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1da177e4 1/*
1da177e4
LT
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 *
0fe23479 7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
1da177e4 8 */
1da177e4 9#include <linux/module.h>
1cc9be68
AV
10#include <linux/blkdev.h>
11#include <linux/elevator.h>
1da177e4 12#include <linux/rbtree.h>
22e2c507 13#include <linux/ioprio.h>
7b679138 14#include <linux/blktrace_api.h>
1da177e4
LT
15
16/*
17 * tunables
18 */
fe094d98
JA
19/* max queue in one round of service */
20static const int cfq_quantum = 4;
64100099 21static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
fe094d98
JA
22/* maximum backwards seek, in KiB */
23static const int cfq_back_max = 16 * 1024;
24/* penalty of a backwards seek */
25static const int cfq_back_penalty = 2;
64100099 26static const int cfq_slice_sync = HZ / 10;
3b18152c 27static int cfq_slice_async = HZ / 25;
64100099 28static const int cfq_slice_async_rq = 2;
caaa5f9f 29static int cfq_slice_idle = HZ / 125;
22e2c507 30
d9e7620e 31/*
0871714e 32 * offset from end of service tree
d9e7620e 33 */
0871714e 34#define CFQ_IDLE_DELAY (HZ / 5)
d9e7620e
JA
35
36/*
37 * below this threshold, we consider thinktime immediate
38 */
39#define CFQ_MIN_TT (2)
40
22e2c507 41#define CFQ_SLICE_SCALE (5)
45333d5a 42#define CFQ_HW_QUEUE_MIN (5)
22e2c507 43
fe094d98
JA
44#define RQ_CIC(rq) \
45 ((struct cfq_io_context *) (rq)->elevator_private)
7b679138 46#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
1da177e4 47
e18b890b
CL
48static struct kmem_cache *cfq_pool;
49static struct kmem_cache *cfq_ioc_pool;
1da177e4 50
245b2e70 51static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
334e94de 52static struct completion *ioc_gone;
9a11b4ed 53static DEFINE_SPINLOCK(ioc_gone_lock);
334e94de 54
22e2c507
JA
55#define CFQ_PRIO_LISTS IOPRIO_BE_NR
56#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
22e2c507
JA
57#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
58
206dc69b
JA
59#define sample_valid(samples) ((samples) > 80)
60
cc09e299
JA
61/*
62 * Most of our rbtree usage is for sorting with min extraction, so
63 * if we cache the leftmost node we don't have to walk down the tree
64 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
65 * move this into the elevator for the rq sorting as well.
66 */
67struct cfq_rb_root {
68 struct rb_root rb;
69 struct rb_node *left;
70};
71#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
72
6118b70b
JA
73/*
74 * Per process-grouping structure
75 */
76struct cfq_queue {
77 /* reference count */
78 atomic_t ref;
79 /* various state flags, see below */
80 unsigned int flags;
81 /* parent cfq_data */
82 struct cfq_data *cfqd;
83 /* service_tree member */
84 struct rb_node rb_node;
85 /* service_tree key */
86 unsigned long rb_key;
87 /* prio tree member */
88 struct rb_node p_node;
89 /* prio tree root we belong to, if any */
90 struct rb_root *p_root;
91 /* sorted list of pending requests */
92 struct rb_root sort_list;
93 /* if fifo isn't expired, next request to serve */
94 struct request *next_rq;
95 /* requests queued in sort_list */
96 int queued[2];
97 /* currently allocated requests */
98 int allocated[2];
99 /* fifo list of requests in sort_list */
100 struct list_head fifo;
101
102 unsigned long slice_end;
103 long slice_resid;
104 unsigned int slice_dispatch;
105
106 /* pending metadata requests */
107 int meta_pending;
108 /* number of requests that are on the dispatch list or inside driver */
109 int dispatched;
110
111 /* io prio of this group */
112 unsigned short ioprio, org_ioprio;
113 unsigned short ioprio_class, org_ioprio_class;
114
115 pid_t pid;
116};
117
22e2c507
JA
118/*
119 * Per block device queue structure
120 */
1da177e4 121struct cfq_data {
165125e1 122 struct request_queue *queue;
22e2c507
JA
123
124 /*
125 * rr list of queues with requests and the count of them
126 */
cc09e299 127 struct cfq_rb_root service_tree;
a36e71f9
JA
128
129 /*
130 * Each priority tree is sorted by next_request position. These
131 * trees are used when determining if two or more queues are
132 * interleaving requests (see cfq_close_cooperator).
133 */
134 struct rb_root prio_trees[CFQ_PRIO_LISTS];
135
22e2c507
JA
136 unsigned int busy_queues;
137
5ad531db 138 int rq_in_driver[2];
3ed9a296 139 int sync_flight;
45333d5a
AC
140
141 /*
142 * queue-depth detection
143 */
144 int rq_queued;
25776e35 145 int hw_tag;
45333d5a
AC
146 int hw_tag_samples;
147 int rq_in_driver_peak;
1da177e4 148
22e2c507
JA
149 /*
150 * idle window management
151 */
152 struct timer_list idle_slice_timer;
23e018a1 153 struct work_struct unplug_work;
1da177e4 154
22e2c507
JA
155 struct cfq_queue *active_queue;
156 struct cfq_io_context *active_cic;
22e2c507 157
c2dea2d1
VT
158 /*
159 * async queue for each priority case
160 */
161 struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
162 struct cfq_queue *async_idle_cfqq;
15c31be4 163
6d048f53 164 sector_t last_position;
1da177e4 165
1da177e4
LT
166 /*
167 * tunables, see top of file
168 */
169 unsigned int cfq_quantum;
22e2c507 170 unsigned int cfq_fifo_expire[2];
1da177e4
LT
171 unsigned int cfq_back_penalty;
172 unsigned int cfq_back_max;
22e2c507
JA
173 unsigned int cfq_slice[2];
174 unsigned int cfq_slice_async_rq;
175 unsigned int cfq_slice_idle;
963b72fc 176 unsigned int cfq_latency;
d9ff4187
AV
177
178 struct list_head cic_list;
1da177e4 179
6118b70b
JA
180 /*
181 * Fallback dummy cfqq for extreme OOM conditions
182 */
183 struct cfq_queue oom_cfqq;
365722bb
VG
184
185 unsigned long last_end_sync_rq;
1da177e4
LT
186};
187
3b18152c 188enum cfqq_state_flags {
b0b8d749
JA
189 CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
190 CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
b029195d 191 CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
b0b8d749 192 CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
b0b8d749
JA
193 CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
194 CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
195 CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
44f7c160 196 CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
91fac317 197 CFQ_CFQQ_FLAG_sync, /* synchronous queue */
a36e71f9 198 CFQ_CFQQ_FLAG_coop, /* has done a coop jump of the queue */
3b18152c
JA
199};
200
201#define CFQ_CFQQ_FNS(name) \
202static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
203{ \
fe094d98 204 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
3b18152c
JA
205} \
206static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
207{ \
fe094d98 208 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
3b18152c
JA
209} \
210static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
211{ \
fe094d98 212 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
3b18152c
JA
213}
214
215CFQ_CFQQ_FNS(on_rr);
216CFQ_CFQQ_FNS(wait_request);
b029195d 217CFQ_CFQQ_FNS(must_dispatch);
3b18152c 218CFQ_CFQQ_FNS(must_alloc_slice);
3b18152c
JA
219CFQ_CFQQ_FNS(fifo_expire);
220CFQ_CFQQ_FNS(idle_window);
221CFQ_CFQQ_FNS(prio_changed);
44f7c160 222CFQ_CFQQ_FNS(slice_new);
91fac317 223CFQ_CFQQ_FNS(sync);
a36e71f9 224CFQ_CFQQ_FNS(coop);
3b18152c
JA
225#undef CFQ_CFQQ_FNS
226
7b679138
JA
227#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
228 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
229#define cfq_log(cfqd, fmt, args...) \
230 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
231
165125e1 232static void cfq_dispatch_insert(struct request_queue *, struct request *);
91fac317 233static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
fd0928df 234 struct io_context *, gfp_t);
4ac845a2 235static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
91fac317
VT
236 struct io_context *);
237
5ad531db
JA
238static inline int rq_in_driver(struct cfq_data *cfqd)
239{
240 return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
241}
242
91fac317
VT
243static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
244 int is_sync)
245{
246 return cic->cfqq[!!is_sync];
247}
248
249static inline void cic_set_cfqq(struct cfq_io_context *cic,
250 struct cfq_queue *cfqq, int is_sync)
251{
252 cic->cfqq[!!is_sync] = cfqq;
253}
254
255/*
256 * We regard a request as SYNC, if it's either a read or has the SYNC bit
257 * set (in which case it could also be direct WRITE).
258 */
259static inline int cfq_bio_sync(struct bio *bio)
260{
1f98a13f 261 if (bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO))
91fac317
VT
262 return 1;
263
264 return 0;
265}
1da177e4 266
99f95e52
AM
267/*
268 * scheduler run of queue, if there are requests pending and no one in the
269 * driver that will restart queueing
270 */
23e018a1 271static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
99f95e52 272{
7b679138
JA
273 if (cfqd->busy_queues) {
274 cfq_log(cfqd, "schedule dispatch");
23e018a1 275 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
7b679138 276 }
99f95e52
AM
277}
278
165125e1 279static int cfq_queue_empty(struct request_queue *q)
99f95e52
AM
280{
281 struct cfq_data *cfqd = q->elevator->elevator_data;
282
b4878f24 283 return !cfqd->busy_queues;
99f95e52
AM
284}
285
44f7c160
JA
286/*
287 * Scale schedule slice based on io priority. Use the sync time slice only
288 * if a queue is marked sync and has sync io queued. A sync queue with async
289 * io only, should not get full sync slice length.
290 */
d9e7620e
JA
291static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
292 unsigned short prio)
44f7c160 293{
d9e7620e 294 const int base_slice = cfqd->cfq_slice[sync];
44f7c160 295
d9e7620e
JA
296 WARN_ON(prio >= IOPRIO_BE_NR);
297
298 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
299}
44f7c160 300
d9e7620e
JA
301static inline int
302cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
303{
304 return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
44f7c160
JA
305}
306
307static inline void
308cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
309{
310 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
7b679138 311 cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
44f7c160
JA
312}
313
314/*
315 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
316 * isn't valid until the first request from the dispatch is activated
317 * and the slice time set.
318 */
319static inline int cfq_slice_used(struct cfq_queue *cfqq)
320{
321 if (cfq_cfqq_slice_new(cfqq))
322 return 0;
323 if (time_before(jiffies, cfqq->slice_end))
324 return 0;
325
326 return 1;
327}
328
1da177e4 329/*
5e705374 330 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
1da177e4 331 * We choose the request that is closest to the head right now. Distance
e8a99053 332 * behind the head is penalized and only allowed to a certain extent.
1da177e4 333 */
5e705374
JA
334static struct request *
335cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
1da177e4
LT
336{
337 sector_t last, s1, s2, d1 = 0, d2 = 0;
1da177e4 338 unsigned long back_max;
e8a99053
AM
339#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
340#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
341 unsigned wrap = 0; /* bit mask: requests behind the disk head? */
1da177e4 342
5e705374
JA
343 if (rq1 == NULL || rq1 == rq2)
344 return rq2;
345 if (rq2 == NULL)
346 return rq1;
9c2c38a1 347
5e705374
JA
348 if (rq_is_sync(rq1) && !rq_is_sync(rq2))
349 return rq1;
350 else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
351 return rq2;
374f84ac
JA
352 if (rq_is_meta(rq1) && !rq_is_meta(rq2))
353 return rq1;
354 else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
355 return rq2;
1da177e4 356
83096ebf
TH
357 s1 = blk_rq_pos(rq1);
358 s2 = blk_rq_pos(rq2);
1da177e4 359
6d048f53 360 last = cfqd->last_position;
1da177e4 361
1da177e4
LT
362 /*
363 * by definition, 1KiB is 2 sectors
364 */
365 back_max = cfqd->cfq_back_max * 2;
366
367 /*
368 * Strict one way elevator _except_ in the case where we allow
369 * short backward seeks which are biased as twice the cost of a
370 * similar forward seek.
371 */
372 if (s1 >= last)
373 d1 = s1 - last;
374 else if (s1 + back_max >= last)
375 d1 = (last - s1) * cfqd->cfq_back_penalty;
376 else
e8a99053 377 wrap |= CFQ_RQ1_WRAP;
1da177e4
LT
378
379 if (s2 >= last)
380 d2 = s2 - last;
381 else if (s2 + back_max >= last)
382 d2 = (last - s2) * cfqd->cfq_back_penalty;
383 else
e8a99053 384 wrap |= CFQ_RQ2_WRAP;
1da177e4
LT
385
386 /* Found required data */
e8a99053
AM
387
388 /*
389 * By doing switch() on the bit mask "wrap" we avoid having to
390 * check two variables for all permutations: --> faster!
