cfq-iosched: fix merge error
[linux-2.6.git] / block / cfq-iosched.c
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/rbtree.h>
13 #include <linux/ioprio.h>
14 #include <linux/blktrace_api.h>
15
16 /*
17  * tunables
18  */
19 /* max queue in one round of service */
20 static const int cfq_quantum = 4;
21 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
22 /* maximum backwards seek, in KiB */
23 static const int cfq_back_max = 16 * 1024;
24 /* penalty of a backwards seek */
25 static const int cfq_back_penalty = 2;
26 static const int cfq_slice_sync = HZ / 10;
27 static int cfq_slice_async = HZ / 25;
28 static const int cfq_slice_async_rq = 2;
29 static int cfq_slice_idle = HZ / 125;
30 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
31 static const int cfq_hist_divisor = 4;
32
33 /*
34  * offset from end of service tree
35  */
36 #define CFQ_IDLE_DELAY          (HZ / 5)
37
38 /*
39  * below this threshold, we consider thinktime immediate
40  */
41 #define CFQ_MIN_TT              (2)
42
43 /*
44  * Allow merged cfqqs to perform this amount of seeky I/O before
45  * deciding to break the queues up again.
46  */
47 #define CFQQ_COOP_TOUT          (HZ)
48
49 #define CFQ_SLICE_SCALE         (5)
50 #define CFQ_HW_QUEUE_MIN        (5)
51
52 #define RQ_CIC(rq)              \
53         ((struct cfq_io_context *) (rq)->elevator_private)
54 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private2)
55
56 static struct kmem_cache *cfq_pool;
57 static struct kmem_cache *cfq_ioc_pool;
58
59 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
60 static struct completion *ioc_gone;
61 static DEFINE_SPINLOCK(ioc_gone_lock);
62
63 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
64 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
65 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
66
67 #define sample_valid(samples)   ((samples) > 80)
68
69 /*
70  * Most of our rbtree usage is for sorting with min extraction, so
71  * if we cache the leftmost node we don't have to walk down the tree
72  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
73  * move this into the elevator for the rq sorting as well.
74  */
75 struct cfq_rb_root {
76         struct rb_root rb;
77         struct rb_node *left;
78         unsigned count;
79 };
80 #define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
81
82 /*
83  * Per process-grouping structure
84  */
85 struct cfq_queue {
86         /* reference count */
87         atomic_t ref;
88         /* various state flags, see below */
89         unsigned int flags;
90         /* parent cfq_data */
91         struct cfq_data *cfqd;
92         /* service_tree member */
93         struct rb_node rb_node;
94         /* service_tree key */
95         unsigned long rb_key;
96         /* prio tree member */
97         struct rb_node p_node;
98         /* prio tree root we belong to, if any */
99         struct rb_root *p_root;
100         /* sorted list of pending requests */
101         struct rb_root sort_list;
102         /* if fifo isn't expired, next request to serve */
103         struct request *next_rq;
104         /* requests queued in sort_list */
105         int queued[2];
106         /* currently allocated requests */
107         int allocated[2];
108         /* fifo list of requests in sort_list */
109         struct list_head fifo;
110
111         unsigned long slice_end;
112         long slice_resid;
113         unsigned int slice_dispatch;
114
115         /* pending metadata requests */
116         int meta_pending;
117         /* number of requests that are on the dispatch list or inside driver */
118         int dispatched;
119
120         /* io prio of this group */
121         unsigned short ioprio, org_ioprio;
122         unsigned short ioprio_class, org_ioprio_class;
123
124         unsigned int seek_samples;
125         u64 seek_total;
126         sector_t seek_mean;
127         sector_t last_request_pos;
128         unsigned long seeky_start;
129
130         pid_t pid;
131
132         struct cfq_rb_root *service_tree;
133         struct cfq_queue *new_cfqq;
134 };
135
136 /*
137  * First index in the service_trees.
138  * IDLE is handled separately, so it has negative index
139  */
140 enum wl_prio_t {
141         IDLE_WORKLOAD = -1,
142         BE_WORKLOAD = 0,
143         RT_WORKLOAD = 1
144 };
145
146 /*
147  * Second index in the service_trees.
148  */
149 enum wl_type_t {
150         ASYNC_WORKLOAD = 0,
151         SYNC_NOIDLE_WORKLOAD = 1,
152         SYNC_WORKLOAD = 2
153 };
154
155
156 /*
157  * Per block device queue structure
158  */
159 struct cfq_data {
160         struct request_queue *queue;
161
162         /*
163          * rr lists of queues with requests, onle rr for each priority class.
164          * Counts are embedded in the cfq_rb_root
165          */
166         struct cfq_rb_root service_trees[2][3];
167         struct cfq_rb_root service_tree_idle;
168         /*
169          * The priority currently being served
170          */
171         enum wl_prio_t serving_prio;
172         enum wl_type_t serving_type;
173         unsigned long workload_expires;
174
175         /*
176          * Each priority tree is sorted by next_request position.  These
177          * trees are used when determining if two or more queues are
178          * interleaving requests (see cfq_close_cooperator).
179          */
180         struct rb_root prio_trees[CFQ_PRIO_LISTS];
181
182         unsigned int busy_queues;
183         unsigned int busy_queues_avg[2];
184
185         int rq_in_driver[2];
186         int sync_flight;
187
188         /*
189          * queue-depth detection
190          */
191         int rq_queued;
192         int hw_tag;
193         int hw_tag_samples;
194         int rq_in_driver_peak;
195
196         /*
197          * idle window management
198          */
199         struct timer_list idle_slice_timer;
200         struct work_struct unplug_work;
201
202         struct cfq_queue *active_queue;
203         struct cfq_io_context *active_cic;
204
205         /*
206          * async queue for each priority case
207          */
208         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
209         struct cfq_queue *async_idle_cfqq;
210
211         sector_t last_position;
212
213         /*
214          * tunables, see top of file
215          */
216         unsigned int cfq_quantum;
217         unsigned int cfq_fifo_expire[2];
218         unsigned int cfq_back_penalty;
219         unsigned int cfq_back_max;
220         unsigned int cfq_slice[2];
221         unsigned int cfq_slice_async_rq;
222         unsigned int cfq_slice_idle;
223         unsigned int cfq_latency;
224
225         struct list_head cic_list;
226
227         /*
228          * Fallback dummy cfqq for extreme OOM conditions
229          */
230         struct cfq_queue oom_cfqq;
231
232         unsigned long last_end_sync_rq;
233 };
234
235 static struct cfq_rb_root *service_tree_for(enum wl_prio_t prio,
236                                             enum wl_type_t type,
237                                             struct cfq_data *cfqd)
238 {
239         if (prio == IDLE_WORKLOAD)
240                 return &cfqd->service_tree_idle;
241
242         return &cfqd->service_trees[prio][type];
243 }
244
245 enum cfqq_state_flags {
246         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
247         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
248         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
249         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
250         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
251         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
252         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
253         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
254         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
255         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
256         CFQ_CFQQ_FLAG_coop_preempt,     /* coop preempt */
257 };
258
259 #define CFQ_CFQQ_FNS(name)                                              \
260 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
261 {                                                                       \
262         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
263 }                                                                       \
264 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
265 {                                                                       \
266         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
267 }                                                                       \
268 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
269 {                                                                       \
270         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
271 }
272
273 CFQ_CFQQ_FNS(on_rr);
274 CFQ_CFQQ_FNS(wait_request);
275 CFQ_CFQQ_FNS(must_dispatch);
276 CFQ_CFQQ_FNS(must_alloc_slice);
277 CFQ_CFQQ_FNS(fifo_expire);
278 CFQ_CFQQ_FNS(idle_window);
279 CFQ_CFQQ_FNS(prio_changed);
280 CFQ_CFQQ_FNS(slice_new);
281 CFQ_CFQQ_FNS(sync);
282 CFQ_CFQQ_FNS(coop);
283 CFQ_CFQQ_FNS(coop_preempt);
284 #undef CFQ_CFQQ_FNS
285
286 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
287         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
288 #define cfq_log(cfqd, fmt, args...)     \
289         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
290
291 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
292 {
293         if (cfq_class_idle(cfqq))
294                 return IDLE_WORKLOAD;
295         if (cfq_class_rt(cfqq))
296                 return RT_WORKLOAD;
297         return BE_WORKLOAD;
298 }
299
300
301 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
302 {
303         if (!cfq_cfqq_sync(cfqq))
304                 return ASYNC_WORKLOAD;
305         if (!cfq_cfqq_idle_window(cfqq))
306                 return SYNC_NOIDLE_WORKLOAD;
307         return SYNC_WORKLOAD;
308 }
309
310 static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
311 {
312         if (wl == IDLE_WORKLOAD)
313                 return cfqd->service_tree_idle.count;
314
315         return cfqd->service_trees[wl][ASYNC_WORKLOAD].count
316                 + cfqd->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
317                 + cfqd->service_trees[wl][SYNC_WORKLOAD].count;
318 }
319
320 static void cfq_dispatch_insert(struct request_queue *, struct request *);
321 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
322                                        struct io_context *, gfp_t);
323 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
324                                                 struct io_context *);
325
326 static inline int rq_in_driver(struct cfq_data *cfqd)
327 {
328         return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
329 }
330
331 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
332                                             bool is_sync)
333 {
334         return cic->cfqq[is_sync];
335 }
336
337 static inline void cic_set_cfqq(struct cfq_io_context *cic,
338                                 struct cfq_queue *cfqq, bool is_sync)
339 {
340         cic->cfqq[is_sync] = cfqq;
341 }
342
343 /*
344  * We regard a request as SYNC, if it's either a read or has the SYNC bit
345  * set (in which case it could also be direct WRITE).
346  */
347 static inline bool cfq_bio_sync(struct bio *bio)
348 {
349         return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
350 }
351
352 /*
353  * scheduler run of queue, if there are requests pending and no one in the
354  * driver that will restart queueing
355  */
356 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
357 {
358         if (cfqd->busy_queues) {
359                 cfq_log(cfqd, "schedule dispatch");
360                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
361         }
362 }
363
364 static int cfq_queue_empty(struct request_queue *q)
365 {
366         struct cfq_data *cfqd = q->elevator->elevator_data;
367
368         return !cfqd->busy_queues;
369 }
370
371 /*
372  * Scale schedule slice based on io priority. Use the sync time slice only
373  * if a queue is marked sync and has sync io queued. A sync queue with async
374  * io only, should not get full sync slice length.
375  */
376 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
377                                  unsigned short prio)
378 {
379         const int base_slice = cfqd->cfq_slice[sync];
380
381         WARN_ON(prio >= IOPRIO_BE_NR);
382
383         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
384 }
385
386 static inline int
387 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
388 {
389         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
390 }
391
392 /*
393  * get averaged number of queues of RT/BE priority.
394  * average is updated, with a formula that gives more weight to higher numbers,
395  * to quickly follows sudden increases and decrease slowly
396  */
397
398 static inline unsigned cfq_get_avg_queues(struct cfq_data *cfqd, bool rt)
399 {
400         unsigned min_q, max_q;
401         unsigned mult  = cfq_hist_divisor - 1;
402         unsigned round = cfq_hist_divisor / 2;
403         unsigned busy = cfq_busy_queues_wl(rt, cfqd);
404
405         min_q = min(cfqd->busy_queues_avg[rt], busy);
406         max_q = max(cfqd->busy_queues_avg[rt], busy);
407         cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
408                 cfq_hist_divisor;
409         return cfqd->busy_queues_avg[rt];
410 }
411
412 static inline void
413 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
414 {
415         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
416         if (cfqd->cfq_latency) {
417                 /* interested queues (we consider only the ones with the same
418                  * priority class) */
419                 unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq));
420                 unsigned sync_slice = cfqd->cfq_slice[1];
421                 unsigned expect_latency = sync_slice * iq;
422                 if (expect_latency > cfq_target_latency) {
423                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
424                         /* scale low_slice according to IO priority
425                          * and sync vs async */
426                         unsigned low_slice =
427                                 min(slice, base_low_slice * slice / sync_slice);
428                         /* the adapted slice value is scaled to fit all iqs
429                          * into the target latency */
430                         slice = max(slice * cfq_target_latency / expect_latency,
431                                     low_slice);
432                 }
433         }
434         cfqq->slice_end = jiffies + slice;
435         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
436 }
437
438 /*
439  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
440  * isn't valid until the first request from the dispatch is activated
441  * and the slice time set.
