq;
181
182 /* Per group busy queus average. Useful for workload slice calc. */
183 unsigned int busy_queues_avg[2];
184 /*
185 * rr lists of queues with requests, onle rr for each priority class.
186 * Counts are embedded in the cfq_rb_root
187 */
188 struct cfq_rb_root service_trees[2][3];
189 struct cfq_rb_root service_tree_idle;
190
191 unsigned long saved_workload_slice;
192 enum wl_type_t saved_workload;
193 enum wl_prio_t saved_serving_prio;
194 struct blkio_group blkg;
195#ifdef CONFIG_CFQ_GROUP_IOSCHED
196 struct hlist_node cfqd_node;
197 atomic_t ref;
198#endif
199};
200
201/*
202 * Per block device queue structure
203 */
204struct cfq_data {
205 struct request_queue *queue;
206 /* Root service tree for cfq_groups */
207 struct cfq_rb_root grp_service_tree;
208 struct cfq_group root_group;
209 /* Number of active cfq groups on group service tree */
210 int nr_groups;
211
212 /*
213 * The priority currently being served
214 */
215 enum wl_prio_t serving_prio;
216 enum wl_type_t serving_type;
217 unsigned long workload_expires;
218 struct cfq_group *serving_group;
219 bool noidle_tree_requires_idle;
220
221 /*
222 * Each priority tree is sorted by next_request position. These
223 * trees are used when determining if two or more queues are
224 * interleaving requests (see cfq_close_cooperator).
225 */
226 struct rb_root prio_trees[CFQ_PRIO_LISTS];
227
228 unsigned int busy_queues;
229
230 int rq_in_driver[2];
231 int sync_flight;
232
233 /*
234 * queue-depth detection
235 */
236 int rq_queued;
237 int hw_tag;
238 /*
239 * hw_tag can be
240 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
241 * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
242 * 0 => no NCQ
243 */
244 int hw_tag_est_depth;
245 unsigned int hw_tag_samples;
246
247 /*
248 * idle window management
249 */
250 struct timer_list idle_slice_timer;
251 struct work_struct unplug_work;
252
253 struct cfq_queue *active_queue;
254 struct cfq_io_context *active_cic;
255
256 /*
257 * async queue for each priority case
258 */
259 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
260 struct cfq_queue *async_idle_cfqq;
261
262 sector_t last_position;
263
264 /*
265 * tunables, see top of file
266 */
267 unsigned int cfq_quantum;
268 unsigned int cfq_fifo_expire[2];
269 unsigned int cfq_back_penalty;
270 unsigned int cfq_back_max;
271 unsigned int cfq_slice[2];
272 unsigned int cfq_slice_async_rq;
273 unsigned int cfq_slice_idle;
274 unsigned int cfq_latency;
275
276 struct list_head cic_list;
277
278 /*
279 * Fallback dummy cfqq for extreme OOM conditions
280 */
281 struct cfq_queue oom_cfqq;
282
283 unsigned long last_end_sync_rq;
284
285 /* List of cfq groups being managed on this device*/
286 struct hlist_head cfqg_list;
287};
288
289static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
290
291static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
292 enum wl_prio_t prio,
293 enum wl_type_t type,
294 struct cfq_data *cfqd)
295{
296 if (!cfqg)
297 return NULL;
298
299 if (prio == IDLE_WORKLOAD)
300 return &cfqg->service_tree_idle;
301
302 return &cfqg->service_trees[prio][type];
303}
304
305enum cfqq_state_flags {
306 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
307 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
308 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
309 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
310 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
311 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
312 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
313 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
314 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
315 CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
316 CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
317};
318
319#define CFQ_CFQQ_FNS(name) \
320static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
321{ \
322 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
323} \
324static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
325{ \
326 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
327} \
328static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
329{ \
330 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
331}
332
333CFQ_CFQQ_FNS(on_rr);
334CFQ_CFQQ_FNS(wait_request);
335CFQ_CFQQ_FNS(must_dispatch);
336CFQ_CFQQ_FNS(must_alloc_slice);
337CFQ_CFQQ_FNS(fifo_expire);
338CFQ_CFQQ_FNS(idle_window);
339CFQ_CFQQ_FNS(prio_changed);
340CFQ_CFQQ_FNS(slice_new);
341CFQ_CFQQ_FNS(sync);
342CFQ_CFQQ_FNS(coop);
343CFQ_CFQQ_FNS(deep);
344#undef CFQ_CFQQ_FNS
345
346#ifdef CONFIG_DEBUG_CFQ_IOSCHED
347#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
348 blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
349 cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
350 blkg_path(&(cfqq)->cfqg->blkg), ##args);
351
352#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
353 blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
354 blkg_path(&(cfqg)->blkg), ##args); \
355
356#else
357#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
358 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
359#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
360#endif
361#define cfq_log(cfqd, fmt, args...) \
362 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
363
364/* Traverses through cfq group service trees */
365#define for_each_cfqg_st(cfqg, i, j, st) \
366 for (i = 0; i <= IDLE_WORKLOAD; i++) \
367 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
368 : &cfqg->service_tree_idle; \
369 (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
370 (i == IDLE_WORKLOAD && j == 0); \
371 j++, st = i < IDLE_WORKLOAD ? \
372 &cfqg->service_trees[i][j]: NULL) \
373
374
375static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
376{
377 if (cfq_class_idle(cfqq))
378 return IDLE_WORKLOAD;
379 if (cfq_class_rt(cfqq))
380 return RT_WORKLOAD;
381 return BE_WORKLOAD;
382}
383
384
385static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
386{
387 if (!cfq_cfqq_sync(cfqq))
388 return ASYNC_WORKLOAD;
389 if (!cfq_cfqq_idle_window(cfqq))
390 return SYNC_NOIDLE_WORKLOAD;
391 return SYNC_WORKLOAD;
392}
393
394static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
395 struct cfq_data *cfqd,
396 struct cfq_group *cfqg)
397{
398 if (wl == IDLE_WORKLOAD)
399 return cfqg->service_tree_idle.count;
400
401 return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
402 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
403 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
404}
405
406static void cfq_dispatch_insert(struct request_queue *, struct request *);
407static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
408 struct io_context *, gfp_t);
409static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
410 struct io_context *);
411
412static inline int rq_in_driver(struct cfq_data *cfqd)
413{
414 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
415}
416
417static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
418 bool is_sync)
419{
420 return cic->cfqq[is_sync];
421}
422
423static inline void cic_set_cfqq(struct cfq_io_context *cic,
424 struct cfq_queue *cfqq, bool is_sync)
425{
426 cic->cfqq[is_sync] = cfqq;
427}
428
429/*
430 * We regard a request as SYNC, if it's either a read or has the SYNC bit
431 * set (in which case it could also be direct WRITE).
432 */
433static inline bool cfq_bio_sync(struct bio *bio)
434{
435 return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
436}
437
438/*
439 * scheduler run of queue, if there are requests pending and no one in the
440 * driver that will restart queueing
441 */
442static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
443{
444 if (cfqd->busy_queues) {
445 cfq_log(cfqd, "schedule dispatch");
446 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
447 }
448}
449
450static int cfq_queue_empty(struct request_queue *q)
451{
452 struct cfq_data *cfqd = q->elevator->elevator_data;
453
454 return !cfqd->rq_queued;
455}
456
457/*
458 * Scale schedule slice based on io priority. Use the sync time slice only
459 * if a queue is marked sync and has sync io queued. A sync queue with async
460 * io only, should not get full sync slice length.
461 */
462static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
463 unsigned short prio)
464{
465 const int base_slice = cfqd->cfq_slice[sync];
466
467 WARN_ON(prio >= IOPRIO_BE_NR);
468
469 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
470}
471
472static inline int
473cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
474{
475 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
476}
477
478static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
479{
480 u64 d = delta << CFQ_SERVICE_SHIFT;
481
482 d = d * BLKIO_WEIGHT_DEFAULT;
483 do_div(d, cfqg->weight);
484 return d;
485}
486
487static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
488{
489 s64 delta = (s64)(vdisktime - min_vdisktime);
490 if (delta > 0)
491 min_vdisktime = vdisktime;
492
493 return min_vdisktime;
494}
495
496static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
497{
498 s64 delta = (s64)(vdisktime - min_vdisktime);
499 if (delta < 0)
500 min_vdisktime = vdisktime;
501
502 return min_vdisktime;
503}
504
505static void update_min_vdisktime(struct cfq_rb_root *st)
506{
507 u64 vdisktime = st->min_vdisktime;
508 struct cfq_group *cfqg;
509
510 if (st->active) {
511 cfqg = rb_entry_cfqg(st->active);
512 vdisktime = cfqg->vdisktime;
513 }
514
515 if (st->left) {
516 cfqg = rb_entry_cfqg(st->left);
517 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
518 }
519
520 st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
521}
522
523/*
524 * get averaged number of queues of RT/BE priority.
525 * average is updated, with a formula that gives more weight to higher numbers,
526 * to quickly follows sudden increases and decrease slowly
527 */
528
529static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
530 struct cfq_group *cfqg, bool rt)
531{
532 unsigned min_q, max_q;
533 unsigned mult = cfq_hist_divisor - 1;
534 unsigned round = cfq_hist_divisor / 2;
535 unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
536
537 min_q = min(cfqg->busy_queues_avg[rt], busy);
538 max_q = max(cfqg->busy_queues_avg[rt], busy);
539 cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
540 cfq_hist_divisor;
541 return cfqg->busy_queues_avg[rt];
542}
543
544static inline unsigned
545cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
546{
547 struct cfq_rb_root *st = &cfqd->grp_service_tree;
548
549 return cfq_target_latency * cfqg->weight / st->total_weight;
550}
551
552static inline void
553cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
554{
555 unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
556 if (cfqd->cfq_latency) {
557 /*
558 * interested queues (we consider only the ones with the same
559 * priority class in the cfq group)
560 */
561 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
562 cfq_class_rt(cfqq));
563 unsigned sync_slice = cfqd->cfq_slice[1];
564 unsigned expect_latency = sync_slice * iq;
565 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
566
567 if (expect_latency > group_slice) {
568 unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
569 /* scale low_slice according to IO priority
570 * and sync vs async */
571 unsigned low_slice =
572 min(slice, base_low_slice * slice / sync_slice);
573 /* the adapted slice value is scaled to fit all iqs
574 * into the target latency */
575 slice = max(slice * group_slice / expect_latency,
576 low_slice);
577 }
578 }
579 cfqq->slice_start = jiffies;
580 cfqq->slice_end = jiffies + slice;
581 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
582}
583
584/*
585 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
586 * isn't valid until the first request from the dispatch is activated
587 * and the slice time set.
588 */
589static inline bool cfq_slice_used(struct cfq_queue *cfqq)
590{
591 if (cfq_cfqq_slice_new(cfqq))
592 return 0;
593 if (time_before(jiffies, cfqq->slice_end))
594 return 0;
595
596 return 1;
597}
598
599/*
600 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
601 * We choose the request that is closest to the head right now. Distance
602 * behind the head is penalized and only allowed to a certain extent.
603 */
604static struct request *
605cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
606{
607 sector_t s1, s2, d1 = 0, d2 = 0;
608 unsigned long back_max;
609#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
610#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
611 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
612
613 if (rq1 == NULL || rq1 == rq2)
614 return rq2;
615 if (rq2 == NULL)
616 return rq1;
617
618 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
619 return rq1;
620 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
621 return rq2;
622 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
623 return rq1;
624 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
625 return rq2;
626
627 s1 = blk_rq_pos(rq1);
628 s2 = blk_rq_pos(rq2);
629
630 /*
631 * by definition, 1KiB is 2 sectors
632 */
633 back_max = cfqd->cfq_back_max * 2;
634
635 /*
636 * Strict one way elevator _except_ in the case where we allow
637 * short backward seeks which are biased as twice the cost of a
638 * similar forward seek.
639 */
640 if (s1 >= last)
641 d1 = s1 - last;
642 else if (s1 + back_max >= last)
643 d1 = (last - s1) * cfqd->cfq_back_penalty;
644 else
645 wrap |= CFQ_RQ1_WRAP;
646
647 if (s2 >= last)
648 d2 = s2 - last;
649 else if (s2 + back_max >= last)
650 d2 = (last - s2) * cfqd->cfq_back_penalty;
651 else
652 wrap |= CFQ_RQ2_WRAP;
653
654 /* Found required data */
655
656 /*
657 * By doing switch() on the bit mask "wrap" we avoid having to
658 * check two variables for all permutations: --> faster!
659 */
660 switch (wrap) {
661 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
662 if (d1 < d2)
663 return rq1;
664 else if (d2 < d1)
665 return rq2;
666 else {
667 if (s1 >= s2)
668 return rq1;
669 else
670 return rq2;
671 }
672
673 case CFQ_RQ2_WRAP:
674 return rq1;
675 case CFQ_RQ1_WRAP:
676 return rq2;
677 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
678 default:
679 /*
680 * Since both rqs are wrapped,
681 * start with the one that's further behind head
682 * (--> only *one* back seek required),
683 * since back seek takes more time than forward.