391 */
392 switch (wrap) {
5e705374 393 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
e8a99053 394 if (d1 < d2)
5e705374 395 return rq1;
e8a99053 396 else if (d2 < d1)
5e705374 397 return rq2;
e8a99053
AM
398 else {
399 if (s1 >= s2)
5e705374 400 return rq1;
e8a99053 401 else
5e705374 402 return rq2;
e8a99053 403 }
1da177e4 404
e8a99053 405 case CFQ_RQ2_WRAP:
5e705374 406 return rq1;
e8a99053 407 case CFQ_RQ1_WRAP:
5e705374
JA
408 return rq2;
409 case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
e8a99053
AM
410 default:
411 /*
412 * Since both rqs are wrapped,
413 * start with the one that's further behind head
414 * (--> only *one* back seek required),
415 * since back seek takes more time than forward.
416 */
417 if (s1 <= s2)
5e705374 418 return rq1;
1da177e4 419 else
5e705374 420 return rq2;
1da177e4
LT
421 }
422}
423
498d3aa2
JA
424/*
425 * The below is leftmost cache rbtree addon
426 */
0871714e 427static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
cc09e299
JA
428{
429 if (!root->left)
430 root->left = rb_first(&root->rb);
431
0871714e
JA
432 if (root->left)
433 return rb_entry(root->left, struct cfq_queue, rb_node);
434
435 return NULL;
cc09e299
JA
436}
437
a36e71f9
JA
438static void rb_erase_init(struct rb_node *n, struct rb_root *root)
439{
440 rb_erase(n, root);
441 RB_CLEAR_NODE(n);
442}
443
cc09e299
JA
444static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
445{
446 if (root->left == n)
447 root->left = NULL;
a36e71f9 448 rb_erase_init(n, &root->rb);
cc09e299
JA
449}
450
1da177e4
LT
451/*
452 * would be nice to take fifo expire time into account as well
453 */
5e705374
JA
454static struct request *
455cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
456 struct request *last)
1da177e4 457{
21183b07
JA
458 struct rb_node *rbnext = rb_next(&last->rb_node);
459 struct rb_node *rbprev = rb_prev(&last->rb_node);
5e705374 460 struct request *next = NULL, *prev = NULL;
1da177e4 461
21183b07 462 BUG_ON(RB_EMPTY_NODE(&last->rb_node));
1da177e4
LT
463
464 if (rbprev)
5e705374 465 prev = rb_entry_rq(rbprev);
1da177e4 466
21183b07 467 if (rbnext)
5e705374 468 next = rb_entry_rq(rbnext);
21183b07
JA
469 else {
470 rbnext = rb_first(&cfqq->sort_list);
471 if (rbnext && rbnext != &last->rb_node)
5e705374 472 next = rb_entry_rq(rbnext);
21183b07 473 }
1da177e4 474
21183b07 475 return cfq_choose_req(cfqd, next, prev);
1da177e4
LT
476}
477
d9e7620e
JA
478static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
479 struct cfq_queue *cfqq)
1da177e4 480{
d9e7620e
JA
481 /*
482 * just an approximation, should be ok.
483 */
67e6b49e
JA
484 return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
485 cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
d9e7620e
JA
486}
487
498d3aa2
JA
488/*
489 * The cfqd->service_tree holds all pending cfq_queue's that have
490 * requests waiting to be processed. It is sorted in the order that
491 * we will service the queues.
492 */
a36e71f9
JA
493static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
494 int add_front)
d9e7620e 495{
0871714e
JA
496 struct rb_node **p, *parent;
497 struct cfq_queue *__cfqq;
d9e7620e 498 unsigned long rb_key;
498d3aa2 499 int left;
d9e7620e 500
0871714e
JA
501 if (cfq_class_idle(cfqq)) {
502 rb_key = CFQ_IDLE_DELAY;
503 parent = rb_last(&cfqd->service_tree.rb);
504 if (parent && parent != &cfqq->rb_node) {
505 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
506 rb_key += __cfqq->rb_key;
507 } else
508 rb_key += jiffies;
509 } else if (!add_front) {
edd75ffd
JA
510 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
511 rb_key += cfqq->slice_resid;
512 cfqq->slice_resid = 0;
48e025e6
CZ
513 } else {
514 rb_key = -HZ;
515 __cfqq = cfq_rb_first(&cfqd->service_tree);
516 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
517 }
1da177e4 518
d9e7620e 519 if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
99f9628a 520 /*
d9e7620e 521 * same position, nothing more to do
99f9628a 522 */
d9e7620e
JA
523 if (rb_key == cfqq->rb_key)
524 return;
1da177e4 525
cc09e299 526 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
1da177e4 527 }
d9e7620e 528
498d3aa2 529 left = 1;
0871714e
JA
530 parent = NULL;
531 p = &cfqd->service_tree.rb.rb_node;
d9e7620e 532 while (*p) {
67060e37 533 struct rb_node **n;
cc09e299 534
d9e7620e
JA
535 parent = *p;
536 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
537
0c534e0a
JA
538 /*
539 * sort RT queues first, we always want to give
67060e37
JA
540 * preference to them. IDLE queues goes to the back.
541 * after that, sort on the next service time.
0c534e0a
JA
542 */
543 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
67060e37 544 n = &(*p)->rb_left;
0c534e0a 545 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
67060e37
JA
546 n = &(*p)->rb_right;
547 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
548 n = &(*p)->rb_left;
549 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
550 n = &(*p)->rb_right;
48e025e6 551 else if (time_before(rb_key, __cfqq->rb_key))
67060e37
JA
552 n = &(*p)->rb_left;
553 else
554 n = &(*p)->rb_right;
555
556 if (n == &(*p)->rb_right)
cc09e299 557 left = 0;
67060e37
JA
558
559 p = n;
d9e7620e
JA
560 }
561
cc09e299
JA
562 if (left)
563 cfqd->service_tree.left = &cfqq->rb_node;
564
d9e7620e
JA
565 cfqq->rb_key = rb_key;
566 rb_link_node(&cfqq->rb_node, parent, p);
cc09e299 567 rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
1da177e4
LT
568}
569
a36e71f9 570static struct cfq_queue *
f2d1f0ae
JA
571cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
572 sector_t sector, struct rb_node **ret_parent,
573 struct rb_node ***rb_link)
a36e71f9 574{
a36e71f9
JA
575 struct rb_node **p, *parent;
576 struct cfq_queue *cfqq = NULL;
577
578 parent = NULL;
579 p = &root->rb_node;
580 while (*p) {
581 struct rb_node **n;
582
583 parent = *p;
584 cfqq = rb_entry(parent, struct cfq_queue, p_node);
585
586 /*
587 * Sort strictly based on sector. Smallest to the left,
588 * largest to the right.
589 */
2e46e8b2 590 if (sector > blk_rq_pos(cfqq->next_rq))
a36e71f9 591 n = &(*p)->rb_right;
2e46e8b2 592 else if (sector < blk_rq_pos(cfqq->next_rq))
a36e71f9
JA
593 n = &(*p)->rb_left;
594 else
595 break;
596 p = n;
3ac6c9f8 597 cfqq = NULL;
a36e71f9
JA
598 }
599
600 *ret_parent = parent;
601 if (rb_link)
602 *rb_link = p;
3ac6c9f8 603 return cfqq;
a36e71f9
JA
604}
605
606static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
607{
a36e71f9
JA
608 struct rb_node **p, *parent;
609 struct cfq_queue *__cfqq;
610
f2d1f0ae
JA
611 if (cfqq->p_root) {
612 rb_erase(&cfqq->p_node, cfqq->p_root);
613 cfqq->p_root = NULL;
614 }
a36e71f9
JA
615
616 if (cfq_class_idle(cfqq))
617 return;
618 if (!cfqq->next_rq)
619 return;
620
f2d1f0ae 621 cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
2e46e8b2
TH
622 __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
623 blk_rq_pos(cfqq->next_rq), &parent, &p);
3ac6c9f8
JA
624 if (!__cfqq) {
625 rb_link_node(&cfqq->p_node, parent, p);
f2d1f0ae
JA
626 rb_insert_color(&cfqq->p_node, cfqq->p_root);
627 } else
628 cfqq->p_root = NULL;
a36e71f9
JA
629}
630
498d3aa2
JA
631/*
632 * Update cfqq's position in the service tree.
633 */
edd75ffd 634static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
6d048f53 635{
6d048f53
JA
636 /*
637 * Resorting requires the cfqq to be on the RR list already.
638 */
a36e71f9 639 if (cfq_cfqq_on_rr(cfqq)) {
edd75ffd 640 cfq_service_tree_add(cfqd, cfqq, 0);
a36e71f9
JA
641 cfq_prio_tree_add(cfqd, cfqq);
642 }
6d048f53
JA
643}
644
1da177e4
LT
645/*
646 * add to busy list of queues for service, trying to be fair in ordering
22e2c507 647 * the pending list according to last request service
1da177e4 648 */
febffd61 649static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1da177e4 650{
7b679138 651 cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
3b18152c
JA
652 BUG_ON(cfq_cfqq_on_rr(cfqq));
653 cfq_mark_cfqq_on_rr(cfqq);
1da177e4
LT
654 cfqd->busy_queues++;
655
edd75ffd 656 cfq_resort_rr_list(cfqd, cfqq);
1da177e4
LT
657}
658
498d3aa2
JA
659/*
660 * Called when the cfqq no longer has requests pending, remove it from
661 * the service tree.
662 */
febffd61 663static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1da177e4 664{
7b679138 665 cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
3b18152c
JA
666 BUG_ON(!cfq_cfqq_on_rr(cfqq));
667 cfq_clear_cfqq_on_rr(cfqq);
1da177e4 668
cc09e299
JA
669 if (!RB_EMPTY_NODE(&cfqq->rb_node))
670 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
f2d1f0ae
JA
671 if (cfqq->p_root) {
672 rb_erase(&cfqq->p_node, cfqq->p_root);
673 cfqq->p_root = NULL;
674 }
d9e7620e 675
1da177e4
LT
676 BUG_ON(!cfqd->busy_queues);
677 cfqd->busy_queues--;
678}
679
680/*
681 * rb tree support functions
682 */
febffd61 683static void cfq_del_rq_rb(struct request *rq)
1da177e4 684{
5e705374 685 struct cfq_queue *cfqq = RQ_CFQQ(rq);
b4878f24 686 struct cfq_data *cfqd = cfqq->cfqd;
5e705374 687 const int sync = rq_is_sync(rq);
1da177e4 688
b4878f24
JA
689 BUG_ON(!cfqq->queued[sync]);
690 cfqq->queued[sync]--;
1da177e4 691
5e705374 692 elv_rb_del(&cfqq->sort_list, rq);
1da177e4 693
dd67d051 694 if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
b4878f24 695 cfq_del_cfqq_rr(cfqd, cfqq);
1da177e4
LT
696}
697
5e705374 698static void cfq_add_rq_rb(struct request *rq)
1da177e4 699{
5e705374 700 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1da177e4 701 struct cfq_data *cfqd = cfqq->cfqd;
a36e71f9 702 struct request *__alias, *prev;
1da177e4 703
5380a101 704 cfqq->queued[rq_is_sync(rq)]++;
1da177e4
LT
705
706 /*
707 * looks a little odd, but the first insert might return an alias.
