diff options
Diffstat (limited to 'drivers/block/as-iosched.c')
| -rw-r--r-- | drivers/block/as-iosched.c | 2131 |
1 files changed, 0 insertions, 2131 deletions
diff --git a/drivers/block/as-iosched.c b/drivers/block/as-iosched.c deleted file mode 100644 index 95c0a3690b0..00000000000 --- a/drivers/block/as-iosched.c +++ /dev/null @@ -1,2131 +0,0 @@ -/* - * linux/drivers/block/as-iosched.c - * - * Anticipatory & deadline i/o scheduler. - * - * Copyright (C) 2002 Jens Axboe <axboe@suse.de> - * Nick Piggin <piggin@cyberone.com.au> - * - */ -#include <linux/kernel.h> -#include <linux/fs.h> -#include <linux/blkdev.h> -#include <linux/elevator.h> -#include <linux/bio.h> -#include <linux/config.h> -#include <linux/module.h> -#include <linux/slab.h> -#include <linux/init.h> -#include <linux/compiler.h> -#include <linux/hash.h> -#include <linux/rbtree.h> -#include <linux/interrupt.h> - -#define REQ_SYNC 1 -#define REQ_ASYNC 0 - -/* - * See Documentation/block/as-iosched.txt - */ - -/* - * max time before a read is submitted. - */ -#define default_read_expire (HZ / 8) - -/* - * ditto for writes, these limits are not hard, even - * if the disk is capable of satisfying them. - */ -#define default_write_expire (HZ / 4) - -/* - * read_batch_expire describes how long we will allow a stream of reads to - * persist before looking to see whether it is time to switch over to writes. - */ -#define default_read_batch_expire (HZ / 2) - -/* - * write_batch_expire describes how long we want a stream of writes to run for. - * This is not a hard limit, but a target we set for the auto-tuning thingy. - * See, the problem is: we can send a lot of writes to disk cache / TCQ in - * a short amount of time... - */ -#define default_write_batch_expire (HZ / 8) - -/* - * max time we may wait to anticipate a read (default around 6ms) - */ -#define default_antic_expire ((HZ / 150) ? HZ / 150 : 1) - -/* - * Keep track of up to 20ms thinktimes. We can go as big as we like here, - * however huge values tend to interfere and not decay fast enough. A program - * might be in a non-io phase of operation. Waiting on user input for example, - * or doing a lengthy computation. A small penalty can be justified there, and - * will still catch out those processes that constantly have large thinktimes. - */ -#define MAX_THINKTIME (HZ/50UL) - -/* Bits in as_io_context.state */ -enum as_io_states { - AS_TASK_RUNNING=0, /* Process has not exitted */ - AS_TASK_IOSTARTED, /* Process has started some IO */ - AS_TASK_IORUNNING, /* Process has completed some IO */ -}; - -enum anticipation_status { - ANTIC_OFF=0, /* Not anticipating (normal operation) */ - ANTIC_WAIT_REQ, /* The last read has not yet completed */ - ANTIC_WAIT_NEXT, /* Currently anticipating a request vs - last read (which has completed) */ - ANTIC_FINISHED, /* Anticipating but have found a candidate - * or timed out */ -}; - -struct as_data { - /* - * run time data - */ - - struct request_queue *q; /* the "owner" queue */ - - /* - * requests (as_rq s) are present on both sort_list and fifo_list - */ - struct rb_root sort_list[2]; - struct list_head fifo_list[2]; - - struct as_rq *next_arq[2]; /* next in sort order */ - sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */ - struct list_head *dispatch; /* driver dispatch queue */ - struct list_head *hash; /* request hash */ - - unsigned long exit_prob; /* probability a task will exit while - being waited on */ - unsigned long new_ttime_total; /* mean thinktime on new proc */ - unsigned long new_ttime_mean; - u64 new_seek_total; /* mean seek on new proc */ - sector_t new_seek_mean; - - unsigned long current_batch_expires; - unsigned long last_check_fifo[2]; - int changed_batch; /* 1: waiting for old batch to end */ - int new_batch; /* 1: waiting on first read complete */ - int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */ - int write_batch_count; /* max # of reqs in a write batch */ - int current_write_count; /* how many requests left this batch */ - int write_batch_idled; /* has the write batch gone idle? */ - mempool_t *arq_pool; - - enum anticipation_status antic_status; - unsigned long antic_start; /* jiffies: when it started */ - struct timer_list antic_timer; /* anticipatory scheduling timer */ - struct work_struct antic_work; /* Deferred unplugging */ - struct io_context *io_context; /* Identify the expected process */ - int ioc_finished; /* IO associated with io_context is finished */ - int nr_dispatched; - - /* - * settings that change how the i/o scheduler behaves - */ - unsigned long fifo_expire[2]; - unsigned long batch_expire[2]; - unsigned long antic_expire; -}; - -#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo) - -/* - * per-request data. - */ -enum arq_state { - AS_RQ_NEW=0, /* New - not referenced and not on any lists */ - AS_RQ_QUEUED, /* In the request queue. It belongs to the - scheduler */ - AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the - driver now */ - AS_RQ_PRESCHED, /* Debug poisoning for requests being used */ - AS_RQ_REMOVED, - AS_RQ_MERGED, - AS_RQ_POSTSCHED, /* when they shouldn't be */ -}; - -struct as_rq { - /* - * rbtree index, key is the starting offset - */ - struct rb_node rb_node; - sector_t rb_key; - - struct request *request; - - struct io_context *io_context; /* The submitting task */ - - /* - * request hash, key is the ending offset (for back merge lookup) - */ - struct list_head hash; - unsigned int on_hash; - - /* - * expire fifo - */ - struct list_head fifo; - unsigned long expires; - - unsigned int is_sync; - enum arq_state state; -}; - -#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private) - -static kmem_cache_t *arq_pool; - -/* - * IO Context helper functions - */ - -/* Called to deallocate the as_io_context */ -static void free_as_io_context(struct as_io_context *aic) -{ - kfree(aic); -} - -/* Called when the task exits */ -static void exit_as_io_context(struct as_io_context *aic) -{ - WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state)); - clear_bit(AS_TASK_RUNNING, &aic->state); -} - -static struct as_io_context *alloc_as_io_context(void) -{ - struct as_io_context *ret; - - ret = kmalloc(sizeof(*ret), GFP_ATOMIC); - if (ret) { - ret->dtor = free_as_io_context; - ret->exit = exit_as_io_context; - ret->state = 1 << AS_TASK_RUNNING; - atomic_set(&ret->nr_queued, 0); - atomic_set(&ret->nr_dispatched, 0); - spin_lock_init(&ret->lock); - ret->ttime_total = 0; - ret->ttime_samples = 0; - ret->ttime_mean = 0; - ret->seek_total = 0; - ret->seek_samples = 0; - ret->seek_mean = 0; - } - - return ret; -} - -/* - * If the current task has no AS IO context then create one and initialise it. - * Then take a ref on the task's io context and return it. - */ -static struct io_context *as_get_io_context(void) -{ - struct io_context *ioc = get_io_context(GFP_ATOMIC); - if (ioc && !ioc->aic) { - ioc->aic = alloc_as_io_context(); - if (!ioc->aic) { - put_io_context(ioc); - ioc = NULL; - } - } - return ioc; -} - -/* - * the back merge hash support functions - */ -static const int as_hash_shift = 6; -#define AS_HASH_BLOCK(sec) ((sec) >> 3) -#define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift)) -#define AS_HASH_ENTRIES (1 << as_hash_shift) -#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) -#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash) - -static inline void __as_del_arq_hash(struct as_rq *arq) -{ - arq->on_hash = 0; - list_del_init(&arq->hash); -} - -static inline void as_del_arq_hash(struct as_rq *arq) -{ - if (arq->on_hash) - __as_del_arq_hash(arq); -} - -static void as_remove_merge_hints(request_queue_t *q, struct as_rq *arq) -{ - as_del_arq_hash(arq); - - if (q->last_merge == arq->request) - q->last_merge = NULL; -} - -static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq) -{ - struct request *rq = arq->request; - - BUG_ON(arq->on_hash); - - arq->on_hash = 1; - list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]); -} - -/* - * move hot entry to front of chain - */ -static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq) -{ - struct request *rq = arq->request; - struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))]; - - if (!arq->on_hash) { - WARN_ON(1); - return; - } - - if (arq->hash.prev != head) { - list_del(&arq->hash); - list_add(&arq->hash, head); - } -} - -static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset) -{ - struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)]; - struct list_head *entry, *next = hash_list->next; - - while ((entry = next) != hash_list) { - struct as_rq *arq = list_entry_hash(entry); - struct request *__rq = arq->request; - - next = entry->next; - - BUG_ON(!arq->on_hash); - - if (!rq_mergeable(__rq)) { - as_remove_merge_hints(ad->q, arq); - continue; - } - - if (rq_hash_key(__rq) == offset) - return __rq; - } - - return NULL; -} - -/* - * rb tree support functions - */ -#define RB_NONE (2) -#define RB_EMPTY(root) ((root)->rb_node == NULL) -#define ON_RB(node) ((node)->rb_color != RB_NONE) -#define RB_CLEAR(node) ((node)->rb_color = RB_NONE) -#define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node) -#define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync]) -#define rq_rb_key(rq) (rq)->sector - -/* - * as_find_first_arq finds the first (lowest sector numbered) request - * for the specified data_dir. Used to sweep back to the start of the disk - * (1-way elevator) after we process the last (highest sector) request. - */ -static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir) -{ - struct rb_node *n = ad->sort_list[data_dir].rb_node; - - if (n == NULL) - return NULL; - - for (;;) { - if (n->rb_left == NULL) - return rb_entry_arq(n); - - n = n->rb_left; - } -} - -/* - * Add the request to the rb tree if it is unique. If there is an alias (an - * existing request against the same sector), which can happen when using - * direct IO, then return the alias. - */ -static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq) -{ - struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node; - struct rb_node *parent = NULL; - struct as_rq *__arq; - struct request *rq = arq->request; - - arq->rb_key = rq_rb_key(rq); - - while (*p) { - parent = *p; - __arq = rb_entry_arq(parent); - - if (arq->rb_key < __arq->rb_key) - p = &(*p)->rb_left; - else if (arq->rb_key > __arq->rb_key) - p = &(*p)->rb_right; - else - return __arq; - } - - rb_link_node(&arq->rb_node, parent, p); - rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); - - return NULL; -} - -static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq) -{ - if (!ON_RB(&arq->rb_node)) { - WARN_ON(1); - return; - } - - rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq)); - RB_CLEAR(&arq->rb_node); -} - -static struct request * -as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir) -{ - struct rb_node *n = ad->sort_list[data_dir].rb_node; - struct as_rq *arq; - - while (n) { - arq = rb_entry_arq(n); - - if (sector < arq->rb_key) - n = n->rb_left; - else if (sector > arq->rb_key) - n = n->rb_right; - else - return arq->request; - } - - return NULL; -} - -/* - * IO Scheduler proper - */ - -#define MAXBACK (1024 * 1024) /* - * Maximum distance the disk will go backward - * for a request. - */ - -#define BACK_PENALTY 2 - -/* - * as_choose_req selects the preferred one of two requests of the same data_dir - * ignoring time - eg. timeouts, which is the job of as_dispatch_request - */ -static struct as_rq * -as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2) -{ - int data_dir; - sector_t last, s1, s2, d1, d2; - int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */ - const sector_t maxback = MAXBACK; - - if (arq1 == NULL || arq1 == arq2) - return arq2; - if (arq2 == NULL) - return arq1; - - data_dir = arq1->is_sync; - - last = ad->last_sector[data_dir]; - s1 = arq1->request->sector; - s2 = arq2->request->sector; - - BUG_ON(data_dir != arq2->is_sync); - - /* - * 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+maxback >= last) - d1 = (last - s1)*BACK_PENALTY; - else { - r1_wrap = 1; - d1 = 0; /* shut up, gcc */ - } - - if (s2 >= last) - d2 = s2 - last; - else if (s2+maxback >= last) - d2 = (last - s2)*BACK_PENALTY; - else { - r2_wrap = 1; - d2 = 0; - } - - /* Found required data */ - if (!r1_wrap && r2_wrap) - return arq1; - else if (!r2_wrap && r1_wrap) - return arq2; - else if (r1_wrap && r2_wrap) { - /* both behind the head */ - if (s1 <= s2) - return arq1; - else - return arq2; - } - - /* Both requests in front of the head */ - if (d1 < d2) - return arq1; - else if (d2 < d1) - return arq2; - else { - if (s1 >= s2) - return arq1; - else - return arq2; - } -} - -/* - * as_find_next_arq finds the next request after @prev in elevator order. - * this with as_choose_req form the basis for how the scheduler chooses - * what request to process next. Anticipation works on top of this. - */ -static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last) -{ - const int data_dir = last->is_sync; - struct as_rq *ret; - struct rb_node *rbnext = rb_next(&last->rb_node); - struct rb_node *rbprev = rb_prev(&last->rb_node); - struct as_rq *arq_next, *arq_prev; - - BUG_ON(!ON_RB(&last->rb_node)); - - if (rbprev) - arq_prev = rb_entry_arq(rbprev); - else - arq_prev = NULL; - - if (rbnext) - arq_next = rb_entry_arq(rbnext); - else { - arq_next = as_find_first_arq(ad, data_dir); - if (arq_next == last) - arq_next = NULL; - } - - ret = as_choose_req(ad, arq_next, arq_prev); - - return ret; -} - -/* - * anticipatory scheduling functions follow - */ - -/* - * as_antic_expired