[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, 2428 insertions, 0 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
new file mode 100644
index 0000000000000..ecacca9c877eb
--- /dev/null
+++ b/block/cfq-iosched.c
@@ -0,0 +1,2428 @@
+/*
+ *  linux/drivers/block/cfq-iosched.c
+ *
+ *  CFQ, or complete fairness queueing, disk scheduler.
+ *
+ *  Based on ideas from a previously unfinished io
+ *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
+ *
+ *  Copyright (C) 2003 Jens Axboe <axboe@suse.de>
+ */
+#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/mempool.h>
+#include <linux/ioprio.h>
+#include <linux/writeback.h>
+
+/*
+ * tunables
+ */
+static int cfq_quantum = 4;		/* max queue in one round of service */
+static int cfq_queued = 8;		/* minimum rq allocate limit per-queue*/
+static int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
+static int cfq_back_max = 16 * 1024;	/* maximum backwards seek, in KiB */
+static int cfq_back_penalty = 2;	/* penalty of a backwards seek */
+
+static int cfq_slice_sync = HZ / 10;
+static int cfq_slice_async = HZ / 25;
+static int cfq_slice_async_rq = 2;
+static int cfq_slice_idle = HZ / 100;
+
+#define CFQ_IDLE_GRACE		(HZ / 10)
+#define CFQ_SLICE_SCALE		(5)
+
+#define CFQ_KEY_ASYNC		(0)
+#define CFQ_KEY_ANY		(0xffff)
+
+/*
+ * disable queueing at the driver/hardware level
+ */
+static int cfq_max_depth = 2;
+
+/*
+ * for the hash of cfqq inside the cfqd
+ */
+#define CFQ_QHASH_SHIFT		6
+#define CFQ_QHASH_ENTRIES	(1 << CFQ_QHASH_SHIFT)
+#define list_entry_qhash(entry)	hlist_entry((entry), struct cfq_queue, cfq_hash)
+
+/*
+ * for the hash of crq inside the cfqq
+ */
+#define CFQ_MHASH_SHIFT		6
+#define CFQ_MHASH_BLOCK(sec)	((sec) >> 3)
+#define CFQ_MHASH_ENTRIES	(1 << CFQ_MHASH_SHIFT)
+#define CFQ_MHASH_FN(sec)	hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
+#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
+#define list_entry_hash(ptr)	hlist_entry((ptr), struct cfq_rq, hash)
+
+#define list_entry_cfqq(ptr)	list_entry((ptr), struct cfq_queue, cfq_list)
+#define list_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
+
+#define RQ_DATA(rq)		(rq)->elevator_private
+
+/*
+ * rb-tree defines
+ */
+#define RB_NONE			(2)
+#define RB_EMPTY(node)		((node)->rb_node == NULL)
+#define RB_CLEAR_COLOR(node)	(node)->rb_color = RB_NONE
+#define RB_CLEAR(node)		do {	\
+	(node)->rb_parent = NULL;	\
+	RB_CLEAR_COLOR((node));		\
+	(node)->rb_right = NULL;	\
+	(node)->rb_left = NULL;		\
+} while (0)
+#define RB_CLEAR_ROOT(root)	((root)->rb_node = NULL)
+#define rb_entry_crq(node)	rb_entry((node), struct cfq_rq, rb_node)
+#define rq_rb_key(rq)		(rq)->sector
+
+static kmem_cache_t *crq_pool;
+static kmem_cache_t *cfq_pool;
+static kmem_cache_t *cfq_ioc_pool;
+
+#define CFQ_PRIO_LISTS		IOPRIO_BE_NR
+#define cfq_class_idle(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
+#define cfq_class_be(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
+#define cfq_class_rt(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
+
+#define ASYNC			(0)
+#define SYNC			(1)
+
+#define cfq_cfqq_dispatched(cfqq)	\
+	((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
+
+#define cfq_cfqq_class_sync(cfqq)	((cfqq)->key != CFQ_KEY_ASYNC)
+
+#define cfq_cfqq_sync(cfqq)		\
+	(cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
+
+/*
+ * Per block device queue structure
+ */
+struct cfq_data {
+	atomic_t ref;
+	request_queue_t *queue;
+
+	/*
+	 * rr list of queues with requests and the count of them
+	 */
+	struct list_head rr_list[CFQ_PRIO_LISTS];
+	struct list_head busy_rr;
+	struct list_head cur_rr;
+	struct list_head idle_rr;
+	unsigned int busy_queues;
+
+	/*
+	 * non-ordered list of empty cfqq's
+	 */
+	struct list_head empty_list;
+
+	/*
+	 * cfqq lookup hash
+	 */
+	struct hlist_head *cfq_hash;
+
+	/*
+	 * global crq hash for all queues
+	 */
+	struct hlist_head *crq_hash;
+
+	unsigned int max_queued;
+
+	mempool_t *crq_pool;
+
+	int rq_in_driver;
+
+	/*
+	 * schedule slice state info
+	 */
+	/*
+	 * idle window management
+	 */
+	struct timer_list idle_slice_timer;
+	struct work_struct unplug_work;
+
+	struct cfq_queue *active_queue;
+	struct cfq_io_context *active_cic;
+	int cur_prio, cur_end_prio;
+	unsigned int dispatch_slice;
+
+	struct timer_list idle_class_timer;
+
+	sector_t last_sector;
+	unsigned long last_end_request;
+
+	unsigned int rq_starved;
+
+	/*
+	 * tunables, see top of file
+	 */
+	unsigned int cfq_quantum;
+	unsigned int cfq_queued;
+	unsigned int cfq_fifo_expire[2];
+	unsigned int cfq_back_penalty;
+	unsigned int cfq_back_max;
+	unsigned int cfq_slice[2];
+	unsigned int cfq_slice_async_rq;
+	unsigned int cfq_slice_idle;
+	unsigned int cfq_max_depth;
+};
+
+/*
+ * Per process-grouping structure
+ */
+struct cfq_queue {
+	/* reference count */
+	atomic_t ref;
+	/* parent cfq_data */
+	struct cfq_data *cfqd;
+	/* cfqq lookup hash */
+	struct hlist_node cfq_hash;
+	/* hash key */
+	unsigned int key;
+	/* on either rr or empty list of cfqd */
+	struct list_head cfq_list;
+	/* sorted list of pending requests */
+	struct rb_root sort_list;
+	/* if fifo isn't expired, next request to serve */
+	struct cfq_rq *next_crq;
+	/* requests queued in sort_list */
+	int queued[2];
+	/* currently allocated requests */
+	int allocated[2];
+	/* fifo list of requests in sort_list */
+	struct list_head fifo;
+
+	unsigned long slice_start;
+	unsigned long slice_end;
+	unsigned long slice_left;
+	unsigned long service_last;
+
+	/* number of requests that are on the dispatch list */
+	int on_dispatch[2];
+
+	/* io prio of this group */
+	unsigned short ioprio, org_ioprio;
+	unsigned short ioprio_class, org_ioprio_class;
+
+	/* various state flags, see below */
+	unsigned int flags;
+};
+
+struct cfq_rq {
+	struct rb_node rb_node;
+	sector_t rb_key;
+	struct request *request;
+	struct hlist_node hash;
+
+	struct cfq_queue *cfq_queue;
+	struct cfq_io_context *io_context;
+
+	unsigned int crq_flags;
+};
+
+enum cfqq_state_flags {
+	CFQ_CFQQ_FLAG_on_rr = 0,
+	CFQ_CFQQ_FLAG_wait_request,
+	CFQ_CFQQ_FLAG_must_alloc,
+	CFQ_CFQQ_FLAG_must_alloc_slice,
+	CFQ_CFQQ_FLAG_must_dispatch,
+	CFQ_CFQQ_FLAG_fifo_expire,
+	CFQ_CFQQ_FLAG_idle_window,
+	CFQ_CFQQ_FLAG_prio_changed,
+	CFQ_CFQQ_FLAG_expired,
+};
+
+#define CFQ_CFQQ_FNS(name)						\
+static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)		\
+{									\
+	cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name);			\
+}									\
+static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)	\
+{									\
+	cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);			\
+}									\
+static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)		\
+{									\
+	return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;	\
+}
+
+CFQ_CFQQ_FNS(on_rr);
+CFQ_CFQQ_FNS(wait_request);
+CFQ_CFQQ_FNS(must_alloc);
+CFQ_CFQQ_FNS(must_alloc_slice);
+CFQ_CFQQ_FNS(must_dispatch);
+CFQ_CFQQ_FNS(fifo_expire);
+CFQ_CFQQ_FNS(idle_window);
+CFQ_CFQQ_FNS(prio_changed);
+CFQ_CFQQ_FNS(expired);
+#undef CFQ_CFQQ_FNS
+
+enum cfq_rq_state_flags {
+	CFQ_CRQ_FLAG_is_sync = 0,
+};
+
+#define CFQ_CRQ_FNS(name)						\
+static inline void cfq_mark_crq_##name(struct cfq_rq *crq)		\
+{									\
+	crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name);			\
+}									\
+static inline void cfq_clear_crq_##name(struct cfq_rq *crq)		\
+{									\
+	crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name);			\
+}									\
+static inline int cfq_crq_##name(const struct cfq_rq *crq)		\
+{									\
+	return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;	\
+}
+
+CFQ_CRQ_FNS(is_sync);
+#undef CFQ_CRQ_FNS
+
+static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
+static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
+static void cfq_put_cfqd(struct cfq_data *cfqd);
+
+#define process_sync(tsk)	((tsk)->flags & PF_SYNCWRITE)
+
+/*
+ * lots of deadline iosched dupes, can be abstracted later...
