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Diffstat (limited to 'block/cfq-iosched.c')
| -rw-r--r-- | block/cfq-iosched.c | 2423 |
1 files changed, 2423 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c new file mode 100644 index 0000000..6a062ee --- /dev/null +++ b/block/cfq-iosched.c @@ -0,0 +1,2423 @@ +/* + * 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/rbtree.h> +#include <linux/ioprio.h> +#include <linux/blktrace_api.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; + +/* + * 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 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, 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 ASYNC (0) +#define SYNC (1) + +#define sample_valid(samples) ((samples) > 80) + +/* + * 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; +}; +#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, } + +/* + * Per block device queue structure + */ +struct cfq_data { + struct request_queue *queue; + + /* + * rr list of queues with requests and the count of them + */ + struct cfq_rb_root service_tree; + unsigned int busy_queues; + + int rq_in_driver; + int sync_flight; + + /* + * queue-depth detection + */ + int rq_queued; + int hw_tag; + int hw_tag_samples; + int rq_in_driver_peak; + + /* + * 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; + unsigned long last_end_request; + + /* + * 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; + + struct list_head cic_list; +}; + +/* + * 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; + /* 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; + + /* 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; + + pid_t pid; +}; + +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_alloc, /* must be allowed rq alloc */ + CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */ + CFQ_CFQQ_FLAG_must_dispatch, /* must dispatch, even if expired */ + 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_queue_new, /* queue never been serviced */ + CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ + CFQ_CFQQ_FLAG_sync, /* synchronous queue */ +}; + +#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_alloc); +CFQ_CFQQ_FNS(must_alloc_slice); +CFQ_CFQQ_FNS(must_dispatch); +CFQ_CFQQ_FNS(fifo_expire); +CFQ_CFQQ_FNS(idle_window); +CFQ_CFQQ_FNS(prio_changed); +CFQ_CFQQ_FNS(queue_new); +CFQ_CFQQ_FNS(slice_new); +CFQ_CFQQ_FNS(sync); +#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) + +static void cfq_dispatch_insert(struct request_queue *, struct request *); +static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, + struct io_context *, gfp_t); +static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *, + struct io_context *); + +static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic, + int is_sync) +{ + return cic->cfqq[!!is_sync]; +} + +static inline void cic_set_cfqq(struct cfq_io_context *cic, + struct cfq_queue *cfqq, int 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 int cfq_bio_sync(struct bio *bio) +{ + if (bio_data_dir(bio) == READ || bio_sync(bio)) + return 1; + + return 0; +} + +/* + * 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->busy_queues; +} + +/* + * 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, int 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 void +cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) +{ + cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; + 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 int 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, 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 = rq1->sector; + s2 = rq2->sector; + + last = cfqd->last_position; + + /* + * 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) +{ + 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 void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root) +{ + if (root->left == n) + root->left = NULL; + + rb_erase(n, &root->rb); + RB_CLEAR_NODE(n); +} + +/* + * 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); +} + +static unsigned long cfq_slice_offset(struct cfq_data *cfqd, + struct cfq_queue *cfqq) +{ + /* + * just an approximation, should be ok. + */ + return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) - + cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio)); +} + +/* + * The cfqd->service_tree 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, int add_front) +{ + struct rb_node **p, *parent; + struct cfq_queue *__cfqq; + unsigned long rb_key; + int left; + + if (cfq_class_idle(cfqq)) { + rb_key = CFQ_IDLE_DELAY; + parent = rb_last(&cfqd->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) { + rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; + rb_key += cfqq->slice_resid; + cfqq->slice_resid = 0; + } else + rb_key = 0; + + if (!RB_EMPTY_NODE(&cfqq->rb_node)) { + /* + * same position, nothing more to do + */ + if (rb_key == cfqq->rb_key) + return; + + cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree); + } + + left = 1; + parent = NULL; + p = &cfqd->service_tree.rb.rb_node; + while (*p) { + struct rb_node **n; + + parent = *p; + __cfqq = rb_entry(parent, struct cfq_queue, rb_node); + + /* + * sort RT queues first, we always want to give + * preference to them. IDLE queues goes to the back. + * after that, sort on the next service time. + */ + if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq)) + n = &(*p)->rb_left; + else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq)) + n = &(*p)->rb_right; + else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq)) + n = &(*p)->rb_left; + else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq)) + n = &(*p)->rb_right; + else if (rb_key < __cfqq->rb_key) + n = &(*p)->rb_left; + else + n = &(*p)->rb_right; + + if (n == &(*p)->rb_right) + left = 0; + + p = n; + } + + if (left) + cfqd->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, &cfqd->service_tree.rb); +} + +/* + * 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); +} + +/* + * 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, &cfqd->service_tree); + + 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); + struct cfq_data *cfqd = cfqq->cfqd; + 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)) + cfq_del_cfqq_rr(cfqd, cfqq); +} + +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; + + 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 + */ + cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); + 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++; + cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d", + cfqd->rq_in_driver); + + cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors; +} + +static void cfq_deactivate_request(struct request_queue *q, struct request *rq) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + + WARN_ON(!cfqd->rq_in_driver); + cfqd->rq_in_driver--; + cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d", + cfqd->rq_in_driver); +} + +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) +{ + /* + * reposition in fifo if next is older than rq + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && + time_before(next->start_time, rq->start_time)) + list_move(&rq->queuelist, &next->queuelist); + + 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 0; + + /* + * 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 0; + + cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio)); + if (cfqq == RQ_CFQQ(rq)) + return 1; + + return 0; +} + +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; + cfq_clear_cfqq_must_alloc_slice(cfqq); + cfq_clear_cfqq_fifo_expire(cfqq); + cfq_mark_cfqq_slice_new(cfqq); + cfq_clear_cfqq_queue_new(cfqq); + } + + 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, + int 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_must_dispatch(cfqq); + 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); + } + + 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, int 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) +{ + if (RB_EMPTY_ROOT(&cfqd->service_tree.rb)) + return NULL; + + return cfq_rb_first(&cfqd->service_tree); +} + +/* + * 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; + + 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 (rq->sector >= cfqd->last_position) + return rq->sector - cfqd->last_position; + else + return cfqd->last_position - rq->sector; +} + +static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq) +{ + struct cfq_io_context *cic = cfqd->active_cic; + + if (!sample_valid(cic->seek_samples)) + return 0; + + return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean; +} + +static int cfq_close_cooperator(struct cfq_data *cfq_data, + struct cfq_queue *cfqq) +{ + /* + * 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. + */ + return 0; +} + +#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024)) + +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_cfqq_idle_window(cfqq)) + return; + + /* + * still requests with the driver, don't idle + */ + if (cfqd->rq_in_driver) + return; + + /* + * task has exited, don't wait + */ + cic = cfqd->active_cic; + if (!cic || !atomic_read(&cic->ioc->nr_tasks)) + return; + + /* + * See if this prio level has a good candidate + */ + if (cfq_close_cooperator(cfqd, cfqq) && + (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2)) + return; + + cfq_mark_cfqq_must_dispatch(cfqq); + cfq_mark_cfqq_wait_request(cfqq); + + /* + * we don't want to idle for seeks, but we do want to allow + * fair distribution of slice time for a process doing back-to-back + * seeks. so allow a little bit of time for him to submit a new rq + */ + sl = cfqd->cfq_slice_idle; + if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic)) + sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT)); + + mod_timer(&cfqd->idle_slice_timer, jiffies + sl); + cfq_log(cfqd, "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"); + + 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 cfq_data *cfqd = cfqq->cfqd; + struct request *rq; + int fifo; + + if (cfq_cfqq_fifo_expire(cfqq)) + return NULL; + + cfq_mark_cfqq_fifo_expire(cfqq); + + if (list_empty(&cfqq->fifo)) + return NULL; + + fifo = cfq_cfqq_sync(cfqq); + rq = rq_entry_fifo(cfqq->fifo.next); + + if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) + rq = NULL; + + cfq_log_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)); +} + +/* + * 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; + + cfqq = cfqd->active_queue; + if (!cfqq) + goto new_queue; + + /* + * The active queue has run out of time, expire it and select new. + */ + if (cfq_slice_used(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; + + /* + * 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_cfqq_idle_window(cfqq))) { + cfqq = NULL; + goto keep_queue; + } + +expire: + cfq_slice_expired(cfqd, 0); +new_queue: + cfqq = cfq_set_active_queue(cfqd); +keep_queue: + return cfqq; +} + +/* + * Dispatch some requests from cfqq, moving them to the request queue + * dispatch list. + */ +static int +__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, + int max_dispatch) +{ + int dispatched = 0; + + BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); + + do { + struct request *rq; + + /* + * follow expired path, else get first next available + */ + rq = cfq_check_fifo(cfqq); + if (rq == NULL) + rq = cfqq->next_rq; + + /* + * finally, insert request into driver dispatch list + */ + cfq_dispatch_insert(cfqd->queue, rq); + + dispatched++; + + if (!cfqd->active_cic) { + atomic_inc(&RQ_CIC(rq)->ioc->refcount); + cfqd->active_cic = RQ_CIC(rq); + } + + if (RB_EMPTY_ROOT(&cfqq->sort_list)) + break; + + } while (dispatched < max_dispatch); + + /* + * 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) && + dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) || + cfq_class_idle(cfqq))) { + cfqq->slice_end = jiffies + 1; + cfq_slice_expired(cfqd, 0); + } + + return dispatched; +} + +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)); + 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_rb_first(&cfqd->service_tree)) != NULL) + dispatched += __cfq_forced_dispatch_cfqq(cfqq); + + cfq_slice_expired(cfqd, 0); + + BUG_ON(cfqd->busy_queues); + + cfq_log(cfqd, "forced_dispatch=%d\n", dispatched); + return dispatched; +} + +static int cfq_dispatch_requests(struct request_queue *q, int force) +{ + struct cfq_data *cfqd = q->elevator->elevator_data; + struct cfq_queue *cfqq; + int dispatched; + + if (!cfqd->busy_queues) + return 0; + + if (unlikely(force)) + return cfq_forced_dispatch(cfqd); + + dispatched = 0; + while ((cfqq = cfq_select_queue(cfqd)) != NULL) { + int max_dispatch; + + max_dispatch = cfqd->cfq_quantum; + if (cfq_class_idle(cfqq)) + max_dispatch = 1; + + if (cfqq->dispatched >= max_dispatch) { + if (cfqd->busy_queues > 1) + break; + if (cfqq->dispatched >= 4 * max_dispatch) + break; + } + + if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq)) + break; + + cfq_clear_cfqq_must_dispatch(cfqq); + cfq_clear_cfqq_wait_request(cfqq); + del_timer(&cfqd->idle_slice_timer); + + dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch); + } + + cfq_log(cfqd, "dispatched=%d", dispatched); + return dispatched; +} + +/* + * 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]); + BUG_ON(cfq_cfqq_on_rr(cfqq)); + + if (unlikely(cfqd->active_queue == cfqq)) { + __cfq_slice_expired(cfqd, cfqq, 0); + cfq_schedule_dispatch(cfqd); + } + + 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(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(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) +{ + if (unlikely(cfqq == cfqd->active_queue)) { + __cfq_slice_expired(cfqd, cfqq, 0); + cfq_schedule_dispatch(cfqd); + } + + 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[ASYNC]) { + cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]); + cic->cfqq[ASYNC] = NULL; + } + + if (cic->cfqq[SYNC]) { + cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]); + cic->cfqq[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); + __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(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[ASYNC]; + if (cfqq) { + struct cfq_queue *new_cfqq; + new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC); + if (new_cfqq) { + cic->cfqq[ASYNC] = new_cfqq; + cfq_put_queue(cfqq); + } + } + + cfqq = cic->cfqq[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 struct cfq_queue * +cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync, + struct io_context *ioc, gfp_t gfp_mask) +{ + struct cfq_queue *cfqq, *new_cfqq = NULL; + struct cfq_io_context *cic; + +retry: + cic = cfq_cic_lookup(cfqd, ioc); + /* cic always exists here */ + cfqq = cic_to_cfqq(cic, is_sync); + + if (!cfqq) { + if (new_cfqq) { + cfqq = new_cfqq; + new_cfqq = NULL; + } else if (gfp_mask & __GFP_WAIT) { + /* + * Inform the allocator of the fact that we will + * just repeat this allocation if it fails, to allow + * the allocator to do whatever it needs to attempt to + * free memory. + */ + spin_unlock_irq(cfqd->queue->queue_lock); + new_cfqq = kmem_cache_alloc_node(cfq_pool, + gfp_mask | __GFP_NOFAIL | __GFP_ZERO, + cfqd->queue->node); + spin_lock_irq(cfqd->queue->queue_lock); + goto retry; + } else { + cfqq = kmem_cache_alloc_node(cfq_pool, + gfp_mask | __GFP_ZERO, + cfqd->queue->node); + if (!cfqq) + goto out; + } + + RB_CLEAR_NODE(&cfqq->rb_node); + INIT_LIST_HEAD(&cfqq->fifo); + + atomic_set(&cfqq->ref, 0); + cfqq->cfqd = cfqd; + + cfq_mark_cfqq_prio_changed(cfqq); + cfq_mark_cfqq_queue_new(cfqq); + + cfq_init_prio_data(cfqq, ioc); + + if (is_sync) { + if (!cfq_class_idle(cfqq)) + cfq_mark_cfqq_idle_window(cfqq); + cfq_mark_cfqq_sync(cfqq); + } + cfqq->pid = current->pid; + cfq_log_cfqq(cfqd, cfqq, "alloced"); + } + + if (new_cfqq) + kmem_cache_free(cfq_pool, new_cfqq); + +out: + WARN_ON((gfp_mask & __GFP_WAIT) && !