+++ /dev/null
-/*
- * Anticipatory & deadline i/o scheduler.
- *
- * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
- * Nick Piggin <nickpiggin@yahoo.com.au>
- *
- */
-#include <linux/kernel.h>
-#include <linux/fs.h>
-#include <linux/blkdev.h>
-#include <linux/elevator.h>
-#include <linux/bio.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/init.h>
-#include <linux/compiler.h>
-#include <linux/rbtree.h>
-#include <linux/interrupt.h>
-
-/*
- * 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 exited */
- 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 request *next_rq[2]; /* next in sort order */
- sector_t last_sector[2]; /* last SYNC & ASYNC sectors */
-
- unsigned long exit_prob; /* probability a task will exit while
- being waited on */
- unsigned long exit_no_coop; /* probablility an exited task will
- not be part of a later cooperating
- request */
- 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 SYNC / 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? */
-
- 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;
-};
-
-/*
- * 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 */
-};
-
-#define RQ_IOC(rq) ((struct io_context *) (rq)->elevator_private)
-#define RQ_STATE(rq) ((enum arq_state)(rq)->elevator_private2)
-#define RQ_SET_STATE(rq, state) ((rq)->elevator_private2 = (void *) state)
-
-static DEFINE_PER_CPU(unsigned long, as_ioc_count);
-static struct completion *ioc_gone;
-static DEFINE_SPINLOCK(ioc_gone_lock);
-
-static void as_move_to_dispatch(struct as_data *ad, struct request *rq);
-static void as_antic_stop(struct as_data *ad);
-
-/*
- * IO Context helper functions
- */
-
-/* Called to deallocate the as_io_context */
-static void free_as_io_context(struct as_io_context *aic)
-{
- kfree(aic);
- elv_ioc_count_dec(as_ioc_count);
- if (ioc_gone) {
- /*
- * AS 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(as_ioc_count)) {
- complete(ioc_gone);
- ioc_gone = NULL;
- }
- spin_unlock(&ioc_gone_lock);
- }
-}
-
-static void as_trim(struct io_context *ioc)
-{
- spin_lock_irq(&ioc->lock);
- if (ioc->aic)
- free_as_io_context(ioc->aic);
- ioc->aic = NULL;
- spin_unlock_irq(&ioc->lock);
-}
-
-/* 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;
- elv_ioc_count_inc(as_ioc_count);
- }
-
- 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(int node)
-{
- struct io_context *ioc = get_io_context(GFP_ATOMIC, node);
- if (ioc && !ioc->aic) {
- ioc->aic = alloc_as_io_context();
- if (!ioc->aic) {
- put_io_context(ioc);
- ioc = NULL;
- }
- }
- return ioc;
-}
-
-static void as_put_io_context(struct request *rq)
-{
- struct as_io_context *aic;
-
- if (unlikely(!RQ_IOC(rq)))
- return;
-
- aic = RQ_IOC(rq)->aic;
-
- if (rq_is_sync(rq) && aic) {
- unsigned long flags;
-
- spin_lock_irqsave(&aic->lock, flags);
- set_bit(AS_TASK_IORUNNING, &aic->state);
- aic->last_end_request = jiffies;
- spin_unlock_irqrestore(&aic->lock, flags);
- }
-
- put_io_context(RQ_IOC(rq));
-}
-
-/*
- * rb tree support functions
- */
-#define RQ_RB_ROOT(ad, rq) (&(ad)->sort_list[rq_is_sync((rq))])
-
-static void as_add_rq_rb(struct as_data *ad, struct request *rq)
-{
- struct request *alias;
-
- while ((unlikely(alias = elv_rb_add(RQ_RB_ROOT(ad, rq), rq)))) {
- as_move_to_dispatch(ad, alias);
- as_antic_stop(ad);
- }
-}
-
-static inline void as_del_rq_rb(struct as_data *ad, struct request *rq)
-{
- elv_rb_del(RQ_RB_ROOT(ad, rq), rq);
-}
-
-/*
- * 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 request *
-as_choose_req(struct as_data *ad, struct request *rq1, struct request *rq2)
-{
- 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 (rq1 == NULL || rq1 == rq2)
- return rq2;
- if (rq2 == NULL)
- return rq1;
-
- data_dir = rq_is_sync(rq1);
-
- last = ad->last_sector[data_dir];
- s1 = blk_rq_pos(rq1);
- s2 = blk_rq_pos(rq2);
-
- BUG_ON(data_dir != rq_is_sync(rq2));
-
- /*
- * 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 rq1;
- else if (!r2_wrap && r1_wrap)
- return rq2;
- else if (r1_wrap && r2_wrap) {