+ */
+static inline void cfq_del_crq_hash(struct cfq_rq *crq)
+{
+	hlist_del_init(&crq->hash);
+}
+
+static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
+{
+	const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
+
+	hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
+}
+
+static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
+{
+	struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
+	struct hlist_node *entry, *next;
+
+	hlist_for_each_safe(entry, next, hash_list) {
+		struct cfq_rq *crq = list_entry_hash(entry);
+		struct request *__rq = crq->request;
+
+		if (!rq_mergeable(__rq)) {
+			cfq_del_crq_hash(crq);
+			continue;
+		}
+
+		if (rq_hash_key(__rq) == offset)
+			return __rq;
+	}
+
+	return NULL;
+}
+
+/*
+ * scheduler run of queue, if there are requests pending and no one in the
+ * driver that will restart queueing
+ */
+static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
+{
+	if (!cfqd->rq_in_driver && cfqd->busy_queues)
+		kblockd_schedule_work(&cfqd->unplug_work);
+}
+
+static int cfq_queue_empty(request_queue_t *q)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	return !cfqd->busy_queues;
+}
+
+/*
+ * Lifted from AS - choose which of crq1 and crq2 that is best served now.
+ * We choose the request that is closest to the head right now. Distance
+ * behind the head are penalized and only allowed to a certain extent.
+ */
+static struct cfq_rq *
+cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
+{
+	sector_t last, s1, s2, d1 = 0, d2 = 0;
+	int r1_wrap = 0, r2_wrap = 0;	/* requests are behind the disk head */
+	unsigned long back_max;
+
+	if (crq1 == NULL || crq1 == crq2)
+		return crq2;
+	if (crq2 == NULL)
+		return crq1;
+
+	if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
+		return crq1;
+	else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
+		return crq2;
+
+	s1 = crq1->request->sector;
+	s2 = crq2->request->sector;
+
+	last = cfqd->last_sector;
+
+	/*
+	 * by definition, 1KiB is 2 sectors
+	 */
+	back_max = cfqd->cfq_back_max * 2;
+
+	/*
+	 * Strict one way elevator _except_ in the case where we allow
+	 * short backward seeks which are biased as twice the cost of a
+	 * similar forward seek.
+	 */
+	if (s1 >= last)
+		d1 = s1 - last;
+	else if (s1 + back_max >= last)
+		d1 = (last - s1) * cfqd->cfq_back_penalty;
+	else
+		r1_wrap = 1;
+
+	if (s2 >= last)
+		d2 = s2 - last;
+	else if (s2 + back_max >= last)
+		d2 = (last - s2) * cfqd->cfq_back_penalty;
+	else
+		r2_wrap = 1;
+
+	/* Found required data */
+	if (!r1_wrap && r2_wrap)
+		return crq1;
+	else if (!r2_wrap && r1_wrap)
+		return crq2;
+	else if (r1_wrap && r2_wrap) {
+		/* both behind the head */
+		if (s1 <= s2)
+			return crq1;
+		else
+			return crq2;
+	}
+
+	/* Both requests in front of the head */
+	if (d1 < d2)
+		return crq1;
+	else if (d2 < d1)
+		return crq2;
+	else {
+		if (s1 >= s2)
+			return crq1;
+		else
+			return crq2;
+	}
+}
+
+/*
+ * would be nice to take fifo expire time into account as well
+ */
+static struct cfq_rq *
+cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		  struct cfq_rq *last)
+{
+	struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
+	struct rb_node *rbnext, *rbprev;
+
+	if (!(rbnext = rb_next(&last->rb_node))) {
+		rbnext = rb_first(&cfqq->sort_list);
+		if (rbnext == &last->rb_node)
+			rbnext = NULL;
+	}
+
+	rbprev = rb_prev(&last->rb_node);
+
+	if (rbprev)
+		crq_prev = rb_entry_crq(rbprev);
+	if (rbnext)
+		crq_next = rb_entry_crq(rbnext);
+
+	return cfq_choose_req(cfqd, crq_next, crq_prev);
+}
+
+static void cfq_update_next_crq(struct cfq_rq *crq)
+{
+	struct cfq_queue *cfqq = crq->cfq_queue;
+
+	if (cfqq->next_crq == crq)
+		cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
+}
+
+static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
+{
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct list_head *list, *entry;
+
+	BUG_ON(!cfq_cfqq_on_rr(cfqq));
+
+	list_del(&cfqq->cfq_list);
+
+	if (cfq_class_rt(cfqq))
+		list = &cfqd->cur_rr;
+	else if (cfq_class_idle(cfqq))
+		list = &cfqd->idle_rr;
+	else {
+		/*
+		 * if cfqq has requests in flight, don't allow it to be
+		 * found in cfq_set_active_queue before it has finished them.
+		 * this is done to increase fairness between a process that
+		 * has lots of io pending vs one that only generates one
+		 * sporadically or synchronously
+		 */
+		if (cfq_cfqq_dispatched(cfqq))
+			list = &cfqd->busy_rr;
+		else
+			list = &cfqd->rr_list[cfqq->ioprio];
+	}
+
+	/*
+	 * if queue was preempted, just add to front to be fair. busy_rr
+	 * isn't sorted.
+	 */
+	if (preempted || list == &cfqd->busy_rr) {
+		list_add(&cfqq->cfq_list, list);
+		return;
+	}
+
+	/*
+	 * sort by when queue was last serviced
+	 */
+	entry = list;
+	while ((entry = entry->prev) != list) {
+		struct cfq_queue *__cfqq = list_entry_cfqq(entry);
+
+		if (!__cfqq->service_last)
+			break;
+		if (time_before(__cfqq->service_last, cfqq->service_last))
+			break;
+	}
+
+	list_add(&cfqq->cfq_list, entry);
+}
+
+/*
+ * add to busy list of queues for service, trying to be fair in ordering
+ * the pending list according to last request service
+ */
+static inline void
+cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	BUG_ON(cfq_cfqq_on_rr(cfqq));
+	cfq_mark_cfqq_on_rr(cfqq);
+	cfqd->busy_queues++;
+
+	cfq_resort_rr_list(cfqq, 0);
+}
+
+static inline void
+cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	BUG_ON(!cfq_cfqq_on_rr(cfqq));
+	cfq_clear_cfqq_on_rr(cfqq);
+	list_move(&cfqq->cfq_list, &cfqd->empty_list);
+
+	BUG_ON(!cfqd->busy_queues);
+	cfqd->busy_queues--;
+}
+
+/*
+ * rb tree support functions
+ */
+static inline void cfq_del_crq_rb(struct cfq_rq *crq)
+{
+	struct cfq_queue *cfqq = crq->cfq_queue;
+	struct cfq_data *cfqd = cfqq->cfqd;
+	const int sync = cfq_crq_is_sync(crq);
+
+	BUG_ON(!cfqq->queued[sync]);
+	cfqq->queued[sync]--;
+
+	cfq_update_next_crq(crq);
+
+	rb_erase(&crq->rb_node, &cfqq->sort_list);
+	RB_CLEAR_COLOR(&crq->rb_node);
+
+	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
+		cfq_del_cfqq_rr(cfqd, cfqq);
+}
+
+static struct cfq_rq *
+__cfq_add_crq_rb(struct cfq_rq *crq)
+{
+	struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
+	struct rb_node *parent = NULL;
+	struct cfq_rq *__crq;
+
+	while (*p) {
+		parent = *p;
+		__crq = rb_entry_crq(parent);
+
+		if (crq->rb_key < __crq->rb_key)
+			p = &(*p)->rb_left;
+		else if (crq->rb_key > __crq->rb_key)
+			p = &(*p)->rb_right;
+		else
+			return __crq;
+	}
+
+	rb_link_node(&crq->rb_node, parent, p);
+	return NULL;
+}
+
+static void cfq_add_crq_rb(struct cfq_rq *crq)
+{
+	struct cfq_queue *cfqq = crq->cfq_queue;
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct request *rq = crq->request;
+	struct cfq_rq *__alias;
+
+	crq->rb_key = rq_rb_key(rq);
+	cfqq->queued[cfq_crq_is_sync(crq)]++;
+
+	/*
+	 * looks a little odd, but the first insert might return an alias.