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, int 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); + if (!cfqq) + return NULL; + } + + /* + * 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_io_context *cic, + struct request *rq) +{ + sector_t sdist; + u64 total; + + if (cic->last_request_pos < rq->sector) + sdist = rq->sector - cic->last_request_pos; + else + sdist = cic->last_request_pos - rq->sector; + + /* + * Don't allow the seek distance to get too large from the + * odd fragment, pagein, etc + */ + if (cic->seek_samples <= 60) /* second&third seek */ + sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024); + else + sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64); + + cic->seek_samples = (7*cic->seek_samples + 256) / 8; + cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8; + total = cic->seek_total + (cic->seek_samples/2); + do_div(total, cic->seek_samples); + cic->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 (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle || + (cfqd->hw_tag && CIC_SEEKY(cic))) + 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 int +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 0; + + if (cfq_slice_used(cfqq)) + return 1; + + if (cfq_class_idle(new_cfqq)) + return 0; + + if (cfq_class_idle(cfqq)) + return 1; + + /* + * 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 1; + + /* + * 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 1; + + if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) + return 0; + + /* + * if this request is as-good as one we would expect from the + * current cfqq, let it preempt + */ + if (cfq_rq_close(cfqd, rq)) + return 1; + + return 0; +} + +/* + * 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, cic, rq); + cfq_update_idle_window(cfqd, cfqq, cic); + + cic->last_request_pos = rq->sector + rq->nr_sectors; + + if (cfqq == cfqd->active_queue) { + /* + * if we are waiting for a request for this queue, let it rip + * immediately and flag that we must not expire this queue + * just now + */ + if (cfq_cfqq_wait_request(cfqq)) { + cfq_mark_cfqq_must_dispatch(cfqq); + del_timer(&cfqd->idle_slice_timer); + blk_start_queueing(cfqd->queue); + } + } 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 + */ + cfq_preempt_queue(cfqd, cfqq); + cfq_mark_cfqq_must_dispatch(cfqq); + blk_start_queueing(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); + + cfq_add_rq_rb(rq); + + list_add_tail(&rq->queuelist, &cfqq->fifo); + + 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) +{ + if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak) + cfqd->rq_in_driver_peak = cfqd->rq_in_driver; + + if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN && + cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN) + return; + + if (cfqd->hw_tag_samples++ < 50) + return; + + if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN) + cfqd->hw_tag = 1; + else + cfqd->hw_tag = 0; + + cfqd->hw_tag_samples = 0; + cfqd->rq_in_driver_peak = 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); + WARN_ON(!cfqq->dispatched); + cfqd->rq_in_driver--; + cfqq->dispatched--; + + if (cfq_cfqq_sync(cfqq)) + cfqd->sync_flight--; + + if (!cfq_class_idle(cfqq)) + cfqd->last_end_request = now; + + if (sync) + RQ_CIC(rq)->last_end_request = 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) { + if (cfq_cfqq_slice_new(cfqq)) { + cfq_set_prio_slice(cfqd, cfqq); + cfq_clear_cfqq_slice_new(cfqq); + } + if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq)) + cfq_slice_expired(cfqd, 1); + else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) + cfq_arm_slice_timer(cfqd); + } + + if (!cfqd->rq_in_driver) + 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 { + /* + * check if we need to unboost the queue + */ + if (cfqq->ioprio_class != cfqq->org_ioprio_class) + cfqq->ioprio_class = cfqq->org_ioprio_class; + if (cfqq->ioprio != cfqq->org_ioprio) + 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(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 & REQ_RW_SYNC); + 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); + } +} + +/* + * 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 int 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; + + cfqq = cic_to_cfqq(cic, is_sync); + if (!cfqq) { + cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); + + if (!cfqq) + goto queue_fail; + + cic_set_cfqq(cic, cfqq, is_sync); + } + + cfqq->allocated[rw]++; + cfq_clear_cfqq_must_alloc(cfqq); + 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; + unsigned long flags; + + spin_lock_irqsave(q->queue_lock, flags); + blk_start_queueing(q); + spin_unlock_irqrestore(q->queue_lock, flags); +} + +/* + * 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; + + /* + * 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)) { + cfq_mark_cfqq_must_dispatch(cfqq); + goto out_kick; + } + } +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); + kblockd_flush_work(&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(elevator_t *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; + + cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node); + if (!cfqd) + return NULL; + + cfqd->service_tree = CFQ_RB_ROOT; + 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->last_end_request = jiffies; + 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->hw_tag = 1; + + 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(elevator_t *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); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(elevator_t *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); +#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), + __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(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"); |