- /* both behind the head */
- if (s1 <= s2)
- return rq1;
- else
- return rq2;
- }
-
- /* Both requests in front of the head */
- if (d1 < d2)
- return rq1;
- else if (d2 < d1)
- return rq2;
- else {
- if (s1 >= s2)
- return rq1;
- else
- return rq2;
- }
-}
-
-/*
- * as_find_next_rq 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 request *
-as_find_next_rq(struct as_data *ad, 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 {
- const int data_dir = rq_is_sync(last);
-
- rbnext = rb_first(&ad->sort_list[data_dir]);
- if (rbnext && rbnext != &last->rb_node)
- next = rb_entry_rq(rbnext);
- }
-
- return as_choose_req(ad, next, prev);
-}
-
-/*
- * 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->q, &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;
- spin_lock(&ad->io_context->lock);
- aic = ad->io_context->aic;
-
- ad->antic_status = ANTIC_FINISHED;
- kblockd_schedule_work(q, &ad->antic_work);
-
- if (aic->ttime_samples == 0) {
- /* process anticipated on has exited or timed out*/
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
- }
- if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
- /* process not "saved" by a cooperating request */
- ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
- }
- spin_unlock(&ad->io_context->lock);
- }
- spin_unlock_irqrestore(q->queue_lock, flags);
-}
-
-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)
-{
- int data_dir = rq_is_sync(rq);
- unsigned long thinktime = 0;
- sector_t seek_dist;
-
- if (aic == NULL)
- return;
-
- if (data_dir == BLK_RW_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);
- }
- as_update_thinktime(ad, aic, thinktime);
-
- /* Calculate read -> read seek distance */
- if (aic->last_request_pos < blk_rq_pos(rq))
- seek_dist = blk_rq_pos(rq) -
- aic->last_request_pos;
- else
- seek_dist = aic->last_request_pos -
- blk_rq_pos(rq);
- as_update_seekdist(ad, aic, seek_dist);
- }
- aic->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
- set_bit(AS_TASK_IOSTARTED, &aic->state);
- spin_unlock(&aic->lock);
- }
-}
-
-/*
- * 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_io_context *aic,
- struct request *rq)
-{
- unsigned long delay; /* jiffies */
- sector_t last = ad->last_sector[ad->batch_data_dir];
- sector_t next = blk_rq_pos(rq);
- sector_t delta; /* acceptable close offset (in sectors) */
- sector_t s;
-
- if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
- delay = 0;
- else
- delay = jiffies - ad->antic_start;
-
- if (delay == 0)
- delta = 8192;
- else if (delay <= (20 * HZ / 1000) && delay <= ad->antic_expire)
- delta = 8192 << delay;
- else
- return 1;
-
- if ((last <= next + (delta>>1)) && (next <= last + delta))
- return 1;
-
- if (last < next)
- s = next - last;
- else
- s = last - next;
-
- if (aic->seek_samples == 0) {
- /*
- * Process has just started IO. Use past statistics to
- * gauge 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_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 exited, 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 request *rq)
-{
- struct io_context *ioc;
- struct as_io_context *aic;
-
- ioc = ad->io_context;
- BUG_ON(!ioc);
- spin_lock(&ioc->lock);
-
- if (rq && ioc == RQ_IOC(rq)) {
- /* request from same process */
- spin_unlock(&ioc->lock);
- 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.
- */
- spin_unlock(&ioc->lock);
- return 1;
- }
-
- aic = ioc->aic;
- if (!aic) {
- spin_unlock(&ioc->lock);
- return 0;
- }
-
- if (atomic_read(&aic->nr_queued) > 0) {
- /* process has more requests queued */
- spin_unlock(&ioc->lock);
- return 1;
- }
-
- if (atomic_read(&aic->nr_dispatched) > 0) {
- /* process has more requests dispatched */
- spin_unlock(&ioc->lock);
- return 1;
- }
-
- if (rq && rq_is_sync(rq) && as_close_req(ad, aic, rq)) {
- /*
- * Found a close request that is not one of ours.
- *
- * This makes close requests from another process update
- * our IO history. Is generally useful when there are
- * two or more cooperating processes working in the same
- * area.
