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Diffstat (limited to 'block/cfq-iosched.c')
| -rw-r--r-- | block/cfq-iosched.c | 3943 |
1 files changed, 3943 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c new file mode 100644 index 00000000000..d0f81463bed --- /dev/null +++ b/block/cfq-iosched.c @@ -0,0 +1,3943 @@ +/* + * CFQ, or complete fairness queueing, disk scheduler. + * + * Based on ideas from a previously unfinished io + * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli. + * + * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> + */ +#include <linux/module.h> +#include <linux/blkdev.h> +#include <linux/elevator.h> +#include <linux/jiffies.h> +#include <linux/rbtree.h> +#include <linux/ioprio.h> +#include <linux/blktrace_api.h> +#include "blk-cgroup.h" + +/* + * tunables + */ +/* max queue in one round of service */ +static const int cfq_quantum = 4; +static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; +/* maximum backwards seek, in KiB */ +static const int cfq_back_max = 16 * 1024; +/* penalty of a backwards seek */ +static const int cfq_back_penalty = 2; +static const int cfq_slice_sync = HZ / 10; +static int cfq_slice_async = HZ / 25; +static const int cfq_slice_async_rq = 2; +static int cfq_slice_idle = HZ / 125; +static const int cfq_target_latency = HZ * 3/10; /* 300 ms */ +static const int cfq_hist_divisor = 4; + +/* + * offset from end of service tree + */ +#define CFQ_IDLE_DELAY (HZ / 5) + +/* + * below this threshold, we consider thinktime immediate + */ +#define CFQ_MIN_TT (2) + +#define CFQ_SLICE_SCALE (5) +#define CFQ_HW_QUEUE_MIN (5) +#define CFQ_SERVICE_SHIFT 12 + +#define CFQQ_SEEK_THR 8 * 1024 +#define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR) + +#define RQ_CIC(rq) \ + ((struct cfq_io_context *) (rq)->elevator_private) +#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2) + +static struct kmem_cache *cfq_pool; +static struct kmem_cache *cfq_ioc_pool; + +static DEFINE_PER_CPU(unsigned long, cfq_ioc_count); +static struct completion *ioc_gone; +static DEFINE_SPINLOCK(ioc_gone_lock); + +#define CFQ_PRIO_LISTS IOPRIO_BE_NR +#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE) +#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT) + +#define sample_valid(samples) ((samples) > 80) +#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node) + +/* + * Most of our rbtree usage is for sorting with min extraction, so + * if we cache the leftmost node we don't have to walk down the tree + * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should + * move this into the elevator for the rq sorting as well. + */ +struct cfq_rb_root { + struct rb_root rb; + struct rb_node *left; + unsigned count; + u64 min_vdisktime; + struct rb_node *active; + unsigned total_weight; +}; +#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, } + +/* + * Per process-grouping structure + */ +struct cfq_queue { + /* reference count */ + atomic_t ref; + /* various state flags, see below */ + unsigned int flags; + /* parent cfq_data */ + struct cfq_data *cfqd; + /* service_tree member */ + struct rb_node rb_node; + /* service_tree key */ + unsigned long rb_key; + /* prio tree member */ + struct rb_node p_node; + /* prio tree root we belong to, if any */ + struct rb_root *p_root; + /* sorted list of pending requests */ + struct rb_root sort_list; + /* if fifo isn't expired, next request to serve */ + struct request *next_rq; + /* requests queued in sort_list */ + int queued[2]; + /* currently allocated requests */ + int allocated[2]; + /* fifo list of requests in sort_list */ + struct list_head fifo; + + /* time when queue got scheduled in to dispatch first request. */ + unsigned long dispatch_start; + unsigned int allocated_slice; + /* time when first request from queue completed and slice started. */ + unsigned long slice_start; + unsigned long slice_end; + long slice_resid; + unsigned int slice_dispatch; + + /* pending metadata requests */ + int meta_pending; + /* number of requests that are on the dispatch list or inside driver */ + int dispatched; + + /* io prio of this group */ + unsigned short ioprio, org_ioprio; + unsigned short ioprio_class, org_ioprio_class; + + unsigned int seek_samples; + u64 seek_total; + sector_t seek_mean; + sector_t last_request_pos; + + pid_t pid; + + struct cfq_rb_root *service_tree; + struct cfq_queue *new_cfqq; + struct cfq_group *cfqg; + struct cfq_group *orig_cfqg; + /* Sectors dispatched in current dispatch round */ + unsigned long nr_sectors; +}; + +/* + * First index in the service_trees. + * IDLE is handled separately, so it has negative index + */ +enum wl_prio_t { + BE_WORKLOAD = 0, + RT_WORKLOAD = 1, + IDLE_WORKLOAD = 2, +}; + +/* + * Second index in the service_trees. + */ +enum wl_type_t { + ASYNC_WORKLOAD = 0, + SYNC_NOIDLE_WORKLOAD = 1, + SYNC_WORKLOAD = 2 +}; + +/* This is per cgroup per device grouping structure */ +struct cfq_group { + /* group service_tree member */ + struct rb_node rb_node; + + /* group service_tree key */ + u64 vdisktime; + unsigned int weight; + bool on_st; + + /* number of cfqq currently on this group */ + int nr_cfqq; + + /* Per group busy queus average. Useful for workload slice calc. */ + unsigned int busy_queues_avg[2]; + /* + * rr lists of queues with requests, onle rr for each priority class. + * Counts are embedded in the cfq_rb_root + */ + struct cfq_rb_root service_trees[2][3]; + struct cfq_rb_root service_tree_idle; + + unsigned long saved_workload_slice; + enum wl_type_t saved_workload; + enum wl_prio_t saved_serving_prio; + struct blkio_group blkg; +#ifdef CONFIG_CFQ_GROUP_IOSCHED + struct hlist_node cfqd_node; + atomic_t ref; +#endif +}; + +/* + * Per block device queue structure + */ +struct cfq_data { + struct request_queue *queue; + /* Root service tree for cfq_groups */ + struct cfq_rb_root grp_service_tree; + struct cfq_group root_group; + + /* + * The priority currently being served + */ + enum wl_prio_t serving_prio; + enum wl_type_t serving_type; + unsigned long workload_expires; + struct cfq_group *serving_group; + bool noidle_tree_requires_idle; + + /* + * Each priority tree is sorted by next_request position. These + * trees are used when determining if two or more queues are + * interleaving requests (see cfq_close_cooperator). + */ + struct rb_root prio_trees[CFQ_PRIO_LISTS]; + + unsigned int busy_queues; + + int rq_in_driver[2]; + int sync_flight; + + /* + * queue-depth detection + */ + int rq_queued; + int hw_tag; + /* + * hw_tag can be + * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection) + * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth) + * 0 => no NCQ + */ + int hw_tag_est_depth; + unsigned int hw_tag_samples; + + /* + * idle window management + */ + struct timer_list idle_slice_timer; + struct work_struct unplug_work; + + struct cfq_queue *active_queue; + struct cfq_io_context *active_cic; + + /* + * async queue for each priority case + */ + struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR]; + struct cfq_queue *async_idle_cfqq; + + sector_t last_position; + + /* + * tunables, see top of file + */ + unsigned int cfq_quantum; + unsigned int cfq_fifo_expire[2]; + unsigned int cfq_back_penalty; + unsigned int cfq_back_max; + unsigned int cfq_slice[2]; + unsigned int cfq_slice_async_rq; + unsigned int cfq_slice_idle; + unsigned int cfq_latency; + unsigned int cfq_group_isolation; + + struct list_head cic_list; + + /* + * Fallback dummy cfqq for extreme OOM conditions + */ + struct cfq_queue oom_cfqq; + + unsigned long last_delayed_sync; + + /* List of cfq groups being managed on this device*/ + struct hlist_head cfqg_list; + struct rcu_head rcu; +}; + +static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd); + +static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg, + enum wl_prio_t prio, + enum wl_type_t type) +{ + if (!cfqg) + return NULL; + + if (prio == IDLE_WORKLOAD) + return &cfqg->service_tree_idle; + + return &cfqg->service_trees[prio][type]; +} + +enum cfqq_state_flags { + CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */ + CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */ + CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */ + CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ + CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ + CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */ + CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */ + CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ + CFQ_CFQQ_FLAG_sync, /* synchronous queue */ + CFQ_CFQQ_FLAG_coop, /* cfqq is shared */ + CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */ + CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */ + CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */ +}; + +#define CFQ_CFQQ_FNS(name) \ +static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \ +{ \ + (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \ +} \ +static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \ +{ \ + (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \ +} \ +static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \ +{ \ + return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \ +} + +CFQ_CFQQ_FNS(on_rr); +CFQ_CFQQ_FNS(wait_request); +CFQ_CFQQ_FNS(must_dispatch); +CFQ_CFQQ_FNS(must_alloc_slice); +CFQ_CFQQ_FNS(fifo_expire); +CFQ_CFQQ_FNS(idle_window); +CFQ_CFQQ_FNS(prio_changed); +CFQ_CFQQ_FNS(slice_new); +CFQ_CFQQ_FNS(sync); +CFQ_CFQQ_FNS(coop); +CFQ_CFQQ_FNS(split_coop); +CFQ_CFQQ_FNS(deep); +CFQ_CFQQ_FNS(wait_busy); +#undef CFQ_CFQQ_FNS + +#ifdef CONFIG_DEBUG_CFQ_IOSCHED +#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ + blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \ + cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \ + blkg_path(&(cfqq)->cfqg->blkg), ##args); + +#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \ + blk_add_trace_msg((cfqd)->queue, "%s " fmt, \ + blkg_path(&(cfqg)->blkg), ##args); \ + +#else +#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ + blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) +#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0); +#endif +#define cfq_log(cfqd, fmt, args...) \ + blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args) + +/* Traverses through cfq group service trees */ +#define for_each_cfqg_st(cfqg, i, j, st) \ + for (i = 0; i <= IDLE_WORKLOAD; i++) \ + for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\ + : &cfqg->service_tree_idle; \ + (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \ + (i == IDLE_WORKLOAD && j == 0); \ + j++, st = i < IDLE_WORKLOAD ? \ + &cfqg->service_trees[i][j]: NULL) \ + + +static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq) +{ + if (cfq_class_idle(cfqq)) + return IDLE_WORKLOAD; + if (cfq_class_rt(cfqq)) + return RT_WORKLOAD; + return BE_WORKLOAD; +} + + +static enum wl_type_t cfqq_type(struct cfq_queue *cfqq) +{ + if (!cfq_cfqq_sync(cfqq)) + return ASYNC_WORKLOAD; + if (!cfq_cfqq_idle_window(cfqq)) + return SYNC_NOIDLE_WORKLOAD; + return SYNC_WORKLOAD; +} + +static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl, + struct cfq_data *cfqd, + struct cfq_group *cfqg) +{ + if (wl == IDLE_WORKLOAD) + return cfqg->service_tree_idle.count; + + return cfqg->service_trees[wl][ASYNC_WORKLOAD].count + + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count + + cfqg->service_trees[wl][SYNC_WORKLOAD].count; +} + +static inline int cfqg_busy_async_queues(struct cfq_data *cfqd, + struct cfq_group *cfqg) +{ + return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count + + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count; +} + +static void cfq_dispatch_insert(struct request_queue *, struct request *); +static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool, + struct io_context *, gfp_t); +static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, + struct io_context *); + +static inline int rq_in_driver(struct cfq_data *cfqd) +{ + return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1]; +} + +static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, + bool is_sync) +{ + return cic->cfqq[is_sync]; +} + +static inline void cic_set_cfqq(struct cfq_io_context *cic, + struct cfq_queue *cfqq, bool is_sync) +{ + cic->cfqq[is_sync] = cfqq; +} + +/* + * We regard a request as SYNC, if it's either a read or has the SYNC bit + * set (in which case it could also be direct WRITE). + */ +static inline bool cfq_bio_sync(struct bio *bio) +{ + return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO); +} + +/* + * scheduler run of queue, if there are requests pending