442  */
443 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
444 {
445         if (cfq_cfqq_slice_new(cfqq))
446                 return 0;
447         if (time_before(jiffies, cfqq->slice_end))
448                 return 0;
449
450         return 1;
451 }
452
453 /*
454  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
455  * We choose the request that is closest to the head right now. Distance
456  * behind the head is penalized and only allowed to a certain extent.
457  */
458 static struct request *
459 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
460 {
461         sector_t last, s1, s2, d1 = 0, d2 = 0;
462         unsigned long back_max;
463 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
464 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
465         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
466
467         if (rq1 == NULL || rq1 == rq2)
468                 return rq2;
469         if (rq2 == NULL)
470                 return rq1;
471
472         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
473                 return rq1;
474         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
475                 return rq2;
476         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
477                 return rq1;
478         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
479                 return rq2;
480
481         s1 = blk_rq_pos(rq1);
482         s2 = blk_rq_pos(rq2);
483
484         last = cfqd->last_position;
485
486         /*
487          * by definition, 1KiB is 2 sectors
488          */
489         back_max = cfqd->cfq_back_max * 2;
490
491         /*
492          * Strict one way elevator _except_ in the case where we allow
493          * short backward seeks which are biased as twice the cost of a
494          * similar forward seek.
495          */
496         if (s1 >= last)
497                 d1 = s1 - last;
498         else if (s1 + back_max >= last)
499                 d1 = (last - s1) * cfqd->cfq_back_penalty;
500         else
501                 wrap |= CFQ_RQ1_WRAP;
502
503         if (s2 >= last)
504                 d2 = s2 - last;
505         else if (s2 + back_max >= last)
506                 d2 = (last - s2) * cfqd->cfq_back_penalty;
507         else
508                 wrap |= CFQ_RQ2_WRAP;
509
510         /* Found required data */
511
512         /*
513          * By doing switch() on the bit mask "wrap" we avoid having to
514          * check two variables for all permutations: --> faster!
515          */
516         switch (wrap) {
517         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
518                 if (d1 < d2)
519                         return rq1;
520                 else if (d2 < d1)
521                         return rq2;
522                 else {
523                         if (s1 >= s2)
524                                 return rq1;
525                         else
526                                 return rq2;
527                 }
528
529         case CFQ_RQ2_WRAP:
530                 return rq1;
531         case CFQ_RQ1_WRAP:
532                 return rq2;
533         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
534         default:
535                 /*
536                  * Since both rqs are wrapped,
537                  * start with the one that's further behind head
538                  * (--> only *one* back seek required),
539                  * since back seek takes more time than forward.
540                  */
541                 if (s1 <= s2)
542                         return rq1;
543                 else
544                         return rq2;
545         }
546 }
547
548 /*
549  * The below is leftmost cache rbtree addon
550  */
551 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
552 {
553         if (!root->left)
554                 root->left = rb_first(&root->rb);
555
556         if (root->left)
557                 return rb_entry(root->left, struct cfq_queue, rb_node);
558
559         return NULL;
560 }
561
562 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
563 {
564         rb_erase(n, root);
565         RB_CLEAR_NODE(n);
566 }
567
568 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
569 {
570         if (root->left == n)
571                 root->left = NULL;
572         rb_erase_init(n, &root->rb);
573         --root->count;
574 }
575
576 /*
577  * would be nice to take fifo expire time into account as well
578  */
579 static struct request *
580 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
581                   struct request *last)
582 {
583         struct rb_node *rbnext = rb_next(&last->rb_node);
584         struct rb_node *rbprev = rb_prev(&last->rb_node);
585         struct request *next = NULL, *prev = NULL;
586
587         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
588
589         if (rbprev)
590                 prev = rb_entry_rq(rbprev);
591
592         if (rbnext)
593                 next = rb_entry_rq(rbnext);
594         else {
595                 rbnext = rb_first(&cfqq->sort_list);
596                 if (rbnext && rbnext != &last->rb_node)
597                         next = rb_entry_rq(rbnext);
598         }
599
600         return cfq_choose_req(cfqd, next, prev);
601 }
602
603 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
604                                       struct cfq_queue *cfqq)
605 {
606         /*
607          * just an approximation, should be ok.
608          */
609         return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
610                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
611 }
612
613 /*
614  * The cfqd->service_trees holds all pending cfq_queue's that have
615  * requests waiting to be processed. It is sorted in the order that
616  * we will service the queues.
617  */
618 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
619                                  bool add_front)
620 {
621         struct rb_node **p, *parent;
622         struct cfq_queue *__cfqq;
623         unsigned long rb_key;
624         struct cfq_rb_root *service_tree;
625         int left;
626
627         service_tree = service_tree_for(cfqq_prio(cfqq), cfqq_type(cfqq), cfqd);
628         if (cfq_class_idle(cfqq)) {
629                 rb_key = CFQ_IDLE_DELAY;
630                 parent = rb_last(&service_tree->rb);
631                 if (parent && parent != &cfqq->rb_node) {
632                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
633                         rb_key += __cfqq->rb_key;
634                 } else
635                         rb_key += jiffies;
636         } else if (!add_front) {
637                 /*
638                  * Get our rb key offset. Subtract any residual slice
639                  * value carried from last service. A negative resid
640                  * count indicates slice overrun, and this should position
641                  * the next service time further away in the tree.
642                  */
643                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
644                 rb_key -= cfqq->slice_resid;
645                 cfqq->slice_resid = 0;
646         } else {
647                 rb_key = -HZ;
648                 __cfqq = cfq_rb_first(service_tree);
649                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
650         }
651
652         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
653                 /*
654                  * same position, nothing more to do
655                  */
656                 if (rb_key == cfqq->rb_key &&
657                     cfqq->service_tree == service_tree)
658                         return;
659
660                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
661                 cfqq->service_tree = NULL;
662         }
663
664         left = 1;
665         parent = NULL;
666         cfqq->service_tree = service_tree;
667         p = &service_tree->rb.rb_node;
668         while (*p) {
669                 struct rb_node **n;
670
671                 parent = *p;
672                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
673
674                 /*
675                  * sort by key, that represents service time.
676                  */
677                 if (time_before(rb_key, __cfqq->rb_key))
678                         n = &(*p)->rb_left;
679                 else {
680                         n = &(*p)->rb_right;
681                         left = 0;
682                 }
683
684                 p = n;
685         }
686
687         if (left)
688                 service_tree->left = &cfqq->rb_node;
689
690         cfqq->rb_key = rb_key;
691         rb_link_node(&cfqq->rb_node, parent, p);
692         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
693         service_tree->count++;
694 }
695
696 static struct cfq_queue *
697 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
698                      sector_t sector, struct rb_node **ret_parent,
699                      struct rb_node ***rb_link)
700 {
701         struct rb_node **p, *parent;
702         struct cfq_queue *cfqq = NULL;
703
704         parent = NULL;
705         p = &root->rb_node;
706         while (*p) {
707                 struct rb_node **n;
708
709                 parent = *p;
710                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
711
712                 /*
713                  * Sort strictly based on sector.  Smallest to the left,
714                  * largest to the right.
715                  */
716                 if (sector > blk_rq_pos(cfqq->next_rq))
717                         n = &(*p)->rb_right;
718                 else if (sector < blk_rq_pos(cfqq->next_rq))
719                         n = &(*p)->rb_left;
720                 else
721                         break;
722                 p = n;
723                 cfqq = NULL;
724         }
725
726         *ret_parent = parent;
727         if (rb_link)
728                 *rb_link = p;
729         return cfqq;
730 }
731
732 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
733 {
734         struct rb_node **p, *parent;
735         struct cfq_queue *__cfqq;
736
737         if (cfqq->p_root) {
738                 rb_erase(&cfqq->p_node, cfqq->p_root);
739                 cfqq->p_root = NULL;
740         }
741
742         if (cfq_class_idle(cfqq))
743                 return;
744         if (!cfqq->next_rq)
745                 return;
746
747         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
748         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
749                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
750         if (!__cfqq) {
751                 rb_link_node(&cfqq->p_node, parent, p);
752                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
753         } else
754                 cfqq->p_root = NULL;
755 }
756
757 /*
758  * Update cfqq's position in the service tree.
759  */
760 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
761 {
762         /*
763          * Resorting requires the cfqq to be on the RR list already.
764          */
765         if (cfq_cfqq_on_rr(cfqq)) {
766                 cfq_service_tree_add(cfqd, cfqq, 0);
767                 cfq_prio_tree_add(cfqd, cfqq);
768         }
769 }
770
771 /*
772  * add to busy list of queues for service, trying to be fair in ordering
773  * the pending list according to last request service
774  */
775 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
776 {
777         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
778         BUG_ON(cfq_cfqq_on_rr(cfqq));
779         cfq_mark_cfqq_on_rr(cfqq);
780         cfqd->busy_queues++;
781
782         cfq_resort_rr_list(cfqd, cfqq);
783 }
784
785 /*
786  * Called when the cfqq no longer has requests pending, remove it from
787  * the service tree.
788  */
789 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
790 {
791         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
792         BUG_ON(!cfq_cfqq_on_rr(cfqq));
793         cfq_clear_cfqq_on_rr(cfqq);
794
795         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
796                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
797                 cfqq->service_tree = NULL;
798         }
799         if (cfqq->p_root) {
800                 rb_erase(&cfqq->p_node, cfqq->p_root);
801                 cfqq->p_root = NULL;
802         }
803
804         BUG_ON(!cfqd->busy_queues);
805         cfqd->busy_queues--;
806 }
807
808 /*
809  * rb tree support functions
810  */
811 static void cfq_del_rq_rb(struct request *rq)
812 {
813         struct cfq_queue *cfqq = RQ_CFQQ(rq);
814         struct cfq_data *cfqd = cfqq->cfqd;
815         const int sync = rq_is_sync(rq);
816
817         BUG_ON(!cfqq->queued[sync]);
818         cfqq->queued[sync]--;
819
820         elv_rb_del(&cfqq->sort_list, rq);
821
822         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
823                 cfq_del_cfqq_rr(cfqd, cfqq);
824 }
825
826 static void cfq_add_rq_rb(struct request *rq)
827 {
828         struct cfq_queue *cfqq = RQ_CFQQ(rq);
829         struct cfq_data *cfqd = cfqq->cfqd;
830         struct request *__alias, *prev;
831
832         cfqq->queued[rq_is_sync(rq)]++;
833
834         /*
835          * looks a little odd, but the first insert might return an alias.