- */
- if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
- if (aic->ttime_samples == 0)
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
-
- ad->exit_no_coop = (7*ad->exit_no_coop)/8;
- }
-
- as_update_iohist(ad, aic, rq);
- spin_unlock(&ioc->lock);
- return 1;
- }
-
- if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
- /* process anticipated on has exited */
- if (aic->ttime_samples == 0)
- ad->exit_prob = (7*ad->exit_prob + 256)/8;
-
- if (ad->exit_no_coop > 128) {
- spin_unlock(&ioc->lock);
- return 1;
- }
- }
-
- if (aic->ttime_samples == 0) {
- if (ad->new_ttime_mean > ad->antic_expire) {
- spin_unlock(&ioc->lock);
- return 1;
- }
- if (ad->exit_prob * ad->exit_no_coop > 128*256) {
- spin_unlock(&ioc->lock);
- return 1;
- }
- } else if (aic->ttime_mean > ad->antic_expire) {
- /* the process thinks too much between requests */
- spin_unlock(&ioc->lock);
- return 1;
- }
- spin_unlock(&ioc->lock);
- return 0;
-}
-
-/*
- * as_can_anticipate indicates whether we should either run rq
- * or keep anticipating a better request.
- */
-static int as_can_anticipate(struct as_data *ad, struct request *rq)
-{
-#if 0 /* disable for now, we need to check tag level as well */
- /*
- * SSD device without seek penalty, disable idling
- */
- if (blk_queue_nonrot(ad->q)) axman
- return 0;
-#endif
-
- 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, rq))
- /*
- * 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;
-}
-
-/*
- * as_update_rq must be called whenever a request (rq) 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_rq(struct as_data *ad, struct request *rq)
-{
- const int data_dir = rq_is_sync(rq);
-
- /* keep the next_rq cache up to date */
- ad->next_rq[data_dir] = as_choose_req(ad, rq, ad->next_rq[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, rq))
- 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[BLK_RW_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(struct request_queue *q, struct request *rq)
-{
- struct as_data *ad = q->elevator->elevator_data;
-
- WARN_ON(!list_empty(&rq->queuelist));
-
- if (RQ_STATE(rq) != AS_RQ_REMOVED) {
- WARN(1, "rq->state %d\n", RQ_STATE(rq));
- goto out;
- }
-
- if (ad->changed_batch && ad->nr_dispatched == 1) {
- ad->current_batch_expires = jiffies +
- ad->batch_expire[ad->batch_data_dir];
- kblockd_schedule_work(q, &ad->antic_work);
- ad->changed_batch = 0;
-
- if (ad->batch_data_dir == BLK_RW_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 == rq_is_sync(rq)) {
- update_write_batch(ad);
- ad->current_batch_expires = jiffies +
- ad->batch_expire[BLK_RW_SYNC];
- ad->new_batch = 0;
- }
-
- if (ad->io_context == RQ_IOC(rq) && 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);
- }
- }
-
- as_put_io_context(rq);
-out:
- RQ_SET_STATE(rq, 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(struct request_queue *q,
- struct request *rq)
-{
- const int data_dir = rq_is_sync(rq);
- struct as_data *ad = q->elevator->elevator_data;
- struct io_context *ioc;
-
- WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED);
-
- ioc = RQ_IOC(rq);
- if (ioc && ioc->aic) {
- BUG_ON(!atomic_read(&ioc->aic->nr_queued));
- atomic_dec(&ioc->aic->nr_queued);
- }
-
- /*
- * Update the "next_rq" cache if we are about to remove its
- * entry
- */
- if (ad->next_rq[data_dir] == rq)
- ad->next_rq[data_dir] = as_find_next_rq(ad, rq);
-
- rq_fifo_clear(rq);
- as_del_rq_rb(ad, rq);
-}
-
-/*
- * as_fifo_expired returns 0 if there are no expired requests 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 request *rq;
- 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;
-
- rq = rq_entry_fifo(ad->fifo_list[adir].next);
-
- return time_after(jiffies, rq_fifo_time(rq));
-}
-
-/*
- * 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 == BLK_RW_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 request *rq)
-{
- const int data_dir = rq_is_sync(rq);
-
- BUG_ON(RB_EMPTY_NODE(&rq->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_rq
- */
- ad->last_sector[data_dir] = blk_rq_pos(rq) + blk_rq_sectors(rq);
-
- if (data_dir == BLK_RW_SYNC) {
- struct io_context *ioc = RQ_IOC(rq);
- /* In case we have to anticipate after this */
- copy_io_context(&ad->io_context, &ioc);
- } 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_rq[data_dir] = as_find_next_rq(ad, rq);
-
- /*
- * take it off the sort and fifo list, add to dispatch queue
- */
- as_remove_queued_request(ad->q, rq);
- WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED);
-
- elv_dispatch_sort(ad->q, rq);
-
- RQ_SET_STATE(rq, AS_RQ_DISPATCHED);
- if (RQ_IOC(rq) && RQ_IOC(rq)->aic)
- atomic_inc(&RQ_IOC(rq)->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 request_queue *q, int force)
-{
- struct as_data *ad = q->elevator->elevator_data;
- const int reads = !list_empty(&ad->fifo_list[BLK_RW_SYNC]);
- const int writes = !list_empty(&ad->fifo_list[BLK_RW_ASYNC]);
- struct request *rq;
-
- if (unlikely(force)) {
- /*
- * Forced dispatch, accounting is useless. Reset
- * accounting states and dump fifo_lists. Note that
- * batch_data_dir is reset to BLK_RW_SYNC to avoid
- * screwing write batch accounting as write batch
- * accounting occurs on W->R transition.