708 * if that happens, put the alias on the dispatch list
709 */
21183b07 710 while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
5e705374 711 cfq_dispatch_insert(cfqd->queue, __alias);
5fccbf61
JA
712
713 if (!cfq_cfqq_on_rr(cfqq))
714 cfq_add_cfqq_rr(cfqd, cfqq);
5044eed4
JA
715
716 /*
717 * check if this request is a better next-serve candidate
718 */
a36e71f9 719 prev = cfqq->next_rq;
5044eed4 720 cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
a36e71f9
JA
721
722 /*
723 * adjust priority tree position, if ->next_rq changes
724 */
725 if (prev != cfqq->next_rq)
726 cfq_prio_tree_add(cfqd, cfqq);
727
5044eed4 728 BUG_ON(!cfqq->next_rq);
1da177e4
LT
729}
730
febffd61 731static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1da177e4 732{
5380a101
JA
733 elv_rb_del(&cfqq->sort_list, rq);
734 cfqq->queued[rq_is_sync(rq)]--;
5e705374 735 cfq_add_rq_rb(rq);
1da177e4
LT
736}
737
206dc69b
JA
738static struct request *
739cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1da177e4 740{
206dc69b 741 struct task_struct *tsk = current;
91fac317 742 struct cfq_io_context *cic;
206dc69b 743 struct cfq_queue *cfqq;
1da177e4 744
4ac845a2 745 cic = cfq_cic_lookup(cfqd, tsk->io_context);
91fac317
VT
746 if (!cic)
747 return NULL;
748
749 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
89850f7e
JA
750 if (cfqq) {
751 sector_t sector = bio->bi_sector + bio_sectors(bio);
752
21183b07 753 return elv_rb_find(&cfqq->sort_list, sector);
89850f7e 754 }
1da177e4 755
1da177e4
LT
756 return NULL;
757}
758
165125e1 759static void cfq_activate_request(struct request_queue *q, struct request *rq)
1da177e4 760{
22e2c507 761 struct cfq_data *cfqd = q->elevator->elevator_data;
3b18152c 762
5ad531db 763 cfqd->rq_in_driver[rq_is_sync(rq)]++;
7b679138 764 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
5ad531db 765 rq_in_driver(cfqd));
25776e35 766
5b93629b 767 cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1da177e4
LT
768}
769
165125e1 770static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1da177e4 771{
b4878f24 772 struct cfq_data *cfqd = q->elevator->elevator_data;
5ad531db 773 const int sync = rq_is_sync(rq);
b4878f24 774
5ad531db
JA
775 WARN_ON(!cfqd->rq_in_driver[sync]);
776 cfqd->rq_in_driver[sync]--;
7b679138 777 cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
5ad531db 778 rq_in_driver(cfqd));
1da177e4
LT
779}
780
b4878f24 781static void cfq_remove_request(struct request *rq)
1da177e4 782{
5e705374 783 struct cfq_queue *cfqq = RQ_CFQQ(rq);
21183b07 784
5e705374
JA
785 if (cfqq->next_rq == rq)
786 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1da177e4 787
b4878f24 788 list_del_init(&rq->queuelist);
5e705374 789 cfq_del_rq_rb(rq);
374f84ac 790
45333d5a 791 cfqq->cfqd->rq_queued--;
374f84ac
JA
792 if (rq_is_meta(rq)) {
793 WARN_ON(!cfqq->meta_pending);
794 cfqq->meta_pending--;
795 }
1da177e4
LT
796}
797
165125e1
JA
798static int cfq_merge(struct request_queue *q, struct request **req,
799 struct bio *bio)
1da177e4
LT
800{
801 struct cfq_data *cfqd = q->elevator->elevator_data;
802 struct request *__rq;
1da177e4 803
206dc69b 804 __rq = cfq_find_rq_fmerge(cfqd, bio);
22e2c507 805 if (__rq && elv_rq_merge_ok(__rq, bio)) {
9817064b
JA
806 *req = __rq;
807 return ELEVATOR_FRONT_MERGE;
1da177e4
LT
808 }
809
810 return ELEVATOR_NO_MERGE;
1da177e4
LT
811}
812
165125e1 813static void cfq_merged_request(struct request_queue *q, struct request *req,
21183b07 814 int type)
1da177e4 815{
21183b07 816 if (type == ELEVATOR_FRONT_MERGE) {
5e705374 817 struct cfq_queue *cfqq = RQ_CFQQ(req);
1da177e4 818
5e705374 819 cfq_reposition_rq_rb(cfqq, req);
1da177e4 820 }
1da177e4
LT
821}
822
823static void
165125e1 824cfq_merged_requests(struct request_queue *q, struct request *rq,
1da177e4
LT
825 struct request *next)
826{
22e2c507
JA
827 /*
828 * reposition in fifo if next is older than rq
829 */
830 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
30996f40 831 time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
22e2c507 832 list_move(&rq->queuelist, &next->queuelist);
30996f40
JA
833 rq_set_fifo_time(rq, rq_fifo_time(next));
834 }
22e2c507 835
b4878f24 836 cfq_remove_request(next);
22e2c507
JA
837}
838
165125e1 839static int cfq_allow_merge(struct request_queue *q, struct request *rq,
da775265
JA
840 struct bio *bio)
841{
842 struct cfq_data *cfqd = q->elevator->elevator_data;
91fac317 843 struct cfq_io_context *cic;
da775265 844 struct cfq_queue *cfqq;
da775265
JA
845
846 /*
ec8acb69 847 * Disallow merge of a sync bio into an async request.
da775265 848 */
91fac317 849 if (cfq_bio_sync(bio) && !rq_is_sync(rq))
da775265
JA
850 return 0;
851
852 /*
719d3402
JA
853 * Lookup the cfqq that this bio will be queued with. Allow
854 * merge only if rq is queued there.
da775265 855 */
4ac845a2 856 cic = cfq_cic_lookup(cfqd, current->io_context);
91fac317
VT
857 if (!cic)
858 return 0;
719d3402 859
91fac317 860 cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
719d3402
JA
861 if (cfqq == RQ_CFQQ(rq))
862 return 1;
da775265 863
ec8acb69 864 return 0;
da775265
JA
865}
866
febffd61
JA
867static void __cfq_set_active_queue(struct cfq_data *cfqd,
868 struct cfq_queue *cfqq)
22e2c507
JA
869{
870 if (cfqq) {
7b679138 871 cfq_log_cfqq(cfqd, cfqq, "set_active");
22e2c507 872 cfqq->slice_end = 0;
2f5cb738
JA
873 cfqq->slice_dispatch = 0;
874
2f5cb738 875 cfq_clear_cfqq_wait_request(cfqq);
b029195d 876 cfq_clear_cfqq_must_dispatch(cfqq);
3b18152c
JA
877 cfq_clear_cfqq_must_alloc_slice(cfqq);
878 cfq_clear_cfqq_fifo_expire(cfqq);
44f7c160 879 cfq_mark_cfqq_slice_new(cfqq);
2f5cb738
JA
880
881 del_timer(&cfqd->idle_slice_timer);
22e2c507
JA
882 }
883
884 cfqd->active_queue = cfqq;
885}
886
7b14e3b5
JA
887/*
888 * current cfqq expired its slice (or was too idle), select new one
889 */
890static void
891__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
6084cdda 892 int timed_out)
7b14e3b5 893{
7b679138
JA
894 cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
895
7b14e3b5
JA
896 if (cfq_cfqq_wait_request(cfqq))
897 del_timer(&cfqd->idle_slice_timer);
898
7b14e3b5
JA
899 cfq_clear_cfqq_wait_request(cfqq);
900
901 /*
6084cdda 902 * store what was left of this slice, if the queue idled/timed out
7b14e3b5 903 */
7b679138 904 if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
c5b680f3 905 cfqq->slice_resid = cfqq->slice_end - jiffies;
7b679138
JA
906 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
907 }
7b14e3b5 908
edd75ffd 909 cfq_resort_rr_list(cfqd, cfqq);
7b14e3b5
JA
910
911 if (cfqq == cfqd->active_queue)
912 cfqd->active_queue = NULL;
913
914 if (cfqd->active_cic) {
915 put_io_context(cfqd->active_cic->ioc);
916 cfqd->active_cic = NULL;
917 }
7b14e3b5
JA
918}
919
6084cdda 920static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
7b14e3b5
JA
921{
922 struct cfq_queue *cfqq = cfqd->active_queue;
923
924 if (cfqq)
6084cdda 925 __cfq_slice_expired(cfqd, cfqq, timed_out);
7b14e3b5
JA
926}
927
498d3aa2
JA
928/*
929 * Get next queue for service. Unless we have a queue preemption,
930 * we'll simply select the first cfqq in the service tree.
931 */
6d048f53 932static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
22e2c507 933{
edd75ffd
JA
934 if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
935 return NULL;
d9e7620e 936
0871714e 937 return cfq_rb_first(&cfqd->service_tree);
6d048f53
JA
938}
939
498d3aa2
JA
940/*
941 * Get and set a new active queue for service.
942 */
a36e71f9
JA
943static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
944 struct cfq_queue *cfqq)
6d048f53 945{
a36e71f9
JA
946 if (!cfqq) {
947 cfqq = cfq_get_next_queue(cfqd);
948 if (cfqq)
949 cfq_clear_cfqq_coop(cfqq);
950 }
6d048f53 951
22e2c507 952 __cfq_set_active_queue(cfqd, cfqq);
3b18152c 953 return cfqq;
22e2c507
JA
954}
955
d9e7620e
JA
956static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
957 struct request *rq)
958{
83096ebf
TH
959 if (blk_rq_pos(rq) >= cfqd->last_position)
960 return blk_rq_pos(rq) - cfqd->last_position;
d9e7620e 961 else
83096ebf 962 return cfqd->last_position - blk_rq_pos(rq);
d9e7620e
JA
963}
964
04dc6e71
JM
965#define CIC_SEEK_THR 8 * 1024
966#define CIC_SEEKY(cic) ((cic)->seek_mean > CIC_SEEK_THR)
967
6d048f53
JA
968static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
969{
970 struct cfq_io_context *cic = cfqd->active_cic;
04dc6e71 971 sector_t sdist = cic->seek_mean;
6d048f53
JA
972
973 if (!sample_valid(cic->seek_samples))
04dc6e71 974 sdist = CIC_SEEK_THR;
6d048f53 975
04dc6e71 976 return cfq_dist_from_last(cfqd, rq) <= sdist;
6d048f53
JA
977}
978
a36e71f9
JA
979static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
980 struct cfq_queue *cur_cfqq)
981{
f2d1f0ae 982 struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
a36e71f9
JA
983 struct rb_node *parent, *node;
984 struct cfq_queue *__cfqq;
985 sector_t sector = cfqd->last_position;
986
987 if (RB_EMPTY_ROOT(root))
988 return NULL;
989
990 /*
991 * First, if we find a request starting at the end of the last
992 * request, choose it.
993 */
f2d1f0ae 994 __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
a36e71f9
JA
995 if (__cfqq)
996 return __cfqq;
997
998 /*
999 * If the exact sector wasn't found, the parent of the NULL leaf
1000 * will contain the closest sector.
1001 */
1002 __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1003 if (cfq_rq_close(cfqd, __cfqq->next_rq))
1004 return __cfqq;
1005
2e46e8b2 1006 if (blk_rq_pos(__cfqq->next_rq) < sector)
a36e71f9
JA
1007 node = rb_next(&__cfqq->p_node);
1008 else
1009 node = rb_prev(&__cfqq->p_node);
1010 if (!node)
1011 return NULL;
1012
1013 __cfqq = rb_entry(node, struct cfq_queue, p_node);
1014 if (cfq_rq_close(cfqd, __cfqq->next_rq))
1015 return __cfqq;
1016
1017 return NULL;
1018}
1019
1020/*
1021 * cfqd - obvious
1022 * cur_cfqq - passed in so that we don't decide that the current queue is
1023 * closely cooperating with itself.
1024 *
1025 * So, basically we're assuming that that cur_cfqq has dispatched at least
1026 * one request, and that cfqd->last_position reflects a position on the disk
1027 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1028 * assumption.
1029 */
1030static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1031 struct cfq_queue *cur_cfqq,
1032 int probe)
6d048f53 1033{
a36e71f9
JA
1034 struct cfq_queue *cfqq;
1035
1036 /*
1037 * A valid cfq_io_context is necessary to compare requests against
1038 * the seek_mean of the current cfqq.
1039 */
1040 if (!cfqd->active_cic)
1041 return NULL;
1042
6d048f53 1043 /*
d9e7620e
JA
1044 * We should notice if some of the queues are cooperating, eg
1045 * working closely on the same area of the disk. In that case,
1046 * we can group them together and don't waste time idling.