+	 * if that happens, put the alias on the dispatch list
+	 */
+	while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
+		cfq_dispatch_insert(cfqd->queue, __alias);
+
+	rb_insert_color(&crq->rb_node, &cfqq->sort_list);
+
+	if (!cfq_cfqq_on_rr(cfqq))
+		cfq_add_cfqq_rr(cfqd, cfqq);
+
+	/*
+	 * check if this request is a better next-serve candidate
+	 */
+	cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
+}
+
+static inline void
+cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
+{
+	rb_erase(&crq->rb_node, &cfqq->sort_list);
+	cfqq->queued[cfq_crq_is_sync(crq)]--;
+
+	cfq_add_crq_rb(crq);
+}
+
+static struct request *cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector)
+
+{
+	struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->pid, CFQ_KEY_ANY);
+	struct rb_node *n;
+
+	if (!cfqq)
+		goto out;
+
+	n = cfqq->sort_list.rb_node;
+	while (n) {
+		struct cfq_rq *crq = rb_entry_crq(n);
+
+		if (sector < crq->rb_key)
+			n = n->rb_left;
+		else if (sector > crq->rb_key)
+			n = n->rb_right;
+		else
+			return crq->request;
+	}
+
+out:
+	return NULL;
+}
+
+static void cfq_activate_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	cfqd->rq_in_driver++;
+}
+
+static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+
+	WARN_ON(!cfqd->rq_in_driver);
+	cfqd->rq_in_driver--;
+}
+
+static void cfq_remove_request(struct request *rq)
+{
+	struct cfq_rq *crq = RQ_DATA(rq);
+
+	list_del_init(&rq->queuelist);
+	cfq_del_crq_rb(crq);
+	cfq_del_crq_hash(crq);
+}
+
+static int
+cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct request *__rq;
+	int ret;
+
+	__rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		ret = ELEVATOR_BACK_MERGE;
+		goto out;
+	}
+
+	__rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio));
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		ret = ELEVATOR_FRONT_MERGE;
+		goto out;
+	}
+
+	return ELEVATOR_NO_MERGE;
+out:
+	*req = __rq;
+	return ret;
+}
+
+static void cfq_merged_request(request_queue_t *q, struct request *req)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_rq *crq = RQ_DATA(req);
+
+	cfq_del_crq_hash(crq);
+	cfq_add_crq_hash(cfqd, crq);
+
+	if (rq_rb_key(req) != crq->rb_key) {
+		struct cfq_queue *cfqq = crq->cfq_queue;
+
+		cfq_update_next_crq(crq);
+		cfq_reposition_crq_rb(cfqq, crq);
+	}
+}
+
+static void
+cfq_merged_requests(request_queue_t *q, struct request *rq,
+		    struct request *next)
+{
+	cfq_merged_request(q, rq);
+
+	/*
+	 * reposition in fifo if next is older than rq
+	 */
+	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
+	    time_before(next->start_time, rq->start_time))
+		list_move(&rq->queuelist, &next->queuelist);
+
+	cfq_remove_request(next);
+}
+
+static inline void
+__cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	if (cfqq) {
+		/*
+		 * stop potential idle class queues waiting service
+		 */
+		del_timer(&cfqd->idle_class_timer);
+
+		cfqq->slice_start = jiffies;
+		cfqq->slice_end = 0;
+		cfqq->slice_left = 0;
+		cfq_clear_cfqq_must_alloc_slice(cfqq);
+		cfq_clear_cfqq_fifo_expire(cfqq);
+		cfq_clear_cfqq_expired(cfqq);
+	}
+
+	cfqd->active_queue = cfqq;
+}
+
+/*
+ * 0
+ * 0,1
+ * 0,1,2
+ * 0,1,2,3
+ * 0,1,2,3,4
+ * 0,1,2,3,4,5
+ * 0,1,2,3,4,5,6
+ * 0,1,2,3,4,5,6,7
+ */
+static int cfq_get_next_prio_level(struct cfq_data *cfqd)
+{
+	int prio, wrap;
+
+	prio = -1;
+	wrap = 0;
+	do {
+		int p;
+
+		for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
+			if (!list_empty(&cfqd->rr_list[p])) {
+				prio = p;
+				break;
+			}
+		}
+
+		if (prio != -1)
+			break;
+		cfqd->cur_prio = 0;
+		if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
+			cfqd->cur_end_prio = 0;
+			if (wrap)
+				break;
+			wrap = 1;
+		}
+	} while (1);
+
+	if (unlikely(prio == -1))
+		return -1;
+
+	BUG_ON(prio >= CFQ_PRIO_LISTS);
+
+	list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
+
+	cfqd->cur_prio = prio + 1;
+	if (cfqd->cur_prio > cfqd->cur_end_prio) {
+		cfqd->cur_end_prio = cfqd->cur_prio;
+		cfqd->cur_prio = 0;
+	}
+	if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
+		cfqd->cur_prio = 0;
+		cfqd->cur_end_prio = 0;
+	}
+
+	return prio;
+}
+
+static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
+{
+	struct cfq_queue *cfqq;
+
+	/*
+	 * if current queue is expired but not done with its requests yet,
+	 * wait for that to happen
+	 */
+	if ((cfqq = cfqd->active_queue) != NULL) {
+		if (cfq_cfqq_expired(cfqq) && cfq_cfqq_dispatched(cfqq))
+			return NULL;
+	}
+
+	/*
+	 * if current list is non-empty, grab first entry. if it is empty,
+	 * get next prio level and grab first entry then if any are spliced
+	 */
+	if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
+		cfqq = list_entry_cfqq(cfqd->cur_rr.next);
+
+	/*
+	 * if we have idle queues and no rt or be queues had pending
+	 * requests, either allow immediate service if the grace period
+	 * has passed or arm the idle grace timer
+	 */
+	if (!cfqq && !list_empty(&cfqd->idle_rr)) {
+		unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
+
+		if (time_after_eq(jiffies, end))
+			cfqq = list_entry_cfqq(cfqd->idle_rr.next);
+		else
+			mod_timer(&cfqd->idle_class_timer, end);
+	}
+
+	__cfq_set_active_queue(cfqd, cfqq);
+	return cfqq;
+}
+
+/*
+ * current cfqq expired its slice (or was too idle), select new one
+ */
+static void
+__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		    int preempted)
+{
+	unsigned long now = jiffies;
+
+	if (cfq_cfqq_wait_request(cfqq))
+		del_timer(&cfqd->idle_slice_timer);
+
+	if (!preempted && !cfq_cfqq_dispatched(cfqq))
+		cfqq->service_last = now;
+
+	cfq_clear_cfqq_must_dispatch(cfqq);
+	cfq_clear_cfqq_wait_request(cfqq);
+
+	/*
+	 * store what was left of this slice, if the queue idled out
+	 * or was preempted
+	 */
+	if (time_after(now, cfqq->slice_end))
+		cfqq->slice_left = now - cfqq->slice_end;
+	else
+		cfqq->slice_left = 0;
+
+	if (cfq_cfqq_on_rr(cfqq))
+		cfq_resort_rr_list(cfqq, preempted);
+
+	if (cfqq == cfqd->active_queue)
+		cfqd->active_queue = NULL;
+
+	if (cfqd->active_cic) {
+		put_io_context(cfqd->active_cic->ioc);
+		cfqd->active_cic = NULL;
+	}
+
+	cfqd->dispatch_slice = 0;
+}
+
+static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
+{
+	struct cfq_queue *cfqq = cfqd->active_queue;
+
+	if (cfqq) {
+		/*
+		 * use deferred expiry, if there are requests in progress as
+		 * not to disturb the slice of the next queue
+		 */
+		if (cfq_cfqq_dispatched(cfqq))
+			cfq_mark_cfqq_expired(cfqq);
+		else
+			__cfq_slice_expired(cfqd, cfqq, preempted);
+	}
+}
+
+static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+
+{
+	WARN_ON(!RB_EMPTY(&cfqq->sort_list));
+	WARN_ON(cfqq != cfqd->active_queue);
+
+	/*
+	 * idle is disabled, either manually or by past process history
+	 */
+	if (!cfqd->cfq_slice_idle)
+		return 0;
+	if (!cfq_cfqq_idle_window(cfqq))
+		return 0;
+	/*
+	 * task has exited, don't wait
+	 */
+	if (cfqd->active_cic && !cfqd->active_cic->ioc->task)
+		return 0;
+
+	cfq_mark_cfqq_must_dispatch(cfqq);
+	cfq_mark_cfqq_wait_request(cfqq);
+
+	if (!timer_pending(&cfqd->idle_slice_timer)) {
+		unsigned long slice_left = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
+
+		cfqd->idle_slice_timer.expires = jiffies + slice_left;
+		add_timer(&cfqd->idle_slice_timer);
+	}
+
+	return 1;
+}
+
+static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = crq->cfq_queue;
+
+	cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
+	cfq_remove_request(crq->request);
+	cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
+	elv_dispatch_sort(q, crq->request);
+}
+
+/*
+ * return expired entry, or NULL to just start from scratch in rbtree
+ */
+static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
+{
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct request *rq;
+	struct cfq_rq *crq;
+
+	if (cfq_cfqq_fifo_expire(cfqq))
+		return NULL;
+
+	if (!list_empty(&cfqq->fifo)) {
+		int fifo = cfq_cfqq_class_sync(cfqq);
+
+		crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
+		rq = crq->request;
+		if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
+			cfq_mark_cfqq_fifo_expire(cfqq);
+			return crq;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Scale schedule slice based on io priority. Use the sync time slice only
+ * if a queue is marked sync and has sync io queued. A sync queue with async
+ * io only, should not get full sync slice length.