tells us when we have anticipated too long. - * The funny "absolute difference" math on the elapsed time is to handle - * jiffy wraps, and disks which have been idle for 0x80000000 jiffies. - */ -static int as_antic_expired(struct as_data *ad) -{ - long delta_jif; - - delta_jif = jiffies - ad->antic_start; - if (unlikely(delta_jif < 0)) - delta_jif = -delta_jif; - if (delta_jif < ad->antic_expire) - return 0; - - return 1; -} - -/* - * as_antic_waitnext starts anticipating that a nice request will soon be - * submitted. See also as_antic_waitreq - */ -static void as_antic_waitnext(struct as_data *ad) -{ - unsigned long timeout; - - BUG_ON(ad->antic_status != ANTIC_OFF - && ad->antic_status != ANTIC_WAIT_REQ); - - timeout = ad->antic_start + ad->antic_expire; - - mod_timer(&ad->antic_timer, timeout); - - ad->antic_status = ANTIC_WAIT_NEXT; -} - -/* - * as_antic_waitreq starts anticipating. We don't start timing the anticipation - * until the request that we're anticipating on has finished. This means we - * are timing from when the candidate process wakes up hopefully. - */ -static void as_antic_waitreq(struct as_data *ad) -{ - BUG_ON(ad->antic_status == ANTIC_FINISHED); - if (ad->antic_status == ANTIC_OFF) { - if (!ad->io_context || ad->ioc_finished) - as_antic_waitnext(ad); - else - ad->antic_status = ANTIC_WAIT_REQ; - } -} - -/* - * This is called directly by the functions in this file to stop anticipation. - * We kill the timer and schedule a call to the request_fn asap. - */ -static void as_antic_stop(struct as_data *ad) -{ - int status = ad->antic_status; - - if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) { - if (status == ANTIC_WAIT_NEXT) - del_timer(&ad->antic_timer); - ad->antic_status = ANTIC_FINISHED; - /* see as_work_handler */ - kblockd_schedule_work(&ad->antic_work); - } -} - -/* - * as_antic_timeout is the timer function set by as_antic_waitnext. - */ -static void as_antic_timeout(unsigned long data) -{ - struct request_queue *q = (struct request_queue *)data; - struct as_data *ad = q->elevator->elevator_data; - unsigned long flags; - - spin_lock_irqsave(q->queue_lock, flags); - if (ad->antic_status == ANTIC_WAIT_REQ - || ad->antic_status == ANTIC_WAIT_NEXT) { - struct as_io_context *aic = ad->io_context->aic; - - ad->antic_status = ANTIC_FINISHED; - kblockd_schedule_work(&ad->antic_work); - - if (aic->ttime_samples == 0) { - /* process anticipated on has exitted or timed out*/ - ad->exit_prob = (7*ad->exit_prob + 256)/8; - } - } - spin_unlock_irqrestore(q->queue_lock, flags); -} - -/* - * as_close_req decides if one request is considered "close" to the - * previous one issued. - */ -static int as_close_req(struct as_data *ad, struct as_rq *arq) -{ - unsigned long delay; /* milliseconds */ - sector_t last = ad->last_sector[ad->batch_data_dir]; - sector_t next = arq->request->sector; - sector_t delta; /* acceptable close offset (in sectors) */ - - if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished) - delay = 0; - else - delay = ((jiffies - ad->antic_start) * 1000) / HZ; - - if (delay <= 1) - delta = 64; - else if (delay <= 20 && delay <= ad->antic_expire) - delta = 64 << (delay-1); - else - return 1; - - return (last - (delta>>1) <= next) && (next <= last + delta); -} - -/* - * as_can_break_anticipation returns true if we have been anticipating this - * request. - * - * It also returns true if the process against which we are anticipating - * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to - * dispatch it ASAP, because we know that application will not be submitting - * any new reads. - * - * If the task which has submitted the request has exitted, break anticipation. - * - * If this task has queued some other IO, do not enter enticipation. - */ -static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq) -{ - struct io_context *ioc; - struct as_io_context *aic; - sector_t s; - - ioc = ad->io_context; - BUG_ON(!ioc); - - if (arq && ioc == arq->io_context) { - /* request from same process */ - return 1; - } - - if (ad->ioc_finished && as_antic_expired(ad)) { - /* - * In this situation status should really be FINISHED, - * however the timer hasn't had the chance to run yet. - */ - return 1; - } - - aic = ioc->aic; - if (!aic) - return 0; - - if (!test_bit(AS_TASK_RUNNING, &aic->state)) { - /* process anticipated on has exitted */ - if (aic->ttime_samples == 0) - ad->exit_prob = (7*ad->exit_prob + 256)/8; - return 1; - } - - if (atomic_read(&aic->nr_queued) > 0) { - /* process has more requests queued */ - return 1; - } - - if (atomic_read(&aic->nr_dispatched) > 0) { - /* process has more requests dispatched */ - return 1; - } - - if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) { - /* - * Found a close request that is not one of ours. - * - * This makes close requests from another process reset - * our thinktime delay. Is generally useful when there are - * two or more cooperating processes working in the same - * area. - */ - spin_lock(&aic->lock); - aic->last_end_request = jiffies; - spin_unlock(&aic->lock); - return 1; - } - - - if (aic->ttime_samples == 0) { - if (ad->new_ttime_mean > ad->antic_expire) - return 1; - if (ad->exit_prob > 128) - return 1; - } else if (aic->ttime_mean > ad->antic_expire) { - /* the process thinks too much between requests */ - return 1; - } - - if (!arq) - return 0; - - if (ad->last_sector[REQ_SYNC] < arq->request->sector) - s = arq->request->sector - ad->last_sector[REQ_SYNC]; - else - s = ad->last_sector[REQ_SYNC] - arq->request->sector; - - if (aic->seek_samples == 0) { - /* - * Process has just started IO. Use past statistics to - * guage success possibility - */ - if (ad->new_seek_mean > s) { - /* this request is better than what we're expecting */ - return 1; - } - - } else { - if (aic->seek_mean > s) { - /* this request is better than what we're expecting */ - return 1; - } - } - - return 0; -} - -/* - * as_can_anticipate indicates weather we should either run arq - * or keep anticipating a better request. - */ -static int as_can_anticipate(struct as_data *ad, struct as_rq *arq) -{ - if (!ad->io_context) - /* - * Last request submitted was a write - */ - return 0; - - if (ad->antic_status == ANTIC_FINISHED) - /* - * Don't restart if we have just finished. Run the next request - */ - return 0; - - if (as_can_break_anticipation(ad, arq)) - /* - * This request is a good candidate. Don't keep anticipating, - * run it. - */ - return 0; - - /* - * OK from here, we haven't finished, and don't have a decent request! - * Status is either ANTIC_OFF so start waiting, - * ANTIC_WAIT_REQ so continue waiting for request to finish - * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request. - * - */ - - return 1; -} - -static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime) -{ - /* fixed point: 1.0 == 1<<8 */ - if (aic->ttime_samples == 0) { - ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8; - ad->new_ttime_mean = ad->new_ttime_total / 256; - - ad->exit_prob = (7*ad->exit_prob)/8; - } - aic->ttime_samples = (7*aic->ttime_samples + 256) / 8; - aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8; - aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples; -} - -static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, sector_t sdist) -{ - u64 total; - - if (aic->seek_samples == 0) { - ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8; - ad->new_seek_mean = ad->new_seek_total / 256; - } - - /* - * Don't allow the seek distance to get too large from the - * odd fragment, pagein, etc - */ - if (aic->seek_samples <= 60) /* second&third seek */ - sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024); - else - sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64); - - aic->seek_samples = (7*aic->seek_samples + 256) / 8; - aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8; - total = aic->seek_total + (aic->seek_samples/2); - do_div(total, aic->seek_samples); - aic->seek_mean = (sector_t)total; -} - -/* - * as_update_iohist keeps a decaying histogram of IO thinktimes, and - * updates @aic->ttime_mean based on that. It is called when a new - * request is queued. - */ -static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - int data_dir = arq->is_sync; - unsigned long thinktime; - sector_t seek_dist; - - if (aic == NULL) - return; - - if (data_dir == REQ_SYNC) { - unsigned long in_flight = atomic_read(&aic->nr_queued) - + atomic_read(&aic->nr_dispatched); - spin_lock(&aic->lock); - if (test_bit(AS_TASK_IORUNNING, &aic->state) || - test_bit(AS_TASK_IOSTARTED, &aic->state)) { - /* Calculate read -> read thinktime */ - if (test_bit(AS_TASK_IORUNNING, &aic->state) - && in_flight == 0) { - thinktime = jiffies - aic->last_end_request; - thinktime = min(thinktime, MAX_THINKTIME-1); - } else - thinktime = 0; - as_update_thinktime(ad, aic, thinktime); - - /* Calculate read -> read seek distance */ - if (aic->last_request_pos < rq->sector) - seek_dist = rq->sector - aic->last_request_pos; - else - seek_dist = aic->last_request_pos - rq->sector; - as_update_seekdist(ad, aic, seek_dist); - } - aic->last_request_pos = rq->sector + rq->nr_sectors; - set_bit(AS_TASK_IOSTARTED, &aic->state); - spin_unlock(&aic->lock); - } -} - -/* - * as_update_arq must be called whenever a request (arq) is added to - * the sort_list. This function keeps caches up to date, and checks if the - * request might be one we are "anticipating" - */ -static void as_update_arq(struct as_data *ad, struct as_rq *arq) -{ - const int data_dir = arq->is_sync; - - /* keep the next_arq cache up to date */ - ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]); - - /* - * have we been anticipating this request? - * or does it come from the same process as the one we are anticipating - * for? - */ - if (ad->antic_status == ANTIC_WAIT_REQ - || ad->antic_status == ANTIC_WAIT_NEXT) { - if (as_can_break_anticipation(ad, arq)) - as_antic_stop(ad); - } -} - -/* - * Gathers timings and resizes the write batch automatically - */ -static void update_write_batch(struct as_data *ad) -{ - unsigned long batch = ad->batch_expire[REQ_ASYNC]; - long write_time; - - write_time = (jiffies - ad->current_batch_expires) + batch; - if (write_time < 0) - write_time = 0; - - if (write_time > batch && !ad->write_batch_idled) { - if (write_time > batch * 3) - ad->write_batch_count /= 2; - else - ad->write_batch_count--; - } else if (write_time < batch && ad->current_write_count == 0) { - if (batch > write_time * 3) - ad->write_batch_count *= 2; - else - ad->write_batch_count++; - } - - if (ad->write_batch_count < 1) - ad->write_batch_count = 1; -} - -/* - * as_completed_request is to be called when a request has completed and - * returned something to the requesting process, be it an error or data. - */ -static void as_completed_request(request_queue_t *q, struct request *rq) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(rq); - - WARN_ON(!list_empty(&rq->queuelist)); - - if (arq->state == AS_RQ_PRESCHED) { - WARN_ON(arq->io_context); - goto out; - } - - if (arq->state == AS_RQ_MERGED) - goto out_ioc; - - if (arq->state != AS_RQ_REMOVED) { - printk("arq->state %d\n", arq->state); - WARN_ON(1); - goto out; - } - - if (!blk_fs_request(rq)) - goto out; - - if (ad->changed_batch && ad->nr_dispatched == 1) { - kblockd_schedule_work(&ad->antic_work); - ad->changed_batch = 0; - - if (ad->batch_data_dir == REQ_SYNC) - ad->new_batch = 1; - } - WARN_ON(ad->nr_dispatched == 0); - ad->nr_dispatched--; - - /* - * Start counting the batch from when a request of that direction is - * actually serviced. This should help devices with big TCQ windows - * and writeback caches - */ - if (ad->new_batch && ad->batch_data_dir == arq->is_sync) { - update_write_batch(ad); - ad->current_batch_expires = jiffies + - ad->batch_expire[REQ_SYNC]; - ad->new_batch = 0; - } - - if (ad->io_context == arq->io_context && ad->io_context) { - ad->antic_start = jiffies; - ad->ioc_finished = 1; - if (ad->antic_status == ANTIC_WAIT_REQ) { - /* - * We were waiting on this request, now anticipate - * the next one - */ - as_antic_waitnext(ad); - } - } - -out_ioc: - if (!arq->io_context) - goto out; - - if (arq->is_sync == REQ_SYNC) { - struct as_io_context *aic = arq->io_context->aic; - if (aic) { - spin_lock(&aic->lock); - set_bit(AS_TASK_IORUNNING, &aic->state); - aic->last_end_request = jiffies; - spin_unlock(&aic->lock); - } - } - - put_io_context(arq->io_context); -out: - arq->state = AS_RQ_POSTSCHED; -} - -/* - * as_remove_queued_request removes a request from the pre dispatch queue - * without updating refcounts. It is expected the caller will drop the - * reference unless it replaces the request at somepart of the elevator - * (ie. the dispatch queue) - */ -static void as_remove_queued_request(request_queue_t *q, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - const int data_dir = arq->is_sync; - struct as_data *ad = q->elevator->elevator_data; - - WARN_ON(arq->state != AS_RQ_QUEUED); - - if (arq->io_context && arq->io_context->aic) { - BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued)); - atomic_dec(&arq->io_context->aic->nr_queued); - } - - /* - * Update the "next_arq" cache if we are about to remove its - * entry - */ - if (ad->next_arq[data_dir] == arq) - ad->next_arq[data_dir] = as_find_next_arq(ad, arq); - - list_del_init(&arq->fifo); - as_remove_merge_hints(q, arq); - as_del_arq_rb(ad, arq); -} - -/* - * as_remove_dispatched_request is called to remove a request which has gone - * to the dispatch list. - */ -static void