684 */
685 if (s1 <= s2)
686 return rq1;
687 else
688 return rq2;
689 }
690}
691
692/*
693 * The below is leftmost cache rbtree addon
694 */
695static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
696{
697 /* Service tree is empty */
698 if (!root->count)
699 return NULL;
700
701 if (!root->left)
702 root->left = rb_first(&root->rb);
703
704 if (root->left)
705 return rb_entry(root->left, struct cfq_queue, rb_node);
706
707 return NULL;
708}
709
710static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
711{
712 if (!root->left)
713 root->left = rb_first(&root->rb);
714
715 if (root->left)
716 return rb_entry_cfqg(root->left);
717
718 return NULL;
719}
720
721static void rb_erase_init(struct rb_node *n, struct rb_root *root)
722{
723 rb_erase(n, root);
724 RB_CLEAR_NODE(n);
725}
726
727static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
728{
729 if (root->left == n)
730 root->left = NULL;
731 rb_erase_init(n, &root->rb);
732 --root->count;
733}
734
735/*
736 * would be nice to take fifo expire time into account as well
737 */
738static struct request *
739cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
740 struct request *last)
741{
742 struct rb_node *rbnext = rb_next(&last->rb_node);
743 struct rb_node *rbprev = rb_prev(&last->rb_node);
744 struct request *next = NULL, *prev = NULL;
745
746 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
747
748 if (rbprev)
749 prev = rb_entry_rq(rbprev);
750
751 if (rbnext)
752 next = rb_entry_rq(rbnext);
753 else {
754 rbnext = rb_first(&cfqq->sort_list);
755 if (rbnext && rbnext != &last->rb_node)
756 next = rb_entry_rq(rbnext);
757 }
758
759 return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
760}
761
762static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
763 struct cfq_queue *cfqq)
764{
765 /*
766 * just an approximation, should be ok.
767 */
768 return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
769 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
770}
771
772static inline s64
773cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
774{
775 return cfqg->vdisktime - st->min_vdisktime;
776}
777
778static void
779__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
780{
781 struct rb_node **node = &st->rb.rb_node;
782 struct rb_node *parent = NULL;
783 struct cfq_group *__cfqg;
784 s64 key = cfqg_key(st, cfqg);
785 int left = 1;
786
787 while (*node != NULL) {
788 parent = *node;
789 __cfqg = rb_entry_cfqg(parent);
790
791 if (key < cfqg_key(st, __cfqg))
792 node = &parent->rb_left;
793 else {
794 node = &parent->rb_right;
795 left = 0;
796 }
797 }
798
799 if (left)
800 st->left = &cfqg->rb_node;
801
802 rb_link_node(&cfqg->rb_node, parent, node);
803 rb_insert_color(&cfqg->rb_node, &st->rb);
804}
805
806static void
807cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
808{
809 struct cfq_rb_root *st = &cfqd->grp_service_tree;
810 struct cfq_group *__cfqg;
811 struct rb_node *n;
812
813 cfqg->nr_cfqq++;
814 if (cfqg->on_st)
815 return;
816
817 /*
818 * Currently put the group at the end. Later implement something
819 * so that groups get lesser vtime based on their weights, so that
820 * if group does not loose all if it was not continously backlogged.
821 */
822 n = rb_last(&st->rb);
823 if (n) {
824 __cfqg = rb_entry_cfqg(n);
825 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
826 } else
827 cfqg->vdisktime = st->min_vdisktime;
828
829 __cfq_group_service_tree_add(st, cfqg);
830 cfqg->on_st = true;
831 cfqd->nr_groups++;
832 st->total_weight += cfqg->weight;
833}
834
835static void
836cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
837{
838 struct cfq_rb_root *st = &cfqd->grp_service_tree;
839
840 if (st->active == &cfqg->rb_node)
841 st->active = NULL;
842
843 BUG_ON(cfqg->nr_cfqq < 1);
844 cfqg->nr_cfqq--;
845
846 /* If there are other cfq queues under this group, don't delete it */
847 if (cfqg->nr_cfqq)
848 return;
849
850 cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
851 cfqg->on_st = false;
852 cfqd->nr_groups--;
853 st->total_weight -= cfqg->weight;
854 if (!RB_EMPTY_NODE(&cfqg->rb_node))
855 cfq_rb_erase(&cfqg->rb_node, st);
856 cfqg->saved_workload_slice = 0;
857 blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
858}
859
860static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
861{
862 unsigned int slice_used, allocated_slice;
863
864 /*
865 * Queue got expired before even a single request completed or
866 * got expired immediately after first request completion.
867 */
868 if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
869 /*
870 * Also charge the seek time incurred to the group, otherwise
871 * if there are mutiple queues in the group, each can dispatch
872 * a single request on seeky media and cause lots of seek time
873 * and group will never know it.
874 */
875 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
876 1);
877 } else {
878 slice_used = jiffies - cfqq->slice_start;
879 allocated_slice = cfqq->slice_end - cfqq->slice_start;
880 if (slice_used > allocated_slice)
881 slice_used = allocated_slice;
882 }
883
884 cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
885 cfqq->nr_sectors);
886 return slice_used;
887}
888
889static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
890 struct cfq_queue *cfqq)
891{
892 struct cfq_rb_root *st = &cfqd->grp_service_tree;
893 unsigned int used_sl;
894
895 used_sl = cfq_cfqq_slice_usage(cfqq);
896
897 /* Can't update vdisktime while group is on service tree */
898 cfq_rb_erase(&cfqg->rb_node, st);
899 cfqg->vdisktime += cfq_scale_slice(used_sl, cfqg);
900 __cfq_group_service_tree_add(st, cfqg);
901
902 /* This group is being expired. Save the context */
903 if (time_after(cfqd->workload_expires, jiffies)) {
904 cfqg->saved_workload_slice = cfqd->workload_expires
905 - jiffies;
906 cfqg->saved_workload = cfqd->serving_type;
907 cfqg->saved_serving_prio = cfqd->serving_prio;
908 } else
909 cfqg->saved_workload_slice = 0;
910
911 cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
912 st->min_vdisktime);
913 blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
914 cfqq->nr_sectors);
915}
916
917#ifdef CONFIG_CFQ_GROUP_IOSCHED
918static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
919{
920 if (blkg)
921 return container_of(blkg, struct cfq_group, blkg);
922 return NULL;
923}
924
925static struct cfq_group *
926cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
927{
928 struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
929 struct cfq_group *cfqg = NULL;
930 void *key = cfqd;
931 int i, j;
932 struct cfq_rb_root *st;
933 struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
934 unsigned int major, minor;
935
936 /* Do we need to take this reference */
937 if (!css_tryget(&blkcg->css))
938 return NULL;;
939
940 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
941 if (cfqg || !create)
942 goto done;
943
944 cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
945 if (!cfqg)
946 goto done;
947
948 cfqg->weight = blkcg->weight;
949 for_each_cfqg_st(cfqg, i, j, st)
950 *st = CFQ_RB_ROOT;
951 RB_CLEAR_NODE(&cfqg->rb_node);
952
953 /*
954 * Take the initial reference that will be released on destroy
955 * This can be thought of a joint reference by cgroup and
956 * elevator which will be dropped by either elevator exit
957 * or cgroup deletion path depending on who is exiting first.
958 */
959 atomic_set(&cfqg->ref, 1);
960
961 /* Add group onto cgroup list */
962 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
963 blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
964 MKDEV(major, minor));
965
966 /* Add group on cfqd list */
967 hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
968
969done:
970 css_put(&blkcg->css);
971 return cfqg;
972}
973
974/*
975 * Search for the cfq group current task belongs to. If create = 1, then also
976 * create the cfq group if it does not exist. request_queue lock must be held.
977 */
978static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
979{
980 struct cgroup *cgroup;
981 struct cfq_group *cfqg = NULL;
982
983 rcu_read_lock();
984 cgroup = task_cgroup(current, blkio_subsys_id);
985 cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
986 if (!cfqg && create)
987 cfqg = &cfqd->root_group;
988 rcu_read_unlock();
989 return cfqg;
990}
991
992static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
993{
994 /* Currently, all async queues are mapped to root group */
995 if (!cfq_cfqq_sync(cfqq))
996 cfqg = &cfqq->cfqd->root_group;
997
998 cfqq->cfqg = cfqg;
999 /* cfqq reference on cfqg */
1000 atomic_inc(&cfqq->cfqg->ref);
1001}
1002
1003static void cfq_put_cfqg(struct cfq_group *cfqg)
1004{
1005 struct cfq_rb_root *st;
1006 int i, j;
1007
1008 BUG_ON(atomic_read(&cfqg->ref) <= 0);
1009 if (!atomic_dec_and_test(&cfqg->ref))
1010 return;
1011 for_each_cfqg_st(cfqg, i, j, st)
1012 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1013 kfree(cfqg);
1014}
1015
1016static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1017{
1018 /* Something wrong if we are trying to remove same group twice */
1019 BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1020
1021 hlist_del_init(&cfqg->cfqd_node);
1022
1023 /*
1024 * Put the reference taken at the time of creation so that when all
1025 * queues are gone, group can be destroyed.
1026 */
1027 cfq_put_cfqg(cfqg);
1028}
1029
1030static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1031{
1032 struct hlist_node *pos, *n;
1033 struct cfq_group *cfqg;
1034
1035 hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1036 /*
1037 * If cgroup removal path got to blk_group first and removed
1038 * it from cgroup list, then it will take care of destroying
1039 * cfqg also.
1040 */
1041 if (!blkiocg_del_blkio_group(&cfqg->blkg))
1042 cfq_destroy_cfqg(cfqd, cfqg);
1043 }
1044}
1045
1046/*
1047 * Blk cgroup controller notification saying that blkio_group object is being
1048 * delinked as associated cgroup object is going away. That also means that
1049 * no new IO will come in this group. So get rid of this group as soon as
1050 * any pending IO in the group is finished.
1051 *
1052 * This function is called under rcu_read_lock(). key is the rcu protected
1053 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1054 * read lock.
1055 *
1056 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1057 * it should not be NULL as even if elevator was exiting, cgroup deltion
1058 * path got to it first.
1059 */
1060void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1061{
1062 unsigned long flags;
1063 struct cfq_data *cfqd = key;
1064
1065 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1066 cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1067 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1068}
1069
1070#else /* GROUP_IOSCHED */
1071static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1072{
1073 return &cfqd->root_group;
1074}
1075static inline void
1076cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1077 cfqq->cfqg = cfqg;
1078}
1079
1080static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1081static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1082
1083#endif /* GROUP_IOSCHED */
1084
1085/*
1086 * The cfqd->service_trees holds all pending cfq_queue's that have
1087 * requests waiting to be processed. It is sorted in the order that
1088 * we will service the queues.
1089 */
1090static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1091 bool add_front)
1092{
1093 struct rb_node **p, *parent;
1094 struct cfq_queue *__cfqq;
1095 unsigned long rb_key;
1096 struct cfq_rb_root *service_tree;
1097 int left;
1098 int new_cfqq = 1;
1099
1100 service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1101 cfqq_type(cfqq), cfqd);
1102 if (cfq_class_idle(cfqq)) {
1103 rb_key = CFQ_IDLE_DELAY;
1104 parent = rb_last(&service_tree->rb);
1105 if (parent && parent != &cfqq->rb_node) {
1106 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1107 rb_key += __cfqq->rb_key;
1108 } else
1109 rb_key += jiffies;
1110 } else if (!add_front) {
1111 /*
1112 * Get our rb key offset. Subtract any residual slice
1113 * value carried from last service. A negative resid
1114 * count indicates slice overrun, and this should position
1115 * the next service time further away in the tree.
1116 */
1117 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1118 rb_key -= cfqq->slice_resid;
1119 cfqq->slice_resid = 0;
1120 } else {
1121 rb_key = -HZ;
1122 __cfqq = cfq_rb_first(service_tree);
1123 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1124 }
1125
1126 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1127 new_cfqq = 0;
1128 /*
1129 * same position, nothing more to do
1130 */
1131 if (rb_key == cfqq->rb_key &&
1132 cfqq->service_tree == service_tree)
1133 return;
1134
1135 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1136 cfqq->service_tree = NULL;
1137 }
1138
1139 left = 1;
1140 parent = NULL;
1141 cfqq->service_tree = service_tree;
1142 p = &service_tree->rb.rb_node;
1143 while (*p) {
1144 struct rb_node **n;
1145
1146 parent = *p;
1147 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1148
1149 /*
1150 * sort by key, that represents service time.