+ */
+static inline int
+cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
+
+	WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
+
+	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
+}
+
+static inline void
+cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
+}
+
+static inline int
+cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	const int base_rq = cfqd->cfq_slice_async_rq;
+
+	WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
+
+	return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
+}
+
+/*
+ * get next queue for service
+ */
+static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd, int force)
+{
+	unsigned long now = jiffies;
+	struct cfq_queue *cfqq;
+
+	cfqq = cfqd->active_queue;
+	if (!cfqq)
+		goto new_queue;
+
+	if (cfq_cfqq_expired(cfqq))
+		goto new_queue;
+
+	/*
+	 * slice has expired
+	 */
+	if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
+		goto expire;
+
+	/*
+	 * if queue has requests, dispatch one. if not, check if
+	 * enough slice is left to wait for one
+	 */
+	if (!RB_EMPTY(&cfqq->sort_list))
+		goto keep_queue;
+	else if (!force && cfq_cfqq_class_sync(cfqq) &&
+		 time_before(now, cfqq->slice_end)) {
+		if (cfq_arm_slice_timer(cfqd, cfqq))
+			return NULL;
+	}
+
+expire:
+	cfq_slice_expired(cfqd, 0);
+new_queue:
+	cfqq = cfq_set_active_queue(cfqd);
+keep_queue:
+	return cfqq;
+}
+
+static int
+__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+			int max_dispatch)
+{
+	int dispatched = 0;
+
+	BUG_ON(RB_EMPTY(&cfqq->sort_list));
+
+	do {
+		struct cfq_rq *crq;
+
+		/*
+		 * follow expired path, else get first next available
+		 */
+		if ((crq = cfq_check_fifo(cfqq)) == NULL)
+			crq = cfqq->next_crq;
+
+		/*
+		 * finally, insert request into driver dispatch list
+		 */
+		cfq_dispatch_insert(cfqd->queue, crq);
+
+		cfqd->dispatch_slice++;
+		dispatched++;
+
+		if (!cfqd->active_cic) {
+			atomic_inc(&crq->io_context->ioc->refcount);
+			cfqd->active_cic = crq->io_context;
+		}
+
+		if (RB_EMPTY(&cfqq->sort_list))
+			break;
+
+	} while (dispatched < max_dispatch);
+
+	/*
+	 * if slice end isn't set yet, set it. if at least one request was
+	 * sync, use the sync time slice value
+	 */
+	if (!cfqq->slice_end)
+		cfq_set_prio_slice(cfqd, cfqq);
+
+	/*
+	 * expire an async queue immediately if it has used up its slice. idle
+	 * queue always expire after 1 dispatch round.
+	 */
+	if ((!cfq_cfqq_sync(cfqq) &&
+	    cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
+	    cfq_class_idle(cfqq))
+		cfq_slice_expired(cfqd, 0);
+
+	return dispatched;
+}
+
+static int
+cfq_dispatch_requests(request_queue_t *q, int force)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq;
+
+	if (!cfqd->busy_queues)
+		return 0;
+
+	cfqq = cfq_select_queue(cfqd, force);
+	if (cfqq) {
+		int max_dispatch;
+
+		/*
+		 * if idle window is disabled, allow queue buildup
+		 */
+		if (!cfq_cfqq_idle_window(cfqq) &&
+		    cfqd->rq_in_driver >= cfqd->cfq_max_depth)
+			return 0;
+
+		cfq_clear_cfqq_must_dispatch(cfqq);
+		cfq_clear_cfqq_wait_request(cfqq);
+		del_timer(&cfqd->idle_slice_timer);
+
+		if (!force) {
+			max_dispatch = cfqd->cfq_quantum;
+			if (cfq_class_idle(cfqq))
+				max_dispatch = 1;
+		} else
+			max_dispatch = INT_MAX;
+
+		return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
+	}
+
+	return 0;
+}
+
+/*
+ * task holds one reference to the queue, dropped when task exits. each crq
+ * in-flight on this queue also holds a reference, dropped when crq is freed.
+ *
+ * queue lock must be held here.
+ */
+static void cfq_put_queue(struct cfq_queue *cfqq)
+{
+	struct cfq_data *cfqd = cfqq->cfqd;
+
+	BUG_ON(atomic_read(&cfqq->ref) <= 0);
+
+	if (!atomic_dec_and_test(&cfqq->ref))
+		return;
+
+	BUG_ON(rb_first(&cfqq->sort_list));
+	BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
+	BUG_ON(cfq_cfqq_on_rr(cfqq));
+
+	if (unlikely(cfqd->active_queue == cfqq)) {
+		__cfq_slice_expired(cfqd, cfqq, 0);
+		cfq_schedule_dispatch(cfqd);
+	}
+
+	cfq_put_cfqd(cfqq->cfqd);
+
+	/*
+	 * it's on the empty list and still hashed
+	 */
+	list_del(&cfqq->cfq_list);
+	hlist_del(&cfqq->cfq_hash);
+	kmem_cache_free(cfq_pool, cfqq);
+}
+
+static inline struct cfq_queue *
+__cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
+		    const int hashval)
+{
+	struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
+	struct hlist_node *entry, *next;
+
+	hlist_for_each_safe(entry, next, hash_list) {
+		struct cfq_queue *__cfqq = list_entry_qhash(entry);
+		const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->ioprio_class, __cfqq->ioprio);
+
+		if (__cfqq->key == key && (__p == prio || prio == CFQ_KEY_ANY))
+			return __cfqq;
+	}
+
+	return NULL;
+}
+
+static struct cfq_queue *
+cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
+{
+	return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
+}
+
+static void cfq_free_io_context(struct cfq_io_context *cic)
+{
+	struct cfq_io_context *__cic;
+	struct list_head *entry, *next;
+
+	list_for_each_safe(entry, next, &cic->list) {
+		__cic = list_entry(entry, struct cfq_io_context, list);
+		kmem_cache_free(cfq_ioc_pool, __cic);
+	}
+
+	kmem_cache_free(cfq_ioc_pool, cic);
+}
+
+/*
+ * Called with interrupts disabled
+ */
+static void cfq_exit_single_io_context(struct cfq_io_context *cic)
+{
+	struct cfq_data *cfqd = cic->cfqq->cfqd;
+	request_queue_t *q = cfqd->queue;
+
+	WARN_ON(!irqs_disabled());
+
+	spin_lock(q->queue_lock);
+
+	if (unlikely(cic->cfqq == cfqd->active_queue)) {
+		__cfq_slice_expired(cfqd, cic->cfqq, 0);
+		cfq_schedule_dispatch(cfqd);
+	}
+
+	cfq_put_queue(cic->cfqq);
+	cic->cfqq = NULL;
+	spin_unlock(q->queue_lock);
+}
+
+/*
+ * Another task may update the task cic list, if it is doing a queue lookup
+ * on its behalf. cfq_cic_lock excludes such concurrent updates
+ */
+static void cfq_exit_io_context(struct cfq_io_context *cic)
+{
+	struct cfq_io_context *__cic;
+	struct list_head *entry;
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	/*
+	 * put the reference this task is holding to the various queues
+	 */
+	list_for_each(entry, &cic->list) {
+		__cic = list_entry(entry, struct cfq_io_context, list);
+		cfq_exit_single_io_context(__cic);
+	}
+
+	cfq_exit_single_io_context(cic);
+	local_irq_restore(flags);
+}
+
+static struct cfq_io_context *
+cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
+{
+	struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
+
+	if (cic) {
+		INIT_LIST_HEAD(&cic->list);
+		cic->cfqq = NULL;
+		cic->key = NULL;
+		cic->last_end_request = jiffies;
+		cic->ttime_total = 0;
+		cic->ttime_samples = 0;
+		cic->ttime_mean = 0;
+		cic->dtor = cfq_free_io_context;
+		cic->exit = cfq_exit_io_context;