6d048f53 1047 */
a36e71f9
JA
1048 cfqq = cfqq_close(cfqd, cur_cfqq);
1049 if (!cfqq)
1050 return NULL;
1051
1052 if (cfq_cfqq_coop(cfqq))
1053 return NULL;
1054
1055 if (!probe)
1056 cfq_mark_cfqq_coop(cfqq);
1057 return cfqq;
6d048f53
JA
1058}
1059
6d048f53 1060static void cfq_arm_slice_timer(struct cfq_data *cfqd)
22e2c507 1061{
1792669c 1062 struct cfq_queue *cfqq = cfqd->active_queue;
206dc69b 1063 struct cfq_io_context *cic;
7b14e3b5
JA
1064 unsigned long sl;
1065
a68bbddb 1066 /*
f7d7b7a7
JA
1067 * SSD device without seek penalty, disable idling. But only do so
1068 * for devices that support queuing, otherwise we still have a problem
1069 * with sync vs async workloads.
a68bbddb 1070 */
f7d7b7a7 1071 if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
a68bbddb
JA
1072 return;
1073
dd67d051 1074 WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
6d048f53 1075 WARN_ON(cfq_cfqq_slice_new(cfqq));
22e2c507
JA
1076
1077 /*
1078 * idle is disabled, either manually or by past process history
1079 */
6d048f53
JA
1080 if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
1081 return;
1082
7b679138
JA
1083 /*
1084 * still requests with the driver, don't idle
1085 */
5ad531db 1086 if (rq_in_driver(cfqd))
7b679138
JA
1087 return;
1088
22e2c507
JA
1089 /*
1090 * task has exited, don't wait
1091 */
206dc69b 1092 cic = cfqd->active_cic;
66dac98e 1093 if (!cic || !atomic_read(&cic->ioc->nr_tasks))
6d048f53
JA
1094 return;
1095
3b18152c 1096 cfq_mark_cfqq_wait_request(cfqq);
22e2c507 1097
206dc69b
JA
1098 /*
1099 * we don't want to idle for seeks, but we do want to allow
1100 * fair distribution of slice time for a process doing back-to-back
1101 * seeks. so allow a little bit of time for him to submit a new rq
1102 */
6d048f53 1103 sl = cfqd->cfq_slice_idle;
caaa5f9f 1104 if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
d9e7620e 1105 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
206dc69b 1106
7b14e3b5 1107 mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
9481ffdc 1108 cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1da177e4
LT
1109}
1110
498d3aa2
JA
1111/*
1112 * Move request from internal lists to the request queue dispatch list.
1113 */
165125e1 1114static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1da177e4 1115{
3ed9a296 1116 struct cfq_data *cfqd = q->elevator->elevator_data;
5e705374 1117 struct cfq_queue *cfqq = RQ_CFQQ(rq);
22e2c507 1118
7b679138
JA
1119 cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1120
06d21886 1121 cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
5380a101 1122 cfq_remove_request(rq);
6d048f53 1123 cfqq->dispatched++;
5380a101 1124 elv_dispatch_sort(q, rq);
3ed9a296
JA
1125
1126 if (cfq_cfqq_sync(cfqq))
1127 cfqd->sync_flight++;
1da177e4
LT
1128}
1129
1130/*
1131 * return expired entry, or NULL to just start from scratch in rbtree
1132 */
febffd61 1133static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1da177e4 1134{
30996f40 1135 struct request *rq = NULL;
1da177e4 1136
3b18152c 1137 if (cfq_cfqq_fifo_expire(cfqq))
1da177e4 1138 return NULL;
cb887411
JA
1139
1140 cfq_mark_cfqq_fifo_expire(cfqq);
1141
89850f7e
JA
1142 if (list_empty(&cfqq->fifo))
1143 return NULL;
1da177e4 1144
89850f7e 1145 rq = rq_entry_fifo(cfqq->fifo.next);
30996f40 1146 if (time_before(jiffies, rq_fifo_time(rq)))
7b679138 1147 rq = NULL;
1da177e4 1148
30996f40 1149 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
6d048f53 1150 return rq;
1da177e4
LT
1151}
1152
22e2c507
JA
1153static inline int
1154cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1155{
1156 const int base_rq = cfqd->cfq_slice_async_rq;
1da177e4 1157
22e2c507 1158 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1da177e4 1159
22e2c507 1160 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1da177e4
LT
1161}
1162
22e2c507 1163/*
498d3aa2
JA
1164 * Select a queue for service. If we have a current active queue,
1165 * check whether to continue servicing it, or retrieve and set a new one.
22e2c507 1166 */
1b5ed5e1 1167static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1da177e4 1168{
a36e71f9 1169 struct cfq_queue *cfqq, *new_cfqq = NULL;
1da177e4 1170
22e2c507
JA
1171 cfqq = cfqd->active_queue;
1172 if (!cfqq)
1173 goto new_queue;
1da177e4 1174
22e2c507 1175 /*
6d048f53 1176 * The active queue has run out of time, expire it and select new.
22e2c507 1177 */
b029195d 1178 if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
3b18152c 1179 goto expire;
1da177e4 1180
22e2c507 1181 /*
6d048f53
JA
1182 * The active queue has requests and isn't expired, allow it to
1183 * dispatch.
22e2c507 1184 */
dd67d051 1185 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
22e2c507 1186 goto keep_queue;
6d048f53 1187
a36e71f9
JA
1188 /*
1189 * If another queue has a request waiting within our mean seek
1190 * distance, let it run. The expire code will check for close
1191 * cooperators and put the close queue at the front of the service
1192 * tree.
1193 */
1194 new_cfqq = cfq_close_cooperator(cfqd, cfqq, 0);
1195 if (new_cfqq)
1196 goto expire;
1197
6d048f53
JA
1198 /*
1199 * No requests pending. If the active queue still has requests in
1200 * flight or is idling for a new request, allow either of these
1201 * conditions to happen (or time out) before selecting a new queue.
1202 */
cc197479
JA
1203 if (timer_pending(&cfqd->idle_slice_timer) ||
1204 (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
caaa5f9f
JA
1205 cfqq = NULL;
1206 goto keep_queue;
22e2c507
JA
1207 }
1208
3b18152c 1209expire:
6084cdda 1210 cfq_slice_expired(cfqd, 0);
3b18152c 1211new_queue:
a36e71f9 1212 cfqq = cfq_set_active_queue(cfqd, new_cfqq);
22e2c507 1213keep_queue:
3b18152c 1214 return cfqq;
22e2c507
JA
1215}
1216
febffd61 1217static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
d9e7620e
JA
1218{
1219 int dispatched = 0;
1220
1221 while (cfqq->next_rq) {
1222 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1223 dispatched++;
1224 }
1225
1226 BUG_ON(!list_empty(&cfqq->fifo));
1227 return dispatched;
1228}
1229
498d3aa2
JA
1230/*
1231 * Drain our current requests. Used for barriers and when switching
1232 * io schedulers on-the-fly.
1233 */
d9e7620e 1234static int cfq_forced_dispatch(struct cfq_data *cfqd)
1b5ed5e1 1235{
0871714e 1236 struct cfq_queue *cfqq;
d9e7620e 1237 int dispatched = 0;
1b5ed5e1 1238
0871714e 1239 while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
d9e7620e 1240 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1b5ed5e1 1241
6084cdda 1242 cfq_slice_expired(cfqd, 0);
1b5ed5e1
TH
1243
1244 BUG_ON(cfqd->busy_queues);
1245
6923715a 1246 cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1b5ed5e1
TH
1247 return dispatched;
1248}
1249
2f5cb738
JA
1250/*
1251 * Dispatch a request from cfqq, moving them to the request queue
1252 * dispatch list.
1253 */
1254static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1255{
1256 struct request *rq;
1257
1258 BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1259
1260 /*
1261 * follow expired path, else get first next available
1262 */
1263 rq = cfq_check_fifo(cfqq);
1264 if (!rq)
1265 rq = cfqq->next_rq;
1266
1267 /*
1268 * insert request into driver dispatch list
1269 */
1270 cfq_dispatch_insert(cfqd->queue, rq);
1271
1272 if (!cfqd->active_cic) {
1273 struct cfq_io_context *cic = RQ_CIC(rq);
1274
d9c7d394 1275 atomic_long_inc(&cic->ioc->refcount);
2f5cb738
JA
1276 cfqd->active_cic = cic;
1277 }
1278}
1279
1280/*
1281 * Find the cfqq that we need to service and move a request from that to the
1282 * dispatch list
1283 */
165125e1 1284static int cfq_dispatch_requests(struct request_queue *q, int force)
22e2c507
JA
1285{
1286 struct cfq_data *cfqd = q->elevator->elevator_data;
6d048f53 1287 struct cfq_queue *cfqq;
2f5cb738 1288 unsigned int max_dispatch;
22e2c507
JA
1289
1290 if (!cfqd->busy_queues)
1291 return 0;
1292
1b5ed5e1
TH
1293 if (unlikely(force))
1294 return cfq_forced_dispatch(cfqd);
1295
2f5cb738
JA
1296 cfqq = cfq_select_queue(cfqd);
1297 if (!cfqq)
1298 return 0;
1299
5ad531db
JA
1300 /*
1301 * Drain async requests before we start sync IO
1302 */
1303 if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
1304 return 0;
1305
2f5cb738
JA
1306 /*
1307 * If this is an async queue and we have sync IO in flight, let it wait
1308 */
1309 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1310 return 0;
1311
1312 max_dispatch = cfqd->cfq_quantum;
1313 if (cfq_class_idle(cfqq))
1314 max_dispatch = 1;
b4878f24 1315
2f5cb738
JA
1316 /*
1317 * Does this cfqq already have too much IO in flight?
1318 */
1319 if (cfqq->dispatched >= max_dispatch) {
1320 /*
1321 * idle queue must always only have a single IO in flight
1322 */
3ed9a296 1323 if (cfq_class_idle(cfqq))
2f5cb738 1324 return 0;
3ed9a296 1325
2f5cb738
JA
1326 /*
1327 * We have other queues, don't allow more IO from this one
1328 */
1329 if (cfqd->busy_queues > 1)
1330 return 0;
9ede209e 1331
365722bb 1332 /*
8e296755 1333 * Sole queue user, allow bigger slice
365722bb 1334 */
8e296755
JA
1335 max_dispatch *= 4;
1336 }
1337
1338 /*
1339 * Async queues must wait a bit before being allowed dispatch.
1340 * We also ramp up the dispatch depth gradually for async IO,
1341 * based on the last sync IO we serviced
1342 */
963b72fc 1343 if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
8e296755
JA
1344 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
1345 unsigned int depth;
365722bb 1346
61f0c1dc 1347 depth = last_sync / cfqd->cfq_slice[1];
e00c54c3
JA
1348 if (!depth && !cfqq->dispatched)
1349 depth = 1;
8e296755
JA
1350 if (depth < max_dispatch)
1351 max_dispatch = depth;
2f5cb738 1352 }
3ed9a296 1353
8e296755
JA
1354 if (cfqq->dispatched >= max_dispatch)
1355 return 0;
1356
2f5cb738
JA
1357 /*
1358 * Dispatch a request from this cfqq
1359 */
1360 cfq_dispatch_request(cfqd, cfqq);
1361 cfqq->slice_dispatch++;
b029195d 1362 cfq_clear_cfqq_must_dispatch(cfqq);
22e2c507 1363
2f5cb738
JA
1364 /*
1365 * expire an async queue immediately if it has used up its slice. idle
1366 * queue always expire after 1 dispatch round.
1367 */
1368 if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1369 cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1370 cfq_class_idle(cfqq))) {
1371 cfqq->slice_end = jiffies + 1;
1372 cfq_slice_expired(cfqd, 0);
1da177e4
LT
1373 }
1374
b217a903 1375 cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2f5cb738 1376 return 1;
1da177e4
LT
1377}
1378
1da177e4 1379/*
5e705374
JA
1380 * task holds one reference to the queue, dropped when task exits. each rq
1381 * in-flight on this queue also holds a reference, dropped when rq is freed.
1da177e4
LT
1382 *
1383 * queue lock must be held here.
1384 */
1385static void cfq_put_queue(struct cfq_queue *cfqq)
1386{
22e2c507
JA
1387 struct cfq_data *cfqd = cfqq->cfqd;
1388
1389 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1da177e4
LT
1390
1391 if (!atomic_dec_and_test(&cfqq->ref))
1392 return;
1393
7b679138 1394 cfq_log_cfqq(cfqd, cfqq, "put_queue");
1da177e4 1395 BUG_ON(rb_first(&cfqq->sort_list));
22e2c507 1396 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
3b18152c 1397 BUG_ON(cfq_cfqq_on_rr(cfqq));
1da177e4 1398
28f95cbc 1399 if (unlikely(cfqd->active_queue == cfqq)) {
6084cdda 1400 __cfq_slice_expired(cfqd, cfqq, 0);
23e018a1 1401 cfq_schedule_dispatch(cfqd);
28f95cbc 1402 }
22e2c507 1403
1da177e4
LT
1404 kmem_cache_free(cfq_pool, cfqq);
1405}
1406
d6de8be7
JA
1407/*
1408 * Must always be called with the rcu_read_lock() held
1409 */
07416d29
JA
1410static void
1411__call_for_each_cic(struct io_context *ioc,
1412 void (*func)(struct io_context *, struct cfq_io_context *))
1413{
1414 struct cfq_io_context *cic;
1415 struct hlist_node *n;
1416
1417 hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1418 func(ioc, cic);
1419}
1420
4ac845a2 1421/*
34e6bbf2 1422 * Call func for each cic attached to this ioc.
