Root/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/slab.h>
11#include <linux/blkdev.h>
12#include <linux/elevator.h>
13#include <linux/jiffies.h>
14#include <linux/rbtree.h>
15#include <linux/ioprio.h>
16#include <linux/blktrace_api.h>
17#include "blk-cgroup.h"
18
19/*
20 * tunables
21 */
22/* max queue in one round of service */
23static const int cfq_quantum = 8;
24static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
25/* maximum backwards seek, in KiB */
26static const int cfq_back_max = 16 * 1024;
27/* penalty of a backwards seek */
28static const int cfq_back_penalty = 2;
29static const int cfq_slice_sync = HZ / 10;
30static int cfq_slice_async = HZ / 25;
31static const int cfq_slice_async_rq = 2;
32static int cfq_slice_idle = HZ / 125;
33static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
34static const int cfq_hist_divisor = 4;
35
36/*
37 * offset from end of service tree
38 */
39#define CFQ_IDLE_DELAY (HZ / 5)
40
41/*
42 * below this threshold, we consider thinktime immediate
43 */
44#define CFQ_MIN_TT (2)
45
46#define CFQ_SLICE_SCALE (5)
47#define CFQ_HW_QUEUE_MIN (5)
48#define CFQ_SERVICE_SHIFT 12
49
50#define CFQQ_SEEK_THR (sector_t)(8 * 100)
51#define CFQQ_CLOSE_THR (sector_t)(8 * 1024)
52#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
53#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
54
55#define RQ_CIC(rq) \
56    ((struct cfq_io_context *) (rq)->elevator_private)
57#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
58
59static struct kmem_cache *cfq_pool;
60static struct kmem_cache *cfq_ioc_pool;
61
62static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
63static struct completion *ioc_gone;
64static DEFINE_SPINLOCK(ioc_gone_lock);
65
66#define CFQ_PRIO_LISTS IOPRIO_BE_NR
67#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
69
70#define sample_valid(samples) ((samples) > 80)
71#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
72
73/*
74 * Most of our rbtree usage is for sorting with min extraction, so
75 * if we cache the leftmost node we don't have to walk down the tree
76 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77 * move this into the elevator for the rq sorting as well.
78 */
79struct cfq_rb_root {
80    struct rb_root rb;
81    struct rb_node *left;
82    unsigned count;
83    unsigned total_weight;
84    u64 min_vdisktime;
85    struct rb_node *active;
86};
87#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
88            .count = 0, .min_vdisktime = 0, }
89
90/*
91 * Per process-grouping structure
92 */
93struct cfq_queue {
94    /* reference count */
95    atomic_t ref;
96    /* various state flags, see below */
97    unsigned int flags;
98    /* parent cfq_data */
99    struct cfq_data *cfqd;
100    /* service_tree member */
101    struct rb_node rb_node;
102    /* service_tree key */
103    unsigned long rb_key;
104    /* prio tree member */
105    struct rb_node p_node;
106    /* prio tree root we belong to, if any */
107    struct rb_root *p_root;
108    /* sorted list of pending requests */
109    struct rb_root sort_list;
110    /* if fifo isn't expired, next request to serve */
111    struct request *next_rq;
112    /* requests queued in sort_list */
113    int queued[2];
114    /* currently allocated requests */
115    int allocated[2];
116    /* fifo list of requests in sort_list */
117    struct list_head fifo;
118
119    /* time when queue got scheduled in to dispatch first request. */
120    unsigned long dispatch_start;
121    unsigned int allocated_slice;
122    unsigned int slice_dispatch;
123    /* time when first request from queue completed and slice started. */
124    unsigned long slice_start;
125    unsigned long slice_end;
126    long slice_resid;
127
128    /* pending metadata requests */
129    int meta_pending;
130    /* number of requests that are on the dispatch list or inside driver */
131    int dispatched;
132
133    /* io prio of this group */
134    unsigned short ioprio, org_ioprio;
135    unsigned short ioprio_class, org_ioprio_class;
136
137    pid_t pid;
138
139    u32 seek_history;
140    sector_t last_request_pos;
141
142    struct cfq_rb_root *service_tree;
143    struct cfq_queue *new_cfqq;
144    struct cfq_group *cfqg;
145    struct cfq_group *orig_cfqg;
146    /* Sectors dispatched in current dispatch round */
147    unsigned long nr_sectors;
148};
149
150/*
151 * First index in the service_trees.
152 * IDLE is handled separately, so it has negative index
153 */
154enum wl_prio_t {
155    BE_WORKLOAD = 0,
156    RT_WORKLOAD = 1,
157    IDLE_WORKLOAD = 2,
158};
159
160/*
161 * Second index in the service_trees.
162 */
163enum wl_type_t {
164    ASYNC_WORKLOAD = 0,
165    SYNC_NOIDLE_WORKLOAD = 1,
166    SYNC_WORKLOAD = 2
167};
168
169/* This is per cgroup per device grouping structure */
170struct cfq_group {
171    /* group service_tree member */
172    struct rb_node rb_node;
173
174    /* group service_tree key */
175    u64 vdisktime;
176    unsigned int weight;
177    bool on_st;
178
179    /* number of cfqq currently on this group */
180    int nr_cfqq;
181
182    /* Per group busy queus average. Useful for workload slice calc. */
183    unsigned int busy_queues_avg[2];
184    /*
185     * rr lists of queues with requests, onle rr for each priority class.
186     * Counts are embedded in the cfq_rb_root
187     */
188    struct cfq_rb_root service_trees[2][3];
189    struct cfq_rb_root service_tree_idle;
190
191    unsigned long saved_workload_slice;
192    enum wl_type_t saved_workload;
193    enum wl_prio_t saved_serving_prio;
194    struct blkio_group blkg;
195#ifdef CONFIG_CFQ_GROUP_IOSCHED
196    struct hlist_node cfqd_node;
197    atomic_t ref;
198#endif
199};
200
201/*
202 * Per block device queue structure
203 */
204struct cfq_data {
205    struct request_queue *queue;
206    /* Root service tree for cfq_groups */
207    struct cfq_rb_root grp_service_tree;
208    struct cfq_group root_group;
209
210    /*
211     * The priority currently being served
212     */
213    enum wl_prio_t serving_prio;
214    enum wl_type_t serving_type;
215    unsigned long workload_expires;
216    struct cfq_group *serving_group;
217    bool noidle_tree_requires_idle;
218
219    /*
220     * Each priority tree is sorted by next_request position. These
221     * trees are used when determining if two or more queues are
222     * interleaving requests (see cfq_close_cooperator).
223     */
224    struct rb_root prio_trees[CFQ_PRIO_LISTS];
225
226    unsigned int busy_queues;
227
228    int rq_in_driver;
229    int rq_in_flight[2];
230
231    /*
232     * queue-depth detection
233     */
234    int rq_queued;
235    int hw_tag;
236    /*
237     * hw_tag can be
238     * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
239     * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
240     * 0 => no NCQ
241     */
242    int hw_tag_est_depth;
243    unsigned int hw_tag_samples;
244
245    /*
246     * idle window management
247     */
248    struct timer_list idle_slice_timer;
249    struct work_struct unplug_work;
250
251    struct cfq_queue *active_queue;
252    struct cfq_io_context *active_cic;
253
254    /*
255     * async queue for each priority case
256     */
257    struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
258    struct cfq_queue *async_idle_cfqq;
259
260    sector_t last_position;
261
262    /*
263     * tunables, see top of file
264     */
265    unsigned int cfq_quantum;
266    unsigned int cfq_fifo_expire[2];
267    unsigned int cfq_back_penalty;
268    unsigned int cfq_back_max;
269    unsigned int cfq_slice[2];
270    unsigned int cfq_slice_async_rq;
271    unsigned int cfq_slice_idle;
272    unsigned int cfq_latency;
273    unsigned int cfq_group_isolation;
274
275    struct list_head cic_list;
276
277    /*
278     * Fallback dummy cfqq for extreme OOM conditions
279     */
280    struct cfq_queue oom_cfqq;
281
282    unsigned long last_delayed_sync;
283
284    /* List of cfq groups being managed on this device*/
285    struct hlist_head cfqg_list;
286    struct rcu_head rcu;
287};
288
289static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
290
291static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
292                        enum wl_prio_t prio,
293                        enum wl_type_t type)
294{
295    if (!cfqg)
296        return NULL;
297
298    if (prio == IDLE_WORKLOAD)
299        return &cfqg->service_tree_idle;
300
301    return &cfqg->service_trees[prio][type];
302}
303
304enum cfqq_state_flags {
305    CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
306    CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
307    CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
308    CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
309    CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
310    CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
311    CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
312    CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
313    CFQ_CFQQ_FLAG_sync, /* synchronous queue */
314    CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
315    CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
316    CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
317    CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
318};
319
320#define CFQ_CFQQ_FNS(name) \
321static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
322{ \
323    (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
324} \
325static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
326{ \
327    (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
328} \
329static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
330{ \
331    return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
332}
333
334CFQ_CFQQ_FNS(on_rr);
335CFQ_CFQQ_FNS(wait_request);
336CFQ_CFQQ_FNS(must_dispatch);
337CFQ_CFQQ_FNS(must_alloc_slice);
338CFQ_CFQQ_FNS(fifo_expire);
339CFQ_CFQQ_FNS(idle_window);
340CFQ_CFQQ_FNS(prio_changed);
341CFQ_CFQQ_FNS(slice_new);
342CFQ_CFQQ_FNS(sync);
343CFQ_CFQQ_FNS(coop);
344CFQ_CFQQ_FNS(split_coop);
345CFQ_CFQQ_FNS(deep);
346CFQ_CFQQ_FNS(wait_busy);
347#undef CFQ_CFQQ_FNS
348
349#ifdef CONFIG_DEBUG_CFQ_IOSCHED
350#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
351    blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
352            cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
353            blkg_path(&(cfqq)->cfqg->blkg), ##args);
354
355#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
356    blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
357                blkg_path(&(cfqg)->blkg), ##args); \
358
359#else
360#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
361    blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
362#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
363#endif
364#define cfq_log(cfqd, fmt, args...) \
365    blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
366
367/* Traverses through cfq group service trees */
368#define for_each_cfqg_st(cfqg, i, j, st) \
369    for (i = 0; i <= IDLE_WORKLOAD; i++) \
370        for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
371            : &cfqg->service_tree_idle; \
372            (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
373            (i == IDLE_WORKLOAD && j == 0); \
374            j++, st = i < IDLE_WORKLOAD ? \
375            &cfqg->service_trees[i][j]: NULL) \
376
377
378static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
379{
380    if (cfq_class_idle(cfqq))
381        return IDLE_WORKLOAD;
382    if (cfq_class_rt(cfqq))
383        return RT_WORKLOAD;
384    return BE_WORKLOAD;
385}
386
387
388static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
389{
390    if (!cfq_cfqq_sync(cfqq))
391        return ASYNC_WORKLOAD;
392    if (!cfq_cfqq_idle_window(cfqq))
393        return SYNC_NOIDLE_WORKLOAD;
394    return SYNC_WORKLOAD;
395}
396
397static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
398                    struct cfq_data *cfqd,
399                    struct cfq_group *cfqg)
400{
401    if (wl == IDLE_WORKLOAD)
402        return cfqg->service_tree_idle.count;
403
404    return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
405        + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
406        + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
407}
408
409static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
410                    struct cfq_group *cfqg)
411{
412    return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
413        + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
414}
415
416static void cfq_dispatch_insert(struct request_queue *, struct request *);
417static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
418                       struct io_context *, gfp_t);
419static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
420                        struct io_context *);
421
422static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
423                        bool is_sync)
424{
425    return cic->cfqq[is_sync];
426}
427
428static inline void cic_set_cfqq(struct cfq_io_context *cic,
429                struct cfq_queue *cfqq, bool is_sync)
430{
431    cic->cfqq[is_sync] = cfqq;
432}
433
434/*
435 * We regard a request as SYNC, if it's either a read or has the SYNC bit
436 * set (in which case it could also be direct WRITE).
437 */
438static inline bool cfq_bio_sync(struct bio *bio)
439{
440    return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
441}
442
443/*
444 * scheduler run of queue, if there are requests pending and no one in the
445 * driver that will restart queueing
446 */
447static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
448{
449    if (cfqd->busy_queues) {
450        cfq_log(cfqd, "schedule dispatch");
451        kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
452    }
453}
454
455static int cfq_queue_empty(struct request_queue *q)
456{
457    struct cfq_data *cfqd = q->elevator->elevator_data;
458
459    return !cfqd->rq_queued;
460}
461
462/*
463 * Scale schedule slice based on io priority. Use the sync time slice only
464 * if a queue is marked sync and has sync io queued. A sync queue with async
465 * io only, should not get full sync slice length.
466 */
467static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
468                 unsigned short prio)
469{
470    const int base_slice = cfqd->cfq_slice[sync];
471
472    WARN_ON(prio >= IOPRIO_BE_NR);
473
474    return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
475}
476
477static inline int
478cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
479{
480    return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
481}
482
483static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
484{
485    u64 d = delta << CFQ_SERVICE_SHIFT;
486
487    d = d * BLKIO_WEIGHT_DEFAULT;
488    do_div(d, cfqg->weight);
489    return d;
490}
491
492static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
493{
494    s64 delta = (s64)(vdisktime - min_vdisktime);
495    if (delta > 0)
496        min_vdisktime = vdisktime;
497
498    return min_vdisktime;
499}
500
501static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
502{
503    s64 delta = (s64)(vdisktime - min_vdisktime);
504    if (delta < 0)
505        min_vdisktime = vdisktime;
506
507    return min_vdisktime;
508}
509
510static void update_min_vdisktime(struct cfq_rb_root *st)
511{
512    u64 vdisktime = st->min_vdisktime;
513    struct cfq_group *cfqg;
514
515    if (st->active) {
516        cfqg = rb_entry_cfqg(st->active);
517        vdisktime = cfqg->vdisktime;
518    }
519
520    if (st->left) {
521        cfqg = rb_entry_cfqg(st->left);
522        vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
523    }
524
525    st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
526}
527
528/*
529 * get averaged number of queues of RT/BE priority.