and no one in the + * driver that will restart queueing + */ +static inline void cfq_schedule_dispatch(struct cfq_data *cfqd) +{ + if (cfqd->busy_queues) { + cfq_log(cfqd, "schedule dispatch"); + kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work); + } +} + +static int cfq_queue_empty(struct request_queue *q) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + + return !cfqd->rq_queued; +} + +/* + * Scale schedule slice based on io priority. Use the sync time slice only + * if a queue is marked sync and has sync io queued. A sync queue with async + * io only, should not get full sync slice length. + */ +static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync, + unsigned short prio) +{ + const int base_slice = cfqd->cfq_slice[sync]; + + WARN_ON(prio >= IOPRIO_BE_NR); + + return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio)); +} + +static inline int +cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio); +} + +static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg) +{ + u64 d = delta << CFQ_SERVICE_SHIFT; + + d = d * BLKIO_WEIGHT_DEFAULT; + do_div(d, cfqg->weight); + return d; +} + +static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime) +{ + s64 delta = (s64)(vdisktime - min_vdisktime); + if (delta > 0) + min_vdisktime = vdisktime; + + return min_vdisktime; +} + +static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime) +{ + s64 delta = (s64)(vdisktime - min_vdisktime); + if (delta < 0) + min_vdisktime = vdisktime; + + return min_vdisktime; +} + +static void update_min_vdisktime(struct cfq_rb_root *st) +{ + u64 vdisktime = st->min_vdisktime; + struct cfq_group *cfqg; + + if (st->active) { + cfqg = rb_entry_cfqg(st->active); + vdisktime = cfqg->vdisktime; + } + + if (st->left) { + cfqg = rb_entry_cfqg(st->left); + vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime); + } + + st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime); +} + +/* + * get averaged number of queues of RT/BE priority. + * average is updated, with a formula that gives more weight to higher numbers, + * to quickly follows sudden increases and decrease slowly + */ + +static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd, + struct cfq_group *cfqg, bool rt) +{ + unsigned min_q, max_q; + unsigned mult = cfq_hist_divisor - 1; + unsigned round = cfq_hist_divisor / 2; + unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg); + + min_q = min(cfqg->busy_queues_avg[rt], busy); + max_q = max(cfqg->busy_queues_avg[rt], busy); + cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) / + cfq_hist_divisor; + return cfqg->busy_queues_avg[rt]; +} + +static inline unsigned +cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg) +{ + struct cfq_rb_root *st = &cfqd->grp_service_tree; + + return cfq_target_latency * cfqg->weight / st->total_weight; +} + +static inline void +cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + unsigned slice = cfq_prio_to_slice(cfqd, cfqq); + if (cfqd->cfq_latency) { + /* + * interested queues (we consider only the ones with the same + * priority class in the cfq group) + */ + unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg, + cfq_class_rt(cfqq)); + unsigned sync_slice = cfqd->cfq_slice[1]; + unsigned expect_latency = sync_slice * iq; + unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg); + + if (expect_latency > group_slice) { + unsigned base_low_slice = 2 * cfqd->cfq_slice_idle; + /* scale low_slice according to IO priority + * and sync vs async */ + unsigned low_slice = + min(slice, base_low_slice * slice / sync_slice); + /* the adapted slice value is scaled to fit all iqs + * into the target latency */ + slice = max(slice * group_slice / expect_latency, + low_slice); + } + } + cfqq->slice_start = jiffies; + cfqq->slice_end = jiffies + slice; + cfqq->allocated_slice = slice; + cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies); +} + +/* + * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end + * isn't valid until the first request from the dispatch is activated + * and the slice time set. + */ +static inline bool cfq_slice_used(struct cfq_queue *cfqq) +{ + if (cfq_cfqq_slice_new(cfqq)) + return 0; + if (time_before(jiffies, cfqq->slice_end)) + return 0; + + return 1; +} + +/* + * Lifted from AS - choose which of rq1 and rq2 that is best served now. + * We choose the request that is closest to the head right now. Distance + * behind the head is penalized and only allowed to a certain extent. + */ +static struct request * +cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last) +{ + sector_t s1, s2, d1 = 0, d2 = 0; + unsigned long back_max; +#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */ +#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */ + unsigned wrap = 0; /* bit mask: requests behind the disk head? */ + + if (rq1 == NULL || rq1 == rq2) + return rq2; + if (rq2 == NULL) + return rq1; + + if (rq_is_sync(rq1) && !rq_is_sync(rq2)) + return rq1; + else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) + return rq2; + if (rq_is_meta(rq1) && !rq_is_meta(rq2)) + return rq1; + else if (rq_is_meta(rq2) && !rq_is_meta(rq1)) + return rq2; + + s1 = blk_rq_pos(rq1); + s2 = blk_rq_pos(rq2); + + /* + * by definition, 1KiB is 2 sectors + */ + back_max = cfqd->cfq_back_max * 2; + + /* + * Strict one way elevator _except_ in the case where we allow + * short backward seeks which are biased as twice the cost of a + * similar forward seek. + */ + if (s1 >= last) + d1 = s1 - last; + else if (s1 + back_max >= last) + d1 = (last - s1) * cfqd->cfq_back_penalty; + else + wrap |= CFQ_RQ1_WRAP; + + if (s2 >= last) + d2 = s2 - last; + else if (s2 + back_max >= last) + d2 = (last - s2) * cfqd->cfq_back_penalty; + else + wrap |= CFQ_RQ2_WRAP; + + /* Found required data */ + + /* + * By doing switch() on the bit mask "wrap" we avoid having to + * check two variables for all permutations: --> faster! + */ + switch (wrap) { + case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ + if (d1 < d2) + return rq1; + else if (d2 < d1) + return rq2; + else { + if (s1 >= s2) + return rq1; + else + return rq2; + } + + case CFQ_RQ2_WRAP: + return rq1; + case CFQ_RQ1_WRAP: + return rq2; + case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */ + default: + /* + * Since both rqs are wrapped, + * start with the one that's further behind head + * (--> only *one* back seek required), + * since back seek takes more time than forward. + */ + if (s1 <= s2) + return rq1; + else + return rq2; + } +} + +/* + * The below is leftmost cache rbtree addon + */ +static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root) +{ + /* Service tree is empty */ + if (!root->count) + return NULL; + + if (!root->left) + root->left = rb_first(&root->rb); + + if (root->left) + return rb_entry(root->left, struct cfq_queue, rb_node); + + return NULL; +} + +static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root) +{ + if (!root->left) + root->left = rb_first(&root->rb); + + if (root->left) + return rb_entry_cfqg(root->left); + + return NULL; +} + +static void rb_erase_init(struct rb_node *n, struct rb_root *root) +{ + rb_erase(n, root); + RB_CLEAR_NODE(n); +} + +static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) +{ + if (root->left == n) + root->left = NULL; + rb_erase_init(n, &root->rb); + --root->count; +} + +/* + * would be nice to take fifo expire time into account as well + */ +static struct request * +cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, + struct request *last) +{ + struct rb_node *rbnext = rb_next(&last->rb_node); + struct rb_node *rbprev = rb_prev(&last->rb_node); + struct request *next = NULL, *prev = NULL; + + BUG_ON(RB_EMPTY_NODE(&last->rb_node)); + + if (rbprev) + prev = rb_entry_rq(rbprev); + + if (rbnext) + next = rb_entry_rq(rbnext); + else { + rbnext = rb_first(&cfqq->sort_list); + if (rbnext && rbnext != &last->rb_node) + next = rb_entry_rq(rbnext); + } + + return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last)); +} + +static unsigned long cfq_slice_offset(struct cfq_data *cfqd, + struct cfq_queue *cfqq) +{ + /* + * just an approximation, should be ok. + */ + return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) - + cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); +} + +static inline s64 +cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg) +{ + return cfqg->vdisktime - st->min_vdisktime; +} + +static void +__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) +{ + struct rb_node **node = &st->rb.rb_node; + struct rb_node *parent = NULL; + struct cfq_group *__cfqg; + s64 key = cfqg_key(st, cfqg); + int left = 1; + + while (*node != NULL) { + parent = *node; + __cfqg = rb_entry_cfqg(parent); + + if (key < cfqg_key(st, __cfqg)) + node = &parent->rb_left; + else { + node = &parent->rb_right; + left = 0; + } + } + + if (left) + st->left = &cfqg->rb_node; + + rb_link_node(&cfqg->rb_node, parent, node); + rb_insert_color(&cfqg->rb_node, &st->rb); +} + +static void +cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg) +{ + struct cfq_rb_root *st = &cfqd->grp_service_tree; + struct cfq_group *__cfqg; + struct rb_node *n; + + cfqg->nr_cfqq++; + if (cfqg->on_st) + return; + + /* + * Currently put the group at the end. Later implement something + * so that groups get lesser vtime based on their weights, so that + * if group does not loose all if it was not continously backlogged. + */ + n = rb_last(&st->rb); + if (n) { + __cfqg = rb_entry_cfqg(n); + cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; + } else + cfqg->vdisktime = st->min_vdisktime; + + __cfq_group_service_tree_add(st, cfqg); + cfqg->on_st = true; + st->total_weight += cfqg->weight; +} + +static void +cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg) +{ + struct cfq_rb_root *st = &cfqd->grp_service_tree; + + if (st->active == &cfqg->rb_node) + st->active = NULL; + + BUG_ON(cfqg->nr_cfqq < 1); + cfqg->nr_cfqq--; + + /* If there are other cfq queues under this group, don't delete it */ + if (cfqg->nr_cfqq) + return; + + cfq_log_cfqg(cfqd, cfqg, "del_from_rr group"); + cfqg->on_st = false; + st->total_weight -= cfqg->weight; + if (!RB_EMPTY_NODE(&cfqg->rb_node)) + cfq_rb_erase(&cfqg->rb_node, st); + cfqg->saved_workload_slice = 0; + blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1); +} + +static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq) +{ + unsigned int slice_used; + + /* + * Queue got expired before even a single request completed or + * got expired immediately after first request completion. + */ + if (!cfqq->slice_start || cfqq->slice_start == jiffies) { + /* + * Also charge the seek time incurred to the group, otherwise + * if there are mutiple queues in the group, each can dispatch + * a single request on seeky media and cause lots of seek time + * and group will never know it. + */ + slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start), + 1); + } else { + slice_used = jiffies - cfqq->slice_start; + if (slice_used > cfqq->allocated_slice) + slice_used = cfqq->allocated_slice; + } + + cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used, + cfqq->nr_sectors); + return slice_used; +} + +static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg, + struct cfq_queue *cfqq) +{ + struct cfq_rb_root *st = &cfqd->grp_service_tree; + unsigned int used_sl, charge_sl; + int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg) + - cfqg->service_tree_idle.count; + + BUG_ON(nr_sync < 0); + used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq); + + if (!cfq_cfqq_sync(cfqq) && !nr_sync) + charge_sl = cfqq->allocated_slice; + + /* Can't update vdisktime while group is on service tree */ + cfq_rb_erase(&cfqg->rb_node, st); + cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg); + __cfq_group_service_tree_add(st, cfqg); + + /* This group is being expired. Save the context */ + if (time_after(cfqd->workload_expires, jiffies)) { + cfqg->saved_workload_slice = cfqd->workload_expires + - jiffies; + cfqg->saved_workload = cfqd->serving_type; + cfqg->saved_serving_prio = cfqd->serving_prio; + } else + cfqg->saved_workload_slice = 0; + + cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime, + st->min_vdisktime); + blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl, + cfqq->nr_sectors); +} + +#ifdef CONFIG_CFQ_GROUP_IOSCHED +static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg) +{ + if (blkg) + return container_of(blkg, struct cfq_group, blkg); + return NULL; +} + +void +cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight) +{ + cfqg_of_blkg(blkg)->weight = weight; +} + +static struct cfq_group * +cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create) +{ + struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup); + struct cfq_group *cfqg = NULL; + void *key = cfqd; + int i, j; + struct cfq_rb_root *st; + struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info; + unsigned int major, minor; + + /* Do we need to take this reference */ + if (!blkiocg_css_tryget(blkcg)) + return NULL;; + + cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key)); + if (cfqg || !create) + goto done; + + cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node); + if (!cfqg) + goto done; + + cfqg->weight = blkcg->weight; + for_each_cfqg_st(cfqg, i, j, st) + *st = CFQ_RB_ROOT; + RB_CLEAR_NODE(&cfqg->rb_node); + + /* + * Take the initial reference that will be released on destroy + * This can be thought of a joint reference by cgroup and + * elevator which will be dropped by either elevator exit + * or cgroup deletion path depending on who is exiting first. + */ + atomic_set(&cfqg->ref, 1); + + /* Add group onto cgroup list */ + sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); + blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd, + MKDEV(major, minor)); + + /* Add group on cfqd list */ + hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list); + +done: + blkiocg_css_put(blkcg); + return cfqg; +} + +/* + * Search for the cfq group current task belongs to. If create = 1, then also + * create the cfq group if it does not exist. request_queue lock must be held. + */ +static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) +{ + struct cgroup *cgroup; + struct cfq_group *cfqg = NULL; + + rcu_read_lock(); + cgroup = task_cgroup(current, blkio_subsys_id); + cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create); + if (!cfqg && create) + cfqg = &cfqd->root_group; + rcu_read_unlock(); + return cfqg; +} + +static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) +{ + /* Currently, all async queues are mapped to root group */ + if (!cfq_cfqq_sync(cfqq)) + cfqg = &cfqq->cfqd->root_group; + + cfqq->cfqg = cfqg; + /* cfqq reference on cfqg */ + atomic_inc(&cfqq->cfqg->ref); +} + +static void cfq_put_cfqg(struct cfq_group *cfqg) +{ + struct cfq_rb_root *st; + int i, j; + + BUG_ON(atomic_read(&cfqg->ref) <= 0); + if (!atomic_dec_and_test(&cfqg->ref)) + return; + for_each_cfqg_st(cfqg, i, j, st) + BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL); + kfree(cfqg); +} + +static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) +{ + /* Something wrong if we are trying to remove same group twice */ + BUG_ON(hlist_unhashed(&cfqg->cfqd_node)); + + hlist_del_init(&cfqg->cfqd_node); + + /* + * Put the reference taken at the time of creation so that when all + * queues are gone, group can be destroyed. + */ + cfq_put_cfqg(cfqg); +} + +static void cfq_release_cfq_groups(struct cfq_data *cfqd) +{ + struct hlist_node *pos, *n; + struct cfq_group *cfqg; + + hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) { + /* + * If cgroup removal path got to blk_group first and removed + * it from cgroup list, then it will take care of destroying + * cfqg also. + */ + if (!blkiocg_del_blkio_group(&cfqg->blkg)) + cfq_destroy_cfqg(cfqd, cfqg); + } +} + +/* + * Blk cgroup controller notification saying that blkio_group object is being + * delinked as associated cgroup object is going away. That also means that + * no new IO will come in this group. So get rid of this group as soon as + * any pending IO in the group is finished. + * + * This function is called under rcu_read_lock(). key is the rcu protected + * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu + * read lock. + * + * "key" was fetched from blkio_group under blkio_cgroup->lock. That means + * it should not be NULL as even if elevator was exiting, cgroup deltion + * path got to it first. + */ +void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg) +{ + unsigned long flags; + struct cfq_data *cfqd = key; + + spin_lock_irqsave(cfqd->queue->queue_lock, flags); + cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg)); + spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); +} + +#else /* GROUP_IOSCHED */ +static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) +{ + return &cfqd->root_group; +} +static inline void +cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { + cfqq->cfqg = cfqg; +} + +static void cfq_release_cfq_groups(struct cfq_data *cfqd) {} +static inline void cfq_put_cfqg(struct cfq_group *cfqg) {} + +#endif /* GROUP_IOSCHED */ + +/* + * The cfqd->service_trees holds all pending cfq_queue's that have + * requests waiting to be processed. It is sorted in the order that + * we will service the queues. + */ +static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, + bool add_front) +{ + struct rb_node **p, *parent; + struct cfq_queue *__cfqq; + unsigned long rb_key; + struct cfq_rb_root *service_tree; + int left; + int new_cfqq = 1; + int group_changed = 0; + +#ifdef CONFIG_CFQ_GROUP_IOSCHED + if (!cfqd->cfq_group_isolation + && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD + && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) { + /* Move this cfq to root group */ + cfq_log_cfqq(cfqd, cfqq, "moving to root group"); + if (!RB_EMPTY_NODE(&cfqq->rb_node)) + cfq_group_service_tree_del(cfqd, cfqq->cfqg); + cfqq->orig_cfqg = cfqq->cfqg; + cfqq->cfqg = &cfqd->root_group; + atomic_inc(&cfqd->root_group.ref); + group_changed = 1; + } else if (!cfqd->cfq_group_isolation + && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) { + /* cfqq is sequential now needs to go to its original group */ + BUG_ON(cfqq->cfqg != &cfqd->root_group); + if (!RB_EMPTY_NODE(&cfqq->rb_node)) + cfq_group_service_tree_del(cfqd, cfqq->cfqg); + cfq_put_cfqg(cfqq->cfqg); + cfqq->cfqg = cfqq->orig_cfqg; + cfqq->orig_cfqg = NULL; + group_changed = 1; + cfq_log_cfqq(cfqd, cfqq, "moved to origin group"); + } +#endif + + service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), + cfqq_type(cfqq)); + if (cfq_class_idle(cfqq)) { + rb_key = CFQ_IDLE_DELAY; + parent = rb_last(&service_tree->rb); + if (parent && parent != &cfqq->rb_node) { + __cfqq = rb_entry(parent, struct cfq_queue, rb_node); + rb_key += __cfqq->rb_key; + } else + rb_key += jiffies; + } else if (!add_front) { + /* + * Get our rb key offset. Subtract any residual slice + * value carried from last service. A negative resid + * count indicates slice overrun, and this should position + * the next service time further away in the tree. + */ + rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; + rb_key -= cfqq->slice_resid; + cfqq->slice_resid = 0; + } else { + rb_key = -HZ; + __cfqq = cfq_rb_first(service_tree); + rb_key += __cfqq ? __cfqq->rb_key : jiffies; + } + + if (!RB_EMPTY_NODE(&cfqq->rb_node)) { + new_cfqq = 0; + /* + * same position, nothing more to do + */ + if (rb_key == cfqq->rb_key && + cfqq->service_tree == service_tree) + return; + + cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); + cfqq->service_tree = NULL; + } + + left = 1; + parent = NULL; + cfqq->service_tree = service_tree; + p = &service_tree->rb.rb_node; + while (*p) { + struct rb_node **n; + + parent = *p; + __cfqq = rb_entry(parent, struct cfq_queue, rb_node); + + /* + * sort by key, that represents service time. + */ + if (time_before(rb_key, __cfqq->rb_key)) + n = &(*p)->rb_left; + else { + n = &(*p)->rb_right; + left = 0; + } + + p = n; + } + + if (left) + service_tree->left = &cfqq->rb_node; + + cfqq->rb_key = rb_key; + rb_link_node(&cfqq->rb_node, parent, p); + rb_insert_color(&cfqq->rb_node, &service_tree->rb); + service_tree->count++; + if ((add_front || !new_cfqq) && !group_changed) + return; + cfq_group_service_tree_add(cfqd, cfqq->cfqg); +} + +static struct cfq_queue * +cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root, + sector_t sector, struct rb_node **ret_parent, + struct rb_node ***rb_link) +{ + struct rb_node **p, *parent; + struct cfq_queue *cfqq = NULL; + + parent = NULL; + p = &root->rb_node; + while (*p) { + struct rb_node **n; + + parent = *p; + cfqq = rb_entry(parent, struct cfq_queue, p_node); + + /* + * Sort strictly based on sector. Smallest to the left, + * largest to the right. + */ + if (sector > blk_rq_pos(cfqq->next_rq)) + n = &(*p)->rb_right; + else if (sector < blk_rq_pos(cfqq->next_rq)) + n = &(*p)->rb_left; + else + break; + p = n; + cfqq = NULL; + } + + *ret_parent = parent; + if (rb_link) + *rb_link = p; + return cfqq; +} + +static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + struct rb_node **p, *parent; + struct cfq_queue *__cfqq; + + if (cfqq->p_root) { + rb_erase(&cfqq->p_node, cfqq->p_root); + cfqq->p_root = NULL; + } + + if (cfq_class_idle(cfqq)) + return; + if (!cfqq->next_rq) + return; + + cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio]; + __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root, + blk_rq_pos(cfqq->next_rq), &parent, &p); + if (!__cfqq) { + rb_link_node(&cfqq->p_node, parent, p); + rb_insert_color(&cfqq->p_node, cfqq->p_root); + } else + cfqq->p_root = NULL; +} + +/* + * Update cfqq's position in the service tree. + */ +static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + /* + * Resorting requires the cfqq to be on the RR list already. + */ + if (cfq_cfqq_on_rr(cfqq)) { + cfq_service_tree_add(cfqd, cfqq, 0); + cfq_prio_tree_add(cfqd, cfqq); + } +} + +/* + * add to busy list of queues for service, trying to be fair in ordering + * the pending list according to last request service + */ +static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + cfq_log_cfqq(cfqd, cfqq, "add_to_rr"); + BUG_ON(cfq_cfqq_on_rr(cfqq)); + cfq_mark_cfqq_on_rr(cfqq); + cfqd->busy_queues++; + + cfq_resort_rr_list(cfqd, cfqq); +} + +/* + * Called when the cfqq no longer has requests pending, remove it from + * the service tree. + */ +static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + cfq_log_cfqq(cfqd, cfqq, "del_from_rr"); + BUG_ON(!cfq_cfqq_on_rr(cfqq)); + cfq_clear_cfqq_on_rr(cfqq); + + if (!RB_EMPTY_NODE(&cfqq->rb_node)) { + cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree); + cfqq->service_tree = NULL; + } + if (cfqq->p_root) { + rb_erase(&cfqq->p_node, cfqq->p_root); + cfqq->p_root = NULL; + } + + cfq_group_service_tree_del(cfqd, cfqq->cfqg); + BUG_ON(!cfqd->busy_queues); + cfqd->busy_queues--; +} + +/* + * rb tree support functions + */ +static void cfq_del_rq_rb(struct request *rq) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + const int sync = rq_is_sync(rq); + + BUG_ON(!cfqq->queued[sync]); + cfqq->queued[sync]--; + + elv_rb_del(&cfqq->sort_list, rq); + + if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) { + /* + * Queue will be deleted from service tree when we actually + * expire it later. Right now just remove it from prio tree + * as it is empty. + */ + if (cfqq->p_root) { + rb_erase(&cfqq->p_node, cfqq->p_root); + cfqq->p_root = NULL; + } + } +} + +static void cfq_add_rq_rb(struct request *rq) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + struct cfq_data *cfqd = cfqq->cfqd; + struct request *__alias, *prev; + + cfqq->queued[rq_is_sync(rq)]++; + + /* + * looks a little odd, but the first insert might return an alias. + * if that happens, put the alias on the dispatch list + */ + while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL) + cfq_dispatch_insert(cfqd->queue, __alias); + + if (!cfq_cfqq_on_rr(cfqq)) + cfq_add_cfqq_rr(cfqd, cfqq); + + /* + * check if this request is a better next-serve candidate + */ + prev = cfqq->next_rq; + cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position); + + /* + * adjust priority tree position, if ->next_rq changes + */ + if (prev != cfqq->next_rq) + cfq_prio_tree_add(cfqd, cfqq); + + BUG_ON(!cfqq->next_rq); +} + +static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq) +{ + elv_rb_del(&cfqq->sort_list, rq); + cfqq->queued[rq_is_sync(rq)]--; + cfq_add_rq_rb(rq); +} + +static struct request * +cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio) +{ + struct task_struct *tsk = current; + struct cfq_io_context *cic; + struct cfq_queue *cfqq; + + cic = cfq_cic_lookup(cfqd, tsk->io_context); + if (!cic) + return NULL; + + cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); + if (cfqq) { + sector_t sector = bio->bi_sector + bio_sectors(bio); + + return elv_rb_find(&cfqq->sort_list, sector); + } + + return NULL; +} + +static void cfq_activate_request(struct request_queue *q, struct request *rq) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + + cfqd->rq_in_driver[rq_is_sync(rq)]++; + cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", + rq_in_driver(cfqd)); + + cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); +} + +static void cfq_deactivate_request(struct request_queue *q, struct request *rq) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + + WARN_ON(!cfqd->rq_in_driver[sync]); + cfqd->rq_in_driver[sync]--; + cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", + rq_in_driver(cfqd)); +} + +static void cfq_remove_request(struct request *rq) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + + if (cfqq->next_rq == rq) + cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq); + + list_del_init(&rq->queuelist); + cfq_del_rq_rb(rq); + + cfqq->cfqd->rq_queued--; + if (rq_is_meta(rq)) { + WARN_ON(!cfqq->meta_pending); + cfqq->meta_pending--; + } +} + +static int cfq_merge(struct request_queue *q, struct request **req, + struct bio *bio) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct request *__rq; + + __rq = cfq_find_rq_fmerge(cfqd, bio); + if (__rq && elv_rq_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_FRONT_MERGE; + } + + return ELEVATOR_NO_MERGE; +} + +static void cfq_merged_request(struct request_queue *q, struct request *req, + int type) +{ + if (type == ELEVATOR_FRONT_MERGE) { + struct cfq_queue *cfqq = RQ_CFQQ(req); + + cfq_reposition_rq_rb(cfqq, req); + } +} + +static void +cfq_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + /* + * reposition in fifo if next is older than rq + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && + time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + + if (cfqq->next_rq == next) + cfqq->next_rq = rq; + cfq_remove_request(next); +} + +static int cfq_allow_merge(struct request_queue *q, struct request *rq, + struct bio *bio) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_io_context *cic; + struct cfq_queue *cfqq; + + /* + * Disallow merge of a sync bio into an async request. + */ + if (cfq_bio_sync(bio) && !rq_is_sync(rq)) + return false; + + /* + * Lookup the cfqq that this bio will be queued with. Allow + * merge only if rq is queued there. + */ + cic = cfq_cic_lookup(cfqd, current->io_context); + if (!cic) + return false; + + cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); + return cfqq == RQ_CFQQ(rq); +} + +static void __cfq_set_active_queue(struct cfq_data *cfqd, + struct cfq_queue *cfqq) +{ + if (cfqq) { + cfq_log_cfqq(cfqd, cfqq, "set_active"); + cfqq->slice_start = 0; + cfqq->dispatch_start = jiffies; + cfqq->allocated_slice = 0; + cfqq->slice_end = 0; + cfqq->slice_dispatch = 0; + cfqq->nr_sectors = 0; + + cfq_clear_cfqq_wait_request(cfqq); + cfq_clear_cfqq_must_dispatch(cfqq); + cfq_clear_cfqq_must_alloc_slice(cfqq); + cfq_clear_cfqq_fifo_expire(cfqq); + cfq_mark_cfqq_slice_new(cfqq); + + del_timer(&cfqd->idle_slice_timer); + } + + cfqd->active_queue = cfqq; +} + +/* + * current cfqq expired its slice (or was too idle), select new one + */ +static void +__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, + bool timed_out) +{ + cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out); + + if (cfq_cfqq_wait_request(cfqq)) + del_timer(&cfqd->idle_slice_timer); + + cfq_clear_cfqq_wait_request(cfqq); + cfq_clear_cfqq_wait_busy(cfqq); + + /* + * If this cfqq is shared between multiple processes, check to + * make sure that those processes are still issuing I/Os within + * the mean seek distance. If not, it may be time to break the + * queues apart again. + */ + if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq)) + cfq_mark_cfqq_split_coop(cfqq); + + /* + * store what was left of this slice, if the queue idled/timed out + */ + if (timed_out && !cfq_cfqq_slice_new(cfqq)) { + cfqq->slice_resid = cfqq->slice_end - jiffies; + cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid); + } + + cfq_group_served(cfqd, cfqq->cfqg, cfqq); + + if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) + cfq_del_cfqq_rr(cfqd, cfqq); + + cfq_resort_rr_list(cfqd, cfqq); + + if (cfqq == cfqd->active_queue) + cfqd->active_queue = NULL; + + if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active) + cfqd->grp_service_tree.active = NULL; + + if (cfqd->active_cic) { + put_io_context(cfqd->active_cic->ioc); + cfqd->active_cic = NULL; + } +} + +static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out) +{ + struct cfq_queue *cfqq = cfqd->active_queue; + + if (cfqq) + __cfq_slice_expired(cfqd, cfqq, timed_out); +} + +/* + * Get next queue for service. Unless we have a queue preemption, + * we'll simply select the first cfqq in the service tree. + */ +static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) +{ + struct cfq_rb_root *service_tree = + service_tree_for(cfqd->serving_group, cfqd->serving_prio, + cfqd->serving_type); + + if (!cfqd->rq_queued) + return NULL; + + /* There is nothing to dispatch */ + if (!service_tree) + return NULL; + if (RB_EMPTY_ROOT(&service_tree->rb)) + return NULL; + return cfq_rb_first(service_tree); +} + +static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd) +{ + struct cfq_group *cfqg; + struct cfq_queue *cfqq; + int i, j; + struct cfq_rb_root *st; + + if (!cfqd->rq_queued) + return NULL; + + cfqg = cfq_get_next_cfqg(cfqd); + if (!cfqg) + return NULL; + + for_each_cfqg_st(cfqg, i, j, st) + if ((cfqq = cfq_rb_first(st)) != NULL) + return cfqq; + return NULL; +} + +/* + * Get and set a new active queue for service. + */ +static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, + struct cfq_queue *cfqq) +{ + if (!cfqq) + cfqq = cfq_get_next_queue(cfqd); + + __cfq_set_active_queue(cfqd, cfqq); + return cfqq; +} + +static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd, + struct request *rq) +{ + if (blk_rq_pos(rq) >= cfqd->last_position) + return blk_rq_pos(rq) - cfqd->last_position; + else + return cfqd->last_position - blk_rq_pos(rq); +} + +static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, + struct request *rq, bool for_preempt) +{ + sector_t sdist = cfqq->seek_mean; + + if (!sample_valid(cfqq->seek_samples)) + sdist = CFQQ_SEEK_THR; + + /* if seek_mean is big, using it as close criteria is meaningless */ + if (sdist > CFQQ_SEEK_THR && !for_preempt) + sdist = CFQQ_SEEK_THR; + + return cfq_dist_from_last(cfqd, rq) <= sdist; +} + +static struct cfq_queue *cfqq_close(struct cfq_data *cfqd, + struct cfq_queue *cur_cfqq) +{ + struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio]; + struct rb_node *parent, *node; + struct cfq_queue *__cfqq; + sector_t sector = cfqd->last_position; + + if (RB_EMPTY_ROOT(root)) + return NULL; + + /* + * First, if we find a request starting at the end of the last + * request, choose it. + */ + __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL); + if (__cfqq) + return __cfqq; + + /* + * If the exact sector wasn't found, the parent of the NULL leaf + * will contain the closest sector. + */ + __cfqq = rb_entry(parent, struct cfq_queue, p_node); + if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false)) + return __cfqq; + + if (blk_rq_pos(__cfqq->next_rq) < sector) + node = rb_next(&__cfqq->p_node); + else + node = rb_prev(&__cfqq->p_node); + if (!node) + return NULL; + + __cfqq = rb_entry(node, struct cfq_queue, p_node); + if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false)) + return __cfqq; + + return NULL; +} + +/* + * cfqd - obvious + * cur_cfqq - passed in so that we don't decide that the current queue is + * closely cooperating with itself. + * + * So, basically we're assuming that that cur_cfqq has dispatched at least + * one request, and that cfqd->last_position reflects a position on the disk + * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid + * assumption. + */ +static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd, + struct cfq_queue *cur_cfqq) +{ + struct cfq_queue *cfqq; + + if (!cfq_cfqq_sync(cur_cfqq)) + return NULL; + if (CFQQ_SEEKY(cur_cfqq)) + return NULL; + + /* + * Don't search priority tree if it's the only queue in the group. + */ + if (cur_cfqq->cfqg->nr_cfqq == 1) + return NULL; + + /* + * We should notice if some of the queues are cooperating, eg + * working closely on the same area of the disk. In that case, + * we can group them together and don't waste time idling. + */ + cfqq = cfqq_close(cfqd, cur_cfqq); + if (!cfqq) + return NULL; + + /* If new queue belongs to different cfq_group, don't choose it */ + if (cur_cfqq->cfqg != cfqq->cfqg) + return NULL; + + /* + * It only makes sense to merge sync queues. + */ + if (!cfq_cfqq_sync(cfqq)) + return NULL; + if (CFQQ_SEEKY(cfqq)) + return NULL; + + /* + * Do not merge queues of different priority classes + */ + if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq)) + return NULL; + + return cfqq; +} + +/* + * Determine whether we should enforce idle window for this queue. + */ + +static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + enum wl_prio_t prio = cfqq_prio(cfqq); + struct cfq_rb_root *service_tree = cfqq->service_tree; + + BUG_ON(!service_tree); + BUG_ON(!service_tree->count); + + /* We never do for idle class queues. */ + if (prio == IDLE_WORKLOAD) + return false; + + /* We do for queues that were marked with idle window flag. */ + if (cfq_cfqq_idle_window(cfqq) && + !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)) + return true; + + /* + * Otherwise, we do only if they are the last ones + * in their service tree. + */ + return service_tree->count == 1 && cfq_cfqq_sync(cfqq); +} + +static void cfq_arm_slice_timer(struct cfq_data *cfqd) +{ + struct cfq_queue *cfqq = cfqd->active_queue; + struct cfq_io_context *cic; + unsigned long sl; + + /* + * SSD device without seek penalty, disable idling. But only do so + * for devices that support queuing, otherwise we still have a problem + * with sync vs async workloads. + */ + if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag) + return; + + WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list)); + WARN_ON(cfq_cfqq_slice_new(cfqq)); + + /* + * idle is disabled, either manually or by past process history + */ + if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq)) + return; + + /* + * still active requests from this queue, don't idle + */ + if (cfqq->dispatched) + return; + + /* + * task has exited, don't wait + */ + cic = cfqd->active_cic; + if (!cic || !atomic_read(&cic->ioc->nr_tasks)) + return; + + /* + * If our average think time is larger than the remaining time + * slice, then don't idle. This avoids overrunning the allotted + * time slice. + */ + if (sample_valid(cic->ttime_samples) && + (cfqq->slice_end - jiffies < cic->ttime_mean)) + return; + + cfq_mark_cfqq_wait_request(cfqq); + + sl = cfqd->cfq_slice_idle; + + mod_timer(&cfqd->idle_slice_timer, jiffies + sl); + cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl); +} + +/* + * Move request from internal lists to the request queue dispatch list. + */ +static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_queue *cfqq = RQ_CFQQ(rq); + + cfq_log_cfqq(cfqd, cfqq, "dispatch_insert"); + + cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq); + cfq_remove_request(rq); + cfqq->dispatched++; + elv_dispatch_sort(q, rq); + + if (cfq_cfqq_sync(cfqq)) + cfqd->sync_flight++; + cfqq->nr_sectors += blk_rq_sectors(rq); +} + +/* + * return expired entry, or NULL to just start from scratch in rbtree + */ +static struct request *cfq_check_fifo(struct cfq_queue *cfqq) +{ + struct request *rq = NULL; + + if (cfq_cfqq_fifo_expire(cfqq)) + return NULL; + + cfq_mark_cfqq_fifo_expire(cfqq); + + if (list_empty(&cfqq->fifo)) + return NULL; + + rq = rq_entry_fifo(cfqq->fifo.next); + if (time_before(jiffies, rq_fifo_time(rq))) + rq = NULL; + + cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); + return rq; +} + +static inline int +cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + const int base_rq = cfqd->cfq_slice_async_rq; + + WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR); + + return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio)); +} + +/* + * Must be called with the queue_lock held. + */ +static int cfqq_process_refs(struct cfq_queue *cfqq) +{ + int process_refs, io_refs; + + io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE]; + process_refs = atomic_read(&cfqq->ref) - io_refs; + BUG_ON(process_refs < 0); + return process_refs; +} + +static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq) +{ + int process_refs, new_process_refs; + struct cfq_queue *__cfqq; + + /* Avoid a circular list and skip interim queue merges */ + while ((__cfqq = new_cfqq->new_cfqq)) { + if (__cfqq == cfqq) + return; + new_cfqq = __cfqq; + } + + process_refs = cfqq_process_refs(cfqq); + /* + * If