+	}
+
+	return cic;
+}
+
+static void cfq_init_prio_data(struct cfq_queue *cfqq)
+{
+	struct task_struct *tsk = current;
+	int ioprio_class;
+
+	if (!cfq_cfqq_prio_changed(cfqq))
+		return;
+
+	ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
+	switch (ioprio_class) {
+		default:
+			printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
+		case IOPRIO_CLASS_NONE:
+			/*
+			 * no prio set, place us in the middle of the BE classes
+			 */
+			cfqq->ioprio = task_nice_ioprio(tsk);
+			cfqq->ioprio_class = IOPRIO_CLASS_BE;
+			break;
+		case IOPRIO_CLASS_RT:
+			cfqq->ioprio = task_ioprio(tsk);
+			cfqq->ioprio_class = IOPRIO_CLASS_RT;
+			break;
+		case IOPRIO_CLASS_BE:
+			cfqq->ioprio = task_ioprio(tsk);
+			cfqq->ioprio_class = IOPRIO_CLASS_BE;
+			break;
+		case IOPRIO_CLASS_IDLE:
+			cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
+			cfqq->ioprio = 7;
+			cfq_clear_cfqq_idle_window(cfqq);
+			break;
+	}
+
+	/*
+	 * keep track of original prio settings in case we have to temporarily
+	 * elevate the priority of this queue
+	 */
+	cfqq->org_ioprio = cfqq->ioprio;
+	cfqq->org_ioprio_class = cfqq->ioprio_class;
+
+	if (cfq_cfqq_on_rr(cfqq))
+		cfq_resort_rr_list(cfqq, 0);
+
+	cfq_clear_cfqq_prio_changed(cfqq);
+}
+
+static inline void changed_ioprio(struct cfq_queue *cfqq)
+{
+	if (cfqq) {
+		struct cfq_data *cfqd = cfqq->cfqd;
+
+		spin_lock(cfqd->queue->queue_lock);
+		cfq_mark_cfqq_prio_changed(cfqq);
+		cfq_init_prio_data(cfqq);
+		spin_unlock(cfqd->queue->queue_lock);
+	}
+}
+
+/*
+ * callback from sys_ioprio_set, irqs are disabled
+ */
+static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
+{
+	struct cfq_io_context *cic = ioc->cic;
+
+	changed_ioprio(cic->cfqq);
+
+	list_for_each_entry(cic, &cic->list, list)
+		changed_ioprio(cic->cfqq);
+
+	return 0;
+}
+
+static struct cfq_queue *
+cfq_get_queue(struct cfq_data *cfqd, unsigned int key, unsigned short ioprio,
+	      gfp_t gfp_mask)
+{
+	const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
+	struct cfq_queue *cfqq, *new_cfqq = NULL;
+
+retry:
+	cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
+
+	if (!cfqq) {
+		if (new_cfqq) {
+			cfqq = new_cfqq;
+			new_cfqq = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			spin_unlock_irq(cfqd->queue->queue_lock);
+			new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
+			spin_lock_irq(cfqd->queue->queue_lock);
+			goto retry;
+		} else {
+			cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
+			if (!cfqq)
+				goto out;
+		}
+
+		memset(cfqq, 0, sizeof(*cfqq));
+
+		INIT_HLIST_NODE(&cfqq->cfq_hash);
+		INIT_LIST_HEAD(&cfqq->cfq_list);
+		RB_CLEAR_ROOT(&cfqq->sort_list);
+		INIT_LIST_HEAD(&cfqq->fifo);
+
+		cfqq->key = key;
+		hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
+		atomic_set(&cfqq->ref, 0);
+		cfqq->cfqd = cfqd;
+		atomic_inc(&cfqd->ref);
+		cfqq->service_last = 0;
+		/*
+		 * set ->slice_left to allow preemption for a new process
+		 */
+		cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
+		cfq_mark_cfqq_idle_window(cfqq);
+		cfq_mark_cfqq_prio_changed(cfqq);
+		cfq_init_prio_data(cfqq);
+	}
+
+	if (new_cfqq)
+		kmem_cache_free(cfq_pool, new_cfqq);
+
+	atomic_inc(&cfqq->ref);
+out:
+	WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
+	return cfqq;
+}
+
+/*
+ * Setup general io context and cfq io context. There can be several cfq
+ * io contexts per general io context, if this process is doing io to more
+ * than one device managed by cfq. Note that caller is holding a reference to
+ * cfqq, so we don't need to worry about it disappearing
+ */
+static struct cfq_io_context *
+cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, gfp_t gfp_mask)
+{
+	struct io_context *ioc = NULL;
+	struct cfq_io_context *cic;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	ioc = get_io_context(gfp_mask);
+	if (!ioc)
+		return NULL;
+
+	if ((cic = ioc->cic) == NULL) {
+		cic = cfq_alloc_io_context(cfqd, gfp_mask);
+
+		if (cic == NULL)
+			goto err;
+
+		/*
+		 * manually increment generic io_context usage count, it
+		 * cannot go away since we are already holding one ref to it
+		 */
+		ioc->cic = cic;
+		ioc->set_ioprio = cfq_ioc_set_ioprio;
+		cic->ioc = ioc;
+		cic->key = cfqd;
+		atomic_inc(&cfqd->ref);
+	} else {
+		struct cfq_io_context *__cic;
+
+		/*
+		 * the first cic on the list is actually the head itself
+		 */
+		if (cic->key == cfqd)
+			goto out;
+
+		/*
+		 * cic exists, check if we already are there. linear search
+		 * should be ok here, the list will usually not be more than
+		 * 1 or a few entries long
+		 */
+		list_for_each_entry(__cic, &cic->list, list) {
+			/*
+			 * this process is already holding a reference to
+			 * this queue, so no need to get one more
+			 */
+			if (__cic->key == cfqd) {
+				cic = __cic;
+				goto out;
+			}
+		}
+
+		/*
+		 * nope, process doesn't have a cic assoicated with this
+		 * cfqq yet. get a new one and add to list
+		 */
+		__cic = cfq_alloc_io_context(cfqd, gfp_mask);
+		if (__cic == NULL)
+			goto err;
+
+		__cic->ioc = ioc;
+		__cic->key = cfqd;
+		atomic_inc(&cfqd->ref);
+		list_add(&__cic->list, &cic->list);
+		cic = __cic;
+	}
+
+out:
+	return cic;
+err:
+	put_io_context(ioc);
+	return NULL;
+}
+
+static void
+cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
+{
+	unsigned long elapsed, ttime;
+
+	/*
+	 * if this context already has stuff queued, thinktime is from
+	 * last queue not last end
+	 */
+#if 0
+	if (time_after(cic->last_end_request, cic->last_queue))
+		elapsed = jiffies - cic->last_end_request;
+	else
+		elapsed = jiffies - cic->last_queue;
+#else
+		elapsed = jiffies - cic->last_end_request;
+#endif
+
+	ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
+
+	cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
+	cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
+	cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
+}
+
+#define sample_valid(samples)	((samples) > 80)
+
+/*
+ * Disable idle window if the process thinks too long or seeks so much that
+ * it doesn't matter
+ */
+static void
+cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		       struct cfq_io_context *cic)
+{
+	int enable_idle = cfq_cfqq_idle_window(cfqq);
+
+	if (!cic->ioc->task || !cfqd->cfq_slice_idle)
+		enable_idle = 0;
+	else if (sample_valid(cic->ttime_samples)) {
+		if (cic->ttime_mean > cfqd->cfq_slice_idle)
+			enable_idle = 0;
+		else
+			enable_idle = 1;
+	}
+
+	if (enable_idle)
+		cfq_mark_cfqq_idle_window(cfqq);
+	else
+		cfq_clear_cfqq_idle_window(cfqq);
+}
+
+
+/*
+ * Check if new_cfqq should preempt the currently active queue. Return 0 for
+ * no or if we aren't sure, a 1 will cause a preempt.