836          * if that happens, put the alias on the dispatch list
837          */
838         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
839                 cfq_dispatch_insert(cfqd->queue, __alias);
840
841         if (!cfq_cfqq_on_rr(cfqq))
842                 cfq_add_cfqq_rr(cfqd, cfqq);
843
844         /*
845          * check if this request is a better next-serve candidate
846          */
847         prev = cfqq->next_rq;
848         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
849
850         /*
851          * adjust priority tree position, if ->next_rq changes
852          */
853         if (prev != cfqq->next_rq)
854                 cfq_prio_tree_add(cfqd, cfqq);
855
856         BUG_ON(!cfqq->next_rq);
857 }
858
859 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
860 {
861         elv_rb_del(&cfqq->sort_list, rq);
862         cfqq->queued[rq_is_sync(rq)]--;
863         cfq_add_rq_rb(rq);
864 }
865
866 static struct request *
867 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
868 {
869         struct task_struct *tsk = current;
870         struct cfq_io_context *cic;
871         struct cfq_queue *cfqq;
872
873         cic = cfq_cic_lookup(cfqd, tsk->io_context);
874         if (!cic)
875                 return NULL;
876
877         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
878         if (cfqq) {
879                 sector_t sector = bio->bi_sector + bio_sectors(bio);
880
881                 return elv_rb_find(&cfqq->sort_list, sector);
882         }
883
884         return NULL;
885 }
886
887 static void cfq_activate_request(struct request_queue *q, struct request *rq)
888 {
889         struct cfq_data *cfqd = q->elevator->elevator_data;
890
891         cfqd->rq_in_driver[rq_is_sync(rq)]++;
892         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
893                                                 rq_in_driver(cfqd));
894
895         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
896 }
897
898 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
899 {
900         struct cfq_data *cfqd = q->elevator->elevator_data;
901         const int sync = rq_is_sync(rq);
902
903         WARN_ON(!cfqd->rq_in_driver[sync]);
904         cfqd->rq_in_driver[sync]--;
905         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
906                                                 rq_in_driver(cfqd));
907 }
908
909 static void cfq_remove_request(struct request *rq)
910 {
911         struct cfq_queue *cfqq = RQ_CFQQ(rq);
912
913         if (cfqq->next_rq == rq)
914                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
915
916         list_del_init(&rq->queuelist);
917         cfq_del_rq_rb(rq);
918
919         cfqq->cfqd->rq_queued--;
920         if (rq_is_meta(rq)) {
921                 WARN_ON(!cfqq->meta_pending);
922                 cfqq->meta_pending--;
923         }
924 }
925
926 static int cfq_merge(struct request_queue *q, struct request **req,
927                      struct bio *bio)
928 {
929         struct cfq_data *cfqd = q->elevator->elevator_data;
930         struct request *__rq;
931
932         __rq = cfq_find_rq_fmerge(cfqd, bio);
933         if (__rq && elv_rq_merge_ok(__rq, bio)) {
934                 *req = __rq;
935                 return ELEVATOR_FRONT_MERGE;
936         }
937
938         return ELEVATOR_NO_MERGE;
939 }
940
941 static void cfq_merged_request(struct request_queue *q, struct request *req,
942                                int type)
943 {
944         if (type == ELEVATOR_FRONT_MERGE) {
945                 struct cfq_queue *cfqq = RQ_CFQQ(req);
946
947                 cfq_reposition_rq_rb(cfqq, req);
948         }
949 }
950
951 static void
952 cfq_merged_requests(struct request_queue *q, struct request *rq,
953                     struct request *next)
954 {
955         /*
956          * reposition in fifo if next is older than rq
957          */
958         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
959             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
960                 list_move(&rq->queuelist, &next->queuelist);
961                 rq_set_fifo_time(rq, rq_fifo_time(next));
962         }
963
964         cfq_remove_request(next);
965 }
966
967 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
968                            struct bio *bio)
969 {
970         struct cfq_data *cfqd = q->elevator->elevator_data;
971         struct cfq_io_context *cic;
972         struct cfq_queue *cfqq;
973
974         /*
975          * Disallow merge of a sync bio into an async request.
976          */
977         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
978                 return false;
979
980         /*
981          * Lookup the cfqq that this bio will be queued with. Allow
982          * merge only if rq is queued there.
983          */
984         cic = cfq_cic_lookup(cfqd, current->io_context);
985         if (!cic)
986                 return false;
987
988         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
989         return cfqq == RQ_CFQQ(rq);
990 }
991
992 static void __cfq_set_active_queue(struct cfq_data *cfqd,
993                                    struct cfq_queue *cfqq)
994 {
995         if (cfqq) {
996                 cfq_log_cfqq(cfqd, cfqq, "set_active");
997                 cfqq->slice_end = 0;
998                 cfqq->slice_dispatch = 0;
999
1000                 cfq_clear_cfqq_wait_request(cfqq);
1001                 cfq_clear_cfqq_must_dispatch(cfqq);
1002                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1003                 cfq_clear_cfqq_fifo_expire(cfqq);
1004                 cfq_mark_cfqq_slice_new(cfqq);
1005
1006                 del_timer(&cfqd->idle_slice_timer);
1007         }
1008
1009         cfqd->active_queue = cfqq;
1010 }
1011
1012 /*
1013  * current cfqq expired its slice (or was too idle), select new one
1014  */
1015 static void
1016 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1017                     bool timed_out)
1018 {
1019         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1020
1021         if (cfq_cfqq_wait_request(cfqq))
1022                 del_timer(&cfqd->idle_slice_timer);
1023
1024         cfq_clear_cfqq_wait_request(cfqq);
1025
1026         /*
1027          * store what was left of this slice, if the queue idled/timed out
1028          */
1029         if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1030                 cfqq->slice_resid = cfqq->slice_end - jiffies;
1031                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1032         }
1033
1034         cfq_resort_rr_list(cfqd, cfqq);
1035
1036         if (cfqq == cfqd->active_queue)
1037                 cfqd->active_queue = NULL;
1038
1039         if (cfqd->active_cic) {
1040                 put_io_context(cfqd->active_cic->ioc);
1041                 cfqd->active_cic = NULL;
1042         }
1043 }
1044
1045 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1046 {
1047         struct cfq_queue *cfqq = cfqd->active_queue;
1048
1049         if (cfqq)
1050                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1051 }
1052
1053 /*
1054  * Get next queue for service. Unless we have a queue preemption,
1055  * we'll simply select the first cfqq in the service tree.
1056  */
1057 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1058 {
1059         struct cfq_rb_root *service_tree =
1060                 service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd);
1061
1062         if (RB_EMPTY_ROOT(&service_tree->rb))
1063                 return NULL;
1064         return cfq_rb_first(service_tree);
1065 }
1066
1067 /*
1068  * Get and set a new active queue for service.
1069  */
1070 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1071                                               struct cfq_queue *cfqq)
1072 {
1073         if (!cfqq) {
1074                 cfqq = cfq_get_next_queue(cfqd);
1075
1076                 if (cfqq && !cfq_cfqq_coop_preempt(cfqq))
1077                         cfq_clear_cfqq_coop(cfqq);
1078         }
1079
1080         if (cfqq)
1081                 cfq_clear_cfqq_coop_preempt(cfqq);
1082
1083         __cfq_set_active_queue(cfqd, cfqq);
1084         return cfqq;
1085 }
1086
1087 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1088                                           struct request *rq)
1089 {
1090         if (blk_rq_pos(rq) >= cfqd->last_position)
1091                 return blk_rq_pos(rq) - cfqd->last_position;
1092         else
1093                 return cfqd->last_position - blk_rq_pos(rq);
1094 }
1095
1096 #define CFQQ_SEEK_THR           8 * 1024
1097 #define CFQQ_SEEKY(cfqq)        ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1098
1099 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1100                                struct request *rq)
1101 {
1102         sector_t sdist = cfqq->seek_mean;
1103
1104         if (!sample_valid(cfqq->seek_samples))
1105                 sdist = CFQQ_SEEK_THR;
1106
1107         return cfq_dist_from_last(cfqd, rq) <= sdist;
1108 }
1109
1110 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1111                                     struct cfq_queue *cur_cfqq)
1112 {
1113         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1114         struct rb_node *parent, *node;
1115         struct cfq_queue *__cfqq;
1116         sector_t sector = cfqd->last_position;
1117
1118         if (RB_EMPTY_ROOT(root))
1119                 return NULL;
1120
1121         /*
1122          * First, if we find a request starting at the end of the last
1123          * request, choose it.
1124          */
1125         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1126         if (__cfqq)
1127                 return __cfqq;
1128
1129         /*
1130          * If the exact sector wasn't found, the parent of the NULL leaf
1131          * will contain the closest sector.
1132          */
1133         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1134         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1135                 return __cfqq;
1136
1137         if (blk_rq_pos(__cfqq->next_rq) < sector)
1138                 node = rb_next(&__cfqq->p_node);
1139         else
1140                 node = rb_prev(&__cfqq->p_node);
1141         if (!node)
1142                 return NULL;
1143
1144         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1145         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1146                 return __cfqq;
1147
1148         return NULL;
1149 }
1150
1151 /*
1152  * cfqd - obvious
1153  * cur_cfqq - passed in so that we don't decide that the current queue is
1154  *            closely cooperating with itself.
1155  *
1156  * So, basically we're assuming that that cur_cfqq has dispatched at least
1157  * one request, and that cfqd->last_position reflects a position on the disk
1158  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1159  * assumption.
1160  */
1161 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1162                                               struct cfq_queue *cur_cfqq)
1163 {
1164         struct cfq_queue *cfqq;
1165
1166         if (!cfq_cfqq_sync(cur_cfqq))
1167                 return NULL;
1168         if (CFQQ_SEEKY(cur_cfqq))
1169                 return NULL;
1170
1171         /*
1172          * We should notice if some of the queues are cooperating, eg
1173          * working closely on the same area of the disk. In that case,
1174          * we can group them together and don't waste time idling.
1175          */
1176         cfqq = cfqq_close(cfqd, cur_cfqq);
1177         if (!cfqq)
1178                 return NULL;
1179
1180         /*
1181          * It only makes sense to merge sync queues.
1182          */
1183         if (!cfq_cfqq_sync(cfqq))
1184                 return NULL;
1185         if (CFQQ_SEEKY(cfqq))
1186                 return NULL;
1187
1188         /*
1189          * Do not merge queues of different priority classes
1190          */
1191         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1192                 return NULL;
1193
1194         return cfqq;
1195 }
1196
1197 /*
1198  * Determine whether we should enforce idle window for this queue.
1199  */
1200
1201 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1202 {
1203         enum wl_prio_t prio = cfqq_prio(cfqq);
1204         struct cfq_rb_root *service_tree = cfqq->service_tree;
1205
1206         /* We never do for idle class queues. */
1207         if (prio == IDLE_WORKLOAD)
1208                 return false;
1209
1210         /* We do for queues that were marked with idle window flag. */
1211         if (cfq_cfqq_idle_window(cfqq))
1212                 return true;
1213
1214         /*
1215          * Otherwise, we do only if they are the last ones
1216          * in their service tree.
1217          */
1218         if (!service_tree)
1219                 service_tree = service_tree_for(prio, cfqq_type(cfqq), cfqd);
1220
1221         if (service_tree->count == 0)
1222                 return true;
1223
1224         return (service_tree->count == 1 && cfq_rb_first(service_tree) == cfqq);
1225 }
1226
1227 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1228 {
1229         struct cfq_queue *cfqq = cfqd->active_queue;
1230         struct cfq_io_context *cic;
1231         unsigned long sl;
1232
1233         /*
1234          * SSD device without seek penalty, disable idling. But only do so
1235          * for devices that support queuing, otherwise we still have a problem
1236          * with sync vs async workloads.
1237          */
1238         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1239                 return;
1240
1241         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1242         WARN_ON(cfq_cfqq_slice_new(cfqq));
1243
1244         /*
1245          * idle is disabled, either manually or by past process history
1246          */
1247         if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1248                 return;
1249
1250         /*
1251          * still requests with the driver, don't idle
1252          */
1253         if (rq_in_driver(cfqd))
1254                 return;
1255
1256         /*
1257          * task has exited, don't wait
1258          */
1259         cic = cfqd->active_cic;
1260         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1261                 return;
1262
1263         /*
1264          * If our average think time is larger than the remaining time
1265          * slice, then don't idle. This avoids overrunning the allotted
1266          * time slice.