1151 */
1152 if (time_before(rb_key, __cfqq->rb_key))
1153 n = &(*p)->rb_left;
1154 else {
1155 n = &(*p)->rb_right;
1156 left = 0;
1157 }
1158
1159 p = n;
1160 }
1161
1162 if (left)
1163 service_tree->left = &cfqq->rb_node;
1164
1165 cfqq->rb_key = rb_key;
1166 rb_link_node(&cfqq->rb_node, parent, p);
1167 rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1168 service_tree->count++;
1169 if (add_front || !new_cfqq)
1170 return;
1171 cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1172}
1173
1174static struct cfq_queue *
1175cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1176 sector_t sector, struct rb_node **ret_parent,
1177 struct rb_node ***rb_link)
1178{
1179 struct rb_node **p, *parent;
1180 struct cfq_queue *cfqq = NULL;
1181
1182 parent = NULL;
1183 p = &root->rb_node;
1184 while (*p) {
1185 struct rb_node **n;
1186
1187 parent = *p;
1188 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1189
1190 /*
1191 * Sort strictly based on sector. Smallest to the left,
1192 * largest to the right.
1193 */
1194 if (sector > blk_rq_pos(cfqq->next_rq))
1195 n = &(*p)->rb_right;
1196 else if (sector < blk_rq_pos(cfqq->next_rq))
1197 n = &(*p)->rb_left;
1198 else
1199 break;
1200 p = n;
1201 cfqq = NULL;
1202 }
1203
1204 *ret_parent = parent;
1205 if (rb_link)
1206 *rb_link = p;
1207 return cfqq;
1208}
1209
1210static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1211{
1212 struct rb_node **p, *parent;
1213 struct cfq_queue *__cfqq;
1214
1215 if (cfqq->p_root) {
1216 rb_erase(&cfqq->p_node, cfqq->p_root);
1217 cfqq->p_root = NULL;
1218 }
1219
1220 if (cfq_class_idle(cfqq))
1221 return;
1222 if (!cfqq->next_rq)
1223 return;
1224
1225 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1226 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1227 blk_rq_pos(cfqq->next_rq), &parent, &p);
1228 if (!__cfqq) {
1229 rb_link_node(&cfqq->p_node, parent, p);
1230 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1231 } else
1232 cfqq->p_root = NULL;
1233}
1234
1235/*
1236 * Update cfqq's position in the service tree.
1237 */
1238static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1239{
1240 /*
1241 * Resorting requires the cfqq to be on the RR list already.
1242 */
1243 if (cfq_cfqq_on_rr(cfqq)) {
1244 cfq_service_tree_add(cfqd, cfqq, 0);
1245 cfq_prio_tree_add(cfqd, cfqq);
1246 }
1247}
1248
1249/*
1250 * add to busy list of queues for service, trying to be fair in ordering
1251 * the pending list according to last request service
1252 */
1253static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1254{
1255 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1256 BUG_ON(cfq_cfqq_on_rr(cfqq));
1257 cfq_mark_cfqq_on_rr(cfqq);
1258 cfqd->busy_queues++;
1259
1260 cfq_resort_rr_list(cfqd, cfqq);
1261}
1262
1263/*
1264 * Called when the cfqq no longer has requests pending, remove it from
1265 * the service tree.
1266 */
1267static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1268{
1269 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1270 BUG_ON(!cfq_cfqq_on_rr(cfqq));
1271 cfq_clear_cfqq_on_rr(cfqq);
1272
1273 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1274 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1275 cfqq->service_tree = NULL;
1276 }
1277 if (cfqq->p_root) {
1278 rb_erase(&cfqq->p_node, cfqq->p_root);
1279 cfqq->p_root = NULL;
1280 }
1281
1282 cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1283 BUG_ON(!cfqd->busy_queues);
1284 cfqd->busy_queues--;
1285}
1286
1287/*
1288 * rb tree support functions
1289 */
1290static void cfq_del_rq_rb(struct request *rq)
1291{
1292 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1293 const int sync = rq_is_sync(rq);
1294
1295 BUG_ON(!cfqq->queued[sync]);
1296 cfqq->queued[sync]--;
1297
1298 elv_rb_del(&cfqq->sort_list, rq);
1299
1300 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1301 /*
1302 * Queue will be deleted from service tree when we actually
1303 * expire it later. Right now just remove it from prio tree
1304 * as it is empty.
1305 */
1306 if (cfqq->p_root) {
1307 rb_erase(&cfqq->p_node, cfqq->p_root);
1308 cfqq->p_root = NULL;
1309 }
1310 }
1311}
1312
1313static void cfq_add_rq_rb(struct request *rq)
1314{
1315 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1316 struct cfq_data *cfqd = cfqq->cfqd;
1317 struct request *__alias, *prev;
1318
1319 cfqq->queued[rq_is_sync(rq)]++;
1320
1321 /*
1322 * looks a little odd, but the first insert might return an alias.
1323 * if that happens, put the alias on the dispatch list
1324 */
1325 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1326 cfq_dispatch_insert(cfqd->queue, __alias);
1327
1328 if (!cfq_cfqq_on_rr(cfqq))
1329 cfq_add_cfqq_rr(cfqd, cfqq);
1330
1331 /*
1332 * check if this request is a better next-serve candidate
1333 */
1334 prev = cfqq->next_rq;
1335 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1336
1337 /*
1338 * adjust priority tree position, if ->next_rq changes
1339 */
1340 if (prev != cfqq->next_rq)
1341 cfq_prio_tree_add(cfqd, cfqq);
1342
1343 BUG_ON(!cfqq->next_rq);
1344}
1345
1346static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1347{
1348 elv_rb_del(&cfqq->sort_list, rq);
1349 cfqq->queued[rq_is_sync(rq)]--;
1350 cfq_add_rq_rb(rq);
1351}
1352
1353static struct request *
1354cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1355{
1356 struct task_struct *tsk = current;
1357 struct cfq_io_context *cic;
1358 struct cfq_queue *cfqq;
1359
1360 cic = cfq_cic_lookup(cfqd, tsk->io_context);
1361 if (!cic)
1362 return NULL;
1363
1364 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1365 if (cfqq) {
1366 sector_t sector = bio->bi_sector + bio_sectors(bio);
1367
1368 return elv_rb_find(&cfqq->sort_list, sector);
1369 }
1370
1371 return NULL;
1372}
1373
1374static void cfq_activate_request(struct request_queue *q, struct request *rq)
1375{
1376 struct cfq_data *cfqd = q->elevator->elevator_data;
1377
1378 cfqd->rq_in_driver[rq_is_sync(rq)]++;
1379 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1380 rq_in_driver(cfqd));
1381
1382 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1383}
1384
1385static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1386{
1387 struct cfq_data *cfqd = q->elevator->elevator_data;
1388 const int sync = rq_is_sync(rq);
1389
1390 WARN_ON(!cfqd->rq_in_driver[sync]);
1391 cfqd->rq_in_driver[sync]--;
1392 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1393 rq_in_driver(cfqd));
1394}
1395
1396static void cfq_remove_request(struct request *rq)
1397{
1398 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1399
1400 if (cfqq->next_rq == rq)
1401 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1402
1403 list_del_init(&rq->queuelist);
1404 cfq_del_rq_rb(rq);
1405
1406 cfqq->cfqd->rq_queued--;
1407 if (rq_is_meta(rq)) {
1408 WARN_ON(!cfqq->meta_pending);
1409 cfqq->meta_pending--;
1410 }
1411}
1412
1413static int cfq_merge(struct request_queue *q, struct request **req,
1414 struct bio *bio)
1415{
1416 struct cfq_data *cfqd = q->elevator->elevator_data;
1417 struct request *__rq;
1418
1419 __rq = cfq_find_rq_fmerge(cfqd, bio);
1420 if (__rq && elv_rq_merge_ok(__rq, bio)) {
1421 *req = __rq;
1422 return ELEVATOR_FRONT_MERGE;
1423 }
1424
1425 return ELEVATOR_NO_MERGE;
1426}
1427
1428static void cfq_merged_request(struct request_queue *q, struct request *req,
1429 int type)
1430{
1431 if (type == ELEVATOR_FRONT_MERGE) {
1432 struct cfq_queue *cfqq = RQ_CFQQ(req);
1433
1434 cfq_reposition_rq_rb(cfqq, req);
1435 }
1436}
1437
1438static void
1439cfq_merged_requests(struct request_queue *q, struct request *rq,
1440 struct request *next)
1441{
1442 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1443 /*
1444 * reposition in fifo if next is older than rq
1445 */
1446 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1447 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1448 list_move(&rq->queuelist, &next->queuelist);
1449 rq_set_fifo_time(rq, rq_fifo_time(next));
1450 }
1451
1452 if (cfqq->next_rq == next)
1453 cfqq->next_rq = rq;
1454 cfq_remove_request(next);
1455}
1456
1457static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1458 struct bio *bio)
1459{
1460 struct cfq_data *cfqd = q->elevator->elevator_data;
1461 struct cfq_io_context *cic;
1462 struct cfq_queue *cfqq;
1463
1464 /* Deny merge if bio and rq don't belong to same cfq group */
1465 if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))
1466 return false;
1467 /*
1468 * Disallow merge of a sync bio into an async request.
1469 */
1470 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1471 return false;
1472
1473 /*
1474 * Lookup the cfqq that this bio will be queued with. Allow
1475 * merge only if rq is queued there.
1476 */
1477 cic = cfq_cic_lookup(cfqd, current->io_context);
1478 if (!cic)
1479 return false;
1480
1481 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1482 return cfqq == RQ_CFQQ(rq);
1483}
1484
1485static void __cfq_set_active_queue(struct cfq_data *cfqd,
1486 struct cfq_queue *cfqq)
1487{
1488 if (cfqq) {
1489 cfq_log_cfqq(cfqd, cfqq, "set_active");
1490 cfqq->slice_start = 0;
1491 cfqq->dispatch_start = jiffies;
1492 cfqq->slice_end = 0;
1493 cfqq->slice_dispatch = 0;
1494 cfqq->nr_sectors = 0;
1495
1496 cfq_clear_cfqq_wait_request(cfqq);
1497 cfq_clear_cfqq_must_dispatch(cfqq);
1498 cfq_clear_cfqq_must_alloc_slice(cfqq);
1499 cfq_clear_cfqq_fifo_expire(cfqq);
1500 cfq_mark_cfqq_slice_new(cfqq);
1501
1502 del_timer(&cfqd->idle_slice_timer);
1503 }
1504
1505 cfqd->active_queue = cfqq;
1506}
1507
1508/*
1509 * current cfqq expired its slice (or was too idle), select new one
1510 */
1511static void
1512__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1513 bool timed_out)
1514{
1515 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1516
1517 if (cfq_cfqq_wait_request(cfqq))
1518 del_timer(&cfqd->idle_slice_timer);
1519
1520 cfq_clear_cfqq_wait_request(cfqq);
1521
1522 /*
1523 * store what was left of this slice, if the queue idled/timed out
1524 */
1525 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1526 cfqq->slice_resid = cfqq->slice_end - jiffies;
1527 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1528 }
1529
1530 cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1531
1532 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1533 cfq_del_cfqq_rr(cfqd, cfqq);
1534
1535 cfq_resort_rr_list(cfqd, cfqq);
1536
1537 if (cfqq == cfqd->active_queue)
1538 cfqd->active_queue = NULL;
1539
1540 if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1541 cfqd->grp_service_tree.active = NULL;
1542
1543 if (cfqd->active_cic) {
1544 put_io_context(cfqd->active_cic->ioc);
1545 cfqd->active_cic = NULL;
1546 }
1547}
1548
1549static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1550{
1551 struct cfq_queue *cfqq = cfqd->active_queue;
1552
1553 if (cfqq)
1554 __cfq_slice_expired(cfqd, cfqq, timed_out);
1555}
1556
1557/*
1558 * Get next queue for service. Unless we have a queue preemption,
1559 * we'll simply select the first cfqq in the service tree.
1560 */
1561static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1562{
1563 struct cfq_rb_root *service_tree =
1564 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1565 cfqd->serving_type, cfqd);
1566
1567 if (!cfqd->rq_queued)
1568 return NULL;
1569
1570 /* There is nothing to dispatch */
1571 if (!service_tree)
1572 return NULL;
1573 if (RB_EMPTY_ROOT(&service_tree->rb))
1574 return NULL;
1575 return cfq_rb_first(service_tree);
1576}
1577
1578static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1579{
1580 struct cfq_group *cfqg;
1581 struct cfq_queue *cfqq;
1582 int i, j;
1583 struct cfq_rb_root *st;
1584
1585 if (!cfqd->rq_queued)
1586 return NULL;
1587
1588 cfqg = cfq_get_next_cfqg(cfqd);
1589 if (!cfqg)
1590 return NULL;
1591
1592 for_each_cfqg_st(cfqg, i, j, st)
1593 if ((cfqq = cfq_rb_first(st)) != NULL)
1594 return cfqq;
1595 return NULL;
1596}
1597
1598/*
1599 * Get and set a new active queue for service.