the process for the cfqq has gone away, there is no + * sense in merging the queues. + */ + if (process_refs == 0) + return; + + /* + * Merge in the direction of the lesser amount of work. + */ + new_process_refs = cfqq_process_refs(new_cfqq); + if (new_process_refs >= process_refs) { + cfqq->new_cfqq = new_cfqq; + atomic_add(process_refs, &new_cfqq->ref); + } else { + new_cfqq->new_cfqq = cfqq; + atomic_add(new_process_refs, &cfqq->ref); + } +} + +static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd, + struct cfq_group *cfqg, enum wl_prio_t prio) +{ + struct cfq_queue *queue; + int i; + bool key_valid = false; + unsigned long lowest_key = 0; + enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; + + for (i = 0; i <= SYNC_WORKLOAD; ++i) { + /* select the one with lowest rb_key */ + queue = cfq_rb_first(service_tree_for(cfqg, prio, i)); + if (queue && + (!key_valid || time_before(queue->rb_key, lowest_key))) { + lowest_key = queue->rb_key; + cur_best = i; + key_valid = true; + } + } + + return cur_best; +} + +static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg) +{ + unsigned slice; + unsigned count; + struct cfq_rb_root *st; + unsigned group_slice; + + if (!cfqg) { + cfqd->serving_prio = IDLE_WORKLOAD; + cfqd->workload_expires = jiffies + 1; + return; + } + + /* Choose next priority. RT > BE > IDLE */ + if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg)) + cfqd->serving_prio = RT_WORKLOAD; + else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg)) + cfqd->serving_prio = BE_WORKLOAD; + else { + cfqd->serving_prio = IDLE_WORKLOAD; + cfqd->workload_expires = jiffies + 1; + return; + } + + /* + * For RT and BE, we have to choose also the type + * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload + * expiration time + */ + st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); + count = st->count; + + /* + * check workload expiration, and that we still have other queues ready + */ + if (count && !time_after(jiffies, cfqd->workload_expires)) + return; + + /* otherwise select new workload type */ + cfqd->serving_type = + cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio); + st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type); + count = st->count; + + /* + * the workload slice is computed as a fraction of target latency + * proportional to the number of queues in that workload, over + * all the queues in the same priority class + */ + group_slice = cfq_group_slice(cfqd, cfqg); + + slice = group_slice * count / + max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio], + cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg)); + + if (cfqd->serving_type == ASYNC_WORKLOAD) { + unsigned int tmp; + + /* + * Async queues are currently system wide. Just taking + * proportion of queues with-in same group will lead to higher + * async ratio system wide as generally root group is going + * to have higher weight. A more accurate thing would be to + * calculate system wide asnc/sync ratio. + */ + tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg); + tmp = tmp/cfqd->busy_queues; + slice = min_t(unsigned, slice, tmp); + + /* async workload slice is scaled down according to + * the sync/async slice ratio. */ + slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1]; + } else + /* sync workload slice is at least 2 * cfq_slice_idle */ + slice = max(slice, 2 * cfqd->cfq_slice_idle); + + slice = max_t(unsigned, slice, CFQ_MIN_TT); + cfqd->workload_expires = jiffies + slice; + cfqd->noidle_tree_requires_idle = false; +} + +static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd) +{ + struct cfq_rb_root *st = &cfqd->grp_service_tree; + struct cfq_group *cfqg; + + if (RB_EMPTY_ROOT(&st->rb)) + return NULL; + cfqg = cfq_rb_first_group(st); + st->active = &cfqg->rb_node; + update_min_vdisktime(st); + return cfqg; +} + +static void cfq_choose_cfqg(struct cfq_data *cfqd) +{ + struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd); + + cfqd->serving_group = cfqg; + + /* Restore the workload type data */ + if (cfqg->saved_workload_slice) { + cfqd->workload_expires = jiffies + cfqg->saved_workload_slice; + cfqd->serving_type = cfqg->saved_workload; + cfqd->serving_prio = cfqg->saved_serving_prio; + } else + cfqd->workload_expires = jiffies - 1; + + choose_service_tree(cfqd, cfqg); +} + +/* + * Select a queue for service. If we have a current active queue, + * check whether to continue servicing it, or retrieve and set a new one. + */ +static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) +{ + struct cfq_queue *cfqq, *new_cfqq = NULL; + + cfqq = cfqd->active_queue; + if (!cfqq) + goto new_queue; + + if (!cfqd->rq_queued) + return NULL; + + /* + * We were waiting for group to get backlogged. Expire the queue + */ + if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list)) + goto expire; + + /* + * The active queue has run out of time, expire it and select new. + */ + if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) { + /* + * If slice had not expired at the completion of last request + * we might not have turned on wait_busy flag. Don't expire + * the queue yet. Allow the group to get backlogged. + * + * The very fact that we have used the slice, that means we + * have been idling all along on this queue and it should be + * ok to wait for this request to complete. + */ + if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list) + && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) { + cfqq = NULL; + goto keep_queue; + } else + goto expire; + } + + /* + * The active queue has requests and isn't expired, allow it to + * dispatch. + */ + if (!RB_EMPTY_ROOT(&cfqq->sort_list)) + goto keep_queue; + + /* + * If another queue has a request waiting within our mean seek + * distance, let it run. The expire code will check for close + * cooperators and put the close queue at the front of the service + * tree. If possible, merge the expiring queue with the new cfqq. + */ + new_cfqq = cfq_close_cooperator(cfqd, cfqq); + if (new_cfqq) { + if (!cfqq->new_cfqq) + cfq_setup_merge(cfqq, new_cfqq); + goto expire; + } + + /* + * No requests pending. If the active queue still has requests in + * flight or is idling for a new request, allow either of these + * conditions to happen (or time out) before selecting a new queue. + */ + if (timer_pending(&cfqd->idle_slice_timer) || + (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) { + cfqq = NULL; + goto keep_queue; + } + +expire: + cfq_slice_expired(cfqd, 0); +new_queue: + /* + * Current queue expired. Check if we have to switch to a new + * service tree + */ + if (!new_cfqq) + cfq_choose_cfqg(cfqd); + + cfqq = cfq_set_active_queue(cfqd, new_cfqq); +keep_queue: + return cfqq; +} + +static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq) +{ + int dispatched = 0; + + while (cfqq->next_rq) { + cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq); + dispatched++; + } + + BUG_ON(!list_empty(&cfqq->fifo)); + + /* By default cfqq is not expired if it is empty. Do it explicitly */ + __cfq_slice_expired(cfqq->cfqd, cfqq, 0); + return dispatched; +} + +/* + * Drain our current requests. Used for barriers and when switching + * io schedulers on-the-fly. + */ +static int cfq_forced_dispatch(struct cfq_data *cfqd) +{ + struct cfq_queue *cfqq; + int dispatched = 0; + + while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) + dispatched += __cfq_forced_dispatch_cfqq(cfqq); + + cfq_slice_expired(cfqd, 0); + BUG_ON(cfqd->busy_queues); + + cfq_log(cfqd, "forced_dispatch=%d", dispatched); + return dispatched; +} + +static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + unsigned int max_dispatch; + + /* + * Drain async requests before we start sync IO + */ + if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC]) + return false; + + /* + * If this is an async queue and we have sync IO in flight, let it wait + */ + if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) + return false; + + max_dispatch = cfqd->cfq_quantum; + if (cfq_class_idle(cfqq)) + max_dispatch = 1; + + /* + * Does this cfqq already have too much IO in flight? + */ + if (cfqq->dispatched >= max_dispatch) { + /* + * idle queue must always only have a single IO in flight + */ + if (cfq_class_idle(cfqq)) + return false; + + /* + * We have other queues, don't allow more IO from this one + */ + if (cfqd->busy_queues > 1) + return false; + + /* + * Sole queue user, no limit + */ + max_dispatch = -1; + } + + /* + * Async queues must wait a bit before being allowed dispatch. + * We also ramp up the dispatch depth gradually for async IO, + * based on the last sync IO we serviced + */ + if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { + unsigned long last_sync = jiffies - cfqd->last_delayed_sync; + unsigned int depth; + + depth = last_sync / cfqd->cfq_slice[1]; + if (!depth && !cfqq->dispatched) + depth = 1; + if (depth < max_dispatch) + max_dispatch = depth; + } + + /* + * If we're below the current max, allow a dispatch + */ + return cfqq->dispatched < max_dispatch; +} + +/* + * Dispatch a request from cfqq, moving them to the request queue + * dispatch list. + */ +static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + struct request *rq; + + BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); + + if (!cfq_may_dispatch(cfqd, cfqq)) + return false; + + /* + * follow expired path, else get first next available + */ + rq = cfq_check_fifo(cfqq); + if (!rq) + rq = cfqq->next_rq; + + /* + * insert request into driver dispatch list + */ + cfq_dispatch_insert(cfqd->queue, rq); + + if (!cfqd->active_cic) { + struct cfq_io_context *cic = RQ_CIC(rq); + + atomic_long_inc(&cic->ioc->refcount); + cfqd->active_cic = cic; + } + + return true; +} + +/* + * Find the cfqq that we need to service and move a request from that to the + * dispatch list + */ +static int cfq_dispatch_requests(struct request_queue *q, int force) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_queue *cfqq; + + if (!cfqd->busy_queues) + return 0; + + if (unlikely(force)) + return cfq_forced_dispatch(cfqd); + + cfqq = cfq_select_queue(cfqd); + if (!cfqq) + return 0; + + /* + * Dispatch a request from this cfqq, if it is allowed + */ + if (!cfq_dispatch_request(cfqd, cfqq)) + return 0; + + cfqq->slice_dispatch++; + cfq_clear_cfqq_must_dispatch(cfqq); + + /* + * expire an async queue immediately if it has used up its slice. idle + * queue always expire after 1 dispatch round. + */ + if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) && + cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) || + cfq_class_idle(cfqq))) { + cfqq->slice_end = jiffies + 1; + cfq_slice_expired(cfqd, 0); + } + + cfq_log_cfqq(cfqd, cfqq, "dispatched a request"); + return 1; +} + +/* + * task holds one reference to the queue, dropped when task exits. each rq + * in-flight on this queue also holds a reference, dropped when rq is freed. + * + * Each cfq queue took a reference on the parent group. Drop it now. + * queue lock must be held here. + */ +static void cfq_put_queue(struct cfq_queue *cfqq) +{ + struct cfq_data *cfqd = cfqq->cfqd; + struct cfq_group *cfqg, *orig_cfqg; + + BUG_ON(atomic_read(&cfqq->ref) <= 0); + + if (!atomic_dec_and_test(&cfqq->ref)) + return; + + cfq_log_cfqq(cfqd, cfqq, "put_queue"); + BUG_ON(rb_first(&cfqq->sort_list)); + BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]); + cfqg = cfqq->cfqg; + orig_cfqg = cfqq->orig_cfqg; + + if (unlikely(cfqd->active_queue == cfqq)) { + __cfq_slice_expired(cfqd, cfqq, 0); + cfq_schedule_dispatch(cfqd); + } + + BUG_ON(cfq_cfqq_on_rr(cfqq)); + kmem_cache_free(cfq_pool, cfqq); + cfq_put_cfqg(cfqg); + if (orig_cfqg) + cfq_put_cfqg(orig_cfqg); +} + +/* + * Must always be called with the rcu_read_lock() held + */ +static void +__call_for_each_cic(struct io_context *ioc, + void (*func)(struct io_context *, struct cfq_io_context *)) +{ + struct cfq_io_context *cic; + struct hlist_node *n; + + hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) + func(ioc, cic); +} + +/* + * Call func for each cic attached to this ioc. + */ +static void +call_for_each_cic(struct io_context *ioc, + void (*func)(struct io_context *, struct cfq_io_context *)) +{ + rcu_read_lock(); + __call_for_each_cic(ioc, func); + rcu_read_unlock(); +} + +static void cfq_cic_free_rcu(struct rcu_head *head) +{ + struct cfq_io_context *cic; + + cic = container_of(head, struct cfq_io_context, rcu_head); + + kmem_cache_free(cfq_ioc_pool, cic); + elv_ioc_count_dec(cfq_ioc_count); + + if (ioc_gone) { + /* + * CFQ scheduler is exiting, grab exit lock and check + * the pending io context count. If