1267          */
1268         if (sample_valid(cic->ttime_samples) &&
1269             (cfqq->slice_end - jiffies < cic->ttime_mean))
1270                 return;
1271
1272         cfq_mark_cfqq_wait_request(cfqq);
1273
1274         sl = cfqd->cfq_slice_idle;
1275         /* are we servicing noidle tree, and there are more queues?
1276          * non-rotational or NCQ: no idle
1277          * non-NCQ rotational : very small idle, to allow
1278          *     fair distribution of slice time for a process doing back-to-back
1279          *     seeks.
1280          */
1281         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
1282             service_tree_for(cfqd->serving_prio, SYNC_NOIDLE_WORKLOAD, cfqd)
1283                 ->count > 0) {
1284                 if (blk_queue_nonrot(cfqd->queue) || cfqd->hw_tag)
1285                         return;
1286                 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
1287         }
1288
1289         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1290         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1291 }
1292
1293 /*
1294  * Move request from internal lists to the request queue dispatch list.
1295  */
1296 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1297 {
1298         struct cfq_data *cfqd = q->elevator->elevator_data;
1299         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1300
1301         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1302
1303         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1304         cfq_remove_request(rq);
1305         cfqq->dispatched++;
1306         elv_dispatch_sort(q, rq);
1307
1308         if (cfq_cfqq_sync(cfqq))
1309                 cfqd->sync_flight++;
1310 }
1311
1312 /*
1313  * return expired entry, or NULL to just start from scratch in rbtree
1314  */
1315 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1316 {
1317         struct request *rq = NULL;
1318
1319         if (cfq_cfqq_fifo_expire(cfqq))
1320                 return NULL;
1321
1322         cfq_mark_cfqq_fifo_expire(cfqq);
1323
1324         if (list_empty(&cfqq->fifo))
1325                 return NULL;
1326
1327         rq = rq_entry_fifo(cfqq->fifo.next);
1328         if (time_before(jiffies, rq_fifo_time(rq)))
1329                 rq = NULL;
1330
1331         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1332         return rq;
1333 }
1334
1335 static inline int
1336 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1337 {
1338         const int base_rq = cfqd->cfq_slice_async_rq;
1339
1340         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1341
1342         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1343 }
1344
1345 /*
1346  * Must be called with the queue_lock held.
1347  */
1348 static int cfqq_process_refs(struct cfq_queue *cfqq)
1349 {
1350         int process_refs, io_refs;
1351
1352         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1353         process_refs = atomic_read(&cfqq->ref) - io_refs;
1354         BUG_ON(process_refs < 0);
1355         return process_refs;
1356 }
1357
1358 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1359 {
1360         int process_refs, new_process_refs;
1361         struct cfq_queue *__cfqq;
1362
1363         /* Avoid a circular list and skip interim queue merges */
1364         while ((__cfqq = new_cfqq->new_cfqq)) {
1365                 if (__cfqq == cfqq)
1366                         return;
1367                 new_cfqq = __cfqq;
1368         }
1369
1370         process_refs = cfqq_process_refs(cfqq);
1371         /*
1372          * If the process for the cfqq has gone away, there is no
1373          * sense in merging the queues.
1374          */
1375         if (process_refs == 0)
1376                 return;
1377
1378         /*
1379          * Merge in the direction of the lesser amount of work.
1380          */
1381         new_process_refs = cfqq_process_refs(new_cfqq);
1382         if (new_process_refs >= process_refs) {
1383                 cfqq->new_cfqq = new_cfqq;
1384                 atomic_add(process_refs, &new_cfqq->ref);
1385         } else {
1386                 new_cfqq->new_cfqq = cfqq;
1387                 atomic_add(new_process_refs, &cfqq->ref);
1388         }
1389 }
1390
1391 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, enum wl_prio_t prio,
1392                                     bool prio_changed)
1393 {
1394         struct cfq_queue *queue;
1395         int i;
1396         bool key_valid = false;
1397         unsigned long lowest_key = 0;
1398         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1399
1400         if (prio_changed) {
1401                 /*
1402                  * When priorities switched, we prefer starting
1403                  * from SYNC_NOIDLE (first choice), or just SYNC
1404                  * over ASYNC
1405                  */
1406                 if (service_tree_for(prio, cur_best, cfqd)->count)
1407                         return cur_best;
1408                 cur_best = SYNC_WORKLOAD;
1409                 if (service_tree_for(prio, cur_best, cfqd)->count)
1410                         return cur_best;
1411
1412                 return ASYNC_WORKLOAD;
1413         }
1414
1415         for (i = 0; i < 3; ++i) {
1416                 /* otherwise, select the one with lowest rb_key */
1417                 queue = cfq_rb_first(service_tree_for(prio, i, cfqd));
1418                 if (queue &&
1419                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
1420                         lowest_key = queue->rb_key;
1421                         cur_best = i;
1422                         key_valid = true;
1423                 }
1424         }
1425
1426         return cur_best;
1427 }
1428
1429 static void choose_service_tree(struct cfq_data *cfqd)
1430 {
1431         enum wl_prio_t previous_prio = cfqd->serving_prio;
1432         bool prio_changed;
1433         unsigned slice;
1434         unsigned count;
1435
1436         /* Choose next priority. RT > BE > IDLE */
1437         if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
1438                 cfqd->serving_prio = RT_WORKLOAD;
1439         else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd))
1440                 cfqd->serving_prio = BE_WORKLOAD;
1441         else {
1442                 cfqd->serving_prio = IDLE_WORKLOAD;
1443                 cfqd->workload_expires = jiffies + 1;
1444                 return;
1445         }
1446
1447         /*
1448          * For RT and BE, we have to choose also the type
1449          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1450          * expiration time
1451          */
1452         prio_changed = (cfqd->serving_prio != previous_prio);
1453         count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1454                 ->count;
1455
1456         /*
1457          * If priority didn't change, check workload expiration,
1458          * and that we still have other queues ready
1459          */
1460         if (!prio_changed && count &&
1461             !time_after(jiffies, cfqd->workload_expires))
1462                 return;
1463
1464         /* otherwise select new workload type */
1465         cfqd->serving_type =
1466                 cfq_choose_wl(cfqd, cfqd->serving_prio, prio_changed);
1467         count = service_tree_for(cfqd->serving_prio, cfqd->serving_type, cfqd)
1468                 ->count;
1469
1470         /*
1471          * the workload slice is computed as a fraction of target latency
1472          * proportional to the number of queues in that workload, over
1473          * all the queues in the same priority class
1474          */
1475         slice = cfq_target_latency * count /
1476                 max_t(unsigned, cfqd->busy_queues_avg[cfqd->serving_prio],
1477                       cfq_busy_queues_wl(cfqd->serving_prio, cfqd));
1478
1479         if (cfqd->serving_type == ASYNC_WORKLOAD)
1480                 /* async workload slice is scaled down according to
1481                  * the sync/async slice ratio. */
1482                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
1483         else
1484                 /* sync workload slice is at least 2 * cfq_slice_idle */
1485                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
1486
1487         slice = max_t(unsigned, slice, CFQ_MIN_TT);
1488         cfqd->workload_expires = jiffies + slice;
1489 }
1490
1491 /*
1492  * Select a queue for service. If we have a current active queue,
1493  * check whether to continue servicing it, or retrieve and set a new one.
1494  */
1495 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1496 {
1497         struct cfq_queue *cfqq, *new_cfqq = NULL;
1498
1499         cfqq = cfqd->active_queue;
1500         if (!cfqq)
1501                 goto new_queue;
1502
1503         /*
1504          * The active queue has run out of time, expire it and select new.
1505          */
1506         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1507                 goto expire;
1508
1509         /*
1510          * The active queue has requests and isn't expired, allow it to
1511          * dispatch.
1512          */
1513         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1514                 goto keep_queue;
1515
1516         /*
1517          * If another queue has a request waiting within our mean seek
1518          * distance, let it run.  The expire code will check for close
1519          * cooperators and put the close queue at the front of the service
1520          * tree.  If possible, merge the expiring queue with the new cfqq.
1521          */
1522         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
1523         if (new_cfqq) {
1524                 if (!cfqq->new_cfqq)
1525                         cfq_setup_merge(cfqq, new_cfqq);
1526                 goto expire;
1527         }
1528
1529         /*
1530          * No requests pending. If the active queue still has requests in
1531          * flight or is idling for a new request, allow either of these
1532          * conditions to happen (or time out) before selecting a new queue.
1533          */
1534         if (timer_pending(&cfqd->idle_slice_timer) ||
1535             (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
1536                 cfqq = NULL;
1537                 goto keep_queue;
1538         }
1539
1540 expire:
1541         cfq_slice_expired(cfqd, 0);
1542 new_queue:
1543         /*
1544          * Current queue expired. Check if we have to switch to a new
1545          * service tree
1546          */
1547         if (!new_cfqq)
1548                 choose_service_tree(cfqd);
1549
1550         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1551 keep_queue:
1552         return cfqq;
1553 }
1554
1555 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1556 {
1557         int dispatched = 0;
1558
1559         while (cfqq->next_rq) {
1560                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1561                 dispatched++;
1562         }
1563
1564         BUG_ON(!list_empty(&cfqq->fifo));
1565         return dispatched;
1566 }
1567
1568 /*
1569  * Drain our current requests. Used for barriers and when switching
1570  * io schedulers on-the-fly.
1571  */
1572 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1573 {
1574         struct cfq_queue *cfqq;
1575         int dispatched = 0;
1576         int i, j;
1577         for (i = 0; i < 2; ++i)
1578                 for (j = 0; j < 3; ++j)
1579                         while ((cfqq = cfq_rb_first(&cfqd->service_trees[i][j]))
1580                                 != NULL)
1581                                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1582
1583         while ((cfqq = cfq_rb_first(&cfqd->service_tree_idle)) != NULL)
1584                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1585
1586         cfq_slice_expired(cfqd, 0);
1587
1588         BUG_ON(cfqd->busy_queues);
1589
1590         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1591         return dispatched;
1592 }
1593
1594 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1595 {
1596         unsigned int max_dispatch;
1597
1598         /*
1599          * Drain async requests before we start sync IO
1600          */
1601         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
1602                 return false;
1603
1604         /*
1605          * If this is an async queue and we have sync IO in flight, let it wait
1606          */
1607         if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1608                 return false;
1609
1610         max_dispatch = cfqd->cfq_quantum;
1611         if (cfq_class_idle(cfqq))
1612                 max_dispatch = 1;
1613
1614         /*
1615          * Does this cfqq already have too much IO in flight?
1616          */
1617         if (cfqq->dispatched >= max_dispatch) {
1618                 /*
1619                  * idle queue must always only have a single IO in flight
1620                  */
1621                 if (cfq_class_idle(cfqq))
1622                         return false;
1623
1624                 /*
1625                  * We have other queues, don't allow more IO from this one
1626                  */
1627                 if (cfqd->busy_queues > 1)
1628                         return false;
1629
1630                 /*
1631                  * Sole queue user, allow bigger slice
1632                  */
1633                 max_dispatch *= 4;
1634         }
1635
1636         /*
1637          * Async queues must wait a bit before being allowed dispatch.
1638          * We also ramp up the dispatch depth gradually for async IO,
1639          * based on the last sync IO we serviced
1640          */
1641         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
1642                 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
1643                 unsigned int depth;
1644
1645                 depth = last_sync / cfqd->cfq_slice[1];
1646                 if (!depth && !cfqq->dispatched)
1647                         depth = 1;
1648                 if (depth < max_dispatch)
1649                         max_dispatch = depth;
1650         }
1651
1652         /*
1653          * If we're below the current max, allow a dispatch
1654          */
1655         return cfqq->dispatched < max_dispatch;
1656 }
1657
1658 /*
1659  * Dispatch a request from cfqq, moving them to the request queue
1660  * dispatch list.