1600 */
1601static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1602 struct cfq_queue *cfqq)
1603{
1604 if (!cfqq)
1605 cfqq = cfq_get_next_queue(cfqd);
1606
1607 __cfq_set_active_queue(cfqd, cfqq);
1608 return cfqq;
1609}
1610
1611static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1612 struct request *rq)
1613{
1614 if (blk_rq_pos(rq) >= cfqd->last_position)
1615 return blk_rq_pos(rq) - cfqd->last_position;
1616 else
1617 return cfqd->last_position - blk_rq_pos(rq);
1618}
1619
1620#define CFQQ_SEEK_THR 8 * 1024
1621#define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1622
1623static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1624 struct request *rq)
1625{
1626 sector_t sdist = cfqq->seek_mean;
1627
1628 if (!sample_valid(cfqq->seek_samples))
1629 sdist = CFQQ_SEEK_THR;
1630
1631 return cfq_dist_from_last(cfqd, rq) <= sdist;
1632}
1633
1634static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1635 struct cfq_queue *cur_cfqq)
1636{
1637 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1638 struct rb_node *parent, *node;
1639 struct cfq_queue *__cfqq;
1640 sector_t sector = cfqd->last_position;
1641
1642 if (RB_EMPTY_ROOT(root))
1643 return NULL;
1644
1645 /*
1646 * First, if we find a request starting at the end of the last
1647 * request, choose it.
1648 */
1649 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1650 if (__cfqq)
1651 return __cfqq;
1652
1653 /*
1654 * If the exact sector wasn't found, the parent of the NULL leaf
1655 * will contain the closest sector.
1656 */
1657 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1658 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1659 return __cfqq;
1660
1661 if (blk_rq_pos(__cfqq->next_rq) < sector)
1662 node = rb_next(&__cfqq->p_node);
1663 else
1664 node = rb_prev(&__cfqq->p_node);
1665 if (!node)
1666 return NULL;
1667
1668 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1669 if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1670 return __cfqq;
1671
1672 return NULL;
1673}
1674
1675/*
1676 * cfqd - obvious
1677 * cur_cfqq - passed in so that we don't decide that the current queue is
1678 * closely cooperating with itself.
1679 *
1680 * So, basically we're assuming that that cur_cfqq has dispatched at least
1681 * one request, and that cfqd->last_position reflects a position on the disk
1682 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1683 * assumption.
1684 */
1685static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1686 struct cfq_queue *cur_cfqq)
1687{
1688 struct cfq_queue *cfqq;
1689
1690 if (!cfq_cfqq_sync(cur_cfqq))
1691 return NULL;
1692 if (CFQQ_SEEKY(cur_cfqq))
1693 return NULL;
1694
1695 /*
1696 * We should notice if some of the queues are cooperating, eg
1697 * working closely on the same area of the disk. In that case,
1698 * we can group them together and don't waste time idling.
1699 */
1700 cfqq = cfqq_close(cfqd, cur_cfqq);
1701 if (!cfqq)
1702 return NULL;
1703
1704 /* If new queue belongs to different cfq_group, don't choose it */
1705 if (cur_cfqq->cfqg != cfqq->cfqg)
1706 return NULL;
1707
1708 /*
1709 * It only makes sense to merge sync queues.
1710 */
1711 if (!cfq_cfqq_sync(cfqq))
1712 return NULL;
1713 if (CFQQ_SEEKY(cfqq))
1714 return NULL;
1715
1716 /*
1717 * Do not merge queues of different priority classes
1718 */
1719 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1720 return NULL;
1721
1722 return cfqq;
1723}
1724
1725/*
1726 * Determine whether we should enforce idle window for this queue.
1727 */
1728
1729static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1730{
1731 enum wl_prio_t prio = cfqq_prio(cfqq);
1732 struct cfq_rb_root *service_tree = cfqq->service_tree;
1733
1734 BUG_ON(!service_tree);
1735 BUG_ON(!service_tree->count);
1736
1737 /* We never do for idle class queues. */
1738 if (prio == IDLE_WORKLOAD)
1739 return false;
1740
1741 /* We do for queues that were marked with idle window flag. */
1742 if (cfq_cfqq_idle_window(cfqq))
1743 return true;
1744
1745 /*
1746 * Otherwise, we do only if they are the last ones
1747 * in their service tree.
1748 */
1749 return service_tree->count == 1;
1750}
1751
1752static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1753{
1754 struct cfq_queue *cfqq = cfqd->active_queue;
1755 struct cfq_io_context *cic;
1756 unsigned long sl;
1757
1758 /*
1759 * SSD device without seek penalty, disable idling. But only do so
1760 * for devices that support queuing, otherwise we still have a problem
1761 * with sync vs async workloads.
1762 */
1763 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1764 return;
1765
1766 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1767 WARN_ON(cfq_cfqq_slice_new(cfqq));
1768
1769 /*
1770 * idle is disabled, either manually or by past process history
1771 */
1772 if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1773 return;
1774
1775 /*
1776 * still active requests from this queue, don't idle
1777 */
1778 if (cfqq->dispatched)
1779 return;
1780
1781 /*
1782 * task has exited, don't wait
1783 */
1784 cic = cfqd->active_cic;
1785 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1786 return;
1787
1788 /*
1789 * If our average think time is larger than the remaining time
1790 * slice, then don't idle. This avoids overrunning the allotted
1791 * time slice.
1792 */
1793 if (sample_valid(cic->ttime_samples) &&
1794 (cfqq->slice_end - jiffies < cic->ttime_mean))
1795 return;
1796
1797 cfq_mark_cfqq_wait_request(cfqq);
1798
1799 sl = cfqd->cfq_slice_idle;
1800
1801 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1802 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1803}
1804
1805/*
1806 * Move request from internal lists to the request queue dispatch list.
1807 */
1808static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1809{
1810 struct cfq_data *cfqd = q->elevator->elevator_data;
1811 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1812
1813 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1814
1815 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1816 cfq_remove_request(rq);
1817 cfqq->dispatched++;
1818 elv_dispatch_sort(q, rq);
1819
1820 if (cfq_cfqq_sync(cfqq))
1821 cfqd->sync_flight++;
1822 cfqq->nr_sectors += blk_rq_sectors(rq);
1823}
1824
1825/*
1826 * return expired entry, or NULL to just start from scratch in rbtree
1827 */
1828static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1829{
1830 struct request *rq = NULL;
1831
1832 if (cfq_cfqq_fifo_expire(cfqq))
1833 return NULL;
1834
1835 cfq_mark_cfqq_fifo_expire(cfqq);
1836
1837 if (list_empty(&cfqq->fifo))
1838 return NULL;
1839
1840 rq = rq_entry_fifo(cfqq->fifo.next);
1841 if (time_before(jiffies, rq_fifo_time(rq)))
1842 rq = NULL;
1843
1844 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1845 return rq;
1846}
1847
1848static inline int
1849cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1850{
1851 const int base_rq = cfqd->cfq_slice_async_rq;
1852
1853 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1854
1855 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1856}
1857
1858/*
1859 * Must be called with the queue_lock held.
1860 */
1861static int cfqq_process_refs(struct cfq_queue *cfqq)
1862{
1863 int process_refs, io_refs;
1864
1865 io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1866 process_refs = atomic_read(&cfqq->ref) - io_refs;
1867 BUG_ON(process_refs < 0);
1868 return process_refs;
1869}
1870
1871static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1872{
1873 int process_refs, new_process_refs;
1874 struct cfq_queue *__cfqq;
1875
1876 /* Avoid a circular list and skip interim queue merges */
1877 while ((__cfqq = new_cfqq->new_cfqq)) {
1878 if (__cfqq == cfqq)
1879 return;
1880 new_cfqq = __cfqq;
1881 }
1882
1883 process_refs = cfqq_process_refs(cfqq);
1884 /*
1885 * If the process for the cfqq has gone away, there is no
1886 * sense in merging the queues.
1887 */
1888 if (process_refs == 0)
1889 return;
1890
1891 /*
1892 * Merge in the direction of the lesser amount of work.
1893 */
1894 new_process_refs = cfqq_process_refs(new_cfqq);
1895 if (new_process_refs >= process_refs) {
1896 cfqq->new_cfqq = new_cfqq;
1897 atomic_add(process_refs, &new_cfqq->ref);
1898 } else {
1899 new_cfqq->new_cfqq = cfqq;
1900 atomic_add(new_process_refs, &cfqq->ref);
1901 }
1902}
1903
1904static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1905 struct cfq_group *cfqg, enum wl_prio_t prio,
1906 bool prio_changed)
1907{
1908 struct cfq_queue *queue;
1909 int i;
1910 bool key_valid = false;
1911 unsigned long lowest_key = 0;
1912 enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1913
1914 if (prio_changed) {
1915 /*
1916 * When priorities switched, we prefer starting
1917 * from SYNC_NOIDLE (first choice), or just SYNC
1918 * over ASYNC
1919 */
1920 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1921 return cur_best;
1922 cur_best = SYNC_WORKLOAD;
1923 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1924 return cur_best;
1925
1926 return ASYNC_WORKLOAD;
1927 }
1928
1929 for (i = 0; i < 3; ++i) {
1930 /* otherwise, select the one with lowest rb_key */
1931 queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
1932 if (queue &&
1933 (!key_valid || time_before(queue->rb_key, lowest_key))) {
1934 lowest_key = queue->rb_key;
1935 cur_best = i;
1936 key_valid = true;
1937 }
1938 }
1939
1940 return cur_best;
1941}
1942
1943static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1944{
1945 enum wl_prio_t previous_prio = cfqd->serving_prio;
1946 bool prio_changed;
1947 unsigned slice;
1948 unsigned count;
1949 struct cfq_rb_root *st;
1950 unsigned group_slice;
1951
1952 if (!cfqg) {
1953 cfqd->serving_prio = IDLE_WORKLOAD;
1954 cfqd->workload_expires = jiffies + 1;
1955 return;
1956 }
1957
1958 /* Choose next priority. RT > BE > IDLE */
1959 if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
1960 cfqd->serving_prio = RT_WORKLOAD;
1961 else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
1962 cfqd->serving_prio = BE_WORKLOAD;
1963 else {
1964 cfqd->serving_prio = IDLE_WORKLOAD;
1965 cfqd->workload_expires = jiffies + 1;
1966 return;
1967 }
1968
1969 /*
1970 * For RT and BE, we have to choose also the type
1971 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1972 * expiration time
1973 */
1974 prio_changed = (cfqd->serving_prio != previous_prio);
1975 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1976 cfqd);
1977 count = st->count;
1978
1979 /*
1980 * If priority didn't change, check workload expiration,
1981 * and that we still have other queues ready
1982 */
1983 if (!prio_changed && count &&
1984 !time_after(jiffies, cfqd->workload_expires))
1985 return;
1986
1987 /* otherwise select new workload type */
1988 cfqd->serving_type =
1989 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
1990 st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1991 cfqd);
1992 count = st->count;
1993
1994 /*
1995 * the workload slice is computed as a fraction of target latency
1996 * proportional to the number of queues in that workload, over
1997 * all the queues in the same priority class
1998 */
1999 group_slice = cfq_group_slice(cfqd, cfqg);
2000
2001 slice = group_slice * count /
2002 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2003 cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2004
2005 if (cfqd->serving_type == ASYNC_WORKLOAD)
2006 /* async workload slice is scaled down according to
2007 * the sync/async slice ratio. */
2008 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2009 else
2010 /* sync workload slice is at least 2 * cfq_slice_idle */
2011 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2012
2013 slice = max_t(unsigned, slice, CFQ_MIN_TT);
2014 cfqd->workload_expires = jiffies + slice;
2015 cfqd->noidle_tree_requires_idle = false;
2016}
2017
2018static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2019{
2020 struct cfq_rb_root *st = &cfqd->grp_service_tree;
2021 struct cfq_group *cfqg;
2022
2023 if (RB_EMPTY_ROOT(&st->rb))
2024 return NULL;
2025 cfqg = cfq_rb_first_group(st);
2026 st->active = &cfqg->rb_node;
2027 update_min_vdisktime(st);
2028 return cfqg;
2029}
2030
2031static void cfq_choose_cfqg(struct cfq_data *cfqd)
2032{
2033 struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2034
2035 cfqd->serving_group = cfqg;
2036
2037 /* Restore the workload type data */
2038 if (cfqg->saved_workload_slice) {
2039 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2040 cfqd->serving_type = cfqg->saved_workload;
2041 cfqd->serving_prio = cfqg->saved_serving_prio;
2042 }
2043 choose_service_tree(cfqd, cfqg);
2044}
2045
2046/*
2047 * Select a queue for service. If we have a current active queue,
2048 * check whether to continue servicing it, or retrieve and set a new one.