as_remove_dispatched_request(request_queue_t *q, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - struct as_io_context *aic; - - if (!arq) { - WARN_ON(1); - return; - } - - WARN_ON(arq->state != AS_RQ_DISPATCHED); - WARN_ON(ON_RB(&arq->rb_node)); - if (arq->io_context && arq->io_context->aic) { - aic = arq->io_context->aic; - if (aic) { - WARN_ON(!atomic_read(&aic->nr_dispatched)); - atomic_dec(&aic->nr_dispatched); - } - } -} - -/* - * as_remove_request is called when a driver has finished with a request. - * This should be only called for dispatched requests, but for some reason - * a POWER4 box running hwscan it does not. - */ -static void as_remove_request(request_queue_t *q, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - - if (unlikely(arq->state == AS_RQ_NEW)) - goto out; - - if (ON_RB(&arq->rb_node)) { - if (arq->state != AS_RQ_QUEUED) { - printk("arq->state %d\n", arq->state); - WARN_ON(1); - goto out; - } - /* - * We'll lose the aliased request(s) here. I don't think this - * will ever happen, but if it does, hopefully someone will - * report it. - */ - WARN_ON(!list_empty(&rq->queuelist)); - as_remove_queued_request(q, rq); - } else { - if (arq->state != AS_RQ_DISPATCHED) { - printk("arq->state %d\n", arq->state); - WARN_ON(1); - goto out; - } - as_remove_dispatched_request(q, rq); - } -out: - arq->state = AS_RQ_REMOVED; -} - -/* - * as_fifo_expired returns 0 if there are no expired reads on the fifo, - * 1 otherwise. It is ratelimited so that we only perform the check once per - * `fifo_expire' interval. Otherwise a large number of expired requests - * would create a hopeless seekstorm. - * - * See as_antic_expired comment. - */ -static int as_fifo_expired(struct as_data *ad, int adir) -{ - struct as_rq *arq; - long delta_jif; - - delta_jif = jiffies - ad->last_check_fifo[adir]; - if (unlikely(delta_jif < 0)) - delta_jif = -delta_jif; - if (delta_jif < ad->fifo_expire[adir]) - return 0; - - ad->last_check_fifo[adir] = jiffies; - - if (list_empty(&ad->fifo_list[adir])) - return 0; - - arq = list_entry_fifo(ad->fifo_list[adir].next); - - return time_after(jiffies, arq->expires); -} - -/* - * as_batch_expired returns true if the current batch has expired. A batch - * is a set of reads or a set of writes. - */ -static inline int as_batch_expired(struct as_data *ad) -{ - if (ad->changed_batch || ad->new_batch) - return 0; - - if (ad->batch_data_dir == REQ_SYNC) - /* TODO! add a check so a complete fifo gets written? */ - return time_after(jiffies, ad->current_batch_expires); - - return time_after(jiffies, ad->current_batch_expires) - || ad->current_write_count == 0; -} - -/* - * move an entry to dispatch queue - */ -static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq) -{ - struct request *rq = arq->request; - struct list_head *insert; - const int data_dir = arq->is_sync; - - BUG_ON(!ON_RB(&arq->rb_node)); - - as_antic_stop(ad); - ad->antic_status = ANTIC_OFF; - - /* - * This has to be set in order to be correctly updated by - * as_find_next_arq - */ - ad->last_sector[data_dir] = rq->sector + rq->nr_sectors; - - if (data_dir == REQ_SYNC) { - /* In case we have to anticipate after this */ - copy_io_context(&ad->io_context, &arq->io_context); - } else { - if (ad->io_context) { - put_io_context(ad->io_context); - ad->io_context = NULL; - } - - if (ad->current_write_count != 0) - ad->current_write_count--; - } - ad->ioc_finished = 0; - - ad->next_arq[data_dir] = as_find_next_arq(ad, arq); - - /* - * take it off the sort and fifo list, add to dispatch queue - */ - insert = ad->dispatch->prev; - - while (!list_empty(&rq->queuelist)) { - struct request *__rq = list_entry_rq(rq->queuelist.next); - struct as_rq *__arq = RQ_DATA(__rq); - - list_move_tail(&__rq->queuelist, ad->dispatch); - - if (__arq->io_context && __arq->io_context->aic) - atomic_inc(&__arq->io_context->aic->nr_dispatched); - - WARN_ON(__arq->state != AS_RQ_QUEUED); - __arq->state = AS_RQ_DISPATCHED; - - ad->nr_dispatched++; - } - - as_remove_queued_request(ad->q, rq); - WARN_ON(arq->state != AS_RQ_QUEUED); - - list_add(&rq->queuelist, insert); - arq->state = AS_RQ_DISPATCHED; - if (arq->io_context && arq->io_context->aic) - atomic_inc(&arq->io_context->aic->nr_dispatched); - ad->nr_dispatched++; -} - -/* - * as_dispatch_request selects the best request according to - * read/write expire, batch expire, etc, and moves it to the dispatch - * queue. Returns 1 if a request was found, 0 otherwise. - */ -static int as_dispatch_request(struct as_data *ad) -{ - struct as_rq *arq; - const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]); - const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]); - - /* Signal that the write batch was uncontended, so we can't time it */ - if (ad->batch_data_dir == REQ_ASYNC && !reads) { - if (ad->current_write_count == 0 || !writes) - ad->write_batch_idled = 1; - } - - if (!(reads || writes) - || ad->antic_status == ANTIC_WAIT_REQ - || ad->antic_status == ANTIC_WAIT_NEXT - || ad->changed_batch) - return 0; - - if (!(reads && writes && as_batch_expired(ad)) ) { - /* - * batch is still running or no reads or no writes - */ - arq = ad->next_arq[ad->batch_data_dir]; - - if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) { - if (as_fifo_expired(ad, REQ_SYNC)) - goto fifo_expired; - - if (as_can_anticipate(ad, arq)) { - as_antic_waitreq(ad); - return 0; - } - } - - if (arq) { - /* we have a "next request" */ - if (reads && !writes) - ad->current_batch_expires = - jiffies + ad->batch_expire[REQ_SYNC]; - goto dispatch_request; - } - } - - /* - * at this point we are not running a batch. select the appropriate - * data direction (read / write) - */ - - if (reads) { - BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC])); - - if (writes && ad->batch_data_dir == REQ_SYNC) - /* - * Last batch was a read, switch to writes - */ - goto dispatch_writes; - - if (ad->batch_data_dir == REQ_ASYNC) { - WARN_ON(ad->new_batch); - ad->changed_batch = 1; - } - ad->batch_data_dir = REQ_SYNC; - arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); - ad->last_check_fifo[ad->batch_data_dir] = jiffies; - goto dispatch_request; - } - - /* - * the last batch was a read - */ - - if (writes) { -dispatch_writes: - BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC])); - - if (ad->batch_data_dir == REQ_SYNC) { - ad->changed_batch = 1; - - /* - * new_batch might be 1 when the queue runs out of - * reads. A subsequent submission of a write might - * cause a change of batch before the read is finished. - */ - ad->new_batch = 0; - } - ad->batch_data_dir = REQ_ASYNC; - ad->current_write_count = ad->write_batch_count; - ad->write_batch_idled = 0; - arq = ad->next_arq[ad->batch_data_dir]; - goto dispatch_request; - } - - BUG(); - return 0; - -dispatch_request: - /* - * If a request has expired, service it. - */ - - if (as_fifo_expired(ad, ad->batch_data_dir)) { -fifo_expired: - arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next); - BUG_ON(arq == NULL); - } - - if (ad->changed_batch) { - WARN_ON(ad->new_batch); - - if (ad->nr_dispatched) - return 0; - - if (ad->batch_data_dir == REQ_ASYNC) - ad->current_batch_expires = jiffies + - ad->batch_expire[REQ_ASYNC]; - else - ad->new_batch = 1; - - ad->changed_batch = 0; - } - - /* - * arq is the selected appropriate request. - */ - as_move_to_dispatch(ad, arq); - - return 1; -} - -static struct request *as_next_request(request_queue_t *q) -{ - struct as_data *ad = q->elevator->elevator_data; - struct request *rq = NULL; - - /* - * if there are still requests on the dispatch queue, grab the first - */ - if (!list_empty(ad->dispatch) || as_dispatch_request(ad)) - rq = list_entry_rq(ad->dispatch->next); - - return rq; -} - -/* - * Add arq to a list behind alias - */ -static inline void -as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias) -{ - struct request *req = arq->request; - struct list_head *insert = alias->request->queuelist.prev; - - /* - * Transfer list of aliases - */ - while (!list_empty(&req->queuelist)) { - struct request *__rq = list_entry_rq(req->queuelist.next); - struct as_rq *__arq = RQ_DATA(__rq); - - list_move_tail(&__rq->queuelist, &alias->request->queuelist); - - WARN_ON(__arq->state != AS_RQ_QUEUED); - } - - /* - * Another request with the same start sector on the rbtree. - * Link this request to that sector. They are untangled in - * as_move_to_dispatch - */ - list_add(&arq->request->queuelist, insert); - - /* - * Don't want to have to handle merges. - */ - as_remove_merge_hints(ad->q, arq); -} - -/* - * add arq to rbtree and fifo - */ -static void as_add_request(struct as_data *ad, struct as_rq *arq) -{ - struct as_rq *alias; - int data_dir; - - if (rq_data_dir(arq->request) == READ - || current->flags&PF_SYNCWRITE) - arq->is_sync = 1; - else - arq->is_sync = 0; - data_dir = arq->is_sync; - - arq->io_context = as_get_io_context(); - - if (arq->io_context) { - as_update_iohist(ad, arq->io_context->aic, arq->request); - atomic_inc(&arq->io_context->aic->nr_queued); - } - - alias = as_add_arq_rb(ad, arq); - if (!alias) { - /* - * set expire time (only used for reads) and add to fifo list - */ - arq->expires = jiffies + ad->fifo_expire[data_dir]; - list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]); - - if (rq_mergeable(arq->request)) { - as_add_arq_hash(ad, arq); - - if (!ad->q->last_merge) - ad->q->last_merge = arq->request; - } - as_update_arq(ad, arq); /* keep state machine up to date */ - - } else { - as_add_aliased_request(ad, arq, alias); - - /* - * have we been anticipating this request? - * or does it come from the same process as the one we are - * anticipating for? - */ - if (ad->antic_status == ANTIC_WAIT_REQ - || ad->antic_status == ANTIC_WAIT_NEXT) { - if (as_can_break_anticipation(ad, arq)) - as_antic_stop(ad); - } - } - - arq->state = AS_RQ_QUEUED; -} - -static void as_deactivate_request(request_queue_t *q, struct request *rq) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(rq); - - if (arq) { - if (arq->state == AS_RQ_REMOVED) { - arq->state = AS_RQ_DISPATCHED; - if (arq->io_context && arq->io_context->aic) - atomic_inc(&arq->io_context->aic->nr_dispatched); - } - } else - WARN_ON(blk_fs_request(rq) - && (!(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) ); - - /* Stop anticipating - let this request get through */ - as_antic_stop(ad); -} - -/* - * requeue the request. The request has not been completed, nor is it a - * new request, so don't touch accounting. - */ -static void as_requeue_request(request_queue_t *q, struct request *rq) -{ - as_deactivate_request(q, rq); - list_add(&rq->queuelist, &q->queue_head); -} - -/* - * Account a request that is inserted directly onto the dispatch queue. - * arq->io_context->aic->nr_dispatched should not need to be incremented - * because only new requests should come through here: requeues go through - * our explicit requeue handler. - */ -static void as_account_queued_request(struct as_data *ad, struct request *rq) -{ - if (blk_fs_request(rq)) { - struct as_rq *arq = RQ_DATA(rq); - arq->state = AS_RQ_DISPATCHED; - ad->nr_dispatched++; - } -} - -static void -as_insert_request(request_queue_t *q, struct request *rq, int where) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(rq); - - if (arq) { - if (arq->state != AS_RQ_PRESCHED) { - printk("arq->state: %d\n", arq->state); - WARN_ON(1); - } - arq->state = AS_RQ_NEW; - } - - /* barriers must flush the reorder queue */ - if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER) - && where == ELEVATOR_INSERT_SORT)) { - WARN_ON(1); - where = ELEVATOR_INSERT_BACK; - } - - switch (where) { - case ELEVATOR_INSERT_BACK: - while (ad->next_arq[REQ_SYNC]) - as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]); - - while (ad->next_arq[REQ_ASYNC]) - as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]); - - list_add_tail(&rq->queuelist, ad->dispatch); - as_account_queued_request(ad, rq); - as_antic_stop(ad); - break; - case ELEVATOR_INSERT_FRONT: - list_add(&rq->queuelist, ad->dispatch); - as_account_queued_request(ad, rq); - as_antic_stop(ad); - break; - case ELEVATOR_INSERT_SORT: - BUG_ON(!blk_fs_request(rq)); - as_add_request(ad, arq); - break; - default: - BUG(); - return; - } -} - -/* - * as_queue_empty tells us if there are requests left in the device. It may - * not be the case that a driver can get the next request even if the queue - * is not empty - it is used in the block layer to check for plugging and - * merging opportunities - */ -static int as_queue_empty(request_queue_t *q) -{ - struct as_data *ad = q->elevator->elevator_data; - - if (!list_empty(&ad->fifo_list[REQ_ASYNC]) - || !list_empty(&ad->fifo_list[REQ_SYNC]) - || !list_empty(ad->dispatch)) - return 0; - - return 1; -} - -static struct request * -as_former_request(request_queue_t *q, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - struct rb_node *rbprev = rb_prev(&arq->rb_node); - struct request *ret = NULL; - - if (rbprev) - ret = rb_entry_arq(rbprev)->request; - - return ret; -} - -static struct request * -as_latter_request(request_queue_t *q, struct request *rq) -{ - struct as_rq *arq = RQ_DATA(rq); - struct rb_node *rbnext = rb_next(&arq->rb_node); - struct request *ret = NULL; - - if (rbnext) - ret = rb_entry_arq(rbnext)->request; - - return ret; -} - -static int -as_merge(request_queue_t *q, struct request **req, struct bio *bio) -{ - struct as_data *ad = q->elevator->elevator_data; - sector_t rb_key = bio->bi_sector + bio_sectors(bio); - struct request *__rq; - int ret; - - /* - * try last_merge to avoid going