530 * average is updated, with a formula that gives more weight to higher numbers,
531 * to quickly follows sudden increases and decrease slowly
532 */
533
534static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
535                    struct cfq_group *cfqg, bool rt)
536{
537    unsigned min_q, max_q;
538    unsigned mult = cfq_hist_divisor - 1;
539    unsigned round = cfq_hist_divisor / 2;
540    unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
541
542    min_q = min(cfqg->busy_queues_avg[rt], busy);
543    max_q = max(cfqg->busy_queues_avg[rt], busy);
544    cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
545        cfq_hist_divisor;
546    return cfqg->busy_queues_avg[rt];
547}
548
549static inline unsigned
550cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
551{
552    struct cfq_rb_root *st = &cfqd->grp_service_tree;
553
554    return cfq_target_latency * cfqg->weight / st->total_weight;
555}
556
557static inline void
558cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
559{
560    unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
561    if (cfqd->cfq_latency) {
562        /*
563         * interested queues (we consider only the ones with the same
564         * priority class in the cfq group)
565         */
566        unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
567                        cfq_class_rt(cfqq));
568        unsigned sync_slice = cfqd->cfq_slice[1];
569        unsigned expect_latency = sync_slice * iq;
570        unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
571
572        if (expect_latency > group_slice) {
573            unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
574            /* scale low_slice according to IO priority
575             * and sync vs async */
576            unsigned low_slice =
577                min(slice, base_low_slice * slice / sync_slice);
578            /* the adapted slice value is scaled to fit all iqs
579             * into the target latency */
580            slice = max(slice * group_slice / expect_latency,
581                    low_slice);
582        }
583    }
584    cfqq->slice_start = jiffies;
585    cfqq->slice_end = jiffies + slice;
586    cfqq->allocated_slice = slice;
587    cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
588}
589
590/*
591 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
592 * isn't valid until the first request from the dispatch is activated
593 * and the slice time set.
594 */
595static inline bool cfq_slice_used(struct cfq_queue *cfqq)
596{
597    if (cfq_cfqq_slice_new(cfqq))
598        return 0;
599    if (time_before(jiffies, cfqq->slice_end))
600        return 0;
601
602    return 1;
603}
604
605/*
606 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
607 * We choose the request that is closest to the head right now. Distance
608 * behind the head is penalized and only allowed to a certain extent.
609 */
610static struct request *
611cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
612{
613    sector_t s1, s2, d1 = 0, d2 = 0;
614    unsigned long back_max;
615#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
616#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
617    unsigned wrap = 0; /* bit mask: requests behind the disk head? */
618
619    if (rq1 == NULL || rq1 == rq2)
620        return rq2;
621    if (rq2 == NULL)
622        return rq1;
623
624    if (rq_is_sync(rq1) && !rq_is_sync(rq2))
625        return rq1;
626    else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
627        return rq2;
628    if (rq_is_meta(rq1) && !rq_is_meta(rq2))
629        return rq1;
630    else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
631        return rq2;
632
633    s1 = blk_rq_pos(rq1);
634    s2 = blk_rq_pos(rq2);
635
636    /*
637     * by definition, 1KiB is 2 sectors
638     */
639    back_max = cfqd->cfq_back_max * 2;
640
641    /*
642     * Strict one way elevator _except_ in the case where we allow
643     * short backward seeks which are biased as twice the cost of a
644     * similar forward seek.
645     */
646    if (s1 >= last)
647        d1 = s1 - last;
648    else if (s1 + back_max >= last)
649        d1 = (last - s1) * cfqd->cfq_back_penalty;
650    else
651        wrap |= CFQ_RQ1_WRAP;
652
653    if (s2 >= last)
654        d2 = s2 - last;
655    else if (s2 + back_max >= last)
656        d2 = (last - s2) * cfqd->cfq_back_penalty;
657    else
658        wrap |= CFQ_RQ2_WRAP;
659
660    /* Found required data */
661
662    /*
663     * By doing switch() on the bit mask "wrap" we avoid having to
664     * check two variables for all permutations: --> faster!
665     */
666    switch (wrap) {
667    case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
668        if (d1 < d2)
669            return rq1;
670        else if (d2 < d1)
671            return rq2;
672        else {
673            if (s1 >= s2)
674                return rq1;
675            else
676                return rq2;
677        }
678
679    case CFQ_RQ2_WRAP:
680        return rq1;
681    case CFQ_RQ1_WRAP:
682        return rq2;
683    case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
684    default:
685        /*
686         * Since both rqs are wrapped,
687         * start with the one that's further behind head
688         * (--> only *one* back seek required),
689         * since back seek takes more time than forward.
690         */
691        if (s1 <= s2)
692            return rq1;
693        else
694            return rq2;
695    }
696}
697
698/*
699 * The below is leftmost cache rbtree addon
700 */
701static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
702{
703    /* Service tree is empty */
704    if (!root->count)
705        return NULL;
706
707    if (!root->left)
708        root->left = rb_first(&root->rb);
709
710    if (root->left)
711        return rb_entry(root->left, struct cfq_queue, rb_node);
712
713    return NULL;
714}
715
716static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
717{
718    if (!root->left)
719        root->left = rb_first(&root->rb);
720
721    if (root->left)
722        return rb_entry_cfqg(root->left);
723
724    return NULL;
725}
726
727static void rb_erase_init(struct rb_node *n, struct rb_root *root)
728{
729    rb_erase(n, root);
730    RB_CLEAR_NODE(n);
731}
732
733static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
734{
735    if (root->left == n)
736        root->left = NULL;
737    rb_erase_init(n, &root->rb);
738    --root->count;
739}
740
741/*
742 * would be nice to take fifo expire time into account as well
743 */
744static struct request *
745cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
746          struct request *last)
747{
748    struct rb_node *rbnext = rb_next(&last->rb_node);
749    struct rb_node *rbprev = rb_prev(&last->rb_node);
750    struct request *next = NULL, *prev = NULL;
751
752    BUG_ON(RB_EMPTY_NODE(&last->rb_node));
753
754    if (rbprev)
755        prev = rb_entry_rq(rbprev);
756
757    if (rbnext)
758        next = rb_entry_rq(rbnext);
759    else {
760        rbnext = rb_first(&cfqq->sort_list);
761        if (rbnext && rbnext != &last->rb_node)
762            next = rb_entry_rq(rbnext);
763    }
764
765    return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
766}
767
768static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
769                      struct cfq_queue *cfqq)
770{
771    /*
772     * just an approximation, should be ok.
773     */
774    return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
775               cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
776}
777
778static inline s64
779cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
780{
781    return cfqg->vdisktime - st->min_vdisktime;
782}
783
784static void
785__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
786{
787    struct rb_node **node = &st->rb.rb_node;
788    struct rb_node *parent = NULL;
789    struct cfq_group *__cfqg;
790    s64 key = cfqg_key(st, cfqg);
791    int left = 1;
792
793    while (*node != NULL) {
794        parent = *node;
795        __cfqg = rb_entry_cfqg(parent);
796
797        if (key < cfqg_key(st, __cfqg))
798            node = &parent->rb_left;
799        else {
800            node = &parent->rb_right;
801            left = 0;
802        }
803    }
804
805    if (left)
806        st->left = &cfqg->rb_node;
807
808    rb_link_node(&cfqg->rb_node, parent, node);
809    rb_insert_color(&cfqg->rb_node, &st->rb);
810}
811
812static void
813cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
814{
815    struct cfq_rb_root *st = &cfqd->grp_service_tree;
816    struct cfq_group *__cfqg;
817    struct rb_node *n;
818
819    cfqg->nr_cfqq++;
820    if (cfqg->on_st)
821        return;
822
823    /*
824     * Currently put the group at the end. Later implement something
825     * so that groups get lesser vtime based on their weights, so that
826     * if group does not loose all if it was not continously backlogged.
827     */
828    n = rb_last(&st->rb);
829    if (n) {
830        __cfqg = rb_entry_cfqg(n);
831        cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
832    } else
833        cfqg->vdisktime = st->min_vdisktime;
834
835    __cfq_group_service_tree_add(st, cfqg);
836    cfqg->on_st = true;
837    st->total_weight += cfqg->weight;
838}
839
840static void
841cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
842{
843    struct cfq_rb_root *st = &cfqd->grp_service_tree;
844
845    if (st->active == &cfqg->rb_node)
846        st->active = NULL;
847
848    BUG_ON(cfqg->nr_cfqq < 1);
849    cfqg->nr_cfqq--;
850
851    /* If there are other cfq queues under this group, don't delete it */
852    if (cfqg->nr_cfqq)
853        return;
854
855    cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
856    cfqg->on_st = false;
857    st->total_weight -= cfqg->weight;
858    if (!RB_EMPTY_NODE(&cfqg->rb_node))
859        cfq_rb_erase(&cfqg->rb_node, st);
860    cfqg->saved_workload_slice = 0;
861    blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
862}
863
864static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
865{
866    unsigned int slice_used;
867
868    /*
869     * Queue got expired before even a single request completed or
870     * got expired immediately after first request completion.
871     */
872    if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
873        /*
874         * Also charge the seek time incurred to the group, otherwise
875         * if there are mutiple queues in the group, each can dispatch
876         * a single request on seeky media and cause lots of seek time
877         * and group will never know it.
878         */
879        slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
880                    1);
881    } else {
882        slice_used = jiffies - cfqq->slice_start;
883        if (slice_used > cfqq->allocated_slice)
884            slice_used = cfqq->allocated_slice;
885    }
886
887    cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
888                cfqq->nr_sectors);
889    return slice_used;
890}
891
892static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
893                struct cfq_queue *cfqq)
894{
895    struct cfq_rb_root *st = &cfqd->grp_service_tree;
896    unsigned int used_sl, charge_sl;
897    int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
898            - cfqg->service_tree_idle.count;
899
900    BUG_ON(nr_sync < 0);
901    used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
902
903    if (!cfq_cfqq_sync(cfqq) && !nr_sync)
904        charge_sl = cfqq->allocated_slice;
905
906    /* Can't update vdisktime while group is on service tree */
907    cfq_rb_erase(&cfqg->rb_node, st);
908    cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
909    __cfq_group_service_tree_add(st, cfqg);
910
911    /* This group is being expired. Save the context */
912    if (time_after(cfqd->workload_expires, jiffies)) {
913        cfqg->saved_workload_slice = cfqd->workload_expires
914                        - jiffies;
915        cfqg->saved_workload = cfqd->serving_type;
916        cfqg->saved_serving_prio = cfqd->serving_prio;
917    } else
918        cfqg->saved_workload_slice = 0;
919
920    cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
921                    st->min_vdisktime);
922    blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
923                        cfqq->nr_sectors);
924}
925
926#ifdef CONFIG_CFQ_GROUP_IOSCHED
927static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
928{
929    if (blkg)
930        return container_of(blkg, struct cfq_group, blkg);
931    return NULL;
932}
933
934void
935cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
936{
937    cfqg_of_blkg(blkg)->weight = weight;
938}
939
940static struct cfq_group *
941cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
942{
943    struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
944    struct cfq_group *cfqg = NULL;
945    void *key = cfqd;
946    int i, j;
947    struct cfq_rb_root *st;
948    struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
949    unsigned int major, minor;
950
951    cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
952    if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
953        sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
954        cfqg->blkg.dev = MKDEV(major, minor);
955        goto done;
956    }
957    if (cfqg || !create)
958        goto done;
959
960    cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
961    if (!cfqg)
962        goto done;
963
964    cfqg->weight = blkcg->weight;
965    for_each_cfqg_st(cfqg, i, j, st)
966        *st = CFQ_RB_ROOT;
967    RB_CLEAR_NODE(&cfqg->rb_node);
968
969    /*
970     * Take the initial reference that will be released on destroy
971     * This can be thought of a joint reference by cgroup and
972     * elevator which will be dropped by either elevator exit
973     * or cgroup deletion path depending on who is exiting first.
974     */
975    atomic_set(&cfqg->ref, 1);
976
977    /* Add group onto cgroup list */
978    sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
979    blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
980                    MKDEV(major, minor));
981
982    /* Add group on cfqd list */
983    hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
984
985done:
986    return cfqg;
987}
988
989/*
990 * Search for the cfq group current task belongs to. If create = 1, then also
991 * create the cfq group if it does not exist. request_queue lock must be held.
992 */
993static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
994{
995    struct cgroup *cgroup;
996    struct cfq_group *cfqg = NULL;
997
998    rcu_read_lock();
999    cgroup = task_cgroup(current, blkio_subsys_id);
1000    cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
1001    if (!cfqg && create)
1002        cfqg = &cfqd->root_group;
1003    rcu_read_unlock();
1004    return cfqg;
1005}
1006
1007static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1008{
1009    /* Currently, all async queues are mapped to root group */
1010    if (!cfq_cfqq_sync(cfqq))
1011        cfqg = &cfqq->cfqd->root_group;
1012
1013    cfqq->cfqg = cfqg;
1014    /* cfqq reference on cfqg */
1015    atomic_inc(&cfqq->cfqg->ref);
1016}
1017
1018static void cfq_put_cfqg(struct cfq_group *cfqg)
1019{
1020    struct cfq_rb_root *st;
1021    int i, j;
1022
1023    BUG_ON(atomic_read(&cfqg->ref) <= 0);
1024    if (!atomic_dec_and_test(&cfqg->ref))
1025        return;
1026    for_each_cfqg_st(cfqg, i, j, st)
1027        BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1028    kfree(cfqg);
1029}
1030
1031static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1032{
1033    /* Something wrong if we are trying to remove same group twice */
1034    BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1035
1036    hlist_del_init(&cfqg->cfqd_node);
1037
1038    /*
1039     * Put the reference taken at the time of creation so that when all
1040     * queues are gone, group can be destroyed.
1041     */
1042    cfq_put_cfqg(cfqg);
1043}
1044
1045static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1046{
1047    struct hlist_node *pos, *n;
1048    struct cfq_group *cfqg;
1049
1050    hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1051        /*
1052         * If cgroup removal path got to blk_group first and removed
1053         * it from cgroup list, then it will take care of destroying
1054         * cfqg also.
1055         */
1056        if (!blkiocg_del_blkio_group(&cfqg->blkg))
1057            cfq_destroy_cfqg(cfqd, cfqg);
1058    }
1059}
1060
1061/*
1062 * Blk cgroup controller notification saying that blkio_group object is being
1063 * delinked as associated cgroup object is going away. That also means that
1064 * no new IO will come in this group. So get rid of this group as soon as
1065 * any pending IO in the group is finished.
1066 *
1067 * This function is called under rcu_read_lock(). key is the rcu protected
1068 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1069 * read lock.