4ac845a2 1423 */
34e6bbf2 1424static void
4ac845a2
JA
1425call_for_each_cic(struct io_context *ioc,
1426 void (*func)(struct io_context *, struct cfq_io_context *))
1da177e4 1427{
4ac845a2 1428 rcu_read_lock();
07416d29 1429 __call_for_each_cic(ioc, func);
4ac845a2 1430 rcu_read_unlock();
34e6bbf2
FC
1431}
1432
1433static void cfq_cic_free_rcu(struct rcu_head *head)
1434{
1435 struct cfq_io_context *cic;
1436
1437 cic = container_of(head, struct cfq_io_context, rcu_head);
1438
1439 kmem_cache_free(cfq_ioc_pool, cic);
245b2e70 1440 elv_ioc_count_dec(cfq_ioc_count);
34e6bbf2 1441
9a11b4ed
JA
1442 if (ioc_gone) {
1443 /*
1444 * CFQ scheduler is exiting, grab exit lock and check
1445 * the pending io context count. If it hits zero,
1446 * complete ioc_gone and set it back to NULL
1447 */
1448 spin_lock(&ioc_gone_lock);
245b2e70 1449 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
9a11b4ed
JA
1450 complete(ioc_gone);
1451 ioc_gone = NULL;
1452 }
1453 spin_unlock(&ioc_gone_lock);
1454 }
34e6bbf2 1455}
4ac845a2 1456
34e6bbf2
FC
1457static void cfq_cic_free(struct cfq_io_context *cic)
1458{
1459 call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
4ac845a2
JA
1460}
1461
1462static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1463{
1464 unsigned long flags;
1465
1466 BUG_ON(!cic->dead_key);
1467
1468 spin_lock_irqsave(&ioc->lock, flags);
1469 radix_tree_delete(&ioc->radix_root, cic->dead_key);
ffc4e759 1470 hlist_del_rcu(&cic->cic_list);
4ac845a2
JA
1471 spin_unlock_irqrestore(&ioc->lock, flags);
1472
34e6bbf2 1473 cfq_cic_free(cic);
4ac845a2
JA
1474}
1475
d6de8be7
JA
1476/*
1477 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1478 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1479 * and ->trim() which is called with the task lock held
1480 */
4ac845a2
JA
1481static void cfq_free_io_context(struct io_context *ioc)
1482{
4ac845a2 1483 /*
34e6bbf2
FC
1484 * ioc->refcount is zero here, or we are called from elv_unregister(),
1485 * so no more cic's are allowed to be linked into this ioc. So it
1486 * should be ok to iterate over the known list, we will see all cic's
1487 * since no new ones are added.
4ac845a2 1488 */
07416d29 1489 __call_for_each_cic(ioc, cic_free_func);
1da177e4
LT
1490}
1491
89850f7e 1492static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1da177e4 1493{
28f95cbc 1494 if (unlikely(cfqq == cfqd->active_queue)) {
6084cdda 1495 __cfq_slice_expired(cfqd, cfqq, 0);
23e018a1 1496 cfq_schedule_dispatch(cfqd);
28f95cbc 1497 }
22e2c507 1498
89850f7e
JA
1499 cfq_put_queue(cfqq);
1500}
22e2c507 1501
89850f7e
JA
1502static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1503 struct cfq_io_context *cic)
1504{
4faa3c81
FC
1505 struct io_context *ioc = cic->ioc;
1506
fc46379d 1507 list_del_init(&cic->queue_list);
4ac845a2
JA
1508
1509 /*
1510 * Make sure key == NULL is seen for dead queues
1511 */
fc46379d 1512 smp_wmb();
4ac845a2 1513 cic->dead_key = (unsigned long) cic->key;
fc46379d
JA
1514 cic->key = NULL;
1515
4faa3c81
FC
1516 if (ioc->ioc_data == cic)
1517 rcu_assign_pointer(ioc->ioc_data, NULL);
1518
ff6657c6
JA
1519 if (cic->cfqq[BLK_RW_ASYNC]) {
1520 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1521 cic->cfqq[BLK_RW_ASYNC] = NULL;
12a05732
AV
1522 }
1523
ff6657c6
JA
1524 if (cic->cfqq[BLK_RW_SYNC]) {
1525 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1526 cic->cfqq[BLK_RW_SYNC] = NULL;
12a05732 1527 }
89850f7e
JA
1528}
1529
4ac845a2
JA
1530static void cfq_exit_single_io_context(struct io_context *ioc,
1531 struct cfq_io_context *cic)
89850f7e
JA
1532{
1533 struct cfq_data *cfqd = cic->key;
1534
89850f7e 1535 if (cfqd) {
165125e1 1536 struct request_queue *q = cfqd->queue;
4ac845a2 1537 unsigned long flags;
89850f7e 1538
4ac845a2 1539 spin_lock_irqsave(q->queue_lock, flags);
62c1fe9d
JA
1540
1541 /*
1542 * Ensure we get a fresh copy of the ->key to prevent
1543 * race between exiting task and queue
1544 */
1545 smp_read_barrier_depends();
1546 if (cic->key)
1547 __cfq_exit_single_io_context(cfqd, cic);
1548
4ac845a2 1549 spin_unlock_irqrestore(q->queue_lock, flags);
89850f7e 1550 }
1da177e4
LT
1551}
1552
498d3aa2
JA
1553/*
1554 * The process that ioc belongs to has exited, we need to clean up
1555 * and put the internal structures we have that belongs to that process.
1556 */
e2d74ac0 1557static void cfq_exit_io_context(struct io_context *ioc)
1da177e4 1558{
4ac845a2 1559 call_for_each_cic(ioc, cfq_exit_single_io_context);
1da177e4
LT
1560}
1561
22e2c507 1562static struct cfq_io_context *
8267e268 1563cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1da177e4 1564{
b5deef90 1565 struct cfq_io_context *cic;
1da177e4 1566
94f6030c
CL
1567 cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1568 cfqd->queue->node);
1da177e4 1569 if (cic) {
22e2c507 1570 cic->last_end_request = jiffies;
553698f9 1571 INIT_LIST_HEAD(&cic->queue_list);
ffc4e759 1572 INIT_HLIST_NODE(&cic->cic_list);
22e2c507
JA
1573 cic->dtor = cfq_free_io_context;
1574 cic->exit = cfq_exit_io_context;
245b2e70 1575 elv_ioc_count_inc(cfq_ioc_count);
1da177e4
LT
1576 }
1577
1578 return cic;
1579}
1580
fd0928df 1581static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
22e2c507
JA
1582{
1583 struct task_struct *tsk = current;
1584 int ioprio_class;
1585
3b18152c 1586 if (!cfq_cfqq_prio_changed(cfqq))
22e2c507
JA
1587 return;
1588
fd0928df 1589 ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
22e2c507 1590 switch (ioprio_class) {
fe094d98
JA
1591 default:
1592 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1593 case IOPRIO_CLASS_NONE:
1594 /*
6d63c275 1595 * no prio set, inherit CPU scheduling settings
fe094d98
JA
1596 */
1597 cfqq->ioprio = task_nice_ioprio(tsk);
6d63c275 1598 cfqq->ioprio_class = task_nice_ioclass(tsk);
fe094d98
JA
1599 break;
1600 case IOPRIO_CLASS_RT:
1601 cfqq->ioprio = task_ioprio(ioc);
1602 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1603 break;
1604 case IOPRIO_CLASS_BE:
1605 cfqq->ioprio = task_ioprio(ioc);
1606 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1607 break;
1608 case IOPRIO_CLASS_IDLE:
1609 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1610 cfqq->ioprio = 7;
1611 cfq_clear_cfqq_idle_window(cfqq);
1612 break;
22e2c507
JA
1613 }
1614
1615 /*
1616 * keep track of original prio settings in case we have to temporarily
1617 * elevate the priority of this queue
1618 */
1619 cfqq->org_ioprio = cfqq->ioprio;
1620 cfqq->org_ioprio_class = cfqq->ioprio_class;
3b18152c 1621 cfq_clear_cfqq_prio_changed(cfqq);
22e2c507
JA
1622}
1623
febffd61 1624static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
22e2c507 1625{
478a82b0
AV
1626 struct cfq_data *cfqd = cic->key;
1627 struct cfq_queue *cfqq;
c1b707d2 1628 unsigned long flags;
35e6077c 1629
caaa5f9f
JA
1630 if (unlikely(!cfqd))
1631 return;
1632
c1b707d2 1633 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
caaa5f9f 1634
ff6657c6 1635 cfqq = cic->cfqq[BLK_RW_ASYNC];
caaa5f9f
JA
1636 if (cfqq) {
1637 struct cfq_queue *new_cfqq;
ff6657c6
JA
1638 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
1639 GFP_ATOMIC);
caaa5f9f 1640 if (new_cfqq) {
ff6657c6 1641 cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
caaa5f9f
JA
1642 cfq_put_queue(cfqq);
1643 }
22e2c507 1644 }
caaa5f9f 1645
ff6657c6 1646 cfqq = cic->cfqq[BLK_RW_SYNC];
caaa5f9f
JA
1647 if (cfqq)
1648 cfq_mark_cfqq_prio_changed(cfqq);
1649
c1b707d2 1650 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
22e2c507
JA
1651}
1652
fc46379d 1653static void cfq_ioc_set_ioprio(struct io_context *ioc)
22e2c507 1654{
4ac845a2 1655 call_for_each_cic(ioc, changed_ioprio);
fc46379d 1656 ioc->ioprio_changed = 0;
22e2c507
JA
1657}
1658
d5036d77
JA
1659static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1660 pid_t pid, int is_sync)
1661{
1662 RB_CLEAR_NODE(&cfqq->rb_node);
1663 RB_CLEAR_NODE(&cfqq->p_node);
1664 INIT_LIST_HEAD(&cfqq->fifo);
1665
1666 atomic_set(&cfqq->ref, 0);
1667 cfqq->cfqd = cfqd;
1668
1669 cfq_mark_cfqq_prio_changed(cfqq);
1670
1671 if (is_sync) {
1672 if (!cfq_class_idle(cfqq))
1673 cfq_mark_cfqq_idle_window(cfqq);
1674 cfq_mark_cfqq_sync(cfqq);
1675 }
1676 cfqq->pid = pid;
1677}
1678
22e2c507 1679static struct cfq_queue *
15c31be4 1680cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
fd0928df 1681 struct io_context *ioc, gfp_t gfp_mask)
22e2c507 1682{
22e2c507 1683 struct cfq_queue *cfqq, *new_cfqq = NULL;
91fac317 1684 struct cfq_io_context *cic;
22e2c507
JA
1685
1686retry:
4ac845a2 1687 cic = cfq_cic_lookup(cfqd, ioc);
91fac317
VT
1688 /* cic always exists here */
1689 cfqq = cic_to_cfqq(cic, is_sync);
22e2c507 1690
6118b70b
JA
1691 /*
1692 * Always try a new alloc if we fell back to the OOM cfqq
1693 * originally, since it should just be a temporary situation.