to hash - */ - ret = elv_try_last_merge(q, bio); - if (ret != ELEVATOR_NO_MERGE) { - __rq = q->last_merge; - goto out_insert; - } - - /* - * see if the merge hash can satisfy a back merge - */ - __rq = as_find_arq_hash(ad, bio->bi_sector); - if (__rq) { - BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector); - - if (elv_rq_merge_ok(__rq, bio)) { - ret = ELEVATOR_BACK_MERGE; - goto out; - } - } - - /* - * check for front merge - */ - __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio)); - if (__rq) { - BUG_ON(rb_key != rq_rb_key(__rq)); - - if (elv_rq_merge_ok(__rq, bio)) { - ret = ELEVATOR_FRONT_MERGE; - goto out; - } - } - - return ELEVATOR_NO_MERGE; -out: - if (rq_mergeable(__rq)) - q->last_merge = __rq; -out_insert: - if (ret) { - if (rq_mergeable(__rq)) - as_hot_arq_hash(ad, RQ_DATA(__rq)); - } - *req = __rq; - return ret; -} - -static void as_merged_request(request_queue_t *q, struct request *req) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(req); - - /* - * hash always needs to be repositioned, key is end sector - */ - as_del_arq_hash(arq); - as_add_arq_hash(ad, arq); - - /* - * if the merge was a front merge, we need to reposition request - */ - if (rq_rb_key(req) != arq->rb_key) { - struct as_rq *alias, *next_arq = NULL; - - if (ad->next_arq[arq->is_sync] == arq) - next_arq = as_find_next_arq(ad, arq); - - /* - * Note! We should really be moving any old aliased requests - * off this request and try to insert them into the rbtree. We - * currently don't bother. Ditto the next function. - */ - as_del_arq_rb(ad, arq); - if ((alias = as_add_arq_rb(ad, arq)) ) { - list_del_init(&arq->fifo); - as_add_aliased_request(ad, arq, alias); - if (next_arq) - ad->next_arq[arq->is_sync] = next_arq; - } - /* - * Note! At this stage of this and the next function, our next - * request may not be optimal - eg the request may have "grown" - * behind the disk head. We currently don't bother adjusting. - */ - } - - if (arq->on_hash) - q->last_merge = req; -} - -static void -as_merged_requests(request_queue_t *q, struct request *req, - struct request *next) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(req); - struct as_rq *anext = RQ_DATA(next); - - BUG_ON(!arq); - BUG_ON(!anext); - - /* - * reposition arq (this is the merged request) in hash, and in rbtree - * in case of a front merge - */ - as_del_arq_hash(arq); - as_add_arq_hash(ad, arq); - - if (rq_rb_key(req) != arq->rb_key) { - struct as_rq *alias, *next_arq = NULL; - - if (ad->next_arq[arq->is_sync] == arq) - next_arq = as_find_next_arq(ad, arq); - - as_del_arq_rb(ad, arq); - if ((alias = as_add_arq_rb(ad, arq)) ) { - list_del_init(&arq->fifo); - as_add_aliased_request(ad, arq, alias); - if (next_arq) - ad->next_arq[arq->is_sync] = next_arq; - } - } - - /* - * if anext expires before arq, assign its expire time to arq - * and move into anext position (anext will be deleted) in fifo - */ - if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) { - if (time_before(anext->expires, arq->expires)) { - list_move(&arq->fifo, &anext->fifo); - arq->expires = anext->expires; - /* - * Don't copy here but swap, because when anext is - * removed below, it must contain the unused context - */ - swap_io_context(&arq->io_context, &anext->io_context); - } - } - - /* - * Transfer list of aliases - */ - while (!list_empty(&next->queuelist)) { - struct request *__rq = list_entry_rq(next->queuelist.next); - struct as_rq *__arq = RQ_DATA(__rq); - - list_move_tail(&__rq->queuelist, &req->queuelist); - - WARN_ON(__arq->state != AS_RQ_QUEUED); - } - - /* - * kill knowledge of next, this one is a goner - */ - as_remove_queued_request(q, next); - - anext->state = AS_RQ_MERGED; -} - -/* - * This is executed in a "deferred" process context, by kblockd. It calls the - * driver's request_fn so the driver can submit that request. - * - * IMPORTANT! This guy will reenter the elevator, so set up all queue global - * state before calling, and don't rely on any state over calls. - * - * FIXME! dispatch queue is not a queue at all! - */ -static void as_work_handler(void *data) -{ - struct request_queue *q = data; - unsigned long flags; - - spin_lock_irqsave(q->queue_lock, flags); - if (as_next_request(q)) - q->request_fn(q); - spin_unlock_irqrestore(q->queue_lock, flags); -} - -static void as_put_request(request_queue_t *q, struct request *rq) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = RQ_DATA(rq); - - if (!arq) { - WARN_ON(1); - return; - } - - if (arq->state != AS_RQ_POSTSCHED && arq->state != AS_RQ_PRESCHED) { - printk("arq->state %d\n", arq->state); - WARN_ON(1); - } - - mempool_free(arq, ad->arq_pool); - rq->elevator_private = NULL; -} - -static int as_set_request(request_queue_t *q, struct request *rq, - struct bio *bio, int gfp_mask) -{ - struct as_data *ad = q->elevator->elevator_data; - struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask); - - if (arq) { - memset(arq, 0, sizeof(*arq)); - RB_CLEAR(&arq->rb_node); - arq->request = rq; - arq->state = AS_RQ_PRESCHED; - arq->io_context = NULL; - INIT_LIST_HEAD(&arq->hash); - arq->on_hash = 0; - INIT_LIST_HEAD(&arq->fifo); - rq->elevator_private = arq; - return 0; - } - - return 1; -} - -static int as_may_queue(request_queue_t *q, int rw, struct bio *bio) -{ - int ret = ELV_MQUEUE_MAY; - struct as_data *ad = q->elevator->elevator_data; - struct io_context *ioc; - if (ad->antic_status == ANTIC_WAIT_REQ || - ad->antic_status == ANTIC_WAIT_NEXT) { - ioc = as_get_io_context(); - if (ad->io_context == ioc) - ret = ELV_MQUEUE_MUST; - put_io_context(ioc); - } - - return ret; -} - -static void as_exit_queue(elevator_t *e) -{ - struct as_data *ad = e->elevator_data; - - del_timer_sync(&ad->antic_timer); - kblockd_flush(); - - BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC])); - BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC])); - - mempool_destroy(ad->arq_pool); - put_io_context(ad->io_context); - kfree(ad->hash); - kfree(ad); -} - -/* - * initialize elevator private data (as_data), and alloc a arq for - * each request on the free lists - */ -static int as_init_queue(request_queue_t *q, elevator_t *e) -{ - struct as_data *ad; - int i; - - if (!arq_pool) - return -ENOMEM; - - ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node); - if (!ad) - return -ENOMEM; - memset(ad, 0, sizeof(*ad)); - - ad->q = q; /* Identify what queue the data belongs to */ - - ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES, - GFP_KERNEL, q->node); - if (!ad->hash) { - kfree(ad); - return -ENOMEM; - } - - ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, - mempool_free_slab, arq_pool, q->node); - if (!ad->arq_pool) { - kfree(ad->hash); - kfree(ad); - return -ENOMEM; - } - - /* anticipatory scheduling helpers */ - ad->antic_timer.function = as_antic_timeout; - ad->antic_timer.data = (unsigned long)q; - init_timer(&ad->antic_timer); - INIT_WORK(&ad->antic_work, as_work_handler, q); - - for (i = 0; i < AS_HASH_ENTRIES; i++) - INIT_LIST_HEAD(&ad->hash[i]); - - INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]); - INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]); - ad->sort_list[REQ_SYNC] = RB_ROOT; - ad->sort_list[REQ_ASYNC] = RB_ROOT; - ad->dispatch = &q->queue_head; - ad->fifo_expire[REQ_SYNC] = default_read_expire; - ad->fifo_expire[REQ_ASYNC] = default_write_expire; - ad->antic_expire = default_antic_expire; - ad->batch_expire[REQ_SYNC] = default_read_batch_expire; - ad->batch_expire[REQ_ASYNC] = default_write_batch_expire; - e->elevator_data = ad; - - ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC]; - ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10; - if (ad->write_batch_count < 2) - ad->write_batch_count = 2; - - return 0; -} - -/* - * sysfs parts below - */ -struct as_fs_entry { - struct attribute attr; - ssize_t (*show)(struct as_data *, char *); - ssize_t (*store)(struct as_data *, const char *, size_t); -}; - -static ssize_t -as_var_show(unsigned int var, char *page) -{ - return sprintf(page, "%d\n", var); -} - -static ssize_t -as_var_store(unsigned long *var, const char *page, size_t count) -{ - char *p = (char *) page; - - *var = simple_strtoul(p, &p, 10); - return count; -} - -static ssize_t as_est_show(struct as_data *ad, char *page) -{ - int pos = 0; - - pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256); - pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean); - pos += sprintf(page+pos, "%llu sectors new seek distance\n", (unsigned long long)ad->new_seek_mean); - - return pos; -} - -#define SHOW_FUNCTION(__FUNC, __VAR) \ -static ssize_t __FUNC(struct as_data *ad, char *page) \ -{ \ - return as_var_show(jiffies_to_msecs((__VAR)), (page)); \ -} -SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]); -SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]); -SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire); -SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[REQ_SYNC]); -SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]); -#undef SHOW_FUNCTION - -#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ -static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \ -{ \ - int ret = as_var_store(__PTR, (page), count); \ - if (*(__PTR) < (MIN)) \ - *(__PTR) = (MIN); \ - else if (*(__PTR) > (MAX)) \ - *(__PTR) = (MAX); \ - *(__PTR) = msecs_to_jiffies(*(__PTR)); \ - return ret; \ -} -STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX); -STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX); -STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX); -STORE_FUNCTION(as_read_batchexpire_store, - &ad->batch_expire[REQ_SYNC], 0, INT_MAX); -STORE_FUNCTION(as_write_batchexpire_store, - &ad->batch_expire[REQ_ASYNC], 0, INT_MAX); -#undef STORE_FUNCTION - -static struct as_fs_entry as_est_entry = { - .attr = {.name = "est_time", .mode = S_IRUGO }, - .show = as_est_show, -}; -static struct as_fs_entry as_readexpire_entry = { - .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR }, - .show = as_readexpire_show, - .store = as_readexpire_store, -}; -static struct as_fs_entry as_writeexpire_entry = { - .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR }, - .show = as_writeexpire_show, - .store = as_writeexpire_store, -}; -static struct as_fs_entry as_anticexpire_entry = { - .attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR }, - .show = as_anticexpire_show, - .store = as_anticexpire_store, -}; -static struct as_fs_entry as_read_batchexpire_entry = { - .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR }, - .show = as_read_batchexpire_show, - .store = as_read_batchexpire_store, -}; -static struct as_fs_entry as_write_batchexpire_entry = { - .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR }, - .show = as_write_batchexpire_show, - .store = as_write_batchexpire_store, -}; - -static struct attribute *default_attrs[] = { - &as_est_entry.attr, - &as_readexpire_entry.attr, - &as_writeexpire_entry.attr, - &as_anticexpire_entry.attr, - &as_read_batchexpire_entry.attr, - &as_write_batchexpire_entry.attr, - NULL, -}; - -#define to_as(atr) container_of((atr), struct as_fs_entry, attr) - -static ssize_t -as_attr_show(struct kobject *kobj, struct attribute *attr, char *page) -{ - elevator_t *e = container_of(kobj, elevator_t, kobj); - struct as_fs_entry *entry = to_as(attr); - - if (!entry->show) - return -EIO; - - return entry->show(e->elevator_data, page); -} - -static ssize_t -as_attr_store(struct kobject *kobj, struct attribute *attr, - const char *page, size_t length) -{ - elevator_t *e = container_of(kobj, elevator_t, kobj); - struct as_fs_entry *entry = to_as(attr); - - if (!entry->store) - return -EIO; - - return entry->store(e->elevator_data, page, length); -} - -static struct sysfs_ops as_sysfs_ops = { - .show = as_attr_show, - .store = as_attr_store, -}; - -static struct kobj_type as_ktype = { - .sysfs_ops = &as_sysfs_ops, - .default_attrs = default_attrs, -}; - -static struct elevator_type iosched_as = { - .ops = { - .elevator_merge_fn = as_merge, - .elevator_merged_fn = as_merged_request, - .elevator_merge_req_fn = as_merged_requests, - .elevator_next_req_fn = as_next_request, - .elevator_add_req_fn = as_insert_request, - .elevator_remove_req_fn = as_remove_request, - .elevator_requeue_req_fn = as_requeue_request, - .elevator_deactivate_req_fn = as_deactivate_request, - .elevator_queue_empty_fn = as_queue_empty, - .elevator_completed_req_fn = as_completed_request, - .elevator_former_req_fn = as_former_request, - .elevator_latter_req_fn = as_latter_request, - .elevator_set_req_fn = as_set_request, - .elevator_put_req_fn = as_put_request, - .elevator_may_queue_fn = as_may_queue, - .elevator_init_fn = as_init_queue, - .elevator_exit_fn = as_exit_queue, - }, - - .elevator_ktype = &as_ktype, - .elevator_name = "anticipatory", - .elevator_owner = THIS_MODULE, -}; - -static int __init as_init(void) -{ - int ret; - - arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq), - 0, 0, NULL, NULL); - if (!arq_pool) - return -ENOMEM; - - ret = elv_register(&iosched_as); - if (!ret) { - /* - * don't allow AS to get unregistered, since we would have - * to browse all tasks in the system and release their - * as_io_context first - */ - __module_get(THIS_MODULE); - return 0; - } - - kmem_cache_destroy(arq_pool); - return ret; -} - -static void __exit as_exit(void) -{ - kmem_cache_destroy(arq_pool); - elv_unregister(&iosched_as); -} - -module_init(as_init); -module_exit(as_exit); - -MODULE_AUTHOR("Nick Piggin"); -MODULE_LICENSE("GPL"); -MODULE_DESCRIPTION("anticipatory IO scheduler"); |