1070 *
1071 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1072 * it should not be NULL as even if elevator was exiting, cgroup deltion
1073 * path got to it first.
1074 */
1075void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1076{
1077    unsigned long flags;
1078    struct cfq_data *cfqd = key;
1079
1080    spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1081    cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1082    spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1083}
1084
1085#else /* GROUP_IOSCHED */
1086static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1087{
1088    return &cfqd->root_group;
1089}
1090static inline void
1091cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1092    cfqq->cfqg = cfqg;
1093}
1094
1095static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1096static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1097
1098#endif /* GROUP_IOSCHED */
1099
1100/*
1101 * The cfqd->service_trees holds all pending cfq_queue's that have
1102 * requests waiting to be processed. It is sorted in the order that
1103 * we will service the queues.
1104 */
1105static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1106                 bool add_front)
1107{
1108    struct rb_node **p, *parent;
1109    struct cfq_queue *__cfqq;
1110    unsigned long rb_key;
1111    struct cfq_rb_root *service_tree;
1112    int left;
1113    int new_cfqq = 1;
1114    int group_changed = 0;
1115
1116#ifdef CONFIG_CFQ_GROUP_IOSCHED
1117    if (!cfqd->cfq_group_isolation
1118        && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
1119        && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) {
1120        /* Move this cfq to root group */
1121        cfq_log_cfqq(cfqd, cfqq, "moving to root group");
1122        if (!RB_EMPTY_NODE(&cfqq->rb_node))
1123            cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1124        cfqq->orig_cfqg = cfqq->cfqg;
1125        cfqq->cfqg = &cfqd->root_group;
1126        atomic_inc(&cfqd->root_group.ref);
1127        group_changed = 1;
1128    } else if (!cfqd->cfq_group_isolation
1129           && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
1130        /* cfqq is sequential now needs to go to its original group */
1131        BUG_ON(cfqq->cfqg != &cfqd->root_group);
1132        if (!RB_EMPTY_NODE(&cfqq->rb_node))
1133            cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1134        cfq_put_cfqg(cfqq->cfqg);
1135        cfqq->cfqg = cfqq->orig_cfqg;
1136        cfqq->orig_cfqg = NULL;
1137        group_changed = 1;
1138        cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
1139    }
1140#endif
1141
1142    service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1143                        cfqq_type(cfqq));
1144    if (cfq_class_idle(cfqq)) {
1145        rb_key = CFQ_IDLE_DELAY;
1146        parent = rb_last(&service_tree->rb);
1147        if (parent && parent != &cfqq->rb_node) {
1148            __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1149            rb_key += __cfqq->rb_key;
1150        } else
1151            rb_key += jiffies;
1152    } else if (!add_front) {
1153        /*
1154         * Get our rb key offset. Subtract any residual slice
1155         * value carried from last service. A negative resid
1156         * count indicates slice overrun, and this should position
1157         * the next service time further away in the tree.
1158         */
1159        rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1160        rb_key -= cfqq->slice_resid;
1161        cfqq->slice_resid = 0;
1162    } else {
1163        rb_key = -HZ;
1164        __cfqq = cfq_rb_first(service_tree);
1165        rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1166    }
1167
1168    if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1169        new_cfqq = 0;
1170        /*
1171         * same position, nothing more to do
1172         */
1173        if (rb_key == cfqq->rb_key &&
1174            cfqq->service_tree == service_tree)
1175            return;
1176
1177        cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1178        cfqq->service_tree = NULL;
1179    }
1180
1181    left = 1;
1182    parent = NULL;
1183    cfqq->service_tree = service_tree;
1184    p = &service_tree->rb.rb_node;
1185    while (*p) {
1186        struct rb_node **n;
1187
1188        parent = *p;
1189        __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1190
1191        /*
1192         * sort by key, that represents service time.
1193         */
1194        if (time_before(rb_key, __cfqq->rb_key))
1195            n = &(*p)->rb_left;
1196        else {
1197            n = &(*p)->rb_right;
1198            left = 0;
1199        }
1200
1201        p = n;
1202    }
1203
1204    if (left)
1205        service_tree->left = &cfqq->rb_node;
1206
1207    cfqq->rb_key = rb_key;
1208    rb_link_node(&cfqq->rb_node, parent, p);
1209    rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1210    service_tree->count++;
1211    if ((add_front || !new_cfqq) && !group_changed)
1212        return;
1213    cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1214}
1215
1216static struct cfq_queue *
1217cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1218             sector_t sector, struct rb_node **ret_parent,
1219             struct rb_node ***rb_link)
1220{
1221    struct rb_node **p, *parent;
1222    struct cfq_queue *cfqq = NULL;
1223
1224    parent = NULL;
1225    p = &root->rb_node;
1226    while (*p) {
1227        struct rb_node **n;
1228
1229        parent = *p;
1230        cfqq = rb_entry(parent, struct cfq_queue, p_node);
1231
1232        /*
1233         * Sort strictly based on sector. Smallest to the left,
1234         * largest to the right.
1235         */
1236        if (sector > blk_rq_pos(cfqq->next_rq))
1237            n = &(*p)->rb_right;
1238        else if (sector < blk_rq_pos(cfqq->next_rq))
1239            n = &(*p)->rb_left;
1240        else
1241            break;
1242        p = n;
1243        cfqq = NULL;
1244    }
1245
1246    *ret_parent = parent;
1247    if (rb_link)
1248        *rb_link = p;
1249    return cfqq;
1250}
1251
1252static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1253{
1254    struct rb_node **p, *parent;
1255    struct cfq_queue *__cfqq;
1256
1257    if (cfqq->p_root) {
1258        rb_erase(&cfqq->p_node, cfqq->p_root);
1259        cfqq->p_root = NULL;
1260    }
1261
1262    if (cfq_class_idle(cfqq))
1263        return;
1264    if (!cfqq->next_rq)
1265        return;
1266
1267    cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1268    __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1269                      blk_rq_pos(cfqq->next_rq), &parent, &p);
1270    if (!__cfqq) {
1271        rb_link_node(&cfqq->p_node, parent, p);
1272        rb_insert_color(&cfqq->p_node, cfqq->p_root);
1273    } else
1274        cfqq->p_root = NULL;
1275}
1276
1277/*
1278 * Update cfqq's position in the service tree.
1279 */
1280static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1281{
1282    /*
1283     * Resorting requires the cfqq to be on the RR list already.
1284     */
1285    if (cfq_cfqq_on_rr(cfqq)) {
1286        cfq_service_tree_add(cfqd, cfqq, 0);
1287        cfq_prio_tree_add(cfqd, cfqq);
1288    }
1289}
1290
1291/*
1292 * add to busy list of queues for service, trying to be fair in ordering
1293 * the pending list according to last request service
1294 */
1295static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1296{
1297    cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1298    BUG_ON(cfq_cfqq_on_rr(cfqq));
1299    cfq_mark_cfqq_on_rr(cfqq);
1300    cfqd->busy_queues++;
1301
1302    cfq_resort_rr_list(cfqd, cfqq);
1303}
1304
1305/*
1306 * Called when the cfqq no longer has requests pending, remove it from
1307 * the service tree.
1308 */
1309static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1310{
1311    cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1312    BUG_ON(!cfq_cfqq_on_rr(cfqq));
1313    cfq_clear_cfqq_on_rr(cfqq);
1314
1315    if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1316        cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1317        cfqq->service_tree = NULL;
1318    }
1319    if (cfqq->p_root) {
1320        rb_erase(&cfqq->p_node, cfqq->p_root);
1321        cfqq->p_root = NULL;
1322    }
1323
1324    cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1325    BUG_ON(!cfqd->busy_queues);
1326    cfqd->busy_queues--;
1327}
1328
1329/*
1330 * rb tree support functions
1331 */
1332static void cfq_del_rq_rb(struct request *rq)
1333{
1334    struct cfq_queue *cfqq = RQ_CFQQ(rq);
1335    const int sync = rq_is_sync(rq);
1336
1337    BUG_ON(!cfqq->queued[sync]);
1338    cfqq->queued[sync]--;
1339
1340    elv_rb_del(&cfqq->sort_list, rq);
1341
1342    if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1343        /*
1344         * Queue will be deleted from service tree when we actually
1345         * expire it later. Right now just remove it from prio tree
1346         * as it is empty.
1347         */
1348        if (cfqq->p_root) {
1349            rb_erase(&cfqq->p_node, cfqq->p_root);
1350            cfqq->p_root = NULL;
1351        }
1352    }
1353}
1354
1355static void cfq_add_rq_rb(struct request *rq)
1356{
1357    struct cfq_queue *cfqq = RQ_CFQQ(rq);
1358    struct cfq_data *cfqd = cfqq->cfqd;
1359    struct request *__alias, *prev;
1360
1361    cfqq->queued[rq_is_sync(rq)]++;
1362
1363    /*
1364     * looks a little odd, but the first insert might return an alias.
1365     * if that happens, put the alias on the dispatch list
1366     */
1367    while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1368        cfq_dispatch_insert(cfqd->queue, __alias);
1369
1370    if (!cfq_cfqq_on_rr(cfqq))
1371        cfq_add_cfqq_rr(cfqd, cfqq);
1372
1373    /*
1374     * check if this request is a better next-serve candidate
1375     */
1376    prev = cfqq->next_rq;
1377    cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1378
1379    /*
1380     * adjust priority tree position, if ->next_rq changes
1381     */
1382    if (prev != cfqq->next_rq)
1383        cfq_prio_tree_add(cfqd, cfqq);
1384
1385    BUG_ON(!cfqq->next_rq);
1386}
1387
1388static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1389{
1390    elv_rb_del(&cfqq->sort_list, rq);
1391    cfqq->queued[rq_is_sync(rq)]--;
1392    cfq_add_rq_rb(rq);
1393}
1394
1395static struct request *
1396cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1397{
1398    struct task_struct *tsk = current;
1399    struct cfq_io_context *cic;
1400    struct cfq_queue *cfqq;
1401
1402    cic = cfq_cic_lookup(cfqd, tsk->io_context);
1403    if (!cic)
1404        return NULL;
1405
1406    cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1407    if (cfqq) {
1408        sector_t sector = bio->bi_sector + bio_sectors(bio);
1409
1410        return elv_rb_find(&cfqq->sort_list, sector);
1411    }
1412
1413    return NULL;
1414}
1415
1416static void cfq_activate_request(struct request_queue *q, struct request *rq)
1417{
1418    struct cfq_data *cfqd = q->elevator->elevator_data;
1419
1420    cfqd->rq_in_driver++;
1421    cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1422                        cfqd->rq_in_driver);
1423
1424    cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1425}
1426
1427static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1428{
1429    struct cfq_data *cfqd = q->elevator->elevator_data;
1430
1431    WARN_ON(!cfqd->rq_in_driver);
1432    cfqd->rq_in_driver--;
1433    cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1434                        cfqd->rq_in_driver);
1435}
1436
1437static void cfq_remove_request(struct request *rq)
1438{
1439    struct cfq_queue *cfqq = RQ_CFQQ(rq);
1440
1441    if (cfqq->next_rq == rq)
1442        cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1443
1444    list_del_init(&rq->queuelist);
1445    cfq_del_rq_rb(rq);
1446
1447    cfqq->cfqd->rq_queued--;
1448    if (rq_is_meta(rq)) {
1449        WARN_ON(!cfqq->meta_pending);
1450        cfqq->meta_pending--;
1451    }
1452}
1453
1454static int cfq_merge(struct request_queue *q, struct request **req,
1455             struct bio *bio)
1456{
1457    struct cfq_data *cfqd = q->elevator->elevator_data;
1458    struct request *__rq;
1459
1460    __rq = cfq_find_rq_fmerge(cfqd, bio);
1461    if (__rq && elv_rq_merge_ok(__rq, bio)) {
1462        *req = __rq;
1463        return ELEVATOR_FRONT_MERGE;
1464    }
1465
1466    return ELEVATOR_NO_MERGE;
1467}
1468
1469static void cfq_merged_request(struct request_queue *q, struct request *req,
1470                   int type)
1471{
1472    if (type == ELEVATOR_FRONT_MERGE) {
1473        struct cfq_queue *cfqq = RQ_CFQQ(req);
1474
1475        cfq_reposition_rq_rb(cfqq, req);
1476    }
1477}
1478
1479static void
1480cfq_merged_requests(struct request_queue *q, struct request *rq,
1481            struct request *next)
1482{
1483    struct cfq_queue *cfqq = RQ_CFQQ(rq);
1484    /*
1485     * reposition in fifo if next is older than rq
1486     */
1487    if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1488        time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1489        list_move(&rq->queuelist, &next->queuelist);
1490        rq_set_fifo_time(rq, rq_fifo_time(next));
1491    }
1492
1493    if (cfqq->next_rq == next)
1494        cfqq->next_rq = rq;
1495    cfq_remove_request(next);
1496}
1497
1498static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1499               struct bio *bio)
1500{
1501    struct cfq_data *cfqd = q->elevator->elevator_data;
1502    struct cfq_io_context *cic;
1503    struct cfq_queue *cfqq;
1504
1505    /*
1506     * Disallow merge of a sync bio into an async request.
1507     */
1508    if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1509        return false;
1510
1511    /*
1512     * Lookup the cfqq that this bio will be queued with. Allow
1513     * merge only if rq is queued there.
1514     */
1515    cic = cfq_cic_lookup(cfqd, current->io_context);
1516    if (!cic)
1517        return false;
1518
1519    cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1520    return cfqq == RQ_CFQQ(rq);
1521}
1522
1523static void __cfq_set_active_queue(struct cfq_data *cfqd,
1524                   struct cfq_queue *cfqq)
1525{
1526    if (cfqq) {
1527        cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1528                cfqd->serving_prio, cfqd->serving_type);
1529        cfqq->slice_start = 0;
1530        cfqq->dispatch_start = jiffies;
1531        cfqq->allocated_slice = 0;
1532        cfqq->slice_end = 0;
1533        cfqq->slice_dispatch = 0;
1534        cfqq->nr_sectors = 0;
1535
1536        cfq_clear_cfqq_wait_request(cfqq);
1537        cfq_clear_cfqq_must_dispatch(cfqq);
1538        cfq_clear_cfqq_must_alloc_slice(cfqq);
1539        cfq_clear_cfqq_fifo_expire(cfqq);
1540        cfq_mark_cfqq_slice_new(cfqq);
1541
1542        del_timer(&cfqd->idle_slice_timer);
1543    }
1544
1545    cfqd->active_queue = cfqq;
1546}
1547
1548/*
1549 * current cfqq expired its slice (or was too idle), select new one
1550 */
1551static void
1552__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1553            bool timed_out)
1554{
1555    cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1556
1557    if (cfq_cfqq_wait_request(cfqq))
1558        del_timer(&cfqd->idle_slice_timer);
1559
1560    cfq_clear_cfqq_wait_request(cfqq);
1561    cfq_clear_cfqq_wait_busy(cfqq);
1562
1563    /*
1564     * If this cfqq is shared between multiple processes, check to
1565     * make sure that those processes are still issuing I/Os within
1566     * the mean seek distance. If not, it may be time to break the
1567     * queues apart again.