+ */
+static int
+cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
+		   struct cfq_rq *crq)
+{
+	struct cfq_queue *cfqq = cfqd->active_queue;
+
+	if (cfq_class_idle(new_cfqq))
+		return 0;
+
+	if (!cfqq)
+		return 1;
+
+	if (cfq_class_idle(cfqq))
+		return 1;
+	if (!cfq_cfqq_wait_request(new_cfqq))
+		return 0;
+	/*
+	 * if it doesn't have slice left, forget it
+	 */
+	if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
+		return 0;
+	if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
+		return 1;
+
+	return 0;
+}
+
+/*
+ * cfqq preempts the active queue. if we allowed preempt with no slice left,
+ * let it have half of its nominal slice.
+ */
+static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	struct cfq_queue *__cfqq, *next;
+
+	list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
+		cfq_resort_rr_list(__cfqq, 1);
+
+	if (!cfqq->slice_left)
+		cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
+
+	cfqq->slice_end = cfqq->slice_left + jiffies;
+	__cfq_slice_expired(cfqd, cfqq, 1);
+	__cfq_set_active_queue(cfqd, cfqq);
+}
+
+/*
+ * should really be a ll_rw_blk.c helper
+ */
+static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+	request_queue_t *q = cfqd->queue;
+
+	if (!blk_queue_plugged(q))
+		q->request_fn(q);
+	else
+		__generic_unplug_device(q);
+}
+
+/*
+ * Called when a new fs request (crq) is added (to cfqq). Check if there's
+ * something we should do about it
+ */
+static void
+cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		 struct cfq_rq *crq)
+{
+	struct cfq_io_context *cic;
+
+	cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
+
+	/*
+	 * we never wait for an async request and we don't allow preemption
+	 * of an async request. so just return early
+	 */
+	if (!cfq_crq_is_sync(crq))
+		return;
+
+	cic = crq->io_context;
+
+	cfq_update_io_thinktime(cfqd, cic);
+	cfq_update_idle_window(cfqd, cfqq, cic);
+
+	cic->last_queue = jiffies;
+
+	if (cfqq == cfqd->active_queue) {
+		/*
+		 * if we are waiting for a request for this queue, let it rip
+		 * immediately and flag that we must not expire this queue
+		 * just now
+		 */
+		if (cfq_cfqq_wait_request(cfqq)) {
+			cfq_mark_cfqq_must_dispatch(cfqq);
+			del_timer(&cfqd->idle_slice_timer);
+			cfq_start_queueing(cfqd, cfqq);
+		}
+	} else if (cfq_should_preempt(cfqd, cfqq, crq)) {
+		/*
+		 * not the active queue - expire current slice if it is
+		 * idle and has expired it's mean thinktime or this new queue
+		 * has some old slice time left and is of higher priority
+		 */
+		cfq_preempt_queue(cfqd, cfqq);
+		cfq_mark_cfqq_must_dispatch(cfqq);
+		cfq_start_queueing(cfqd, cfqq);
+	}
+}
+
+static void cfq_insert_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_rq *crq = RQ_DATA(rq);
+	struct cfq_queue *cfqq = crq->cfq_queue;
+
+	cfq_init_prio_data(cfqq);
+
+	cfq_add_crq_rb(crq);
+
+	list_add_tail(&rq->queuelist, &cfqq->fifo);
+
+	if (rq_mergeable(rq))
+		cfq_add_crq_hash(cfqd, crq);
+
+	cfq_crq_enqueued(cfqd, cfqq, crq);
+}
+
+static void cfq_completed_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_rq *crq = RQ_DATA(rq);
+	struct cfq_queue *cfqq = crq->cfq_queue;
+	struct cfq_data *cfqd = cfqq->cfqd;
+	const int sync = cfq_crq_is_sync(crq);
+	unsigned long now;
+
+	now = jiffies;
+
+	WARN_ON(!cfqd->rq_in_driver);
+	WARN_ON(!cfqq->on_dispatch[sync]);
+	cfqd->rq_in_driver--;
+	cfqq->on_dispatch[sync]--;
+
+	if (!cfq_class_idle(cfqq))
+		cfqd->last_end_request = now;
+
+	if (!cfq_cfqq_dispatched(cfqq)) {
+		if (cfq_cfqq_on_rr(cfqq)) {
+			cfqq->service_last = now;
+			cfq_resort_rr_list(cfqq, 0);
+		}
+		if (cfq_cfqq_expired(cfqq)) {
+			__cfq_slice_expired(cfqd, cfqq, 0);
+			cfq_schedule_dispatch(cfqd);
+		}
+	}
+
+	if (cfq_crq_is_sync(crq))
+		crq->io_context->last_end_request = now;
+}
+
+static struct request *
+cfq_former_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_rq *crq = RQ_DATA(rq);
+	struct rb_node *rbprev = rb_prev(&crq->rb_node);
+
+	if (rbprev)
+		return rb_entry_crq(rbprev)->request;
+
+	return NULL;
+}
+
+static struct request *
+cfq_latter_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_rq *crq = RQ_DATA(rq);
+	struct rb_node *rbnext = rb_next(&crq->rb_node);
+
+	if (rbnext)
+		return rb_entry_crq(rbnext)->request;
+
+	return NULL;
+}
+
+/*
+ * we temporarily boost lower priority queues if they are holding fs exclusive
+ * resources. they are boosted to normal prio (CLASS_BE/4)
+ */
+static void cfq_prio_boost(struct cfq_queue *cfqq)
+{
+	const int ioprio_class = cfqq->ioprio_class;
+	const int ioprio = cfqq->ioprio;
+
+	if (has_fs_excl()) {
+		/*
+		 * boost idle prio on transactions that would lock out other
+		 * users of the filesystem
+		 */
+		if (cfq_class_idle(cfqq))
+			cfqq->ioprio_class = IOPRIO_CLASS_BE;
+		if (cfqq->ioprio > IOPRIO_NORM)
+			cfqq->ioprio = IOPRIO_NORM;
+	} else {
+		/*
+		 * check if we need to unboost the queue
+		 */
+		if (cfqq->ioprio_class != cfqq->org_ioprio_class)
+			cfqq->ioprio_class = cfqq->org_ioprio_class;
+		if (cfqq->ioprio != cfqq->org_ioprio)
+			cfqq->ioprio = cfqq->org_ioprio;
+	}
+
+	/*
+	 * refile between round-robin lists if we moved the priority class
+	 */
+	if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
+	    cfq_cfqq_on_rr(cfqq))
+		cfq_resort_rr_list(cfqq, 0);
+}
+
+static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
+{
+	if (rw == READ || process_sync(task))
+		return task->pid;
+
+	return CFQ_KEY_ASYNC;
+}
+
+static inline int
+__cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
+		struct task_struct *task, int rw)
+{
+#if 1
+	if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
+	    !cfq_cfqq_must_alloc_slice(cfqq)) {
+		cfq_mark_cfqq_must_alloc_slice(cfqq);
+		return ELV_MQUEUE_MUST;
+	}
+
+	return ELV_MQUEUE_MAY;
+#else
+	if (!cfqq || task->flags & PF_MEMALLOC)
+		return ELV_MQUEUE_MAY;
+	if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
+		if (cfq_cfqq_wait_request(cfqq))
+			return ELV_MQUEUE_MUST;
+
+		/*
+		 * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
+		 * can quickly flood the queue with writes from a single task
+		 */
+		if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
+			cfq_mark_cfqq_must_alloc_slice(cfqq);
+			return ELV_MQUEUE_MUST;
+		}
+
+		return ELV_MQUEUE_MAY;
+	}
+	if (cfq_class_idle(cfqq))
+		return ELV_MQUEUE_NO;
+	if (cfqq->allocated[rw] >= cfqd->max_queued) {
+		struct io_context *ioc = get_io_context(GFP_ATOMIC);
+		int ret = ELV_MQUEUE_NO;
+
+		if (ioc && ioc->nr_batch_requests)
+			ret = ELV_MQUEUE_MAY;
+
+		put_io_context(ioc);
+		return ret;
+	}
+
+	return ELV_MQUEUE_MAY;
+#endif
+}
+
+static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct task_struct *tsk = current;
+	struct cfq_queue *cfqq;
+
+	/*
+	 * don't force setup of a queue from here, as a call to may_queue
+	 * does not necessarily imply that a request actually will be queued.