2049 */
2050static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2051{
2052 struct cfq_queue *cfqq, *new_cfqq = NULL;
2053
2054 cfqq = cfqd->active_queue;
2055 if (!cfqq)
2056 goto new_queue;
2057
2058 if (!cfqd->rq_queued)
2059 return NULL;
2060 /*
2061 * The active queue has run out of time, expire it and select new.
2062 */
2063 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
2064 goto expire;
2065
2066 /*
2067 * The active queue has requests and isn't expired, allow it to
2068 * dispatch.
2069 */
2070 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2071 goto keep_queue;
2072
2073 /*
2074 * If another queue has a request waiting within our mean seek
2075 * distance, let it run. The expire code will check for close
2076 * cooperators and put the close queue at the front of the service
2077 * tree. If possible, merge the expiring queue with the new cfqq.
2078 */
2079 new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2080 if (new_cfqq) {
2081 if (!cfqq->new_cfqq)
2082 cfq_setup_merge(cfqq, new_cfqq);
2083 goto expire;
2084 }
2085
2086 /*
2087 * No requests pending. If the active queue still has requests in
2088 * flight or is idling for a new request, allow either of these
2089 * conditions to happen (or time out) before selecting a new queue.
2090 */
2091 if (timer_pending(&cfqd->idle_slice_timer) ||
2092 (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2093 cfqq = NULL;
2094 goto keep_queue;
2095 }
2096
2097expire:
2098 cfq_slice_expired(cfqd, 0);
2099new_queue:
2100 /*
2101 * Current queue expired. Check if we have to switch to a new
2102 * service tree
2103 */
2104 if (!new_cfqq)
2105 cfq_choose_cfqg(cfqd);
2106
2107 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2108keep_queue:
2109 return cfqq;
2110}
2111
2112static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2113{
2114 int dispatched = 0;
2115
2116 while (cfqq->next_rq) {
2117 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2118 dispatched++;
2119 }
2120
2121 BUG_ON(!list_empty(&cfqq->fifo));
2122
2123 /* By default cfqq is not expired if it is empty. Do it explicitly */
2124 __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2125 return dispatched;
2126}
2127
2128/*
2129 * Drain our current requests. Used for barriers and when switching
2130 * io schedulers on-the-fly.
2131 */
2132static int cfq_forced_dispatch(struct cfq_data *cfqd)
2133{
2134 struct cfq_queue *cfqq;
2135 int dispatched = 0;
2136
2137 while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
2138 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2139
2140 cfq_slice_expired(cfqd, 0);
2141 BUG_ON(cfqd->busy_queues);
2142
2143 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2144 return dispatched;
2145}
2146
2147static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2148{
2149 unsigned int max_dispatch;
2150
2151 /*
2152 * Drain async requests before we start sync IO
2153 */
2154 if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
2155 return false;
2156
2157 /*
2158 * If this is an async queue and we have sync IO in flight, let it wait
2159 */
2160 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
2161 return false;
2162
2163 max_dispatch = cfqd->cfq_quantum;
2164 if (cfq_class_idle(cfqq))
2165 max_dispatch = 1;
2166
2167 /*
2168 * Does this cfqq already have too much IO in flight?
2169 */
2170 if (cfqq->dispatched >= max_dispatch) {
2171 /*
2172 * idle queue must always only have a single IO in flight
2173 */
2174 if (cfq_class_idle(cfqq))
2175 return false;
2176
2177 /*
2178 * We have other queues, don't allow more IO from this one
2179 */
2180 if (cfqd->busy_queues > 1)
2181 return false;
2182
2183 /*
2184 * Sole queue user, no limit
2185 */
2186 max_dispatch = -1;
2187 }
2188
2189 /*
2190 * Async queues must wait a bit before being allowed dispatch.
2191 * We also ramp up the dispatch depth gradually for async IO,
2192 * based on the last sync IO we serviced
2193 */
2194 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2195 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
2196 unsigned int depth;
2197
2198 depth = last_sync / cfqd->cfq_slice[1];
2199 if (!depth && !cfqq->dispatched)
2200 depth = 1;
2201 if (depth < max_dispatch)
2202 max_dispatch = depth;
2203 }
2204
2205 /*
2206 * If we're below the current max, allow a dispatch
2207 */
2208 return cfqq->dispatched < max_dispatch;
2209}
2210
2211/*
2212 * Dispatch a request from cfqq, moving them to the request queue
2213 * dispatch list.
2214 */
2215static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2216{
2217 struct request *rq;
2218
2219 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2220
2221 if (!cfq_may_dispatch(cfqd, cfqq))
2222 return false;
2223
2224 /*
2225 * follow expired path, else get first next available
2226 */
2227 rq = cfq_check_fifo(cfqq);
2228 if (!rq)
2229 rq = cfqq->next_rq;
2230
2231 /*
2232 * insert request into driver dispatch list
2233 */
2234 cfq_dispatch_insert(cfqd->queue, rq);
2235
2236 if (!cfqd->active_cic) {
2237 struct cfq_io_context *cic = RQ_CIC(rq);
2238
2239 atomic_long_inc(&cic->ioc->refcount);
2240 cfqd->active_cic = cic;
2241 }
2242
2243 return true;
2244}
2245
2246/*
2247 * Find the cfqq that we need to service and move a request from that to the
2248 * dispatch list
2249 */
2250static int cfq_dispatch_requests(struct request_queue *q, int force)
2251{
2252 struct cfq_data *cfqd = q->elevator->elevator_data;
2253 struct cfq_queue *cfqq;
2254
2255 if (!cfqd->busy_queues)
2256 return 0;
2257
2258 if (unlikely(force))
2259 return cfq_forced_dispatch(cfqd);
2260
2261 cfqq = cfq_select_queue(cfqd);
2262 if (!cfqq)
2263 return 0;
2264
2265 /*
2266 * Dispatch a request from this cfqq, if it is allowed
2267 */
2268 if (!cfq_dispatch_request(cfqd, cfqq))
2269 return 0;
2270
2271 cfqq->slice_dispatch++;
2272 cfq_clear_cfqq_must_dispatch(cfqq);
2273
2274 /*
2275 * expire an async queue immediately if it has used up its slice. idle
2276 * queue always expire after 1 dispatch round.
2277 */
2278 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2279 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2280 cfq_class_idle(cfqq))) {
2281 cfqq->slice_end = jiffies + 1;
2282 cfq_slice_expired(cfqd, 0);
2283 }
2284
2285 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2286 return 1;
2287}
2288
2289/*
2290 * task holds one reference to the queue, dropped when task exits. each rq
2291 * in-flight on this queue also holds a reference, dropped when rq is freed.
2292 *
2293 * Each cfq queue took a reference on the parent group. Drop it now.
2294 * queue lock must be held here.
2295 */
2296static void cfq_put_queue(struct cfq_queue *cfqq)
2297{
2298 struct cfq_data *cfqd = cfqq->cfqd;
2299 struct cfq_group *cfqg;
2300
2301 BUG_ON(atomic_read(&cfqq->ref) <= 0);
2302
2303 if (!atomic_dec_and_test(&cfqq->ref))
2304 return;
2305
2306 cfq_log_cfqq(cfqd, cfqq, "put_queue");
2307 BUG_ON(rb_first(&cfqq->sort_list));
2308 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2309 cfqg = cfqq->cfqg;
2310
2311 if (unlikely(cfqd->active_queue == cfqq)) {
2312 __cfq_slice_expired(cfqd, cfqq, 0);
2313 cfq_schedule_dispatch(cfqd);
2314 }
2315
2316 BUG_ON(cfq_cfqq_on_rr(cfqq));
2317 kmem_cache_free(cfq_pool, cfqq);
2318 cfq_put_cfqg(cfqg);
2319}
2320
2321/*
2322 * Must always be called with the rcu_read_lock() held
2323 */
2324static void
2325__call_for_each_cic(struct io_context *ioc,
2326 void (*func)(struct io_context *, struct cfq_io_context *))
2327{
2328 struct cfq_io_context *cic;
2329 struct hlist_node *n;
2330
2331 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2332 func(ioc, cic);
2333}
2334
2335/*
2336 * Call func for each cic attached to this ioc.
2337 */
2338static void
2339call_for_each_cic(struct io_context *ioc,
2340 void (*func)(struct io_context *, struct cfq_io_context *))
2341{
2342 rcu_read_lock();
2343 __call_for_each_cic(ioc, func);
2344 rcu_read_unlock();
2345}
2346
2347static void cfq_cic_free_rcu(struct rcu_head *head)
2348{
2349 struct cfq_io_context *cic;
2350
2351 cic = container_of(head, struct cfq_io_context, rcu_head);
2352
2353 kmem_cache_free(cfq_ioc_pool, cic);
2354 elv_ioc_count_dec(cfq_ioc_count);
2355
2356 if (ioc_gone) {
2357 /*
2358 * CFQ scheduler is exiting, grab exit lock and check
2359 * the pending io context count. If it hits zero,
2360 * complete ioc_gone and set it back to NULL
2361 */
2362 spin_lock(&ioc_gone_lock);
2363 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2364 complete(ioc_gone);
2365 ioc_gone = NULL;
2366 }
2367 spin_unlock(&ioc_gone_lock);
2368 }
2369}
2370
2371static void cfq_cic_free(struct cfq_io_context *cic)
2372{
2373 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2374}
2375
2376static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2377{
2378 unsigned long flags;
2379
2380 BUG_ON(!cic->dead_key);
2381
2382 spin_lock_irqsave(&ioc->lock, flags);
2383 radix_tree_delete(&ioc->radix_root, cic->dead_key);
2384 hlist_del_rcu(&cic->cic_list);
2385 spin_unlock_irqrestore(&ioc->lock, flags);
2386
2387 cfq_cic_free(cic);
2388}
2389
2390/*
2391 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2392 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2393 * and ->trim() which is called with the task lock held
2394 */
2395static void cfq_free_io_context(struct io_context *ioc)
2396{
2397 /*
2398 * ioc->refcount is zero here, or we are called from elv_unregister(),
2399 * so no more cic's are allowed to be linked into this ioc. So it
2400 * should be ok to iterate over the known list, we will see all cic's
2401 * since no new ones are added.
2402 */
2403 __call_for_each_cic(ioc, cic_free_func);
2404}
2405
2406static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2407{
2408 struct cfq_queue *__cfqq, *next;
2409
2410 if (unlikely(cfqq == cfqd->active_queue)) {
2411 __cfq_slice_expired(cfqd, cfqq, 0);
2412 cfq_schedule_dispatch(cfqd);
2413 }
2414
2415 /*
2416 * If this queue was scheduled to merge with another queue, be
2417 * sure to drop the reference taken on that queue (and others in
2418 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2419 */
2420 __cfqq = cfqq->new_cfqq;
2421 while (__cfqq) {
2422 if (__cfqq == cfqq) {
2423 WARN(1, "cfqq->new_cfqq loop detected\n");
2424 break;
2425 }
2426 next = __cfqq->new_cfqq;
2427 cfq_put_queue(__cfqq);
2428 __cfqq = next;
2429 }
2430
2431 cfq_put_queue(cfqq);
2432}
2433
2434static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2435 struct cfq_io_context *cic)
2436{
2437 struct io_context *ioc = cic->ioc;
2438
2439 list_del_init(&cic->queue_list);
2440
2441 /*
2442 * Make sure key == NULL is seen for dead queues
2443 */
2444 smp_wmb();
2445 cic->dead_key = (unsigned long) cic->key;
2446 cic->key = NULL;
2447
2448 if (ioc->ioc_data == cic)
2449 rcu_assign_pointer(ioc->ioc_data, NULL);
2450
2451 if (cic->cfqq[BLK_RW_ASYNC]) {
2452 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2453 cic->cfqq[BLK_RW_ASYNC] = NULL;
2454 }
2455
2456 if (cic->cfqq[BLK_RW_SYNC]) {
2457 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2458 cic->cfqq[BLK_RW_SYNC] = NULL;
2459 }
2460}
2461
2462static void cfq_exit_single_io_context(struct io_context *ioc,
2463 struct cfq_io_context *cic)
2464{
2465 struct cfq_data *cfqd = cic->key;
2466
2467 if (cfqd) {
2468 struct request_queue *q = cfqd->queue;
2469 unsigned long flags;
2470
2471 spin_lock_irqsave(q->queue_lock, flags);
2472
2473 /*
2474 * Ensure we get a fresh copy of the ->key to prevent
2475 * race between exiting task and queue
2476 */
2477 smp_read_barrier_depends();
2478 if (cic->key)
2479 __cfq_exit_single_io_context(cfqd, cic);
2480
2481 spin_unlock_irqrestore(q->queue_lock, flags);
2482 }
2483}
2484
2485/*
2486 * The process that ioc belongs to has exited, we need to clean up
2487 * and put the internal structures we have that belongs to that process.