1661  */
1662 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1663 {
1664         struct request *rq;
1665
1666         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1667
1668         if (!cfq_may_dispatch(cfqd, cfqq))
1669                 return false;
1670
1671         /*
1672          * follow expired path, else get first next available
1673          */
1674         rq = cfq_check_fifo(cfqq);
1675         if (!rq)
1676                 rq = cfqq->next_rq;
1677
1678         /*
1679          * insert request into driver dispatch list
1680          */
1681         cfq_dispatch_insert(cfqd->queue, rq);
1682
1683         if (!cfqd->active_cic) {
1684                 struct cfq_io_context *cic = RQ_CIC(rq);
1685
1686                 atomic_long_inc(&cic->ioc->refcount);
1687                 cfqd->active_cic = cic;
1688         }
1689
1690         return true;
1691 }
1692
1693 /*
1694  * Find the cfqq that we need to service and move a request from that to the
1695  * dispatch list
1696  */
1697 static int cfq_dispatch_requests(struct request_queue *q, int force)
1698 {
1699         struct cfq_data *cfqd = q->elevator->elevator_data;
1700         struct cfq_queue *cfqq;
1701
1702         if (!cfqd->busy_queues)
1703                 return 0;
1704
1705         if (unlikely(force))
1706                 return cfq_forced_dispatch(cfqd);
1707
1708         cfqq = cfq_select_queue(cfqd);
1709         if (!cfqq)
1710                 return 0;
1711
1712         /*
1713          * Dispatch a request from this cfqq, if it is allowed
1714          */
1715         if (!cfq_dispatch_request(cfqd, cfqq))
1716                 return 0;
1717
1718         cfqq->slice_dispatch++;
1719         cfq_clear_cfqq_must_dispatch(cfqq);
1720
1721         /*
1722          * expire an async queue immediately if it has used up its slice. idle
1723          * queue always expire after 1 dispatch round.
1724          */
1725         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1726             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1727             cfq_class_idle(cfqq))) {
1728                 cfqq->slice_end = jiffies + 1;
1729                 cfq_slice_expired(cfqd, 0);
1730         }
1731
1732         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
1733         return 1;
1734 }
1735
1736 /*
1737  * task holds one reference to the queue, dropped when task exits. each rq
1738  * in-flight on this queue also holds a reference, dropped when rq is freed.
1739  *
1740  * queue lock must be held here.
1741  */
1742 static void cfq_put_queue(struct cfq_queue *cfqq)
1743 {
1744         struct cfq_data *cfqd = cfqq->cfqd;
1745
1746         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1747
1748         if (!atomic_dec_and_test(&cfqq->ref))
1749                 return;
1750
1751         cfq_log_cfqq(cfqd, cfqq, "put_queue");
1752         BUG_ON(rb_first(&cfqq->sort_list));
1753         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1754         BUG_ON(cfq_cfqq_on_rr(cfqq));
1755
1756         if (unlikely(cfqd->active_queue == cfqq)) {
1757                 __cfq_slice_expired(cfqd, cfqq, 0);
1758                 cfq_schedule_dispatch(cfqd);
1759         }
1760
1761         kmem_cache_free(cfq_pool, cfqq);
1762 }
1763
1764 /*
1765  * Must always be called with the rcu_read_lock() held
1766  */
1767 static void
1768 __call_for_each_cic(struct io_context *ioc,
1769                     void (*func)(struct io_context *, struct cfq_io_context *))
1770 {
1771         struct cfq_io_context *cic;
1772         struct hlist_node *n;
1773
1774         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1775                 func(ioc, cic);
1776 }
1777
1778 /*
1779  * Call func for each cic attached to this ioc.
1780  */
1781 static void
1782 call_for_each_cic(struct io_context *ioc,
1783                   void (*func)(struct io_context *, struct cfq_io_context *))
1784 {
1785         rcu_read_lock();
1786         __call_for_each_cic(ioc, func);
1787         rcu_read_unlock();
1788 }
1789
1790 static void cfq_cic_free_rcu(struct rcu_head *head)
1791 {
1792         struct cfq_io_context *cic;
1793
1794         cic = container_of(head, struct cfq_io_context, rcu_head);
1795
1796         kmem_cache_free(cfq_ioc_pool, cic);
1797         elv_ioc_count_dec(cfq_ioc_count);
1798
1799         if (ioc_gone) {
1800                 /*
1801                  * CFQ scheduler is exiting, grab exit lock and check
1802                  * the pending io context count. If it hits zero,
1803                  * complete ioc_gone and set it back to NULL
1804                  */
1805                 spin_lock(&ioc_gone_lock);
1806                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
1807                         complete(ioc_gone);
1808                         ioc_gone = NULL;
1809                 }
1810                 spin_unlock(&ioc_gone_lock);
1811         }
1812 }
1813
1814 static void cfq_cic_free(struct cfq_io_context *cic)
1815 {
1816         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1817 }
1818
1819 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1820 {
1821         unsigned long flags;
1822
1823         BUG_ON(!cic->dead_key);
1824
1825         spin_lock_irqsave(&ioc->lock, flags);
1826         radix_tree_delete(&ioc->radix_root, cic->dead_key);
1827         hlist_del_rcu(&cic->cic_list);
1828         spin_unlock_irqrestore(&ioc->lock, flags);
1829
1830         cfq_cic_free(cic);
1831 }
1832
1833 /*
1834  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1835  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1836  * and ->trim() which is called with the task lock held
1837  */
1838 static void cfq_free_io_context(struct io_context *ioc)
1839 {
1840         /*
1841          * ioc->refcount is zero here, or we are called from elv_unregister(),
1842          * so no more cic's are allowed to be linked into this ioc.  So it
1843          * should be ok to iterate over the known list, we will see all cic's
1844          * since no new ones are added.
1845          */
1846         __call_for_each_cic(ioc, cic_free_func);
1847 }
1848
1849 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1850 {
1851         struct cfq_queue *__cfqq, *next;
1852
1853         if (unlikely(cfqq == cfqd->active_queue)) {
1854                 __cfq_slice_expired(cfqd, cfqq, 0);
1855                 cfq_schedule_dispatch(cfqd);
1856         }
1857
1858         /*
1859          * If this queue was scheduled to merge with another queue, be
1860          * sure to drop the reference taken on that queue (and others in
1861          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
1862          */
1863         __cfqq = cfqq->new_cfqq;
1864         while (__cfqq) {
1865                 if (__cfqq == cfqq) {
1866                         WARN(1, "cfqq->new_cfqq loop detected\n");
1867                         break;
1868                 }
1869                 next = __cfqq->new_cfqq;
1870                 cfq_put_queue(__cfqq);
1871                 __cfqq = next;
1872         }
1873
1874         cfq_put_queue(cfqq);
1875 }
1876
1877 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1878                                          struct cfq_io_context *cic)
1879 {
1880         struct io_context *ioc = cic->ioc;
1881
1882         list_del_init(&cic->queue_list);
1883
1884         /*
1885          * Make sure key == NULL is seen for dead queues
1886          */
1887         smp_wmb();
1888         cic->dead_key = (unsigned long) cic->key;
1889         cic->key = NULL;
1890
1891         if (ioc->ioc_data == cic)
1892                 rcu_assign_pointer(ioc->ioc_data, NULL);
1893
1894         if (cic->cfqq[BLK_RW_ASYNC]) {
1895                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1896                 cic->cfqq[BLK_RW_ASYNC] = NULL;
1897         }
1898
1899         if (cic->cfqq[BLK_RW_SYNC]) {
1900                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1901                 cic->cfqq[BLK_RW_SYNC] = NULL;
1902         }
1903 }
1904
1905 static void cfq_exit_single_io_context(struct io_context *ioc,
1906                                        struct cfq_io_context *cic)
1907 {
1908         struct cfq_data *cfqd = cic->key;
1909
1910         if (cfqd) {
1911                 struct request_queue *q = cfqd->queue;
1912                 unsigned long flags;
1913
1914                 spin_lock_irqsave(q->queue_lock, flags);
1915
1916                 /*
1917                  * Ensure we get a fresh copy of the ->key to prevent
1918                  * race between exiting task and queue
1919                  */
1920                 smp_read_barrier_depends();
1921                 if (cic->key)
1922                         __cfq_exit_single_io_context(cfqd, cic);
1923
1924                 spin_unlock_irqrestore(q->queue_lock, flags);
1925         }
1926 }
1927
1928 /*
1929  * The process that ioc belongs to has exited, we need to clean up
1930  * and put the internal structures we have that belongs to that process.
1931  */
1932 static void cfq_exit_io_context(struct io_context *ioc)
1933 {
1934         call_for_each_cic(ioc, cfq_exit_single_io_context);
1935 }
1936
1937 static struct cfq_io_context *
1938 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1939 {
1940         struct cfq_io_context *cic;
1941
1942         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1943                                                         cfqd->queue->node);
1944         if (cic) {
1945                 cic->last_end_request = jiffies;
1946                 INIT_LIST_HEAD(&cic->queue_list);
1947                 INIT_HLIST_NODE(&cic->cic_list);
1948                 cic->dtor = cfq_free_io_context;
1949                 cic->exit = cfq_exit_io_context;
1950                 elv_ioc_count_inc(cfq_ioc_count);
1951         }
1952
1953         return cic;
1954 }
1955
1956 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1957 {
1958         struct task_struct *tsk = current;
1959         int ioprio_class;
1960
1961         if (!cfq_cfqq_prio_changed(cfqq))
1962                 return;
1963
1964         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1965         switch (ioprio_class) {
1966         default:
1967                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1968         case IOPRIO_CLASS_NONE:
1969                 /*
1970                  * no prio set, inherit CPU scheduling settings
1971                  */
1972                 cfqq->ioprio = task_nice_ioprio(tsk);
1973                 cfqq->ioprio_class = task_nice_ioclass(tsk);
1974                 break;
1975         case IOPRIO_CLASS_RT:
1976                 cfqq->ioprio = task_ioprio(ioc);
1977                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1978                 break;
1979         case IOPRIO_CLASS_BE:
1980                 cfqq->ioprio = task_ioprio(ioc);
1981                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1982                 break;
1983         case IOPRIO_CLASS_IDLE:
1984                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1985                 cfqq->ioprio = 7;
1986                 cfq_clear_cfqq_idle_window(cfqq);
1987                 break;
1988         }
1989
1990         /*
1991          * keep track of original prio settings in case we have to temporarily
1992          * elevate the priority of this queue
1993          */
1994         cfqq->org_ioprio = cfqq->ioprio;
1995         cfqq->org_ioprio_class = cfqq->ioprio_class;
1996         cfq_clear_cfqq_prio_changed(cfqq);
1997 }
1998
1999 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2000 {
2001         struct cfq_data *cfqd = cic->key;
2002         struct cfq_queue *cfqq;
2003         unsigned long flags;
2004
2005         if (unlikely(!cfqd))
2006                 return;
2007
2008         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2009
2010         cfqq = cic->cfqq[BLK_RW_ASYNC];
2011         if (cfqq) {
2012                 struct cfq_queue *new_cfqq;
2013                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2014                                                 GFP_ATOMIC);
2015                 if (new_cfqq) {
2016                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2017                         cfq_put_queue(cfqq);
2018                 }
2019         }
2020
2021         cfqq = cic->cfqq[BLK_RW_SYNC];
2022         if (cfqq)
2023                 cfq_mark_cfqq_prio_changed(cfqq);
2024
2025         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2026 }
2027
2028 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2029 {
2030         call_for_each_cic(ioc, changed_ioprio);
2031         ioc->ioprio_changed = 0;
2032 }
2033
2034 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2035                           pid_t pid, bool is_sync)
2036 {
2037         RB_CLEAR_NODE(&cfqq->rb_node);
2038         RB_CLEAR_NODE(&cfqq->p_node);
2039         INIT_LIST_HEAD(&cfqq->fifo);
2040
2041         atomic_set(&cfqq->ref, 0);
2042         cfqq->cfqd = cfqd;
2043
2044         cfq_mark_cfqq_prio_changed(cfqq);
2045
2046         if (is_sync) {
2047                 if (!cfq_class_idle(cfqq))
2048                         cfq_mark_cfqq_idle_window(cfqq);
2049                 cfq_mark_cfqq_sync(cfqq);
2050         }
2051         cfqq->pid = pid;
2052 }
2053
2054 static struct cfq_queue *
2055 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2056                      struct io_context *ioc, gfp_t gfp_mask)
2057 {
2058         struct cfq_queue *cfqq, *new_cfqq = NULL;
2059         struct cfq_io_context *cic;
2060
2061 retry:
2062         cic = cfq_cic_lookup(cfqd, ioc);
2063         /* cic always exists here */
2064         cfqq = cic_to_cfqq(cic, is_sync);
2065
2066         /*
2067          * Always try a new alloc if we fell back to the OOM cfqq
2068          * originally, since it should just be a temporary situation.