it hits zero, + * complete ioc_gone and set it back to NULL + */ + spin_lock(&ioc_gone_lock); + if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) { + complete(ioc_gone); + ioc_gone = NULL; + } + spin_unlock(&ioc_gone_lock); + } +} + +static void cfq_cic_free(struct cfq_io_context *cic) +{ + call_rcu(&cic->rcu_head, cfq_cic_free_rcu); +} + +static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic) +{ + unsigned long flags; + + BUG_ON(!cic->dead_key); + + spin_lock_irqsave(&ioc->lock, flags); + radix_tree_delete(&ioc->radix_root, cic->dead_key); + hlist_del_rcu(&cic->cic_list); + spin_unlock_irqrestore(&ioc->lock, flags); + + cfq_cic_free(cic); +} + +/* + * Must be called with rcu_read_lock() held or preemption otherwise disabled. + * Only two callers of this - ->dtor() which is called with the rcu_read_lock(), + * and ->trim() which is called with the task lock held + */ +static void cfq_free_io_context(struct io_context *ioc) +{ + /* + * ioc->refcount is zero here, or we are called from elv_unregister(), + * so no more cic's are allowed to be linked into this ioc. So it + * should be ok to iterate over the known list, we will see all cic's + * since no new ones are added. + */ + __call_for_each_cic(ioc, cic_free_func); +} + +static void cfq_put_cooperator(struct cfq_queue *cfqq) +{ + struct cfq_queue *__cfqq, *next; + + /* + * If this queue was scheduled to merge with another queue, be + * sure to drop the reference taken on that queue (and others in + * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs. + */ + __cfqq = cfqq->new_cfqq; + while (__cfqq) { + if (__cfqq == cfqq) { + WARN(1, "cfqq->new_cfqq loop detected\n"); + break; + } + next = __cfqq->new_cfqq; + cfq_put_queue(__cfqq); + __cfqq = next; + } +} + +static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + if (unlikely(cfqq == cfqd->active_queue)) { + __cfq_slice_expired(cfqd, cfqq, 0); + cfq_schedule_dispatch(cfqd); + } + + cfq_put_cooperator(cfqq); + + cfq_put_queue(cfqq); +} + +static void __cfq_exit_single_io_context(struct cfq_data *cfqd, + struct cfq_io_context *cic) +{ + struct io_context *ioc = cic->ioc; + + list_del_init(&cic->queue_list); + + /* + * Make sure key == NULL is seen for dead queues + */ + smp_wmb(); + cic->dead_key = (unsigned long) cic->key; + cic->key = NULL; + + if (ioc->ioc_data == cic) + rcu_assign_pointer(ioc->ioc_data, NULL); + + if (cic->cfqq[BLK_RW_ASYNC]) { + cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); + cic->cfqq[BLK_RW_ASYNC] = NULL; + } + + if (cic->cfqq[BLK_RW_SYNC]) { + cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]); + cic->cfqq[BLK_RW_SYNC] = NULL; + } +} + +static void cfq_exit_single_io_context(struct io_context *ioc, + struct cfq_io_context *cic) +{ + struct cfq_data *cfqd = cic->key; + + if (cfqd) { + struct request_queue *q = cfqd->queue; + unsigned long flags; + + spin_lock_irqsave(q->queue_lock, flags); + + /* + * Ensure we get a fresh copy of the ->key to prevent + * race between exiting task and queue + */ + smp_read_barrier_depends(); + if (cic->key) + __cfq_exit_single_io_context(cfqd, cic); + + spin_unlock_irqrestore(q->queue_lock, flags); + } +} + +/* + * The process that ioc belongs to has exited, we need to clean up + * and put the internal structures we have that belongs to that process. + */ +static void cfq_exit_io_context(struct io_context *ioc) +{ + call_for_each_cic(ioc, cfq_exit_single_io_context); +} + +static struct cfq_io_context * +cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) +{ + struct cfq_io_context *cic; + + cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO, + cfqd->queue->node); + if (cic) { + cic->last_end_request = jiffies; + INIT_LIST_HEAD(&cic->queue_list); + INIT_HLIST_NODE(&cic->cic_list); + cic->dtor = cfq_free_io_context; + cic->exit = cfq_exit_io_context; + elv_ioc_count_inc(cfq_ioc_count); + } + + return cic; +} + +static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc) +{ + struct task_struct *tsk = current; + int ioprio_class; + + if (!cfq_cfqq_prio_changed(cfqq)) + return; + + ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); + switch (ioprio_class) { + default: + printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class); + case IOPRIO_CLASS_NONE: + /* + * no prio set, inherit CPU scheduling settings + */ + cfqq->ioprio = task_nice_ioprio(tsk); + cfqq->ioprio_class = task_nice_ioclass(tsk); + break; + case IOPRIO_CLASS_RT: + cfqq->ioprio = task_ioprio(ioc); + cfqq->ioprio_class = IOPRIO_CLASS_RT; + break; + case IOPRIO_CLASS_BE: + cfqq->ioprio = task_ioprio(ioc); + cfqq->ioprio_class = IOPRIO_CLASS_BE; + break; + case IOPRIO_CLASS_IDLE: + cfqq->ioprio_class = IOPRIO_CLASS_IDLE; + cfqq->ioprio = 7; + cfq_clear_cfqq_idle_window(cfqq); + break; + } + + /* + * keep track of original prio settings in case we have to temporarily + * elevate the priority of this queue + */ + cfqq->org_ioprio = cfqq->ioprio; + cfqq->org_ioprio_class = cfqq->ioprio_class; + cfq_clear_cfqq_prio_changed(cfqq); +} + +static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) +{ + struct cfq_data *cfqd = cic->key; + struct cfq_queue *cfqq; + unsigned long flags; + + if (unlikely(!cfqd)) + return; + + spin_lock_irqsave(cfqd->queue->queue_lock, flags); + + cfqq = cic->cfqq[BLK_RW_ASYNC]; + if (cfqq) { + struct cfq_queue *new_cfqq; + new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc, + GFP_ATOMIC); + if (new_cfqq) { + cic->cfqq[BLK_RW_ASYNC] = new_cfqq; + cfq_put_queue(cfqq); + } + } + + cfqq = cic->cfqq[BLK_RW_SYNC]; + if (cfqq) + cfq_mark_cfqq_prio_changed(cfqq); + + spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); +} + +static void cfq_ioc_set_ioprio(struct io_context *ioc) +{ + call_for_each_cic(ioc, changed_ioprio); + ioc->ioprio_changed = 0; +} + +static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, + pid_t pid, bool is_sync) +{ + RB_CLEAR_NODE(&cfqq->rb_node); + RB_CLEAR_NODE(&cfqq->p_node); + INIT_LIST_HEAD(&cfqq->fifo); + + atomic_set(&cfqq->ref, 0); + cfqq->cfqd = cfqd; + + cfq_mark_cfqq_prio_changed(cfqq); + + if (is_sync) { + if (!cfq_class_idle(cfqq)) + cfq_mark_cfqq_idle_window(cfqq); + cfq_mark_cfqq_sync(cfqq); + } + cfqq->pid = pid; +} + +#ifdef CONFIG_CFQ_GROUP_IOSCHED +static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic) +{ + struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1); + struct cfq_data *cfqd = cic->key; + unsigned long flags; + struct request_queue *q; + + if (unlikely(!cfqd)) + return; + + q = cfqd->queue; + + spin_lock_irqsave(q->queue_lock, flags); + + if (sync_cfqq) { + /* + * Drop reference to sync queue. A new sync queue will be + * assigned in new group upon arrival of a fresh request. + */ + cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup"); + cic_set_cfqq(cic, NULL, 1); + cfq_put_queue(sync_cfqq); + } + + spin_unlock_irqrestore(q->queue_lock, flags); +} + +static void cfq_ioc_set_cgroup(struct io_context *ioc) +{ + call_for_each_cic(ioc, changed_cgroup); + ioc->cgroup_changed = 0; +} +#endif /* CONFIG_CFQ_GROUP_IOSCHED */ + +static struct cfq_queue * +cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, + struct io_context *ioc, gfp_t gfp_mask) +{ + struct cfq_queue *cfqq, *new_cfqq = NULL; + struct cfq_io_context *cic; + struct cfq_group *cfqg; + +retry: + cfqg = cfq_get_cfqg(cfqd, 1); + cic = cfq_cic_lookup(cfqd, ioc); + /* cic always exists here */ + cfqq = cic_to_cfqq(cic, is_sync); + + /* + * Always try a new alloc if we fell back to the OOM cfqq + * originally, since it should just be a temporary situation. + */ + if (!cfqq || cfqq == &cfqd->oom_cfqq) { + cfqq = NULL; + if (new_cfqq) { + cfqq = new_cfqq; + new_cfqq = NULL; + } else if (gfp_mask & __GFP_WAIT) { + spin_unlock_irq(cfqd->queue->queue_lock); + new_cfqq = kmem_cache_alloc_node(cfq_pool, + gfp_mask | __GFP_ZERO, + cfqd->queue->node); + spin_lock_irq(cfqd->queue->queue_lock); + if (new_cfqq) + goto retry; + } else { + cfqq = kmem_cache_alloc_node(cfq_pool, + gfp_mask | __GFP_ZERO, + cfqd->queue->node); + } + + if (cfqq) { + cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); + cfq_init_prio_data(cfqq, ioc); + cfq_link_cfqq_cfqg(cfqq, cfqg); + cfq_log_cfqq(cfqd, cfqq, "alloced"); + } else + cfqq = &cfqd->oom_cfqq; + } + + if (new_cfqq) + kmem_cache_free(cfq_pool, new_cfqq); + + return cfqq; +} + +static struct cfq_queue ** +cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio) +{ + switch (ioprio_class) { + case IOPRIO_CLASS_RT: + return &cfqd->async_cfqq[0][ioprio]; + case IOPRIO_CLASS_BE: + return &cfqd->async_cfqq[1][ioprio]; + case IOPRIO_CLASS_IDLE: + return &cfqd->async_idle_cfqq; + default: + BUG(); + } +} + +static struct cfq_queue * +cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc, + gfp_t gfp_mask) +{ + const int ioprio = task_ioprio(ioc); + const int ioprio_class = task_ioprio_class(ioc); + struct cfq_queue **async_cfqq = NULL; + struct cfq_queue *cfqq = NULL; + + if (!is_sync) { + async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio); + cfqq = *async_cfqq; + } + + if (!cfqq) + cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); + + /* + * pin the queue now that it's allocated, scheduler exit will prune it + */ + if (!is_sync && !(*async_cfqq)) { + atomic_inc(&cfqq->ref); + *async_cfqq = cfqq; + } + + atomic_inc(&cfqq->ref); + return cfqq; +} + +/* + * We drop cfq io contexts lazily, so we may find a dead one. + */ +static void +cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc, + struct cfq_io_context *cic) +{ + unsigned long flags; + + WARN_ON(!list_empty(&cic->queue_list)); + + spin_lock_irqsave(&ioc->lock, flags); + + BUG_ON(ioc->ioc_data == cic); + + radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd); + hlist_del_rcu(&cic->cic_list); + spin_unlock_irqrestore(&ioc->lock, flags); + + cfq_cic_free(cic); +} + +static struct cfq_io_context * +cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc) +{ + struct cfq_io_context *cic; + unsigned long flags; + void *k; + + if (unlikely(!ioc)) + return NULL; + + rcu_read_lock(); + + /* + * we maintain a last-hit cache, to avoid browsing over the tree + */ + cic = rcu_dereference(ioc->ioc_data); + if (cic && cic->key == cfqd) { + rcu_read_unlock(); + return cic; + } + + do { + cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd); + rcu_read_unlock(); + if (!cic) + break; + /* ->key must be copied to avoid race with cfq_exit_queue() */ + k = cic->key; + if (unlikely(!k)) { + cfq_drop_dead_cic(cfqd, ioc, cic); + rcu_read_lock(); + continue; + } + + spin_lock_irqsave(&ioc->lock, flags); + rcu_assign_pointer(ioc->ioc_data, cic); + spin_unlock_irqrestore(&ioc->lock, flags); + break; + } while (1); + + return cic; +} + +/* + * Add cic into ioc, using cfqd as the search key. This enables us to lookup + * the process specific cfq io context when entered from the block layer. + * Also adds the cic to a per-cfqd list, used when this queue is removed. + */ +static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc, + struct cfq_io_context *cic, gfp_t gfp_mask) +{ + unsigned long flags; + int ret; + + ret = radix_tree_preload(gfp_mask); + if (!ret) { + cic->ioc = ioc; + cic->key = cfqd; + + spin_lock_irqsave(&ioc->lock, flags); + ret = radix_tree_insert(&ioc->radix_root, + (unsigned long) cfqd, cic); + if (!ret) + hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list); + spin_unlock_irqrestore(&ioc->lock, flags); + + radix_tree_preload_end(); + + if (!ret) { + spin_lock_irqsave(cfqd->queue->queue_lock, flags); + list_add(&cic->queue_list, &cfqd->cic_list); + spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); + } + } + + if (ret) + printk(KERN_ERR "cfq: cic link failed!