1568     */
1569    if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1570        cfq_mark_cfqq_split_coop(cfqq);
1571
1572    /*
1573     * store what was left of this slice, if the queue idled/timed out
1574     */
1575    if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1576        cfqq->slice_resid = cfqq->slice_end - jiffies;
1577        cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1578    }
1579
1580    cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1581
1582    if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1583        cfq_del_cfqq_rr(cfqd, cfqq);
1584
1585    cfq_resort_rr_list(cfqd, cfqq);
1586
1587    if (cfqq == cfqd->active_queue)
1588        cfqd->active_queue = NULL;
1589
1590    if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1591        cfqd->grp_service_tree.active = NULL;
1592
1593    if (cfqd->active_cic) {
1594        put_io_context(cfqd->active_cic->ioc);
1595        cfqd->active_cic = NULL;
1596    }
1597}
1598
1599static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1600{
1601    struct cfq_queue *cfqq = cfqd->active_queue;
1602
1603    if (cfqq)
1604        __cfq_slice_expired(cfqd, cfqq, timed_out);
1605}
1606
1607/*
1608 * Get next queue for service. Unless we have a queue preemption,
1609 * we'll simply select the first cfqq in the service tree.
1610 */
1611static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1612{
1613    struct cfq_rb_root *service_tree =
1614        service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1615                    cfqd->serving_type);
1616
1617    if (!cfqd->rq_queued)
1618        return NULL;
1619
1620    /* There is nothing to dispatch */
1621    if (!service_tree)
1622        return NULL;
1623    if (RB_EMPTY_ROOT(&service_tree->rb))
1624        return NULL;
1625    return cfq_rb_first(service_tree);
1626}
1627
1628static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1629{
1630    struct cfq_group *cfqg;
1631    struct cfq_queue *cfqq;
1632    int i, j;
1633    struct cfq_rb_root *st;
1634
1635    if (!cfqd->rq_queued)
1636        return NULL;
1637
1638    cfqg = cfq_get_next_cfqg(cfqd);
1639    if (!cfqg)
1640        return NULL;
1641
1642    for_each_cfqg_st(cfqg, i, j, st)
1643        if ((cfqq = cfq_rb_first(st)) != NULL)
1644            return cfqq;
1645    return NULL;
1646}
1647
1648/*
1649 * Get and set a new active queue for service.
1650 */
1651static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1652                          struct cfq_queue *cfqq)
1653{
1654    if (!cfqq)
1655        cfqq = cfq_get_next_queue(cfqd);
1656
1657    __cfq_set_active_queue(cfqd, cfqq);
1658    return cfqq;
1659}
1660
1661static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1662                      struct request *rq)
1663{
1664    if (blk_rq_pos(rq) >= cfqd->last_position)
1665        return blk_rq_pos(rq) - cfqd->last_position;
1666    else
1667        return cfqd->last_position - blk_rq_pos(rq);
1668}
1669
1670static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1671                   struct request *rq)
1672{
1673    return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1674}
1675
1676static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1677                    struct cfq_queue *cur_cfqq)
1678{
1679    struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1680    struct rb_node *parent, *node;
1681    struct cfq_queue *__cfqq;
1682    sector_t sector = cfqd->last_position;
1683
1684    if (RB_EMPTY_ROOT(root))
1685        return NULL;
1686
1687    /*
1688     * First, if we find a request starting at the end of the last
1689     * request, choose it.
1690     */
1691    __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1692    if (__cfqq)
1693        return __cfqq;
1694
1695    /*
1696     * If the exact sector wasn't found, the parent of the NULL leaf
1697     * will contain the closest sector.
1698     */
1699    __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1700    if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1701        return __cfqq;
1702
1703    if (blk_rq_pos(__cfqq->next_rq) < sector)
1704        node = rb_next(&__cfqq->p_node);
1705    else
1706        node = rb_prev(&__cfqq->p_node);
1707    if (!node)
1708        return NULL;
1709
1710    __cfqq = rb_entry(node, struct cfq_queue, p_node);
1711    if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1712        return __cfqq;
1713
1714    return NULL;
1715}
1716
1717/*
1718 * cfqd - obvious
1719 * cur_cfqq - passed in so that we don't decide that the current queue is
1720 * closely cooperating with itself.
1721 *
1722 * So, basically we're assuming that that cur_cfqq has dispatched at least
1723 * one request, and that cfqd->last_position reflects a position on the disk
1724 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1725 * assumption.
1726 */
1727static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1728                          struct cfq_queue *cur_cfqq)
1729{
1730    struct cfq_queue *cfqq;
1731
1732    if (cfq_class_idle(cur_cfqq))
1733        return NULL;
1734    if (!cfq_cfqq_sync(cur_cfqq))
1735        return NULL;
1736    if (CFQQ_SEEKY(cur_cfqq))
1737        return NULL;
1738
1739    /*
1740     * Don't search priority tree if it's the only queue in the group.
1741     */
1742    if (cur_cfqq->cfqg->nr_cfqq == 1)
1743        return NULL;
1744
1745    /*
1746     * We should notice if some of the queues are cooperating, eg
1747     * working closely on the same area of the disk. In that case,
1748     * we can group them together and don't waste time idling.
1749     */
1750    cfqq = cfqq_close(cfqd, cur_cfqq);
1751    if (!cfqq)
1752        return NULL;
1753
1754    /* If new queue belongs to different cfq_group, don't choose it */
1755    if (cur_cfqq->cfqg != cfqq->cfqg)
1756        return NULL;
1757
1758    /*
1759     * It only makes sense to merge sync queues.
1760     */
1761    if (!cfq_cfqq_sync(cfqq))
1762        return NULL;
1763    if (CFQQ_SEEKY(cfqq))
1764        return NULL;
1765
1766    /*
1767     * Do not merge queues of different priority classes
1768     */
1769    if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1770        return NULL;
1771
1772    return cfqq;
1773}
1774
1775/*
1776 * Determine whether we should enforce idle window for this queue.
1777 */
1778
1779static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1780{
1781    enum wl_prio_t prio = cfqq_prio(cfqq);
1782    struct cfq_rb_root *service_tree = cfqq->service_tree;
1783
1784    BUG_ON(!service_tree);
1785    BUG_ON(!service_tree->count);
1786
1787    /* We never do for idle class queues. */
1788    if (prio == IDLE_WORKLOAD)
1789        return false;
1790
1791    /* We do for queues that were marked with idle window flag. */
1792    if (cfq_cfqq_idle_window(cfqq) &&
1793       !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1794        return true;
1795
1796    /*
1797     * Otherwise, we do only if they are the last ones
1798     * in their service tree.
1799     */
1800    if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
1801        return 1;
1802    cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
1803            service_tree->count);
1804    return 0;
1805}
1806
1807static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1808{
1809    struct cfq_queue *cfqq = cfqd->active_queue;
1810    struct cfq_io_context *cic;
1811    unsigned long sl;
1812
1813    /*
1814     * SSD device without seek penalty, disable idling. But only do so
1815     * for devices that support queuing, otherwise we still have a problem
1816     * with sync vs async workloads.
1817     */
1818    if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1819        return;
1820
1821    WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1822    WARN_ON(cfq_cfqq_slice_new(cfqq));
1823
1824    /*
1825     * idle is disabled, either manually or by past process history
1826     */
1827    if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1828        return;
1829
1830    /*
1831     * still active requests from this queue, don't idle
1832     */
1833    if (cfqq->dispatched)
1834        return;
1835
1836    /*
1837     * task has exited, don't wait
1838     */
1839    cic = cfqd->active_cic;
1840    if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1841        return;
1842
1843    /*
1844     * If our average think time is larger than the remaining time
1845     * slice, then don't idle. This avoids overrunning the allotted
1846     * time slice.
1847     */
1848    if (sample_valid(cic->ttime_samples) &&
1849        (cfqq->slice_end - jiffies < cic->ttime_mean)) {
1850        cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
1851                cic->ttime_mean);
1852        return;
1853    }
1854
1855    cfq_mark_cfqq_wait_request(cfqq);
1856
1857    sl = cfqd->cfq_slice_idle;
1858
1859    mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1860    cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1861}
1862
1863/*
1864 * Move request from internal lists to the request queue dispatch list.
1865 */
1866static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1867{
1868    struct cfq_data *cfqd = q->elevator->elevator_data;
1869    struct cfq_queue *cfqq = RQ_CFQQ(rq);
1870
1871    cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1872
1873    cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1874    cfq_remove_request(rq);
1875    cfqq->dispatched++;
1876    elv_dispatch_sort(q, rq);
1877
1878    cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
1879    cfqq->nr_sectors += blk_rq_sectors(rq);
1880}
1881
1882/*
1883 * return expired entry, or NULL to just start from scratch in rbtree
1884 */
1885static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1886{
1887    struct request *rq = NULL;
1888
1889    if (cfq_cfqq_fifo_expire(cfqq))
1890        return NULL;
1891
1892    cfq_mark_cfqq_fifo_expire(cfqq);
1893
1894    if (list_empty(&cfqq->fifo))
1895        return NULL;
1896
1897    rq = rq_entry_fifo(cfqq->fifo.next);
1898    if (time_before(jiffies, rq_fifo_time(rq)))
1899        rq = NULL;
1900
1901    cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1902    return rq;
1903}
1904
1905static inline int
1906cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1907{
1908    const int base_rq = cfqd->cfq_slice_async_rq;
1909
1910    WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1911
1912    return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1913}
1914
1915/*
1916 * Must be called with the queue_lock held.
1917 */
1918static int cfqq_process_refs(struct cfq_queue *cfqq)
1919{
1920    int process_refs, io_refs;
1921
1922    io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1923    process_refs = atomic_read(&cfqq->ref) - io_refs;
1924    BUG_ON(process_refs < 0);
1925    return process_refs;
1926}
1927
1928static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1929{
1930    int process_refs, new_process_refs;
1931    struct cfq_queue *__cfqq;
1932
1933    /* Avoid a circular list and skip interim queue merges */
1934    while ((__cfqq = new_cfqq->new_cfqq)) {
1935        if (__cfqq == cfqq)
1936            return;
1937        new_cfqq = __cfqq;
1938    }
1939
1940    process_refs = cfqq_process_refs(cfqq);
1941    /*
1942     * If the process for the cfqq has gone away, there is no
1943     * sense in merging the queues.
1944     */
1945    if (process_refs == 0)
1946        return;
1947
1948    /*
1949     * Merge in the direction of the lesser amount of work.
1950     */
1951    new_process_refs = cfqq_process_refs(new_cfqq);
1952    if (new_process_refs >= process_refs) {
1953        cfqq->new_cfqq = new_cfqq;
1954        atomic_add(process_refs, &new_cfqq->ref);
1955    } else {
1956        new_cfqq->new_cfqq = cfqq;
1957        atomic_add(new_process_refs, &cfqq->ref);
1958    }
1959}
1960
1961static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1962                struct cfq_group *cfqg, enum wl_prio_t prio)
1963{
1964    struct cfq_queue *queue;
1965    int i;
1966    bool key_valid = false;
1967    unsigned long lowest_key = 0;
1968    enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1969
1970    for (i = 0; i <= SYNC_WORKLOAD; ++i) {
1971        /* select the one with lowest rb_key */
1972        queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
1973        if (queue &&
1974            (!key_valid || time_before(queue->rb_key, lowest_key))) {
1975            lowest_key = queue->rb_key;
1976            cur_best = i;
1977            key_valid = true;
1978        }
1979    }
1980
1981    return cur_best;
1982}
1983
1984static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1985{
1986    unsigned slice;
1987    unsigned count;
1988    struct cfq_rb_root *st;
1989    unsigned group_slice;
1990
1991    if (!cfqg) {
1992        cfqd->serving_prio = IDLE_WORKLOAD;
1993        cfqd->workload_expires = jiffies + 1;
1994        return;
1995    }
1996
1997    /* Choose next priority. RT > BE > IDLE */
1998    if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
1999        cfqd->serving_prio = RT_WORKLOAD;
2000    else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2001        cfqd->serving_prio = BE_WORKLOAD;
2002    else {
2003        cfqd->serving_prio = IDLE_WORKLOAD;
2004        cfqd->workload_expires = jiffies + 1;
2005        return;
2006    }
2007
2008    /*
2009     * For RT and BE, we have to choose also the type
2010     * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2011     * expiration time
2012     */
2013    st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2014    count = st->count;
2015
2016    /*
2017     * check workload expiration, and that we still have other queues ready
2018     */
2019    if (count && !time_after(jiffies, cfqd->workload_expires))
2020        return;
2021
2022    /* otherwise select new workload type */
2023    cfqd->serving_type =
2024        cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2025    st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2026    count = st->count;
2027
2028    /*
2029     * the workload slice is computed as a fraction of target latency
2030     * proportional to the number of queues in that workload, over
2031     * all the queues in the same priority class
2032     */
2033    group_slice = cfq_group_slice(cfqd, cfqg);
2034
2035    slice = group_slice * count /
2036        max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2037              cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2038
2039    if (cfqd->serving_type == ASYNC_WORKLOAD) {
2040        unsigned int tmp;
2041
2042        /*
2043         * Async queues are currently system wide. Just taking
2044         * proportion of queues with-in same group will lead to higher
2045         * async ratio system wide as generally root group is going
2046         * to have higher weight. A more accurate thing would be to
2047         * calculate system wide asnc/sync ratio.