- */
- int dispatched = 0;
-
- ad->batch_data_dir = BLK_RW_SYNC;
- ad->changed_batch = 0;
- ad->new_batch = 0;
-
- while (ad->next_rq[BLK_RW_SYNC]) {
- as_move_to_dispatch(ad, ad->next_rq[BLK_RW_SYNC]);
- dispatched++;
- }
- ad->last_check_fifo[BLK_RW_SYNC] = jiffies;
-
- while (ad->next_rq[BLK_RW_ASYNC]) {
- as_move_to_dispatch(ad, ad->next_rq[BLK_RW_ASYNC]);
- dispatched++;
- }
- ad->last_check_fifo[BLK_RW_ASYNC] = jiffies;
-
- return dispatched;
- }
-
- /* Signal that the write batch was uncontended, so we can't time it */
- if (ad->batch_data_dir == BLK_RW_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
- */
- rq = ad->next_rq[ad->batch_data_dir];
-
- if (ad->batch_data_dir == BLK_RW_SYNC && ad->antic_expire) {
- if (as_fifo_expired(ad, BLK_RW_SYNC))
- goto fifo_expired;
-
- if (as_can_anticipate(ad, rq)) {
- as_antic_waitreq(ad);
- return 0;
- }
- }
-
- if (rq) {
- /* we have a "next request" */
- if (reads && !writes)
- ad->current_batch_expires =
- jiffies + ad->batch_expire[BLK_RW_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_ROOT(&ad->sort_list[BLK_RW_SYNC]));
-
- if (writes && ad->batch_data_dir == BLK_RW_SYNC)
- /*
- * Last batch was a read, switch to writes
- */
- goto dispatch_writes;
-
- if (ad->batch_data_dir == BLK_RW_ASYNC) {
- WARN_ON(ad->new_batch);
- ad->changed_batch = 1;
- }
- ad->batch_data_dir = BLK_RW_SYNC;
- rq = rq_entry_fifo(ad->fifo_list[BLK_RW_SYNC].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_ROOT(&ad->sort_list[BLK_RW_ASYNC]));
-
- if (ad->batch_data_dir == BLK_RW_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 = BLK_RW_ASYNC;
- ad->current_write_count = ad->write_batch_count;
- ad->write_batch_idled = 0;
- rq = rq_entry_fifo(ad->fifo_list[BLK_RW_ASYNC].next);
- ad->last_check_fifo[BLK_RW_ASYNC] = jiffies;
- 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:
- rq = rq_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
- }
-
- if (ad->changed_batch) {
- WARN_ON(ad->new_batch);
-
- if (ad->nr_dispatched)
- return 0;
-
- if (ad->batch_data_dir == BLK_RW_ASYNC)
- ad->current_batch_expires = jiffies +
- ad->batch_expire[BLK_RW_ASYNC];
- else
- ad->new_batch = 1;
-
- ad->changed_batch = 0;
- }
-
- /*
- * rq is the selected appropriate request.