2488 */
2489static void cfq_exit_io_context(struct io_context *ioc)
2490{
2491 call_for_each_cic(ioc, cfq_exit_single_io_context);
2492}
2493
2494static struct cfq_io_context *
2495cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2496{
2497 struct cfq_io_context *cic;
2498
2499 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2500 cfqd->queue->node);
2501 if (cic) {
2502 cic->last_end_request = jiffies;
2503 INIT_LIST_HEAD(&cic->queue_list);
2504 INIT_HLIST_NODE(&cic->cic_list);
2505 cic->dtor = cfq_free_io_context;
2506 cic->exit = cfq_exit_io_context;
2507 elv_ioc_count_inc(cfq_ioc_count);
2508 }
2509
2510 return cic;
2511}
2512
2513static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2514{
2515 struct task_struct *tsk = current;
2516 int ioprio_class;
2517
2518 if (!cfq_cfqq_prio_changed(cfqq))
2519 return;
2520
2521 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2522 switch (ioprio_class) {
2523 default:
2524 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2525 case IOPRIO_CLASS_NONE:
2526 /*
2527 * no prio set, inherit CPU scheduling settings
2528 */
2529 cfqq->ioprio = task_nice_ioprio(tsk);
2530 cfqq->ioprio_class = task_nice_ioclass(tsk);
2531 break;
2532 case IOPRIO_CLASS_RT:
2533 cfqq->ioprio = task_ioprio(ioc);
2534 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2535 break;
2536 case IOPRIO_CLASS_BE:
2537 cfqq->ioprio = task_ioprio(ioc);
2538 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2539 break;
2540 case IOPRIO_CLASS_IDLE:
2541 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2542 cfqq->ioprio = 7;
2543 cfq_clear_cfqq_idle_window(cfqq);
2544 break;
2545 }
2546
2547 /*
2548 * keep track of original prio settings in case we have to temporarily
2549 * elevate the priority of this queue
2550 */
2551 cfqq->org_ioprio = cfqq->ioprio;
2552 cfqq->org_ioprio_class = cfqq->ioprio_class;
2553 cfq_clear_cfqq_prio_changed(cfqq);
2554}
2555
2556static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2557{
2558 struct cfq_data *cfqd = cic->key;
2559 struct cfq_queue *cfqq;
2560 unsigned long flags;
2561
2562 if (unlikely(!cfqd))
2563 return;
2564
2565 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2566
2567 cfqq = cic->cfqq[BLK_RW_ASYNC];
2568 if (cfqq) {
2569 struct cfq_queue *new_cfqq;
2570 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2571 GFP_ATOMIC);
2572 if (new_cfqq) {
2573 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2574 cfq_put_queue(cfqq);
2575 }
2576 }
2577
2578 cfqq = cic->cfqq[BLK_RW_SYNC];
2579 if (cfqq)
2580 cfq_mark_cfqq_prio_changed(cfqq);
2581
2582 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2583}
2584
2585static void cfq_ioc_set_ioprio(struct io_context *ioc)
2586{
2587 call_for_each_cic(ioc, changed_ioprio);
2588 ioc->ioprio_changed = 0;
2589}
2590
2591static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2592 pid_t pid, bool is_sync)
2593{
2594 RB_CLEAR_NODE(&cfqq->rb_node);
2595 RB_CLEAR_NODE(&cfqq->p_node);
2596 INIT_LIST_HEAD(&cfqq->fifo);
2597
2598 atomic_set(&cfqq->ref, 0);
2599 cfqq->cfqd = cfqd;
2600
2601 cfq_mark_cfqq_prio_changed(cfqq);
2602
2603 if (is_sync) {
2604 if (!cfq_class_idle(cfqq))
2605 cfq_mark_cfqq_idle_window(cfqq);
2606 cfq_mark_cfqq_sync(cfqq);
2607 }
2608 cfqq->pid = pid;
2609}
2610
2611static struct cfq_queue *
2612cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2613 struct io_context *ioc, gfp_t gfp_mask)
2614{
2615 struct cfq_queue *cfqq, *new_cfqq = NULL;
2616 struct cfq_io_context *cic;
2617 struct cfq_group *cfqg;
2618
2619retry:
2620 cfqg = cfq_get_cfqg(cfqd, 1);
2621 cic = cfq_cic_lookup(cfqd, ioc);
2622 /* cic always exists here */
2623 cfqq = cic_to_cfqq(cic, is_sync);
2624
2625 /*
2626 * Always try a new alloc if we fell back to the OOM cfqq
2627 * originally, since it should just be a temporary situation.
2628 */
2629 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2630 cfqq = NULL;
2631 if (new_cfqq) {
2632 cfqq = new_cfqq;
2633 new_cfqq = NULL;
2634 } else if (gfp_mask & __GFP_WAIT) {
2635 spin_unlock_irq(cfqd->queue->queue_lock);
2636 new_cfqq = kmem_cache_alloc_node(cfq_pool,
2637 gfp_mask | __GFP_ZERO,
2638 cfqd->queue->node);
2639 spin_lock_irq(cfqd->queue->queue_lock);
2640 if (new_cfqq)
2641 goto retry;
2642 } else {
2643 cfqq = kmem_cache_alloc_node(cfq_pool,
2644 gfp_mask | __GFP_ZERO,
2645 cfqd->queue->node);
2646 }
2647
2648 if (cfqq) {
2649 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2650 cfq_init_prio_data(cfqq, ioc);
2651 cfq_link_cfqq_cfqg(cfqq, cfqg);
2652 cfq_log_cfqq(cfqd, cfqq, "alloced");
2653 } else
2654 cfqq = &cfqd->oom_cfqq;
2655 }
2656
2657 if (new_cfqq)
2658 kmem_cache_free(cfq_pool, new_cfqq);
2659
2660 return cfqq;
2661}
2662
2663static struct cfq_queue **
2664cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2665{
2666 switch (ioprio_class) {
2667 case IOPRIO_CLASS_RT:
2668 return &cfqd->async_cfqq[0][ioprio];
2669 case IOPRIO_CLASS_BE:
2670 return &cfqd->async_cfqq[1][ioprio];
2671 case IOPRIO_CLASS_IDLE:
2672 return &cfqd->async_idle_cfqq;
2673 default:
2674 BUG();
2675 }
2676}
2677
2678static struct cfq_queue *
2679cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2680 gfp_t gfp_mask)
2681{
2682 const int ioprio = task_ioprio(ioc);
2683 const int ioprio_class = task_ioprio_class(ioc);
2684 struct cfq_queue **async_cfqq = NULL;
2685 struct cfq_queue *cfqq = NULL;
2686
2687 if (!is_sync) {
2688 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2689 cfqq = *async_cfqq;
2690 }
2691
2692 if (!cfqq)
2693 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2694
2695 /*
2696 * pin the queue now that it's allocated, scheduler exit will prune it
2697 */
2698 if (!is_sync && !(*async_cfqq)) {
2699 atomic_inc(&cfqq->ref);
2700 *async_cfqq = cfqq;
2701 }
2702
2703 atomic_inc(&cfqq->ref);
2704 return cfqq;
2705}
2706
2707/*
2708 * We drop cfq io contexts lazily, so we may find a dead one.
2709 */
2710static void
2711cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2712 struct cfq_io_context *cic)
2713{
2714 unsigned long flags;
2715
2716 WARN_ON(!list_empty(&cic->queue_list));
2717
2718 spin_lock_irqsave(&ioc->lock, flags);
2719
2720 BUG_ON(ioc->ioc_data == cic);
2721
2722 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2723 hlist_del_rcu(&cic->cic_list);
2724 spin_unlock_irqrestore(&ioc->lock, flags);
2725
2726 cfq_cic_free(cic);
2727}
2728
2729static struct cfq_io_context *
2730cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2731{
2732 struct cfq_io_context *cic;
2733 unsigned long flags;
2734 void *k;
2735
2736 if (unlikely(!ioc))
2737 return NULL;
2738
2739 rcu_read_lock();
2740
2741 /*
2742 * we maintain a last-hit cache, to avoid browsing over the tree
2743 */
2744 cic = rcu_dereference(ioc->ioc_data);
2745 if (cic && cic->key == cfqd) {
2746 rcu_read_unlock();
2747 return cic;
2748 }
2749
2750 do {
2751 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2752 rcu_read_unlock();
2753 if (!cic)
2754 break;
2755 /* ->key must be copied to avoid race with cfq_exit_queue() */
2756 k = cic->key;
2757 if (unlikely(!k)) {
2758 cfq_drop_dead_cic(cfqd, ioc, cic);
2759 rcu_read_lock();
2760 continue;
2761 }
2762
2763 spin_lock_irqsave(&ioc->lock, flags);
2764 rcu_assign_pointer(ioc->ioc_data, cic);
2765 spin_unlock_irqrestore(&ioc->lock, flags);
2766 break;
2767 } while (1);
2768
2769 return cic;
2770}
2771
2772/*
2773 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2774 * the process specific cfq io context when entered from the block layer.
2775 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2776 */
2777static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2778 struct cfq_io_context *cic, gfp_t gfp_mask)
2779{
2780 unsigned long flags;
2781 int ret;
2782
2783 ret = radix_tree_preload(gfp_mask);
2784 if (!ret) {
2785 cic->ioc = ioc;
2786 cic->key = cfqd;
2787
2788 spin_lock_irqsave(&ioc->lock, flags);
2789 ret = radix_tree_insert(&ioc->radix_root,
2790 (unsigned long) cfqd, cic);
2791 if (!ret)
2792 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2793 spin_unlock_irqrestore(&ioc->lock, flags);
2794
2795 radix_tree_preload_end();
2796
2797 if (!ret) {
2798 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2799 list_add(&cic->queue_list, &cfqd->cic_list);
2800 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2801 }
2802 }
2803
2804 if (ret)
2805 printk(KERN_ERR "cfq: cic link failed!\n");
2806
2807 return ret;
2808}
2809
2810/*
2811 * Setup general io context and cfq io context. There can be several cfq
2812 * io contexts per general io context, if this process is doing io to more
2813 * than one device managed by cfq.
2814 */
2815static struct cfq_io_context *
2816cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2817{
2818 struct io_context *ioc = NULL;
2819 struct cfq_io_context *cic;
2820
2821 might_sleep_if(gfp_mask & __GFP_WAIT);
2822
2823 ioc = get_io_context(gfp_mask, cfqd->queue->node);
2824 if (!ioc)
2825 return NULL;
2826
2827 cic = cfq_cic_lookup(cfqd, ioc);
2828 if (cic)
2829 goto out;
2830
2831 cic = cfq_alloc_io_context(cfqd, gfp_mask);
2832 if (cic == NULL)
2833 goto err;
2834
2835 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2836 goto err_free;
2837
2838out:
2839 smp_read_barrier_depends();
2840 if (unlikely(ioc->ioprio_changed))
2841 cfq_ioc_set_ioprio(ioc);
2842
2843 return cic;
2844err_free:
2845 cfq_cic_free(cic);
2846err:
2847 put_io_context(ioc);
2848 return NULL;
2849}
2850
2851static void
2852cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2853{
2854 unsigned long elapsed = jiffies - cic->last_end_request;
2855 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2856
2857 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2858 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2859 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2860}
2861
2862static void
2863cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2864 struct request *rq)
2865{
2866 sector_t sdist;
2867 u64 total;
2868
2869 if (!cfqq->last_request_pos)
2870 sdist = 0;
2871 else if (cfqq->last_request_pos < blk_rq_pos(rq))
2872 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2873 else
2874 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2875
2876 /*
2877 * Don't allow the seek distance to get too large from the
2878 * odd fragment, pagein, etc
2879 */
2880 if (cfqq->seek_samples <= 60) /* second&third seek */
2881 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2882 else
2883 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2884
2885 cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2886 cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2887 total = cfqq->seek_total + (cfqq->seek_samples/2);
2888 do_div(total, cfqq->seek_samples);
2889 cfqq->seek_mean = (sector_t)total;
2890
2891 /*
2892 * If this cfqq is shared between multiple processes, check to
2893 * make sure that those processes are still issuing I/Os within
2894 * the mean seek distance. If not, it may be time to break the
2895 * queues apart again.
2896 */
2897 if (cfq_cfqq_coop(cfqq)) {
2898 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2899 cfqq->seeky_start = jiffies;
2900 else if (!CFQQ_SEEKY(cfqq))
2901 cfqq->seeky_start = 0;
2902 }
2903}
2904
2905/*
2906 * Disable idle window if the process thinks too long or seeks so much that
2907 * it doesn't matter
2908 */
2909static void
2910cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2911 struct cfq_io_context *cic)
2912{
2913 int old_idle, enable_idle;
2914
2915 /*
2916 * Don't idle for async or idle io prio class
2917 */
2918 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2919 return;
2920
2921 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2922
2923 if (cfqq->queued[0] + cfqq->queued[1] >= 4)
2924 cfq_mark_cfqq_deep(cfqq);
2925
2926 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2927 (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
2928 && CFQQ_SEEKY(cfqq)))
2929 enable_idle = 0;
2930 else if (sample_valid(cic->ttime_samples)) {
2931 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2932 enable_idle = 0;
2933 else
2934 enable_idle = 1;
2935 }
2936
2937 if (old_idle != enable_idle) {
2938 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2939 if (enable_idle)
2940 cfq_mark_cfqq_idle_window(cfqq);
2941 else
2942 cfq_clear_cfqq_idle_window(cfqq);
2943 }
2944}
2945
2946/*
2947 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2948 * no or if we aren't sure, a 1 will cause a preempt.