2069          */
2070         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2071                 cfqq = NULL;
2072                 if (new_cfqq) {
2073                         cfqq = new_cfqq;
2074                         new_cfqq = NULL;
2075                 } else if (gfp_mask & __GFP_WAIT) {
2076                         spin_unlock_irq(cfqd->queue->queue_lock);
2077                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2078                                         gfp_mask | __GFP_ZERO,
2079                                         cfqd->queue->node);
2080                         spin_lock_irq(cfqd->queue->queue_lock);
2081                         if (new_cfqq)
2082                                 goto retry;
2083                 } else {
2084                         cfqq = kmem_cache_alloc_node(cfq_pool,
2085                                         gfp_mask | __GFP_ZERO,
2086                                         cfqd->queue->node);
2087                 }
2088
2089                 if (cfqq) {
2090                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2091                         cfq_init_prio_data(cfqq, ioc);
2092                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2093                 } else
2094                         cfqq = &cfqd->oom_cfqq;
2095         }
2096
2097         if (new_cfqq)
2098                 kmem_cache_free(cfq_pool, new_cfqq);
2099
2100         return cfqq;
2101 }
2102
2103 static struct cfq_queue **
2104 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2105 {
2106         switch (ioprio_class) {
2107         case IOPRIO_CLASS_RT:
2108                 return &cfqd->async_cfqq[0][ioprio];
2109         case IOPRIO_CLASS_BE:
2110                 return &cfqd->async_cfqq[1][ioprio];
2111         case IOPRIO_CLASS_IDLE:
2112                 return &cfqd->async_idle_cfqq;
2113         default:
2114                 BUG();
2115         }
2116 }
2117
2118 static struct cfq_queue *
2119 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2120               gfp_t gfp_mask)
2121 {
2122         const int ioprio = task_ioprio(ioc);
2123         const int ioprio_class = task_ioprio_class(ioc);
2124         struct cfq_queue **async_cfqq = NULL;
2125         struct cfq_queue *cfqq = NULL;
2126
2127         if (!is_sync) {
2128                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2129                 cfqq = *async_cfqq;
2130         }
2131
2132         if (!cfqq)
2133                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2134
2135         /*
2136          * pin the queue now that it's allocated, scheduler exit will prune it
2137          */
2138         if (!is_sync && !(*async_cfqq)) {
2139                 atomic_inc(&cfqq->ref);
2140                 *async_cfqq = cfqq;
2141         }
2142
2143         atomic_inc(&cfqq->ref);
2144         return cfqq;
2145 }
2146
2147 /*
2148  * We drop cfq io contexts lazily, so we may find a dead one.
2149  */
2150 static void
2151 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2152                   struct cfq_io_context *cic)
2153 {
2154         unsigned long flags;
2155
2156         WARN_ON(!list_empty(&cic->queue_list));
2157
2158         spin_lock_irqsave(&ioc->lock, flags);
2159
2160         BUG_ON(ioc->ioc_data == cic);
2161
2162         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2163         hlist_del_rcu(&cic->cic_list);
2164         spin_unlock_irqrestore(&ioc->lock, flags);
2165
2166         cfq_cic_free(cic);
2167 }
2168
2169 static struct cfq_io_context *
2170 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2171 {
2172         struct cfq_io_context *cic;
2173         unsigned long flags;
2174         void *k;
2175
2176         if (unlikely(!ioc))
2177                 return NULL;
2178
2179         rcu_read_lock();
2180
2181         /*
2182          * we maintain a last-hit cache, to avoid browsing over the tree
2183          */
2184         cic = rcu_dereference(ioc->ioc_data);
2185         if (cic && cic->key == cfqd) {
2186                 rcu_read_unlock();
2187                 return cic;
2188         }
2189
2190         do {
2191                 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2192                 rcu_read_unlock();
2193                 if (!cic)
2194                         break;
2195                 /* ->key must be copied to avoid race with cfq_exit_queue() */
2196                 k = cic->key;
2197                 if (unlikely(!k)) {
2198                         cfq_drop_dead_cic(cfqd, ioc, cic);
2199                         rcu_read_lock();
2200                         continue;
2201                 }
2202
2203                 spin_lock_irqsave(&ioc->lock, flags);
2204                 rcu_assign_pointer(ioc->ioc_data, cic);
2205                 spin_unlock_irqrestore(&ioc->lock, flags);
2206                 break;
2207         } while (1);
2208
2209         return cic;
2210 }
2211
2212 /*
2213  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2214  * the process specific cfq io context when entered from the block layer.
2215  * Also adds the cic to a per-cfqd list, used when this queue is removed.
2216  */
2217 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2218                         struct cfq_io_context *cic, gfp_t gfp_mask)
2219 {
2220         unsigned long flags;
2221         int ret;
2222
2223         ret = radix_tree_preload(gfp_mask);
2224         if (!ret) {
2225                 cic->ioc = ioc;
2226                 cic->key = cfqd;
2227
2228                 spin_lock_irqsave(&ioc->lock, flags);
2229                 ret = radix_tree_insert(&ioc->radix_root,
2230                                                 (unsigned long) cfqd, cic);
2231                 if (!ret)
2232                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2233                 spin_unlock_irqrestore(&ioc->lock, flags);
2234
2235                 radix_tree_preload_end();
2236
2237                 if (!ret) {
2238                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2239                         list_add(&cic->queue_list, &cfqd->cic_list);
2240                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2241                 }
2242         }
2243
2244         if (ret)
2245                 printk(KERN_ERR "cfq: cic link failed!\n");
2246
2247         return ret;
2248 }
2249
2250 /*
2251  * Setup general io context and cfq io context. There can be several cfq
2252  * io contexts per general io context, if this process is doing io to more
2253  * than one device managed by cfq.
2254  */
2255 static struct cfq_io_context *
2256 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2257 {
2258         struct io_context *ioc = NULL;
2259         struct cfq_io_context *cic;
2260
2261         might_sleep_if(gfp_mask & __GFP_WAIT);
2262
2263         ioc = get_io_context(gfp_mask, cfqd->queue->node);
2264         if (!ioc)
2265                 return NULL;
2266
2267         cic = cfq_cic_lookup(cfqd, ioc);
2268         if (cic)
2269                 goto out;
2270
2271         cic = cfq_alloc_io_context(cfqd, gfp_mask);
2272         if (cic == NULL)
2273                 goto err;
2274
2275         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2276                 goto err_free;
2277
2278 out:
2279         smp_read_barrier_depends();
2280         if (unlikely(ioc->ioprio_changed))
2281                 cfq_ioc_set_ioprio(ioc);
2282
2283         return cic;
2284 err_free:
2285         cfq_cic_free(cic);
2286 err:
2287         put_io_context(ioc);
2288         return NULL;
2289 }
2290
2291 static void
2292 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2293 {
2294         unsigned long elapsed = jiffies - cic->last_end_request;
2295         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2296
2297         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2298         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2299         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2300 }
2301
2302 static void
2303 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2304                        struct request *rq)
2305 {
2306         sector_t sdist;
2307         u64 total;
2308
2309         if (!cfqq->last_request_pos)
2310                 sdist = 0;
2311         else if (cfqq->last_request_pos < blk_rq_pos(rq))
2312                 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2313         else
2314                 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2315
2316         /*
2317          * Don't allow the seek distance to get too large from the
2318          * odd fragment, pagein, etc
2319          */
2320         if (cfqq->seek_samples <= 60) /* second&third seek */
2321                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2322         else
2323                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2324
2325         cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2326         cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2327         total = cfqq->seek_total + (cfqq->seek_samples/2);
2328         do_div(total, cfqq->seek_samples);
2329         cfqq->seek_mean = (sector_t)total;
2330
2331         /*
2332          * If this cfqq is shared between multiple processes, check to
2333          * make sure that those processes are still issuing I/Os within
2334          * the mean seek distance.  If not, it may be time to break the
2335          * queues apart again.
2336          */
2337         if (cfq_cfqq_coop(cfqq)) {
2338                 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2339                         cfqq->seeky_start = jiffies;
2340                 else if (!CFQQ_SEEKY(cfqq))
2341                         cfqq->seeky_start = 0;
2342         }
2343 }
2344
2345 /*
2346  * Disable idle window if the process thinks too long or seeks so much that
2347  * it doesn't matter
2348  */
2349 static void
2350 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2351                        struct cfq_io_context *cic)
2352 {
2353         int old_idle, enable_idle;
2354
2355         /*
2356          * Don't idle for async or idle io prio class
2357          */
2358         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2359                 return;
2360
2361         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2362
2363         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2364             (sample_valid(cfqq->seek_samples) && CFQQ_SEEKY(cfqq)))
2365                 enable_idle = 0;
2366         else if (sample_valid(cic->ttime_samples)) {
2367                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2368                         enable_idle = 0;
2369                 else
2370                         enable_idle = 1;
2371         }
2372
2373         if (old_idle != enable_idle) {
2374                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2375                 if (enable_idle)
2376                         cfq_mark_cfqq_idle_window(cfqq);
2377                 else
2378                         cfq_clear_cfqq_idle_window(cfqq);
2379         }
2380 }
2381
2382 /*
2383  * Check if new_cfqq should preempt the currently active queue. Return 0 for
2384  * no or if we aren't sure, a 1 will cause a preempt.
2385  */
2386 static bool
2387 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2388                    struct request *rq)
2389 {
2390         struct cfq_queue *cfqq;
2391
2392         cfqq = cfqd->active_queue;
2393         if (!cfqq)
2394                 return false;
2395
2396         if (cfq_slice_used(cfqq))
2397                 return true;
2398
2399         if (cfq_class_idle(new_cfqq))
2400                 return false;
2401
2402         if (cfq_class_idle(cfqq))
2403                 return true;
2404
2405         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD
2406             && new_cfqq->service_tree == cfqq->service_tree)
2407                 return true;
2408
2409         /*
2410          * if the new request is sync, but the currently running queue is
2411          * not, let the sync request have priority.
2412          */
2413         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2414                 return true;
2415
2416         /*
2417          * So both queues are sync. Let the new request get disk time if
2418          * it's a metadata request and the current queue is doing regular IO.
2419          */
2420         if (rq_is_meta(rq) && !cfqq->meta_pending)
2421                 return true;
2422
2423         /*
2424          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2425          */
2426         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2427                 return true;
2428
2429         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2430                 return false;
2431
2432         /*
2433          * if this request is as-good as one we would expect from the
2434          * current cfqq, let it preempt
2435          */
2436         if (cfq_rq_close(cfqd, cfqq, rq) && (!cfq_cfqq_coop(new_cfqq) ||
2437             cfqd->busy_queues == 1)) {
2438                 /*
2439                  * Mark new queue coop_preempt, so its coop flag will not be
2440                  * cleared when new queue gets scheduled at the very first time
2441                  */
2442                 cfq_mark_cfqq_coop_preempt(new_cfqq);
2443                 cfq_mark_cfqq_coop(new_cfqq);
2444                 return true;
2445         }
2446
2447         return false;
2448 }
2449
2450 /*
2451  * cfqq preempts the active queue. if we allowed preempt with no slice left,
2452  * let it have half of its nominal slice.
