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