2949 */
2950static bool
2951cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2952 struct request *rq)
2953{
2954 struct cfq_queue *cfqq;
2955
2956 cfqq = cfqd->active_queue;
2957 if (!cfqq)
2958 return false;
2959
2960 if (cfq_class_idle(new_cfqq))
2961 return false;
2962
2963 if (cfq_class_idle(cfqq))
2964 return true;
2965
2966 /*
2967 * if the new request is sync, but the currently running queue is
2968 * not, let the sync request have priority.
2969 */
2970 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2971 return true;
2972
2973 if (new_cfqq->cfqg != cfqq->cfqg)
2974 return false;
2975
2976 if (cfq_slice_used(cfqq))
2977 return true;
2978
2979 /* Allow preemption only if we are idling on sync-noidle tree */
2980 if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
2981 cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
2982 new_cfqq->service_tree->count == 2 &&
2983 RB_EMPTY_ROOT(&cfqq->sort_list))
2984 return true;
2985
2986 /*
2987 * So both queues are sync. Let the new request get disk time if
2988 * it's a metadata request and the current queue is doing regular IO.
2989 */
2990 if (rq_is_meta(rq) && !cfqq->meta_pending)
2991 return true;
2992
2993 /*
2994 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2995 */
2996 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2997 return true;
2998
2999 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3000 return false;
3001
3002 /*
3003 * if this request is as-good as one we would expect from the
3004 * current cfqq, let it preempt
3005 */
3006 if (cfq_rq_close(cfqd, cfqq, rq))
3007 return true;
3008
3009 return false;
3010}
3011
3012/*
3013 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3014 * let it have half of its nominal slice.
3015 */
3016static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3017{
3018 cfq_log_cfqq(cfqd, cfqq, "preempt");
3019 cfq_slice_expired(cfqd, 1);
3020
3021 /*
3022 * Put the new queue at the front of the of the current list,
3023 * so we know that it will be selected next.
3024 */
3025 BUG_ON(!cfq_cfqq_on_rr(cfqq));
3026
3027 cfq_service_tree_add(cfqd, cfqq, 1);
3028
3029 cfqq->slice_end = 0;
3030 cfq_mark_cfqq_slice_new(cfqq);
3031}
3032
3033/*
3034 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3035 * something we should do about it
3036 */
3037static void
3038cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3039 struct request *rq)
3040{
3041 struct cfq_io_context *cic = RQ_CIC(rq);
3042
3043 cfqd->rq_queued++;
3044 if (rq_is_meta(rq))
3045 cfqq->meta_pending++;
3046
3047 cfq_update_io_thinktime(cfqd, cic);
3048 cfq_update_io_seektime(cfqd, cfqq, rq);
3049 cfq_update_idle_window(cfqd, cfqq, cic);
3050
3051 cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3052
3053 if (cfqq == cfqd->active_queue) {
3054 /*
3055 * Remember that we saw a request from this process, but
3056 * don't start queuing just yet. Otherwise we risk seeing lots
3057 * of tiny requests, because we disrupt the normal plugging
3058 * and merging. If the request is already larger than a single
3059 * page, let it rip immediately. For that case we assume that
3060 * merging is already done. Ditto for a busy system that
3061 * has other work pending, don't risk delaying until the
3062 * idle timer unplug to continue working.
3063 */
3064 if (cfq_cfqq_wait_request(cfqq)) {
3065 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3066 cfqd->busy_queues > 1) {
3067 del_timer(&cfqd->idle_slice_timer);
3068 __blk_run_queue(cfqd->queue);
3069 } else
3070 cfq_mark_cfqq_must_dispatch(cfqq);
3071 }
3072 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3073 /*
3074 * not the active queue - expire current slice if it is
3075 * idle and has expired it's mean thinktime or this new queue
3076 * has some old slice time left and is of higher priority or
3077 * this new queue is RT and the current one is BE
3078 */
3079 cfq_preempt_queue(cfqd, cfqq);
3080 __blk_run_queue(cfqd->queue);
3081 }
3082}
3083
3084static void cfq_insert_request(struct request_queue *q, struct request *rq)
3085{
3086 struct cfq_data *cfqd = q->elevator->elevator_data;
3087 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3088
3089 cfq_log_cfqq(cfqd, cfqq, "insert_request");
3090 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3091
3092 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3093 list_add_tail(&rq->queuelist, &cfqq->fifo);
3094 cfq_add_rq_rb(rq);
3095
3096 cfq_rq_enqueued(cfqd, cfqq, rq);
3097}
3098
3099/*
3100 * Update hw_tag based on peak queue depth over 50 samples under
3101 * sufficient load.
3102 */
3103static void cfq_update_hw_tag(struct cfq_data *cfqd)
3104{
3105 struct cfq_queue *cfqq = cfqd->active_queue;
3106
3107 if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
3108 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
3109
3110 if (cfqd->hw_tag == 1)
3111 return;
3112
3113 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3114 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
3115 return;
3116
3117 /*
3118 * If active queue hasn't enough requests and can idle, cfq might not
3119 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3120 * case
3121 */
3122 if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3123 cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3124 CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
3125 return;
3126
3127 if (cfqd->hw_tag_samples++ < 50)
3128 return;
3129
3130 if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3131 cfqd->hw_tag = 1;
3132 else
3133 cfqd->hw_tag = 0;
3134}
3135
3136static void cfq_completed_request(struct request_queue *q, struct request *rq)
3137{
3138 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3139 struct cfq_data *cfqd = cfqq->cfqd;
3140 const int sync = rq_is_sync(rq);
3141 unsigned long now;
3142
3143 now = jiffies;
3144 cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3145
3146 cfq_update_hw_tag(cfqd);
3147
3148 WARN_ON(!cfqd->rq_in_driver[sync]);
3149 WARN_ON(!cfqq->dispatched);
3150 cfqd->rq_in_driver[sync]--;
3151 cfqq->dispatched--;
3152
3153 if (cfq_cfqq_sync(cfqq))
3154 cfqd->sync_flight--;
3155
3156 if (sync) {
3157 RQ_CIC(rq)->last_end_request = now;
3158 cfqd->last_end_sync_rq = now;
3159 }
3160
3161 /*
3162 * If this is the active queue, check if it needs to be expired,
3163 * or if we want to idle in case it has no pending requests.
3164 */
3165 if (cfqd->active_queue == cfqq) {
3166 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3167
3168 if (cfq_cfqq_slice_new(cfqq)) {
3169 cfq_set_prio_slice(cfqd, cfqq);
3170 cfq_clear_cfqq_slice_new(cfqq);
3171 }
3172 /*
3173 * Idling is not enabled on:
3174 * - expired queues
3175 * - idle-priority queues
3176 * - async queues
3177 * - queues with still some requests queued
3178 * - when there is a close cooperator
3179 */
3180 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3181 cfq_slice_expired(cfqd, 1);
3182 else if (sync && cfqq_empty &&
3183 !cfq_close_cooperator(cfqd, cfqq)) {
3184 cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3185 /*
3186 * Idling is enabled for SYNC_WORKLOAD.
3187 * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3188 * only if we processed at least one !rq_noidle request
3189 */
3190 if (cfqd->serving_type == SYNC_WORKLOAD
3191 || cfqd->noidle_tree_requires_idle)
3192 cfq_arm_slice_timer(cfqd);
3193 }
3194 }
3195
3196 if (!rq_in_driver(cfqd))
3197 cfq_schedule_dispatch(cfqd);
3198}
3199
3200/*
3201 * we temporarily boost lower priority queues if they are holding fs exclusive
3202 * resources. they are boosted to normal prio (CLASS_BE/4)
3203 */
3204static void cfq_prio_boost(struct cfq_queue *cfqq)
3205{
3206 if (has_fs_excl()) {
3207 /*
3208 * boost idle prio on transactions that would lock out other
3209 * users of the filesystem
3210 */
3211 if (cfq_class_idle(cfqq))
3212 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3213 if (cfqq->ioprio > IOPRIO_NORM)
3214 cfqq->ioprio = IOPRIO_NORM;
3215 } else {
3216 /*
3217 * unboost the queue (if needed)
3218 */
3219 cfqq->ioprio_class = cfqq->org_ioprio_class;
3220 cfqq->ioprio = cfqq->org_ioprio;
3221 }
3222}
3223
3224static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3225{
3226 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3227 cfq_mark_cfqq_must_alloc_slice(cfqq);
3228 return ELV_MQUEUE_MUST;
3229 }
3230
3231 return ELV_MQUEUE_MAY;
3232}
3233
3234static int cfq_may_queue(struct request_queue *q, int rw)
3235{
3236 struct cfq_data *cfqd = q->elevator->elevator_data;
3237 struct task_struct *tsk = current;
3238 struct cfq_io_context *cic;
3239 struct cfq_queue *cfqq;
3240
3241 /*
3242 * don't force setup of a queue from here, as a call to may_queue
3243 * does not necessarily imply that a request actually will be queued.
3244 * so just lookup a possibly existing queue, or return 'may queue'
3245 * if that fails
3246 */
3247 cic = cfq_cic_lookup(cfqd, tsk->io_context);
3248 if (!cic)
3249 return ELV_MQUEUE_MAY;
3250
3251 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3252 if (cfqq) {
3253 cfq_init_prio_data(cfqq, cic->ioc);
3254 cfq_prio_boost(cfqq);
3255
3256 return __cfq_may_queue(cfqq);
3257 }
3258
3259 return ELV_MQUEUE_MAY;
3260}
3261
3262/*
3263 * queue lock held here
3264 */
3265static void cfq_put_request(struct request *rq)
3266{
3267 struct cfq_queue *cfqq = RQ_CFQQ(rq);
3268
3269 if (cfqq) {
3270 const int rw = rq_data_dir(rq);
3271
3272 BUG_ON(!cfqq->allocated[rw]);
3273 cfqq->allocated[rw]--;
3274
3275 put_io_context(RQ_CIC(rq)->ioc);
3276
3277 rq->elevator_private = NULL;
3278 rq->elevator_private2 = NULL;
3279
3280 cfq_put_queue(cfqq);
3281 }
3282}
3283
3284static struct cfq_queue *
3285cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3286 struct cfq_queue *cfqq)
3287{
3288 cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3289 cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3290 cfq_mark_cfqq_coop(cfqq->new_cfqq);
3291 cfq_put_queue(cfqq);
3292 return cic_to_cfqq(cic, 1);
3293}
3294
3295static int should_split_cfqq(struct cfq_queue *cfqq)
3296{
3297 if (cfqq->seeky_start &&
3298 time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
3299 return 1;
3300 return 0;
3301}
3302
3303/*
3304 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3305 * was the last process referring to said cfqq.
3306 */
3307static struct cfq_queue *
3308split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3309{
3310 if (cfqq_process_refs(cfqq) == 1) {
3311 cfqq->seeky_start = 0;
3312 cfqq->pid = current->pid;
3313 cfq_clear_cfqq_coop(cfqq);
3314 return cfqq;
3315 }
3316
3317 cic_set_cfqq(cic, NULL, 1);
3318 cfq_put_queue(cfqq);
3319 return NULL;
3320}
3321/*
3322 * Allocate cfq data structures associated with this request.
3323 */
3324static int
3325cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3326{
3327 struct cfq_data *cfqd = q->elevator->elevator_data;
3328 struct cfq_io_context *cic;
3329 const int rw = rq_data_dir(rq);
3330 const bool is_sync = rq_is_sync(rq);
3331 struct cfq_queue *cfqq;
3332 unsigned long flags;
3333
3334 might_sleep_if(gfp_mask & __GFP_WAIT);
3335
3336 cic = cfq_get_io_context(cfqd, gfp_mask);
3337
3338 spin_lock_irqsave(q->queue_lock, flags);
3339
3340 if (!cic)
3341 goto queue_fail;
3342
3343new_queue:
3344 cfqq = cic_to_cfqq(cic, is_sync);
3345 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3346 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3347 cic_set_cfqq(cic, cfqq, is_sync);
3348 } else {
3349 /*
3350 * If the queue was seeky for too long, break it apart.