+	 * so just lookup a possibly existing queue, or return 'may queue'
+	 * if that fails
+	 */
+	cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
+	if (cfqq) {
+		cfq_init_prio_data(cfqq);
+		cfq_prio_boost(cfqq);
+
+		return __cfq_may_queue(cfqd, cfqq, tsk, rw);
+	}
+
+	return ELV_MQUEUE_MAY;
+}
+
+static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct request_list *rl = &q->rq;
+
+	if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
+		smp_mb();
+		if (waitqueue_active(&rl->wait[READ]))
+			wake_up(&rl->wait[READ]);
+	}
+
+	if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
+		smp_mb();
+		if (waitqueue_active(&rl->wait[WRITE]))
+			wake_up(&rl->wait[WRITE]);
+	}
+}
+
+/*
+ * queue lock held here
+ */
+static void cfq_put_request(request_queue_t *q, struct request *rq)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_rq *crq = RQ_DATA(rq);
+
+	if (crq) {
+		struct cfq_queue *cfqq = crq->cfq_queue;
+		const int rw = rq_data_dir(rq);
+
+		BUG_ON(!cfqq->allocated[rw]);
+		cfqq->allocated[rw]--;
+
+		put_io_context(crq->io_context->ioc);
+
+		mempool_free(crq, cfqd->crq_pool);
+		rq->elevator_private = NULL;
+
+		cfq_check_waiters(q, cfqq);
+		cfq_put_queue(cfqq);
+	}
+}
+
+/*
+ * Allocate cfq data structures associated with this request.
+ */
+static int
+cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
+		gfp_t gfp_mask)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct task_struct *tsk = current;
+	struct cfq_io_context *cic;
+	const int rw = rq_data_dir(rq);
+	pid_t key = cfq_queue_pid(tsk, rw);
+	struct cfq_queue *cfqq;
+	struct cfq_rq *crq;
+	unsigned long flags;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+
+	cic = cfq_get_io_context(cfqd, key, gfp_mask);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	if (!cic)
+		goto queue_fail;
+
+	if (!cic->cfqq) {
+		cfqq = cfq_get_queue(cfqd, key, tsk->ioprio, gfp_mask);
+		if (!cfqq)
+			goto queue_fail;
+
+		cic->cfqq = cfqq;
+	} else
+		cfqq = cic->cfqq;
+
+	cfqq->allocated[rw]++;
+	cfq_clear_cfqq_must_alloc(cfqq);
+	cfqd->rq_starved = 0;
+	atomic_inc(&cfqq->ref);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
+	if (crq) {
+		RB_CLEAR(&crq->rb_node);
+		crq->rb_key = 0;
+		crq->request = rq;
+		INIT_HLIST_NODE(&crq->hash);
+		crq->cfq_queue = cfqq;
+		crq->io_context = cic;
+
+		if (rw == READ || process_sync(tsk))
+			cfq_mark_crq_is_sync(crq);
+		else
+			cfq_clear_crq_is_sync(crq);
+
+		rq->elevator_private = crq;
+		return 0;
+	}
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	cfqq->allocated[rw]--;
+	if (!(cfqq->allocated[0] + cfqq->allocated[1]))
+		cfq_mark_cfqq_must_alloc(cfqq);
+	cfq_put_queue(cfqq);
+queue_fail:
+	if (cic)
+		put_io_context(cic->ioc);
+	/*
+	 * mark us rq allocation starved. we need to kickstart the process
+	 * ourselves if there are no pending requests that can do it for us.
+	 * that would be an extremely rare OOM situation
+	 */
+	cfqd->rq_starved = 1;
+	cfq_schedule_dispatch(cfqd);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return 1;
+}
+
+static void cfq_kick_queue(void *data)
+{
+	request_queue_t *q = data;
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	if (cfqd->rq_starved) {
+		struct request_list *rl = &q->rq;
+
+		/*
+		 * we aren't guaranteed to get a request after this, but we
+		 * have to be opportunistic
+		 */
+		smp_mb();
+		if (waitqueue_active(&rl->wait[READ]))
+			wake_up(&rl->wait[READ]);
+		if (waitqueue_active(&rl->wait[WRITE]))
+			wake_up(&rl->wait[WRITE]);
+	}
+
+	blk_remove_plug(q);
+	q->request_fn(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/*
+ * Timer running if the active_queue is currently idling inside its time slice
+ */
+static void cfq_idle_slice_timer(unsigned long data)
+{
+	struct cfq_data *cfqd = (struct cfq_data *) data;
+	struct cfq_queue *cfqq;
+	unsigned long flags;
+
+	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+
+	if ((cfqq = cfqd->active_queue) != NULL) {
+		unsigned long now = jiffies;
+
+		/*
+		 * expired
+		 */
+		if (time_after(now, cfqq->slice_end))
+			goto expire;
+
+		/*
+		 * only expire and reinvoke request handler, if there are
+		 * other queues with pending requests
+		 */
+		if (!cfqd->busy_queues) {
+			cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
+			add_timer(&cfqd->idle_slice_timer);
+			goto out_cont;
+		}
+
+		/*
+		 * not expired and it has a request pending, let it dispatch
+		 */
+		if (!RB_EMPTY(&cfqq->sort_list)) {
+			cfq_mark_cfqq_must_dispatch(cfqq);
+			goto out_kick;
+		}
+	}
+expire:
+	cfq_slice_expired(cfqd, 0);
+out_kick:
+	cfq_schedule_dispatch(cfqd);
+out_cont:
+	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+}
+
+/*
+ * Timer running if an idle class queue is waiting for service
+ */
+static void cfq_idle_class_timer(unsigned long data)
+{
+	struct cfq_data *cfqd = (struct cfq_data *) data;
+	unsigned long flags, end;
+
+	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+
+	/*
+	 * race with a non-idle queue, reset timer
+	 */
+	end = cfqd->last_end_request + CFQ_IDLE_GRACE;
+	if (!time_after_eq(jiffies, end)) {
+		cfqd->idle_class_timer.expires = end;
+		add_timer(&cfqd->idle_class_timer);
+	} else
+		cfq_schedule_dispatch(cfqd);
+
+	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+}
+
+static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
+{
+	del_timer_sync(&cfqd->idle_slice_timer);
+	del_timer_sync(&cfqd->idle_class_timer);
+	blk_sync_queue(cfqd->queue);
+}
+
+static void cfq_put_cfqd(struct cfq_data *cfqd)
+{
+	request_queue_t *q = cfqd->queue;
+
+	if (!atomic_dec_and_test(&cfqd->ref))
+		return;
+
+	cfq_shutdown_timer_wq(cfqd);
+	blk_put_queue(q);
+
+	mempool_destroy(cfqd->crq_pool);
+	kfree(cfqd->crq_hash);
+	kfree(cfqd->cfq_hash);
+	kfree(cfqd);
+}
+
+static void cfq_exit_queue(elevator_t *e)
+{
+	struct cfq_data *cfqd = e->elevator_data;
+
+	cfq_shutdown_timer_wq(cfqd);
+	cfq_put_cfqd(cfqd);
+}
+
+static int cfq_init_queue(request_queue_t *q, elevator_t *e)
+{
+	struct cfq_data *cfqd;
+	int i;
+
+	cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
+	if (!cfqd)
+		return -ENOMEM;
+
+	memset(cfqd, 0, sizeof(*cfqd));
+
+	for (i = 0; i < CFQ_PRIO_LISTS; i++)
+		INIT_LIST_HEAD(&cfqd->rr_list[i]);
+
+	INIT_LIST_HEAD(&cfqd->busy_rr);
+	INIT_LIST_HEAD(&cfqd->cur_rr);
+	INIT_LIST_HEAD(&cfqd->idle_rr);
+	INIT_LIST_HEAD(&cfqd->empty_list);
+
+	cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
+	if (!cfqd->crq_hash)
+		goto out_crqhash;
+
+	cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
+	if (!cfqd->cfq_hash)
+		goto out_cfqhash;
+
+	cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool);
+	if (!cfqd->crq_pool)
+		goto out_crqpool;
+
+	for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
+		INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
+	for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
+		INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
+
+	e->elevator_data = cfqd;
+
+	cfqd->queue = q;
+	atomic_inc(&q->refcnt);
+
+	cfqd->max_queued = q->nr_requests / 4;
+	q->nr_batching = cfq_queued;
+
+	init_timer(&cfqd->idle_slice_timer);
+	cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
+	cfqd->idle_slice_timer.data = (unsigned long) cfqd;
+
+	init_timer(&cfqd->idle_class_timer);
+	cfqd->idle_class_timer.function = cfq_idle_class_timer;
+	cfqd->idle_class_timer.data = (unsigned long) cfqd;
+
+	INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
+
+	atomic_set(&cfqd->ref, 1);
+
+	cfqd->cfq_queued = cfq_queued;
+	cfqd->cfq_quantum = cfq_quantum;
+	cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
+	cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
+	cfqd->cfq_back_max = cfq_back_max;