2453  */
2454 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2455 {
2456         cfq_log_cfqq(cfqd, cfqq, "preempt");
2457         cfq_slice_expired(cfqd, 1);
2458
2459         /*
2460          * Put the new queue at the front of the of the current list,
2461          * so we know that it will be selected next.
2462          */
2463         BUG_ON(!cfq_cfqq_on_rr(cfqq));
2464
2465         cfq_service_tree_add(cfqd, cfqq, 1);
2466
2467         cfqq->slice_end = 0;
2468         cfq_mark_cfqq_slice_new(cfqq);
2469 }
2470
2471 /*
2472  * Called when a new fs request (rq) is added (to cfqq). Check if there's
2473  * something we should do about it
2474  */
2475 static void
2476 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2477                 struct request *rq)
2478 {
2479         struct cfq_io_context *cic = RQ_CIC(rq);
2480
2481         cfqd->rq_queued++;
2482         if (rq_is_meta(rq))
2483                 cfqq->meta_pending++;
2484
2485         cfq_update_io_thinktime(cfqd, cic);
2486         cfq_update_io_seektime(cfqd, cfqq, rq);
2487         cfq_update_idle_window(cfqd, cfqq, cic);
2488
2489         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2490
2491         if (cfqq == cfqd->active_queue) {
2492                 /*
2493                  * Remember that we saw a request from this process, but
2494                  * don't start queuing just yet. Otherwise we risk seeing lots
2495                  * of tiny requests, because we disrupt the normal plugging
2496                  * and merging. If the request is already larger than a single
2497                  * page, let it rip immediately. For that case we assume that
2498                  * merging is already done. Ditto for a busy system that
2499                  * has other work pending, don't risk delaying until the
2500                  * idle timer unplug to continue working.
2501                  */
2502                 if (cfq_cfqq_wait_request(cfqq)) {
2503                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2504                             cfqd->busy_queues > 1) {
2505                                 del_timer(&cfqd->idle_slice_timer);
2506                         __blk_run_queue(cfqd->queue);
2507                         }
2508                         cfq_mark_cfqq_must_dispatch(cfqq);
2509                 }
2510         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2511                 /*
2512                  * not the active queue - expire current slice if it is
2513                  * idle and has expired it's mean thinktime or this new queue
2514                  * has some old slice time left and is of higher priority or
2515                  * this new queue is RT and the current one is BE
2516                  */
2517                 cfq_preempt_queue(cfqd, cfqq);
2518                 __blk_run_queue(cfqd->queue);
2519         }
2520 }
2521
2522 static void cfq_insert_request(struct request_queue *q, struct request *rq)
2523 {
2524         struct cfq_data *cfqd = q->elevator->elevator_data;
2525         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2526
2527         cfq_log_cfqq(cfqd, cfqq, "insert_request");
2528         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2529
2530         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
2531         list_add_tail(&rq->queuelist, &cfqq->fifo);
2532         cfq_add_rq_rb(rq);
2533
2534         cfq_rq_enqueued(cfqd, cfqq, rq);
2535 }
2536
2537 /*
2538  * Update hw_tag based on peak queue depth over 50 samples under
2539  * sufficient load.
2540  */
2541 static void cfq_update_hw_tag(struct cfq_data *cfqd)
2542 {
2543         struct cfq_queue *cfqq = cfqd->active_queue;
2544
2545         if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
2546                 cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
2547
2548         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2549             rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
2550                 return;
2551
2552         /*
2553          * If active queue hasn't enough requests and can idle, cfq might not
2554          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2555          * case
2556          */
2557         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
2558             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
2559             CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
2560                 return;
2561
2562         if (cfqd->hw_tag_samples++ < 50)
2563                 return;
2564
2565         if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
2566                 cfqd->hw_tag = 1;
2567         else
2568                 cfqd->hw_tag = 0;
2569
2570         cfqd->hw_tag_samples = 0;
2571         cfqd->rq_in_driver_peak = 0;
2572 }
2573
2574 static void cfq_completed_request(struct request_queue *q, struct request *rq)
2575 {
2576         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2577         struct cfq_data *cfqd = cfqq->cfqd;
2578         const int sync = rq_is_sync(rq);
2579         unsigned long now;
2580
2581         now = jiffies;
2582         cfq_log_cfqq(cfqd, cfqq, "complete");
2583
2584         cfq_update_hw_tag(cfqd);
2585
2586         WARN_ON(!cfqd->rq_in_driver[sync]);
2587         WARN_ON(!cfqq->dispatched);
2588         cfqd->rq_in_driver[sync]--;
2589         cfqq->dispatched--;
2590
2591         if (cfq_cfqq_sync(cfqq))
2592                 cfqd->sync_flight--;
2593
2594         if (sync) {
2595                 RQ_CIC(rq)->last_end_request = now;
2596                 cfqd->last_end_sync_rq = now;
2597         }
2598
2599         /*
2600          * If this is the active queue, check if it needs to be expired,
2601          * or if we want to idle in case it has no pending requests.
2602          */
2603         if (cfqd->active_queue == cfqq) {
2604                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2605
2606                 if (cfq_cfqq_slice_new(cfqq)) {
2607                         cfq_set_prio_slice(cfqd, cfqq);
2608                         cfq_clear_cfqq_slice_new(cfqq);
2609                 }
2610                 /*
2611                  * If there are no requests waiting in this queue, and
2612                  * there are other queues ready to issue requests, AND
2613                  * those other queues are issuing requests within our
2614                  * mean seek distance, give them a chance to run instead
2615                  * of idling.
2616                  */
2617                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
2618                         cfq_slice_expired(cfqd, 1);
2619                 else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq) &&
2620                          sync && !rq_noidle(rq))
2621                         cfq_arm_slice_timer(cfqd);
2622         }
2623
2624         if (!rq_in_driver(cfqd))
2625                 cfq_schedule_dispatch(cfqd);
2626 }
2627
2628 /*
2629  * we temporarily boost lower priority queues if they are holding fs exclusive
2630  * resources. they are boosted to normal prio (CLASS_BE/4)
2631  */
2632 static void cfq_prio_boost(struct cfq_queue *cfqq)
2633 {
2634         if (has_fs_excl()) {
2635                 /*
2636                  * boost idle prio on transactions that would lock out other
2637                  * users of the filesystem
2638                  */
2639                 if (cfq_class_idle(cfqq))
2640                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
2641                 if (cfqq->ioprio > IOPRIO_NORM)
2642                         cfqq->ioprio = IOPRIO_NORM;
2643         } else {
2644                 /*
2645                  * unboost the queue (if needed)
2646                  */
2647                 cfqq->ioprio_class = cfqq->org_ioprio_class;
2648                 cfqq->ioprio = cfqq->org_ioprio;
2649         }
2650 }
2651
2652 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
2653 {
2654         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
2655                 cfq_mark_cfqq_must_alloc_slice(cfqq);
2656                 return ELV_MQUEUE_MUST;
2657         }
2658
2659         return ELV_MQUEUE_MAY;
2660 }
2661
2662 static int cfq_may_queue(struct request_queue *q, int rw)
2663 {
2664         struct cfq_data *cfqd = q->elevator->elevator_data;
2665         struct task_struct *tsk = current;
2666         struct cfq_io_context *cic;
2667         struct cfq_queue *cfqq;
2668
2669         /*
2670          * don't force setup of a queue from here, as a call to may_queue
2671          * does not necessarily imply that a request actually will be queued.
2672          * so just lookup a possibly existing queue, or return 'may queue'
2673          * if that fails
2674          */
2675         cic = cfq_cic_lookup(cfqd, tsk->io_context);
2676         if (!cic)
2677                 return ELV_MQUEUE_MAY;
2678
2679         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
2680         if (cfqq) {
2681                 cfq_init_prio_data(cfqq, cic->ioc);
2682                 cfq_prio_boost(cfqq);
2683
2684                 return __cfq_may_queue(cfqq);
2685         }
2686
2687         return ELV_MQUEUE_MAY;
2688 }
2689
2690 /*
2691  * queue lock held here
2692  */
2693 static void cfq_put_request(struct request *rq)
2694 {
2695         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2696
2697         if (cfqq) {
2698                 const int rw = rq_data_dir(rq);
2699
2700                 BUG_ON(!cfqq->allocated[rw]);
2701                 cfqq->allocated[rw]--;
2702
2703                 put_io_context(RQ_CIC(rq)->ioc);
2704
2705                 rq->elevator_private = NULL;
2706                 rq->elevator_private2 = NULL;
2707
2708                 cfq_put_queue(cfqq);
2709         }
2710 }
2711
2712 static struct cfq_queue *
2713 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
2714                 struct cfq_queue *cfqq)
2715 {
2716         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
2717         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
2718         cfq_mark_cfqq_coop(cfqq->new_cfqq);
2719         cfq_put_queue(cfqq);
2720         return cic_to_cfqq(cic, 1);
2721 }
2722
2723 static int should_split_cfqq(struct cfq_queue *cfqq)
2724 {
2725         if (cfqq->seeky_start &&
2726             time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
2727                 return 1;
2728         return 0;
2729 }
2730
2731 /*
2732  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2733  * was the last process referring to said cfqq.
2734  */
2735 static struct cfq_queue *
2736 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
2737 {
2738         if (cfqq_process_refs(cfqq) == 1) {
2739                 cfqq->seeky_start = 0;
2740                 cfqq->pid = current->pid;
2741                 cfq_clear_cfqq_coop(cfqq);
2742                 return cfqq;
2743         }
2744
2745         cic_set_cfqq(cic, NULL, 1);
2746         cfq_put_queue(cfqq);
2747         return NULL;
2748 }
2749 /*
2750  * Allocate cfq data structures associated with this request.
2751  */
2752 static int
2753 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2754 {
2755         struct cfq_data *cfqd = q->elevator->elevator_data;
2756         struct cfq_io_context *cic;
2757         const int rw = rq_data_dir(rq);
2758         const bool is_sync = rq_is_sync(rq);
2759         struct cfq_queue *cfqq;
2760         unsigned long flags;
2761
2762         might_sleep_if(gfp_mask & __GFP_WAIT);
2763
2764         cic = cfq_get_io_context(cfqd, gfp_mask);
2765
2766         spin_lock_irqsave(q->queue_lock, flags);
2767
2768         if (!cic)
2769                 goto queue_fail;
2770
2771 new_queue:
2772         cfqq = cic_to_cfqq(cic, is_sync);
2773         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2774                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2775                 cic_set_cfqq(cic, cfqq, is_sync);
2776         } else {
2777                 /*
2778                  * If the queue was seeky for too long, break it apart.
2779                  */
2780                 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
2781                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
2782                         cfqq = split_cfqq(cic, cfqq);
2783                         if (!cfqq)
2784                                 goto new_queue;
2785                 }
2786
2787                 /*
2788                  * Check to see if this queue is scheduled to merge with
2789                  * another, closely cooperating queue.  The merging of
2790                  * queues happens here as it must be done in process context.
2791                  * The reference on new_cfqq was taken in merge_cfqqs.