1694 */
1695 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
1696 cfqq = NULL;
22e2c507
JA
1697 if (new_cfqq) {
1698 cfqq = new_cfqq;
1699 new_cfqq = NULL;
1700 } else if (gfp_mask & __GFP_WAIT) {
1701 spin_unlock_irq(cfqd->queue->queue_lock);
94f6030c 1702 new_cfqq = kmem_cache_alloc_node(cfq_pool,
6118b70b 1703 gfp_mask | __GFP_ZERO,
94f6030c 1704 cfqd->queue->node);
22e2c507 1705 spin_lock_irq(cfqd->queue->queue_lock);
6118b70b
JA
1706 if (new_cfqq)
1707 goto retry;
22e2c507 1708 } else {
94f6030c
CL
1709 cfqq = kmem_cache_alloc_node(cfq_pool,
1710 gfp_mask | __GFP_ZERO,
1711 cfqd->queue->node);
22e2c507
JA
1712 }
1713
6118b70b
JA
1714 if (cfqq) {
1715 cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
1716 cfq_init_prio_data(cfqq, ioc);
1717 cfq_log_cfqq(cfqd, cfqq, "alloced");
1718 } else
1719 cfqq = &cfqd->oom_cfqq;
22e2c507
JA
1720 }
1721
1722 if (new_cfqq)
1723 kmem_cache_free(cfq_pool, new_cfqq);
1724
22e2c507
JA
1725 return cfqq;
1726}
1727
c2dea2d1
VT
1728static struct cfq_queue **
1729cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1730{
fe094d98 1731 switch (ioprio_class) {
c2dea2d1
VT
1732 case IOPRIO_CLASS_RT:
1733 return &cfqd->async_cfqq[0][ioprio];
1734 case IOPRIO_CLASS_BE:
1735 return &cfqd->async_cfqq[1][ioprio];
1736 case IOPRIO_CLASS_IDLE:
1737 return &cfqd->async_idle_cfqq;
1738 default:
1739 BUG();
1740 }
1741}
1742
15c31be4 1743static struct cfq_queue *
fd0928df 1744cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
15c31be4
JA
1745 gfp_t gfp_mask)
1746{
fd0928df
JA
1747 const int ioprio = task_ioprio(ioc);
1748 const int ioprio_class = task_ioprio_class(ioc);
c2dea2d1 1749 struct cfq_queue **async_cfqq = NULL;
15c31be4
JA
1750 struct cfq_queue *cfqq = NULL;
1751
c2dea2d1
VT
1752 if (!is_sync) {
1753 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1754 cfqq = *async_cfqq;
1755 }
1756
6118b70b 1757 if (!cfqq)
fd0928df 1758 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
15c31be4
JA
1759
1760 /*
1761 * pin the queue now that it's allocated, scheduler exit will prune it
1762 */
c2dea2d1 1763 if (!is_sync && !(*async_cfqq)) {
15c31be4 1764 atomic_inc(&cfqq->ref);
c2dea2d1 1765 *async_cfqq = cfqq;
15c31be4
JA
1766 }
1767
1768 atomic_inc(&cfqq->ref);
1769 return cfqq;
1770}
1771
498d3aa2
JA
1772/*
1773 * We drop cfq io contexts lazily, so we may find a dead one.
1774 */
dbecf3ab 1775static void
4ac845a2
JA
1776cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
1777 struct cfq_io_context *cic)
dbecf3ab 1778{
4ac845a2
JA
1779 unsigned long flags;
1780
fc46379d 1781 WARN_ON(!list_empty(&cic->queue_list));
597bc485 1782
4ac845a2
JA
1783 spin_lock_irqsave(&ioc->lock, flags);
1784
4faa3c81 1785 BUG_ON(ioc->ioc_data == cic);
597bc485 1786
4ac845a2 1787 radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
ffc4e759 1788 hlist_del_rcu(&cic->cic_list);
4ac845a2
JA
1789 spin_unlock_irqrestore(&ioc->lock, flags);
1790
1791 cfq_cic_free(cic);
dbecf3ab
OH
1792}
1793
e2d74ac0 1794static struct cfq_io_context *
4ac845a2 1795cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
e2d74ac0 1796{
e2d74ac0 1797 struct cfq_io_context *cic;
d6de8be7 1798 unsigned long flags;
4ac845a2 1799 void *k;
e2d74ac0 1800
91fac317
VT
1801 if (unlikely(!ioc))
1802 return NULL;
1803
d6de8be7
JA
1804 rcu_read_lock();
1805
597bc485
JA
1806 /*
1807 * we maintain a last-hit cache, to avoid browsing over the tree
1808 */
4ac845a2 1809 cic = rcu_dereference(ioc->ioc_data);
d6de8be7
JA
1810 if (cic && cic->key == cfqd) {
1811 rcu_read_unlock();
597bc485 1812 return cic;
d6de8be7 1813 }
597bc485 1814
4ac845a2 1815 do {
4ac845a2
JA
1816 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
1817 rcu_read_unlock();
1818 if (!cic)
1819 break;
be3b0753
OH
1820 /* ->key must be copied to avoid race with cfq_exit_queue() */
1821 k = cic->key;
1822 if (unlikely(!k)) {
4ac845a2 1823 cfq_drop_dead_cic(cfqd, ioc, cic);
d6de8be7 1824 rcu_read_lock();
4ac845a2 1825 continue;
dbecf3ab 1826 }
e2d74ac0 1827
d6de8be7 1828 spin_lock_irqsave(&ioc->lock, flags);
4ac845a2 1829 rcu_assign_pointer(ioc->ioc_data, cic);
d6de8be7 1830 spin_unlock_irqrestore(&ioc->lock, flags);
4ac845a2
JA
1831 break;
1832 } while (1);
e2d74ac0 1833
4ac845a2 1834 return cic;
e2d74ac0
JA
1835}
1836
4ac845a2
JA
1837/*
1838 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
1839 * the process specific cfq io context when entered from the block layer.
1840 * Also adds the cic to a per-cfqd list, used when this queue is removed.
1841 */
febffd61
JA
1842static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1843 struct cfq_io_context *cic, gfp_t gfp_mask)
e2d74ac0 1844{
0261d688 1845 unsigned long flags;
4ac845a2 1846 int ret;
e2d74ac0 1847
4ac845a2
JA
1848 ret = radix_tree_preload(gfp_mask);
1849 if (!ret) {
1850 cic->ioc = ioc;
1851 cic->key = cfqd;
e2d74ac0 1852
4ac845a2
JA
1853 spin_lock_irqsave(&ioc->lock, flags);
1854 ret = radix_tree_insert(&ioc->radix_root,
1855 (unsigned long) cfqd, cic);
ffc4e759
JA
1856 if (!ret)
1857 hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
4ac845a2 1858 spin_unlock_irqrestore(&ioc->lock, flags);
e2d74ac0 1859
4ac845a2
JA
1860 radix_tree_preload_end();
1861
1862 if (!ret) {
1863 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1864 list_add(&cic->queue_list, &cfqd->cic_list);
1865 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1866 }
e2d74ac0
JA
1867 }
1868
4ac845a2
JA
1869 if (ret)
1870 printk(KERN_ERR "cfq: cic link failed!\n");
fc46379d 1871
4ac845a2 1872 return ret;
e2d74ac0
JA
1873}
1874
1da177e4
LT
1875/*
1876 * Setup general io context and cfq io context. There can be several cfq
1877 * io contexts per general io context, if this process is doing io to more
e2d74ac0 1878 * than one device managed by cfq.
1da177e4
LT
1879 */
1880static struct cfq_io_context *
e2d74ac0 1881cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1da177e4 1882{
22e2c507 1883 struct io_context *ioc = NULL;
1da177e4 1884 struct cfq_io_context *cic;
1da177e4 1885
22e2c507 1886 might_sleep_if(gfp_mask & __GFP_WAIT);
1da177e4 1887
b5deef90 1888 ioc = get_io_context(gfp_mask, cfqd->queue->node);
1da177e4
LT
1889 if (!ioc)
1890 return NULL;
1891
4ac845a2 1892 cic = cfq_cic_lookup(cfqd, ioc);
e2d74ac0
JA
1893 if (cic)
1894 goto out;
1da177e4 1895
e2d74ac0
JA
1896 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1897 if (cic == NULL)
1898 goto err;
1da177e4 1899
4ac845a2
JA
1900 if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
1901 goto err_free;
1902
1da177e4 1903out:
fc46379d
JA
1904 smp_read_barrier_depends();
1905 if (unlikely(ioc->ioprio_changed))
1906 cfq_ioc_set_ioprio(ioc);
1907
1da177e4 1908 return cic;
4ac845a2
JA
1909err_free:
1910 cfq_cic_free(cic);
1da177e4
LT
1911err:
1912 put_io_context(ioc);
1913 return NULL;
1914}
1915
22e2c507
JA
1916static void
1917cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1da177e4 1918{
aaf1228d
JA
1919 unsigned long elapsed = jiffies - cic->last_end_request;
1920 unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
db3b5848 1921
22e2c507
JA
1922 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1923 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1924 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1925}
1da177e4 1926
206dc69b 1927static void
6d048f53
JA
1928cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1929 struct request *rq)
206dc69b
JA
1930{
1931 sector_t sdist;
1932 u64 total;
1933
4d00aa47
JM
1934 if (!cic->last_request_pos)
1935 sdist = 0;
83096ebf
TH
1936 else if (cic->last_request_pos < blk_rq_pos(rq))
1937 sdist = blk_rq_pos(rq) - cic->last_request_pos;
206dc69b 1938 else
83096ebf 1939 sdist = cic->last_request_pos - blk_rq_pos(rq);
206dc69b
JA
1940
1941 /*
1942 * Don't allow the seek distance to get too large from the
1943 * odd fragment, pagein, etc
1944 */
1945 if (cic->seek_samples <= 60) /* second&third seek */
1946 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1947 else
1948 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1949
1950 cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1951 cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1952 total = cic->seek_total + (cic->seek_samples/2);
1953 do_div(total, cic->seek_samples);
1954 cic->seek_mean = (sector_t)total;
1955}
1da177e4 1956
22e2c507
JA
1957/*
1958 * Disable idle window if the process thinks too long or seeks so much that
1959 * it doesn't matter
1960 */
1961static void
1962cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1963 struct cfq_io_context *cic)
1964{
7b679138 1965 int old_idle, enable_idle;
1be92f2f 1966
0871714e
JA
1967 /*
1968 * Don't idle for async or idle io prio class
1969 */
1970 if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
1be92f2f
JA
1971 return;
1972
c265a7f4 1973 enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
1da177e4 1974
66dac98e 1975 if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
963b72fc 1976 (!cfqd->cfq_latency && cfqd->hw_tag && CIC_SEEKY(cic)))
22e2c507
JA
1977 enable_idle = 0;
1978 else if (sample_valid(cic->ttime_samples)) {
1979 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1980 enable_idle = 0;
1981 else
1982 enable_idle = 1;
1da177e4
LT
1983 }
1984
7b679138
JA
1985 if (old_idle != enable_idle) {
1986 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
1987 if (enable_idle)
1988 cfq_mark_cfqq_idle_window(cfqq);
1989 else
1990 cfq_clear_cfqq_idle_window(cfqq);
1991 }
22e2c507 1992}
1da177e4 1993
22e2c507
JA
1994/*
1995 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1996 * no or if we aren't sure, a 1 will cause a preempt.
1997 */
1998static int
1999cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
5e705374 2000 struct request *rq)
22e2c507 2001{
6d048f53 2002 struct cfq_queue *cfqq;
22e2c507 2003
6d048f53
JA
2004 cfqq = cfqd->active_queue;
2005 if (!cfqq)
22e2c507
JA
2006 return 0;
2007
6d048f53
JA
2008 if (cfq_slice_used(cfqq))
2009 return 1;
2010
2011 if (cfq_class_idle(new_cfqq))
caaa5f9f 2012 return 0;
22e2c507
JA
2013
2014 if (cfq_class_idle(cfqq))
2015 return 1;
1e3335de 2016
374f84ac
JA
2017 /*
2018 * if the new request is sync, but the currently running queue is
2019 * not, let the sync request have priority.
2020 */
5e705374 2021 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
22e2c507 2022 return 1;
1e3335de 2023
374f84ac
JA
2024 /*
2025 * So both queues are sync. Let the new request get disk time if
2026 * it's a metadata request and the current queue is doing regular IO.
2027 */
2028 if (rq_is_meta(rq) && !cfqq->meta_pending)
2029 return 1;
22e2c507 2030
3a9a3f6c
DS
2031 /*
2032 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2033 */
2034 if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2035 return 1;
2036
1e3335de
JA
2037 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2038 return 0;
2039
2040 /*
2041 * if this request is as-good as one we would expect from the
2042 * current cfqq, let it preempt
2043 */
6d048f53 2044 if (cfq_rq_close(cfqd, rq))
1e3335de
JA
2045 return 1;
2046
22e2c507
JA
2047 return 0;
2048}
2049
2050/*
2051 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2052 * let it have half of its nominal slice.
2053 */
2054static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2055{
7b679138 2056 cfq_log_cfqq(cfqd, cfqq, "preempt");
6084cdda 2057 cfq_slice_expired(cfqd, 1);
22e2c507 2058
bf572256
JA
2059 /*
2060 * Put the new queue at the front of the of the current list,
2061 * so we know that it will be selected next.