2048         */
2049        tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2050        tmp = tmp/cfqd->busy_queues;
2051        slice = min_t(unsigned, slice, tmp);
2052
2053        /* async workload slice is scaled down according to
2054         * the sync/async slice ratio. */
2055        slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2056    } else
2057        /* sync workload slice is at least 2 * cfq_slice_idle */
2058        slice = max(slice, 2 * cfqd->cfq_slice_idle);
2059
2060    slice = max_t(unsigned, slice, CFQ_MIN_TT);
2061    cfq_log(cfqd, "workload slice:%d", slice);
2062    cfqd->workload_expires = jiffies + slice;
2063    cfqd->noidle_tree_requires_idle = false;
2064}
2065
2066static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2067{
2068    struct cfq_rb_root *st = &cfqd->grp_service_tree;
2069    struct cfq_group *cfqg;
2070
2071    if (RB_EMPTY_ROOT(&st->rb))
2072        return NULL;
2073    cfqg = cfq_rb_first_group(st);
2074    st->active = &cfqg->rb_node;
2075    update_min_vdisktime(st);
2076    return cfqg;
2077}
2078
2079static void cfq_choose_cfqg(struct cfq_data *cfqd)
2080{
2081    struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2082
2083    cfqd->serving_group = cfqg;
2084
2085    /* Restore the workload type data */
2086    if (cfqg->saved_workload_slice) {
2087        cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2088        cfqd->serving_type = cfqg->saved_workload;
2089        cfqd->serving_prio = cfqg->saved_serving_prio;
2090    } else
2091        cfqd->workload_expires = jiffies - 1;
2092
2093    choose_service_tree(cfqd, cfqg);
2094}
2095
2096/*
2097 * Select a queue for service. If we have a current active queue,
2098 * check whether to continue servicing it, or retrieve and set a new one.
2099 */
2100static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2101{
2102    struct cfq_queue *cfqq, *new_cfqq = NULL;
2103
2104    cfqq = cfqd->active_queue;
2105    if (!cfqq)
2106        goto new_queue;
2107
2108    if (!cfqd->rq_queued)
2109        return NULL;
2110
2111    /*
2112     * We were waiting for group to get backlogged. Expire the queue
2113     */
2114    if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2115        goto expire;
2116
2117    /*
2118     * The active queue has run out of time, expire it and select new.
2119     */
2120    if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2121        /*
2122         * If slice had not expired at the completion of last request
2123         * we might not have turned on wait_busy flag. Don't expire
2124         * the queue yet. Allow the group to get backlogged.
2125         *
2126         * The very fact that we have used the slice, that means we
2127         * have been idling all along on this queue and it should be
2128         * ok to wait for this request to complete.
2129         */
2130        if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2131            && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2132            cfqq = NULL;
2133            goto keep_queue;
2134        } else
2135            goto expire;
2136    }
2137
2138    /*
2139     * The active queue has requests and isn't expired, allow it to
2140     * dispatch.
2141     */
2142    if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2143        goto keep_queue;
2144
2145    /*
2146     * If another queue has a request waiting within our mean seek
2147     * distance, let it run. The expire code will check for close
2148     * cooperators and put the close queue at the front of the service
2149     * tree. If possible, merge the expiring queue with the new cfqq.
2150     */
2151    new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2152    if (new_cfqq) {
2153        if (!cfqq->new_cfqq)
2154            cfq_setup_merge(cfqq, new_cfqq);
2155        goto expire;
2156    }
2157
2158    /*
2159     * No requests pending. If the active queue still has requests in
2160     * flight or is idling for a new request, allow either of these
2161     * conditions to happen (or time out) before selecting a new queue.
2162     */
2163    if (timer_pending(&cfqd->idle_slice_timer) ||
2164        (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2165        cfqq = NULL;
2166        goto keep_queue;
2167    }
2168
2169expire:
2170    cfq_slice_expired(cfqd, 0);
2171new_queue:
2172    /*
2173     * Current queue expired. Check if we have to switch to a new
2174     * service tree
2175     */
2176    if (!new_cfqq)
2177        cfq_choose_cfqg(cfqd);
2178
2179    cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2180keep_queue:
2181    return cfqq;
2182}
2183
2184static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2185{
2186    int dispatched = 0;
2187
2188    while (cfqq->next_rq) {
2189        cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2190        dispatched++;
2191    }
2192
2193    BUG_ON(!list_empty(&cfqq->fifo));
2194
2195    /* By default cfqq is not expired if it is empty. Do it explicitly */
2196    __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2197    return dispatched;
2198}
2199
2200/*
2201 * Drain our current requests. Used for barriers and when switching
2202 * io schedulers on-the-fly.
2203 */
2204static int cfq_forced_dispatch(struct cfq_data *cfqd)
2205{
2206    struct cfq_queue *cfqq;
2207    int dispatched = 0;
2208
2209    /* Expire the timeslice of the current active queue first */
2210    cfq_slice_expired(cfqd, 0);
2211    while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2212        __cfq_set_active_queue(cfqd, cfqq);
2213        dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2214    }
2215
2216    BUG_ON(cfqd->busy_queues);
2217
2218    cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2219    return dispatched;
2220}
2221
2222static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2223    struct cfq_queue *cfqq)
2224{
2225    /* the queue hasn't finished any request, can't estimate */
2226    if (cfq_cfqq_slice_new(cfqq))
2227        return 1;
2228    if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2229        cfqq->slice_end))
2230        return 1;
2231
2232    return 0;
2233}
2234
2235static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2236{
2237    unsigned int max_dispatch;
2238
2239    /*
2240     * Drain async requests before we start sync IO
2241     */
2242    if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2243        return false;
2244
2245    /*
2246     * If this is an async queue and we have sync IO in flight, let it wait
2247     */
2248    if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2249        return false;
2250
2251    max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2252    if (cfq_class_idle(cfqq))
2253        max_dispatch = 1;
2254
2255    /*
2256     * Does this cfqq already have too much IO in flight?
2257     */
2258    if (cfqq->dispatched >= max_dispatch) {
2259        /*
2260         * idle queue must always only have a single IO in flight
2261         */
2262        if (cfq_class_idle(cfqq))
2263            return false;
2264
2265        /*
2266         * We have other queues, don't allow more IO from this one
2267         */
2268        if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq))
2269            return false;
2270
2271        /*
2272         * Sole queue user, no limit
2273         */
2274        if (cfqd->busy_queues == 1)
2275            max_dispatch = -1;
2276        else
2277            /*
2278             * Normally we start throttling cfqq when cfq_quantum/2
2279             * requests have been dispatched. But we can drive
2280             * deeper queue depths at the beginning of slice
2281             * subjected to upper limit of cfq_quantum.
2282             * */
2283            max_dispatch = cfqd->cfq_quantum;
2284    }
2285
2286    /*
2287     * Async queues must wait a bit before being allowed dispatch.
2288     * We also ramp up the dispatch depth gradually for async IO,
2289     * based on the last sync IO we serviced
2290     */
2291    if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2292        unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2293        unsigned int depth;
2294
2295        depth = last_sync / cfqd->cfq_slice[1];
2296        if (!depth && !cfqq->dispatched)
2297            depth = 1;
2298        if (depth < max_dispatch)
2299            max_dispatch = depth;
2300    }
2301
2302    /*
2303     * If we're below the current max, allow a dispatch
2304     */
2305    return cfqq->dispatched < max_dispatch;
2306}
2307
2308/*
2309 * Dispatch a request from cfqq, moving them to the request queue
2310 * dispatch list.
2311 */
2312static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2313{
2314    struct request *rq;
2315
2316    BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2317
2318    if (!cfq_may_dispatch(cfqd, cfqq))
2319        return false;
2320
2321    /*
2322     * follow expired path, else get first next available
2323     */
2324    rq = cfq_check_fifo(cfqq);
2325    if (!rq)
2326        rq = cfqq->next_rq;
2327
2328    /*
2329     * insert request into driver dispatch list
2330     */
2331    cfq_dispatch_insert(cfqd->queue, rq);
2332
2333    if (!cfqd->active_cic) {
2334        struct cfq_io_context *cic = RQ_CIC(rq);
2335
2336        atomic_long_inc(&cic->ioc->refcount);
2337        cfqd->active_cic = cic;
2338    }
2339
2340    return true;
2341}
2342
2343/*
2344 * Find the cfqq that we need to service and move a request from that to the
2345 * dispatch list
2346 */
2347static int cfq_dispatch_requests(struct request_queue *q, int force)
2348{
2349    struct cfq_data *cfqd = q->elevator->elevator_data;
2350    struct cfq_queue *cfqq;
2351
2352    if (!cfqd->busy_queues)
2353        return 0;
2354
2355    if (unlikely(force))
2356        return cfq_forced_dispatch(cfqd);
2357
2358    cfqq = cfq_select_queue(cfqd);
2359    if (!cfqq)
2360        return 0;
2361
2362    /*
2363     * Dispatch a request from this cfqq, if it is allowed
2364     */
2365    if (!cfq_dispatch_request(cfqd, cfqq))
2366        return 0;
2367
2368    cfqq->slice_dispatch++;
2369    cfq_clear_cfqq_must_dispatch(cfqq);
2370
2371    /*
2372     * expire an async queue immediately if it has used up its slice. idle
2373     * queue always expire after 1 dispatch round.
2374     */
2375    if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2376        cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2377        cfq_class_idle(cfqq))) {
2378        cfqq->slice_end = jiffies + 1;
2379        cfq_slice_expired(cfqd, 0);
2380    }
2381
2382    cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2383    return 1;
2384}
2385
2386/*
2387 * task holds one reference to the queue, dropped when task exits. each rq
2388 * in-flight on this queue also holds a reference, dropped when rq is freed.
2389 *
2390 * Each cfq queue took a reference on the parent group. Drop it now.
2391 * queue lock must be held here.
2392 */
2393static void cfq_put_queue(struct cfq_queue *cfqq)
2394{
2395    struct cfq_data *cfqd = cfqq->cfqd;
2396    struct cfq_group *cfqg, *orig_cfqg;
2397
2398    BUG_ON(atomic_read(&cfqq->ref) <= 0);
2399
2400    if (!atomic_dec_and_test(&cfqq->ref))
2401        return;
2402
2403    cfq_log_cfqq(cfqd, cfqq, "put_queue");
2404    BUG_ON(rb_first(&cfqq->sort_list));
2405    BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2406    cfqg = cfqq->cfqg;
2407    orig_cfqg = cfqq->orig_cfqg;
2408
2409    if (unlikely(cfqd->active_queue == cfqq)) {
2410        __cfq_slice_expired(cfqd, cfqq, 0);
2411        cfq_schedule_dispatch(cfqd);
2412    }
2413
2414    BUG_ON(cfq_cfqq_on_rr(cfqq));
2415    kmem_cache_free(cfq_pool, cfqq);
2416    cfq_put_cfqg(cfqg);
2417    if (orig_cfqg)
2418        cfq_put_cfqg(orig_cfqg);
2419}
2420
2421/*
2422 * Must always be called with the rcu_read_lock() held
2423 */
2424static void
2425__call_for_each_cic(struct io_context *ioc,
2426            void (*func)(struct io_context *, struct cfq_io_context *))
2427{
2428    struct cfq_io_context *cic;
2429    struct hlist_node *n;
2430
2431    hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2432        func(ioc, cic);
2433}
2434
2435/*
2436 * Call func for each cic attached to this ioc.
2437 */
2438static void
2439call_for_each_cic(struct io_context *ioc,
2440          void (*func)(struct io_context *, struct cfq_io_context *))
2441{
2442    rcu_read_lock();
2443    __call_for_each_cic(ioc, func);
2444    rcu_read_unlock();
2445}
2446
2447static void cfq_cic_free_rcu(struct rcu_head *head)
2448{
2449    struct cfq_io_context *cic;
2450
2451    cic = container_of(head, struct cfq_io_context, rcu_head);
2452
2453    kmem_cache_free(cfq_ioc_pool, cic);
2454    elv_ioc_count_dec(cfq_ioc_count);
2455
2456    if (ioc_gone) {
2457        /*
2458         * CFQ scheduler is exiting, grab exit lock and check
2459         * the pending io context count. If it hits zero,
2460         * complete ioc_gone and set it back to NULL
2461         */
2462        spin_lock(&ioc_gone_lock);
2463        if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2464            complete(ioc_gone);
2465            ioc_gone = NULL;
2466        }
2467        spin_unlock(&ioc_gone_lock);
2468    }
2469}
2470
2471static void cfq_cic_free(struct cfq_io_context *cic)
2472{
2473    call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2474}
2475
2476static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2477{
2478    unsigned long flags;
2479
2480    BUG_ON(!cic->dead_key);
2481
2482    spin_lock_irqsave(&ioc->lock, flags);
2483    radix_tree_delete(&ioc->radix_root, cic->dead_key);
2484    hlist_del_rcu(&cic->cic_list);
2485    spin_unlock_irqrestore(&ioc->lock, flags);
2486
2487    cfq_cic_free(cic);
2488}
2489
2490/*
2491 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2492 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2493 * and ->trim() which is called with the task lock held
2494 */
2495static void cfq_free_io_context(struct io_context *ioc)
2496{
2497    /*
2498     * ioc->refcount is zero here, or we are called from elv_unregister(),
2499     * so no more cic's are allowed to be linked into this ioc. So it
2500     * should be ok to iterate over the known list, we will see all cic's
2501     * since no new ones are added.