2792                  */
2793                 if (cfqq->new_cfqq)
2794                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
2795         }
2796
2797         cfqq->allocated[rw]++;
2798         atomic_inc(&cfqq->ref);
2799
2800         spin_unlock_irqrestore(q->queue_lock, flags);
2801
2802         rq->elevator_private = cic;
2803         rq->elevator_private2 = cfqq;
2804         return 0;
2805
2806 queue_fail:
2807         if (cic)
2808                 put_io_context(cic->ioc);
2809
2810         cfq_schedule_dispatch(cfqd);
2811         spin_unlock_irqrestore(q->queue_lock, flags);
2812         cfq_log(cfqd, "set_request fail");
2813         return 1;
2814 }
2815
2816 static void cfq_kick_queue(struct work_struct *work)
2817 {
2818         struct cfq_data *cfqd =
2819                 container_of(work, struct cfq_data, unplug_work);
2820         struct request_queue *q = cfqd->queue;
2821
2822         spin_lock_irq(q->queue_lock);
2823         __blk_run_queue(cfqd->queue);
2824         spin_unlock_irq(q->queue_lock);
2825 }
2826
2827 /*
2828  * Timer running if the active_queue is currently idling inside its time slice
2829  */
2830 static void cfq_idle_slice_timer(unsigned long data)
2831 {
2832         struct cfq_data *cfqd = (struct cfq_data *) data;
2833         struct cfq_queue *cfqq;
2834         unsigned long flags;
2835         int timed_out = 1;
2836
2837         cfq_log(cfqd, "idle timer fired");
2838
2839         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2840
2841         cfqq = cfqd->active_queue;
2842         if (cfqq) {
2843                 timed_out = 0;
2844
2845                 /*
2846                  * We saw a request before the queue expired, let it through
2847                  */
2848                 if (cfq_cfqq_must_dispatch(cfqq))
2849                         goto out_kick;
2850
2851                 /*
2852                  * expired
2853                  */
2854                 if (cfq_slice_used(cfqq))
2855                         goto expire;
2856
2857                 /*
2858                  * only expire and reinvoke request handler, if there are
2859                  * other queues with pending requests
2860                  */
2861                 if (!cfqd->busy_queues)
2862                         goto out_cont;
2863
2864                 /*
2865                  * not expired and it has a request pending, let it dispatch
2866                  */
2867                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2868                         goto out_kick;
2869         }
2870 expire:
2871         cfq_slice_expired(cfqd, timed_out);
2872 out_kick:
2873         cfq_schedule_dispatch(cfqd);
2874 out_cont:
2875         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2876 }
2877
2878 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2879 {
2880         del_timer_sync(&cfqd->idle_slice_timer);
2881         cancel_work_sync(&cfqd->unplug_work);
2882 }
2883
2884 static void cfq_put_async_queues(struct cfq_data *cfqd)
2885 {
2886         int i;
2887
2888         for (i = 0; i < IOPRIO_BE_NR; i++) {
2889                 if (cfqd->async_cfqq[0][i])
2890                         cfq_put_queue(cfqd->async_cfqq[0][i]);
2891                 if (cfqd->async_cfqq[1][i])
2892                         cfq_put_queue(cfqd->async_cfqq[1][i]);
2893         }
2894
2895         if (cfqd->async_idle_cfqq)
2896                 cfq_put_queue(cfqd->async_idle_cfqq);
2897 }
2898
2899 static void cfq_exit_queue(struct elevator_queue *e)
2900 {
2901         struct cfq_data *cfqd = e->elevator_data;
2902         struct request_queue *q = cfqd->queue;
2903
2904         cfq_shutdown_timer_wq(cfqd);
2905
2906         spin_lock_irq(q->queue_lock);
2907
2908         if (cfqd->active_queue)
2909                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2910
2911         while (!list_empty(&cfqd->cic_list)) {
2912                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2913                                                         struct cfq_io_context,
2914                                                         queue_list);
2915
2916                 __cfq_exit_single_io_context(cfqd, cic);
2917         }
2918
2919         cfq_put_async_queues(cfqd);
2920
2921         spin_unlock_irq(q->queue_lock);
2922
2923         cfq_shutdown_timer_wq(cfqd);
2924
2925         kfree(cfqd);
2926 }
2927
2928 static void *cfq_init_queue(struct request_queue *q)
2929 {
2930         struct cfq_data *cfqd;
2931         int i, j;
2932
2933         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2934         if (!cfqd)
2935                 return NULL;
2936
2937         for (i = 0; i < 2; ++i)
2938                 for (j = 0; j < 3; ++j)
2939                         cfqd->service_trees[i][j] = CFQ_RB_ROOT;
2940         cfqd->service_tree_idle = CFQ_RB_ROOT;
2941
2942         /*
2943          * Not strictly needed (since RB_ROOT just clears the node and we
2944          * zeroed cfqd on alloc), but better be safe in case someone decides
2945          * to add magic to the rb code
2946          */
2947         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2948                 cfqd->prio_trees[i] = RB_ROOT;
2949
2950         /*
2951          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2952          * Grab a permanent reference to it, so that the normal code flow
2953          * will not attempt to free it.
2954          */
2955         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
2956         atomic_inc(&cfqd->oom_cfqq.ref);
2957
2958         INIT_LIST_HEAD(&cfqd->cic_list);
2959
2960         cfqd->queue = q;
2961
2962         init_timer(&cfqd->idle_slice_timer);
2963         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2964         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2965
2966         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2967
2968         cfqd->cfq_quantum = cfq_quantum;
2969         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2970         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2971         cfqd->cfq_back_max = cfq_back_max;
2972         cfqd->cfq_back_penalty = cfq_back_penalty;
2973         cfqd->cfq_slice[0] = cfq_slice_async;
2974         cfqd->cfq_slice[1] = cfq_slice_sync;
2975         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2976         cfqd->cfq_slice_idle = cfq_slice_idle;
2977         cfqd->cfq_latency = 1;
2978         cfqd->hw_tag = 1;
2979         cfqd->last_end_sync_rq = jiffies;
2980         return cfqd;
2981 }
2982
2983 static void cfq_slab_kill(void)
2984 {
2985         /*
2986          * Caller already ensured that pending RCU callbacks are completed,
2987          * so we should have no busy allocations at this point.
2988          */
2989         if (cfq_pool)
2990                 kmem_cache_destroy(cfq_pool);
2991         if (cfq_ioc_pool)
2992                 kmem_cache_destroy(cfq_ioc_pool);
2993 }
2994
2995 static int __init cfq_slab_setup(void)
2996 {
2997         cfq_pool = KMEM_CACHE(cfq_queue, 0);
2998         if (!cfq_pool)
2999                 goto fail;
3000
3001         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3002         if (!cfq_ioc_pool)
3003                 goto fail;
3004
3005         return 0;
3006 fail:
3007         cfq_slab_kill();
3008         return -ENOMEM;
3009 }
3010
3011 /*
3012  * sysfs parts below -->
3013  */
3014 static ssize_t
3015 cfq_var_show(unsigned int var, char *page)
3016 {
3017         return sprintf(page, "%d\n", var);
3018 }
3019
3020 static ssize_t
3021 cfq_var_store(unsigned int *var, const char *page, size_t count)
3022 {
3023         char *p = (char *) page;
3024
3025         *var = simple_strtoul(p, &p, 10);
3026         return count;
3027 }
3028
3029 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3030 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3031 {                                                                       \
3032         struct cfq_data *cfqd = e->elevator_data;                       \
3033         unsigned int __data = __VAR;                                    \
3034         if (__CONV)                                                     \
3035                 __data = jiffies_to_msecs(__data);                      \
3036         return cfq_var_show(__data, (page));                            \
3037 }
3038 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3039 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3040 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3041 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3042 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3043 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3044 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3045 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3046 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3047 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3048 #undef SHOW_FUNCTION
3049
3050 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3051 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3052 {                                                                       \
3053         struct cfq_data *cfqd = e->elevator_data;                       \
3054         unsigned int __data;                                            \
3055         int ret = cfq_var_store(&__data, (page), count);                \
3056         if (__data < (MIN))                                             \
3057                 __data = (MIN);                                         \
3058         else if (__data > (MAX))                                        \
3059                 __data = (MAX);                                         \
3060         if (__CONV)                                                     \
3061                 *(__PTR) = msecs_to_jiffies(__data);                    \
3062         else                                                            \
3063                 *(__PTR) = __data;                                      \
3064         return ret;                                                     \
3065 }
3066 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3067 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3068                 UINT_MAX, 1);
3069 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3070                 UINT_MAX, 1);
3071 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3072 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3073                 UINT_MAX, 0);
3074 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3075 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3076 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3077 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3078                 UINT_MAX, 0);
3079 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3080 #undef STORE_FUNCTION
3081
3082 #define CFQ_ATTR(name) \
3083         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3084
3085 static struct elv_fs_entry cfq_attrs[] = {
3086         CFQ_ATTR(quantum),
3087         CFQ_ATTR(fifo_expire_sync),
3088         CFQ_ATTR(fifo_expire_async),
3089         CFQ_ATTR(back_seek_max),
3090         CFQ_ATTR(back_seek_penalty),
3091         CFQ_ATTR(slice_sync),
3092         CFQ_ATTR(slice_async),
3093         CFQ_ATTR(slice_async_rq),
3094         CFQ_ATTR(slice_idle),
3095         CFQ_ATTR(low_latency),
3096         __ATTR_NULL
3097 };
3098
3099 static struct elevator_type iosched_cfq = {
3100         .ops = {
3101                 .elevator_merge_fn =            cfq_merge,
3102                 .elevator_merged_fn =           cfq_merged_request,
3103                 .elevator_merge_req_fn =        cfq_merged_requests,
3104                 .elevator_allow_merge_fn =      cfq_allow_merge,
3105                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3106                 .elevator_add_req_fn =          cfq_insert_request,
3107                 .elevator_activate_req_fn =     cfq_activate_request,
3108                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3109                 .elevator_queue_empty_fn =      cfq_queue_empty,
3110                 .elevator_completed_req_fn =    cfq_completed_request,
3111                 .elevator_former_req_fn =       elv_rb_former_request,
3112                 .elevator_latter_req_fn =       elv_rb_latter_request,
3113                 .elevator_set_req_fn =          cfq_set_request,
3114                 .elevator_put_req_fn =          cfq_put_request,
3115                 .elevator_may_queue_fn =        cfq_may_queue,
3116                 .elevator_init_fn =             cfq_init_queue,
3117                 .elevator_exit_fn =             cfq_exit_queue,
3118                 .trim =                         cfq_free_io_context,
3119         },
3120         .elevator_attrs =       cfq_attrs,
3121         .elevator_name =        "cfq",
3122         .elevator_owner =       THIS_MODULE,
3123 };
3124
3125 static int __init cfq_init(void)
3126 {
3127         /*
3128          * could be 0 on HZ < 1000 setups
3129          */
3130         if (!cfq_slice_async)
3131                 cfq_slice_async = 1;
3132         if (!cfq_slice_idle)
3133                 cfq_slice_idle = 1;
3134
3135         if (cfq_slab_setup())
3136                 return -ENOMEM;
3137
3138         elv_register(&iosched_cfq);
3139
3140         return 0;
3141 }
3142
3143 static void __exit cfq_exit(void)
3144 {
3145         DECLARE_COMPLETION_ONSTACK(all_gone);
3146         elv_unregister(&iosched_cfq);
3147         ioc_gone = &all_gone;
3148         /* ioc_gone's update must be visible before reading ioc_count */
3149         smp_wmb();
3150
3151         /*
3152          * this also protects us from entering cfq_slab_kill() with
3153          * pending RCU callbacks
3154          */
3155         if (elv_ioc_count_read(cfq_ioc_count))
3156                 wait_for_completion(&all_gone);
3157         cfq_slab_kill();
3158 }
3159
3160 module_init(cfq_init);
3161 module_exit(cfq_exit);
3162
3163 MODULE_AUTHOR("Jens Axboe");
3164 MODULE_LICENSE("GPL");
3165 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");