/* * 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 */ #include #include #include #include #include #include #include #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) /* * Allow merged cfqqs to perform this amount of seeky I/O before * deciding to break the queues up again. */ #define CFQQ_COOP_TOUT (HZ) #define CFQ_SLICE_SCALE (5) #define CFQ_HW_QUEUE_MIN (5) #define CFQ_SERVICE_SHIFT 12 #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; }; #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; 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; unsigned long seeky_start; pid_t pid; struct cfq_rb_root *service_tree; struct cfq_queue *new_cfqq; struct cfq_group *cfqg; }; /* * 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; /* * 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; }; /* * 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; unsigned int busy_queues_avg[2]; 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; struct list_head cic_list; /* * Fallback dummy cfqq for extreme OOM conditions */ struct cfq_queue oom_cfqq; unsigned long last_end_sync_rq; }; static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg, enum wl_prio_t prio, enum wl_type_t type, struct cfq_data *cfqd) { 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_deep, /* sync cfqq experienced large depth */ }; #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(deep); #undef CFQ_CFQQ_FNS #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args) #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_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd) { struct cfq_group *cfqg = &cfqd->root_group; 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 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_get_avg_queues(struct cfq_data *cfqd, bool rt) { unsigned min_q, max_q; unsigned mult = cfq_hist_divisor - 1; unsigned round = cfq_hist_divisor / 2; unsigned busy = cfq_busy_queues_wl(rt, cfqd); min_q = min(cfqd->busy_queues_avg[rt], busy); max_q = max(cfqd->busy_queues_avg[rt], busy); cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) / cfq_hist_divisor; return cfqd->busy_queues_avg[rt]; } 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) */ unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq)); unsigned sync_slice = cfqd->cfq_slice[1]; unsigned expect_latency = sync_slice * iq; if (expect_latency > cfq_target_latency) { 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 * cfq_target_latency / expect_latency, low_slice); } } cfqq->slice_end = jiffies + 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; } 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; cfqg->on_st = false; if (!RB_EMPTY_NODE(&cfqg->rb_node)) cfq_rb_erase(&cfqg->rb_node, st); } /* * 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; service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq), cfqq_type(cfqq), cfqd); 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)) { /* * 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++; 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_end = 0; cfqq->slice_dispatch = 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); /* * 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); } 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 (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, cfqd); 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 = &cfqd->root_group; struct cfq_queue *cfqq; int i, j; struct cfq_rb_root *st; if (!cfqd->rq_queued) 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); } #define CFQQ_SEEK_THR 8 * 1024 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR) static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq, struct request *rq) { sector_t sdist = cfqq->seek_mean; if (!sample_valid(cfqq->seek_samples)) 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)) 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)) 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; /* * 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; /* * 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)) return true; /* * Otherwise, we do only if they are the last ones * in their service tree. */ return service_tree->count == 1; } 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++; } /* * 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, bool prio_changed) { struct cfq_queue *queue; int i; bool key_valid = false; unsigned long lowest_key = 0; enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD; if (prio_changed) { /* * When priorities switched, we prefer starting * from SYNC_NOIDLE (first choice), or just SYNC * over ASYNC */ if (service_tree_for(cfqg, prio, cur_best, cfqd)->count) return cur_best; cur_best = SYNC_WORKLOAD; if (service_tree_for(cfqg, prio, cur_best, cfqd)->count) return cur_best; return ASYNC_WORKLOAD; } for (i = 0; i < 3; ++i) { /* otherwise, select the one with lowest rb_key */ queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd)); 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) { enum wl_prio_t previous_prio = cfqd->serving_prio; bool prio_changed; unsigned slice; unsigned count; struct cfq_rb_root *st; if (!cfqg) { cfqd->serving_prio = IDLE_WORKLOAD; cfqd->workload_expires = jiffies + 1; return; } /* Choose next priority. RT > BE > IDLE */ if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd)) cfqd->serving_prio = RT_WORKLOAD; else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd)) 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 */ prio_changed = (cfqd->serving_prio != previous_prio); st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type, cfqd); count = st->count; /* * If priority didn't change, check workload expiration, * and that we still have other queues ready */ if (!prio_changed && count && !time_after(jiffies, cfqd->workload_expires)) return; /* otherwise select new workload type */ cfqd->serving_type = cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed); st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type, cfqd); 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 */ slice = cfq_target_latency * count / max_t(unsigned, cfqd->busy_queues_avg[cfqd->serving_prio], cfq_busy_queues_wl(cfqd->serving_prio, cfqd)); if (cfqd->serving_type == ASYNC_WORKLOAD) /* 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; 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; /* * The active queue has run out of time, expire it and select new. */ if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) 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_end_sync_rq; 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. * * queue lock must be held here. */ static void cfq_put_queue(struct cfq_queue *cfqq) { struct cfq_data *cfqd = cfqq->cfqd; 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]); 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); } /* * 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_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq) { struct cfq_queue *__cfqq, *next; if (unlikely(cfqq == cfqd->active_queue)) { __cfq_slice_expired(cfqd, cfqq, 0); cfq_schedule_dispatch(cfqd); } /* * 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; } 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; } static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { cfqq->cfqg = cfqg; } static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) { return &cfqd->root_group; } 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); 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; /* * 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)) { if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start) cfqq->seeky_start = jiffies; else if (!CFQQ_SEEKY(cfqq)) cfqq->seeky_start = 0; } } /* * 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_slice_used(cfqq)) return true; if (cfq_class_idle(new_cfqq)) return false; if (cfq_class_idle(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; /* * 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; /* * 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)) 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); __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 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"); 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; cfqd->last_end_sync_rq = 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); } /* * 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) 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); } static int should_split_cfqq(struct cfq_queue *cfqq) { if (cfqq->seeky_start && time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT)) return 1; return 0; } /* * 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->seeky_start = 0; cfqq->pid = current->pid; cfq_clear_cfqq_coop(cfqq); return cfqq; } cic_set_cfqq(cic, NULL, 1); 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) && should_split_cfqq(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_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); spin_unlock_irq(q->queue_lock); cfq_shutdown_timer_wq(cfqd); kfree(cfqd); } 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; /* * 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->hw_tag = -1; cfqd->last_end_sync_rq = jiffies; 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); #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); #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), __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, }; 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); return 0; } static void __exit cfq_exit(void) { DECLARE_COMPLETION_ONSTACK(all_gone); 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");