2062 */
2063 BUG_ON(!cfq_cfqq_on_rr(cfqq));
edd75ffd
JA
2064
2065 cfq_service_tree_add(cfqd, cfqq, 1);
bf572256 2066
44f7c160
JA
2067 cfqq->slice_end = 0;
2068 cfq_mark_cfqq_slice_new(cfqq);
22e2c507
JA
2069}
2070
22e2c507 2071/*
5e705374 2072 * Called when a new fs request (rq) is added (to cfqq). Check if there's
22e2c507
JA
2073 * something we should do about it
2074 */
2075static void
5e705374
JA
2076cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2077 struct request *rq)
22e2c507 2078{
5e705374 2079 struct cfq_io_context *cic = RQ_CIC(rq);
12e9fddd 2080
45333d5a 2081 cfqd->rq_queued++;
374f84ac
JA
2082 if (rq_is_meta(rq))
2083 cfqq->meta_pending++;
2084
9c2c38a1 2085 cfq_update_io_thinktime(cfqd, cic);
6d048f53 2086 cfq_update_io_seektime(cfqd, cic, rq);
9c2c38a1
JA
2087 cfq_update_idle_window(cfqd, cfqq, cic);
2088
83096ebf 2089 cic->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
22e2c507
JA
2090
2091 if (cfqq == cfqd->active_queue) {
2092 /*
b029195d
JA
2093 * Remember that we saw a request from this process, but
2094 * don't start queuing just yet. Otherwise we risk seeing lots
2095 * of tiny requests, because we disrupt the normal plugging
d6ceb25e
JA
2096 * and merging. If the request is already larger than a single
2097 * page, let it rip immediately. For that case we assume that
2d870722
JA
2098 * merging is already done. Ditto for a busy system that
2099 * has other work pending, don't risk delaying until the
2100 * idle timer unplug to continue working.
22e2c507 2101 */
d6ceb25e 2102 if (cfq_cfqq_wait_request(cfqq)) {
2d870722
JA
2103 if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2104 cfqd->busy_queues > 1) {
d6ceb25e 2105 del_timer(&cfqd->idle_slice_timer);
a7f55792 2106 __blk_run_queue(cfqd->queue);
d6ceb25e 2107 }
b029195d 2108 cfq_mark_cfqq_must_dispatch(cfqq);
d6ceb25e 2109 }
5e705374 2110 } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
22e2c507
JA
2111 /*
2112 * not the active queue - expire current slice if it is
2113 * idle and has expired it's mean thinktime or this new queue
3a9a3f6c
DS
2114 * has some old slice time left and is of higher priority or
2115 * this new queue is RT and the current one is BE
22e2c507
JA
2116 */
2117 cfq_preempt_queue(cfqd, cfqq);
a7f55792 2118 __blk_run_queue(cfqd->queue);
22e2c507 2119 }
1da177e4
LT
2120}
2121
165125e1 2122static void cfq_insert_request(struct request_queue *q, struct request *rq)
1da177e4 2123{
b4878f24 2124 struct cfq_data *cfqd = q->elevator->elevator_data;
5e705374 2125 struct cfq_queue *cfqq = RQ_CFQQ(rq);
22e2c507 2126
7b679138 2127 cfq_log_cfqq(cfqd, cfqq, "insert_request");
fd0928df 2128 cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
1da177e4 2129
5e705374 2130 cfq_add_rq_rb(rq);
1da177e4 2131
30996f40 2132 rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
22e2c507
JA
2133 list_add_tail(&rq->queuelist, &cfqq->fifo);
2134
5e705374 2135 cfq_rq_enqueued(cfqd, cfqq, rq);
1da177e4
LT
2136}
2137
45333d5a
AC
2138/*
2139 * Update hw_tag based on peak queue depth over 50 samples under
2140 * sufficient load.
2141 */
2142static void cfq_update_hw_tag(struct cfq_data *cfqd)
2143{
5ad531db
JA
2144 if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
2145 cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
45333d5a
AC
2146
2147 if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
5ad531db 2148 rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
45333d5a
AC
2149 return;
2150
2151 if (cfqd->hw_tag_samples++ < 50)
2152 return;
2153
2154 if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
2155 cfqd->hw_tag = 1;
2156 else
2157 cfqd->hw_tag = 0;
2158
2159 cfqd->hw_tag_samples = 0;
2160 cfqd->rq_in_driver_peak = 0;
2161}
2162
165125e1 2163static void cfq_completed_request(struct request_queue *q, struct request *rq)
1da177e4 2164{
5e705374 2165 struct cfq_queue *cfqq = RQ_CFQQ(rq);
b4878f24 2166 struct cfq_data *cfqd = cfqq->cfqd;
5380a101 2167 const int sync = rq_is_sync(rq);
b4878f24 2168 unsigned long now;
1da177e4 2169
b4878f24 2170 now = jiffies;
7b679138 2171 cfq_log_cfqq(cfqd, cfqq, "complete");
1da177e4 2172
45333d5a
AC
2173 cfq_update_hw_tag(cfqd);
2174
5ad531db 2175 WARN_ON(!cfqd->rq_in_driver[sync]);
6d048f53 2176 WARN_ON(!cfqq->dispatched);
5ad531db 2177 cfqd->rq_in_driver[sync]--;
6d048f53 2178 cfqq->dispatched--;
1da177e4 2179
3ed9a296
JA
2180 if (cfq_cfqq_sync(cfqq))
2181 cfqd->sync_flight--;
2182
365722bb 2183 if (sync) {
5e705374 2184 RQ_CIC(rq)->last_end_request = now;
365722bb
VG
2185 cfqd->last_end_sync_rq = now;
2186 }
caaa5f9f
JA
2187
2188 /*
2189 * If this is the active queue, check if it needs to be expired,
2190 * or if we want to idle in case it has no pending requests.
2191 */
2192 if (cfqd->active_queue == cfqq) {
a36e71f9
JA
2193 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2194
44f7c160
JA
2195 if (cfq_cfqq_slice_new(cfqq)) {
2196 cfq_set_prio_slice(cfqd, cfqq);
2197 cfq_clear_cfqq_slice_new(cfqq);
2198 }
a36e71f9
JA
2199 /*
2200 * If there are no requests waiting in this queue, and
2201 * there are other queues ready to issue requests, AND
2202 * those other queues are issuing requests within our
2203 * mean seek distance, give them a chance to run instead
2204 * of idling.
2205 */
0871714e 2206 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
6084cdda 2207 cfq_slice_expired(cfqd, 1);
a36e71f9
JA
2208 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq, 1) &&
2209 sync && !rq_noidle(rq))
6d048f53 2210 cfq_arm_slice_timer(cfqd);
caaa5f9f 2211 }
6d048f53 2212
5ad531db 2213 if (!rq_in_driver(cfqd))
23e018a1 2214 cfq_schedule_dispatch(cfqd);
1da177e4
LT
2215}
2216
22e2c507
JA
2217/*
2218 * we temporarily boost lower priority queues if they are holding fs exclusive
2219 * resources. they are boosted to normal prio (CLASS_BE/4)
2220 */
2221static void cfq_prio_boost(struct cfq_queue *cfqq)
1da177e4 2222{
22e2c507
JA
2223 if (has_fs_excl()) {
2224 /*
2225 * boost idle prio on transactions that would lock out other
2226 * users of the filesystem
2227 */
2228 if (cfq_class_idle(cfqq))
2229 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2230 if (cfqq->ioprio > IOPRIO_NORM)
2231 cfqq->ioprio = IOPRIO_NORM;
2232 } else {
2233 /*
2234 * check if we need to unboost the queue
2235 */
2236 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
2237 cfqq->ioprio_class = cfqq->org_ioprio_class;
2238 if (cfqq->ioprio != cfqq->org_ioprio)
2239 cfqq->ioprio = cfqq->org_ioprio;
2240 }
22e2c507 2241}
1da177e4 2242
89850f7e 2243static inline int __cfq_may_queue(struct cfq_queue *cfqq)
22e2c507 2244{
1b379d8d 2245 if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3b18152c 2246 cfq_mark_cfqq_must_alloc_slice(cfqq);
22e2c507 2247 return ELV_MQUEUE_MUST;
3b18152c 2248 }
1da177e4 2249
22e2c507 2250 return ELV_MQUEUE_MAY;
22e2c507
JA
2251}
2252
165125e1 2253static int cfq_may_queue(struct request_queue *q, int rw)
22e2c507
JA
2254{
2255 struct cfq_data *cfqd = q->elevator->elevator_data;
2256 struct task_struct *tsk = current;
91fac317 2257 struct cfq_io_context *cic;
22e2c507
JA
2258 struct cfq_queue *cfqq;
2259
2260 /*
2261 * don't force setup of a queue from here, as a call to may_queue
2262 * does not necessarily imply that a request actually will be queued.
2263 * so just lookup a possibly existing queue, or return 'may queue'
2264 * if that fails
2265 */
4ac845a2 2266 cic = cfq_cic_lookup(cfqd, tsk->io_context);
91fac317
VT
2267 if (!cic)
2268 return ELV_MQUEUE_MAY;
2269
b0b78f81 2270 cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
22e2c507 2271 if (cfqq) {
fd0928df 2272 cfq_init_prio_data(cfqq, cic->ioc);
22e2c507
JA
2273 cfq_prio_boost(cfqq);
2274
89850f7e 2275 return __cfq_may_queue(cfqq);
22e2c507
JA
2276 }
2277
2278 return ELV_MQUEUE_MAY;
1da177e4
LT
2279}
2280
1da177e4
LT
2281/*
2282 * queue lock held here
2283 */
bb37b94c 2284static void cfq_put_request(struct request *rq)
1da177e4 2285{
5e705374 2286 struct cfq_queue *cfqq = RQ_CFQQ(rq);
1da177e4 2287
5e705374 2288 if (cfqq) {
22e2c507 2289 const int rw = rq_data_dir(rq);
1da177e4 2290
22e2c507
JA
2291 BUG_ON(!cfqq->allocated[rw]);
2292 cfqq->allocated[rw]--;
1da177e4 2293
5e705374 2294 put_io_context(RQ_CIC(rq)->ioc);
1da177e4 2295
1da177e4 2296 rq->elevator_private = NULL;
5e705374 2297 rq->elevator_private2 = NULL;
1da177e4 2298
1da177e4
LT
2299 cfq_put_queue(cfqq);
2300 }
2301}
2302
2303/*
22e2c507 2304 * Allocate cfq data structures associated with this request.