\n"); + + return ret; +} + +/* + * Setup general io context and cfq io context. There can be several cfq + * io contexts per general io context, if this process is doing io to more + * than one device managed by cfq. + */ +static struct cfq_io_context * +cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) +{ + struct io_context *ioc = NULL; + struct cfq_io_context *cic; + + might_sleep_if(gfp_mask & __GFP_WAIT); + + ioc = get_io_context(gfp_mask, cfqd->queue->node); + if (!ioc) + return NULL; + + cic = cfq_cic_lookup(cfqd, ioc); + if (cic) + goto out; + + cic = cfq_alloc_io_context(cfqd, gfp_mask); + if (cic == NULL) + goto err; + + if (cfq_cic_link(cfqd, ioc, cic, gfp_mask)) + goto err_free; + +out: + smp_read_barrier_depends(); + if (unlikely(ioc->ioprio_changed)) + cfq_ioc_set_ioprio(ioc); + +#ifdef CONFIG_CFQ_GROUP_IOSCHED + if (unlikely(ioc->cgroup_changed)) + cfq_ioc_set_cgroup(ioc); +#endif + return cic; +err_free: + cfq_cic_free(cic); +err: + put_io_context(ioc); + return NULL; +} + +static void +cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic) +{ + unsigned long elapsed = jiffies - cic->last_end_request; + unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle); + + cic->ttime_samples = (7*cic->ttime_samples + 256) / 8; + cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8; + cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples; +} + +static void +cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq, + struct request *rq) +{ + sector_t sdist; + u64 total; + + if (!cfqq->last_request_pos) + sdist = 0; + else if (cfqq->last_request_pos < blk_rq_pos(rq)) + sdist = blk_rq_pos(rq) - cfqq->last_request_pos; + else + sdist = cfqq->last_request_pos - blk_rq_pos(rq); + + /* + * Don't allow the seek distance to get too large from the + * odd fragment, pagein, etc + */ + if (cfqq->seek_samples <= 60) /* second&third seek */ + sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024); + else + sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64); + + cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8; + cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8; + total = cfqq->seek_total + (cfqq->seek_samples/2); + do_div(total, cfqq->seek_samples); + cfqq->seek_mean = (sector_t)total; +} + +/* + * Disable idle window if the process thinks too long or seeks so much that + * it doesn't matter + */ +static void +cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, + struct cfq_io_context *cic) +{ + int old_idle, enable_idle; + + /* + * Don't idle for async or idle io prio class + */ + if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq)) + return; + + enable_idle = old_idle = cfq_cfqq_idle_window(cfqq); + + if (cfqq->queued[0] + cfqq->queued[1] >= 4) + cfq_mark_cfqq_deep(cfqq); + + if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || + (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples) + && CFQQ_SEEKY(cfqq))) + enable_idle = 0; + else if (sample_valid(cic->ttime_samples)) { + if (cic->ttime_mean > cfqd->cfq_slice_idle) + enable_idle = 0; + else + enable_idle = 1; + } + + if (old_idle != enable_idle) { + cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle); + if (enable_idle) + cfq_mark_cfqq_idle_window(cfqq); + else + cfq_clear_cfqq_idle_window(cfqq); + } +} + +/* + * Check if new_cfqq should preempt the currently active queue. Return 0 for + * no or if we aren't sure, a 1 will cause a preempt. + */ +static bool +cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, + struct request *rq) +{ + struct cfq_queue *cfqq; + + cfqq = cfqd->active_queue; + if (!cfqq) + return false; + + if (cfq_class_idle(new_cfqq)) + return false; + + if (cfq_class_idle(cfqq)) + return true; + + /* + * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice. + */ + if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq)) + return false; + + /* + * if the new request is sync, but the currently running queue is + * not, let the sync request have priority. + */ + if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) + return true; + + if (new_cfqq->cfqg != cfqq->cfqg) + return false; + + if (cfq_slice_used(cfqq)) + return true; + + /* Allow preemption only if we are idling on sync-noidle tree */ + if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD && + cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD && + new_cfqq->service_tree->count == 2 && + RB_EMPTY_ROOT(&cfqq->sort_list)) + return true; + + /* + * So both queues are sync. Let the new request get disk time if + * it's a metadata request and the current queue is doing regular IO. + */ + if (rq_is_meta(rq) && !cfqq->meta_pending) + return true; + + /* + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. + */ + if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq)) + return true; + + if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) + return false; + + /* + * if this request is as-good as one we would expect from the + * current cfqq, let it preempt + */ + if (cfq_rq_close(cfqd, cfqq, rq, true)) + return true; + + return false; +} + +/* + * cfqq preempts the active queue. if we allowed preempt with no slice left, + * let it have half of its nominal slice. + */ +static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + cfq_log_cfqq(cfqd, cfqq, "preempt"); + cfq_slice_expired(cfqd, 1); + + /* + * Put the new queue at the front of the of the current list, + * so we know that it will be selected next. + */ + BUG_ON(!cfq_cfqq_on_rr(cfqq)); + + cfq_service_tree_add(cfqd, cfqq, 1); + + cfqq->slice_end = 0; + cfq_mark_cfqq_slice_new(cfqq); +} + +/* + * Called when a new fs request (rq) is added (to cfqq). Check if there's + * something we should do about it + */ +static void +cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, + struct request *rq) +{ + struct cfq_io_context *cic = RQ_CIC(rq); + + cfqd->rq_queued++; + if (rq_is_meta(rq)) + cfqq->meta_pending++; + + cfq_update_io_thinktime(cfqd, cic); + cfq_update_io_seektime(cfqd, cfqq, rq); + cfq_update_idle_window(cfqd, cfqq, cic); + + cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); + + if (cfqq == cfqd->active_queue) { + /* + * Remember that we saw a request from this process, but + * don't start queuing just yet. Otherwise we risk seeing lots + * of tiny requests, because we disrupt the normal plugging + * and merging. If the request is already larger than a single + * page, let it rip immediately. For that case we assume that + * merging is already done. Ditto for a busy system that + * has other work pending, don't risk delaying until the + * idle timer unplug to continue working. + */ + if (cfq_cfqq_wait_request(cfqq)) { + if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE || + cfqd->busy_queues > 1) { + del_timer(&cfqd->idle_slice_timer); + cfq_clear_cfqq_wait_request(cfqq); + __blk_run_queue(cfqd->queue); + } else + cfq_mark_cfqq_must_dispatch(cfqq); + } + } else if (cfq_should_preempt(cfqd, cfqq, rq)) { + /* + * not the active queue - expire current slice if it is + * idle and has expired it's mean thinktime or this new queue + * has some old slice time left and is of higher priority or + * this new queue is RT and the current one is BE + */ + cfq_preempt_queue(cfqd, cfqq); + __blk_run_queue(cfqd->queue); + } +} + +static void cfq_insert_request(struct request_queue *q, struct request *rq) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_queue *cfqq = RQ_CFQQ(rq); + + cfq_log_cfqq(cfqd, cfqq, "insert_request"); + cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc); + + rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]); + list_add_tail(&rq->queuelist, &cfqq->fifo); + cfq_add_rq_rb(rq); + + cfq_rq_enqueued(cfqd, cfqq, rq); +} + +/* + * Update hw_tag based on peak queue depth over 50 samples under + * sufficient load. + */ +static void cfq_update_hw_tag(struct cfq_data *cfqd) +{ + struct cfq_queue *cfqq = cfqd->active_queue; + + if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth) + cfqd->hw_tag_est_depth = rq_in_driver(cfqd); + + if (cfqd->hw_tag == 1) + return; + + if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && + rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN) + return; + + /* + * If active queue hasn't enough requests and can idle, cfq might not + * dispatch sufficient requests to hardware. Don't zero hw_tag in this + * case + */ + if (cfqq && cfq_cfqq_idle_window(cfqq) && + cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] < + CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN) + return; + + if (cfqd->hw_tag_samples++ < 50) + return; + + if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN) + cfqd->hw_tag = 1; + else + cfqd->hw_tag = 0; +} + +static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + struct cfq_io_context *cic = cfqd->active_cic; + + /* If there are other queues in the group, don't wait */ + if (cfqq->cfqg->nr_cfqq > 1) + return false; + + if (cfq_slice_used(cfqq)) + return true; + + /* if slice left is less than think time, wait busy */ + if (cic && sample_valid(cic->ttime_samples) + && (cfqq->slice_end - jiffies < cic->ttime_mean)) + return true; + + /* + * If think times is less than a jiffy than ttime_mean=0 and above + * will not be true. It might happen that slice has not expired yet + * but will expire soon (4-5 ns) during select_queue(). To cover the + * case where think time is less than a jiffy, mark the queue wait + * busy if only 1 jiffy is left in the slice. + */ + if (cfqq->slice_end - jiffies == 1) + return true; + + return false; +} + +static void cfq_completed_request(struct request_queue *q, struct request *rq) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + struct cfq_data *cfqd = cfqq->cfqd; + const int sync = rq_is_sync(rq); + unsigned long now; + + now = jiffies; + cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq)); + + cfq_update_hw_tag(cfqd); + + WARN_ON(!cfqd->rq_in_driver[sync]); + WARN_ON(!cfqq->dispatched); + cfqd->rq_in_driver[sync]--; + cfqq->dispatched--; + + if (cfq_cfqq_sync(cfqq)) + cfqd->sync_flight--; + + if (sync) { + RQ_CIC(rq)->last_end_request = now; + if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now)) + cfqd->last_delayed_sync = now; + } + + /* + * If this is the active queue, check if it needs to be expired, + * or if we want to idle in case it has no pending requests. + */ + if (cfqd->active_queue == cfqq) { + const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list); + + if (cfq_cfqq_slice_new(cfqq)) { + cfq_set_prio_slice(cfqd, cfqq); + cfq_clear_cfqq_slice_new(cfqq); + } + + /* + * Should we wait for next request to come in before we expire + * the queue. + */ + if (cfq_should_wait_busy(cfqd, cfqq)) { + cfqq->slice_end = jiffies + cfqd->cfq_slice_idle; + cfq_mark_cfqq_wait_busy(cfqq); + } + + /* + * Idling is not enabled on: + * - expired queues + * - idle-priority queues + * - async queues + * - queues with still some requests queued + * - when there is a close cooperator + */ + if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) + cfq_slice_expired(cfqd, 1); + else if (sync && cfqq_empty && + !cfq_close_cooperator(cfqd, cfqq)) { + cfqd->noidle_tree_requires_idle |= !rq_noidle(rq); + /* + * Idling is enabled for SYNC_WORKLOAD. + * SYNC_NOIDLE_WORKLOAD idles at the end of the tree + * only if we processed at least one !rq_noidle request + */ + if (cfqd->serving_type == SYNC_WORKLOAD + || cfqd->noidle_tree_requires_idle + || cfqq->cfqg->nr_cfqq == 1) + cfq_arm_slice_timer(cfqd); + } + } + + if (!rq_in_driver(cfqd)) + cfq_schedule_dispatch(cfqd); +} + +/* + * we temporarily boost lower priority queues if they are holding fs exclusive + * resources. they are boosted to normal prio (CLASS_BE/4) + */ +static void cfq_prio_boost(struct cfq_queue *cfqq) +{ + if (has_fs_excl()) { + /* + * boost idle prio on transactions that would lock out other + * users of the filesystem + */ + if (cfq_class_idle(cfqq)) + cfqq->ioprio_class = IOPRIO_CLASS_BE; + if (cfqq->ioprio > IOPRIO_NORM) + cfqq->ioprio = IOPRIO_NORM; + } else { + /* + * unboost the queue (if needed) + */ + cfqq->ioprio_class = cfqq->org_ioprio_class; + cfqq->ioprio = cfqq->org_ioprio; + } +} + +static inline int __cfq_may_queue(struct cfq_queue *cfqq) +{ + if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) { + cfq_mark_cfqq_must_alloc_slice(cfqq); + return ELV_MQUEUE_MUST; + } + + return ELV_MQUEUE_MAY; +} + +static int cfq_may_queue(struct request_queue *q, int rw) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct task_struct *tsk = current; + struct cfq_io_context *cic; + struct cfq_queue *cfqq; + + /* + * don't force setup of a queue from here, as a call to may_queue + * does not necessarily imply that a request actually will be queued. + * so just lookup a possibly existing queue, or return 'may queue' + * if that fails + */ + cic = cfq_cic_lookup(cfqd, tsk->io_context); + if (!cic) + return ELV_MQUEUE_MAY; + + cfqq = cic_to_cfqq(cic, rw_is_sync(rw)); + if (cfqq) { + cfq_init_prio_data(cfqq, cic->ioc); + cfq_prio_boost(cfqq); + + return __cfq_may_queue(cfqq); + } + + return ELV_MQUEUE_MAY; +} + +/* + * queue lock held here + */ +static void cfq_put_request(struct request *rq) +{ + struct cfq_queue *cfqq = RQ_CFQQ(rq); + + if (cfqq) { + const int rw = rq_data_dir(rq); + + BUG_ON(!cfqq->allocated[rw]); + cfqq->allocated[rw]--; + + put_io_context(RQ_CIC(rq)->ioc); + + rq->elevator_private = NULL; + rq->elevator_private2 = NULL; + + cfq_put_queue(cfqq); + } +} + +static struct cfq_queue * +cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic, + struct cfq_queue *cfqq) +{ + cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq); + cic_set_cfqq(cic, cfqq->new_cfqq, 1); + cfq_mark_cfqq_coop(cfqq->new_cfqq); + cfq_put_queue(cfqq); + return cic_to_cfqq(cic, 1); +} + +/* + * Returns NULL if a new cfqq should be allocated, or the old cfqq if this + * was the last process referring to said cfqq. + */ +static struct cfq_queue * +split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq) +{ + if (cfqq_process_refs(cfqq) == 1) { + cfqq->pid = current->pid; + cfq_clear_cfqq_coop(cfqq); + cfq_clear_cfqq_split_coop(cfqq); + return cfqq; + } + + cic_set_cfqq(cic, NULL, 1); + + cfq_put_cooperator(cfqq); + + cfq_put_queue(cfqq); + return NULL; +} +/* + * Allocate cfq data structures associated with this request. + */ +static int +cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_io_context *cic; + const int rw = rq_data_dir(rq); + const bool is_sync = rq_is_sync(rq); + struct cfq_queue *cfqq; + unsigned long flags; + + might_sleep_if(gfp_mask & __GFP_WAIT); + + cic = cfq_get_io_context(cfqd, gfp_mask); + + spin_lock_irqsave(q->queue_lock, flags); + + if (!cic) + goto queue_fail; + +new_queue: + cfqq = cic_to_cfqq(cic, is_sync); + if (!cfqq || cfqq == &cfqd->oom_cfqq) { + cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); + cic_set_cfqq(cic, cfqq, is_sync); + } else { + /* + * If the queue was seeky for too long, break it apart. + */ + if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) { + cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq"); + cfqq = split_cfqq(cic, cfqq); + if (!cfqq) + goto new_queue; + } + + /* + * Check to see if this queue is scheduled to merge with + * another, closely cooperating queue. The merging of + * queues happens here as it must be done in process context. + * The reference on new_cfqq was taken in merge_cfqqs. + */ + if (cfqq->new_cfqq) + cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq); + } + + cfqq->allocated[rw]++; + atomic_inc(&cfqq->ref); + + spin_unlock_irqrestore(q->queue_lock, flags); + + rq->elevator_private = cic; + rq->elevator_private2 = cfqq; + return 0; + +queue_fail: + if (cic) + put_io_context(cic->ioc); + + cfq_schedule_dispatch(cfqd); + spin_unlock_irqrestore(q->queue_lock, flags); + cfq_log(cfqd, "set_request fail"); + return 1; +} + +static void cfq_kick_queue(struct work_struct *work) +{ + struct cfq_data *cfqd = + container_of(work, struct cfq_data, unplug_work); + struct request_queue *q = cfqd->queue; + + spin_lock_irq(q->queue_lock); + __blk_run_queue(cfqd->queue); + spin_unlock_irq(q->queue_lock); +} + +/* + * Timer running if the active_queue is currently idling inside its time slice + */ +static void cfq_idle_slice_timer(unsigned long data) +{ + struct cfq_data *cfqd = (struct cfq_data *) data; + struct cfq_queue *cfqq; + unsigned long flags; + int timed_out = 1; + + cfq_log(cfqd, "idle timer fired"); + + spin_lock_irqsave(cfqd->queue->queue_lock, flags); + + cfqq = cfqd->active_queue; + if (cfqq) { + timed_out = 0; + + /* + * We saw a request before the queue expired, let it through + */ + if (cfq_cfqq_must_dispatch(cfqq)) + goto out_kick; + + /* + * expired + */ + if (cfq_slice_used(cfqq)) + goto expire; + + /* + * only expire and reinvoke request handler, if there are + * other queues with pending requests + */ + if (!cfqd->busy_queues) + goto out_cont; + + /* + * not expired and it has a request pending, let it dispatch + */ + if (!RB_EMPTY_ROOT(&cfqq->sort_list)) + goto out_kick; + + /* + * Queue depth flag is reset only when the idle didn't succeed + */ + cfq_clear_cfqq_deep(cfqq); + } +expire: + cfq_slice_expired(cfqd, timed_out); +out_kick: + cfq_schedule_dispatch(cfqd); +out_cont: + spin_unlock_irqrestore(cfqd->queue->queue_lock, flags); +} + +static void cfq_shutdown_timer_wq(struct cfq_data *cfqd) +{ + del_timer_sync(&cfqd->idle_slice_timer); + cancel_work_sync(&cfqd->unplug_work); +} + +static void cfq_put_async_queues(struct cfq_data *cfqd) +{ + int i; + + for (i = 0; i < IOPRIO_BE_NR; i++) { + if (cfqd->async_cfqq[0][i]) + cfq_put_queue(cfqd->async_cfqq[0][i]); + if (cfqd->async_cfqq[1][i]) + cfq_put_queue(cfqd->async_cfqq[1][i]); + } + + if (cfqd->async_idle_cfqq) + cfq_put_queue(cfqd->async_idle_cfqq); +} + +static void cfq_cfqd_free(struct rcu_head *head) +{ + kfree(container_of(head, struct cfq_data, rcu)); +} + +static void cfq_exit_queue(struct elevator_queue *e) +{ + struct cfq_data *cfqd = e->elevator_data; + struct request_queue *q = cfqd->queue; + + cfq_shutdown_timer_wq(cfqd); + + spin_lock_irq(q->queue_lock); + + if (cfqd->active_queue) + __cfq_slice_expired(cfqd, cfqd->active_queue, 0); + + while (!list_empty(&cfqd->cic_list)) { + struct cfq_io_context *cic = list_entry(cfqd->cic_list.next, + struct cfq_io_context, + queue_list); + + __cfq_exit_single_io_context(cfqd, cic); + } + + cfq_put_async_queues(cfqd); + cfq_release_cfq_groups(cfqd); + blkiocg_del_blkio_group(&cfqd->root_group.blkg); + + spin_unlock_irq(q->queue_lock); + + cfq_shutdown_timer_wq(cfqd); + + /* Wait for cfqg->blkg->key accessors to exit their grace periods. */ + call_rcu(&cfqd->rcu, cfq_cfqd_free); +} + +static void *cfq_init_queue(struct request_queue *q) +{ + struct cfq_data *cfqd; + int i, j; + struct cfq_group *cfqg; + struct cfq_rb_root *st; + + cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); + if (!cfqd) + return NULL; + + /* Init root service tree */ + cfqd->grp_service_tree = CFQ_RB_ROOT; + + /* Init root group */ + cfqg = &cfqd->root_group; + for_each_cfqg_st(cfqg, i, j, st) + *st = CFQ_RB_ROOT; + RB_CLEAR_NODE(&cfqg->rb_node); + + /* Give preference to root group over other groups */ + cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT; + +#ifdef CONFIG_CFQ_GROUP_IOSCHED + /* + * Take a reference to root group which we never drop. This is just + * to make sure that cfq_put_cfqg() does not try to kfree root group + */ + atomic_set(&cfqg->ref, 1); + blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd, + 0); +#endif + /* + * Not strictly needed (since RB_ROOT just clears the node and we + * zeroed cfqd on alloc), but better be safe in case someone decides + * to add magic to the rb code + */ + for (i = 0; i < CFQ_PRIO_LISTS; i++) + cfqd->prio_trees[i] = RB_ROOT; + + /* + * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues. + * Grab a permanent reference to it, so that the normal code flow + * will not attempt to free it. + */ + cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0); + atomic_inc(&cfqd->oom_cfqq.ref); + cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group); + + INIT_LIST_HEAD(&cfqd->cic_list); + + cfqd->queue = q; + + init_timer(&cfqd->idle_slice_timer); + cfqd->idle_slice_timer.function = cfq_idle_slice_timer; + cfqd->idle_slice_timer.data = (unsigned long) cfqd; + + INIT_WORK(&cfqd->unplug_work, cfq_kick_queue); + + cfqd->cfq_quantum = cfq_quantum; + cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0]; + cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1]; + cfqd->cfq_back_max = cfq_back_max; + cfqd->cfq_back_penalty = cfq_back_penalty; + cfqd->cfq_slice[0] = cfq_slice_async; + cfqd->cfq_slice[1] = cfq_slice_sync; + cfqd->cfq_slice_async_rq = cfq_slice_async_rq; + cfqd->cfq_slice_idle = cfq_slice_idle; + cfqd->cfq_latency = 1; + cfqd->cfq_group_isolation = 0; + cfqd->hw_tag = -1; + /* + * we optimistically start assuming sync ops weren't delayed in last + * second, in order to have larger depth for async operations. + */ + cfqd->last_delayed_sync = jiffies - HZ; + INIT_RCU_HEAD(&cfqd->rcu); + return cfqd; +} + +static void cfq_slab_kill(void) +{ + /* + * Caller already ensured that pending RCU callbacks are completed, + * so we should have no busy allocations at this point. + */ + if (cfq_pool) + kmem_cache_destroy(cfq_pool); + if (cfq_ioc_pool) + kmem_cache_destroy(cfq_ioc_pool); +} + +static int __init cfq_slab_setup(void) +{ + cfq_pool = KMEM_CACHE(cfq_queue, 0); + if (!cfq_pool) + goto fail; + + cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0); + if (!cfq_ioc_pool) + goto fail; + + return 0; +fail: + cfq_slab_kill(); + return -ENOMEM; +} + +/* + * sysfs parts below --> + */ +static ssize_t +cfq_var_show(unsigned int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +cfq_var_store(unsigned int *var, const char *page, size_t count) +{ + char *p = (char *) page; + + *var = simple_strtoul(p, &p, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct cfq_data *cfqd = e->elevator_data; \ + unsigned int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return cfq_var_show(__data, (page)); \ +} +SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0); +SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1); +SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1); +SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0); +SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0); +SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); +SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); +SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); +SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); +SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); +SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct cfq_data *cfqd = e->elevator_data; \ + unsigned int __data; \ + int ret = cfq_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0); +STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, + UINT_MAX, 1); +STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, + UINT_MAX, 1); +STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0); +STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, + UINT_MAX, 0); +STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1); +STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); +STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); +STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, + UINT_MAX, 0); +STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); +STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0); +#undef STORE_FUNCTION + +#define CFQ_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) + +static struct elv_fs_entry cfq_attrs[] = { + CFQ_ATTR(quantum), + CFQ_ATTR(fifo_expire_sync), + CFQ_ATTR(fifo_expire_async), + CFQ_ATTR(back_seek_max), + CFQ_ATTR(back_seek_penalty), + CFQ_ATTR(slice_sync), + CFQ_ATTR(slice_async), + CFQ_ATTR(slice_async_rq), + CFQ_ATTR(slice_idle), + CFQ_ATTR(low_latency), + CFQ_ATTR(group_isolation), + __ATTR_NULL +}; + +static struct elevator_type iosched_cfq = { + .ops = { + .elevator_merge_fn = cfq_merge, + .elevator_merged_fn = cfq_merged_request, + .elevator_merge_req_fn = cfq_merged_requests, + .elevator_allow_merge_fn = cfq_allow_merge, + .elevator_dispatch_fn = cfq_dispatch_requests, + .elevator_add_req_fn = cfq_insert_request, + .elevator_activate_req_fn = cfq_activate_request, + .elevator_deactivate_req_fn = cfq_deactivate_request, + .elevator_queue_empty_fn = cfq_queue_empty, + .elevator_completed_req_fn = cfq_completed_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_set_req_fn = cfq_set_request, + .elevator_put_req_fn = cfq_put_request, + .elevator_may_queue_fn = cfq_may_queue, + .elevator_init_fn = cfq_init_queue, + .elevator_exit_fn = cfq_exit_queue, + .trim = cfq_free_io_context, + }, + .elevator_attrs = cfq_attrs, + .elevator_name = "cfq", + .elevator_owner = THIS_MODULE, +}; + +#ifdef CONFIG_CFQ_GROUP_IOSCHED +static struct blkio_policy_type blkio_policy_cfq = { + .ops = { + .blkio_unlink_group_fn = cfq_unlink_blkio_group, + .blkio_update_group_weight_fn = cfq_update_blkio_group_weight, + }, +}; +#else +static struct blkio_policy_type blkio_policy_cfq; +#endif + +static int __init cfq_init(void) +{ + /* + * could be 0 on HZ < 1000 setups + */ + if (!cfq_slice_async) + cfq_slice_async = 1; + if (!cfq_slice_idle) + cfq_slice_idle = 1; + + if (cfq_slab_setup()) + return -ENOMEM; + + elv_register(&iosched_cfq); + blkio_policy_register(&blkio_policy_cfq); + + return 0; +} + +static void __exit cfq_exit(void) +{ + DECLARE_COMPLETION_ONSTACK(all_gone); + blkio_policy_unregister(&blkio_policy_cfq); + elv_unregister(&iosched_cfq); + ioc_gone = &all_gone; + /* ioc_gone's update must be visible before reading ioc_count */ + smp_wmb(); + + /* + * this also protects us from entering cfq_slab_kill() with + * pending RCU callbacks + */ + if (elv_ioc_count_read(cfq_ioc_count)) + wait_for_completion(&all_gone); + cfq_slab_kill(); +} + +module_init(cfq_init); +module_exit(cfq_exit); + +MODULE_AUTHOR("Jens Axboe"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler"); 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