3351 */
3352 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
3353 cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3354 cfqq = split_cfqq(cic, cfqq);
3355 if (!cfqq)
3356 goto new_queue;
3357 }
3358
3359 /*
3360 * Check to see if this queue is scheduled to merge with
3361 * another, closely cooperating queue. The merging of
3362 * queues happens here as it must be done in process context.
3363 * The reference on new_cfqq was taken in merge_cfqqs.
3364 */
3365 if (cfqq->new_cfqq)
3366 cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3367 }
3368
3369 cfqq->allocated[rw]++;
3370 atomic_inc(&cfqq->ref);
3371
3372 spin_unlock_irqrestore(q->queue_lock, flags);
3373
3374 rq->elevator_private = cic;
3375 rq->elevator_private2 = cfqq;
3376 return 0;
3377
3378queue_fail:
3379 if (cic)
3380 put_io_context(cic->ioc);
3381
3382 cfq_schedule_dispatch(cfqd);
3383 spin_unlock_irqrestore(q->queue_lock, flags);
3384 cfq_log(cfqd, "set_request fail");
3385 return 1;
3386}
3387
3388static void cfq_kick_queue(struct work_struct *work)
3389{
3390 struct cfq_data *cfqd =
3391 container_of(work, struct cfq_data, unplug_work);
3392 struct request_queue *q = cfqd->queue;
3393
3394 spin_lock_irq(q->queue_lock);
3395 __blk_run_queue(cfqd->queue);
3396 spin_unlock_irq(q->queue_lock);
3397}
3398
3399/*
3400 * Timer running if the active_queue is currently idling inside its time slice
3401 */
3402static void cfq_idle_slice_timer(unsigned long data)
3403{
3404 struct cfq_data *cfqd = (struct cfq_data *) data;
3405 struct cfq_queue *cfqq;
3406 unsigned long flags;
3407 int timed_out = 1;
3408
3409 cfq_log(cfqd, "idle timer fired");
3410
3411 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3412
3413 cfqq = cfqd->active_queue;
3414 if (cfqq) {
3415 timed_out = 0;
3416
3417 /*
3418 * We saw a request before the queue expired, let it through
3419 */
3420 if (cfq_cfqq_must_dispatch(cfqq))
3421 goto out_kick;
3422
3423 /*
3424 * expired
3425 */
3426 if (cfq_slice_used(cfqq))
3427 goto expire;
3428
3429 /*
3430 * only expire and reinvoke request handler, if there are
3431 * other queues with pending requests
3432 */
3433 if (!cfqd->busy_queues)
3434 goto out_cont;
3435
3436 /*
3437 * not expired and it has a request pending, let it dispatch
3438 */
3439 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3440 goto out_kick;
3441
3442 /*
3443 * Queue depth flag is reset only when the idle didn't succeed
3444 */
3445 cfq_clear_cfqq_deep(cfqq);
3446 }
3447expire:
3448 cfq_slice_expired(cfqd, timed_out);
3449out_kick:
3450 cfq_schedule_dispatch(cfqd);
3451out_cont:
3452 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3453}
3454
3455static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3456{
3457 del_timer_sync(&cfqd->idle_slice_timer);
3458 cancel_work_sync(&cfqd->unplug_work);
3459}
3460
3461static void cfq_put_async_queues(struct cfq_data *cfqd)
3462{
3463 int i;
3464
3465 for (i = 0; i < IOPRIO_BE_NR; i++) {
3466 if (cfqd->async_cfqq[0][i])
3467 cfq_put_queue(cfqd->async_cfqq[0][i]);
3468 if (cfqd->async_cfqq[1][i])
3469 cfq_put_queue(cfqd->async_cfqq[1][i]);
3470 }
3471
3472 if (cfqd->async_idle_cfqq)
3473 cfq_put_queue(cfqd->async_idle_cfqq);
3474}
3475
3476static void cfq_exit_queue(struct elevator_queue *e)
3477{
3478 struct cfq_data *cfqd = e->elevator_data;
3479 struct request_queue *q = cfqd->queue;
3480
3481 cfq_shutdown_timer_wq(cfqd);
3482
3483 spin_lock_irq(q->queue_lock);
3484
3485 if (cfqd->active_queue)
3486 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3487
3488 while (!list_empty(&cfqd->cic_list)) {
3489 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3490 struct cfq_io_context,
3491 queue_list);
3492
3493 __cfq_exit_single_io_context(cfqd, cic);
3494 }
3495
3496 cfq_put_async_queues(cfqd);
3497 cfq_release_cfq_groups(cfqd);
3498 blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3499
3500 spin_unlock_irq(q->queue_lock);
3501
3502 cfq_shutdown_timer_wq(cfqd);
3503
3504 /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3505 synchronize_rcu();
3506 kfree(cfqd);
3507}
3508
3509static void *cfq_init_queue(struct request_queue *q)
3510{
3511 struct cfq_data *cfqd;
3512 int i, j;
3513 struct cfq_group *cfqg;
3514 struct cfq_rb_root *st;
3515
3516 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3517 if (!cfqd)
3518 return NULL;
3519
3520 /* Init root service tree */
3521 cfqd->grp_service_tree = CFQ_RB_ROOT;
3522
3523 /* Init root group */
3524 cfqg = &cfqd->root_group;
3525 for_each_cfqg_st(cfqg, i, j, st)
3526 *st = CFQ_RB_ROOT;
3527 RB_CLEAR_NODE(&cfqg->rb_node);
3528
3529 /* Give preference to root group over other groups */
3530 cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3531
3532#ifdef CONFIG_CFQ_GROUP_IOSCHED
3533 /*
3534 * Take a reference to root group which we never drop. This is just
3535 * to make sure that cfq_put_cfqg() does not try to kfree root group
3536 */
3537 atomic_set(&cfqg->ref, 1);
3538 blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3539 0);
3540#endif
3541 /*
3542 * Not strictly needed (since RB_ROOT just clears the node and we
3543 * zeroed cfqd on alloc), but better be safe in case someone decides
3544 * to add magic to the rb code
3545 */
3546 for (i = 0; i < CFQ_PRIO_LISTS; i++)
3547 cfqd->prio_trees[i] = RB_ROOT;
3548
3549 /*
3550 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3551 * Grab a permanent reference to it, so that the normal code flow
3552 * will not attempt to free it.
3553 */
3554 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3555 atomic_inc(&cfqd->oom_cfqq.ref);
3556 cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3557
3558 INIT_LIST_HEAD(&cfqd->cic_list);
3559
3560 cfqd->queue = q;
3561
3562 init_timer(&cfqd->idle_slice_timer);
3563 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3564 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3565
3566 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3567
3568 cfqd->cfq_quantum = cfq_quantum;
3569 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3570 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3571 cfqd->cfq_back_max = cfq_back_max;
3572 cfqd->cfq_back_penalty = cfq_back_penalty;
3573 cfqd->cfq_slice[0] = cfq_slice_async;
3574 cfqd->cfq_slice[1] = cfq_slice_sync;
3575 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3576 cfqd->cfq_slice_idle = cfq_slice_idle;
3577 cfqd->cfq_latency = 1;
3578 cfqd->hw_tag = -1;
3579 cfqd->last_end_sync_rq = jiffies;
3580 return cfqd;
3581}
3582
3583static void cfq_slab_kill(void)
3584{
3585 /*
3586 * Caller already ensured that pending RCU callbacks are completed,
3587 * so we should have no busy allocations at this point.
3588 */
3589 if (cfq_pool)
3590 kmem_cache_destroy(cfq_pool);
3591 if (cfq_ioc_pool)
3592 kmem_cache_destroy(cfq_ioc_pool);
3593}
3594
3595static int __init cfq_slab_setup(void)
3596{
3597 cfq_pool = KMEM_CACHE(cfq_queue, 0);
3598 if (!cfq_pool)
3599 goto fail;
3600
3601 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3602 if (!cfq_ioc_pool)
3603 goto fail;
3604
3605 return 0;
3606fail:
3607 cfq_slab_kill();
3608 return -ENOMEM;
3609}
3610
3611/*
3612 * sysfs parts below -->
3613 */
3614static ssize_t
3615cfq_var_show(unsigned int var, char *page)
3616{
3617 return sprintf(page, "%d\n", var);
3618}
3619
3620static ssize_t
3621cfq_var_store(unsigned int *var, const char *page, size_t count)
3622{
3623 char *p = (char *) page;
3624
3625 *var = simple_strtoul(p, &p, 10);
3626 return count;
3627}
3628
3629#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3630static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3631{ \
3632 struct cfq_data *cfqd = e->elevator_data; \
3633 unsigned int __data = __VAR; \
3634 if (__CONV) \
3635 __data = jiffies_to_msecs(__data); \
3636 return cfq_var_show(__data, (page)); \
3637}
3638SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3639SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3640SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3641SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3642SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3643SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3644SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3645SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3646SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3647SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3648#undef SHOW_FUNCTION
3649
3650#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3651static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3652{ \
3653 struct cfq_data *cfqd = e->elevator_data; \
3654 unsigned int __data; \
3655 int ret = cfq_var_store(&__data, (page), count); \
3656 if (__data < (MIN)) \
3657 __data = (MIN); \
3658 else if (__data > (MAX)) \
3659 __data = (MAX); \
3660 if (__CONV) \
3661 *(__PTR) = msecs_to_jiffies(__data); \
3662 else \
3663 *(__PTR) = __data; \
3664 return ret; \
3665}
3666STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3667STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3668 UINT_MAX, 1);
3669STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3670 UINT_MAX, 1);
3671STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3672STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3673 UINT_MAX, 0);
3674STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3675STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3676STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3677STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3678 UINT_MAX, 0);
3679STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3680#undef STORE_FUNCTION
3681
3682#define CFQ_ATTR(name) \
3683 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3684
3685static struct elv_fs_entry cfq_attrs[] = {
3686 CFQ_ATTR(quantum),
3687 CFQ_ATTR(fifo_expire_sync),
3688 CFQ_ATTR(fifo_expire_async),
3689 CFQ_ATTR(back_seek_max),
3690 CFQ_ATTR(back_seek_penalty),
3691 CFQ_ATTR(slice_sync),
3692 CFQ_ATTR(slice_async),
3693 CFQ_ATTR(slice_async_rq),
3694 CFQ_ATTR(slice_idle),
3695 CFQ_ATTR(low_latency),
3696 __ATTR_NULL
3697};
3698
3699static struct elevator_type iosched_cfq = {
3700 .ops = {
3701 .elevator_merge_fn = cfq_merge,
3702 .elevator_merged_fn = cfq_merged_request,
3703 .elevator_merge_req_fn = cfq_merged_requests,
3704 .elevator_allow_merge_fn = cfq_allow_merge,
3705 .elevator_dispatch_fn = cfq_dispatch_requests,
3706 .elevator_add_req_fn = cfq_insert_request,
3707 .elevator_activate_req_fn = cfq_activate_request,
3708 .elevator_deactivate_req_fn = cfq_deactivate_request,
3709 .elevator_queue_empty_fn = cfq_queue_empty,
3710 .elevator_completed_req_fn = cfq_completed_request,
3711 .elevator_former_req_fn = elv_rb_former_request,
3712 .elevator_latter_req_fn = elv_rb_latter_request,
3713 .elevator_set_req_fn = cfq_set_request,
3714 .elevator_put_req_fn = cfq_put_request,
3715 .elevator_may_queue_fn = cfq_may_queue,
3716 .elevator_init_fn = cfq_init_queue,
3717 .elevator_exit_fn = cfq_exit_queue,
3718 .trim = cfq_free_io_context,
3719 },
3720 .elevator_attrs = cfq_attrs,
3721 .elevator_name = "cfq",
3722 .elevator_owner = THIS_MODULE,
3723};
3724
3725static int __init cfq_init(void)
3726{
3727 /*
3728 * could be 0 on HZ < 1000 setups
3729 */
3730 if (!cfq_slice_async)
3731 cfq_slice_async = 1;
3732 if (!cfq_slice_idle)
3733 cfq_slice_idle = 1;
3734
3735 if (cfq_slab_setup())
3736 return -ENOMEM;
3737
3738 elv_register(&iosched_cfq);
3739
3740 return 0;
3741}
3742
3743static void __exit cfq_exit(void)
3744{
3745 DECLARE_COMPLETION_ONSTACK(all_gone);
3746 elv_unregister(&iosched_cfq);
3747 ioc_gone = &all_gone;
3748 /* ioc_gone's update must be visible before reading ioc_count */
3749 smp_wmb();
3750
3751 /*
3752 * this also protects us from entering cfq_slab_kill() with
3753 * pending RCU callbacks
3754 */
3755 if (elv_ioc_count_read(cfq_ioc_count))
3756 wait_for_completion(&all_gone);
3757 cfq_slab_kill();
3758}
3759
3760module_init(cfq_init);
3761module_exit(cfq_exit);
3762
3763MODULE_AUTHOR("Jens Axboe");
3764MODULE_LICENSE("GPL");
3765MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");