2502     */
2503    __call_for_each_cic(ioc, cic_free_func);
2504}
2505
2506static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2507{
2508    struct cfq_queue *__cfqq, *next;
2509
2510    if (unlikely(cfqq == cfqd->active_queue)) {
2511        __cfq_slice_expired(cfqd, cfqq, 0);
2512        cfq_schedule_dispatch(cfqd);
2513    }
2514
2515    /*
2516     * If this queue was scheduled to merge with another queue, be
2517     * sure to drop the reference taken on that queue (and others in
2518     * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
2519     */
2520    __cfqq = cfqq->new_cfqq;
2521    while (__cfqq) {
2522        if (__cfqq == cfqq) {
2523            WARN(1, "cfqq->new_cfqq loop detected\n");
2524            break;
2525        }
2526        next = __cfqq->new_cfqq;
2527        cfq_put_queue(__cfqq);
2528        __cfqq = next;
2529    }
2530
2531    cfq_put_queue(cfqq);
2532}
2533
2534static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2535                     struct cfq_io_context *cic)
2536{
2537    struct io_context *ioc = cic->ioc;
2538
2539    list_del_init(&cic->queue_list);
2540
2541    /*
2542     * Make sure key == NULL is seen for dead queues
2543     */
2544    smp_wmb();
2545    cic->dead_key = (unsigned long) cic->key;
2546    cic->key = NULL;
2547
2548    if (ioc->ioc_data == cic)
2549        rcu_assign_pointer(ioc->ioc_data, NULL);
2550
2551    if (cic->cfqq[BLK_RW_ASYNC]) {
2552        cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2553        cic->cfqq[BLK_RW_ASYNC] = NULL;
2554    }
2555
2556    if (cic->cfqq[BLK_RW_SYNC]) {
2557        cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2558        cic->cfqq[BLK_RW_SYNC] = NULL;
2559    }
2560}
2561
2562static void cfq_exit_single_io_context(struct io_context *ioc,
2563                       struct cfq_io_context *cic)
2564{
2565    struct cfq_data *cfqd = cic->key;
2566
2567    if (cfqd) {
2568        struct request_queue *q = cfqd->queue;
2569        unsigned long flags;
2570
2571        spin_lock_irqsave(q->queue_lock, flags);
2572
2573        /*
2574         * Ensure we get a fresh copy of the ->key to prevent
2575         * race between exiting task and queue
2576         */
2577        smp_read_barrier_depends();
2578        if (cic->key)
2579            __cfq_exit_single_io_context(cfqd, cic);
2580
2581        spin_unlock_irqrestore(q->queue_lock, flags);
2582    }
2583}
2584
2585/*
2586 * The process that ioc belongs to has exited, we need to clean up
2587 * and put the internal structures we have that belongs to that process.
2588 */
2589static void cfq_exit_io_context(struct io_context *ioc)
2590{
2591    call_for_each_cic(ioc, cfq_exit_single_io_context);
2592}
2593
2594static struct cfq_io_context *
2595cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2596{
2597    struct cfq_io_context *cic;
2598
2599    cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2600                            cfqd->queue->node);
2601    if (cic) {
2602        cic->last_end_request = jiffies;
2603        INIT_LIST_HEAD(&cic->queue_list);
2604        INIT_HLIST_NODE(&cic->cic_list);
2605        cic->dtor = cfq_free_io_context;
2606        cic->exit = cfq_exit_io_context;
2607        elv_ioc_count_inc(cfq_ioc_count);
2608    }
2609
2610    return cic;
2611}
2612
2613static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2614{
2615    struct task_struct *tsk = current;
2616    int ioprio_class;
2617
2618    if (!cfq_cfqq_prio_changed(cfqq))
2619        return;
2620
2621    ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2622    switch (ioprio_class) {
2623    default:
2624        printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2625    case IOPRIO_CLASS_NONE:
2626        /*
2627         * no prio set, inherit CPU scheduling settings
2628         */
2629        cfqq->ioprio = task_nice_ioprio(tsk);
2630        cfqq->ioprio_class = task_nice_ioclass(tsk);
2631        break;
2632    case IOPRIO_CLASS_RT:
2633        cfqq->ioprio = task_ioprio(ioc);
2634        cfqq->ioprio_class = IOPRIO_CLASS_RT;
2635        break;
2636    case IOPRIO_CLASS_BE:
2637        cfqq->ioprio = task_ioprio(ioc);
2638        cfqq->ioprio_class = IOPRIO_CLASS_BE;
2639        break;
2640    case IOPRIO_CLASS_IDLE:
2641        cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2642        cfqq->ioprio = 7;
2643        cfq_clear_cfqq_idle_window(cfqq);
2644        break;
2645    }
2646
2647    /*
2648     * keep track of original prio settings in case we have to temporarily
2649     * elevate the priority of this queue
2650     */
2651    cfqq->org_ioprio = cfqq->ioprio;
2652    cfqq->org_ioprio_class = cfqq->ioprio_class;
2653    cfq_clear_cfqq_prio_changed(cfqq);
2654}
2655
2656static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2657{
2658    struct cfq_data *cfqd = cic->key;
2659    struct cfq_queue *cfqq;
2660    unsigned long flags;
2661
2662    if (unlikely(!cfqd))
2663        return;
2664
2665    spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2666
2667    cfqq = cic->cfqq[BLK_RW_ASYNC];
2668    if (cfqq) {
2669        struct cfq_queue *new_cfqq;
2670        new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2671                        GFP_ATOMIC);
2672        if (new_cfqq) {
2673            cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2674            cfq_put_queue(cfqq);
2675        }
2676    }
2677
2678    cfqq = cic->cfqq[BLK_RW_SYNC];
2679    if (cfqq)
2680        cfq_mark_cfqq_prio_changed(cfqq);
2681
2682    spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2683}
2684
2685static void cfq_ioc_set_ioprio(struct io_context *ioc)
2686{
2687    call_for_each_cic(ioc, changed_ioprio);
2688    ioc->ioprio_changed = 0;
2689}
2690
2691static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2692              pid_t pid, bool is_sync)
2693{
2694    RB_CLEAR_NODE(&cfqq->rb_node);
2695    RB_CLEAR_NODE(&cfqq->p_node);
2696    INIT_LIST_HEAD(&cfqq->fifo);
2697
2698    atomic_set(&cfqq->ref, 0);
2699    cfqq->cfqd = cfqd;
2700
2701    cfq_mark_cfqq_prio_changed(cfqq);
2702
2703    if (is_sync) {
2704        if (!cfq_class_idle(cfqq))
2705            cfq_mark_cfqq_idle_window(cfqq);
2706        cfq_mark_cfqq_sync(cfqq);
2707    }
2708    cfqq->pid = pid;
2709}
2710
2711#ifdef CONFIG_CFQ_GROUP_IOSCHED
2712static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2713{
2714    struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2715    struct cfq_data *cfqd = cic->key;
2716    unsigned long flags;
2717    struct request_queue *q;
2718
2719    if (unlikely(!cfqd))
2720        return;
2721
2722    q = cfqd->queue;
2723
2724    spin_lock_irqsave(q->queue_lock, flags);
2725
2726    if (sync_cfqq) {
2727        /*
2728         * Drop reference to sync queue. A new sync queue will be
2729         * assigned in new group upon arrival of a fresh request.
2730         */
2731        cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2732        cic_set_cfqq(cic, NULL, 1);
2733        cfq_put_queue(sync_cfqq);
2734    }
2735
2736    spin_unlock_irqrestore(q->queue_lock, flags);
2737}
2738
2739static void cfq_ioc_set_cgroup(struct io_context *ioc)
2740{
2741    call_for_each_cic(ioc, changed_cgroup);
2742    ioc->cgroup_changed = 0;
2743}
2744#endif /* CONFIG_CFQ_GROUP_IOSCHED */
2745
2746static struct cfq_queue *
2747cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2748             struct io_context *ioc, gfp_t gfp_mask)
2749{
2750    struct cfq_queue *cfqq, *new_cfqq = NULL;
2751    struct cfq_io_context *cic;
2752    struct cfq_group *cfqg;
2753
2754retry:
2755    cfqg = cfq_get_cfqg(cfqd, 1);
2756    cic = cfq_cic_lookup(cfqd, ioc);
2757    /* cic always exists here */
2758    cfqq = cic_to_cfqq(cic, is_sync);
2759
2760    /*
2761     * Always try a new alloc if we fell back to the OOM cfqq
2762     * originally, since it should just be a temporary situation.
2763     */
2764    if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2765        cfqq = NULL;
2766        if (new_cfqq) {
2767            cfqq = new_cfqq;
2768            new_cfqq = NULL;
2769        } else if (gfp_mask & __GFP_WAIT) {
2770            spin_unlock_irq(cfqd->queue->queue_lock);
2771            new_cfqq = kmem_cache_alloc_node(cfq_pool,
2772                    gfp_mask | __GFP_ZERO,
2773                    cfqd->queue->node);
2774            spin_lock_irq(cfqd->queue->queue_lock);
2775            if (new_cfqq)
2776                goto retry;
2777        } else {
2778            cfqq = kmem_cache_alloc_node(cfq_pool,
2779                    gfp_mask | __GFP_ZERO,
2780                    cfqd->queue->node);
2781        }
2782
2783        if (cfqq) {
2784            cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2785            cfq_init_prio_data(cfqq, ioc);
2786            cfq_link_cfqq_cfqg(cfqq, cfqg);
2787            cfq_log_cfqq(cfqd, cfqq, "alloced");
2788        } else
2789            cfqq = &cfqd->oom_cfqq;
2790    }
2791
2792    if (new_cfqq)
2793        kmem_cache_free(cfq_pool, new_cfqq);
2794
2795    return cfqq;
2796}
2797
2798static struct cfq_queue **
2799cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2800{
2801    switch (ioprio_class) {
2802    case IOPRIO_CLASS_RT:
2803        return &cfqd->async_cfqq[0][ioprio];
2804    case IOPRIO_CLASS_BE:
2805        return &cfqd->async_cfqq[1][ioprio];
2806    case IOPRIO_CLASS_IDLE:
2807        return &cfqd->async_idle_cfqq;
2808    default:
2809        BUG();
2810    }
2811}
2812
2813static struct cfq_queue *
2814cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2815          gfp_t gfp_mask)
2816{
2817    const int ioprio = task_ioprio(ioc);
2818    const int ioprio_class = task_ioprio_class(ioc);
2819    struct cfq_queue **async_cfqq = NULL;
2820    struct cfq_queue *cfqq = NULL;
2821
2822    if (!is_sync) {
2823        async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2824        cfqq = *async_cfqq;
2825    }
2826
2827    if (!cfqq)
2828        cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2829
2830    /*
2831     * pin the queue now that it's allocated, scheduler exit will prune it
2832     */
2833    if (!is_sync && !(*async_cfqq)) {
2834        atomic_inc(&cfqq->ref);
2835        *async_cfqq = cfqq;
2836    }
2837
2838    atomic_inc(&cfqq->ref);
2839    return cfqq;
2840}
2841
2842/*
2843 * We drop cfq io contexts lazily, so we may find a dead one.
2844 */
2845static void
2846cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2847          struct cfq_io_context *cic)
2848{
2849    unsigned long flags;
2850
2851    WARN_ON(!list_empty(&cic->queue_list));
2852
2853    spin_lock_irqsave(&ioc->lock, flags);
2854
2855    BUG_ON(ioc->ioc_data == cic);
2856
2857    radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2858    hlist_del_rcu(&cic->cic_list);
2859    spin_unlock_irqrestore(&ioc->lock, flags);
2860
2861    cfq_cic_free(cic);
2862}
2863
2864static struct cfq_io_context *
2865cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2866{
2867    struct cfq_io_context *cic;
2868    unsigned long flags;
2869    void *k;
2870
2871    if (unlikely(!ioc))
2872        return NULL;
2873
2874    rcu_read_lock();
2875
2876    /*
2877     * we maintain a last-hit cache, to avoid browsing over the tree
2878     */
2879    cic = rcu_dereference(ioc->ioc_data);
2880    if (cic && cic->key == cfqd) {
2881        rcu_read_unlock();
2882        return cic;
2883    }
2884
2885    do {
2886        cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2887        rcu_read_unlock();
2888        if (!cic)
2889            break;
2890        /* ->key must be copied to avoid race with cfq_exit_queue() */
2891        k = cic->key;
2892        if (unlikely(!k)) {
2893            cfq_drop_dead_cic(cfqd, ioc, cic);
2894            rcu_read_lock();
2895            continue;
2896        }
2897
2898        spin_lock_irqsave(&ioc->lock, flags);
2899        rcu_assign_pointer(ioc->ioc_data, cic);
2900        spin_unlock_irqrestore(&ioc->lock, flags);
2901        break;
2902    } while (1);
2903
2904    return cic;
2905}
2906
2907/*
2908 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2909 * the process specific cfq io context when entered from the block layer.
2910 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2911 */
2912static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2913            struct cfq_io_context *cic, gfp_t gfp_mask)
2914{
2915    unsigned long flags;
2916    int ret;
2917
2918    ret = radix_tree_preload(gfp_mask);
2919    if (!ret) {
2920        cic->ioc = ioc;
2921        cic->key = cfqd;
2922
2923        spin_lock_irqsave(&ioc->lock, flags);
2924        ret = radix_tree_insert(&ioc->radix_root,
2925                        (unsigned long) cfqd, cic);
2926        if (!ret)
2927            hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2928        spin_unlock_irqrestore(&ioc->lock, flags);
2929
2930        radix_tree_preload_end();
2931
2932        if (!ret) {
2933            spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2934            list_add(&cic->queue_list, &cfqd->cic_list);
2935            spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2936        }
2937    }
2938
2939    if (ret)
2940        printk(KERN_ERR "cfq: cic link failed!\n");
2941
2942    return ret;
2943}
2944
2945/*
2946 * Setup general io context and cfq io context. There can be several cfq
2947 * io contexts per general io context, if this process is doing io to more
2948 * than one device managed by cfq.
2949 */
2950static struct cfq_io_context *
2951cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2952{
2953    struct io_context *ioc = NULL;
2954    struct cfq_io_context *cic;
2955
2956    might_sleep_if(gfp_mask & __GFP_WAIT);
2957
2958    ioc = get_io_context(gfp_mask, cfqd->queue->node);
2959    if (!ioc)
2960        return NULL;
2961
2962    cic = cfq_cic_lookup(cfqd, ioc);
2963    if (cic)
2964        goto out;
2965
2966    cic = cfq_alloc_io_context(cfqd, gfp_mask);
2967    if (cic == NULL)
2968        goto err;
2969
2970    if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2971        goto err_free;
2972
2973out:
2974    smp_read_barrier_depends();
2975    if (unlikely(ioc->ioprio_changed))
2976        cfq_ioc_set_ioprio(ioc);
2977
2978#ifdef CONFIG_CFQ_GROUP_IOSCHED
2979    if (unlikely(ioc->cgroup_changed))
2980        cfq_ioc_set_cgroup(ioc);
2981#endif
2982    return cic;
2983err_free:
2984    cfq_cic_free(cic);
2985err:
2986    put_io_context(ioc);
2987    return NULL;
2988}
2989
2990static void
2991cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2992{
2993    unsigned long elapsed = jiffies - cic->last_end_request;
2994    unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2995
2996    cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2997    cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2998    cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2999}
3000
3001static void
3002cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3003               struct request *rq)
3004{
3005    sector_t sdist = 0;
3006    sector_t n_sec = blk_rq_sectors(rq);
3007    if (cfqq->last_request_pos) {
3008        if (cfqq->last_request_pos < blk_rq_pos(rq))
3009            sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3010        else
3011            sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3012    }
3013
3014    cfqq->seek_history <<= 1;
3015    if (blk_queue_nonrot(cfqd->queue))
3016        cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3017    else
3018        cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3019}
3020
3021/*
3022 * Disable idle window if the process thinks too long or seeks so much that
3023 * it doesn't matter
3024 */
3025static void
3026cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3027               struct cfq_io_context *cic)
3028{
3029    int old_idle, enable_idle;
3030
3031    /*
3032     * Don't idle for async or idle io prio class
3033     */
3034    if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3035        return;
3036
3037    enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3038
3039    if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3040        cfq_mark_cfqq_deep(cfqq);
3041
3042    if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3043        (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3044        enable_idle = 0;
3045    else if (sample_valid(cic->ttime_samples)) {
3046        if (cic->ttime_mean > cfqd->cfq_slice_idle)
3047            enable_idle = 0;
3048        else
3049            enable_idle = 1;
3050    }
3051
3052    if (old_idle != enable_idle) {
3053        cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3054        if (enable_idle)
3055            cfq_mark_cfqq_idle_window(cfqq);
3056        else
3057            cfq_clear_cfqq_idle_window(cfqq);
3058    }
3059}
3060
3061/*
3062 * Check if new_cfqq should preempt the currently active queue. Return 0 for
3063 * no or if we aren't sure, a 1 will cause a preempt.