+	cfqd->cfq_back_penalty = cfq_back_penalty;
+	cfqd->cfq_slice[0] = cfq_slice_async;
+	cfqd->cfq_slice[1] = cfq_slice_sync;
+	cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
+	cfqd->cfq_slice_idle = cfq_slice_idle;
+	cfqd->cfq_max_depth = cfq_max_depth;
+
+	return 0;
+out_crqpool:
+	kfree(cfqd->cfq_hash);
+out_cfqhash:
+	kfree(cfqd->crq_hash);
+out_crqhash:
+	kfree(cfqd);
+	return -ENOMEM;
+}
+
+static void cfq_slab_kill(void)
+{
+	if (crq_pool)
+		kmem_cache_destroy(crq_pool);
+	if (cfq_pool)
+		kmem_cache_destroy(cfq_pool);
+	if (cfq_ioc_pool)
+		kmem_cache_destroy(cfq_ioc_pool);
+}
+
+static int __init cfq_slab_setup(void)
+{
+	crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
+					NULL, NULL);
+	if (!crq_pool)
+		goto fail;
+
+	cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
+					NULL, NULL);
+	if (!cfq_pool)
+		goto fail;
+
+	cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
+			sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
+	if (!cfq_ioc_pool)
+		goto fail;
+
+	return 0;
+fail:
+	cfq_slab_kill();
+	return -ENOMEM;
+}
+
+/*
+ * sysfs parts below -->
+ */
+struct cfq_fs_entry {
+	struct attribute attr;
+	ssize_t (*show)(struct cfq_data *, char *);
+	ssize_t (*store)(struct cfq_data *, const char *, size_t);
+};
+
+static ssize_t
+cfq_var_show(unsigned int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+cfq_var_store(unsigned int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtoul(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct cfq_data *cfqd, char *page)		\
+{									\
+	unsigned int __data = __VAR;					\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return cfq_var_show(__data, (page));				\
+}
+SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
+SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
+SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
+SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
+SHOW_FUNCTION(cfq_back_max_show, cfqd->cfq_back_max, 0);
+SHOW_FUNCTION(cfq_back_penalty_show, cfqd->cfq_back_penalty, 0);
+SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
+SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
+SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
+SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
+SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count)	\
+{									\
+	unsigned int __data;						\
+	int ret = cfq_var_store(&__data, (page), count);		\
+	if (__data < (MIN))						\
+		__data = (MIN);						\
+	else if (__data > (MAX))					\
+		__data = (MAX);						\
+	if (__CONV)							\
+		*(__PTR) = msecs_to_jiffies(__data);			\
+	else								\
+		*(__PTR) = __data;					\
+	return ret;							\
+}
+STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
+STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
+STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_back_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
+STORE_FUNCTION(cfq_back_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
+STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
+STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
+STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
+#undef STORE_FUNCTION
+
+static struct cfq_fs_entry cfq_quantum_entry = {
+	.attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_quantum_show,
+	.store = cfq_quantum_store,
+};
+static struct cfq_fs_entry cfq_queued_entry = {
+	.attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_queued_show,
+	.store = cfq_queued_store,
+};
+static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
+	.attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_fifo_expire_sync_show,
+	.store = cfq_fifo_expire_sync_store,
+};
+static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
+	.attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_fifo_expire_async_show,
+	.store = cfq_fifo_expire_async_store,
+};
+static struct cfq_fs_entry cfq_back_max_entry = {
+	.attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_back_max_show,
+	.store = cfq_back_max_store,
+};
+static struct cfq_fs_entry cfq_back_penalty_entry = {
+	.attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_back_penalty_show,
+	.store = cfq_back_penalty_store,
+};
+static struct cfq_fs_entry cfq_slice_sync_entry = {
+	.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_slice_sync_show,
+	.store = cfq_slice_sync_store,
+};
+static struct cfq_fs_entry cfq_slice_async_entry = {
+	.attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_slice_async_show,
+	.store = cfq_slice_async_store,
+};
+static struct cfq_fs_entry cfq_slice_async_rq_entry = {
+	.attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_slice_async_rq_show,
+	.store = cfq_slice_async_rq_store,
+};
+static struct cfq_fs_entry cfq_slice_idle_entry = {
+	.attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_slice_idle_show,
+	.store = cfq_slice_idle_store,
+};
+static struct cfq_fs_entry cfq_max_depth_entry = {
+	.attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
+	.show = cfq_max_depth_show,
+	.store = cfq_max_depth_store,
+};
+
+static struct attribute *default_attrs[] = {
+	&cfq_quantum_entry.attr,
+	&cfq_queued_entry.attr,
+	&cfq_fifo_expire_sync_entry.attr,
+	&cfq_fifo_expire_async_entry.attr,
+	&cfq_back_max_entry.attr,
+	&cfq_back_penalty_entry.attr,
+	&cfq_slice_sync_entry.attr,
+	&cfq_slice_async_entry.attr,
+	&cfq_slice_async_rq_entry.attr,
+	&cfq_slice_idle_entry.attr,
+	&cfq_max_depth_entry.attr,
+	NULL,
+};
+
+#define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
+
+static ssize_t
+cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct cfq_fs_entry *entry = to_cfq(attr);
+
+	if (!entry->show)
+		return -EIO;
+
+	return entry->show(e->elevator_data, page);
+}
+
+static ssize_t
+cfq_attr_store(struct kobject *kobj, struct attribute *attr,
+	       const char *page, size_t length)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct cfq_fs_entry *entry = to_cfq(attr);
+
+	if (!entry->store)
+		return -EIO;
+
+	return entry->store(e->elevator_data, page, length);
+}
+
+static struct sysfs_ops cfq_sysfs_ops = {
+	.show	= cfq_attr_show,
+	.store	= cfq_attr_store,
+};
+
+static struct kobj_type cfq_ktype = {
+	.sysfs_ops	= &cfq_sysfs_ops,
+	.default_attrs	= default_attrs,
+};
+
+static struct elevator_type iosched_cfq = {
+	.ops = {
+		.elevator_merge_fn = 		cfq_merge,
+		.elevator_merged_fn =		cfq_merged_request,
+		.elevator_merge_req_fn =	cfq_merged_requests,
+		.elevator_dispatch_fn =		cfq_dispatch_requests,
+		.elevator_add_req_fn =		cfq_insert_request,
+		.elevator_activate_req_fn =	cfq_activate_request,
+		.elevator_deactivate_req_fn =	cfq_deactivate_request,
+		.elevator_queue_empty_fn =	cfq_queue_empty,
+		.elevator_completed_req_fn =	cfq_completed_request,
+		.elevator_former_req_fn =	cfq_former_request,
+		.elevator_latter_req_fn =	cfq_latter_request,
+		.elevator_set_req_fn =		cfq_set_request,
+		.elevator_put_req_fn =		cfq_put_request,
+		.elevator_may_queue_fn =	cfq_may_queue,
+		.elevator_init_fn =		cfq_init_queue,
+		.elevator_exit_fn =		cfq_exit_queue,
+	},
+	.elevator_ktype =	&cfq_ktype,
+	.elevator_name =	"cfq",
+	.elevator_owner =	THIS_MODULE,
+};
+
+static int __init cfq_init(void)
+{
+	int ret;
+
+	/*
+	 * could be 0 on HZ < 1000 setups
+	 */
+	if (!cfq_slice_async)
+		cfq_slice_async = 1;
+	if (!cfq_slice_idle)
+		cfq_slice_idle = 1;
+
+	if (cfq_slab_setup())
+		return -ENOMEM;
+
+	ret = elv_register(&iosched_cfq);
+	if (ret)
+		cfq_slab_kill();
+
+	return ret;
+}
+
+static void __exit cfq_exit(void)
+{
+	elv_unregister(&iosched_cfq);
+	cfq_slab_kill();
+}
+
+module_init(cfq_init);
+module_exit(cfq_exit);
+
+MODULE_AUTHOR("Jens Axboe");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");