- */
- as_move_to_dispatch(ad, rq);
-
- return 1;
-}
-
-/*
- * add rq to rbtree and fifo
- */
-static void as_add_request(struct request_queue *q, struct request *rq)
-{
- struct as_data *ad = q->elevator->elevator_data;
- int data_dir;
-
- RQ_SET_STATE(rq, AS_RQ_NEW);
-
- data_dir = rq_is_sync(rq);
-
- rq->elevator_private = as_get_io_context(q->node);
-
- if (RQ_IOC(rq)) {
- as_update_iohist(ad, RQ_IOC(rq)->aic, rq);
- atomic_inc(&RQ_IOC(rq)->aic->nr_queued);
- }
-
- as_add_rq_rb(ad, rq);
-
- /*
- * set expire time and add to fifo list
- */
- rq_set_fifo_time(rq, jiffies + ad->fifo_expire[data_dir]);
- list_add_tail(&rq->queuelist, &ad->fifo_list[data_dir]);
-
- as_update_rq(ad, rq); /* keep state machine up to date */
- RQ_SET_STATE(rq, AS_RQ_QUEUED);
-}
-
-static void as_activate_request(struct request_queue *q, struct request *rq)
-{
- WARN_ON(RQ_STATE(rq) != AS_RQ_DISPATCHED);
- RQ_SET_STATE(rq, AS_RQ_REMOVED);
- if (RQ_IOC(rq) && RQ_IOC(rq)->aic)
- atomic_dec(&RQ_IOC(rq)->aic->nr_dispatched);
-}
-
-static void as_deactivate_request(struct request_queue *q, struct request *rq)
-{
- WARN_ON(RQ_STATE(rq) != AS_RQ_REMOVED);
- RQ_SET_STATE(rq, AS_RQ_DISPATCHED);
- if (RQ_IOC(rq) && RQ_IOC(rq)->aic)
- atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched);
-}
-
-/*
- * 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(struct request_queue *q)
-{
- struct as_data *ad = q->elevator->elevator_data;
-
- return list_empty(&ad->fifo_list[BLK_RW_ASYNC])
- && list_empty(&ad->fifo_list[BLK_RW_SYNC]);
-}
-
-static int
-as_merge(struct request_queue *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;
-
- /*
- * check for front merge
- */
- __rq = elv_rb_find(&ad->sort_list[bio_data_dir(bio)], rb_key);
- if (__rq && elv_rq_merge_ok(__rq, bio)) {
- *req = __rq;
- return ELEVATOR_FRONT_MERGE;
- }
-
- return ELEVATOR_NO_MERGE;
-}
-
-static void as_merged_request(struct request_queue *q, struct request *req,
- int type)
-{
- struct as_data *ad = q->elevator->elevator_data;
-
- /*
- * if the merge was a front merge, we need to reposition request
- */
- if (type == ELEVATOR_FRONT_MERGE) {
- as_del_rq_rb(ad, req);
- as_add_rq_rb(ad, req);
- /*
- * 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.
- */
- }
-}
-
-static void as_merged_requests(struct request_queue *q, struct request *req,
- struct request *next)
-{
- /*
- * if next expires before rq, assign its expire time to arq
- * and move into next position (next will be deleted) in fifo
- */
- if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
- if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
- list_move(&req->queuelist, &next->queuelist);
- rq_set_fifo_time(req, rq_fifo_time(next));
- }
- }
-
- /*
- * kill knowledge of next, this one is a goner
- */
- as_remove_queued_request(q, next);
- as_put_io_context(next);
-
- RQ_SET_STATE(next, 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(struct work_struct *work)
-{
- struct as_data *ad = container_of(work, struct as_data, antic_work);
-
- blk_run_queue(ad->q);
-}
-
-static int as_may_queue(struct request_queue *q, int rw)
-{
- 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(q->node);
- if (ad->io_context == ioc)
- ret = ELV_MQUEUE_MUST;
- put_io_context(ioc);
- }
-
- return ret;
-}
-
-static void as_exit_queue(struct elevator_queue *e)
-{
- struct as_data *ad = e->elevator_data;
-
- del_timer_sync(&ad->antic_timer);
- cancel_work_sync(&ad->antic_work);
-
- BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_SYNC]));
- BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_ASYNC]));
-
- put_io_context(ad->io_context);
- kfree(ad);
-}
-
-/*
- * initialize elevator private data (as_data).