3064 */
3065static bool
3066cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3067           struct request *rq)
3068{
3069    struct cfq_queue *cfqq;
3070
3071    cfqq = cfqd->active_queue;
3072    if (!cfqq)
3073        return false;
3074
3075    if (cfq_class_idle(new_cfqq))
3076        return false;
3077
3078    if (cfq_class_idle(cfqq))
3079        return true;
3080
3081    /*
3082     * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3083     */
3084    if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3085        return false;
3086
3087    /*
3088     * if the new request is sync, but the currently running queue is
3089     * not, let the sync request have priority.
3090     */
3091    if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3092        return true;
3093
3094    if (new_cfqq->cfqg != cfqq->cfqg)
3095        return false;
3096
3097    if (cfq_slice_used(cfqq))
3098        return true;
3099
3100    /* Allow preemption only if we are idling on sync-noidle tree */
3101    if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3102        cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3103        new_cfqq->service_tree->count == 2 &&
3104        RB_EMPTY_ROOT(&cfqq->sort_list))
3105        return true;
3106
3107    /*
3108     * So both queues are sync. Let the new request get disk time if
3109     * it's a metadata request and the current queue is doing regular IO.
3110     */
3111    if (rq_is_meta(rq) && !cfqq->meta_pending)
3112        return true;
3113
3114    /*
3115     * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3116     */
3117    if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3118        return true;
3119
3120    if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3121        return false;
3122
3123    /*
3124     * if this request is as-good as one we would expect from the
3125     * current cfqq, let it preempt
3126     */
3127    if (cfq_rq_close(cfqd, cfqq, rq))
3128        return true;
3129
3130    return false;
3131}
3132
3133/*
3134 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3135 * let it have half of its nominal slice.
3136 */
3137static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3138{
3139    cfq_log_cfqq(cfqd, cfqq, "preempt");
3140    cfq_slice_expired(cfqd, 1);
3141
3142    /*
3143     * Put the new queue at the front of the of the current list,
3144     * so we know that it will be selected next.
3145     */
3146    BUG_ON(!cfq_cfqq_on_rr(cfqq));
3147
3148    cfq_service_tree_add(cfqd, cfqq, 1);
3149
3150    cfqq->slice_end = 0;
3151    cfq_mark_cfqq_slice_new(cfqq);
3152}
3153
3154/*
3155 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3156 * something we should do about it
3157 */
3158static void
3159cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3160        struct request *rq)
3161{
3162    struct cfq_io_context *cic = RQ_CIC(rq);
3163
3164    cfqd->rq_queued++;
3165    if (rq_is_meta(rq))
3166        cfqq->meta_pending++;
3167
3168    cfq_update_io_thinktime(cfqd, cic);
3169    cfq_update_io_seektime(cfqd, cfqq, rq);
3170    cfq_update_idle_window(cfqd, cfqq, cic);
3171
3172    cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3173
3174    if (cfqq == cfqd->active_queue) {
3175        /*
3176         * Remember that we saw a request from this process, but
3177         * don't start queuing just yet. Otherwise we risk seeing lots
3178         * of tiny requests, because we disrupt the normal plugging
3179         * and merging. If the request is already larger than a single
3180         * page, let it rip immediately. For that case we assume that
3181         * merging is already done. Ditto for a busy system that
3182         * has other work pending, don't risk delaying until the
3183         * idle timer unplug to continue working.
3184         */
3185        if (cfq_cfqq_wait_request(cfqq)) {
3186            if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3187                cfqd->busy_queues > 1) {
3188                del_timer(&cfqd->idle_slice_timer);
3189                cfq_clear_cfqq_wait_request(cfqq);
3190                __blk_run_queue(cfqd->queue);
3191            } else
3192                cfq_mark_cfqq_must_dispatch(cfqq);
3193        }
3194    } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3195        /*
3196         * not the active queue - expire current slice if it is
3197         * idle and has expired it's mean thinktime or this new queue
3198         * has some old slice time left and is of higher priority or
3199         * this new queue is RT and the current one is BE
3200         */
3201        cfq_preempt_queue(cfqd, cfqq);
3202        __blk_run_queue(cfqd->queue);
3203    }
3204}
3205
3206static void cfq_insert_request(struct request_queue *q, struct request *rq)
3207{
3208    struct cfq_data *cfqd = q->elevator->elevator_data;
3209    struct cfq_queue *cfqq = RQ_CFQQ(rq);
3210
3211    cfq_log_cfqq(cfqd, cfqq, "insert_request");
3212    cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3213
3214    rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3215    list_add_tail(&rq->queuelist, &cfqq->fifo);
3216    cfq_add_rq_rb(rq);
3217
3218    cfq_rq_enqueued(cfqd, cfqq, rq);
3219}
3220
3221/*
3222 * Update hw_tag based on peak queue depth over 50 samples under
3223 * sufficient load.
3224 */
3225static void cfq_update_hw_tag(struct cfq_data *cfqd)
3226{
3227    struct cfq_queue *cfqq = cfqd->active_queue;
3228
3229    if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3230        cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3231
3232    if (cfqd->hw_tag == 1)
3233        return;
3234
3235    if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3236        cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3237        return;
3238
3239    /*
3240     * If active queue hasn't enough requests and can idle, cfq might not
3241     * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3242     * case
3243     */
3244    if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3245        cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3246        CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3247        return;
3248
3249    if (cfqd->hw_tag_samples++ < 50)
3250        return;
3251
3252    if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3253        cfqd->hw_tag = 1;
3254    else
3255        cfqd->hw_tag = 0;
3256}
3257
3258static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3259{
3260    struct cfq_io_context *cic = cfqd->active_cic;
3261
3262    /* If there are other queues in the group, don't wait */
3263    if (cfqq->cfqg->nr_cfqq > 1)
3264        return false;
3265
3266    if (cfq_slice_used(cfqq))
3267        return true;
3268
3269    /* if slice left is less than think time, wait busy */
3270    if (cic && sample_valid(cic->ttime_samples)
3271        && (cfqq->slice_end - jiffies < cic->ttime_mean))
3272        return true;
3273
3274    /*
3275     * If think times is less than a jiffy than ttime_mean=0 and above
3276     * will not be true. It might happen that slice has not expired yet
3277     * but will expire soon (4-5 ns) during select_queue(). To cover the
3278     * case where think time is less than a jiffy, mark the queue wait
3279     * busy if only 1 jiffy is left in the slice.
3280     */
3281    if (cfqq->slice_end - jiffies == 1)
3282        return true;
3283
3284    return false;
3285}
3286
3287static void cfq_completed_request(struct request_queue *q, struct request *rq)
3288{
3289    struct cfq_queue *cfqq = RQ_CFQQ(rq);
3290    struct cfq_data *cfqd = cfqq->cfqd;
3291    const int sync = rq_is_sync(rq);
3292    unsigned long now;
3293
3294    now = jiffies;
3295    cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3296
3297    cfq_update_hw_tag(cfqd);
3298
3299    WARN_ON(!cfqd->rq_in_driver);
3300    WARN_ON(!cfqq->dispatched);
3301    cfqd->rq_in_driver--;
3302    cfqq->dispatched--;
3303
3304    cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3305
3306    if (sync) {
3307        RQ_CIC(rq)->last_end_request = now;
3308        if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3309            cfqd->last_delayed_sync = now;
3310    }
3311
3312    /*
3313     * If this is the active queue, check if it needs to be expired,
3314     * or if we want to idle in case it has no pending requests.
3315     */
3316    if (cfqd->active_queue == cfqq) {
3317        const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3318
3319        if (cfq_cfqq_slice_new(cfqq)) {
3320            cfq_set_prio_slice(cfqd, cfqq);
3321            cfq_clear_cfqq_slice_new(cfqq);
3322        }
3323
3324        /*
3325         * Should we wait for next request to come in before we expire
3326         * the queue.
3327         */
3328        if (cfq_should_wait_busy(cfqd, cfqq)) {
3329            cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
3330            cfq_mark_cfqq_wait_busy(cfqq);
3331            cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3332        }
3333
3334        /*
3335         * Idling is not enabled on:
3336         * - expired queues
3337         * - idle-priority queues
3338         * - async queues
3339         * - queues with still some requests queued
3340         * - when there is a close cooperator
3341         */
3342        if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3343            cfq_slice_expired(cfqd, 1);
3344        else if (sync && cfqq_empty &&
3345             !cfq_close_cooperator(cfqd, cfqq)) {
3346            cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3347            /*
3348             * Idling is enabled for SYNC_WORKLOAD.
3349             * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3350             * only if we processed at least one !rq_noidle request
3351             */
3352            if (cfqd->serving_type == SYNC_WORKLOAD
3353                || cfqd->noidle_tree_requires_idle
3354                || cfqq->cfqg->nr_cfqq == 1)
3355                cfq_arm_slice_timer(cfqd);
3356        }
3357    }
3358
3359    if (!cfqd->rq_in_driver)
3360        cfq_schedule_dispatch(cfqd);
3361}
3362
3363/*
3364 * we temporarily boost lower priority queues if they are holding fs exclusive
3365 * resources. they are boosted to normal prio (CLASS_BE/4)
3366 */
3367static void cfq_prio_boost(struct cfq_queue *cfqq)
3368{
3369    if (has_fs_excl()) {
3370        /*
3371         * boost idle prio on transactions that would lock out other
3372         * users of the filesystem
3373         */
3374        if (cfq_class_idle(cfqq))
3375            cfqq->ioprio_class = IOPRIO_CLASS_BE;
3376        if (cfqq->ioprio > IOPRIO_NORM)
3377            cfqq->ioprio = IOPRIO_NORM;
3378    } else {
3379        /*
3380         * unboost the queue (if needed)
3381         */
3382        cfqq->ioprio_class = cfqq->org_ioprio_class;
3383        cfqq->ioprio = cfqq->org_ioprio;
3384    }
3385}
3386
3387static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3388{
3389    if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3390        cfq_mark_cfqq_must_alloc_slice(cfqq);
3391        return ELV_MQUEUE_MUST;
3392    }
3393
3394    return ELV_MQUEUE_MAY;
3395}
3396
3397static int cfq_may_queue(struct request_queue *q, int rw)
3398{
3399    struct cfq_data *cfqd = q->elevator->elevator_data;
3400    struct task_struct *tsk = current;
3401    struct cfq_io_context *cic;
3402    struct cfq_queue *cfqq;
3403
3404    /*
3405     * don't force setup of a queue from here, as a call to may_queue
3406     * does not necessarily imply that a request actually will be queued.
3407     * so just lookup a possibly existing queue, or return 'may queue'
3408     * if that fails
3409     */
3410    cic = cfq_cic_lookup(cfqd, tsk->io_context);
3411    if (!cic)
3412        return ELV_MQUEUE_MAY;
3413
3414    cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3415    if (cfqq) {
3416        cfq_init_prio_data(cfqq, cic->ioc);
3417        cfq_prio_boost(cfqq);
3418
3419        return __cfq_may_queue(cfqq);
3420    }
3421
3422    return ELV_MQUEUE_MAY;
3423}
3424
3425/*
3426 * queue lock held here
3427 */
3428static void cfq_put_request(struct request *rq)
3429{
3430    struct cfq_queue *cfqq = RQ_CFQQ(rq);
3431
3432    if (cfqq) {
3433        const int rw = rq_data_dir(rq);
3434
3435        BUG_ON(!cfqq->allocated[rw]);
3436        cfqq->allocated[rw]--;
3437
3438        put_io_context(RQ_CIC(rq)->ioc);
3439
3440        rq->elevator_private = NULL;
3441        rq->elevator_private2 = NULL;
3442
3443        cfq_put_queue(cfqq);
3444    }
3445}
3446
3447static struct cfq_queue *
3448cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3449        struct cfq_queue *cfqq)
3450{
3451    cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3452    cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3453    cfq_mark_cfqq_coop(cfqq->new_cfqq);
3454    cfq_put_queue(cfqq);
3455    return cic_to_cfqq(cic, 1);
3456}
3457
3458/*
3459 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3460 * was the last process referring to said cfqq.
3461 */
3462static struct cfq_queue *
3463split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3464{
3465    if (cfqq_process_refs(cfqq) == 1) {
3466        cfqq->pid = current->pid;
3467        cfq_clear_cfqq_coop(cfqq);
3468        cfq_clear_cfqq_split_coop(cfqq);
3469        return cfqq;
3470    }
3471
3472    cic_set_cfqq(cic, NULL, 1);
3473    cfq_put_queue(cfqq);
3474    return NULL;
3475}
3476/*
3477 * Allocate cfq data structures associated with this request.
3478 */
3479static int
3480cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3481{
3482    struct cfq_data *cfqd = q->elevator->elevator_data;
3483    struct cfq_io_context *cic;
3484    const int rw = rq_data_dir(rq);
3485    const bool is_sync = rq_is_sync(rq);
3486    struct cfq_queue *cfqq;
3487    unsigned long flags;
3488
3489    might_sleep_if(gfp_mask & __GFP_WAIT);
3490
3491    cic = cfq_get_io_context(cfqd, gfp_mask);
3492
3493    spin_lock_irqsave(q->queue_lock, flags);
3494
3495    if (!cic)
3496        goto queue_fail;
3497
3498new_queue:
3499    cfqq = cic_to_cfqq(cic, is_sync);
3500    if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3501        cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3502        cic_set_cfqq(cic, cfqq, is_sync);
3503    } else {
3504        /*
3505         * If the queue was seeky for too long, break it apart.
