[BLOCK] Move all core block layer code to new block/ directory

drivers/block/ is right now a mix of core and driver parts. Lets move
the core parts to a new top level directory. Al will move the fs/
related block parts to block/ next.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 0 insertions, 1985 deletions

diff --git a/drivers/block/as-iosched.c b/drivers/block/as-iosched.c
deleted file mode 100644
index c6744ff3829..00000000000
--- a/drivers/block/as-iosched.c
+++ /dev/null
@@ -1,1985 +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 *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;
-}
-
-static void as_put_io_context(struct as_rq *arq)
-{
-	struct as_io_context *aic;
-
-	if (unlikely(!arq->io_context))
-		return;
-
-	aic = arq->io_context->aic;
-
-	if (arq->is_sync == REQ_SYNC && 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);
-}
-
-/*
- * 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_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_del_arq_hash(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_REMOVED) {
-		printk("arq->state %d\n", arq->state);
-		WARN_ON(1);
-		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);
-		}
-	}
-
-	as_put_io_context(arq);
-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_del_arq_hash(arq);
-	as_del_arq_rb(ad, arq);
-}
-
-/*
- * 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;
-	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
-	 */
-	while (!list_empty(&rq->queuelist)) {
-		struct request *__rq = list_entry_rq(rq->queuelist.next);
-		struct as_rq *__arq = RQ_DATA(__rq);
-
-		list_del(&__rq->queuelist);
-
-		elv_dispatch_add_tail(ad->q, __rq);
-
-		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);
-
-	elv_dispatch_sort(ad->q, rq);
-
-	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(request_queue_t *q, int force)
-{
-	struct as_data *ad = q->elevator->elevator_data;
-	struct as_rq *arq;
-	const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
-	const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
-
-	if (unlikely(force)) {
-		/*
-		 * Forced dispatch, accounting is useless.  Reset
-		 * accounting states and dump fifo_lists.  Note that
-		 * batch_data_dir is reset to REQ_SYNC to avoid
-		 * screwing write batch accounting as write batch
-		 * accounting occurs on W->R transition.
-		 */
-		int dispatched = 0;
-
-		ad->batch_data_dir = REQ_SYNC;
-		ad->changed_batch = 0;
-		ad->new_batch = 0;
-
-		while (ad->next_arq[REQ_SYNC]) {
-			as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
-			dispatched++;
-		}
-		ad->last_check_fifo[REQ_SYNC] = jiffies;
-
-		while (ad->next_arq[REQ_ASYNC]) {
-			as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
-			dispatched++;
-		}
-		ad->last_check_fifo[REQ_ASYNC] = jiffies;
-
-		return dispatched;
-	}
-
-	/* 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;
-}
-
-/*
- * 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_del_arq_hash(arq);
-	arq->request->flags |= REQ_NOMERGE;
-}
-
-/*
- * add arq to rbtree and fifo
- */
-static void as_add_request(request_queue_t *q, struct request *rq)
-{
-	struct as_data *ad = q->elevator->elevator_data;
-	struct as_rq *arq = RQ_DATA(rq);
-	struct as_rq *alias;
-	int data_dir;
-
-	if (arq->state != AS_RQ_PRESCHED) {
-		printk("arq->state: %d\n", arq->state);
-		WARN_ON(1);
-	}
-	arq->state = AS_RQ_NEW;
-
-	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);
-		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_activate_request(request_queue_t *q, struct request *rq)
-{
-	struct as_rq *arq = RQ_DATA(rq);
-
-	WARN_ON(arq->state != AS_RQ_DISPATCHED);
-	arq->state = AS_RQ_REMOVED;
-	if (arq->io_context && arq->io_context->aic)
-		atomic_dec(&arq->io_context->aic->nr_dispatched);
-}
-
-static void as_deactivate_request(request_queue_t *q, struct request *rq)
-{
-	struct as_rq *arq = RQ_DATA(rq);
-
-	WARN_ON(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);
-}
-
-/*
- * 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;
-
-	return list_empty(&ad->fifo_list[REQ_ASYNC])
-		&& list_empty(&ad->fifo_list[REQ_SYNC]);
-}
-
-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;
-
-	/*
-	 * 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 (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.
-		 */
-	}
-}
-
-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);
-	as_put_io_context(anext);
-
-	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_queue_empty(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 (unlikely(arq->state != AS_RQ_POSTSCHED &&
-		     arq->state != AS_RQ_PRESCHED &&
-		     arq->state != AS_RQ_MERGED)) {
-		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, gfp_t 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->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_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 =	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)
-{
-	elv_unregister(&iosched_as);
-	kmem_cache_destroy(arq_pool);
-}
-
-module_init(as_init);
-module_exit(as_exit);
-
-MODULE_AUTHOR("Nick Piggin");
-MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("anticipatory IO scheduler");