- */
-static void *as_init_queue(struct request_queue *q)
-{
- struct as_data *ad;
-
- ad = kmalloc_node(sizeof(*ad), GFP_KERNEL | __GFP_ZERO, q->node);
- if (!ad)
- return NULL;
-
- ad->q = q; /* Identify what queue the data belongs to */
-
- /* 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);
-
- INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_SYNC]);
- INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_ASYNC]);
- ad->sort_list[BLK_RW_SYNC] = RB_ROOT;
- ad->sort_list[BLK_RW_ASYNC] = RB_ROOT;
- ad->fifo_expire[BLK_RW_SYNC] = default_read_expire;
- ad->fifo_expire[BLK_RW_ASYNC] = default_write_expire;
- ad->antic_expire = default_antic_expire;
- ad->batch_expire[BLK_RW_SYNC] = default_read_batch_expire;
- ad->batch_expire[BLK_RW_ASYNC] = default_write_batch_expire;
-
- ad->current_batch_expires = jiffies + ad->batch_expire[BLK_RW_SYNC];
- ad->write_batch_count = ad->batch_expire[BLK_RW_ASYNC] / 10;
- if (ad->write_batch_count < 2)
- ad->write_batch_count = 2;
-
- return ad;
-}
-
-/*
- * sysfs parts below
- */
-
-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 est_time_show(struct elevator_queue *e, char *page)
-{
- struct as_data *ad = e->elevator_data;
- int pos = 0;
-
- pos += sprintf(page+pos, "%lu %% exit probability\n",
- 100*ad->exit_prob/256);
- pos += sprintf(page+pos, "%lu %% probability of exiting without a "
- "cooperating process submitting IO\n",
- 100*ad->exit_no_coop/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 elevator_queue *e, char *page) \
-{ \
- struct as_data *ad = e->elevator_data; \
- return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
-}
-SHOW_FUNCTION(as_read_expire_show, ad->fifo_expire[BLK_RW_SYNC]);
-SHOW_FUNCTION(as_write_expire_show, ad->fifo_expire[BLK_RW_ASYNC]);
-SHOW_FUNCTION(as_antic_expire_show, ad->antic_expire);
-SHOW_FUNCTION(as_read_batch_expire_show, ad->batch_expire[BLK_RW_SYNC]);
-SHOW_FUNCTION(as_write_batch_expire_show, ad->batch_expire[BLK_RW_ASYNC]);
-#undef SHOW_FUNCTION
-
-#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
-static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
-{ \
- struct as_data *ad = e->elevator_data; \
- 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_read_expire_store, &ad->fifo_expire[BLK_RW_SYNC], 0, INT_MAX);
-STORE_FUNCTION(as_write_expire_store,
- &ad->fifo_expire[BLK_RW_ASYNC], 0, INT_MAX);
-STORE_FUNCTION(as_antic_expire_store, &ad->antic_expire, 0, INT_MAX);
-STORE_FUNCTION(as_read_batch_expire_store,
- &ad->batch_expire[BLK_RW_SYNC], 0, INT_MAX);
-STORE_FUNCTION(as_write_batch_expire_store,
- &ad->batch_expire[BLK_RW_ASYNC], 0, INT_MAX);
-#undef STORE_FUNCTION
-
-#define AS_ATTR(name) \
- __ATTR(name, S_IRUGO|S_IWUSR, as_##name##_show, as_##name##_store)
-
-static struct elv_fs_entry as_attrs[] = {
- __ATTR_RO(est_time),
- AS_ATTR(read_expire),
- AS_ATTR(write_expire),
- AS_ATTR(antic_expire),
- AS_ATTR(read_batch_expire),
- AS_ATTR(write_batch_expire),
- __ATTR_NULL
-};
-
-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_dispatch_fn = as_dispatch_request,
- .elevator_add_req_fn = as_add_request,
- .elevator_activate_req_fn = as_activate_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 = elv_rb_former_request,
- .elevator_latter_req_fn = elv_rb_latter_request,
- .elevator_may_queue_fn = as_may_queue,
- .elevator_init_fn = as_init_queue,
- .elevator_exit_fn = as_exit_queue,
- .trim = as_trim,
- },
-
- .elevator_attrs = as_attrs,
- .elevator_name = "anticipatory",
- .elevator_owner = THIS_MODULE,
-};
-
-static int __init as_init(void)
-{
- elv_register(&iosched_as);
-
- return 0;
-}
-
-static void __exit as_exit(void)
-{
- DECLARE_COMPLETION_ONSTACK(all_gone);
- elv_unregister(&iosched_as);
- ioc_gone = &all_gone;
- /* ioc_gone's update must be visible before reading ioc_count */
- smp_wmb();
- if (elv_ioc_count_read(as_ioc_count))
- wait_for_completion(&all_gone);
- synchronize_rcu();
-}
-
-module_init(as_init);
-module_exit(as_exit);
-
-MODULE_AUTHOR("Nick Piggin");
-MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("anticipatory IO scheduler");
git://ftp.safe.ca / safe / jmp / linux-2.6 / commitdiff