3506         */
3507        if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3508            cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3509            cfqq = split_cfqq(cic, cfqq);
3510            if (!cfqq)
3511                goto new_queue;
3512        }
3513
3514        /*
3515         * Check to see if this queue is scheduled to merge with
3516         * another, closely cooperating queue. The merging of
3517         * queues happens here as it must be done in process context.
3518         * The reference on new_cfqq was taken in merge_cfqqs.
3519         */
3520        if (cfqq->new_cfqq)
3521            cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3522    }
3523
3524    cfqq->allocated[rw]++;
3525    atomic_inc(&cfqq->ref);
3526
3527    spin_unlock_irqrestore(q->queue_lock, flags);
3528
3529    rq->elevator_private = cic;
3530    rq->elevator_private2 = cfqq;
3531    return 0;
3532
3533queue_fail:
3534    if (cic)
3535        put_io_context(cic->ioc);
3536
3537    cfq_schedule_dispatch(cfqd);
3538    spin_unlock_irqrestore(q->queue_lock, flags);
3539    cfq_log(cfqd, "set_request fail");
3540    return 1;
3541}
3542
3543static void cfq_kick_queue(struct work_struct *work)
3544{
3545    struct cfq_data *cfqd =
3546        container_of(work, struct cfq_data, unplug_work);
3547    struct request_queue *q = cfqd->queue;
3548
3549    spin_lock_irq(q->queue_lock);
3550    __blk_run_queue(cfqd->queue);
3551    spin_unlock_irq(q->queue_lock);
3552}
3553
3554/*
3555 * Timer running if the active_queue is currently idling inside its time slice
3556 */
3557static void cfq_idle_slice_timer(unsigned long data)
3558{
3559    struct cfq_data *cfqd = (struct cfq_data *) data;
3560    struct cfq_queue *cfqq;
3561    unsigned long flags;
3562    int timed_out = 1;
3563
3564    cfq_log(cfqd, "idle timer fired");
3565
3566    spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3567
3568    cfqq = cfqd->active_queue;
3569    if (cfqq) {
3570        timed_out = 0;
3571
3572        /*
3573         * We saw a request before the queue expired, let it through
3574         */
3575        if (cfq_cfqq_must_dispatch(cfqq))
3576            goto out_kick;
3577
3578        /*
3579         * expired
3580         */
3581        if (cfq_slice_used(cfqq))
3582            goto expire;
3583
3584        /*
3585         * only expire and reinvoke request handler, if there are
3586         * other queues with pending requests
3587         */
3588        if (!cfqd->busy_queues)
3589            goto out_cont;
3590
3591        /*
3592         * not expired and it has a request pending, let it dispatch
3593         */
3594        if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3595            goto out_kick;
3596
3597        /*
3598         * Queue depth flag is reset only when the idle didn't succeed
3599         */
3600        cfq_clear_cfqq_deep(cfqq);
3601    }
3602expire:
3603    cfq_slice_expired(cfqd, timed_out);
3604out_kick:
3605    cfq_schedule_dispatch(cfqd);
3606out_cont:
3607    spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3608}
3609
3610static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3611{
3612    del_timer_sync(&cfqd->idle_slice_timer);
3613    cancel_work_sync(&cfqd->unplug_work);
3614}
3615
3616static void cfq_put_async_queues(struct cfq_data *cfqd)
3617{
3618    int i;
3619
3620    for (i = 0; i < IOPRIO_BE_NR; i++) {
3621        if (cfqd->async_cfqq[0][i])
3622            cfq_put_queue(cfqd->async_cfqq[0][i]);
3623        if (cfqd->async_cfqq[1][i])
3624            cfq_put_queue(cfqd->async_cfqq[1][i]);
3625    }
3626
3627    if (cfqd->async_idle_cfqq)
3628        cfq_put_queue(cfqd->async_idle_cfqq);
3629}
3630
3631static void cfq_cfqd_free(struct rcu_head *head)
3632{
3633    kfree(container_of(head, struct cfq_data, rcu));
3634}
3635
3636static void cfq_exit_queue(struct elevator_queue *e)
3637{
3638    struct cfq_data *cfqd = e->elevator_data;
3639    struct request_queue *q = cfqd->queue;
3640
3641    cfq_shutdown_timer_wq(cfqd);
3642
3643    spin_lock_irq(q->queue_lock);
3644
3645    if (cfqd->active_queue)
3646        __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3647
3648    while (!list_empty(&cfqd->cic_list)) {
3649        struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3650                            struct cfq_io_context,
3651                            queue_list);
3652
3653        __cfq_exit_single_io_context(cfqd, cic);
3654    }
3655
3656    cfq_put_async_queues(cfqd);
3657    cfq_release_cfq_groups(cfqd);
3658    blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3659
3660    spin_unlock_irq(q->queue_lock);
3661
3662    cfq_shutdown_timer_wq(cfqd);
3663
3664    /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3665    call_rcu(&cfqd->rcu, cfq_cfqd_free);
3666}
3667
3668static void *cfq_init_queue(struct request_queue *q)
3669{
3670    struct cfq_data *cfqd;
3671    int i, j;
3672    struct cfq_group *cfqg;
3673    struct cfq_rb_root *st;
3674
3675    cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3676    if (!cfqd)
3677        return NULL;
3678
3679    /* Init root service tree */
3680    cfqd->grp_service_tree = CFQ_RB_ROOT;
3681
3682    /* Init root group */
3683    cfqg = &cfqd->root_group;
3684    for_each_cfqg_st(cfqg, i, j, st)
3685        *st = CFQ_RB_ROOT;
3686    RB_CLEAR_NODE(&cfqg->rb_node);
3687
3688    /* Give preference to root group over other groups */
3689    cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3690
3691#ifdef CONFIG_CFQ_GROUP_IOSCHED
3692    /*
3693     * Take a reference to root group which we never drop. This is just
3694     * to make sure that cfq_put_cfqg() does not try to kfree root group
3695     */
3696    atomic_set(&cfqg->ref, 1);
3697    blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3698                    0);
3699#endif
3700    /*
3701     * Not strictly needed (since RB_ROOT just clears the node and we
3702     * zeroed cfqd on alloc), but better be safe in case someone decides
3703     * to add magic to the rb code
3704     */
3705    for (i = 0; i < CFQ_PRIO_LISTS; i++)
3706        cfqd->prio_trees[i] = RB_ROOT;
3707
3708    /*
3709     * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3710     * Grab a permanent reference to it, so that the normal code flow
3711     * will not attempt to free it.
3712     */
3713    cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3714    atomic_inc(&cfqd->oom_cfqq.ref);
3715    cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3716
3717    INIT_LIST_HEAD(&cfqd->cic_list);
3718
3719    cfqd->queue = q;
3720
3721    init_timer(&cfqd->idle_slice_timer);
3722    cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3723    cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3724
3725    INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3726
3727    cfqd->cfq_quantum = cfq_quantum;
3728    cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3729    cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3730    cfqd->cfq_back_max = cfq_back_max;
3731    cfqd->cfq_back_penalty = cfq_back_penalty;
3732    cfqd->cfq_slice[0] = cfq_slice_async;
3733    cfqd->cfq_slice[1] = cfq_slice_sync;
3734    cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3735    cfqd->cfq_slice_idle = cfq_slice_idle;
3736    cfqd->cfq_latency = 1;
3737    cfqd->cfq_group_isolation = 0;
3738    cfqd->hw_tag = -1;
3739    /*
3740     * we optimistically start assuming sync ops weren't delayed in last
3741     * second, in order to have larger depth for async operations.
3742     */
3743    cfqd->last_delayed_sync = jiffies - HZ;
3744    INIT_RCU_HEAD(&cfqd->rcu);
3745    return cfqd;
3746}
3747
3748static void cfq_slab_kill(void)
3749{
3750    /*
3751     * Caller already ensured that pending RCU callbacks are completed,
3752     * so we should have no busy allocations at this point.
3753     */
3754    if (cfq_pool)
3755        kmem_cache_destroy(cfq_pool);
3756    if (cfq_ioc_pool)
3757        kmem_cache_destroy(cfq_ioc_pool);
3758}
3759
3760static int __init cfq_slab_setup(void)
3761{
3762    cfq_pool = KMEM_CACHE(cfq_queue, 0);
3763    if (!cfq_pool)
3764        goto fail;
3765
3766    cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3767    if (!cfq_ioc_pool)
3768        goto fail;
3769
3770    return 0;
3771fail:
3772    cfq_slab_kill();
3773    return -ENOMEM;
3774}
3775
3776/*
3777 * sysfs parts below -->
3778 */
3779static ssize_t
3780cfq_var_show(unsigned int var, char *page)
3781{
3782    return sprintf(page, "%d\n", var);
3783}
3784
3785static ssize_t
3786cfq_var_store(unsigned int *var, const char *page, size_t count)
3787{
3788    char *p = (char *) page;
3789
3790    *var = simple_strtoul(p, &p, 10);
3791    return count;
3792}
3793
3794#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3795static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3796{ \
3797    struct cfq_data *cfqd = e->elevator_data; \
3798    unsigned int __data = __VAR; \
3799    if (__CONV) \
3800        __data = jiffies_to_msecs(__data); \
3801    return cfq_var_show(__data, (page)); \
3802}
3803SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3804SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3805SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3806SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3807SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3808SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3809SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3810SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3811SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3812SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3813SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
3814#undef SHOW_FUNCTION
3815
3816#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3817static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3818{ \
3819    struct cfq_data *cfqd = e->elevator_data; \
3820    unsigned int __data; \
3821    int ret = cfq_var_store(&__data, (page), count); \
3822    if (__data < (MIN)) \
3823        __data = (MIN); \
3824    else if (__data > (MAX)) \
3825        __data = (MAX); \
3826    if (__CONV) \
3827        *(__PTR) = msecs_to_jiffies(__data); \
3828    else \
3829        *(__PTR) = __data; \
3830    return ret; \
3831}
3832STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3833STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3834        UINT_MAX, 1);
3835STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3836        UINT_MAX, 1);
3837STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3838STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3839        UINT_MAX, 0);
3840STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3841STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3842STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3843STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3844        UINT_MAX, 0);
3845STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3846STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
3847#undef STORE_FUNCTION
3848
3849#define CFQ_ATTR(name) \
3850    __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3851
3852static struct elv_fs_entry cfq_attrs[] = {
3853    CFQ_ATTR(quantum),
3854    CFQ_ATTR(fifo_expire_sync),
3855    CFQ_ATTR(fifo_expire_async),
3856    CFQ_ATTR(back_seek_max),
3857    CFQ_ATTR(back_seek_penalty),
3858    CFQ_ATTR(slice_sync),
3859    CFQ_ATTR(slice_async),
3860    CFQ_ATTR(slice_async_rq),
3861    CFQ_ATTR(slice_idle),
3862    CFQ_ATTR(low_latency),
3863    CFQ_ATTR(group_isolation),
3864    __ATTR_NULL
3865};
3866
3867static struct elevator_type iosched_cfq = {
3868    .ops = {
3869        .elevator_merge_fn = cfq_merge,
3870        .elevator_merged_fn = cfq_merged_request,
3871        .elevator_merge_req_fn = cfq_merged_requests,
3872        .elevator_allow_merge_fn = cfq_allow_merge,
3873        .elevator_dispatch_fn = cfq_dispatch_requests,
3874        .elevator_add_req_fn = cfq_insert_request,
3875        .elevator_activate_req_fn = cfq_activate_request,
3876        .elevator_deactivate_req_fn = cfq_deactivate_request,
3877        .elevator_queue_empty_fn = cfq_queue_empty,
3878        .elevator_completed_req_fn = cfq_completed_request,
3879        .elevator_former_req_fn = elv_rb_former_request,
3880        .elevator_latter_req_fn = elv_rb_latter_request,
3881        .elevator_set_req_fn = cfq_set_request,
3882        .elevator_put_req_fn = cfq_put_request,
3883        .elevator_may_queue_fn = cfq_may_queue,
3884        .elevator_init_fn = cfq_init_queue,
3885        .elevator_exit_fn = cfq_exit_queue,
3886        .trim = cfq_free_io_context,
3887    },
3888    .elevator_attrs = cfq_attrs,
3889    .elevator_name = "cfq",
3890    .elevator_owner = THIS_MODULE,
3891};
3892
3893#ifdef CONFIG_CFQ_GROUP_IOSCHED
3894static struct blkio_policy_type blkio_policy_cfq = {
3895    .ops = {
3896        .blkio_unlink_group_fn = cfq_unlink_blkio_group,
3897        .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
3898    },
3899};
3900#else
3901static struct blkio_policy_type blkio_policy_cfq;
3902#endif
3903
3904static int __init cfq_init(void)
3905{
3906    /*
3907     * could be 0 on HZ < 1000 setups
3908     */
3909    if (!cfq_slice_async)
3910        cfq_slice_async = 1;
3911    if (!cfq_slice_idle)
3912        cfq_slice_idle = 1;
3913
3914    if (cfq_slab_setup())
3915        return -ENOMEM;
3916
3917    elv_register(&iosched_cfq);
3918    blkio_policy_register(&blkio_policy_cfq);
3919
3920    return 0;
3921}
3922
3923static void __exit cfq_exit(void)
3924{
3925    DECLARE_COMPLETION_ONSTACK(all_gone);
3926    blkio_policy_unregister(&blkio_policy_cfq);
3927    elv_unregister(&iosched_cfq);
3928    ioc_gone = &all_gone;
3929    /* ioc_gone's update must be visible before reading ioc_count */
3930    smp_wmb();
3931
3932    /*
3933     * this also protects us from entering cfq_slab_kill() with
3934     * pending RCU callbacks
3935     */
3936    if (elv_ioc_count_read(cfq_ioc_count))
3937        wait_for_completion(&all_gone);
3938    cfq_slab_kill();
3939}
3940
3941module_init(cfq_init);
3942module_exit(cfq_exit);
3943
3944MODULE_AUTHOR("Jens Axboe");
3945MODULE_LICENSE("GPL");
3946MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
3947

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