1da177e4 2305 */
22e2c507 2306static int
165125e1 2307cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
1da177e4
LT
2308{
2309 struct cfq_data *cfqd = q->elevator->elevator_data;
2310 struct cfq_io_context *cic;
2311 const int rw = rq_data_dir(rq);
7749a8d4 2312 const int is_sync = rq_is_sync(rq);
22e2c507 2313 struct cfq_queue *cfqq;
1da177e4
LT
2314 unsigned long flags;
2315
2316 might_sleep_if(gfp_mask & __GFP_WAIT);
2317
e2d74ac0 2318 cic = cfq_get_io_context(cfqd, gfp_mask);
22e2c507 2319
1da177e4
LT
2320 spin_lock_irqsave(q->queue_lock, flags);
2321
22e2c507
JA
2322 if (!cic)
2323 goto queue_fail;
2324
91fac317 2325 cfqq = cic_to_cfqq(cic, is_sync);
32f2e807 2326 if (!cfqq || cfqq == &cfqd->oom_cfqq) {
fd0928df 2327 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
91fac317
VT
2328 cic_set_cfqq(cic, cfqq, is_sync);
2329 }
1da177e4
LT
2330
2331 cfqq->allocated[rw]++;
22e2c507 2332 atomic_inc(&cfqq->ref);
1da177e4 2333
5e705374 2334 spin_unlock_irqrestore(q->queue_lock, flags);
3b18152c 2335
5e705374
JA
2336 rq->elevator_private = cic;
2337 rq->elevator_private2 = cfqq;
2338 return 0;
1da177e4 2339
22e2c507
JA
2340queue_fail:
2341 if (cic)
2342 put_io_context(cic->ioc);
89850f7e 2343
23e018a1 2344 cfq_schedule_dispatch(cfqd);
1da177e4 2345 spin_unlock_irqrestore(q->queue_lock, flags);
7b679138 2346 cfq_log(cfqd, "set_request fail");
1da177e4
LT
2347 return 1;
2348}
2349
65f27f38 2350static void cfq_kick_queue(struct work_struct *work)
22e2c507 2351{
65f27f38 2352 struct cfq_data *cfqd =
23e018a1 2353 container_of(work, struct cfq_data, unplug_work);
165125e1 2354 struct request_queue *q = cfqd->queue;
22e2c507 2355
40bb54d1 2356 spin_lock_irq(q->queue_lock);
a7f55792 2357 __blk_run_queue(cfqd->queue);
40bb54d1 2358 spin_unlock_irq(q->queue_lock);
22e2c507
JA
2359}
2360
2361/*
2362 * Timer running if the active_queue is currently idling inside its time slice
2363 */
2364static void cfq_idle_slice_timer(unsigned long data)
2365{
2366 struct cfq_data *cfqd = (struct cfq_data *) data;
2367 struct cfq_queue *cfqq;
2368 unsigned long flags;
3c6bd2f8 2369 int timed_out = 1;
22e2c507 2370
7b679138
JA
2371 cfq_log(cfqd, "idle timer fired");
2372
22e2c507
JA
2373 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2374
fe094d98
JA
2375 cfqq = cfqd->active_queue;
2376 if (cfqq) {
3c6bd2f8
JA
2377 timed_out = 0;
2378
b029195d
JA
2379 /*
2380 * We saw a request before the queue expired, let it through
2381 */
2382 if (cfq_cfqq_must_dispatch(cfqq))
2383 goto out_kick;
2384
22e2c507
JA
2385 /*
2386 * expired
2387 */
44f7c160 2388 if (cfq_slice_used(cfqq))
22e2c507
JA
2389 goto expire;
2390
2391 /*
2392 * only expire and reinvoke request handler, if there are
2393 * other queues with pending requests
2394 */
caaa5f9f 2395 if (!cfqd->busy_queues)
22e2c507 2396 goto out_cont;
22e2c507
JA
2397
2398 /*
2399 * not expired and it has a request pending, let it dispatch
2400 */
75e50984 2401 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
22e2c507 2402 goto out_kick;
22e2c507
JA
2403 }
2404expire:
6084cdda 2405 cfq_slice_expired(cfqd, timed_out);
22e2c507 2406out_kick:
23e018a1 2407 cfq_schedule_dispatch(cfqd);
22e2c507
JA
2408out_cont:
2409 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2410}
2411
3b18152c
JA
2412static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2413{
2414 del_timer_sync(&cfqd->idle_slice_timer);
23e018a1 2415 cancel_work_sync(&cfqd->unplug_work);
3b18152c 2416}
22e2c507 2417
c2dea2d1
VT
2418static void cfq_put_async_queues(struct cfq_data *cfqd)
2419{
2420 int i;
2421
2422 for (i = 0; i < IOPRIO_BE_NR; i++) {
2423 if (cfqd->async_cfqq[0][i])
2424 cfq_put_queue(cfqd->async_cfqq[0][i]);
2425 if (cfqd->async_cfqq[1][i])
2426 cfq_put_queue(cfqd->async_cfqq[1][i]);
c2dea2d1 2427 }
2389d1ef
ON
2428
2429 if (cfqd->async_idle_cfqq)
2430 cfq_put_queue(cfqd->async_idle_cfqq);
c2dea2d1
VT
2431}
2432
b374d18a 2433static void cfq_exit_queue(struct elevator_queue *e)
1da177e4 2434{
22e2c507 2435 struct cfq_data *cfqd = e->elevator_data;
165125e1 2436 struct request_queue *q = cfqd->queue;
22e2c507 2437
3b18152c 2438 cfq_shutdown_timer_wq(cfqd);
e2d74ac0 2439
d9ff4187 2440 spin_lock_irq(q->queue_lock);
e2d74ac0 2441
d9ff4187 2442 if (cfqd->active_queue)
6084cdda 2443 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
e2d74ac0
JA
2444
2445 while (!list_empty(&cfqd->cic_list)) {
d9ff4187
AV
2446 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2447 struct cfq_io_context,
2448 queue_list);
89850f7e
JA
2449
2450 __cfq_exit_single_io_context(cfqd, cic);
d9ff4187 2451 }
e2d74ac0 2452
c2dea2d1 2453 cfq_put_async_queues(cfqd);
15c31be4 2454
d9ff4187 2455 spin_unlock_irq(q->queue_lock);
a90d742e
AV
2456
2457 cfq_shutdown_timer_wq(cfqd);
2458
a90d742e 2459 kfree(cfqd);
1da177e4
LT
2460}
2461
165125e1 2462static void *cfq_init_queue(struct request_queue *q)
1da177e4
LT
2463{
2464 struct cfq_data *cfqd;
26a2ac00 2465 int i;
1da177e4 2466
94f6030c 2467 cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
1da177e4 2468 if (!cfqd)
bc1c1169 2469 return NULL;
1da177e4 2470
cc09e299 2471 cfqd->service_tree = CFQ_RB_ROOT;
26a2ac00
JA
2472
2473 /*
2474 * Not strictly needed (since RB_ROOT just clears the node and we
2475 * zeroed cfqd on alloc), but better be safe in case someone decides
2476 * to add magic to the rb code
2477 */
2478 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2479 cfqd->prio_trees[i] = RB_ROOT;
2480
6118b70b
JA
2481 /*
2482 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2483 * Grab a permanent reference to it, so that the normal code flow
2484 * will not attempt to free it.
2485 */
2486 cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
2487 atomic_inc(&cfqd->oom_cfqq.ref);
2488
d9ff4187 2489 INIT_LIST_HEAD(&cfqd->cic_list);
1da177e4 2490
1da177e4 2491 cfqd->queue = q;
1da177e4 2492
22e2c507
JA
2493 init_timer(&cfqd->idle_slice_timer);
2494 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2495 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2496
23e018a1 2497 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
22e2c507 2498
1da177e4 2499 cfqd->cfq_quantum = cfq_quantum;
22e2c507
JA
2500 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2501 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
1da177e4
LT
2502 cfqd->cfq_back_max = cfq_back_max;
2503 cfqd->cfq_back_penalty = cfq_back_penalty;
22e2c507
JA
2504 cfqd->cfq_slice[0] = cfq_slice_async;
2505 cfqd->cfq_slice[1] = cfq_slice_sync;
2506 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2507 cfqd->cfq_slice_idle = cfq_slice_idle;
963b72fc 2508 cfqd->cfq_latency = 1;
45333d5a 2509 cfqd->hw_tag = 1;
365722bb 2510 cfqd->last_end_sync_rq = jiffies;
bc1c1169 2511 return cfqd;
1da177e4
LT
2512}
2513
2514static void cfq_slab_kill(void)
2515{
d6de8be7
JA
2516 /*
2517 * Caller already ensured that pending RCU callbacks are completed,
2518 * so we should have no busy allocations at this point.
2519 */
1da177e4
LT
2520 if (cfq_pool)
2521 kmem_cache_destroy(cfq_pool);
2522 if (cfq_ioc_pool)
2523 kmem_cache_destroy(cfq_ioc_pool);
2524}
2525
2526static int __init cfq_slab_setup(void)
2527{
0a31bd5f 2528 cfq_pool = KMEM_CACHE(cfq_queue, 0);
1da177e4
LT
2529 if (!cfq_pool)
2530 goto fail;
2531
34e6bbf2 2532 cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
1da177e4
LT
2533 if (!cfq_ioc_pool)
2534 goto fail;
2535
2536 return 0;
2537fail:
2538 cfq_slab_kill();
2539 return -ENOMEM;
2540}
2541
1da177e4
LT
2542/*
2543 * sysfs parts below -->
2544 */
1da177e4
LT
2545static ssize_t
2546cfq_var_show(unsigned int var, char *page)
2547{
2548 return sprintf(page, "%d\n", var);
2549}
2550
2551static ssize_t
2552cfq_var_store(unsigned int *var, const char *page, size_t count)
2553{
2554 char *p = (char *) page;
2555
2556 *var = simple_strtoul(p, &p, 10);
2557 return count;
2558}
2559
1da177e4 2560#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
b374d18a 2561static ssize_t __FUNC(struct elevator_queue *e, char *page) \
1da177e4 2562{ \
3d1ab40f 2563 struct cfq_data *cfqd = e->elevator_data; \
1da177e4
LT
2564 unsigned int __data = __VAR; \
2565 if (__CONV) \
2566 __data = jiffies_to_msecs(__data); \
2567 return cfq_var_show(__data, (page)); \
2568}
2569SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
22e2c507
JA
2570SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2571SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
e572ec7e
AV
2572SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2573SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
22e2c507
JA
2574SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2575SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2576SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2577SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
963b72fc 2578SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
1da177e4
LT
2579#undef SHOW_FUNCTION
2580
2581#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
b374d18a 2582static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
1da177e4 2583{ \
3d1ab40f 2584 struct cfq_data *cfqd = e->elevator_data; \
1da177e4
LT
2585 unsigned int __data; \
2586 int ret = cfq_var_store(&__data, (page), count); \
2587 if (__data < (MIN)) \
2588 __data = (MIN); \
2589 else if (__data > (MAX)) \
2590 __data = (MAX); \
2591 if (__CONV) \
2592 *(__PTR) = msecs_to_jiffies(__data); \
2593 else \
2594 *(__PTR) = __data; \
2595 return ret; \
2596}
2597STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
fe094d98
JA
2598STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
2599 UINT_MAX, 1);
2600STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
2601 UINT_MAX, 1);
e572ec7e 2602STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
fe094d98
JA
2603STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
2604 UINT_MAX, 0);
22e2c507
JA
2605STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2606STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2607STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
fe094d98
JA
2608STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
2609 UINT_MAX, 0);
963b72fc 2610STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
1da177e4
LT
2611#undef STORE_FUNCTION
2612
e572ec7e
AV
2613#define CFQ_ATTR(name) \
2614 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2615
2616static struct elv_fs_entry cfq_attrs[] = {
2617 CFQ_ATTR(quantum),
e572ec7e
AV
2618 CFQ_ATTR(fifo_expire_sync),
2619 CFQ_ATTR(fifo_expire_async),
2620 CFQ_ATTR(back_seek_max),
2621 CFQ_ATTR(back_seek_penalty),
2622 CFQ_ATTR(slice_sync),
2623 CFQ_ATTR(slice_async),
2624 CFQ_ATTR(slice_async_rq),
2625 CFQ_ATTR(slice_idle),
963b72fc 2626 CFQ_ATTR(low_latency),
e572ec7e 2627 __ATTR_NULL
1da177e4
LT
2628};
2629
1da177e4
LT
2630static struct elevator_type iosched_cfq = {
2631 .ops = {
2632 .elevator_merge_fn = cfq_merge,
2633 .elevator_merged_fn = cfq_merged_request,
2634 .elevator_merge_req_fn = cfq_merged_requests,
da775265 2635 .elevator_allow_merge_fn = cfq_allow_merge,
b4878f24 2636 .elevator_dispatch_fn = cfq_dispatch_requests,
1da177e4 2637 .elevator_add_req_fn = cfq_insert_request,
b4878f24 2638 .elevator_activate_req_fn = cfq_activate_request,
1da177e4
LT
2639 .elevator_deactivate_req_fn = cfq_deactivate_request,
2640 .elevator_queue_empty_fn = cfq_queue_empty,
2641 .elevator_completed_req_fn = cfq_completed_request,
21183b07
JA
2642 .elevator_former_req_fn = elv_rb_former_request,
2643 .elevator_latter_req_fn = elv_rb_latter_request,
1da177e4
LT
2644 .elevator_set_req_fn = cfq_set_request,
2645 .elevator_put_req_fn = cfq_put_request,
2646 .elevator_may_queue_fn = cfq_may_queue,
2647 .elevator_init_fn = cfq_init_queue,
2648 .elevator_exit_fn = cfq_exit_queue,
fc46379d 2649 .trim = cfq_free_io_context,
1da177e4 2650 },
3d1ab40f 2651 .elevator_attrs = cfq_attrs,
1da177e4
LT
2652 .elevator_name = "cfq",
2653 .elevator_owner = THIS_MODULE,
2654};
2655
2656static int __init cfq_init(void)
2657{
22e2c507
JA
2658 /*
2659 * could be 0 on HZ < 1000 setups
2660 */
2661 if (!cfq_slice_async)
2662 cfq_slice_async = 1;
2663 if (!cfq_slice_idle)
2664 cfq_slice_idle = 1;
2665
1da177e4
LT
2666 if (cfq_slab_setup())
2667 return -ENOMEM;
2668
2fdd82bd 2669 elv_register(&iosched_cfq);
1da177e4 2670
2fdd82bd 2671 return 0;
1da177e4
LT
2672}
2673
2674static void __exit cfq_exit(void)
2675{
6e9a4738 2676 DECLARE_COMPLETION_ONSTACK(all_gone);
1da177e4 2677 elv_unregister(&iosched_cfq);
334e94de 2678 ioc_gone = &all_gone;
fba82272
OH
2679 /* ioc_gone's update must be visible before reading ioc_count */
2680 smp_wmb();
d6de8be7
JA
2681
2682 /*
2683 * this also protects us from entering cfq_slab_kill() with
2684 * pending RCU callbacks
2685 */
245b2e70 2686 if (elv_ioc_count_read(cfq_ioc_count))
9a11b4ed 2687 wait_for_completion(&all_gone);
83521d3e 2688 cfq_slab_kill();
1da177e4
LT
2689}
2690
2691module_init(cfq_init);
2692module_exit(cfq_exit);
2693
2694MODULE_AUTHOR("Jens Axboe");
2695MODULE_LICENSE("GPL");
2696MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");